summaryrefslogtreecommitdiffstats
path: root/doc/bashref.html
blob: 928b3ff19156ca6527ecbf6466152fe8fe07ff55 (plain) 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
2713
2714
2715
2716
2717
2718
2719
2720
2721
2722
2723
2724
2725
2726
2727
2728
2729
2730
2731
2732
2733
2734
2735
2736
2737
2738
2739
2740
2741
2742
2743
2744
2745
2746
2747
2748
2749
2750
2751
2752
2753
2754
2755
2756
2757
2758
2759
2760
2761
2762
2763
2764
2765
2766
2767
2768
2769
2770
2771
2772
2773
2774
2775
2776
2777
2778
2779
2780
2781
2782
2783
2784
2785
2786
2787
2788
2789
2790
2791
2792
2793
2794
2795
2796
2797
2798
2799
2800
2801
2802
2803
2804
2805
2806
2807
2808
2809
2810
2811
2812
2813
2814
2815
2816
2817
2818
2819
2820
2821
2822
2823
2824
2825
2826
2827
2828
2829
2830
2831
2832
2833
2834
2835
2836
2837
2838
2839
2840
2841
2842
2843
2844
2845
2846
2847
2848
2849
2850
2851
2852
2853
2854
2855
2856
2857
2858
2859
2860
2861
2862
2863
2864
2865
2866
2867
2868
2869
2870
2871
2872
2873
2874
2875
2876
2877
2878
2879
2880
2881
2882
2883
2884
2885
2886
2887
2888
2889
2890
2891
2892
2893
2894
2895
2896
2897
2898
2899
2900
2901
2902
2903
2904
2905
2906
2907
2908
2909
2910
2911
2912
2913
2914
2915
2916
2917
2918
2919
2920
2921
2922
2923
2924
2925
2926
2927
2928
2929
2930
2931
2932
2933
2934
2935
2936
2937
2938
2939
2940
2941
2942
2943
2944
2945
2946
2947
2948
2949
2950
2951
2952
2953
2954
2955
2956
2957
2958
2959
2960
2961
2962
2963
2964
2965
2966
2967
2968
2969
2970
2971
2972
2973
2974
2975
2976
2977
2978
2979
2980
2981
2982
2983
2984
2985
2986
2987
2988
2989
2990
2991
2992
2993
2994
2995
2996
2997
2998
2999
3000
3001
3002
3003
3004
3005
3006
3007
3008
3009
3010
3011
3012
3013
3014
3015
3016
3017
3018
3019
3020
3021
3022
3023
3024
3025
3026
3027
3028
3029
3030
3031
3032
3033
3034
3035
3036
3037
3038
3039
3040
3041
3042
3043
3044
3045
3046
3047
3048
3049
3050
3051
3052
3053
3054
3055
3056
3057
3058
3059
3060
3061
3062
3063
3064
3065
3066
3067
3068
3069
3070
3071
3072
3073
3074
3075
3076
3077
3078
3079
3080
3081
3082
3083
3084
3085
3086
3087
3088
3089
3090
3091
3092
3093
3094
3095
3096
3097
3098
3099
3100
3101
3102
3103
3104
3105
3106
3107
3108
3109
3110
3111
3112
3113
3114
3115
3116
3117
3118
3119
3120
3121
3122
3123
3124
3125
3126
3127
3128
3129
3130
3131
3132
3133
3134
3135
3136
3137
3138
3139
3140
3141
3142
3143
3144
3145
3146
3147
3148
3149
3150
3151
3152
3153
3154
3155
3156
3157
3158
3159
3160
3161
3162
3163
3164
3165
3166
3167
3168
3169
3170
3171
3172
3173
3174
3175
3176
3177
3178
3179
3180
3181
3182
3183
3184
3185
3186
3187
3188
3189
3190
3191
3192
3193
3194
3195
3196
3197
3198
3199
3200
3201
3202
3203
3204
3205
3206
3207
3208
3209
3210
3211
3212
3213
3214
3215
3216
3217
3218
3219
3220
3221
3222
3223
3224
3225
3226
3227
3228
3229
3230
3231
3232
3233
3234
3235
3236
3237
3238
3239
3240
3241
3242
3243
3244
3245
3246
3247
3248
3249
3250
3251
3252
3253
3254
3255
3256
3257
3258
3259
3260
3261
3262
3263
3264
3265
3266
3267
3268
3269
3270
3271
3272
3273
3274
3275
3276
3277
3278
3279
3280
3281
3282
3283
3284
3285
3286
3287
3288
3289
3290
3291
3292
3293
3294
3295
3296
3297
3298
3299
3300
3301
3302
3303
3304
3305
3306
3307
3308
3309
3310
3311
3312
3313
3314
3315
3316
3317
3318
3319
3320
3321
3322
3323
3324
3325
3326
3327
3328
3329
3330
3331
3332
3333
3334
3335
3336
3337
3338
3339
3340
3341
3342
3343
3344
3345
3346
3347
3348
3349
3350
3351
3352
3353
3354
3355
3356
3357
3358
3359
3360
3361
3362
3363
3364
3365
3366
3367
3368
3369
3370
3371
3372
3373
3374
3375
3376
3377
3378
3379
3380
3381
3382
3383
3384
3385
3386
3387
3388
3389
3390
3391
3392
3393
3394
3395
3396
3397
3398
3399
3400
3401
3402
3403
3404
3405
3406
3407
3408
3409
3410
3411
3412
3413
3414
3415
3416
3417
3418
3419
3420
3421
3422
3423
3424
3425
3426
3427
3428
3429
3430
3431
3432
3433
3434
3435
3436
3437
3438
3439
3440
3441
3442
3443
3444
3445
3446
3447
3448
3449
3450
3451
3452
3453
3454
3455
3456
3457
3458
3459
3460
3461
3462
3463
3464
3465
3466
3467
3468
3469
3470
3471
3472
3473
3474
3475
3476
3477
3478
3479
3480
3481
3482
3483
3484
3485
3486
3487
3488
3489
3490
3491
3492
3493
3494
3495
3496
3497
3498
3499
3500
3501
3502
3503
3504
3505
3506
3507
3508
3509
3510
3511
3512
3513
3514
3515
3516
3517
3518
3519
3520
3521
3522
3523
3524
3525
3526
3527
3528
3529
3530
3531
3532
3533
3534
3535
3536
3537
3538
3539
3540
3541
3542
3543
3544
3545
3546
3547
3548
3549
3550
3551
3552
3553
3554
3555
3556
3557
3558
3559
3560
3561
3562
3563
3564
3565
3566
3567
3568
3569
3570
3571
3572
3573
3574
3575
3576
3577
3578
3579
3580
3581
3582
3583
3584
3585
3586
3587
3588
3589
3590
3591
3592
3593
3594
3595
3596
3597
3598
3599
3600
3601
3602
3603
3604
3605
3606
3607
3608
3609
3610
3611
3612
3613
3614
3615
3616
3617
3618
3619
3620
3621
3622
3623
3624
3625
3626
3627
3628
3629
3630
3631
3632
3633
3634
3635
3636
3637
3638
3639
3640
3641
3642
3643
3644
3645
3646
3647
3648
3649
3650
3651
3652
3653
3654
3655
3656
3657
3658
3659
3660
3661
3662
3663
3664
3665
3666
3667
3668
3669
3670
3671
3672
3673
3674
3675
3676
3677
3678
3679
3680
3681
3682
3683
3684
3685
3686
3687
3688
3689
3690
3691
3692
3693
3694
3695
3696
3697
3698
3699
3700
3701
3702
3703
3704
3705
3706
3707
3708
3709
3710
3711
3712
3713
3714
3715
3716
3717
3718
3719
3720
3721
3722
3723
3724
3725
3726
3727
3728
3729
3730
3731
3732
3733
3734
3735
3736
3737
3738
3739
3740
3741
3742
3743
3744
3745
3746
3747
3748
3749
3750
3751
3752
3753
3754
3755
3756
3757
3758
3759
3760
3761
3762
3763
3764
3765
3766
3767
3768
3769
3770
3771
3772
3773
3774
3775
3776
3777
3778
3779
3780
3781
3782
3783
3784
3785
3786
3787
3788
3789
3790
3791
3792
3793
3794
3795
3796
3797
3798
3799
3800
3801
3802
3803
3804
3805
3806
3807
3808
3809
3810
3811
3812
3813
3814
3815
3816
3817
3818
3819
3820
3821
3822
3823
3824
3825
3826
3827
3828
3829
3830
3831
3832
3833
3834
3835
3836
3837
3838
3839
3840
3841
3842
3843
3844
3845
3846
3847
3848
3849
3850
3851
3852
3853
3854
3855
3856
3857
3858
3859
3860
3861
3862
3863
3864
3865
3866
3867
3868
3869
3870
3871
3872
3873
3874
3875
3876
3877
3878
3879
3880
3881
3882
3883
3884
3885
3886
3887
3888
3889
3890
3891
3892
3893
3894
3895
3896
3897
3898
3899
3900
3901
3902
3903
3904
3905
3906
3907
3908
3909
3910
3911
3912
3913
3914
3915
3916
3917
3918
3919
3920
3921
3922
3923
3924
3925
3926
3927
3928
3929
3930
3931
3932
3933
3934
3935
3936
3937
3938
3939
3940
3941
3942
3943
3944
3945
3946
3947
3948
3949
3950
3951
3952
3953
3954
3955
3956
3957
3958
3959
3960
3961
3962
3963
3964
3965
3966
3967
3968
3969
3970
3971
3972
3973
3974
3975
3976
3977
3978
3979
3980
3981
3982
3983
3984
3985
3986
3987
3988
3989
3990
3991
3992
3993
3994
3995
3996
3997
3998
3999
4000
4001
4002
4003
4004
4005
4006
4007
4008
4009
4010
4011
4012
4013
4014
4015
4016
4017
4018
4019
4020
4021
4022
4023
4024
4025
4026
4027
4028
4029
4030
4031
4032
4033
4034
4035
4036
4037
4038
4039
4040
4041
4042
4043
4044
4045
4046
4047
4048
4049
4050
4051
4052
4053
4054
4055
4056
4057
4058
4059
4060
4061
4062
4063
4064
4065
4066
4067
4068
4069
4070
4071
4072
4073
4074
4075
4076
4077
4078
4079
4080
4081
4082
4083
4084
4085
4086
4087
4088
4089
4090
4091
4092
4093
4094
4095
4096
4097
4098
4099
4100
4101
4102
4103
4104
4105
4106
4107
4108
4109
4110
4111
4112
4113
4114
4115
4116
4117
4118
4119
4120
4121
4122
4123
4124
4125
4126
4127
4128
4129
4130
4131
4132
4133
4134
4135
4136
4137
4138
4139
4140
4141
4142
4143
4144
4145
4146
4147
4148
4149
4150
4151
4152
4153
4154
4155
4156
4157
4158
4159
4160
4161
4162
4163
4164
4165
4166
4167
4168
4169
4170
4171
4172
4173
4174
4175
4176
4177
4178
4179
4180
4181
4182
4183
4184
4185
4186
4187
4188
4189
4190
4191
4192
4193
4194
4195
4196
4197
4198
4199
4200
4201
4202
4203
4204
4205
4206
4207
4208
4209
4210
4211
4212
4213
4214
4215
4216
4217
4218
4219
4220
4221
4222
4223
4224
4225
4226
4227
4228
4229
4230
4231
4232
4233
4234
4235
4236
4237
4238
4239
4240
4241
4242
4243
4244
4245
4246
4247
4248
4249
4250
4251
4252
4253
4254
4255
4256
4257
4258
4259
4260
4261
4262
4263
4264
4265
4266
4267
4268
4269
4270
4271
4272
4273
4274
4275
4276
4277
4278
4279
4280
4281
4282
4283
4284
4285
4286
4287
4288
4289
4290
4291
4292
4293
4294
4295
4296
4297
4298
4299
4300
4301
4302
4303
4304
4305
4306
4307
4308
4309
4310
4311
4312
4313
4314
4315
4316
4317
4318
4319
4320
4321
4322
4323
4324
4325
4326
4327
4328
4329
4330
4331
4332
4333
4334
4335
4336
4337
4338
4339
4340
4341
4342
4343
4344
4345
4346
4347
4348
4349
4350
4351
4352
4353
4354
4355
4356
4357
4358
4359
4360
4361
4362
4363
4364
4365
4366
4367
4368
4369
4370
4371
4372
4373
4374
4375
4376
4377
4378
4379
4380
4381
4382
4383
4384
4385
4386
4387
4388
4389
4390
4391
4392
4393
4394
4395
4396
4397
4398
4399
4400
4401
4402
4403
4404
4405
4406
4407
4408
4409
4410
4411
4412
4413
4414
4415
4416
4417
4418
4419
4420
4421
4422
4423
4424
4425
4426
4427
4428
4429
4430
4431
4432
4433
4434
4435
4436
4437
4438
4439
4440
4441
4442
4443
4444
4445
4446
4447
4448
4449
4450
4451
4452
4453
4454
4455
4456
4457
4458
4459
4460
4461
4462
4463
4464
4465
4466
4467
4468
4469
4470
4471
4472
4473
4474
4475
4476
4477
4478
4479
4480
4481
4482
4483
4484
4485
4486
4487
4488
4489
4490
4491
4492
4493
4494
4495
4496
4497
4498
4499
4500
4501
4502
4503
4504
4505
4506
4507
4508
4509
4510
4511
4512
4513
4514
4515
4516
4517
4518
4519
4520
4521
4522
4523
4524
4525
4526
4527
4528
4529
4530
4531
4532
4533
4534
4535
4536
4537
4538
4539
4540
4541
4542
4543
4544
4545
4546
4547
4548
4549
4550
4551
4552
4553
4554
4555
4556
4557
4558
4559
4560
4561
4562
4563
4564
4565
4566
4567
4568
4569
4570
4571
4572
4573
4574
4575
4576
4577
4578
4579
4580
4581
4582
4583
4584
4585
4586
4587
4588
4589
4590
4591
4592
4593
4594
4595
4596
4597
4598
4599
4600
4601
4602
4603
4604
4605
4606
4607
4608
4609
4610
4611
4612
4613
4614
4615
4616
4617
4618
4619
4620
4621
4622
4623
4624
4625
4626
4627
4628
4629
4630
4631
4632
4633
4634
4635
4636
4637
4638
4639
4640
4641
4642
4643
4644
4645
4646
4647
4648
4649
4650
4651
4652
4653
4654
4655
4656
4657
4658
4659
4660
4661
4662
4663
4664
4665
4666
4667
4668
4669
4670
4671
4672
4673
4674
4675
4676
4677
4678
4679
4680
4681
4682
4683
4684
4685
4686
4687
4688
4689
4690
4691
4692
4693
4694
4695
4696
4697
4698
4699
4700
4701
4702
4703
4704
4705
4706
4707
4708
4709
4710
4711
4712
4713
4714
4715
4716
4717
4718
4719
4720
4721
4722
4723
4724
4725
4726
4727
4728
4729
4730
4731
4732
4733
4734
4735
4736
4737
4738
4739
4740
4741
4742
4743
4744
4745
4746
4747
4748
4749
4750
4751
4752
4753
4754
4755
4756
4757
4758
4759
4760
4761
4762
4763
4764
4765
4766
4767
4768
4769
4770
4771
4772
4773
4774
4775
4776
4777
4778
4779
4780
4781
4782
4783
4784
4785
4786
4787
4788
4789
4790
4791
4792
4793
4794
4795
4796
4797
4798
4799
4800
4801
4802
4803
4804
4805
4806
4807
4808
4809
4810
4811
4812
4813
4814
4815
4816
4817
4818
4819
4820
4821
4822
4823
4824
4825
4826
4827
4828
4829
4830
4831
4832
4833
4834
4835
4836
4837
4838
4839
4840
4841
4842
4843
4844
4845
4846
4847
4848
4849
4850
4851
4852
4853
4854
4855
4856
4857
4858
4859
4860
4861
4862
4863
4864
4865
4866
4867
4868
4869
4870
4871
4872
4873
4874
4875
4876
4877
4878
4879
4880
4881
4882
4883
4884
4885
4886
4887
4888
4889
4890
4891
4892
4893
4894
4895
4896
4897
4898
4899
4900
4901
4902
4903
4904
4905
4906
4907
4908
4909
4910
4911
4912
4913
4914
4915
4916
4917
4918
4919
4920
4921
4922
4923
4924
4925
4926
4927
4928
4929
4930
4931
4932
4933
4934
4935
4936
4937
4938
4939
4940
4941
4942
4943
4944
4945
4946
4947
4948
4949
4950
4951
4952
4953
4954
4955
4956
4957
4958
4959
4960
4961
4962
4963
4964
4965
4966
4967
4968
4969
4970
4971
4972
4973
4974
4975
4976
4977
4978
4979
4980
4981
4982
4983
4984
4985
4986
4987
4988
4989
4990
4991
4992
4993
4994
4995
4996
4997
4998
4999
5000
5001
5002
5003
5004
5005
5006
5007
5008
5009
5010
5011
5012
5013
5014
5015
5016
5017
5018
5019
5020
5021
5022
5023
5024
5025
5026
5027
5028
5029
5030
5031
5032
5033
5034
5035
5036
5037
5038
5039
5040
5041
5042
5043
5044
5045
5046
5047
5048
5049
5050
5051
5052
5053
5054
5055
5056
5057
5058
5059
5060
5061
5062
5063
5064
5065
5066
5067
5068
5069
5070
5071
5072
5073
5074
5075
5076
5077
5078
5079
5080
5081
5082
5083
5084
5085
5086
5087
5088
5089
5090
5091
5092
5093
5094
5095
5096
5097
5098
5099
5100
5101
5102
5103
5104
5105
5106
5107
5108
5109
5110
5111
5112
5113
5114
5115
5116
5117
5118
5119
5120
5121
5122
5123
5124
5125
5126
5127
5128
5129
5130
5131
5132
5133
5134
5135
5136
5137
5138
5139
5140
5141
5142
5143
5144
5145
5146
5147
5148
5149
5150
5151
5152
5153
5154
5155
5156
5157
5158
5159
5160
5161
5162
5163
5164
5165
5166
5167
5168
5169
5170
5171
5172
5173
5174
5175
5176
5177
5178
5179
5180
5181
5182
5183
5184
5185
5186
5187
5188
5189
5190
5191
5192
5193
5194
5195
5196
5197
5198
5199
5200
5201
5202
5203
5204
5205
5206
5207
5208
5209
5210
5211
5212
5213
5214
5215
5216
5217
5218
5219
5220
5221
5222
5223
5224
5225
5226
5227
5228
5229
5230
5231
5232
5233
5234
5235
5236
5237
5238
5239
5240
5241
5242
5243
5244
5245
5246
5247
5248
5249
5250
5251
5252
5253
5254
5255
5256
5257
5258
5259
5260
5261
5262
5263
5264
5265
5266
5267
5268
5269
5270
5271
5272
5273
5274
5275
5276
5277
5278
5279
5280
5281
5282
5283
5284
5285
5286
5287
5288
5289
5290
5291
5292
5293
5294
5295
5296
5297
5298
5299
5300
5301
5302
5303
5304
5305
5306
5307
5308
5309
5310
5311
5312
5313
5314
5315
5316
5317
5318
5319
5320
5321
5322
5323
5324
5325
5326
5327
5328
5329
5330
5331
5332
5333
5334
5335
5336
5337
5338
5339
5340
5341
5342
5343
5344
5345
5346
5347
5348
5349
5350
5351
5352
5353
5354
5355
5356
5357
5358
5359
5360
5361
5362
5363
5364
5365
5366
5367
5368
5369
5370
5371
5372
5373
5374
5375
5376
5377
5378
5379
5380
5381
5382
5383
5384
5385
5386
5387
5388
5389
5390
5391
5392
5393
5394
5395
5396
5397
5398
5399
5400
5401
5402
5403
5404
5405
5406
5407
5408
5409
5410
5411
5412
5413
5414
5415
5416
5417
5418
5419
5420
5421
5422
5423
5424
5425
5426
5427
5428
5429
5430
5431
5432
5433
5434
5435
5436
5437
5438
5439
5440
5441
5442
5443
5444
5445
5446
5447
5448
5449
5450
5451
5452
5453
5454
5455
5456
5457
5458
5459
5460
5461
5462
5463
5464
5465
5466
5467
5468
5469
5470
5471
5472
5473
5474
5475
5476
5477
5478
5479
5480
5481
5482
5483
5484
5485
5486
5487
5488
5489
5490
5491
5492
5493
5494
5495
5496
5497
5498
5499
5500
5501
5502
5503
5504
5505
5506
5507
5508
5509
5510
5511
5512
5513
5514
5515
5516
5517
5518
5519
5520
5521
5522
5523
5524
5525
5526
5527
5528
5529
5530
5531
5532
5533
5534
5535
5536
5537
5538
5539
5540
5541
5542
5543
5544
5545
5546
5547
5548
5549
5550
5551
5552
5553
5554
5555
5556
5557
5558
5559
5560
5561
5562
5563
5564
5565
5566
5567
5568
5569
5570
5571
5572
5573
5574
5575
5576
5577
5578
5579
5580
5581
5582
5583
5584
5585
5586
5587
5588
5589
5590
5591
5592
5593
5594
5595
5596
5597
5598
5599
5600
5601
5602
5603
5604
5605
5606
5607
5608
5609
5610
5611
5612
5613
5614
5615
5616
5617
5618
5619
5620
5621
5622
5623
5624
5625
5626
5627
5628
5629
5630
5631
5632
5633
5634
5635
5636
5637
5638
5639
5640
5641
5642
5643
5644
5645
5646
5647
5648
5649
5650
5651
5652
5653
5654
5655
5656
5657
5658
5659
5660
5661
5662
5663
5664
5665
5666
5667
5668
5669
5670
5671
5672
5673
5674
5675
5676
5677
5678
5679
5680
5681
5682
5683
5684
5685
5686
5687
5688
5689
5690
5691
5692
5693
5694
5695
5696
5697
5698
5699
5700
5701
5702
5703
5704
5705
5706
5707
5708
5709
5710
5711
5712
5713
5714
5715
5716
5717
5718
5719
5720
5721
5722
5723
5724
5725
5726
5727
5728
5729
5730
5731
5732
5733
5734
5735
5736
5737
5738
5739
5740
5741
5742
5743
5744
5745
5746
5747
5748
5749
5750
5751
5752
5753
5754
5755
5756
5757
5758
5759
5760
5761
5762
5763
5764
5765
5766
5767
5768
5769
5770
5771
5772
5773
5774
5775
5776
5777
5778
5779
5780
5781
5782
5783
5784
5785
5786
5787
5788
5789
5790
5791
5792
5793
5794
5795
5796
5797
5798
5799
5800
5801
5802
5803
5804
5805
5806
5807
5808
5809
5810
5811
5812
5813
5814
5815
5816
5817
5818
5819
5820
5821
5822
5823
5824
5825
5826
5827
5828
5829
5830
5831
5832
5833
5834
5835
5836
5837
5838
5839
5840
5841
5842
5843
5844
5845
5846
5847
5848
5849
5850
5851
5852
5853
5854
5855
5856
5857
5858
5859
5860
5861
5862
5863
5864
5865
5866
5867
5868
5869
5870
5871
5872
5873
5874
5875
5876
5877
5878
5879
5880
5881
5882
5883
5884
5885
5886
5887
5888
5889
5890
5891
5892
5893
5894
5895
5896
5897
5898
5899
5900
5901
5902
5903
5904
5905
5906
5907
5908
5909
5910
5911
5912
5913
5914
5915
5916
5917
5918
5919
5920
5921
5922
5923
5924
5925
5926
5927
5928
5929
5930
5931
5932
5933
5934
5935
5936
5937
5938
5939
5940
5941
5942
5943
5944
5945
5946
5947
5948
5949
5950
5951
5952
5953
5954
5955
5956
5957
5958
5959
5960
5961
5962
5963
5964
5965
5966
5967
5968
5969
5970
5971
5972
5973
5974
5975
5976
5977
5978
5979
5980
5981
5982
5983
5984
5985
5986
5987
5988
5989
5990
5991
5992
5993
5994
5995
5996
5997
5998
5999
6000
6001
6002
6003
6004
6005
6006
6007
6008
6009
6010
6011
6012
6013
6014
6015
6016
6017
6018
6019
6020
6021
6022
6023
6024
6025
6026
6027
6028
6029
6030
6031
6032
6033
6034
6035
6036
6037
6038
6039
6040
6041
6042
6043
6044
6045
6046
6047
6048
6049
6050
6051
6052
6053
6054
6055
6056
6057
6058
6059
6060
6061
6062
6063
6064
6065
6066
6067
6068
6069
6070
6071
6072
6073
6074
6075
6076
6077
6078
6079
6080
6081
6082
6083
6084
6085
6086
6087
6088
6089
6090
6091
6092
6093
6094
6095
6096
6097
6098
6099
6100
6101
6102
6103
6104
6105
6106
6107
6108
6109
6110
6111
6112
6113
6114
6115
6116
6117
6118
6119
6120
6121
6122
6123
6124
6125
6126
6127
6128
6129
6130
6131
6132
6133
6134
6135
6136
6137
6138
6139
6140
6141
6142
6143
6144
6145
6146
6147
6148
6149
6150
6151
6152
6153
6154
6155
6156
6157
6158
6159
6160
6161
6162
6163
6164
6165
6166
6167
6168
6169
6170
6171
6172
6173
6174
6175
6176
6177
6178
6179
6180
6181
6182
6183
6184
6185
6186
6187
6188
6189
6190
6191
6192
6193
6194
6195
6196
6197
6198
6199
6200
6201
6202
6203
6204
6205
6206
6207
6208
6209
6210
6211
6212
6213
6214
6215
6216
6217
6218
6219
6220
6221
6222
6223
6224
6225
6226
6227
6228
6229
6230
6231
6232
6233
6234
6235
6236
6237
6238
6239
6240
6241
6242
6243
6244
6245
6246
6247
6248
6249
6250
6251
6252
6253
6254
6255
6256
6257
6258
6259
6260
6261
6262
6263
6264
6265
6266
6267
6268
6269
6270
6271
6272
6273
6274
6275
6276
6277
6278
6279
6280
6281
6282
6283
6284
6285
6286
6287
6288
6289
6290
6291
6292
6293
6294
6295
6296
6297
6298
6299
6300
6301
6302
6303
6304
6305
6306
6307
6308
6309
6310
6311
6312
6313
6314
6315
6316
6317
6318
6319
6320
6321
6322
6323
6324
6325
6326
6327
6328
6329
6330
6331
6332
6333
6334
6335
6336
6337
6338
6339
6340
6341
6342
6343
6344
6345
6346
6347
6348
6349
6350
6351
6352
6353
6354
6355
6356
6357
6358
6359
6360
6361
6362
6363
6364
6365
6366
6367
6368
6369
6370
6371
6372
6373
6374
6375
6376
6377
6378
6379
6380
6381
6382
6383
6384
6385
6386
6387
6388
6389
6390
6391
6392
6393
6394
6395
6396
6397
6398
6399
6400
6401
6402
6403
6404
6405
6406
6407
6408
6409
6410
6411
6412
6413
6414
6415
6416
6417
6418
6419
6420
6421
6422
6423
6424
6425
6426
6427
6428
6429
6430
6431
6432
6433
6434
6435
6436
6437
6438
6439
6440
6441
6442
6443
6444
6445
6446
6447
6448
6449
6450
6451
6452
6453
6454
6455
6456
6457
6458
6459
6460
6461
6462
6463
6464
6465
6466
6467
6468
6469
6470
6471
6472
6473
6474
6475
6476
6477
6478
6479
6480
6481
6482
6483
6484
6485
6486
6487
6488
6489
6490
6491
6492
6493
6494
6495
6496
6497
6498
6499
6500
6501
6502
6503
6504
6505
6506
6507
6508
6509
6510
6511
6512
6513
6514
6515
6516
6517
6518
6519
6520
6521
6522
6523
6524
6525
6526
6527
6528
6529
6530
6531
6532
6533
6534
6535
6536
6537
6538
6539
6540
6541
6542
6543
6544
6545
6546
6547
6548
6549
6550
6551
6552
6553
6554
6555
6556
6557
6558
6559
6560
6561
6562
6563
6564
6565
6566
6567
6568
6569
6570
6571
6572
6573
6574
6575
6576
6577
6578
6579
6580
6581
6582
6583
6584
6585
6586
6587
6588
6589
6590
6591
6592
6593
6594
6595
6596
6597
6598
6599
6600
6601
6602
6603
6604
6605
6606
6607
6608
6609
6610
6611
6612
6613
6614
6615
6616
6617
6618
6619
6620
6621
6622
6623
6624
6625
6626
6627
6628
6629
6630
6631
6632
6633
6634
6635
6636
6637
6638
6639
6640
6641
6642
6643
6644
6645
6646
6647
6648
6649
6650
6651
6652
6653
6654
6655
6656
6657
6658
6659
6660
6661
6662
6663
6664
6665
6666
6667
6668
6669
6670
6671
6672
6673
6674
6675
6676
6677
6678
6679
6680
6681
6682
6683
6684
6685
6686
6687
6688
6689
6690
6691
6692
6693
6694
6695
6696
6697
6698
6699
6700
6701
6702
6703
6704
6705
6706
6707
6708
6709
6710
6711
6712
6713
6714
6715
6716
6717
6718
6719
6720
6721
6722
6723
6724
6725
6726
6727
6728
6729
6730
6731
6732
6733
6734
6735
6736
6737
6738
6739
6740
6741
6742
6743
6744
6745
6746
6747
6748
6749
6750
6751
6752
6753
6754
6755
6756
6757
6758
6759
6760
6761
6762
6763
6764
6765
6766
6767
6768
6769
6770
6771
6772
6773
6774
6775
6776
6777
6778
6779
6780
6781
6782
6783
6784
6785
6786
6787
6788
6789
6790
6791
6792
6793
6794
6795
6796
6797
6798
6799
6800
6801
6802
6803
6804
6805
6806
6807
6808
6809
6810
6811
6812
6813
6814
6815
6816
6817
6818
6819
6820
6821
6822
6823
6824
6825
6826
6827
6828
6829
6830
6831
6832
6833
6834
6835
6836
6837
6838
6839
6840
6841
6842
6843
6844
6845
6846
6847
6848
6849
6850
6851
6852
6853
6854
6855
6856
6857
6858
6859
6860
6861
6862
6863
6864
6865
6866
6867
6868
6869
6870
6871
6872
6873
6874
6875
6876
6877
6878
6879
6880
6881
6882
6883
6884
6885
6886
6887
6888
6889
6890
6891
6892
6893
6894
6895
6896
6897
6898
6899
6900
6901
6902
6903
6904
6905
6906
6907
6908
6909
6910
6911
6912
6913
6914
6915
6916
6917
6918
6919
6920
6921
6922
6923
6924
6925
6926
6927
6928
6929
6930
6931
6932
6933
6934
6935
6936
6937
6938
6939
6940
6941
6942
6943
6944
6945
6946
6947
6948
6949
6950
6951
6952
6953
6954
6955
6956
6957
6958
6959
6960
6961
6962
6963
6964
6965
6966
6967
6968
6969
6970
6971
6972
6973
6974
6975
6976
6977
6978
6979
6980
6981
6982
6983
6984
6985
6986
6987
6988
6989
6990
6991
6992
6993
6994
6995
6996
6997
6998
6999
7000
7001
7002
7003
7004
7005
7006
7007
7008
7009
7010
7011
7012
7013
7014
7015
7016
7017
7018
7019
7020
7021
7022
7023
7024
7025
7026
7027
7028
7029
7030
7031
7032
7033
7034
7035
7036
7037
7038
7039
7040
7041
7042
7043
7044
7045
7046
7047
7048
7049
7050
7051
7052
7053
7054
7055
7056
7057
7058
7059
7060
7061
7062
7063
7064
7065
7066
7067
7068
7069
7070
7071
7072
7073
7074
7075
7076
7077
7078
7079
7080
7081
7082
7083
7084
7085
7086
7087
7088
7089
7090
7091
7092
7093
7094
7095
7096
7097
7098
7099
7100
7101
7102
7103
7104
7105
7106
7107
7108
7109
7110
7111
7112
7113
7114
7115
7116
7117
7118
7119
7120
7121
7122
7123
7124
7125
7126
7127
7128
7129
7130
7131
7132
7133
7134
7135
7136
7137
7138
7139
7140
7141
7142
7143
7144
7145
7146
7147
7148
7149
7150
7151
7152
7153
7154
7155
7156
7157
7158
7159
7160
7161
7162
7163
7164
7165
7166
7167
7168
7169
7170
7171
7172
7173
7174
7175
7176
7177
7178
7179
7180
7181
7182
7183
7184
7185
7186
7187
7188
7189
7190
7191
7192
7193
7194
7195
7196
7197
7198
7199
7200
7201
7202
7203
7204
7205
7206
7207
7208
7209
7210
7211
7212
7213
7214
7215
7216
7217
7218
7219
7220
7221
7222
7223
7224
7225
7226
7227
7228
7229
7230
7231
7232
7233
7234
7235
7236
7237
7238
7239
7240
7241
7242
7243
7244
7245
7246
7247
7248
7249
7250
7251
7252
7253
7254
7255
7256
7257
7258
7259
7260
7261
7262
7263
7264
7265
7266
7267
7268
7269
7270
7271
7272
7273
7274
7275
7276
7277
7278
7279
7280
7281
7282
7283
7284
7285
7286
7287
7288
7289
7290
7291
7292
7293
7294
7295
7296
7297
7298
7299
7300
7301
7302
7303
7304
7305
7306
7307
7308
7309
7310
7311
7312
7313
7314
7315
7316
7317
7318
7319
7320
7321
7322
7323
7324
7325
7326
7327
7328
7329
7330
7331
7332
7333
7334
7335
7336
7337
7338
7339
7340
7341
7342
7343
7344
7345
7346
7347
7348
7349
7350
7351
7352
7353
7354
7355
7356
7357
7358
7359
7360
7361
7362
7363
7364
7365
7366
7367
7368
7369
7370
7371
7372
7373
7374
7375
7376
7377
7378
7379
7380
7381
7382
7383
7384
7385
7386
7387
7388
7389
7390
7391
7392
7393
7394
7395
7396
7397
7398
7399
7400
7401
7402
7403
7404
7405
7406
7407
7408
7409
7410
7411
7412
7413
7414
7415
7416
7417
7418
7419
7420
7421
7422
7423
7424
7425
7426
7427
7428
7429
7430
7431
7432
7433
7434
7435
7436
7437
7438
7439
7440
7441
7442
7443
7444
7445
7446
7447
7448
7449
7450
7451
7452
7453
7454
7455
7456
7457
7458
7459
7460
7461
7462
7463
7464
7465
7466
7467
7468
7469
7470
7471
7472
7473
7474
7475
7476
7477
7478
7479
7480
7481
7482
7483
7484
7485
7486
7487
7488
7489
7490
7491
7492
7493
7494
7495
7496
7497
7498
7499
7500
7501
7502
7503
7504
7505
7506
7507
7508
7509
7510
7511
7512
7513
7514
7515
7516
7517
7518
7519
7520
7521
7522
7523
7524
7525
7526
7527
7528
7529
7530
7531
7532
7533
7534
7535
7536
7537
7538
7539
7540
7541
7542
7543
7544
7545
7546
7547
7548
7549
7550
7551
7552
7553
7554
7555
7556
7557
7558
7559
7560
7561
7562
7563
7564
7565
7566
7567
7568
7569
7570
7571
7572
7573
7574
7575
7576
7577
7578
7579
7580
7581
7582
7583
7584
7585
7586
7587
7588
7589
7590
7591
7592
7593
7594
7595
7596
7597
7598
7599
7600
7601
7602
7603
7604
7605
7606
7607
7608
7609
7610
7611
7612
7613
7614
7615
7616
7617
7618
7619
7620
7621
7622
7623
7624
7625
7626
7627
7628
7629
7630
7631
7632
7633
7634
7635
7636
7637
7638
7639
7640
7641
7642
7643
7644
7645
7646
7647
7648
7649
7650
7651
7652
7653
7654
7655
7656
7657
7658
7659
7660
7661
7662
7663
7664
7665
7666
7667
7668
7669
7670
7671
7672
7673
7674
7675
7676
7677
7678
7679
7680
7681
7682
7683
7684
7685
7686
7687
7688
7689
7690
7691
7692
7693
7694
7695
7696
7697
7698
7699
7700
7701
7702
7703
7704
7705
7706
7707
7708
7709
7710
7711
7712
7713
7714
7715
7716
7717
7718
7719
7720
7721
7722
7723
7724
7725
7726
7727
7728
7729
7730
7731
7732
7733
7734
7735
7736
7737
7738
7739
7740
7741
7742
7743
7744
7745
7746
7747
7748
7749
7750
7751
7752
7753
7754
7755
7756
7757
7758
7759
7760
7761
7762
7763
7764
7765
7766
7767
7768
7769
7770
7771
7772
7773
7774
7775
7776
7777
7778
7779
7780
7781
7782
7783
7784
7785
7786
7787
7788
7789
7790
7791
7792
7793
7794
7795
7796
7797
7798
7799
7800
7801
7802
7803
7804
7805
7806
7807
7808
7809
7810
7811
7812
7813
7814
7815
7816
7817
7818
7819
7820
7821
7822
7823
7824
7825
7826
7827
7828
7829
7830
7831
7832
7833
7834
7835
7836
7837
7838
7839
7840
7841
7842
7843
7844
7845
7846
7847
7848
7849
7850
7851
7852
7853
7854
7855
7856
7857
7858
7859
7860
7861
7862
7863
7864
7865
7866
7867
7868
7869
7870
7871
7872
7873
7874
7875
7876
7877
7878
7879
7880
7881
7882
7883
7884
7885
7886
7887
7888
7889
7890
7891
7892
7893
7894
7895
7896
7897
7898
7899
7900
7901
7902
7903
7904
7905
7906
7907
7908
7909
7910
7911
7912
7913
7914
7915
7916
7917
7918
7919
7920
7921
7922
7923
7924
7925
7926
7927
7928
7929
7930
7931
7932
7933
7934
7935
7936
7937
7938
7939
7940
7941
7942
7943
7944
7945
7946
7947
7948
7949
7950
7951
7952
7953
7954
7955
7956
7957
7958
7959
7960
7961
7962
7963
7964
7965
7966
7967
7968
7969
7970
7971
7972
7973
7974
7975
7976
7977
7978
7979
7980
7981
7982
7983
7984
7985
7986
7987
7988
7989
7990
7991
7992
7993
7994
7995
7996
7997
7998
7999
8000
8001
8002
8003
8004
8005
8006
8007
8008
8009
8010
8011
8012
8013
8014
8015
8016
8017
8018
8019
8020
8021
8022
8023
8024
8025
8026
8027
8028
8029
8030
8031
8032
8033
8034
8035
8036
8037
8038
8039
8040
8041
8042
8043
8044
8045
8046
8047
8048
8049
8050
8051
8052
8053
8054
8055
8056
8057
8058
8059
8060
8061
8062
8063
8064
8065
8066
8067
8068
8069
8070
8071
8072
8073
8074
8075
8076
8077
8078
8079
8080
8081
8082
8083
8084
8085
8086
8087
8088
8089
8090
8091
8092
8093
8094
8095
8096
8097
8098
8099
8100
8101
8102
8103
8104
8105
8106
8107
8108
8109
8110
8111
8112
8113
8114
8115
8116
8117
8118
8119
8120
8121
8122
8123
8124
8125
8126
8127
8128
8129
8130
8131
8132
8133
8134
8135
8136
8137
8138
8139
8140
8141
8142
8143
8144
8145
8146
8147
8148
8149
8150
8151
8152
8153
8154
8155
8156
8157
8158
8159
8160
8161
8162
8163
8164
8165
8166
8167
8168
8169
8170
8171
8172
8173
8174
8175
8176
8177
8178
8179
8180
8181
8182
8183
8184
8185
8186
8187
8188
8189
8190
8191
8192
8193
8194
8195
8196
8197
8198
8199
8200
8201
8202
8203
8204
8205
8206
8207
8208
8209
8210
8211
8212
8213
8214
8215
8216
8217
8218
8219
8220
8221
8222
8223
8224
8225
8226
8227
8228
8229
8230
8231
8232
8233
8234
8235
8236
8237
8238
8239
8240
8241
8242
8243
8244
8245
8246
8247
8248
8249
8250
8251
8252
8253
8254
8255
8256
8257
8258
8259
8260
8261
8262
8263
8264
8265
8266
8267
8268
8269
8270
8271
8272
8273
8274
8275
8276
8277
8278
8279
8280
8281
8282
8283
8284
8285
8286
8287
8288
8289
8290
8291
8292
8293
8294
8295
8296
8297
8298
8299
8300
8301
8302
8303
8304
8305
8306
8307
8308
8309
8310
8311
8312
8313
8314
8315
8316
8317
8318
8319
8320
8321
8322
8323
8324
8325
8326
8327
8328
8329
8330
8331
8332
8333
8334
8335
8336
8337
8338
8339
8340
8341
8342
8343
8344
8345
8346
8347
8348
8349
8350
8351
8352
8353
8354
8355
8356
8357
8358
8359
8360
8361
8362
8363
8364
8365
8366
8367
8368
8369
8370
8371
8372
8373
8374
8375
8376
8377
8378
8379
8380
8381
8382
8383
8384
8385
8386
8387
8388
8389
8390
8391
8392
8393
8394
8395
8396
8397
8398
8399
8400
8401
8402
8403
8404
8405
8406
8407
8408
8409
8410
8411
8412
8413
8414
8415
8416
8417
8418
8419
8420
8421
8422
8423
8424
8425
8426
8427
8428
8429
8430
8431
8432
8433
8434
8435
8436
8437
8438
8439
8440
8441
8442
8443
8444
8445
8446
8447
8448
8449
8450
8451
8452
8453
8454
8455
8456
8457
8458
8459
8460
8461
8462
8463
8464
8465
8466
8467
8468
8469
8470
8471
8472
8473
8474
8475
8476
8477
8478
8479
8480
8481
8482
8483
8484
8485
8486
8487
8488
8489
8490
8491
8492
8493
8494
8495
8496
8497
8498
8499
8500
8501
8502
8503
8504
8505
8506
8507
8508
8509
8510
8511
8512
8513
8514
8515
8516
8517
8518
8519
8520
8521
8522
8523
8524
8525
8526
8527
8528
8529
8530
8531
8532
8533
8534
8535
8536
8537
8538
8539
8540
8541
8542
8543
8544
8545
8546
8547
8548
8549
8550
8551
8552
8553
8554
8555
8556
8557
8558
8559
8560
8561
8562
8563
8564
8565
8566
8567
8568
8569
8570
8571
8572
8573
8574
8575
8576
8577
8578
8579
8580
8581
8582
8583
8584
8585
8586
8587
8588
8589
8590
8591
8592
8593
8594
8595
8596
8597
8598
8599
8600
8601
8602
8603
8604
8605
8606
8607
8608
8609
8610
8611
8612
8613
8614
8615
8616
8617
8618
8619
8620
8621
8622
8623
8624
8625
8626
8627
8628
8629
8630
8631
8632
8633
8634
8635
8636
8637
8638
8639
8640
8641
8642
8643
8644
8645
8646
8647
8648
8649
8650
8651
8652
8653
8654
8655
8656
8657
8658
8659
8660
8661
8662
8663
8664
8665
8666
8667
8668
8669
8670
8671
8672
8673
8674
8675
8676
8677
8678
8679
8680
8681
8682
8683
8684
8685
8686
8687
8688
8689
8690
8691
8692
8693
8694
8695
8696
8697
8698
8699
8700
8701
8702
8703
8704
8705
8706
8707
8708
8709
8710
8711
8712
8713
8714
8715
8716
8717
8718
8719
8720
8721
8722
8723
8724
8725
8726
8727
8728
8729
8730
8731
8732
8733
8734
8735
8736
8737
8738
8739
8740
8741
8742
8743
8744
8745
8746
8747
8748
8749
8750
8751
8752
8753
8754
8755
8756
8757
8758
8759
8760
8761
8762
8763
8764
8765
8766
8767
8768
8769
8770
8771
8772
8773
8774
8775
8776
8777
8778
8779
8780
8781
8782
8783
8784
8785
8786
8787
8788
8789
8790
8791
8792
8793
8794
8795
8796
8797
8798
8799
8800
8801
8802
8803
8804
8805
8806
8807
8808
8809
8810
8811
8812
8813
8814
8815
8816
8817
8818
8819
8820
8821
8822
8823
8824
8825
8826
8827
8828
8829
8830
8831
8832
8833
8834
8835
8836
8837
8838
8839
8840
8841
8842
8843
8844
8845
8846
8847
8848
8849
8850
8851
8852
8853
8854
8855
8856
8857
8858
8859
8860
8861
8862
8863
8864
8865
8866
8867
8868
8869
8870
8871
8872
8873
8874
8875
8876
8877
8878
8879
8880
8881
8882
8883
8884
8885
8886
8887
8888
8889
8890
8891
8892
8893
8894
8895
8896
8897
8898
8899
8900
8901
8902
8903
8904
8905
8906
8907
8908
8909
8910
8911
8912
8913
8914
8915
8916
8917
8918
8919
8920
8921
8922
8923
8924
8925
8926
8927
8928
8929
8930
8931
8932
8933
8934
8935
8936
8937
8938
8939
8940
8941
8942
8943
8944
8945
8946
8947
8948
8949
8950
8951
8952
8953
8954
8955
8956
8957
8958
8959
8960
8961
8962
8963
8964
8965
8966
8967
8968
8969
8970
8971
8972
8973
8974
8975
8976
8977
8978
8979
8980
8981
8982
8983
8984
8985
8986
8987
8988
8989
8990
8991
8992
8993
8994
8995
8996
8997
8998
8999
9000
9001
9002
9003
9004
9005
9006
9007
9008
9009
9010
9011
9012
9013
9014
9015
9016
9017
9018
9019
9020
9021
9022
9023
9024
9025
9026
9027
9028
9029
9030
9031
9032
9033
9034
9035
9036
9037
9038
9039
9040
9041
9042
9043
9044
9045
9046
9047
9048
9049
9050
9051
9052
9053
9054
9055
9056
9057
9058
9059
9060
9061
9062
9063
9064
9065
9066
9067
9068
9069
9070
9071
9072
9073
9074
9075
9076
9077
9078
9079
9080
9081
9082
9083
9084
9085
9086
9087
9088
9089
9090
9091
9092
9093
9094
9095
9096
9097
9098
9099
9100
9101
9102
9103
9104
9105
9106
9107
9108
9109
9110
9111
9112
9113
9114
9115
9116
9117
9118
9119
9120
9121
9122
9123
9124
9125
9126
9127
9128
9129
9130
9131
9132
9133
9134
9135
9136
9137
9138
9139
9140
9141
9142
9143
9144
9145
9146
9147
9148
9149
9150
9151
9152
9153
9154
9155
9156
9157
9158
9159
9160
9161
9162
9163
9164
9165
9166
9167
9168
9169
9170
9171
9172
9173
9174
9175
9176
9177
9178
9179
9180
9181
9182
9183
9184
9185
9186
9187
9188
9189
9190
9191
9192
9193
9194
9195
9196
9197
9198
9199
9200
9201
9202
9203
9204
9205
9206
9207
9208
9209
9210
9211
9212
9213
9214
9215
9216
9217
9218
9219
9220
9221
9222
9223
9224
9225
9226
9227
9228
9229
9230
9231
9232
9233
9234
9235
9236
9237
9238
9239
9240
9241
9242
9243
9244
9245
9246
9247
9248
9249
9250
9251
9252
9253
9254
9255
9256
9257
9258
9259
9260
9261
9262
9263
9264
9265
9266
9267
9268
9269
9270
9271
9272
9273
9274
9275
9276
9277
9278
9279
9280
9281
9282
9283
9284
9285
9286
9287
9288
9289
9290
9291
9292
9293
9294
9295
9296
9297
9298
9299
9300
9301
9302
9303
9304
9305
9306
9307
9308
9309
9310
9311
9312
9313
9314
9315
9316
9317
9318
9319
9320
9321
9322
9323
9324
9325
9326
9327
9328
9329
9330
9331
9332
9333
9334
9335
9336
9337
9338
9339
9340
9341
9342
9343
9344
9345
9346
9347
9348
9349
9350
9351
9352
9353
9354
9355
9356
9357
9358
9359
9360
9361
9362
9363
9364
9365
9366
9367
9368
9369
9370
9371
9372
9373
9374
9375
9376
9377
9378
9379
9380
9381
9382
9383
9384
9385
9386
9387
9388
9389
9390
9391
9392
9393
9394
9395
9396
9397
9398
9399
9400
9401
9402
9403
9404
9405
9406
9407
9408
9409
9410
9411
9412
9413
9414
9415
9416
9417
9418
9419
9420
9421
9422
9423
9424
9425
9426
9427
9428
9429
9430
9431
9432
9433
9434
9435
9436
9437
9438
9439
9440
9441
9442
9443
9444
9445
9446
9447
9448
9449
9450
9451
9452
9453
9454
9455
9456
9457
9458
9459
9460
9461
9462
9463
9464
9465
9466
9467
9468
9469
9470
9471
9472
9473
9474
9475
9476
9477
9478
9479
9480
9481
9482
9483
9484
9485
9486
9487
9488
9489
9490
9491
9492
9493
9494
9495
9496
9497
9498
9499
9500
9501
9502
9503
9504
9505
9506
9507
9508
9509
9510
9511
9512
9513
9514
9515
9516
9517
9518
9519
9520
9521
9522
9523
9524
9525
9526
9527
9528
9529
9530
9531
9532
9533
9534
9535
9536
9537
9538
9539
9540
9541
9542
9543
9544
9545
9546
9547
9548
9549
9550
9551
9552
9553
9554
9555
9556
9557
9558
9559
9560
9561
9562
9563
9564
9565
9566
9567
9568
9569
9570
9571
9572
9573
9574
9575
9576
9577
9578
9579
9580
9581
9582
9583
9584
9585
9586
9587
9588
9589
9590
9591
9592
9593
9594
9595
9596
9597
9598
9599
9600
9601
9602
9603
9604
9605
9606
9607
9608
9609
9610
9611
9612
9613
9614
9615
9616
9617
9618
9619
9620
9621
9622
9623
9624
9625
9626
9627
9628
9629
9630
9631
9632
9633
9634
9635
9636
9637
9638
9639
9640
9641
9642
9643
9644
9645
9646
9647
9648
9649
9650
9651
9652
9653
9654
9655
9656
9657
9658
9659
9660
9661
9662
9663
9664
9665
9666
9667
9668
9669
9670
9671
9672
9673
9674
9675
9676
9677
9678
9679
9680
9681
9682
9683
9684
9685
9686
9687
9688
9689
9690
9691
9692
9693
9694
9695
9696
9697
9698
9699
9700
9701
9702
9703
9704
9705
9706
9707
9708
9709
9710
9711
9712
9713
9714
9715
9716
9717
9718
9719
9720
9721
9722
9723
9724
9725
9726
9727
9728
9729
9730
9731
9732
9733
9734
9735
9736
9737
9738
9739
9740
9741
9742
9743
9744
9745
9746
9747
9748
9749
9750
9751
9752
9753
9754
9755
9756
9757
9758
9759
9760
9761
9762
9763
9764
9765
9766
9767
9768
9769
9770
9771
9772
9773
9774
9775
9776
9777
9778
9779
9780
9781
9782
9783
9784
9785
9786
9787
9788
9789
9790
9791
9792
9793
9794
9795
9796
9797
9798
9799
9800
9801
9802
9803
9804
9805
9806
9807
9808
9809
9810
9811
9812
9813
9814
9815
9816
9817
9818
9819
9820
9821
9822
9823
9824
9825
9826
9827
9828
9829
9830
9831
9832
9833
9834
9835
9836
9837
9838
9839
9840
9841
9842
9843
9844
9845
9846
9847
9848
9849
9850
9851
9852
9853
9854
9855
9856
9857
9858
9859
9860
9861
9862
9863
9864
9865
9866
9867
9868
9869
9870
9871
9872
9873
9874
9875
9876
9877
9878
9879
9880
9881
9882
9883
9884
9885
9886
9887
9888
9889
9890
9891
9892
9893
9894
9895
9896
9897
9898
9899
9900
9901
9902
9903
9904
9905
9906
9907
9908
9909
9910
9911
9912
9913
9914
9915
9916
9917
9918
9919
9920
9921
9922
9923
9924
9925
9926
9927
9928
9929
9930
9931
9932
9933
9934
9935
9936
9937
9938
9939
9940
9941
9942
9943
9944
9945
9946
9947
9948
9949
9950
9951
9952
9953
9954
9955
9956
9957
9958
9959
9960
9961
9962
9963
9964
9965
9966
9967
9968
9969
9970
9971
9972
9973
9974
9975
9976
9977
9978
9979
9980
9981
9982
9983
9984
9985
9986
9987
9988
9989
9990
9991
9992
9993
9994
9995
9996
9997
9998
9999
10000
10001
10002
10003
10004
10005
10006
10007
10008
10009
10010
10011
10012
10013
10014
10015
10016
10017
10018
10019
10020
10021
10022
10023
10024
10025
10026
10027
10028
10029
10030
10031
10032
10033
10034
10035
10036
10037
10038
10039
10040
10041
10042
10043
10044
10045
10046
10047
10048
10049
10050
10051
10052
10053
10054
10055
10056
10057
10058
10059
10060
10061
10062
10063
10064
10065
10066
10067
10068
10069
10070
10071
10072
10073
10074
10075
10076
10077
10078
10079
10080
10081
10082
10083
10084
10085
10086
10087
10088
10089
10090
10091
10092
10093
10094
10095
10096
10097
10098
10099
10100
10101
10102
10103
10104
10105
10106
10107
10108
10109
10110
10111
10112
10113
10114
10115
10116
10117
10118
10119
10120
10121
10122
10123
10124
10125
10126
10127
10128
10129
10130
10131
10132
10133
10134
10135
10136
10137
10138
10139
10140
10141
10142
10143
10144
10145
10146
10147
10148
10149
10150
10151
10152
10153
10154
10155
10156
10157
10158
10159
10160
10161
10162
10163
10164
10165
10166
10167
10168
10169
10170
10171
10172
10173
10174
10175
10176
10177
10178
10179
10180
10181
10182
10183
10184
10185
10186
10187
10188
10189
10190
10191
10192
10193
10194
10195
10196
10197
10198
10199
10200
10201
10202
10203
10204
10205
10206
10207
10208
10209
10210
10211
10212
10213
10214
10215
10216
10217
10218
10219
10220
10221
10222
10223
10224
10225
10226
10227
10228
10229
10230
10231
10232
10233
10234
10235
10236
10237
10238
10239
10240
10241
10242
10243
10244
10245
10246
10247
10248
10249
10250
10251
10252
10253
10254
10255
10256
10257
10258
10259
10260
10261
10262
10263
10264
10265
10266
10267
10268
10269
10270
10271
10272
10273
10274
10275
10276
10277
10278
10279
10280
10281
10282
10283
10284
10285
10286
10287
10288
10289
10290
10291
10292
10293
10294
10295
10296
10297
10298
10299
10300
10301
10302
10303
10304
10305
10306
10307
10308
10309
10310
10311
10312
10313
10314
10315
10316
10317
10318
10319
10320
10321
10322
10323
10324
10325
10326
10327
10328
10329
10330
10331
10332
10333
10334
10335
10336
10337
10338
10339
10340
10341
10342
10343
10344
10345
10346
10347
10348
10349
10350
10351
10352
10353
10354
10355
10356
10357
10358
10359
10360
10361
10362
10363
10364
10365
10366
10367
10368
10369
10370
10371
10372
10373
10374
10375
10376
10377
10378
10379
10380
10381
10382
10383
10384
10385
10386
10387
10388
10389
10390
10391
10392
10393
10394
10395
10396
10397
10398
10399
10400
10401
10402
10403
10404
10405
10406
10407
10408
10409
10410
10411
10412
10413
10414
10415
10416
10417
10418
10419
10420
10421
10422
10423
10424
10425
10426
10427
10428
10429
10430
10431
10432
10433
10434
10435
10436
10437
10438
10439
10440
10441
10442
10443
10444
10445
10446
10447
10448
10449
10450
10451
10452
10453
10454
10455
10456
10457
10458
10459
10460
10461
10462
10463
10464
10465
10466
10467
10468
10469
10470
10471
10472
10473
10474
10475
10476
10477
10478
10479
10480
10481
10482
10483
10484
10485
10486
10487
10488
10489
10490
10491
10492
10493
10494
10495
10496
10497
10498
10499
10500
10501
10502
10503
10504
10505
10506
10507
10508
10509
10510
10511
10512
10513
10514
10515
10516
10517
10518
10519
10520
10521
10522
10523
10524
10525
10526
10527
10528
10529
10530
10531
10532
10533
10534
10535
10536
10537
10538
10539
10540
10541
10542
10543
10544
10545
10546
10547
10548
10549
10550
10551
10552
10553
10554
10555
10556
10557
10558
10559
10560
10561
10562
10563
10564
10565
10566
10567
10568
10569
10570
10571
10572
10573
10574
10575
10576
10577
10578
10579
10580
10581
10582
10583
10584
10585
10586
10587
10588
10589
10590
10591
10592
10593
10594
10595
10596
10597
10598
10599
10600
10601
10602
10603
10604
10605
10606
10607
10608
10609
10610
10611
10612
10613
10614
10615
10616
10617
10618
10619
10620
10621
10622
10623
10624
10625
10626
10627
10628
10629
10630
10631
10632
10633
10634
10635
10636
10637
10638
10639
10640
10641
10642
10643
10644
10645
10646
10647
10648
10649
10650
10651
10652
10653
10654
10655
10656
10657
10658
10659
10660
10661
10662
10663
10664
10665
10666
10667
10668
10669
10670
10671
10672
10673
10674
10675
10676
10677
10678
10679
10680
10681
10682
10683
10684
10685
10686
10687
10688
10689
10690
10691
10692
10693
10694
10695
10696
10697
10698
10699
10700
10701
10702
10703
10704
10705
10706
10707
10708
10709
10710
10711
10712
10713
10714
10715
10716
10717
10718
10719
10720
10721
10722
10723
10724
10725
10726
10727
10728
10729
10730
10731
10732
10733
10734
10735
10736
10737
10738
10739
10740
10741
10742
10743
10744
10745
10746
10747
10748
10749
10750
10751
10752
10753
10754
10755
10756
10757
10758
10759
10760
10761
10762
10763
10764
10765
10766
10767
10768
10769
10770
10771
10772
10773
10774
10775
10776
10777
10778
10779
10780
10781
10782
10783
10784
10785
10786
10787
10788
10789
10790
10791
10792
10793
10794
10795
10796
10797
10798
10799
10800
10801
10802
10803
10804
10805
10806
10807
10808
10809
10810
10811
10812
10813
10814
10815
10816
10817
10818
10819
10820
10821
10822
10823
10824
10825
10826
10827
10828
10829
10830
10831
10832
10833
10834
10835
10836
10837
10838
10839
10840
10841
10842
10843
10844
10845
10846
10847
10848
10849
10850
10851
10852
10853
10854
10855
10856
10857
10858
10859
10860
10861
10862
10863
10864
10865
10866
10867
10868
10869
10870
10871
10872
10873
10874
10875
10876
10877
10878
10879
10880
10881
10882
10883
10884
10885
10886
10887
10888
10889
10890
10891
10892
10893
10894
10895
10896
10897
10898
10899
10900
10901
10902
10903
10904
10905
10906
10907
10908
10909
10910
10911
10912
10913
10914
10915
10916
10917
10918
10919
10920
10921
10922
10923
10924
10925
10926
10927
10928
10929
10930
10931
10932
10933
10934
10935
10936
10937
10938
10939
10940
10941
10942
10943
10944
10945
10946
10947
10948
10949
10950
10951
10952
10953
10954
10955
10956
10957
10958
10959
10960
10961
10962
10963
10964
10965
10966
10967
10968
10969
10970
10971
10972
10973
10974
10975
10976
10977
10978
10979
10980
10981
10982
10983
10984
10985
10986
10987
10988
10989
10990
10991
10992
10993
10994
10995
10996
10997
10998
10999
11000
11001
11002
11003
11004
11005
11006
11007
11008
11009
11010
11011
11012
11013
11014
11015
11016
11017
11018
11019
11020
11021
11022
11023
11024
11025
11026
11027
11028
11029
11030
11031
11032
11033
11034
11035
11036
11037
11038
11039
11040
11041
11042
11043
11044
11045
11046
11047
11048
11049
11050
11051
11052
11053
11054
11055
11056
11057
11058
11059
11060
11061
11062
11063
11064
11065
11066
11067
11068
11069
11070
11071
11072
11073
11074
11075
11076
11077
11078
11079
11080
11081
11082
11083
11084
11085
11086
11087
11088
11089
11090
11091
11092
11093
11094
11095
11096
11097
11098
11099
11100
11101
11102
11103
11104
11105
11106
11107
11108
11109
11110
11111
11112
11113
11114
11115
11116
11117
11118
11119
11120
11121
11122
11123
11124
11125
11126
11127
11128
11129
11130
11131
11132
11133
11134
11135
11136
11137
11138
11139
11140
11141
11142
11143
11144
11145
11146
11147
11148
11149
11150
11151
11152
11153
11154
11155
11156
11157
11158
11159
11160
11161
11162
11163
11164
11165
11166
11167
11168
11169
11170
11171
11172
11173
11174
11175
11176
11177
11178
11179
11180
11181
11182
11183
11184
11185
11186
11187
11188
11189
11190
11191
11192
11193
11194
11195
11196
11197
11198
11199
11200
11201
11202
11203
11204
11205
11206
11207
11208
11209
11210
11211
11212
11213
11214
11215
11216
11217
11218
11219
11220
11221
11222
11223
11224
11225
11226
11227
11228
11229
11230
11231
11232
11233
11234
11235
11236
11237
11238
11239
11240
11241
11242
11243
11244
11245
11246
11247
11248
11249
11250
11251
11252
11253
11254
11255
11256
11257
11258
11259
11260
11261
11262
11263
11264
11265
11266
11267
11268
11269
11270
11271
11272
11273
11274
11275
11276
11277
11278
11279
11280
11281
11282
11283
11284
11285
11286
11287
11288
11289
11290
11291
11292
11293
11294
11295
11296
11297
11298
11299
11300
11301
11302
11303
11304
11305
11306
11307
11308
11309
11310
11311
11312
11313
11314
11315
11316
11317
11318
11319
11320
11321
11322
11323
11324
11325
11326
11327
11328
11329
11330
11331
11332
11333
11334
11335
11336
11337
11338
11339
11340
11341
11342
11343
11344
11345
11346
11347
11348
11349
11350
11351
11352
11353
11354
11355
11356
11357
11358
11359
11360
11361
11362
11363
11364
11365
11366
11367
11368
11369
11370
11371
11372
11373
11374
11375
11376
11377
11378
11379
11380
11381
11382
11383
11384
11385
11386
11387
11388
11389
11390
11391
11392
11393
11394
11395
11396
11397
11398
11399
11400
11401
11402
11403
11404
11405
11406
11407
11408
11409
11410
11411
11412
11413
11414
11415
11416
11417
11418
11419
11420
11421
11422
11423
11424
11425
11426
11427
11428
11429
11430
11431
11432
11433
11434
11435
11436
11437
11438
11439
11440
11441
11442
11443
11444
11445
11446
11447
11448
11449
11450
11451
11452
11453
11454
11455
11456
11457
11458
11459
11460
11461
11462
11463
11464
11465
11466
11467
11468
11469
11470
11471
11472
11473
11474
11475
11476
11477
11478
11479
11480
11481
11482
11483
11484
11485
11486
11487
11488
11489
11490
11491
11492
11493
11494
11495
11496
11497
11498
11499
11500
11501
11502
11503
11504
11505
11506
11507
11508
11509
11510
11511
11512
11513
11514
11515
11516
11517
11518
11519
11520
11521
11522
11523
11524
11525
11526
11527
11528
11529
11530
11531
11532
11533
11534
11535
11536
11537
11538
11539
11540
11541
11542
11543
11544
11545
11546
11547
11548
11549
11550
11551
11552
11553
11554
11555
11556
11557
11558
11559
11560
11561
11562
11563
11564
11565
11566
11567
11568
11569
11570
11571
11572
11573
11574
11575
11576
11577
11578
11579
11580
11581
11582
11583
11584
11585
11586
11587
11588
11589
11590
11591
11592
11593
11594
11595
11596
11597
11598
11599
11600
11601
11602
11603
11604
11605
11606
11607
11608
11609
11610
11611
11612
11613
11614
11615
11616
11617
11618
11619
11620
11621
11622
11623
11624
11625
11626
11627
11628
11629
11630
11631
11632
11633
11634
11635
11636
11637
11638
11639
11640
11641
11642
11643
11644
11645
11646
11647
11648
11649
11650
11651
11652
11653
11654
11655
11656
11657
11658
11659
11660
11661
11662
11663
11664
11665
11666
11667
11668
11669
11670
11671
11672
11673
11674
11675
11676
11677
11678
11679
11680
11681
11682
11683
11684
11685
11686
11687
11688
11689
11690
11691
11692
11693
11694
11695
11696
11697
11698
11699
11700
11701
11702
11703
11704
11705
11706
11707
11708
11709
11710
11711
11712
11713
11714
11715
11716
11717
11718
11719
11720
11721
11722
11723
11724
11725
11726
11727
11728
11729
11730
11731
11732
11733
11734
11735
11736
11737
11738
11739
11740
11741
11742
11743
11744
11745
11746
11747
11748
11749
11750
11751
11752
11753
11754
11755
11756
11757
11758
11759
11760
11761
11762
11763
11764
11765
11766
11767
11768
11769
11770
11771
11772
11773
11774
11775
11776
11777
11778
11779
11780
11781
11782
11783
11784
11785
11786
11787
11788
11789
11790
11791
11792
11793
11794
11795
11796
11797
11798
11799
11800
11801
11802
11803
11804
11805
11806
11807
11808
11809
11810
11811
11812
11813
11814
11815
11816
11817
11818
11819
11820
11821
11822
11823
11824
11825
11826
11827
11828
11829
11830
11831
11832
11833
11834
11835
11836
11837
11838
11839
11840
11841
11842
11843
11844
11845
11846
11847
11848
11849
11850
11851
11852
11853
11854
11855
11856
11857
11858
11859
11860
11861
11862
11863
11864
11865
11866
11867
11868
11869
11870
11871
11872
11873
11874
11875
11876
11877
11878
11879
11880
11881
11882
11883
11884
11885
11886
11887
11888
11889
11890
11891
11892
11893
11894
11895
11896
11897
11898
11899
11900
11901
11902
11903
11904
11905
11906
11907
11908
11909
11910
11911
11912
11913
11914
11915
11916
11917
11918
11919
11920
11921
11922
11923
11924
11925
11926
11927
11928
11929
11930
11931
11932
11933
11934
11935
11936
11937
11938
11939
11940
11941
11942
11943
11944
11945
11946
11947
11948
11949
11950
11951
11952
11953
11954
11955
11956
11957
11958
11959
11960
11961
11962
11963
11964
11965
11966
11967
11968
11969
11970
11971
11972
11973
11974
11975
11976
11977
11978
11979
11980
11981
11982
11983
11984
11985
11986
11987
11988
11989
11990
11991
11992
11993
11994
11995
11996
11997
11998
11999
12000
12001
12002
12003
12004
12005
12006
12007
12008
12009
12010
12011
12012
12013
12014
12015
12016
12017
12018
12019
12020
12021
12022
12023
12024
12025
12026
12027
12028
12029
12030
12031
12032
12033
12034
12035
12036
12037
12038
12039
12040
12041
12042
12043
12044
12045
12046
12047
12048
12049
12050
12051
12052
12053
12054
12055
12056
12057
12058
12059
12060
12061
12062
12063
12064
12065
12066
12067
12068
12069
12070
12071
12072
12073
12074
12075
12076
12077
12078
12079
12080
12081
12082
12083
12084
12085
12086
12087
12088
12089
12090
12091
12092
12093
12094
12095
12096
12097
12098
12099
12100
12101
12102
12103
12104
12105
12106
12107
12108
12109
12110
12111
12112
12113
12114
12115
12116
12117
12118
12119
12120
12121
12122
12123
12124
12125
12126
12127
12128
12129
12130
12131
12132
12133
12134
12135
12136
12137
12138
12139
12140
12141
12142
12143
12144
12145
12146
12147
12148
12149
12150
12151
12152
12153
12154
12155
12156
12157
12158
12159
12160
12161
12162
12163
12164
12165
12166
12167
12168
12169
12170
12171
12172
12173
12174
12175
12176
12177
12178
12179
12180
12181
12182
12183
12184
12185
12186
12187
12188
12189
12190
12191
12192
12193
12194
12195
12196
12197
12198
12199
12200
12201
12202
12203
12204
12205
12206
12207
12208
12209
12210
12211
12212
12213
12214
12215
12216
12217
12218
12219
12220
12221
12222
12223
12224
12225
12226
12227
12228
12229
12230
12231
12232
12233
12234
12235
12236
12237
12238
12239
12240
12241
12242
12243
12244
12245
12246
12247
12248
12249
12250
12251
12252
12253
12254
12255
12256
12257
12258
12259
12260
12261
12262
12263
12264
12265
12266
12267
12268
12269
12270
12271
12272
12273
12274
12275
12276
12277
12278
12279
12280
12281
12282
12283
12284
12285
12286
12287
12288
12289
12290
12291
12292
12293
12294
12295
12296
12297
12298
12299
12300
12301
12302
12303
12304
12305
12306
12307
12308
12309
12310
12311
12312
12313
12314
12315
12316
12317
12318
12319
12320
12321
12322
12323
12324
12325
12326
12327
12328
12329
12330
12331
12332
12333
12334
12335
12336
12337
12338
12339
12340
12341
12342
12343
12344
12345
12346
12347
12348
12349
12350
12351
12352
12353
12354
12355
12356
12357
12358
12359
12360
12361
12362
12363
12364
12365
12366
12367
12368
12369
12370
12371
12372
12373
12374
12375
12376
12377
12378
12379
12380
12381
12382
12383
12384
12385
12386
12387
12388
12389
12390
12391
12392
12393
12394
12395
12396
12397
12398
12399
12400
12401
12402
12403
12404
12405
12406
12407
12408
12409
12410
12411
12412
12413
12414
12415
12416
12417
12418
12419
12420
12421
12422
12423
12424
12425
12426
12427
12428
12429
12430
12431
12432
12433
12434
12435
12436
12437
12438
12439
12440
12441
12442
12443
12444
12445
12446
12447
12448
12449
12450
12451
12452
12453
12454
12455
12456
12457
12458
12459
12460
12461
12462
12463
12464
12465
12466
12467
12468
12469
12470
12471
12472
12473
12474
12475
12476
12477
12478
12479
12480
12481
12482
12483
12484
12485
12486
12487
12488
12489
12490
12491
12492
12493
12494
12495
12496
12497
12498
12499
12500
12501
12502
12503
12504
12505
12506
12507
12508
12509
12510
12511
12512
12513
12514
12515
12516
12517
12518
12519
12520
12521
12522
12523
12524
12525
12526
12527
12528
12529
12530
12531
12532
12533
12534
12535
12536
12537
12538
12539
12540
12541
12542
12543
12544
12545
12546
12547
12548
12549
12550
12551
12552
12553
12554
12555
12556
12557
12558
12559
12560
12561
12562
12563
12564
12565
12566
12567
12568
12569
12570
12571
12572
12573
12574
12575
12576
12577
12578
12579
12580
12581
12582
12583
12584
12585
12586
12587
12588
12589
12590
12591
12592
12593
12594
12595
12596
12597
12598
12599
12600
12601
12602
12603
12604
12605
12606
12607
12608
12609
12610
12611
12612
12613
12614
12615
12616
12617
12618
12619
12620
12621
12622
12623
12624
12625
12626
12627
12628
12629
12630
12631
12632
12633
12634
12635
12636
12637
12638
12639
12640
12641
12642
12643
12644
12645
12646
12647
12648
12649
12650
12651
12652
12653
12654
12655
12656
12657
12658
12659
12660
12661
12662
12663
12664
12665
12666
12667
12668
12669
12670
12671
12672
12673
12674
12675
12676
12677
12678
12679
12680
12681
12682
12683
12684
12685
12686
12687
12688
12689
12690
12691
12692
12693
12694
12695
12696
12697
12698
12699
12700
12701
12702
12703
12704
12705
12706
12707
12708
12709
12710
12711
12712
12713
12714
12715
12716
12717
12718
12719
12720
12721
12722
12723
12724
12725
12726
12727
12728
12729
12730
12731
12732
12733
12734
12735
12736
12737
12738
12739
12740
12741
12742
12743
12744
12745
12746
12747
12748
12749
12750
12751
12752
12753
12754
12755
12756
12757
12758
12759
12760
12761
12762
12763
12764
12765
12766
12767
12768
12769
12770
12771
12772
12773
12774
12775
12776
12777
12778
12779
12780
12781
12782
12783
12784
12785
12786
12787
12788
12789
12790
12791
12792
12793
12794
12795
12796
12797
12798
12799
12800
12801
12802
12803
12804
12805
12806
12807
12808
12809
12810
12811
12812
12813
12814
12815
12816
12817
12818
12819
12820
12821
12822
12823
12824
12825
12826
12827
12828
12829
12830
12831
12832
12833
12834
12835
12836
12837
12838
12839
12840
12841
12842
12843
12844
12845
12846
12847
12848
12849
12850
12851
12852
12853
12854
12855
12856
12857
12858
12859
12860
12861
12862
12863
12864
12865
12866
12867
12868
12869
12870
12871
12872
12873
12874
12875
12876
12877
12878
12879
12880
12881
12882
12883
12884
12885
12886
12887
12888
12889
12890
12891
12892
12893
12894
12895
12896
12897
12898
12899
12900
12901
12902
12903
12904
12905
12906
12907
12908
12909
12910
12911
12912
12913
12914
12915
12916
12917
12918
12919
12920
12921
12922
12923
12924
12925
12926
12927
12928
12929
12930
12931
12932
12933
12934
12935
12936
12937
12938
12939
12940
12941
12942
12943
12944
12945
12946
12947
12948
12949
12950
12951
12952
12953
12954
12955
12956
12957
12958
12959
12960
12961
12962
12963
12964
12965
12966
12967
12968
12969
12970
12971
12972
12973
12974
12975
12976
12977
12978
12979
12980
12981
12982
12983
12984
12985
12986
12987
12988
12989
12990
12991
12992
12993
12994
12995
12996
12997
12998
12999
13000
13001
13002
13003
13004
13005
13006
13007
13008
13009
13010
13011
13012
13013
13014
13015
13016
13017
13018
13019
13020
13021
13022
13023
13024
13025
13026
13027
13028
13029
13030
13031
13032
13033
13034
13035
13036
13037
13038
13039
13040
13041
13042
13043
13044
13045
13046
13047
13048
13049
13050
13051
13052
13053
13054
13055
13056
13057
13058
13059
13060
13061
13062
13063
13064
13065
13066
13067
13068
13069
13070
13071
13072
13073
13074
13075
13076
13077
13078
13079
13080
13081
13082
13083
13084
13085
13086
13087
13088
13089
13090
13091
13092
13093
13094
13095
13096
13097
13098
13099
13100
13101
13102
13103
13104
13105
13106
13107
13108
13109
13110
13111
13112
13113
13114
13115
13116
13117
13118
13119
13120
13121
13122
13123
13124
13125
13126
13127
13128
13129
13130
13131
13132
13133
13134
13135
13136
13137
13138
13139
13140
13141
13142
13143
13144
13145
13146
13147
13148
13149
13150
13151
13152
13153
13154
13155
13156
13157
13158
13159
13160
13161
13162
13163
13164
13165
13166
13167
13168
13169
13170
13171
13172
13173
13174
13175
13176
13177
13178
13179
13180
13181
13182
13183
13184
13185
13186
13187
13188
13189
13190
13191
13192
13193
13194
13195
13196
13197
13198
13199
13200
13201
13202
13203
13204
13205
13206
13207
13208
13209
13210
13211
13212
13213
13214
13215
13216
13217
13218
13219
13220
13221
13222
13223
13224
13225
13226
13227
13228
13229
13230
13231
13232
13233
13234
13235
13236
13237
13238
13239
13240
13241
13242
13243
13244
13245
13246
13247
13248
13249
13250
13251
13252
13253
13254
13255
13256
13257
13258
13259
13260
13261
13262
13263
13264
13265
13266
13267
13268
13269
13270
13271
13272
13273
13274
13275
13276
13277
13278
13279
13280
13281
13282
13283
13284
13285
13286
13287
13288
13289
13290
13291
13292
13293
13294
13295
13296
13297
13298
13299
13300
13301
13302
13303
13304
13305
13306
13307
13308
13309
13310
13311
13312
13313
13314
13315
13316
13317
13318
13319
13320
13321
13322
13323
13324
13325
13326
13327
13328
13329
13330
13331
13332
13333
13334
13335
13336
13337
13338
13339
13340
13341
13342
13343
13344
13345
13346
13347
13348
13349
13350
13351
13352
13353
13354
13355
13356
13357
13358
13359
13360
13361
13362
13363
13364
13365
13366
13367
13368
13369
13370
13371
13372
13373
13374
13375
13376
13377
13378
13379
13380
13381
13382
13383
13384
13385
13386
13387
13388
13389
13390
13391
13392
13393
13394
13395
13396
13397
13398
13399
13400
13401
13402
13403
13404
13405
13406
13407
13408
13409
13410
13411
13412
13413
13414
13415
13416
13417
13418
13419
13420
13421
13422
13423
13424
13425
13426
13427
13428
13429
13430
13431
13432
13433
13434
13435
13436
13437
13438
13439
13440
13441
13442
13443
13444
13445
13446
13447
13448
13449
13450
13451
13452
13453
13454
13455
13456
13457
13458
13459
13460
13461
13462
13463
13464
13465
13466
13467
13468
13469
13470
13471
13472
13473
13474
13475
13476
13477
13478
13479
13480
13481
13482
13483
13484
13485
13486
13487
13488
13489
13490
13491
13492
13493
13494
13495
13496
13497
13498
13499
13500
13501
13502
13503
13504
13505
13506
13507
13508
13509
13510
13511
13512
13513
13514
13515
13516
13517
13518
13519
13520
13521
13522
13523
13524
13525
13526
13527
13528
13529
13530
13531
13532
13533
13534
13535
13536
13537
13538
13539
13540
13541
13542
13543
13544
13545
13546
13547
13548
13549
13550
13551
13552
13553
13554
13555
13556
13557
13558
13559
13560
13561
13562
13563
13564
13565
13566
13567
13568
13569
13570
13571
13572
13573
13574
13575
13576
13577
13578
13579
13580
13581
13582
13583
13584
13585
13586
13587
13588
13589
13590
13591
13592
13593
13594
13595
13596
13597
13598
13599
13600
13601
13602
13603
13604
13605
13606
13607
13608
13609
13610
13611
13612
13613
13614
13615
13616
13617
13618
13619
13620
13621
13622
13623
13624
13625
13626
13627
13628
13629
13630
13631
13632
13633
13634
13635
13636
13637
13638
13639
13640
13641
13642
13643
13644
13645
13646
13647
13648
13649
13650
13651
13652
13653
13654
13655
13656
13657
13658
13659
13660
13661
13662
13663
13664
13665
13666
13667
13668
13669
13670
13671
13672
13673
13674
13675
13676
13677
13678
13679
13680
13681
13682
13683
13684
13685
13686
13687
13688
13689
13690
13691
13692
13693
13694
13695
13696
13697
13698
13699
13700
13701
13702
13703
13704
13705
13706
13707
13708
13709
13710
13711
13712
13713
13714
13715
13716
13717
13718
13719
13720
13721
13722
13723
13724
13725
13726
13727
13728
13729
13730
13731
13732
13733
13734
13735
13736
13737
13738
13739
13740
13741
13742
13743
13744
13745
13746
13747
13748
13749
13750
13751
13752
13753
13754
13755
13756
13757
13758
13759
13760
13761
13762
13763
13764
13765
13766
13767
13768
13769
13770
13771
13772
13773
13774
13775
13776
13777
13778
13779
13780
13781
13782
13783
13784
13785
13786
13787
13788
13789
13790
13791
13792
13793
13794
13795
13796
13797
13798
13799
13800
13801
13802
13803
13804
13805
13806
13807
13808
13809
13810
13811
13812
13813
13814
13815
13816
13817
13818
13819
13820
13821
13822
13823
13824
13825
13826
13827
13828
13829
13830
13831
13832
13833
13834
13835
13836
13837
13838
13839
13840
13841
13842
13843
13844
13845
13846
13847
13848
13849
13850
13851
13852
13853
13854
13855
13856
13857
13858
13859
13860
13861
13862
13863
13864
13865
13866
13867
13868
13869
13870
13871
13872
13873
13874
13875
13876
13877
13878
13879
13880
13881
13882
13883
13884
13885
13886
13887
13888
13889
13890
13891
13892
13893
13894
13895
13896
13897
13898
13899
13900
13901
13902
13903
13904
13905
13906
13907
13908
13909
13910
13911
13912
13913
13914
13915
13916
13917
13918
13919
13920
13921
13922
13923
13924
13925
13926
13927
13928
13929
13930
13931
13932
13933
13934
13935
13936
13937
13938
13939
13940
13941
13942
13943
13944
13945
13946
13947
13948
13949
13950
13951
13952
13953
13954
13955
13956
13957
13958
13959
13960
13961
13962
13963
13964
13965
13966
13967
13968
13969
13970
13971
13972
13973
13974
13975
13976
13977
13978
13979
13980
13981
13982
13983
13984
13985
13986
13987
13988
13989
13990
13991
13992
13993
13994
13995
13996
13997
13998
13999
14000
14001
14002
14003
14004
14005
14006
14007
14008
14009
14010
14011
14012
14013
14014
14015
14016
14017
14018
14019
14020
14021
14022
14023
14024
14025
14026
14027
14028
14029
14030
14031
14032
14033
14034
14035
14036
14037
14038
14039
14040
14041
14042
14043
14044
14045
14046
14047
14048
14049
14050
14051
14052
14053
14054
14055
14056
14057
14058
14059
14060
14061
14062
14063
14064
14065
14066
14067
14068
14069
14070
14071
14072
14073
14074
14075
14076
14077
14078
14079
14080
14081
14082
14083
14084
14085
14086
14087
14088
14089
14090
14091
14092
14093
14094
14095
14096
14097
14098
14099
14100
14101
14102
14103
14104
14105
14106
14107
14108
14109
14110
14111
14112
14113
14114
14115
14116
14117
14118
14119
14120
14121
14122
14123
14124
14125
14126
14127
14128
14129
14130
14131
14132
14133
14134
14135
14136
14137
14138
14139
14140
14141
14142
14143
14144
14145
14146
14147
14148
14149
14150
14151
14152
14153
14154
14155
14156
14157
14158
14159
14160
14161
14162
14163
14164
14165
14166
14167
14168
14169
14170
14171
14172
14173
14174
14175
14176
14177
14178
14179
14180
14181
14182
14183
14184
14185
14186
14187
14188
14189
14190
14191
14192
14193
14194
14195
14196
14197
14198
14199
14200
14201
14202
14203
14204
14205
14206
14207
14208
14209
14210
14211
14212
14213
14214
14215
14216
14217
14218
14219
14220
14221
14222
14223
14224
14225
14226
14227
14228
14229
14230
14231
14232
14233
14234
14235
14236
14237
14238
14239
14240
14241
14242
14243
14244
14245
14246
14247
14248
14249
14250
14251
14252
14253
14254
14255
14256
14257
14258
14259
14260
14261
14262
14263
14264
14265
14266
14267
14268
14269
14270
14271
14272
14273
14274
14275
14276
14277
14278
14279
14280
14281
14282
14283
14284
14285
14286
14287
14288
14289
14290
14291
14292
14293
14294
14295
14296
14297
14298
14299
14300
14301
14302
14303
14304
14305
14306
14307
14308
14309
14310
14311
14312
14313
14314
14315
14316
14317
14318
14319
14320
14321
14322
14323
14324
14325
14326
14327
14328
14329
14330
14331
14332
14333
14334
14335
14336
14337
14338
14339
14340
14341
14342
14343
14344
14345
14346
14347
14348
14349
14350
14351
14352
14353
14354
14355
14356
14357
14358
14359
14360
14361
14362
14363
14364
14365
14366
14367
14368
14369
14370
14371
14372
14373
14374
14375
14376
14377
14378
14379
14380
14381
14382
14383
14384
14385
14386
14387
14388
14389
14390
14391
14392
14393
14394
14395
14396
14397
14398
14399
14400
14401
14402
14403
14404
14405
14406
14407
14408
14409
14410
14411
14412
14413
14414
14415
14416
14417
14418
14419
14420
14421
14422
14423
14424
14425
14426
14427
14428
14429
14430
14431
14432
14433
14434
14435
14436
14437
14438
14439
14440
14441
14442
14443
14444
14445
14446
14447
14448
14449
14450
14451
14452
14453
14454
14455
14456
14457
14458
14459
14460
14461
14462
14463
14464
14465
14466
14467
14468
14469
14470
14471
14472
14473
14474
14475
14476
14477
14478
14479
14480
14481
14482
14483
14484
14485
14486
14487
14488
14489
14490
14491
14492
14493
14494
14495
14496
14497
14498
14499
14500
14501
14502
14503
14504
14505
14506
14507
14508
14509
14510
14511
14512
14513
14514
14515
14516
14517
14518
14519
14520
14521
14522
14523
14524
14525
14526
14527
14528
14529
14530
14531
14532
14533
14534
14535
14536
14537
14538
14539
14540
14541
14542
14543
14544
14545
14546
14547
14548
14549
14550
14551
14552
14553
14554
14555
14556
14557
14558
14559
14560
14561
14562
14563
14564
14565
14566
14567
14568
14569
14570
14571
14572
14573
14574
14575
14576
14577
14578
14579
14580
14581
14582
14583
14584
14585
14586
14587
14588
14589
14590
14591
14592
14593
14594
14595
14596
14597
14598
14599
14600
14601
14602
14603
14604
14605
14606
14607
14608
14609
14610
14611
14612
14613
14614
14615
14616
14617
14618
14619
14620
14621
14622
14623
14624
14625
14626
14627
14628
14629
14630
14631
14632
14633
14634
14635
14636
14637
14638
14639
14640
14641
14642
14643
14644
14645
14646
14647
14648
14649
14650
14651
14652
14653
14654
14655
14656
14657
14658
14659
14660
14661
14662
14663
14664
14665
14666
14667
14668
14669
14670
14671
14672
14673
14674
14675
14676
14677
14678
14679
14680
14681
14682
14683
14684
14685
14686
14687
14688
14689
14690
14691
14692
14693
14694
14695
14696
14697
14698
14699
14700
14701
14702
14703
14704
14705
14706
14707
14708
14709
14710
14711
14712
14713
14714
14715
14716
14717
14718
14719
14720
14721
14722
14723
14724
14725
14726
14727
14728
14729
14730
14731
14732
14733
14734
14735
14736
14737
14738
14739
14740
14741
14742
14743
14744
14745
14746
14747
14748
14749
14750
14751
14752
14753
14754
14755
14756
14757
14758
14759
14760
14761
14762
14763
14764
14765
14766
14767
14768
14769
14770
14771
14772
14773
14774
14775
14776
14777
14778
14779
14780
14781
14782
14783
14784
14785
14786
14787
14788
14789
14790
14791
14792
14793
14794
14795
14796
14797
14798
14799
14800
14801
14802
14803
14804
14805
14806
14807
14808
14809
14810
14811
14812
14813
14814
14815
14816
14817
14818
14819
14820
14821
14822
14823
14824
14825
14826
14827
14828
14829
14830
14831
14832
14833
14834
14835
14836
14837
14838
14839
14840
14841
14842
14843
14844
14845
14846
14847
14848
14849
14850
14851
14852
14853
14854
14855
14856
14857
14858
14859
14860
14861
14862
14863
14864
14865
14866
14867
14868
14869
14870
14871
14872
14873
14874
14875
14876
14877
14878
14879
14880
14881
14882
14883
14884
14885
14886
14887
14888
14889
14890
14891
14892
14893
14894
14895
14896
14897
14898
14899
14900
14901
14902
14903
14904
14905
14906
14907
14908
14909
14910
14911
14912
14913
14914
14915
14916
14917
14918
14919
14920
14921
14922
14923
14924
14925
14926
14927
14928
14929
14930
14931
14932
14933
14934
14935
14936
14937
14938
14939
14940
14941
14942
14943
14944
14945
14946
14947
14948
14949
14950
14951
14952
14953
14954
14955
14956
14957
14958
14959
14960
14961
14962
14963
14964
14965
14966
14967
14968
14969
14970
14971
14972
14973
14974
14975
14976
14977
14978
14979
14980
14981
14982
14983
14984
14985
14986
14987
14988
14989
14990
14991
14992
14993
14994
14995
14996
14997
14998
14999
15000
15001
15002
15003
15004
15005
15006
15007
15008
15009
15010
15011
15012
15013
15014
15015
15016
15017
15018
15019
15020
15021
15022
15023
15024
15025
15026
15027
15028
15029
15030
15031
15032
15033
15034
15035
15036
15037
15038
15039
15040
15041
15042
15043
15044
15045
15046
15047
15048
15049
15050
15051
15052
15053
15054
15055
15056
15057
15058
15059
15060
15061
15062
15063
15064
15065
15066
15067
15068
15069
15070
15071
15072
15073
15074
15075
15076
15077
15078
15079
15080
15081
15082
15083
15084
15085
15086
15087
15088
15089
15090
15091
15092
15093
15094
15095
15096
15097
15098
15099
15100
15101
15102
15103
15104
15105
15106
15107
15108
15109
15110
15111
15112
15113
15114
15115
15116
15117
15118
15119
15120
15121
15122
15123
15124
15125
15126
15127
15128
15129
15130
15131
15132
15133
15134
15135
15136
15137
15138
15139
15140
15141
15142
15143
15144
15145
15146
15147
15148
15149
15150
15151
15152
15153
15154
15155
15156
15157
15158
15159
15160
15161
15162
15163
15164
15165
15166
15167
15168
15169
15170
15171
15172
15173
15174
15175
15176
15177
15178
15179
15180
15181
15182
15183
15184
15185
15186
15187
15188
15189
15190
15191
15192
15193
15194
15195
15196
15197
15198
15199
15200
15201
15202
15203
15204
15205
15206
15207
15208
15209
15210
15211
15212
15213
15214
15215
15216
15217
15218
15219
15220
15221
15222
15223
15224
15225
15226
15227
15228
15229
15230
15231
15232
15233
15234
15235
15236
15237
15238
15239
15240
15241
15242
15243
15244
15245
15246
15247
15248
15249
15250
15251
15252
15253
15254
15255
15256
15257
15258
15259
15260
15261
15262
15263
15264
15265
15266
15267
15268
15269
15270
15271
15272
15273
15274
15275
15276
15277
15278
15279
15280
15281
15282
15283
15284
15285
15286
15287
15288
15289
15290
15291
15292
15293
15294
15295
15296
15297
15298
15299
15300
15301
15302
15303
15304
15305
15306
15307
15308
15309
15310
15311
15312
15313
15314
15315
15316
15317
15318
15319
15320
15321
15322
15323
15324
15325
15326
15327
15328
15329
15330
15331
15332
15333
15334
15335
15336
15337
15338
15339
15340
15341
15342
15343
15344
15345
15346
15347
15348
15349
15350
15351
15352
15353
15354
15355
15356
15357
15358
15359
15360
15361
15362
15363
15364
15365
15366
15367
15368
15369
15370
15371
15372
15373
15374
15375
15376
15377
15378
15379
15380
15381
15382
15383
15384
15385
15386
15387
15388
15389
15390
15391
15392
15393
15394
15395
15396
15397
15398
15399
15400
15401
15402
15403
15404
15405
15406
15407
15408
15409
15410
15411
15412
15413
15414
15415
15416
15417
15418
15419
15420
15421
15422
15423
15424
15425
15426
15427
15428
15429
15430
15431
15432
15433
15434
15435
15436
15437
15438
15439
15440
15441
15442
15443
15444
15445
15446
15447
15448
15449
15450
15451
15452
15453
15454
15455
15456
15457
15458
15459
15460
15461
15462
15463
15464
15465
15466
15467
15468
15469
15470
15471
15472
15473
15474
15475
15476
15477
15478
15479
15480
15481
15482
15483
15484
15485
15486
15487
15488
15489
15490
15491
15492
15493
15494
15495
15496
15497
15498
15499
15500
15501
15502
15503
15504
15505
15506
15507
15508
15509
15510
15511
15512
15513
15514
15515
15516
15517
15518
15519
15520
15521
15522
15523
15524
15525
15526
15527
15528
15529
15530
15531
15532
15533
15534
15535
15536
15537
15538
15539
15540
15541
15542
15543
15544
15545
15546
15547
15548
15549
15550
15551
15552
15553
15554
15555
15556
15557
15558
15559
15560
15561
15562
15563
15564
15565
15566
15567
15568
15569
15570
15571
15572
15573
15574
15575
15576
15577
15578
15579
15580
15581
15582
15583
15584
15585
15586
15587
15588
15589
15590
15591
15592
15593
15594
15595
15596
15597
15598
15599
15600
15601
15602
15603
15604
15605
15606
15607
15608
15609
15610
15611
15612
15613
15614
15615
15616
15617
15618
15619
15620
15621
15622
15623
15624
15625
15626
15627
15628
15629
15630
15631
15632
15633
15634
15635
15636
15637
15638
15639
15640
15641
15642
15643
15644
15645
15646
15647
15648
15649
15650
15651
15652
15653
15654
15655
15656
15657
15658
15659
15660
15661
15662
15663
15664
15665
15666
15667
15668
15669
15670
15671
15672
15673
15674
15675
15676
15677
15678
15679
15680
15681
15682
15683
15684
15685
15686
15687
15688
15689
15690
15691
15692
15693
15694
15695
15696
15697
15698
15699
15700
15701
15702
15703
15704
15705
15706
15707
15708
15709
15710
15711
15712
15713
15714
15715
15716
15717
15718
15719
15720
15721
15722
15723
15724
15725
15726
15727
15728
15729
15730
15731
15732
15733
15734
15735
15736
15737
15738
15739
15740
15741
15742
15743
15744
15745
15746
15747
15748
15749
15750
15751
15752
15753
15754
15755
15756
15757
15758
15759
15760
15761
15762
15763
15764
15765
15766
15767
15768
15769
15770
15771
15772
15773
15774
15775
15776
15777
15778
15779
15780
15781
15782
15783
15784
15785
15786
15787
15788
15789
15790
15791
15792
15793
15794
15795
15796
15797
15798
15799
15800
15801
15802
15803
15804
15805
15806
15807
15808
15809
15810
15811
15812
15813
15814
15815
15816
15817
15818
15819
15820
15821
15822
15823
15824
15825
15826
15827
15828
15829
15830
15831
15832
15833
15834
15835
15836
15837
15838
15839
15840
15841
15842
15843
15844
15845
15846
15847
15848
15849
15850
15851
15852
15853
15854
15855
15856
15857
15858
15859
15860
15861
15862
15863
15864
15865
15866
15867
15868
15869
15870
15871
15872
15873
15874
15875
15876
15877
15878
15879
15880
15881
15882
15883
15884
15885
15886
15887
15888
15889
15890
15891
15892
15893
15894
15895
15896
15897
15898
15899
15900
15901
15902
15903
15904
15905
15906
15907
15908
15909
15910
15911
15912
15913
15914
15915
15916
15917
15918
15919
15920
15921
15922
15923
15924
15925
15926
15927
15928
15929
15930
15931
15932
15933
15934
15935
15936
15937
15938
15939
15940
15941
15942
15943
15944
15945
15946
15947
15948
15949
15950
15951
15952
15953
15954
15955
15956
15957
15958
15959
15960
15961
15962
15963
15964
15965
15966
15967
15968
15969
15970
15971
15972
15973
15974
15975
15976
15977
15978
15979
15980
15981
15982
15983
15984
15985
15986
15987
15988
15989
15990
15991
15992
15993
15994
15995
15996
15997
15998
15999
16000
16001
16002
16003
16004
16005
16006
16007
16008
16009
16010
16011
16012
16013
16014
16015
16016
16017
16018
16019
16020
16021
16022
16023
16024
16025
16026
16027
16028
16029
16030
16031
16032
16033

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<!-- Created by GNU Texinfo 6.8, https://www.gnu.org/software/texinfo/ -->
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<!-- This text is a brief description of the features that are present in
the Bash shell (version 5.2, 19 September 2022).

This is Edition 5.2, last updated 19 September 2022,
of The GNU Bash Reference Manual,
for Bash, Version 5.2.

Copyright (C) 1988-2022 Free Software Foundation, Inc.

Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with no
Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
A copy of the license is included in the section entitled
"GNU Free Documentation License". -->
<title>Bash Reference Manual</title>

<meta name="description" content="Bash Reference Manual">
<meta name="keywords" content="Bash Reference Manual">
<meta name="resource-type" content="document">
<meta name="distribution" content="global">
<meta name="Generator" content="makeinfo">
<meta name="viewport" content="width=device-width,initial-scale=1">

<link href="#Top" rel="start" title="Top">
<link href="#Indexes" rel="index" title="Indexes">
<link href="#SEC_Contents" rel="contents" title="Table of Contents">
<link href="dir.html#Top" rel="up" title="(dir)">
<link href="#Introduction" rel="next" title="Introduction">
<link href="dir.html#Top" rel="prev" title="(dir)">
<style type="text/css">
<!--
a.copiable-anchor {visibility: hidden; text-decoration: none; line-height: 0em}
a.summary-letter {text-decoration: none}
blockquote.indentedblock {margin-right: 0em}
div.display {margin-left: 3.2em}
div.example {margin-left: 3.2em}
kbd {font-style: oblique}
pre.display {font-family: inherit}
pre.format {font-family: inherit}
pre.menu-comment {font-family: serif}
pre.menu-preformatted {font-family: serif}
span.nolinebreak {white-space: nowrap}
span.roman {font-family: initial; font-weight: normal}
span.sansserif {font-family: sans-serif; font-weight: normal}
span:hover a.copiable-anchor {visibility: visible}
ul.no-bullet {list-style: none}
-->
</style>


</head>

<body lang="en">
<h1 class="settitle" align="center">Bash Reference Manual</h1>











<div class="top" id="Top">
<div class="header">
<p>
Next: <a href="#Introduction" accesskey="n" rel="next">Introduction</a>, Previous: <a href="dir.html#Top" accesskey="p" rel="prev">(dir)</a>, Up: <a href="dir.html#Top" accesskey="u" rel="up">(dir)</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Bash-Features-1"></span><h1 class="top">Bash Features</h1>

<p>This text is a brief description of the features that are present in
the Bash shell (version 5.2, 19 September 2022).
The Bash home page is <a href="http://www.gnu.org/software/bash/">http://www.gnu.org/software/bash/</a>.
</p>
<p>This is Edition 5.2, last updated 19 September 2022,
of <cite>The GNU Bash Reference Manual</cite>,
for <code>Bash</code>, Version 5.2.
</p>
<p>Bash contains features that appear in other popular shells, and some
features that only appear in Bash.  Some of the shells that Bash has
borrowed concepts from are the Bourne Shell (<samp>sh</samp>), the Korn Shell
(<samp>ksh</samp>), and the C-shell (<samp>csh</samp> and its successor,
<samp>tcsh</samp>).  The following menu breaks the features up into
categories, noting which features were inspired by other shells and
which are specific to Bash.
</p>
<p>This manual is meant as a brief introduction to features found in
Bash.  The Bash manual page should be used as the definitive
reference on shell behavior.
</p>

<div class="Contents_element" id="SEC_Contents">
<h2 class="contents-heading">Table of Contents</h2>

<div class="contents">

<ul class="no-bullet">
  <li><a id="toc-Introduction-1" href="#Introduction">1 Introduction</a>
  <ul class="no-bullet">
    <li><a id="toc-What-is-Bash_003f-1" href="#What-is-Bash_003f">1.1 What is Bash?</a></li>
    <li><a id="toc-What-is-a-shell_003f-1" href="#What-is-a-shell_003f">1.2 What is a shell?</a></li>
  </ul></li>
  <li><a id="toc-Definitions-1" href="#Definitions">2 Definitions</a></li>
  <li><a id="toc-Basic-Shell-Features-1" href="#Basic-Shell-Features">3 Basic Shell Features</a>
  <ul class="no-bullet">
    <li><a id="toc-Shell-Syntax-1" href="#Shell-Syntax">3.1 Shell Syntax</a>
    <ul class="no-bullet">
      <li><a id="toc-Shell-Operation-1" href="#Shell-Operation">3.1.1 Shell Operation</a></li>
      <li><a id="toc-Quoting-1" href="#Quoting">3.1.2 Quoting</a>
      <ul class="no-bullet">
        <li><a id="toc-Escape-Character-1" href="#Escape-Character">3.1.2.1 Escape Character</a></li>
        <li><a id="toc-Single-Quotes-1" href="#Single-Quotes">3.1.2.2 Single Quotes</a></li>
        <li><a id="toc-Double-Quotes-1" href="#Double-Quotes">3.1.2.3 Double Quotes</a></li>
        <li><a id="toc-ANSI_002dC-Quoting-1" href="#ANSI_002dC-Quoting">3.1.2.4 ANSI-C Quoting</a></li>
        <li><a id="toc-Locale_002dSpecific-Translation" href="#Locale-Translation">3.1.2.5 Locale-Specific Translation</a></li>
      </ul></li>
      <li><a id="toc-Comments-1" href="#Comments">3.1.3 Comments</a></li>
    </ul></li>
    <li><a id="toc-Shell-Commands-1" href="#Shell-Commands">3.2 Shell Commands</a>
    <ul class="no-bullet">
      <li><a id="toc-Reserved-Words-1" href="#Reserved-Words">3.2.1 Reserved Words</a></li>
      <li><a id="toc-Simple-Commands-1" href="#Simple-Commands">3.2.2 Simple Commands</a></li>
      <li><a id="toc-Pipelines-1" href="#Pipelines">3.2.3 Pipelines</a></li>
      <li><a id="toc-Lists-of-Commands" href="#Lists">3.2.4 Lists of Commands</a></li>
      <li><a id="toc-Compound-Commands-1" href="#Compound-Commands">3.2.5 Compound Commands</a>
      <ul class="no-bullet">
        <li><a id="toc-Looping-Constructs-1" href="#Looping-Constructs">3.2.5.1 Looping Constructs</a></li>
        <li><a id="toc-Conditional-Constructs-1" href="#Conditional-Constructs">3.2.5.2 Conditional Constructs</a></li>
        <li><a id="toc-Grouping-Commands" href="#Command-Grouping">3.2.5.3 Grouping Commands</a></li>
      </ul></li>
      <li><a id="toc-Coprocesses-1" href="#Coprocesses">3.2.6 Coprocesses</a></li>
      <li><a id="toc-GNU-Parallel-1" href="#GNU-Parallel">3.2.7 GNU Parallel</a></li>
    </ul></li>
    <li><a id="toc-Shell-Functions-1" href="#Shell-Functions">3.3 Shell Functions</a></li>
    <li><a id="toc-Shell-Parameters-1" href="#Shell-Parameters">3.4 Shell Parameters</a>
    <ul class="no-bullet">
      <li><a id="toc-Positional-Parameters-1" href="#Positional-Parameters">3.4.1 Positional Parameters</a></li>
      <li><a id="toc-Special-Parameters-1" href="#Special-Parameters">3.4.2 Special Parameters</a></li>
    </ul></li>
    <li><a id="toc-Shell-Expansions-1" href="#Shell-Expansions">3.5 Shell Expansions</a>
    <ul class="no-bullet">
      <li><a id="toc-Brace-Expansion-1" href="#Brace-Expansion">3.5.1 Brace Expansion</a></li>
      <li><a id="toc-Tilde-Expansion-1" href="#Tilde-Expansion">3.5.2 Tilde Expansion</a></li>
      <li><a id="toc-Shell-Parameter-Expansion-1" href="#Shell-Parameter-Expansion">3.5.3 Shell Parameter Expansion</a></li>
      <li><a id="toc-Command-Substitution-1" href="#Command-Substitution">3.5.4 Command Substitution</a></li>
      <li><a id="toc-Arithmetic-Expansion-1" href="#Arithmetic-Expansion">3.5.5 Arithmetic Expansion</a></li>
      <li><a id="toc-Process-Substitution-1" href="#Process-Substitution">3.5.6 Process Substitution</a></li>
      <li><a id="toc-Word-Splitting-1" href="#Word-Splitting">3.5.7 Word Splitting</a></li>
      <li><a id="toc-Filename-Expansion-1" href="#Filename-Expansion">3.5.8 Filename Expansion</a>
      <ul class="no-bullet">
        <li><a id="toc-Pattern-Matching-1" href="#Pattern-Matching">3.5.8.1 Pattern Matching</a></li>
      </ul></li>
      <li><a id="toc-Quote-Removal-1" href="#Quote-Removal">3.5.9 Quote Removal</a></li>
    </ul></li>
    <li><a id="toc-Redirections-1" href="#Redirections">3.6 Redirections</a>
    <ul class="no-bullet">
      <li><a id="toc-Redirecting-Input" href="#Redirecting-Input">3.6.1 Redirecting Input</a></li>
      <li><a id="toc-Redirecting-Output" href="#Redirecting-Output">3.6.2 Redirecting Output</a></li>
      <li><a id="toc-Appending-Redirected-Output" href="#Appending-Redirected-Output">3.6.3 Appending Redirected Output</a></li>
      <li><a id="toc-Redirecting-Standard-Output-and-Standard-Error" href="#Redirecting-Standard-Output-and-Standard-Error">3.6.4 Redirecting Standard Output and Standard Error</a></li>
      <li><a id="toc-Appending-Standard-Output-and-Standard-Error" href="#Appending-Standard-Output-and-Standard-Error">3.6.5 Appending Standard Output and Standard Error</a></li>
      <li><a id="toc-Here-Documents" href="#Here-Documents">3.6.6 Here Documents</a></li>
      <li><a id="toc-Here-Strings" href="#Here-Strings">3.6.7 Here Strings</a></li>
      <li><a id="toc-Duplicating-File-Descriptors" href="#Duplicating-File-Descriptors">3.6.8 Duplicating File Descriptors</a></li>
      <li><a id="toc-Moving-File-Descriptors" href="#Moving-File-Descriptors">3.6.9 Moving File Descriptors</a></li>
      <li><a id="toc-Opening-File-Descriptors-for-Reading-and-Writing" href="#Opening-File-Descriptors-for-Reading-and-Writing">3.6.10 Opening File Descriptors for Reading and Writing</a></li>
    </ul></li>
    <li><a id="toc-Executing-Commands-1" href="#Executing-Commands">3.7 Executing Commands</a>
    <ul class="no-bullet">
      <li><a id="toc-Simple-Command-Expansion-1" href="#Simple-Command-Expansion">3.7.1 Simple Command Expansion</a></li>
      <li><a id="toc-Command-Search-and-Execution-1" href="#Command-Search-and-Execution">3.7.2 Command Search and Execution</a></li>
      <li><a id="toc-Command-Execution-Environment-1" href="#Command-Execution-Environment">3.7.3 Command Execution Environment</a></li>
      <li><a id="toc-Environment-1" href="#Environment">3.7.4 Environment</a></li>
      <li><a id="toc-Exit-Status-1" href="#Exit-Status">3.7.5 Exit Status</a></li>
      <li><a id="toc-Signals-1" href="#Signals">3.7.6 Signals</a></li>
    </ul></li>
    <li><a id="toc-Shell-Scripts-1" href="#Shell-Scripts">3.8 Shell Scripts</a></li>
  </ul></li>
  <li><a id="toc-Shell-Builtin-Commands-1" href="#Shell-Builtin-Commands">4 Shell Builtin Commands</a>
  <ul class="no-bullet">
    <li><a id="toc-Bourne-Shell-Builtins-1" href="#Bourne-Shell-Builtins">4.1 Bourne Shell Builtins</a></li>
    <li><a id="toc-Bash-Builtin-Commands" href="#Bash-Builtins">4.2 Bash Builtin Commands</a></li>
    <li><a id="toc-Modifying-Shell-Behavior-1" href="#Modifying-Shell-Behavior">4.3 Modifying Shell Behavior</a>
    <ul class="no-bullet">
      <li><a id="toc-The-Set-Builtin-1" href="#The-Set-Builtin">4.3.1 The Set Builtin</a></li>
      <li><a id="toc-The-Shopt-Builtin-1" href="#The-Shopt-Builtin">4.3.2 The Shopt Builtin</a></li>
    </ul></li>
    <li><a id="toc-Special-Builtins-1" href="#Special-Builtins">4.4 Special Builtins</a></li>
  </ul></li>
  <li><a id="toc-Shell-Variables-1" href="#Shell-Variables">5 Shell Variables</a>
  <ul class="no-bullet">
    <li><a id="toc-Bourne-Shell-Variables-1" href="#Bourne-Shell-Variables">5.1 Bourne Shell Variables</a></li>
    <li><a id="toc-Bash-Variables-1" href="#Bash-Variables">5.2 Bash Variables</a></li>
  </ul></li>
  <li><a id="toc-Bash-Features-2" href="#Bash-Features">6 Bash Features</a>
  <ul class="no-bullet">
    <li><a id="toc-Invoking-Bash-1" href="#Invoking-Bash">6.1 Invoking Bash</a></li>
    <li><a id="toc-Bash-Startup-Files-1" href="#Bash-Startup-Files">6.2 Bash Startup Files</a></li>
    <li><a id="toc-Interactive-Shells-1" href="#Interactive-Shells">6.3 Interactive Shells</a>
    <ul class="no-bullet">
      <li><a id="toc-What-is-an-Interactive-Shell_003f-1" href="#What-is-an-Interactive-Shell_003f">6.3.1 What is an Interactive Shell?</a></li>
      <li><a id="toc-Is-this-Shell-Interactive_003f-1" href="#Is-this-Shell-Interactive_003f">6.3.2 Is this Shell Interactive?</a></li>
      <li><a id="toc-Interactive-Shell-Behavior-1" href="#Interactive-Shell-Behavior">6.3.3 Interactive Shell Behavior</a></li>
    </ul></li>
    <li><a id="toc-Bash-Conditional-Expressions-1" href="#Bash-Conditional-Expressions">6.4 Bash Conditional Expressions</a></li>
    <li><a id="toc-Shell-Arithmetic-1" href="#Shell-Arithmetic">6.5 Shell Arithmetic</a></li>
    <li><a id="toc-Aliases-1" href="#Aliases">6.6 Aliases</a></li>
    <li><a id="toc-Arrays-1" href="#Arrays">6.7 Arrays</a></li>
    <li><a id="toc-The-Directory-Stack-1" href="#The-Directory-Stack">6.8 The Directory Stack</a>
    <ul class="no-bullet">
      <li><a id="toc-Directory-Stack-Builtins-1" href="#Directory-Stack-Builtins">6.8.1 Directory Stack Builtins</a></li>
    </ul></li>
    <li><a id="toc-Controlling-the-Prompt-1" href="#Controlling-the-Prompt">6.9 Controlling the Prompt</a></li>
    <li><a id="toc-The-Restricted-Shell-1" href="#The-Restricted-Shell">6.10 The Restricted Shell</a></li>
    <li><a id="toc-Bash-POSIX-Mode-1" href="#Bash-POSIX-Mode">6.11 Bash POSIX Mode</a></li>
    <li><a id="toc-Shell-Compatibility-Mode-1" href="#Shell-Compatibility-Mode">6.12 Shell Compatibility Mode</a></li>
  </ul></li>
  <li><a id="toc-Job-Control-1" href="#Job-Control">7 Job Control</a>
  <ul class="no-bullet">
    <li><a id="toc-Job-Control-Basics-1" href="#Job-Control-Basics">7.1 Job Control Basics</a></li>
    <li><a id="toc-Job-Control-Builtins-1" href="#Job-Control-Builtins">7.2 Job Control Builtins</a></li>
    <li><a id="toc-Job-Control-Variables-1" href="#Job-Control-Variables">7.3 Job Control Variables</a></li>
  </ul></li>
  <li><a id="toc-Command-Line-Editing-1" href="#Command-Line-Editing">8 Command Line Editing</a>
  <ul class="no-bullet">
    <li><a id="toc-Introduction-to-Line-Editing" href="#Introduction-and-Notation">8.1 Introduction to Line Editing</a></li>
    <li><a id="toc-Readline-Interaction-1" href="#Readline-Interaction">8.2 Readline Interaction</a>
    <ul class="no-bullet">
      <li><a id="toc-Readline-Bare-Essentials-1" href="#Readline-Bare-Essentials">8.2.1 Readline Bare Essentials</a></li>
      <li><a id="toc-Readline-Movement-Commands-1" href="#Readline-Movement-Commands">8.2.2 Readline Movement Commands</a></li>
      <li><a id="toc-Readline-Killing-Commands-1" href="#Readline-Killing-Commands">8.2.3 Readline Killing Commands</a></li>
      <li><a id="toc-Readline-Arguments-1" href="#Readline-Arguments">8.2.4 Readline Arguments</a></li>
      <li><a id="toc-Searching-for-Commands-in-the-History" href="#Searching">8.2.5 Searching for Commands in the History</a></li>
    </ul></li>
    <li><a id="toc-Readline-Init-File-1" href="#Readline-Init-File">8.3 Readline Init File</a>
    <ul class="no-bullet">
      <li><a id="toc-Readline-Init-File-Syntax-1" href="#Readline-Init-File-Syntax">8.3.1 Readline Init File Syntax</a></li>
      <li><a id="toc-Conditional-Init-Constructs-1" href="#Conditional-Init-Constructs">8.3.2 Conditional Init Constructs</a></li>
      <li><a id="toc-Sample-Init-File-1" href="#Sample-Init-File">8.3.3 Sample Init File</a></li>
    </ul></li>
    <li><a id="toc-Bindable-Readline-Commands-1" href="#Bindable-Readline-Commands">8.4 Bindable Readline Commands</a>
    <ul class="no-bullet">
      <li><a id="toc-Commands-For-Moving-1" href="#Commands-For-Moving">8.4.1 Commands For Moving</a></li>
      <li><a id="toc-Commands-For-Manipulating-The-History" href="#Commands-For-History">8.4.2 Commands For Manipulating The History</a></li>
      <li><a id="toc-Commands-For-Changing-Text" href="#Commands-For-Text">8.4.3 Commands For Changing Text</a></li>
      <li><a id="toc-Killing-And-Yanking" href="#Commands-For-Killing">8.4.4 Killing And Yanking</a></li>
      <li><a id="toc-Specifying-Numeric-Arguments" href="#Numeric-Arguments">8.4.5 Specifying Numeric Arguments</a></li>
      <li><a id="toc-Letting-Readline-Type-For-You" href="#Commands-For-Completion">8.4.6 Letting Readline Type For You</a></li>
      <li><a id="toc-Keyboard-Macros-1" href="#Keyboard-Macros">8.4.7 Keyboard Macros</a></li>
      <li><a id="toc-Some-Miscellaneous-Commands" href="#Miscellaneous-Commands">8.4.8 Some Miscellaneous Commands</a></li>
    </ul></li>
    <li><a id="toc-Readline-vi-Mode-1" href="#Readline-vi-Mode">8.5 Readline vi Mode</a></li>
    <li><a id="toc-Programmable-Completion-1" href="#Programmable-Completion">8.6 Programmable Completion</a></li>
    <li><a id="toc-Programmable-Completion-Builtins-1" href="#Programmable-Completion-Builtins">8.7 Programmable Completion Builtins</a></li>
    <li><a id="toc-A-Programmable-Completion-Example-1" href="#A-Programmable-Completion-Example">8.8 A Programmable Completion Example</a></li>
  </ul></li>
  <li><a id="toc-Using-History-Interactively-1" href="#Using-History-Interactively">9 Using History Interactively</a>
  <ul class="no-bullet">
    <li><a id="toc-Bash-History-Facilities-1" href="#Bash-History-Facilities">9.1 Bash History Facilities</a></li>
    <li><a id="toc-Bash-History-Builtins-1" href="#Bash-History-Builtins">9.2 Bash History Builtins</a></li>
    <li><a id="toc-History-Expansion" href="#History-Interaction">9.3 History Expansion</a>
    <ul class="no-bullet">
      <li><a id="toc-Event-Designators-1" href="#Event-Designators">9.3.1 Event Designators</a></li>
      <li><a id="toc-Word-Designators-1" href="#Word-Designators">9.3.2 Word Designators</a></li>
      <li><a id="toc-Modifiers-1" href="#Modifiers">9.3.3 Modifiers</a></li>
    </ul></li>
  </ul></li>
  <li><a id="toc-Installing-Bash-1" href="#Installing-Bash">10 Installing Bash</a>
  <ul class="no-bullet">
    <li><a id="toc-Basic-Installation-1" href="#Basic-Installation">10.1 Basic Installation</a></li>
    <li><a id="toc-Compilers-and-Options-1" href="#Compilers-and-Options">10.2 Compilers and Options</a></li>
    <li><a id="toc-Compiling-For-Multiple-Architectures-1" href="#Compiling-For-Multiple-Architectures">10.3 Compiling For Multiple Architectures</a></li>
    <li><a id="toc-Installation-Names-1" href="#Installation-Names">10.4 Installation Names</a></li>
    <li><a id="toc-Specifying-the-System-Type-1" href="#Specifying-the-System-Type">10.5 Specifying the System Type</a></li>
    <li><a id="toc-Sharing-Defaults-1" href="#Sharing-Defaults">10.6 Sharing Defaults</a></li>
    <li><a id="toc-Operation-Controls-1" href="#Operation-Controls">10.7 Operation Controls</a></li>
    <li><a id="toc-Optional-Features-1" href="#Optional-Features">10.8 Optional Features</a></li>
  </ul></li>
  <li><a id="toc-Reporting-Bugs-1" href="#Reporting-Bugs">Appendix A Reporting Bugs</a></li>
  <li><a id="toc-Major-Differences-From-The-Bourne-Shell-1" href="#Major-Differences-From-The-Bourne-Shell">Appendix B Major Differences From The Bourne Shell</a>
  <ul class="no-bullet">
    <li><a id="toc-Implementation-Differences-From-The-SVR4_002e2-Shell" href="#Implementation-Differences-From-The-SVR4_002e2-Shell">B.1 Implementation Differences From The SVR4.2 Shell</a></li>
  </ul></li>
  <li><a id="toc-GNU-Free-Documentation-License-1" href="#GNU-Free-Documentation-License">Appendix C GNU Free Documentation License</a></li>
  <li><a id="toc-Indexes-1" href="#Indexes">Appendix D Indexes</a>
  <ul class="no-bullet">
    <li><a id="toc-Index-of-Shell-Builtin-Commands" href="#Builtin-Index" rel="index">D.1 Index of Shell Builtin Commands</a></li>
    <li><a id="toc-Index-of-Shell-Reserved-Words" href="#Reserved-Word-Index" rel="index">D.2 Index of Shell Reserved Words</a></li>
    <li><a id="toc-Parameter-and-Variable-Index" href="#Variable-Index" rel="index">D.3 Parameter and Variable Index</a></li>
    <li><a id="toc-Function-Index-1" href="#Function-Index" rel="index">D.4 Function Index</a></li>
    <li><a id="toc-Concept-Index-1" href="#Concept-Index" rel="index">D.5 Concept Index</a></li>
  </ul></li>
</ul>
</div>
</div>
<hr>
<div class="chapter" id="Introduction">
<div class="header">
<p>
Next: <a href="#Definitions" accesskey="n" rel="next">Definitions</a>, Up: <a href="#Top" accesskey="u" rel="up">Bash Features</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Introduction-1"></span><h2 class="chapter">1 Introduction</h2>

<ul class="section-toc">
<li><a href="#What-is-Bash_003f" accesskey="1">What is Bash?</a></li>
<li><a href="#What-is-a-shell_003f" accesskey="2">What is a shell?</a></li>
</ul>
<hr>
<div class="section" id="What-is-Bash_003f">
<div class="header">
<p>
Next: <a href="#What-is-a-shell_003f" accesskey="n" rel="next">What is a shell?</a>, Up: <a href="#Introduction" accesskey="u" rel="up">Introduction</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="What-is-Bash_003f-1"></span><h3 class="section">1.1 What is Bash?</h3>

<p>Bash is the shell, or command language interpreter,
for the <small>GNU</small> operating system.
The name is an acronym for the &lsquo;<samp>Bourne-Again SHell</samp>&rsquo;,
a pun on Stephen Bourne, the author of the direct ancestor of
the current Unix shell <code>sh</code>, 
which appeared in the Seventh Edition Bell Labs Research version
of Unix.
</p>
<p>Bash is largely compatible with <code>sh</code> and incorporates useful
features from the Korn shell <code>ksh</code> and the C shell <code>csh</code>.
It is intended to be a conformant implementation of the <small>IEEE</small>
<small>POSIX</small> Shell and Tools portion of the <small>IEEE</small> <small>POSIX</small>
specification (<small>IEEE</small> Standard 1003.1).
It offers functional improvements over <code>sh</code> for both interactive and
programming use.
</p>
<p>While the <small>GNU</small> operating system provides other shells, including
a version of <code>csh</code>, Bash is the default shell.
Like other <small>GNU</small> software, Bash is quite portable.  It currently runs
on nearly every version of Unix and a few other operating systems -
independently-supported ports exist for <small>MS-DOS</small>, <small>OS/2</small>,
and Windows platforms.
</p>
<hr>
</div>
<div class="section" id="What-is-a-shell_003f">
<div class="header">
<p>
Previous: <a href="#What-is-Bash_003f" accesskey="p" rel="prev">What is Bash?</a>, Up: <a href="#Introduction" accesskey="u" rel="up">Introduction</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="What-is-a-shell_003f-1"></span><h3 class="section">1.2 What is a shell?</h3>

<p>At its base, a shell is simply a macro processor that executes
commands.  The term macro processor means functionality where text
and symbols are expanded to create larger expressions.
</p>
<p>A Unix shell is both a command interpreter and a programming
language.  As a command interpreter, the shell provides the user
interface to the rich set of <small>GNU</small> utilities.  The programming
language features allow these utilities to be combined.
Files containing commands can be created, and become
commands themselves.  These new commands have the same status as
system commands in directories such as <samp>/bin</samp>, allowing users
or groups to establish custom environments to automate their common
tasks.
</p>
<p>Shells may be used interactively or non-interactively.  In
interactive mode, they accept input typed from the keyboard.
When executing non-interactively, shells execute commands read
from a file.
</p>
<p>A shell allows execution of <small>GNU</small> commands, both synchronously and
asynchronously.
The shell waits for synchronous commands to complete before accepting
more input; asynchronous commands continue to execute in parallel
with the shell while it reads and executes additional commands.
The <em>redirection</em> constructs permit
fine-grained control of the input and output of those commands.
Moreover, the shell allows control over the contents of commands&rsquo;
environments.
</p>
<p>Shells also provide a small set of built-in
commands (<em>builtins</em>) implementing functionality impossible
or inconvenient to obtain via separate utilities.
For example, <code>cd</code>, <code>break</code>, <code>continue</code>, and
<code>exec</code> cannot be implemented outside of the shell because
they directly manipulate the shell itself.
The <code>history</code>, <code>getopts</code>, <code>kill</code>, or <code>pwd</code>
builtins, among others, could be implemented in separate utilities,
but they are more convenient to use as builtin commands.
All of the shell builtins are described in
subsequent sections.
</p>
<p>While executing commands is essential, most of the power (and
complexity) of shells is due to their embedded programming
languages.  Like any high-level language, the shell provides
variables, flow control constructs, quoting, and functions. 
</p>
<p>Shells offer features geared specifically for
interactive use rather than to augment the programming language. 
These interactive features include job control, command line
editing, command history and aliases.  Each of these features is
described in this manual.
</p>
<hr>
</div>
</div>
<div class="chapter" id="Definitions">
<div class="header">
<p>
Next: <a href="#Basic-Shell-Features" accesskey="n" rel="next">Basic Shell Features</a>, Previous: <a href="#Introduction" accesskey="p" rel="prev">Introduction</a>, Up: <a href="#Top" accesskey="u" rel="up">Bash Features</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Definitions-1"></span><h2 class="chapter">2 Definitions</h2>
<p>These definitions are used throughout the remainder of this manual.
</p>
<dl compact="compact">
<dt id='index-POSIX'><span><code>POSIX</code><a href='#index-POSIX' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A family of open system standards based on Unix.  Bash
is primarily concerned with the Shell and Utilities portion of the
<small>POSIX</small> 1003.1 standard. 
</p>
</dd>
<dt><span><code>blank</code></span></dt>
<dd><p>A space or tab character.
</p>
</dd>
<dt id='index-builtin-1'><span><code>builtin</code><a href='#index-builtin-1' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A command that is implemented internally by the shell itself, rather
than by an executable program somewhere in the file system.
</p>
</dd>
<dt id='index-control-operator'><span><code>control operator</code><a href='#index-control-operator' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A <code>token</code> that performs a control function.  It is a <code>newline</code>
or one of the following:
&lsquo;<samp>||</samp>&rsquo;, &lsquo;<samp>&amp;&amp;</samp>&rsquo;, &lsquo;<samp>&amp;</samp>&rsquo;, &lsquo;<samp>;</samp>&rsquo;, &lsquo;<samp>;;</samp>&rsquo;, &lsquo;<samp>;&amp;</samp>&rsquo;, &lsquo;<samp>;;&amp;</samp>&rsquo;,
&lsquo;<samp>|</samp>&rsquo;, &lsquo;<samp>|&amp;</samp>&rsquo;, &lsquo;<samp>(</samp>&rsquo;, or &lsquo;<samp>)</samp>&rsquo;.
</p>
</dd>
<dt id='index-exit-status'><span><code>exit status</code><a href='#index-exit-status' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The value returned by a command to its caller.  The value is restricted
to eight bits, so the maximum value is 255.
</p>
</dd>
<dt id='index-field'><span><code>field</code><a href='#index-field' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A unit of text that is the result of one of the shell expansions.  After
expansion, when executing a command, the resulting fields are used as
the command name and arguments.
</p>
</dd>
<dt id='index-filename'><span><code>filename</code><a href='#index-filename' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A string of characters used to identify a file.
</p>
</dd>
<dt id='index-job'><span><code>job</code><a href='#index-job' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A set of processes comprising a pipeline, and any processes descended
from it, that are all in the same process group.
</p>
</dd>
<dt id='index-job-control'><span><code>job control</code><a href='#index-job-control' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A mechanism by which users can selectively stop (suspend) and restart
(resume) execution of processes.
</p>
</dd>
<dt id='index-metacharacter'><span><code>metacharacter</code><a href='#index-metacharacter' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A character that, when unquoted, separates words.  A metacharacter is
a <code>space</code>, <code>tab</code>, <code>newline</code>, or one of the following characters:
&lsquo;<samp>|</samp>&rsquo;, &lsquo;<samp>&amp;</samp>&rsquo;, &lsquo;<samp>;</samp>&rsquo;, &lsquo;<samp>(</samp>&rsquo;, &lsquo;<samp>)</samp>&rsquo;, &lsquo;<samp>&lt;</samp>&rsquo;, or
&lsquo;<samp>&gt;</samp>&rsquo;.
</p>
</dd>
<dt id='index-name'><span><code>name</code><a href='#index-name' class='copiable-anchor'> &para;</a></span></dt>
<dd><span id="index-identifier"></span>
<p>A <code>word</code> consisting solely of letters, numbers, and underscores,
and beginning with a letter or underscore.  <code>Name</code>s are used as
shell variable and function names.
Also referred to as an <code>identifier</code>.
</p>
</dd>
<dt id='index-operator_002c-shell'><span><code>operator</code><a href='#index-operator_002c-shell' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A <code>control operator</code> or a <code>redirection operator</code>.
See <a href="#Redirections">Redirections</a>, for a list of redirection operators.
Operators contain at least one unquoted <code>metacharacter</code>.
</p>
</dd>
<dt id='index-process-group'><span><code>process group</code><a href='#index-process-group' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A collection of related processes each having the same process
group <small>ID</small>.
</p>
</dd>
<dt id='index-process-group-ID'><span><code>process group ID</code><a href='#index-process-group-ID' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A unique identifier that represents a <code>process group</code>
during its lifetime.
</p>
</dd>
<dt id='index-reserved-word'><span><code>reserved word</code><a href='#index-reserved-word' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A <code>word</code> that has a special meaning to the shell.  Most reserved
words introduce shell flow control constructs, such as <code>for</code> and
<code>while</code>.
</p>
</dd>
<dt id='index-return-status'><span><code>return status</code><a href='#index-return-status' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A synonym for <code>exit status</code>.
</p>
</dd>
<dt id='index-signal'><span><code>signal</code><a href='#index-signal' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A mechanism by which a process may be notified by the kernel
of an event occurring in the system.
</p>
</dd>
<dt id='index-special-builtin'><span><code>special builtin</code><a href='#index-special-builtin' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A shell builtin command that has been classified as special by the
<small>POSIX</small> standard.
</p>
</dd>
<dt id='index-token'><span><code>token</code><a href='#index-token' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A sequence of characters considered a single unit by the shell.
It is either a <code>word</code> or an <code>operator</code>.
</p>
</dd>
<dt id='index-word'><span><code>word</code><a href='#index-word' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A sequence of characters treated as a unit by the shell.
Words may not include unquoted <code>metacharacters</code>.
</p></dd>
</dl>

<hr>
</div>
<div class="chapter" id="Basic-Shell-Features">
<div class="header">
<p>
Next: <a href="#Shell-Builtin-Commands" accesskey="n" rel="next">Shell Builtin Commands</a>, Previous: <a href="#Definitions" accesskey="p" rel="prev">Definitions</a>, Up: <a href="#Top" accesskey="u" rel="up">Bash Features</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Basic-Shell-Features-1"></span><h2 class="chapter">3 Basic Shell Features</h2>
<span id="index-Bourne-shell"></span>

<p>Bash is an acronym for &lsquo;<samp>Bourne-Again SHell</samp>&rsquo;.
The Bourne shell is
the traditional Unix shell originally written by Stephen Bourne.
All of the Bourne shell builtin commands are available in Bash,
The rules for evaluation and quoting are taken from the <small>POSIX</small>
specification for the &lsquo;standard&rsquo; Unix shell.
</p>
<p>This chapter briefly summarizes the shell&rsquo;s &lsquo;building blocks&rsquo;:
commands, control structures, shell functions, shell <i>parameters</i>,
shell expansions,
<i>redirections</i>, which are a way to direct input and output from
and to named files, and how the shell executes commands.
</p>

<ul class="section-toc">
<li><a href="#Shell-Syntax" accesskey="1">Shell Syntax</a></li>
<li><a href="#Shell-Commands" accesskey="2">Shell Commands</a></li>
<li><a href="#Shell-Functions" accesskey="3">Shell Functions</a></li>
<li><a href="#Shell-Parameters" accesskey="4">Shell Parameters</a></li>
<li><a href="#Shell-Expansions" accesskey="5">Shell Expansions</a></li>
<li><a href="#Redirections" accesskey="6">Redirections</a></li>
<li><a href="#Executing-Commands" accesskey="7">Executing Commands</a></li>
<li><a href="#Shell-Scripts" accesskey="8">Shell Scripts</a></li>
</ul>
<hr>
<div class="section" id="Shell-Syntax">
<div class="header">
<p>
Next: <a href="#Shell-Commands" accesskey="n" rel="next">Shell Commands</a>, Up: <a href="#Basic-Shell-Features" accesskey="u" rel="up">Basic Shell Features</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Shell-Syntax-1"></span><h3 class="section">3.1 Shell Syntax</h3>

<p>When the shell reads input, it proceeds through a
sequence of operations.  If the input indicates the beginning of a
comment, the shell ignores the comment symbol (&lsquo;<samp>#</samp>&rsquo;), and the rest
of that line.
</p>                                
<p>Otherwise, roughly speaking,  the shell reads its input and
divides the input into words and operators, employing the quoting rules
to select which meanings to assign various words and characters.
</p>
<p>The shell then parses these tokens into commands and other constructs,
removes the special meaning of certain words or characters, expands
others, redirects input and output as needed, executes the specified
command, waits for the command&rsquo;s exit status, and makes that exit status
available for further inspection or processing.
</p>
<ul class="section-toc">
<li><a href="#Shell-Operation" accesskey="1">Shell Operation</a></li>
<li><a href="#Quoting" accesskey="2">Quoting</a></li>
<li><a href="#Comments" accesskey="3">Comments</a></li>
</ul>
<hr>
<div class="subsection" id="Shell-Operation">
<div class="header">
<p>
Next: <a href="#Quoting" accesskey="n" rel="next">Quoting</a>, Up: <a href="#Shell-Syntax" accesskey="u" rel="up">Shell Syntax</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Shell-Operation-1"></span><h4 class="subsection">3.1.1 Shell Operation</h4>

<p>The following is a brief description of the shell&rsquo;s operation when it
reads and executes a command.  Basically, the shell does the
following:
</p>
<ol>
<li> Reads its input from a file (see <a href="#Shell-Scripts">Shell Scripts</a>), from a string
supplied as an argument to the <samp>-c</samp> invocation option
(see <a href="#Invoking-Bash">Invoking Bash</a>), or from the user&rsquo;s terminal.

</li><li> Breaks the input into words and operators, obeying the quoting rules
described in <a href="#Quoting">Quoting</a>.  These tokens are separated by
<code>metacharacters</code>.  Alias expansion is performed by this step
(see <a href="#Aliases">Aliases</a>).

</li><li> Parses the tokens into simple and compound commands
(see <a href="#Shell-Commands">Shell Commands</a>).

</li><li> Performs the various shell expansions (see <a href="#Shell-Expansions">Shell Expansions</a>), breaking
the expanded tokens into lists of filenames (see <a href="#Filename-Expansion">Filename Expansion</a>)
and commands and arguments.

</li><li> Performs any necessary redirections (see <a href="#Redirections">Redirections</a>) and removes
the redirection operators and their operands from the argument list.

</li><li> Executes the command (see <a href="#Executing-Commands">Executing Commands</a>).

</li><li> Optionally waits for the command to complete and collects its exit
status (see <a href="#Exit-Status">Exit Status</a>).

</li></ol>

<hr>
</div>
<div class="subsection" id="Quoting">
<div class="header">
<p>
Next: <a href="#Comments" accesskey="n" rel="next">Comments</a>, Previous: <a href="#Shell-Operation" accesskey="p" rel="prev">Shell Operation</a>, Up: <a href="#Shell-Syntax" accesskey="u" rel="up">Shell Syntax</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Quoting-1"></span><h4 class="subsection">3.1.2 Quoting</h4>
<span id="index-quoting"></span>

<p>Quoting is used to remove the special meaning of certain
characters or words to the shell.  Quoting can be used to
disable special treatment for special characters, to prevent
reserved words from being recognized as such, and to prevent
parameter expansion.
</p>
<p>Each of the shell metacharacters (see <a href="#Definitions">Definitions</a>)
has special meaning to the shell and must be quoted if it is to
represent itself.
When the command history expansion facilities are being used
(see <a href="#History-Interaction">History Expansion</a>), the
<em>history expansion</em> character, usually &lsquo;<samp>!</samp>&rsquo;, must be quoted
to prevent history expansion.  See <a href="#Bash-History-Facilities">Bash History Facilities</a>, for
more details concerning history expansion.
</p>
<p>There are three quoting mechanisms: the
<em>escape character</em>, single quotes, and double quotes.
</p>
<ul class="section-toc">
<li><a href="#Escape-Character" accesskey="1">Escape Character</a></li>
<li><a href="#Single-Quotes" accesskey="2">Single Quotes</a></li>
<li><a href="#Double-Quotes" accesskey="3">Double Quotes</a></li>
<li><a href="#ANSI_002dC-Quoting" accesskey="4">ANSI-C Quoting</a></li>
<li><a href="#Locale-Translation" accesskey="5">Locale-Specific Translation</a></li>
</ul>
<hr>
<div class="subsubsection" id="Escape-Character">
<div class="header">
<p>
Next: <a href="#Single-Quotes" accesskey="n" rel="next">Single Quotes</a>, Up: <a href="#Quoting" accesskey="u" rel="up">Quoting</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Escape-Character-1"></span><h4 class="subsubsection">3.1.2.1 Escape Character</h4>
<p>A non-quoted backslash &lsquo;<samp>\</samp>&rsquo; is the Bash escape character.
It preserves the literal value of the next character that follows,
with the exception of <code>newline</code>.  If a <code>\newline</code> pair
appears, and the backslash itself is not quoted, the <code>\newline</code>
is treated as a line continuation (that is, it is removed from
the input stream and effectively ignored).
</p>
<hr>
</div>
<div class="subsubsection" id="Single-Quotes">
<div class="header">
<p>
Next: <a href="#Double-Quotes" accesskey="n" rel="next">Double Quotes</a>, Previous: <a href="#Escape-Character" accesskey="p" rel="prev">Escape Character</a>, Up: <a href="#Quoting" accesskey="u" rel="up">Quoting</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Single-Quotes-1"></span><h4 class="subsubsection">3.1.2.2 Single Quotes</h4>

<p>Enclosing characters in single quotes (&lsquo;<samp>'</samp>&rsquo;) preserves the literal value
of each character within the quotes.  A single quote may not occur
between single quotes, even when preceded by a backslash.
</p>
<hr>
</div>
<div class="subsubsection" id="Double-Quotes">
<div class="header">
<p>
Next: <a href="#ANSI_002dC-Quoting" accesskey="n" rel="next">ANSI-C Quoting</a>, Previous: <a href="#Single-Quotes" accesskey="p" rel="prev">Single Quotes</a>, Up: <a href="#Quoting" accesskey="u" rel="up">Quoting</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Double-Quotes-1"></span><h4 class="subsubsection">3.1.2.3 Double Quotes</h4>

<p>Enclosing characters in double quotes (&lsquo;<samp>&quot;</samp>&rsquo;) preserves the literal value
of all characters within the quotes, with the exception of
&lsquo;<samp>$</samp>&rsquo;, &lsquo;<samp>`</samp>&rsquo;, &lsquo;<samp>\</samp>&rsquo;,
and, when history expansion is enabled, &lsquo;<samp>!</samp>&rsquo;.
When the shell is in
<small>POSIX</small> mode (see <a href="#Bash-POSIX-Mode">Bash POSIX Mode</a>),
the &lsquo;<samp>!</samp>&rsquo; has no special meaning
within double quotes, even when history expansion is enabled.
The characters &lsquo;<samp>$</samp>&rsquo; and &lsquo;<samp>`</samp>&rsquo;
retain their special meaning within double quotes (see <a href="#Shell-Expansions">Shell Expansions</a>).
The backslash retains its special meaning only when followed by one of
the following characters:
&lsquo;<samp>$</samp>&rsquo;, &lsquo;<samp>`</samp>&rsquo;, &lsquo;<samp>&quot;</samp>&rsquo;, &lsquo;<samp>\</samp>&rsquo;, or <code>newline</code>.
Within double quotes, backslashes that are followed by one of these
characters are removed.  Backslashes preceding characters without a
special meaning are left unmodified.
A double quote may be quoted within double quotes by preceding it with
a backslash.
If enabled, history expansion will be performed unless an &lsquo;<samp>!</samp>&rsquo;
appearing in double quotes is escaped using a backslash.
The backslash preceding the &lsquo;<samp>!</samp>&rsquo; is not removed.
</p>
<p>The special parameters &lsquo;<samp>*</samp>&rsquo; and &lsquo;<samp>@</samp>&rsquo; have special meaning
when in double quotes (see <a href="#Shell-Parameter-Expansion">Shell Parameter Expansion</a>).
</p>
<hr>
</div>
<div class="subsubsection" id="ANSI_002dC-Quoting">
<div class="header">
<p>
Next: <a href="#Locale-Translation" accesskey="n" rel="next">Locale-Specific Translation</a>, Previous: <a href="#Double-Quotes" accesskey="p" rel="prev">Double Quotes</a>, Up: <a href="#Quoting" accesskey="u" rel="up">Quoting</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="ANSI_002dC-Quoting-1"></span><h4 class="subsubsection">3.1.2.4 ANSI-C Quoting</h4>
<span id="index-quoting_002c-ANSI"></span>

<p>Character sequences of the form $&rsquo;<var>string</var>&rsquo; are treated as a special
kind of single quotes.
The sequence expands to <var>string</var>, with backslash-escaped characters
in <var>string</var> replaced as specified by the ANSI C standard.
Backslash escape sequences, if present, are decoded as follows:
</p>
<dl compact="compact">
<dt><span><code>\a</code></span></dt>
<dd><p>alert (bell)
</p></dd>
<dt><span><code>\b</code></span></dt>
<dd><p>backspace
</p></dd>
<dt><span><code>\e</code></span></dt>
<dt><span><code>\E</code></span></dt>
<dd><p>an escape character (not ANSI C)
</p></dd>
<dt><span><code>\f</code></span></dt>
<dd><p>form feed
</p></dd>
<dt><span><code>\n</code></span></dt>
<dd><p>newline
</p></dd>
<dt><span><code>\r</code></span></dt>
<dd><p>carriage return
</p></dd>
<dt><span><code>\t</code></span></dt>
<dd><p>horizontal tab
</p></dd>
<dt><span><code>\v</code></span></dt>
<dd><p>vertical tab
</p></dd>
<dt><span><code>\\</code></span></dt>
<dd><p>backslash
</p></dd>
<dt><span><code>\'</code></span></dt>
<dd><p>single quote
</p></dd>
<dt><span><code>\&quot;</code></span></dt>
<dd><p>double quote
</p></dd>
<dt><span><code>\?</code></span></dt>
<dd><p>question mark
</p></dd>
<dt><span><code>\<var>nnn</var></code></span></dt>
<dd><p>the eight-bit character whose value is the octal value <var>nnn</var>
(one to three octal digits)
</p></dd>
<dt><span><code>\x<var>HH</var></code></span></dt>
<dd><p>the eight-bit character whose value is the hexadecimal value <var>HH</var>
(one or two hex digits)
</p></dd>
<dt><span><code>\u<var>HHHH</var></code></span></dt>
<dd><p>the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value
<var>HHHH</var> (one to four hex digits)
</p></dd>
<dt><span><code>\U<var>HHHHHHHH</var></code></span></dt>
<dd><p>the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value
<var>HHHHHHHH</var> (one to eight hex digits)
</p></dd>
<dt><span><code>\c<var>x</var></code></span></dt>
<dd><p>a control-<var>x</var> character
</p></dd>
</dl>

<p>The expanded result is single-quoted, as if the dollar sign had not
been present.
</p>
<hr>
</div>
<div class="subsubsection" id="Locale-Translation">
<div class="header">
<p>
Previous: <a href="#ANSI_002dC-Quoting" accesskey="p" rel="prev">ANSI-C Quoting</a>, Up: <a href="#Quoting" accesskey="u" rel="up">Quoting</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Locale_002dSpecific-Translation"></span><h4 class="subsubsection">3.1.2.5 Locale-Specific Translation</h4>
<span id="index-localization"></span>
<span id="index-internationalization"></span>
<span id="index-native-languages"></span>
<span id="index-translation_002c-native-languages"></span>

<p>Prefixing a double-quoted string with a dollar sign (&lsquo;<samp>$</samp>&rsquo;), such
as <tt>$&quot;hello, world&quot;</tt>,
will cause the string to be translated according to the current locale.
The <code>gettext</code> infrastructure performs the lookup and 
translation, using the <code>LC_MESSAGES</code>, <code>TEXTDOMAINDIR</code>,
and <code>TEXTDOMAIN</code> shell variables, as explained below.
See the gettext documentation for additional details not covered here.
If the current locale is <code>C</code> or <code>POSIX</code>,
if there are no translations available,
of if the string is not translated,
the dollar sign is ignored.
Since this is a form of double quoting, the string remains double-quoted
by default, whether or not it is translated and replaced.
If the <code>noexpand_translation</code> option is enabled
using the <code>shopt</code> builtin (see <a href="#The-Shopt-Builtin">The Shopt Builtin</a>),
translated strings are single-quoted instead of double-quoted.
</p>
<p>The rest of this section is a brief overview of how you use gettext to
create translations for strings in a shell script named <var>scriptname</var>.
There are more details in the gettext documentation.
</p>
<hr>
<span id="Creating-Internationalized-Scripts"></span><div class="header">
<p>
 &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<h4 class="node-heading">Creating Internationalized Scripts</h4>
<span id="index-internationalized-scripts"></span>
<span id="index-string-translations"></span>
<p>Once you&rsquo;ve marked the strings in your script
that you want to translate using $&quot;...&quot;,
you create a gettext &quot;template&quot; file using the command
</p>
<div class="example">
<pre class="example">bash --dump-po-strings <var>scriptname</var> &gt; <var>domain</var>.pot
</pre></div>

<p>The <var>domain</var> is your <em>message domain</em>.
It&rsquo;s just an arbitrary string that&rsquo;s used to identify the files gettext
needs, like a package or script name.
It needs to be unique among all
the message domains on systems where you install the translations, so
gettext knows which translations correspond to your script.
You&rsquo;ll use the template file to create translations for each target language.
The template file conventionally has the suffix &lsquo;<samp>.pot</samp>&rsquo;.
</p>
<p>You copy this template file to a separate file for each target language
you want to support (called &quot;PO&quot; files, which use the suffix &lsquo;<samp>.po</samp>&rsquo;).
PO files use various naming conventions, but
when you are working to translate a template file into a particular
language, you first copy the template file to a file whose name is the
language you want to target, with the &lsquo;<samp>.po</samp>&rsquo; suffix.
For instance, the Spanish translations of your strings would be
in a file named &lsquo;<samp>es.po</samp>&rsquo;, and to get started using a message
domain named &quot;example,&quot; you would run
</p>
<div class="example">
<pre class="example">cp example.pot es.po
</pre></div>

<p>Ultimately, PO files are often named <var>domain</var>.po and installed in
directories that contain multiple translation files for a particular language.
</p>
<p>Whichever naming convention you choose, you will need to translate the
strings in the PO files into the appropriate languages.
This has to be done manually.
</p>
<p>When you have the translations and PO files complete, you&rsquo;ll use the
gettext tools to produce what are called &quot;MO&quot; files, which are compiled
versions of the PO files the gettext tools use to look up translations
efficiently.
MO files are also called &quot;message catalog&quot; files.
You use the <code>msgfmt</code> program to do this.
For instance, if you had a file with Spanish translations, you could run
</p>
<div class="example">
<pre class="example">msgfmt -o es.mo es.po
</pre></div>

<p>to produce the corresponding MO file.
</p>
<p>Once you have the MO files, you decide where to install them and use the
<code>TEXTDOMAINDIR</code> shell variable to tell the gettext tools where they are.
Make sure to use the same message domain to name the MO files 
as you did for the PO files when you install them.
</p>
<span id="index-LANG"></span>
<span id="index-LC_005fMESSAGES"></span>
<span id="index-TEXTDOMAIN"></span>
<span id="index-TEXTDOMAINDIR"></span>
<p>Your users will use the <code>LANG</code> or <code>LC_MESSAGES</code> shell variables to
select the desired language.
</p>
<p>You set the <code>TEXTDOMAIN</code> variable to the script&rsquo;s message domain.
As above, you use the message domain to name your translation files.
</p>
<p>You, or possibly your users, set the <code>TEXTDOMAINDIR</code> variable to the
name of a directory where the message catalog files are stored.
If you install the message files into the system&rsquo;s standard message catalog
directory, you don&rsquo;t need to worry about this variable.
</p>
<p>The directory where the message catalog files are stored varies between
systems.
Some use the message catalog selected by the <code>LC_MESSAGES</code>
shell variable.
Others create the name of the message catalog from the value of the
<code>TEXTDOMAIN</code> shell variable, possibly adding the &lsquo;<samp>.mo</samp>&rsquo; suffix.
If you use the <code>TEXTDOMAIN</code> variable, you may need to set the
<code>TEXTDOMAINDIR</code> variable to the location of the message catalog files,
as above.
It&rsquo;s common to use both variables in this fashion:
<code>$TEXTDOMAINDIR</code>/<code>$LC_MESSAGES</code>/LC_MESSAGES/<code>$TEXTDOMAIN</code>.mo.
</p>
<p>If you used that last convention, and you wanted to store the message
catalog files with Spanish (es) and Esperanto (eo) translations into a
local directory you use for custom translation files, you could run
</p>
<div class="example">
<pre class="example">TEXTDOMAIN=example
TEXTDOMAINDIR=/usr/local/share/locale

cp es.mo ${TEXTDOMAINDIR}/es/LC_MESSAGES/${TEXTDOMAIN}.mo
cp eo.mo ${TEXTDOMAINDIR}/eo/LC_MESSAGES/${TEXTDOMAIN}.mo
</pre></div>

<p>When all of this is done, and the message catalog files containing the
compiled translations are installed in the correct location,
your users will be able to see translated strings
in any of the supported languages by setting the <code>LANG</code> or
<code>LC_MESSAGES</code> environment variables before running your script.
</p>
<hr>
</div>
</div>
<div class="subsection" id="Comments">
<div class="header">
<p>
Previous: <a href="#Quoting" accesskey="p" rel="prev">Quoting</a>, Up: <a href="#Shell-Syntax" accesskey="u" rel="up">Shell Syntax</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Comments-1"></span><h4 class="subsection">3.1.3 Comments</h4>
<span id="index-comments_002c-shell"></span>

<p>In a non-interactive shell, or an interactive shell in which the
<code>interactive_comments</code> option to the <code>shopt</code>
builtin is enabled (see <a href="#The-Shopt-Builtin">The Shopt Builtin</a>),
a word beginning with &lsquo;<samp>#</samp>&rsquo;
causes that word and all remaining characters on that line to
be ignored.  An interactive shell without the <code>interactive_comments</code>
option enabled does not allow comments.  The <code>interactive_comments</code>
option is on by default in interactive shells.
See <a href="#Interactive-Shells">Interactive Shells</a>, for a description of what makes
a shell interactive.
</p>
<hr>
</div>
</div>
<div class="section" id="Shell-Commands">
<div class="header">
<p>
Next: <a href="#Shell-Functions" accesskey="n" rel="next">Shell Functions</a>, Previous: <a href="#Shell-Syntax" accesskey="p" rel="prev">Shell Syntax</a>, Up: <a href="#Basic-Shell-Features" accesskey="u" rel="up">Basic Shell Features</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Shell-Commands-1"></span><h3 class="section">3.2 Shell Commands</h3>
<span id="index-commands_002c-shell"></span>

<p>A simple shell command such as <code>echo a b c</code> consists of the command
itself followed by arguments, separated by spaces.
</p>
<p>More complex shell commands are composed of simple commands arranged together
in a variety of ways: in a pipeline in which the output of one command
becomes the input of a second, in a loop or conditional construct, or in
some other grouping.
</p>

<ul class="section-toc">
<li><a href="#Reserved-Words" accesskey="1">Reserved Words</a></li>
<li><a href="#Simple-Commands" accesskey="2">Simple Commands</a></li>
<li><a href="#Pipelines" accesskey="3">Pipelines</a></li>
<li><a href="#Lists" accesskey="4">Lists of Commands</a></li>
<li><a href="#Compound-Commands" accesskey="5">Compound Commands</a></li>
<li><a href="#Coprocesses" accesskey="6">Coprocesses</a></li>
<li><a href="#GNU-Parallel" accesskey="7">GNU Parallel</a></li>
</ul>
<hr>
<div class="subsection" id="Reserved-Words">
<div class="header">
<p>
Next: <a href="#Simple-Commands" accesskey="n" rel="next">Simple Commands</a>, Up: <a href="#Shell-Commands" accesskey="u" rel="up">Shell Commands</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Reserved-Words-1"></span><h4 class="subsection">3.2.1 Reserved Words</h4>
<span id="index-reserved-words"></span>

<p>Reserved words are words that have special meaning to the shell.
They are used to begin and end the shell&rsquo;s compound commands.
</p>
<p>The following words are recognized as reserved when unquoted and 
the first word of a command (see below for exceptions):
</p>
<table>
<tr><td width="10%"><code>if</code></td><td width="10%"><code>then</code></td><td width="10%"><code>elif</code></td><td width="10%"><code>else</code></td><td width="12%"><code>fi</code></td><td width="10%"><code>time</code></td></tr>
<tr><td width="10%"><code>for</code></td><td width="10%"><code>in</code></td><td width="10%"><code>until</code></td><td width="10%"><code>while</code></td><td width="12%"><code>do</code></td><td width="10%"><code>done</code></td></tr>
<tr><td width="10%"><code>case</code></td><td width="10%"><code>esac</code></td><td width="10%"><code>coproc</code></td><td width="10%"><code>select</code></td><td width="12%"><code>function</code></td></tr>
<tr><td width="10%"><code>{</code></td><td width="10%"><code>}</code></td><td width="10%"><code>[[</code></td><td width="10%"><code>]]</code></td><td width="12%"><code>!</code></td></tr>
</table>

<p><code>in</code> is recognized as a reserved word if it is the third word of a
<code>case</code> or <code>select</code> command.
<code>in</code> and <code>do</code> are recognized as reserved
words if they are the third word in a <code>for</code> command.
</p>
<hr>
</div>
<div class="subsection" id="Simple-Commands">
<div class="header">
<p>
Next: <a href="#Pipelines" accesskey="n" rel="next">Pipelines</a>, Previous: <a href="#Reserved-Words" accesskey="p" rel="prev">Reserved Words</a>, Up: <a href="#Shell-Commands" accesskey="u" rel="up">Shell Commands</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Simple-Commands-1"></span><h4 class="subsection">3.2.2 Simple Commands</h4>
<span id="index-commands_002c-simple"></span>

<p>A simple command is the kind of command encountered most often.
It&rsquo;s just a sequence of words separated by <code>blank</code>s, terminated
by one of the shell&rsquo;s control operators (see <a href="#Definitions">Definitions</a>).  The
first word generally specifies a command to be executed, with the
rest of the words being that command&rsquo;s arguments.
</p>
<p>The return status (see <a href="#Exit-Status">Exit Status</a>) of a simple command is
its exit status as provided
by the <small>POSIX</small> 1003.1 <code>waitpid</code> function, or 128+<var>n</var> if
the command was terminated by signal <var>n</var>.
</p>
<hr>
</div>
<div class="subsection" id="Pipelines">
<div class="header">
<p>
Next: <a href="#Lists" accesskey="n" rel="next">Lists of Commands</a>, Previous: <a href="#Simple-Commands" accesskey="p" rel="prev">Simple Commands</a>, Up: <a href="#Shell-Commands" accesskey="u" rel="up">Shell Commands</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Pipelines-1"></span><h4 class="subsection">3.2.3 Pipelines</h4>
<span id="index-pipeline"></span>
<span id="index-commands_002c-pipelines"></span>

<p>A <code>pipeline</code> is a sequence of one or more commands separated by
one of the control operators &lsquo;<samp>|</samp>&rsquo; or &lsquo;<samp>|&amp;</samp>&rsquo;.
</p>
<span id="index-time"></span>
<span id="index-_0021"></span>
<span id="index-command-timing"></span>
<p>The format for a pipeline is
</p><div class="example">
<pre class="example">[time [-p]] [!] <var>command1</var> [ | or |&amp; <var>command2</var> ] &hellip;
</pre></div>

<p>The output of each command in the pipeline is connected via a pipe
to the input of the next command.
That is, each command reads the previous command&rsquo;s output.  This
connection is performed before any redirections specified by
<var>command1</var>.
</p>
<p>If &lsquo;<samp>|&amp;</samp>&rsquo; is used, <var>command1</var>&rsquo;s standard error, in addition to
its standard output, is connected to
<var>command2</var>&rsquo;s standard input through the pipe;
it is shorthand for <code>2&gt;&amp;1 |</code>.
This implicit redirection of the standard error to the standard output is
performed after any redirections specified by <var>command1</var>.
</p>
<p>The reserved word <code>time</code> causes timing statistics
to be printed for the pipeline once it finishes.
The statistics currently consist of elapsed (wall-clock) time and
user and system time consumed by the command&rsquo;s execution.
The <samp>-p</samp> option changes the output format to that specified
by <small>POSIX</small>.
When the shell is in <small>POSIX</small> mode (see <a href="#Bash-POSIX-Mode">Bash POSIX Mode</a>),
it does not recognize <code>time</code> as a reserved word if the next
token begins with a &lsquo;<samp>-</samp>&rsquo;.
The <code>TIMEFORMAT</code> variable may be set to a format string that
specifies how the timing information should be displayed.
See <a href="#Bash-Variables">Bash Variables</a>, for a description of the available formats.
The use of <code>time</code> as a reserved word permits the timing of
shell builtins, shell functions, and pipelines.  An external
<code>time</code> command cannot time these easily.
</p>
<p>When the shell is in <small>POSIX</small> mode (see <a href="#Bash-POSIX-Mode">Bash POSIX Mode</a>), <code>time</code>
may be followed by a newline.  In this case, the shell displays the
total user and system time consumed by the shell and its children.
The <code>TIMEFORMAT</code> variable may be used to specify the format of
the time information.
</p>
<p>If the pipeline is not executed asynchronously (see <a href="#Lists">Lists of Commands</a>), the
shell waits for all commands in the pipeline to complete.
</p>
<p>Each command in a multi-command pipeline,
where pipes are created,
is executed in its own <em>subshell</em>, which is a
separate process (see <a href="#Command-Execution-Environment">Command Execution Environment</a>).
If the <code>lastpipe</code> option is enabled using the <code>shopt</code> builtin
(see <a href="#The-Shopt-Builtin">The Shopt Builtin</a>),
the last element of a pipeline may be run by the shell process
when job control is not active.
</p>
<p>The exit
status of a pipeline is the exit status of the last command in the
pipeline, unless the <code>pipefail</code> option is enabled
(see <a href="#The-Set-Builtin">The Set Builtin</a>).
If <code>pipefail</code> is enabled, the pipeline&rsquo;s return status is the
value of the last (rightmost) command to exit with a non-zero status,
or zero if all commands exit successfully.
If the reserved word &lsquo;<samp>!</samp>&rsquo; precedes the pipeline, the
exit status is the logical negation of the exit status as described
above.
The shell waits for all commands in the pipeline to terminate before
returning a value.
</p>
<hr>
</div>
<div class="subsection" id="Lists">
<div class="header">
<p>
Next: <a href="#Compound-Commands" accesskey="n" rel="next">Compound Commands</a>, Previous: <a href="#Pipelines" accesskey="p" rel="prev">Pipelines</a>, Up: <a href="#Shell-Commands" accesskey="u" rel="up">Shell Commands</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Lists-of-Commands"></span><h4 class="subsection">3.2.4 Lists of Commands</h4>
<span id="index-commands_002c-lists"></span>

<p>A <code>list</code> is a sequence of one or more pipelines separated by one
of the operators &lsquo;<samp>;</samp>&rsquo;, &lsquo;<samp>&amp;</samp>&rsquo;, &lsquo;<samp>&amp;&amp;</samp>&rsquo;, or &lsquo;<samp>||</samp>&rsquo;,
and optionally terminated by one of &lsquo;<samp>;</samp>&rsquo;, &lsquo;<samp>&amp;</samp>&rsquo;, or a
<code>newline</code>.
</p>
<p>Of these list operators, &lsquo;<samp>&amp;&amp;</samp>&rsquo; and &lsquo;<samp>||</samp>&rsquo;
have equal precedence, followed by &lsquo;<samp>;</samp>&rsquo; and &lsquo;<samp>&amp;</samp>&rsquo;,
which have equal precedence.
</p>
<p>A sequence of one or more newlines may appear in a <code>list</code>
to delimit commands, equivalent to a semicolon.
</p>
<p>If a command is terminated by the control operator &lsquo;<samp>&amp;</samp>&rsquo;,
the shell executes the command asynchronously in a subshell.
This is known as executing the command in the <em>background</em>,
and these are referred to as <em>asynchronous</em> commands.
The shell does not wait for the command to finish, and the return
status is 0 (true).
When job control is not active (see <a href="#Job-Control">Job Control</a>),
the standard input for asynchronous commands, in the absence of any
explicit redirections, is redirected from <code>/dev/null</code>.
</p>
<p>Commands separated by a &lsquo;<samp>;</samp>&rsquo; are executed sequentially; the shell
waits for each command to terminate in turn.  The return status is the
exit status of the last command executed.
</p>
<p><small>AND</small> and <small>OR</small> lists are sequences of one or more pipelines
separated by the control operators &lsquo;<samp>&amp;&amp;</samp>&rsquo; and &lsquo;<samp>||</samp>&rsquo;,
respectively.  <small>AND</small> and <small>OR</small> lists are executed with left
associativity.
</p>
<p>An <small>AND</small> list has the form
</p><div class="example">
<pre class="example"><var>command1</var> &amp;&amp; <var>command2</var>
</pre></div>

<p><var>command2</var> is executed if, and only if, <var>command1</var>
returns an exit status of zero (success).
</p>
<p>An <small>OR</small> list has the form
</p><div class="example">
<pre class="example"><var>command1</var> || <var>command2</var>
</pre></div>

<p><var>command2</var> is executed if, and only if, <var>command1</var>
returns a non-zero exit status.
</p>
<p>The return status of
<small>AND</small> and <small>OR</small> lists is the exit status of the last command
executed in the list.
</p>
<hr>
</div>
<div class="subsection" id="Compound-Commands">
<div class="header">
<p>
Next: <a href="#Coprocesses" accesskey="n" rel="next">Coprocesses</a>, Previous: <a href="#Lists" accesskey="p" rel="prev">Lists of Commands</a>, Up: <a href="#Shell-Commands" accesskey="u" rel="up">Shell Commands</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Compound-Commands-1"></span><h4 class="subsection">3.2.5 Compound Commands</h4>
<span id="index-commands_002c-compound"></span>


<p>Compound commands are the shell programming language constructs.
Each construct begins with a reserved word or control operator and is
terminated by a corresponding reserved word or operator.
Any redirections (see <a href="#Redirections">Redirections</a>) associated with a compound command
apply to all commands within that compound command unless explicitly overridden.
</p>
<p>In most cases a list of commands in a compound command&rsquo;s description may be
separated from the rest of the command by one or more newlines, and may be
followed by a newline in place of a semicolon.
</p>
<p>Bash provides looping constructs, conditional commands, and mechanisms
to group commands and execute them as a unit.
</p>
<ul class="section-toc">
<li><a href="#Looping-Constructs" accesskey="1">Looping Constructs</a></li>
<li><a href="#Conditional-Constructs" accesskey="2">Conditional Constructs</a></li>
<li><a href="#Command-Grouping" accesskey="3">Grouping Commands</a></li>
</ul>
<hr>
<div class="subsubsection" id="Looping-Constructs">
<div class="header">
<p>
Next: <a href="#Conditional-Constructs" accesskey="n" rel="next">Conditional Constructs</a>, Up: <a href="#Compound-Commands" accesskey="u" rel="up">Compound Commands</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Looping-Constructs-1"></span><h4 class="subsubsection">3.2.5.1 Looping Constructs</h4>
<span id="index-commands_002c-looping"></span>

<p>Bash supports the following looping constructs.
</p>
<p>Note that wherever a &lsquo;<samp>;</samp>&rsquo; appears in the description of a
command&rsquo;s syntax, it may be replaced with one or more newlines.
</p>
<dl compact="compact">
<dt id='index-until'><span><code>until</code><a href='#index-until' class='copiable-anchor'> &para;</a></span></dt>
<dd><span id="index-do"></span>
<span id="index-done"></span>
<p>The syntax of the <code>until</code> command is:
</p>
<div class="example">
<pre class="example">until <var>test-commands</var>; do <var>consequent-commands</var>; done
</pre></div>

<p>Execute <var>consequent-commands</var> as long as
<var>test-commands</var> has an exit status which is not zero.
The return status is the exit status of the last command executed
in <var>consequent-commands</var>, or zero if none was executed.
</p>
</dd>
<dt id='index-while'><span><code>while</code><a href='#index-while' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The syntax of the <code>while</code> command is:
</p>
<div class="example">
<pre class="example">while <var>test-commands</var>; do <var>consequent-commands</var>; done
</pre></div>

<p>Execute <var>consequent-commands</var> as long as
<var>test-commands</var> has an exit status of zero.
The return status is the exit status of the last command executed
in <var>consequent-commands</var>, or zero if none was executed.
</p>
</dd>
<dt id='index-for'><span><code>for</code><a href='#index-for' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The syntax of the <code>for</code> command is:
</p>
<div class="example">
<pre class="example">for <var>name</var> [ [in [<var>words</var> &hellip;] ] ; ] do <var>commands</var>; done
</pre></div>

<p>Expand <var>words</var> (see <a href="#Shell-Expansions">Shell Expansions</a>), and execute <var>commands</var>
once for each member
in the resultant list, with <var>name</var> bound to the current member.
If &lsquo;<samp>in <var>words</var></samp>&rsquo; is not present, the <code>for</code> command
executes the <var>commands</var> once for each positional parameter that is
set, as if &lsquo;<samp>in &quot;$@&quot;</samp>&rsquo; had been specified
(see <a href="#Special-Parameters">Special Parameters</a>).
</p>
<p>The return status is the exit status of the last command that executes.
If there are no items in the expansion of <var>words</var>, no commands are
executed, and the return status is zero.
</p>
<p>An alternate form of the <code>for</code> command is also supported:
</p>
<div class="example">
<pre class="example">for (( <var>expr1</var> ; <var>expr2</var> ; <var>expr3</var> )) ; do <var>commands</var> ; done
</pre></div>

<p>First, the arithmetic expression <var>expr1</var> is evaluated according
to the rules described below (see <a href="#Shell-Arithmetic">Shell Arithmetic</a>).
The arithmetic expression <var>expr2</var> is then evaluated repeatedly
until it evaluates to zero.   
Each time <var>expr2</var> evaluates to a non-zero value, <var>commands</var> are
executed and the arithmetic expression <var>expr3</var> is evaluated.       
If any expression is omitted, it behaves as if it evaluates to 1.
The return value is the exit status of the last command in <var>commands</var>
that is executed, or false if any of the expressions is invalid.
</p></dd>
</dl>

<p>The <code>break</code> and <code>continue</code> builtins (see <a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a>)
may be used to control loop execution.
</p>
<hr>
</div>
<div class="subsubsection" id="Conditional-Constructs">
<div class="header">
<p>
Next: <a href="#Command-Grouping" accesskey="n" rel="next">Grouping Commands</a>, Previous: <a href="#Looping-Constructs" accesskey="p" rel="prev">Looping Constructs</a>, Up: <a href="#Compound-Commands" accesskey="u" rel="up">Compound Commands</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Conditional-Constructs-1"></span><h4 class="subsubsection">3.2.5.2 Conditional Constructs</h4>
<span id="index-commands_002c-conditional"></span>

<dl compact="compact">
<dt id='index-if'><span><code>if</code><a href='#index-if' class='copiable-anchor'> &para;</a></span></dt>
<dd><span id="index-then"></span>
<span id="index-else"></span>
<span id="index-elif"></span>
<span id="index-fi"></span>
<p>The syntax of the <code>if</code> command is:
</p>
<div class="example">
<pre class="example">if <var>test-commands</var>; then
  <var>consequent-commands</var>;
[elif <var>more-test-commands</var>; then
  <var>more-consequents</var>;]
[else <var>alternate-consequents</var>;]
fi
</pre></div>

<p>The <var>test-commands</var> list is executed, and if its return status is zero,
the <var>consequent-commands</var> list is executed.
If <var>test-commands</var> returns a non-zero status, each <code>elif</code> list
is executed in turn, and if its exit status is zero,
the corresponding <var>more-consequents</var> is executed and the   
command completes.
If &lsquo;<samp>else <var>alternate-consequents</var></samp>&rsquo; is present, and
the final command in the final <code>if</code> or <code>elif</code> clause
has a non-zero exit status, then <var>alternate-consequents</var> is executed.
The return status is the exit status of the last command executed, or
zero if no condition tested true.
</p>
</dd>
<dt id='index-case'><span><code>case</code><a href='#index-case' class='copiable-anchor'> &para;</a></span></dt>
<dd><span id="index-in"></span>
<span id="index-esac"></span>
<p>The syntax of the <code>case</code> command is:
</p>
<div class="example">
<pre class="example">case <var>word</var> in
    [ [(] <var>pattern</var> [| <var>pattern</var>]&hellip;) <var>command-list</var> ;;]&hellip;
esac
</pre></div>

<p><code>case</code> will selectively execute the <var>command-list</var> corresponding to
the first <var>pattern</var> that matches <var>word</var>.
The match is performed according
to the rules described below in <a href="#Pattern-Matching">Pattern Matching</a>.
If the <code>nocasematch</code> shell option
(see the description of <code>shopt</code> in <a href="#The-Shopt-Builtin">The Shopt Builtin</a>)
is enabled, the match is performed without regard to the case
of alphabetic characters.
The &lsquo;<samp>|</samp>&rsquo; is used to separate multiple patterns, and the &lsquo;<samp>)</samp>&rsquo;
operator terminates a pattern list.
A list of patterns and an associated command-list is known
as a <var>clause</var>.
</p>
<p>Each clause must be terminated with &lsquo;<samp>;;</samp>&rsquo;, &lsquo;<samp>;&amp;</samp>&rsquo;, or &lsquo;<samp>;;&amp;</samp>&rsquo;.
The <var>word</var> undergoes tilde expansion, parameter expansion, command
substitution, arithmetic expansion, and quote removal
(see <a href="#Shell-Parameter-Expansion">Shell Parameter Expansion</a>)
before matching is attempted.
Each <var>pattern</var> undergoes tilde expansion, parameter expansion,
command substitution, arithmetic expansion, process substitution, and
quote removal.
</p>
<p>There may be an arbitrary number of <code>case</code> clauses, each terminated
by a &lsquo;<samp>;;</samp>&rsquo;, &lsquo;<samp>;&amp;</samp>&rsquo;, or &lsquo;<samp>;;&amp;</samp>&rsquo;.
The first pattern that matches determines the
command-list that is executed.
It&rsquo;s a common idiom to use &lsquo;<samp>*</samp>&rsquo; as the final pattern to define the
default case, since that pattern will always match.
</p>
<p>Here is an example using <code>case</code> in a script that could be used to
describe one interesting feature of an animal:
</p>
<div class="example">
<pre class="example">echo -n &quot;Enter the name of an animal: &quot;
read ANIMAL
echo -n &quot;The $ANIMAL has &quot;
case $ANIMAL in
  horse | dog | cat) echo -n &quot;four&quot;;;
  man | kangaroo ) echo -n &quot;two&quot;;;
  *) echo -n &quot;an unknown number of&quot;;;
esac
echo &quot; legs.&quot;
</pre></div>


<p>If the &lsquo;<samp>;;</samp>&rsquo; operator is used, no subsequent matches are attempted after
the first pattern match.
Using &lsquo;<samp>;&amp;</samp>&rsquo;  in place of &lsquo;<samp>;;</samp>&rsquo; causes execution to continue with
the <var>command-list</var> associated with the next clause, if any.
Using &lsquo;<samp>;;&amp;</samp>&rsquo; in place of &lsquo;<samp>;;</samp>&rsquo; causes the shell to test the patterns
in the next clause, if any, and execute any associated <var>command-list</var>
on a successful match,
continuing the case statement execution as if the pattern list had not matched.
</p>
<p>The return status is zero if no <var>pattern</var> is matched.  Otherwise, the
return status is the exit status of the <var>command-list</var> executed.
</p>
</dd>
<dt id='index-select'><span><code>select</code><a href='#index-select' class='copiable-anchor'> &para;</a></span></dt>
<dd>
<p>The <code>select</code> construct allows the easy generation of menus.
It has almost the same syntax as the <code>for</code> command:
</p>
<div class="example">
<pre class="example">select <var>name</var> [in <var>words</var> &hellip;]; do <var>commands</var>; done
</pre></div>

<p>The list of words following <code>in</code> is expanded, generating a list
of items, and the set of expanded words is printed on the standard
error output stream, each preceded by a number.  If the
&lsquo;<samp>in <var>words</var></samp>&rsquo; is omitted, the positional parameters are printed,
as if &lsquo;<samp>in &quot;$@&quot;</samp>&rsquo; had been specified.
<code>select</code> then displays the <code>PS3</code>
prompt and reads a line from the standard input.
If the line consists of a number corresponding to one of the displayed
words, then the value of <var>name</var> is set to that word.
If the line is empty, the words and prompt are displayed again.
If <code>EOF</code> is read, the <code>select</code> command completes and returns 1.
Any other value read causes <var>name</var> to be set to null.
The line read is saved in the variable <code>REPLY</code>.
</p>
<p>The <var>commands</var> are executed after each selection until a
<code>break</code> command is executed, at which
point the <code>select</code> command completes.
</p>
<p>Here is an example that allows the user to pick a filename from the
current directory, and displays the name and index of the file
selected.
</p>
<div class="example">
<pre class="example">select fname in *;
do
	echo you picked $fname \($REPLY\)
	break;
done
</pre></div>

</dd>
<dt><span><code>((&hellip;))</code></span></dt>
<dd><div class="example">
<pre class="example">(( <var>expression</var> ))
</pre></div>

<p>The arithmetic <var>expression</var> is evaluated according to the rules
described below (see <a href="#Shell-Arithmetic">Shell Arithmetic</a>).
The <var>expression</var> undergoes the same expansions
as if it were within double quotes,
but double quote characters in <var>expression</var> are not treated specially
are removed.
If the value of the expression is non-zero, the return status is 0;
otherwise the return status is 1. 
</p>

</dd>
<dt id='index-_005b_005b'><span><code>[[&hellip;]]</code><a href='#index-_005b_005b' class='copiable-anchor'> &para;</a></span></dt>
<dd><span id="index-_005d_005d"></span>
<div class="example">
<pre class="example">[[ <var>expression</var> ]]
</pre></div>

<p>Return a status of 0 or 1 depending on the evaluation of
the conditional expression <var>expression</var>.
Expressions are composed of the primaries described below in
<a href="#Bash-Conditional-Expressions">Bash Conditional Expressions</a>.
The words between the <code>[[</code> and <code>]]</code> do not undergo word splitting
and filename expansion.
The shell performs tilde expansion, parameter and
variable expansion, arithmetic expansion, command substitution, process
substitution, and quote removal on those words
(the expansions that would occur if the words were enclosed in double quotes).
Conditional operators such as &lsquo;<samp>-f</samp>&rsquo; must be unquoted to be recognized
as primaries.
</p>
<p>When used with <code>[[</code>, the &lsquo;<samp>&lt;</samp>&rsquo; and &lsquo;<samp>&gt;</samp>&rsquo; operators sort
lexicographically using the current locale.
</p>
<p>When the &lsquo;<samp>==</samp>&rsquo; and &lsquo;<samp>!=</samp>&rsquo; operators are used, the string to the
right of the operator is considered a pattern and matched according
to the rules described below in <a href="#Pattern-Matching">Pattern Matching</a>,
as if the <code>extglob</code> shell option were enabled.
The &lsquo;<samp>=</samp>&rsquo; operator is identical to &lsquo;<samp>==</samp>&rsquo;.
If the <code>nocasematch</code> shell option
(see the description of <code>shopt</code> in <a href="#The-Shopt-Builtin">The Shopt Builtin</a>)
is enabled, the match is performed without regard to the case
of alphabetic characters.
The return value is 0 if the string matches (&lsquo;<samp>==</samp>&rsquo;) or does not
match (&lsquo;<samp>!=</samp>&rsquo;) the pattern, and 1 otherwise.
</p>
<p>If you quote any part of the pattern,
using any of the shell&rsquo;s quoting mechanisms,
the quoted portion is matched literally.
This means every character in the quoted portion matches itself,
instead of having any special pattern matching meaning.
</p>
<p>An additional binary operator, &lsquo;<samp>=~</samp>&rsquo;, is available, with the same
precedence as &lsquo;<samp>==</samp>&rsquo; and &lsquo;<samp>!=</samp>&rsquo;.
When you use &lsquo;<samp>=~</samp>&rsquo;, the string to the right of the operator is considered
a <small>POSIX</small> extended regular expression pattern and matched accordingly
(using the <small>POSIX</small> <code>regcomp</code> and <code>regexec</code> interfaces
usually described in <i>regex</i>(3)).
The return value is 0 if the string matches the pattern, and 1 if it does not.
If the regular expression is syntactically incorrect, the conditional
expression returns 2.
If the <code>nocasematch</code> shell option
(see the description of <code>shopt</code> in <a href="#The-Shopt-Builtin">The Shopt Builtin</a>)
is enabled, the match is performed without regard to the case
of alphabetic characters.
</p>
<p>You can quote any part of the pattern
to force the quoted portion to be matched literally
instead of as a regular expression (see above).
If the pattern is stored in a shell variable, quoting the variable
expansion forces the entire pattern to be matched literally.
</p>
<p>The pattern will match if it matches any part of the string.
If you want to force the pattern to match the entire string,
anchor the pattern using the &lsquo;<samp>^</samp>&rsquo; and &lsquo;<samp>$</samp>&rsquo; regular expression
operators.
</p>
<p>For example, the following will match a line
(stored in the shell variable <code>line</code>)
if there is a sequence of characters anywhere in the value consisting of
any number, including zero, of 
characters in the <code>space</code> character class,
immediately followed by zero or one instances of &lsquo;<samp>a</samp>&rsquo;,
then a &lsquo;<samp>b</samp>&rsquo;:
</p>
<div class="example">
<pre class="example">[[ $line =~ [[:space:]]*(a)?b ]]
</pre></div>

<p>That means values for <code>line</code> like
&lsquo;<samp>aab</samp>&rsquo;, &lsquo;<samp>  aaaaaab</samp>&rsquo;, &lsquo;<samp>xaby</samp>&rsquo;, and &lsquo;<samp> ab</samp>&rsquo;
will all match,
as will a line containing a &lsquo;<samp>b</samp>&rsquo; anywhere in its value.
</p>
<p>If you want to match a character that&rsquo;s special to the regular expression
grammar (&lsquo;<samp>^$|[]()\.*+?</samp>&rsquo;), it has to be quoted to remove its special
meaning.
This means that in the pattern &lsquo;<samp>xxx.txt</samp>&rsquo;, the &lsquo;<samp>.</samp>&rsquo; matches any
character in the string (its usual regular expression meaning), but in the
pattern &lsquo;<samp>&quot;xxx.txt&quot;</samp>&rsquo;, it can only match a literal &lsquo;<samp>.</samp>&rsquo;.
</p>
<p>Likewise, if you want to include a character in your pattern that has a
special meaning to the regular expression grammar, you must make sure it&rsquo;s
not quoted.
If you want to anchor a pattern at the beginning or end of the string,
for instance, you cannot quote the &lsquo;<samp>^</samp>&rsquo; or &lsquo;<samp>$</samp>&rsquo;
characters using any form of shell quoting.
</p>
<p>If you want to match &lsquo;<samp>initial string</samp>&rsquo; at the start of a line,
the following will work:
</p><div class="example">
<pre class="example">[[ $line =~ ^&quot;initial string&quot; ]]
</pre></div>
<p>but this will not:
</p><div class="example">
<pre class="example">[[ $line =~ &quot;^initial string&quot; ]]
</pre></div>
<p>because in the second example the &lsquo;<samp>^</samp>&rsquo; is quoted and doesn&rsquo;t have its
usual special meaning.
</p>
<p>It is sometimes difficult to specify a regular expression properly
without using quotes, or to keep track of the quoting used by regular
expressions while paying attention to
shell quoting and the shell&rsquo;s quote removal.
Storing the regular expression in a shell variable is often a useful
way to avoid problems with quoting characters that are special to the
shell.
For example, the following is equivalent to the pattern used above:
</p>
<div class="example">
<pre class="example">pattern='[[:space:]]*(a)?b'
[[ $line =~ $pattern ]]
</pre></div>

<p>Shell programmers should take special care with backslashes, since
backslashes are used by both the shell and regular expressions to remove
the special meaning from the following character.
This means that after the shell&rsquo;s word expansions complete
(see <a href="#Shell-Expansions">Shell Expansions</a>),
any backslashes remaining in parts of the pattern
that were originally not quoted can remove the
special meaning of pattern characters.
If any part of the pattern is quoted, the shell does its best to ensure that
the regular expression treats those remaining backslashes as literal,
if they appeared in a quoted portion.
</p>
<p>The following two sets of commands are <em>not</em> equivalent:
</p>
<div class="example">
<pre class="example">pattern='\.'

[[ . =~ $pattern ]]
[[ . =~ \. ]]

[[ . =~ &quot;$pattern&quot; ]]
[[ . =~ '\.' ]]
</pre></div>

<p>The first two matches will succeed, but the second two will not, because
in the second two the backslash will be part of the pattern to be matched.
In the first two examples, the pattern passed to the regular expression
parser is &lsquo;<samp>\.</samp>&rsquo;. The backslash removes the special meaning from
&lsquo;<samp>.</samp>&rsquo;, so the literal &lsquo;<samp>.</samp>&rsquo; matches.
In the second two examples, the pattern passed to the regular expression
parser has the backslash quoted (e.g., &lsquo;<samp>\\\.</samp>&rsquo;), which will not match
the string, since it does not contain a backslash.
If the string in the first examples were anything other than &lsquo;<samp>.</samp>&rsquo;, say
&lsquo;<samp>a</samp>&rsquo;, the pattern would not match, because the quoted &lsquo;<samp>.</samp>&rsquo; in the
pattern loses its special meaning of matching any single character.
</p>
<p>Bracket expressions in regular expressions can be sources of errors as well,
since characters that are normally special in regular expressions
lose their special meanings between brackets.
However, you can use bracket expressions to match special pattern characters
without quoting them, so they are sometimes useful for this purpose.
</p>
<p>Though it might seem like a strange way to write it, the following pattern
will match a &lsquo;<samp>.</samp>&rsquo; in the string:
</p>
<div class="example">
<pre class="example">[[ . =~ [.] ]]
</pre></div>

<p>The shell performs any word expansions before passing the pattern
to the regular expression functions,
so you can assume that the shell&rsquo;s quoting takes precedence.
As noted above, the regular expression parser will interpret any
unquoted backslashes remaining in the pattern after shell expansion
according to its own rules.
The intention is to avoid making shell programmers quote things twice
as much as possible, so shell quoting should be sufficient to quote
special pattern characters where that&rsquo;s necessary.
</p>
<p>The array variable <code>BASH_REMATCH</code> records which parts of the string
matched the pattern.
The element of <code>BASH_REMATCH</code> with index 0 contains the portion of
the string matching the entire regular expression.
Substrings matched by parenthesized subexpressions within the regular
expression are saved in the remaining <code>BASH_REMATCH</code> indices.
The element of <code>BASH_REMATCH</code> with index <var>n</var> is the portion of the
string matching the <var>n</var>th parenthesized subexpression.
</p>
<p>Bash sets
<code>BASH_REMATCH</code>
in the global scope; declaring it as a local variable will lead to
unexpected results.
</p>
<p>Expressions may be combined using the following operators, listed
in decreasing order of precedence:
</p>
<dl compact="compact">
<dt><span><code>( <var>expression</var> )</code></span></dt>
<dd><p>Returns the value of <var>expression</var>.
This may be used to override the normal precedence of operators.
</p>
</dd>
<dt><span><code>! <var>expression</var></code></span></dt>
<dd><p>True if <var>expression</var> is false.
</p>
</dd>
<dt><span><code><var>expression1</var> &amp;&amp; <var>expression2</var></code></span></dt>
<dd><p>True if both <var>expression1</var> and <var>expression2</var> are true.
</p>
</dd>
<dt><span><code><var>expression1</var> || <var>expression2</var></code></span></dt>
<dd><p>True if either <var>expression1</var> or <var>expression2</var> is true.
</p></dd>
</dl>

<p>The <code>&amp;&amp;</code> and <code>||</code> operators do not evaluate <var>expression2</var> if the
value of <var>expression1</var> is sufficient to determine the return
value of the entire conditional expression.
</p></dd>
</dl>

<hr>
</div>
<div class="subsubsection" id="Command-Grouping">
<div class="header">
<p>
Previous: <a href="#Conditional-Constructs" accesskey="p" rel="prev">Conditional Constructs</a>, Up: <a href="#Compound-Commands" accesskey="u" rel="up">Compound Commands</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Grouping-Commands"></span><h4 class="subsubsection">3.2.5.3 Grouping Commands</h4>
<span id="index-commands_002c-grouping"></span>

<p>Bash provides two ways to group a list of commands to be executed
as a unit.  When commands are grouped, redirections may be applied
to the entire command list.  For example, the output of all the
commands in the list may be redirected to a single stream.
</p>
<dl compact="compact">
<dt><span><code>()</code></span></dt>
<dd><div class="example">
<pre class="example">( <var>list</var> )
</pre></div>

<p>Placing a list of commands between parentheses forces the shell to create
a subshell (see <a href="#Command-Execution-Environment">Command Execution Environment</a>), and each
of the commands in <var>list</var> is executed in that subshell environment.
Since the <var>list</var> is executed in a subshell, variable assignments do not
remain in effect after the subshell completes. 
</p>
</dd>
<dt id='index-_007b'><span><code>{}</code><a href='#index-_007b' class='copiable-anchor'> &para;</a></span></dt>
<dd><span id="index-_007d"></span>
<div class="example">
<pre class="example">{ <var>list</var>; }
</pre></div>

<p>Placing a list of commands between curly braces causes the list to
be executed in the current shell context.  No subshell is created.
The semicolon (or newline) following <var>list</var> is required.
</p></dd>
</dl>

<p>In addition to the creation of a subshell, there is a subtle difference
between these two constructs due to historical reasons.  The braces
are reserved words, so they must be separated from the <var>list</var>
by <code>blank</code>s or other shell metacharacters.
The parentheses are operators, and are
recognized as separate tokens by the shell even if they are not separated
from the <var>list</var> by whitespace.
</p>
<p>The exit status of both of these constructs is the exit status of
<var>list</var>.
</p>
<hr>
</div>
</div>
<div class="subsection" id="Coprocesses">
<div class="header">
<p>
Next: <a href="#GNU-Parallel" accesskey="n" rel="next">GNU Parallel</a>, Previous: <a href="#Compound-Commands" accesskey="p" rel="prev">Compound Commands</a>, Up: <a href="#Shell-Commands" accesskey="u" rel="up">Shell Commands</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Coprocesses-1"></span><h4 class="subsection">3.2.6 Coprocesses</h4>
<span id="index-coprocess"></span>

<p>A <code>coprocess</code> is a shell command preceded by the <code>coproc</code>
reserved word.
A coprocess is executed asynchronously in a subshell, as if the command
had been terminated with the &lsquo;<samp>&amp;</samp>&rsquo; control operator, with a two-way pipe
established between the executing shell and the coprocess.
</p>
<p>The syntax for a coprocess is:
</p>
<div class="example">
<pre class="example">coproc [<var>NAME</var>] <var>command</var> [<var>redirections</var>]
</pre></div>

<p>This creates a coprocess named <var>NAME</var>.
<var>command</var> may be either a simple command (see <a href="#Simple-Commands">Simple Commands</a>)
or a compound command (see <a href="#Compound-Commands">Compound Commands</a>).
<var>NAME</var> is a shell variable name.
If <var>NAME</var> is not supplied, the default name is <code>COPROC</code>.
</p>
<p>The recommended form to use for a coprocess is
</p>
<div class="example">
<pre class="example">coproc <var>NAME</var> { <var>command</var>; }
</pre></div>

<p>This form is recommended because simple commands result in the coprocess
always being named <code>COPROC</code>, and it is simpler to use and more complete
than the other compound commands.
</p>
<p>There are other forms of coprocesses:
</p>
<div class="example">
<pre class="example">coproc <var>NAME</var> <var>compound-command</var>
coproc <var>compound-command</var>
coproc <var>simple-command</var>
</pre></div>

<p>If <var>command</var> is a compound command, <var>NAME</var> is optional. The
word following <code>coproc</code> determines whether that word is interpreted
as a variable name: it is interpreted as <var>NAME</var> if it is not a
reserved word that introduces a compound command.
If <var>command</var> is a simple command, <var>NAME</var> is not allowed; this
is to avoid confusion between <var>NAME</var> and the first word of the simple
command.
</p>
<p>When the coprocess is executed, the shell creates an array variable
(see <a href="#Arrays">Arrays</a>)
named <var>NAME</var> in the context of the executing shell.
The standard output of <var>command</var>
is connected via a pipe to a file descriptor in the executing shell,
and that file descriptor is assigned to <var>NAME</var>[0].
The standard input of <var>command</var>
is connected via a pipe to a file descriptor in the executing shell,
and that file descriptor is assigned to <var>NAME</var>[1].
This pipe is established before any redirections specified by the
command (see <a href="#Redirections">Redirections</a>).
The file descriptors can be utilized as arguments to shell commands
and redirections using standard word expansions.
Other than those created to execute command and process substitutions,
the file descriptors are not available in subshells.
</p>
<p>The process ID of the shell spawned to execute the coprocess is
available as the value of the variable <code><var>NAME</var>_PID</code>.
The <code>wait</code>
builtin command may be used to wait for the coprocess to terminate.
</p>
<p>Since the coprocess is created as an asynchronous command,
the <code>coproc</code> command always returns success.
The return status of a coprocess is the exit status of <var>command</var>.
</p>
<hr>
</div>
<div class="subsection" id="GNU-Parallel">
<div class="header">
<p>
Previous: <a href="#Coprocesses" accesskey="p" rel="prev">Coprocesses</a>, Up: <a href="#Shell-Commands" accesskey="u" rel="up">Shell Commands</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="GNU-Parallel-1"></span><h4 class="subsection">3.2.7 GNU Parallel</h4>

<p>There are ways to run commands in parallel that are not built into Bash.
GNU Parallel is a tool to do just that.
</p>
<p>GNU Parallel, as its name suggests, can be used to build and run commands
in parallel.  You may run the same command with different arguments, whether
they are filenames, usernames, hostnames, or lines read from files.  GNU
Parallel provides shorthand references to many of the most common operations
(input lines, various portions of the input line, different ways to specify
the input source, and so on).  Parallel can replace <code>xargs</code> or feed
commands from its input sources to several different instances of Bash.
</p>
<p>For a complete description, refer to the GNU Parallel documentation, which
is available at
<a href="https://www.gnu.org/software/parallel/parallel_tutorial.html">https://www.gnu.org/software/parallel/parallel_tutorial.html</a>.
</p>
<hr>
</div>
</div>
<div class="section" id="Shell-Functions">
<div class="header">
<p>
Next: <a href="#Shell-Parameters" accesskey="n" rel="next">Shell Parameters</a>, Previous: <a href="#Shell-Commands" accesskey="p" rel="prev">Shell Commands</a>, Up: <a href="#Basic-Shell-Features" accesskey="u" rel="up">Basic Shell Features</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Shell-Functions-1"></span><h3 class="section">3.3 Shell Functions</h3>
<span id="index-shell-function"></span>
<span id="index-functions_002c-shell"></span>

<p>Shell functions are a way to group commands for later execution
using a single name for the group.  They are executed just like
a &quot;regular&quot; command.
When the name of a shell function is used as a simple command name,
the list of commands associated with that function name is executed.
Shell functions are executed in the current
shell context; no new process is created to interpret them.
</p>
<p>Functions are declared using this syntax:
<span id="index-function"></span>
</p><div class="example">
<pre class="example"><var>fname</var> () <var>compound-command</var> [ <var>redirections</var> ]
</pre></div>

<p>or
</p>
<div class="example">
<pre class="example">function <var>fname</var> [()] <var>compound-command</var> [ <var>redirections</var> ]
</pre></div>

<p>This defines a shell function named <var>fname</var>.  The reserved
word <code>function</code> is optional.
If the <code>function</code> reserved
word is supplied, the parentheses are optional.
The <em>body</em> of the function is the compound command
<var>compound-command</var> (see <a href="#Compound-Commands">Compound Commands</a>).
That command is usually a <var>list</var> enclosed between { and }, but
may be any compound command listed above.
If the <code>function</code> reserved word is used, but the
parentheses are not supplied, the braces are recommended.
<var>compound-command</var> is executed whenever <var>fname</var> is specified as the
name of a simple command.
When the shell is in <small>POSIX</small> mode (see <a href="#Bash-POSIX-Mode">Bash POSIX Mode</a>),
<var>fname</var> must be a valid shell name and
may not be the same as one of the special builtins
(see <a href="#Special-Builtins">Special Builtins</a>).
In default mode, a function name can be any unquoted shell word that does
not contain &lsquo;<samp>$</samp>&rsquo;.
Any redirections (see <a href="#Redirections">Redirections</a>) associated with the shell function
are performed when the function is executed.
A function definition may be deleted using the <samp>-f</samp> option to the
<code>unset</code> builtin (see <a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a>).
</p>
<p>The exit status of a function definition is zero unless a syntax error
occurs or a readonly function with the same name already exists.
When executed, the exit status of a function is the exit status of the
last command executed in the body.
</p>
<p>Note that for historical reasons, in the most common usage the curly braces
that surround the body of the function must be separated from the body by
<code>blank</code>s or newlines.
This is because the braces are reserved words and are only recognized
as such when they are separated from the command list
by whitespace or another shell metacharacter.
Also, when using the braces, the <var>list</var> must be terminated by a semicolon,
a &lsquo;<samp>&amp;</samp>&rsquo;, or a newline.
</p>
<p>When a function is executed, the arguments to the
function become the positional parameters
during its execution (see <a href="#Positional-Parameters">Positional Parameters</a>).
The special parameter &lsquo;<samp>#</samp>&rsquo; that expands to the number of
positional parameters is updated to reflect the change.
Special parameter <code>0</code> is unchanged.
The first element of the <code>FUNCNAME</code> variable is set to the
name of the function while the function is executing.
</p>
<p>All other aspects of the shell execution
environment are identical between a function and its caller
with these exceptions:
the <code>DEBUG</code> and <code>RETURN</code> traps
are not inherited unless the function has been given the
<code>trace</code> attribute using the <code>declare</code> builtin or
the <code>-o functrace</code> option has been enabled with
the <code>set</code> builtin,
(in which case all functions inherit the <code>DEBUG</code> and <code>RETURN</code> traps),
and the <code>ERR</code> trap is not inherited unless the <code>-o errtrace</code>
shell option has been enabled.
See <a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a>, for the description of the
<code>trap</code> builtin.
</p>
<p>The <code>FUNCNEST</code> variable, if set to a numeric value greater
than 0, defines a maximum function nesting level.  Function
invocations that exceed the limit cause the entire command to
abort.
</p>
<p>If the builtin command <code>return</code>
is executed in a function, the function completes and
execution resumes with the next command after the function
call.
Any command associated with the <code>RETURN</code> trap is executed
before execution resumes.
When a function completes, the values of the
positional parameters and the special parameter &lsquo;<samp>#</samp>&rsquo;
are restored to the values they had prior to the function&rsquo;s
execution.  If a numeric argument is given to <code>return</code>,
that is the function&rsquo;s return status; otherwise the function&rsquo;s
return status is the exit status of the last command executed
before the <code>return</code>.
</p>
<p>Variables local to the function may be declared with the
<code>local</code> builtin (<em>local variables</em>).
Ordinarily, variables and their values
are shared between a function and its caller.
These variables are visible only to
the function and the commands it invokes.  This is particularly
important when a shell function calls other functions.
</p>
<p>In the following description, the <em>current scope</em> is a currently-
executing function.
Previous scopes consist of that function&rsquo;s caller and so on,
back to the &quot;global&quot; scope, where the shell is not executing
any shell function.
Consequently, a local variable at the current local scope is a variable
declared using the <code>local</code> or <code>declare</code> builtins in the
function that is currently executing.
</p>
<p>Local variables &quot;shadow&quot; variables with the same name declared at
previous scopes.  For instance, a local variable declared in a function
hides a global variable of the same name: references and assignments
refer to the local variable, leaving the global variable unmodified.
When the function returns, the global variable is once again visible.
</p>
<p>The shell uses <em>dynamic scoping</em> to control a variable&rsquo;s visibility
within functions.
With dynamic scoping, visible variables and their values
are a result of the sequence of function calls that caused execution
to reach the current function.
The value of a variable that a function sees depends
on its value within its caller, if any, whether that caller is
the &quot;global&quot; scope or another shell function.
This is also the value that a local variable
declaration &quot;shadows&quot;, and the value that is restored when the function
returns.
</p>
<p>For example, if a variable <code>var</code> is declared as local in function
<code>func1</code>, and <code>func1</code> calls another function <code>func2</code>,
references to <code>var</code> made from within <code>func2</code> will resolve to the
local variable <code>var</code> from <code>func1</code>, shadowing any global variable
named <code>var</code>.
</p>
<p>The following script demonstrates this behavior.
When executed, the script displays
</p>
<div class="example">
<pre class="example">In func2, var = func1 local
</pre></div>

<div class="example">
<pre class="example">func1()
{
    local var='func1 local'
    func2
}

func2()
{
    echo &quot;In func2, var = $var&quot;
}

var=global
func1
</pre></div>

<p>The <code>unset</code> builtin also acts using the same dynamic scope: if a  
variable is local to the current scope, <code>unset</code> will unset it;         
otherwise the unset will refer to the variable found in any calling scope 
as described above.
If a variable at the current local scope is unset, it will remain so
(appearing as unset)
until it is reset in that scope or until the function returns.
Once the function returns, any instance of the variable at a previous
scope will become visible.
If the unset acts on a variable at a previous scope, any instance of a   
variable with that name that had been shadowed will become visible
(see below how <code>localvar_unset</code>shell option changes this behavior).
</p>
<p>Function names and definitions may be listed with the
<samp>-f</samp> option to the <code>declare</code> (<code>typeset</code>)
builtin command (see <a href="#Bash-Builtins">Bash Builtin Commands</a>).
The <samp>-F</samp> option to <code>declare</code> or <code>typeset</code>
will list the function names only
(and optionally the source file and line number, if the <code>extdebug</code>
shell option is enabled).
Functions may be exported so that child shell processes
(those created when executing a separate shell invocation)
automatically have them defined with the
<samp>-f</samp> option to the <code>export</code> builtin
(see <a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a>).
</p>
<p>Functions may be recursive.
The <code>FUNCNEST</code> variable may be used to limit the depth of the
function call stack and restrict the number of function invocations.
By default, no limit is placed on the number of recursive  calls.
</p>
<hr>
</div>
<div class="section" id="Shell-Parameters">
<div class="header">
<p>
Next: <a href="#Shell-Expansions" accesskey="n" rel="next">Shell Expansions</a>, Previous: <a href="#Shell-Functions" accesskey="p" rel="prev">Shell Functions</a>, Up: <a href="#Basic-Shell-Features" accesskey="u" rel="up">Basic Shell Features</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Shell-Parameters-1"></span><h3 class="section">3.4 Shell Parameters</h3>
<span id="index-parameters"></span>
<span id="index-variable_002c-shell"></span>
<span id="index-shell-variable"></span>


<p>A <em>parameter</em> is an entity that stores values.
It can be a <code>name</code>, a number, or one of the special characters
listed below.
A <em>variable</em> is a parameter denoted by a <code>name</code>.
A variable has a <code>value</code> and zero or more <code>attributes</code>.
Attributes are assigned using the <code>declare</code> builtin command
(see the description of the <code>declare</code> builtin in <a href="#Bash-Builtins">Bash Builtin Commands</a>).
</p>
<p>A parameter is set if it has been assigned a value.  The null string is
a valid value.  Once a variable is set, it may be unset only by using
the <code>unset</code> builtin command.
</p>
<p>A variable may be assigned to by a statement of the form
</p><div class="example">
<pre class="example"><var>name</var>=[<var>value</var>]
</pre></div>
<p>If <var>value</var>
is not given, the variable is assigned the null string.  All
<var>value</var>s undergo tilde expansion, parameter and variable expansion,
command substitution, arithmetic expansion, and quote
removal (see <a href="#Shell-Parameter-Expansion">Shell Parameter Expansion</a>).
If the variable has its <code>integer</code>
attribute set, then <var>value</var> 
is evaluated as an arithmetic expression even if the <code>$((&hellip;))</code>
expansion is not used (see <a href="#Arithmetic-Expansion">Arithmetic Expansion</a>).
Word splitting and filename expansion are not performed.
Assignment statements may also appear as arguments to the
<code>alias</code>, 
<code>declare</code>, <code>typeset</code>, <code>export</code>, <code>readonly</code>,
and <code>local</code> builtin commands (<em>declaration</em> commands).
When in <small>POSIX</small> mode (see <a href="#Bash-POSIX-Mode">Bash POSIX Mode</a>), these builtins may appear
in a command after one or more instances of the <code>command</code> builtin
and retain these assignment statement properties.
</p>
<p>In the context where an assignment statement is assigning a value  
to a shell variable or array index (see <a href="#Arrays">Arrays</a>), the &lsquo;<samp>+=</samp>&rsquo;
operator can be used to   
append to or add to the variable&rsquo;s previous value.
This includes arguments to builtin commands such as <code>declare</code> that
accept assignment statements (declaration commands).
When &lsquo;<samp>+=</samp>&rsquo; is applied to a variable for which the <code>integer</code> attribute
has been set, <var>value</var> is evaluated as an arithmetic expression and
added to the variable&rsquo;s current value, which is also evaluated.
When &lsquo;<samp>+=</samp>&rsquo; is applied to an array variable using compound assignment
(see <a href="#Arrays">Arrays</a>), the
variable&rsquo;s value is not unset (as it is when using &lsquo;<samp>=</samp>&rsquo;), and new
values are appended to the array beginning at one greater than the array&rsquo;s
maximum index (for indexed arrays),  or added as additional key-value pairs
in an associative array.
When applied to a string-valued variable, <var>value</var> is expanded and
appended to the variable&rsquo;s value.
</p>
<p>A variable can be assigned the <code>nameref</code> attribute using the
<samp>-n</samp> option to the <code>declare</code> or <code>local</code> builtin commands
(see <a href="#Bash-Builtins">Bash Builtin Commands</a>)
to create a <em>nameref</em>, or a reference to another variable.
This allows variables to be manipulated indirectly.
Whenever the nameref variable is referenced, assigned to, unset, or has
its attributes modified (other than using or changing the nameref
attribute itself), the
operation is actually performed on the variable specified by the nameref
variable&rsquo;s value.
A nameref is commonly used within shell functions to refer to a variable
whose name is passed as an argument to the function.
For instance, if a variable name is passed to a shell function as its first
argument, running
</p><div class="example">
<pre class="example">declare -n ref=$1
</pre></div>
<p>inside the function creates a nameref variable <code>ref</code> whose value is
the variable name passed as the first argument.
References and assignments to <code>ref</code>, and changes to its attributes,
are treated as references, assignments, and attribute modifications
to the variable whose name was passed as <code>$1</code>.
</p>
<p>If the control variable in a <code>for</code> loop has the nameref attribute,
the list of words can be a list of shell variables, and a name reference
will be established for each word in the list, in turn, when the loop is
executed.
Array variables cannot be given the nameref attribute.
However, nameref variables can reference array variables and subscripted
array variables.
Namerefs can be unset using the <samp>-n</samp> option to the <code>unset</code> builtin
(see <a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a>).
Otherwise, if <code>unset</code> is executed with the name of a nameref variable
as an argument, the variable referenced by the nameref variable will be unset.
</p>
<ul class="section-toc">
<li><a href="#Positional-Parameters" accesskey="1">Positional Parameters</a></li>
<li><a href="#Special-Parameters" accesskey="2">Special Parameters</a></li>
</ul>
<hr>
<div class="subsection" id="Positional-Parameters">
<div class="header">
<p>
Next: <a href="#Special-Parameters" accesskey="n" rel="next">Special Parameters</a>, Up: <a href="#Shell-Parameters" accesskey="u" rel="up">Shell Parameters</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Positional-Parameters-1"></span><h4 class="subsection">3.4.1 Positional Parameters</h4>
<span id="index-parameters_002c-positional"></span>

<p>A <em>positional parameter</em> is a parameter denoted by one or more
digits, other than the single digit <code>0</code>.  Positional parameters are
assigned from the shell&rsquo;s arguments when it is invoked,
and may be reassigned using the <code>set</code> builtin command.
Positional parameter <code>N</code> may be referenced as <code>${N}</code>, or
as <code>$N</code> when <code>N</code> consists of a single digit.
Positional parameters may not be assigned to with assignment statements.
The <code>set</code> and <code>shift</code> builtins are used to set and
unset them (see <a href="#Shell-Builtin-Commands">Shell Builtin Commands</a>).
The positional parameters are
temporarily replaced when a shell function is executed
(see <a href="#Shell-Functions">Shell Functions</a>).
</p>
<p>When a positional parameter consisting of more than a single
digit is expanded, it must be enclosed in braces.
</p>
<hr>
</div>
<div class="subsection" id="Special-Parameters">
<div class="header">
<p>
Previous: <a href="#Positional-Parameters" accesskey="p" rel="prev">Positional Parameters</a>, Up: <a href="#Shell-Parameters" accesskey="u" rel="up">Shell Parameters</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Special-Parameters-1"></span><h4 class="subsection">3.4.2 Special Parameters</h4>
<span id="index-parameters_002c-special"></span>

<p>The shell treats several parameters specially.  These parameters may
only be referenced; assignment to them is not allowed.
</p>
<dl compact="compact">
<dt id='index-_002a'><span><code>*</code><a href='#index-_002a' class='copiable-anchor'> &para;</a></span></dt>
<dd><span id="index-_0024_002a"></span>
<p>($*) Expands to the positional parameters, starting from one.
When the expansion is not within double quotes, each positional parameter
expands to a separate word.
In contexts where it is performed, those words
are subject to further word splitting and filename expansion.
When the expansion occurs within double quotes, it expands to a single word
with the value of each parameter separated by the first character of the
<code>IFS</code> special variable.  That is, <code>&quot;$*&quot;</code> is equivalent
to <code>&quot;$1<var>c</var>$2<var>c</var>&hellip;&quot;</code>, where <var>c</var>
is the first character of the value of the <code>IFS</code>
variable.
If <code>IFS</code> is unset, the parameters are separated by spaces.
If <code>IFS</code> is null, the parameters are joined without intervening
separators.
</p>
</dd>
<dt id='index-_0040'><span><code>@</code><a href='#index-_0040' class='copiable-anchor'> &para;</a></span></dt>
<dd><span id="index-_0024_0040"></span>
<p>($@) Expands to the positional parameters, starting from one.
In contexts where word splitting is performed, this expands each
positional parameter to a separate word; if not within double
quotes, these words are subject to word splitting.
In contexts where word splitting is not performed,
this expands to a single word
with each positional parameter separated by a space.
When the
expansion occurs within double quotes, and word splitting is performed,
each parameter expands to a
separate word.  That is, <code>&quot;$@&quot;</code> is equivalent to
<code>&quot;$1&quot; &quot;$2&quot; &hellip;</code>.
If the double-quoted expansion occurs within a word, the expansion of
the first parameter is joined with the beginning part of the original
word, and the expansion of the last parameter is joined with the last
part of the original word.
When there are no positional parameters, <code>&quot;$@&quot;</code> and
<code>$@</code>
expand to nothing (i.e., they are removed).
</p>
</dd>
<dt id='index-_0023'><span><code>#</code><a href='#index-_0023' class='copiable-anchor'> &para;</a></span></dt>
<dd><span id="index-_0024_0023"></span>
<p>($#) Expands to the number of positional parameters in decimal.
</p>
</dd>
<dt id='index-_003f'><span><code>?</code><a href='#index-_003f' class='copiable-anchor'> &para;</a></span></dt>
<dd><span id="index-_0024_003f"></span>
<p>($?) Expands to the exit status of the most recently executed foreground
pipeline.
</p>
</dd>
<dt id='index-_002d'><span><code>-</code><a href='#index-_002d' class='copiable-anchor'> &para;</a></span></dt>
<dd><span id="index-_0024_002d"></span>
<p>($-, a hyphen.)  Expands to the current option flags as specified upon
invocation, by the <code>set</code>
builtin command, or those set by the shell itself
(such as the <samp>-i</samp> option).
</p>
</dd>
<dt id='index-_0024'><span><code>$</code><a href='#index-_0024' class='copiable-anchor'> &para;</a></span></dt>
<dd><span id="index-_0024_0024"></span>
<p>($$) Expands to the process <small>ID</small> of the shell.  In a subshell, it
expands to the process <small>ID</small> of the invoking shell, not the subshell.
</p>
</dd>
<dt id='index-_0021-1'><span><code>!</code><a href='#index-_0021-1' class='copiable-anchor'> &para;</a></span></dt>
<dd><span id="index-_0024_0021"></span>
<p>($!) Expands to the process <small>ID</small> of the job most recently placed into the
background, whether executed as an asynchronous command or using
the <code>bg</code> builtin (see <a href="#Job-Control-Builtins">Job Control Builtins</a>).
</p>
</dd>
<dt id='index-0'><span><code>0</code><a href='#index-0' class='copiable-anchor'> &para;</a></span></dt>
<dd><span id="index-_00240"></span>
<p>($0) Expands to the name of the shell or shell script.  This is set at
shell initialization.  If Bash is invoked with a file of commands
(see <a href="#Shell-Scripts">Shell Scripts</a>), <code>$0</code> is set to the name of that file.
If Bash is started with the <samp>-c</samp> option (see <a href="#Invoking-Bash">Invoking Bash</a>),
then <code>$0</code> is set to the first argument after the string to be
executed, if one is present.  Otherwise, it is set
to the filename used to invoke Bash, as given by argument zero.
</p></dd>
</dl>

<hr>
</div>
</div>
<div class="section" id="Shell-Expansions">
<div class="header">
<p>
Next: <a href="#Redirections" accesskey="n" rel="next">Redirections</a>, Previous: <a href="#Shell-Parameters" accesskey="p" rel="prev">Shell Parameters</a>, Up: <a href="#Basic-Shell-Features" accesskey="u" rel="up">Basic Shell Features</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Shell-Expansions-1"></span><h3 class="section">3.5 Shell Expansions</h3>
<span id="index-expansion"></span>

<p>Expansion is performed on the command line after it has been split into
<code>token</code>s.  There are seven kinds of expansion performed:
</p>
<ul>
<li> brace expansion
</li><li> tilde expansion
</li><li> parameter and variable expansion
</li><li> command substitution
</li><li> arithmetic expansion
</li><li> word splitting
</li><li> filename expansion
</li></ul>


<p>The order of expansions is:
brace expansion;
tilde expansion, parameter and variable expansion, arithmetic expansion,
and command substitution (done in a left-to-right fashion);
word splitting;
and filename expansion.
</p>
<p>On systems that can support it, there is an additional expansion
available: <em>process substitution</em>.
This is performed at the
same time as tilde, parameter, variable, and arithmetic expansion and
command substitution.
</p>
<p>After these expansions are performed, quote characters present in the
original word are removed unless they have been quoted themselves
(<em>quote removal</em>).
</p>
<p>Only brace expansion, word splitting, and filename expansion
can increase the number of words of the expansion; other expansions
expand a single word to a single word.
The only exceptions to this are the expansions of
<code>&quot;$@&quot;</code> and <code>$*</code> (see <a href="#Special-Parameters">Special Parameters</a>), and
<code>&quot;${<var>name</var>[@]}&quot;</code> and <code>${<var>name</var>[*]}</code>
(see <a href="#Arrays">Arrays</a>).
</p>
<p>After all expansions, <code>quote removal</code> (see <a href="#Quote-Removal">Quote Removal</a>)
is performed.
</p>
<ul class="section-toc">
<li><a href="#Brace-Expansion" accesskey="1">Brace Expansion</a></li>
<li><a href="#Tilde-Expansion" accesskey="2">Tilde Expansion</a></li>
<li><a href="#Shell-Parameter-Expansion" accesskey="3">Shell Parameter Expansion</a></li>
<li><a href="#Command-Substitution" accesskey="4">Command Substitution</a></li>
<li><a href="#Arithmetic-Expansion" accesskey="5">Arithmetic Expansion</a></li>
<li><a href="#Process-Substitution" accesskey="6">Process Substitution</a></li>
<li><a href="#Word-Splitting" accesskey="7">Word Splitting</a></li>
<li><a href="#Filename-Expansion" accesskey="8">Filename Expansion</a></li>
<li><a href="#Quote-Removal" accesskey="9">Quote Removal</a></li>
</ul>
<hr>
<div class="subsection" id="Brace-Expansion">
<div class="header">
<p>
Next: <a href="#Tilde-Expansion" accesskey="n" rel="next">Tilde Expansion</a>, Up: <a href="#Shell-Expansions" accesskey="u" rel="up">Shell Expansions</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Brace-Expansion-1"></span><h4 class="subsection">3.5.1 Brace Expansion</h4>
<span id="index-brace-expansion"></span>
<span id="index-expansion_002c-brace"></span>

<p>Brace expansion is a mechanism by which arbitrary strings may be generated.
This mechanism is similar to
<em>filename expansion</em> (see <a href="#Filename-Expansion">Filename Expansion</a>),
but the filenames generated need not exist.
Patterns to be brace expanded take the form of an optional <var>preamble</var>,
followed by either a series of comma-separated strings or a sequence expression
between a pair of braces,
followed by an optional <var>postscript</var>.
The preamble is prefixed to each string contained within the braces, and
the postscript is then appended to each resulting string, expanding left
to right.
</p>
<p>Brace expansions may be nested.
The results of each expanded string are not sorted; left to right order
is preserved.
For example,
</p><div class="example">
<pre class="example">bash$ echo a{d,c,b}e
ade ace abe
</pre></div>

<p>A sequence expression takes the form <code>{<var>x</var>..<var>y</var>[..<var>incr</var>]}</code>,
where <var>x</var> and <var>y</var> are either integers or letters,
and <var>incr</var>, an optional increment, is an integer.
When integers are supplied, the expression expands to each number between
<var>x</var> and <var>y</var>, inclusive.
Supplied integers may be prefixed with &lsquo;<samp>0</samp>&rsquo; to force each term to have the
same width.
When either <var>x</var> or <var>y</var> begins with a zero, the shell
attempts to force all generated terms to contain the same number of digits,
zero-padding where necessary.
When letters are supplied, the expression expands to each character
lexicographically between <var>x</var> and <var>y</var>, inclusive,
using the default C locale.
Note that both <var>x</var> and <var>y</var> must be of the same type
(integer or letter).
When the increment is supplied, it is used as the difference between
each term.  The default increment is 1 or -1 as appropriate.
</p>
<p>Brace expansion is performed before any other expansions,
and any characters special to other expansions are preserved
in the result.  It is strictly textual.  Bash
does not apply any syntactic interpretation to the context of the
expansion or the text between the braces.
</p>
<p>A correctly-formed brace expansion must contain unquoted opening
and closing braces, and at least one unquoted comma or a valid
sequence expression.
Any incorrectly formed brace expansion is left unchanged.
</p>
<p>A { or &lsquo;<samp>,</samp>&rsquo; may be quoted with a backslash to prevent its
being considered part of a brace expression.
To avoid conflicts with parameter expansion, the string &lsquo;<samp>${</samp>&rsquo;
is not considered eligible for brace expansion,
and inhibits brace expansion until the closing &lsquo;<samp>}</samp>&rsquo;.
</p>
<p>This construct is typically used as shorthand when the common
prefix of the strings to be generated is longer than in the
above example:
</p><div class="example">
<pre class="example">mkdir /usr/local/src/bash/{old,new,dist,bugs}
</pre></div>
<p>or
</p><div class="example">
<pre class="example">chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}
</pre></div>

<hr>
</div>
<div class="subsection" id="Tilde-Expansion">
<div class="header">
<p>
Next: <a href="#Shell-Parameter-Expansion" accesskey="n" rel="next">Shell Parameter Expansion</a>, Previous: <a href="#Brace-Expansion" accesskey="p" rel="prev">Brace Expansion</a>, Up: <a href="#Shell-Expansions" accesskey="u" rel="up">Shell Expansions</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Tilde-Expansion-1"></span><h4 class="subsection">3.5.2 Tilde Expansion</h4>
<span id="index-tilde-expansion"></span>
<span id="index-expansion_002c-tilde"></span>

<p>If a word begins with an unquoted tilde character (&lsquo;<samp>~</samp>&rsquo;), all of the
characters up to the first unquoted slash (or all characters,
if there is no unquoted slash) are considered a <em>tilde-prefix</em>.
If none of the characters in the tilde-prefix are quoted, the
characters in the tilde-prefix following the tilde are treated as a
possible <em>login name</em>.
If this login name is the null string, the tilde is replaced with the
value of the <code>HOME</code> shell variable.
If <code>HOME</code> is unset, the home directory of the user executing the
shell is substituted instead.
Otherwise, the tilde-prefix is replaced with the home directory
associated with the specified login name.
</p>
<p>If the tilde-prefix is &lsquo;<samp>~+</samp>&rsquo;, the value of
the shell variable <code>PWD</code> replaces the tilde-prefix.
If the tilde-prefix is &lsquo;<samp>~-</samp>&rsquo;, the value of the shell variable
<code>OLDPWD</code>, if it is set, is substituted.
</p>
<p>If the characters following the tilde in the tilde-prefix consist of a
number <var>N</var>, optionally prefixed by a &lsquo;<samp>+</samp>&rsquo; or a &lsquo;<samp>-</samp>&rsquo;,
the tilde-prefix is replaced with the
corresponding element from the directory stack, as it would be displayed
by the <code>dirs</code> builtin invoked with the characters following tilde
in the tilde-prefix as an argument (see <a href="#The-Directory-Stack">The Directory Stack</a>).
If the tilde-prefix, sans the tilde, consists of a number without a
leading &lsquo;<samp>+</samp>&rsquo; or &lsquo;<samp>-</samp>&rsquo;, &lsquo;<samp>+</samp>&rsquo; is assumed.
</p>
<p>If the login name is invalid, or the tilde expansion fails, the word is
left unchanged.
</p>
<p>Each variable assignment is checked for unquoted tilde-prefixes immediately
following a &lsquo;<samp>:</samp>&rsquo; or the first &lsquo;<samp>=</samp>&rsquo;.
In these cases, tilde expansion is also performed.
Consequently, one may use filenames with tildes in assignments to
<code>PATH</code>, <code>MAILPATH</code>, and <code>CDPATH</code>,
and the shell assigns the expanded value.
</p>
<p>The following table shows how Bash treats unquoted tilde-prefixes:
</p>
<dl compact="compact">
<dt><span><code>~</code></span></dt>
<dd><p>The value of <code>$HOME</code>
</p></dd>
<dt><span><code>~/foo</code></span></dt>
<dd><p><samp>$HOME/foo</samp>
</p>
</dd>
<dt><span><code>~fred/foo</code></span></dt>
<dd><p>The subdirectory <code>foo</code> of the home directory of the user
<code>fred</code>
</p>
</dd>
<dt><span><code>~+/foo</code></span></dt>
<dd><p><samp>$PWD/foo</samp>
</p>
</dd>
<dt><span><code>~-/foo</code></span></dt>
<dd><p><samp>${OLDPWD-'~-'}/foo</samp>
</p>
</dd>
<dt><span><code>~<var>N</var></code></span></dt>
<dd><p>The string that would be displayed by &lsquo;<samp>dirs +<var>N</var></samp>&rsquo;
</p>
</dd>
<dt><span><code>~+<var>N</var></code></span></dt>
<dd><p>The string that would be displayed by &lsquo;<samp>dirs +<var>N</var></samp>&rsquo;
</p>
</dd>
<dt><span><code>~-<var>N</var></code></span></dt>
<dd><p>The string that would be displayed by &lsquo;<samp>dirs -<var>N</var></samp>&rsquo;
</p></dd>
</dl>

<p>Bash also performs tilde expansion on words satisfying the conditions of
variable assignments (see <a href="#Shell-Parameters">Shell Parameters</a>)
when they appear as arguments to simple commands.
Bash does not do this, except for the declaration commands listed
above, when in <small>POSIX</small> mode.
</p>
<hr>
</div>
<div class="subsection" id="Shell-Parameter-Expansion">
<div class="header">
<p>
Next: <a href="#Command-Substitution" accesskey="n" rel="next">Command Substitution</a>, Previous: <a href="#Tilde-Expansion" accesskey="p" rel="prev">Tilde Expansion</a>, Up: <a href="#Shell-Expansions" accesskey="u" rel="up">Shell Expansions</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Shell-Parameter-Expansion-1"></span><h4 class="subsection">3.5.3 Shell Parameter Expansion</h4>
<span id="index-parameter-expansion"></span>
<span id="index-expansion_002c-parameter"></span>

<p>The &lsquo;<samp>$</samp>&rsquo; character introduces parameter expansion,
command substitution, or arithmetic expansion.  The parameter name
or symbol to be expanded may be enclosed in braces, which
are optional but serve to protect the variable to be expanded from
characters immediately following it which could be
interpreted as part of the name.
</p>
<p>When braces are used, the matching ending brace is the first &lsquo;<samp>}</samp>&rsquo;
not escaped by a backslash or within a quoted string, and not within an
embedded arithmetic expansion, command substitution, or parameter
expansion.
</p>
<p>The basic form of parameter expansion is ${<var>parameter</var>}.
The value of <var>parameter</var> is substituted.
The <var>parameter</var> is a shell parameter as described above
(see <a href="#Shell-Parameters">Shell Parameters</a>) or an array reference (see <a href="#Arrays">Arrays</a>).
The braces are required when <var>parameter</var>
is a positional parameter with more than one digit,
or when <var>parameter</var> is followed by a character that is not to be
interpreted as part of its name.
</p>
<p>If the first character of <var>parameter</var> is an exclamation point (!),
and <var>parameter</var> is not a nameref,
it introduces a level of indirection.
Bash uses the value formed by expanding the rest of
<var>parameter</var> as the new <var>parameter</var>; this is then
expanded and that value is used in the rest of the expansion, rather
than the expansion of the original <var>parameter</var>.
This is known as <code>indirect expansion</code>.
The value is subject to tilde expansion,
parameter expansion, command substitution, and arithmetic expansion.
If <var>parameter</var> is a nameref, this expands to the name of the
variable referenced by <var>parameter</var> instead of performing the
complete indirect expansion.
The exceptions to this are the expansions of ${!<var>prefix</var>*}
and ${!<var>name</var>[@]}
described below.
The exclamation point must immediately follow the left brace in order to
introduce indirection.
</p>
<p>In each of the cases below, <var>word</var> is subject to tilde expansion,
parameter expansion, command substitution, and arithmetic expansion.
</p>
<p>When not performing substring expansion, using the form described
below (e.g., &lsquo;<samp>:-</samp>&rsquo;), Bash tests for a parameter that is unset or null.
Omitting the colon results in a test only for a parameter that is unset.
Put another way, if the colon is included,
the operator tests for both <var>parameter</var>&rsquo;s existence and that its value
is not null; if the colon is omitted, the operator tests only for existence.
</p>
<dl compact="compact">
<dt><span><code>${<var>parameter</var>:-<var>word</var>}</code></span></dt>
<dd><p>If <var>parameter</var> is unset or null, the expansion of
<var>word</var> is substituted.  Otherwise, the value of
<var>parameter</var> is substituted.
</p>
<div class="example">
<pre class="example">$ v=123
$ echo ${v-unset}
123
</pre></div>

</dd>
<dt><span><code>${<var>parameter</var>:=<var>word</var>}</code></span></dt>
<dd><p>If <var>parameter</var>
is unset or null, the expansion of <var>word</var>
is assigned to <var>parameter</var>.
The value of <var>parameter</var> is then substituted. 
Positional parameters and special parameters may not be assigned to
in this way.
</p>
<div class="example">
<pre class="example">$ var=
$ : ${var:=DEFAULT}
$ echo $var
DEFAULT
</pre></div>

</dd>
<dt><span><code>${<var>parameter</var>:?<var>word</var>}</code></span></dt>
<dd><p>If <var>parameter</var>
is null or unset, the expansion of <var>word</var> (or a message
to that effect if <var>word</var>
is not present) is written to the standard error and the shell, if it
is not interactive, exits.  Otherwise, the value of <var>parameter</var> is
substituted.
</p>
<div class="example">
<pre class="example">$ var=
$ : ${var:?var is unset or null}
bash: var: var is unset or null
</pre></div>

</dd>
<dt><span><code>${<var>parameter</var>:+<var>word</var>}</code></span></dt>
<dd><p>If <var>parameter</var>
is null or unset, nothing is substituted, otherwise the expansion of
<var>word</var> is substituted.
</p>
<div class="example">
<pre class="example">$ var=123
$ echo ${var:+var is set and not null}
var is set and not null
</pre></div>

</dd>
<dt><span><code>${<var>parameter</var>:<var>offset</var>}</code></span></dt>
<dt><span><code>${<var>parameter</var>:<var>offset</var>:<var>length</var>}</code></span></dt>
<dd><p>This is referred to as Substring Expansion.
It expands to up to <var>length</var> characters of the value of <var>parameter</var>
starting at the character specified by <var>offset</var>.
If <var>parameter</var> is &lsquo;<samp>@</samp>&rsquo; or &lsquo;<samp>*</samp>&rsquo;, an indexed array subscripted by
&lsquo;<samp>@</samp>&rsquo; or &lsquo;<samp>*</samp>&rsquo;, or an associative array name, the results differ as
described below.
If <var>length</var> is omitted, it expands to the substring of the value of
<var>parameter</var> starting at the character specified by <var>offset</var>
and extending to the end of the value.
<var>length</var> and <var>offset</var> are arithmetic expressions
(see <a href="#Shell-Arithmetic">Shell Arithmetic</a>).
</p>
<p>If <var>offset</var> evaluates to a number less than zero, the value
is used as an offset in characters
from the end of the value of <var>parameter</var>.
If <var>length</var> evaluates to a number less than zero,
it is interpreted as an offset in characters
from the end of the value of <var>parameter</var> rather than
a number of characters, and the expansion is the characters between
<var>offset</var> and that result.
Note that a negative offset must be separated from the colon by at least
one space to avoid being confused with the &lsquo;<samp>:-</samp>&rsquo; expansion.
</p>
<p>Here are some examples illustrating substring expansion on parameters and
subscripted arrays:
</p>
<pre class="verbatim">$ string=01234567890abcdefgh
$ echo ${string:7}
7890abcdefgh
$ echo ${string:7:0}

$ echo ${string:7:2}
78
$ echo ${string:7:-2}
7890abcdef
$ echo ${string: -7}
bcdefgh
$ echo ${string: -7:0}

$ echo ${string: -7:2}
bc
$ echo ${string: -7:-2}
bcdef
$ set -- 01234567890abcdefgh
$ echo ${1:7}
7890abcdefgh
$ echo ${1:7:0}

$ echo ${1:7:2}
78
$ echo ${1:7:-2}
7890abcdef
$ echo ${1: -7}
bcdefgh
$ echo ${1: -7:0}

$ echo ${1: -7:2}
bc
$ echo ${1: -7:-2}
bcdef
$ array[0]=01234567890abcdefgh
$ echo ${array[0]:7}
7890abcdefgh
$ echo ${array[0]:7:0}

$ echo ${array[0]:7:2}
78
$ echo ${array[0]:7:-2}
7890abcdef
$ echo ${array[0]: -7}
bcdefgh
$ echo ${array[0]: -7:0}

$ echo ${array[0]: -7:2}
bc
$ echo ${array[0]: -7:-2}
bcdef
</pre>
<p>If <var>parameter</var> is &lsquo;<samp>@</samp>&rsquo; or &lsquo;<samp>*</samp>&rsquo;, the result is <var>length</var>
positional parameters beginning at <var>offset</var>.
A negative <var>offset</var> is taken relative to one greater than the greatest
positional parameter, so an offset of -1 evaluates to the last positional
parameter.
It is an expansion error if <var>length</var> evaluates to a number less than zero.
</p>
<p>The following examples illustrate substring expansion using positional
parameters:
</p>
<pre class="verbatim">$ set -- 1 2 3 4 5 6 7 8 9 0 a b c d e f g h
$ echo ${@:7}
7 8 9 0 a b c d e f g h
$ echo ${@:7:0}

$ echo ${@:7:2}
7 8
$ echo ${@:7:-2}
bash: -2: substring expression &lt; 0
$ echo ${@: -7:2}
b c
$ echo ${@:0}
./bash 1 2 3 4 5 6 7 8 9 0 a b c d e f g h
$ echo ${@:0:2}
./bash 1
$ echo ${@: -7:0}

</pre>
<p>If <var>parameter</var> is an indexed array name subscripted
by &lsquo;<samp>@</samp>&rsquo; or &lsquo;<samp>*</samp>&rsquo;, the result is the <var>length</var>
members of the array beginning with <code>${<var>parameter</var>[<var>offset</var>]}</code>.
A negative <var>offset</var> is taken relative to one greater than the maximum
index of the specified array.
It is an expansion error if <var>length</var> evaluates to a number less than zero.
</p>
<p>These examples show how you can use substring expansion with indexed
arrays:
</p>
<pre class="verbatim">$ array=(0 1 2 3 4 5 6 7 8 9 0 a b c d e f g h)
$ echo ${array[@]:7}
7 8 9 0 a b c d e f g h
$ echo ${array[@]:7:2}
7 8
$ echo ${array[@]: -7:2}
b c
$ echo ${array[@]: -7:-2}
bash: -2: substring expression &lt; 0
$ echo ${array[@]:0}
0 1 2 3 4 5 6 7 8 9 0 a b c d e f g h
$ echo ${array[@]:0:2}
0 1
$ echo ${array[@]: -7:0}

</pre>
<p>Substring expansion applied to an associative array produces undefined
results.
</p>
<p>Substring indexing is zero-based unless the positional parameters
are used, in which case the indexing starts at 1 by default.
If <var>offset</var> is 0, and the positional parameters are used, <code>$0</code> is
prefixed to the list.
</p>
</dd>
<dt><span><code>${!<var>prefix</var>*}</code></span></dt>
<dt><span><code>${!<var>prefix</var>@}</code></span></dt>
<dd><p>Expands to the names of variables whose names begin with <var>prefix</var>,
separated by the first character of the <code>IFS</code> special variable.
When &lsquo;<samp>@</samp>&rsquo; is used and the expansion appears within double quotes, each
variable name expands to a separate word.
</p>
</dd>
<dt><span><code>${!<var>name</var>[@]}</code></span></dt>
<dt><span><code>${!<var>name</var>[*]}</code></span></dt>
<dd><p>If <var>name</var> is an array variable, expands to the list of array indices
(keys) assigned in <var>name</var>.
If <var>name</var> is not an array, expands to 0 if <var>name</var> is set and null
otherwise.
When &lsquo;<samp>@</samp>&rsquo; is used and the expansion appears within double quotes, each
key expands to a separate word.
</p>
</dd>
<dt><span><code>${#<var>parameter</var>}</code></span></dt>
<dd><p>The length in characters of the expanded value of <var>parameter</var> is
substituted.
If <var>parameter</var> is &lsquo;<samp>*</samp>&rsquo; or &lsquo;<samp>@</samp>&rsquo;, the value substituted
is the number of positional parameters.
If <var>parameter</var> is an array name subscripted by &lsquo;<samp>*</samp>&rsquo; or &lsquo;<samp>@</samp>&rsquo;, 
the value substituted is the number of elements in the array.
If <var>parameter</var>
is an indexed array name subscripted by a negative number, that number is
interpreted as relative to one greater than the maximum index of
<var>parameter</var>, so negative indices count back from the end of the
array, and an index of -1 references the last element.
</p>
</dd>
<dt><span><code>${<var>parameter</var>#<var>word</var>}</code></span></dt>
<dt><span><code>${<var>parameter</var>##<var>word</var>}</code></span></dt>
<dd><p>The <var>word</var>
is expanded to produce a pattern and matched according to the rules
described below (see <a href="#Pattern-Matching">Pattern Matching</a>).  If the pattern matches
the beginning of the expanded value of <var>parameter</var>,
then the result of the expansion is the expanded value of <var>parameter</var>
with the shortest matching pattern (the &lsquo;<samp>#</samp>&rsquo; case) or the
longest matching pattern (the &lsquo;<samp>##</samp>&rsquo; case) deleted.
If <var>parameter</var> is &lsquo;<samp>@</samp>&rsquo; or &lsquo;<samp>*</samp>&rsquo;,
the pattern removal operation is applied to each positional
parameter in turn, and the expansion is the resultant list.
If <var>parameter</var> is an array variable subscripted with
&lsquo;<samp>@</samp>&rsquo; or &lsquo;<samp>*</samp>&rsquo;,
the pattern removal operation is applied to each member of the
array in turn, and the expansion is the resultant list.
</p>
</dd>
<dt><span><code>${<var>parameter</var>%<var>word</var>}</code></span></dt>
<dt><span><code>${<var>parameter</var>%%<var>word</var>}</code></span></dt>
<dd><p>The <var>word</var>
is expanded to produce a pattern and matched according to the rules
described below (see <a href="#Pattern-Matching">Pattern Matching</a>).
If the pattern matches a trailing portion of the expanded value of
<var>parameter</var>, then the result of the expansion is the value of
<var>parameter</var> with the shortest matching pattern (the &lsquo;<samp>%</samp>&rsquo; case)
or the longest matching pattern (the &lsquo;<samp>%%</samp>&rsquo; case) deleted.
If <var>parameter</var> is &lsquo;<samp>@</samp>&rsquo; or &lsquo;<samp>*</samp>&rsquo;,
the pattern removal operation is applied to each positional
parameter in turn, and the expansion is the resultant list.
If <var>parameter</var>
is an array variable subscripted with &lsquo;<samp>@</samp>&rsquo; or &lsquo;<samp>*</samp>&rsquo;,
the pattern removal operation is applied to each member of the
array in turn, and the expansion is the resultant list.
</p>
</dd>
<dt><span><code>${<var>parameter</var>/<var>pattern</var>/<var>string</var>}</code></span></dt>
<dt><span><code>${<var>parameter</var>//<var>pattern</var>/<var>string</var>}</code></span></dt>
<dt><span><code>${<var>parameter</var>/#<var>pattern</var>/<var>string</var>}</code></span></dt>
<dt><span><code>${<var>parameter</var>/%<var>pattern</var>/<var>string</var>}</code></span></dt>
<dd><p>The <var>pattern</var> is expanded to produce a pattern just as in
filename expansion.
<var>Parameter</var> is expanded and the longest match of <var>pattern</var>
against its value is replaced with <var>string</var>.
<var>string</var> undergoes tilde expansion, parameter and variable expansion,
arithmetic expansion, command and process substitution, and quote removal.
The match is performed according to the rules described below
(see <a href="#Pattern-Matching">Pattern Matching</a>).
</p>
<p>In the first form above, only the first match is replaced.
If there are two slashes separating <var>parameter</var> and <var>pattern</var>
(the second form above), all matches of <var>pattern</var> are
replaced with <var>string</var>.
If <var>pattern</var> is preceded by &lsquo;<samp>#</samp>&rsquo; (the third form above),
it must match at the beginning of the expanded value of <var>parameter</var>.
If <var>pattern</var> is preceded by &lsquo;<samp>%</samp>&rsquo; (the fourth form above),
it must match at the end of the expanded value of <var>parameter</var>.
If the expansion of <var>string</var> is null,
matches of <var>pattern</var> are deleted.
If <var>string</var> is null,
matches of <var>pattern</var> are deleted
and the &lsquo;<samp>/</samp>&rsquo; following <var>pattern</var> may be omitted.
</p>
<p>If the <code>patsub_replacement</code> shell option is enabled using <code>shopt</code>,
any unquoted instances of &lsquo;<samp>&amp;</samp>&rsquo; in <var>string</var> are replaced with the
matching portion of <var>pattern</var>.
This is intended to duplicate a common <code>sed</code> idiom.
</p>
<p>Quoting any part of <var>string</var> inhibits replacement in the
expansion of the quoted portion, including replacement strings stored
in shell variables.
Backslash will escape &lsquo;<samp>&amp;</samp>&rsquo; in <var>string</var>; the backslash is removed
in order to permit a literal &lsquo;<samp>&amp;</samp>&rsquo; in the replacement string.
Users should take care if <var>string</var> is double-quoted to avoid
unwanted interactions between the backslash and double-quoting, since
backslash has special meaning within double quotes.
Pattern substitution performs the check for unquoted &lsquo;<samp>&amp;</samp>&rsquo; after
expanding <var>string</var>,
so users should ensure to properly quote any occurrences of &lsquo;<samp>&amp;</samp>&rsquo;
they want to be taken literally in the replacement
and ensure any instances of &lsquo;<samp>&amp;</samp>&rsquo; they want to be replaced are unquoted.
</p>
<p>For instance,
</p>
<div class="example">
<pre class="example">var=abcdef
rep='&amp; '
echo ${var/abc/&amp; }
echo &quot;${var/abc/&amp; }&quot;
echo ${var/abc/$rep}
echo &quot;${var/abc/$rep}&quot;
</pre></div>

<p>will display four lines of &quot;abc def&quot;, while
</p>
<div class="example">
<pre class="example">var=abcdef
rep='&amp; '
echo ${var/abc/\&amp; }
echo &quot;${var/abc/\&amp; }&quot;
echo ${var/abc/&quot;&amp; &quot;}
echo ${var/abc/&quot;$rep&quot;}
</pre></div>

<p>will display four lines of &quot;&amp; def&quot;.
Like the pattern removal operators, double quotes surrounding the
replacement string quote the expanded characters, while double quotes
enclosing the entire parameter substitution do not, since
the expansion is performed in a
context that doesn&rsquo;t take any enclosing double quotes into account.
</p>
<p>Since backslash can escape &lsquo;<samp>&amp;</samp>&rsquo;, it can also escape a backslash in
the replacement string.
This means that &lsquo;<samp>\\</samp>&rsquo; will insert a literal
backslash into the replacement, so these two <code>echo</code> commands
</p>
<div class="example">
<pre class="example">var=abcdef
rep='\\&amp;xyz'
echo ${var/abc/\\&amp;xyz}
echo ${var/abc/$rep}
</pre></div>

<p>will both output &lsquo;<samp>\abcxyzdef</samp>&rsquo;.
</p>
<p>It should rarely be necessary to enclose only <var>string</var> in double
quotes.
</p>
<p>If the <code>nocasematch</code> shell option   
(see the description of <code>shopt</code> in <a href="#The-Shopt-Builtin">The Shopt Builtin</a>)
is enabled, the match is performed without regard to the case   
of alphabetic characters.
If <var>parameter</var> is &lsquo;<samp>@</samp>&rsquo; or &lsquo;<samp>*</samp>&rsquo;,
the substitution operation is applied to each positional
parameter in turn, and the expansion is the resultant list.
If <var>parameter</var>
is an array variable subscripted with &lsquo;<samp>@</samp>&rsquo; or &lsquo;<samp>*</samp>&rsquo;,
the substitution operation is applied to each member of the
array in turn, and the expansion is the resultant list.
</p>
</dd>
<dt><span><code>${<var>parameter</var>^<var>pattern</var>}</code></span></dt>
<dt><span><code>${<var>parameter</var>^^<var>pattern</var>}</code></span></dt>
<dt><span><code>${<var>parameter</var>,<var>pattern</var>}</code></span></dt>
<dt><span><code>${<var>parameter</var>,,<var>pattern</var>}</code></span></dt>
<dd><p>This expansion modifies the case of alphabetic characters in <var>parameter</var>.
The <var>pattern</var> is expanded to produce a pattern just as in
filename expansion.
Each character in the expanded value of <var>parameter</var> is tested against
<var>pattern</var>, and, if it matches the pattern, its case is converted.
The pattern should not attempt to match more than one character.
</p>
<p>The &lsquo;<samp>^</samp>&rsquo; operator converts lowercase letters matching <var>pattern</var>
to uppercase; the &lsquo;<samp>,</samp>&rsquo; operator converts matching uppercase letters
to lowercase.
The &lsquo;<samp>^^</samp>&rsquo; and &lsquo;<samp>,,</samp>&rsquo; expansions convert each matched character in the
expanded value; the &lsquo;<samp>^</samp>&rsquo; and &lsquo;<samp>,</samp>&rsquo; expansions match and convert only
the first character in the expanded value.
If <var>pattern</var> is omitted, it is treated like a &lsquo;<samp>?</samp>&rsquo;, which matches
every character.
</p>
<p>If <var>parameter</var> is &lsquo;<samp>@</samp>&rsquo; or &lsquo;<samp>*</samp>&rsquo;,
the case modification operation is applied to each positional
parameter in turn, and the expansion is the resultant list.
If <var>parameter</var>
is an array variable subscripted with &lsquo;<samp>@</samp>&rsquo; or &lsquo;<samp>*</samp>&rsquo;,
the case modification operation is applied to each member of the
array in turn, and the expansion is the resultant list.
</p>
</dd>
<dt><span><code>${<var>parameter</var>@<var>operator</var>}</code></span></dt>
<dd><p>The expansion is either a transformation of the value of <var>parameter</var>
or information about <var>parameter</var> itself, depending on the value of
<var>operator</var>.  Each <var>operator</var> is a single letter:
</p>
<dl compact="compact">
<dt><span><code>U</code></span></dt>
<dd><p>The expansion is a string that is the value of <var>parameter</var> with lowercase
alphabetic characters converted to uppercase.
</p></dd>
<dt><span><code>u</code></span></dt>
<dd><p>The expansion is a string that is the value of <var>parameter</var> with the first
character converted to uppercase, if it is alphabetic.
</p></dd>
<dt><span><code>L</code></span></dt>
<dd><p>The expansion is a string that is the value of <var>parameter</var> with uppercase
alphabetic characters converted to lowercase.
</p></dd>
<dt><span><code>Q</code></span></dt>
<dd><p>The expansion is a string that is the value of <var>parameter</var> quoted in a
format that can be reused as input.
</p></dd>
<dt><span><code>E</code></span></dt>
<dd><p>The expansion is a string that is the value of <var>parameter</var> with backslash
escape sequences expanded as with the <code>$'&hellip;'</code> quoting mechanism.
</p></dd>
<dt><span><code>P</code></span></dt>
<dd><p>The expansion is a string that is the result of expanding the value of
<var>parameter</var> as if it were a prompt string (see <a href="#Controlling-the-Prompt">Controlling the Prompt</a>).
</p></dd>
<dt><span><code>A</code></span></dt>
<dd><p>The expansion is a string in the form of
an assignment statement or <code>declare</code> command that, if
evaluated, will recreate <var>parameter</var> with its attributes and value.
</p></dd>
<dt><span><code>K</code></span></dt>
<dd><p>Produces a possibly-quoted version of the value of <var>parameter</var>,
except that it prints the values of
indexed and associative arrays as a sequence of quoted key-value pairs
(see <a href="#Arrays">Arrays</a>).
</p></dd>
<dt><span><code>a</code></span></dt>
<dd><p>The expansion is a string consisting of flag values representing
<var>parameter</var>&rsquo;s attributes.
</p></dd>
<dt><span><code>k</code></span></dt>
<dd><p>Like the &lsquo;<samp>K</samp>&rsquo; transformation, but expands the keys and values of
indexed and associative arrays to separate words after word splitting.
</p></dd>
</dl>

<p>If <var>parameter</var> is &lsquo;<samp>@</samp>&rsquo; or &lsquo;<samp>*</samp>&rsquo;,
the operation is applied to each positional
parameter in turn, and the expansion is the resultant list.
If <var>parameter</var>
is an array variable subscripted with &lsquo;<samp>@</samp>&rsquo; or &lsquo;<samp>*</samp>&rsquo;,
the operation is applied to each member of the
array in turn, and the expansion is the resultant list.
</p>
<p>The result of the expansion is subject to word splitting and filename
expansion as described below.
</p></dd>
</dl>

<hr>
</div>
<div class="subsection" id="Command-Substitution">
<div class="header">
<p>
Next: <a href="#Arithmetic-Expansion" accesskey="n" rel="next">Arithmetic Expansion</a>, Previous: <a href="#Shell-Parameter-Expansion" accesskey="p" rel="prev">Shell Parameter Expansion</a>, Up: <a href="#Shell-Expansions" accesskey="u" rel="up">Shell Expansions</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Command-Substitution-1"></span><h4 class="subsection">3.5.4 Command Substitution</h4>
<span id="index-command-substitution"></span>

<p>Command substitution allows the output of a command to replace
the command itself.
Command substitution occurs when a command is enclosed as follows:
</p><div class="example">
<pre class="example">$(<var>command</var>)
</pre></div>
<p>or
</p><div class="example">
<pre class="example">`<var>command</var>`
</pre></div>

<p>Bash performs the expansion by executing <var>command</var> in a subshell environment
and replacing the command substitution with the standard output of the
command, with any trailing newlines deleted.
Embedded newlines are not deleted, but they may be removed during
word splitting.
The command substitution <code>$(cat <var>file</var>)</code> can be
replaced by the equivalent but faster <code>$(&lt; <var>file</var>)</code>.
</p>
<p>When the old-style backquote form of substitution is used,
backslash retains its literal meaning except when followed by
&lsquo;<samp>$</samp>&rsquo;, &lsquo;<samp>`</samp>&rsquo;, or &lsquo;<samp>\</samp>&rsquo;. 
The first backquote not preceded by a backslash terminates the
command substitution.
When using the <code>$(<var>command</var>)</code> form, all characters between
the parentheses make up the command; none are treated specially.
</p>
<p>Command substitutions may be nested.  To nest when using the backquoted
form, escape the inner backquotes with backslashes.
</p>
<p>If the substitution appears within double quotes, word splitting and
filename expansion are not performed on the results.
</p>
<hr>
</div>
<div class="subsection" id="Arithmetic-Expansion">
<div class="header">
<p>
Next: <a href="#Process-Substitution" accesskey="n" rel="next">Process Substitution</a>, Previous: <a href="#Command-Substitution" accesskey="p" rel="prev">Command Substitution</a>, Up: <a href="#Shell-Expansions" accesskey="u" rel="up">Shell Expansions</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Arithmetic-Expansion-1"></span><h4 class="subsection">3.5.5 Arithmetic Expansion</h4>
<span id="index-expansion_002c-arithmetic"></span>
<span id="index-arithmetic-expansion"></span>

<p>Arithmetic expansion allows the evaluation of an arithmetic expression
and the substitution of the result.  The format for arithmetic expansion is:
</p>
<div class="example">
<pre class="example">$(( <var>expression</var> ))
</pre></div>

<p>The <var>expression</var> undergoes the same expansions
as if it were within double quotes,
but double quote characters in <var>expression</var> are not treated specially
and are removed.
All tokens in the expression undergo parameter and variable expansion,
command substitution, and quote removal.
The result is treated as the arithmetic expression to be evaluated.
Arithmetic expansions may be nested. 
</p>
<p>The evaluation is performed according to the rules listed below
(see <a href="#Shell-Arithmetic">Shell Arithmetic</a>).
If the expression is invalid, Bash prints a message indicating
failure to the standard error and no substitution occurs.
</p>
<hr>
</div>
<div class="subsection" id="Process-Substitution">
<div class="header">
<p>
Next: <a href="#Word-Splitting" accesskey="n" rel="next">Word Splitting</a>, Previous: <a href="#Arithmetic-Expansion" accesskey="p" rel="prev">Arithmetic Expansion</a>, Up: <a href="#Shell-Expansions" accesskey="u" rel="up">Shell Expansions</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Process-Substitution-1"></span><h4 class="subsection">3.5.6 Process Substitution</h4>
<span id="index-process-substitution"></span>

<p>Process substitution allows a process&rsquo;s input or output to be
referred to using a filename.
It takes the form of 
</p><div class="example">
<pre class="example">&lt;(<var>list</var>)
</pre></div>
<p>or
</p><div class="example">
<pre class="example">&gt;(<var>list</var>)
</pre></div>
<p>The process <var>list</var> is run asynchronously, and its input or output 
appears as a filename.
This filename is
passed as an argument to the current command as the result of the
expansion.
If the <code>&gt;(<var>list</var>)</code> form is used, writing to
the file will provide input for <var>list</var>.  If the
<code>&lt;(<var>list</var>)</code> form is used, the file passed as an
argument should be read to obtain the output of <var>list</var>.
Note that no space may appear between the <code>&lt;</code> or <code>&gt;</code>
and the left parenthesis, otherwise the construct would be interpreted
as a redirection.
Process substitution is supported on systems that support named
pipes (<small>FIFO</small>s) or the <samp>/dev/fd</samp> method of naming open files.
</p>
<p>When available, process substitution is performed simultaneously with
parameter and variable expansion, command substitution, and arithmetic
expansion.
</p>
<hr>
</div>
<div class="subsection" id="Word-Splitting">
<div class="header">
<p>
Next: <a href="#Filename-Expansion" accesskey="n" rel="next">Filename Expansion</a>, Previous: <a href="#Process-Substitution" accesskey="p" rel="prev">Process Substitution</a>, Up: <a href="#Shell-Expansions" accesskey="u" rel="up">Shell Expansions</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Word-Splitting-1"></span><h4 class="subsection">3.5.7 Word Splitting</h4>
<span id="index-word-splitting"></span>

<p>The shell scans the results of parameter expansion, command substitution,
and arithmetic expansion that did not occur within double quotes for
word splitting.
</p>
<p>The shell treats each character of <code>$IFS</code> as a delimiter, and splits
the results of the other expansions into words using these characters
as field terminators.
If <code>IFS</code> is unset, or its value is exactly <code>&lt;space&gt;&lt;tab&gt;&lt;newline&gt;</code>,
the default, then sequences of
<code> &lt;space&gt;</code>, <code>&lt;tab&gt;</code>, and <code>&lt;newline&gt;</code>
at the beginning and end of the results of the previous
expansions are ignored, and any sequence of <code>IFS</code>
characters not at the beginning or end serves to delimit words.
If <code>IFS</code> has a value other than the default, then sequences of
the whitespace characters <code>space</code>, <code>tab</code>, and <code>newline</code>
are ignored at the beginning and end of the
word, as long as the whitespace character is in the
value of <code>IFS</code> (an <code>IFS</code> whitespace character).
Any character in <code>IFS</code> that is not <code>IFS</code>
whitespace, along with any adjacent <code>IFS</code>
whitespace characters, delimits a field.  A sequence of <code>IFS</code>
whitespace characters is also treated as a delimiter.
If the value of <code>IFS</code> is null, no word splitting occurs.
</p>
<p>Explicit null arguments (<code>&quot;&quot;</code> or <code>''</code>) are retained
and passed to commands as empty strings.
Unquoted implicit null arguments, resulting from the expansion of
parameters that have no values, are removed.
If a parameter with no value is expanded within double quotes, a
null argument results and is retained
and passed to a command as an empty string.
When a quoted null argument appears as part of a word whose expansion is
non-null, the null argument is removed.
That is, the word
<code>-d''</code> becomes <code>-d</code> after word splitting and
null argument removal.
</p>
<p>Note that if no expansion occurs, no splitting
is performed.
</p>
<hr>
</div>
<div class="subsection" id="Filename-Expansion">
<div class="header">
<p>
Next: <a href="#Quote-Removal" accesskey="n" rel="next">Quote Removal</a>, Previous: <a href="#Word-Splitting" accesskey="p" rel="prev">Word Splitting</a>, Up: <a href="#Shell-Expansions" accesskey="u" rel="up">Shell Expansions</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Filename-Expansion-1"></span><h4 class="subsection">3.5.8 Filename Expansion</h4>
<span id="index-expansion_002c-filename"></span>
<span id="index-expansion_002c-pathname"></span>
<span id="index-filename-expansion"></span>
<span id="index-pathname-expansion"></span>

<p>After word splitting, unless the <samp>-f</samp> option has been set
(see <a href="#The-Set-Builtin">The Set Builtin</a>), Bash scans each word for the characters
&lsquo;<samp>*</samp>&rsquo;, &lsquo;<samp>?</samp>&rsquo;, and &lsquo;<samp>[</samp>&rsquo;.
If one of these characters appears, and is not quoted, then the word is
regarded as a <var>pattern</var>,
and replaced with an alphabetically sorted list of
filenames matching the pattern (see <a href="#Pattern-Matching">Pattern Matching</a>).
If no matching filenames are found,
and the shell option <code>nullglob</code> is disabled, the word is left
unchanged.
If the <code>nullglob</code> option is set, and no matches are found, the word
is removed.
If the <code>failglob</code> shell option is set, and no matches are found,
an error message is printed and the command is not executed.
If the shell option <code>nocaseglob</code> is enabled, the match is performed
without regard to the case of alphabetic characters.
</p>
<p>When a pattern is used for filename expansion, the character &lsquo;<samp>.</samp>&rsquo;
at the start of a filename or immediately following a slash
must be matched explicitly, unless the shell option <code>dotglob</code> is set.
In order to match the filenames &lsquo;<samp>.</samp>&rsquo; and &lsquo;<samp>..</samp>&rsquo;,
the pattern must begin with &lsquo;<samp>.</samp>&rsquo; (for example, &lsquo;<samp>.?</samp>&rsquo;),
even if <code>dotglob</code> is set.
If the <code>globskipdots</code> shell option is enabled, the filenames
&lsquo;<samp>.</samp>&rsquo; and &lsquo;<samp>..</samp>&rsquo; are never matched, even if the pattern begins
with a &lsquo;<samp>.</samp>&rsquo;.
When not matching filenames, the &lsquo;<samp>.</samp>&rsquo; character is not treated specially.
</p>
<p>When matching a filename, the slash character must always be
matched explicitly by a slash in the pattern, but in other matching
contexts it can be matched by a special pattern character as described
below (see <a href="#Pattern-Matching">Pattern Matching</a>).
</p>
<p>See the description of <code>shopt</code> in <a href="#The-Shopt-Builtin">The Shopt Builtin</a>,
for a description of the <code>nocaseglob</code>, <code>nullglob</code>,
<code>globskipdots</code>,
<code>failglob</code>, and <code>dotglob</code> options.
</p>
<p>The <code>GLOBIGNORE</code>
shell variable may be used to restrict the set of file names matching a
pattern.  If <code>GLOBIGNORE</code>
is set, each matching file name that also matches one of the patterns in
<code>GLOBIGNORE</code> is removed from the list of matches.
If the <code>nocaseglob</code> option is set, the matching against the patterns in
<code>GLOBIGNORE</code> is performed without regard to case.
The filenames
<samp>.</samp> and <samp>..</samp>
are always ignored when <code>GLOBIGNORE</code>
is set and not null.
However, setting <code>GLOBIGNORE</code> to a non-null value has the effect of
enabling the <code>dotglob</code>
shell option, so all other filenames beginning with a
&lsquo;<samp>.</samp>&rsquo; will match.
To get the old behavior of ignoring filenames beginning with a
&lsquo;<samp>.</samp>&rsquo;, make &lsquo;<samp>.*</samp>&rsquo; one of the patterns in <code>GLOBIGNORE</code>.
The <code>dotglob</code> option is disabled when <code>GLOBIGNORE</code>
is unset.
</p>
<ul class="section-toc">
<li><a href="#Pattern-Matching" accesskey="1">Pattern Matching</a></li>
</ul>
<hr>
<div class="subsubsection" id="Pattern-Matching">
<div class="header">
<p>
Up: <a href="#Filename-Expansion" accesskey="u" rel="up">Filename Expansion</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Pattern-Matching-1"></span><h4 class="subsubsection">3.5.8.1 Pattern Matching</h4>
<span id="index-pattern-matching"></span>
<span id="index-matching_002c-pattern"></span>

<p>Any character that appears in a pattern, other than the special pattern
characters described below, matches itself.
The <small>NUL</small> character may not occur in a pattern.
A backslash escapes the following character; the
escaping backslash is discarded when matching.
The special pattern characters must be quoted if they are to be matched
literally.
</p>
<p>The special pattern characters have the following meanings:
</p><dl compact="compact">
<dt><span><code>*</code></span></dt>
<dd><p>Matches any string, including the null string.
When the <code>globstar</code> shell option is enabled, and &lsquo;<samp>*</samp>&rsquo; is used in
a filename expansion context, two adjacent &lsquo;<samp>*</samp>&rsquo;s used as a single
pattern will match all files and zero or more directories and
subdirectories.
If followed by a &lsquo;<samp>/</samp>&rsquo;, two adjacent &lsquo;<samp>*</samp>&rsquo;s will match only
directories and subdirectories.
</p></dd>
<dt><span><code>?</code></span></dt>
<dd><p>Matches any single character.
</p></dd>
<dt><span><code>[&hellip;]</code></span></dt>
<dd><p>Matches any one of the enclosed characters.  A pair of characters
separated by a hyphen denotes a <var>range expression</var>;
any character that falls between those two characters, inclusive,
using the current locale&rsquo;s collating sequence and character set,
is matched.  If the first character following the
&lsquo;<samp>[</samp>&rsquo; is a &lsquo;<samp>!</samp>&rsquo;  or a &lsquo;<samp>^</samp>&rsquo;
then any character not enclosed is matched.  A &lsquo;<samp>-</samp>&rsquo;
may be matched by including it as the first or last character
in the set.  A &lsquo;<samp>]</samp>&rsquo; may be matched by including it as the first
character in the set.
The sorting order of characters in range expressions,
and the characters included in the range,
are determined by
the current locale and the values of the
<code>LC_COLLATE</code> and <code>LC_ALL</code> shell variables, if set.
</p>
<p>For example, in the default C locale, &lsquo;<samp>[a-dx-z]</samp>&rsquo; is equivalent to
&lsquo;<samp>[abcdxyz]</samp>&rsquo;.  Many locales sort characters in dictionary order, and in
these locales &lsquo;<samp>[a-dx-z]</samp>&rsquo; is typically not equivalent to &lsquo;<samp>[abcdxyz]</samp>&rsquo;;
it might be equivalent to &lsquo;<samp>[aBbCcDdxYyZz]</samp>&rsquo;, for example.  To obtain
the traditional interpretation of ranges in bracket expressions, you can
force the use of the C locale by setting the <code>LC_COLLATE</code> or
<code>LC_ALL</code> environment variable to the value &lsquo;<samp>C</samp>&rsquo;, or enable the
<code>globasciiranges</code> shell option.
</p>
<p>Within &lsquo;<samp>[</samp>&rsquo; and &lsquo;<samp>]</samp>&rsquo;, <em>character classes</em> can be specified
using the syntax
<code>[:</code><var>class</var><code>:]</code>, where <var>class</var> is one of the
following classes defined in the <small>POSIX</small> standard:
</p><div class="example">
<pre class="example">alnum   alpha   ascii   blank   cntrl   digit   graph   lower
print   punct   space   upper   word    xdigit
</pre></div>
<p>A character class matches any character belonging to that class.
The <code>word</code> character class matches letters, digits, and the character
&lsquo;<samp>_</samp>&rsquo;.
</p>
<p>Within &lsquo;<samp>[</samp>&rsquo; and &lsquo;<samp>]</samp>&rsquo;, an <em>equivalence class</em> can be
specified using the syntax <code>[=</code><var>c</var><code>=]</code>, which
matches all characters with the same collation weight (as defined
by the current locale) as the character <var>c</var>.
</p>
<p>Within &lsquo;<samp>[</samp>&rsquo; and &lsquo;<samp>]</samp>&rsquo;, the syntax <code>[.</code><var>symbol</var><code>.]</code>
matches the collating symbol <var>symbol</var>.
</p></dd>
</dl>

<p>If the <code>extglob</code> shell option is enabled using the <code>shopt</code>
builtin, the shell recognizes several extended pattern matching operators.
In the following description, a <var>pattern-list</var> is a list of one
or more patterns separated by a &lsquo;<samp>|</samp>&rsquo;.
When matching filenames, the <code>dotglob</code> shell option determines
the set of filenames that are tested, as described above.
Composite patterns may be formed using one or more of the following
sub-patterns:
</p>
<dl compact="compact">
<dt><span><code>?(<var>pattern-list</var>)</code></span></dt>
<dd><p>Matches zero or one occurrence of the given patterns.
</p>
</dd>
<dt><span><code>*(<var>pattern-list</var>)</code></span></dt>
<dd><p>Matches zero or more occurrences of the given patterns.
</p>
</dd>
<dt><span><code>+(<var>pattern-list</var>)</code></span></dt>
<dd><p>Matches one or more occurrences of the given patterns.
</p>
</dd>
<dt><span><code>@(<var>pattern-list</var>)</code></span></dt>
<dd><p>Matches one of the given patterns.
</p>
</dd>
<dt><span><code>!(<var>pattern-list</var>)</code></span></dt>
<dd><p>Matches anything except one of the given patterns.
</p></dd>
</dl>

<p>The <code>extglob</code> option changes the behavior of the parser, since the
parentheses are normally treated as operators with syntactic meaning.
To ensure that extended matching patterns are parsed correctly, make sure
that <code>extglob</code> is enabled before parsing constructs containing the
patterns, including shell functions and command substitutions.
</p>
<p>When matching filenames, the <code>dotglob</code> shell option determines
the set of filenames that are tested:
when <code>dotglob</code> is enabled, the set of filenames includes all files
beginning with &lsquo;<samp>.</samp>&rsquo;, but the filenames
&lsquo;<samp>.</samp>&rsquo; and &lsquo;<samp>..</samp>&rsquo; must be matched by a
pattern or sub-pattern that begins with a dot;
when it is disabled, the set does not
include any filenames beginning with &ldquo;.&rdquo; unless the pattern
or sub-pattern begins with a &lsquo;<samp>.</samp>&rsquo;.
As above, &lsquo;<samp>.</samp>&rsquo; only has a special meaning when matching filenames. 
</p>
<p>Complicated extended pattern matching against long strings is slow,
especially when the patterns contain alternations and the strings
contain multiple matches.
Using separate matches against shorter strings, or using arrays of
strings instead of a single long string, may be faster.
</p>
<hr>
</div>
</div>
<div class="subsection" id="Quote-Removal">
<div class="header">
<p>
Previous: <a href="#Filename-Expansion" accesskey="p" rel="prev">Filename Expansion</a>, Up: <a href="#Shell-Expansions" accesskey="u" rel="up">Shell Expansions</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Quote-Removal-1"></span><h4 class="subsection">3.5.9 Quote Removal</h4>

<p>After the preceding expansions, all unquoted occurrences of the
characters &lsquo;<samp>\</samp>&rsquo;, &lsquo;<samp>'</samp>&rsquo;, and &lsquo;<samp>&quot;</samp>&rsquo; that did not
result from one of the above expansions are removed.
</p>
<hr>
</div>
</div>
<div class="section" id="Redirections">
<div class="header">
<p>
Next: <a href="#Executing-Commands" accesskey="n" rel="next">Executing Commands</a>, Previous: <a href="#Shell-Expansions" accesskey="p" rel="prev">Shell Expansions</a>, Up: <a href="#Basic-Shell-Features" accesskey="u" rel="up">Basic Shell Features</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Redirections-1"></span><h3 class="section">3.6 Redirections</h3>
<span id="index-redirection"></span>

<p>Before a command is executed, its input and output
may be <em>redirected</em>
using a special notation interpreted by the shell.
<em>Redirection</em> allows commands&rsquo; file handles to be
duplicated, opened, closed,
made to refer to different files,
and can change the files the command reads from and writes to.
Redirection may also be used to modify file handles in the
current shell execution environment.  The following redirection
operators may precede or appear anywhere within a
simple command or may follow a command.
Redirections are processed in the order they appear, from
left to right.
</p>
<p>Each redirection that may be preceded by a file descriptor number
may instead be preceded by a word of the form {<var>varname</var>}.
In this case, for each redirection operator except
&gt;&amp;- and &lt;&amp;-, the shell will allocate a file descriptor greater
than 10 and assign it to {<var>varname</var>}.  If &gt;&amp;- or &lt;&amp;- is preceded
by {<var>varname</var>}, the value of <var>varname</var> defines the file
descriptor to close.
If {<var>varname</var>} is supplied, the redirection persists beyond
the scope of the command, allowing the shell programmer to manage
the file descriptor&rsquo;s lifetime manually.
The <code>varredir_close</code> shell option manages this behavior
(see <a href="#The-Shopt-Builtin">The Shopt Builtin</a>).
</p>
<p>In the following descriptions, if the file descriptor number is
omitted, and the first character of the redirection operator is
&lsquo;<samp>&lt;</samp>&rsquo;, the redirection refers to the standard input (file
descriptor 0).  If the first character of the redirection operator
is &lsquo;<samp>&gt;</samp>&rsquo;, the redirection refers to the standard output (file
descriptor 1).
</p>
<p>The word following the redirection operator in the following
descriptions, unless otherwise noted, is subjected to brace expansion,
tilde expansion, parameter expansion, command substitution, arithmetic
expansion, quote removal, filename expansion, and word splitting.
If it expands to more than one word, Bash reports an error.
</p>
<p>Note that the order of redirections is significant.  For example,
the command
</p><div class="example">
<pre class="example">ls &gt; <var>dirlist</var> 2&gt;&amp;1
</pre></div>
<p>directs both standard output (file descriptor 1) and standard error
(file descriptor 2) to the file <var>dirlist</var>, while the command
</p><div class="example">
<pre class="example">ls 2&gt;&amp;1 &gt; <var>dirlist</var>
</pre></div>
<p>directs only the standard output to file <var>dirlist</var>,
because the standard error was made a copy of the standard output
before the standard output was redirected to <var>dirlist</var>.
</p>
<p>Bash handles several filenames specially when they are used in
redirections, as described in the following table.
If the operating system on which Bash is running provides these
special files, bash will use them; otherwise it will emulate them
internally with the behavior described below.
</p>
<dl compact="compact">
<dt><span><code>/dev/fd/<var>fd</var></code></span></dt>
<dd><p>If <var>fd</var> is a valid integer, file descriptor <var>fd</var> is duplicated.
</p>
</dd>
<dt><span><code>/dev/stdin</code></span></dt>
<dd><p>File descriptor 0 is duplicated.
</p>
</dd>
<dt><span><code>/dev/stdout</code></span></dt>
<dd><p>File descriptor 1 is duplicated.
</p>
</dd>
<dt><span><code>/dev/stderr</code></span></dt>
<dd><p>File descriptor 2 is duplicated.
</p>
</dd>
<dt><span><code>/dev/tcp/<var>host</var>/<var>port</var></code></span></dt>
<dd><p>If <var>host</var> is a valid hostname or Internet address, and <var>port</var>
is an integer port number or service name, Bash attempts to open
the corresponding TCP socket.
</p>
</dd>
<dt><span><code>/dev/udp/<var>host</var>/<var>port</var></code></span></dt>
<dd><p>If <var>host</var> is a valid hostname or Internet address, and <var>port</var>
is an integer port number or service name, Bash attempts to open 
the corresponding UDP socket.
</p></dd>
</dl>

<p>A failure to open or create a file causes the redirection to fail.
</p>
<p>Redirections using file descriptors greater than 9 should be used with
care, as they may conflict with file descriptors the shell uses
internally.
</p>
<ul class="section-toc">
<li><a href="#Redirecting-Input" accesskey="1">Redirecting Input</a></li>
<li><a href="#Redirecting-Output" accesskey="2">Redirecting Output</a></li>
<li><a href="#Appending-Redirected-Output" accesskey="3">Appending Redirected Output</a></li>
<li><a href="#Redirecting-Standard-Output-and-Standard-Error" accesskey="4">Redirecting Standard Output and Standard Error</a></li>
<li><a href="#Appending-Standard-Output-and-Standard-Error" accesskey="5">Appending Standard Output and Standard Error</a></li>
<li><a href="#Here-Documents" accesskey="6">Here Documents</a></li>
<li><a href="#Here-Strings" accesskey="7">Here Strings</a></li>
<li><a href="#Duplicating-File-Descriptors" accesskey="8">Duplicating File Descriptors</a></li>
<li><a href="#Moving-File-Descriptors" accesskey="9">Moving File Descriptors</a></li>
<li><a href="#Opening-File-Descriptors-for-Reading-and-Writing">Opening File Descriptors for Reading and Writing</a></li>
</ul>
<div class="subsection" id="Redirecting-Input">
<h4 class="subsection">3.6.1 Redirecting Input</h4>
<p>Redirection of input causes the file whose name results from
the expansion of <var>word</var>
to be opened for reading on file descriptor <code>n</code>,
or the standard input (file descriptor 0) if <code>n</code>
is not specified.
</p>
<p>The general format for redirecting input is:
</p><div class="example">
<pre class="example">[<var>n</var>]&lt;<var>word</var>
</pre></div>

</div>
<div class="subsection" id="Redirecting-Output">
<h4 class="subsection">3.6.2 Redirecting Output</h4>
<p>Redirection of output causes the file whose name results from
the expansion of <var>word</var>
to be opened for writing on file descriptor <var>n</var>,
or the standard output (file descriptor 1) if <var>n</var>
is not specified.  If the file does not exist it is created;
if it does exist it is truncated to zero size.
</p>
<p>The general format for redirecting output is:
</p><div class="example">
<pre class="example">[<var>n</var>]&gt;[|]<var>word</var>
</pre></div>

<p>If the redirection operator is &lsquo;<samp>&gt;</samp>&rsquo;, and the <code>noclobber</code>
option to the <code>set</code> builtin has been enabled, the redirection
will fail if the file whose name results from the expansion of
<var>word</var> exists and is a regular file.
If the redirection operator is &lsquo;<samp>&gt;|</samp>&rsquo;, or the redirection operator is
&lsquo;<samp>&gt;</samp>&rsquo; and the <code>noclobber</code> option is not enabled, the redirection
is attempted even if the file named by <var>word</var> exists.
</p>
</div>
<div class="subsection" id="Appending-Redirected-Output">
<h4 class="subsection">3.6.3 Appending Redirected Output</h4>
<p>Redirection of output in this fashion
causes the file whose name results from
the expansion of <var>word</var>
to be opened for appending on file descriptor <var>n</var>,
or the standard output (file descriptor 1) if <var>n</var>
is not specified.  If the file does not exist it is created.
</p>
<p>The general format for appending output is:
</p><div class="example">
<pre class="example">[<var>n</var>]&gt;&gt;<var>word</var>
</pre></div>

</div>
<div class="subsection" id="Redirecting-Standard-Output-and-Standard-Error">
<h4 class="subsection">3.6.4 Redirecting Standard Output and Standard Error</h4>
<p>This construct allows both the
standard output (file descriptor 1) and
the standard error output (file descriptor 2)
to be redirected to the file whose name is the
expansion of <var>word</var>.
</p>
<p>There are two formats for redirecting standard output and
standard error:
</p><div class="example">
<pre class="example">&amp;&gt;<var>word</var>
</pre></div>
<p>and
</p><div class="example">
<pre class="example">&gt;&amp;<var>word</var>
</pre></div>
<p>Of the two forms, the first is preferred.
This is semantically equivalent to
</p><div class="example">
<pre class="example">&gt;<var>word</var> 2&gt;&amp;1
</pre></div>
<p>When using the second form, <var>word</var> may not expand to a number or
&lsquo;<samp>-</samp>&rsquo;.  If it does, other redirection operators apply
(see Duplicating File Descriptors below) for compatibility reasons.
</p>
</div>
<div class="subsection" id="Appending-Standard-Output-and-Standard-Error">
<h4 class="subsection">3.6.5 Appending Standard Output and Standard Error</h4>
<p>This construct allows both the
standard output (file descriptor 1) and
the standard error output (file descriptor 2)
to be appended to the file whose name is the
expansion of <var>word</var>.
</p>
<p>The format for appending standard output and standard error is:
</p><div class="example">
<pre class="example">&amp;&gt;&gt;<var>word</var>
</pre></div>
<p>This is semantically equivalent to
</p><div class="example">
<pre class="example">&gt;&gt;<var>word</var> 2&gt;&amp;1
</pre></div>
<p>(see Duplicating File Descriptors below).
</p>
</div>
<div class="subsection" id="Here-Documents">
<h4 class="subsection">3.6.6 Here Documents</h4>
<p>This type of redirection instructs the shell to read input from the
current source until a line containing only <var>word</var>
(with no trailing blanks) is seen.  All of
the lines read up to that point are then used as the standard
input (or file descriptor <var>n</var> if <var>n</var> is specified) for a command.
</p>
<p>The format of here-documents is:
</p><div class="example">
<pre class="example">[<var>n</var>]&lt;&lt;[-]<var>word</var>
        <var>here-document</var>
<var>delimiter</var>
</pre></div>

<p>No parameter and variable expansion, command substitution,
arithmetic expansion, or filename expansion is performed on
<var>word</var>.  If any part of <var>word</var> is quoted, the
<var>delimiter</var> is the result of quote removal on <var>word</var>,
and the lines in the here-document are not expanded.
If <var>word</var> is unquoted,
all lines of the here-document are subjected to
parameter expansion, command substitution, and arithmetic expansion,
the character sequence <code>\newline</code> is ignored, and &lsquo;<samp>\</samp>&rsquo;
must be used to quote the characters
&lsquo;<samp>\</samp>&rsquo;, &lsquo;<samp>$</samp>&rsquo;, and &lsquo;<samp>`</samp>&rsquo;.
</p>
<p>If the redirection operator is &lsquo;<samp>&lt;&lt;-</samp>&rsquo;,
then all leading tab characters are stripped from input lines and the
line containing <var>delimiter</var>.
This allows here-documents within shell scripts to be indented in a
natural fashion.
</p>
</div>
<div class="subsection" id="Here-Strings">
<h4 class="subsection">3.6.7 Here Strings</h4>
<p>A variant of here documents, the format is:
</p><div class="example">
<pre class="example">[<var>n</var>]&lt;&lt;&lt; <var>word</var>
</pre></div>

<p>The <var>word</var> undergoes
tilde expansion, parameter and variable expansion,
command substitution, arithmetic expansion, and quote removal.
Filename expansion and word splitting are not performed.
The result is supplied as a single string,
with a newline appended,
to the command on its
standard input (or file descriptor <var>n</var> if <var>n</var> is specified).
</p>
</div>
<div class="subsection" id="Duplicating-File-Descriptors">
<h4 class="subsection">3.6.8 Duplicating File Descriptors</h4>
<p>The redirection operator
</p><div class="example">
<pre class="example">[<var>n</var>]&lt;&amp;<var>word</var>
</pre></div>
<p>is used to duplicate input file descriptors.
If <var>word</var>
expands to one or more digits, the file descriptor denoted by <var>n</var>
is made to be a copy of that file descriptor.
If the digits in <var>word</var> do not specify a file descriptor open for
input, a redirection error occurs.
If <var>word</var>
evaluates to &lsquo;<samp>-</samp>&rsquo;, file descriptor <var>n</var> is closed.
If <var>n</var> is not specified, the standard input (file descriptor 0) is used.
</p>
<p>The operator
</p><div class="example">
<pre class="example">[<var>n</var>]&gt;&amp;<var>word</var>
</pre></div>
<p>is used similarly to duplicate output file descriptors.  If
<var>n</var> is not specified, the standard output (file descriptor 1) is used.
If the digits in <var>word</var> do not specify a file descriptor open for
output, a redirection error occurs.
If <var>word</var>
evaluates to &lsquo;<samp>-</samp>&rsquo;, file descriptor <var>n</var> is closed.
As a special case, if <var>n</var> is omitted, and <var>word</var> does not
expand to one or more digits or &lsquo;<samp>-</samp>&rsquo;, the standard output and standard
error are redirected as described previously.
</p>
</div>
<div class="subsection" id="Moving-File-Descriptors">
<h4 class="subsection">3.6.9 Moving File Descriptors</h4>
<p>The redirection operator
</p><div class="example">
<pre class="example">[<var>n</var>]&lt;&amp;<var>digit</var>-
</pre></div>
<p>moves the file descriptor <var>digit</var> to file descriptor <var>n</var>,
or the standard input (file descriptor 0) if <var>n</var> is not specified.
<var>digit</var> is closed after being duplicated to <var>n</var>.
</p>
<p>Similarly, the redirection operator
</p><div class="example">
<pre class="example">[<var>n</var>]&gt;&amp;<var>digit</var>-
</pre></div>
<p>moves the file descriptor <var>digit</var> to file descriptor <var>n</var>,
or the standard output (file descriptor 1) if <var>n</var> is not specified.
</p>
</div>
<div class="subsection" id="Opening-File-Descriptors-for-Reading-and-Writing">
<h4 class="subsection">3.6.10 Opening File Descriptors for Reading and Writing</h4>
<p>The redirection operator
</p><div class="example">
<pre class="example">[<var>n</var>]&lt;&gt;<var>word</var>
</pre></div>
<p>causes the file whose name is the expansion of <var>word</var>
to be opened for both reading and writing on file descriptor
<var>n</var>, or on file descriptor 0 if <var>n</var>
is not specified.  If the file does not exist, it is created.
</p>
<hr>
</div>
</div>
<div class="section" id="Executing-Commands">
<div class="header">
<p>
Next: <a href="#Shell-Scripts" accesskey="n" rel="next">Shell Scripts</a>, Previous: <a href="#Redirections" accesskey="p" rel="prev">Redirections</a>, Up: <a href="#Basic-Shell-Features" accesskey="u" rel="up">Basic Shell Features</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Executing-Commands-1"></span><h3 class="section">3.7 Executing Commands</h3>


<ul class="section-toc">
<li><a href="#Simple-Command-Expansion" accesskey="1">Simple Command Expansion</a></li>
<li><a href="#Command-Search-and-Execution" accesskey="2">Command Search and Execution</a></li>
<li><a href="#Command-Execution-Environment" accesskey="3">Command Execution Environment</a></li>
<li><a href="#Environment" accesskey="4">Environment</a></li>
<li><a href="#Exit-Status" accesskey="5">Exit Status</a></li>
<li><a href="#Signals" accesskey="6">Signals</a></li>
</ul>
<hr>
<div class="subsection" id="Simple-Command-Expansion">
<div class="header">
<p>
Next: <a href="#Command-Search-and-Execution" accesskey="n" rel="next">Command Search and Execution</a>, Up: <a href="#Executing-Commands" accesskey="u" rel="up">Executing Commands</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Simple-Command-Expansion-1"></span><h4 class="subsection">3.7.1 Simple Command Expansion</h4>
<span id="index-command-expansion"></span>

<p>When a simple command is executed, the shell performs the following
expansions, assignments, and redirections, from left to right, in
the following order.
</p>
<ol>
<li> The words that the parser has marked as variable assignments (those
preceding the command name) and redirections are saved for later
processing.

</li><li> The words that are not variable assignments or redirections are
expanded (see <a href="#Shell-Expansions">Shell Expansions</a>).
If any words remain after expansion, the first word
is taken to be the name of the command and the remaining words are
the arguments.

</li><li> Redirections are performed as described above (see <a href="#Redirections">Redirections</a>).

</li><li> The text after the &lsquo;<samp>=</samp>&rsquo; in each variable assignment undergoes tilde
expansion, parameter expansion, command substitution, arithmetic expansion,
and quote removal before being assigned to the variable.
</li></ol>

<p>If no command name results, the variable assignments affect the current
shell environment.
In the case of such a command (one that consists only of assignment
statements and redirections), assignment statements are performed before
redirections.
Otherwise, the variables are added to the environment
of the executed command and do not affect the current shell environment.
If any of the assignments attempts to assign a value to a readonly variable,
an error occurs, and the command exits with a non-zero status.
</p>
<p>If no command name results, redirections are performed, but do not
affect the current shell environment.  A redirection error causes the
command to exit with a non-zero status.
</p>
<p>If there is a command name left after expansion, execution proceeds as
described below.  Otherwise, the command exits.  If one of the expansions
contained a command substitution, the exit status of the command is
the exit status of the last command substitution performed.  If there
were no command substitutions, the command exits with a status of zero.
</p>
<hr>
</div>
<div class="subsection" id="Command-Search-and-Execution">
<div class="header">
<p>
Next: <a href="#Command-Execution-Environment" accesskey="n" rel="next">Command Execution Environment</a>, Previous: <a href="#Simple-Command-Expansion" accesskey="p" rel="prev">Simple Command Expansion</a>, Up: <a href="#Executing-Commands" accesskey="u" rel="up">Executing Commands</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Command-Search-and-Execution-1"></span><h4 class="subsection">3.7.2 Command Search and Execution</h4>
<span id="index-command-execution"></span>
<span id="index-command-search"></span>

<p>After a command has been split into words, if it results in a
simple command and an optional list of arguments, the following
actions are taken.
</p>
<ol>
<li> If the command name contains no slashes, the shell attempts to
locate it.  If there exists a shell function by that name, that
function is invoked as described in <a href="#Shell-Functions">Shell Functions</a>.

</li><li> If the name does not match a function, the shell searches for
it in the list of shell builtins.  If a match is found, that
builtin is invoked.

</li><li> If the name is neither a shell function nor a builtin,
and contains no slashes, Bash searches each element of
<code>$PATH</code> for a directory containing an executable file
by that name.  Bash uses a hash table to remember the full
pathnames of executable files to avoid multiple <code>PATH</code> searches
(see the description of <code>hash</code> in <a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a>).
A full search of the directories in <code>$PATH</code>
is performed only if the command is not found in the hash table.
If the search is unsuccessful, the shell searches for a defined shell
function named <code>command_not_found_handle</code>.
If that function exists, it is invoked in a separate execution environment
with the original command and
the original command&rsquo;s arguments as its arguments, and the function&rsquo;s
exit status becomes the exit status of that subshell.
If that function is not defined, the shell prints an error
message and returns an exit status of 127.

</li><li> If the search is successful, or if the command name contains
one or more slashes, the shell executes the named program in
a separate execution environment.
Argument 0 is set to the name given, and the remaining arguments
to the command are set to the arguments supplied, if any.

</li><li> If this execution fails because the file is not in executable
format, and the file is not a directory, it is assumed to be a
<em>shell script</em> and the shell executes it as described in
<a href="#Shell-Scripts">Shell Scripts</a>.

</li><li> If the command was not begun asynchronously, the shell waits for
the command to complete and collects its exit status.

</li></ol>

<hr>
</div>
<div class="subsection" id="Command-Execution-Environment">
<div class="header">
<p>
Next: <a href="#Environment" accesskey="n" rel="next">Environment</a>, Previous: <a href="#Command-Search-and-Execution" accesskey="p" rel="prev">Command Search and Execution</a>, Up: <a href="#Executing-Commands" accesskey="u" rel="up">Executing Commands</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Command-Execution-Environment-1"></span><h4 class="subsection">3.7.3 Command Execution Environment</h4>
<span id="index-execution-environment"></span>

<p>The shell has an <em>execution environment</em>, which consists of the
following:
</p>
<ul>
<li> open files inherited by the shell at invocation, as modified by
redirections supplied to the <code>exec</code> builtin

</li><li> the current working directory as set by <code>cd</code>, <code>pushd</code>, or
<code>popd</code>, or inherited by the shell at invocation

</li><li> the file creation mode mask as set by <code>umask</code> or inherited from
the shell&rsquo;s parent

</li><li> current traps set by <code>trap</code>

</li><li> shell parameters that are set by variable assignment or with <code>set</code>
or inherited from the shell&rsquo;s parent in the environment

</li><li> shell functions defined during execution or inherited from the shell&rsquo;s
parent in the environment

</li><li> options enabled at invocation (either by default or with command-line
arguments) or by <code>set</code>

</li><li> options enabled by <code>shopt</code> (see <a href="#The-Shopt-Builtin">The Shopt Builtin</a>)

</li><li> shell aliases defined with <code>alias</code> (see <a href="#Aliases">Aliases</a>)

</li><li> various process <small>ID</small>s, including those of background jobs
(see <a href="#Lists">Lists of Commands</a>), the value of <code>$$</code>, and the value of
<code>$PPID</code>

</li></ul>

<p>When a simple command other than a builtin or shell function
is to be executed, it
is invoked in a separate execution environment that consists of
the following.  Unless otherwise noted, the values are inherited
from the shell.
</p>
<ul>
<li> the shell&rsquo;s open files, plus any modifications and additions specified
by redirections to the command

</li><li> the current working directory

</li><li> the file creation mode mask

</li><li> shell variables and functions marked for export, along with variables
exported for the command, passed in the environment (see <a href="#Environment">Environment</a>)

</li><li> traps caught by the shell are reset to the values inherited from the
shell&rsquo;s parent, and traps ignored by the shell are ignored

</li></ul>

<p>A command invoked in this separate environment cannot affect the
shell&rsquo;s execution environment.
</p>
<p>A <em>subshell</em> is a copy of the shell process.
</p>
<p>Command substitution, commands grouped with parentheses,
and asynchronous commands are invoked in a
subshell environment that is a duplicate of the shell environment,
except that traps caught by the shell are reset to the values
that the shell inherited from its parent at invocation.  Builtin
commands that are invoked as part of a pipeline are also executed
in a subshell environment.  Changes made to the subshell environment
cannot affect the shell&rsquo;s execution environment.
</p>
<p>Subshells spawned to execute command substitutions inherit the value of
the <samp>-e</samp> option from the parent shell.  When not in <small>POSIX</small> mode,
Bash clears the <samp>-e</samp> option in such subshells.
</p>
<p>If a command is followed by a &lsquo;<samp>&amp;</samp>&rsquo; and job control is not active, the
default standard input for the command is the empty file <samp>/dev/null</samp>.
Otherwise, the invoked command inherits the file descriptors of the calling
shell as modified by redirections.
</p>
<hr>
</div>
<div class="subsection" id="Environment">
<div class="header">
<p>
Next: <a href="#Exit-Status" accesskey="n" rel="next">Exit Status</a>, Previous: <a href="#Command-Execution-Environment" accesskey="p" rel="prev">Command Execution Environment</a>, Up: <a href="#Executing-Commands" accesskey="u" rel="up">Executing Commands</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Environment-1"></span><h4 class="subsection">3.7.4 Environment</h4>
<span id="index-environment"></span>

<p>When a program is invoked it is given an array of strings
called the <em>environment</em>.
This is a list of name-value pairs, of the form <code>name=value</code>.
</p>
<p>Bash provides several ways to manipulate the environment.
On invocation, the shell scans its own environment and
creates a parameter for each name found, automatically marking
it for <code>export</code>
to child processes.  Executed commands inherit the environment.
The <code>export</code> and &lsquo;<samp>declare -x</samp>&rsquo;
commands allow parameters and functions to be added to and
deleted from the environment.  If the value of a parameter
in the environment is modified, the new value becomes part
of the environment, replacing the old.  The environment
inherited by any executed command consists of the shell&rsquo;s
initial environment, whose values may be modified in the shell,
less any pairs removed by the <code>unset</code> and &lsquo;<samp>export -n</samp>&rsquo;
commands, plus any additions via the <code>export</code> and
&lsquo;<samp>declare -x</samp>&rsquo; commands.
</p>
<p>The environment for any simple command
or function may be augmented temporarily by prefixing it with
parameter assignments, as described in <a href="#Shell-Parameters">Shell Parameters</a>.
These assignment statements affect only the environment seen
by that command.
</p>
<p>If the <samp>-k</samp> option is set (see <a href="#The-Set-Builtin">The Set Builtin</a>), then all
parameter assignments are placed in the environment for a command,
not just those that precede the command name.
</p>
<p>When Bash invokes an external command, the variable &lsquo;<samp>$_</samp>&rsquo;
is set to the full pathname of the command and passed to that
command in its environment.
</p>
<hr>
</div>
<div class="subsection" id="Exit-Status">
<div class="header">
<p>
Next: <a href="#Signals" accesskey="n" rel="next">Signals</a>, Previous: <a href="#Environment" accesskey="p" rel="prev">Environment</a>, Up: <a href="#Executing-Commands" accesskey="u" rel="up">Executing Commands</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Exit-Status-1"></span><h4 class="subsection">3.7.5 Exit Status</h4>
<span id="index-exit-status-1"></span>

<p>The exit status of an executed command is the value returned by the
<code>waitpid</code> system call or equivalent function.  Exit statuses    
fall between 0 and 255, though, as explained below, the shell may
use values above 125 specially.  Exit statuses from shell builtins and
compound commands are also limited to this range.  Under certain
circumstances, the shell will use special values to indicate specific
failure modes.
</p>
<p>For the shell&rsquo;s purposes, a command which exits with a
zero exit status has succeeded.
A non-zero exit status indicates failure.
This seemingly counter-intuitive scheme is used so there
is one well-defined way to indicate success and a variety of
ways to indicate various failure modes.
When a command terminates on a fatal signal whose number is <var>N</var>,
Bash uses the value 128+<var>N</var> as the exit status.
</p>
<p>If a command is not found, the child process created to
execute it returns a status of 127.  If a command is found  
but is not executable, the return status is 126.
</p>
<p>If a command fails because of an error during expansion or redirection,
the exit status is greater than zero.
</p>
<p>The exit status is used by the Bash conditional commands
(see <a href="#Conditional-Constructs">Conditional Constructs</a>) and some of the list
constructs (see <a href="#Lists">Lists of Commands</a>).
</p>
<p>All of the Bash builtins return an exit status of zero if they succeed
and a non-zero status on failure, so they may be used by the
conditional and list constructs.
All builtins return an exit status of 2 to indicate incorrect usage,
generally invalid options or missing arguments.
</p>
<p>The exit status of the last command is available in the special
parameter $? (see <a href="#Special-Parameters">Special Parameters</a>).
</p>
<hr>
</div>
<div class="subsection" id="Signals">
<div class="header">
<p>
Previous: <a href="#Exit-Status" accesskey="p" rel="prev">Exit Status</a>, Up: <a href="#Executing-Commands" accesskey="u" rel="up">Executing Commands</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Signals-1"></span><h4 class="subsection">3.7.6 Signals</h4>
<span id="index-signal-handling"></span>

<p>When Bash is interactive, in the absence of any traps, it ignores
<code>SIGTERM</code> (so that &lsquo;<samp>kill 0</samp>&rsquo; does not kill an interactive shell),
and <code>SIGINT</code>
is caught and handled (so that the <code>wait</code> builtin is interruptible).
When Bash receives a <code>SIGINT</code>, it breaks out of any executing loops.
In all cases, Bash ignores <code>SIGQUIT</code>.
If job control is in effect (see <a href="#Job-Control">Job Control</a>), Bash
ignores <code>SIGTTIN</code>, <code>SIGTTOU</code>, and <code>SIGTSTP</code>.
</p>
<p>Non-builtin commands started by Bash have signal handlers set to the
values inherited by the shell from its parent.
When job control is not in effect, asynchronous commands
ignore <code>SIGINT</code> and <code>SIGQUIT</code> in addition to these inherited
handlers.
Commands run as a result of
command substitution ignore the keyboard-generated job control signals
<code>SIGTTIN</code>, <code>SIGTTOU</code>, and <code>SIGTSTP</code>.
</p>
<p>The shell exits by default upon receipt of a <code>SIGHUP</code>.
Before exiting, an interactive shell resends the <code>SIGHUP</code> to
all jobs, running or stopped.
Stopped jobs are sent <code>SIGCONT</code> to ensure that they receive
the <code>SIGHUP</code>.
To prevent the shell from sending the <code>SIGHUP</code> signal to a
particular job, it should be removed
from the jobs table with the <code>disown</code>
builtin (see <a href="#Job-Control-Builtins">Job Control Builtins</a>) or marked
to not receive <code>SIGHUP</code> using <code>disown -h</code>.
</p>
<p>If the  <code>huponexit</code> shell option has been set with <code>shopt</code>
(see <a href="#The-Shopt-Builtin">The Shopt Builtin</a>), Bash sends a <code>SIGHUP</code> to all jobs when
an interactive login shell exits.
</p>
<p>If Bash is waiting for a command to complete and receives a signal
for which a trap has been set, the trap will not be executed until
the command completes.
When Bash is waiting for an asynchronous
command via the <code>wait</code> builtin, the reception of a signal for
which a trap has been set will cause the <code>wait</code> builtin to return
immediately with an exit status greater than 128, immediately after
which the trap is executed.
</p>
<p>When job control is not enabled, and Bash is waiting for a foreground
command to complete, the shell receives keyboard-generated signals
such as <code>SIGINT</code> (usually generated by &lsquo;<samp>^C</samp>&rsquo;) that users
commonly intend to send to that command.
This happens because the shell and the command are in the same process
group as the terminal, and &lsquo;<samp>^C</samp>&rsquo; sends <code>SIGINT</code> to all processes
in that process group.
See <a href="#Job-Control">Job Control</a>, for a more in-depth discussion of process groups.
</p>
<p>When Bash is running without job control enabled and receives <code>SIGINT</code>
while waiting for a foreground command, it waits until that foreground
command terminates and then decides what to do about the <code>SIGINT</code>:
</p>
<ol>
<li> If the command terminates due to the <code>SIGINT</code>, Bash concludes
that the user meant to end the entire script, and acts on the
<code>SIGINT</code> (e.g., by running a <code>SIGINT</code> trap or exiting itself);

</li><li> If the pipeline does not terminate due to <code>SIGINT</code>, the program
handled the <code>SIGINT</code> itself and did not treat it as a fatal signal.
In that case, Bash does not treat <code>SIGINT</code> as a fatal signal,
either, instead assuming that the <code>SIGINT</code> was used as part of the
program&rsquo;s normal operation (e.g., <code>emacs</code> uses it to abort editing
commands) or deliberately discarded. However, Bash will run any
trap set on <code>SIGINT</code>, as it does with any other trapped signal it
receives while it is waiting for the foreground command to
complete, for compatibility.
</li></ol>

<hr>
</div>
</div>
<div class="section" id="Shell-Scripts">
<div class="header">
<p>
Previous: <a href="#Executing-Commands" accesskey="p" rel="prev">Executing Commands</a>, Up: <a href="#Basic-Shell-Features" accesskey="u" rel="up">Basic Shell Features</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Shell-Scripts-1"></span><h3 class="section">3.8 Shell Scripts</h3>
<span id="index-shell-script"></span>

<p>A shell script is a text file containing shell commands.  When such
a file is used as the first non-option argument when invoking Bash,
and neither the <samp>-c</samp> nor <samp>-s</samp> option is supplied
(see <a href="#Invoking-Bash">Invoking Bash</a>), 
Bash reads and executes commands from the file, then exits.  This
mode of operation creates a non-interactive shell.  The shell first
searches for the file in the current directory, and looks in the
directories in <code>$PATH</code> if not found there.
</p>
<p>When Bash runs
a shell script, it sets the special parameter <code>0</code> to the name
of the file, rather than the name of the shell, and the positional
parameters are set to the remaining arguments, if any are given.
If no additional arguments are supplied, the positional parameters
are unset.
</p>
<p>A shell script may be made executable by using the <code>chmod</code> command
to turn on the execute bit.  When Bash finds such a file while
searching the <code>$PATH</code> for a command, it creates a
new instance of itself
to execute it.
In other words, executing
</p><div class="example">
<pre class="example">filename <var>arguments</var>
</pre></div>
<p>is equivalent to executing
</p><div class="example">
<pre class="example">bash filename <var>arguments</var>
</pre></div>

<p>if <code>filename</code> is an executable shell script.
This subshell reinitializes itself, so that the effect is as if a
new shell had been invoked to interpret the script, with the
exception that the locations of commands remembered by the parent
(see the description of <code>hash</code> in <a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a>)
are retained by the child.
</p>
<p>Most versions of Unix make this a part of the operating system&rsquo;s command
execution mechanism.  If the first line of a script begins with
the two characters &lsquo;<samp>#!</samp>&rsquo;, the remainder of the line specifies
an interpreter for the program and, depending on the operating system, one
or more optional arguments for that interpreter.
Thus, you can specify Bash, <code>awk</code>, Perl, or some other
interpreter and write the rest of the script file in that language.
</p>
<p>The arguments to the interpreter
consist of one or more optional arguments following the interpreter
name on the first line of the script file, followed by the name of
the script file, followed by the rest of the arguments supplied to the
script.
The details of how the interpreter line is split into an interpreter name
and a set of arguments vary across systems.
Bash will perform this action on operating systems that do not handle it
themselves.
Note that some older versions of Unix limit the interpreter
name and a single argument to a maximum of 32 characters, so it&rsquo;s not
portable to assume that using more than one argument will work.
</p>
<p>Bash scripts often begin with <code>#! /bin/bash</code> (assuming that
Bash has been installed in <samp>/bin</samp>), since this ensures that
Bash will be used to interpret the script, even if it is executed
under another shell. It&rsquo;s a common idiom to use <code>env</code> to find
<code>bash</code> even if it&rsquo;s been installed in another directory:
<code>#!/usr/bin/env bash</code> will find the first occurrence of <code>bash</code>
in <code>$PATH</code>.
</p>
<hr>
</div>
</div>
<div class="chapter" id="Shell-Builtin-Commands">
<div class="header">
<p>
Next: <a href="#Shell-Variables" accesskey="n" rel="next">Shell Variables</a>, Previous: <a href="#Basic-Shell-Features" accesskey="p" rel="prev">Basic Shell Features</a>, Up: <a href="#Top" accesskey="u" rel="up">Bash Features</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Shell-Builtin-Commands-1"></span><h2 class="chapter">4 Shell Builtin Commands</h2>


<p>Builtin commands are contained within the shell itself.
When the name of a builtin command is used as the first word of
a simple command (see <a href="#Simple-Commands">Simple Commands</a>), the shell executes
the command directly, without invoking another program.
Builtin commands are necessary to implement functionality impossible
or inconvenient to obtain with separate utilities.
</p>
<p>This section briefly describes the builtins which Bash inherits from
the Bourne Shell, as well as the builtin commands which are unique
to or have been extended in Bash.
</p>
<p>Several builtin commands are described in other chapters: builtin
commands which provide the Bash interface to the job control
facilities (see <a href="#Job-Control-Builtins">Job Control Builtins</a>), the directory stack
(see <a href="#Directory-Stack-Builtins">Directory Stack Builtins</a>), the command history
(see <a href="#Bash-History-Builtins">Bash History Builtins</a>), and the programmable completion
facilities (see <a href="#Programmable-Completion-Builtins">Programmable Completion Builtins</a>).
</p>
<p>Many of the builtins have been extended by <small>POSIX</small> or Bash.
</p>
<p>Unless otherwise noted, each builtin command documented as accepting
options preceded by &lsquo;<samp>-</samp>&rsquo; accepts &lsquo;<samp>--</samp>&rsquo;
to signify the end of the options.
The <code>:</code>, <code>true</code>, <code>false</code>, and <code>test</code>/<code>[</code>
builtins do not accept options and do not treat &lsquo;<samp>--</samp>&rsquo; specially.
The <code>exit</code>, <code>logout</code>, <code>return</code>,
<code>break</code>, <code>continue</code>, <code>let</code>,
and <code>shift</code> builtins accept and process arguments beginning
with &lsquo;<samp>-</samp>&rsquo; without requiring &lsquo;<samp>--</samp>&rsquo;.
Other builtins that accept arguments but are not specified as accepting
options interpret arguments beginning with &lsquo;<samp>-</samp>&rsquo; as invalid options and
require &lsquo;<samp>--</samp>&rsquo; to prevent this interpretation.
</p>
<ul class="section-toc">
<li><a href="#Bourne-Shell-Builtins" accesskey="1">Bourne Shell Builtins</a></li>
<li><a href="#Bash-Builtins" accesskey="2">Bash Builtin Commands</a></li>
<li><a href="#Modifying-Shell-Behavior" accesskey="3">Modifying Shell Behavior</a></li>
<li><a href="#Special-Builtins" accesskey="4">Special Builtins</a></li>
</ul>
<hr>
<div class="section" id="Bourne-Shell-Builtins">
<div class="header">
<p>
Next: <a href="#Bash-Builtins" accesskey="n" rel="next">Bash Builtin Commands</a>, Up: <a href="#Shell-Builtin-Commands" accesskey="u" rel="up">Shell Builtin Commands</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Bourne-Shell-Builtins-1"></span><h3 class="section">4.1 Bourne Shell Builtins</h3>

<p>The following shell builtin commands are inherited from the Bourne Shell.
These commands are implemented as specified by the <small>POSIX</small> standard.
</p>
<dl compact="compact">
<dt id='index-_003a'><span><code>:    <span class="roman">(a colon)</span></code><a href='#index-_003a' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">: [<var>arguments</var>]
</pre></div>

<p>Do nothing beyond expanding <var>arguments</var> and performing redirections.
The return status is zero.
</p>
</dd>
<dt id='index-_002e'><span><code>.    <span class="roman">(a period)</span></code><a href='#index-_002e' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">. <var>filename</var> [<var>arguments</var>]
</pre></div>

<p>Read and execute commands from the <var>filename</var> argument in the
current shell context.  If <var>filename</var> does not contain a slash,
the <code>PATH</code> variable is used to find <var>filename</var>,
but <var>filename</var> does not need to be executable.
When Bash is not in <small>POSIX</small> mode, it searches the current directory
if <var>filename</var> is not found in <code>$PATH</code>.
If any <var>arguments</var> are supplied, they become the positional
parameters when <var>filename</var> is executed.  Otherwise the positional
parameters are unchanged.
If the <samp>-T</samp> option is enabled, <code>.</code> inherits any trap on
<code>DEBUG</code>; if it is not, any <code>DEBUG</code> trap string is saved and
restored around the call to <code>.</code>, and <code>.</code> unsets the
<code>DEBUG</code> trap while it executes.
If <samp>-T</samp> is not set, and the sourced file changes
the <code>DEBUG</code> trap, the new value is retained when <code>.</code> completes.
The return status is the exit status of the last command executed, or
zero if no commands are executed.  If <var>filename</var> is not found, or
cannot be read, the return status is non-zero.
This builtin is equivalent to <code>source</code>.
</p>
</dd>
<dt id='index-break'><span><code>break</code><a href='#index-break' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">break [<var>n</var>]
</pre></div>

<p>Exit from a <code>for</code>, <code>while</code>, <code>until</code>, or <code>select</code> loop.
If <var>n</var> is supplied, the <var>n</var>th enclosing loop is exited.
<var>n</var> must be greater than or equal to 1.
The return status is zero unless <var>n</var> is not greater than or equal to 1.
</p>
</dd>
<dt id='index-cd'><span><code>cd</code><a href='#index-cd' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">cd [-L|[-P [-e]] [-@] [<var>directory</var>]
</pre></div>

<p>Change the current working directory to <var>directory</var>.
If <var>directory</var> is not supplied, the value of the <code>HOME</code>
shell variable is used.
If the shell variable
<code>CDPATH</code> exists, it is used as a search path:
each directory name in <code>CDPATH</code> is searched for
<var>directory</var>, with alternative directory names in <code>CDPATH</code>
separated by a colon (&lsquo;<samp>:</samp>&rsquo;).
If <var>directory</var> begins with a slash, <code>CDPATH</code> is not used.
</p>
<p>The <samp>-P</samp> option means to not follow symbolic links: symbolic links
are resolved while <code>cd</code> is traversing <var>directory</var> and before
processing an instance of &lsquo;<samp>..</samp>&rsquo; in <var>directory</var>.
</p>
<p>By default, or when the <samp>-L</samp> option is supplied, symbolic links
in <var>directory</var> are resolved after <code>cd</code> processes an instance
of &lsquo;<samp>..</samp>&rsquo; in <var>directory</var>.
</p>
<p>If &lsquo;<samp>..</samp>&rsquo; appears in <var>directory</var>, it is processed by removing the
immediately preceding pathname component, back to a slash or the beginning
of <var>directory</var>.
</p>
<p>If the <samp>-e</samp> option is supplied with <samp>-P</samp>
and the current working directory cannot be successfully determined
after a successful directory change, <code>cd</code> will return an unsuccessful
status.
</p>
<p>On systems that support it, the <samp>-@</samp> option presents the extended
attributes associated with a file as a directory.              
</p>
<p>If <var>directory</var> is &lsquo;<samp>-</samp>&rsquo;, it is converted to <code>$OLDPWD</code>
before the directory change is attempted.
</p>
<p>If a non-empty directory name from <code>CDPATH</code> is used, or if
&lsquo;<samp>-</samp>&rsquo; is the first argument, and the directory change is
successful, the absolute pathname of the new working directory is
written to the standard output.
</p>
<p>If the directory change is successful, <code>cd</code> sets the value of the
<code>PWD</code> environment variable to the new directory name, and sets the
<code>OLDPWD</code> environment variable to the value of the current working
directory before the change.
</p>
<p>The return status is zero if the directory is successfully changed,
non-zero otherwise.
</p>
</dd>
<dt id='index-continue'><span><code>continue</code><a href='#index-continue' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">continue [<var>n</var>]
</pre></div>

<p>Resume the next iteration of an enclosing <code>for</code>, <code>while</code>,
<code>until</code>, or <code>select</code> loop.
If <var>n</var> is supplied, the execution of the <var>n</var>th enclosing loop
is resumed.
<var>n</var> must be greater than or equal to 1.
The return status is zero unless <var>n</var> is not greater than or equal to 1.
</p>
</dd>
<dt id='index-eval'><span><code>eval</code><a href='#index-eval' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">eval [<var>arguments</var>]
</pre></div>

<p>The arguments are concatenated together into a single command, which is
then read and executed, and its exit status returned as the exit status
of <code>eval</code>.
If there are no arguments or only empty arguments, the return status is
zero.
</p>
</dd>
<dt id='index-exec'><span><code>exec</code><a href='#index-exec' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">exec [-cl] [-a <var>name</var>] [<var>command</var> [<var>arguments</var>]]
</pre></div>

<p>If <var>command</var>
is supplied, it replaces the shell without creating a new process.
If the <samp>-l</samp> option is supplied, the shell places a dash at the
beginning of the zeroth argument passed to <var>command</var>.
This is what the <code>login</code> program does.
The <samp>-c</samp> option causes <var>command</var> to be executed with an empty
environment.
If <samp>-a</samp> is supplied, the shell passes <var>name</var> as the zeroth
argument to <var>command</var>.
If <var>command</var>
cannot be executed for some reason, a non-interactive shell exits,
unless the <code>execfail</code> shell option
is enabled.  In that case, it returns failure.
An interactive shell returns failure if the file cannot be executed.
A subshell exits unconditionally if <code>exec</code> fails.
If no <var>command</var> is specified, redirections may be used to affect
the current shell environment.  If there are no redirection errors, the
return status is zero; otherwise the return status is non-zero.
</p>
</dd>
<dt id='index-exit'><span><code>exit</code><a href='#index-exit' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">exit [<var>n</var>]
</pre></div>

<p>Exit the shell, returning a status of <var>n</var> to the shell&rsquo;s parent.
If <var>n</var> is omitted, the exit status is that of the last command executed.
Any trap on <code>EXIT</code> is executed before the shell terminates.
</p>
</dd>
<dt id='index-export'><span><code>export</code><a href='#index-export' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">export [-fn] [-p] [<var>name</var>[=<var>value</var>]]
</pre></div>

<p>Mark each <var>name</var> to be passed to child processes
in the environment.  If the <samp>-f</samp> option is supplied, the <var>name</var>s
refer to shell functions; otherwise the names refer to shell variables.
The <samp>-n</samp> option means to no longer mark each <var>name</var> for export.
If no <var>name</var>s are supplied, or if the <samp>-p</samp> option is given, a
list of names of all exported variables is displayed.
The <samp>-p</samp> option displays output in a form that may be reused as input.
If a variable name is followed by =<var>value</var>, the value of
the variable is set to <var>value</var>.
</p>
<p>The return status is zero unless an invalid option is supplied, one of
the names is not a valid shell variable name, or <samp>-f</samp> is supplied
with a name that is not a shell function.
</p>
</dd>
<dt id='index-getopts'><span><code>getopts</code><a href='#index-getopts' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">getopts <var>optstring</var> <var>name</var> [<var>arg</var> &hellip;]
</pre></div>

<p><code>getopts</code> is used by shell scripts to parse positional parameters.
<var>optstring</var> contains the option characters to be recognized; if a
character is followed by a colon, the option is expected to have an
argument, which should be separated from it by whitespace.
The colon (&lsquo;<samp>:</samp>&rsquo;) and question mark (&lsquo;<samp>?</samp>&rsquo;) may not be
used as option characters.
Each time it is invoked, <code>getopts</code>
places the next option in the shell variable <var>name</var>, initializing
<var>name</var> if it does not exist,
and the index of the next argument to be processed into the
variable <code>OPTIND</code>.
<code>OPTIND</code> is initialized to 1 each time the shell or a shell script
is invoked.
When an option requires an argument,
<code>getopts</code> places that argument into the variable <code>OPTARG</code>.
The shell does not reset <code>OPTIND</code> automatically; it must be manually
reset between multiple calls to <code>getopts</code> within the same shell
invocation if a new set of parameters is to be used.
</p>
<p>When the end of options is encountered, <code>getopts</code> exits with a
return value greater than zero.
<code>OPTIND</code> is set to the index of the first non-option argument,
and <var>name</var> is set to &lsquo;<samp>?</samp>&rsquo;.
</p>
<p><code>getopts</code>
normally parses the positional parameters, but if more arguments are
supplied as <var>arg</var> values, <code>getopts</code> parses those instead.
</p>
<p><code>getopts</code> can report errors in two ways.  If the first character of
<var>optstring</var> is a colon, <var>silent</var>
error reporting is used.  In normal operation, diagnostic messages
are printed when invalid options or missing option arguments are
encountered.
If the variable <code>OPTERR</code>
is set to 0, no error messages will be displayed, even if the first
character of <code>optstring</code> is not a colon.
</p>
<p>If an invalid option is seen,
<code>getopts</code> places &lsquo;<samp>?</samp>&rsquo; into <var>name</var> and, if not silent,
prints an error message and unsets <code>OPTARG</code>.
If <code>getopts</code> is silent, the option character found is placed in
<code>OPTARG</code> and no diagnostic message is printed.
</p>
<p>If a required argument is not found, and <code>getopts</code>
is not silent, a question mark (&lsquo;<samp>?</samp>&rsquo;) is placed in <var>name</var>,
<code>OPTARG</code> is unset, and a diagnostic message is printed.
If <code>getopts</code> is silent, then a colon (&lsquo;<samp>:</samp>&rsquo;) is placed in
<var>name</var> and <code>OPTARG</code> is set to the option character found.
</p>
</dd>
<dt id='index-hash'><span><code>hash</code><a href='#index-hash' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">hash [-r] [-p <var>filename</var>] [-dt] [<var>name</var>]
</pre></div>

<p>Each time <code>hash</code> is invoked, it remembers the full pathnames of the
commands specified as <var>name</var> arguments,
so they need not be searched for on subsequent invocations.
The commands are found by searching through the directories listed in
<code>$PATH</code>.
Any previously-remembered pathname is discarded.
The <samp>-p</samp> option inhibits the path search, and <var>filename</var> is
used as the location of <var>name</var>.
The <samp>-r</samp> option causes the shell to forget all remembered locations.
The <samp>-d</samp> option causes the shell to forget the remembered location
of each <var>name</var>.
If the <samp>-t</samp> option is supplied, the full pathname to which each
<var>name</var> corresponds is printed.  If multiple <var>name</var> arguments are
supplied with <samp>-t</samp>, the <var>name</var> is printed before the hashed
full pathname.
The <samp>-l</samp> option causes output to be displayed in a format
that may be reused as input.
If no arguments are given, or if only <samp>-l</samp> is supplied,
information about remembered commands is printed.
The return status is zero unless a <var>name</var> is not found or an invalid
option is supplied.
</p>
</dd>
<dt id='index-pwd'><span><code>pwd</code><a href='#index-pwd' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">pwd [-LP]
</pre></div>

<p>Print the absolute pathname of the current working directory.
If the <samp>-P</samp> option is supplied, the pathname printed will not
contain symbolic links.
If the <samp>-L</samp> option is supplied, the pathname printed may contain
symbolic links.
The return status is zero unless an error is encountered while
determining the name of the current directory or an invalid option
is supplied.
</p>
</dd>
<dt id='index-readonly'><span><code>readonly</code><a href='#index-readonly' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">readonly [-aAf] [-p] [<var>name</var>[=<var>value</var>]] &hellip;
</pre></div>

<p>Mark each <var>name</var> as readonly.
The values of these names may not be changed by subsequent assignment.
If the <samp>-f</samp> option is supplied, each <var>name</var> refers to a shell
function.
The <samp>-a</samp> option means each <var>name</var> refers to an indexed
array variable; the <samp>-A</samp> option means each <var>name</var> refers
to an associative array variable.
If both options are supplied, <samp>-A</samp> takes precedence.
If no <var>name</var> arguments are given, or if the <samp>-p</samp>
option is supplied, a list of all readonly names is printed.
The other options may be used to restrict the output to a subset of
the set of readonly names.
The <samp>-p</samp> option causes output to be displayed in a format that
may be reused as input.
If a variable name is followed by =<var>value</var>, the value of
the variable is set to <var>value</var>.
The return status is zero unless an invalid option is supplied, one of
the <var>name</var> arguments is not a valid shell variable or function name,
or the <samp>-f</samp> option is supplied with a name that is not a shell function.
</p>
</dd>
<dt id='index-return'><span><code>return</code><a href='#index-return' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">return [<var>n</var>]
</pre></div>

<p>Cause a shell function to stop executing and return the value <var>n</var>
to its caller.
If <var>n</var> is not supplied, the return value is the exit status of the
last command executed in the function.
If <code>return</code> is executed by a trap handler, the last command used to
determine the status is the last command executed before the trap handler.
If <code>return</code> is executed during a <code>DEBUG</code> trap, the last command
used to determine the status is the last command executed by the trap
handler before <code>return</code> was invoked.
<code>return</code> may also be used to terminate execution of a script
being executed with the <code>.</code> (<code>source</code>) builtin,
returning either <var>n</var> or
the exit status of the last command executed within the script as the exit
status of the script.
If <var>n</var> is supplied, the return value is its least significant
8 bits.
Any command associated with the <code>RETURN</code> trap is executed
before execution resumes after the function or script.
The return status is non-zero if <code>return</code> is supplied a non-numeric
argument or is used outside a function
and not during the execution of a script by <code>.</code> or <code>source</code>.
</p>
</dd>
<dt id='index-shift'><span><code>shift</code><a href='#index-shift' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">shift [<var>n</var>]
</pre></div>

<p>Shift the positional parameters to the left by <var>n</var>.
The positional parameters from <var>n</var>+1 &hellip; <code>$#</code> are
renamed to <code>$1</code> &hellip; <code>$#</code>-<var>n</var>.
Parameters represented by the numbers <code>$#</code> down to <code>$#</code>-<var>n</var>+1
are unset.
<var>n</var> must be a non-negative number less than or equal to <code>$#</code>.
If <var>n</var> is zero or greater than <code>$#</code>, the positional parameters
are not changed.
If <var>n</var> is not supplied, it is assumed to be 1.
The return status is zero unless <var>n</var> is greater than <code>$#</code> or
less than zero, non-zero otherwise.
</p>
</dd>
<dt id='index-test'><span><code>test</code><a href='#index-test' class='copiable-anchor'> &para;</a></span></dt>
<dt><span><code>[</code></span></dt>
<dd><span id="index-_005b"></span>
<div class="example">
<pre class="example">test <var>expr</var>
</pre></div>

<p>Evaluate a conditional expression <var>expr</var> and return a status of 0
(true) or 1 (false).
Each operator and operand must be a separate argument.
Expressions are composed of the primaries described below in
<a href="#Bash-Conditional-Expressions">Bash Conditional Expressions</a>.
<code>test</code> does not accept any options, nor does it accept and ignore
an argument of <samp>--</samp> as signifying the end of options.
</p>
<p>When the <code>[</code> form is used, the last argument to the command must
be a <code>]</code>.
</p>
<p>Expressions may be combined using the following operators, listed in
decreasing order of precedence.
The evaluation depends on the number of arguments; see below.
Operator precedence is used when there are five or more arguments.
</p>
<dl compact="compact">
<dt><span><code>! <var>expr</var></code></span></dt>
<dd><p>True if <var>expr</var> is false.
</p>
</dd>
<dt><span><code>( <var>expr</var> )</code></span></dt>
<dd><p>Returns the value of <var>expr</var>.
This may be used to override the normal precedence of operators.
</p>
</dd>
<dt><span><code><var>expr1</var> -a <var>expr2</var></code></span></dt>
<dd><p>True if both <var>expr1</var> and <var>expr2</var> are true.
</p>
</dd>
<dt><span><code><var>expr1</var> -o <var>expr2</var></code></span></dt>
<dd><p>True if either <var>expr1</var> or <var>expr2</var> is true.
</p></dd>
</dl>

<p>The <code>test</code> and <code>[</code> builtins evaluate conditional
expressions using a set of rules based on the number of arguments.
</p>
<dl compact="compact">
<dt><span>0 arguments</span></dt>
<dd><p>The expression is false.
</p>
</dd>
<dt><span>1 argument</span></dt>
<dd><p>The expression is true if, and only if, the argument is not null.
</p>
</dd>
<dt><span>2 arguments</span></dt>
<dd><p>If the first argument is &lsquo;<samp>!</samp>&rsquo;, the expression is true if and
only if the second argument is null.
If the first argument is one of the unary conditional operators
(see <a href="#Bash-Conditional-Expressions">Bash Conditional Expressions</a>), the expression
is true if the unary test is true.
If the first argument is not a valid unary operator, the expression is
false.
</p>
</dd>
<dt><span>3 arguments</span></dt>
<dd><p>The following conditions are applied in the order listed.
</p>
<ol>
<li> If the second argument is one of the binary conditional
operators (see <a href="#Bash-Conditional-Expressions">Bash Conditional Expressions</a>), the
result of the expression is the result of the binary test using the
first and third arguments as operands.
The &lsquo;<samp>-a</samp>&rsquo; and &lsquo;<samp>-o</samp>&rsquo; operators are considered binary operators
when there are three arguments.
</li><li> If the first argument is &lsquo;<samp>!</samp>&rsquo;, the value is the negation of
the two-argument test using the second and third arguments.
</li><li> If the first argument is exactly &lsquo;<samp>(</samp>&rsquo; and the third argument is
exactly &lsquo;<samp>)</samp>&rsquo;, the result is the one-argument test of the second
argument.
</li><li> Otherwise, the expression is false.
</li></ol>

</dd>
<dt><span>4 arguments</span></dt>
<dd><p>The following conditions are applied in the order listed.
</p>
<ol>
<li> If the first argument is &lsquo;<samp>!</samp>&rsquo;, the result is the negation of
the three-argument expression composed of the remaining arguments.
</li><li> If the first argument is exactly &lsquo;<samp>(</samp>&rsquo; and the fourth argument is
exactly &lsquo;<samp>)</samp>&rsquo;, the result is the two-argument test of the second
and third arguments.
</li><li> Otherwise, the expression is parsed and evaluated according to
precedence using the rules listed above.
</li></ol>

</dd>
<dt><span>5 or more arguments</span></dt>
<dd><p>The expression is parsed and evaluated according to precedence
using the rules listed above.
</p></dd>
</dl>

<p>When used with <code>test</code> or &lsquo;<samp>[</samp>&rsquo;, the &lsquo;<samp>&lt;</samp>&rsquo; and &lsquo;<samp>&gt;</samp>&rsquo;
operators sort lexicographically using ASCII ordering.
</p>
</dd>
<dt id='index-times'><span><code>times</code><a href='#index-times' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">times
</pre></div>

<p>Print out the user and system times used by the shell and its children.
The return status is zero.
</p>
</dd>
<dt id='index-trap'><span><code>trap</code><a href='#index-trap' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">trap [-lp] [<var>arg</var>] [<var>sigspec</var> &hellip;]
</pre></div>

<p>The commands in <var>arg</var> are to be read and executed when the
shell receives signal <var>sigspec</var>.  If <var>arg</var> is absent (and
there is a single <var>sigspec</var>) or
equal to &lsquo;<samp>-</samp>&rsquo;, each specified signal&rsquo;s disposition is reset
to the value it had when the shell was started.
If <var>arg</var> is the null string, then the signal specified by
each <var>sigspec</var> is ignored by the shell and commands it invokes.
If <var>arg</var> is not present and <samp>-p</samp> has been supplied,
the shell displays the trap commands associated with each <var>sigspec</var>.
If no arguments are supplied, or
only <samp>-p</samp> is given, <code>trap</code> prints the list of commands
associated with each signal number in a form that may be reused as
shell input.
The <samp>-l</samp> option causes the shell to print a list of signal names
and their corresponding numbers.
Each <var>sigspec</var> is either a signal name or a signal number.
Signal names are case insensitive and the <code>SIG</code> prefix is optional.
</p>
<p>If a <var>sigspec</var>
is <code>0</code> or <code>EXIT</code>, <var>arg</var> is executed when the shell exits.
If a <var>sigspec</var> is <code>DEBUG</code>, the command <var>arg</var> is executed
before every simple command, <code>for</code> command, <code>case</code> command,
<code>select</code> command, every arithmetic <code>for</code> command, and before
the first command executes in a shell function.
Refer to the description of the <code>extdebug</code> option to the
<code>shopt</code> builtin (see <a href="#The-Shopt-Builtin">The Shopt Builtin</a>) for details of its
effect on the <code>DEBUG</code> trap.
If a <var>sigspec</var> is <code>RETURN</code>, the command <var>arg</var> is executed
each time a shell function or a script executed with the <code>.</code> or
<code>source</code> builtins finishes executing.
</p>
<p>If a <var>sigspec</var> is <code>ERR</code>, the command <var>arg</var> 
is executed whenever
a pipeline (which may consist of a single simple
command), a list, or a compound command returns a
non-zero exit status,
subject to the following conditions.
The <code>ERR</code> trap is not executed if the failed command is part of the
command list immediately following an <code>until</code> or <code>while</code> keyword,
part of the test following the <code>if</code> or <code>elif</code> reserved words,
part of a command executed in a <code>&amp;&amp;</code> or <code>||</code> list
except the command following the final <code>&amp;&amp;</code> or <code>||</code>,
any command in a pipeline but the last,
or if the command&rsquo;s return
status is being inverted using <code>!</code>.
These are the same conditions obeyed by the <code>errexit</code> (<samp>-e</samp>)
option.
</p>
<p>Signals ignored upon entry to the shell cannot be trapped or reset.
Trapped signals that are not being ignored are reset to their original
values in a subshell or subshell environment when one is created.
</p>
<p>The return status is zero unless a <var>sigspec</var> does not specify a
valid signal.
</p>
</dd>
<dt id='index-umask'><span><code>umask</code><a href='#index-umask' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">umask [-p] [-S] [<var>mode</var>]
</pre></div>

<p>Set the shell process&rsquo;s file creation mask to <var>mode</var>.  If
<var>mode</var> begins with a digit, it is interpreted as an octal number;
if not, it is interpreted as a symbolic mode mask similar
to that accepted by the <code>chmod</code> command.  If <var>mode</var> is
omitted, the current value of the mask is printed.  If the <samp>-S</samp>
option is supplied without a <var>mode</var> argument, the mask is printed
in a symbolic format.
If the  <samp>-p</samp> option is supplied, and <var>mode</var>
is omitted, the output is in a form that may be reused as input.
The return status is zero if the mode is successfully changed or if
no <var>mode</var> argument is supplied, and non-zero otherwise.
</p>
<p>Note that when the mode is interpreted as an octal number, each number
of the umask is subtracted from <code>7</code>.  Thus, a umask of <code>022</code>
results in permissions of <code>755</code>.
</p>
</dd>
<dt id='index-unset'><span><code>unset</code><a href='#index-unset' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">unset [-fnv] [<var>name</var>]
</pre></div>

<p>Remove each variable or function <var>name</var>.
If the <samp>-v</samp> option is given, each
<var>name</var> refers to a shell variable and that variable is removed.
If the <samp>-f</samp> option is given, the <var>name</var>s refer to shell
functions, and the function definition is removed.
If the <samp>-n</samp> option is supplied, and <var>name</var> is a variable with
the <code>nameref</code> attribute, <var>name</var> will be unset rather than the
variable it references.
<samp>-n</samp> has no effect if the <samp>-f</samp> option is supplied.
If no options are supplied, each <var>name</var> refers to a variable; if
there is no variable by that name, a function with that name, if any, is
unset.
Readonly variables and functions may not be unset.
Some shell variables lose their special behavior if they are unset; such
behavior is noted in the description of the individual variables.
The return status is zero unless a <var>name</var> is readonly or may not be unset.
</p></dd>
</dl>

<hr>
</div>
<div class="section" id="Bash-Builtins">
<div class="header">
<p>
Next: <a href="#Modifying-Shell-Behavior" accesskey="n" rel="next">Modifying Shell Behavior</a>, Previous: <a href="#Bourne-Shell-Builtins" accesskey="p" rel="prev">Bourne Shell Builtins</a>, Up: <a href="#Shell-Builtin-Commands" accesskey="u" rel="up">Shell Builtin Commands</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Bash-Builtin-Commands"></span><h3 class="section">4.2 Bash Builtin Commands</h3>

<p>This section describes builtin commands which are unique to
or have been extended in Bash.
Some of these commands are specified in the <small>POSIX</small> standard.
</p>
<dl compact="compact">
<dt id='index-alias'><span><code>alias</code><a href='#index-alias' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">alias [-p] [<var>name</var>[=<var>value</var>] &hellip;]
</pre></div>

<p>Without arguments or with the <samp>-p</samp> option, <code>alias</code> prints
the list of aliases on the standard output in a form that allows
them to be reused as input.
If arguments are supplied, an alias is defined for each <var>name</var>
whose <var>value</var> is given.  If no <var>value</var> is given, the name
and value of the alias is printed.
Aliases are described in <a href="#Aliases">Aliases</a>.
</p>
</dd>
<dt id='index-bind'><span><code>bind</code><a href='#index-bind' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">bind [-m <var>keymap</var>] [-lpsvPSVX]
bind [-m <var>keymap</var>] [-q <var>function</var>] [-u <var>function</var>] [-r <var>keyseq</var>]
bind [-m <var>keymap</var>] -f <var>filename</var>
bind [-m <var>keymap</var>] -x <var>keyseq:shell-command</var>
bind [-m <var>keymap</var>] <var>keyseq:function-name</var>
bind [-m <var>keymap</var>] <var>keyseq:readline-command</var>
bind <var>readline-command-line</var>
</pre></div>

<p>Display current Readline (see <a href="#Command-Line-Editing">Command Line Editing</a>)
key and function bindings,
bind a key sequence to a Readline function or macro,
or set a Readline variable.
Each non-option argument is a command as it would appear in a
Readline initialization file (see <a href="#Readline-Init-File">Readline Init File</a>),
but each binding or command must be passed as a separate argument;  e.g.,
&lsquo;<samp>&quot;\C-x\C-r&quot;:re-read-init-file</samp>&rsquo;.
</p>
<p>Options, if supplied, have the following meanings:
</p>
<dl compact="compact">
<dt><span><code>-m <var>keymap</var></code></span></dt>
<dd><p>Use <var>keymap</var> as the keymap to be affected by
the subsequent bindings.  Acceptable <var>keymap</var>
names are
<code>emacs</code>,
<code>emacs-standard</code>,
<code>emacs-meta</code>,
<code>emacs-ctlx</code>,
<code>vi</code>,
<code>vi-move</code>,
<code>vi-command</code>, and
<code>vi-insert</code>.
<code>vi</code> is equivalent to <code>vi-command</code> (<code>vi-move</code> is also a
synonym); <code>emacs</code> is equivalent to <code>emacs-standard</code>.
</p>
</dd>
<dt><span><code>-l</code></span></dt>
<dd><p>List the names of all Readline functions.
</p>
</dd>
<dt><span><code>-p</code></span></dt>
<dd><p>Display Readline function names and bindings in such a way that they
can be used as input or in a Readline initialization file.
</p>
</dd>
<dt><span><code>-P</code></span></dt>
<dd><p>List current Readline function names and bindings.
</p>
</dd>
<dt><span><code>-v</code></span></dt>
<dd><p>Display Readline variable names and values in such a way that they
can be used as input or in a Readline initialization file.
</p>
</dd>
<dt><span><code>-V</code></span></dt>
<dd><p>List current Readline variable names and values.
</p>
</dd>
<dt><span><code>-s</code></span></dt>
<dd><p>Display Readline key sequences bound to macros and the strings they output
in such a way that they can be used as input or in a Readline
initialization file.
</p>
</dd>
<dt><span><code>-S</code></span></dt>
<dd><p>Display Readline key sequences bound to macros and the strings they output.
</p>
</dd>
<dt><span><code>-f <var>filename</var></code></span></dt>
<dd><p>Read key bindings from <var>filename</var>.
</p>
</dd>
<dt><span><code>-q <var>function</var></code></span></dt>
<dd><p>Query about which keys invoke the named <var>function</var>.
</p>
</dd>
<dt><span><code>-u <var>function</var></code></span></dt>
<dd><p>Unbind all keys bound to the named <var>function</var>.
</p>
</dd>
<dt><span><code>-r <var>keyseq</var></code></span></dt>
<dd><p>Remove any current binding for <var>keyseq</var>.
</p>
</dd>
<dt><span><code>-x <var>keyseq:shell-command</var></code></span></dt>
<dd><p>Cause <var>shell-command</var> to be executed whenever <var>keyseq</var> is
entered.
When <var>shell-command</var> is executed, the shell sets the
<code>READLINE_LINE</code> variable to the contents of the Readline line
buffer and the <code>READLINE_POINT</code> and <code>READLINE_MARK</code> variables
to the current location of the insertion point and the saved insertion
point (the <var>mark</var>), respectively.
The shell assigns any numeric argument the user supplied to the
<code>READLINE_ARGUMENT</code> variable.
If there was no argument, that variable is not set.
If the executed command changes the value of any of <code>READLINE_LINE</code>,
<code>READLINE_POINT</code>, or <code>READLINE_MARK</code>, those new values will be
reflected in the editing state.
</p>
</dd>
<dt><span><code>-X</code></span></dt>
<dd><p>List all key sequences bound to shell commands and the associated commands
in a format that can be reused as input.
</p></dd>
</dl>

<p>The return status is zero unless an invalid option is supplied or an
error occurs.
</p>
</dd>
<dt id='index-builtin'><span><code>builtin</code><a href='#index-builtin' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">builtin [<var>shell-builtin</var> [<var>args</var>]]
</pre></div>

<p>Run a shell builtin, passing it <var>args</var>, and return its exit status.
This is useful when defining a shell function with the same
name as a shell builtin, retaining the functionality of the builtin within
the function.
The return status is non-zero if <var>shell-builtin</var> is not a shell
builtin command.
</p>
</dd>
<dt id='index-caller'><span><code>caller</code><a href='#index-caller' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">caller [<var>expr</var>]
</pre></div>

<p>Returns the context of any active subroutine call (a shell function or
a script executed with the <code>.</code> or <code>source</code> builtins).
</p>
<p>Without <var>expr</var>, <code>caller</code> displays the line number and source
filename of the current subroutine call.
If a non-negative integer is supplied as <var>expr</var>, <code>caller</code>
displays the line number, subroutine name, and source file corresponding
to that position in the current execution call stack.  This extra
information may be used, for example, to print a stack trace.  The
current frame is frame 0.
</p>
<p>The return value is 0 unless the shell is not executing a subroutine
call or <var>expr</var> does not correspond to a valid position in the
call stack.
</p>
</dd>
<dt id='index-command'><span><code>command</code><a href='#index-command' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">command [-pVv] <var>command</var> [<var>arguments</var> &hellip;]
</pre></div>

<p>Runs <var>command</var> with <var>arguments</var> ignoring any shell function
named <var>command</var>.
Only shell builtin commands or commands found by searching the
<code>PATH</code> are executed.
If there is a shell function named <code>ls</code>, running &lsquo;<samp>command ls</samp>&rsquo;
within the function will execute the external command <code>ls</code>
instead of calling the function recursively.
The <samp>-p</samp> option means to use a default value for <code>PATH</code>
that is guaranteed to find all of the standard utilities.
The return status in this case is 127 if <var>command</var> cannot be
found or an error occurred, and the exit status of <var>command</var>
otherwise.
</p>
<p>If either the <samp>-V</samp> or <samp>-v</samp> option is supplied, a
description of <var>command</var> is printed.  The <samp>-v</samp> option
causes a single word indicating the command or file name used to
invoke <var>command</var> to be displayed; the <samp>-V</samp> option produces
a more verbose description.  In this case, the return status is
zero if <var>command</var> is found, and non-zero if not.
</p>
</dd>
<dt id='index-declare'><span><code>declare</code><a href='#index-declare' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">declare [-aAfFgiIlnrtux] [-p] [<var>name</var>[=<var>value</var>] &hellip;]
</pre></div>

<p>Declare variables and give them attributes.  If no <var>name</var>s
are given, then display the values of variables instead. 
</p>
<p>The <samp>-p</samp> option will display the attributes and values of each
<var>name</var>.
When <samp>-p</samp> is used with <var>name</var> arguments, additional options,
other than <samp>-f</samp> and <samp>-F</samp>, are ignored.
</p>
<p>When <samp>-p</samp> is supplied without <var>name</var> arguments, <code>declare</code>
will display the attributes and values of all variables having the
attributes specified by the additional options.
If no other options are supplied with <samp>-p</samp>, <code>declare</code> will
display the attributes and values of all shell variables.  The <samp>-f</samp>
option will restrict the display to shell functions.
</p>
<p>The <samp>-F</samp> option inhibits the display of function definitions;
only the function name and attributes are printed.
If the <code>extdebug</code> shell option is enabled using <code>shopt</code>
(see <a href="#The-Shopt-Builtin">The Shopt Builtin</a>), the source file name and line number where
each <var>name</var> is defined are displayed as well.
<samp>-F</samp> implies <samp>-f</samp>.
</p>
<p>The <samp>-g</samp> option forces variables to be created or modified at
the global scope, even when <code>declare</code> is executed in a shell function.
It is ignored in all other cases.
</p>
<p>The <samp>-I</samp> option causes local variables to inherit the attributes
(except the <code>nameref</code> attribute)
and value of any existing variable with the same
<var>name</var> at a surrounding scope.
If there is no existing variable, the local variable is initially unset.
</p>
<p>The following options can be used to restrict output to variables with
the specified attributes or to give variables attributes:
</p>
<dl compact="compact">
<dt><span><code>-a</code></span></dt>
<dd><p>Each <var>name</var> is an indexed array variable (see <a href="#Arrays">Arrays</a>).
</p>
</dd>
<dt><span><code>-A</code></span></dt>
<dd><p>Each <var>name</var> is an associative array variable (see <a href="#Arrays">Arrays</a>).
</p>
</dd>
<dt><span><code>-f</code></span></dt>
<dd><p>Use function names only.
</p>
</dd>
<dt><span><code>-i</code></span></dt>
<dd><p>The variable is to be treated as
an integer; arithmetic evaluation (see <a href="#Shell-Arithmetic">Shell Arithmetic</a>) is
performed when the variable is assigned a value.
</p>
</dd>
<dt><span><code>-l</code></span></dt>
<dd><p>When the variable is assigned a value, all upper-case characters are
converted to lower-case.
The upper-case attribute is disabled.
</p>
</dd>
<dt><span><code>-n</code></span></dt>
<dd><p>Give each <var>name</var> the <code>nameref</code> attribute, making
it a name reference to another variable.
That other variable is defined by the value of <var>name</var>.
All references, assignments, and attribute modifications
to <var>name</var>, except for those using or changing the
<samp>-n</samp> attribute itself, are performed on the variable referenced by
<var>name</var>&rsquo;s value.
The nameref attribute cannot be applied to array variables.
</p>
</dd>
<dt><span><code>-r</code></span></dt>
<dd><p>Make <var>name</var>s readonly.  These names cannot then be assigned values
by subsequent assignment statements or unset.
</p>
</dd>
<dt><span><code>-t</code></span></dt>
<dd><p>Give each <var>name</var> the <code>trace</code> attribute.
Traced functions inherit the <code>DEBUG</code> and <code>RETURN</code> traps from
the calling shell.
The trace attribute has no special meaning for variables.
</p>
</dd>
<dt><span><code>-u</code></span></dt>
<dd><p>When the variable is assigned a value, all lower-case characters are
converted to upper-case.
The lower-case attribute is disabled.
</p>
</dd>
<dt><span><code>-x</code></span></dt>
<dd><p>Mark each <var>name</var> for export to subsequent commands via
the environment.
</p></dd>
</dl>

<p>Using &lsquo;<samp>+</samp>&rsquo; instead of &lsquo;<samp>-</samp>&rsquo; turns off the attribute instead,
with the exceptions that &lsquo;<samp>+a</samp>&rsquo; and &lsquo;<samp>+A</samp>&rsquo;
may not be used to destroy array variables and &lsquo;<samp>+r</samp>&rsquo; will not
remove the readonly attribute.
When used in a function, <code>declare</code> makes each <var>name</var> local,
as with the <code>local</code> command, unless the <samp>-g</samp> option is used.
If a variable name is followed by =<var>value</var>, the value of the variable
is set to <var>value</var>.
</p>
<p>When using <samp>-a</samp> or <samp>-A</samp> and the compound assignment syntax to 
create array variables, additional attributes do not take effect until
subsequent assignments.
</p>
<p>The return status is zero unless an invalid option is encountered,
an attempt is made to define a function using &lsquo;<samp>-f foo=bar</samp>&rsquo;,
an attempt is made to assign a value to a readonly variable,
an attempt is made to assign a value to an array variable without
using the compound assignment syntax (see <a href="#Arrays">Arrays</a>),
one of the <var>name</var>s is not a valid shell variable name,
an attempt is made to turn off readonly status for a readonly variable,
an attempt is made to turn off array status for an array variable,
or an attempt is made to display a non-existent function with <samp>-f</samp>.
</p>
</dd>
<dt id='index-echo'><span><code>echo</code><a href='#index-echo' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">echo [-neE] [<var>arg</var> &hellip;]
</pre></div>

<p>Output the <var>arg</var>s, separated by spaces, terminated with a
newline.
The return status is 0 unless a write error occurs.
If <samp>-n</samp> is specified, the trailing newline is suppressed.
If the <samp>-e</samp> option is given, interpretation of the following
backslash-escaped characters is enabled.
The <samp>-E</samp> option disables the interpretation of these escape characters,
even on systems where they are interpreted by default.
The <code>xpg_echo</code> shell option may be used to
dynamically determine whether or not <code>echo</code> expands these
escape characters by default.
<code>echo</code> does not interpret <samp>--</samp> to mean the end of options.
</p>
<p><code>echo</code> interprets the following escape sequences:
</p><dl compact="compact">
<dt><span><code>\a</code></span></dt>
<dd><p>alert (bell)
</p></dd>
<dt><span><code>\b</code></span></dt>
<dd><p>backspace
</p></dd>
<dt><span><code>\c</code></span></dt>
<dd><p>suppress further output
</p></dd>
<dt><span><code>\e</code></span></dt>
<dt><span><code>\E</code></span></dt>
<dd><p>escape
</p></dd>
<dt><span><code>\f</code></span></dt>
<dd><p>form feed
</p></dd>
<dt><span><code>\n</code></span></dt>
<dd><p>new line
</p></dd>
<dt><span><code>\r</code></span></dt>
<dd><p>carriage return
</p></dd>
<dt><span><code>\t</code></span></dt>
<dd><p>horizontal tab
</p></dd>
<dt><span><code>\v</code></span></dt>
<dd><p>vertical tab
</p></dd>
<dt><span><code>\\</code></span></dt>
<dd><p>backslash
</p></dd>
<dt><span><code>\0<var>nnn</var></code></span></dt>
<dd><p>the eight-bit character whose value is the octal value <var>nnn</var>
(zero to three octal digits)
</p></dd>
<dt><span><code>\x<var>HH</var></code></span></dt>
<dd><p>the eight-bit character whose value is the hexadecimal value <var>HH</var>
(one or two hex digits)
</p></dd>
<dt><span><code>\u<var>HHHH</var></code></span></dt>
<dd><p>the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value
<var>HHHH</var> (one to four hex digits)
</p></dd>
<dt><span><code>\U<var>HHHHHHHH</var></code></span></dt>
<dd><p>the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value
<var>HHHHHHHH</var> (one to eight hex digits)
</p></dd>
</dl>

</dd>
<dt id='index-enable'><span><code>enable</code><a href='#index-enable' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">enable [-a] [-dnps] [-f <var>filename</var>] [<var>name</var> &hellip;]
</pre></div>

<p>Enable and disable builtin shell commands.
Disabling a builtin allows a disk command which has the same name
as a shell builtin to be executed without specifying a full pathname,
even though the shell normally searches for builtins before disk commands.
If <samp>-n</samp> is used, the <var>name</var>s become disabled.  Otherwise
<var>name</var>s are enabled.  For example, to use the <code>test</code> binary
found via <code>$PATH</code> instead of the shell builtin version, type
&lsquo;<samp>enable -n test</samp>&rsquo;.
</p>
<p>If the <samp>-p</samp> option is supplied, or no <var>name</var> arguments appear,
a list of shell builtins is printed.  With no other arguments, the list
consists of all enabled shell builtins.
The <samp>-a</samp> option means to list
each builtin with an indication of whether or not it is enabled. 
</p>
<p>The <samp>-f</samp> option means to load the new builtin command <var>name</var>
from shared object <var>filename</var>, on systems that support dynamic loading.
Bash will use the value of the <code>BASH_LOADABLES_PATH</code> variable as a
colon-separated list of directories in which to search for <var>filename</var>.
The default is system-dependent.
The <samp>-d</samp> option will delete a builtin loaded with <samp>-f</samp>.
</p>
<p>If there are no options, a list of the shell builtins is displayed.
The <samp>-s</samp> option restricts <code>enable</code> to the <small>POSIX</small> special
builtins.  If <samp>-s</samp> is used with <samp>-f</samp>, the new builtin becomes
a special builtin (see <a href="#Special-Builtins">Special Builtins</a>).
</p>
<p>If no options are supplied and a <var>name</var> is not a shell builtin,
<code>enable</code> will attempt to load <var>name</var> from a shared object named
<var>name</var>, as if the command were
&lsquo;<samp>enable -f <var>name</var> <var>name</var></samp>&rsquo;.
</p>
<p>The return status is zero unless a <var>name</var> is not a shell builtin
or there is an error loading a new builtin from a shared object.
</p>
</dd>
<dt id='index-help'><span><code>help</code><a href='#index-help' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">help [-dms] [<var>pattern</var>]
</pre></div>

<p>Display helpful information about builtin commands.
If <var>pattern</var> is specified, <code>help</code> gives detailed help
on all commands matching <var>pattern</var>, otherwise a list of
the builtins is printed.
</p>
<p>Options, if supplied, have the following meanings:
</p>
<dl compact="compact">
<dt><span><code>-d</code></span></dt>
<dd><p>Display a short description of each <var>pattern</var>
</p></dd>
<dt><span><code>-m</code></span></dt>
<dd><p>Display the description of each <var>pattern</var> in a manpage-like format
</p></dd>
<dt><span><code>-s</code></span></dt>
<dd><p>Display only a short usage synopsis for each <var>pattern</var>
</p></dd>
</dl>

<p>The return status is zero unless no command matches <var>pattern</var>.
</p>
</dd>
<dt id='index-let'><span><code>let</code><a href='#index-let' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">let <var>expression</var> [<var>expression</var> &hellip;]
</pre></div>

<p>The <code>let</code> builtin allows arithmetic to be performed on shell
variables.  Each <var>expression</var> is evaluated according to the
rules given below in <a href="#Shell-Arithmetic">Shell Arithmetic</a>.  If the
last <var>expression</var> evaluates to 0, <code>let</code> returns 1;
otherwise 0 is returned.
</p>
</dd>
<dt id='index-local'><span><code>local</code><a href='#index-local' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">local [<var>option</var>] <var>name</var>[=<var>value</var>] &hellip;
</pre></div>

<p>For each argument, a local variable named <var>name</var> is created,
and assigned <var>value</var>.
The <var>option</var> can be any of the options accepted by <code>declare</code>.
<code>local</code> can only be used within a function; it makes the variable
<var>name</var> have a visible scope restricted to that function and its
children.
If <var>name</var> is &lsquo;<samp>-</samp>&rsquo;, the set of shell options is made local to the
function in which <code>local</code> is invoked: shell options changed using
the <code>set</code> builtin inside the function are restored to their original
values when the function returns.
The restore is effected as if a series of <code>set</code> commands were executed
to restore the values that were in place before the function.
The return status is zero unless <code>local</code> is used outside
a function, an invalid <var>name</var> is supplied, or <var>name</var> is a
readonly variable.
</p>
</dd>
<dt id='index-logout'><span><code>logout</code><a href='#index-logout' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">logout [<var>n</var>]
</pre></div>

<p>Exit a login shell, returning a status of <var>n</var> to the shell&rsquo;s
parent.
</p>
</dd>
<dt id='index-mapfile'><span><code>mapfile</code><a href='#index-mapfile' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">mapfile [-d <var>delim</var>] [-n <var>count</var>] [-O <var>origin</var>] [-s <var>count</var>]
    [-t] [-u <var>fd</var>] [-C <var>callback</var>] [-c <var>quantum</var>] [<var>array</var>]
</pre></div>

<p>Read lines from the standard input into the indexed array variable <var>array</var>,
or from file descriptor <var>fd</var>
if the <samp>-u</samp> option is supplied.
The variable <code>MAPFILE</code> is the default <var>array</var>.
Options, if supplied, have the following meanings:
</p>
<dl compact="compact">
<dt><span><code>-d</code></span></dt>
<dd><p>The first character of <var>delim</var> is used to terminate each input line,
rather than newline.
If <var>delim</var> is the empty string, <code>mapfile</code> will terminate a line
when it reads a NUL character.
</p></dd>
<dt><span><code>-n</code></span></dt>
<dd><p>Copy at most <var>count</var> lines.  If <var>count</var> is 0, all lines are copied.
</p></dd>
<dt><span><code>-O</code></span></dt>
<dd><p>Begin assigning to <var>array</var> at index <var>origin</var>.
The default index is 0.
</p></dd>
<dt><span><code>-s</code></span></dt>
<dd><p>Discard the first <var>count</var> lines read.
</p></dd>
<dt><span><code>-t</code></span></dt>
<dd><p>Remove a trailing <var>delim</var> (default newline) from each line read.
</p></dd>
<dt><span><code>-u</code></span></dt>
<dd><p>Read lines from file descriptor <var>fd</var> instead of the standard input.
</p></dd>
<dt><span><code>-C</code></span></dt>
<dd><p>Evaluate <var>callback</var> each time <var>quantum</var> lines are read.
The <samp>-c</samp> option specifies <var>quantum</var>.
</p></dd>
<dt><span><code>-c</code></span></dt>
<dd><p>Specify the number of lines read between each call to <var>callback</var>.
</p></dd>
</dl>

<p>If <samp>-C</samp> is specified without <samp>-c</samp>,
the default quantum is 5000.
When <var>callback</var>  is evaluated, it is supplied the index of the next
array element to be assigned and the line to be assigned to that element
as additional arguments.
<var>callback</var> is evaluated after the line is read but before the
array element is assigned.
</p>
<p>If not supplied with an explicit origin, <code>mapfile</code> will clear <var>array</var>
before assigning to it.
</p>
<p><code>mapfile</code> returns successfully unless an invalid option or option
argument is supplied, <var>array</var> is invalid or unassignable, or <var>array</var>
is not an indexed array.
</p>
</dd>
<dt id='index-printf'><span><code>printf</code><a href='#index-printf' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">printf [-v <var>var</var>] <var>format</var> [<var>arguments</var>]
</pre></div>

<p>Write the formatted <var>arguments</var> to the standard output under the
control of the <var>format</var>.
The <samp>-v</samp> option causes the output to be assigned to the variable
<var>var</var> rather than being printed to the standard output.
</p>
<p>The <var>format</var> is a character string which contains three types of objects:
plain characters, which are simply copied to standard output, character
escape sequences, which are converted and copied to the standard output, and
format specifications, each of which causes printing of the next successive
<var>argument</var>.
In addition to the standard <code>printf(1)</code> formats, <code>printf</code>
interprets the following extensions:
</p>
<dl compact="compact">
<dt><span><code>%b</code></span></dt>
<dd><p>Causes <code>printf</code> to expand backslash escape sequences in the
corresponding <var>argument</var> in the same way as <code>echo -e</code>
(see <a href="#Bash-Builtins">Bash Builtin Commands</a>).
</p></dd>
<dt><span><code>%q</code></span></dt>
<dd><p>Causes <code>printf</code> to output the
corresponding <var>argument</var> in a format that can be reused as shell input.
</p></dd>
<dt><span><code>%Q</code></span></dt>
<dd><p>like <code>%q</code>, but applies any supplied precision to the <var>argument</var>
before quoting it.
</p></dd>
<dt><span><code>%(<var>datefmt</var>)T</code></span></dt>
<dd><p>Causes <code>printf</code> to output the date-time string resulting from using
<var>datefmt</var> as a format string for <code>strftime</code>(3).
The corresponding <var>argument</var> is an integer representing the number of
seconds since the epoch.
Two special argument values may be used: -1 represents the current
time, and -2 represents the time the shell was invoked.
If no argument is specified, conversion behaves as if -1 had been given.
This is an exception to the usual <code>printf</code> behavior.
</p></dd>
</dl>

<p>The %b, %q, and %T directives all use the field width and precision
arguments from the format specification and write that many bytes from    
(or use that wide a field for) the expanded argument, which usually
contains more characters than the original.
</p>
<p>Arguments to non-string format specifiers are treated as C language constants,
except that a leading plus or minus sign is allowed, and if the leading
character is a single or double quote, the value is the ASCII value of
the following character.
</p>
<p>The <var>format</var> is reused as necessary to consume all of the <var>arguments</var>.
If the <var>format</var> requires more <var>arguments</var> than are supplied, the
extra format specifications behave as if a zero value or null string, as
appropriate, had been supplied.  The return value is zero on success,
non-zero on failure.
</p>
</dd>
<dt id='index-read'><span><code>read</code><a href='#index-read' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">read [-ers] [-a <var>aname</var>] [-d <var>delim</var>] [-i <var>text</var>] [-n <var>nchars</var>]
    [-N <var>nchars</var>] [-p <var>prompt</var>] [-t <var>timeout</var>] [-u <var>fd</var>] [<var>name</var> &hellip;]
</pre></div>

<p>One line is read from the standard input, or from the file descriptor
<var>fd</var> supplied as an argument to the <samp>-u</samp> option,
split into words as described above in <a href="#Word-Splitting">Word Splitting</a>,
and the first word
is assigned to the first <var>name</var>, the second word to the second <var>name</var>,
and so on.
If there are more words than names,
the remaining words and their intervening delimiters are assigned
to the last <var>name</var>.
If there are fewer words read from the input stream than names,
the remaining names are assigned empty values.
The characters in the value of the <code>IFS</code> variable
are used to split the line into words using the same rules the shell
uses for expansion (described above in <a href="#Word-Splitting">Word Splitting</a>).
The backslash character &lsquo;<samp>\</samp>&rsquo; may be used to remove any special
meaning for the next character read and for line continuation.
</p>
<p>Options, if supplied, have the following meanings:
</p>
<dl compact="compact">
<dt><span><code>-a <var>aname</var></code></span></dt>
<dd><p>The words are assigned to sequential indices of the array variable
<var>aname</var>, starting at 0.
All elements are removed from <var>aname</var> before the assignment.
Other <var>name</var> arguments are ignored.
</p>
</dd>
<dt><span><code>-d <var>delim</var></code></span></dt>
<dd><p>The first character of <var>delim</var> is used to terminate the input line,
rather than newline.
If <var>delim</var> is the empty string, <code>read</code> will terminate a line
when it reads a NUL character.
</p>
</dd>
<dt><span><code>-e</code></span></dt>
<dd><p>Readline (see <a href="#Command-Line-Editing">Command Line Editing</a>) is used to obtain the line.
Readline uses the current (or default, if line editing was not previously
active) editing settings, but uses Readline&rsquo;s default filename completion.
</p>
</dd>
<dt><span><code>-i <var>text</var></code></span></dt>
<dd><p>If Readline is being used to read the line, <var>text</var> is placed into
the editing buffer before editing begins.
</p>
</dd>
<dt><span><code>-n <var>nchars</var></code></span></dt>
<dd><p><code>read</code> returns after reading <var>nchars</var> characters rather than
waiting for a complete line of input, but honors a delimiter if fewer
than <var>nchars</var> characters are read before the delimiter.
</p>
</dd>
<dt><span><code>-N <var>nchars</var></code></span></dt>
<dd><p><code>read</code> returns after reading exactly <var>nchars</var> characters rather
than waiting for a complete line of input, unless EOF is encountered or
<code>read</code> times out.
Delimiter characters encountered in the input are
not treated specially and do not cause <code>read</code> to return until
<var>nchars</var> characters are read.
The result is not split on the characters in <code>IFS</code>; the intent is
that the variable is assigned exactly the characters read
(with the exception of backslash; see the <samp>-r</samp> option below).
</p>
</dd>
<dt><span><code>-p <var>prompt</var></code></span></dt>
<dd><p>Display <var>prompt</var>, without a trailing newline, before attempting
to read any input.
The prompt is displayed only if input is coming from a terminal.
</p>
</dd>
<dt><span><code>-r</code></span></dt>
<dd><p>If this option is given, backslash does not act as an escape character.
The backslash is considered to be part of the line.
In particular, a backslash-newline pair may not then be used as a line
continuation.
</p>
</dd>
<dt><span><code>-s</code></span></dt>
<dd><p>Silent mode.  If input is coming from a terminal, characters are
not echoed.
</p>
</dd>
<dt><span><code>-t <var>timeout</var></code></span></dt>
<dd><p>Cause <code>read</code> to time out and return failure if a complete line of
input (or a specified number of characters)
is not read within <var>timeout</var> seconds.
<var>timeout</var>  may be a decimal number with a fractional portion following
the decimal point.
This option is only effective if <code>read</code> is reading input from a
terminal, pipe, or other special file; it has no effect when reading
from regular files.
If <code>read</code> times out, <code>read</code> saves any partial input read into
the specified variable <var>name</var>.
If <var>timeout</var> is 0, <code>read</code> returns immediately, without trying to
read any data.
The exit status is 0 if input is available on the specified file descriptor,
or the read will return EOF,
non-zero otherwise.
The exit status is greater than 128 if the timeout is exceeded.
</p>
</dd>
<dt><span><code>-u <var>fd</var></code></span></dt>
<dd><p>Read input from file descriptor <var>fd</var>.
</p></dd>
</dl>

<p>If no <var>name</var>s are supplied, the line read,
without the ending delimiter but otherwise unmodified,
is assigned to the
variable <code>REPLY</code>.
The exit status is zero, unless end-of-file is encountered, <code>read</code>
times out (in which case the status is greater than 128),
a variable assignment error (such as assigning to a readonly variable) occurs,
or an invalid file descriptor is supplied as the argument to <samp>-u</samp>.
</p>
</dd>
<dt id='index-readarray'><span><code>readarray</code><a href='#index-readarray' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">readarray [-d <var>delim</var>] [-n <var>count</var>] [-O <var>origin</var>] [-s <var>count</var>]
    [-t] [-u <var>fd</var>] [-C <var>callback</var>] [-c <var>quantum</var>] [<var>array</var>]
</pre></div>

<p>Read lines from the standard input into the indexed array variable <var>array</var>,
or from file descriptor <var>fd</var>
if the <samp>-u</samp> option is supplied.
</p>
<p>A synonym for <code>mapfile</code>.
</p>
</dd>
<dt id='index-source'><span><code>source</code><a href='#index-source' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">source <var>filename</var>
</pre></div>

<p>A synonym for <code>.</code> (see <a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a>).
</p>
</dd>
<dt id='index-type'><span><code>type</code><a href='#index-type' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">type [-afptP] [<var>name</var> &hellip;]
</pre></div>

<p>For each <var>name</var>, indicate how it would be interpreted if used as a
command name.
</p>
<p>If the <samp>-t</samp> option is used, <code>type</code> prints a single word
which is one of &lsquo;<samp>alias</samp>&rsquo;, &lsquo;<samp>function</samp>&rsquo;, &lsquo;<samp>builtin</samp>&rsquo;,
&lsquo;<samp>file</samp>&rsquo; or &lsquo;<samp>keyword</samp>&rsquo;,
if <var>name</var> is an alias, shell function, shell builtin,
disk file, or shell reserved word, respectively.
If the <var>name</var> is not found, then nothing is printed, and
<code>type</code> returns a failure status.
</p>
<p>If the <samp>-p</samp> option is used, <code>type</code> either returns the name
of the disk file that would be executed, or nothing if <samp>-t</samp>
would not return &lsquo;<samp>file</samp>&rsquo;.
</p>
<p>The <samp>-P</samp> option forces a path search for each <var>name</var>, even if
<samp>-t</samp> would not return &lsquo;<samp>file</samp>&rsquo;.
</p>
<p>If a command is hashed, <samp>-p</samp> and <samp>-P</samp> print the hashed value,
which is not necessarily the file that appears first in <code>$PATH</code>.
</p>
<p>If the <samp>-a</samp> option is used, <code>type</code> returns all of the places
that contain an executable named <var>file</var>.
This includes aliases and functions, if and only if the <samp>-p</samp> option
is not also used.
</p>
<p>If the <samp>-f</samp> option is used, <code>type</code> does not attempt to find
shell functions, as with the <code>command</code> builtin.
</p>
<p>The return status is zero if all of the <var>name</var>s are found, non-zero
if any are not found.
</p>
</dd>
<dt id='index-typeset'><span><code>typeset</code><a href='#index-typeset' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">typeset [-afFgrxilnrtux] [-p] [<var>name</var>[=<var>value</var>] &hellip;]
</pre></div>

<p>The <code>typeset</code> command is supplied for compatibility with the Korn
shell.
It is a synonym for the <code>declare</code> builtin command.
</p>
</dd>
<dt id='index-ulimit'><span><code>ulimit</code><a href='#index-ulimit' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">ulimit [-HS] -a
ulimit [-HS] [-bcdefiklmnpqrstuvxPRT] [<var>limit</var>]
</pre></div>

<p><code>ulimit</code> provides control over the resources available to processes
started by the shell, on systems that allow such control.  If an
option is given, it is interpreted as follows:
</p>
<dl compact="compact">
<dt><span><code>-S</code></span></dt>
<dd><p>Change and report the soft limit associated with a resource.
</p>
</dd>
<dt><span><code>-H</code></span></dt>
<dd><p>Change and report the hard limit associated with a resource.
</p>
</dd>
<dt><span><code>-a</code></span></dt>
<dd><p>All current limits are reported; no limits are set.
</p>
</dd>
<dt><span><code>-b</code></span></dt>
<dd><p>The maximum socket buffer size.
</p>
</dd>
<dt><span><code>-c</code></span></dt>
<dd><p>The maximum size of core files created.
</p>
</dd>
<dt><span><code>-d</code></span></dt>
<dd><p>The maximum size of a process&rsquo;s data segment.
</p>
</dd>
<dt><span><code>-e</code></span></dt>
<dd><p>The maximum scheduling priority (&quot;nice&quot;).
</p>
</dd>
<dt><span><code>-f</code></span></dt>
<dd><p>The maximum size of files written by the shell and its children.
</p>
</dd>
<dt><span><code>-i</code></span></dt>
<dd><p>The maximum number of pending signals.
</p>
</dd>
<dt><span><code>-k</code></span></dt>
<dd><p>The maximum number of kqueues that may be allocated.
</p>
</dd>
<dt><span><code>-l</code></span></dt>
<dd><p>The maximum size that may be locked into memory.
</p>
</dd>
<dt><span><code>-m</code></span></dt>
<dd><p>The maximum resident set size (many systems do not honor this limit).
</p>
</dd>
<dt><span><code>-n</code></span></dt>
<dd><p>The maximum number of open file descriptors (most systems do not
allow this value to be set).
</p>
</dd>
<dt><span><code>-p</code></span></dt>
<dd><p>The pipe buffer size.
</p>
</dd>
<dt><span><code>-q</code></span></dt>
<dd><p>The maximum number of bytes in <small>POSIX</small> message queues.
</p>
</dd>
<dt><span><code>-r</code></span></dt>
<dd><p>The maximum real-time scheduling priority.
</p>
</dd>
<dt><span><code>-s</code></span></dt>
<dd><p>The maximum stack size.
</p>
</dd>
<dt><span><code>-t</code></span></dt>
<dd><p>The maximum amount of cpu time in seconds.
</p>
</dd>
<dt><span><code>-u</code></span></dt>
<dd><p>The maximum number of processes available to a single user.
</p>
</dd>
<dt><span><code>-v</code></span></dt>
<dd><p>The maximum amount of virtual memory available to the shell, and, on
some systems, to its children.
</p>
</dd>
<dt><span><code>-x</code></span></dt>
<dd><p>The maximum number of file locks.
</p>
</dd>
<dt><span><code>-P</code></span></dt>
<dd><p>The maximum number of pseudoterminals.
</p>
</dd>
<dt><span><code>-R</code></span></dt>
<dd><p>The maximum time a real-time process can run before blocking, in microseconds.
</p>
</dd>
<dt><span><code>-T</code></span></dt>
<dd><p>The maximum number of threads.
</p></dd>
</dl>

<p>If <var>limit</var> is given, and the <samp>-a</samp> option is not used,
<var>limit</var> is the new value of the specified resource.
The special <var>limit</var> values <code>hard</code>, <code>soft</code>, and
<code>unlimited</code> stand for the current hard limit, the current soft limit,
and no limit, respectively.
A hard limit cannot be increased by a non-root user once it is set;
a soft limit may be increased up to the value of the hard limit.
Otherwise, the current value of the soft limit for the specified resource
is printed, unless the <samp>-H</samp> option is supplied.
When more than one
resource is specified, the limit name and unit, if appropriate,
are printed before the value.
When setting new limits, if neither <samp>-H</samp> nor <samp>-S</samp> is supplied,
both the hard and soft limits are set.
If no option is given, then <samp>-f</samp> is assumed.  Values are in 1024-byte
increments, except for
<samp>-t</samp>, which is in seconds;
<samp>-R</samp>, which is in microseconds;
<samp>-p</samp>, which is in units of 512-byte blocks;
<samp>-P</samp>,
<samp>-T</samp>,
<samp>-b</samp>,
<samp>-k</samp>,
<samp>-n</samp> and <samp>-u</samp>, which are unscaled values;
and, when in <small>POSIX</small> Mode (see <a href="#Bash-POSIX-Mode">Bash POSIX Mode</a>),
<samp>-c</samp> and <samp>-f</samp>, which are in 512-byte increments.
</p>
<p>The return status is zero unless an invalid option or argument is supplied,
or an error occurs while setting a new limit.
</p>
</dd>
<dt id='index-unalias'><span><code>unalias</code><a href='#index-unalias' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">unalias [-a] [<var>name</var> &hellip; ]
</pre></div>

<p>Remove each <var>name</var> from the list of aliases.  If <samp>-a</samp> is
supplied, all aliases are removed.
Aliases are described in <a href="#Aliases">Aliases</a>.
</p></dd>
</dl>

<hr>
</div>
<div class="section" id="Modifying-Shell-Behavior">
<div class="header">
<p>
Next: <a href="#Special-Builtins" accesskey="n" rel="next">Special Builtins</a>, Previous: <a href="#Bash-Builtins" accesskey="p" rel="prev">Bash Builtin Commands</a>, Up: <a href="#Shell-Builtin-Commands" accesskey="u" rel="up">Shell Builtin Commands</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Modifying-Shell-Behavior-1"></span><h3 class="section">4.3 Modifying Shell Behavior</h3>
 

<ul class="section-toc">
<li><a href="#The-Set-Builtin" accesskey="1">The Set Builtin</a></li>
<li><a href="#The-Shopt-Builtin" accesskey="2">The Shopt Builtin</a></li>
</ul>
<hr>
<div class="subsection" id="The-Set-Builtin">
<div class="header">
<p>
Next: <a href="#The-Shopt-Builtin" accesskey="n" rel="next">The Shopt Builtin</a>, Up: <a href="#Modifying-Shell-Behavior" accesskey="u" rel="up">Modifying Shell Behavior</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="The-Set-Builtin-1"></span><h4 class="subsection">4.3.1 The Set Builtin</h4>

<p>This builtin is so complicated that it deserves its own section.  <code>set</code>
allows you to change the values of shell options and set the positional
parameters, or to display the names and values of shell variables.
</p>
<dl compact="compact">
<dt id='index-set'><span><code>set</code><a href='#index-set' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">set [-abefhkmnptuvxBCEHPT] [-o <var>option-name</var>] [--] [-] [<var>argument</var> &hellip;]
set [+abefhkmnptuvxBCEHPT] [+o <var>option-name</var>] [--] [-] [<var>argument</var> &hellip;]
</pre></div>

<p>If no options or arguments are supplied, <code>set</code> displays the names
and values of all shell variables and functions, sorted according to the
current locale, in a format that may be reused as input
for setting or resetting the currently-set variables.
Read-only variables cannot be reset.
In <small>POSIX</small> mode, only shell variables are listed.
</p>
<p>When options are supplied, they set or unset shell attributes.
Options, if specified, have the following meanings:
</p>
<dl compact="compact">
<dt><span><code>-a</code></span></dt>
<dd><p>Each variable or function that is created or modified is given the
export attribute and marked for export to the environment of
subsequent commands.
</p>
</dd>
<dt><span><code>-b</code></span></dt>
<dd><p>Cause the status of terminated background jobs to be reported
immediately, rather than before printing the next primary prompt.
</p>
</dd>
<dt><span><code>-e</code></span></dt>
<dd><p>Exit immediately if
a pipeline (see <a href="#Pipelines">Pipelines</a>), which may consist of a single simple command
(see <a href="#Simple-Commands">Simple Commands</a>),
a list (see <a href="#Lists">Lists of Commands</a>),
or a compound command (see <a href="#Compound-Commands">Compound Commands</a>)
returns a non-zero status.
The shell does not exit if the command that fails is part of the
command list immediately following a <code>while</code> or <code>until</code> keyword,
part of the test in an <code>if</code> statement,
part of any command executed in a <code>&amp;&amp;</code> or <code>||</code> list except
the command following the final <code>&amp;&amp;</code> or <code>||</code>,
any command in a pipeline but the last,
or if the command&rsquo;s return status is being inverted with <code>!</code>.
If a compound command other than a subshell
returns a non-zero status because a command failed
while <samp>-e</samp> was being ignored, the shell does not exit.
A trap on <code>ERR</code>, if set, is executed before the shell exits.
</p>
<p>This option applies to the shell environment and each subshell environment
separately (see <a href="#Command-Execution-Environment">Command Execution Environment</a>), and may cause
subshells to exit before executing all the commands in the subshell.
</p>
<p>If a compound command or shell function executes in a context where
<samp>-e</samp> is being ignored,
none of the commands executed within the compound command or function body
will be affected by the <samp>-e</samp> setting, even if <samp>-e</samp> is set
and a command returns a failure status.
If a compound command or shell function sets <samp>-e</samp> while executing in
a context where <samp>-e</samp> is ignored, that setting will not have any
effect until the compound command or the command containing the function
call completes.
</p>
</dd>
<dt><span><code>-f</code></span></dt>
<dd><p>Disable filename expansion (globbing).
</p>
</dd>
<dt><span><code>-h</code></span></dt>
<dd><p>Locate and remember (hash) commands as they are looked up for execution.
This option is enabled by default.
</p>
</dd>
<dt><span><code>-k</code></span></dt>
<dd><p>All arguments in the form of assignment statements are placed
in the environment for a command, not just those that precede
the command name.
</p>
</dd>
<dt><span><code>-m</code></span></dt>
<dd><p>Job control is enabled (see <a href="#Job-Control">Job Control</a>).
All processes run in a separate process group.
When a background job completes, the shell prints a line
containing its exit status.
</p>
</dd>
<dt><span><code>-n</code></span></dt>
<dd><p>Read commands but do not execute them.
This may be used to check a script for syntax errors.
This option is ignored by interactive shells.
</p>
</dd>
<dt><span><code>-o <var>option-name</var></code></span></dt>
<dd>
<p>Set the option corresponding to <var>option-name</var>:
</p>
<dl compact="compact">
<dt><span><code>allexport</code></span></dt>
<dd><p>Same as <code>-a</code>.
</p>
</dd>
<dt><span><code>braceexpand</code></span></dt>
<dd><p>Same as <code>-B</code>.
</p>
</dd>
<dt><span><code>emacs</code></span></dt>
<dd><p>Use an <code>emacs</code>-style line editing interface (see <a href="#Command-Line-Editing">Command Line Editing</a>).
This also affects the editing interface used for <code>read -e</code>.
</p>
</dd>
<dt><span><code>errexit</code></span></dt>
<dd><p>Same as <code>-e</code>.
</p>
</dd>
<dt><span><code>errtrace</code></span></dt>
<dd><p>Same as <code>-E</code>.
</p>
</dd>
<dt><span><code>functrace</code></span></dt>
<dd><p>Same as <code>-T</code>.
</p>
</dd>
<dt><span><code>hashall</code></span></dt>
<dd><p>Same as <code>-h</code>.
</p>
</dd>
<dt><span><code>histexpand</code></span></dt>
<dd><p>Same as <code>-H</code>.
</p>
</dd>
<dt><span><code>history</code></span></dt>
<dd><p>Enable command history, as described in <a href="#Bash-History-Facilities">Bash History Facilities</a>.
This option is on by default in interactive shells.
</p>
</dd>
<dt><span><code>ignoreeof</code></span></dt>
<dd><p>An interactive shell will not exit upon reading EOF.
</p>
</dd>
<dt><span><code>keyword</code></span></dt>
<dd><p>Same as <code>-k</code>.
</p>
</dd>
<dt><span><code>monitor</code></span></dt>
<dd><p>Same as <code>-m</code>.
</p>
</dd>
<dt><span><code>noclobber</code></span></dt>
<dd><p>Same as <code>-C</code>.
</p>
</dd>
<dt><span><code>noexec</code></span></dt>
<dd><p>Same as <code>-n</code>.
</p>
</dd>
<dt><span><code>noglob</code></span></dt>
<dd><p>Same as <code>-f</code>.
</p>
</dd>
<dt><span><code>nolog</code></span></dt>
<dd><p>Currently ignored.
</p>
</dd>
<dt><span><code>notify</code></span></dt>
<dd><p>Same as <code>-b</code>.
</p>
</dd>
<dt><span><code>nounset</code></span></dt>
<dd><p>Same as <code>-u</code>.
</p>
</dd>
<dt><span><code>onecmd</code></span></dt>
<dd><p>Same as <code>-t</code>.
</p>
</dd>
<dt><span><code>physical</code></span></dt>
<dd><p>Same as <code>-P</code>.
</p>
</dd>
<dt><span><code>pipefail</code></span></dt>
<dd><p>If set, the return value of a pipeline is the value of the last
(rightmost) command to exit with a non-zero status, or zero if all
commands in the pipeline exit successfully.
This option is disabled by default.
</p>
</dd>
<dt><span><code>posix</code></span></dt>
<dd><p>Change the behavior of Bash where the default operation differs
from the <small>POSIX</small> standard to match the standard
(see <a href="#Bash-POSIX-Mode">Bash POSIX Mode</a>).
This is intended to make Bash behave as a strict superset of that
standard.
</p>
</dd>
<dt><span><code>privileged</code></span></dt>
<dd><p>Same as <code>-p</code>.
</p>
</dd>
<dt><span><code>verbose</code></span></dt>
<dd><p>Same as <code>-v</code>.
</p>
</dd>
<dt><span><code>vi</code></span></dt>
<dd><p>Use a <code>vi</code>-style line editing interface.
This also affects the editing interface used for <code>read -e</code>.
</p>
</dd>
<dt><span><code>xtrace</code></span></dt>
<dd><p>Same as <code>-x</code>.
</p></dd>
</dl>

</dd>
<dt><span><code>-p</code></span></dt>
<dd><p>Turn on privileged mode.
In this mode, the <code>$BASH_ENV</code> and <code>$ENV</code> files are not
processed, shell functions are not inherited from the environment,
and the <code>SHELLOPTS</code>, <code>BASHOPTS</code>, <code>CDPATH</code> and <code>GLOBIGNORE</code>
variables, if they appear in the environment, are ignored.
If the shell is started with the effective user (group) id not equal to the
real user (group) id, and the <samp>-p</samp> option is not supplied, these actions
are taken and the effective user id is set to the real user id.
If the <samp>-p</samp> option is supplied at startup, the effective user id is
not reset.
Turning this option off causes the effective user
and group ids to be set to the real user and group ids.
</p>
</dd>
<dt><span><code>-r</code></span></dt>
<dd><p>Enable restricted shell mode.
This option cannot be unset once it has been set.
</p>
</dd>
<dt><span><code>-t</code></span></dt>
<dd><p>Exit after reading and executing one command.
</p>
</dd>
<dt><span><code>-u</code></span></dt>
<dd><p>Treat unset variables and parameters other than the special parameters
&lsquo;<samp>@</samp>&rsquo; or &lsquo;<samp>*</samp>&rsquo;,
or array variables subscripted with &lsquo;<samp>@</samp>&rsquo; or &lsquo;<samp>*</samp>&rsquo;,
as an error when performing parameter expansion.
An error message will be written to the standard error, and a non-interactive
shell will exit.
</p>
</dd>
<dt><span><code>-v</code></span></dt>
<dd><p>Print shell input lines as they are read.
</p>
</dd>
<dt><span><code>-x</code></span></dt>
<dd><p>Print a trace of simple commands, <code>for</code> commands, <code>case</code>
commands, <code>select</code> commands, and arithmetic <code>for</code> commands
and their arguments or associated word lists after they are
expanded and before they are executed.  The value of the <code>PS4</code>
variable is expanded and the resultant value is printed before
the command and its expanded arguments.
</p>
</dd>
<dt><span><code>-B</code></span></dt>
<dd><p>The shell will perform brace expansion (see <a href="#Brace-Expansion">Brace Expansion</a>).
This option is on by default.
</p>
</dd>
<dt><span><code>-C</code></span></dt>
<dd><p>Prevent output redirection using &lsquo;<samp>&gt;</samp>&rsquo;, &lsquo;<samp>&gt;&amp;</samp>&rsquo;, and &lsquo;<samp>&lt;&gt;</samp>&rsquo;
from overwriting existing files.
</p>
</dd>
<dt><span><code>-E</code></span></dt>
<dd><p>If set, any trap on <code>ERR</code> is inherited by shell functions, command
substitutions, and commands executed in a subshell environment.
The <code>ERR</code> trap is normally not inherited in such cases.
</p>
</dd>
<dt><span><code>-H</code></span></dt>
<dd><p>Enable &lsquo;<samp>!</samp>&rsquo; style history substitution (see <a href="#History-Interaction">History Expansion</a>).
This option is on by default for interactive shells.
</p>
</dd>
<dt><span><code>-P</code></span></dt>
<dd><p>If set, do not resolve symbolic links when performing commands such as
<code>cd</code> which change the current directory.  The physical directory
is used instead.  By default, Bash follows
the logical chain of directories when performing commands
which change the current directory.
</p>
<p>For example, if <samp>/usr/sys</samp> is a symbolic link to <samp>/usr/local/sys</samp>
then:
</p><div class="example">
<pre class="example">$ cd /usr/sys; echo $PWD
/usr/sys
$ cd ..; pwd
/usr
</pre></div>

<p>If <code>set -P</code> is on, then:
</p><div class="example">
<pre class="example">$ cd /usr/sys; echo $PWD
/usr/local/sys
$ cd ..; pwd
/usr/local
</pre></div>

</dd>
<dt><span><code>-T</code></span></dt>
<dd><p>If set, any trap on <code>DEBUG</code> and <code>RETURN</code> are inherited by
shell functions, command substitutions, and commands executed
in a subshell environment.
The <code>DEBUG</code> and <code>RETURN</code> traps are normally not inherited
in such cases.
</p>
</dd>
<dt><span><code>--</code></span></dt>
<dd><p>If no arguments follow this option, then the positional parameters are
unset.  Otherwise, the positional parameters are set to the
<var>arguments</var>, even if some of them begin with a &lsquo;<samp>-</samp>&rsquo;.
</p>
</dd>
<dt><span><code>-</code></span></dt>
<dd><p>Signal the end of options, cause all remaining <var>arguments</var>
to be assigned to the positional parameters.  The <samp>-x</samp>
and <samp>-v</samp>  options are turned off.
If there are no arguments, the positional parameters remain unchanged.
</p></dd>
</dl>

<p>Using &lsquo;<samp>+</samp>&rsquo; rather than &lsquo;<samp>-</samp>&rsquo; causes these options to be
turned off.  The options can also be used upon invocation of the
shell.  The current set of options may be found in <code>$-</code>.
</p>
<p>The remaining N <var>arguments</var> are positional parameters and are
assigned, in order, to <code>$1</code>, <code>$2</code>, &hellip;  <code>$N</code>.
The special parameter <code>#</code> is set to N.
</p>
<p>The return status is always zero unless an invalid option is supplied.
</p></dd>
</dl>

<hr>
</div>
<div class="subsection" id="The-Shopt-Builtin">
<div class="header">
<p>
Previous: <a href="#The-Set-Builtin" accesskey="p" rel="prev">The Set Builtin</a>, Up: <a href="#Modifying-Shell-Behavior" accesskey="u" rel="up">Modifying Shell Behavior</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="The-Shopt-Builtin-1"></span><h4 class="subsection">4.3.2 The Shopt Builtin</h4>

<p>This builtin allows you to change additional shell optional behavior.
</p>
<dl compact="compact">
<dt id='index-shopt'><span><code>shopt</code><a href='#index-shopt' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">shopt [-pqsu] [-o] [<var>optname</var> &hellip;]
</pre></div>

<p>Toggle the values of settings controlling optional shell behavior.
The settings can be either those listed below, or, if the
<samp>-o</samp> option is used, those available with the <samp>-o</samp>
option to the <code>set</code> builtin command (see <a href="#The-Set-Builtin">The Set Builtin</a>).
With no options, or with the <samp>-p</samp> option, a list of all settable
options is displayed, with an indication of whether or not each is set;
if <var>optname</var>s are supplied, the output is restricted to those options.
The <samp>-p</samp> option causes output to be displayed in a form that
may be reused as input.
Other options have the following meanings:
</p>
<dl compact="compact">
<dt><span><code>-s</code></span></dt>
<dd><p>Enable (set) each <var>optname</var>.
</p>
</dd>
<dt><span><code>-u</code></span></dt>
<dd><p>Disable (unset) each <var>optname</var>.
</p>
</dd>
<dt><span><code>-q</code></span></dt>
<dd><p>Suppresses normal output; the return status
indicates whether the <var>optname</var> is set or unset.
If multiple <var>optname</var> arguments are given with <samp>-q</samp>,
the return status is zero if all <var>optname</var>s are enabled;
non-zero otherwise.
</p>
</dd>
<dt><span><code>-o</code></span></dt>
<dd><p>Restricts the values of
<var>optname</var> to be those defined for the <samp>-o</samp> option to the
<code>set</code> builtin (see <a href="#The-Set-Builtin">The Set Builtin</a>).
</p></dd>
</dl>

<p>If either <samp>-s</samp> or <samp>-u</samp>
is used with no <var>optname</var> arguments, <code>shopt</code> shows only
those options which are set or unset, respectively.
</p>
<p>Unless otherwise noted, the <code>shopt</code> options are disabled (off)
by default.
</p>
<p>The return status when listing options is zero if all <var>optname</var>s
are enabled, non-zero otherwise.  When setting or unsetting options,
the return status is zero unless an <var>optname</var> is not a valid shell
option.
</p>
<p>The list of <code>shopt</code> options is:
</p><dl compact="compact">
<dt><span><code>assoc_expand_once</code></span></dt>
<dd><p>If set, the shell suppresses multiple evaluation of associative array
subscripts during arithmetic expression evaluation, while executing
builtins that can perform variable assignments,
and while executing builtins that perform array dereferencing.
</p>
</dd>
<dt><span><code>autocd</code></span></dt>
<dd><p>If set, a command name that is the name of a directory is executed as if
it were the argument to the <code>cd</code> command.
This option is only used by interactive shells.
</p>
</dd>
<dt><span><code>cdable_vars</code></span></dt>
<dd><p>If this is set, an argument to the <code>cd</code> builtin command that
is not a directory is assumed to be the name of a variable whose
value is the directory to change to.
</p>
</dd>
<dt><span><code>cdspell</code></span></dt>
<dd><p>If set, minor errors in the spelling of a directory component in a
<code>cd</code> command will be corrected.
The errors checked for are transposed characters,
a missing character, and a character too many.
If a correction is found, the corrected path is printed,
and the command proceeds.
This option is only used by interactive shells.
</p>
</dd>
<dt><span><code>checkhash</code></span></dt>
<dd><p>If this is set, Bash checks that a command found in the hash
table exists before trying to execute it.  If a hashed command no
longer exists, a normal path search is performed.
</p>
</dd>
<dt><span><code>checkjobs</code></span></dt>
<dd><p>If set, Bash lists the status of any stopped and running jobs before
exiting an interactive shell.  If any jobs are running, this causes
the exit to be deferred until a second exit is attempted without an
intervening command (see <a href="#Job-Control">Job Control</a>).
The shell always postpones exiting if any jobs are stopped.
</p>
</dd>
<dt><span><code>checkwinsize</code></span></dt>
<dd><p>If set, Bash checks the window size after each external (non-builtin)
command and, if necessary, updates the values of    
<code>LINES</code> and <code>COLUMNS</code>.
This option is enabled by default.
</p>
</dd>
<dt><span><code>cmdhist</code></span></dt>
<dd><p>If set, Bash
attempts to save all lines of a multiple-line
command in the same history entry.  This allows
easy re-editing of multi-line commands.
This option is enabled by default, but only has an effect if command
history is enabled (see <a href="#Bash-History-Facilities">Bash History Facilities</a>).
</p>
</dd>
<dt><span><code>compat31</code></span></dt>
<dt><span><code>compat32</code></span></dt>
<dt><span><code>compat40</code></span></dt>
<dt><span><code>compat41</code></span></dt>
<dt><span><code>compat42</code></span></dt>
<dt><span><code>compat43</code></span></dt>
<dt><span><code>compat44</code></span></dt>
<dd><p>These control aspects of the shell&rsquo;s compatibility mode
(see <a href="#Shell-Compatibility-Mode">Shell Compatibility Mode</a>).
</p>
</dd>
<dt><span><code>complete_fullquote</code></span></dt>
<dd><p>If set, Bash
quotes all shell metacharacters in filenames and directory names when
performing completion.
If not set, Bash
removes metacharacters such as the dollar sign from the set of
characters that will be quoted in completed filenames
when these metacharacters appear in shell variable references in words to be
completed.
This means that dollar signs in variable names that expand to directories
will not be quoted;
however, any dollar signs appearing in filenames will not be quoted, either.
This is active only when bash is using backslashes to quote completed
filenames.
This variable is set by default, which is the default Bash behavior in
versions through 4.2.
</p>
</dd>
<dt><span><code>direxpand</code></span></dt>
<dd><p>If set, Bash
replaces directory names with the results of word expansion when performing
filename completion.  This changes the contents of the Readline editing
buffer.
If not set, Bash attempts to preserve what the user typed.
</p>
</dd>
<dt><span><code>dirspell</code></span></dt>
<dd><p>If set, Bash
attempts spelling correction on directory names during word completion 
if the directory name initially supplied does not exist.
</p>
</dd>
<dt><span><code>dotglob</code></span></dt>
<dd><p>If set, Bash includes filenames beginning with a &lsquo;.&rsquo; in
the results of filename expansion.
The filenames &lsquo;<samp>.</samp>&rsquo; and &lsquo;<samp>..</samp>&rsquo; must always be matched explicitly,
even if <code>dotglob</code> is set.
</p>
</dd>
<dt><span><code>execfail</code></span></dt>
<dd><p>If this is set, a non-interactive shell will not exit if
it cannot execute the file specified as an argument to the <code>exec</code>
builtin command.  An interactive shell does not exit if <code>exec</code>
fails.
</p>
</dd>
<dt><span><code>expand_aliases</code></span></dt>
<dd><p>If set, aliases are expanded as described below under Aliases,
<a href="#Aliases">Aliases</a>.
This option is enabled by default for interactive shells.
</p>
</dd>
<dt><span><code>extdebug</code></span></dt>
<dd><p>If set at shell invocation,
or in a shell startup file,
arrange to execute the debugger profile
before the shell starts, identical to the <samp>--debugger</samp> option.
If set after invocation, behavior intended for use by debuggers is enabled:
</p>
<ol>
<li> The <samp>-F</samp> option to the <code>declare</code> builtin (see <a href="#Bash-Builtins">Bash Builtin Commands</a>)
displays the source file name and line number corresponding to each function
name supplied as an argument.

</li><li> If the command run by the <code>DEBUG</code> trap returns a non-zero value, the
next command is skipped and not executed.

</li><li> If the command run by the <code>DEBUG</code> trap returns a value of 2, and the
shell is executing in a subroutine (a shell function or a shell script
executed by the <code>.</code> or <code>source</code> builtins), the shell simulates
a call to <code>return</code>.

</li><li> <code>BASH_ARGC</code> and <code>BASH_ARGV</code> are updated as described in their
descriptions (see <a href="#Bash-Variables">Bash Variables</a>).

</li><li> Function tracing is enabled: command substitution, shell functions, and
subshells invoked with <code>( <var>command</var> )</code> inherit the
<code>DEBUG</code> and <code>RETURN</code> traps.

</li><li> Error tracing is enabled: command substitution, shell functions, and
subshells invoked with <code>( <var>command</var> )</code> inherit the
<code>ERR</code> trap.
</li></ol>

</dd>
<dt><span><code>extglob</code></span></dt>
<dd><p>If set, the extended pattern matching features described above
(see <a href="#Pattern-Matching">Pattern Matching</a>) are enabled.
</p>
</dd>
<dt><span><code>extquote</code></span></dt>
<dd><p>If set, <code>$'<var>string</var>'</code> and <code>$&quot;<var>string</var>&quot;</code> quoting is  
performed within <code>${<var>parameter</var>}</code> expansions                     
enclosed in double quotes.  This option is enabled by default. 
</p>
</dd>
<dt><span><code>failglob</code></span></dt>
<dd><p>If set, patterns which fail to match filenames during filename expansion
result in an expansion error.
</p>
</dd>
<dt><span><code>force_fignore</code></span></dt>
<dd><p>If set, the suffixes specified by the <code>FIGNORE</code> shell variable
cause words to be ignored when performing word completion even if
the ignored words are the only possible completions.
See <a href="#Bash-Variables">Bash Variables</a>, for a description of <code>FIGNORE</code>.
This option is enabled by default.
</p>
</dd>
<dt><span><code>globasciiranges</code></span></dt>
<dd><p>If set, range expressions used in pattern matching bracket expressions
(see <a href="#Pattern-Matching">Pattern Matching</a>)
behave as if in the traditional C locale when performing
comparisons.  That is, the current locale&rsquo;s collating sequence
is not taken into account, so
&lsquo;<samp>b</samp>&rsquo; will not collate between &lsquo;<samp>A</samp>&rsquo; and &lsquo;<samp>B</samp>&rsquo;,
and upper-case and lower-case ASCII characters will collate together.   
</p>
</dd>
<dt><span><code>globskipdots</code></span></dt>
<dd><p>If set, filename expansion will never match the filenames
&lsquo;<samp>.</samp>&rsquo; and &lsquo;<samp>..</samp>&rsquo;,
even if the pattern begins with a &lsquo;<samp>.</samp>&rsquo;.
This option is enabled by default.
</p>
</dd>
<dt><span><code>globstar</code></span></dt>
<dd><p>If set, the pattern &lsquo;<samp>**</samp>&rsquo; used in a filename expansion context will
match all files and zero or more directories and subdirectories.
If the pattern is followed by a &lsquo;<samp>/</samp>&rsquo;, only directories and
subdirectories match.
</p>
</dd>
<dt><span><code>gnu_errfmt</code></span></dt>
<dd><p>If set, shell error messages are written in the standard <small>GNU</small> error
message format.
</p>
</dd>
<dt><span><code>histappend</code></span></dt>
<dd><p>If set, the history list is appended to the file named by the value
of the <code>HISTFILE</code>
variable when the shell exits, rather than overwriting the file.
</p>
</dd>
<dt><span><code>histreedit</code></span></dt>
<dd><p>If set, and Readline
is being used, a user is given the opportunity to re-edit a
failed history substitution.
</p>
</dd>
<dt><span><code>histverify</code></span></dt>
<dd><p>If set, and Readline
is being used, the results of history substitution are not immediately
passed to the shell parser.  Instead, the resulting line is loaded into
the Readline editing buffer, allowing further modification.
</p>
</dd>
<dt><span><code>hostcomplete</code></span></dt>
<dd><p>If set, and Readline is being used, Bash will attempt to perform
hostname completion when a word containing a &lsquo;<samp>@</samp>&rsquo; is being
completed (see <a href="#Commands-For-Completion">Letting Readline Type For You</a>).  This option is enabled
by default.
</p>
</dd>
<dt><span><code>huponexit</code></span></dt>
<dd><p>If set, Bash will send <code>SIGHUP</code> to all jobs when an interactive
login shell exits (see <a href="#Signals">Signals</a>).
</p>
</dd>
<dt><span><code>inherit_errexit</code></span></dt>
<dd><p>If set, command substitution inherits the value of the <code>errexit</code> option,
instead of unsetting it in the subshell environment.
This option is enabled when <small>POSIX</small> mode is enabled.
</p>
</dd>
<dt><span><code>interactive_comments</code></span></dt>
<dd><p>Allow a word beginning with &lsquo;<samp>#</samp>&rsquo;
to cause that word and all remaining characters on that
line to be ignored in an interactive shell.
This option is enabled by default.
</p>
</dd>
<dt><span><code>lastpipe</code></span></dt>
<dd><p>If set, and job control is not active, the shell runs the last command of
a pipeline not executed in the background in the current shell environment.
</p>
</dd>
<dt><span><code>lithist</code></span></dt>
<dd><p>If enabled, and the <code>cmdhist</code>
option is enabled, multi-line commands are saved to the history with
embedded newlines rather than using semicolon separators where possible.
</p>
</dd>
<dt><span><code>localvar_inherit</code></span></dt>
<dd><p>If set, local variables inherit the value and attributes of a variable of
the same name that exists at a previous scope before any new value is
assigned.  The <code>nameref</code> attribute is not inherited.
</p>
</dd>
<dt><span><code>localvar_unset</code></span></dt>
<dd><p>If set, calling <code>unset</code> on local variables in previous function scopes
marks them so subsequent lookups find them unset until that function
returns. This is identical to the behavior of unsetting local variables
at the current function scope.
</p>
</dd>
<dt><span><code>login_shell</code></span></dt>
<dd><p>The shell sets this option if it is started as a login shell
(see <a href="#Invoking-Bash">Invoking Bash</a>).
The value may not be changed.
</p>
</dd>
<dt><span><code>mailwarn</code></span></dt>
<dd><p>If set, and a file that Bash is checking for mail has been
accessed since the last time it was checked, the message
<code>&quot;The mail in <var>mailfile</var> has been read&quot;</code> is displayed.
</p>
</dd>
<dt><span><code>no_empty_cmd_completion</code></span></dt>
<dd><p>If set, and Readline is being used, Bash will not attempt to search
the <code>PATH</code> for possible completions when completion is attempted
on an empty line.
</p>
</dd>
<dt><span><code>nocaseglob</code></span></dt>
<dd><p>If set, Bash matches filenames in a case-insensitive fashion when
performing filename expansion.
</p>
</dd>
<dt><span><code>nocasematch</code></span></dt>
<dd><p>If set, Bash matches patterns in a case-insensitive fashion when
performing matching while executing <code>case</code> or <code>[[</code>
conditional commands (see <a href="#Conditional-Constructs">Conditional Constructs</a>,
when performing pattern substitution word expansions,
or when filtering possible completions as part of programmable completion.
</p>
</dd>
<dt><span><code>noexpand_translation</code></span></dt>
<dd><p>If set, Bash
encloses the translated results of $&quot;...&quot; quoting in single quotes
instead of double quotes.
If the string is not translated, this has no effect.
</p>
</dd>
<dt><span><code>nullglob</code></span></dt>
<dd><p>If set, Bash allows filename patterns which match no
files to expand to a null string, rather than themselves.
</p>
</dd>
<dt><span><code>patsub_replacement</code></span></dt>
<dd><p>If set, Bash
expands occurrences of &lsquo;<samp>&amp;</samp>&rsquo; in the replacement string of pattern
substitution to the text matched by the pattern, as described
above (see <a href="#Shell-Parameter-Expansion">Shell Parameter Expansion</a>).
This option is enabled by default.
</p>
</dd>
<dt><span><code>progcomp</code></span></dt>
<dd><p>If set, the programmable completion facilities
(see <a href="#Programmable-Completion">Programmable Completion</a>) are enabled.
This option is enabled by default.
</p>
</dd>
<dt><span><code>progcomp_alias</code></span></dt>
<dd><p>If set, and programmable completion is enabled, Bash treats a command
name that doesn&rsquo;t have any completions as a possible alias and attempts
alias expansion. If it has an alias, Bash attempts programmable
completion using the command word resulting from the expanded alias.
</p>
</dd>
<dt><span><code>promptvars</code></span></dt>
<dd><p>If set, prompt strings undergo
parameter expansion, command substitution, arithmetic
expansion, and quote removal after being expanded
as described below (see <a href="#Controlling-the-Prompt">Controlling the Prompt</a>).
This option is enabled by default.
</p>
</dd>
<dt><span><code>restricted_shell</code></span></dt>
<dd><p>The shell sets this option if it is started in restricted mode
(see <a href="#The-Restricted-Shell">The Restricted Shell</a>).
The value may not be changed.
This is not reset when the startup files are executed, allowing
the startup files to discover whether or not a shell is restricted.
</p>
</dd>
<dt><span><code>shift_verbose</code></span></dt>
<dd><p>If this is set, the <code>shift</code>
builtin prints an error message when the shift count exceeds the
number of positional parameters.
</p>
</dd>
<dt><span><code>sourcepath</code></span></dt>
<dd><p>If set, the <code>.</code> (<code>source</code>) builtin uses the value of <code>PATH</code>
to find the directory containing the file supplied as an argument.
This option is enabled by default.
</p>
</dd>
<dt><span><code>varredir_close</code></span></dt>
<dd><p>If set, the shell automatically closes file descriptors assigned using the
<code>{varname}</code> redirection syntax (see <a href="#Redirections">Redirections</a>) instead of
leaving them open when the command completes.
</p>
</dd>
<dt><span><code>xpg_echo</code></span></dt>
<dd><p>If set, the <code>echo</code> builtin expands backslash-escape sequences
by default.
</p>
</dd>
</dl>
</dd>
</dl>

<hr>
</div>
</div>
<div class="section" id="Special-Builtins">
<div class="header">
<p>
Previous: <a href="#Modifying-Shell-Behavior" accesskey="p" rel="prev">Modifying Shell Behavior</a>, Up: <a href="#Shell-Builtin-Commands" accesskey="u" rel="up">Shell Builtin Commands</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Special-Builtins-1"></span><h3 class="section">4.4 Special Builtins</h3>
<span id="index-special-builtin-1"></span>

<p>For historical reasons, the <small>POSIX</small> standard has classified
several builtin commands as <em>special</em>.
When Bash is executing in <small>POSIX</small> mode, the special builtins
differ from other builtin commands in three respects:
</p>
<ol>
<li> Special builtins are found before shell functions during command lookup.

</li><li> If a special builtin returns an error status, a non-interactive shell exits.

</li><li> Assignment statements preceding the command stay in effect in the shell
environment after the command completes.
</li></ol>

<p>When Bash is not executing in <small>POSIX</small> mode, these builtins behave no
differently than the rest of the Bash builtin commands.
The Bash <small>POSIX</small> mode is described in <a href="#Bash-POSIX-Mode">Bash POSIX Mode</a>. 
</p>
<p>These are the <small>POSIX</small> special builtins:
</p><div class="example">
<pre class="example">break : . continue eval exec exit export readonly return set<!-- /@w -->
shift trap unset<!-- /@w -->
</pre></div>

<hr>
</div>
</div>
<div class="chapter" id="Shell-Variables">
<div class="header">
<p>
Next: <a href="#Bash-Features" accesskey="n" rel="next">Bash Features</a>, Previous: <a href="#Shell-Builtin-Commands" accesskey="p" rel="prev">Shell Builtin Commands</a>, Up: <a href="#Top" accesskey="u" rel="up">Bash Features</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Shell-Variables-1"></span><h2 class="chapter">5 Shell Variables</h2>


<p>This chapter describes the shell variables that Bash uses.
Bash automatically assigns default values to a number of variables.
</p>
<ul class="section-toc">
<li><a href="#Bourne-Shell-Variables" accesskey="1">Bourne Shell Variables</a></li>
<li><a href="#Bash-Variables" accesskey="2">Bash Variables</a></li>
</ul>
<hr>
<div class="section" id="Bourne-Shell-Variables">
<div class="header">
<p>
Next: <a href="#Bash-Variables" accesskey="n" rel="next">Bash Variables</a>, Up: <a href="#Shell-Variables" accesskey="u" rel="up">Shell Variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Bourne-Shell-Variables-1"></span><h3 class="section">5.1 Bourne Shell Variables</h3>

<p>Bash uses certain shell variables in the same way as the Bourne shell.
In some cases, Bash assigns a default value to the variable.
</p>
<dl compact="compact">
<dt id='index-CDPATH'><span><code>CDPATH</code><a href='#index-CDPATH' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A colon-separated list of directories used as a search path for
the <code>cd</code> builtin command.
</p>
</dd>
<dt id='index-HOME'><span><code>HOME</code><a href='#index-HOME' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The current user&rsquo;s home directory; the default for the <code>cd</code> builtin
command.
The value of this variable is also used by tilde expansion
(see <a href="#Tilde-Expansion">Tilde Expansion</a>).
</p>
</dd>
<dt id='index-IFS'><span><code>IFS</code><a href='#index-IFS' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A list of characters that separate fields; used when the shell splits
words as part of expansion.
</p>
</dd>
<dt id='index-MAIL'><span><code>MAIL</code><a href='#index-MAIL' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>If this parameter is set to a filename or directory name
and the <code>MAILPATH</code> variable
is not set, Bash informs the user of the arrival of mail in
the specified file or Maildir-format directory.
</p>
</dd>
<dt id='index-MAILPATH'><span><code>MAILPATH</code><a href='#index-MAILPATH' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A colon-separated list of filenames which the shell periodically checks
for new mail.
Each list entry can specify the message that is printed when new mail
arrives in the mail file by separating the filename from the message with
a &lsquo;<samp>?</samp>&rsquo;.
When used in the text of the message, <code>$_</code> expands to the name of
the current mail file.
</p>
</dd>
<dt id='index-OPTARG'><span><code>OPTARG</code><a href='#index-OPTARG' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The value of the last option argument processed by the <code>getopts</code> builtin.
</p>
</dd>
<dt id='index-OPTIND'><span><code>OPTIND</code><a href='#index-OPTIND' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The index of the last option argument processed by the <code>getopts</code> builtin.
</p>
</dd>
<dt id='index-PATH'><span><code>PATH</code><a href='#index-PATH' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A colon-separated list of directories in which the shell looks for
commands.
A zero-length (null) directory name in the value of <code>PATH</code> indicates the
current directory.
A null directory name may appear as two adjacent colons, or as an initial
or trailing colon.
</p>
</dd>
<dt id='index-PS1'><span><code>PS1</code><a href='#index-PS1' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The primary prompt string.  The default value is &lsquo;<samp>\s-\v\$ </samp>&rsquo;.
See <a href="#Controlling-the-Prompt">Controlling the Prompt</a>, for the complete list of escape
sequences that are expanded before <code>PS1</code> is displayed.
</p>
</dd>
<dt id='index-PS2'><span><code>PS2</code><a href='#index-PS2' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The secondary prompt string.  The default value is &lsquo;<samp>&gt; </samp>&rsquo;.
<code>PS2</code> is expanded in the same way as <code>PS1</code> before being
displayed.
</p>
</dd>
</dl>

<hr>
</div>
<div class="section" id="Bash-Variables">
<div class="header">
<p>
Previous: <a href="#Bourne-Shell-Variables" accesskey="p" rel="prev">Bourne Shell Variables</a>, Up: <a href="#Shell-Variables" accesskey="u" rel="up">Shell Variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Bash-Variables-1"></span><h3 class="section">5.2 Bash Variables</h3>

<p>These variables are set or used by Bash, but other shells
do not normally treat them specially.
</p>
<p>A few variables used by Bash are described in different chapters:
variables for controlling the job control facilities
(see <a href="#Job-Control-Variables">Job Control Variables</a>).
</p>
<dl compact="compact">
<dt id='index-_005f'><span><code>_</code><a href='#index-_005f' class='copiable-anchor'> &para;</a></span></dt>
<dd><span id="index-_0024_005f"></span>
<p>($_, an underscore.)
At shell startup, set to the pathname used to invoke the
shell or shell script being executed as passed in the environment
or argument list.
Subsequently, expands to the last argument to the previous simple
command executed in the foreground, after expansion. 
Also set to the full pathname used to invoke each command executed
and placed in the environment exported to that command.
When checking mail, this parameter holds the name of the mail file.
</p>
</dd>
<dt id='index-BASH'><span><code>BASH</code><a href='#index-BASH' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The full pathname used to execute the current instance of Bash.
</p>
</dd>
<dt id='index-BASHOPTS'><span><code>BASHOPTS</code><a href='#index-BASHOPTS' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A colon-separated list of enabled shell options.  Each word in
the list is a valid argument for the <samp>-s</samp> option to the
<code>shopt</code> builtin command (see <a href="#The-Shopt-Builtin">The Shopt Builtin</a>).
The options appearing in <code>BASHOPTS</code> are those reported
as &lsquo;<samp>on</samp>&rsquo; by &lsquo;<samp>shopt</samp>&rsquo;.
If this variable is in the environment when Bash
starts up, each shell option in the list will be enabled before
reading any startup files.  This variable is readonly.
</p>
</dd>
<dt id='index-BASHPID'><span><code>BASHPID</code><a href='#index-BASHPID' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Expands to the process ID of the current Bash process.
This differs from <code>$$</code> under certain circumstances, such as subshells
that do not require Bash to be re-initialized.
Assignments to <code>BASHPID</code> have no effect.
If <code>BASHPID</code>
is unset, it loses its special properties, even if it is
subsequently reset.
</p>
</dd>
<dt id='index-BASH_005fALIASES'><span><code>BASH_ALIASES</code><a href='#index-BASH_005fALIASES' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>An associative array variable whose members correspond to the internal
list of aliases as maintained by the <code>alias</code> builtin.
(see <a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a>).
Elements added to this array appear in the alias list; however,
unsetting array elements currently does not cause aliases to be removed
from the alias list.
If <code>BASH_ALIASES</code>
is unset, it loses its special properties, even if it is
subsequently reset.
</p>
</dd>
<dt id='index-BASH_005fARGC'><span><code>BASH_ARGC</code><a href='#index-BASH_005fARGC' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>An array variable whose values are the number of parameters in each
frame of the current bash execution call stack.  The number of
parameters to the current subroutine (shell function or script executed
with <code>.</code> or <code>source</code>) is at the top of the stack.  When a
subroutine is executed, the number of parameters passed is pushed onto
<code>BASH_ARGC</code>.
The shell sets <code>BASH_ARGC</code> only when in extended debugging mode
(see <a href="#The-Shopt-Builtin">The Shopt Builtin</a>
for a description of the <code>extdebug</code> option to the <code>shopt</code>
builtin).
Setting <code>extdebug</code> after the shell has started to execute a script,
or referencing this variable when <code>extdebug</code> is not set,
may result in inconsistent values.
</p>
</dd>
<dt id='index-BASH_005fARGV'><span><code>BASH_ARGV</code><a href='#index-BASH_005fARGV' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>An array variable containing all of the parameters in the current bash
execution call stack.  The final parameter of the last subroutine call
is at the top of the stack; the first parameter of the initial call is
at the bottom.  When a subroutine is executed, the parameters supplied
are pushed onto <code>BASH_ARGV</code>.
The shell sets <code>BASH_ARGV</code> only when in extended debugging mode
(see <a href="#The-Shopt-Builtin">The Shopt Builtin</a>
for a description of the <code>extdebug</code> option to the <code>shopt</code>
builtin).
Setting <code>extdebug</code> after the shell has started to execute a script,
or referencing this variable when <code>extdebug</code> is not set,
may result in inconsistent values.
</p>
</dd>
<dt id='index-BASH_005fARGV0'><span><code>BASH_ARGV0</code><a href='#index-BASH_005fARGV0' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>When referenced, this variable expands to the name of the shell or shell
script (identical to <code>$0</code>; See <a href="#Special-Parameters">Special Parameters</a>,
for the description of special parameter 0).
Assignment to <code>BASH_ARGV0</code>
causes the value assigned to also be assigned to <code>$0</code>.
If <code>BASH_ARGV0</code>
is unset, it loses its special properties, even if it is
subsequently reset.
</p>
</dd>
<dt id='index-BASH_005fCMDS'><span><code>BASH_CMDS</code><a href='#index-BASH_005fCMDS' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>An associative array variable whose members correspond to the internal
hash table of commands as maintained by the <code>hash</code> builtin
(see <a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a>).
Elements added to this array appear in the hash table; however,
unsetting array elements currently does not cause command names to be removed
from the hash table.
If <code>BASH_CMDS</code>
is unset, it loses its special properties, even if it is
subsequently reset.
</p>
</dd>
<dt id='index-BASH_005fCOMMAND'><span><code>BASH_COMMAND</code><a href='#index-BASH_005fCOMMAND' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The command currently being executed or about to be executed, unless the
shell is executing a command as the result of a trap,
in which case it is the command executing at the time of the trap.
If <code>BASH_COMMAND</code>
is unset, it loses its special properties, even if it is
subsequently reset.
</p>
</dd>
<dt id='index-BASH_005fCOMPAT'><span><code>BASH_COMPAT</code><a href='#index-BASH_005fCOMPAT' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The value is used to set the shell&rsquo;s compatibility level.
See <a href="#Shell-Compatibility-Mode">Shell Compatibility Mode</a>, for a description of the various
compatibility levels and their effects.
The value may be a decimal number (e.g., 4.2) or an integer (e.g., 42)
corresponding to the desired compatibility level.
If <code>BASH_COMPAT</code> is unset or set to the empty string, the compatibility
level is set to the default for the current version.
If <code>BASH_COMPAT</code> is set to a value that is not one of the valid
compatibility levels, the shell prints an error message and sets the
compatibility level to the default for the current version.
The valid values correspond to the compatibility levels
described below (see <a href="#Shell-Compatibility-Mode">Shell Compatibility Mode</a>).
For example, 4.2 and 42 are valid values that correspond
to the <code>compat42</code> <code>shopt</code> option
and set the compatibility level to 42.
The current version is also a valid value.
</p>
</dd>
<dt id='index-BASH_005fENV'><span><code>BASH_ENV</code><a href='#index-BASH_005fENV' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>If this variable is set when Bash is invoked to execute a shell
script, its value is expanded and used as the name of a startup file
to read before executing the script.  See <a href="#Bash-Startup-Files">Bash Startup Files</a>.
</p>
</dd>
<dt id='index-BASH_005fEXECUTION_005fSTRING'><span><code>BASH_EXECUTION_STRING</code><a href='#index-BASH_005fEXECUTION_005fSTRING' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The command argument to the <samp>-c</samp> invocation option.
</p>
</dd>
<dt id='index-BASH_005fLINENO'><span><code>BASH_LINENO</code><a href='#index-BASH_005fLINENO' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>An array variable whose members are the line numbers in source files
where each corresponding member of <code>FUNCNAME</code> was invoked.
<code>${BASH_LINENO[$i]}</code> is the line number in the source file
(<code>${BASH_SOURCE[$i+1]}</code>) where
<code>${FUNCNAME[$i]}</code> was called (or <code>${BASH_LINENO[$i-1]}</code> if
referenced within another shell function). 
Use <code>LINENO</code> to obtain the current line number.
</p>
</dd>
<dt id='index-BASH_005fLOADABLES_005fPATH'><span><code>BASH_LOADABLES_PATH</code><a href='#index-BASH_005fLOADABLES_005fPATH' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A colon-separated list of directories in which the shell looks for
dynamically loadable builtins specified by the
<code>enable</code> command.
</p>
</dd>
<dt id='index-BASH_005fREMATCH'><span><code>BASH_REMATCH</code><a href='#index-BASH_005fREMATCH' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>An array variable whose members are assigned by the &lsquo;<samp>=~</samp>&rsquo; binary
operator to the <code>[[</code> conditional command
(see <a href="#Conditional-Constructs">Conditional Constructs</a>).
The element with index 0 is the portion of the string
matching the entire regular expression.
The element with index <var>n</var> is the portion of the
string matching the <var>n</var>th parenthesized subexpression.
</p>
</dd>
<dt id='index-BASH_005fSOURCE'><span><code>BASH_SOURCE</code><a href='#index-BASH_005fSOURCE' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>An array variable whose members are the source filenames where the
corresponding shell function names in the <code>FUNCNAME</code> array
variable are defined.
The shell function <code>${FUNCNAME[$i]}</code> is defined in the file
<code>${BASH_SOURCE[$i]}</code> and called from <code>${BASH_SOURCE[$i+1]}</code>
</p>
</dd>
<dt id='index-BASH_005fSUBSHELL'><span><code>BASH_SUBSHELL</code><a href='#index-BASH_005fSUBSHELL' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Incremented by one within each subshell or subshell environment when
the shell begins executing in that environment.
The initial value is 0.
If <code>BASH_SUBSHELL</code>
is unset, it loses its special properties, even if it is
subsequently reset.
</p>
</dd>
<dt id='index-BASH_005fVERSINFO'><span><code>BASH_VERSINFO</code><a href='#index-BASH_005fVERSINFO' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A readonly array variable (see <a href="#Arrays">Arrays</a>)
whose members hold version information for this instance of Bash.
The values assigned to the array members are as follows:
</p>
<dl compact="compact">
<dt><span><code>BASH_VERSINFO[0]</code></span></dt>
<dd><p>The major version number (the <em>release</em>).
</p>
</dd>
<dt><span><code>BASH_VERSINFO[1]</code></span></dt>
<dd><p>The minor version number (the <em>version</em>).
</p>
</dd>
<dt><span><code>BASH_VERSINFO[2]</code></span></dt>
<dd><p>The patch level.
</p>
</dd>
<dt><span><code>BASH_VERSINFO[3]</code></span></dt>
<dd><p>The build version.
</p>
</dd>
<dt><span><code>BASH_VERSINFO[4]</code></span></dt>
<dd><p>The release status (e.g., <code>beta1</code>).
</p>
</dd>
<dt><span><code>BASH_VERSINFO[5]</code></span></dt>
<dd><p>The value of <code>MACHTYPE</code>.
</p></dd>
</dl>

</dd>
<dt id='index-BASH_005fVERSION'><span><code>BASH_VERSION</code><a href='#index-BASH_005fVERSION' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The version number of the current instance of Bash.
</p>
</dd>
<dt id='index-BASH_005fXTRACEFD'><span><code>BASH_XTRACEFD</code><a href='#index-BASH_005fXTRACEFD' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>If set to an integer corresponding to a valid file descriptor, Bash
will write the trace output generated when &lsquo;<samp>set -x</samp>&rsquo;
is enabled to that file descriptor.
This allows tracing output to be separated from diagnostic and error
messages.
The file descriptor is closed when <code>BASH_XTRACEFD</code> is unset or assigned
a new value.
Unsetting <code>BASH_XTRACEFD</code> or assigning it the empty string causes the
trace output to be sent to the standard error.
Note that setting <code>BASH_XTRACEFD</code> to 2 (the standard error file
descriptor) and then unsetting it will result in the standard error
being closed.
</p>
</dd>
<dt id='index-CHILD_005fMAX'><span><code>CHILD_MAX</code><a href='#index-CHILD_005fMAX' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Set the number of exited child status values for the shell to remember.
Bash will not allow this value to be decreased below a <small>POSIX</small>-mandated
minimum, and there is a maximum value (currently 8192) that this may
not exceed.
The minimum value is system-dependent.
</p>
</dd>
<dt id='index-COLUMNS'><span><code>COLUMNS</code><a href='#index-COLUMNS' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Used by the <code>select</code> command to determine the terminal width
when printing selection lists.
Automatically set if the <code>checkwinsize</code> option is enabled
(see <a href="#The-Shopt-Builtin">The Shopt Builtin</a>), or in an interactive shell upon receipt of a
<code>SIGWINCH</code>.
</p>
</dd>
<dt id='index-COMP_005fCWORD'><span><code>COMP_CWORD</code><a href='#index-COMP_005fCWORD' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>An index into <code>${COMP_WORDS}</code> of the word containing the current
cursor position.
This variable is available only in shell functions invoked by the
programmable completion facilities (see <a href="#Programmable-Completion">Programmable Completion</a>).
</p>
</dd>
<dt id='index-COMP_005fLINE'><span><code>COMP_LINE</code><a href='#index-COMP_005fLINE' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The current command line.
This variable is available only in shell functions and external
commands invoked by the
programmable completion facilities (see <a href="#Programmable-Completion">Programmable Completion</a>).
</p>
</dd>
<dt id='index-COMP_005fPOINT'><span><code>COMP_POINT</code><a href='#index-COMP_005fPOINT' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The index of the current cursor position relative to the beginning of
the current command.
If the current cursor position is at the end of the current command,
the value of this variable is equal to <code>${#COMP_LINE}</code>.
This variable is available only in shell functions and external
commands invoked by the
programmable completion facilities (see <a href="#Programmable-Completion">Programmable Completion</a>).
</p>
</dd>
<dt id='index-COMP_005fTYPE'><span><code>COMP_TYPE</code><a href='#index-COMP_005fTYPE' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Set to an integer value corresponding to the type of completion attempted
that caused a completion function to be called:
<tt class="key">TAB</tt>, for normal completion,
&lsquo;<samp>?</samp>&rsquo;, for listing completions after successive tabs,
&lsquo;<samp>!</samp>&rsquo;, for listing alternatives on partial word completion,
&lsquo;<samp>@</samp>&rsquo;, to list completions if the word is not unmodified,
or
&lsquo;<samp>%</samp>&rsquo;, for menu completion.
This variable is available only in shell functions and external
commands invoked by the
programmable completion facilities (see <a href="#Programmable-Completion">Programmable Completion</a>).
</p>
</dd>
<dt id='index-COMP_005fKEY'><span><code>COMP_KEY</code><a href='#index-COMP_005fKEY' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The key (or final key of a key sequence) used to invoke the current
completion function.
</p>
</dd>
<dt id='index-COMP_005fWORDBREAKS'><span><code>COMP_WORDBREAKS</code><a href='#index-COMP_005fWORDBREAKS' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The set of characters that the Readline library treats as word
separators when performing word completion.
If <code>COMP_WORDBREAKS</code>
is unset, it loses its special properties,
even if it is subsequently reset.
</p>
</dd>
<dt id='index-COMP_005fWORDS'><span><code>COMP_WORDS</code><a href='#index-COMP_005fWORDS' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>An array variable consisting of the individual
words in the current command line.
The line is split into words as Readline would split it, using
<code>COMP_WORDBREAKS</code> as described above.
This variable is available only in shell functions invoked by the
programmable completion facilities (see <a href="#Programmable-Completion">Programmable Completion</a>).
</p>
</dd>
<dt id='index-COMPREPLY'><span><code>COMPREPLY</code><a href='#index-COMPREPLY' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>An array variable from which Bash reads the possible completions
generated by a shell function invoked by the programmable completion
facility (see <a href="#Programmable-Completion">Programmable Completion</a>).
Each array element contains one possible completion.
</p>
</dd>
<dt id='index-COPROC'><span><code>COPROC</code><a href='#index-COPROC' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>An array variable created to hold the file descriptors
for output from and input to an unnamed coprocess (see <a href="#Coprocesses">Coprocesses</a>).
</p>
</dd>
<dt id='index-DIRSTACK'><span><code>DIRSTACK</code><a href='#index-DIRSTACK' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>An array variable containing the current contents of the directory stack.
Directories appear in the stack in the order they are displayed by the
<code>dirs</code> builtin.
Assigning to members of this array variable may be used to modify
directories already in the stack, but the <code>pushd</code> and <code>popd</code>
builtins must be used to add and remove directories.
Assignment to this variable will not change the current directory.
If <code>DIRSTACK</code>
is unset, it loses its special properties, even if
it is subsequently reset.
</p>
</dd>
<dt id='index-EMACS'><span><code>EMACS</code><a href='#index-EMACS' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>If Bash finds this variable in the environment when the shell
starts with value &lsquo;<samp>t</samp>&rsquo;, it assumes that the shell is running in an
Emacs shell buffer and disables line editing.
</p>
</dd>
<dt id='index-ENV'><span><code>ENV</code><a href='#index-ENV' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Expanded and executed similarly to <code>BASH_ENV</code>
(see <a href="#Bash-Startup-Files">Bash Startup Files</a>)
when an interactive shell is invoked in
<small>POSIX</small> Mode (see <a href="#Bash-POSIX-Mode">Bash POSIX Mode</a>).
</p>
</dd>
<dt id='index-EPOCHREALTIME'><span><code>EPOCHREALTIME</code><a href='#index-EPOCHREALTIME' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Each time this parameter is referenced, it expands to the number of seconds
since the Unix Epoch as a floating point value with micro-second granularity
(see the documentation for the C library function <code>time</code> for the
definition of Epoch).
Assignments to <code>EPOCHREALTIME</code> are ignored.
If <code>EPOCHREALTIME</code>
is unset, it loses its special properties, even if
it is subsequently reset.
</p>
</dd>
<dt id='index-EPOCHSECONDS'><span><code>EPOCHSECONDS</code><a href='#index-EPOCHSECONDS' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Each time this parameter is referenced, it expands to the number of seconds
since the Unix Epoch (see the documentation for the C library function
<code>time</code> for the definition of Epoch).
Assignments to <code>EPOCHSECONDS</code> are ignored.
If <code>EPOCHSECONDS</code>
is unset, it loses its special properties, even if
it is subsequently reset.
</p>
</dd>
<dt id='index-EUID'><span><code>EUID</code><a href='#index-EUID' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The numeric effective user id of the current user.  This variable
is readonly.
</p>
</dd>
<dt id='index-EXECIGNORE'><span><code>EXECIGNORE</code><a href='#index-EXECIGNORE' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A colon-separated list of shell patterns (see <a href="#Pattern-Matching">Pattern Matching</a>)
defining the list of filenames to be ignored by command search using
<code>PATH</code>.
Files whose full pathnames match one of these patterns are not considered
executable files for the purposes of completion and command execution
via <code>PATH</code> lookup.
This does not affect the behavior of the <code>[</code>, <code>test</code>, and <code>[[</code>
commands.
Full pathnames in the command hash table are not subject to <code>EXECIGNORE</code>.
Use this variable to ignore shared library files that have the executable
bit set, but are not executable files.
The pattern matching honors the setting of the <code>extglob</code> shell 
option.
</p>
</dd>
<dt id='index-FCEDIT'><span><code>FCEDIT</code><a href='#index-FCEDIT' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The editor used as a default by the <samp>-e</samp> option to the <code>fc</code>
builtin command.
</p>
</dd>
<dt id='index-FIGNORE'><span><code>FIGNORE</code><a href='#index-FIGNORE' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A colon-separated list of suffixes to ignore when performing
filename completion.
A filename whose suffix matches one of the entries in 
<code>FIGNORE</code>
is excluded from the list of matched filenames.  A sample
value is &lsquo;<samp>.o:~</samp>&rsquo;
</p>
</dd>
<dt id='index-FUNCNAME'><span><code>FUNCNAME</code><a href='#index-FUNCNAME' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>An array variable containing the names of all shell functions
currently in the execution call stack.
The element with index 0 is the name of any currently-executing
shell function.
The bottom-most element (the one with the highest index)
is <code>&quot;main&quot;</code>.
This variable exists only when a shell function is executing.
Assignments to <code>FUNCNAME</code> have no effect.
If <code>FUNCNAME</code>
is unset, it loses its special properties, even if
it is subsequently reset.
</p>
<p>This variable can be used with <code>BASH_LINENO</code> and <code>BASH_SOURCE</code>.
Each element of <code>FUNCNAME</code> has corresponding elements in
<code>BASH_LINENO</code> and <code>BASH_SOURCE</code> to describe the call stack.
For instance, <code>${FUNCNAME[$i]}</code> was called from the file
<code>${BASH_SOURCE[$i+1]}</code> at line number <code>${BASH_LINENO[$i]}</code>.
The <code>caller</code> builtin displays the current call stack using this
information.
</p>
</dd>
<dt id='index-FUNCNEST'><span><code>FUNCNEST</code><a href='#index-FUNCNEST' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>If set to a numeric value greater than 0, defines a maximum function
nesting level.  Function invocations that exceed this nesting level
will cause the current command to abort.
</p>
</dd>
<dt id='index-GLOBIGNORE'><span><code>GLOBIGNORE</code><a href='#index-GLOBIGNORE' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A colon-separated list of patterns defining the set of file names to
be ignored by filename expansion.
If a file name matched by a filename expansion pattern also matches one
of the patterns in <code>GLOBIGNORE</code>, it is removed from the list
of matches.
The pattern matching honors the setting of the <code>extglob</code> shell
option.
</p>
</dd>
<dt id='index-GROUPS'><span><code>GROUPS</code><a href='#index-GROUPS' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>An array variable containing the list of groups of which the current    
user is a member.
Assignments to <code>GROUPS</code> have no effect.
If <code>GROUPS</code>
is unset, it loses its special properties, even if it is
subsequently reset.
</p>
</dd>
<dt id='index-histchars'><span><code>histchars</code><a href='#index-histchars' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Up to three characters which control history expansion, quick
substitution, and tokenization (see <a href="#History-Interaction">History Expansion</a>).
The first character is the
<em>history expansion</em> character, that is, the character which signifies the
start of a history expansion, normally &lsquo;<samp>!</samp>&rsquo;.  The second character is the
character which signifies &lsquo;quick substitution&rsquo; when seen as the first
character on a line, normally &lsquo;<samp>^</samp>&rsquo;.  The optional third character is the
character which indicates that the remainder of the line is a comment when
found as the first character of a word, usually &lsquo;<samp>#</samp>&rsquo;.  The history
comment character causes history substitution to be skipped for the
remaining words on the line.  It does not necessarily cause the shell
parser to treat the rest of the line as a comment.
</p>
</dd>
<dt id='index-HISTCMD'><span><code>HISTCMD</code><a href='#index-HISTCMD' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The history number, or index in the history list, of the current
command.
Assignments to <code>HISTCMD</code> are ignored.
If <code>HISTCMD</code>
is unset, it loses its special properties,
even if it is subsequently reset.
</p>
</dd>
<dt id='index-HISTCONTROL'><span><code>HISTCONTROL</code><a href='#index-HISTCONTROL' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A colon-separated list of values controlling how commands are saved on
the history list.
If the list of values includes &lsquo;<samp>ignorespace</samp>&rsquo;, lines which begin
with a space character are not saved in the history list.
A value of &lsquo;<samp>ignoredups</samp>&rsquo; causes lines which match the previous
history entry to not be saved.
A value of &lsquo;<samp>ignoreboth</samp>&rsquo; is shorthand for
&lsquo;<samp>ignorespace</samp>&rsquo; and &lsquo;<samp>ignoredups</samp>&rsquo;.
A value of &lsquo;<samp>erasedups</samp>&rsquo; causes all previous lines matching the
current line to be removed from the history list before that line
is saved.
Any value not in the above list is ignored.
If <code>HISTCONTROL</code> is unset, or does not include a valid value, 
all lines read by the shell parser are saved on the history list, 
subject to the value of <code>HISTIGNORE</code>.
The second and subsequent lines of a multi-line compound command are
not tested, and are added to the history regardless of the value of
<code>HISTCONTROL</code>.
</p>
</dd>
<dt id='index-HISTFILE'><span><code>HISTFILE</code><a href='#index-HISTFILE' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The name of the file to which the command history is saved.  The
default value is <samp>~/.bash_history</samp>.
</p>
</dd>
<dt id='index-HISTFILESIZE'><span><code>HISTFILESIZE</code><a href='#index-HISTFILESIZE' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The maximum number of lines contained in the history file.
When this variable is assigned a value, the history file is truncated,
if necessary, to contain no more than that number of lines
by removing the oldest entries.
The history file is also truncated to this size after
writing it when a shell exits.
If the value is 0, the history file is truncated to zero size.
Non-numeric values and numeric values less than zero inhibit truncation.
The shell sets the default value to the value of <code>HISTSIZE</code>
after reading any startup files.
</p>
</dd>
<dt id='index-HISTIGNORE'><span><code>HISTIGNORE</code><a href='#index-HISTIGNORE' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A colon-separated list of patterns used to decide which command
lines should be saved on the history list.  Each pattern is
anchored at the beginning of the line and must match the complete
line (no implicit &lsquo;<samp>*</samp>&rsquo; is appended).  Each pattern is tested
against the line after the checks specified by <code>HISTCONTROL</code>
are applied.  In addition to the normal shell pattern matching
characters, &lsquo;<samp>&amp;</samp>&rsquo; matches the previous history line.  &lsquo;<samp>&amp;</samp>&rsquo;
may be escaped using a backslash; the backslash is removed
before attempting a match. 
The second and subsequent lines of a multi-line compound command are
not tested, and are added to the history regardless of the value of
<code>HISTIGNORE</code>.
The pattern matching honors the setting of the <code>extglob</code> shell
option.
</p>
<p><code>HISTIGNORE</code> subsumes the function of <code>HISTCONTROL</code>.  A
pattern of &lsquo;<samp>&amp;</samp>&rsquo; is identical to <code>ignoredups</code>, and a
pattern of &lsquo;<samp>[ ]*</samp>&rsquo; is identical to <code>ignorespace</code>. 
Combining these two patterns, separating them with a colon,
provides the functionality of <code>ignoreboth</code>. 
</p>
</dd>
<dt id='index-HISTSIZE'><span><code>HISTSIZE</code><a href='#index-HISTSIZE' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The maximum number of commands to remember on the history list.
If the value is 0, commands are not saved in the history list.
Numeric values less than zero result in every command being saved
on the history list (there is no limit).
The shell sets the default value to 500 after reading any startup files.
</p>
</dd>
<dt id='index-HISTTIMEFORMAT'><span><code>HISTTIMEFORMAT</code><a href='#index-HISTTIMEFORMAT' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>If this variable is set and not null, its value is used as a format string
for <code>strftime</code> to print the time stamp associated with each history
entry displayed by the <code>history</code> builtin.
If this variable is set, time stamps are written to the history file so
they may be preserved across shell sessions.
This uses the history comment character to distinguish timestamps from
other history lines.
</p>
</dd>
<dt id='index-HOSTFILE'><span><code>HOSTFILE</code><a href='#index-HOSTFILE' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Contains the name of a file in the same format as <samp>/etc/hosts</samp> that
should be read when the shell needs to complete a hostname.
The list of possible hostname completions may be changed while the shell
is running;
the next time hostname completion is attempted after the
value is changed, Bash adds the contents of the new file to the
existing list.
If <code>HOSTFILE</code> is set, but has no value, or does not name a readable file,
Bash attempts to read 
<samp>/etc/hosts</samp> to obtain the list of possible hostname completions.
When <code>HOSTFILE</code> is unset, the hostname list is cleared.
</p>
</dd>
<dt id='index-HOSTNAME'><span><code>HOSTNAME</code><a href='#index-HOSTNAME' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The name of the current host.
</p>
</dd>
<dt id='index-HOSTTYPE'><span><code>HOSTTYPE</code><a href='#index-HOSTTYPE' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A string describing the machine Bash is running on.
</p>
</dd>
<dt id='index-IGNOREEOF'><span><code>IGNOREEOF</code><a href='#index-IGNOREEOF' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Controls the action of the shell on receipt of an <code>EOF</code> character
as the sole input.  If set, the value denotes the number
of consecutive <code>EOF</code> characters that can be read as the
first character on an input line
before the shell will exit.  If the variable exists but does not
have a numeric value, or has no value, then the default is 10.
If the variable does not exist, then <code>EOF</code> signifies the end of 
input to the shell.  This is only in effect for interactive shells.
</p>
</dd>
<dt id='index-INPUTRC'><span><code>INPUTRC</code><a href='#index-INPUTRC' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The name of the Readline initialization file, overriding the default
of <samp>~/.inputrc</samp>.
</p>
</dd>
<dt id='index-INSIDE_005fEMACS'><span><code>INSIDE_EMACS</code><a href='#index-INSIDE_005fEMACS' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>If Bash finds this variable in the environment when the shell
starts, it assumes that the shell is running in an Emacs shell buffer
and may disable line editing depending on the value of <code>TERM</code>.
</p>
</dd>
<dt id='index-LANG-1'><span><code>LANG</code><a href='#index-LANG-1' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Used to determine the locale category for any category not specifically
selected with a variable starting with <code>LC_</code>.
</p>
</dd>
<dt id='index-LC_005fALL'><span><code>LC_ALL</code><a href='#index-LC_005fALL' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>This variable overrides the value of <code>LANG</code> and any other
<code>LC_</code> variable specifying a locale category.
</p>
</dd>
<dt id='index-LC_005fCOLLATE'><span><code>LC_COLLATE</code><a href='#index-LC_005fCOLLATE' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>This variable determines the collation order used when sorting the
results of filename expansion, and
determines the behavior of range expressions, equivalence classes,
and collating sequences within filename expansion and pattern matching
(see <a href="#Filename-Expansion">Filename Expansion</a>).
</p>
</dd>
<dt id='index-LC_005fCTYPE'><span><code>LC_CTYPE</code><a href='#index-LC_005fCTYPE' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>This variable determines the interpretation of characters and the
behavior of character classes within filename expansion and pattern
matching (see <a href="#Filename-Expansion">Filename Expansion</a>).
</p>
</dd>
<dt id='index-LC_005fMESSAGES-1'><span><code>LC_MESSAGES</code><a href='#index-LC_005fMESSAGES-1' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>This variable determines the locale used to translate double-quoted
strings preceded by a &lsquo;<samp>$</samp>&rsquo; (see <a href="#Locale-Translation">Locale-Specific Translation</a>).
</p>
</dd>
<dt id='index-LC_005fNUMERIC'><span><code>LC_NUMERIC</code><a href='#index-LC_005fNUMERIC' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>This variable determines the locale category used for number formatting.
</p>
</dd>
<dt id='index-LC_005fTIME'><span><code>LC_TIME</code><a href='#index-LC_005fTIME' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>This variable determines the locale category used for data and time
formatting.
</p>
</dd>
<dt id='index-LINENO'><span><code>LINENO</code><a href='#index-LINENO' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The line number in the script or shell function currently executing.
If <code>LINENO</code>
is unset, it loses its special properties, even if it is
subsequently reset.
</p>
</dd>
<dt id='index-LINES'><span><code>LINES</code><a href='#index-LINES' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Used by the <code>select</code> command to determine the column length
for printing selection lists.
Automatically set if the <code>checkwinsize</code> option is enabled
(see <a href="#The-Shopt-Builtin">The Shopt Builtin</a>), or in an interactive shell upon receipt of a
<code>SIGWINCH</code>.
</p>
</dd>
<dt id='index-MACHTYPE'><span><code>MACHTYPE</code><a href='#index-MACHTYPE' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A string that fully describes the system type on which Bash
is executing, in the standard <small>GNU</small> <var>cpu-company-system</var> format.
</p>
</dd>
<dt id='index-MAILCHECK'><span><code>MAILCHECK</code><a href='#index-MAILCHECK' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>How often (in seconds) that the shell should check for mail in the
files specified in the <code>MAILPATH</code> or <code>MAIL</code> variables.
The default is 60 seconds.  When it is time to check
for mail, the shell does so before displaying the primary prompt.
If this variable is unset, or set to a value that is not a number
greater than or equal to zero, the shell disables mail checking.
</p>
</dd>
<dt id='index-MAPFILE'><span><code>MAPFILE</code><a href='#index-MAPFILE' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>An array variable created to hold the text read by the
<code>mapfile</code> builtin when no variable name is supplied.
</p>
</dd>
<dt id='index-OLDPWD'><span><code>OLDPWD</code><a href='#index-OLDPWD' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The previous working directory as set by the <code>cd</code> builtin.
</p>
</dd>
<dt id='index-OPTERR'><span><code>OPTERR</code><a href='#index-OPTERR' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>If set to the value 1, Bash displays error messages
generated by the <code>getopts</code> builtin command.
</p>
</dd>
<dt id='index-OSTYPE'><span><code>OSTYPE</code><a href='#index-OSTYPE' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A string describing the operating system Bash is running on.
</p>
</dd>
<dt id='index-PIPESTATUS'><span><code>PIPESTATUS</code><a href='#index-PIPESTATUS' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>An array variable (see <a href="#Arrays">Arrays</a>)
containing a list of exit status values from the processes
in the most-recently-executed foreground pipeline (which may
contain only a single command).
</p>
</dd>
<dt id='index-POSIXLY_005fCORRECT'><span><code>POSIXLY_CORRECT</code><a href='#index-POSIXLY_005fCORRECT' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>If this variable is in the environment when Bash starts, the shell
enters <small>POSIX</small> mode (see <a href="#Bash-POSIX-Mode">Bash POSIX Mode</a>) before reading the
startup files, as if the <samp>--posix</samp> invocation option had been supplied.
If it is set while the shell is running, Bash enables <small>POSIX</small> mode,
as if the command
</p><div class="example">
<pre class="example"><code>set -o posix</code>
</pre></div>
<p>had been executed.
When the shell enters <small>POSIX</small> mode, it sets this variable if it was
not already set.
</p>
</dd>
<dt id='index-PPID'><span><code>PPID</code><a href='#index-PPID' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The process <small>ID</small> of the shell&rsquo;s parent process.  This variable
is readonly.
</p>
</dd>
<dt id='index-PROMPT_005fCOMMAND'><span><code>PROMPT_COMMAND</code><a href='#index-PROMPT_005fCOMMAND' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>If this variable is set, and is an array,
the value of each set element is interpreted as a command to execute
before printing the primary prompt (<code>$PS1</code>).
If this is set but not an array variable,
its value is used as a command to execute instead.
</p>
</dd>
<dt id='index-PROMPT_005fDIRTRIM'><span><code>PROMPT_DIRTRIM</code><a href='#index-PROMPT_005fDIRTRIM' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>If set to a number greater than zero, the value is used as the number of
trailing directory components to retain when expanding the <code>\w</code> and
<code>\W</code> prompt string escapes (see <a href="#Controlling-the-Prompt">Controlling the Prompt</a>).
Characters removed are replaced with an ellipsis.
</p>
</dd>
<dt id='index-PS0'><span><code>PS0</code><a href='#index-PS0' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The value of this parameter is expanded like <code>PS1</code>
and displayed by interactive shells after reading a command
and before the command is executed.
</p>
</dd>
<dt id='index-PS3'><span><code>PS3</code><a href='#index-PS3' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The value of this variable is used as the prompt for the
<code>select</code> command.  If this variable is not set, the
<code>select</code> command prompts with &lsquo;<samp>#? </samp>&rsquo;
</p>
</dd>
<dt id='index-PS4'><span><code>PS4</code><a href='#index-PS4' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The value of this parameter is expanded like <code>PS1</code>
and the expanded value is the prompt printed before the command line
is echoed when the <samp>-x</samp> option is set (see <a href="#The-Set-Builtin">The Set Builtin</a>).
The first character of the expanded value is replicated multiple times,
as necessary, to indicate multiple levels of indirection.
The default is &lsquo;<samp>+ </samp>&rsquo;.
</p>
</dd>
<dt id='index-PWD'><span><code>PWD</code><a href='#index-PWD' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The current working directory as set by the <code>cd</code> builtin.
</p>
</dd>
<dt id='index-RANDOM'><span><code>RANDOM</code><a href='#index-RANDOM' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Each time this parameter is referenced, it expands to a random integer
between 0 and 32767. Assigning a value to this
variable seeds the random number generator.
If <code>RANDOM</code>
is unset, it loses its special properties, even if it is
subsequently reset.
</p>
</dd>
<dt id='index-READLINE_005fARGUMENT'><span><code>READLINE_ARGUMENT</code><a href='#index-READLINE_005fARGUMENT' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Any numeric argument given to a Readline command that was defined using
&lsquo;<samp>bind -x</samp>&rsquo; (see <a href="#Bash-Builtins">Bash Builtin Commands</a>
when it was invoked.
</p>
</dd>
<dt id='index-READLINE_005fLINE'><span><code>READLINE_LINE</code><a href='#index-READLINE_005fLINE' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The contents of the Readline line buffer, for use
with &lsquo;<samp>bind -x</samp>&rsquo; (see <a href="#Bash-Builtins">Bash Builtin Commands</a>).
</p>
</dd>
<dt id='index-READLINE_005fMARK'><span><code>READLINE_MARK</code><a href='#index-READLINE_005fMARK' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The position of the <em>mark</em> (saved insertion point) in the
Readline line buffer, for use
with &lsquo;<samp>bind -x</samp>&rsquo; (see <a href="#Bash-Builtins">Bash Builtin Commands</a>).
The characters between the insertion point and the mark are often
called the <em>region</em>.
</p>
</dd>
<dt id='index-READLINE_005fPOINT'><span><code>READLINE_POINT</code><a href='#index-READLINE_005fPOINT' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The position of the insertion point in the Readline line buffer, for use
with &lsquo;<samp>bind -x</samp>&rsquo; (see <a href="#Bash-Builtins">Bash Builtin Commands</a>).
</p>
</dd>
<dt id='index-REPLY'><span><code>REPLY</code><a href='#index-REPLY' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The default variable for the <code>read</code> builtin.
</p>
</dd>
<dt id='index-SECONDS'><span><code>SECONDS</code><a href='#index-SECONDS' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>This variable expands to the number of seconds since the shell was started. 
Assignment to this variable resets the count to the value assigned, and the
expanded value becomes the value assigned plus the number of seconds
since the assignment.
The number of seconds at shell invocation and the current time are always
determined by querying the system clock.
If <code>SECONDS</code>
is unset, it loses its special properties,
even if it is subsequently reset.
</p>
</dd>
<dt id='index-SHELL'><span><code>SHELL</code><a href='#index-SHELL' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>This environment variable expands to the full pathname to the shell.
If it is not set when the shell starts,
Bash assigns to it the full pathname of the current user&rsquo;s login shell.
</p>
</dd>
<dt id='index-SHELLOPTS'><span><code>SHELLOPTS</code><a href='#index-SHELLOPTS' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A colon-separated list of enabled shell options.  Each word in
the list is a valid argument for the <samp>-o</samp> option to the
<code>set</code> builtin command (see <a href="#The-Set-Builtin">The Set Builtin</a>).
The options appearing in <code>SHELLOPTS</code> are those reported
as &lsquo;<samp>on</samp>&rsquo; by &lsquo;<samp>set -o</samp>&rsquo;.
If this variable is in the environment when Bash
starts up, each shell option in the list will be enabled before
reading any startup files.  This variable is readonly.
</p>
</dd>
<dt id='index-SHLVL'><span><code>SHLVL</code><a href='#index-SHLVL' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Incremented by one each time a new instance of Bash is started.  This is
intended to be a count of how deeply your Bash shells are nested.
</p>
</dd>
<dt id='index-SRANDOM'><span><code>SRANDOM</code><a href='#index-SRANDOM' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>This variable expands to a 32-bit pseudo-random number each time it is
referenced. The random number generator is not linear on systems that
support <samp>/dev/urandom</samp> or <code>arc4random</code>, so each returned number
has no relationship to the numbers preceding it.
The random number generator cannot be seeded, so assignments to this
variable have no effect.
If <code>SRANDOM</code>
is unset, it loses its special properties,
even if it is subsequently reset.
</p>
</dd>
<dt id='index-TIMEFORMAT'><span><code>TIMEFORMAT</code><a href='#index-TIMEFORMAT' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The value of this parameter is used as a format string specifying
how the timing information for pipelines prefixed with the <code>time</code>
reserved word should be displayed.
The &lsquo;<samp>%</samp>&rsquo; character introduces an
escape sequence that is expanded to a time value or other
information.
The escape sequences and their meanings are as
follows; the braces denote optional portions. 
</p>
<dl compact="compact">
<dt><span><code>%%</code></span></dt>
<dd><p>A literal &lsquo;<samp>%</samp>&rsquo;.
</p>
</dd>
<dt><span><code>%[<var>p</var>][l]R</code></span></dt>
<dd><p>The elapsed time in seconds. 
</p>
</dd>
<dt><span><code>%[<var>p</var>][l]U</code></span></dt>
<dd><p>The number of CPU seconds spent in user mode. 
</p>
</dd>
<dt><span><code>%[<var>p</var>][l]S</code></span></dt>
<dd><p>The number of CPU seconds spent in system mode. 
</p>
</dd>
<dt><span><code>%P</code></span></dt>
<dd><p>The CPU percentage, computed as (%U + %S) / %R. 
</p></dd>
</dl>

<p>The optional <var>p</var> is a digit specifying the precision, the number of
fractional digits after a decimal point.
A value of 0 causes no decimal point or fraction to be output.
At most three places after the decimal point may be specified; values
of <var>p</var> greater than 3 are changed to 3.
If <var>p</var> is not specified, the value 3 is used. 
</p>
<p>The optional <code>l</code> specifies a longer format, including minutes, of
the form <var>MM</var>m<var>SS</var>.<var>FF</var>s.
The value of <var>p</var> determines whether or not the fraction is included. 
</p>
<p>If this variable is not set, Bash acts as if it had the value
</p><div class="example">
<pre class="example"><code>$'\nreal\t%3lR\nuser\t%3lU\nsys\t%3lS'</code>
</pre></div>
<p>If the value is null, no timing information is displayed.
A trailing newline is added when the format string is displayed.
</p>
</dd>
<dt id='index-TMOUT'><span><code>TMOUT</code><a href='#index-TMOUT' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>If set to a value greater than zero, <code>TMOUT</code> is treated as the
default timeout for the <code>read</code> builtin (see <a href="#Bash-Builtins">Bash Builtin Commands</a>).
The <code>select</code> command (see <a href="#Conditional-Constructs">Conditional Constructs</a>) terminates
if input does not arrive after <code>TMOUT</code> seconds when input is coming
from a terminal.
</p>
<p>In an interactive shell, the value is interpreted as
the number of seconds to wait for a line of input after issuing
the primary prompt.
Bash
terminates after waiting for that number of seconds if a complete
line of input does not arrive.
</p>
</dd>
<dt id='index-TMPDIR'><span><code>TMPDIR</code><a href='#index-TMPDIR' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>If set, Bash uses its value as the name of a directory in which
Bash creates temporary files for the shell&rsquo;s use.
</p>
</dd>
<dt id='index-UID'><span><code>UID</code><a href='#index-UID' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The numeric real user id of the current user.  This variable is readonly.
</p>
</dd>
</dl>

<hr>
</div>
</div>
<div class="chapter" id="Bash-Features">
<div class="header">
<p>
Next: <a href="#Job-Control" accesskey="n" rel="next">Job Control</a>, Previous: <a href="#Shell-Variables" accesskey="p" rel="prev">Shell Variables</a>, Up: <a href="#Top" accesskey="u" rel="up">Bash Features</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Bash-Features-2"></span><h2 class="chapter">6 Bash Features</h2>

<p>This chapter describes features unique to Bash.
</p>

<ul class="section-toc">
<li><a href="#Invoking-Bash" accesskey="1">Invoking Bash</a></li>
<li><a href="#Bash-Startup-Files" accesskey="2">Bash Startup Files</a></li>
<li><a href="#Interactive-Shells" accesskey="3">Interactive Shells</a></li>
<li><a href="#Bash-Conditional-Expressions" accesskey="4">Bash Conditional Expressions</a></li>
<li><a href="#Shell-Arithmetic" accesskey="5">Shell Arithmetic</a></li>
<li><a href="#Aliases" accesskey="6">Aliases</a></li>
<li><a href="#Arrays" accesskey="7">Arrays</a></li>
<li><a href="#The-Directory-Stack" accesskey="8">The Directory Stack</a></li>
<li><a href="#Controlling-the-Prompt" accesskey="9">Controlling the Prompt</a></li>
<li><a href="#The-Restricted-Shell">The Restricted Shell</a></li>
<li><a href="#Bash-POSIX-Mode">Bash POSIX Mode</a></li>
<li><a href="#Shell-Compatibility-Mode">Shell Compatibility Mode</a></li>
</ul>
<hr>
<div class="section" id="Invoking-Bash">
<div class="header">
<p>
Next: <a href="#Bash-Startup-Files" accesskey="n" rel="next">Bash Startup Files</a>, Up: <a href="#Bash-Features" accesskey="u" rel="up">Bash Features</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Invoking-Bash-1"></span><h3 class="section">6.1 Invoking Bash</h3>

<div class="example">
<pre class="example">bash [long-opt] [-ir] [-abefhkmnptuvxdBCDHP] [-o <var>option</var>]
    [-O <var>shopt_option</var>] [<var>argument</var> &hellip;]
bash [long-opt] [-abefhkmnptuvxdBCDHP] [-o <var>option</var>]
    [-O <var>shopt_option</var>] -c <var>string</var> [<var>argument</var> &hellip;]
bash [long-opt] -s [-abefhkmnptuvxdBCDHP] [-o <var>option</var>]
    [-O <var>shopt_option</var>] [<var>argument</var> &hellip;]
</pre></div>

<p>All of the single-character options used with the <code>set</code> builtin
(see <a href="#The-Set-Builtin">The Set Builtin</a>) can be used as options when the shell is invoked.
In addition, there are several multi-character
options that you can use.  These options must appear on the command
line before the single-character options to be recognized. 
</p>
<dl compact="compact">
<dt><span><code>--debugger</code></span></dt>
<dd><p>Arrange for the debugger profile to be executed before the shell
starts.  Turns on extended debugging mode (see <a href="#The-Shopt-Builtin">The Shopt Builtin</a>
for a description of the <code>extdebug</code> option to the <code>shopt</code>
builtin).
</p>
</dd>
<dt><span><code>--dump-po-strings</code></span></dt>
<dd><p>A list of all double-quoted strings preceded by &lsquo;<samp>$</samp>&rsquo;
is printed on the standard output
in the <small>GNU</small> <code>gettext</code> PO (portable object) file format.
Equivalent to <samp>-D</samp> except for the output format.
</p>
</dd>
<dt><span><code>--dump-strings</code></span></dt>
<dd><p>Equivalent to <samp>-D</samp>.
</p>
</dd>
<dt><span><code>--help</code></span></dt>
<dd><p>Display a usage message on standard output and exit successfully.
</p>
</dd>
<dt><span><code>--init-file <var>filename</var></code></span></dt>
<dt><span><code>--rcfile <var>filename</var></code></span></dt>
<dd><p>Execute commands from <var>filename</var> (instead of <samp>~/.bashrc</samp>)
in an interactive shell.
</p>
</dd>
<dt><span><code>--login</code></span></dt>
<dd><p>Equivalent to <samp>-l</samp>.
</p>
</dd>
<dt><span><code>--noediting</code></span></dt>
<dd><p>Do not use the <small>GNU</small> Readline library (see <a href="#Command-Line-Editing">Command Line Editing</a>)
to read  command lines when the shell is interactive.
</p>
</dd>
<dt><span><code>--noprofile</code></span></dt>
<dd><p>Don&rsquo;t load the system-wide startup file <samp>/etc/profile</samp>
or any of the personal initialization files
<samp>~/.bash_profile</samp>, <samp>~/.bash_login</samp>, or <samp>~/.profile</samp>
when Bash is invoked as a login shell.
</p>
</dd>
<dt><span><code>--norc</code></span></dt>
<dd><p>Don&rsquo;t read the <samp>~/.bashrc</samp> initialization file in an
interactive shell.  This is on by default if the shell is
invoked as <code>sh</code>.
</p>
</dd>
<dt><span><code>--posix</code></span></dt>
<dd><p>Change the behavior of Bash where the default operation differs
from the <small>POSIX</small> standard to match the standard.  This
is intended to make Bash behave as a strict superset of that
standard.  See <a href="#Bash-POSIX-Mode">Bash POSIX Mode</a>, for a description of the Bash
<small>POSIX</small> mode.
</p>
</dd>
<dt><span><code>--restricted</code></span></dt>
<dd><p>Make the shell a restricted shell (see <a href="#The-Restricted-Shell">The Restricted Shell</a>).
</p>
</dd>
<dt><span><code>--verbose</code></span></dt>
<dd><p>Equivalent to <samp>-v</samp>.  Print shell input lines as they&rsquo;re read.
</p>
</dd>
<dt><span><code>--version</code></span></dt>
<dd><p>Show version information for this instance of
Bash on the standard output and exit successfully.
</p></dd>
</dl>

<p>There are several single-character options that may be supplied at
invocation which are not available with the <code>set</code> builtin.
</p>
<dl compact="compact">
<dt><span><code>-c</code></span></dt>
<dd><p>Read and execute commands from the first non-option argument
<var>command_string</var>, then exit. 
If there are arguments after the <var>command_string</var>,
the first argument is assigned to <code>$0</code>
and any remaining arguments are assigned to the positional parameters.
The assignment to <code>$0</code> sets the name of the shell, which is used
in warning and error messages.
</p>
</dd>
<dt><span><code>-i</code></span></dt>
<dd><p>Force the shell to run interactively.  Interactive shells are
described in <a href="#Interactive-Shells">Interactive Shells</a>.
</p>
</dd>
<dt><span><code>-l</code></span></dt>
<dd><p>Make this shell act as if it had been directly invoked by login.
When the shell is interactive, this is equivalent to starting a
login shell with &lsquo;<samp>exec -l bash</samp>&rsquo;.
When the shell is not interactive, the login shell startup files will
be executed.
&lsquo;<samp>exec bash -l</samp>&rsquo; or &lsquo;<samp>exec bash --login</samp>&rsquo;
will replace the current shell with a Bash login shell.
See <a href="#Bash-Startup-Files">Bash Startup Files</a>, for a description of the special behavior
of a login shell.
</p>
</dd>
<dt><span><code>-r</code></span></dt>
<dd><p>Make the shell a restricted shell (see <a href="#The-Restricted-Shell">The Restricted Shell</a>).
</p>
</dd>
<dt><span><code>-s</code></span></dt>
<dd><p>If this option is present, or if no arguments remain after option
processing, then commands are read from the standard input.
This option allows the positional parameters to be set
when invoking an interactive shell or when reading input
through a pipe.
</p>
</dd>
<dt><span><code>-D</code></span></dt>
<dd><p>A list of all double-quoted strings preceded by &lsquo;<samp>$</samp>&rsquo;
is printed on the standard output.
These are the strings that
are subject to language translation when the current locale
is not <code>C</code> or <code>POSIX</code> (see <a href="#Locale-Translation">Locale-Specific Translation</a>).
This implies the <samp>-n</samp> option; no commands will be executed.
</p>
</dd>
<dt><span><code>[-+]O [<var>shopt_option</var>]</code></span></dt>
<dd><p><var>shopt_option</var> is one of the shell options accepted by the
<code>shopt</code> builtin (see <a href="#The-Shopt-Builtin">The Shopt Builtin</a>).
If <var>shopt_option</var> is present, <samp>-O</samp> sets the value of that option;
<samp>+O</samp> unsets it.  
If <var>shopt_option</var> is not supplied, the names and values of the shell
options accepted by <code>shopt</code> are printed on the standard output.
If the invocation option is <samp>+O</samp>, the output is displayed in a format
that may be reused as input.
</p>
</dd>
<dt><span><code>--</code></span></dt>
<dd><p>A <code>--</code> signals the end of options and disables further option
processing.
Any arguments after the <code>--</code> are treated as filenames and arguments.
</p></dd>
</dl>

<span id="index-login-shell"></span>
<p>A <em>login</em> shell is one whose first character of argument zero is
&lsquo;<samp>-</samp>&rsquo;, or one invoked with the <samp>--login</samp> option.
</p>
<span id="index-interactive-shell"></span>
<p>An <em>interactive</em> shell is one started without non-option arguments,
unless <samp>-s</samp> is specified,
without specifying the <samp>-c</samp> option, and whose input and output are both
connected to terminals (as determined by <code>isatty(3)</code>), or one
started with the <samp>-i</samp> option.  See <a href="#Interactive-Shells">Interactive Shells</a>, for more
information.
</p>
<p>If arguments remain after option processing, and neither the
<samp>-c</samp> nor the <samp>-s</samp>
option has been supplied, the first argument is assumed to
be the name of a file containing shell commands (see <a href="#Shell-Scripts">Shell Scripts</a>).
When Bash is invoked in this fashion, <code>$0</code>
is set to the name of the file, and the positional parameters
are set to the remaining arguments.
Bash reads and executes commands from this file, then exits.   
Bash&rsquo;s exit status is the exit status of the last command executed
in the script.  If no commands are executed, the exit status is 0.
</p>
<hr>
</div>
<div class="section" id="Bash-Startup-Files">
<div class="header">
<p>
Next: <a href="#Interactive-Shells" accesskey="n" rel="next">Interactive Shells</a>, Previous: <a href="#Invoking-Bash" accesskey="p" rel="prev">Invoking Bash</a>, Up: <a href="#Bash-Features" accesskey="u" rel="up">Bash Features</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Bash-Startup-Files-1"></span><h3 class="section">6.2 Bash Startup Files</h3>
<span id="index-startup-files"></span>

<p>This section describes how Bash executes its startup files.
If any of the files exist but cannot be read, Bash reports an error.
Tildes are expanded in filenames as described above under
Tilde Expansion (see <a href="#Tilde-Expansion">Tilde Expansion</a>).
</p>
<p>Interactive shells are described in <a href="#Interactive-Shells">Interactive Shells</a>.
</p>
<span id="Invoked-as-an-interactive-login-shell_002c-or-with-_002d_002dlogin"></span><h4 class="subsubheading">Invoked as an interactive login shell, or with <samp>--login</samp></h4>

<p>When Bash is invoked as an interactive login shell, or as a
non-interactive shell with the <samp>--login</samp> option, it first reads and
executes commands from the file <samp>/etc/profile</samp>, if that file exists.
After reading that file, it looks for <samp>~/.bash_profile</samp>,
<samp>~/.bash_login</samp>, and <samp>~/.profile</samp>, in that order, and reads
and executes commands from the first one that exists and is readable.
The <samp>--noprofile</samp> option may be used when the shell is started to
inhibit this behavior.
</p>
<p>When an interactive login shell exits,
or a non-interactive login shell executes the <code>exit</code> builtin command,
Bash reads and executes commands from
the file <samp>~/.bash_logout</samp>, if it exists.
</p>
<span id="Invoked-as-an-interactive-non_002dlogin-shell"></span><h4 class="subsubheading">Invoked as an interactive non-login shell</h4>

<p>When an interactive shell that is not a login shell is started, Bash
reads and executes commands from <samp>~/.bashrc</samp>, if that file exists.
This may be inhibited by using the <samp>--norc</samp> option.
The <samp>--rcfile <var>file</var></samp> option will force Bash to read and
execute commands from <var>file</var> instead of <samp>~/.bashrc</samp>.
</p>
<p>So, typically, your <samp>~/.bash_profile</samp> contains the line
</p><div class="example">
<pre class="example"><code>if [ -f ~/.bashrc ]; then . ~/.bashrc; fi</code>
</pre></div>
<p>after (or before) any login-specific initializations.
</p>
<span id="Invoked-non_002dinteractively"></span><h4 class="subsubheading">Invoked non-interactively</h4>

<p>When Bash is started non-interactively, to run a shell script,
for example, it looks for the variable <code>BASH_ENV</code> in the environment,
expands its value if it appears there, and uses the expanded value as
the name of a file to read and execute.  Bash behaves as if the
following command were executed:
</p><div class="example">
<pre class="example"><code>if [ -n &quot;$BASH_ENV&quot; ]; then . &quot;$BASH_ENV&quot;; fi</code>
</pre></div>
<p>but the value of the <code>PATH</code> variable is not used to search for the
filename.
</p>
<p>As noted above, if a non-interactive shell is invoked with the
<samp>--login</samp> option, Bash attempts to read and execute commands from the
login shell startup files. 
</p>
<span id="Invoked-with-name-sh"></span><h4 class="subsubheading">Invoked with name <code>sh</code></h4>

<p>If Bash is invoked with the name <code>sh</code>, it tries to mimic the
startup behavior of historical versions of <code>sh</code> as closely as
possible, while conforming to the <small>POSIX</small> standard as well.
</p>
<p>When invoked as an interactive login shell, or as a non-interactive
shell with the <samp>--login</samp> option, it first attempts to read
and execute commands from <samp>/etc/profile</samp> and <samp>~/.profile</samp>, in
that order.
The <samp>--noprofile</samp> option may be used to inhibit this behavior.
When invoked as an interactive shell with the name <code>sh</code>, Bash
looks for the variable <code>ENV</code>, expands its value if it is defined,
and uses the expanded value as the name of a file to read and execute.
Since a shell invoked as <code>sh</code> does not attempt to read and execute
commands from any other startup files, the <samp>--rcfile</samp> option has
no effect.
A non-interactive shell invoked with the name <code>sh</code> does not attempt
to read any other startup files.
</p>
<p>When invoked as <code>sh</code>, Bash enters <small>POSIX</small> mode after
the startup files are read.
</p>
<span id="Invoked-in-POSIX-mode"></span><h4 class="subsubheading">Invoked in <small>POSIX</small> mode</h4>

<p>When Bash is started in <small>POSIX</small> mode, as with the
<samp>--posix</samp> command line option, it follows the <small>POSIX</small> standard
for startup files.
In this mode, interactive shells expand the <code>ENV</code> variable
and commands are read and executed from the file whose name is the
expanded value.
No other startup files are read.
</p>
<span id="Invoked-by-remote-shell-daemon"></span><h4 class="subsubheading">Invoked by remote shell daemon</h4>

<p>Bash attempts to determine when it is being run with its standard input
connected to a network connection, as when executed by
the historical remote shell daemon, usually <code>rshd</code>,
or the secure shell daemon <code>sshd</code>.
If Bash
determines it is being run non-interactively in this fashion,
it reads and executes commands from <samp>~/.bashrc</samp>, if that
file exists and is readable.
It will not do this if invoked as <code>sh</code>.
The <samp>--norc</samp> option may be used to inhibit this behavior, and the
<samp>--rcfile</samp> option may be used to force another file to be read, but
neither <code>rshd</code> nor <code>sshd</code> generally invoke the shell with those
options or allow them to be specified.
</p>
<span id="Invoked-with-unequal-effective-and-real-UID_002fGIDs"></span><h4 class="subsubheading">Invoked with unequal effective and real <small>UID/GID</small>s</h4>

<p>If Bash is started with the effective user (group) id not equal to the
real user (group) id, and the <samp>-p</samp> option is not supplied, no startup
files are read, shell functions are not inherited from the environment,
the <code>SHELLOPTS</code>, <code>BASHOPTS</code>, <code>CDPATH</code>, and <code>GLOBIGNORE</code>
variables, if they appear in the environment, are ignored, and the effective
user id is set to the real user id.
If the <samp>-p</samp> option is supplied at invocation, the startup behavior is
the same, but the effective user id is not reset.
</p>
<hr>
</div>
<div class="section" id="Interactive-Shells">
<div class="header">
<p>
Next: <a href="#Bash-Conditional-Expressions" accesskey="n" rel="next">Bash Conditional Expressions</a>, Previous: <a href="#Bash-Startup-Files" accesskey="p" rel="prev">Bash Startup Files</a>, Up: <a href="#Bash-Features" accesskey="u" rel="up">Bash Features</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Interactive-Shells-1"></span><h3 class="section">6.3 Interactive Shells</h3>
<span id="index-interactive-shell-1"></span>
<span id="index-shell_002c-interactive"></span>


<ul class="section-toc">
<li><a href="#What-is-an-Interactive-Shell_003f" accesskey="1">What is an Interactive Shell?</a></li>
<li><a href="#Is-this-Shell-Interactive_003f" accesskey="2">Is this Shell Interactive?</a></li>
<li><a href="#Interactive-Shell-Behavior" accesskey="3">Interactive Shell Behavior</a></li>
</ul>
<hr>
<div class="subsection" id="What-is-an-Interactive-Shell_003f">
<div class="header">
<p>
Next: <a href="#Is-this-Shell-Interactive_003f" accesskey="n" rel="next">Is this Shell Interactive?</a>, Up: <a href="#Interactive-Shells" accesskey="u" rel="up">Interactive Shells</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="What-is-an-Interactive-Shell_003f-1"></span><h4 class="subsection">6.3.1 What is an Interactive Shell?</h4>

<p>An interactive shell
is one started without non-option arguments
(unless <samp>-s</samp> is specified)
and without specifying the <samp>-c</samp> option,
whose input and error output are both
connected to terminals (as determined by <code>isatty(3)</code>),
or one started with the <samp>-i</samp> option.
</p>
<p>An interactive shell generally reads from and writes to a user&rsquo;s
terminal.
</p>
<p>The <samp>-s</samp> invocation option may be used to set the positional parameters
when an interactive shell is started.
</p>
<hr>
</div>
<div class="subsection" id="Is-this-Shell-Interactive_003f">
<div class="header">
<p>
Next: <a href="#Interactive-Shell-Behavior" accesskey="n" rel="next">Interactive Shell Behavior</a>, Previous: <a href="#What-is-an-Interactive-Shell_003f" accesskey="p" rel="prev">What is an Interactive Shell?</a>, Up: <a href="#Interactive-Shells" accesskey="u" rel="up">Interactive Shells</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Is-this-Shell-Interactive_003f-1"></span><h4 class="subsection">6.3.2 Is this Shell Interactive?</h4>

<p>To determine within a startup script whether or not Bash is
running interactively,
test the value of the &lsquo;<samp>-</samp>&rsquo; special parameter.
It contains <code>i</code> when the shell is interactive.  For example:
</p>
<div class="example">
<pre class="example">case &quot;$-&quot; in
*i*)	echo This shell is interactive ;;
*)	echo This shell is not interactive ;;
esac
</pre></div>

<p>Alternatively, startup scripts may examine the variable
<code>PS1</code>; it is unset in non-interactive shells, and set in
interactive shells.  Thus:
</p>
<div class="example">
<pre class="example">if [ -z &quot;$PS1&quot; ]; then
        echo This shell is not interactive
else
        echo This shell is interactive
fi
</pre></div>

<hr>
</div>
<div class="subsection" id="Interactive-Shell-Behavior">
<div class="header">
<p>
Previous: <a href="#Is-this-Shell-Interactive_003f" accesskey="p" rel="prev">Is this Shell Interactive?</a>, Up: <a href="#Interactive-Shells" accesskey="u" rel="up">Interactive Shells</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Interactive-Shell-Behavior-1"></span><h4 class="subsection">6.3.3 Interactive Shell Behavior</h4>

<p>When the shell is running interactively, it changes its behavior in
several ways.
</p>
<ol>
<li> Startup files are read and executed as described in <a href="#Bash-Startup-Files">Bash Startup Files</a>.

</li><li> Job Control (see <a href="#Job-Control">Job Control</a>) is enabled by default.  When job
control is in effect, Bash ignores the keyboard-generated job control
signals <code>SIGTTIN</code>, <code>SIGTTOU</code>, and <code>SIGTSTP</code>.

</li><li> Bash expands and displays <code>PS1</code> before reading the first line
of a command, and expands and displays <code>PS2</code> before reading the
second and subsequent lines of a multi-line command.
Bash expands and displays <code>PS0</code> after it reads a command but before
executing it.
See <a href="#Controlling-the-Prompt">Controlling the Prompt</a>, for a complete list of prompt
string escape sequences.

</li><li> Bash executes the values of the set elements of the <code>PROMPT_COMMAND</code>
array variable as commands before printing the primary prompt, <code>$PS1</code>
(see <a href="#Bash-Variables">Bash Variables</a>).

</li><li> Readline (see <a href="#Command-Line-Editing">Command Line Editing</a>) is used to read commands from
the user&rsquo;s terminal.

</li><li> Bash inspects the value of the <code>ignoreeof</code> option to <code>set -o</code>
instead of exiting immediately when it receives an <code>EOF</code> on its
standard input when reading a command (see <a href="#The-Set-Builtin">The Set Builtin</a>).

</li><li> Command history (see <a href="#Bash-History-Facilities">Bash History Facilities</a>)
and history expansion (see <a href="#History-Interaction">History Expansion</a>)
are enabled by default.
Bash will save the command history to the file named by <code>$HISTFILE</code>
when a shell with history enabled exits.

</li><li> Alias expansion (see <a href="#Aliases">Aliases</a>) is performed by default.

</li><li> In the absence of any traps, Bash ignores <code>SIGTERM</code>
(see <a href="#Signals">Signals</a>).

</li><li> In the absence of any traps, <code>SIGINT</code> is caught and handled
(see <a href="#Signals">Signals</a>).
<code>SIGINT</code> will interrupt some shell builtins.

</li><li> An interactive login shell sends a <code>SIGHUP</code> to all jobs on exit
if the <code>huponexit</code> shell option has been enabled (see <a href="#Signals">Signals</a>).

</li><li> The <samp>-n</samp> invocation option is ignored, and &lsquo;<samp>set -n</samp>&rsquo; has
no effect (see <a href="#The-Set-Builtin">The Set Builtin</a>).

</li><li> Bash will check for mail periodically, depending on the values of the
<code>MAIL</code>, <code>MAILPATH</code>, and <code>MAILCHECK</code> shell variables
(see <a href="#Bash-Variables">Bash Variables</a>).

</li><li> Expansion errors due to references to unbound shell variables after
&lsquo;<samp>set -u</samp>&rsquo; has been enabled will not cause the shell to exit
(see <a href="#The-Set-Builtin">The Set Builtin</a>).

</li><li> The shell will not exit on expansion errors caused by <var>var</var> being unset
or null in <code>${<var>var</var>:?<var>word</var>}</code> expansions
(see <a href="#Shell-Parameter-Expansion">Shell Parameter Expansion</a>).

</li><li> Redirection errors encountered by shell builtins will not cause the
shell to exit.

</li><li> When running in <small>POSIX</small> mode, a special builtin returning an error
status will not cause the shell to exit (see <a href="#Bash-POSIX-Mode">Bash POSIX Mode</a>).

</li><li> A failed <code>exec</code> will not cause the shell to exit
(see <a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a>).

</li><li> Parser syntax errors will not cause the shell to exit.

</li><li> If the <code>cdspell</code> shell option is enabled, the shell will attempt
simple spelling correction for directory arguments to the <code>cd</code>
builtin (see the description of the <code>cdspell</code>
option to the <code>shopt</code> builtin in <a href="#The-Shopt-Builtin">The Shopt Builtin</a>).
The <code>cdspell</code> option is only effective in interactive shells.

</li><li> The shell will check the value of the <code>TMOUT</code> variable and exit
if a command is not read within the specified number of seconds after
printing <code>$PS1</code> (see <a href="#Bash-Variables">Bash Variables</a>).

</li></ol>

<hr>
</div>
</div>
<div class="section" id="Bash-Conditional-Expressions">
<div class="header">
<p>
Next: <a href="#Shell-Arithmetic" accesskey="n" rel="next">Shell Arithmetic</a>, Previous: <a href="#Interactive-Shells" accesskey="p" rel="prev">Interactive Shells</a>, Up: <a href="#Bash-Features" accesskey="u" rel="up">Bash Features</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Bash-Conditional-Expressions-1"></span><h3 class="section">6.4 Bash Conditional Expressions</h3>
<span id="index-expressions_002c-conditional"></span>

<p>Conditional expressions are used by the <code>[[</code> compound command
(see <a href="#Conditional-Constructs">Conditional Constructs</a>)
and the <code>test</code> and <code>[</code> builtin commands
(see <a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a>).
The <code>test</code>
and <code>[</code> commands determine their behavior based on the number
of arguments; see the descriptions of those commands for any other
command-specific actions.
</p>
<p>Expressions may be unary or binary,
and are formed from the following primaries.
Unary expressions are often used to examine the status of a file.
There are string operators and numeric comparison operators as well.
Bash handles several filenames specially when they are used in
expressions.
If the operating system on which Bash is running provides these
special files, Bash will use them; otherwise it will emulate them
internally with this behavior:
If the <var>file</var> argument to one of the primaries is of the form
<samp>/dev/fd/<var>N</var></samp>, then file descriptor <var>N</var> is checked.
If the <var>file</var> argument to one of the primaries is one of
<samp>/dev/stdin</samp>, <samp>/dev/stdout</samp>, or <samp>/dev/stderr</samp>, file
descriptor 0, 1, or 2, respectively, is checked.
</p>
<p>When used with <code>[[</code>, the &lsquo;<samp>&lt;</samp>&rsquo; and &lsquo;<samp>&gt;</samp>&rsquo; operators sort
lexicographically using the current locale.
The <code>test</code> command uses ASCII ordering.
</p>
<p>Unless otherwise specified, primaries that operate on files follow symbolic
links and operate on the target of the link, rather than the link itself.
</p>
<dl compact="compact">
<dt><span><code>-a <var>file</var></code></span></dt>
<dd><p>True if <var>file</var> exists.
</p>
</dd>
<dt><span><code>-b <var>file</var></code></span></dt>
<dd><p>True if <var>file</var> exists and is a block special file.
</p>
</dd>
<dt><span><code>-c <var>file</var></code></span></dt>
<dd><p>True if <var>file</var> exists and is a character special file.
</p>
</dd>
<dt><span><code>-d <var>file</var></code></span></dt>
<dd><p>True if <var>file</var> exists and is a directory.
</p>
</dd>
<dt><span><code>-e <var>file</var></code></span></dt>
<dd><p>True if <var>file</var> exists.
</p>
</dd>
<dt><span><code>-f <var>file</var></code></span></dt>
<dd><p>True if <var>file</var> exists and is a regular file.
</p>
</dd>
<dt><span><code>-g <var>file</var></code></span></dt>
<dd><p>True if <var>file</var> exists and its set-group-id bit is set.
</p>
</dd>
<dt><span><code>-h <var>file</var></code></span></dt>
<dd><p>True if <var>file</var> exists and is a symbolic link.
</p>
</dd>
<dt><span><code>-k <var>file</var></code></span></dt>
<dd><p>True if <var>file</var> exists and its &quot;sticky&quot; bit is set.
</p>
</dd>
<dt><span><code>-p <var>file</var></code></span></dt>
<dd><p>True if <var>file</var> exists and is a named pipe (FIFO).
</p>
</dd>
<dt><span><code>-r <var>file</var></code></span></dt>
<dd><p>True if <var>file</var> exists and is readable.
</p>
</dd>
<dt><span><code>-s <var>file</var></code></span></dt>
<dd><p>True if <var>file</var> exists and has a size greater than zero.
</p>
</dd>
<dt><span><code>-t <var>fd</var></code></span></dt>
<dd><p>True if file descriptor <var>fd</var> is open and refers to a terminal.
</p>
</dd>
<dt><span><code>-u <var>file</var></code></span></dt>
<dd><p>True if <var>file</var> exists and its set-user-id bit is set.
</p>
</dd>
<dt><span><code>-w <var>file</var></code></span></dt>
<dd><p>True if <var>file</var> exists and is writable.
</p>
</dd>
<dt><span><code>-x <var>file</var></code></span></dt>
<dd><p>True if <var>file</var> exists and is executable.
</p>
</dd>
<dt><span><code>-G <var>file</var></code></span></dt>
<dd><p>True if <var>file</var> exists and is owned by the effective group id.
</p>
</dd>
<dt><span><code>-L <var>file</var></code></span></dt>
<dd><p>True if <var>file</var> exists and is a symbolic link.
</p>
</dd>
<dt><span><code>-N <var>file</var></code></span></dt>
<dd><p>True if <var>file</var> exists and has been modified since it was last read.
</p>
</dd>
<dt><span><code>-O <var>file</var></code></span></dt>
<dd><p>True if <var>file</var> exists and is owned by the effective user id.
</p>
</dd>
<dt><span><code>-S <var>file</var></code></span></dt>
<dd><p>True if <var>file</var> exists and is a socket.
</p>
</dd>
<dt><span><code><var>file1</var> -ef <var>file2</var></code></span></dt>
<dd><p>True if <var>file1</var> and <var>file2</var> refer to the same device and
inode numbers.
</p>
</dd>
<dt><span><code><var>file1</var> -nt <var>file2</var></code></span></dt>
<dd><p>True if <var>file1</var> is newer (according to modification date)
than <var>file2</var>, or if <var>file1</var> exists and <var>file2</var> does not.
</p>
</dd>
<dt><span><code><var>file1</var> -ot <var>file2</var></code></span></dt>
<dd><p>True if <var>file1</var> is older than <var>file2</var>,
or if <var>file2</var> exists and <var>file1</var> does not.
</p>
</dd>
<dt><span><code>-o <var>optname</var></code></span></dt>
<dd><p>True if the shell option <var>optname</var> is enabled.
The list of options appears in the description of the <samp>-o</samp>
option to the <code>set</code> builtin (see <a href="#The-Set-Builtin">The Set Builtin</a>).
</p>
</dd>
<dt><span><code>-v <var>varname</var></code></span></dt>
<dd><p>True if the shell variable <var>varname</var> is set (has been assigned a value).
</p>
</dd>
<dt><span><code>-R <var>varname</var></code></span></dt>
<dd><p>True if the shell variable <var>varname</var> is set and is a name reference.
</p>
</dd>
<dt><span><code>-z <var>string</var></code></span></dt>
<dd><p>True if the length of <var>string</var> is zero.
</p>
</dd>
<dt><span><code>-n <var>string</var></code></span></dt>
<dt><span><code><var>string</var></code></span></dt>
<dd><p>True if the length of <var>string</var> is non-zero.
</p>
</dd>
<dt><span><code><var>string1</var> == <var>string2</var></code></span></dt>
<dt><span><code><var>string1</var> = <var>string2</var></code></span></dt>
<dd><p>True if the strings are equal.
When used with the <code>[[</code> command, this performs pattern matching as
described above (see <a href="#Conditional-Constructs">Conditional Constructs</a>).
</p>
<p>&lsquo;<samp>=</samp>&rsquo; should be used with the <code>test</code> command for <small>POSIX</small> conformance.
</p>
</dd>
<dt><span><code><var>string1</var> != <var>string2</var></code></span></dt>
<dd><p>True if the strings are not equal.
</p>
</dd>
<dt><span><code><var>string1</var> &lt; <var>string2</var></code></span></dt>
<dd><p>True if <var>string1</var> sorts before <var>string2</var> lexicographically.
</p>
</dd>
<dt><span><code><var>string1</var> &gt; <var>string2</var></code></span></dt>
<dd><p>True if <var>string1</var> sorts after <var>string2</var> lexicographically.
</p>
</dd>
<dt><span><code><var>arg1</var> OP <var>arg2</var></code></span></dt>
<dd><p><code>OP</code> is one of 
&lsquo;<samp>-eq</samp>&rsquo;, &lsquo;<samp>-ne</samp>&rsquo;, &lsquo;<samp>-lt</samp>&rsquo;, &lsquo;<samp>-le</samp>&rsquo;, &lsquo;<samp>-gt</samp>&rsquo;, or &lsquo;<samp>-ge</samp>&rsquo;.
These arithmetic binary operators return true if <var>arg1</var>
is equal to, not equal to, less than, less than or equal to,
greater than, or greater than or equal to <var>arg2</var>,
respectively.  <var>Arg1</var> and <var>arg2</var>
may be positive or negative integers.
When used with the <code>[[</code> command, <var>Arg1</var> and <var>Arg2</var>
are evaluated as arithmetic expressions (see <a href="#Shell-Arithmetic">Shell Arithmetic</a>).
</p></dd>
</dl>

<hr>
</div>
<div class="section" id="Shell-Arithmetic">
<div class="header">
<p>
Next: <a href="#Aliases" accesskey="n" rel="next">Aliases</a>, Previous: <a href="#Bash-Conditional-Expressions" accesskey="p" rel="prev">Bash Conditional Expressions</a>, Up: <a href="#Bash-Features" accesskey="u" rel="up">Bash Features</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Shell-Arithmetic-1"></span><h3 class="section">6.5 Shell Arithmetic</h3>
<span id="index-arithmetic_002c-shell"></span>
<span id="index-shell-arithmetic"></span>
<span id="index-expressions_002c-arithmetic"></span>
<span id="index-evaluation_002c-arithmetic"></span>
<span id="index-arithmetic-evaluation"></span>

<p>The shell allows arithmetic expressions to be evaluated, as one of
the shell expansions or by using the <code>((</code> compound command, the
<code>let</code> builtin, or the <samp>-i</samp> option to the <code>declare</code> builtin.
</p>
<p>Evaluation is done in fixed-width integers with no check for overflow,
though division by 0 is trapped and flagged as an error.
The operators and their precedence, associativity, and values
are the same as in the C language.
The following list of operators is grouped into levels of
equal-precedence operators.
The levels are listed in order of decreasing precedence. 
</p>
<dl compact="compact">
<dt><span><code><var>id</var>++ <var>id</var>--</code></span></dt>
<dd><p>variable post-increment and post-decrement 
</p>
</dd>
<dt><span><code>++<var>id</var> --<var>id</var></code></span></dt>
<dd><p>variable pre-increment and pre-decrement
</p>
</dd>
<dt><span><code>- +</code></span></dt>
<dd><p>unary minus and plus
</p>
</dd>
<dt><span><code>! ~</code></span></dt>
<dd><p>logical and bitwise negation
</p>
</dd>
<dt><span><code>**</code></span></dt>
<dd><p>exponentiation
</p>
</dd>
<dt><span><code>* / %</code></span></dt>
<dd><p>multiplication, division, remainder
</p>
</dd>
<dt><span><code>+ -</code></span></dt>
<dd><p>addition, subtraction
</p>
</dd>
<dt><span><code>&lt;&lt; &gt;&gt;</code></span></dt>
<dd><p>left and right bitwise shifts
</p>
</dd>
<dt><span><code>&lt;= &gt;= &lt; &gt;</code></span></dt>
<dd><p>comparison
</p>
</dd>
<dt><span><code>== !=</code></span></dt>
<dd><p>equality and inequality
</p>
</dd>
<dt><span><code>&amp;</code></span></dt>
<dd><p>bitwise AND
</p>
</dd>
<dt><span><code>^</code></span></dt>
<dd><p>bitwise exclusive OR
</p>
</dd>
<dt><span><code>|</code></span></dt>
<dd><p>bitwise OR
</p>
</dd>
<dt><span><code>&amp;&amp;</code></span></dt>
<dd><p>logical AND
</p>
</dd>
<dt><span><code>||</code></span></dt>
<dd><p>logical OR
</p>
</dd>
<dt><span><code>expr ? expr : expr</code></span></dt>
<dd><p>conditional operator
</p>
</dd>
<dt><span><code>= *= /= %= += -= &lt;&lt;= &gt;&gt;= &amp;= ^= |=</code></span></dt>
<dd><p>assignment
</p>
</dd>
<dt><span><code>expr1 , expr2</code></span></dt>
<dd><p>comma
</p></dd>
</dl>

<p>Shell variables are allowed as operands; parameter expansion is
performed before the expression is evaluated. 
Within an expression, shell variables may also be referenced by name
without using the parameter expansion syntax.
A shell variable that is null or unset evaluates to 0 when referenced
by name without using the parameter expansion syntax.
The value of a variable is evaluated as an arithmetic expression
when it is referenced, or when a variable which has been given the  
<code>integer</code> attribute using &lsquo;<samp>declare -i</samp>&rsquo; is assigned a value.
A null value evaluates to 0.
A shell variable need not have its <code>integer</code> attribute turned on
to be used in an expression.
</p>
<p>Integer constants follow the C language definition, without suffixes or
character constants.
Constants with a leading 0 are interpreted as octal numbers.
A leading &lsquo;<samp>0x</samp>&rsquo; or &lsquo;<samp>0X</samp>&rsquo; denotes hexadecimal.  Otherwise,
numbers take the form [<var>base</var><code>#</code>]<var>n</var>, where the optional <var>base</var>
is a decimal number between 2 and 64 representing the arithmetic
base, and <var>n</var> is a number in that base.
If <var>base</var><code>#</code> is omitted, then base 10 is used.
When specifying <var>n</var>,
if a non-digit is required,
the digits greater than 9 are represented by the lowercase letters,
the uppercase letters, &lsquo;<samp>@</samp>&rsquo;, and &lsquo;<samp>_</samp>&rsquo;, in that order.
If <var>base</var> is less than or equal to 36, lowercase and uppercase
letters may be used interchangeably to represent numbers between 10
and 35.
</p>
<p>Operators are evaluated in order of precedence.  Sub-expressions in
parentheses are evaluated first and may override the precedence
rules above.
</p>
<hr>
</div>
<div class="section" id="Aliases">
<div class="header">
<p>
Next: <a href="#Arrays" accesskey="n" rel="next">Arrays</a>, Previous: <a href="#Shell-Arithmetic" accesskey="p" rel="prev">Shell Arithmetic</a>, Up: <a href="#Bash-Features" accesskey="u" rel="up">Bash Features</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Aliases-1"></span><h3 class="section">6.6 Aliases</h3>
<span id="index-alias-expansion"></span>

<p><em>Aliases</em> allow a string to be substituted for a word when it is used
as the first word of a simple command.
The shell maintains a list of aliases that may be set and unset with
the <code>alias</code> and <code>unalias</code> builtin commands.
</p>
<p>The first word of each simple command, if unquoted, is checked to see
if it has an alias.
If so, that word is replaced by the text of the alias.
The characters &lsquo;<samp>/</samp>&rsquo;, &lsquo;<samp>$</samp>&rsquo;, &lsquo;<samp>`</samp>&rsquo;, &lsquo;<samp>=</samp>&rsquo; and any of the
shell metacharacters or quoting characters listed above may not appear
in an alias name.
The replacement text may contain any valid
shell input, including shell metacharacters.
The first word of the replacement text is tested for
aliases, but a word that is identical to an alias being expanded
is not expanded a second time.
This means that one may alias <code>ls</code> to <code>&quot;ls -F&quot;</code>,
for instance, and Bash does not try to recursively expand the
replacement text.
If the last character of the alias value is a
<code>blank</code>, then the next command word following the
alias is also checked for alias expansion.
</p>
<p>Aliases are created and listed with the <code>alias</code>
command, and removed with the <code>unalias</code> command.
</p>
<p>There is no mechanism for using arguments in the replacement text,
as in <code>csh</code>.
If arguments are needed, use a shell function
(see <a href="#Shell-Functions">Shell Functions</a>).
</p>
<p>Aliases are not expanded when the shell is not interactive,
unless the <code>expand_aliases</code> shell option is set using
<code>shopt</code> (see <a href="#The-Shopt-Builtin">The Shopt Builtin</a>).
</p>
<p>The rules concerning the definition and use of aliases are
somewhat confusing. Bash
always reads at least one complete line of input,
and all lines that make up a compound command,
before executing any of the commands on that line or the compound command.
Aliases are expanded when a
command is read, not when it is executed.  Therefore, an
alias definition appearing on the same line as another
command does not take effect until the next line of input is read.
The commands following the alias definition
on that line are not affected by the new alias.
This behavior is also an issue when functions are executed.
Aliases are expanded when a function definition is read,
not when the function is executed, because a function definition
is itself a command.  As a consequence, aliases
defined in a function are not available until after that
function is executed.  To be safe, always put
alias definitions on a separate line, and do not use <code>alias</code>
in compound commands.
</p>
<p>For almost every purpose, shell functions are preferred over aliases.
</p>
<hr>
</div>
<div class="section" id="Arrays">
<div class="header">
<p>
Next: <a href="#The-Directory-Stack" accesskey="n" rel="next">The Directory Stack</a>, Previous: <a href="#Aliases" accesskey="p" rel="prev">Aliases</a>, Up: <a href="#Bash-Features" accesskey="u" rel="up">Bash Features</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Arrays-1"></span><h3 class="section">6.7 Arrays</h3>
<span id="index-arrays"></span>

<p>Bash provides one-dimensional indexed and associative array variables.
Any variable may be used as an indexed array;
the <code>declare</code> builtin will explicitly declare an array.
There is no maximum
limit on the size of an array, nor any requirement that members
be indexed or assigned contiguously.
Indexed arrays are referenced using integers (including arithmetic
expressions (see <a href="#Shell-Arithmetic">Shell Arithmetic</a>)) and are zero-based;
associative arrays use arbitrary strings.
Unless otherwise noted, indexed array indices must be non-negative integers.
</p>
<p>An indexed array is created automatically if any variable is assigned to
using the syntax
</p><div class="example">
<pre class="example"><var>name</var>[<var>subscript</var>]=<var>value</var>
</pre></div>

<p>The <var>subscript</var>
is treated as an arithmetic expression that must evaluate to a number.
To explicitly declare an array, use
</p><div class="example">
<pre class="example">declare -a <var>name</var>
</pre></div>
<p>The syntax
</p><div class="example">
<pre class="example">declare -a <var>name</var>[<var>subscript</var>]
</pre></div>
<p>is also accepted; the <var>subscript</var> is ignored.
</p>
<p>Associative arrays are created using
</p><div class="example">
<pre class="example">declare -A <var>name</var>
</pre></div>

<p>Attributes may be
specified for an array variable using the <code>declare</code> and
<code>readonly</code> builtins.  Each attribute applies to all members of
an array.
</p>
<p>Arrays are assigned to using compound assignments of the form
</p><div class="example">
<pre class="example"><var>name</var>=(<var>value1</var> <var>value2</var> &hellip; )
</pre></div>
<p>where each
<var>value</var> may be of the form <code>[<var>subscript</var>]=</code><var>string</var>.
Indexed array assignments do not require anything but <var>string</var>.
When assigning to indexed arrays, if
the optional subscript is supplied, that index is assigned to;
otherwise the index of the element assigned is the last index assigned
to by the statement plus one.  Indexing starts at zero.
</p>
<p>Each <var>value</var> in the list undergoes all the shell expansions
described above (see <a href="#Shell-Expansions">Shell Expansions</a>).
</p>
<p>When assigning to an associative array, the words in a compound assignment
may be either assignment statements, for which the subscript is required,
or a list of words that is interpreted as a sequence of alternating keys
and values:
<var>name</var>=(<var>key1</var> <var>value1</var> <var>key2</var> <var>value2</var> &hellip; ).
These are treated identically to
<var>name</var>=( [<var>key1</var>]=<var>value1</var> [<var>key2</var>]=<var>value2</var> &hellip; ).
The first word in the list determines how the remaining words
are interpreted; all assignments in a list must be of the same type.
When using key/value pairs, the keys may not be missing or empty;
a final missing value is treated like the empty string.
</p>
<p>This syntax is also accepted by the <code>declare</code>
builtin.  Individual array elements may be assigned to using the
<code><var>name</var>[<var>subscript</var>]=<var>value</var></code> syntax introduced above.
</p>
<p>When assigning to an indexed array, if <var>name</var>
is subscripted by a negative number, that number is
interpreted as relative to one greater than the maximum index of
<var>name</var>, so negative indices count back from the end of the
array, and an index of -1 references the last element.
</p>
<p>The &lsquo;<samp>+=</samp>&rsquo; operator will append to an array variable when assigning
using the compound assignment syntax; see <a href="#Shell-Parameters">Shell Parameters</a> above.
</p>
<p>Any element of an array may be referenced using
<code>${<var>name</var>[<var>subscript</var>]}</code>.
The braces are required to avoid
conflicts with the shell&rsquo;s filename expansion operators.  If the
<var>subscript</var> is &lsquo;<samp>@</samp>&rsquo; or &lsquo;<samp>*</samp>&rsquo;, the word expands to all members
of the array <var>name</var>.  These subscripts differ only when the word
appears within double quotes.
If the word is double-quoted,
<code>${<var>name</var>[*]}</code> expands to a single word with
the value of each array member separated by the first character of the
<code>IFS</code> variable, and <code>${<var>name</var>[@]}</code> expands each element of
<var>name</var> to a separate word.  When there are no array members,
<code>${<var>name</var>[@]}</code> expands to nothing.
If the double-quoted expansion occurs within a word, the expansion of
the first parameter is joined with the beginning part of the original
word, and the expansion of the last parameter is joined with the last
part of the original word.
This is analogous to the
expansion of the special parameters &lsquo;<samp>@</samp>&rsquo; and &lsquo;<samp>*</samp>&rsquo;. 
<code>${#<var>name</var>[<var>subscript</var>]}</code> expands to the length of
<code>${<var>name</var>[<var>subscript</var>]}</code>.
If <var>subscript</var> is &lsquo;<samp>@</samp>&rsquo; or
&lsquo;<samp>*</samp>&rsquo;, the expansion is the number of elements in the array. 
If the <var>subscript</var>
used to reference an element of an indexed array
evaluates to a number less than zero, it is
interpreted as relative to one greater than the maximum index of the array,
so negative indices count back from the end of the array,
and an index of -1 refers to the last element.
</p>
<p>Referencing an array variable without a subscript is equivalent to
referencing with a subscript of 0.
Any reference to a variable using a valid subscript is legal, and
<code>bash</code> will create an array if necessary.
</p>
<p>An array variable is considered set if a subscript has been assigned a
value.  The null string is a valid value.
</p>
<p>It is possible to obtain the keys (indices) of an array as well as the values.
${!<var>name</var>[@]} and ${!<var>name</var>[*]} expand to the indices
assigned in array variable <var>name</var>.
The treatment when in double quotes is similar to the expansion of the
special parameters &lsquo;<samp>@</samp>&rsquo; and &lsquo;<samp>*</samp>&rsquo; within double quotes.
</p>
<p>The <code>unset</code> builtin is used to destroy arrays.
<code>unset <var>name</var>[<var>subscript</var>]</code>
destroys the array element at index <var>subscript</var>.
Negative subscripts to indexed arrays are interpreted as described above.
Unsetting the last element of an array variable does not unset the variable.
<code>unset <var>name</var></code>, where <var>name</var> is an array, removes the
entire array.
<code>unset <var>name</var>[<var>subscript</var>]</code> behaves differently
depending on the array type when given a
subscript of &lsquo;<samp>*</samp>&rsquo; or &lsquo;<samp>@</samp>&rsquo;.
When <var>name</var> is an associative array, it removes the element with key
&lsquo;<samp>*</samp>&rsquo; or &lsquo;<samp>@</samp>&rsquo;.
If <var>name</var> is an indexed array, <code>unset</code> removes all of the elements,
but does not remove the array itself.
</p>
<p>When using a variable name with a subscript as an argument to a command,
such as with <code>unset</code>, without using the word expansion syntax
described above, the argument is subject to the shell&rsquo;s filename expansion.
If filename expansion is not desired, the argument should be quoted.
</p>
<p>The <code>declare</code>, <code>local</code>, and <code>readonly</code>
builtins each accept a <samp>-a</samp> option to specify an indexed
array and a <samp>-A</samp> option to specify an associative array.
If both options are supplied, <samp>-A</samp> takes precedence.
The <code>read</code> builtin accepts a <samp>-a</samp>
option to assign a list of words read from the standard input
to an array, and can read values from the standard input into
individual array elements.  The <code>set</code> and <code>declare</code>
builtins display array values in a way that allows them to be
reused as input.
</p>
<hr>
</div>
<div class="section" id="The-Directory-Stack">
<div class="header">
<p>
Next: <a href="#Controlling-the-Prompt" accesskey="n" rel="next">Controlling the Prompt</a>, Previous: <a href="#Arrays" accesskey="p" rel="prev">Arrays</a>, Up: <a href="#Bash-Features" accesskey="u" rel="up">Bash Features</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="The-Directory-Stack-1"></span><h3 class="section">6.8 The Directory Stack</h3>
<span id="index-directory-stack"></span>


<p>The directory stack is a list of recently-visited directories.  The
<code>pushd</code> builtin adds directories to the stack as it changes
the current directory, and the <code>popd</code> builtin removes specified
directories from the stack and changes the current directory to
the directory removed.  The <code>dirs</code> builtin displays the contents
of the directory stack.  The current directory is always the &quot;top&quot;
of the directory stack.
</p>
<p>The contents of the directory stack are also visible
as the value of the <code>DIRSTACK</code> shell variable.
</p>
<ul class="section-toc">
<li><a href="#Directory-Stack-Builtins" accesskey="1">Directory Stack Builtins</a></li>
</ul>
<hr>
<div class="subsection" id="Directory-Stack-Builtins">
<div class="header">
<p>
Up: <a href="#The-Directory-Stack" accesskey="u" rel="up">The Directory Stack</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Directory-Stack-Builtins-1"></span><h4 class="subsection">6.8.1 Directory Stack Builtins</h4>

<dl compact="compact">
<dt id='index-dirs'><span><code>dirs</code><a href='#index-dirs' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">dirs [-clpv] [+<var>N</var> | -<var>N</var>]
</pre></div>

<p>Display the list of currently remembered directories.  Directories
are added to the list with the <code>pushd</code> command; the
<code>popd</code> command removes directories from the list.
The current directory is always the first directory in the stack.
</p>
<dl compact="compact">
<dt><span><code>-c</code></span></dt>
<dd><p>Clears the directory stack by deleting all of the elements.
</p></dd>
<dt><span><code>-l</code></span></dt>
<dd><p>Produces a listing using full pathnames;
the default listing format uses a tilde to denote the home directory.
</p></dd>
<dt><span><code>-p</code></span></dt>
<dd><p>Causes <code>dirs</code> to print the directory stack with one entry per
line.
</p></dd>
<dt><span><code>-v</code></span></dt>
<dd><p>Causes <code>dirs</code> to print the directory stack with one entry per
line, prefixing each entry with its index in the stack.
</p></dd>
<dt><span><code>+<var>N</var></code></span></dt>
<dd><p>Displays the <var>N</var>th directory (counting from the left of the
list printed by <code>dirs</code> when invoked without options), starting
with zero.
</p></dd>
<dt><span><code>-<var>N</var></code></span></dt>
<dd><p>Displays the <var>N</var>th directory (counting from the right of the
list printed by <code>dirs</code> when invoked without options), starting
with zero.
</p></dd>
</dl>

</dd>
<dt id='index-popd'><span><code>popd</code><a href='#index-popd' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">popd [-n] [+<var>N</var> | -<var>N</var>]
</pre></div>

<p>Removes elements from the directory stack.
The elements are numbered from 0 starting at the first directory
listed by <code>dirs</code>;
that is, <code>popd</code> is equivalent to <code>popd +0</code>.
</p>
<p>When no arguments are given, <code>popd</code>
removes the top directory from the stack and changes to
the new top directory.
</p>
<p>Arguments, if supplied, have the following meanings:
</p>
<dl compact="compact">
<dt><span><code>-n</code></span></dt>
<dd><p>Suppresses the normal change of directory when removing directories
from the stack, so that only the stack is manipulated.
</p></dd>
<dt><span><code>+<var>N</var></code></span></dt>
<dd><p>Removes the <var>N</var>th directory (counting from the left of the
list printed by <code>dirs</code>), starting with zero, from the stack.
</p></dd>
<dt><span><code>-<var>N</var></code></span></dt>
<dd><p>Removes the <var>N</var>th directory (counting from the right of the
list printed by <code>dirs</code>), starting with zero, from the stack.
</p></dd>
</dl>

<p>If the top element of the directory stack is modified, and
the <samp>-n</samp> option was not supplied, <code>popd</code> uses the <code>cd</code>
builtin to change to the directory at the top of the stack.
If the <code>cd</code> fails, <code>popd</code> returns a non-zero value.
</p>
<p>Otherwise, <code>popd</code> returns an unsuccessful status if
an invalid option is encountered, the directory stack
is empty, or a non-existent directory stack entry is specified.
</p>
<p>If the <code>popd</code> command is successful,
Bash runs <code>dirs</code> to show the final contents of the directory stack,
and the return status is 0.
</p>
<span id="index-pushd"></span>
</dd>
<dt><span><code>pushd</code></span></dt>
<dd><div class="example">
<pre class="example">pushd [-n] [<var>+N</var> | <var>-N</var> | <var>dir</var>]
</pre></div>

<p>Adds a directory to the top of the directory stack, or rotates
the stack, making the new top of the stack the current working
directory.
With no arguments, <code>pushd</code> exchanges the top two elements
of the directory stack.
</p>
<p>Arguments, if supplied, have the following meanings:
</p>
<dl compact="compact">
<dt><span><code>-n</code></span></dt>
<dd><p>Suppresses the normal change of directory when rotating or
adding directories to the stack, so that only the stack is manipulated.
</p></dd>
<dt><span><code>+<var>N</var></code></span></dt>
<dd><p>Brings the <var>N</var>th directory (counting from the left of the
list printed by <code>dirs</code>, starting with zero) to the top of
the list by rotating the stack.
</p></dd>
<dt><span><code>-<var>N</var></code></span></dt>
<dd><p>Brings the <var>N</var>th directory (counting from the right of the
list printed by <code>dirs</code>, starting with zero) to the top of
the list by rotating the stack.
</p></dd>
<dt><span><code><var>dir</var></code></span></dt>
<dd><p>Makes <var>dir</var> be the top of the stack.
</p></dd>
</dl>

<p>After the stack has been modified, if the <samp>-n</samp> option was not
supplied, <code>pushd</code> uses the <code>cd</code> builtin to change to the
directory at the top of the stack.
If the <code>cd</code> fails, <code>pushd</code> returns a non-zero value.
</p>
<p>Otherwise, if no arguments are supplied, <code>pushd</code> returns 0 unless the
directory stack is empty.
When rotating the directory stack, <code>pushd</code> returns 0 unless
the directory stack is empty or a non-existent directory stack element
is specified.
</p>
<p>If the <code>pushd</code> command is successful,
Bash runs <code>dirs</code> to show the final contents of the directory stack.
</p>
</dd>
</dl>

<hr>
</div>
</div>
<div class="section" id="Controlling-the-Prompt">
<div class="header">
<p>
Next: <a href="#The-Restricted-Shell" accesskey="n" rel="next">The Restricted Shell</a>, Previous: <a href="#The-Directory-Stack" accesskey="p" rel="prev">The Directory Stack</a>, Up: <a href="#Bash-Features" accesskey="u" rel="up">Bash Features</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Controlling-the-Prompt-1"></span><h3 class="section">6.9 Controlling the Prompt</h3>
<span id="index-prompting"></span>

<p>Bash examines the value of the array variable <code>PROMPT_COMMAND</code> just before
printing each primary prompt.
If any elements in  <code>PROMPT_COMMAND</code> are set and non-null, Bash
executes each value, in numeric order,
just as if it had been typed on the command line.
</p>
<p>In addition, the following table describes the special characters which
can appear in the prompt variables <code>PS0</code>, <code>PS1</code>, <code>PS2</code>, and
<code>PS4</code>:
</p>
<dl compact="compact">
<dt><span><code>\a</code></span></dt>
<dd><p>A bell character.
</p></dd>
<dt><span><code>\d</code></span></dt>
<dd><p>The date, in &quot;Weekday Month Date&quot; format (e.g., &quot;Tue May 26&quot;).
</p></dd>
<dt><span><code>\D{<var>format</var>}</code></span></dt>
<dd><p>The <var>format</var> is passed to <code>strftime</code>(3) and the result is inserted
into the prompt string; an empty <var>format</var> results in a locale-specific
time representation.  The braces are required.
</p></dd>
<dt><span><code>\e</code></span></dt>
<dd><p>An escape character.
</p></dd>
<dt><span><code>\h</code></span></dt>
<dd><p>The hostname, up to the first &lsquo;.&rsquo;.
</p></dd>
<dt><span><code>\H</code></span></dt>
<dd><p>The hostname.
</p></dd>
<dt><span><code>\j</code></span></dt>
<dd><p>The number of jobs currently managed by the shell.
</p></dd>
<dt><span><code>\l</code></span></dt>
<dd><p>The basename of the shell&rsquo;s terminal device name.
</p></dd>
<dt><span><code>\n</code></span></dt>
<dd><p>A newline.
</p></dd>
<dt><span><code>\r</code></span></dt>
<dd><p>A carriage return.
</p></dd>
<dt><span><code>\s</code></span></dt>
<dd><p>The name of the shell, the basename of <code>$0</code> (the portion
following the final slash).
</p></dd>
<dt><span><code>\t</code></span></dt>
<dd><p>The time, in 24-hour HH:MM:SS format.
</p></dd>
<dt><span><code>\T</code></span></dt>
<dd><p>The time, in 12-hour HH:MM:SS format.
</p></dd>
<dt><span><code>\@</code></span></dt>
<dd><p>The time, in 12-hour am/pm format.
</p></dd>
<dt><span><code>\A</code></span></dt>
<dd><p>The time, in 24-hour HH:MM format.
</p></dd>
<dt><span><code>\u</code></span></dt>
<dd><p>The username of the current user.
</p></dd>
<dt><span><code>\v</code></span></dt>
<dd><p>The version of Bash (e.g., 2.00)          
</p></dd>
<dt><span><code>\V</code></span></dt>
<dd><p>The release of Bash, version + patchlevel (e.g., 2.00.0)
</p></dd>
<dt><span><code>\w</code></span></dt>
<dd><p>The value of the <code>PWD</code> shell variable (<code>$PWD</code>),
with <code>$HOME</code> abbreviated with a tilde
(uses the <code>$PROMPT_DIRTRIM</code> variable).
</p></dd>
<dt><span><code>\W</code></span></dt>
<dd><p>The basename of <code>$PWD</code>, with <code>$HOME</code> abbreviated with a tilde.
</p></dd>
<dt><span><code>\!</code></span></dt>
<dd><p>The history number of this command.
</p></dd>
<dt><span><code>\#</code></span></dt>
<dd><p>The command number of this command.
</p></dd>
<dt><span><code>\$</code></span></dt>
<dd><p>If the effective uid is 0, <code>#</code>, otherwise <code>$</code>.
</p></dd>
<dt><span><code>\<var>nnn</var></code></span></dt>
<dd><p>The character whose ASCII code is the octal value <var>nnn</var>.
</p></dd>
<dt><span><code>\\</code></span></dt>
<dd><p>A backslash.
</p></dd>
<dt><span><code>\[</code></span></dt>
<dd><p>Begin a sequence of non-printing characters.  This could be used to
embed a terminal control sequence into the prompt.
</p></dd>
<dt><span><code>\]</code></span></dt>
<dd><p>End a sequence of non-printing characters.
</p></dd>
</dl>

<p>The command number and the history number are usually different:
the history number of a command is its position in the history
list, which may include commands restored from the history file
(see <a href="#Bash-History-Facilities">Bash History Facilities</a>), while the command number is
the position in the sequence of commands executed during the current
shell session.
</p>
<p>After the string is decoded, it is expanded via
parameter expansion, command substitution, arithmetic
expansion, and quote removal, subject to the value of the
<code>promptvars</code> shell option (see <a href="#The-Shopt-Builtin">The Shopt Builtin</a>).
This can have unwanted side effects if escaped portions of the string
appear within command substitution or contain characters special to
word expansion.
</p>
<hr>
</div>
<div class="section" id="The-Restricted-Shell">
<div class="header">
<p>
Next: <a href="#Bash-POSIX-Mode" accesskey="n" rel="next">Bash POSIX Mode</a>, Previous: <a href="#Controlling-the-Prompt" accesskey="p" rel="prev">Controlling the Prompt</a>, Up: <a href="#Bash-Features" accesskey="u" rel="up">Bash Features</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="The-Restricted-Shell-1"></span><h3 class="section">6.10 The Restricted Shell</h3>
<span id="index-restricted-shell"></span>

<p>If Bash is started with the name <code>rbash</code>, or the
<samp>--restricted</samp>
or
<samp>-r</samp>
option is supplied at invocation, the shell becomes restricted.
A restricted shell is used to
set up an environment more controlled than the standard shell.
A restricted shell behaves identically to <code>bash</code>
with the exception that the following are disallowed or not performed:
</p>
<ul>
<li> Changing directories with the <code>cd</code> builtin.
</li><li> Setting or unsetting the values of the <code>SHELL</code>, <code>PATH</code>,
<code>HISTFILE</code>,
<code>ENV</code>, or <code>BASH_ENV</code> variables.
</li><li> Specifying command names containing slashes.
</li><li> Specifying a filename containing a slash as an argument to the <code>.</code>
builtin command.
</li><li> Specifying a filename containing a slash as an argument to the <code>history</code>
builtin command.
</li><li> Specifying a filename containing a slash as an argument to the <samp>-p</samp>
option to the <code>hash</code> builtin command.
</li><li> Importing function definitions from the shell environment at startup.
</li><li> Parsing the value of <code>SHELLOPTS</code> from the shell environment at startup.
</li><li> Redirecting output using the &lsquo;<samp>&gt;</samp>&rsquo;, &lsquo;<samp>&gt;|</samp>&rsquo;, &lsquo;<samp>&lt;&gt;</samp>&rsquo;, &lsquo;<samp>&gt;&amp;</samp>&rsquo;,
&lsquo;<samp>&amp;&gt;</samp>&rsquo;, and &lsquo;<samp>&gt;&gt;</samp>&rsquo; redirection operators.
</li><li> Using the <code>exec</code> builtin to replace the shell with another command.
</li><li> Adding or deleting builtin commands with the
<samp>-f</samp> and <samp>-d</samp> options to the <code>enable</code> builtin.
</li><li> Using the <code>enable</code> builtin command to enable disabled shell builtins.
</li><li> Specifying the <samp>-p</samp> option to the <code>command</code> builtin.
</li><li> Turning off restricted mode with &lsquo;<samp>set +r</samp>&rsquo; or &lsquo;<samp>shopt -u restricted_shell</samp>&rsquo;.
</li></ul>

<p>These restrictions are enforced after any startup files are read.
</p>
<p>When a command that is found to be a shell script is executed
(see <a href="#Shell-Scripts">Shell Scripts</a>), <code>rbash</code> turns off any restrictions in
the shell spawned to execute the script.
</p>
<p>The restricted shell mode is only one component of a useful restricted
environment. It should be accompanied by setting <code>PATH</code> to a value
that allows execution of only a few verified commands (commands that
allow shell escapes are particularly vulnerable), changing the current
directory to a non-writable directory other than <code>$HOME</code> after login,
not allowing the restricted shell to execute shell scripts, and cleaning
the environment of variables that cause some commands to modify their
behavior (e.g., <code>VISUAL</code> or <code>PAGER</code>).
</p>
<p>Modern systems provide more secure ways to implement a restricted environment,
such as <code>jails</code>, <code>zones</code>, or <code>containers</code>.
</p>

<hr>
</div>
<div class="section" id="Bash-POSIX-Mode">
<div class="header">
<p>
Next: <a href="#Shell-Compatibility-Mode" accesskey="n" rel="next">Shell Compatibility Mode</a>, Previous: <a href="#The-Restricted-Shell" accesskey="p" rel="prev">The Restricted Shell</a>, Up: <a href="#Bash-Features" accesskey="u" rel="up">Bash Features</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Bash-POSIX-Mode-1"></span><h3 class="section">6.11 Bash POSIX Mode</h3>
<span id="index-POSIX-Mode"></span>

<p>Starting Bash with the <samp>--posix</samp> command-line option or executing
&lsquo;<samp>set -o posix</samp>&rsquo; while Bash is running will cause Bash to conform more
closely to the <small>POSIX</small> standard by changing the behavior to
match that specified by <small>POSIX</small> in areas where the Bash default differs.
</p>
<p>When invoked as <code>sh</code>, Bash enters <small>POSIX</small> mode after reading the
startup files.
</p>
<p>The following list is what&rsquo;s changed when &lsquo;<small>POSIX</small> mode&rsquo; is in effect:
</p>
<ol>
<li> Bash ensures that the <code>POSIXLY_CORRECT</code> variable is set.

</li><li> When a command in the hash table no longer exists, Bash will re-search
<code>$PATH</code> to find the new location.  This is also available with
&lsquo;<samp>shopt -s checkhash</samp>&rsquo;.

</li><li> Bash will not insert a command without the execute bit set into the
command hash table, even if it returns it as a (last-ditch) result
from a <code>$PATH</code> search.

</li><li> The message printed by the job control code and builtins when a job
exits with a non-zero status is &lsquo;Done(status)&rsquo;.

</li><li> The message printed by the job control code and builtins when a job
is stopped is &lsquo;Stopped(<var>signame</var>)&rsquo;, where <var>signame</var> is, for
example, <code>SIGTSTP</code>.

</li><li> Alias expansion is always enabled, even in non-interactive shells.

</li><li> Reserved words appearing in a context where reserved words are recognized
do not undergo alias expansion.

</li><li> Alias expansion is performed when initially parsing a command substitution.
The default mode generally defers it, when enabled, until the command
substitution is executed. This means that command substitution will not
expand aliases that are defined after the command substitution is initially
parsed (e.g., as part of a function definition).

</li><li> The <small>POSIX</small> <code>PS1</code> and <code>PS2</code> expansions of &lsquo;<samp>!</samp>&rsquo; to
the history number and &lsquo;<samp>!!</samp>&rsquo; to &lsquo;<samp>!</samp>&rsquo; are enabled,
and parameter expansion is performed on the values of <code>PS1</code> and
<code>PS2</code> regardless of the setting of the <code>promptvars</code> option.

</li><li> The <small>POSIX</small> startup files are executed (<code>$ENV</code>) rather than
the normal Bash files.

</li><li> Tilde expansion is only performed on assignments preceding a command
name, rather than on all assignment statements on the line.

</li><li> The default history file is <samp>~/.sh_history</samp> (this is the
default value of <code>$HISTFILE</code>).

</li><li> Redirection operators do not perform filename expansion on the word
in the redirection unless the shell is interactive.

</li><li> Redirection operators do not perform word splitting on the word in the
redirection.

</li><li> Function names must be valid shell <code>name</code>s.  That is, they may not
contain characters other than letters, digits, and underscores, and
may not start with a digit.  Declaring a function with an invalid name
causes a fatal syntax error in non-interactive shells.

</li><li> Function names may not be the same as one of the <small>POSIX</small> special
builtins.

</li><li> <small>POSIX</small> special builtins are found before shell functions
during command lookup.

</li><li> When printing shell function definitions (e.g., by <code>type</code>), Bash does
not print the <code>function</code> keyword.

</li><li> Literal tildes that appear as the first character in elements of
the <code>PATH</code> variable are not expanded as described above
under <a href="#Tilde-Expansion">Tilde Expansion</a>.

</li><li> The <code>time</code> reserved word may be used by itself as a command.  When
used in this way, it displays timing statistics for the shell and its
completed children.  The <code>TIMEFORMAT</code> variable controls the format
of the timing information.

</li><li> When parsing and expanding a ${&hellip;} expansion that appears within
double quotes, single quotes are no longer special and cannot be used to
quote a closing brace or other special character, unless the operator is
one of those defined to perform pattern removal.  In this case, they do
not have to appear as matched pairs.

</li><li> The parser does not recognize <code>time</code> as a reserved word if the next
token begins with a &lsquo;<samp>-</samp>&rsquo;.


</li><li> The &lsquo;<samp>!</samp>&rsquo; character does not introduce history expansion within a
double-quoted string, even if the <code>histexpand</code> option is enabled.

</li><li> If a <small>POSIX</small> special builtin returns an error status, a
non-interactive shell exits.  The fatal errors are those listed in
the <small>POSIX</small> standard, and include things like passing incorrect options,
redirection errors, variable assignment errors for assignments preceding
the command name, and so on.

</li><li> A non-interactive shell exits with an error status if a variable
assignment error occurs when no command name follows the assignment
statements.
A variable assignment error occurs, for example, when trying to assign
a value to a readonly variable.

</li><li> A non-interactive shell exits with an error status if a variable
assignment error occurs in an assignment statement preceding a special
builtin, but not with any other simple command. For any other simple
command, the shell aborts execution of that command, and execution continues
at the top level (&quot;the shell shall not perform any further processing of the
command in which the error occurred&quot;).

</li><li> A non-interactive shell exits with an error status if the iteration
variable in a <code>for</code> statement or the selection variable in a
<code>select</code> statement is a readonly variable.

</li><li> Non-interactive shells exit if <var>filename</var> in <code>.</code> <var>filename</var>
is not found.

</li><li> Non-interactive shells exit if a syntax error in an arithmetic expansion
results in an invalid expression.

</li><li> Non-interactive shells exit if a parameter expansion error occurs.

</li><li> Non-interactive shells exit if there is a syntax error in a script read
with the <code>.</code> or <code>source</code> builtins, or in a string processed by
the <code>eval</code> builtin.

</li><li> While variable indirection is available, it may not be applied to the
&lsquo;<samp>#</samp>&rsquo; and &lsquo;<samp>?</samp>&rsquo; special parameters.

</li><li> Expanding the &lsquo;<samp>*</samp>&rsquo; special parameter in a pattern context where the
expansion is double-quoted does not treat the <code>$*</code> as if it were
double-quoted.

</li><li> Assignment statements preceding <small>POSIX</small> special builtins
persist in the shell environment after the builtin completes.

</li><li> The <code>command</code> builtin does not prevent builtins that take assignment
statements as arguments from expanding them as assignment statements;
when not in <small>POSIX</small> mode, assignment builtins lose their assignment
statement expansion properties when preceded by <code>command</code>.

</li><li> The <code>bg</code> builtin uses the required format to describe each job placed
in the background, which does not include an indication of whether the job
is the current or previous job.

</li><li> The output of &lsquo;<samp>kill -l</samp>&rsquo; prints all the signal names on a single line,
separated by spaces, without the &lsquo;<samp>SIG</samp>&rsquo; prefix.

</li><li> The <code>kill</code> builtin does not accept signal names with a &lsquo;<samp>SIG</samp>&rsquo;
prefix.

</li><li> The <code>export</code> and <code>readonly</code> builtin commands display their
output in the format required by <small>POSIX</small>.

</li><li> The <code>trap</code> builtin displays signal names without the leading
<code>SIG</code>.

</li><li> The <code>trap</code> builtin doesn&rsquo;t check the first argument for a possible
signal specification and revert the signal handling to the original
disposition if it is, unless that argument consists solely of digits and
is a valid signal number.  If users want to reset the handler for a given
signal to the original disposition, they should use &lsquo;<samp>-</samp>&rsquo; as the
first argument.

</li><li> <code>trap -p</code> displays signals whose dispositions are set to SIG_DFL and
those that were ignored when the shell started.

</li><li> The <code>.</code> and <code>source</code> builtins do not search the current directory
for the filename argument if it is not found by searching <code>PATH</code>.

</li><li> Enabling <small>POSIX</small> mode has the effect of setting the
<code>inherit_errexit</code> option, so
subshells spawned to execute command substitutions inherit the value of
the <samp>-e</samp> option from the parent shell.
When the <code>inherit_errexit</code> option is not enabled,
Bash clears the <samp>-e</samp> option in such subshells.

</li><li> Enabling <small>POSIX</small> mode has the effect of setting the
<code>shift_verbose</code> option, so numeric arguments to <code>shift</code>
that exceed the number of positional parameters will result in an
error message.

</li><li> When the <code>alias</code> builtin displays alias definitions, it does not
display them with a leading &lsquo;<samp>alias </samp>&rsquo; unless the <samp>-p</samp> option
is supplied.

</li><li> When the <code>set</code> builtin is invoked without options, it does not display
shell function names and definitions.

</li><li> When the <code>set</code> builtin is invoked without options, it displays
variable values without quotes, unless they contain shell metacharacters,
even if the result contains nonprinting characters.

</li><li> When the <code>cd</code> builtin is invoked in logical mode, and the pathname
constructed from <code>$PWD</code> and the directory name supplied as an argument
does not refer to an existing directory, <code>cd</code> will fail instead of
falling back to physical mode.

</li><li> When the <code>cd</code> builtin cannot change a directory because the
length of the pathname 
constructed from <code>$PWD</code> and the directory name supplied as an argument
exceeds <code>PATH_MAX</code> when all symbolic links are expanded, <code>cd</code> will
fail instead of attempting to use only the supplied directory name.

</li><li> The <code>pwd</code> builtin verifies that the value it prints is the same as the
current directory, even if it is not asked to check the file system with the
<samp>-P</samp> option.

</li><li> When listing the history, the <code>fc</code> builtin does not include an
indication of whether or not a history entry has been modified.

</li><li> The default editor used by <code>fc</code> is <code>ed</code>.

</li><li> The <code>type</code> and <code>command</code> builtins will not report a non-executable
file as having been found, though the shell will attempt to execute such a
file if it is the only so-named file found in <code>$PATH</code>.

</li><li> The <code>vi</code> editing mode will invoke the <code>vi</code> editor directly when
the &lsquo;<samp>v</samp>&rsquo; command is run, instead of checking <code>$VISUAL</code> and
<code>$EDITOR</code>.

</li><li> When the <code>xpg_echo</code> option is enabled, Bash does not attempt to interpret
any arguments to <code>echo</code> as options.  Each argument is displayed, after
escape characters are converted.

</li><li> The <code>ulimit</code> builtin uses a block size of 512 bytes for the <samp>-c</samp>
and <samp>-f</samp> options.

</li><li> The arrival of <code>SIGCHLD</code>  when a trap is set on <code>SIGCHLD</code> does
not interrupt the <code>wait</code> builtin and cause it to return immediately.
The trap command is run once for each child that exits.

</li><li> The <code>read</code> builtin may be interrupted by a signal for which a trap
has been set.
If Bash receives a trapped signal while executing <code>read</code>, the trap
handler executes and <code>read</code> returns an exit status greater than 128.

</li><li> The <code>printf</code> builtin uses <code>double</code> (via <code>strtod</code>) to convert
arguments corresponding to floating point conversion specifiers, instead of
<code>long double</code> if it&rsquo;s available. The &lsquo;<samp>L</samp>&rsquo; length modifier forces
<code>printf</code> to use <code>long double</code> if it&rsquo;s available.

</li><li> Bash removes an exited background process&rsquo;s status from the list of such
statuses after the <code>wait</code> builtin is used to obtain it.

</li></ol>

<p>There is other <small>POSIX</small> behavior that Bash does not implement by
default even when in <small>POSIX</small> mode.
Specifically:
</p>
<ol>
<li> The <code>fc</code> builtin checks <code>$EDITOR</code> as a program to edit history
entries if <code>FCEDIT</code> is unset, rather than defaulting directly to
<code>ed</code>.  <code>fc</code> uses <code>ed</code> if <code>EDITOR</code> is unset.

</li><li> As noted above, Bash requires the <code>xpg_echo</code> option to be enabled for
the <code>echo</code> builtin to be fully conformant.

</li></ol>

<p>Bash can be configured to be <small>POSIX</small>-conformant by default, by specifying
the <samp>--enable-strict-posix-default</samp> to <code>configure</code> when building
(see <a href="#Optional-Features">Optional Features</a>).
</p>
<hr>
</div>
<div class="section" id="Shell-Compatibility-Mode">
<div class="header">
<p>
Previous: <a href="#Bash-POSIX-Mode" accesskey="p" rel="prev">Bash POSIX Mode</a>, Up: <a href="#Bash-Features" accesskey="u" rel="up">Bash Features</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Shell-Compatibility-Mode-1"></span><h3 class="section">6.12 Shell Compatibility Mode</h3>
<span id="index-Compatibility-Level"></span>
<span id="index-Compatibility-Mode"></span>

<p>Bash-4.0 introduced the concept of a <em>shell compatibility level</em>,
specified as a set of options to the shopt builtin
(<code>compat31</code>,
<code>compat32</code>,
<code>compat40</code>,
<code>compat41</code>,
and so on).
There is only one current
compatibility level &ndash; each option is mutually exclusive.
The compatibility level is intended to allow users to select behavior
from previous versions that is incompatible with newer versions
while they migrate scripts to use current features and
behavior. It&rsquo;s intended to be a temporary solution.
</p>
<p>This section does not mention behavior that is standard for a particular
version (e.g., setting <code>compat32</code> means that quoting the rhs of the regexp
matching operator quotes special regexp characters in the word, which is
default behavior in bash-3.2 and subsequent versions). 
</p>
<p>If a user enables, say, <code>compat32</code>, it may affect the behavior of other
compatibility levels up to and including the current compatibility level.
The idea is that each compatibility level controls behavior that changed
in that version of Bash,
but that behavior may have been present in earlier versions.
For instance, the change to use locale-based comparisons with the <code>[[</code>
command came in bash-4.1, and earlier versions used ASCII-based comparisons,
so enabling <code>compat32</code> will enable ASCII-based comparisons as well.
That granularity may not be sufficient for
all uses, and as a result users should employ compatibility levels carefully.
Read the documentation for a particular feature to find out the
current behavior.
</p>
<p>Bash-4.3 introduced a new shell variable: <code>BASH_COMPAT</code>.
The value assigned
to this variable (a decimal version number like 4.2, or an integer
corresponding to the <code>compat</code><var>NN</var> option, like 42) determines the
compatibility level.
</p>
<p>Starting with bash-4.4, Bash has begun deprecating older compatibility
levels.
Eventually, the options will be removed in favor of <code>BASH_COMPAT</code>.
</p>
<p>Bash-5.0 is the final version for which there will be an individual shopt
option for the previous version. Users should use <code>BASH_COMPAT</code>
on bash-5.0 and later versions.
</p>
<p>The following table describes the behavior changes controlled by each
compatibility level setting.
The <code>compat</code><var>NN</var> tag is used as shorthand for setting the
compatibility level
to <var>NN</var> using one of the following mechanisms.
For versions prior to bash-5.0, the compatibility level may be set using
the corresponding <code>compat</code><var>NN</var> shopt option.
For bash-4.3 and later versions, the <code>BASH_COMPAT</code> variable is preferred,
and it is required for bash-5.1 and later versions.
</p>
<dl compact="compact">
<dt><span><code>compat31</code></span></dt>
<dd><ul>
<li> quoting the rhs of the <code>[[</code> command&rsquo;s regexp matching operator (=~)
has no special effect
</li></ul>

</dd>
<dt><span><code>compat32</code></span></dt>
<dd><ul>
<li> interrupting a command list such as &quot;a ; b ; c&quot; causes the execution
of the next command in the list (in bash-4.0 and later versions,
the shell acts as if it received the interrupt, so
interrupting one command in a list aborts the execution of the
entire list)
</li></ul>

</dd>
<dt><span><code>compat40</code></span></dt>
<dd><ul>
<li> the &lsquo;<samp>&lt;</samp>&rsquo; and &lsquo;<samp>&gt;</samp>&rsquo; operators to the <code>[[</code> command do not
consider the current locale when comparing strings; they use ASCII
ordering.
Bash versions prior to bash-4.1 use ASCII collation and strcmp(3);
bash-4.1 and later use the current locale&rsquo;s collation sequence and
strcoll(3).
</li></ul>

</dd>
<dt><span><code>compat41</code></span></dt>
<dd><ul>
<li> in posix mode, <code>time</code> may be followed by options and still be
recognized as a reserved word (this is <small>POSIX</small> interpretation 267)
</li><li> in posix mode, the parser requires that an even number of single
quotes occur in the <var>word</var> portion of a double-quoted ${&hellip;}
parameter expansion and treats them specially, so that characters within
the single quotes are considered quoted
(this is <small>POSIX</small> interpretation 221)
</li></ul>

</dd>
<dt><span><code>compat42</code></span></dt>
<dd><ul>
<li> the replacement string in double-quoted pattern substitution does not
undergo quote removal, as it does in versions after bash-4.2
</li><li> in posix mode, single quotes are considered special when expanding
the <var>word</var> portion of a double-quoted ${&hellip;} parameter expansion
and can be used to quote a closing brace or other special character
(this is part of <small>POSIX</small> interpretation 221);
in later versions, single quotes
are not special within double-quoted word expansions
</li></ul>

</dd>
<dt><span><code>compat43</code></span></dt>
<dd><ul>
<li> the shell does not print a warning message if an attempt is made to
use a quoted compound assignment as an argument to declare
(e.g., declare -a foo=&rsquo;(1 2)&rsquo;). Later versions warn that this usage is
deprecated
</li><li> word expansion errors are considered non-fatal errors that cause the
current command to fail, even in posix mode
(the default behavior is to make them fatal errors that cause the shell
to exit)
</li><li> when executing a shell function, the loop state (while/until/etc.)
is not reset, so <code>break</code> or <code>continue</code> in that function will break
or continue loops in the calling context. Bash-4.4 and later reset
the loop state to prevent this
</li></ul>

</dd>
<dt><span><code>compat44</code></span></dt>
<dd><ul>
<li> the shell sets up the values used by <code>BASH_ARGV</code> and <code>BASH_ARGC</code>
so they can expand to the shell&rsquo;s positional parameters even if extended
debugging mode is not enabled
</li><li> a subshell inherits loops from its parent context, so <code>break</code>
or <code>continue</code> will cause the subshell to exit.
Bash-5.0 and later reset the loop state to prevent the exit
</li><li> variable assignments preceding builtins like <code>export</code> and <code>readonly</code>
that set attributes continue to affect variables with the same
name in the calling environment even if the shell is not in posix
mode
</li></ul>

</dd>
<dt><span><code>compat50 (set using BASH_COMPAT)</code></span></dt>
<dd><ul>
<li> Bash-5.1 changed the way <code>$RANDOM</code> is generated to introduce slightly
more randomness. If the shell compatibility level is set to 50 or
lower, it reverts to the method from bash-5.0 and previous versions,
so seeding the random number generator by assigning a value to
<code>RANDOM</code> will produce the same sequence as in bash-5.0
</li><li> If the command hash table is empty, Bash versions prior to bash-5.1
printed an informational message to that effect, even when producing
output that can be reused as input. Bash-5.1 suppresses that message
when the <samp>-l</samp> option is supplied.
</li></ul>

</dd>
<dt><span><code>compat51 (set using BASH_COMPAT)</code></span></dt>
<dd><ul>
<li> The <code>unset</code> builtin will unset the array <code>a</code> given an argument like
&lsquo;<samp>a[@]</samp>&rsquo;.
Bash-5.2 will unset an element with key &lsquo;<samp>@</samp>&rsquo; (associative arrays)
or remove all the elements without unsetting the array (indexed arrays)
</li><li> arithmetic commands ( ((...)) ) and the expressions in an arithmetic for
statement can be expanded more than once
</li><li> expressions used as arguments to arithmetic operators in the <code>[[</code>
conditional command can be expanded more than once
</li><li> the expressions in substring parameter brace expansion can be
expanded more than once
</li><li> the expressions in the $(( ... )) word expansion can be expanded
more than once
</li><li> arithmetic expressions used as indexed array subscripts can be
expanded more than once
</li><li> <code>test -v</code>, when given an argument of &lsquo;<samp>A[@]</samp>&rsquo;, where <var>A</var> is
an existing associative array, will return true if the array has any set
elements.
Bash-5.2 will look for and report on a key named &lsquo;<samp>@</samp>&rsquo;
</li><li> the ${<var>parameter</var>[:]=<var>value</var>} word expansion will return
<var>value</var>, before any variable-specific transformations have been
performed (e.g., converting to lowercase).
Bash-5.2 will return the final value assigned to the variable.
</li><li> Parsing command substitutions will behave as if extended glob
(see <a href="#The-Shopt-Builtin">The Shopt Builtin</a>)
is enabled, so that parsing a command substitution containing an extglob
pattern (say, as part of a shell function) will not fail.
This assumes the intent is to enable extglob before the command is executed
and word expansions are performed.
It will fail at word expansion time if extglob hasn&rsquo;t been
enabled by the time the command is executed.
</li></ul>
</dd>
</dl>

<hr>
</div>
</div>
<div class="chapter" id="Job-Control">
<div class="header">
<p>
Next: <a href="#Command-Line-Editing" accesskey="n" rel="next">Command Line Editing</a>, Previous: <a href="#Bash-Features" accesskey="p" rel="prev">Bash Features</a>, Up: <a href="#Top" accesskey="u" rel="up">Bash Features</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Job-Control-1"></span><h2 class="chapter">7 Job Control</h2>

<p>This chapter discusses what job control is, how it works, and how
Bash allows you to access its facilities.
</p>

<ul class="section-toc">
<li><a href="#Job-Control-Basics" accesskey="1">Job Control Basics</a></li>
<li><a href="#Job-Control-Builtins" accesskey="2">Job Control Builtins</a></li>
<li><a href="#Job-Control-Variables" accesskey="3">Job Control Variables</a></li>
</ul>
<hr>
<div class="section" id="Job-Control-Basics">
<div class="header">
<p>
Next: <a href="#Job-Control-Builtins" accesskey="n" rel="next">Job Control Builtins</a>, Up: <a href="#Job-Control" accesskey="u" rel="up">Job Control</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Job-Control-Basics-1"></span><h3 class="section">7.1 Job Control Basics</h3>
<span id="index-job-control-1"></span>
<span id="index-foreground"></span>
<span id="index-background"></span>
<span id="index-suspending-jobs"></span>

<p>Job control
refers to the ability to selectively stop (suspend)
the execution of processes and continue (resume)
their execution at a later point.  A user typically employs
this facility via an interactive interface supplied jointly
by the operating system kernel&rsquo;s terminal driver and Bash.
</p>
<p>The shell associates a <var>job</var> with each pipeline.  It keeps a
table of currently executing jobs, which may be listed with the
<code>jobs</code> command.  When Bash starts a job
asynchronously, it prints a line that looks
like:
</p><div class="example">
<pre class="example">[1] 25647
</pre></div>
<p>indicating that this job is job number 1 and that the process <small>ID</small>
of the last process in the pipeline associated with this job is
25647.  All of the processes in a single pipeline are members of
the same job.  Bash uses the <var>job</var> abstraction as the
basis for job control. 
</p>
<p>To facilitate the implementation of the user interface to job
control, the operating system maintains the notion of a current terminal
process group <small>ID</small>.  Members of this process group (processes whose
process group <small>ID</small> is equal to the current terminal process group
<small>ID</small>) receive keyboard-generated signals such as <code>SIGINT</code>. 
These processes are said to be in the foreground.  Background
processes are those whose process group <small>ID</small> differs from the
terminal&rsquo;s; such processes are immune to keyboard-generated
signals.  Only foreground processes are allowed to read from or, if
the user so specifies with <code>stty tostop</code>, write to the terminal.
Background processes which attempt to
read from (write to when <code>stty tostop</code> is in effect) the
terminal are sent a <code>SIGTTIN</code> (<code>SIGTTOU</code>)
signal by the kernel&rsquo;s terminal driver,
which, unless caught, suspends the process. 
</p>
<p>If the operating system on which Bash is running supports
job control, Bash contains facilities to use it.  Typing the
<em>suspend</em> character (typically &lsquo;<samp>^Z</samp>&rsquo;, Control-Z) while a
process is running causes that process to be stopped and returns
control to Bash.  Typing the <em>delayed suspend</em> character
(typically &lsquo;<samp>^Y</samp>&rsquo;, Control-Y) causes the process to be stopped
when it attempts to read input from the terminal, and control to
be returned to Bash.  The user then manipulates the state of
this job, using the <code>bg</code> command to continue it in the
background, the <code>fg</code> command to continue it in the
foreground, or the <code>kill</code> command to kill it.  A &lsquo;<samp>^Z</samp>&rsquo;
takes effect immediately, and has the additional side effect of
causing pending output and typeahead to be discarded. 
</p>
<p>There are a number of ways to refer to a job in the shell.  The
character &lsquo;<samp>%</samp>&rsquo; introduces a job specification (<em>jobspec</em>).
</p>
<p>Job number <code>n</code> may be referred to as &lsquo;<samp>%n</samp>&rsquo;.
The symbols &lsquo;<samp>%%</samp>&rsquo; and  &lsquo;<samp>%+</samp>&rsquo; refer to the shell&rsquo;s notion of the
current job, which is the last job stopped while it was in the foreground
or started in the background.
A single &lsquo;<samp>%</samp>&rsquo; (with no accompanying job specification) also refers
to the current job.
The previous job may be referenced using &lsquo;<samp>%-</samp>&rsquo;.
If there is only a single job, &lsquo;<samp>%+</samp>&rsquo; and &lsquo;<samp>%-</samp>&rsquo; can both be used
to refer to that job.
In output pertaining to jobs (e.g., the output of the <code>jobs</code>
command), the current job is always flagged with a &lsquo;<samp>+</samp>&rsquo;, and the
previous job with a &lsquo;<samp>-</samp>&rsquo;. 
</p>
<p>A job may also be referred to
using a prefix of the name used to start it, or using a substring
that appears in its command line.  For example, &lsquo;<samp>%ce</samp>&rsquo; refers
to a stopped job whose command name begins with &lsquo;<samp>ce</samp>&rsquo;.
Using &lsquo;<samp>%?ce</samp>&rsquo;, on the
other hand, refers to any job containing the string &lsquo;<samp>ce</samp>&rsquo; in
its command line.  If the prefix or substring matches more than one job,
Bash reports an error.
</p>
<p>Simply naming a job can be used to bring it into the foreground:
&lsquo;<samp>%1</samp>&rsquo; is a synonym for &lsquo;<samp>fg %1</samp>&rsquo;, bringing job 1 from the
background into the foreground.  Similarly, &lsquo;<samp>%1 &amp;</samp>&rsquo; resumes
job 1 in the background, equivalent to &lsquo;<samp>bg %1</samp>&rsquo;
</p>
<p>The shell learns immediately whenever a job changes state. 
Normally, Bash waits until it is about to print a prompt
before reporting changes in a job&rsquo;s status so as to not interrupt
any other output.
If the <samp>-b</samp> option to the <code>set</code> builtin is enabled,
Bash reports such changes immediately (see <a href="#The-Set-Builtin">The Set Builtin</a>).
Any trap on <code>SIGCHLD</code> is executed for each child process
that exits.
</p>
<p>If an attempt to exit Bash is made while jobs are stopped, (or running, if
the <code>checkjobs</code> option is enabled &ndash; see <a href="#The-Shopt-Builtin">The Shopt Builtin</a>), the
shell prints a warning message, and if the <code>checkjobs</code> option is
enabled, lists the jobs and their statuses.
The <code>jobs</code> command may then be used to inspect their status.
If a second attempt to exit is made without an intervening command,
Bash does not print another warning, and any stopped jobs are terminated.
</p>
<p>When the shell is waiting for a job or process using the <code>wait</code>
builtin, and job control is enabled, <code>wait</code> will return when the
job changes state. The <samp>-f</samp> option causes <code>wait</code> to wait
until the job or process terminates before returning.
</p>
<hr>
</div>
<div class="section" id="Job-Control-Builtins">
<div class="header">
<p>
Next: <a href="#Job-Control-Variables" accesskey="n" rel="next">Job Control Variables</a>, Previous: <a href="#Job-Control-Basics" accesskey="p" rel="prev">Job Control Basics</a>, Up: <a href="#Job-Control" accesskey="u" rel="up">Job Control</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Job-Control-Builtins-1"></span><h3 class="section">7.2 Job Control Builtins</h3>

<dl compact="compact">
<dt id='index-bg'><span><code>bg</code><a href='#index-bg' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">bg [<var>jobspec</var> &hellip;]
</pre></div>

<p>Resume each suspended job <var>jobspec</var> in the background, as if it
had been started with &lsquo;<samp>&amp;</samp>&rsquo;.
If <var>jobspec</var> is not supplied, the current job is used.
The return status is zero unless it is run when job control is not
enabled, or, when run with job control enabled, any
<var>jobspec</var> was not found or specifies a job
that was started without job control.
</p>
</dd>
<dt id='index-fg'><span><code>fg</code><a href='#index-fg' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">fg [<var>jobspec</var>]
</pre></div>

<p>Resume the job <var>jobspec</var> in the foreground and make it the current job.
If <var>jobspec</var> is not supplied, the current job is used.
The return status is that of the command placed into the foreground,
or non-zero if run when job control is disabled or, when run with
job control enabled, <var>jobspec</var> does not specify a valid job or
<var>jobspec</var> specifies a job that was started without job control.
</p>
</dd>
<dt id='index-jobs'><span><code>jobs</code><a href='#index-jobs' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">jobs [-lnprs] [<var>jobspec</var>]
jobs -x <var>command</var> [<var>arguments</var>]
</pre></div>

<p>The first form lists the active jobs.  The options have the
following meanings:
</p>
<dl compact="compact">
<dt><span><code>-l</code></span></dt>
<dd><p>List process <small>ID</small>s in addition to the normal information.
</p>
</dd>
<dt><span><code>-n</code></span></dt>
<dd><p>Display information only about jobs that have changed status since
the user was last notified of their status.
</p>
</dd>
<dt><span><code>-p</code></span></dt>
<dd><p>List only the process <small>ID</small> of the job&rsquo;s process group leader.
</p>
</dd>
<dt><span><code>-r</code></span></dt>
<dd><p>Display only running jobs.
</p>
</dd>
<dt><span><code>-s</code></span></dt>
<dd><p>Display only stopped jobs.
</p></dd>
</dl>

<p>If <var>jobspec</var> is given,
output is restricted to information about that job. 
If <var>jobspec</var> is not supplied, the status of all jobs is
listed.
</p>
<p>If the <samp>-x</samp> option is supplied, <code>jobs</code> replaces any
<var>jobspec</var> found in <var>command</var> or <var>arguments</var> with the
corresponding process group <small>ID</small>, and executes <var>command</var>,
passing it <var>argument</var>s, returning its exit status. 
</p>
</dd>
<dt id='index-kill'><span><code>kill</code><a href='#index-kill' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">kill [-s <var>sigspec</var>] [-n <var>signum</var>] [-<var>sigspec</var>] <var>jobspec</var> or <var>pid</var>
kill -l|-L [<var>exit_status</var>]
</pre></div>

<p>Send a signal specified by <var>sigspec</var> or <var>signum</var> to the process
named by job specification <var>jobspec</var> or process <small>ID</small> <var>pid</var>.
<var>sigspec</var> is either a case-insensitive signal name such as
<code>SIGINT</code> (with or without the <code>SIG</code> prefix)
or a signal number; <var>signum</var> is a signal number.
If <var>sigspec</var> and <var>signum</var> are not present, <code>SIGTERM</code> is used.
The <samp>-l</samp> option lists the signal names.
If any arguments are supplied when <samp>-l</samp> is given, the names of the
signals corresponding to the arguments are listed, and the return status
is zero.
<var>exit_status</var> is a number specifying a signal number or the exit
status of a process terminated by a signal.
The <samp>-L</samp> option is equivalent to <samp>-l</samp>.
The return status is zero if at least one signal was successfully sent,
or non-zero if an error occurs or an invalid option is encountered.
</p>
</dd>
<dt id='index-wait'><span><code>wait</code><a href='#index-wait' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">wait [-fn] [-p <var>varname</var>] [<var>jobspec</var> or <var>pid</var> &hellip;]
</pre></div>

<p>Wait until the child process specified by each process <small>ID</small> <var>pid</var>
or job specification <var>jobspec</var> exits and return the exit status of the
last command waited for.
If a job spec is given, all processes in the job are waited for.
If no arguments are given,
<code>wait</code> waits for all running background jobs and
the last-executed process substitution, if its process id is the same as
<var>$!</var>,
and the return status is zero.
If the <samp>-n</samp> option is supplied, <code>wait</code> waits for a single job
from the list of <var>pid</var>s or <var>jobspec</var>s or, if no arguments are
supplied, any job, 
to complete and returns its exit status.
If none of the supplied arguments is a child of the shell, or if no arguments
are supplied and the shell has no unwaited-for children, the exit status
is 127.
If the <samp>-p</samp> option is supplied, the process or job identifier of the job
for which the exit status is returned is assigned to the variable
<var>varname</var> named by the option argument.
The variable will be unset initially, before any assignment.
This is useful only when the <samp>-n</samp> option is supplied.
Supplying the <samp>-f</samp> option, when job control is enabled,
forces <code>wait</code> to wait for each <var>pid</var> or <var>jobspec</var> to
terminate before returning its status, instead of returning when it changes
status.
If neither <var>jobspec</var> nor <var>pid</var> specifies an active child process
of the shell, the return status is 127.
If <code>wait</code> is interrupted by a signal, the return status will be greater
than 128, as described above (see <a href="#Signals">Signals</a>).
Otherwise, the return status is the exit  status
of the last process or job waited for.
</p>
</dd>
<dt id='index-disown'><span><code>disown</code><a href='#index-disown' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">disown [-ar] [-h] [<var>jobspec</var> &hellip; | <var>pid</var> &hellip; ]
</pre></div>

<p>Without options, remove each <var>jobspec</var> from the table of
active jobs.
If the <samp>-h</samp> option is given, the job is not removed from the table,
but is marked so that <code>SIGHUP</code> is not sent to the job if the shell
receives a <code>SIGHUP</code>.
If <var>jobspec</var> is not present, and neither the <samp>-a</samp> nor the
<samp>-r</samp> option is supplied, the current job is used.
If no <var>jobspec</var> is supplied, the <samp>-a</samp> option means to remove or
mark all jobs; the <samp>-r</samp> option without a <var>jobspec</var>
argument restricts operation to running jobs.
</p>
</dd>
<dt id='index-suspend'><span><code>suspend</code><a href='#index-suspend' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">suspend [-f]
</pre></div>

<p>Suspend the execution of this shell until it receives a
<code>SIGCONT</code> signal.
A login shell,
or a shell without job control enabled,
cannot be suspended; the <samp>-f</samp>
option can be used to override this and force the suspension.
The return status is 0 unless the shell is a login shell
or job control is not enabled
and
<samp>-f</samp>
is not supplied.
</p>
</dd>
</dl>

<p>When job control is not active, the <code>kill</code> and <code>wait</code>
builtins do not accept <var>jobspec</var> arguments.  They must be
supplied process <small>ID</small>s.
</p>
<hr>
</div>
<div class="section" id="Job-Control-Variables">
<div class="header">
<p>
Previous: <a href="#Job-Control-Builtins" accesskey="p" rel="prev">Job Control Builtins</a>, Up: <a href="#Job-Control" accesskey="u" rel="up">Job Control</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Job-Control-Variables-1"></span><h3 class="section">7.3 Job Control Variables</h3>

<dl compact="compact">
<dt id='index-auto_005fresume'><span><code>auto_resume</code><a href='#index-auto_005fresume' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>This variable controls how the shell interacts with the user and
job control.  If this variable exists then single word simple
commands without redirections are treated as candidates for resumption
of an existing job.  There is no ambiguity allowed; if there is
more than one job beginning with the string typed, then
the most recently accessed job will be selected.
The name of a stopped job, in this context, is the command line
used to start it.  If this variable is set to the value &lsquo;<samp>exact</samp>&rsquo;,
the string supplied must match the name of a stopped job exactly;
if set to &lsquo;<samp>substring</samp>&rsquo;,
the string supplied needs to match a substring of the name of a
stopped job.  The &lsquo;<samp>substring</samp>&rsquo; value provides functionality
analogous to the &lsquo;<samp>%?</samp>&rsquo; job <small>ID</small> (see <a href="#Job-Control-Basics">Job Control Basics</a>).
If set to any other value, the supplied string must
be a prefix of a stopped job&rsquo;s name; this provides functionality
analogous to the &lsquo;<samp>%</samp>&rsquo; job <small>ID</small>.
</p>
</dd>
</dl>

<span id="index-Readline_002c-how-to-use"></span>




<hr>
</div>
</div>
<div class="chapter" id="Command-Line-Editing">
<div class="header">
<p>
Next: <a href="#Using-History-Interactively" accesskey="n" rel="next">Using History Interactively</a>, Previous: <a href="#Job-Control" accesskey="p" rel="prev">Job Control</a>, Up: <a href="#Top" accesskey="u" rel="up">Bash Features</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Command-Line-Editing-1"></span><h2 class="chapter">8 Command Line Editing</h2>

<p>This chapter describes the basic features of the <small>GNU</small>
command line editing interface.
Command line editing is provided by the Readline library, which is
used by several different programs, including Bash.
Command line editing is enabled by default when using an interactive shell,
unless the <samp>--noediting</samp> option is supplied at shell invocation.
Line editing is also used when using the <samp>-e</samp> option to the
<code>read</code> builtin command (see <a href="#Bash-Builtins">Bash Builtin Commands</a>).
By default, the line editing commands are similar to those of Emacs.
A vi-style line editing interface is also available.
Line editing can be enabled at any time using the <samp>-o emacs</samp> or
<samp>-o vi</samp> options to the <code>set</code> builtin command
(see <a href="#The-Set-Builtin">The Set Builtin</a>), or disabled using the <samp>+o emacs</samp> or 
<samp>+o vi</samp> options to <code>set</code>.
</p>

<ul class="section-toc">
<li><a href="#Introduction-and-Notation" accesskey="1">Introduction to Line Editing</a></li>
<li><a href="#Readline-Interaction" accesskey="2">Readline Interaction</a></li>
<li><a href="#Readline-Init-File" accesskey="3">Readline Init File</a></li>
<li><a href="#Bindable-Readline-Commands" accesskey="4">Bindable Readline Commands</a></li>
<li><a href="#Readline-vi-Mode" accesskey="5">Readline vi Mode</a></li>
<li><a href="#Programmable-Completion" accesskey="6">Programmable Completion</a></li>
<li><a href="#Programmable-Completion-Builtins" accesskey="7">Programmable Completion Builtins</a></li>
<li><a href="#A-Programmable-Completion-Example" accesskey="8">A Programmable Completion Example</a></li>
</ul>
<hr>
<div class="section" id="Introduction-and-Notation">
<div class="header">
<p>
Next: <a href="#Readline-Interaction" accesskey="n" rel="next">Readline Interaction</a>, Up: <a href="#Command-Line-Editing" accesskey="u" rel="up">Command Line Editing</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Introduction-to-Line-Editing"></span><h3 class="section">8.1 Introduction to Line Editing</h3>

<p>The following paragraphs describe the notation used to represent
keystrokes.
</p>
<p>The text <kbd>C-k</kbd> is read as &lsquo;Control-K&rsquo; and describes the character
produced when the <tt class="key">k</tt> key is pressed while the Control key
is depressed.
</p>
<p>The text <kbd>M-k</kbd> is read as &lsquo;Meta-K&rsquo; and describes the character
produced when the Meta key (if you have one) is depressed, and the <tt class="key">k</tt>
key is pressed.
The Meta key is labeled <tt class="key">ALT</tt> on many keyboards.
On keyboards with two keys labeled <tt class="key">ALT</tt> (usually to either side of
the space bar), the <tt class="key">ALT</tt> on the left side is generally set to
work as a Meta key.
The <tt class="key">ALT</tt> key on the right may also be configured to work as a
Meta key or may be configured as some other modifier, such as a
Compose key for typing accented characters.
</p>
<p>If you do not have a Meta or <tt class="key">ALT</tt> key, or another key working as
a Meta key, the identical keystroke can be generated by typing <tt class="key">ESC</tt>
<em>first</em>, and then typing <tt class="key">k</tt>.
Either process is known as <em>metafying</em> the <tt class="key">k</tt> key.
</p>
<p>The text <kbd>M-C-k</kbd> is read as &lsquo;Meta-Control-k&rsquo; and describes the
character produced by <em>metafying</em> <kbd>C-k</kbd>.
</p>
<p>In addition, several keys have their own names.  Specifically,
<tt class="key">DEL</tt>, <tt class="key">ESC</tt>, <tt class="key">LFD</tt>, <tt class="key">SPC</tt>, <tt class="key">RET</tt>, and <tt class="key">TAB</tt> all
stand for themselves when seen in this text, or in an init file
(see <a href="#Readline-Init-File">Readline Init File</a>).
If your keyboard lacks a <tt class="key">LFD</tt> key, typing <tt class="key">C-j</tt> will
produce the desired character.
The <tt class="key">RET</tt> key may be labeled <tt class="key">Return</tt> or <tt class="key">Enter</tt> on
some keyboards.
</p>
<hr>
</div>
<div class="section" id="Readline-Interaction">
<div class="header">
<p>
Next: <a href="#Readline-Init-File" accesskey="n" rel="next">Readline Init File</a>, Previous: <a href="#Introduction-and-Notation" accesskey="p" rel="prev">Introduction to Line Editing</a>, Up: <a href="#Command-Line-Editing" accesskey="u" rel="up">Command Line Editing</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Readline-Interaction-1"></span><h3 class="section">8.2 Readline Interaction</h3>
<span id="index-interaction_002c-readline"></span>

<p>Often during an interactive session you type in a long line of text,
only to notice that the first word on the line is misspelled.  The
Readline library gives you a set of commands for manipulating the text
as you type it in, allowing you to just fix your typo, and not forcing
you to retype the majority of the line.  Using these editing commands,
you move the cursor to the place that needs correction, and delete or
insert the text of the corrections.  Then, when you are satisfied with
the line, you simply press <tt class="key">RET</tt>.  You do not have to be at the
end of the line to press <tt class="key">RET</tt>; the entire line is accepted
regardless of the location of the cursor within the line.
</p>

<ul class="section-toc">
<li><a href="#Readline-Bare-Essentials" accesskey="1">Readline Bare Essentials</a></li>
<li><a href="#Readline-Movement-Commands" accesskey="2">Readline Movement Commands</a></li>
<li><a href="#Readline-Killing-Commands" accesskey="3">Readline Killing Commands</a></li>
<li><a href="#Readline-Arguments" accesskey="4">Readline Arguments</a></li>
<li><a href="#Searching" accesskey="5">Searching for Commands in the History</a></li>
</ul>
<hr>
<div class="subsection" id="Readline-Bare-Essentials">
<div class="header">
<p>
Next: <a href="#Readline-Movement-Commands" accesskey="n" rel="next">Readline Movement Commands</a>, Up: <a href="#Readline-Interaction" accesskey="u" rel="up">Readline Interaction</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Readline-Bare-Essentials-1"></span><h4 class="subsection">8.2.1 Readline Bare Essentials</h4>
<span id="index-notation_002c-readline"></span>
<span id="index-command-editing"></span>
<span id="index-editing-command-lines"></span>

<p>In order to enter characters into the line, simply type them.  The typed
character appears where the cursor was, and then the cursor moves one
space to the right.  If you mistype a character, you can use your
erase character to back up and delete the mistyped character.
</p>
<p>Sometimes you may mistype a character, and
not notice the error until you have typed several other characters.  In
that case, you can type <kbd>C-b</kbd> to move the cursor to the left, and then
correct your mistake.  Afterwards, you can move the cursor to the right
with <kbd>C-f</kbd>.
</p>
<p>When you add text in the middle of a line, you will notice that characters
to the right of the cursor are &lsquo;pushed over&rsquo; to make room for the text
that you have inserted.  Likewise, when you delete text behind the cursor,
characters to the right of the cursor are &lsquo;pulled back&rsquo; to fill in the
blank space created by the removal of the text.  A list of the bare
essentials for editing the text of an input line follows.
</p>
<dl compact="compact">
<dt><span><kbd>C-b</kbd></span></dt>
<dd><p>Move back one character.
</p></dd>
<dt><span><kbd>C-f</kbd></span></dt>
<dd><p>Move forward one character.
</p></dd>
<dt><span><tt class="key">DEL</tt> or <tt class="key">Backspace</tt></span></dt>
<dd><p>Delete the character to the left of the cursor.
</p></dd>
<dt><span><kbd>C-d</kbd></span></dt>
<dd><p>Delete the character underneath the cursor.
</p></dd>
<dt><span>Printing&nbsp;characters<!-- /@w --></span></dt>
<dd><p>Insert the character into the line at the cursor.
</p></dd>
<dt><span><kbd>C-_</kbd> or <kbd>C-x C-u</kbd></span></dt>
<dd><p>Undo the last editing command.  You can undo all the way back to an
empty line.
</p></dd>
</dl>

<p>(Depending on your configuration, the <tt class="key">Backspace</tt> key might be set to
delete the character to the left of the cursor and the <tt class="key">DEL</tt> key set
to delete the character underneath the cursor, like <kbd>C-d</kbd>, rather
than the character to the left of the cursor.)
</p>
<hr>
</div>
<div class="subsection" id="Readline-Movement-Commands">
<div class="header">
<p>
Next: <a href="#Readline-Killing-Commands" accesskey="n" rel="next">Readline Killing Commands</a>, Previous: <a href="#Readline-Bare-Essentials" accesskey="p" rel="prev">Readline Bare Essentials</a>, Up: <a href="#Readline-Interaction" accesskey="u" rel="up">Readline Interaction</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Readline-Movement-Commands-1"></span><h4 class="subsection">8.2.2 Readline Movement Commands</h4>


<p>The above table describes the most basic keystrokes that you need
in order to do editing of the input line.  For your convenience, many
other commands have been added in addition to <kbd>C-b</kbd>, <kbd>C-f</kbd>,
<kbd>C-d</kbd>, and <tt class="key">DEL</tt>.  Here are some commands for moving more rapidly
about the line.
</p>
<dl compact="compact">
<dt><span><kbd>C-a</kbd></span></dt>
<dd><p>Move to the start of the line.
</p></dd>
<dt><span><kbd>C-e</kbd></span></dt>
<dd><p>Move to the end of the line.
</p></dd>
<dt><span><kbd>M-f</kbd></span></dt>
<dd><p>Move forward a word, where a word is composed of letters and digits.
</p></dd>
<dt><span><kbd>M-b</kbd></span></dt>
<dd><p>Move backward a word.
</p></dd>
<dt><span><kbd>C-l</kbd></span></dt>
<dd><p>Clear the screen, reprinting the current line at the top.
</p></dd>
</dl>

<p>Notice how <kbd>C-f</kbd> moves forward a character, while <kbd>M-f</kbd> moves
forward a word.  It is a loose convention that control keystrokes
operate on characters while meta keystrokes operate on words.
</p>
<hr>
</div>
<div class="subsection" id="Readline-Killing-Commands">
<div class="header">
<p>
Next: <a href="#Readline-Arguments" accesskey="n" rel="next">Readline Arguments</a>, Previous: <a href="#Readline-Movement-Commands" accesskey="p" rel="prev">Readline Movement Commands</a>, Up: <a href="#Readline-Interaction" accesskey="u" rel="up">Readline Interaction</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Readline-Killing-Commands-1"></span><h4 class="subsection">8.2.3 Readline Killing Commands</h4>

<span id="index-killing-text"></span>
<span id="index-yanking-text"></span>

<p><em>Killing</em> text means to delete the text from the line, but to save
it away for later use, usually by <em>yanking</em> (re-inserting)
it back into the line.
(&lsquo;Cut&rsquo; and &lsquo;paste&rsquo; are more recent jargon for &lsquo;kill&rsquo; and &lsquo;yank&rsquo;.)
</p>
<p>If the description for a command says that it &lsquo;kills&rsquo; text, then you can
be sure that you can get the text back in a different (or the same)
place later.
</p>
<p>When you use a kill command, the text is saved in a <em>kill-ring</em>.
Any number of consecutive kills save all of the killed text together, so
that when you yank it back, you get it all.  The kill
ring is not line specific; the text that you killed on a previously
typed line is available to be yanked back later, when you are typing
another line.
<span id="index-kill-ring"></span>
</p>
<p>Here is the list of commands for killing text.
</p>
<dl compact="compact">
<dt><span><kbd>C-k</kbd></span></dt>
<dd><p>Kill the text from the current cursor position to the end of the line.
</p>
</dd>
<dt><span><kbd>M-d</kbd></span></dt>
<dd><p>Kill from the cursor to the end of the current word, or, if between
words, to the end of the next word.
Word boundaries are the same as those used by <kbd>M-f</kbd>.
</p>
</dd>
<dt><span><kbd>M-<span class="key">DEL</span></kbd></span></dt>
<dd><p>Kill from the cursor to the start of the current word, or, if between
words, to the start of the previous word.
Word boundaries are the same as those used by <kbd>M-b</kbd>.
</p>
</dd>
<dt><span><kbd>C-w</kbd></span></dt>
<dd><p>Kill from the cursor to the previous whitespace.  This is different than
<kbd>M-<span class="key">DEL</span></kbd> because the word boundaries differ.
</p>
</dd>
</dl>

<p>Here is how to <em>yank</em> the text back into the line.  Yanking
means to copy the most-recently-killed text from the kill buffer.
</p>
<dl compact="compact">
<dt><span><kbd>C-y</kbd></span></dt>
<dd><p>Yank the most recently killed text back into the buffer at the cursor.
</p>
</dd>
<dt><span><kbd>M-y</kbd></span></dt>
<dd><p>Rotate the kill-ring, and yank the new top.  You can only do this if
the prior command is <kbd>C-y</kbd> or <kbd>M-y</kbd>.
</p></dd>
</dl>

<hr>
</div>
<div class="subsection" id="Readline-Arguments">
<div class="header">
<p>
Next: <a href="#Searching" accesskey="n" rel="next">Searching for Commands in the History</a>, Previous: <a href="#Readline-Killing-Commands" accesskey="p" rel="prev">Readline Killing Commands</a>, Up: <a href="#Readline-Interaction" accesskey="u" rel="up">Readline Interaction</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Readline-Arguments-1"></span><h4 class="subsection">8.2.4 Readline Arguments</h4>

<p>You can pass numeric arguments to Readline commands.  Sometimes the
argument acts as a repeat count, other times it is the <i>sign</i> of the
argument that is significant.  If you pass a negative argument to a
command which normally acts in a forward direction, that command will
act in a backward direction.  For example, to kill text back to the
start of the line, you might type &lsquo;<samp>M-- C-k</samp>&rsquo;.
</p>
<p>The general way to pass numeric arguments to a command is to type meta
digits before the command.  If the first &lsquo;digit&rsquo; typed is a minus
sign (&lsquo;<samp>-</samp>&rsquo;), then the sign of the argument will be negative.  Once
you have typed one meta digit to get the argument started, you can type
the remainder of the digits, and then the command.  For example, to give
the <kbd>C-d</kbd> command an argument of 10, you could type &lsquo;<samp>M-1 0 C-d</samp>&rsquo;,
which will delete the next ten characters on the input line.
</p>
<hr>
</div>
<div class="subsection" id="Searching">
<div class="header">
<p>
Previous: <a href="#Readline-Arguments" accesskey="p" rel="prev">Readline Arguments</a>, Up: <a href="#Readline-Interaction" accesskey="u" rel="up">Readline Interaction</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Searching-for-Commands-in-the-History"></span><h4 class="subsection">8.2.5 Searching for Commands in the History</h4>

<p>Readline provides commands for searching through the command history
(see <a href="#Bash-History-Facilities">Bash History Facilities</a>)
for lines containing a specified string.
There are two search modes:  <em>incremental</em> and <em>non-incremental</em>.
</p>
<p>Incremental searches begin before the user has finished typing the
search string.
As each character of the search string is typed, Readline displays
the next entry from the history matching the string typed so far.
An incremental search requires only as many characters as needed to
find the desired history entry.
To search backward in the history for a particular string, type
<kbd>C-r</kbd>.  Typing <kbd>C-s</kbd> searches forward through the history.
The characters present in the value of the <code>isearch-terminators</code> variable
are used to terminate an incremental search.
If that variable has not been assigned a value, the <tt class="key">ESC</tt> and
<kbd>C-J</kbd> characters will terminate an incremental search.
<kbd>C-g</kbd> will abort an incremental search and restore the original line.
When the search is terminated, the history entry containing the
search string becomes the current line.
</p>
<p>To find other matching entries in the history list, type <kbd>C-r</kbd> or
<kbd>C-s</kbd> as appropriate.
This will search backward or forward in the history for the next
entry matching the search string typed so far.
Any other key sequence bound to a Readline command will terminate
the search and execute that command.
For instance, a <tt class="key">RET</tt> will terminate the search and accept
the line, thereby executing the command from the history list.
A movement command will terminate the search, make the last line found
the current line, and begin editing.
</p>
<p>Readline remembers the last incremental search string.  If two
<kbd>C-r</kbd>s are typed without any intervening characters defining a new
search string, any remembered search string is used.
</p>
<p>Non-incremental searches read the entire search string before starting
to search for matching history lines.  The search string may be
typed by the user or be part of the contents of the current line.
</p>
<hr>
</div>
</div>
<div class="section" id="Readline-Init-File">
<div class="header">
<p>
Next: <a href="#Bindable-Readline-Commands" accesskey="n" rel="next">Bindable Readline Commands</a>, Previous: <a href="#Readline-Interaction" accesskey="p" rel="prev">Readline Interaction</a>, Up: <a href="#Command-Line-Editing" accesskey="u" rel="up">Command Line Editing</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Readline-Init-File-1"></span><h3 class="section">8.3 Readline Init File</h3>
<span id="index-initialization-file_002c-readline"></span>

<p>Although the Readline library comes with a set of Emacs-like
keybindings installed by default, it is possible to use a different set
of keybindings.
Any user can customize programs that use Readline by putting
commands in an <em>inputrc</em> file,
conventionally in their home directory.
The name of this
file is taken from the value of the shell variable <code>INPUTRC</code>.  If
that variable is unset, the default is <samp>~/.inputrc</samp>.  If that
file does not exist or cannot be read, the ultimate default is
<samp>/etc/inputrc</samp>.
The <code>bind</code><!-- /@w --> builtin command can also be used to set Readline
keybindings and variables.
See <a href="#Bash-Builtins">Bash Builtin Commands</a>.
</p>
<p>When a program which uses the Readline library starts up, the
init file is read, and the key bindings are set.
</p>
<p>In addition, the <code>C-x C-r</code> command re-reads this init file, thus
incorporating any changes that you might have made to it.
</p>

<ul class="section-toc">
<li><a href="#Readline-Init-File-Syntax" accesskey="1">Readline Init File Syntax</a></li>
<li><a href="#Conditional-Init-Constructs" accesskey="2">Conditional Init Constructs</a></li>
<li><a href="#Sample-Init-File" accesskey="3">Sample Init File</a></li>
</ul>
<hr>
<div class="subsection" id="Readline-Init-File-Syntax">
<div class="header">
<p>
Next: <a href="#Conditional-Init-Constructs" accesskey="n" rel="next">Conditional Init Constructs</a>, Up: <a href="#Readline-Init-File" accesskey="u" rel="up">Readline Init File</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Readline-Init-File-Syntax-1"></span><h4 class="subsection">8.3.1 Readline Init File Syntax</h4>

<p>There are only a few basic constructs allowed in the
Readline init file.  Blank lines are ignored.
Lines beginning with a &lsquo;<samp>#</samp>&rsquo; are comments.
Lines beginning with a &lsquo;<samp>$</samp>&rsquo; indicate conditional
constructs (see <a href="#Conditional-Init-Constructs">Conditional Init Constructs</a>).  Other lines
denote variable settings and key bindings.
</p>
<dl compact="compact">
<dt><span>Variable Settings</span></dt>
<dd><p>You can modify the run-time behavior of Readline by
altering the values of variables in Readline
using the <code>set</code> command within the init file.
The syntax is simple:
</p>
<div class="example">
<pre class="example">set <var>variable</var> <var>value</var>
</pre></div>

<p>Here, for example, is how to
change from the default Emacs-like key binding to use
<code>vi</code> line editing commands:
</p>
<div class="example">
<pre class="example">set editing-mode vi
</pre></div>

<p>Variable names and values, where appropriate, are recognized without regard
to case.  Unrecognized variable names are ignored.
</p>
<p>Boolean variables (those that can be set to on or off) are set to on if
the value is null or empty, <var>on</var> (case-insensitive), or 1.  Any other
value results in the variable being set to off.
</p>
<p>The <code>bind&nbsp;<span class="nolinebreak">-V</span></code><!-- /@w --> command lists the current Readline variable names
and values.  See <a href="#Bash-Builtins">Bash Builtin Commands</a>.
</p>
<p>A great deal of run-time behavior is changeable with the following
variables.
</p>
<span id="index-variables_002c-readline"></span>
<dl compact="compact">
<dt id='index-active_002dregion_002dstart_002dcolor'><span><code>active-region-start-color</code><a href='#index-active_002dregion_002dstart_002dcolor' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A string variable that controls the text color and background when displaying
the text in the active region (see the description of
<code>enable-active-region</code> below).
This string must not take up any physical character positions on the display,
so it should consist only of terminal escape sequences.
It is output to the terminal before displaying the text in the active region.
This variable is reset to the default value whenever the terminal type changes.
The default value is the string that puts the terminal in standout mode,
as obtained from the terminal&rsquo;s terminfo description.
A sample value might be &lsquo;<samp>\e[01;33m</samp>&rsquo;.
</p>
</dd>
<dt id='index-active_002dregion_002dend_002dcolor'><span><code>active-region-end-color</code><a href='#index-active_002dregion_002dend_002dcolor' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A string variable that &quot;undoes&quot; the effects of <code>active-region-start-color</code>
and restores &quot;normal&quot; terminal display appearance after displaying text
in the active region.
This string must not take up any physical character positions on the display,
so it should consist only of terminal escape sequences.
It is output to the terminal after displaying the text in the active region.
This variable is reset to the default value whenever the terminal type changes.
The default value is the string that restores the terminal from standout mode,
as obtained from the terminal&rsquo;s terminfo description.
A sample value might be &lsquo;<samp>\e[0m</samp>&rsquo;.
</p>
</dd>
<dt id='index-bell_002dstyle'><span><code>bell-style</code><a href='#index-bell_002dstyle' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Controls what happens when Readline wants to ring the terminal bell.
If set to &lsquo;<samp>none</samp>&rsquo;, Readline never rings the bell.  If set to
&lsquo;<samp>visible</samp>&rsquo;, Readline uses a visible bell if one is available.
If set to &lsquo;<samp>audible</samp>&rsquo; (the default), Readline attempts to ring
the terminal&rsquo;s bell.
</p>
</dd>
<dt id='index-bind_002dtty_002dspecial_002dchars'><span><code>bind-tty-special-chars</code><a href='#index-bind_002dtty_002dspecial_002dchars' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>If set to &lsquo;<samp>on</samp>&rsquo; (the default), Readline attempts to bind the control
characters   treated specially by the kernel&rsquo;s terminal driver to their
Readline equivalents.
</p>
</dd>
<dt id='index-blink_002dmatching_002dparen'><span><code>blink-matching-paren</code><a href='#index-blink_002dmatching_002dparen' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>If set to &lsquo;<samp>on</samp>&rsquo;, Readline attempts to briefly move the cursor to an
opening parenthesis when a closing parenthesis is inserted.  The default
is &lsquo;<samp>off</samp>&rsquo;.
</p>
</dd>
<dt id='index-colored_002dcompletion_002dprefix'><span><code>colored-completion-prefix</code><a href='#index-colored_002dcompletion_002dprefix' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>If set to &lsquo;<samp>on</samp>&rsquo;, when listing completions, Readline displays the
common prefix of the set of possible completions using a different color.
The color definitions are taken from the value of the <code>LS_COLORS</code>
environment variable.
If there is a color definition in <code>LS_COLORS</code> for the custom suffix
&lsquo;<samp>readline-colored-completion-prefix</samp>&rsquo;, Readline uses this color for
the common prefix instead of its default.
The default is &lsquo;<samp>off</samp>&rsquo;.
</p>
</dd>
<dt id='index-colored_002dstats'><span><code>colored-stats</code><a href='#index-colored_002dstats' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>If set to &lsquo;<samp>on</samp>&rsquo;, Readline displays possible completions using different
colors to indicate their file type.
The color definitions are taken from the value of the <code>LS_COLORS</code>
environment variable.
The default is &lsquo;<samp>off</samp>&rsquo;.
</p>
</dd>
<dt id='index-comment_002dbegin'><span><code>comment-begin</code><a href='#index-comment_002dbegin' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The string to insert at the beginning of the line when the
<code>insert-comment</code> command is executed.  The default value
is <code>&quot;#&quot;</code>.
</p>
</dd>
<dt id='index-completion_002ddisplay_002dwidth'><span><code>completion-display-width</code><a href='#index-completion_002ddisplay_002dwidth' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The number of screen columns used to display possible matches
when performing completion.
The value is ignored if it is less than 0 or greater than the terminal
screen width.
A value of 0 will cause matches to be displayed one per line.
The default value is -1.
</p>
</dd>
<dt id='index-completion_002dignore_002dcase'><span><code>completion-ignore-case</code><a href='#index-completion_002dignore_002dcase' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>If set to &lsquo;<samp>on</samp>&rsquo;, Readline performs filename matching and completion
in a case-insensitive fashion.
The default value is &lsquo;<samp>off</samp>&rsquo;.
</p>
</dd>
<dt id='index-completion_002dmap_002dcase'><span><code>completion-map-case</code><a href='#index-completion_002dmap_002dcase' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>If set to &lsquo;<samp>on</samp>&rsquo;, and <var>completion-ignore-case</var> is enabled, Readline
treats hyphens (&lsquo;<samp>-</samp>&rsquo;) and underscores (&lsquo;<samp>_</samp>&rsquo;) as equivalent when
performing case-insensitive filename matching and completion.
The default value is &lsquo;<samp>off</samp>&rsquo;.
</p>
</dd>
<dt id='index-completion_002dprefix_002ddisplay_002dlength'><span><code>completion-prefix-display-length</code><a href='#index-completion_002dprefix_002ddisplay_002dlength' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The length in characters of the common prefix of a list of possible
completions that is displayed without modification.  When set to a
value greater than zero, common prefixes longer than this value are
replaced with an ellipsis when displaying possible completions.
</p>
</dd>
<dt id='index-completion_002dquery_002ditems'><span><code>completion-query-items</code><a href='#index-completion_002dquery_002ditems' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The number of possible completions that determines when the user is
asked whether the list of possibilities should be displayed.
If the number of possible completions is greater than or equal to this value,
Readline will ask whether or not the user wishes to view them;
otherwise, they are simply listed.
This variable must be set to an integer value greater than or equal to zero.
A zero value means Readline should never ask; negative values are
treated as zero.
The default limit is <code>100</code>.
</p>
</dd>
<dt id='index-convert_002dmeta'><span><code>convert-meta</code><a href='#index-convert_002dmeta' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>If set to &lsquo;<samp>on</samp>&rsquo;, Readline will convert characters with the
eighth bit set to an <small>ASCII</small> key sequence by stripping the eighth
bit and prefixing an <tt class="key">ESC</tt> character, converting them to a
meta-prefixed key sequence.
The default value is &lsquo;<samp>on</samp>&rsquo;, but
will be set to &lsquo;<samp>off</samp>&rsquo; if the locale is one that contains
eight-bit characters.
This variable is dependent on the <code>LC_CTYPE</code> locale category, and
may change if the locale is changed.
</p>
</dd>
<dt id='index-disable_002dcompletion'><span><code>disable-completion</code><a href='#index-disable_002dcompletion' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>If set to &lsquo;<samp>On</samp>&rsquo;, Readline will inhibit word completion.
Completion  characters will be inserted into the line as if they had
been mapped to <code>self-insert</code>.  The default is &lsquo;<samp>off</samp>&rsquo;.
</p>
</dd>
<dt id='index-echo_002dcontrol_002dcharacters'><span><code>echo-control-characters</code><a href='#index-echo_002dcontrol_002dcharacters' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>When set to &lsquo;<samp>on</samp>&rsquo;, on operating systems that indicate they support it,
Readline echoes a character corresponding to a signal generated from the
keyboard.  The default is &lsquo;<samp>on</samp>&rsquo;.
</p>
</dd>
<dt id='index-editing_002dmode'><span><code>editing-mode</code><a href='#index-editing_002dmode' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The <code>editing-mode</code> variable controls which default set of
key bindings is used.  By default, Readline starts up in Emacs editing
mode, where the keystrokes are most similar to Emacs.  This variable can be
set to either &lsquo;<samp>emacs</samp>&rsquo; or &lsquo;<samp>vi</samp>&rsquo;.
</p>
</dd>
<dt id='index-emacs_002dmode_002dstring'><span><code>emacs-mode-string</code><a href='#index-emacs_002dmode_002dstring' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>If the <var>show-mode-in-prompt</var> variable is enabled,
this string is displayed immediately before the last line of the primary
prompt when emacs editing mode is active.  The value is expanded like a
key binding, so the standard set of meta- and control prefixes and
backslash escape sequences is available.
Use the &lsquo;<samp>\1</samp>&rsquo; and &lsquo;<samp>\2</samp>&rsquo; escapes to begin and end sequences of
non-printing characters, which can be used to embed a terminal control
sequence into the mode string.
The default is &lsquo;<samp>@</samp>&rsquo;.
</p>
</dd>
<dt id='index-enable_002dactive_002dregion'><span><code>enable-active-region</code><a href='#index-enable_002dactive_002dregion' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The <em>point</em> is the current cursor position, and <em>mark</em> refers
to a saved cursor position (see <a href="#Commands-For-Moving">Commands For Moving</a>).
The text between the point and mark is referred to as the <em>region</em>.
When this variable is set to &lsquo;<samp>On</samp>&rsquo;, Readline allows certain commands
to designate the region as <em>active</em>.
When the region is active, Readline highlights the text in the region using
the value of the <code>active-region-start-color</code>, which defaults to the
string that enables
the terminal&rsquo;s standout mode.
The active region shows the text inserted by bracketed-paste and any
matching text found by incremental and non-incremental history searches.
The default is &lsquo;<samp>On</samp>&rsquo;.
</p>
</dd>
<dt id='index-enable_002dbracketed_002dpaste'><span><code>enable-bracketed-paste</code><a href='#index-enable_002dbracketed_002dpaste' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>When set to &lsquo;<samp>On</samp>&rsquo;, Readline configures the terminal to insert each
paste into the editing buffer as a single string of characters, instead
of treating each character as if it had been read from the keyboard.
This is called putting the terminal into <em>bracketed paste mode</em>;
it prevents Readline from executing any editing commands bound to key
sequences appearing in the pasted text.
The default is &lsquo;<samp>On</samp>&rsquo;.
</p>
</dd>
<dt id='index-enable_002dkeypad'><span><code>enable-keypad</code><a href='#index-enable_002dkeypad' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>When set to &lsquo;<samp>on</samp>&rsquo;, Readline will try to enable the application
keypad when it is called.  Some systems need this to enable the
arrow keys.  The default is &lsquo;<samp>off</samp>&rsquo;.
</p>
</dd>
<dt><span><code>enable-meta-key</code></span></dt>
<dd><p>When set to &lsquo;<samp>on</samp>&rsquo;, Readline will try to enable any meta modifier
key the terminal claims to support when it is called.  On many terminals,
the meta key is used to send eight-bit characters.
The default is &lsquo;<samp>on</samp>&rsquo;.
</p>
</dd>
<dt id='index-expand_002dtilde'><span><code>expand-tilde</code><a href='#index-expand_002dtilde' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>If set to &lsquo;<samp>on</samp>&rsquo;, tilde expansion is performed when Readline
attempts word completion.  The default is &lsquo;<samp>off</samp>&rsquo;.
</p>
</dd>
<dt id='index-history_002dpreserve_002dpoint'><span><code>history-preserve-point</code><a href='#index-history_002dpreserve_002dpoint' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>If set to &lsquo;<samp>on</samp>&rsquo;, the history code attempts to place the point (the
current cursor position) at the
same location on each history line retrieved with <code>previous-history</code>
or <code>next-history</code>.  The default is &lsquo;<samp>off</samp>&rsquo;.
</p>
</dd>
<dt id='index-history_002dsize'><span><code>history-size</code><a href='#index-history_002dsize' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Set the maximum number of history entries saved in the history list.
If set to zero, any existing history entries are deleted and no new entries
are saved.
If set to a value less than zero, the number of history entries is not
limited.
By default, the number of history entries is not limited.
If an attempt is made to set <var>history-size</var> to a non-numeric value,
the maximum number of history entries will be set to 500.
</p>
</dd>
<dt id='index-horizontal_002dscroll_002dmode'><span><code>horizontal-scroll-mode</code><a href='#index-horizontal_002dscroll_002dmode' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>This variable can be set to either &lsquo;<samp>on</samp>&rsquo; or &lsquo;<samp>off</samp>&rsquo;.  Setting it
to &lsquo;<samp>on</samp>&rsquo; means that the text of the lines being edited will scroll
horizontally on a single screen line when they are longer than the width
of the screen, instead of wrapping onto a new screen line.
This variable is automatically set to &lsquo;<samp>on</samp>&rsquo; for terminals of height 1.
By default, this variable is set to &lsquo;<samp>off</samp>&rsquo;.
</p>
</dd>
<dt id='index-input_002dmeta'><span><code>input-meta</code><a href='#index-input_002dmeta' class='copiable-anchor'> &para;</a></span></dt>
<dd><span id="index-meta_002dflag"></span>
<p>If set to &lsquo;<samp>on</samp>&rsquo;, Readline will enable eight-bit input (it
will not clear the eighth bit in the characters it reads),
regardless of what the terminal claims it can support.  The
default value is &lsquo;<samp>off</samp>&rsquo;, but Readline will set it to &lsquo;<samp>on</samp>&rsquo; if the 
locale contains eight-bit characters.
The name <code>meta-flag</code> is a synonym for this variable.
This variable is dependent on the <code>LC_CTYPE</code> locale category, and
may change if the locale is changed.
</p>
</dd>
<dt id='index-isearch_002dterminators'><span><code>isearch-terminators</code><a href='#index-isearch_002dterminators' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The string of characters that should terminate an incremental search without
subsequently executing the character as a command (see <a href="#Searching">Searching for Commands in the History</a>).
If this variable has not been given a value, the characters <tt class="key">ESC</tt> and
<kbd>C-J</kbd> will terminate an incremental search.
</p>
</dd>
<dt id='index-keymap'><span><code>keymap</code><a href='#index-keymap' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Sets Readline&rsquo;s idea of the current keymap for key binding commands.
Built-in <code>keymap</code> names are
<code>emacs</code>,
<code>emacs-standard</code>,
<code>emacs-meta</code>,
<code>emacs-ctlx</code>,
<code>vi</code>,
<code>vi-move</code>,
<code>vi-command</code>, and
<code>vi-insert</code>.
<code>vi</code> is equivalent to <code>vi-command</code> (<code>vi-move</code> is also a
synonym); <code>emacs</code> is equivalent to <code>emacs-standard</code>.
Applications may add additional names.
The default value is <code>emacs</code>.
The value of the <code>editing-mode</code> variable also affects the
default keymap.
</p>
</dd>
<dt><span><code>keyseq-timeout</code></span></dt>
<dd><p>Specifies the duration Readline will wait for a character when reading an
ambiguous key sequence (one that can form a complete key sequence using
the input read so far, or can take additional input to complete a longer
key sequence).
If no input is received within the timeout, Readline will use the shorter
but complete key sequence.
Readline uses this value to determine whether or not input is
available on the current input source (<code>rl_instream</code> by default).
The value is specified in milliseconds, so a value of 1000 means that
Readline will wait one second for additional input.
If this variable is set to a value less than or equal to zero, or to a
non-numeric value, Readline will wait until another key is pressed to
decide which key sequence to complete.
The default value is <code>500</code>.
</p>
</dd>
<dt><span><code>mark-directories</code></span></dt>
<dd><p>If set to &lsquo;<samp>on</samp>&rsquo;, completed directory names have a slash
appended.  The default is &lsquo;<samp>on</samp>&rsquo;.
</p>
</dd>
<dt id='index-mark_002dmodified_002dlines'><span><code>mark-modified-lines</code><a href='#index-mark_002dmodified_002dlines' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>This variable, when set to &lsquo;<samp>on</samp>&rsquo;, causes Readline to display an
asterisk (&lsquo;<samp>*</samp>&rsquo;) at the start of history lines which have been modified.
This variable is &lsquo;<samp>off</samp>&rsquo; by default.
</p>
</dd>
<dt id='index-mark_002dsymlinked_002ddirectories'><span><code>mark-symlinked-directories</code><a href='#index-mark_002dsymlinked_002ddirectories' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>If set to &lsquo;<samp>on</samp>&rsquo;, completed names which are symbolic links
to directories have a slash appended (subject to the value of
<code>mark-directories</code>).
The default is &lsquo;<samp>off</samp>&rsquo;.
</p>
</dd>
<dt id='index-match_002dhidden_002dfiles'><span><code>match-hidden-files</code><a href='#index-match_002dhidden_002dfiles' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>This variable, when set to &lsquo;<samp>on</samp>&rsquo;, causes Readline to match files whose
names begin with a &lsquo;<samp>.</samp>&rsquo; (hidden files) when performing filename
completion.
If set to &lsquo;<samp>off</samp>&rsquo;, the leading &lsquo;<samp>.</samp>&rsquo; must be
supplied by the user in the filename to be completed.
This variable is &lsquo;<samp>on</samp>&rsquo; by default.
</p>
</dd>
<dt id='index-menu_002dcomplete_002ddisplay_002dprefix'><span><code>menu-complete-display-prefix</code><a href='#index-menu_002dcomplete_002ddisplay_002dprefix' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>If set to &lsquo;<samp>on</samp>&rsquo;, menu completion displays the common prefix of the
list of possible completions (which may be empty) before cycling through
the list.  The default is &lsquo;<samp>off</samp>&rsquo;.
</p>
</dd>
<dt id='index-output_002dmeta'><span><code>output-meta</code><a href='#index-output_002dmeta' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>If set to &lsquo;<samp>on</samp>&rsquo;, Readline will display characters with the
eighth bit set directly rather than as a meta-prefixed escape
sequence.
The default is &lsquo;<samp>off</samp>&rsquo;, but Readline will set it to &lsquo;<samp>on</samp>&rsquo; if the
locale contains eight-bit characters.
This variable is dependent on the <code>LC_CTYPE</code> locale category, and
may change if the locale is changed.
</p>
</dd>
<dt id='index-page_002dcompletions'><span><code>page-completions</code><a href='#index-page_002dcompletions' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>If set to &lsquo;<samp>on</samp>&rsquo;, Readline uses an internal <code>more</code>-like pager
to display a screenful of possible completions at a time.
This variable is &lsquo;<samp>on</samp>&rsquo; by default.
</p>
</dd>
<dt><span><code>print-completions-horizontally</code></span></dt>
<dd><p>If set to &lsquo;<samp>on</samp>&rsquo;, Readline will display completions with matches
sorted horizontally in alphabetical order, rather than down the screen.
The default is &lsquo;<samp>off</samp>&rsquo;.
</p>
</dd>
<dt id='index-revert_002dall_002dat_002dnewline'><span><code>revert-all-at-newline</code><a href='#index-revert_002dall_002dat_002dnewline' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>If set to &lsquo;<samp>on</samp>&rsquo;, Readline will undo all changes to history lines
before returning when <code>accept-line</code> is executed.  By default,
history lines may be modified and retain individual undo lists across
calls to <code>readline()</code>.  The default is &lsquo;<samp>off</samp>&rsquo;.
</p>
</dd>
<dt id='index-show_002dall_002dif_002dambiguous'><span><code>show-all-if-ambiguous</code><a href='#index-show_002dall_002dif_002dambiguous' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>This alters the default behavior of the completion functions.  If
set to &lsquo;<samp>on</samp>&rsquo;, 
words which have more than one possible completion cause the
matches to be listed immediately instead of ringing the bell.
The default value is &lsquo;<samp>off</samp>&rsquo;.
</p>
</dd>
<dt id='index-show_002dall_002dif_002dunmodified'><span><code>show-all-if-unmodified</code><a href='#index-show_002dall_002dif_002dunmodified' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>This alters the default behavior of the completion functions in
a fashion similar to <var>show-all-if-ambiguous</var>.
If set to &lsquo;<samp>on</samp>&rsquo;, 
words which have more than one possible completion without any
possible partial completion (the possible completions don&rsquo;t share
a common prefix) cause the matches to be listed immediately instead
of ringing the bell.
The default value is &lsquo;<samp>off</samp>&rsquo;.
</p>
</dd>
<dt id='index-show_002dmode_002din_002dprompt'><span><code>show-mode-in-prompt</code><a href='#index-show_002dmode_002din_002dprompt' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>If set to &lsquo;<samp>on</samp>&rsquo;, add a string to the beginning of the prompt
indicating the editing mode: emacs, vi command, or vi insertion.
The mode strings are user-settable (e.g., <var>emacs-mode-string</var>).
The default value is &lsquo;<samp>off</samp>&rsquo;.
</p>
</dd>
<dt id='index-skip_002dcompleted_002dtext'><span><code>skip-completed-text</code><a href='#index-skip_002dcompleted_002dtext' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>If set to &lsquo;<samp>on</samp>&rsquo;, this alters the default completion behavior when
inserting a single match into the line.  It&rsquo;s only active when
performing completion in the middle of a word.  If enabled, Readline
does not insert characters from the completion that match characters
after point in the word being completed, so portions of the word
following the cursor are not duplicated.
For instance, if this is enabled, attempting completion when the cursor
is after the &lsquo;<samp>e</samp>&rsquo; in &lsquo;<samp>Makefile</samp>&rsquo; will result in &lsquo;<samp>Makefile</samp>&rsquo;
rather than &lsquo;<samp>Makefilefile</samp>&rsquo;, assuming there is a single possible
completion.
The default value is &lsquo;<samp>off</samp>&rsquo;.
</p>
</dd>
<dt id='index-vi_002dcmd_002dmode_002dstring'><span><code>vi-cmd-mode-string</code><a href='#index-vi_002dcmd_002dmode_002dstring' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>If the <var>show-mode-in-prompt</var> variable is enabled,
this string is displayed immediately before the last line of the primary
prompt when vi editing mode is active and in command mode.
The value is expanded like a
key binding, so the standard set of meta- and control prefixes and
backslash escape sequences is available.
Use the &lsquo;<samp>\1</samp>&rsquo; and &lsquo;<samp>\2</samp>&rsquo; escapes to begin and end sequences of
non-printing characters, which can be used to embed a terminal control
sequence into the mode string.
The default is &lsquo;<samp>(cmd)</samp>&rsquo;.
</p>
</dd>
<dt id='index-vi_002dins_002dmode_002dstring'><span><code>vi-ins-mode-string</code><a href='#index-vi_002dins_002dmode_002dstring' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>If the <var>show-mode-in-prompt</var> variable is enabled,
this string is displayed immediately before the last line of the primary
prompt when vi editing mode is active and in insertion mode.
The value is expanded like a
key binding, so the standard set of meta- and control prefixes and
backslash escape sequences is available.
Use the &lsquo;<samp>\1</samp>&rsquo; and &lsquo;<samp>\2</samp>&rsquo; escapes to begin and end sequences of
non-printing characters, which can be used to embed a terminal control
sequence into the mode string.
The default is &lsquo;<samp>(ins)</samp>&rsquo;.
</p>
</dd>
<dt id='index-visible_002dstats'><span><code>visible-stats</code><a href='#index-visible_002dstats' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>If set to &lsquo;<samp>on</samp>&rsquo;, a character denoting a file&rsquo;s type
is appended to the filename when listing possible
completions.  The default is &lsquo;<samp>off</samp>&rsquo;.
</p>
</dd>
</dl>

</dd>
<dt><span>Key Bindings</span></dt>
<dd><p>The syntax for controlling key bindings in the init file is
simple.  First you need to find the name of the command that you
want to change.  The following sections contain tables of the command
name, the default keybinding, if any, and a short description of what
the command does.
</p>
<p>Once you know the name of the command, simply place on a line
in the init file the name of the key
you wish to bind the command to, a colon, and then the name of the
command.
There can be no space between the key name and the colon &ndash; that will be
interpreted as part of the key name.
The name of the key can be expressed in different ways, depending on
what you find most comfortable.
</p>
<p>In addition to command names, Readline allows keys to be bound
to a string that is inserted when the key is pressed (a <var>macro</var>).
</p>
<p>The <code>bind&nbsp;<span class="nolinebreak">-p</span></code><!-- /@w --> command displays Readline function names and
bindings in a format that can be put directly into an initialization file.
See <a href="#Bash-Builtins">Bash Builtin Commands</a>.
</p>
<dl compact="compact">
<dt><span><var>keyname</var>:&nbsp;<var><span class="nolinebreak">function-name</span></var>&nbsp;or&nbsp;<var>macro</var><!-- /@w --></span></dt>
<dd><p><var>keyname</var> is the name of a key spelled out in English.  For example:
</p><div class="example">
<pre class="example">Control-u: universal-argument
Meta-Rubout: backward-kill-word
Control-o: &quot;&gt; output&quot;
</pre></div>

<p>In the example above, <kbd>C-u</kbd> is bound to the function
<code>universal-argument</code>,
<kbd>M-DEL</kbd> is bound to the function <code>backward-kill-word</code>, and
<kbd>C-o</kbd> is bound to run the macro
expressed on the right hand side (that is, to insert the text
&lsquo;<samp>&gt; output</samp>&rsquo; into the line).
</p>
<p>A number of symbolic character names are recognized while
processing this key binding syntax:
<var>DEL</var>,
<var>ESC</var>,
<var>ESCAPE</var>,
<var>LFD</var>,
<var>NEWLINE</var>,
<var>RET</var>,
<var>RETURN</var>,
<var>RUBOUT</var>,
<var>SPACE</var>,
<var>SPC</var>,
and
<var>TAB</var>.
</p>
</dd>
<dt><span>&quot;<var>keyseq</var>&quot;:&nbsp;<var><span class="nolinebreak">function-name</span></var>&nbsp;or&nbsp;<var>macro</var><!-- /@w --></span></dt>
<dd><p><var>keyseq</var> differs from <var>keyname</var> above in that strings
denoting an entire key sequence can be specified, by placing
the key sequence in double quotes.  Some <small>GNU</small> Emacs style key
escapes can be used, as in the following example, but the
special character names are not recognized.
</p>
<div class="example">
<pre class="example">&quot;\C-u&quot;: universal-argument
&quot;\C-x\C-r&quot;: re-read-init-file
&quot;\e[11~&quot;: &quot;Function Key 1&quot;
</pre></div>

<p>In the above example, <kbd>C-u</kbd> is again bound to the function
<code>universal-argument</code> (just as it was in the first example),
&lsquo;<samp><kbd>C-x</kbd> <kbd>C-r</kbd></samp>&rsquo; is bound to the function <code>re-read-init-file</code>,
and &lsquo;<samp><span class="key">ESC</span> <span class="key">[</span> <span class="key">1</span> <span class="key">1</span> <span class="key">~</span></samp>&rsquo; is bound to insert
the text &lsquo;<samp>Function Key 1</samp>&rsquo;.
</p>
</dd>
</dl>

<p>The following <small>GNU</small> Emacs style escape sequences are available when
specifying key sequences:
</p>
<dl compact="compact">
<dt><span><code><kbd>\C-</kbd></code></span></dt>
<dd><p>control prefix
</p></dd>
<dt><span><code><kbd>\M-</kbd></code></span></dt>
<dd><p>meta prefix
</p></dd>
<dt><span><code><kbd>\e</kbd></code></span></dt>
<dd><p>an escape character
</p></dd>
<dt><span><code><kbd>\\</kbd></code></span></dt>
<dd><p>backslash
</p></dd>
<dt><span><code><kbd>\&quot;</kbd></code></span></dt>
<dd><p><tt class="key">&quot;</tt>, a double quotation mark
</p></dd>
<dt><span><code><kbd>\'</kbd></code></span></dt>
<dd><p><tt class="key">'</tt>, a single quote or apostrophe
</p></dd>
</dl>

<p>In addition to the <small>GNU</small> Emacs style escape sequences, a second
set of backslash escapes is available:
</p>
<dl compact="compact">
<dt><span><code>\a</code></span></dt>
<dd><p>alert (bell)
</p></dd>
<dt><span><code>\b</code></span></dt>
<dd><p>backspace
</p></dd>
<dt><span><code>\d</code></span></dt>
<dd><p>delete
</p></dd>
<dt><span><code>\f</code></span></dt>
<dd><p>form feed
</p></dd>
<dt><span><code>\n</code></span></dt>
<dd><p>newline
</p></dd>
<dt><span><code>\r</code></span></dt>
<dd><p>carriage return
</p></dd>
<dt><span><code>\t</code></span></dt>
<dd><p>horizontal tab
</p></dd>
<dt><span><code>\v</code></span></dt>
<dd><p>vertical tab
</p></dd>
<dt><span><code>\<var>nnn</var></code></span></dt>
<dd><p>the eight-bit character whose value is the octal value <var>nnn</var>
(one to three digits)
</p></dd>
<dt><span><code>\x<var>HH</var></code></span></dt>
<dd><p>the eight-bit character whose value is the hexadecimal value <var>HH</var>
(one or two hex digits)
</p></dd>
</dl>

<p>When entering the text of a macro, single or double quotes must
be used to indicate a macro definition.
Unquoted text is assumed to be a function name.
In the macro body, the backslash escapes described above are expanded.
Backslash will quote any other character in the macro text,
including &lsquo;<samp>&quot;</samp>&rsquo; and &lsquo;<samp>'</samp>&rsquo;.
For example, the following binding will make &lsquo;<samp><kbd>C-x</kbd> \</samp>&rsquo;
insert a single &lsquo;<samp>\</samp>&rsquo; into the line:
</p><div class="example">
<pre class="example">&quot;\C-x\\&quot;: &quot;\\&quot;
</pre></div>

</dd>
</dl>

<hr>
</div>
<div class="subsection" id="Conditional-Init-Constructs">
<div class="header">
<p>
Next: <a href="#Sample-Init-File" accesskey="n" rel="next">Sample Init File</a>, Previous: <a href="#Readline-Init-File-Syntax" accesskey="p" rel="prev">Readline Init File Syntax</a>, Up: <a href="#Readline-Init-File" accesskey="u" rel="up">Readline Init File</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Conditional-Init-Constructs-1"></span><h4 class="subsection">8.3.2 Conditional Init Constructs</h4>

<p>Readline implements a facility similar in spirit to the conditional
compilation features of the C preprocessor which allows key
bindings and variable settings to be performed as the result
of tests.  There are four parser directives used.
</p>
<dl compact="compact">
<dt><span><code>$if</code></span></dt>
<dd><p>The <code>$if</code> construct allows bindings to be made based on the
editing mode, the terminal being used, or the application using
Readline.  The text of the test, after any comparison operator,
extends to the end of the line;
unless otherwise noted, no characters are required to isolate it.
</p>
<dl compact="compact">
<dt><span><code>mode</code></span></dt>
<dd><p>The <code>mode=</code> form of the <code>$if</code> directive is used to test
whether Readline is in <code>emacs</code> or <code>vi</code> mode.
This may be used in conjunction
with the &lsquo;<samp>set keymap</samp>&rsquo; command, for instance, to set bindings in
the <code>emacs-standard</code> and <code>emacs-ctlx</code> keymaps only if
Readline is starting out in <code>emacs</code> mode.
</p>
</dd>
<dt><span><code>term</code></span></dt>
<dd><p>The <code>term=</code> form may be used to include terminal-specific
key bindings, perhaps to bind the key sequences output by the
terminal&rsquo;s function keys.  The word on the right side of the
&lsquo;<samp>=</samp>&rsquo; is tested against both the full name of the terminal and
the portion of the terminal name before the first &lsquo;<samp>-</samp>&rsquo;.  This
allows <code>sun</code> to match both <code>sun</code> and <code>sun-cmd</code>,
for instance.
</p>
</dd>
<dt><span><code>version</code></span></dt>
<dd><p>The <code>version</code> test may be used to perform comparisons against
specific Readline versions.
The <code>version</code> expands to the current Readline version.
The set of comparison operators includes
&lsquo;<samp>=</samp>&rsquo; (and &lsquo;<samp>==</samp>&rsquo;), &lsquo;<samp>!=</samp>&rsquo;, &lsquo;<samp>&lt;=</samp>&rsquo;, &lsquo;<samp>&gt;=</samp>&rsquo;, &lsquo;<samp>&lt;</samp>&rsquo;,
and &lsquo;<samp>&gt;</samp>&rsquo;.
The version number supplied on the right side of the operator consists
of a major version number, an optional decimal point, and an optional
minor version (e.g., &lsquo;<samp>7.1</samp>&rsquo;). If the minor version is omitted, it
is assumed to be &lsquo;<samp>0</samp>&rsquo;.
The operator may be separated from the string <code>version</code> and
from the version number argument by whitespace.
The following example sets a variable if the Readline version being used
is 7.0 or newer:
</p><div class="example">
<pre class="example">$if version &gt;= 7.0
set show-mode-in-prompt on
$endif
</pre></div>

</dd>
<dt><span><code>application</code></span></dt>
<dd><p>The <var>application</var> construct is used to include
application-specific settings.  Each program using the Readline
library sets the <var>application name</var>, and you can test for
a particular value. 
This could be used to bind key sequences to functions useful for
a specific program.  For instance, the following command adds a
key sequence that quotes the current or previous word in Bash:
</p><div class="example">
<pre class="example">$if Bash
# Quote the current or previous word
&quot;\C-xq&quot;: &quot;\eb\&quot;\ef\&quot;&quot;
$endif
</pre></div>

</dd>
<dt><span><code>variable</code></span></dt>
<dd><p>The <var>variable</var> construct provides simple equality tests for Readline
variables and values.
The permitted comparison operators are &lsquo;<samp>=</samp>&rsquo;, &lsquo;<samp>==</samp>&rsquo;, and &lsquo;<samp>!=</samp>&rsquo;.
The variable name must be separated from the comparison operator by
whitespace; the operator may be separated from the value on the right hand
side by whitespace.
Both string and boolean variables may be tested. Boolean variables must be
tested against the values <var>on</var> and <var>off</var>.
The following example is equivalent to the <code>mode=emacs</code> test described
above:
</p><div class="example">
<pre class="example">$if editing-mode == emacs
set show-mode-in-prompt on
$endif
</pre></div>
</dd>
</dl>

</dd>
<dt><span><code>$endif</code></span></dt>
<dd><p>This command, as seen in the previous example, terminates an
<code>$if</code> command.
</p>
</dd>
<dt><span><code>$else</code></span></dt>
<dd><p>Commands in this branch of the <code>$if</code> directive are executed if
the test fails.
</p>
</dd>
<dt><span><code>$include</code></span></dt>
<dd><p>This directive takes a single filename as an argument and reads commands
and bindings from that file.
For example, the following directive reads from <samp>/etc/inputrc</samp>:
</p><div class="example">
<pre class="example">$include /etc/inputrc
</pre></div>
</dd>
</dl>

<hr>
</div>
<div class="subsection" id="Sample-Init-File">
<div class="header">
<p>
Previous: <a href="#Conditional-Init-Constructs" accesskey="p" rel="prev">Conditional Init Constructs</a>, Up: <a href="#Readline-Init-File" accesskey="u" rel="up">Readline Init File</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Sample-Init-File-1"></span><h4 class="subsection">8.3.3 Sample Init File</h4>

<p>Here is an example of an <var>inputrc</var> file.  This illustrates key
binding, variable assignment, and conditional syntax.
</p>
<div class="example">
<pre class="example"># This file controls the behaviour of line input editing for
# programs that use the GNU Readline library.  Existing
# programs include FTP, Bash, and GDB.
#
# You can re-read the inputrc file with C-x C-r.
# Lines beginning with '#' are comments.
#
# First, include any system-wide bindings and variable
# assignments from /etc/Inputrc
$include /etc/Inputrc

#
# Set various bindings for emacs mode.

set editing-mode emacs 

$if mode=emacs

Meta-Control-h:	backward-kill-word	Text after the function name is ignored

#
# Arrow keys in keypad mode
#
#&quot;\M-OD&quot;:        backward-char
#&quot;\M-OC&quot;:        forward-char
#&quot;\M-OA&quot;:        previous-history
#&quot;\M-OB&quot;:        next-history
#
# Arrow keys in ANSI mode
#
&quot;\M-[D&quot;:        backward-char
&quot;\M-[C&quot;:        forward-char
&quot;\M-[A&quot;:        previous-history
&quot;\M-[B&quot;:        next-history
#
# Arrow keys in 8 bit keypad mode
#
#&quot;\M-\C-OD&quot;:       backward-char
#&quot;\M-\C-OC&quot;:       forward-char
#&quot;\M-\C-OA&quot;:       previous-history
#&quot;\M-\C-OB&quot;:       next-history
#
# Arrow keys in 8 bit ANSI mode
#
#&quot;\M-\C-[D&quot;:       backward-char
#&quot;\M-\C-[C&quot;:       forward-char
#&quot;\M-\C-[A&quot;:       previous-history
#&quot;\M-\C-[B&quot;:       next-history

C-q: quoted-insert

$endif

# An old-style binding.  This happens to be the default.
TAB: complete

# Macros that are convenient for shell interaction
$if Bash
# edit the path
&quot;\C-xp&quot;: &quot;PATH=${PATH}\e\C-e\C-a\ef\C-f&quot;
# prepare to type a quoted word --
# insert open and close double quotes
# and move to just after the open quote
&quot;\C-x\&quot;&quot;: &quot;\&quot;\&quot;\C-b&quot;
# insert a backslash (testing backslash escapes
# in sequences and macros)
&quot;\C-x\\&quot;: &quot;\\&quot;
# Quote the current or previous word
&quot;\C-xq&quot;: &quot;\eb\&quot;\ef\&quot;&quot;
# Add a binding to refresh the line, which is unbound
&quot;\C-xr&quot;: redraw-current-line
# Edit variable on current line.
&quot;\M-\C-v&quot;: &quot;\C-a\C-k$\C-y\M-\C-e\C-a\C-y=&quot;
$endif

# use a visible bell if one is available
set bell-style visible

# don't strip characters to 7 bits when reading
set input-meta on

# allow iso-latin1 characters to be inserted rather
# than converted to prefix-meta sequences
set convert-meta off

# display characters with the eighth bit set directly
# rather than as meta-prefixed characters
set output-meta on

# if there are 150 or more possible completions for a word,
# ask whether or not the user wants to see all of them
set completion-query-items 150

# For FTP
$if Ftp
&quot;\C-xg&quot;: &quot;get \M-?&quot;
&quot;\C-xt&quot;: &quot;put \M-?&quot;
&quot;\M-.&quot;: yank-last-arg
$endif
</pre></div>

<hr>
</div>
</div>
<div class="section" id="Bindable-Readline-Commands">
<div class="header">
<p>
Next: <a href="#Readline-vi-Mode" accesskey="n" rel="next">Readline vi Mode</a>, Previous: <a href="#Readline-Init-File" accesskey="p" rel="prev">Readline Init File</a>, Up: <a href="#Command-Line-Editing" accesskey="u" rel="up">Command Line Editing</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Bindable-Readline-Commands-1"></span><h3 class="section">8.4 Bindable Readline Commands</h3>


<p>This section describes Readline commands that may be bound to key
sequences.
You can list your key bindings by executing
<code>bind&nbsp;<span class="nolinebreak">-P</span></code><!-- /@w --> or, for a more terse format, suitable for an
<var>inputrc</var> file, <code>bind&nbsp;<span class="nolinebreak">-p</span></code><!-- /@w -->.  (See <a href="#Bash-Builtins">Bash Builtin Commands</a>.)
Command names without an accompanying key sequence are unbound by default.
</p>
<p>In the following descriptions, <em>point</em> refers to the current cursor
position, and <em>mark</em> refers to a cursor position saved by the
<code>set-mark</code> command.
The text between the point and mark is referred to as the <em>region</em>.
</p>
<ul class="section-toc">
<li><a href="#Commands-For-Moving" accesskey="1">Commands For Moving</a></li>
<li><a href="#Commands-For-History" accesskey="2">Commands For Manipulating The History</a></li>
<li><a href="#Commands-For-Text" accesskey="3">Commands For Changing Text</a></li>
<li><a href="#Commands-For-Killing" accesskey="4">Killing And Yanking</a></li>
<li><a href="#Numeric-Arguments" accesskey="5">Specifying Numeric Arguments</a></li>
<li><a href="#Commands-For-Completion" accesskey="6">Letting Readline Type For You</a></li>
<li><a href="#Keyboard-Macros" accesskey="7">Keyboard Macros</a></li>
<li><a href="#Miscellaneous-Commands" accesskey="8">Some Miscellaneous Commands</a></li>
</ul>
<hr>
<div class="subsection" id="Commands-For-Moving">
<div class="header">
<p>
Next: <a href="#Commands-For-History" accesskey="n" rel="next">Commands For Manipulating The History</a>, Up: <a href="#Bindable-Readline-Commands" accesskey="u" rel="up">Bindable Readline Commands</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Commands-For-Moving-1"></span><h4 class="subsection">8.4.1 Commands For Moving</h4>
<dl compact="compact">
<dt id='index-beginning_002dof_002dline-_0028C_002da_0029'><span><code>beginning-of-line (C-a)</code><a href='#index-beginning_002dof_002dline-_0028C_002da_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Move to the start of the current line.
</p>
</dd>
<dt id='index-end_002dof_002dline-_0028C_002de_0029'><span><code>end-of-line (C-e)</code><a href='#index-end_002dof_002dline-_0028C_002de_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Move to the end of the line.
</p>
</dd>
<dt id='index-forward_002dchar-_0028C_002df_0029'><span><code>forward-char (C-f)</code><a href='#index-forward_002dchar-_0028C_002df_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Move forward a character.
</p>
</dd>
<dt id='index-backward_002dchar-_0028C_002db_0029'><span><code>backward-char (C-b)</code><a href='#index-backward_002dchar-_0028C_002db_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Move back a character.
</p>
</dd>
<dt id='index-forward_002dword-_0028M_002df_0029'><span><code>forward-word (M-f)</code><a href='#index-forward_002dword-_0028M_002df_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Move forward to the end of the next word.
Words are composed of letters and digits.
</p>
</dd>
<dt id='index-backward_002dword-_0028M_002db_0029'><span><code>backward-word (M-b)</code><a href='#index-backward_002dword-_0028M_002db_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Move back to the start of the current or previous word.
Words are composed of letters and digits.
</p>
</dd>
<dt id='index-shell_002dforward_002dword-_0028M_002dC_002df_0029'><span><code>shell-forward-word (M-C-f)</code><a href='#index-shell_002dforward_002dword-_0028M_002dC_002df_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Move forward to the end of the next word.
Words are delimited by non-quoted shell metacharacters.
</p>
</dd>
<dt id='index-shell_002dbackward_002dword-_0028M_002dC_002db_0029'><span><code>shell-backward-word (M-C-b)</code><a href='#index-shell_002dbackward_002dword-_0028M_002dC_002db_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Move back to the start of the current or previous word.
Words are delimited by non-quoted shell metacharacters.
</p>
</dd>
<dt id='index-previous_002dscreen_002dline-_0028_0029'><span><code>previous-screen-line ()</code><a href='#index-previous_002dscreen_002dline-_0028_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Attempt to move point to the same physical screen column on the previous
physical screen line. This will not have the desired effect if the current
Readline line does not take up more than one physical line or if point is not
greater than the length of the prompt plus the screen width.
</p>
</dd>
<dt id='index-next_002dscreen_002dline-_0028_0029'><span><code>next-screen-line ()</code><a href='#index-next_002dscreen_002dline-_0028_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Attempt to move point to the same physical screen column on the next
physical screen line. This will not have the desired effect if the current
Readline line does not take up more than one physical line or if the length
of the current Readline line is not greater than the length of the prompt
plus the screen width.
</p>
</dd>
<dt id='index-clear_002ddisplay-_0028M_002dC_002dl_0029'><span><code>clear-display (M-C-l)</code><a href='#index-clear_002ddisplay-_0028M_002dC_002dl_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Clear the screen and, if possible, the terminal&rsquo;s scrollback buffer,
then redraw the current line,
leaving the current line at the top of the screen.
</p>
</dd>
<dt id='index-clear_002dscreen-_0028C_002dl_0029'><span><code>clear-screen (C-l)</code><a href='#index-clear_002dscreen-_0028C_002dl_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Clear the screen,
then redraw the current line,
leaving the current line at the top of the screen.
</p>
</dd>
<dt id='index-redraw_002dcurrent_002dline-_0028_0029'><span><code>redraw-current-line ()</code><a href='#index-redraw_002dcurrent_002dline-_0028_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Refresh the current line.  By default, this is unbound.
</p>
</dd>
</dl>

<hr>
</div>
<div class="subsection" id="Commands-For-History">
<div class="header">
<p>
Next: <a href="#Commands-For-Text" accesskey="n" rel="next">Commands For Changing Text</a>, Previous: <a href="#Commands-For-Moving" accesskey="p" rel="prev">Commands For Moving</a>, Up: <a href="#Bindable-Readline-Commands" accesskey="u" rel="up">Bindable Readline Commands</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Commands-For-Manipulating-The-History"></span><h4 class="subsection">8.4.2 Commands For Manipulating The History</h4>

<dl compact="compact">
<dt id='index-accept_002dline-_0028Newline-or-Return_0029'><span><code>accept-line (Newline or Return)</code><a href='#index-accept_002dline-_0028Newline-or-Return_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Accept the line regardless of where the cursor is.
If this line is
non-empty, add it to the history list according to the setting of
the <code>HISTCONTROL</code> and <code>HISTIGNORE</code> variables.
If this line is a modified history line, then restore the history line
to its original state.
</p>
</dd>
<dt id='index-previous_002dhistory-_0028C_002dp_0029'><span><code>previous-history (C-p)</code><a href='#index-previous_002dhistory-_0028C_002dp_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Move &lsquo;back&rsquo; through the history list, fetching the previous command.
</p>
</dd>
<dt id='index-next_002dhistory-_0028C_002dn_0029'><span><code>next-history (C-n)</code><a href='#index-next_002dhistory-_0028C_002dn_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Move &lsquo;forward&rsquo; through the history list, fetching the next command.
</p>
</dd>
<dt id='index-beginning_002dof_002dhistory-_0028M_002d_003c_0029'><span><code>beginning-of-history (M-&lt;)</code><a href='#index-beginning_002dof_002dhistory-_0028M_002d_003c_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Move to the first line in the history.
</p>
</dd>
<dt id='index-end_002dof_002dhistory-_0028M_002d_003e_0029'><span><code>end-of-history (M-&gt;)</code><a href='#index-end_002dof_002dhistory-_0028M_002d_003e_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Move to the end of the input history, i.e., the line currently
being entered.
</p>
</dd>
<dt id='index-reverse_002dsearch_002dhistory-_0028C_002dr_0029'><span><code>reverse-search-history (C-r)</code><a href='#index-reverse_002dsearch_002dhistory-_0028C_002dr_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Search backward starting at the current line and moving &lsquo;up&rsquo; through
the history as necessary.  This is an incremental search.
This command sets the region to the matched text and activates the mark.
</p>
</dd>
<dt id='index-forward_002dsearch_002dhistory-_0028C_002ds_0029'><span><code>forward-search-history (C-s)</code><a href='#index-forward_002dsearch_002dhistory-_0028C_002ds_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Search forward starting at the current line and moving &lsquo;down&rsquo; through
the history as necessary.  This is an incremental search.
This command sets the region to the matched text and activates the mark.
</p>
</dd>
<dt id='index-non_002dincremental_002dreverse_002dsearch_002dhistory-_0028M_002dp_0029'><span><code>non-incremental-reverse-search-history (M-p)</code><a href='#index-non_002dincremental_002dreverse_002dsearch_002dhistory-_0028M_002dp_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Search backward starting at the current line and moving &lsquo;up&rsquo;
through the history as necessary using a non-incremental search
for a string supplied by the user.
The search string may match anywhere in a history line.
</p>
</dd>
<dt id='index-non_002dincremental_002dforward_002dsearch_002dhistory-_0028M_002dn_0029'><span><code>non-incremental-forward-search-history (M-n)</code><a href='#index-non_002dincremental_002dforward_002dsearch_002dhistory-_0028M_002dn_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Search forward starting at the current line and moving &lsquo;down&rsquo;
through the history as necessary using a non-incremental search
for a string supplied by the user.
The search string may match anywhere in a history line.
</p>
</dd>
<dt id='index-history_002dsearch_002dforward-_0028_0029'><span><code>history-search-forward ()</code><a href='#index-history_002dsearch_002dforward-_0028_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Search forward through the history for the string of characters
between the start of the current line and the point.
The search string must match at the beginning of a history line.
This is a non-incremental search.
By default, this command is unbound.
</p>
</dd>
<dt id='index-history_002dsearch_002dbackward-_0028_0029'><span><code>history-search-backward ()</code><a href='#index-history_002dsearch_002dbackward-_0028_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Search backward through the history for the string of characters
between the start of the current line and the point.
The search string must match at the beginning of a history line.
This is a non-incremental search.
By default, this command is unbound.
</p>
</dd>
<dt id='index-history_002dsubstring_002dsearch_002dforward-_0028_0029'><span><code>history-substring-search-forward ()</code><a href='#index-history_002dsubstring_002dsearch_002dforward-_0028_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Search forward through the history for the string of characters
between the start of the current line and the point.
The search string may match anywhere in a history line.
This is a non-incremental search.
By default, this command is unbound.
</p>
</dd>
<dt id='index-history_002dsubstring_002dsearch_002dbackward-_0028_0029'><span><code>history-substring-search-backward ()</code><a href='#index-history_002dsubstring_002dsearch_002dbackward-_0028_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Search backward through the history for the string of characters
between the start of the current line and the point.
The search string may match anywhere in a history line.
This is a non-incremental search.
By default, this command is unbound.
</p>
</dd>
<dt id='index-yank_002dnth_002darg-_0028M_002dC_002dy_0029'><span><code>yank-nth-arg (M-C-y)</code><a href='#index-yank_002dnth_002darg-_0028M_002dC_002dy_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Insert the first argument to the previous command (usually
the second word on the previous line) at point.
With an argument <var>n</var>,
insert the <var>n</var>th word from the previous command (the words
in the previous command begin with word 0).  A negative argument
inserts the <var>n</var>th word from the end of the previous command.
Once the argument <var>n</var> is computed, the argument is extracted
as if the &lsquo;<samp>!<var>n</var></samp>&rsquo; history expansion had been specified.
</p>
</dd>
<dt id='index-yank_002dlast_002darg-_0028M_002d_002e-or-M_002d_005f_0029'><span><code>yank-last-arg (M-. or M-_)</code><a href='#index-yank_002dlast_002darg-_0028M_002d_002e-or-M_002d_005f_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Insert last argument to the previous command (the last word of the
previous history entry).
With a numeric argument, behave exactly like <code>yank-nth-arg</code>.
Successive calls to <code>yank-last-arg</code> move back through the history
list, inserting the last word (or the word specified by the argument to
the first call) of each line in turn.
Any numeric argument supplied to these successive calls determines
the direction to move through the history.  A negative argument switches
the direction through the history (back or forward).
The history expansion facilities are used to extract the last argument,
as if the &lsquo;<samp>!$</samp>&rsquo; history expansion had been specified.
</p>
</dd>
<dt id='index-operate_002dand_002dget_002dnext-_0028C_002do_0029'><span><code>operate-and-get-next (C-o)</code><a href='#index-operate_002dand_002dget_002dnext-_0028C_002do_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Accept the current line for return to the calling application as if a
newline had been entered,
and fetch the next line relative to the current line from the history
for editing.
A numeric argument, if supplied, specifies the history entry to use instead
of the current line.
</p>
</dd>
<dt id='index-fetch_002dhistory-_0028_0029'><span><code>fetch-history ()</code><a href='#index-fetch_002dhistory-_0028_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>With a numeric argument, fetch that entry from the history list
and make it the current line.
Without an argument, move back to the first entry in the history list.
</p>
</dd>
</dl>

<hr>
</div>
<div class="subsection" id="Commands-For-Text">
<div class="header">
<p>
Next: <a href="#Commands-For-Killing" accesskey="n" rel="next">Killing And Yanking</a>, Previous: <a href="#Commands-For-History" accesskey="p" rel="prev">Commands For Manipulating The History</a>, Up: <a href="#Bindable-Readline-Commands" accesskey="u" rel="up">Bindable Readline Commands</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Commands-For-Changing-Text"></span><h4 class="subsection">8.4.3 Commands For Changing Text</h4>

<dl compact="compact">
<dt id='index-end_002dof_002dfile-_0028usually-C_002dd_0029'><span><code><i>end-of-file</i> (usually C-d)</code><a href='#index-end_002dof_002dfile-_0028usually-C_002dd_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The character indicating end-of-file as set, for example, by
<code>stty</code>.  If this character is read when there are no characters
on the line, and point is at the beginning of the line, Readline
interprets it as the end of input and returns <small>EOF</small>.
</p>
</dd>
<dt id='index-delete_002dchar-_0028C_002dd_0029'><span><code>delete-char (C-d)</code><a href='#index-delete_002dchar-_0028C_002dd_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Delete the character at point.  If this function is bound to the
same character as the tty <small>EOF</small> character, as <kbd>C-d</kbd>
commonly is, see above for the effects.
</p>
</dd>
<dt id='index-backward_002ddelete_002dchar-_0028Rubout_0029'><span><code>backward-delete-char (Rubout)</code><a href='#index-backward_002ddelete_002dchar-_0028Rubout_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Delete the character behind the cursor.  A numeric argument means
to kill the characters instead of deleting them.
</p>
</dd>
<dt id='index-forward_002dbackward_002ddelete_002dchar-_0028_0029'><span><code>forward-backward-delete-char ()</code><a href='#index-forward_002dbackward_002ddelete_002dchar-_0028_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Delete the character under the cursor, unless the cursor is at the
end of the line, in which case the character behind the cursor is
deleted.  By default, this is not bound to a key.
</p>
</dd>
<dt id='index-quoted_002dinsert-_0028C_002dq-or-C_002dv_0029'><span><code>quoted-insert (C-q or C-v)</code><a href='#index-quoted_002dinsert-_0028C_002dq-or-C_002dv_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Add the next character typed to the line verbatim.  This is
how to insert key sequences like <kbd>C-q</kbd>, for example.
</p>

</dd>
<dt id='index-self_002dinsert-_0028a_002c-b_002c-A_002c-1_002c-_0021_002c-_2026_0029'><span><code>self-insert (a, b, A, 1, !, &hellip;)</code><a href='#index-self_002dinsert-_0028a_002c-b_002c-A_002c-1_002c-_0021_002c-_2026_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Insert yourself.
</p>
</dd>
<dt id='index-bracketed_002dpaste_002dbegin-_0028_0029'><span><code>bracketed-paste-begin ()</code><a href='#index-bracketed_002dpaste_002dbegin-_0028_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>This function is intended to be bound to the &quot;bracketed paste&quot; escape
sequence sent by some terminals, and such a binding is assigned by default.
It allows Readline to insert the pasted text as a single unit without treating
each character as if it had been read from the keyboard.  The characters
are inserted as if each one was bound to <code>self-insert</code> instead of
executing any editing commands.
</p>
<p>Bracketed paste sets the region (the characters between point and the mark)
to the inserted text. It uses the concept of an <em>active mark</em>: when the
mark is active, Readline redisplay uses the terminal&rsquo;s standout mode to
denote the region.
</p>
</dd>
<dt id='index-transpose_002dchars-_0028C_002dt_0029'><span><code>transpose-chars (C-t)</code><a href='#index-transpose_002dchars-_0028C_002dt_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Drag the character before the cursor forward over
the character at the cursor, moving the
cursor forward as well.  If the insertion point
is at the end of the line, then this
transposes the last two characters of the line.
Negative arguments have no effect.
</p>
</dd>
<dt id='index-transpose_002dwords-_0028M_002dt_0029'><span><code>transpose-words (M-t)</code><a href='#index-transpose_002dwords-_0028M_002dt_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Drag the word before point past the word after point,
moving point past that word as well.
If the insertion point is at the end of the line, this transposes
the last two words on the line.
</p>
</dd>
<dt id='index-upcase_002dword-_0028M_002du_0029'><span><code>upcase-word (M-u)</code><a href='#index-upcase_002dword-_0028M_002du_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Uppercase the current (or following) word.  With a negative argument,
uppercase the previous word, but do not move the cursor.
</p>
</dd>
<dt id='index-downcase_002dword-_0028M_002dl_0029'><span><code>downcase-word (M-l)</code><a href='#index-downcase_002dword-_0028M_002dl_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Lowercase the current (or following) word.  With a negative argument,
lowercase the previous word, but do not move the cursor.
</p>
</dd>
<dt id='index-capitalize_002dword-_0028M_002dc_0029'><span><code>capitalize-word (M-c)</code><a href='#index-capitalize_002dword-_0028M_002dc_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Capitalize the current (or following) word.  With a negative argument,
capitalize the previous word, but do not move the cursor.
</p>
</dd>
<dt id='index-overwrite_002dmode-_0028_0029'><span><code>overwrite-mode ()</code><a href='#index-overwrite_002dmode-_0028_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Toggle overwrite mode.  With an explicit positive numeric argument,
switches to overwrite mode.  With an explicit non-positive numeric
argument, switches to insert mode.  This command affects only
<code>emacs</code> mode; <code>vi</code> mode does overwrite differently.
Each call to <code>readline()</code> starts in insert mode.
</p>
<p>In overwrite mode, characters bound to <code>self-insert</code> replace
the text at point rather than pushing the text to the right.
Characters bound to <code>backward-delete-char</code> replace the character
before point with a space.
</p>
<p>By default, this command is unbound.
</p>
</dd>
</dl>

<hr>
</div>
<div class="subsection" id="Commands-For-Killing">
<div class="header">
<p>
Next: <a href="#Numeric-Arguments" accesskey="n" rel="next">Specifying Numeric Arguments</a>, Previous: <a href="#Commands-For-Text" accesskey="p" rel="prev">Commands For Changing Text</a>, Up: <a href="#Bindable-Readline-Commands" accesskey="u" rel="up">Bindable Readline Commands</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Killing-And-Yanking"></span><h4 class="subsection">8.4.4 Killing And Yanking</h4>

<dl compact="compact">
<dt id='index-kill_002dline-_0028C_002dk_0029'><span><code>kill-line (C-k)</code><a href='#index-kill_002dline-_0028C_002dk_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Kill the text from point to the end of the line.
With a negative numeric argument, kill backward from the cursor to the
beginning of the current line.
</p>
</dd>
<dt id='index-backward_002dkill_002dline-_0028C_002dx-Rubout_0029'><span><code>backward-kill-line (C-x Rubout)</code><a href='#index-backward_002dkill_002dline-_0028C_002dx-Rubout_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Kill backward from the cursor to the beginning of the current line.
With a negative numeric argument, kill forward from the cursor to the
end of the current line.
</p>
</dd>
<dt id='index-unix_002dline_002ddiscard-_0028C_002du_0029'><span><code>unix-line-discard (C-u)</code><a href='#index-unix_002dline_002ddiscard-_0028C_002du_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Kill backward from the cursor to the beginning of the current line.
</p>
</dd>
<dt id='index-kill_002dwhole_002dline-_0028_0029'><span><code>kill-whole-line ()</code><a href='#index-kill_002dwhole_002dline-_0028_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Kill all characters on the current line, no matter where point is.
By default, this is unbound.
</p>
</dd>
<dt id='index-kill_002dword-_0028M_002dd_0029'><span><code>kill-word (M-d)</code><a href='#index-kill_002dword-_0028M_002dd_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Kill from point to the end of the current word, or if between
words, to the end of the next word.
Word boundaries are the same as <code>forward-word</code>.
</p>
</dd>
<dt id='index-backward_002dkill_002dword-_0028M_002dDEL_0029'><span><code>backward-kill-word (M-<span class="key">DEL</span>)</code><a href='#index-backward_002dkill_002dword-_0028M_002dDEL_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Kill the word behind point.
Word boundaries are the same as <code>backward-word</code>.
</p>
</dd>
<dt id='index-shell_002dkill_002dword-_0028M_002dC_002dd_0029'><span><code>shell-kill-word (M-C-d)</code><a href='#index-shell_002dkill_002dword-_0028M_002dC_002dd_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Kill from point to the end of the current word, or if between
words, to the end of the next word.
Word boundaries are the same as <code>shell-forward-word</code>.
</p>
</dd>
<dt id='index-shell_002dbackward_002dkill_002dword-_0028_0029'><span><code>shell-backward-kill-word ()</code><a href='#index-shell_002dbackward_002dkill_002dword-_0028_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Kill the word behind point.
Word boundaries are the same as <code>shell-backward-word</code>.
</p>
</dd>
<dt id='index-shell_002dtranspose_002dwords-_0028M_002dC_002dt_0029'><span><code>shell-transpose-words (M-C-t)</code><a href='#index-shell_002dtranspose_002dwords-_0028M_002dC_002dt_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Drag the word before point past the word after point,
moving point past that word as well.
If the insertion point is at the end of the line, this transposes
the last two words on the line.
Word boundaries are the same as <code>shell-forward-word</code> and
<code>shell-backward-word</code>.
</p>
</dd>
<dt id='index-unix_002dword_002drubout-_0028C_002dw_0029'><span><code>unix-word-rubout (C-w)</code><a href='#index-unix_002dword_002drubout-_0028C_002dw_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Kill the word behind point, using white space as a word boundary.
The killed text is saved on the kill-ring.
</p>
</dd>
<dt id='index-unix_002dfilename_002drubout-_0028_0029'><span><code>unix-filename-rubout ()</code><a href='#index-unix_002dfilename_002drubout-_0028_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Kill the word behind point, using white space and the slash character
as the word boundaries.
The killed text is saved on the kill-ring.
</p>
</dd>
<dt id='index-delete_002dhorizontal_002dspace-_0028_0029'><span><code>delete-horizontal-space ()</code><a href='#index-delete_002dhorizontal_002dspace-_0028_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Delete all spaces and tabs around point.  By default, this is unbound.
</p>
</dd>
<dt id='index-kill_002dregion-_0028_0029'><span><code>kill-region ()</code><a href='#index-kill_002dregion-_0028_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Kill the text in the current region.
By default, this command is unbound.
</p>
</dd>
<dt id='index-copy_002dregion_002das_002dkill-_0028_0029'><span><code>copy-region-as-kill ()</code><a href='#index-copy_002dregion_002das_002dkill-_0028_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Copy the text in the region to the kill buffer, so it can be yanked
right away.  By default, this command is unbound.
</p>
</dd>
<dt id='index-copy_002dbackward_002dword-_0028_0029'><span><code>copy-backward-word ()</code><a href='#index-copy_002dbackward_002dword-_0028_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Copy the word before point to the kill buffer.
The word boundaries are the same as <code>backward-word</code>.
By default, this command is unbound.
</p>
</dd>
<dt id='index-copy_002dforward_002dword-_0028_0029'><span><code>copy-forward-word ()</code><a href='#index-copy_002dforward_002dword-_0028_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Copy the word following point to the kill buffer.
The word boundaries are the same as <code>forward-word</code>.
By default, this command is unbound.
</p>
</dd>
<dt id='index-yank-_0028C_002dy_0029'><span><code>yank (C-y)</code><a href='#index-yank-_0028C_002dy_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Yank the top of the kill ring into the buffer at point.
</p>
</dd>
<dt id='index-yank_002dpop-_0028M_002dy_0029'><span><code>yank-pop (M-y)</code><a href='#index-yank_002dpop-_0028M_002dy_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Rotate the kill-ring, and yank the new top.  You can only do this if
the prior command is <code>yank</code> or <code>yank-pop</code>.
</p></dd>
</dl>

<hr>
</div>
<div class="subsection" id="Numeric-Arguments">
<div class="header">
<p>
Next: <a href="#Commands-For-Completion" accesskey="n" rel="next">Letting Readline Type For You</a>, Previous: <a href="#Commands-For-Killing" accesskey="p" rel="prev">Killing And Yanking</a>, Up: <a href="#Bindable-Readline-Commands" accesskey="u" rel="up">Bindable Readline Commands</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Specifying-Numeric-Arguments"></span><h4 class="subsection">8.4.5 Specifying Numeric Arguments</h4>
<dl compact="compact">
<dt id='index-digit_002dargument-_0028M_002d0_002c-M_002d1_002c-_2026-M_002d_002d_0029'><span><code>digit-argument (<kbd>M-0</kbd>, <kbd>M-1</kbd>, &hellip; <kbd>M--</kbd>)</code><a href='#index-digit_002dargument-_0028M_002d0_002c-M_002d1_002c-_2026-M_002d_002d_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Add this digit to the argument already accumulating, or start a new
argument.  <kbd>M--</kbd> starts a negative argument.
</p>
</dd>
<dt id='index-universal_002dargument-_0028_0029'><span><code>universal-argument ()</code><a href='#index-universal_002dargument-_0028_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>This is another way to specify an argument.
If this command is followed by one or more digits, optionally with a
leading minus sign, those digits define the argument.
If the command is followed by digits, executing <code>universal-argument</code>
again ends the numeric argument, but is otherwise ignored.
As a special case, if this command is immediately followed by a
character that is neither a digit nor minus sign, the argument count
for the next command is multiplied by four.
The argument count is initially one, so executing this function the
first time makes the argument count four, a second time makes the
argument count sixteen, and so on.
By default, this is not bound to a key.
</p></dd>
</dl>

<hr>
</div>
<div class="subsection" id="Commands-For-Completion">
<div class="header">
<p>
Next: <a href="#Keyboard-Macros" accesskey="n" rel="next">Keyboard Macros</a>, Previous: <a href="#Numeric-Arguments" accesskey="p" rel="prev">Specifying Numeric Arguments</a>, Up: <a href="#Bindable-Readline-Commands" accesskey="u" rel="up">Bindable Readline Commands</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Letting-Readline-Type-For-You"></span><h4 class="subsection">8.4.6 Letting Readline Type For You</h4>

<dl compact="compact">
<dt id='index-complete-_0028TAB_0029'><span><code>complete (<span class="key">TAB</span>)</code><a href='#index-complete-_0028TAB_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Attempt to perform completion on the text before point.
The actual completion performed is application-specific.
Bash attempts completion treating the text as a variable (if the
text begins with &lsquo;<samp>$</samp>&rsquo;), username (if the text begins with
&lsquo;<samp>~</samp>&rsquo;), hostname (if the text begins with &lsquo;<samp>@</samp>&rsquo;), or
command (including aliases and functions) in turn.  If none 
of these produces a match, filename completion is attempted.
</p>
</dd>
<dt id='index-possible_002dcompletions-_0028M_002d_003f_0029'><span><code>possible-completions (M-?)</code><a href='#index-possible_002dcompletions-_0028M_002d_003f_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>List the possible completions of the text before point.
When displaying completions, Readline sets the number of columns used
for display to the value of <code>completion-display-width</code>, the value of
the environment variable <code>COLUMNS</code>, or the screen width, in that order.
</p>
</dd>
<dt id='index-insert_002dcompletions-_0028M_002d_002a_0029'><span><code>insert-completions (M-*)</code><a href='#index-insert_002dcompletions-_0028M_002d_002a_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Insert all completions of the text before point that would have
been generated by <code>possible-completions</code>.
</p>
</dd>
<dt id='index-menu_002dcomplete-_0028_0029'><span><code>menu-complete ()</code><a href='#index-menu_002dcomplete-_0028_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Similar to <code>complete</code>, but replaces the word to be completed
with a single match from the list of possible completions.
Repeated execution of <code>menu-complete</code> steps through the list
of possible completions, inserting each match in turn.
At the end of the list of completions, the bell is rung
(subject to the setting of <code>bell-style</code>)
and the original text is restored.
An argument of <var>n</var> moves <var>n</var> positions forward in the list
of matches; a negative argument may be used to move backward
through the list.
This command is intended to be bound to <tt class="key">TAB</tt>, but is unbound
by default.
</p>
</dd>
<dt id='index-menu_002dcomplete_002dbackward-_0028_0029'><span><code>menu-complete-backward ()</code><a href='#index-menu_002dcomplete_002dbackward-_0028_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Identical to <code>menu-complete</code>, but moves backward through the list
of possible completions, as if <code>menu-complete</code> had been given a
negative argument.
</p>
</dd>
<dt id='index-delete_002dchar_002dor_002dlist-_0028_0029'><span><code>delete-char-or-list ()</code><a href='#index-delete_002dchar_002dor_002dlist-_0028_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Deletes the character under the cursor if not at the beginning or
end of the line (like <code>delete-char</code>).
If at the end of the line, behaves identically to
<code>possible-completions</code>.
This command is unbound by default.
</p>
</dd>
<dt id='index-complete_002dfilename-_0028M_002d_002f_0029'><span><code>complete-filename (M-/)</code><a href='#index-complete_002dfilename-_0028M_002d_002f_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Attempt filename completion on the text before point.
</p>
</dd>
<dt id='index-possible_002dfilename_002dcompletions-_0028C_002dx-_002f_0029'><span><code>possible-filename-completions (C-x /)</code><a href='#index-possible_002dfilename_002dcompletions-_0028C_002dx-_002f_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>List the possible completions of the text before point,
treating it as a filename.
</p>
</dd>
<dt id='index-complete_002dusername-_0028M_002d_007e_0029'><span><code>complete-username (M-~)</code><a href='#index-complete_002dusername-_0028M_002d_007e_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Attempt completion on the text before point, treating
it as a username.
</p>
</dd>
<dt id='index-possible_002dusername_002dcompletions-_0028C_002dx-_007e_0029'><span><code>possible-username-completions (C-x ~)</code><a href='#index-possible_002dusername_002dcompletions-_0028C_002dx-_007e_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>List the possible completions of the text before point,
treating it as a username.
</p>
</dd>
<dt id='index-complete_002dvariable-_0028M_002d_0024_0029'><span><code>complete-variable (M-$)</code><a href='#index-complete_002dvariable-_0028M_002d_0024_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Attempt completion on the text before point, treating
it as a shell variable.
</p>
</dd>
<dt id='index-possible_002dvariable_002dcompletions-_0028C_002dx-_0024_0029'><span><code>possible-variable-completions (C-x $)</code><a href='#index-possible_002dvariable_002dcompletions-_0028C_002dx-_0024_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>List the possible completions of the text before point,
treating it as a shell variable.
</p>
</dd>
<dt id='index-complete_002dhostname-_0028M_002d_0040_0029'><span><code>complete-hostname (M-@)</code><a href='#index-complete_002dhostname-_0028M_002d_0040_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Attempt completion on the text before point, treating
it as a hostname.
</p>
</dd>
<dt id='index-possible_002dhostname_002dcompletions-_0028C_002dx-_0040_0029'><span><code>possible-hostname-completions (C-x @)</code><a href='#index-possible_002dhostname_002dcompletions-_0028C_002dx-_0040_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>List the possible completions of the text before point,
treating it as a hostname.
</p>
</dd>
<dt id='index-complete_002dcommand-_0028M_002d_0021_0029'><span><code>complete-command (M-!)</code><a href='#index-complete_002dcommand-_0028M_002d_0021_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Attempt completion on the text before point, treating
it as a command name.  Command completion attempts to
match the text against aliases, reserved words, shell
functions, shell builtins, and finally executable filenames,
in that order.
</p>
</dd>
<dt id='index-possible_002dcommand_002dcompletions-_0028C_002dx-_0021_0029'><span><code>possible-command-completions (C-x !)</code><a href='#index-possible_002dcommand_002dcompletions-_0028C_002dx-_0021_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>List the possible completions of the text before point,
treating it as a command name.
</p>
</dd>
<dt id='index-dynamic_002dcomplete_002dhistory-_0028M_002dTAB_0029'><span><code>dynamic-complete-history (M-<span class="key">TAB</span>)</code><a href='#index-dynamic_002dcomplete_002dhistory-_0028M_002dTAB_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Attempt completion on the text before point, comparing
the text against lines from the history list for possible
completion matches.
</p>
</dd>
<dt id='index-dabbrev_002dexpand-_0028_0029'><span><code>dabbrev-expand ()</code><a href='#index-dabbrev_002dexpand-_0028_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Attempt menu completion on the text before point, comparing
the text against lines from the history list for possible
completion matches.
</p>
</dd>
<dt id='index-complete_002dinto_002dbraces-_0028M_002d_007b_0029'><span><code>complete-into-braces (M-{)</code><a href='#index-complete_002dinto_002dbraces-_0028M_002d_007b_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Perform filename completion and insert the list of possible completions
enclosed within braces so the list is available to the shell
(see <a href="#Brace-Expansion">Brace Expansion</a>).
</p>
</dd>
</dl>

<hr>
</div>
<div class="subsection" id="Keyboard-Macros">
<div class="header">
<p>
Next: <a href="#Miscellaneous-Commands" accesskey="n" rel="next">Some Miscellaneous Commands</a>, Previous: <a href="#Commands-For-Completion" accesskey="p" rel="prev">Letting Readline Type For You</a>, Up: <a href="#Bindable-Readline-Commands" accesskey="u" rel="up">Bindable Readline Commands</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Keyboard-Macros-1"></span><h4 class="subsection">8.4.7 Keyboard Macros</h4>
<dl compact="compact">
<dt id='index-start_002dkbd_002dmacro-_0028C_002dx-_0028_0029'><span><code>start-kbd-macro (C-x ()</code><a href='#index-start_002dkbd_002dmacro-_0028C_002dx-_0028_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Begin saving the characters typed into the current keyboard macro.
</p>
</dd>
<dt id='index-end_002dkbd_002dmacro-_0028C_002dx-_0029_0029'><span><code>end-kbd-macro (C-x ))</code><a href='#index-end_002dkbd_002dmacro-_0028C_002dx-_0029_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Stop saving the characters typed into the current keyboard macro
and save the definition.
</p>
</dd>
<dt id='index-call_002dlast_002dkbd_002dmacro-_0028C_002dx-e_0029'><span><code>call-last-kbd-macro (C-x e)</code><a href='#index-call_002dlast_002dkbd_002dmacro-_0028C_002dx-e_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Re-execute the last keyboard macro defined, by making the characters
in the macro appear as if typed at the keyboard.
</p>
</dd>
<dt id='index-print_002dlast_002dkbd_002dmacro-_0028_0029'><span><code>print-last-kbd-macro ()</code><a href='#index-print_002dlast_002dkbd_002dmacro-_0028_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Print the last keyboard macro defined in a format suitable for the
<var>inputrc</var> file.
</p>
</dd>
</dl>

<hr>
</div>
<div class="subsection" id="Miscellaneous-Commands">
<div class="header">
<p>
Previous: <a href="#Keyboard-Macros" accesskey="p" rel="prev">Keyboard Macros</a>, Up: <a href="#Bindable-Readline-Commands" accesskey="u" rel="up">Bindable Readline Commands</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Some-Miscellaneous-Commands"></span><h4 class="subsection">8.4.8 Some Miscellaneous Commands</h4>
<dl compact="compact">
<dt id='index-re_002dread_002dinit_002dfile-_0028C_002dx-C_002dr_0029'><span><code>re-read-init-file (C-x C-r)</code><a href='#index-re_002dread_002dinit_002dfile-_0028C_002dx-C_002dr_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Read in the contents of the <var>inputrc</var> file, and incorporate
any bindings or variable assignments found there.
</p>
</dd>
<dt id='index-abort-_0028C_002dg_0029'><span><code>abort (C-g)</code><a href='#index-abort-_0028C_002dg_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Abort the current editing command and
ring the terminal&rsquo;s bell (subject to the setting of
<code>bell-style</code>).
</p>
</dd>
<dt id='index-do_002dlowercase_002dversion-_0028M_002dA_002c-M_002dB_002c-M_002dx_002c-_2026_0029'><span><code>do-lowercase-version (M-A, M-B, M-<var>x</var>, &hellip;)</code><a href='#index-do_002dlowercase_002dversion-_0028M_002dA_002c-M_002dB_002c-M_002dx_002c-_2026_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>If the metafied character <var>x</var> is upper case, run the command
that is bound to the corresponding metafied lower case character.
The behavior is undefined if <var>x</var> is already lower case.
</p>
</dd>
<dt id='index-prefix_002dmeta-_0028ESC_0029'><span><code>prefix-meta (<span class="key">ESC</span>)</code><a href='#index-prefix_002dmeta-_0028ESC_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Metafy the next character typed.  This is for keyboards
without a meta key.  Typing &lsquo;<samp><span class="key">ESC</span> f</samp>&rsquo; is equivalent to typing
<kbd>M-f</kbd>.
</p>
</dd>
<dt id='index-undo-_0028C_002d_005f-or-C_002dx-C_002du_0029'><span><code>undo (C-_ or C-x C-u)</code><a href='#index-undo-_0028C_002d_005f-or-C_002dx-C_002du_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Incremental undo, separately remembered for each line.
</p>
</dd>
<dt id='index-revert_002dline-_0028M_002dr_0029'><span><code>revert-line (M-r)</code><a href='#index-revert_002dline-_0028M_002dr_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Undo all changes made to this line.  This is like executing the <code>undo</code>
command enough times to get back to the beginning.
</p>
</dd>
<dt id='index-tilde_002dexpand-_0028M_002d_0026_0029'><span><code>tilde-expand (M-&amp;)</code><a href='#index-tilde_002dexpand-_0028M_002d_0026_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Perform tilde expansion on the current word.
</p>
</dd>
<dt id='index-set_002dmark-_0028C_002d_0040_0029'><span><code>set-mark (C-@)</code><a href='#index-set_002dmark-_0028C_002d_0040_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Set the mark to the point.  If a
numeric argument is supplied, the mark is set to that position.
</p>
</dd>
<dt id='index-exchange_002dpoint_002dand_002dmark-_0028C_002dx-C_002dx_0029'><span><code>exchange-point-and-mark (C-x C-x)</code><a href='#index-exchange_002dpoint_002dand_002dmark-_0028C_002dx-C_002dx_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Swap the point with the mark.  The current cursor position is set to
the saved position, and the old cursor position is saved as the mark.
</p>
</dd>
<dt id='index-character_002dsearch-_0028C_002d_005d_0029'><span><code>character-search (C-])</code><a href='#index-character_002dsearch-_0028C_002d_005d_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A character is read and point is moved to the next occurrence of that
character.  A negative argument searches for previous occurrences.
</p>
</dd>
<dt id='index-character_002dsearch_002dbackward-_0028M_002dC_002d_005d_0029'><span><code>character-search-backward (M-C-])</code><a href='#index-character_002dsearch_002dbackward-_0028M_002dC_002d_005d_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A character is read and point is moved to the previous occurrence
of that character.  A negative argument searches for subsequent
occurrences.
</p>
</dd>
<dt id='index-skip_002dcsi_002dsequence-_0028_0029'><span><code>skip-csi-sequence ()</code><a href='#index-skip_002dcsi_002dsequence-_0028_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Read enough characters to consume a multi-key sequence such as those
defined for keys like Home and End.  Such sequences begin with a
Control Sequence Indicator (CSI), usually ESC-[.  If this sequence is
bound to &quot;\e[&quot;, keys producing such sequences will have no effect
unless explicitly bound to a Readline command, instead of inserting
stray characters into the editing buffer.  This is unbound by default,
but usually bound to ESC-[.
</p>
</dd>
<dt id='index-insert_002dcomment-_0028M_002d_0023_0029'><span><code>insert-comment (M-#)</code><a href='#index-insert_002dcomment-_0028M_002d_0023_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Without a numeric argument, the value of the <code>comment-begin</code>
variable is inserted at the beginning of the current line.
If a numeric argument is supplied, this command acts as a toggle:  if
the characters at the beginning of the line do not match the value
of <code>comment-begin</code>, the value is inserted, otherwise
the characters in <code>comment-begin</code> are deleted from the beginning of
the line.
In either case, the line is accepted as if a newline had been typed.
The default value of <code>comment-begin</code> causes this command
to make the current line a shell comment.
If a numeric argument causes the comment character to be removed, the line
will be executed by the shell.
</p>
</dd>
<dt id='index-dump_002dfunctions-_0028_0029'><span><code>dump-functions ()</code><a href='#index-dump_002dfunctions-_0028_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Print all of the functions and their key bindings to the
Readline output stream.  If a numeric argument is supplied,
the output is formatted in such a way that it can be made part
of an <var>inputrc</var> file.  This command is unbound by default.
</p>
</dd>
<dt id='index-dump_002dvariables-_0028_0029'><span><code>dump-variables ()</code><a href='#index-dump_002dvariables-_0028_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Print all of the settable variables and their values to the
Readline output stream.  If a numeric argument is supplied,
the output is formatted in such a way that it can be made part
of an <var>inputrc</var> file.  This command is unbound by default.
</p>
</dd>
<dt id='index-dump_002dmacros-_0028_0029'><span><code>dump-macros ()</code><a href='#index-dump_002dmacros-_0028_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Print all of the Readline key sequences bound to macros and the
strings they output.  If a numeric argument is supplied,
the output is formatted in such a way that it can be made part
of an <var>inputrc</var> file.  This command is unbound by default.
</p>
</dd>
<dt id='index-spell_002dcorrect_002dword-_0028C_002dx-s_0029'><span><code>spell-correct-word (C-x s)</code><a href='#index-spell_002dcorrect_002dword-_0028C_002dx-s_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Perform spelling correction on the current word, treating it as a directory
or filename, in the same way as the <code>cdspell</code> shell option.
Word boundaries are the same as those used by <code>shell-forward-word</code>.
</p>
</dd>
<dt id='index-glob_002dcomplete_002dword-_0028M_002dg_0029'><span><code>glob-complete-word (M-g)</code><a href='#index-glob_002dcomplete_002dword-_0028M_002dg_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The word before point is treated as a pattern for pathname expansion,
with an asterisk implicitly appended.  This pattern is used to
generate a list of matching file names for possible completions.
</p>
</dd>
<dt id='index-glob_002dexpand_002dword-_0028C_002dx-_002a_0029'><span><code>glob-expand-word (C-x *)</code><a href='#index-glob_002dexpand_002dword-_0028C_002dx-_002a_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The word before point is treated as a pattern for pathname expansion,
and the list of matching file names is inserted, replacing the word.
If a numeric argument is supplied, a &lsquo;<samp>*</samp>&rsquo; is appended before
pathname expansion.
</p>
</dd>
<dt id='index-glob_002dlist_002dexpansions-_0028C_002dx-g_0029'><span><code>glob-list-expansions (C-x g)</code><a href='#index-glob_002dlist_002dexpansions-_0028C_002dx-g_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The list of expansions that would have been generated by
<code>glob-expand-word</code> is displayed, and the line is redrawn.
If a numeric argument is supplied, a &lsquo;<samp>*</samp>&rsquo; is appended before
pathname expansion.
</p>
</dd>
<dt id='index-display_002dshell_002dversion-_0028C_002dx-C_002dv_0029'><span><code>display-shell-version (C-x C-v)</code><a href='#index-display_002dshell_002dversion-_0028C_002dx-C_002dv_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Display version information about the current instance of Bash.
</p>
</dd>
<dt id='index-shell_002dexpand_002dline-_0028M_002dC_002de_0029'><span><code>shell-expand-line (M-C-e)</code><a href='#index-shell_002dexpand_002dline-_0028M_002dC_002de_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Expand the line as the shell does.
This performs alias and history expansion as well as all of the shell
word expansions (see <a href="#Shell-Expansions">Shell Expansions</a>).
</p>
</dd>
<dt id='index-history_002dexpand_002dline-_0028M_002d_005e_0029'><span><code>history-expand-line (M-^)</code><a href='#index-history_002dexpand_002dline-_0028M_002d_005e_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Perform history expansion on the current line.
</p>
</dd>
<dt id='index-magic_002dspace-_0028_0029'><span><code>magic-space ()</code><a href='#index-magic_002dspace-_0028_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Perform history expansion on the current line and insert a space
(see <a href="#History-Interaction">History Expansion</a>).
</p>
</dd>
<dt id='index-alias_002dexpand_002dline-_0028_0029'><span><code>alias-expand-line ()</code><a href='#index-alias_002dexpand_002dline-_0028_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Perform alias expansion on the current line (see <a href="#Aliases">Aliases</a>).
</p>
</dd>
<dt id='index-history_002dand_002dalias_002dexpand_002dline-_0028_0029'><span><code>history-and-alias-expand-line ()</code><a href='#index-history_002dand_002dalias_002dexpand_002dline-_0028_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Perform history and alias expansion on the current line.
</p>
</dd>
<dt id='index-insert_002dlast_002dargument-_0028M_002d_002e-or-M_002d_005f_0029'><span><code>insert-last-argument (M-. or M-_)</code><a href='#index-insert_002dlast_002dargument-_0028M_002d_002e-or-M_002d_005f_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>A synonym for <code>yank-last-arg</code>.
</p>
</dd>
<dt id='index-edit_002dand_002dexecute_002dcommand-_0028C_002dx-C_002de_0029'><span><code>edit-and-execute-command (C-x C-e)</code><a href='#index-edit_002dand_002dexecute_002dcommand-_0028C_002dx-C_002de_0029' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>Invoke an editor on the current command line, and execute the result as shell
commands.
Bash attempts to invoke
<code>$VISUAL</code>, <code>$EDITOR</code>, and <code>emacs</code>
as the editor, in that order.
</p>


</dd>
</dl>

<hr>
</div>
</div>
<div class="section" id="Readline-vi-Mode">
<div class="header">
<p>
Next: <a href="#Programmable-Completion" accesskey="n" rel="next">Programmable Completion</a>, Previous: <a href="#Bindable-Readline-Commands" accesskey="p" rel="prev">Bindable Readline Commands</a>, Up: <a href="#Command-Line-Editing" accesskey="u" rel="up">Command Line Editing</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Readline-vi-Mode-1"></span><h3 class="section">8.5 Readline vi Mode</h3>

<p>While the Readline library does not have a full set of <code>vi</code>
editing functions, it does contain enough to allow simple editing
of the line.  The Readline <code>vi</code> mode behaves as specified in
the <small>POSIX</small> standard.
</p>
<p>In order to switch interactively between <code>emacs</code> and <code>vi</code>
editing modes, use the &lsquo;<samp>set -o emacs</samp>&rsquo; and &lsquo;<samp>set -o vi</samp>&rsquo;
commands (see <a href="#The-Set-Builtin">The Set Builtin</a>).
The Readline default is <code>emacs</code> mode.
</p>
<p>When you enter a line in <code>vi</code> mode, you are already placed in
&lsquo;insertion&rsquo; mode, as if you had typed an &lsquo;<samp>i</samp>&rsquo;.  Pressing <tt class="key">ESC</tt>
switches you into &lsquo;command&rsquo; mode, where you can edit the text of the
line with the standard <code>vi</code> movement keys, move to previous
history lines with &lsquo;<samp>k</samp>&rsquo; and subsequent lines with &lsquo;<samp>j</samp>&rsquo;, and
so forth.
</p>
<hr>
</div>
<div class="section" id="Programmable-Completion">
<div class="header">
<p>
Next: <a href="#Programmable-Completion-Builtins" accesskey="n" rel="next">Programmable Completion Builtins</a>, Previous: <a href="#Readline-vi-Mode" accesskey="p" rel="prev">Readline vi Mode</a>, Up: <a href="#Command-Line-Editing" accesskey="u" rel="up">Command Line Editing</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Programmable-Completion-1"></span><h3 class="section">8.6 Programmable Completion</h3>
<span id="index-programmable-completion"></span>

<p>When word completion is attempted for an argument to a command for
which a completion specification (a <var>compspec</var>) has been defined
using the <code>complete</code> builtin (see <a href="#Programmable-Completion-Builtins">Programmable Completion Builtins</a>),
the programmable completion facilities are invoked. 
</p>
<p>First, the command name is identified.
If a compspec has been defined for that command, the
compspec is used to generate the list of possible completions for the word.
If the command word is the empty string (completion attempted at the
beginning of an empty line), any compspec defined with
the <samp>-E</samp> option to <code>complete</code> is used.
If the command word is a full pathname, a compspec for the full
pathname is searched for first.
If no compspec is found for the full pathname, an attempt is made to
find a compspec for the portion following the final slash.
If those searches do not result in a compspec, any compspec defined with
the <samp>-D</samp> option to <code>complete</code> is used as the default.
If there is no default compspec, Bash attempts alias expansion
on the command word as a final resort, and attempts to find a compspec
for the command word from any successful expansion 
</p>
<p>Once a compspec has been found, it is used to generate the list of
matching words.
If a compspec is not found, the default Bash completion
described above (see <a href="#Commands-For-Completion">Letting Readline Type For You</a>) is performed.
</p>
<p>First, the actions specified by the compspec are used.
Only matches which are prefixed by the word being completed are
returned.
When the <samp>-f</samp> or <samp>-d</samp> option is used for filename or
directory name completion, the shell variable <code>FIGNORE</code> is
used to filter the matches.
See <a href="#Bash-Variables">Bash Variables</a>, for a description of <code>FIGNORE</code>.
</p>
<p>Any completions specified by a filename expansion pattern to the
<samp>-G</samp> option are generated next.
The words generated by the pattern need not match the word being completed.
The <code>GLOBIGNORE</code> shell variable is not used to filter the matches,
but the <code>FIGNORE</code> shell variable is used.
</p>
<p>Next, the string specified as the argument to the <samp>-W</samp> option
is considered.
The string is first split using the characters in the <code>IFS</code>
special variable as delimiters.
Shell quoting is honored within the string, in order to provide a
mechanism for the words to contain shell metacharacters or characters
in the value of <code>IFS</code>.
Each word is then expanded using
brace expansion, tilde expansion, parameter and variable expansion,
command substitution, and arithmetic expansion,
as described above (see <a href="#Shell-Expansions">Shell Expansions</a>).
The results are split using the rules described above
(see <a href="#Word-Splitting">Word Splitting</a>).
The results of the expansion are prefix-matched against the word being
completed, and the matching words become the possible completions.
</p>
<p>After these matches have been generated, any shell function or command
specified with the <samp>-F</samp> and <samp>-C</samp> options is invoked.
When the command or function is invoked, the <code>COMP_LINE</code>,
<code>COMP_POINT</code>, <code>COMP_KEY</code>, and <code>COMP_TYPE</code> variables are
assigned values as described above (see <a href="#Bash-Variables">Bash Variables</a>).
If a shell function is being invoked, the <code>COMP_WORDS</code> and
<code>COMP_CWORD</code> variables are also set.
When the function or command is invoked, the first argument ($1) is the
name of the command whose arguments are being completed, the
second argument ($2) is the word being completed, and the third argument
($3) is the word preceding the word being completed on the current command
line.
No filtering of the generated completions against the word being completed
is performed; the function or command has complete freedom in generating
the matches.
</p>
<p>Any function specified with <samp>-F</samp> is invoked first.
The function may use any of the shell facilities, including the
<code>compgen</code> and <code>compopt</code> builtins described below
(see <a href="#Programmable-Completion-Builtins">Programmable Completion Builtins</a>), to generate the matches.
It must put the possible completions in the <code>COMPREPLY</code> array
variable, one per array element.
</p>
<p>Next, any command specified with the <samp>-C</samp> option is invoked
in an environment equivalent to command substitution.
It should print a list of completions, one per line, to
the standard output.
Backslash may be used to escape a newline, if necessary.
</p>
<p>After all of the possible completions are generated, any filter
specified with the <samp>-X</samp> option is applied to the list.
The filter is a pattern as used for pathname expansion; a &lsquo;<samp>&amp;</samp>&rsquo;
in the pattern is replaced with the text of the word being completed.
A literal &lsquo;<samp>&amp;</samp>&rsquo; may be escaped with a backslash; the backslash
is removed before attempting a match.
Any completion that matches the pattern will be removed from the list.
A leading &lsquo;<samp>!</samp>&rsquo; negates the pattern; in this case any completion
not matching the pattern will be removed.
If the <code>nocasematch</code> shell option
(see the description of <code>shopt</code> in <a href="#The-Shopt-Builtin">The Shopt Builtin</a>)
is enabled, the match is performed without regard to the case
of alphabetic characters.
</p>
<p>Finally, any prefix and suffix specified with the <samp>-P</samp> and <samp>-S</samp>
options are added to each member of the completion list, and the result is
returned to the Readline completion code as the list of possible
completions.
</p>
<p>If the previously-applied actions do not generate any matches, and the
<samp>-o dirnames</samp> option was supplied to <code>complete</code> when the
compspec was defined, directory name completion is attempted. 
</p>
<p>If the <samp>-o plusdirs</samp> option was supplied to <code>complete</code> when
the compspec was defined, directory name completion is attempted and any
matches are added to the results of the other actions.
</p>
<p>By default, if a compspec is found, whatever it generates is returned to
the completion code as the full set of possible completions.
The default Bash completions are not attempted, and the Readline default
of filename completion is disabled.
If the <samp>-o bashdefault</samp> option was supplied to <code>complete</code> when
the compspec was defined, the default Bash completions are attempted
if the compspec generates no matches.
If the <samp>-o default</samp> option was supplied to <code>complete</code> when the
compspec was defined, Readline&rsquo;s default completion will be performed
if the compspec (and, if attempted, the default Bash completions)
generate no matches.
</p>
<p>When a compspec indicates that directory name completion is desired,
the programmable completion functions force Readline to append a slash
to completed names which are symbolic links to directories, subject to
the value of the <var>mark-directories</var> Readline variable, regardless
of the setting of the <var>mark-symlinked-directories</var> Readline variable.
</p>
<p>There is some support for dynamically modifying completions.  This is
most useful when used in combination with a default completion specified
with <samp>-D</samp>.  It&rsquo;s possible for shell functions executed as completion
handlers to indicate that completion should be retried by returning an
exit status of 124.  If a shell function returns 124, and changes
the compspec associated with the command on which completion is being
attempted (supplied as the first argument when the function is executed),
programmable completion restarts from the beginning, with an
attempt to find a new compspec for that command.  This allows a set of
completions to be built dynamically as completion is attempted, rather than
being loaded all at once.
</p>
<p>For instance, assuming that there is a library of compspecs, each kept in a
file corresponding to the name of the command, the following default
completion function would load completions dynamically:
</p>
<div class="example">
<pre class="example">_completion_loader()
{
    . &quot;/etc/bash_completion.d/$1.sh&quot; &gt;/dev/null 2&gt;&amp;1 &amp;&amp; return 124
}
complete -D -F _completion_loader -o bashdefault -o default
</pre></div>

<hr>
</div>
<div class="section" id="Programmable-Completion-Builtins">
<div class="header">
<p>
Next: <a href="#A-Programmable-Completion-Example" accesskey="n" rel="next">A Programmable Completion Example</a>, Previous: <a href="#Programmable-Completion" accesskey="p" rel="prev">Programmable Completion</a>, Up: <a href="#Command-Line-Editing" accesskey="u" rel="up">Command Line Editing</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Programmable-Completion-Builtins-1"></span><h3 class="section">8.7 Programmable Completion Builtins</h3>
<span id="index-completion-builtins"></span>

<p>Three builtin commands are available to manipulate the programmable completion
facilities: one to specify how the arguments to a particular command are to
be completed, and two to modify the completion as it is happening.
</p>
<dl compact="compact">
<dt id='index-compgen'><span><code>compgen</code><a href='#index-compgen' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example"><code>compgen [<var>option</var>] [<var>word</var>]</code>
</pre></div>

<p>Generate possible completion matches for <var>word</var> according to
the <var>option</var>s, which may be any option accepted by the
<code>complete</code>
builtin with the exception of <samp>-p</samp> and <samp>-r</samp>, and write
the matches to the standard output.
When using the <samp>-F</samp> or <samp>-C</samp> options, the various shell variables
set by the programmable completion facilities, while available, will not
have useful values.
</p>
<p>The matches will be generated in the same way as if the programmable
completion code had generated them directly from a completion specification
with the same flags.
If <var>word</var> is specified, only those completions matching <var>word</var>
will be displayed.
</p>
<p>The return value is true unless an invalid option is supplied, or no
matches were generated.
</p>
</dd>
<dt id='index-complete'><span><code>complete</code><a href='#index-complete' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example"><code>complete [-abcdefgjksuv] [-o <var>comp-option</var>] [-DEI] [-A <var>action</var>] [-G <var>globpat</var>]
[-W <var>wordlist</var>] [-F <var>function</var>] [-C <var>command</var>] [-X <var>filterpat</var>]
[-P <var>prefix</var>] [-S <var>suffix</var>] <var>name</var> [<var>name</var> &hellip;]</code>
<code>complete -pr [-DEI] [<var>name</var> &hellip;]</code>
</pre></div>

<p>Specify how arguments to each <var>name</var> should be completed.
If the <samp>-p</samp> option is supplied, or if no options are supplied, existing
completion specifications are printed in a way that allows them to be
reused as input.
The <samp>-r</samp> option removes a completion specification for
each <var>name</var>, or, if no <var>name</var>s are supplied, all
completion specifications.
The <samp>-D</samp> option indicates that other supplied options and actions should
apply to the &ldquo;default&rdquo; command completion; that is, completion attempted
on a command for which no completion has previously been defined.
The <samp>-E</samp> option indicates that other supplied options and actions should
apply to &ldquo;empty&rdquo; command completion; that is, completion attempted on a 
blank line.
The <samp>-I</samp> option indicates that other supplied options and actions should
apply to completion on the initial non-assignment word on the line, or after a
command delimiter such as &lsquo;<samp>;</samp>&rsquo; or &lsquo;<samp>|</samp>&rsquo;, which is usually command
name completion.
If multiple options are supplied, the <samp>-D</samp> option takes precedence
over <samp>-E</samp>, and both take precedence over <samp>-I</samp>.
If any of <samp>-D</samp>, <samp>-E</samp>, or <samp>-I</samp> are supplied, any other
<var>name</var> arguments are ignored; these completions only apply to the case
specified by the option.
</p>
<p>The process of applying these completion specifications when word completion
is attempted is described above (see <a href="#Programmable-Completion">Programmable Completion</a>).
</p>
<p>Other options, if specified, have the following meanings.
The arguments to the <samp>-G</samp>, <samp>-W</samp>, and <samp>-X</samp> options
(and, if necessary, the <samp>-P</samp> and <samp>-S</samp> options)
should be quoted to protect them from expansion before the
<code>complete</code> builtin is invoked.
</p>

<dl compact="compact">
<dt><span><code>-o <var>comp-option</var></code></span></dt>
<dd><p>The <var>comp-option</var> controls several aspects of the compspec&rsquo;s behavior
beyond the simple generation of completions.
<var>comp-option</var> may be one of: 
</p>
<dl compact="compact">
<dt><span><code>bashdefault</code></span></dt>
<dd><p>Perform the rest of the default Bash completions if the compspec
generates no matches.
</p>
</dd>
<dt><span><code>default</code></span></dt>
<dd><p>Use Readline&rsquo;s default filename completion if the compspec generates
no matches.
</p>
</dd>
<dt><span><code>dirnames</code></span></dt>
<dd><p>Perform directory name completion if the compspec generates no matches.
</p>
</dd>
<dt><span><code>filenames</code></span></dt>
<dd><p>Tell Readline that the compspec generates filenames, so it can perform any
filename-specific processing (like adding a slash to directory names,
quoting special characters, or suppressing trailing spaces).
This option is intended to be used with shell functions specified
with <samp>-F</samp>.
</p>
</dd>
<dt><span><code>noquote</code></span></dt>
<dd><p>Tell Readline not to quote the completed words if they are filenames
(quoting filenames is the default).
</p>
</dd>
<dt><span><code>nosort</code></span></dt>
<dd><p>Tell Readline not to sort the list of possible completions alphabetically.
</p>
</dd>
<dt><span><code>nospace</code></span></dt>
<dd><p>Tell Readline not to append a space (the default) to words completed at
the end of the line.
</p>
</dd>
<dt><span><code>plusdirs</code></span></dt>
<dd><p>After any matches defined by the compspec are generated, 
directory name completion is attempted and any
matches are added to the results of the other actions.
</p>
</dd>
</dl>

</dd>
<dt><span><code>-A <var>action</var></code></span></dt>
<dd><p>The <var>action</var> may be one of the following to generate a list of possible
completions:
</p>
<dl compact="compact">
<dt><span><code>alias</code></span></dt>
<dd><p>Alias names.  May also be specified as <samp>-a</samp>.
</p>
</dd>
<dt><span><code>arrayvar</code></span></dt>
<dd><p>Array variable names.
</p>
</dd>
<dt><span><code>binding</code></span></dt>
<dd><p>Readline key binding names (see <a href="#Bindable-Readline-Commands">Bindable Readline Commands</a>).
</p>
</dd>
<dt><span><code>builtin</code></span></dt>
<dd><p>Names of shell builtin commands.  May also be specified as <samp>-b</samp>.
</p>
</dd>
<dt><span><code>command</code></span></dt>
<dd><p>Command names.  May also be specified as <samp>-c</samp>.
</p>
</dd>
<dt><span><code>directory</code></span></dt>
<dd><p>Directory names.  May also be specified as <samp>-d</samp>.
</p>
</dd>
<dt><span><code>disabled</code></span></dt>
<dd><p>Names of disabled shell builtins.
</p>
</dd>
<dt><span><code>enabled</code></span></dt>
<dd><p>Names of enabled shell builtins.
</p>
</dd>
<dt><span><code>export</code></span></dt>
<dd><p>Names of exported shell variables.  May also be specified as <samp>-e</samp>.
</p>
</dd>
<dt><span><code>file</code></span></dt>
<dd><p>File names.  May also be specified as <samp>-f</samp>.
</p>
</dd>
<dt><span><code>function</code></span></dt>
<dd><p>Names of shell functions.
</p>
</dd>
<dt><span><code>group</code></span></dt>
<dd><p>Group names.  May also be specified as <samp>-g</samp>.
</p>
</dd>
<dt><span><code>helptopic</code></span></dt>
<dd><p>Help topics as accepted by the <code>help</code> builtin (see <a href="#Bash-Builtins">Bash Builtin Commands</a>).
</p>
</dd>
<dt><span><code>hostname</code></span></dt>
<dd><p>Hostnames, as taken from the file specified by the
<code>HOSTFILE</code> shell variable (see <a href="#Bash-Variables">Bash Variables</a>).
</p>
</dd>
<dt><span><code>job</code></span></dt>
<dd><p>Job names, if job control is active.  May also be specified as <samp>-j</samp>.
</p>
</dd>
<dt><span><code>keyword</code></span></dt>
<dd><p>Shell reserved words.  May also be specified as <samp>-k</samp>.
</p>
</dd>
<dt><span><code>running</code></span></dt>
<dd><p>Names of running jobs, if job control is active.
</p>
</dd>
<dt><span><code>service</code></span></dt>
<dd><p>Service names.  May also be specified as <samp>-s</samp>.
</p>
</dd>
<dt><span><code>setopt</code></span></dt>
<dd><p>Valid arguments for the <samp>-o</samp> option to the <code>set</code> builtin
(see <a href="#The-Set-Builtin">The Set Builtin</a>).
</p>
</dd>
<dt><span><code>shopt</code></span></dt>
<dd><p>Shell option names as accepted by the <code>shopt</code> builtin
(see <a href="#Bash-Builtins">Bash Builtin Commands</a>).
</p>
</dd>
<dt><span><code>signal</code></span></dt>
<dd><p>Signal names.
</p>
</dd>
<dt><span><code>stopped</code></span></dt>
<dd><p>Names of stopped jobs, if job control is active.
</p>
</dd>
<dt><span><code>user</code></span></dt>
<dd><p>User names.  May also be specified as <samp>-u</samp>.
</p>
</dd>
<dt><span><code>variable</code></span></dt>
<dd><p>Names of all shell variables.  May also be specified as <samp>-v</samp>.
</p></dd>
</dl>

</dd>
<dt><span><code>-C <var>command</var></code></span></dt>
<dd><p><var>command</var> is executed in a subshell environment, and its output is
used as the possible completions.
Arguments are passed as with the <samp>-F</samp> option.
</p>
</dd>
<dt><span><code>-F <var>function</var></code></span></dt>
<dd><p>The shell function <var>function</var> is executed in the current shell
environment.
When it is executed, $1 is the name of the command whose arguments are
being completed, $2 is the word being completed, and $3 is the word
preceding the word being completed, as described above
(see <a href="#Programmable-Completion">Programmable Completion</a>).
When it finishes, the possible completions are retrieved from the value
of the <code>COMPREPLY</code> array variable.
</p>
</dd>
<dt><span><code>-G <var>globpat</var></code></span></dt>
<dd><p>The filename expansion pattern <var>globpat</var> is expanded to generate
the possible completions.
</p>
</dd>
<dt><span><code>-P <var>prefix</var></code></span></dt>
<dd><p><var>prefix</var> is added at the beginning of each possible completion
after all other options have been applied.
</p>
</dd>
<dt><span><code>-S <var>suffix</var></code></span></dt>
<dd><p><var>suffix</var> is appended to each possible completion
after all other options have been applied.
</p>
</dd>
<dt><span><code>-W <var>wordlist</var></code></span></dt>
<dd><p>The <var>wordlist</var> is split using the characters in the
<code>IFS</code> special variable as delimiters, and each resultant word
is expanded.
The possible completions are the members of the resultant list which
match the word being completed.
</p>
</dd>
<dt><span><code>-X <var>filterpat</var></code></span></dt>
<dd><p><var>filterpat</var> is a pattern as used for filename expansion.
It is applied to the list of possible completions generated by the
preceding options and arguments, and each completion matching
<var>filterpat</var> is removed from the list.
A leading &lsquo;<samp>!</samp>&rsquo; in <var>filterpat</var> negates the pattern; in this
case, any completion not matching <var>filterpat</var> is removed.
</p></dd>
</dl>

<p>The return value is true unless an invalid option is supplied, an option
other than <samp>-p</samp> or <samp>-r</samp> is supplied without a <var>name</var>
argument, an attempt is made to remove a completion specification for
a <var>name</var> for which no specification exists, or
an error occurs adding a completion specification.
</p>
</dd>
<dt id='index-compopt'><span><code>compopt</code><a href='#index-compopt' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example"><code>compopt</code> [-o <var>option</var>] [-DEI] [+o <var>option</var>] [<var>name</var>]
</pre></div>
<p>Modify completion options for each <var>name</var> according to the
<var>option</var>s, or for the currently-executing completion if no <var>name</var>s
are supplied.
If no <var>option</var>s are given, display the completion options for each
<var>name</var> or the current completion.
The possible values of <var>option</var> are those valid for the <code>complete</code>
builtin described above.
The <samp>-D</samp> option indicates that other supplied options should
apply to the &ldquo;default&rdquo; command completion; that is, completion attempted
on a command for which no completion has previously been defined.
The <samp>-E</samp> option indicates that other supplied options should
apply to &ldquo;empty&rdquo; command completion; that is, completion attempted on a 
blank line.
The <samp>-I</samp> option indicates that other supplied options should
apply to completion on the initial non-assignment word on the line, or after a
command delimiter such as &lsquo;<samp>;</samp>&rsquo; or &lsquo;<samp>|</samp>&rsquo;, which is usually command
name completion.
</p>
<p>If multiple options are supplied, the <samp>-D</samp> option takes precedence
over <samp>-E</samp>, and both take precedence over <samp>-I</samp>
</p>
<p>The return value is true unless an invalid option is supplied, an attempt
is made to modify the options for a <var>name</var> for which no completion
specification exists, or an output error occurs.
</p>
</dd>
</dl>

<hr>
</div>
<div class="section" id="A-Programmable-Completion-Example">
<div class="header">
<p>
Previous: <a href="#Programmable-Completion-Builtins" accesskey="p" rel="prev">Programmable Completion Builtins</a>, Up: <a href="#Command-Line-Editing" accesskey="u" rel="up">Command Line Editing</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="A-Programmable-Completion-Example-1"></span><h3 class="section">8.8 A Programmable Completion Example</h3>

<p>The most common way to obtain additional completion functionality beyond
the default actions <code>complete</code> and <code>compgen</code> provide is to use
a shell function and bind it to a particular command using <code>complete -F</code>.
</p>
<p>The following function provides completions for the <code>cd</code> builtin.
It is a reasonably good example of what shell functions must do when
used for completion.  This function uses the word passed as <code>$2</code>
to determine the directory name to complete.  You can also use the
<code>COMP_WORDS</code> array variable; the current word is indexed by the
<code>COMP_CWORD</code> variable.
</p>
<p>The function relies on the <code>complete</code> and <code>compgen</code> builtins
to do much of the work, adding only the things that the Bash <code>cd</code>
does beyond accepting basic directory names:
tilde expansion (see <a href="#Tilde-Expansion">Tilde Expansion</a>),
searching directories in <var>$CDPATH</var>, which is described above
(see <a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a>),
and basic support for the <code>cdable_vars</code> shell option
(see <a href="#The-Shopt-Builtin">The Shopt Builtin</a>).
<code>_comp_cd</code> modifies the value of <var>IFS</var> so that it contains only
a newline to accommodate file names containing spaces and tabs &ndash;
<code>compgen</code> prints the possible completions it generates one per line.
</p>
<p>Possible completions go into the <var>COMPREPLY</var> array variable, one
completion per array element.  The programmable completion system retrieves
the completions from there when the function returns.
</p>
<div class="example">
<pre class="example"># A completion function for the cd builtin
# based on the cd completion function from the bash_completion package
_comp_cd()
{
    local IFS=$' \t\n'    # normalize IFS
    local cur _skipdot _cdpath
    local i j k

    # Tilde expansion, which also expands tilde to full pathname
    case &quot;$2&quot; in
    \~*)    eval cur=&quot;$2&quot; ;;
    *)      cur=$2 ;;
    esac

    # no cdpath or absolute pathname -- straight directory completion
    if [[ -z &quot;${CDPATH:-}&quot; ]] || [[ &quot;$cur&quot; == @(./*|../*|/*) ]]; then
        # compgen prints paths one per line; could also use while loop
        IFS=$'\n'
        COMPREPLY=( $(compgen -d -- &quot;$cur&quot;) )
        IFS=$' \t\n'
    # CDPATH+directories in the current directory if not in CDPATH
    else
        IFS=$'\n'
        _skipdot=false
        # preprocess CDPATH to convert null directory names to .
        _cdpath=${CDPATH/#:/.:}
        _cdpath=${_cdpath//::/:.:}
        _cdpath=${_cdpath/%:/:.}
        for i in ${_cdpath//:/$'\n'}; do
            if [[ $i -ef . ]]; then _skipdot=true; fi
            k=&quot;${#COMPREPLY[@]}&quot;
            for j in $( compgen -d -- &quot;$i/$cur&quot; ); do
                COMPREPLY[k++]=${j#$i/}        # cut off directory
            done
        done
        $_skipdot || COMPREPLY+=( $(compgen -d -- &quot;$cur&quot;) )
        IFS=$' \t\n'
    fi

    # variable names if appropriate shell option set and no completions
    if shopt -q cdable_vars &amp;&amp; [[ ${#COMPREPLY[@]} -eq 0 ]]; then
        COMPREPLY=( $(compgen -v -- &quot;$cur&quot;) )
    fi

    return 0
}
</pre></div>

<p>We install the completion function using the <samp>-F</samp> option to
<code>complete</code>:
</p>
<div class="example">
<pre class="example"># Tell readline to quote appropriate and append slashes to directories;
# use the bash default completion for other arguments
complete -o filenames -o nospace -o bashdefault -F _comp_cd cd
</pre></div>

<p>Since we&rsquo;d like Bash and Readline to take care of some
of the other details for us, we use several other options to tell Bash
and Readline what to do.  The <samp>-o filenames</samp> option tells Readline
that the possible completions should be treated as filenames, and quoted
appropriately.  That option will also cause Readline to append a slash to
filenames it can determine are directories (which is why we might want to
extend <code>_comp_cd</code> to append a slash if we&rsquo;re using directories found
via <var>CDPATH</var>: Readline can&rsquo;t tell those completions are directories).
The <samp>-o nospace</samp> option tells Readline to not append a space
character to the directory name, in case we want to append to it.
The <samp>-o bashdefault</samp> option brings in the rest of the &quot;Bash default&quot;
completions &ndash; possible completions that Bash adds to the default Readline
set.  These include things like command name completion, variable completion
for words beginning with &lsquo;<samp>$</samp>&rsquo; or &lsquo;<samp>${</samp>&rsquo;, completions containing pathname
expansion patterns (see <a href="#Filename-Expansion">Filename Expansion</a>), and so on.
</p>
<p>Once installed using <code>complete</code>, <code>_comp_cd</code> will be called every
time we attempt word completion for a <code>cd</code> command.
</p>
<p>Many more examples &ndash; an extensive collection of completions for most of
the common GNU, Unix, and Linux commands &ndash; are available as part of the
bash_completion project.  This is installed by default on many GNU/Linux
distributions.  Originally written by Ian Macdonald, the project now lives
at <a href="https://github.com/scop/bash-completion/">https://github.com/scop/bash-completion/</a>.  There are ports for
other systems such as Solaris and Mac OS X.
</p>
<p>An older version of the bash_completion package is distributed with bash
in the <samp>examples/complete</samp> subdirectory.
</p>
<span id="index-History_002c-how-to-use"></span>

<hr>
</div>
</div>
<div class="chapter" id="Using-History-Interactively">
<div class="header">
<p>
Next: <a href="#Installing-Bash" accesskey="n" rel="next">Installing Bash</a>, Previous: <a href="#Command-Line-Editing" accesskey="p" rel="prev">Command Line Editing</a>, Up: <a href="#Top" accesskey="u" rel="up">Bash Features</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Using-History-Interactively-1"></span><h2 class="chapter">9 Using History Interactively</h2>


<p>This chapter describes how to use the <small>GNU</small> History Library
interactively, from a user&rsquo;s standpoint.
It should be considered a user&rsquo;s guide.
For information on using the <small>GNU</small> History Library in other programs,
see the <small>GNU</small> Readline Library Manual.
</p>

<ul class="section-toc">
<li><a href="#Bash-History-Facilities" accesskey="1">Bash History Facilities</a></li>
<li><a href="#Bash-History-Builtins" accesskey="2">Bash History Builtins</a></li>
<li><a href="#History-Interaction" accesskey="3">History Expansion</a></li>
</ul>
<hr>
<div class="section" id="Bash-History-Facilities">
<div class="header">
<p>
Next: <a href="#Bash-History-Builtins" accesskey="n" rel="next">Bash History Builtins</a>, Up: <a href="#Using-History-Interactively" accesskey="u" rel="up">Using History Interactively</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Bash-History-Facilities-1"></span><h3 class="section">9.1 Bash History Facilities</h3>
<span id="index-command-history"></span>
<span id="index-history-list"></span>

<p>When the <samp>-o history</samp> option to the <code>set</code> builtin
is enabled (see <a href="#The-Set-Builtin">The Set Builtin</a>),
the shell provides access to the <em>command history</em>,
the list of commands previously typed.
The value of the <code>HISTSIZE</code> shell variable is used as the
number of commands to save in a history list.
The text of the last <code>$HISTSIZE</code>
commands (default 500) is saved.
The shell stores each command in the history list prior to
parameter and variable expansion
but after history expansion is performed, subject to the
values of the shell variables
<code>HISTIGNORE</code> and <code>HISTCONTROL</code>.
</p>
<p>When the shell starts up, the history is initialized from the
file named by the <code>HISTFILE</code> variable (default <samp>~/.bash_history</samp>).
The file named by the value of <code>HISTFILE</code> is truncated, if
necessary, to contain no more than the number of lines specified by
the value of the <code>HISTFILESIZE</code> variable.
When a shell with history enabled exits, the last
<code>$HISTSIZE</code> lines are copied from the history list to the file
named by <code>$HISTFILE</code>.
If the <code>histappend</code> shell option is set (see <a href="#Bash-Builtins">Bash Builtin Commands</a>),
the lines are appended to the history file,
otherwise the history file is overwritten.
If <code>HISTFILE</code>
is unset, or if the history file is unwritable, the history is not saved.
After saving the history, the history file is truncated
to contain no more than <code>$HISTFILESIZE</code> lines.
If <code>HISTFILESIZE</code> is unset, or set to null, a non-numeric value, or
a numeric value less than zero, the history file is not truncated.
</p>
<p>If the <code>HISTTIMEFORMAT</code> is set, the time stamp information
associated with each history entry is written to the history file,
marked with the history comment character.
When the history file is read, lines beginning with the history
comment character followed immediately by a digit are interpreted
as timestamps for the following history entry.
</p>
<p>The builtin command <code>fc</code> may be used to list or edit and re-execute
a portion of the history list.
The <code>history</code> builtin may be used to display or modify the history
list and manipulate the history file.
When using command-line editing, search commands
are available in each editing mode that provide access to the
history list (see <a href="#Commands-For-History">Commands For Manipulating The History</a>).
</p>
<p>The shell allows control over which commands are saved on the history
list.  The <code>HISTCONTROL</code> and <code>HISTIGNORE</code>
variables may be set to cause the shell to save only a subset of the
commands entered.
The <code>cmdhist</code>
shell option, if enabled, causes the shell to attempt to save each
line of a multi-line command in the same history entry, adding
semicolons where necessary to preserve syntactic correctness.
The <code>lithist</code>
shell option causes the shell to save the command with embedded newlines
instead of semicolons.
The <code>shopt</code> builtin is used to set these options.
See <a href="#The-Shopt-Builtin">The Shopt Builtin</a>, for a description of <code>shopt</code>.
</p>
<hr>
</div>
<div class="section" id="Bash-History-Builtins">
<div class="header">
<p>
Next: <a href="#History-Interaction" accesskey="n" rel="next">History Expansion</a>, Previous: <a href="#Bash-History-Facilities" accesskey="p" rel="prev">Bash History Facilities</a>, Up: <a href="#Using-History-Interactively" accesskey="u" rel="up">Using History Interactively</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Bash-History-Builtins-1"></span><h3 class="section">9.2 Bash History Builtins</h3>
<span id="index-history-builtins"></span>

<p>Bash provides two builtin commands which manipulate the
history list and history file.
</p>
<dl compact="compact">
<dt id='index-fc'><span><code>fc</code><a href='#index-fc' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example"><code>fc [-e <var>ename</var>] [-lnr] [<var>first</var>] [<var>last</var>]</code>
<code>fc -s [<var>pat</var>=<var>rep</var>] [<var>command</var>]</code>
</pre></div>

<p>The first form selects a range of commands from <var>first</var> to
<var>last</var> from the history list and displays or edits and re-executes
them.
Both <var>first</var> and
<var>last</var> may be specified as a string (to locate the most recent
command beginning with that string) or as a number (an index into the
history list, where a negative number is used as an offset from the
current command number).
</p>
<p>When listing, a <var>first</var> or <var>last</var> of 0 is equivalent to -1
and -0 is equivalent to the current command (usually the <code>fc</code>
command);
otherwise 0 is equivalent to -1 and -0 is invalid.
</p>
<p>If <var>last</var> is not specified, it is set to
<var>first</var>.  If <var>first</var> is not specified, it is set to the previous
command for editing and -16 for listing.  If the <samp>-l</samp> flag is
given, the commands are listed on standard output.  The <samp>-n</samp> flag
suppresses the command numbers when listing.  The <samp>-r</samp> flag
reverses the order of the listing.  Otherwise, the editor given by
<var>ename</var> is invoked on a file containing those commands.  If
<var>ename</var> is not given, the value of the following variable expansion
is used: <code>${FCEDIT:-${EDITOR:-vi}}</code>.  This says to use the
value of the <code>FCEDIT</code> variable if set, or the value of the
<code>EDITOR</code> variable if that is set, or <code>vi</code> if neither is set.
When editing is complete, the edited commands are echoed and executed.
</p>
<p>In the second form, <var>command</var> is re-executed after each instance
of <var>pat</var> in the selected command is replaced by <var>rep</var>.
<var>command</var> is interpreted the same as <var>first</var> above.
</p>
<p>A useful alias to use with the <code>fc</code> command is <code>r='fc -s'</code>, so
that typing &lsquo;<samp>r cc</samp>&rsquo; runs the last command beginning with <code>cc</code>
and typing &lsquo;<samp>r</samp>&rsquo; re-executes the last command (see <a href="#Aliases">Aliases</a>).
</p>
</dd>
<dt id='index-history'><span><code>history</code><a href='#index-history' class='copiable-anchor'> &para;</a></span></dt>
<dd><div class="example">
<pre class="example">history [<var>n</var>]
history -c
history -d <var>offset</var>
history -d <var>start</var>-<var>end</var>
history [-anrw] [<var>filename</var>]
history -ps <var>arg</var>
</pre></div>

<p>With no options, display the history list with line numbers.
Lines prefixed with a &lsquo;<samp>*</samp>&rsquo; have been modified.
An argument of <var>n</var> lists only the last <var>n</var> lines.
If the shell variable <code>HISTTIMEFORMAT</code> is set and not null,
it is used as a format string for <var>strftime</var> to display
the time stamp associated with each displayed history entry.
No intervening blank is printed between the formatted time stamp
and the history line.
</p>
<p>Options, if supplied, have the following meanings:
</p>
<dl compact="compact">
<dt><span><code>-c</code></span></dt>
<dd><p>Clear the history list.  This may be combined
with the other options to replace the history list completely.
</p>
</dd>
<dt><span><code>-d <var>offset</var></code></span></dt>
<dd><p>Delete the history entry at position <var>offset</var>.
If <var>offset</var> is positive, it should be specified as it appears when
the history is displayed.
If <var>offset</var> is negative, it is interpreted as relative to one greater
than the last history position, so negative indices count back from the
end of the history, and an index of &lsquo;<samp>-1</samp>&rsquo; refers to the current
<code>history -d</code> command.
</p>
</dd>
<dt><span><code>-d <var>start</var>-<var>end</var></code></span></dt>
<dd><p>Delete the range of history entries between positions <var>start</var> and
<var>end</var>, inclusive.
Positive and negative values for <var>start</var> and <var>end</var>
are interpreted as described above.
</p>
</dd>
<dt><span><code>-a</code></span></dt>
<dd><p>Append the new history lines to the history file.
These are history lines entered since the beginning of the current
Bash session, but not already appended to the history file.
</p>
</dd>
<dt><span><code>-n</code></span></dt>
<dd><p>Append the history lines not already read from the history file
to the current history list.  These are lines appended to the history
file since the beginning of the current Bash session.
</p>
</dd>
<dt><span><code>-r</code></span></dt>
<dd><p>Read the history file and append its contents to
the history list.
</p>
</dd>
<dt><span><code>-w</code></span></dt>
<dd><p>Write out the current history list to the history file.
</p>
</dd>
<dt><span><code>-p</code></span></dt>
<dd><p>Perform history substitution on the <var>arg</var>s and display the result
on the standard output, without storing the results in the history list.
</p>
</dd>
<dt><span><code>-s</code></span></dt>
<dd><p>The <var>arg</var>s are added to the end of
the history list as a single entry.
</p>
</dd>
</dl>

<p>If a <var>filename</var> argument is supplied
when any of the <samp>-w</samp>, <samp>-r</samp>, <samp>-a</samp>, or <samp>-n</samp> options
is used, Bash uses <var>filename</var> as the history file.
If not, then the value of the <code>HISTFILE</code> variable is used.
</p>
<p>The return value is 0 unless an invalid option is encountered, an
error occurs while reading or writing the history file, an invalid
<var>offset</var> or range is supplied as an argument to <samp>-d</samp>, or the
history expansion supplied as an argument to <samp>-p</samp> fails.
</p>
</dd>
</dl>

<hr>
</div>
<div class="section" id="History-Interaction">
<div class="header">
<p>
Previous: <a href="#Bash-History-Builtins" accesskey="p" rel="prev">Bash History Builtins</a>, Up: <a href="#Using-History-Interactively" accesskey="u" rel="up">Using History Interactively</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="History-Expansion"></span><h3 class="section">9.3 History Expansion</h3>
<span id="index-history-expansion"></span>

<p>The History library provides a history expansion feature that is similar
to the history expansion provided by <code>csh</code>.  This section
describes the syntax used to manipulate the history information.
</p>
<p>History expansions introduce words from the history list into
the input stream, making it easy to repeat commands, insert the
arguments to a previous command into the current input line, or
fix errors in previous commands quickly.
</p>
<p>History expansion is performed immediately after a complete line
is read, before the shell breaks it into words, and is performed
on each line individually.  Bash attempts to inform the history
expansion functions about quoting still in effect from previous lines.
</p>
<p>History expansion takes place in two parts.  The first is to determine
which line from the history list should be used during substitution.
The second is to select portions of that line for inclusion into the
current one.  The line selected from the history is called the
<em>event</em>, and the portions of that line that are acted upon are
called <em>words</em>.  Various <em>modifiers</em> are available to manipulate
the selected words.  The line is broken into words in the same fashion
that Bash does, so that several words
surrounded by quotes are considered one word.
History expansions are introduced by the appearance of the
history expansion character, which is &lsquo;<samp>!</samp>&rsquo; by default.
</p>
<p>History expansion implements shell-like quoting conventions:
a backslash can be used to remove the special handling for the next character;
single quotes enclose verbatim sequences of characters, and can be used to
inhibit history expansion;
and characters enclosed within double quotes may be subject to history
expansion, since backslash can escape the history expansion character,
but single quotes may not, since they are not treated specially within
double quotes.
</p>
<p>When using the shell, only &lsquo;<samp>\</samp>&rsquo; and &lsquo;<samp>'</samp>&rsquo; may be used to escape the
history expansion character, but the history expansion character is
also treated as quoted if it immediately precedes the closing double quote
in a double-quoted string. 
</p>
<p>Several shell options settable with the <code>shopt</code>
builtin (see <a href="#The-Shopt-Builtin">The Shopt Builtin</a>) may be used to tailor
the behavior of history expansion.  If the
<code>histverify</code> shell option is enabled, and Readline
is being used, history substitutions are not immediately passed to
the shell parser.
Instead, the expanded line is reloaded into the Readline
editing buffer for further modification.
If Readline is being used, and the <code>histreedit</code>
shell option is enabled, a failed history expansion will be
reloaded into the Readline editing buffer for correction.
The <samp>-p</samp> option to the <code>history</code> builtin command
may be used to see what a history expansion will do before using it.
The <samp>-s</samp> option to the <code>history</code> builtin may be used to
add commands to the end of the history list without actually executing
them, so that they are available for subsequent recall.
This is most useful in conjunction with Readline.
</p>
<p>The shell allows control of the various characters used by the
history expansion mechanism with the <code>histchars</code> variable,
as explained above (see <a href="#Bash-Variables">Bash Variables</a>).  The shell uses
the history comment character to mark history timestamps when
writing the history file.
</p>

<ul class="section-toc">
<li><a href="#Event-Designators" accesskey="1">Event Designators</a></li>
<li><a href="#Word-Designators" accesskey="2">Word Designators</a></li>
<li><a href="#Modifiers" accesskey="3">Modifiers</a></li>
</ul>
<hr>
<div class="subsection" id="Event-Designators">
<div class="header">
<p>
Next: <a href="#Word-Designators" accesskey="n" rel="next">Word Designators</a>, Up: <a href="#History-Interaction" accesskey="u" rel="up">History Expansion</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Event-Designators-1"></span><h4 class="subsection">9.3.1 Event Designators</h4>
<span id="index-event-designators"></span>

<p>An event designator is a reference to a command line entry in the
history list.
Unless the reference is absolute, events are relative to the current
position in the history list.
<span id="index-history-events"></span>
</p>
<dl compact="compact">
<dt><span><code>!</code></span></dt>
<dd><p>Start a history substitution, except when followed by a space, tab,
the end of the line, &lsquo;<samp>=</samp>&rsquo; or &lsquo;<samp>(</samp>&rsquo; (when the
<code>extglob</code> shell option is enabled using the <code>shopt</code> builtin).
</p>
</dd>
<dt><span><code>!<var>n</var></code></span></dt>
<dd><p>Refer to command line <var>n</var>.
</p>
</dd>
<dt><span><code>!-<var>n</var></code></span></dt>
<dd><p>Refer to the command <var>n</var> lines back.
</p>
</dd>
<dt><span><code>!!</code></span></dt>
<dd><p>Refer to the previous command.  This is a synonym for &lsquo;<samp>!-1</samp>&rsquo;.
</p>
</dd>
<dt><span><code>!<var>string</var></code></span></dt>
<dd><p>Refer to the most recent command
preceding the current position in the history list
starting with <var>string</var>.
</p>
</dd>
<dt><span><code>!?<var>string</var>[?]</code></span></dt>
<dd><p>Refer to the most recent command
preceding the current position in the history list
containing <var>string</var>.
The trailing
&lsquo;<samp>?</samp>&rsquo; may be omitted if the <var>string</var> is followed immediately by
a newline.
If <var>string</var> is missing, the string from the most recent search is used;
it is an error if there is no previous search string.
</p>
</dd>
<dt><span><code>^<var>string1</var>^<var>string2</var>^</code></span></dt>
<dd><p>Quick Substitution.  Repeat the last command, replacing <var>string1</var>
with <var>string2</var>.  Equivalent to
<code>!!:s^<var>string1</var>^<var>string2</var>^</code>.
</p>
</dd>
<dt><span><code>!#</code></span></dt>
<dd><p>The entire command line typed so far.
</p>
</dd>
</dl>

<hr>
</div>
<div class="subsection" id="Word-Designators">
<div class="header">
<p>
Next: <a href="#Modifiers" accesskey="n" rel="next">Modifiers</a>, Previous: <a href="#Event-Designators" accesskey="p" rel="prev">Event Designators</a>, Up: <a href="#History-Interaction" accesskey="u" rel="up">History Expansion</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Word-Designators-1"></span><h4 class="subsection">9.3.2 Word Designators</h4>

<p>Word designators are used to select desired words from the event.
A &lsquo;<samp>:</samp>&rsquo; separates the event specification from the word designator.  It
may be omitted if the word designator begins with a &lsquo;<samp>^</samp>&rsquo;, &lsquo;<samp>$</samp>&rsquo;,
&lsquo;<samp>*</samp>&rsquo;, &lsquo;<samp>-</samp>&rsquo;, or &lsquo;<samp>%</samp>&rsquo;.  Words are numbered from the beginning
of the line, with the first word being denoted by 0 (zero).  Words are
inserted into the current line separated by single spaces.
</p>
<p>For example,
</p>
<dl compact="compact">
<dt><span><code>!!</code></span></dt>
<dd><p>designates the preceding command.  When you type this, the preceding
command is repeated in toto.
</p>
</dd>
<dt><span><code>!!:$</code></span></dt>
<dd><p>designates the last argument of the preceding command.  This may be
shortened to <code>!$</code>.
</p>
</dd>
<dt><span><code>!fi:2</code></span></dt>
<dd><p>designates the second argument of the most recent command starting with
the letters <code>fi</code>.
</p></dd>
</dl>

<p>Here are the word designators:
</p> 
<dl compact="compact">
<dt><span><code>0 (zero)</code></span></dt>
<dd><p>The <code>0</code>th word.  For many applications, this is the command word.
</p>
</dd>
<dt><span><code><var>n</var></code></span></dt>
<dd><p>The <var>n</var>th word.
</p>
</dd>
<dt><span><code>^</code></span></dt>
<dd><p>The first argument; that is, word 1.
</p>
</dd>
<dt><span><code>$</code></span></dt>
<dd><p>The last argument.
</p>
</dd>
<dt><span><code>%</code></span></dt>
<dd><p>The first word matched by the most recent &lsquo;<samp>?<var>string</var>?</samp>&rsquo; search,
if the search string begins with a character that is part of a word.
</p>
</dd>
<dt><span><code><var>x</var>-<var>y</var></code></span></dt>
<dd><p>A range of words; &lsquo;<samp>-<var>y</var></samp>&rsquo; abbreviates &lsquo;<samp>0-<var>y</var></samp>&rsquo;.
</p>
</dd>
<dt><span><code>*</code></span></dt>
<dd><p>All of the words, except the <code>0</code>th.  This is a synonym for &lsquo;<samp>1-$</samp>&rsquo;.
It is not an error to use &lsquo;<samp>*</samp>&rsquo; if there is just one word in the event;
the empty string is returned in that case.
</p>
</dd>
<dt><span><code><var>x</var>*</code></span></dt>
<dd><p>Abbreviates &lsquo;<samp><var>x</var>-$</samp>&rsquo;
</p>
</dd>
<dt><span><code><var>x</var>-</code></span></dt>
<dd><p>Abbreviates &lsquo;<samp><var>x</var>-$</samp>&rsquo; like &lsquo;<samp><var>x</var>*</samp>&rsquo;, but omits the last word.
If &lsquo;<samp>x</samp>&rsquo; is missing, it defaults to 0.
</p>
</dd>
</dl>

<p>If a word designator is supplied without an event specification, the
previous command is used as the event.
</p>
<hr>
</div>
<div class="subsection" id="Modifiers">
<div class="header">
<p>
Previous: <a href="#Word-Designators" accesskey="p" rel="prev">Word Designators</a>, Up: <a href="#History-Interaction" accesskey="u" rel="up">History Expansion</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Modifiers-1"></span><h4 class="subsection">9.3.3 Modifiers</h4>

<p>After the optional word designator, you can add a sequence of one or more
of the following modifiers, each preceded by a &lsquo;<samp>:</samp>&rsquo;.
These modify, or edit, the word or words selected from the history event.
</p>
<dl compact="compact">
<dt><span><code>h</code></span></dt>
<dd><p>Remove a trailing pathname component, leaving only the head.
</p>
</dd>
<dt><span><code>t</code></span></dt>
<dd><p>Remove all leading pathname components, leaving the tail.
</p>
</dd>
<dt><span><code>r</code></span></dt>
<dd><p>Remove a trailing suffix of the form &lsquo;<samp>.<var>suffix</var></samp>&rsquo;, leaving
the basename.
</p>
</dd>
<dt><span><code>e</code></span></dt>
<dd><p>Remove all but the trailing suffix.
</p>
</dd>
<dt><span><code>p</code></span></dt>
<dd><p>Print the new command but do not execute it.
</p>
</dd>
<dt><span><code>q</code></span></dt>
<dd><p>Quote the substituted words, escaping further substitutions.
</p>
</dd>
<dt><span><code>x</code></span></dt>
<dd><p>Quote the substituted words as with &lsquo;<samp>q</samp>&rsquo;,
but break into words at spaces, tabs, and newlines.
The &lsquo;<samp>q</samp>&rsquo; and &lsquo;<samp>x</samp>&rsquo; modifiers are mutually exclusive; the last one
supplied is used.
</p>
</dd>
<dt><span><code>s/<var>old</var>/<var>new</var>/</code></span></dt>
<dd><p>Substitute <var>new</var> for the first occurrence of <var>old</var> in the
event line.
Any character may be used as the delimiter in place of &lsquo;<samp>/</samp>&rsquo;.
The delimiter may be quoted in <var>old</var> and <var>new</var>
with a single backslash.  If &lsquo;<samp>&amp;</samp>&rsquo; appears in <var>new</var>,
it is replaced by <var>old</var>.  A single backslash will quote
the &lsquo;<samp>&amp;</samp>&rsquo;.
If <var>old</var> is null, it is set to the last <var>old</var>
substituted, or, if no previous history substitutions took place,
the last <var>string</var>
in a !?<var>string</var><code>[?]</code>
search.
If <var>new</var> is null, each matching <var>old</var> is deleted.
The final delimiter is optional if it is the last
character on the input line.
</p>
</dd>
<dt><span><code>&amp;</code></span></dt>
<dd><p>Repeat the previous substitution.
</p>
</dd>
<dt><span><code>g</code></span></dt>
<dt><span><code>a</code></span></dt>
<dd><p>Cause changes to be applied over the entire event line.  Used in
conjunction with &lsquo;<samp>s</samp>&rsquo;, as in <code>gs/<var>old</var>/<var>new</var>/</code>,
or with &lsquo;<samp>&amp;</samp>&rsquo;.
</p>
</dd>
<dt><span><code>G</code></span></dt>
<dd><p>Apply the following &lsquo;<samp>s</samp>&rsquo; or &lsquo;<samp>&amp;</samp>&rsquo; modifier once to each word
in the event.
</p>
</dd>
</dl>

<hr>
</div>
</div>
</div>
<div class="chapter" id="Installing-Bash">
<div class="header">
<p>
Next: <a href="#Reporting-Bugs" accesskey="n" rel="next">Reporting Bugs</a>, Previous: <a href="#Using-History-Interactively" accesskey="p" rel="prev">Using History Interactively</a>, Up: <a href="#Top" accesskey="u" rel="up">Bash Features</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Installing-Bash-1"></span><h2 class="chapter">10 Installing Bash</h2>

<p>This chapter provides basic instructions for installing Bash on
the various supported platforms.  The distribution supports the
<small>GNU</small> operating systems, nearly every version of Unix, and several
non-Unix systems such as BeOS and Interix.
Other independent ports exist for
<small>MS-DOS</small>, <small>OS/2</small>, and Windows platforms.
</p>

<ul class="section-toc">
<li><a href="#Basic-Installation" accesskey="1">Basic Installation</a></li>
<li><a href="#Compilers-and-Options" accesskey="2">Compilers and Options</a></li>
<li><a href="#Compiling-For-Multiple-Architectures" accesskey="3">Compiling For Multiple Architectures</a></li>
<li><a href="#Installation-Names" accesskey="4">Installation Names</a></li>
<li><a href="#Specifying-the-System-Type" accesskey="5">Specifying the System Type</a></li>
<li><a href="#Sharing-Defaults" accesskey="6">Sharing Defaults</a></li>
<li><a href="#Operation-Controls" accesskey="7">Operation Controls</a></li>
<li><a href="#Optional-Features" accesskey="8">Optional Features</a></li>
</ul>
<hr>
<div class="section" id="Basic-Installation">
<div class="header">
<p>
Next: <a href="#Compilers-and-Options" accesskey="n" rel="next">Compilers and Options</a>, Up: <a href="#Installing-Bash" accesskey="u" rel="up">Installing Bash</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Basic-Installation-1"></span><h3 class="section">10.1 Basic Installation</h3>
<span id="index-installation"></span>
<span id="index-configuration"></span>
<span id="index-Bash-installation"></span>
<span id="index-Bash-configuration"></span>

<p>These are installation instructions for Bash.
</p>
<p>The simplest way to compile Bash is:
</p>
<ol>
<li> <code>cd</code> to the directory containing the source code and type
&lsquo;<samp>./configure</samp>&rsquo; to configure Bash for your system.  If you&rsquo;re
using <code>csh</code> on an old version of System V, you might need to
type &lsquo;<samp>sh ./configure</samp>&rsquo; instead to prevent <code>csh</code> from trying
to execute <code>configure</code> itself.

<p>Running <code>configure</code> takes some time.
While running, it prints messages telling which features it is
checking for.
</p>
</li><li> Type &lsquo;<samp>make</samp>&rsquo; to compile Bash and build the <code>bashbug</code> bug
reporting script.

</li><li> Optionally, type &lsquo;<samp>make tests</samp>&rsquo; to run the Bash test suite.

</li><li> Type &lsquo;<samp>make install</samp>&rsquo; to install <code>bash</code> and <code>bashbug</code>.
This will also install the manual pages and Info file, message translation
files, some supplemental documentation, a number of example loadable
builtin commands, and a set of header files for developing loadable
builtins.
You may need additional privileges to install <code>bash</code> to your
desired destination, so &lsquo;<samp>sudo make install</samp>&rsquo; might be required.
More information about controlling the locations where <code>bash</code> and
other files are installed is below (see <a href="#Installation-Names">Installation Names</a>).

</li></ol>

<p>The <code>configure</code> shell script attempts to guess correct
values for various system-dependent variables used during
compilation.  It uses those values to create a <samp>Makefile</samp> in
each directory of the package (the top directory, the
<samp>builtins</samp>, <samp>doc</samp>, <samp>po</samp>, and <samp>support</samp> directories,
each directory under <samp>lib</samp>, and several others).  It also creates a
<samp>config.h</samp> file containing system-dependent definitions. 
Finally, it creates a shell script named <code>config.status</code> that you
can run in the future to recreate the current configuration, a
file <samp>config.cache</samp> that saves the results of its tests to
speed up reconfiguring, and a file <samp>config.log</samp> containing
compiler output (useful mainly for debugging <code>configure</code>). 
If at some point
<samp>config.cache</samp> contains results you don&rsquo;t want to keep, you
may remove or edit it. 
</p>
<p>To find out more about the options and arguments that the
<code>configure</code> script understands, type 
</p>
<div class="example">
<pre class="example">bash-4.2$ ./configure --help
</pre></div>

<p>at the Bash prompt in your Bash source directory.
</p>
<p>If you want to build Bash in a directory separate from the source
directory &ndash; to build for multiple architectures, for example &ndash;
just use the full path to the configure script. The following commands
will build bash in a directory under <samp>/usr/local/build</samp> from
the source code in <samp>/usr/local/src/bash-4.4</samp>:
</p>
<div class="example">
<pre class="example">mkdir /usr/local/build/bash-4.4
cd /usr/local/build/bash-4.4
bash /usr/local/src/bash-4.4/configure
make
</pre></div>

<p>See <a href="#Compiling-For-Multiple-Architectures">Compiling For Multiple Architectures</a> for more information
about building in a directory separate from the source.
</p>
<p>If you need to do unusual things to compile Bash, please
try to figure out how <code>configure</code> could check whether or not
to do them, and mail diffs or instructions to
<a href="mailto:bash-maintainers@gnu.org">bash-maintainers@gnu.org</a> so they can be
considered for the next release.
</p>
<p>The file <samp>configure.ac</samp> is used to create <code>configure</code>
by a program called Autoconf.
You only need <samp>configure.ac</samp> if you want to change it or regenerate
<code>configure</code> using a newer version of Autoconf.
If you do this, make sure you are using Autoconf version 2.69 or
newer.
</p>
<p>You can remove the program binaries and object files from the
source code directory by typing &lsquo;<samp>make clean</samp>&rsquo;.  To also remove the
files that <code>configure</code> created (so you can compile Bash for
a different kind of computer), type &lsquo;<samp>make distclean</samp>&rsquo;.
</p>
<hr>
</div>
<div class="section" id="Compilers-and-Options">
<div class="header">
<p>
Next: <a href="#Compiling-For-Multiple-Architectures" accesskey="n" rel="next">Compiling For Multiple Architectures</a>, Previous: <a href="#Basic-Installation" accesskey="p" rel="prev">Basic Installation</a>, Up: <a href="#Installing-Bash" accesskey="u" rel="up">Installing Bash</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Compilers-and-Options-1"></span><h3 class="section">10.2 Compilers and Options</h3>

<p>Some systems require unusual options for compilation or linking
that the <code>configure</code> script does not know about.  You can
give <code>configure</code> initial values for variables by setting
them in the environment.  Using a Bourne-compatible shell, you
can do that on the command line like this:
</p>
<div class="example">
<pre class="example">CC=c89 CFLAGS=-O2 LIBS=-lposix ./configure
</pre></div>

<p>On systems that have the <code>env</code> program, you can do it like this:
</p>
<div class="example">
<pre class="example">env CPPFLAGS=-I/usr/local/include LDFLAGS=-s ./configure
</pre></div>

<p>The configuration process uses GCC to build Bash if it
is available.
</p>
<hr>
</div>
<div class="section" id="Compiling-For-Multiple-Architectures">
<div class="header">
<p>
Next: <a href="#Installation-Names" accesskey="n" rel="next">Installation Names</a>, Previous: <a href="#Compilers-and-Options" accesskey="p" rel="prev">Compilers and Options</a>, Up: <a href="#Installing-Bash" accesskey="u" rel="up">Installing Bash</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Compiling-For-Multiple-Architectures-1"></span><h3 class="section">10.3 Compiling For Multiple Architectures</h3>

<p>You can compile Bash for more than one kind of computer at the
same time, by placing the object files for each architecture in their
own directory.  To do this, you must use a version of <code>make</code> that
supports the <code>VPATH</code> variable, such as GNU <code>make</code>.
<code>cd</code> to the
directory where you want the object files and executables to go and run
the <code>configure</code> script from the source directory
(see <a href="#Basic-Installation">Basic Installation</a>).
You may need to
supply the <samp>--srcdir=PATH</samp> argument to tell <code>configure</code> where the
source files are.  <code>configure</code> automatically checks for the
source code in the directory that <code>configure</code> is in and in &lsquo;..&rsquo;.
</p>
<p>If you have to use a <code>make</code> that does not support the <code>VPATH</code>
variable, you can compile Bash for one architecture at a
time in the source code directory.  After you have installed
Bash for one architecture, use &lsquo;<samp>make distclean</samp>&rsquo; before
reconfiguring for another architecture.
</p>
<p>Alternatively, if your system supports symbolic links, you can use the
<samp>support/mkclone</samp> script to create a build tree which has
symbolic links back to each file in the source directory.  Here&rsquo;s an
example that creates a build directory in the current directory from a
source directory <samp>/usr/gnu/src/bash-2.0</samp>:
</p>
<div class="example">
<pre class="example">bash /usr/gnu/src/bash-2.0/support/mkclone -s /usr/gnu/src/bash-2.0 .
</pre></div>

<p>The <code>mkclone</code> script requires Bash, so you must have already built
Bash for at least one architecture before you can create build
directories for other architectures.
</p>
<hr>
</div>
<div class="section" id="Installation-Names">
<div class="header">
<p>
Next: <a href="#Specifying-the-System-Type" accesskey="n" rel="next">Specifying the System Type</a>, Previous: <a href="#Compiling-For-Multiple-Architectures" accesskey="p" rel="prev">Compiling For Multiple Architectures</a>, Up: <a href="#Installing-Bash" accesskey="u" rel="up">Installing Bash</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Installation-Names-1"></span><h3 class="section">10.4 Installation Names</h3>

<p>By default, &lsquo;<samp>make install</samp>&rsquo; will install into
<samp>/usr/local/bin</samp>, <samp>/usr/local/man</samp>, etc.;
that is, the <em>installation prefix</em> defaults to <samp>/usr/local</samp>.
You can specify an installation prefix other than <samp>/usr/local</samp> by
giving <code>configure</code> the option <samp>--prefix=<var>PATH</var></samp>,
or by specifying a value for the <code>prefix</code> &lsquo;<samp>make</samp>&rsquo;
variable when running &lsquo;<samp>make install</samp>&rsquo;
(e.g., &lsquo;<samp>make install prefix=<var>PATH</var></samp>&rsquo;).
The <code>prefix</code> variable provides a default for <code>exec_prefix</code> and
other variables used when installing bash.
</p>
<p>You can specify separate installation prefixes for
architecture-specific files and architecture-independent files. 
If you give <code>configure</code> the option
<samp>--exec-prefix=<var>PATH</var></samp>, &lsquo;<samp>make install</samp>&rsquo; will use
<var>PATH</var> as the prefix for installing programs and libraries.
Documentation and other data files will still use the regular prefix.
</p>
<p>If you would like to change the installation locations for a single run,
you can specify these variables as arguments to <code>make</code>:
&lsquo;<samp>make install exec_prefix=/</samp>&rsquo; will install <code>bash</code> and
<code>bashbug</code> into <samp>/bin</samp> instead of the default <samp>/usr/local/bin</samp>.
</p>
<p>If you want to see the files bash will install and where it will install
them without changing anything on your system, specify the variable
<code>DESTDIR</code> as an argument to <code>make</code>. Its value should be the
absolute directory path you&rsquo;d like to use as the root of your sample
installation tree. For example,
</p>
<div class="example">
<pre class="example">mkdir /fs1/bash-install
make install DESTDIR=/fs1/bash-install
</pre></div>

<p>will install <code>bash</code> into <samp>/fs1/bash-install/usr/local/bin/bash</samp>,
the documentation into directories within
<samp>/fs1/bash-install/usr/local/share</samp>, the example loadable builtins into
<samp>/fs1/bash-install/usr/local/lib/bash</samp>, and so on.
You can use the usual <code>exec_prefix</code> and <code>prefix</code> variables to alter
the directory paths beneath the value of <code>DESTDIR</code>.
</p>
<p>The GNU Makefile standards provide a more complete description of these
variables and their effects.
</p>
<hr>
</div>
<div class="section" id="Specifying-the-System-Type">
<div class="header">
<p>
Next: <a href="#Sharing-Defaults" accesskey="n" rel="next">Sharing Defaults</a>, Previous: <a href="#Installation-Names" accesskey="p" rel="prev">Installation Names</a>, Up: <a href="#Installing-Bash" accesskey="u" rel="up">Installing Bash</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Specifying-the-System-Type-1"></span><h3 class="section">10.5 Specifying the System Type</h3>

<p>There may be some features <code>configure</code> can not figure out
automatically, but needs to determine by the type of host Bash
will run on.  Usually <code>configure</code> can figure that
out, but if it prints a message saying it can not guess the host
type, give it the <samp>--host=TYPE</samp> option.  &lsquo;<samp>TYPE</samp>&rsquo; can
either be a short name for the system type, such as &lsquo;<samp>sun4</samp>&rsquo;,
or a canonical name with three fields: &lsquo;<samp>CPU-COMPANY-SYSTEM</samp>&rsquo;
(e.g., &lsquo;<samp>i386-unknown-freebsd4.2</samp>&rsquo;).
</p>
<p>See the file <samp>support/config.sub</samp> for the possible
values of each field. 
</p>
<hr>
</div>
<div class="section" id="Sharing-Defaults">
<div class="header">
<p>
Next: <a href="#Operation-Controls" accesskey="n" rel="next">Operation Controls</a>, Previous: <a href="#Specifying-the-System-Type" accesskey="p" rel="prev">Specifying the System Type</a>, Up: <a href="#Installing-Bash" accesskey="u" rel="up">Installing Bash</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Sharing-Defaults-1"></span><h3 class="section">10.6 Sharing Defaults</h3>

<p>If you want to set default values for <code>configure</code> scripts to
share, you can create a site shell script called
<code>config.site</code> that gives default values for variables like
<code>CC</code>, <code>cache_file</code>, and <code>prefix</code>.  <code>configure</code>
looks for <samp>PREFIX/share/config.site</samp> if it exists, then
<samp>PREFIX/etc/config.site</samp> if it exists.  Or, you can set the
<code>CONFIG_SITE</code> environment variable to the location of the site
script.  A warning: the Bash <code>configure</code> looks for a site script,
but not all <code>configure</code> scripts do.
</p>
<hr>
</div>
<div class="section" id="Operation-Controls">
<div class="header">
<p>
Next: <a href="#Optional-Features" accesskey="n" rel="next">Optional Features</a>, Previous: <a href="#Sharing-Defaults" accesskey="p" rel="prev">Sharing Defaults</a>, Up: <a href="#Installing-Bash" accesskey="u" rel="up">Installing Bash</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Operation-Controls-1"></span><h3 class="section">10.7 Operation Controls</h3>

<p><code>configure</code> recognizes the following options to control how it
operates.
</p>
<dl compact="compact">
<dt><span><code>--cache-file=<var>file</var></code></span></dt>
<dd><p>Use and save the results of the tests in
<var>file</var> instead of <samp>./config.cache</samp>.  Set <var>file</var> to
<samp>/dev/null</samp> to disable caching, for debugging
<code>configure</code>. 
</p>
</dd>
<dt><span><code>--help</code></span></dt>
<dd><p>Print a summary of the options to <code>configure</code>, and exit.
</p>
</dd>
<dt><span><code>--quiet</code></span></dt>
<dt><span><code>--silent</code></span></dt>
<dt><span><code>-q</code></span></dt>
<dd><p>Do not print messages saying which checks are being made.
</p>
</dd>
<dt><span><code>--srcdir=<var>dir</var></code></span></dt>
<dd><p>Look for the Bash source code in directory <var>dir</var>.  Usually
<code>configure</code> can determine that directory automatically.
</p>
</dd>
<dt><span><code>--version</code></span></dt>
<dd><p>Print the version of Autoconf used to generate the <code>configure</code>
script, and exit.
</p></dd>
</dl>

<p><code>configure</code> also accepts some other, not widely used, boilerplate
options.  &lsquo;<samp>configure --help</samp>&rsquo; prints the complete list.
</p>
<hr>
</div>
<div class="section" id="Optional-Features">
<div class="header">
<p>
Previous: <a href="#Operation-Controls" accesskey="p" rel="prev">Operation Controls</a>, Up: <a href="#Installing-Bash" accesskey="u" rel="up">Installing Bash</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Optional-Features-1"></span><h3 class="section">10.8 Optional Features</h3>

<p>The Bash <code>configure</code> has a number of <samp>--enable-<var>feature</var></samp>
options, where <var>feature</var> indicates an optional part of Bash.
There are also several <samp>--with-<var>package</var></samp> options,
where <var>package</var> is something like &lsquo;<samp>bash-malloc</samp>&rsquo; or &lsquo;<samp>purify</samp>&rsquo;.
To turn off the default use of a package, use
<samp>--without-<var>package</var></samp>.  To configure Bash without a feature
that is enabled by default, use <samp>--disable-<var>feature</var></samp>.
</p>
<p>Here is a complete list of the <samp>--enable-</samp> and
<samp>--with-</samp> options that the Bash <code>configure</code> recognizes. 
</p>
<dl compact="compact">
<dt><span><code>--with-afs</code></span></dt>
<dd><p>Define if you are using the Andrew File System from Transarc.
</p>
</dd>
<dt><span><code>--with-bash-malloc</code></span></dt>
<dd><p>Use the Bash version of
<code>malloc</code> in the directory <samp>lib/malloc</samp>.  This is not the same
<code>malloc</code> that appears in <small>GNU</small> libc, but an older version
originally derived from the 4.2 <small>BSD</small> <code>malloc</code>.  This <code>malloc</code>
is very fast, but wastes some space on each allocation.
This option is enabled by default.
The <samp>NOTES</samp> file contains a list of systems for
which this should be turned off, and <code>configure</code> disables this
option automatically for a number of systems.
</p>
</dd>
<dt><span><code>--with-curses</code></span></dt>
<dd><p>Use the curses library instead of the termcap library.  This should
be supplied if your system has an inadequate or incomplete termcap
database.
</p>
</dd>
<dt><span><code>--with-gnu-malloc</code></span></dt>
<dd><p>A synonym for <code>--with-bash-malloc</code>.
</p>
</dd>
<dt><span><code>--with-installed-readline[=<var>PREFIX</var>]</code></span></dt>
<dd><p>Define this to make Bash link with a locally-installed version of Readline
rather than the version in <samp>lib/readline</samp>.  This works only with
Readline 5.0 and later versions.  If <var>PREFIX</var> is <code>yes</code> or not
supplied, <code>configure</code> uses the values of the make variables
<code>includedir</code> and <code>libdir</code>, which are subdirectories of <code>prefix</code>
by default, to find the installed version of Readline if it is not in
the standard system include and library directories.
If <var>PREFIX</var> is <code>no</code>, Bash links with the version in
<samp>lib/readline</samp>.
If <var>PREFIX</var> is set to any other value, <code>configure</code> treats it as
a directory pathname and looks for
the installed version of Readline in subdirectories of that directory
(include files in <var>PREFIX</var>/<code>include</code> and the library in
<var>PREFIX</var>/<code>lib</code>).
</p>
</dd>
<dt><span><code>--with-libintl-prefix[=<var>PREFIX</var>]</code></span></dt>
<dd><p>Define this to make Bash link with a locally-installed version of the
libintl library instead of the version in <samp>lib/intl</samp>.
</p>
</dd>
<dt><span><code>--with-libiconv-prefix[=<var>PREFIX</var>]</code></span></dt>
<dd><p>Define this to make Bash look for libiconv in <var>PREFIX</var> instead of the
standard system locations. There is no version included with Bash.
</p>
</dd>
<dt><span><code>--enable-minimal-config</code></span></dt>
<dd><p>This produces a shell with minimal features, close to the historical
Bourne shell.
</p></dd>
</dl>

<p>There are several <samp>--enable-</samp> options that alter how Bash is
compiled, linked, and installed, rather than changing run-time features.
</p>
<dl compact="compact">
<dt><span><code>--enable-largefile</code></span></dt>
<dd><p>Enable support for <a href="http://www.unix.org/version2/whatsnew/lfs20mar.html">large files</a> if the operating system requires special compiler options
to build programs which can access large files.  This is enabled by
default, if the operating system provides large file support.
</p>
</dd>
<dt><span><code>--enable-profiling</code></span></dt>
<dd><p>This builds a Bash binary that produces profiling information to be
processed by <code>gprof</code> each time it is executed.
</p>
</dd>
<dt><span><code>--enable-separate-helpfiles</code></span></dt>
<dd><p>Use external files for the documentation displayed by the <code>help</code> builtin
instead of storing the text internally.
</p>
</dd>
<dt><span><code>--enable-static-link</code></span></dt>
<dd><p>This causes Bash to be linked statically, if <code>gcc</code> is being used.
This could be used to build a version to use as root&rsquo;s shell.
</p>
</dd>
</dl>

<p>The &lsquo;<samp>minimal-config</samp>&rsquo; option can be used to disable all of
the following options, but it is processed first, so individual
options may be enabled using &lsquo;<samp>enable-<var>feature</var></samp>&rsquo;. 
</p>
<p>All of the following options except for
&lsquo;<samp>alt-array-implementation</samp>&rsquo;,
&lsquo;<samp>disabled-builtins</samp>&rsquo;,
&lsquo;<samp>direxpand-default</samp>&rsquo;,
&lsquo;<samp>strict-posix-default</samp>&rsquo;,
and
&lsquo;<samp>xpg-echo-default</samp>&rsquo; are
enabled by default, unless the operating system does not provide the
necessary support.
</p>
<dl compact="compact">
<dt><span><code>--enable-alias</code></span></dt>
<dd><p>Allow alias expansion and include the <code>alias</code> and <code>unalias</code>
builtins (see <a href="#Aliases">Aliases</a>).
</p>
</dd>
<dt><span><code>--enable-alt-array-implementation</code></span></dt>
<dd><p>This builds bash using an alternate implementation of arrays
(see <a href="#Arrays">Arrays</a>) that provides faster access at the expense of using
more memory (sometimes many times more, depending on how sparse an array is).
</p>
</dd>
<dt><span><code>--enable-arith-for-command</code></span></dt>
<dd><p>Include support for the alternate form of the <code>for</code> command
that behaves like the C language <code>for</code> statement
(see <a href="#Looping-Constructs">Looping Constructs</a>).
</p>
</dd>
<dt><span><code>--enable-array-variables</code></span></dt>
<dd><p>Include support for one-dimensional array shell variables
(see <a href="#Arrays">Arrays</a>).
</p>
</dd>
<dt><span><code>--enable-bang-history</code></span></dt>
<dd><p>Include support for <code>csh</code>-like history substitution
(see <a href="#History-Interaction">History Expansion</a>).
</p>
</dd>
<dt><span><code>--enable-brace-expansion</code></span></dt>
<dd><p>Include <code>csh</code>-like brace expansion
( <code>b{a,b}c</code> &rarr; <code>bac bbc</code> ).
See <a href="#Brace-Expansion">Brace Expansion</a>, for a complete description.
</p>
</dd>
<dt><span><code>--enable-casemod-attributes</code></span></dt>
<dd><p>Include support for case-modifying attributes in the <code>declare</code> builtin
and assignment statements.  Variables with the <code>uppercase</code> attribute,
for example, will have their values converted to uppercase upon assignment.
</p>
</dd>
<dt><span><code>--enable-casemod-expansion</code></span></dt>
<dd><p>Include support for case-modifying word expansions.
</p>
</dd>
<dt><span><code>--enable-command-timing</code></span></dt>
<dd><p>Include support for recognizing <code>time</code> as a reserved word and for
displaying timing statistics for the pipeline following <code>time</code>
(see <a href="#Pipelines">Pipelines</a>).
This allows pipelines as well as shell builtins and functions to be timed.
</p>
</dd>
<dt><span><code>--enable-cond-command</code></span></dt>
<dd><p>Include support for the <code>[[</code> conditional command.
(see <a href="#Conditional-Constructs">Conditional Constructs</a>).
</p>
</dd>
<dt><span><code>--enable-cond-regexp</code></span></dt>
<dd><p>Include support for matching <small>POSIX</small> regular expressions using the
&lsquo;<samp>=~</samp>&rsquo; binary operator in the <code>[[</code> conditional command.
(see <a href="#Conditional-Constructs">Conditional Constructs</a>).
</p>
</dd>
<dt><span><code>--enable-coprocesses</code></span></dt>
<dd><p>Include support for coprocesses and the <code>coproc</code> reserved word
(see <a href="#Pipelines">Pipelines</a>).
</p>
</dd>
<dt><span><code>--enable-debugger</code></span></dt>
<dd><p>Include support for the bash debugger (distributed separately).
</p>
</dd>
<dt><span><code>--enable-dev-fd-stat-broken</code></span></dt>
<dd><p>If calling <code>stat</code> on /dev/fd/<var>N</var> returns different results than
calling <code>fstat</code> on file descriptor <var>N</var>, supply this option to
enable a workaround.
This has implications for conditional commands that test file attributes.
</p>
</dd>
<dt><span><code>--enable-direxpand-default</code></span></dt>
<dd><p>Cause the <code>direxpand</code> shell option (see <a href="#The-Shopt-Builtin">The Shopt Builtin</a>)
to be enabled by default when the shell starts.
It is normally disabled by default.
</p>
</dd>
<dt><span><code>--enable-directory-stack</code></span></dt>
<dd><p>Include support for a <code>csh</code>-like directory stack and the
<code>pushd</code>, <code>popd</code>, and <code>dirs</code> builtins
(see <a href="#The-Directory-Stack">The Directory Stack</a>).
</p>
</dd>
<dt><span><code>--enable-disabled-builtins</code></span></dt>
<dd><p>Allow builtin commands to be invoked via &lsquo;<samp>builtin xxx</samp>&rsquo;
even after <code>xxx</code> has been disabled using &lsquo;<samp>enable -n xxx</samp>&rsquo;.
See <a href="#Bash-Builtins">Bash Builtin Commands</a>, for details of the <code>builtin</code> and
<code>enable</code> builtin commands.
</p>
</dd>
<dt><span><code>--enable-dparen-arithmetic</code></span></dt>
<dd><p>Include support for the <code>((&hellip;))</code> command
(see <a href="#Conditional-Constructs">Conditional Constructs</a>).
</p>
</dd>
<dt><span><code>--enable-extended-glob</code></span></dt>
<dd><p>Include support for the extended pattern matching features described
above under <a href="#Pattern-Matching">Pattern Matching</a>.
</p>
</dd>
<dt><span><code>--enable-extended-glob-default</code></span></dt>
<dd><p>Set the default value of the <code>extglob</code> shell option described
above under <a href="#The-Shopt-Builtin">The Shopt Builtin</a> to be enabled.
</p>
</dd>
<dt><span><code>--enable-function-import</code></span></dt>
<dd><p>Include support for importing function definitions exported by another
instance of the shell from the environment.  This option is enabled by
default.
</p>
</dd>
<dt><span><code>--enable-glob-asciirange-default</code></span></dt>
<dd><p>Set the default value of the <code>globasciiranges</code> shell option described
above under <a href="#The-Shopt-Builtin">The Shopt Builtin</a> to be enabled.
This controls the behavior of character ranges when used in pattern matching
bracket expressions.
</p>
</dd>
<dt><span><code>--enable-help-builtin</code></span></dt>
<dd><p>Include the <code>help</code> builtin, which displays help on shell builtins and
variables (see <a href="#Bash-Builtins">Bash Builtin Commands</a>).
</p>
</dd>
<dt><span><code>--enable-history</code></span></dt>
<dd><p>Include command history and the <code>fc</code> and <code>history</code>
builtin commands (see <a href="#Bash-History-Facilities">Bash History Facilities</a>).
</p>
</dd>
<dt><span><code>--enable-job-control</code></span></dt>
<dd><p>This enables the job control features (see <a href="#Job-Control">Job Control</a>),
if the operating system supports them.
</p>
</dd>
<dt><span><code>--enable-multibyte</code></span></dt>
<dd><p>This enables support for multibyte characters if the operating
system provides the necessary support.
</p>
</dd>
<dt><span><code>--enable-net-redirections</code></span></dt>
<dd><p>This enables the special handling of filenames of the form
<code>/dev/tcp/<var>host</var>/<var>port</var></code> and
<code>/dev/udp/<var>host</var>/<var>port</var></code>
when used in redirections (see <a href="#Redirections">Redirections</a>).
</p>
</dd>
<dt><span><code>--enable-process-substitution</code></span></dt>
<dd><p>This enables process substitution (see <a href="#Process-Substitution">Process Substitution</a>) if
the operating system provides the necessary support.
</p>
</dd>
<dt><span><code>--enable-progcomp</code></span></dt>
<dd><p>Enable the programmable completion facilities
(see <a href="#Programmable-Completion">Programmable Completion</a>).
If Readline is not enabled, this option has no effect.
</p>
</dd>
<dt><span><code>--enable-prompt-string-decoding</code></span></dt>
<dd><p>Turn on the interpretation of a number of backslash-escaped characters
in the <code>$PS0</code>, <code>$PS1</code>, <code>$PS2</code>, and <code>$PS4</code> prompt
strings.  See <a href="#Controlling-the-Prompt">Controlling the Prompt</a>, for a complete list of prompt
string escape sequences.
</p>
</dd>
<dt><span><code>--enable-readline</code></span></dt>
<dd><p>Include support for command-line editing and history with the Bash
version of the Readline library (see <a href="#Command-Line-Editing">Command Line Editing</a>).
</p>
</dd>
<dt><span><code>--enable-restricted</code></span></dt>
<dd><p>Include support for a <em>restricted shell</em>.  If this is enabled, Bash,
when called as <code>rbash</code>, enters a restricted mode.  See
<a href="#The-Restricted-Shell">The Restricted Shell</a>, for a description of restricted mode.
</p>
</dd>
<dt><span><code>--enable-select</code></span></dt>
<dd><p>Include the <code>select</code> compound command, which allows the generation of
simple menus (see <a href="#Conditional-Constructs">Conditional Constructs</a>).
</p>
</dd>
<dt><span><code>--enable-single-help-strings</code></span></dt>
<dd><p>Store the text displayed by the <code>help</code> builtin as a single string for
each help topic.  This aids in translating the text to different languages.
You may need to disable this if your compiler cannot handle very long string
literals.
</p>
</dd>
<dt><span><code>--enable-strict-posix-default</code></span></dt>
<dd><p>Make Bash <small>POSIX</small>-conformant by default (see <a href="#Bash-POSIX-Mode">Bash POSIX Mode</a>).
</p>
</dd>
<dt><span><code>--enable-translatable-strings</code></span></dt>
<dd><p>Enable support for <code>$&quot;<var>string</var>&quot;</code> translatable strings
(see <a href="#Locale-Translation">Locale-Specific Translation</a>).
</p>
</dd>
<dt><span><code>--enable-usg-echo-default</code></span></dt>
<dd><p>A synonym for <code>--enable-xpg-echo-default</code>.
</p>
</dd>
<dt><span><code>--enable-xpg-echo-default</code></span></dt>
<dd><p>Make the <code>echo</code> builtin expand backslash-escaped characters by default,
without requiring the <samp>-e</samp> option.
This sets the default value of the <code>xpg_echo</code> shell option to <code>on</code>,
which makes the Bash <code>echo</code> behave more like the version specified in
the Single Unix Specification, version 3.
See <a href="#Bash-Builtins">Bash Builtin Commands</a>, for a description of the escape sequences that
<code>echo</code> recognizes.
</p></dd>
</dl>

<p>The file <samp>config-top.h</samp> contains C Preprocessor
&lsquo;<samp>#define</samp>&rsquo; statements for options which are not settable from
<code>configure</code>.
Some of these are not meant to be changed; beware of the consequences if
you do.
Read the comments associated with each definition for more
information about its effect.
</p>
<hr>
</div>
</div>
<div class="appendix" id="Reporting-Bugs">
<div class="header">
<p>
Next: <a href="#Major-Differences-From-The-Bourne-Shell" accesskey="n" rel="next">Major Differences From The Bourne Shell</a>, Previous: <a href="#Installing-Bash" accesskey="p" rel="prev">Installing Bash</a>, Up: <a href="#Top" accesskey="u" rel="up">Bash Features</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Reporting-Bugs-1"></span><h2 class="appendix">Appendix A Reporting Bugs</h2>

<p>Please report all bugs you find in Bash.
But first, you should
make sure that it really is a bug, and that it appears in the latest
version of Bash.
The latest version of Bash is always available for FTP from
<a href="ftp://ftp.gnu.org/pub/gnu/bash/">ftp://ftp.gnu.org/pub/gnu/bash/</a> and from
<a href="http://git.savannah.gnu.org/cgit/bash.git/snapshot/bash-master.tar.gz">http://git.savannah.gnu.org/cgit/bash.git/snapshot/bash-master.tar.gz</a>.
</p>
<p>Once you have determined that a bug actually exists, use the
<code>bashbug</code> command to submit a bug report.
If you have a fix, you are encouraged to mail that as well!
Suggestions and &lsquo;philosophical&rsquo; bug reports may be mailed
to <a href="mailto:bug-bash@gnu.org">bug-bash@gnu.org</a> or posted to the Usenet
newsgroup <code>gnu.bash.bug</code>.
</p>
<p>All bug reports should include:
</p><ul>
<li> The version number of Bash.
</li><li> The hardware and operating system.
</li><li> The compiler used to compile Bash.
</li><li> A description of the bug behaviour.
</li><li> A short script or &lsquo;recipe&rsquo; which exercises the bug and may be used
to reproduce it.
</li></ul>

<p><code>bashbug</code> inserts the first three items automatically into
the template it provides for filing a bug report.
</p>
<p>Please send all reports concerning this manual to
<a href="mailto:bug-bash@gnu.org">bug-bash@gnu.org</a>.
</p>
<hr>
</div>
<div class="appendix" id="Major-Differences-From-The-Bourne-Shell">
<div class="header">
<p>
Next: <a href="#GNU-Free-Documentation-License" accesskey="n" rel="next">GNU Free Documentation License</a>, Previous: <a href="#Reporting-Bugs" accesskey="p" rel="prev">Reporting Bugs</a>, Up: <a href="#Top" accesskey="u" rel="up">Bash Features</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Major-Differences-From-The-Bourne-Shell-1"></span><h2 class="appendix">Appendix B Major Differences From The Bourne Shell</h2>

<p>Bash implements essentially the same grammar, parameter and
variable expansion, redirection, and quoting as the Bourne Shell. 
Bash uses the <small>POSIX</small> standard as the specification of
how these features are to be implemented.  There are some
differences between the traditional Bourne shell and Bash; this
section quickly details the differences of significance.  A
number of these differences are explained in greater depth in
previous sections.
This section uses the version of <code>sh</code> included in SVR4.2 (the
last version of the historical Bourne shell) as the baseline reference.
</p>
<ul>
<li> Bash is <small>POSIX</small>-conformant, even where the <small>POSIX</small> specification
differs from traditional <code>sh</code> behavior (see <a href="#Bash-POSIX-Mode">Bash POSIX Mode</a>).

</li><li> Bash has multi-character invocation options (see <a href="#Invoking-Bash">Invoking Bash</a>).

</li><li> Bash has command-line editing (see <a href="#Command-Line-Editing">Command Line Editing</a>) and
the <code>bind</code> builtin.

</li><li> Bash provides a programmable word completion mechanism
(see <a href="#Programmable-Completion">Programmable Completion</a>), and builtin commands
<code>complete</code>, <code>compgen</code>, and <code>compopt</code>, to
manipulate it.

</li><li> Bash has command history (see <a href="#Bash-History-Facilities">Bash History Facilities</a>) and the
<code>history</code> and <code>fc</code> builtins to manipulate it.
The Bash history list maintains timestamp information and uses the
value of the <code>HISTTIMEFORMAT</code> variable to display it.

</li><li> Bash implements <code>csh</code>-like history expansion
(see <a href="#History-Interaction">History Expansion</a>).

</li><li> Bash has one-dimensional array variables (see <a href="#Arrays">Arrays</a>), and the
appropriate variable expansions and assignment syntax to use them.
Several of the Bash builtins take options to act on arrays.
Bash provides a number of built-in array variables.

</li><li> The <code>$'&hellip;'</code> quoting syntax, which expands ANSI-C
backslash-escaped characters in the text between the single quotes,
is supported (see <a href="#ANSI_002dC-Quoting">ANSI-C Quoting</a>).

</li><li> Bash supports the <code>$&quot;&hellip;&quot;</code> quoting syntax to do
locale-specific translation of the characters between the double
quotes.  The <samp>-D</samp>, <samp>--dump-strings</samp>, and <samp>--dump-po-strings</samp>
invocation options list the translatable strings found in a script
(see <a href="#Locale-Translation">Locale-Specific Translation</a>).

</li><li> Bash implements the <code>!</code> keyword to negate the return value of
a pipeline (see <a href="#Pipelines">Pipelines</a>).
Very useful when an <code>if</code> statement needs to act only if a test fails.
The Bash &lsquo;<samp>-o pipefail</samp>&rsquo; option to <code>set</code> will cause a pipeline to
return a failure status if any command fails.

</li><li> Bash has the <code>time</code> reserved word and command timing (see <a href="#Pipelines">Pipelines</a>).
The display of the timing statistics may be controlled with the
<code>TIMEFORMAT</code> variable.

</li><li> Bash implements the <code>for (( <var>expr1</var> ; <var>expr2</var> ; <var>expr3</var> ))</code>
arithmetic for command, similar to the C language (see <a href="#Looping-Constructs">Looping Constructs</a>).

</li><li> Bash includes the <code>select</code> compound command, which allows the
generation of simple menus (see <a href="#Conditional-Constructs">Conditional Constructs</a>).

</li><li> Bash includes the <code>[[</code> compound command, which makes conditional
testing part of the shell grammar (see <a href="#Conditional-Constructs">Conditional Constructs</a>), including
optional regular expression matching.

</li><li> Bash provides optional case-insensitive matching for the <code>case</code> and
<code>[[</code> constructs.

</li><li> Bash includes brace expansion (see <a href="#Brace-Expansion">Brace Expansion</a>) and tilde
expansion (see <a href="#Tilde-Expansion">Tilde Expansion</a>).

</li><li> Bash implements command aliases and the <code>alias</code> and <code>unalias</code>
builtins (see <a href="#Aliases">Aliases</a>).

</li><li> Bash provides shell arithmetic, the <code>((</code> compound command
(see <a href="#Conditional-Constructs">Conditional Constructs</a>),
and arithmetic expansion (see <a href="#Shell-Arithmetic">Shell Arithmetic</a>).

</li><li> Variables present in the shell&rsquo;s initial environment are automatically
exported to child processes.  The Bourne shell does not normally do
this unless the variables are explicitly marked using the <code>export</code>
command.

</li><li> Bash supports the &lsquo;<samp>+=</samp>&rsquo; assignment operator, which appends to the value
of the variable named on the left hand side.

</li><li> Bash includes the <small>POSIX</small> pattern removal &lsquo;<samp>%</samp>&rsquo;, &lsquo;<samp>#</samp>&rsquo;, &lsquo;<samp>%%</samp>&rsquo;
and &lsquo;<samp>##</samp>&rsquo; expansions to remove leading or trailing substrings from
variable values (see <a href="#Shell-Parameter-Expansion">Shell Parameter Expansion</a>).

</li><li> The expansion <code>${#xx}</code>, which returns the length of <code>${xx}</code>,
is supported (see <a href="#Shell-Parameter-Expansion">Shell Parameter Expansion</a>).

</li><li> The expansion <code>${var:</code><var>offset</var><code>[:</code><var>length</var><code>]}</code>,
which expands to the substring of <code>var</code>&rsquo;s value of length
<var>length</var>, beginning at <var>offset</var>, is present
(see <a href="#Shell-Parameter-Expansion">Shell Parameter Expansion</a>).

</li><li> The expansion
<code>${<var>var</var>/[/]</code><var>pattern</var><code>[/</code><var>replacement</var><code>]}</code>,
which matches <var>pattern</var> and replaces it with <var>replacement</var> in
the value of <var>var</var>, is available (see <a href="#Shell-Parameter-Expansion">Shell Parameter Expansion</a>).

</li><li> The expansion <code>${!<var>prefix</var>*}</code> expansion, which expands to
the names of all shell variables whose names begin with <var>prefix</var>,
is available (see <a href="#Shell-Parameter-Expansion">Shell Parameter Expansion</a>).

</li><li> Bash has indirect variable expansion using <code>${!word}</code>
(see <a href="#Shell-Parameter-Expansion">Shell Parameter Expansion</a>).

</li><li> Bash can expand positional parameters beyond <code>$9</code> using
<code>${<var>num</var>}</code>.

</li><li> The <small>POSIX</small> <code>$()</code> form of command substitution
is implemented (see <a href="#Command-Substitution">Command Substitution</a>),
and preferred to the Bourne shell&rsquo;s <code>``</code> (which
is also implemented for backwards compatibility).

</li><li> Bash has process substitution (see <a href="#Process-Substitution">Process Substitution</a>).

</li><li> Bash automatically assigns variables that provide information about the
current user (<code>UID</code>, <code>EUID</code>, and <code>GROUPS</code>), the current host
(<code>HOSTTYPE</code>, <code>OSTYPE</code>, <code>MACHTYPE</code>, and <code>HOSTNAME</code>),
and the instance of Bash that is running (<code>BASH</code>,
<code>BASH_VERSION</code>, and <code>BASH_VERSINFO</code>).  See <a href="#Bash-Variables">Bash Variables</a>,
for details.

</li><li> The <code>IFS</code> variable is used to split only the results of expansion,
not all words (see <a href="#Word-Splitting">Word Splitting</a>).
This closes a longstanding shell security hole.

</li><li> The filename expansion bracket expression code uses &lsquo;<samp>!</samp>&rsquo; and &lsquo;<samp>^</samp>&rsquo;
to negate the set of characters between the brackets.
The Bourne shell uses only &lsquo;<samp>!</samp>&rsquo;.

</li><li> Bash implements the full set of <small>POSIX</small> filename expansion operators,
including character classes, equivalence classes, and
collating symbols (see <a href="#Filename-Expansion">Filename Expansion</a>).

</li><li> Bash implements extended pattern matching features when the <code>extglob</code>
shell option is enabled (see <a href="#Pattern-Matching">Pattern Matching</a>).

</li><li> It is possible to have a variable and a function with the same name;
<code>sh</code> does not separate the two name spaces.

</li><li> Bash functions are permitted to have local variables using the
<code>local</code> builtin, and thus useful recursive functions may be written
(see <a href="#Bash-Builtins">Bash Builtin Commands</a>).

</li><li> Variable assignments preceding commands affect only that command, even
builtins and functions (see <a href="#Environment">Environment</a>).
In <code>sh</code>, all variable assignments 
preceding commands are global unless the command is executed from the
file system.

</li><li> Bash performs filename expansion on filenames specified as operands
to input and output redirection operators (see <a href="#Redirections">Redirections</a>).

</li><li> Bash contains the &lsquo;<samp>&lt;&gt;</samp>&rsquo; redirection operator, allowing a file to be
opened for both reading and writing, and the &lsquo;<samp>&amp;&gt;</samp>&rsquo; redirection
operator, for directing standard output and standard error to the same
file (see <a href="#Redirections">Redirections</a>).

</li><li> Bash includes the &lsquo;<samp>&lt;&lt;&lt;</samp>&rsquo; redirection operator, allowing a string to
be used as the standard input to a command.

</li><li> Bash implements the &lsquo;<samp>[n]&lt;&amp;<var>word</var></samp>&rsquo; and &lsquo;<samp>[n]&gt;&amp;<var>word</var></samp>&rsquo;
redirection operators, which move one file descriptor to another.

</li><li> Bash treats a number of filenames specially when they are
used in redirection operators (see <a href="#Redirections">Redirections</a>).

</li><li> Bash can open network connections to arbitrary machines and services
with the redirection operators (see <a href="#Redirections">Redirections</a>).

</li><li> The <code>noclobber</code> option is available to avoid overwriting existing
files with output redirection (see <a href="#The-Set-Builtin">The Set Builtin</a>).
The &lsquo;<samp>&gt;|</samp>&rsquo; redirection operator may be used to override <code>noclobber</code>.

</li><li> The Bash <code>cd</code> and <code>pwd</code> builtins (see <a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a>)
each take <samp>-L</samp> and <samp>-P</samp> options to switch between logical and
physical modes.

</li><li> Bash allows a function to override a builtin with the same name, and provides
access to that builtin&rsquo;s functionality within the function via the
<code>builtin</code> and <code>command</code> builtins (see <a href="#Bash-Builtins">Bash Builtin Commands</a>).

</li><li> The <code>command</code> builtin allows selective disabling of functions
when command lookup is performed (see <a href="#Bash-Builtins">Bash Builtin Commands</a>).

</li><li> Individual builtins may be enabled or disabled using the <code>enable</code>
builtin (see <a href="#Bash-Builtins">Bash Builtin Commands</a>).

</li><li> The Bash <code>exec</code> builtin takes additional options that allow users
to control the contents of the environment passed to the executed
command, and what the zeroth argument to the command is to be
(see <a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a>).

</li><li> Shell functions may be exported to children via the environment
using <code>export -f</code> (see <a href="#Shell-Functions">Shell Functions</a>).

</li><li> The Bash <code>export</code>, <code>readonly</code>, and <code>declare</code> builtins can
take a <samp>-f</samp> option to act on shell functions, a <samp>-p</samp> option to
display variables with various attributes set in a format that can be
used as shell input, a <samp>-n</samp> option to remove various variable
attributes, and &lsquo;<samp>name=value</samp>&rsquo; arguments to set variable attributes
and values simultaneously.

</li><li> The Bash <code>hash</code> builtin allows a name to be associated with
an arbitrary filename, even when that filename cannot be found by
searching the <code>$PATH</code>, using &lsquo;<samp>hash -p</samp>&rsquo;
(see <a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a>).

</li><li> Bash includes a <code>help</code> builtin for quick reference to shell
facilities (see <a href="#Bash-Builtins">Bash Builtin Commands</a>).

</li><li> The <code>printf</code> builtin is available to display formatted output
(see <a href="#Bash-Builtins">Bash Builtin Commands</a>).

</li><li> The Bash <code>read</code> builtin (see <a href="#Bash-Builtins">Bash Builtin Commands</a>)
will read a line ending in &lsquo;<samp>\</samp>&rsquo; with
the <samp>-r</samp> option, and will use the <code>REPLY</code> variable as a
default if no non-option arguments are supplied.
The Bash <code>read</code> builtin
also accepts a prompt string with the <samp>-p</samp> option and will use
Readline to obtain the line when given the <samp>-e</samp> option.
The <code>read</code> builtin also has additional options to control input:
the <samp>-s</samp> option will turn off echoing of input characters as
they are read, the <samp>-t</samp> option will allow <code>read</code> to time out
if input does not arrive within a specified number of seconds, the
<samp>-n</samp> option will allow reading only a specified number of
characters rather than a full line, and the <samp>-d</samp> option will read
until a particular character rather than newline.

</li><li> The <code>return</code> builtin may be used to abort execution of scripts
executed with the <code>.</code> or <code>source</code> builtins
(see <a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a>).

</li><li> Bash includes the <code>shopt</code> builtin, for finer control of shell
optional capabilities (see <a href="#The-Shopt-Builtin">The Shopt Builtin</a>), and allows these options
to be set and unset at shell invocation (see <a href="#Invoking-Bash">Invoking Bash</a>).

</li><li> Bash has much more optional behavior controllable with the <code>set</code>
builtin (see <a href="#The-Set-Builtin">The Set Builtin</a>).

</li><li> The &lsquo;<samp>-x</samp>&rsquo; (<samp>xtrace</samp>) option displays commands other than
simple commands when performing an execution trace
(see <a href="#The-Set-Builtin">The Set Builtin</a>).

</li><li> The <code>test</code> builtin (see <a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a>)
is slightly different, as it implements the <small>POSIX</small> algorithm,
which specifies the behavior based on the number of arguments.

</li><li> Bash includes the <code>caller</code> builtin, which displays the context of
any active subroutine call (a shell function or a script executed with
the <code>.</code> or <code>source</code> builtins).  This supports the Bash
debugger.

</li><li> The <code>trap</code> builtin (see <a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a>) allows a
<code>DEBUG</code> pseudo-signal specification, similar to <code>EXIT</code>.
Commands specified with a <code>DEBUG</code> trap are executed before every
simple command, <code>for</code> command, <code>case</code> command,
<code>select</code> command, every arithmetic <code>for</code> command, and before
the first command executes in a shell function.
The <code>DEBUG</code> trap is not inherited by shell functions unless the
function has been given the <code>trace</code> attribute or the
<code>functrace</code> option has been enabled using the <code>shopt</code> builtin.
The <code>extdebug</code> shell option has additional effects on the
<code>DEBUG</code> trap.

<p>The <code>trap</code> builtin (see <a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a>) allows an
<code>ERR</code> pseudo-signal specification, similar to <code>EXIT</code> and <code>DEBUG</code>.
Commands specified with an <code>ERR</code> trap are executed after a simple
command fails, with a few exceptions.
The <code>ERR</code> trap is not inherited by shell functions unless the
<code>-o errtrace</code> option to the <code>set</code> builtin is enabled.
</p>
<p>The <code>trap</code> builtin (see <a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a>) allows a
<code>RETURN</code> pseudo-signal specification, similar to
<code>EXIT</code> and <code>DEBUG</code>.
Commands specified with a <code>RETURN</code> trap are executed before
execution resumes after a shell function or a shell script executed with
<code>.</code> or <code>source</code> returns.
The <code>RETURN</code> trap is not inherited by shell functions unless the
function has been given the <code>trace</code> attribute or the
<code>functrace</code> option has been enabled using the <code>shopt</code> builtin.
</p>
</li><li> The Bash <code>type</code> builtin is more extensive and gives more information
about the names it finds (see <a href="#Bash-Builtins">Bash Builtin Commands</a>).

</li><li> The Bash <code>umask</code> builtin permits a <samp>-p</samp> option to cause
the output to be displayed in the form of a <code>umask</code> command
that may be reused as input (see <a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a>).

</li><li> Bash implements a <code>csh</code>-like directory stack, and provides the
<code>pushd</code>, <code>popd</code>, and <code>dirs</code> builtins to manipulate it
(see <a href="#The-Directory-Stack">The Directory Stack</a>).
Bash also makes the directory stack visible as the value of the
<code>DIRSTACK</code> shell variable.

</li><li> Bash interprets special backslash-escaped characters in the prompt
strings when interactive (see <a href="#Controlling-the-Prompt">Controlling the Prompt</a>).

</li><li> The Bash restricted mode is more useful (see <a href="#The-Restricted-Shell">The Restricted Shell</a>);
the SVR4.2 shell restricted mode is too limited.

</li><li> The <code>disown</code> builtin can remove a job from the internal shell
job table (see <a href="#Job-Control-Builtins">Job Control Builtins</a>) or suppress the sending
of <code>SIGHUP</code> to a job when the shell exits as the result of a
<code>SIGHUP</code>.

</li><li> Bash includes a number of features to support a separate debugger for
shell scripts.

</li><li> The SVR4.2 shell has two privilege-related builtins
(<code>mldmode</code> and <code>priv</code>) not present in Bash.

</li><li> Bash does not have the <code>stop</code> or <code>newgrp</code> builtins.

</li><li> Bash does not use the <code>SHACCT</code> variable or perform shell accounting.

</li><li> The SVR4.2 <code>sh</code> uses a <code>TIMEOUT</code> variable like Bash uses
<code>TMOUT</code>.

</li></ul>

<p>More features unique to Bash may be found in <a href="#Bash-Features">Bash Features</a>.
</p>

<ul class="section-toc">
<li><a href="#Implementation-Differences-From-The-SVR4_002e2-Shell" accesskey="1">Implementation Differences From The SVR4.2 Shell</a></li>
</ul>
<div class="appendixsec" id="Implementation-Differences-From-The-SVR4_002e2-Shell">
<h3 class="appendixsec">B.1 Implementation Differences From The SVR4.2 Shell</h3>

<p>Since Bash is a completely new implementation, it does not suffer from
many of the limitations of the SVR4.2 shell.  For instance:
</p>
<ul>
<li> Bash does not fork a subshell when redirecting into or out of
a shell control structure such as  an <code>if</code> or <code>while</code>
statement.

</li><li> Bash does not allow unbalanced quotes.  The SVR4.2 shell will silently
insert a needed closing quote at <code>EOF</code> under certain circumstances.
This can be the cause of some hard-to-find errors.

</li><li> The SVR4.2 shell uses a baroque memory management scheme based on
trapping <code>SIGSEGV</code>.  If the shell is started from a process with
<code>SIGSEGV</code> blocked (e.g., by using the <code>system()</code> C library
function call), it misbehaves badly.

</li><li> In a questionable attempt at security, the SVR4.2 shell,
when invoked without the <samp>-p</samp> option, will alter its real
and effective <small>UID</small> and <small>GID</small> if they are less than some
magic threshold value, commonly 100.
This can lead to unexpected results.

</li><li> The SVR4.2 shell does not allow users to trap <code>SIGSEGV</code>,
<code>SIGALRM</code>, or <code>SIGCHLD</code>.

</li><li> The SVR4.2 shell does not allow the <code>IFS</code>, <code>MAILCHECK</code>,
<code>PATH</code>, <code>PS1</code>, or <code>PS2</code> variables to be unset.

</li><li> The SVR4.2 shell treats &lsquo;<samp>^</samp>&rsquo; as the undocumented equivalent of
&lsquo;<samp>|</samp>&rsquo;.

</li><li> Bash allows multiple option arguments when it is invoked (<code>-x -v</code>);
the SVR4.2 shell allows only one option argument (<code>-xv</code>).  In
fact, some versions of the shell dump core if the second argument begins
with a &lsquo;<samp>-</samp>&rsquo;.

</li><li> The SVR4.2 shell exits a script if any builtin fails; Bash exits
a script only if one of the <small>POSIX</small> special builtins fails, and
only for certain failures, as enumerated in the <small>POSIX</small> standard.

</li><li> The SVR4.2 shell behaves differently when invoked as <code>jsh</code>
(it turns on job control).
</li></ul>

<hr>
</div>
</div>
<div class="appendix" id="GNU-Free-Documentation-License">
<div class="header">
<p>
Next: <a href="#Indexes" accesskey="n" rel="next">Indexes</a>, Previous: <a href="#Major-Differences-From-The-Bourne-Shell" accesskey="p" rel="prev">Major Differences From The Bourne Shell</a>, Up: <a href="#Top" accesskey="u" rel="up">Bash Features</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="GNU-Free-Documentation-License-1"></span><h2 class="appendix">Appendix C GNU Free Documentation License</h2>

<div align="center">Version 1.3, 3 November 2008
</div>

<div class="display">
<pre class="display">Copyright &copy; 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
<a href="http://fsf.org/">http://fsf.org/</a>

Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
</pre></div>

<ol start="0">
<li> PREAMBLE

<p>The purpose of this License is to make a manual, textbook, or other
functional and useful document <em>free</em> in the sense of freedom: to
assure everyone the effective freedom to copy and redistribute it,
with or without modifying it, either commercially or noncommercially.
Secondarily, this License preserves for the author and publisher a way
to get credit for their work, while not being considered responsible
for modifications made by others.
</p>
<p>This License is a kind of &ldquo;copyleft&rdquo;, which means that derivative
works of the document must themselves be free in the same sense.  It
complements the GNU General Public License, which is a copyleft
license designed for free software.
</p>
<p>We have designed this License in order to use it for manuals for free
software, because free software needs free documentation: a free
program should come with manuals providing the same freedoms that the
software does.  But this License is not limited to software manuals;
it can be used for any textual work, regardless of subject matter or
whether it is published as a printed book.  We recommend this License
principally for works whose purpose is instruction or reference.
</p>
</li><li> APPLICABILITY AND DEFINITIONS

<p>This License applies to any manual or other work, in any medium, that
contains a notice placed by the copyright holder saying it can be
distributed under the terms of this License.  Such a notice grants a
world-wide, royalty-free license, unlimited in duration, to use that
work under the conditions stated herein.  The &ldquo;Document&rdquo;, below,
refers to any such manual or work.  Any member of the public is a
licensee, and is addressed as &ldquo;you&rdquo;.  You accept the license if you
copy, modify or distribute the work in a way requiring permission
under copyright law.
</p>
<p>A &ldquo;Modified Version&rdquo; of the Document means any work containing the
Document or a portion of it, either copied verbatim, or with
modifications and/or translated into another language.
</p>
<p>A &ldquo;Secondary Section&rdquo; is a named appendix or a front-matter section
of the Document that deals exclusively with the relationship of the
publishers or authors of the Document to the Document&rsquo;s overall
subject (or to related matters) and contains nothing that could fall
directly within that overall subject.  (Thus, if the Document is in
part a textbook of mathematics, a Secondary Section may not explain
any mathematics.)  The relationship could be a matter of historical
connection with the subject or with related matters, or of legal,
commercial, philosophical, ethical or political position regarding
them.
</p>
<p>The &ldquo;Invariant Sections&rdquo; are certain Secondary Sections whose titles
are designated, as being those of Invariant Sections, in the notice
that says that the Document is released under this License.  If a
section does not fit the above definition of Secondary then it is not
allowed to be designated as Invariant.  The Document may contain zero
Invariant Sections.  If the Document does not identify any Invariant
Sections then there are none.
</p>
<p>The &ldquo;Cover Texts&rdquo; are certain short passages of text that are listed,
as Front-Cover Texts or Back-Cover Texts, in the notice that says that
the Document is released under this License.  A Front-Cover Text may
be at most 5 words, and a Back-Cover Text may be at most 25 words.
</p>
<p>A &ldquo;Transparent&rdquo; copy of the Document means a machine-readable copy,
represented in a format whose specification is available to the
general public, that is suitable for revising the document
straightforwardly with generic text editors or (for images composed of
pixels) generic paint programs or (for drawings) some widely available
drawing editor, and that is suitable for input to text formatters or
for automatic translation to a variety of formats suitable for input
to text formatters.  A copy made in an otherwise Transparent file
format whose markup, or absence of markup, has been arranged to thwart
or discourage subsequent modification by readers is not Transparent.
An image format is not Transparent if used for any substantial amount
of text.  A copy that is not &ldquo;Transparent&rdquo; is called &ldquo;Opaque&rdquo;.
</p>
<p>Examples of suitable formats for Transparent copies include plain
<small>ASCII</small> without markup, Texinfo input format, LaTeX input
format, <acronym>SGML</acronym> or <acronym>XML</acronym> using a publicly available
<acronym>DTD</acronym>, and standard-conforming simple <acronym>HTML</acronym>,
PostScript or <acronym>PDF</acronym> designed for human modification.  Examples
of transparent image formats include <acronym>PNG</acronym>, <acronym>XCF</acronym> and
<acronym>JPG</acronym>.  Opaque formats include proprietary formats that can be
read and edited only by proprietary word processors, <acronym>SGML</acronym> or
<acronym>XML</acronym> for which the <acronym>DTD</acronym> and/or processing tools are
not generally available, and the machine-generated <acronym>HTML</acronym>,
PostScript or <acronym>PDF</acronym> produced by some word processors for
output purposes only.
</p>
<p>The &ldquo;Title Page&rdquo; means, for a printed book, the title page itself,
plus such following pages as are needed to hold, legibly, the material
this License requires to appear in the title page.  For works in
formats which do not have any title page as such, &ldquo;Title Page&rdquo; means
the text near the most prominent appearance of the work&rsquo;s title,
preceding the beginning of the body of the text.
</p>
<p>The &ldquo;publisher&rdquo; means any person or entity that distributes copies
of the Document to the public.
</p>
<p>A section &ldquo;Entitled XYZ&rdquo; means a named subunit of the Document whose
title either is precisely XYZ or contains XYZ in parentheses following
text that translates XYZ in another language.  (Here XYZ stands for a
specific section name mentioned below, such as &ldquo;Acknowledgements&rdquo;,
&ldquo;Dedications&rdquo;, &ldquo;Endorsements&rdquo;, or &ldquo;History&rdquo;.)  To &ldquo;Preserve the Title&rdquo;
of such a section when you modify the Document means that it remains a
section &ldquo;Entitled XYZ&rdquo; according to this definition.
</p>
<p>The Document may include Warranty Disclaimers next to the notice which
states that this License applies to the Document.  These Warranty
Disclaimers are considered to be included by reference in this
License, but only as regards disclaiming warranties: any other
implication that these Warranty Disclaimers may have is void and has
no effect on the meaning of this License.
</p>
</li><li> VERBATIM COPYING

<p>You may copy and distribute the Document in any medium, either
commercially or noncommercially, provided that this License, the
copyright notices, and the license notice saying this License applies
to the Document are reproduced in all copies, and that you add no other
conditions whatsoever to those of this License.  You may not use
technical measures to obstruct or control the reading or further
copying of the copies you make or distribute.  However, you may accept
compensation in exchange for copies.  If you distribute a large enough
number of copies you must also follow the conditions in section 3.
</p>
<p>You may also lend copies, under the same conditions stated above, and
you may publicly display copies.
</p>
</li><li> COPYING IN QUANTITY

<p>If you publish printed copies (or copies in media that commonly have
printed covers) of the Document, numbering more than 100, and the
Document&rsquo;s license notice requires Cover Texts, you must enclose the
copies in covers that carry, clearly and legibly, all these Cover
Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
the back cover.  Both covers must also clearly and legibly identify
you as the publisher of these copies.  The front cover must present
the full title with all words of the title equally prominent and
visible.  You may add other material on the covers in addition.
Copying with changes limited to the covers, as long as they preserve
the title of the Document and satisfy these conditions, can be treated
as verbatim copying in other respects.
</p>
<p>If the required texts for either cover are too voluminous to fit
legibly, you should put the first ones listed (as many as fit
reasonably) on the actual cover, and continue the rest onto adjacent
pages.
</p>
<p>If you publish or distribute Opaque copies of the Document numbering
more than 100, you must either include a machine-readable Transparent
copy along with each Opaque copy, or state in or with each Opaque copy
a computer-network location from which the general network-using
public has access to download using public-standard network protocols
a complete Transparent copy of the Document, free of added material.
If you use the latter option, you must take reasonably prudent steps,
when you begin distribution of Opaque copies in quantity, to ensure
that this Transparent copy will remain thus accessible at the stated
location until at least one year after the last time you distribute an
Opaque copy (directly or through your agents or retailers) of that
edition to the public.
</p>
<p>It is requested, but not required, that you contact the authors of the
Document well before redistributing any large number of copies, to give
them a chance to provide you with an updated version of the Document.
</p>
</li><li> MODIFICATIONS

<p>You may copy and distribute a Modified Version of the Document under
the conditions of sections 2 and 3 above, provided that you release
the Modified Version under precisely this License, with the Modified
Version filling the role of the Document, thus licensing distribution
and modification of the Modified Version to whoever possesses a copy
of it.  In addition, you must do these things in the Modified Version:
</p>
<ol type="A" start="1">
<li> Use in the Title Page (and on the covers, if any) a title distinct
from that of the Document, and from those of previous versions
(which should, if there were any, be listed in the History section
of the Document).  You may use the same title as a previous version
if the original publisher of that version gives permission.

</li><li> List on the Title Page, as authors, one or more persons or entities
responsible for authorship of the modifications in the Modified
Version, together with at least five of the principal authors of the
Document (all of its principal authors, if it has fewer than five),
unless they release you from this requirement.

</li><li> State on the Title page the name of the publisher of the
Modified Version, as the publisher.

</li><li> Preserve all the copyright notices of the Document.

</li><li> Add an appropriate copyright notice for your modifications
adjacent to the other copyright notices.

</li><li> Include, immediately after the copyright notices, a license notice
giving the public permission to use the Modified Version under the
terms of this License, in the form shown in the Addendum below.

</li><li> Preserve in that license notice the full lists of Invariant Sections
and required Cover Texts given in the Document&rsquo;s license notice.

</li><li> Include an unaltered copy of this License.

</li><li> Preserve the section Entitled &ldquo;History&rdquo;, Preserve its Title, and add
to it an item stating at least the title, year, new authors, and
publisher of the Modified Version as given on the Title Page.  If
there is no section Entitled &ldquo;History&rdquo; in the Document, create one
stating the title, year, authors, and publisher of the Document as
given on its Title Page, then add an item describing the Modified
Version as stated in the previous sentence.

</li><li> Preserve the network location, if any, given in the Document for
public access to a Transparent copy of the Document, and likewise
the network locations given in the Document for previous versions
it was based on.  These may be placed in the &ldquo;History&rdquo; section.
You may omit a network location for a work that was published at
least four years before the Document itself, or if the original
publisher of the version it refers to gives permission.

</li><li> For any section Entitled &ldquo;Acknowledgements&rdquo; or &ldquo;Dedications&rdquo;, Preserve
the Title of the section, and preserve in the section all the
substance and tone of each of the contributor acknowledgements and/or
dedications given therein.

</li><li> Preserve all the Invariant Sections of the Document,
unaltered in their text and in their titles.  Section numbers
or the equivalent are not considered part of the section titles.

</li><li> Delete any section Entitled &ldquo;Endorsements&rdquo;.  Such a section
may not be included in the Modified Version.

</li><li> Do not retitle any existing section to be Entitled &ldquo;Endorsements&rdquo; or
to conflict in title with any Invariant Section.

</li><li> Preserve any Warranty Disclaimers.
</li></ol>

<p>If the Modified Version includes new front-matter sections or
appendices that qualify as Secondary Sections and contain no material
copied from the Document, you may at your option designate some or all
of these sections as invariant.  To do this, add their titles to the
list of Invariant Sections in the Modified Version&rsquo;s license notice.
These titles must be distinct from any other section titles.
</p>
<p>You may add a section Entitled &ldquo;Endorsements&rdquo;, provided it contains
nothing but endorsements of your Modified Version by various
parties&mdash;for example, statements of peer review or that the text has
been approved by an organization as the authoritative definition of a
standard.
</p>
<p>You may add a passage of up to five words as a Front-Cover Text, and a
passage of up to 25 words as a Back-Cover Text, to the end of the list
of Cover Texts in the Modified Version.  Only one passage of
Front-Cover Text and one of Back-Cover Text may be added by (or
through arrangements made by) any one entity.  If the Document already
includes a cover text for the same cover, previously added by you or
by arrangement made by the same entity you are acting on behalf of,
you may not add another; but you may replace the old one, on explicit
permission from the previous publisher that added the old one.
</p>
<p>The author(s) and publisher(s) of the Document do not by this License
give permission to use their names for publicity for or to assert or
imply endorsement of any Modified Version.
</p>
</li><li> COMBINING DOCUMENTS

<p>You may combine the Document with other documents released under this
License, under the terms defined in section 4 above for modified
versions, provided that you include in the combination all of the
Invariant Sections of all of the original documents, unmodified, and
list them all as Invariant Sections of your combined work in its
license notice, and that you preserve all their Warranty Disclaimers.
</p>
<p>The combined work need only contain one copy of this License, and
multiple identical Invariant Sections may be replaced with a single
copy.  If there are multiple Invariant Sections with the same name but
different contents, make the title of each such section unique by
adding at the end of it, in parentheses, the name of the original
author or publisher of that section if known, or else a unique number.
Make the same adjustment to the section titles in the list of
Invariant Sections in the license notice of the combined work.
</p>
<p>In the combination, you must combine any sections Entitled &ldquo;History&rdquo;
in the various original documents, forming one section Entitled
&ldquo;History&rdquo;; likewise combine any sections Entitled &ldquo;Acknowledgements&rdquo;,
and any sections Entitled &ldquo;Dedications&rdquo;.  You must delete all
sections Entitled &ldquo;Endorsements.&rdquo;
</p>
</li><li> COLLECTIONS OF DOCUMENTS

<p>You may make a collection consisting of the Document and other documents
released under this License, and replace the individual copies of this
License in the various documents with a single copy that is included in
the collection, provided that you follow the rules of this License for
verbatim copying of each of the documents in all other respects.
</p>
<p>You may extract a single document from such a collection, and distribute
it individually under this License, provided you insert a copy of this
License into the extracted document, and follow this License in all
other respects regarding verbatim copying of that document.
</p>
</li><li> AGGREGATION WITH INDEPENDENT WORKS

<p>A compilation of the Document or its derivatives with other separate
and independent documents or works, in or on a volume of a storage or
distribution medium, is called an &ldquo;aggregate&rdquo; if the copyright
resulting from the compilation is not used to limit the legal rights
of the compilation&rsquo;s users beyond what the individual works permit.
When the Document is included in an aggregate, this License does not
apply to the other works in the aggregate which are not themselves
derivative works of the Document.
</p>
<p>If the Cover Text requirement of section 3 is applicable to these
copies of the Document, then if the Document is less than one half of
the entire aggregate, the Document&rsquo;s Cover Texts may be placed on
covers that bracket the Document within the aggregate, or the
electronic equivalent of covers if the Document is in electronic form.
Otherwise they must appear on printed covers that bracket the whole
aggregate.
</p>
</li><li> TRANSLATION

<p>Translation is considered a kind of modification, so you may
distribute translations of the Document under the terms of section 4.
Replacing Invariant Sections with translations requires special
permission from their copyright holders, but you may include
translations of some or all Invariant Sections in addition to the
original versions of these Invariant Sections.  You may include a
translation of this License, and all the license notices in the
Document, and any Warranty Disclaimers, provided that you also include
the original English version of this License and the original versions
of those notices and disclaimers.  In case of a disagreement between
the translation and the original version of this License or a notice
or disclaimer, the original version will prevail.
</p>
<p>If a section in the Document is Entitled &ldquo;Acknowledgements&rdquo;,
&ldquo;Dedications&rdquo;, or &ldquo;History&rdquo;, the requirement (section 4) to Preserve
its Title (section 1) will typically require changing the actual
title.
</p>
</li><li> TERMINATION

<p>You may not copy, modify, sublicense, or distribute the Document
except as expressly provided under this License.  Any attempt
otherwise to copy, modify, sublicense, or distribute it is void, and
will automatically terminate your rights under this License.
</p>
<p>However, if you cease all violation of this License, then your license
from a particular copyright holder is reinstated (a) provisionally,
unless and until the copyright holder explicitly and finally
terminates your license, and (b) permanently, if the copyright holder
fails to notify you of the violation by some reasonable means prior to
60 days after the cessation.
</p>
<p>Moreover, your license from a particular copyright holder is
reinstated permanently if the copyright holder notifies you of the
violation by some reasonable means, this is the first time you have
received notice of violation of this License (for any work) from that
copyright holder, and you cure the violation prior to 30 days after
your receipt of the notice.
</p>
<p>Termination of your rights under this section does not terminate the
licenses of parties who have received copies or rights from you under
this License.  If your rights have been terminated and not permanently
reinstated, receipt of a copy of some or all of the same material does
not give you any rights to use it.
</p>
</li><li> FUTURE REVISIONS OF THIS LICENSE

<p>The Free Software Foundation may publish new, revised versions
of the GNU Free Documentation License from time to time.  Such new
versions will be similar in spirit to the present version, but may
differ in detail to address new problems or concerns.  See
<a href="http://www.gnu.org/copyleft/">http://www.gnu.org/copyleft/</a>.
</p>
<p>Each version of the License is given a distinguishing version number.
If the Document specifies that a particular numbered version of this
License &ldquo;or any later version&rdquo; applies to it, you have the option of
following the terms and conditions either of that specified version or
of any later version that has been published (not as a draft) by the
Free Software Foundation.  If the Document does not specify a version
number of this License, you may choose any version ever published (not
as a draft) by the Free Software Foundation.  If the Document
specifies that a proxy can decide which future versions of this
License can be used, that proxy&rsquo;s public statement of acceptance of a
version permanently authorizes you to choose that version for the
Document.
</p>
</li><li> RELICENSING

<p>&ldquo;Massive Multiauthor Collaboration Site&rdquo; (or &ldquo;MMC Site&rdquo;) means any
World Wide Web server that publishes copyrightable works and also
provides prominent facilities for anybody to edit those works.  A
public wiki that anybody can edit is an example of such a server.  A
&ldquo;Massive Multiauthor Collaboration&rdquo; (or &ldquo;MMC&rdquo;) contained in the
site means any set of copyrightable works thus published on the MMC
site.
</p>
<p>&ldquo;CC-BY-SA&rdquo; means the Creative Commons Attribution-Share Alike 3.0
license published by Creative Commons Corporation, a not-for-profit
corporation with a principal place of business in San Francisco,
California, as well as future copyleft versions of that license
published by that same organization.
</p>
<p>&ldquo;Incorporate&rdquo; means to publish or republish a Document, in whole or
in part, as part of another Document.
</p>
<p>An MMC is &ldquo;eligible for relicensing&rdquo; if it is licensed under this
License, and if all works that were first published under this License
somewhere other than this MMC, and subsequently incorporated in whole
or in part into the MMC, (1) had no cover texts or invariant sections,
and (2) were thus incorporated prior to November 1, 2008.
</p>
<p>The operator of an MMC Site may republish an MMC contained in the site
under CC-BY-SA on the same site at any time before August 1, 2009,
provided the MMC is eligible for relicensing.
</p>
</li></ol>

<span id="ADDENDUM_003a-How-to-use-this-License-for-your-documents"></span><h3 class="heading">ADDENDUM: How to use this License for your documents</h3>

<p>To use this License in a document you have written, include a copy of
the License in the document and put the following copyright and
license notices just after the title page:
</p>
<div class="example">
<pre class="example">  Copyright (C)  <var>year</var>  <var>your name</var>.
  Permission is granted to copy, distribute and/or modify this document
  under the terms of the GNU Free Documentation License, Version 1.3
  or any later version published by the Free Software Foundation;
  with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
  Texts.  A copy of the license is included in the section entitled ``GNU
  Free Documentation License''.
</pre></div>

<p>If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
replace the &ldquo;with&hellip;Texts.&rdquo; line with this:
</p>
<div class="example">
<pre class="example">    with the Invariant Sections being <var>list their titles</var>, with
    the Front-Cover Texts being <var>list</var>, and with the Back-Cover Texts
    being <var>list</var>.
</pre></div>

<p>If you have Invariant Sections without Cover Texts, or some other
combination of the three, merge those two alternatives to suit the
situation.
</p>
<p>If your document contains nontrivial examples of program code, we
recommend releasing these examples in parallel under your choice of
free software license, such as the GNU General Public License,
to permit their use in free software.
</p>


<hr>
</div>
<div class="appendix" id="Indexes">
<div class="header">
<p>
Previous: <a href="#GNU-Free-Documentation-License" accesskey="p" rel="prev">GNU Free Documentation License</a>, Up: <a href="#Top" accesskey="u" rel="up">Bash Features</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Indexes-1"></span><h2 class="appendix">Appendix D Indexes</h2>


<ul class="section-toc">
<li><a href="#Builtin-Index" accesskey="1">Index of Shell Builtin Commands</a></li>
<li><a href="#Reserved-Word-Index" accesskey="2">Index of Shell Reserved Words</a></li>
<li><a href="#Variable-Index" accesskey="3">Parameter and Variable Index</a></li>
<li><a href="#Function-Index" accesskey="4">Function Index</a></li>
<li><a href="#Concept-Index" accesskey="5">Concept Index</a></li>
</ul>
<hr>
<div class="appendixsec" id="Builtin-Index">
<div class="header">
<p>
Next: <a href="#Reserved-Word-Index" accesskey="n" rel="next">Index of Shell Reserved Words</a>, Up: <a href="#Indexes" accesskey="u" rel="up">Indexes</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Index-of-Shell-Builtin-Commands"></span><h3 class="appendixsec">D.1 Index of Shell Builtin Commands</h3>
<table><tr><th valign="top">Jump to: &nbsp; </th><td><a class="summary-letter" href="#Builtin-Index_bt_symbol-1"><b>.</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_symbol-2"><b>:</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_symbol-3"><b>[</b></a>
 &nbsp; 
<br>
<a class="summary-letter" href="#Builtin-Index_bt_letter-A"><b>A</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_letter-B"><b>B</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_letter-C"><b>C</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_letter-D"><b>D</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_letter-E"><b>E</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_letter-F"><b>F</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_letter-G"><b>G</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_letter-H"><b>H</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_letter-J"><b>J</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_letter-K"><b>K</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_letter-L"><b>L</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_letter-M"><b>M</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_letter-P"><b>P</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_letter-R"><b>R</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_letter-S"><b>S</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_letter-T"><b>T</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_letter-U"><b>U</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_letter-W"><b>W</b></a>
 &nbsp; 
</td></tr></table>
<table class="index-bt" border="0">
<tr><td></td><th align="left">Index Entry</th><td>&nbsp;</td><th align="left"> Section</th></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Builtin-Index_bt_symbol-1">.</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-_002e"><code>.</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Builtin-Index_bt_symbol-2">:</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-_003a"><code>:</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Builtin-Index_bt_symbol-3">[</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-_005b"><code>[</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Builtin-Index_bt_letter-A">A</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-alias"><code>alias</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Builtins">Bash Builtins</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Builtin-Index_bt_letter-B">B</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-bg"><code>bg</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Job-Control-Builtins">Job Control Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-bind"><code>bind</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Builtins">Bash Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-break"><code>break</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-builtin"><code>builtin</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Builtins">Bash Builtins</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Builtin-Index_bt_letter-C">C</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-caller"><code>caller</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Builtins">Bash Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-cd"><code>cd</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-command"><code>command</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Builtins">Bash Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-compgen"><code>compgen</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Programmable-Completion-Builtins">Programmable Completion Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-complete"><code>complete</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Programmable-Completion-Builtins">Programmable Completion Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-compopt"><code>compopt</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Programmable-Completion-Builtins">Programmable Completion Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-continue"><code>continue</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Builtin-Index_bt_letter-D">D</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-declare"><code>declare</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Builtins">Bash Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-dirs"><code>dirs</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Directory-Stack-Builtins">Directory Stack Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-disown"><code>disown</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Job-Control-Builtins">Job Control Builtins</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Builtin-Index_bt_letter-E">E</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-echo"><code>echo</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Builtins">Bash Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-enable"><code>enable</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Builtins">Bash Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-eval"><code>eval</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-exec"><code>exec</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-exit"><code>exit</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-export"><code>export</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Builtin-Index_bt_letter-F">F</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-fc"><code>fc</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-History-Builtins">Bash History Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-fg"><code>fg</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Job-Control-Builtins">Job Control Builtins</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Builtin-Index_bt_letter-G">G</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-getopts"><code>getopts</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Builtin-Index_bt_letter-H">H</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-hash"><code>hash</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-help"><code>help</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Builtins">Bash Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-history"><code>history</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-History-Builtins">Bash History Builtins</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Builtin-Index_bt_letter-J">J</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-jobs"><code>jobs</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Job-Control-Builtins">Job Control Builtins</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Builtin-Index_bt_letter-K">K</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-kill"><code>kill</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Job-Control-Builtins">Job Control Builtins</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Builtin-Index_bt_letter-L">L</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-let"><code>let</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Builtins">Bash Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-local"><code>local</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Builtins">Bash Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-logout"><code>logout</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Builtins">Bash Builtins</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Builtin-Index_bt_letter-M">M</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-mapfile"><code>mapfile</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Builtins">Bash Builtins</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Builtin-Index_bt_letter-P">P</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-popd"><code>popd</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Directory-Stack-Builtins">Directory Stack Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-printf"><code>printf</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Builtins">Bash Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-pushd"><code>pushd</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Directory-Stack-Builtins">Directory Stack Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-pwd"><code>pwd</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Builtin-Index_bt_letter-R">R</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-read"><code>read</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Builtins">Bash Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-readarray"><code>readarray</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Builtins">Bash Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-readonly"><code>readonly</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-return"><code>return</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Builtin-Index_bt_letter-S">S</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-set"><code>set</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#The-Set-Builtin">The Set Builtin</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-shift"><code>shift</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-shopt"><code>shopt</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#The-Shopt-Builtin">The Shopt Builtin</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-source"><code>source</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Builtins">Bash Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-suspend"><code>suspend</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Job-Control-Builtins">Job Control Builtins</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Builtin-Index_bt_letter-T">T</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-test"><code>test</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-times"><code>times</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-trap"><code>trap</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-type"><code>type</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Builtins">Bash Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-typeset"><code>typeset</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Builtins">Bash Builtins</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Builtin-Index_bt_letter-U">U</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-ulimit"><code>ulimit</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Builtins">Bash Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-umask"><code>umask</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-unalias"><code>unalias</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Builtins">Bash Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-unset"><code>unset</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Builtin-Index_bt_letter-W">W</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-wait"><code>wait</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Job-Control-Builtins">Job Control Builtins</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
</table>
<table><tr><th valign="top">Jump to: &nbsp; </th><td><a class="summary-letter" href="#Builtin-Index_bt_symbol-1"><b>.</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_symbol-2"><b>:</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_symbol-3"><b>[</b></a>
 &nbsp; 
<br>
<a class="summary-letter" href="#Builtin-Index_bt_letter-A"><b>A</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_letter-B"><b>B</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_letter-C"><b>C</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_letter-D"><b>D</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_letter-E"><b>E</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_letter-F"><b>F</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_letter-G"><b>G</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_letter-H"><b>H</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_letter-J"><b>J</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_letter-K"><b>K</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_letter-L"><b>L</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_letter-M"><b>M</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_letter-P"><b>P</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_letter-R"><b>R</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_letter-S"><b>S</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_letter-T"><b>T</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_letter-U"><b>U</b></a>
 &nbsp; 
<a class="summary-letter" href="#Builtin-Index_bt_letter-W"><b>W</b></a>
 &nbsp; 
</td></tr></table>

<hr>
</div>
<div class="appendixsec" id="Reserved-Word-Index">
<div class="header">
<p>
Next: <a href="#Variable-Index" accesskey="n" rel="next">Parameter and Variable Index</a>, Previous: <a href="#Builtin-Index" accesskey="p" rel="prev">Index of Shell Builtin Commands</a>, Up: <a href="#Indexes" accesskey="u" rel="up">Indexes</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Index-of-Shell-Reserved-Words"></span><h3 class="appendixsec">D.2 Index of Shell Reserved Words</h3>
<table><tr><th valign="top">Jump to: &nbsp; </th><td><a class="summary-letter" href="#Reserved-Word-Index_rw_symbol-1"><b>!</b></a>
 &nbsp; 
<a class="summary-letter" href="#Reserved-Word-Index_rw_symbol-2"><b>[</b></a>
 &nbsp; 
<a class="summary-letter" href="#Reserved-Word-Index_rw_symbol-3"><b>]</b></a>
 &nbsp; 
<a class="summary-letter" href="#Reserved-Word-Index_rw_symbol-4"><b>{</b></a>
 &nbsp; 
<a class="summary-letter" href="#Reserved-Word-Index_rw_symbol-5"><b>}</b></a>
 &nbsp; 
<br>
<a class="summary-letter" href="#Reserved-Word-Index_rw_letter-C"><b>C</b></a>
 &nbsp; 
<a class="summary-letter" href="#Reserved-Word-Index_rw_letter-D"><b>D</b></a>
 &nbsp; 
<a class="summary-letter" href="#Reserved-Word-Index_rw_letter-E"><b>E</b></a>
 &nbsp; 
<a class="summary-letter" href="#Reserved-Word-Index_rw_letter-F"><b>F</b></a>
 &nbsp; 
<a class="summary-letter" href="#Reserved-Word-Index_rw_letter-I"><b>I</b></a>
 &nbsp; 
<a class="summary-letter" href="#Reserved-Word-Index_rw_letter-S"><b>S</b></a>
 &nbsp; 
<a class="summary-letter" href="#Reserved-Word-Index_rw_letter-T"><b>T</b></a>
 &nbsp; 
<a class="summary-letter" href="#Reserved-Word-Index_rw_letter-U"><b>U</b></a>
 &nbsp; 
<a class="summary-letter" href="#Reserved-Word-Index_rw_letter-W"><b>W</b></a>
 &nbsp; 
</td></tr></table>
<table class="index-rw" border="0">
<tr><td></td><th align="left">Index Entry</th><td>&nbsp;</td><th align="left"> Section</th></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Reserved-Word-Index_rw_symbol-1">!</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-_0021"><code>!</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Pipelines">Pipelines</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Reserved-Word-Index_rw_symbol-2">[</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-_005b_005b"><code>[[</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Conditional-Constructs">Conditional Constructs</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Reserved-Word-Index_rw_symbol-3">]</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-_005d_005d"><code>]]</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Conditional-Constructs">Conditional Constructs</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Reserved-Word-Index_rw_symbol-4">{</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-_007b"><code>{</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Command-Grouping">Command Grouping</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Reserved-Word-Index_rw_symbol-5">}</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-_007d"><code>}</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Command-Grouping">Command Grouping</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Reserved-Word-Index_rw_letter-C">C</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-case"><code>case</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Conditional-Constructs">Conditional Constructs</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Reserved-Word-Index_rw_letter-D">D</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-do"><code>do</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Looping-Constructs">Looping Constructs</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-done"><code>done</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Looping-Constructs">Looping Constructs</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Reserved-Word-Index_rw_letter-E">E</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-elif"><code>elif</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Conditional-Constructs">Conditional Constructs</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-else"><code>else</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Conditional-Constructs">Conditional Constructs</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-esac"><code>esac</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Conditional-Constructs">Conditional Constructs</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Reserved-Word-Index_rw_letter-F">F</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-fi"><code>fi</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Conditional-Constructs">Conditional Constructs</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-for"><code>for</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Looping-Constructs">Looping Constructs</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-function"><code>function</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Shell-Functions">Shell Functions</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Reserved-Word-Index_rw_letter-I">I</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-if"><code>if</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Conditional-Constructs">Conditional Constructs</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-in"><code>in</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Conditional-Constructs">Conditional Constructs</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Reserved-Word-Index_rw_letter-S">S</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-select"><code>select</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Conditional-Constructs">Conditional Constructs</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Reserved-Word-Index_rw_letter-T">T</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-then"><code>then</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Conditional-Constructs">Conditional Constructs</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-time"><code>time</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Pipelines">Pipelines</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Reserved-Word-Index_rw_letter-U">U</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-until"><code>until</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Looping-Constructs">Looping Constructs</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Reserved-Word-Index_rw_letter-W">W</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-while"><code>while</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Looping-Constructs">Looping Constructs</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
</table>
<table><tr><th valign="top">Jump to: &nbsp; </th><td><a class="summary-letter" href="#Reserved-Word-Index_rw_symbol-1"><b>!</b></a>
 &nbsp; 
<a class="summary-letter" href="#Reserved-Word-Index_rw_symbol-2"><b>[</b></a>
 &nbsp; 
<a class="summary-letter" href="#Reserved-Word-Index_rw_symbol-3"><b>]</b></a>
 &nbsp; 
<a class="summary-letter" href="#Reserved-Word-Index_rw_symbol-4"><b>{</b></a>
 &nbsp; 
<a class="summary-letter" href="#Reserved-Word-Index_rw_symbol-5"><b>}</b></a>
 &nbsp; 
<br>
<a class="summary-letter" href="#Reserved-Word-Index_rw_letter-C"><b>C</b></a>
 &nbsp; 
<a class="summary-letter" href="#Reserved-Word-Index_rw_letter-D"><b>D</b></a>
 &nbsp; 
<a class="summary-letter" href="#Reserved-Word-Index_rw_letter-E"><b>E</b></a>
 &nbsp; 
<a class="summary-letter" href="#Reserved-Word-Index_rw_letter-F"><b>F</b></a>
 &nbsp; 
<a class="summary-letter" href="#Reserved-Word-Index_rw_letter-I"><b>I</b></a>
 &nbsp; 
<a class="summary-letter" href="#Reserved-Word-Index_rw_letter-S"><b>S</b></a>
 &nbsp; 
<a class="summary-letter" href="#Reserved-Word-Index_rw_letter-T"><b>T</b></a>
 &nbsp; 
<a class="summary-letter" href="#Reserved-Word-Index_rw_letter-U"><b>U</b></a>
 &nbsp; 
<a class="summary-letter" href="#Reserved-Word-Index_rw_letter-W"><b>W</b></a>
 &nbsp; 
</td></tr></table>

<hr>
</div>
<div class="appendixsec" id="Variable-Index">
<div class="header">
<p>
Next: <a href="#Function-Index" accesskey="n" rel="next">Function Index</a>, Previous: <a href="#Reserved-Word-Index" accesskey="p" rel="prev">Index of Shell Reserved Words</a>, Up: <a href="#Indexes" accesskey="u" rel="up">Indexes</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Parameter-and-Variable-Index"></span><h3 class="appendixsec">D.3 Parameter and Variable Index</h3>
<table><tr><th valign="top">Jump to: &nbsp; </th><td><a class="summary-letter" href="#Variable-Index_vr_symbol-1"><b>!</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_symbol-2"><b>#</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_symbol-3"><b>$</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_symbol-4"><b>*</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_symbol-5"><b>-</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_symbol-6"><b>0</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_symbol-7"><b>?</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_symbol-8"><b>@</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_symbol-9"><b>_</b></a>
 &nbsp; 
<br>
<a class="summary-letter" href="#Variable-Index_vr_letter-A"><b>A</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-B"><b>B</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-C"><b>C</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-D"><b>D</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-E"><b>E</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-F"><b>F</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-G"><b>G</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-H"><b>H</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-I"><b>I</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-K"><b>K</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-L"><b>L</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-M"><b>M</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-O"><b>O</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-P"><b>P</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-R"><b>R</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-S"><b>S</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-T"><b>T</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-U"><b>U</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-V"><b>V</b></a>
 &nbsp; 
</td></tr></table>
<table class="index-vr" border="0">
<tr><td></td><th align="left">Index Entry</th><td>&nbsp;</td><th align="left"> Section</th></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Variable-Index_vr_symbol-1">!</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-_0021-1"><code>!</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Special-Parameters">Special Parameters</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Variable-Index_vr_symbol-2">#</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-_0023"><code>#</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Special-Parameters">Special Parameters</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Variable-Index_vr_symbol-3">$</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-_0024"><code>$</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Special-Parameters">Special Parameters</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-_0024_0021"><code>$!</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Special-Parameters">Special Parameters</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-_0024_0023"><code>$#</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Special-Parameters">Special Parameters</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-_0024_0024"><code>$$</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Special-Parameters">Special Parameters</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-_0024_002a"><code>$*</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Special-Parameters">Special Parameters</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-_0024_002d"><code>$-</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Special-Parameters">Special Parameters</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-_00240"><code>$0</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Special-Parameters">Special Parameters</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-_0024_003f"><code>$?</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Special-Parameters">Special Parameters</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-_0024_0040"><code>$@</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Special-Parameters">Special Parameters</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-_0024_005f"><code>$_</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Variable-Index_vr_symbol-4">*</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-_002a"><code>*</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Special-Parameters">Special Parameters</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Variable-Index_vr_symbol-5">-</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-_002d"><code>-</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Special-Parameters">Special Parameters</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Variable-Index_vr_symbol-6">0</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-0"><code>0</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Special-Parameters">Special Parameters</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Variable-Index_vr_symbol-7">?</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-_003f"><code>?</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Special-Parameters">Special Parameters</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Variable-Index_vr_symbol-8">@</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-_0040"><code>@</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Special-Parameters">Special Parameters</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Variable-Index_vr_symbol-9">_</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-_005f"><code>_</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Variable-Index_vr_letter-A">A</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-active_002dregion_002dend_002dcolor"><code>active-region-end-color</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-active_002dregion_002dstart_002dcolor"><code>active-region-start-color</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-auto_005fresume"><code>auto_resume</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Job-Control-Variables">Job Control Variables</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Variable-Index_vr_letter-B">B</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-BASH"><code>BASH</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-BASHOPTS"><code>BASHOPTS</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-BASHPID"><code>BASHPID</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-BASH_005fALIASES"><code>BASH_ALIASES</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-BASH_005fARGC"><code>BASH_ARGC</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-BASH_005fARGV"><code>BASH_ARGV</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-BASH_005fARGV0"><code>BASH_ARGV0</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-BASH_005fCMDS"><code>BASH_CMDS</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-BASH_005fCOMMAND"><code>BASH_COMMAND</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-BASH_005fCOMPAT"><code>BASH_COMPAT</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-BASH_005fENV"><code>BASH_ENV</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-BASH_005fEXECUTION_005fSTRING"><code>BASH_EXECUTION_STRING</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-BASH_005fLINENO"><code>BASH_LINENO</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-BASH_005fLOADABLES_005fPATH"><code>BASH_LOADABLES_PATH</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-BASH_005fREMATCH"><code>BASH_REMATCH</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-BASH_005fSOURCE"><code>BASH_SOURCE</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-BASH_005fSUBSHELL"><code>BASH_SUBSHELL</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-BASH_005fVERSINFO"><code>BASH_VERSINFO</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-BASH_005fVERSION"><code>BASH_VERSION</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-BASH_005fXTRACEFD"><code>BASH_XTRACEFD</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-bell_002dstyle"><code>bell-style</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-bind_002dtty_002dspecial_002dchars"><code>bind-tty-special-chars</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-blink_002dmatching_002dparen"><code>blink-matching-paren</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Variable-Index_vr_letter-C">C</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-CDPATH"><code>CDPATH</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bourne-Shell-Variables">Bourne Shell Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-CHILD_005fMAX"><code>CHILD_MAX</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-colored_002dcompletion_002dprefix"><code>colored-completion-prefix</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-colored_002dstats"><code>colored-stats</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-COLUMNS"><code>COLUMNS</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-comment_002dbegin"><code>comment-begin</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-completion_002ddisplay_002dwidth"><code>completion-display-width</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-completion_002dignore_002dcase"><code>completion-ignore-case</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-completion_002dmap_002dcase"><code>completion-map-case</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-completion_002dprefix_002ddisplay_002dlength"><code>completion-prefix-display-length</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-completion_002dquery_002ditems"><code>completion-query-items</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-COMPREPLY"><code>COMPREPLY</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-COMP_005fCWORD"><code>COMP_CWORD</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-COMP_005fKEY"><code>COMP_KEY</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-COMP_005fLINE"><code>COMP_LINE</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-COMP_005fPOINT"><code>COMP_POINT</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-COMP_005fTYPE"><code>COMP_TYPE</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-COMP_005fWORDBREAKS"><code>COMP_WORDBREAKS</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-COMP_005fWORDS"><code>COMP_WORDS</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-convert_002dmeta"><code>convert-meta</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-COPROC"><code>COPROC</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Variable-Index_vr_letter-D">D</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-DIRSTACK"><code>DIRSTACK</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-disable_002dcompletion"><code>disable-completion</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Variable-Index_vr_letter-E">E</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-echo_002dcontrol_002dcharacters"><code>echo-control-characters</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-editing_002dmode"><code>editing-mode</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-EMACS"><code>EMACS</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-emacs_002dmode_002dstring"><code>emacs-mode-string</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-enable_002dactive_002dregion"><code>enable-active-region</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-enable_002dbracketed_002dpaste"><code>enable-bracketed-paste</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-enable_002dkeypad"><code>enable-keypad</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-ENV"><code>ENV</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-EPOCHREALTIME"><code>EPOCHREALTIME</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-EPOCHSECONDS"><code>EPOCHSECONDS</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-EUID"><code>EUID</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-EXECIGNORE"><code>EXECIGNORE</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-expand_002dtilde"><code>expand-tilde</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Variable-Index_vr_letter-F">F</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-FCEDIT"><code>FCEDIT</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-FIGNORE"><code>FIGNORE</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-FUNCNAME"><code>FUNCNAME</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-FUNCNEST"><code>FUNCNEST</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Variable-Index_vr_letter-G">G</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-GLOBIGNORE"><code>GLOBIGNORE</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-GROUPS"><code>GROUPS</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Variable-Index_vr_letter-H">H</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-histchars"><code>histchars</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-HISTCMD"><code>HISTCMD</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-HISTCONTROL"><code>HISTCONTROL</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-HISTFILE"><code>HISTFILE</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-HISTFILESIZE"><code>HISTFILESIZE</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-HISTIGNORE"><code>HISTIGNORE</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-history_002dpreserve_002dpoint"><code>history-preserve-point</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-history_002dsize"><code>history-size</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-HISTSIZE"><code>HISTSIZE</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-HISTTIMEFORMAT"><code>HISTTIMEFORMAT</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-HOME"><code>HOME</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bourne-Shell-Variables">Bourne Shell Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-horizontal_002dscroll_002dmode"><code>horizontal-scroll-mode</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-HOSTFILE"><code>HOSTFILE</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-HOSTNAME"><code>HOSTNAME</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-HOSTTYPE"><code>HOSTTYPE</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Variable-Index_vr_letter-I">I</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-IFS"><code>IFS</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bourne-Shell-Variables">Bourne Shell Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-IGNOREEOF"><code>IGNOREEOF</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-input_002dmeta"><code>input-meta</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-INPUTRC"><code>INPUTRC</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-INSIDE_005fEMACS"><code>INSIDE_EMACS</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-isearch_002dterminators"><code>isearch-terminators</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Variable-Index_vr_letter-K">K</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-keymap"><code>keymap</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Variable-Index_vr_letter-L">L</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-LANG"><code>LANG</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Creating-Internationalized-Scripts">Creating Internationalized Scripts</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-LANG-1"><code>LANG</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-LC_005fALL"><code>LC_ALL</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-LC_005fCOLLATE"><code>LC_COLLATE</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-LC_005fCTYPE"><code>LC_CTYPE</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-LC_005fMESSAGES"><code>LC_MESSAGES</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Creating-Internationalized-Scripts">Creating Internationalized Scripts</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-LC_005fMESSAGES-1"><code>LC_MESSAGES</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-LC_005fNUMERIC"><code>LC_NUMERIC</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-LC_005fTIME"><code>LC_TIME</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-LINENO"><code>LINENO</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-LINES"><code>LINES</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Variable-Index_vr_letter-M">M</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-MACHTYPE"><code>MACHTYPE</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-MAIL"><code>MAIL</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bourne-Shell-Variables">Bourne Shell Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-MAILCHECK"><code>MAILCHECK</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-MAILPATH"><code>MAILPATH</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bourne-Shell-Variables">Bourne Shell Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-MAPFILE"><code>MAPFILE</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-mark_002dmodified_002dlines"><code>mark-modified-lines</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-mark_002dsymlinked_002ddirectories"><code>mark-symlinked-directories</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-match_002dhidden_002dfiles"><code>match-hidden-files</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-menu_002dcomplete_002ddisplay_002dprefix"><code>menu-complete-display-prefix</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-meta_002dflag"><code>meta-flag</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Variable-Index_vr_letter-O">O</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-OLDPWD"><code>OLDPWD</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-OPTARG"><code>OPTARG</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bourne-Shell-Variables">Bourne Shell Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-OPTERR"><code>OPTERR</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-OPTIND"><code>OPTIND</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bourne-Shell-Variables">Bourne Shell Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-OSTYPE"><code>OSTYPE</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-output_002dmeta"><code>output-meta</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Variable-Index_vr_letter-P">P</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-page_002dcompletions"><code>page-completions</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-PATH"><code>PATH</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bourne-Shell-Variables">Bourne Shell Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-PIPESTATUS"><code>PIPESTATUS</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-POSIXLY_005fCORRECT"><code>POSIXLY_CORRECT</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-PPID"><code>PPID</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-PROMPT_005fCOMMAND"><code>PROMPT_COMMAND</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-PROMPT_005fDIRTRIM"><code>PROMPT_DIRTRIM</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-PS0"><code>PS0</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-PS1"><code>PS1</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bourne-Shell-Variables">Bourne Shell Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-PS2"><code>PS2</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bourne-Shell-Variables">Bourne Shell Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-PS3"><code>PS3</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-PS4"><code>PS4</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-PWD"><code>PWD</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Variable-Index_vr_letter-R">R</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-RANDOM"><code>RANDOM</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-READLINE_005fARGUMENT"><code>READLINE_ARGUMENT</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-READLINE_005fLINE"><code>READLINE_LINE</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-READLINE_005fMARK"><code>READLINE_MARK</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-READLINE_005fPOINT"><code>READLINE_POINT</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-REPLY"><code>REPLY</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-revert_002dall_002dat_002dnewline"><code>revert-all-at-newline</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Variable-Index_vr_letter-S">S</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-SECONDS"><code>SECONDS</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-SHELL"><code>SHELL</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-SHELLOPTS"><code>SHELLOPTS</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-SHLVL"><code>SHLVL</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-show_002dall_002dif_002dambiguous"><code>show-all-if-ambiguous</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-show_002dall_002dif_002dunmodified"><code>show-all-if-unmodified</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-show_002dmode_002din_002dprompt"><code>show-mode-in-prompt</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-skip_002dcompleted_002dtext"><code>skip-completed-text</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-SRANDOM"><code>SRANDOM</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Variable-Index_vr_letter-T">T</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-TEXTDOMAIN"><code>TEXTDOMAIN</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Creating-Internationalized-Scripts">Creating Internationalized Scripts</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-TEXTDOMAINDIR"><code>TEXTDOMAINDIR</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Creating-Internationalized-Scripts">Creating Internationalized Scripts</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-TIMEFORMAT"><code>TIMEFORMAT</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-TMOUT"><code>TMOUT</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-TMPDIR"><code>TMPDIR</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Variable-Index_vr_letter-U">U</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-UID"><code>UID</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Variables">Bash Variables</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Variable-Index_vr_letter-V">V</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-vi_002dcmd_002dmode_002dstring"><code>vi-cmd-mode-string</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-vi_002dins_002dmode_002dstring"><code>vi-ins-mode-string</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-visible_002dstats"><code>visible-stats</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
</table>
<table><tr><th valign="top">Jump to: &nbsp; </th><td><a class="summary-letter" href="#Variable-Index_vr_symbol-1"><b>!</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_symbol-2"><b>#</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_symbol-3"><b>$</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_symbol-4"><b>*</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_symbol-5"><b>-</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_symbol-6"><b>0</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_symbol-7"><b>?</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_symbol-8"><b>@</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_symbol-9"><b>_</b></a>
 &nbsp; 
<br>
<a class="summary-letter" href="#Variable-Index_vr_letter-A"><b>A</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-B"><b>B</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-C"><b>C</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-D"><b>D</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-E"><b>E</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-F"><b>F</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-G"><b>G</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-H"><b>H</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-I"><b>I</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-K"><b>K</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-L"><b>L</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-M"><b>M</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-O"><b>O</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-P"><b>P</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-R"><b>R</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-S"><b>S</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-T"><b>T</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-U"><b>U</b></a>
 &nbsp; 
<a class="summary-letter" href="#Variable-Index_vr_letter-V"><b>V</b></a>
 &nbsp; 
</td></tr></table>

<hr>
</div>
<div class="appendixsec" id="Function-Index">
<div class="header">
<p>
Next: <a href="#Concept-Index" accesskey="n" rel="next">Concept Index</a>, Previous: <a href="#Variable-Index" accesskey="p" rel="prev">Parameter and Variable Index</a>, Up: <a href="#Indexes" accesskey="u" rel="up">Indexes</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Function-Index-1"></span><h3 class="appendixsec">D.4 Function Index</h3>
<table><tr><th valign="top">Jump to: &nbsp; </th><td><a class="summary-letter" href="#Function-Index_fn_letter-A"><b>A</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-B"><b>B</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-C"><b>C</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-D"><b>D</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-E"><b>E</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-F"><b>F</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-G"><b>G</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-H"><b>H</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-I"><b>I</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-K"><b>K</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-M"><b>M</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-N"><b>N</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-O"><b>O</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-P"><b>P</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-Q"><b>Q</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-R"><b>R</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-S"><b>S</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-T"><b>T</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-U"><b>U</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-Y"><b>Y</b></a>
 &nbsp; 
</td></tr></table>
<table class="index-fn" border="0">
<tr><td></td><th align="left">Index Entry</th><td>&nbsp;</td><th align="left"> Section</th></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Function-Index_fn_letter-A">A</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-abort-_0028C_002dg_0029"><code>abort (C-g)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Miscellaneous-Commands">Miscellaneous Commands</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-accept_002dline-_0028Newline-or-Return_0029"><code>accept-line (Newline or Return)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-History">Commands For History</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-alias_002dexpand_002dline-_0028_0029"><code>alias-expand-line ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Miscellaneous-Commands">Miscellaneous Commands</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Function-Index_fn_letter-B">B</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-backward_002dchar-_0028C_002db_0029"><code>backward-char (C-b)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Moving">Commands For Moving</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-backward_002ddelete_002dchar-_0028Rubout_0029"><code>backward-delete-char (Rubout)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Text">Commands For Text</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-backward_002dkill_002dline-_0028C_002dx-Rubout_0029"><code>backward-kill-line (C-x Rubout)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Killing">Commands For Killing</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-backward_002dkill_002dword-_0028M_002dDEL_0029"><code>backward-kill-word (M-<span class="key">DEL</span>)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Killing">Commands For Killing</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-backward_002dword-_0028M_002db_0029"><code>backward-word (M-b)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Moving">Commands For Moving</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-beginning_002dof_002dhistory-_0028M_002d_003c_0029"><code>beginning-of-history (M-&lt;)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-History">Commands For History</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-beginning_002dof_002dline-_0028C_002da_0029"><code>beginning-of-line (C-a)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Moving">Commands For Moving</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-bracketed_002dpaste_002dbegin-_0028_0029"><code>bracketed-paste-begin ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Text">Commands For Text</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Function-Index_fn_letter-C">C</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-call_002dlast_002dkbd_002dmacro-_0028C_002dx-e_0029"><code>call-last-kbd-macro (C-x e)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Keyboard-Macros">Keyboard Macros</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-capitalize_002dword-_0028M_002dc_0029"><code>capitalize-word (M-c)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Text">Commands For Text</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-character_002dsearch-_0028C_002d_005d_0029"><code>character-search (C-])</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Miscellaneous-Commands">Miscellaneous Commands</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-character_002dsearch_002dbackward-_0028M_002dC_002d_005d_0029"><code>character-search-backward (M-C-])</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Miscellaneous-Commands">Miscellaneous Commands</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-clear_002ddisplay-_0028M_002dC_002dl_0029"><code>clear-display (M-C-l)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Moving">Commands For Moving</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-clear_002dscreen-_0028C_002dl_0029"><code>clear-screen (C-l)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Moving">Commands For Moving</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-complete-_0028TAB_0029"><code>complete (<span class="key">TAB</span>)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Completion">Commands For Completion</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-complete_002dcommand-_0028M_002d_0021_0029"><code>complete-command (M-!)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Completion">Commands For Completion</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-complete_002dfilename-_0028M_002d_002f_0029"><code>complete-filename (M-/)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Completion">Commands For Completion</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-complete_002dhostname-_0028M_002d_0040_0029"><code>complete-hostname (M-@)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Completion">Commands For Completion</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-complete_002dinto_002dbraces-_0028M_002d_007b_0029"><code>complete-into-braces (M-{)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Completion">Commands For Completion</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-complete_002dusername-_0028M_002d_007e_0029"><code>complete-username (M-~)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Completion">Commands For Completion</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-complete_002dvariable-_0028M_002d_0024_0029"><code>complete-variable (M-$)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Completion">Commands For Completion</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-copy_002dbackward_002dword-_0028_0029"><code>copy-backward-word ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Killing">Commands For Killing</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-copy_002dforward_002dword-_0028_0029"><code>copy-forward-word ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Killing">Commands For Killing</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-copy_002dregion_002das_002dkill-_0028_0029"><code>copy-region-as-kill ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Killing">Commands For Killing</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Function-Index_fn_letter-D">D</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-dabbrev_002dexpand-_0028_0029"><code>dabbrev-expand ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Completion">Commands For Completion</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-delete_002dchar-_0028C_002dd_0029"><code>delete-char (C-d)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Text">Commands For Text</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-delete_002dchar_002dor_002dlist-_0028_0029"><code>delete-char-or-list ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Completion">Commands For Completion</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-delete_002dhorizontal_002dspace-_0028_0029"><code>delete-horizontal-space ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Killing">Commands For Killing</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-digit_002dargument-_0028M_002d0_002c-M_002d1_002c-_2026-M_002d_002d_0029"><code>digit-argument (<kbd>M-0</kbd>, <kbd>M-1</kbd>, &hellip; <kbd>M--</kbd>)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Numeric-Arguments">Numeric Arguments</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-display_002dshell_002dversion-_0028C_002dx-C_002dv_0029"><code>display-shell-version (C-x C-v)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Miscellaneous-Commands">Miscellaneous Commands</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-do_002dlowercase_002dversion-_0028M_002dA_002c-M_002dB_002c-M_002dx_002c-_2026_0029"><code>do-lowercase-version (M-A, M-B, M-<var>x</var>, &hellip;)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Miscellaneous-Commands">Miscellaneous Commands</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-downcase_002dword-_0028M_002dl_0029"><code>downcase-word (M-l)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Text">Commands For Text</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-dump_002dfunctions-_0028_0029"><code>dump-functions ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Miscellaneous-Commands">Miscellaneous Commands</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-dump_002dmacros-_0028_0029"><code>dump-macros ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Miscellaneous-Commands">Miscellaneous Commands</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-dump_002dvariables-_0028_0029"><code>dump-variables ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Miscellaneous-Commands">Miscellaneous Commands</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-dynamic_002dcomplete_002dhistory-_0028M_002dTAB_0029"><code>dynamic-complete-history (M-<span class="key">TAB</span>)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Completion">Commands For Completion</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Function-Index_fn_letter-E">E</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-edit_002dand_002dexecute_002dcommand-_0028C_002dx-C_002de_0029"><code>edit-and-execute-command (C-x C-e)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Miscellaneous-Commands">Miscellaneous Commands</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-end_002dkbd_002dmacro-_0028C_002dx-_0029_0029"><code>end-kbd-macro (C-x ))</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Keyboard-Macros">Keyboard Macros</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-end_002dof_002dfile-_0028usually-C_002dd_0029"><code><i>end-of-file</i> (usually C-d)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Text">Commands For Text</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-end_002dof_002dhistory-_0028M_002d_003e_0029"><code>end-of-history (M-&gt;)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-History">Commands For History</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-end_002dof_002dline-_0028C_002de_0029"><code>end-of-line (C-e)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Moving">Commands For Moving</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-exchange_002dpoint_002dand_002dmark-_0028C_002dx-C_002dx_0029"><code>exchange-point-and-mark (C-x C-x)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Miscellaneous-Commands">Miscellaneous Commands</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Function-Index_fn_letter-F">F</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-fetch_002dhistory-_0028_0029"><code>fetch-history ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-History">Commands For History</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-forward_002dbackward_002ddelete_002dchar-_0028_0029"><code>forward-backward-delete-char ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Text">Commands For Text</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-forward_002dchar-_0028C_002df_0029"><code>forward-char (C-f)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Moving">Commands For Moving</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-forward_002dsearch_002dhistory-_0028C_002ds_0029"><code>forward-search-history (C-s)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-History">Commands For History</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-forward_002dword-_0028M_002df_0029"><code>forward-word (M-f)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Moving">Commands For Moving</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Function-Index_fn_letter-G">G</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-glob_002dcomplete_002dword-_0028M_002dg_0029"><code>glob-complete-word (M-g)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Miscellaneous-Commands">Miscellaneous Commands</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-glob_002dexpand_002dword-_0028C_002dx-_002a_0029"><code>glob-expand-word (C-x *)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Miscellaneous-Commands">Miscellaneous Commands</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-glob_002dlist_002dexpansions-_0028C_002dx-g_0029"><code>glob-list-expansions (C-x g)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Miscellaneous-Commands">Miscellaneous Commands</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Function-Index_fn_letter-H">H</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-history_002dand_002dalias_002dexpand_002dline-_0028_0029"><code>history-and-alias-expand-line ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Miscellaneous-Commands">Miscellaneous Commands</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-history_002dexpand_002dline-_0028M_002d_005e_0029"><code>history-expand-line (M-^)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Miscellaneous-Commands">Miscellaneous Commands</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-history_002dsearch_002dbackward-_0028_0029"><code>history-search-backward ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-History">Commands For History</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-history_002dsearch_002dforward-_0028_0029"><code>history-search-forward ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-History">Commands For History</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-history_002dsubstring_002dsearch_002dbackward-_0028_0029"><code>history-substring-search-backward ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-History">Commands For History</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-history_002dsubstring_002dsearch_002dforward-_0028_0029"><code>history-substring-search-forward ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-History">Commands For History</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Function-Index_fn_letter-I">I</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-insert_002dcomment-_0028M_002d_0023_0029"><code>insert-comment (M-#)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Miscellaneous-Commands">Miscellaneous Commands</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-insert_002dcompletions-_0028M_002d_002a_0029"><code>insert-completions (M-*)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Completion">Commands For Completion</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-insert_002dlast_002dargument-_0028M_002d_002e-or-M_002d_005f_0029"><code>insert-last-argument (M-. or M-_)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Miscellaneous-Commands">Miscellaneous Commands</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Function-Index_fn_letter-K">K</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-kill_002dline-_0028C_002dk_0029"><code>kill-line (C-k)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Killing">Commands For Killing</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-kill_002dregion-_0028_0029"><code>kill-region ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Killing">Commands For Killing</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-kill_002dwhole_002dline-_0028_0029"><code>kill-whole-line ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Killing">Commands For Killing</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-kill_002dword-_0028M_002dd_0029"><code>kill-word (M-d)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Killing">Commands For Killing</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Function-Index_fn_letter-M">M</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-magic_002dspace-_0028_0029"><code>magic-space ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Miscellaneous-Commands">Miscellaneous Commands</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-menu_002dcomplete-_0028_0029"><code>menu-complete ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Completion">Commands For Completion</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-menu_002dcomplete_002dbackward-_0028_0029"><code>menu-complete-backward ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Completion">Commands For Completion</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Function-Index_fn_letter-N">N</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-next_002dhistory-_0028C_002dn_0029"><code>next-history (C-n)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-History">Commands For History</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-next_002dscreen_002dline-_0028_0029"><code>next-screen-line ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Moving">Commands For Moving</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-non_002dincremental_002dforward_002dsearch_002dhistory-_0028M_002dn_0029"><code>non-incremental-forward-search-history (M-n)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-History">Commands For History</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-non_002dincremental_002dreverse_002dsearch_002dhistory-_0028M_002dp_0029"><code>non-incremental-reverse-search-history (M-p)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-History">Commands For History</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Function-Index_fn_letter-O">O</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-operate_002dand_002dget_002dnext-_0028C_002do_0029"><code>operate-and-get-next (C-o)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-History">Commands For History</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-overwrite_002dmode-_0028_0029"><code>overwrite-mode ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Text">Commands For Text</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Function-Index_fn_letter-P">P</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-possible_002dcommand_002dcompletions-_0028C_002dx-_0021_0029"><code>possible-command-completions (C-x !)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Completion">Commands For Completion</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-possible_002dcompletions-_0028M_002d_003f_0029"><code>possible-completions (M-?)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Completion">Commands For Completion</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-possible_002dfilename_002dcompletions-_0028C_002dx-_002f_0029"><code>possible-filename-completions (C-x /)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Completion">Commands For Completion</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-possible_002dhostname_002dcompletions-_0028C_002dx-_0040_0029"><code>possible-hostname-completions (C-x @)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Completion">Commands For Completion</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-possible_002dusername_002dcompletions-_0028C_002dx-_007e_0029"><code>possible-username-completions (C-x ~)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Completion">Commands For Completion</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-possible_002dvariable_002dcompletions-_0028C_002dx-_0024_0029"><code>possible-variable-completions (C-x $)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Completion">Commands For Completion</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-prefix_002dmeta-_0028ESC_0029"><code>prefix-meta (<span class="key">ESC</span>)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Miscellaneous-Commands">Miscellaneous Commands</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-previous_002dhistory-_0028C_002dp_0029"><code>previous-history (C-p)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-History">Commands For History</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-previous_002dscreen_002dline-_0028_0029"><code>previous-screen-line ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Moving">Commands For Moving</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-print_002dlast_002dkbd_002dmacro-_0028_0029"><code>print-last-kbd-macro ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Keyboard-Macros">Keyboard Macros</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Function-Index_fn_letter-Q">Q</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-quoted_002dinsert-_0028C_002dq-or-C_002dv_0029"><code>quoted-insert (C-q or C-v)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Text">Commands For Text</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Function-Index_fn_letter-R">R</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-re_002dread_002dinit_002dfile-_0028C_002dx-C_002dr_0029"><code>re-read-init-file (C-x C-r)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Miscellaneous-Commands">Miscellaneous Commands</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-redraw_002dcurrent_002dline-_0028_0029"><code>redraw-current-line ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Moving">Commands For Moving</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-reverse_002dsearch_002dhistory-_0028C_002dr_0029"><code>reverse-search-history (C-r)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-History">Commands For History</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-revert_002dline-_0028M_002dr_0029"><code>revert-line (M-r)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Miscellaneous-Commands">Miscellaneous Commands</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Function-Index_fn_letter-S">S</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-self_002dinsert-_0028a_002c-b_002c-A_002c-1_002c-_0021_002c-_2026_0029"><code>self-insert (a, b, A, 1, !, &hellip;)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Text">Commands For Text</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-set_002dmark-_0028C_002d_0040_0029"><code>set-mark (C-@)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Miscellaneous-Commands">Miscellaneous Commands</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-shell_002dbackward_002dkill_002dword-_0028_0029"><code>shell-backward-kill-word ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Killing">Commands For Killing</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-shell_002dbackward_002dword-_0028M_002dC_002db_0029"><code>shell-backward-word (M-C-b)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Moving">Commands For Moving</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-shell_002dexpand_002dline-_0028M_002dC_002de_0029"><code>shell-expand-line (M-C-e)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Miscellaneous-Commands">Miscellaneous Commands</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-shell_002dforward_002dword-_0028M_002dC_002df_0029"><code>shell-forward-word (M-C-f)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Moving">Commands For Moving</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-shell_002dkill_002dword-_0028M_002dC_002dd_0029"><code>shell-kill-word (M-C-d)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Killing">Commands For Killing</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-shell_002dtranspose_002dwords-_0028M_002dC_002dt_0029"><code>shell-transpose-words (M-C-t)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Killing">Commands For Killing</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-skip_002dcsi_002dsequence-_0028_0029"><code>skip-csi-sequence ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Miscellaneous-Commands">Miscellaneous Commands</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-spell_002dcorrect_002dword-_0028C_002dx-s_0029"><code>spell-correct-word (C-x s)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Miscellaneous-Commands">Miscellaneous Commands</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-start_002dkbd_002dmacro-_0028C_002dx-_0028_0029"><code>start-kbd-macro (C-x ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Keyboard-Macros">Keyboard Macros</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Function-Index_fn_letter-T">T</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-tilde_002dexpand-_0028M_002d_0026_0029"><code>tilde-expand (M-&amp;)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Miscellaneous-Commands">Miscellaneous Commands</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-transpose_002dchars-_0028C_002dt_0029"><code>transpose-chars (C-t)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Text">Commands For Text</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-transpose_002dwords-_0028M_002dt_0029"><code>transpose-words (M-t)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Text">Commands For Text</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Function-Index_fn_letter-U">U</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-undo-_0028C_002d_005f-or-C_002dx-C_002du_0029"><code>undo (C-_ or C-x C-u)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Miscellaneous-Commands">Miscellaneous Commands</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-universal_002dargument-_0028_0029"><code>universal-argument ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Numeric-Arguments">Numeric Arguments</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-unix_002dfilename_002drubout-_0028_0029"><code>unix-filename-rubout ()</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Killing">Commands For Killing</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-unix_002dline_002ddiscard-_0028C_002du_0029"><code>unix-line-discard (C-u)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Killing">Commands For Killing</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-unix_002dword_002drubout-_0028C_002dw_0029"><code>unix-word-rubout (C-w)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Killing">Commands For Killing</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-upcase_002dword-_0028M_002du_0029"><code>upcase-word (M-u)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Text">Commands For Text</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Function-Index_fn_letter-Y">Y</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-yank-_0028C_002dy_0029"><code>yank (C-y)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Killing">Commands For Killing</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-yank_002dlast_002darg-_0028M_002d_002e-or-M_002d_005f_0029"><code>yank-last-arg (M-. or M-_)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-History">Commands For History</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-yank_002dnth_002darg-_0028M_002dC_002dy_0029"><code>yank-nth-arg (M-C-y)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-History">Commands For History</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-yank_002dpop-_0028M_002dy_0029"><code>yank-pop (M-y)</code></a>:</td><td>&nbsp;</td><td valign="top"><a href="#Commands-For-Killing">Commands For Killing</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
</table>
<table><tr><th valign="top">Jump to: &nbsp; </th><td><a class="summary-letter" href="#Function-Index_fn_letter-A"><b>A</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-B"><b>B</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-C"><b>C</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-D"><b>D</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-E"><b>E</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-F"><b>F</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-G"><b>G</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-H"><b>H</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-I"><b>I</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-K"><b>K</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-M"><b>M</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-N"><b>N</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-O"><b>O</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-P"><b>P</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-Q"><b>Q</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-R"><b>R</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-S"><b>S</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-T"><b>T</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-U"><b>U</b></a>
 &nbsp; 
<a class="summary-letter" href="#Function-Index_fn_letter-Y"><b>Y</b></a>
 &nbsp; 
</td></tr></table>

<hr>
</div>
<div class="appendixsec" id="Concept-Index">
<div class="header">
<p>
Previous: <a href="#Function-Index" accesskey="p" rel="prev">Function Index</a>, Up: <a href="#Indexes" accesskey="u" rel="up">Indexes</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Indexes" title="Index" rel="index">Index</a>]</p>
</div>
<span id="Concept-Index-1"></span><h3 class="appendixsec">D.5 Concept Index</h3>
<table><tr><th valign="top">Jump to: &nbsp; </th><td><a class="summary-letter" href="#Concept-Index_cp_letter-A"><b>A</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-B"><b>B</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-C"><b>C</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-D"><b>D</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-E"><b>E</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-F"><b>F</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-H"><b>H</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-I"><b>I</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-J"><b>J</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-K"><b>K</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-L"><b>L</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-M"><b>M</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-N"><b>N</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-O"><b>O</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-P"><b>P</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-Q"><b>Q</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-R"><b>R</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-S"><b>S</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-T"><b>T</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-V"><b>V</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-W"><b>W</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-Y"><b>Y</b></a>
 &nbsp; 
</td></tr></table>
<table class="index-cp" border="0">
<tr><td></td><th align="left">Index Entry</th><td>&nbsp;</td><th align="left"> Section</th></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Concept-Index_cp_letter-A">A</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-alias-expansion">alias expansion</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Aliases">Aliases</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-arithmetic-evaluation">arithmetic evaluation</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Shell-Arithmetic">Shell Arithmetic</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-arithmetic-expansion">arithmetic expansion</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Arithmetic-Expansion">Arithmetic Expansion</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-arithmetic_002c-shell">arithmetic, shell</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Shell-Arithmetic">Shell Arithmetic</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-arrays">arrays</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Arrays">Arrays</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Concept-Index_cp_letter-B">B</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-background">background</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Job-Control-Basics">Job Control Basics</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-Bash-configuration">Bash configuration</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Basic-Installation">Basic Installation</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-Bash-installation">Bash installation</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Basic-Installation">Basic Installation</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-Bourne-shell">Bourne shell</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Basic-Shell-Features">Basic Shell Features</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-brace-expansion">brace expansion</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Brace-Expansion">Brace Expansion</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-builtin-1">builtin</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Definitions">Definitions</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Concept-Index_cp_letter-C">C</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-command-editing">command editing</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Bare-Essentials">Readline Bare Essentials</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-command-execution">command execution</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Command-Search-and-Execution">Command Search and Execution</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-command-expansion">command expansion</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Simple-Command-Expansion">Simple Command Expansion</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-command-history">command history</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-History-Facilities">Bash History Facilities</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-command-search">command search</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Command-Search-and-Execution">Command Search and Execution</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-command-substitution">command substitution</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Command-Substitution">Command Substitution</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-command-timing">command timing</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Pipelines">Pipelines</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-commands_002c-compound">commands, compound</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Compound-Commands">Compound Commands</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-commands_002c-conditional">commands, conditional</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Conditional-Constructs">Conditional Constructs</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-commands_002c-grouping">commands, grouping</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Command-Grouping">Command Grouping</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-commands_002c-lists">commands, lists</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Lists">Lists</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-commands_002c-looping">commands, looping</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Looping-Constructs">Looping Constructs</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-commands_002c-pipelines">commands, pipelines</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Pipelines">Pipelines</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-commands_002c-shell">commands, shell</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Shell-Commands">Shell Commands</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-commands_002c-simple">commands, simple</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Simple-Commands">Simple Commands</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-comments_002c-shell">comments, shell</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Comments">Comments</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-Compatibility-Level">Compatibility Level</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Shell-Compatibility-Mode">Shell Compatibility Mode</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-Compatibility-Mode">Compatibility Mode</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Shell-Compatibility-Mode">Shell Compatibility Mode</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-completion-builtins">completion builtins</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Programmable-Completion-Builtins">Programmable Completion Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-configuration">configuration</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Basic-Installation">Basic Installation</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-control-operator">control operator</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Definitions">Definitions</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-coprocess">coprocess</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Coprocesses">Coprocesses</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Concept-Index_cp_letter-D">D</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-directory-stack">directory stack</a>:</td><td>&nbsp;</td><td valign="top"><a href="#The-Directory-Stack">The Directory Stack</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Concept-Index_cp_letter-E">E</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-editing-command-lines">editing command lines</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Bare-Essentials">Readline Bare Essentials</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-environment">environment</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Environment">Environment</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-evaluation_002c-arithmetic">evaluation, arithmetic</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Shell-Arithmetic">Shell Arithmetic</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-event-designators">event designators</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Event-Designators">Event Designators</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-execution-environment">execution environment</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Command-Execution-Environment">Command Execution Environment</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-exit-status">exit status</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Definitions">Definitions</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-exit-status-1">exit status</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Exit-Status">Exit Status</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-expansion">expansion</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Shell-Expansions">Shell Expansions</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-expansion_002c-arithmetic">expansion, arithmetic</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Arithmetic-Expansion">Arithmetic Expansion</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-expansion_002c-brace">expansion, brace</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Brace-Expansion">Brace Expansion</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-expansion_002c-filename">expansion, filename</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Filename-Expansion">Filename Expansion</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-expansion_002c-parameter">expansion, parameter</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Shell-Parameter-Expansion">Shell Parameter Expansion</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-expansion_002c-pathname">expansion, pathname</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Filename-Expansion">Filename Expansion</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-expansion_002c-tilde">expansion, tilde</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Tilde-Expansion">Tilde Expansion</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-expressions_002c-arithmetic">expressions, arithmetic</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Shell-Arithmetic">Shell Arithmetic</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-expressions_002c-conditional">expressions, conditional</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Conditional-Expressions">Bash Conditional Expressions</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Concept-Index_cp_letter-F">F</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-field">field</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Definitions">Definitions</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-filename">filename</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Definitions">Definitions</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-filename-expansion">filename expansion</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Filename-Expansion">Filename Expansion</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-foreground">foreground</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Job-Control-Basics">Job Control Basics</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-functions_002c-shell">functions, shell</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Shell-Functions">Shell Functions</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Concept-Index_cp_letter-H">H</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-history-builtins">history builtins</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-History-Builtins">Bash History Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-history-events">history events</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Event-Designators">Event Designators</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-history-expansion">history expansion</a>:</td><td>&nbsp;</td><td valign="top"><a href="#History-Interaction">History Interaction</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-history-list">history list</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-History-Facilities">Bash History Facilities</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-History_002c-how-to-use">History, how to use</a>:</td><td>&nbsp;</td><td valign="top"><a href="#A-Programmable-Completion-Example">A Programmable Completion Example</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Concept-Index_cp_letter-I">I</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-identifier">identifier</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Definitions">Definitions</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-initialization-file_002c-readline">initialization file, readline</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File">Readline Init File</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-installation">installation</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Basic-Installation">Basic Installation</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-interaction_002c-readline">interaction, readline</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Interaction">Readline Interaction</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-interactive-shell">interactive shell</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Invoking-Bash">Invoking Bash</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-interactive-shell-1">interactive shell</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Interactive-Shells">Interactive Shells</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-internationalization">internationalization</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Locale-Translation">Locale Translation</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-internationalized-scripts">internationalized scripts</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Creating-Internationalized-Scripts">Creating Internationalized Scripts</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Concept-Index_cp_letter-J">J</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-job">job</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Definitions">Definitions</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-job-control">job control</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Definitions">Definitions</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-job-control-1">job control</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Job-Control-Basics">Job Control Basics</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Concept-Index_cp_letter-K">K</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-kill-ring">kill ring</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Killing-Commands">Readline Killing Commands</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-killing-text">killing text</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Killing-Commands">Readline Killing Commands</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Concept-Index_cp_letter-L">L</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-localization">localization</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Locale-Translation">Locale Translation</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-login-shell">login shell</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Invoking-Bash">Invoking Bash</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Concept-Index_cp_letter-M">M</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-matching_002c-pattern">matching, pattern</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Pattern-Matching">Pattern Matching</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-metacharacter">metacharacter</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Definitions">Definitions</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Concept-Index_cp_letter-N">N</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-name">name</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Definitions">Definitions</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-native-languages">native languages</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Locale-Translation">Locale Translation</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-notation_002c-readline">notation, readline</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Bare-Essentials">Readline Bare Essentials</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Concept-Index_cp_letter-O">O</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-operator_002c-shell">operator, shell</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Definitions">Definitions</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Concept-Index_cp_letter-P">P</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-parameter-expansion">parameter expansion</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Shell-Parameter-Expansion">Shell Parameter Expansion</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-parameters">parameters</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Shell-Parameters">Shell Parameters</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-parameters_002c-positional">parameters, positional</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Positional-Parameters">Positional Parameters</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-parameters_002c-special">parameters, special</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Special-Parameters">Special Parameters</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-pathname-expansion">pathname expansion</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Filename-Expansion">Filename Expansion</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-pattern-matching">pattern matching</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Pattern-Matching">Pattern Matching</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-pipeline">pipeline</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Pipelines">Pipelines</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-POSIX">POSIX</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Definitions">Definitions</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-POSIX-Mode">POSIX Mode</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-POSIX-Mode">Bash POSIX Mode</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-process-group">process group</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Definitions">Definitions</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-process-group-ID">process group ID</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Definitions">Definitions</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-process-substitution">process substitution</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Process-Substitution">Process Substitution</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-programmable-completion">programmable completion</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Programmable-Completion">Programmable Completion</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-prompting">prompting</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Controlling-the-Prompt">Controlling the Prompt</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Concept-Index_cp_letter-Q">Q</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-quoting">quoting</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Quoting">Quoting</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-quoting_002c-ANSI">quoting, ANSI</a>:</td><td>&nbsp;</td><td valign="top"><a href="#ANSI_002dC-Quoting">ANSI-C Quoting</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Concept-Index_cp_letter-R">R</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-Readline_002c-how-to-use">Readline, how to use</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Job-Control-Variables">Job Control Variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-redirection">redirection</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Redirections">Redirections</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-reserved-word">reserved word</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Definitions">Definitions</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-reserved-words">reserved words</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Reserved-Words">Reserved Words</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-restricted-shell">restricted shell</a>:</td><td>&nbsp;</td><td valign="top"><a href="#The-Restricted-Shell">The Restricted Shell</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-return-status">return status</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Definitions">Definitions</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Concept-Index_cp_letter-S">S</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-shell-arithmetic">shell arithmetic</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Shell-Arithmetic">Shell Arithmetic</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-shell-function">shell function</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Shell-Functions">Shell Functions</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-shell-script">shell script</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Shell-Scripts">Shell Scripts</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-shell-variable">shell variable</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Shell-Parameters">Shell Parameters</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-shell_002c-interactive">shell, interactive</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Interactive-Shells">Interactive Shells</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-signal">signal</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Definitions">Definitions</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-signal-handling">signal handling</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Signals">Signals</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-special-builtin">special builtin</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Definitions">Definitions</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-special-builtin-1">special builtin</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Special-Builtins">Special Builtins</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-startup-files">startup files</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Bash-Startup-Files">Bash Startup Files</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-string-translations">string translations</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Creating-Internationalized-Scripts">Creating Internationalized Scripts</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-suspending-jobs">suspending jobs</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Job-Control-Basics">Job Control Basics</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Concept-Index_cp_letter-T">T</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-tilde-expansion">tilde expansion</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Tilde-Expansion">Tilde Expansion</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-token">token</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Definitions">Definitions</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-translation_002c-native-languages">translation, native languages</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Locale-Translation">Locale Translation</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Concept-Index_cp_letter-V">V</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-variable_002c-shell">variable, shell</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Shell-Parameters">Shell Parameters</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-variables_002c-readline">variables, readline</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Init-File-Syntax">Readline Init File Syntax</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Concept-Index_cp_letter-W">W</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-word">word</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Definitions">Definitions</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-word-splitting">word splitting</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Word-Splitting">Word Splitting</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th id="Concept-Index_cp_letter-Y">Y</th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-yanking-text">yanking text</a>:</td><td>&nbsp;</td><td valign="top"><a href="#Readline-Killing-Commands">Readline Killing Commands</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
</table>
<table><tr><th valign="top">Jump to: &nbsp; </th><td><a class="summary-letter" href="#Concept-Index_cp_letter-A"><b>A</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-B"><b>B</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-C"><b>C</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-D"><b>D</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-E"><b>E</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-F"><b>F</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-H"><b>H</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-I"><b>I</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-J"><b>J</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-K"><b>K</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-L"><b>L</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-M"><b>M</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-N"><b>N</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-O"><b>O</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-P"><b>P</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-Q"><b>Q</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-R"><b>R</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-S"><b>S</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-T"><b>T</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-V"><b>V</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-W"><b>W</b></a>
 &nbsp; 
<a class="summary-letter" href="#Concept-Index_cp_letter-Y"><b>Y</b></a>
 &nbsp; 
</td></tr></table>

</div>
</div>
</div>



</body>
</html>
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-25 06:14:11 +0000