summaryrefslogtreecommitdiffstats
path: root/doc/bash.1
blob: 55c562208ab98d9f5a36bbd095f8a6dea6376577 (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
.\"
.\" MAN PAGE COMMENTS to
.\"
.\"	Chet Ramey
.\"	Case Western Reserve University
.\"	chet.ramey@case.edu
.\"
.\"	Last Change: Mon Sep 19 11:13:21 EDT 2022
.\"
.\" bash_builtins, strip all but Built-Ins section
.if \n(zZ=1 .ig zZ
.if \n(zY=1 .ig zY
.TH BASH 1 "2022 September 19" "GNU Bash 5.2"
.\"
.\" There's some problem with having a `@'
.\" in a tagged paragraph with the BSD man macros.
.\" It has to do with `@' appearing in the }1 macro.
.\" This is a problem on 4.3 BSD and Ultrix, but Sun
.\" appears to have fixed it.
.\" If you're seeing the characters
.\" `@u-3p' appearing before the lines reading
.\" `possible-hostname-completions
.\" and `complete-hostname' down in READLINE,
.\" then uncomment this redefinition.
.\"
.\" .de }1
.\" .ds ]X \&\\*(]B\\
.\" .nr )E 0
.\" .if !"\\$1"" .nr )I \\$1n
.\" .}f
.\" .ll \\n(LLu
.\" .in \\n()Ru+\\n(INu+\\n()Iu
.\" .ti \\n(INu
.\" .ie !\\n()Iu+\\n()Ru-\w\\*(]Xu-3p \{\\*(]X
.\" .br\}
.\" .el \\*(]X\h|\\n()Iu+\\n()Ru\c
.\" .}f
.\" ..
.\"
.\" File Name macro.  This used to be `.PN', for Path Name,
.\" but Sun doesn't seem to like that very much.
.\"
.de FN
\fI\|\\$1\|\fP
..
.SH NAME
bash \- GNU Bourne-Again SHell
.SH SYNOPSIS
.B bash
[options]
[command_string | file]
.SH COPYRIGHT
.if n Bash is Copyright (C) 1989-2022 by the Free Software Foundation, Inc.
.if t Bash is Copyright \(co 1989-2022 by the Free Software Foundation, Inc.
.SH DESCRIPTION
.B Bash
is an \fBsh\fR-compatible command language interpreter that
executes commands read from the standard input or from a file.
.B Bash
also incorporates useful features from the \fIKorn\fP and \fIC\fP
shells (\fBksh\fP and \fBcsh\fP).
.PP
.B Bash
is intended to be a conformant implementation of the
Shell and Utilities portion of the IEEE POSIX specification
(IEEE Standard 1003.1).
.B Bash
can be configured to be POSIX-conformant by default.
.SH OPTIONS
All of the single-character shell options documented in the
description of the \fBset\fR builtin command, including \fB\-o\fP,
can be used as options when the shell is invoked.
In addition, \fBbash\fR
interprets the following options when it is invoked:
.PP
.PD 0
.TP 10
.B \-c
If the
.B \-c
option is present, then commands are read from the first non-option argument
.IR command_string .
If there are arguments after the
.IR command_string ,
the first argument is assigned to
.B $0
and any remaining arguments are assigned to the positional parameters.
The assignment to
.B $0
sets the name of the shell, which is used in warning and error messages.
.TP
.B \-i
If the
.B \-i
option is present, the shell is
.IR interactive .
.TP
.B \-l
Make
.B bash
act as if it had been invoked as a login shell (see
.SM
.B INVOCATION
below).
.TP
.B \-r
If the
.B \-r
option is present, the shell becomes
.I restricted
(see
.SM
.B "RESTRICTED SHELL"
below).
.TP
.B \-s
If the
.B \-s
option is present, or if no arguments remain after option
processing, then commands are read from the standard input.
This option allows the positional parameters to be set
when invoking an interactive shell or when reading input
through a pipe.
.TP
.B \-D
A list of all double-quoted strings preceded by \fB$\fP
is printed on the standard output.
These are the strings that
are subject to language translation when the current locale
is not \fBC\fP or \fBPOSIX\fP.
This implies the \fB\-n\fP option; no commands will be executed.
.TP
.B [\-+]O [\fIshopt_option\fP]
\fIshopt_option\fP is one of the shell options accepted by the
\fBshopt\fP builtin (see
.SM
.B SHELL BUILTIN COMMANDS
below).
If \fIshopt_option\fP is present, \fB\-O\fP sets the value of that option;
\fB+O\fP unsets it.
If \fIshopt_option\fP is not supplied, the names and values of the shell
options accepted by \fBshopt\fP are printed on the standard output.
If the invocation option is \fB+O\fP, the output is displayed in a format
that may be reused as input.
.TP
.B \-\-
A
.B \-\-
signals the end of options and disables further option processing.
Any arguments after the
.B \-\-
are treated as filenames and arguments.  An argument of
.B \-
is equivalent to \fB\-\-\fP.
.PD
.PP
.B Bash
also interprets a number of multi-character options.
These options must appear on the command line before the
single-character options to be recognized.
.PP
.PD 0
.TP
.B \-\-debugger
Arrange for the debugger profile to be executed before the shell
starts.
Turns on extended debugging mode (see the description of the
.B extdebug
option to the
.B shopt
builtin below).
.TP
.B \-\-dump\-po\-strings
Equivalent to \fB\-D\fP, but the output is in the GNU \fIgettext\fP
\fBpo\fP (portable object) file format.
.TP
.B \-\-dump\-strings
Equivalent to \fB\-D\fP.
.TP
.B \-\-help
Display a usage message on standard output and exit successfully.
.TP
\fB\-\-init\-file\fP \fIfile\fP
.PD 0
.TP
\fB\-\-rcfile\fP \fIfile\fP
.PD
Execute commands from
.I file
instead of the standard personal initialization file
.I ~/.bashrc
if the shell is interactive (see
.SM
.B INVOCATION
below).
.TP
.B \-\-login
Equivalent to \fB\-l\fP.
.TP
.B \-\-noediting
Do not use the GNU
.B readline
library to read command lines when the shell is interactive.
.TP
.B \-\-noprofile
Do not read either the system-wide startup file
.FN /etc/profile
or any of the personal initialization files
.IR ~/.bash_profile ,
.IR ~/.bash_login ,
or
.IR ~/.profile .
By default,
.B bash
reads these files when it is invoked as a login shell (see
.SM
.B INVOCATION
below).
.TP
.B \-\-norc
Do not read and execute the personal initialization file
.I ~/.bashrc
if the shell is interactive.
This option is on by default if the shell is invoked as
.BR sh .
.TP
.B \-\-posix
Change the behavior of \fBbash\fP where the default operation differs
from the POSIX standard to match the standard (\fIposix mode\fP).
See
.SM
.B "SEE ALSO"
below for a reference to a document that details how posix mode affects
bash's behavior.
.TP
.B \-\-restricted
The shell becomes restricted (see
.SM
.B "RESTRICTED SHELL"
below).
.TP
.B \-\-verbose
Equivalent to \fB\-v\fP.
.TP
.B \-\-version
Show version information for this instance of
.B bash
on the standard output and exit successfully.
.PD
.SH ARGUMENTS
If arguments remain after option processing, and neither the
.B \-c
nor the
.B \-s
option has been supplied, the first argument is assumed to
be the name of a file containing shell commands.
If
.B bash
is invoked in this fashion,
.B $0
is set to the name of the file, and the positional parameters
are set to the remaining arguments.
.B Bash
reads and executes commands from this file, then exits.
\fBBash\fP'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.
An attempt is first made to open the file in the current directory, and,
if no file is found, then the shell searches the directories in
.SM
.B PATH
for the script.
.SH INVOCATION
A \fIlogin shell\fP is one whose first character of argument zero is a
.BR \- ,
or one started with the
.B \-\-login
option.
.PP
An \fIinteractive\fP shell is one started without non-option arguments
(unless \fB\-s\fP is specified)
and without the
.B \-c
option,
whose standard input and error are
both connected to terminals (as determined by
.IR isatty (3)),
or one started with the
.B \-i
option.
.SM
.B PS1
is set and
.B $\-
includes
.B i
if
.B bash
is interactive,
allowing a shell script or a startup file to test this state.
.PP
The following paragraphs describe how
.B bash
executes its startup files.
If any of the files exist but cannot be read,
.B bash
reports an error.
Tildes are expanded in filenames as described below under
.B "Tilde Expansion"
in the
.SM
.B EXPANSION
section.
.PP
When
.B bash
is invoked as an interactive login shell, or as a non-interactive shell
with the \fB\-\-login\fP option, it first reads and
executes commands from the file \fI/etc/profile\fP, if that
file exists.
After reading that file, it looks for \fI~/.bash_profile\fP,
\fI~/.bash_login\fP, and \fI~/.profile\fP, in that order, and reads
and executes commands from the first one that exists and is readable.
The
.B \-\-noprofile
option may be used when the shell is started to inhibit this behavior.
.PP
When an interactive login shell exits,
or a non-interactive login shell executes the \fBexit\fP builtin command,
.B bash
reads and executes commands from the file \fI~/.bash_logout\fP, if it
exists.
.PP
When an interactive shell that is not a login shell is started,
.B bash
reads and executes commands from \fI~/.bashrc\fP, if that file exists.
This may be inhibited by using the
.B \-\-norc
option.
The \fB\-\-rcfile\fP \fIfile\fP option will force
.B bash
to read and execute commands from \fIfile\fP instead of \fI~/.bashrc\fP.
.PP
When
.B bash
is started non-interactively, to run a shell script, for example, it
looks for the variable
.SM
.B BASH_ENV
in the environment, expands its value if it appears there, and uses the
expanded value as the name of a file to read and execute.
.B Bash
behaves as if the following command were executed:
.sp .5
.RS
.if t \f(CWif [ \-n "$BASH_ENV" ]; then . "$BASH_ENV"; fi\fP
.if n if [ \-n "$BASH_ENV" ]; then . "$BASH_ENV"; fi
.RE
.sp .5
but the value of the
.SM
.B PATH
variable is not used to search for the filename.
.PP
If
.B bash
is invoked with the name
.BR sh ,
it tries to mimic the startup behavior of historical versions of
.B sh
as closely as possible,
while conforming to the POSIX standard as well.
When invoked as an interactive login shell, or a non-interactive
shell with the \fB\-\-login\fP option, it first attempts to
read and execute commands from
.I /etc/profile
and
.IR ~/.profile ,
in that order.
The
.B \-\-noprofile
option may be used to inhibit this behavior.
When invoked as an interactive shell with the name
.BR sh ,
.B bash
looks for the variable
.SM
.BR ENV ,
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
.B sh
does not attempt to read and execute commands from any other startup
files, the
.B \-\-rcfile
option has no effect.
A non-interactive shell invoked with the name
.B sh
does not attempt to read any other startup files.
When invoked as
.BR sh ,
.B bash
enters
.I posix
mode after the startup files are read.
.PP
When
.B bash
is started in
.I posix
mode, as with the
.B \-\-posix
command line option, it follows the POSIX standard for startup files.
In this mode, interactive shells expand the
.SM
.B ENV
variable and commands are read and executed from the file
whose name is the expanded value.
No other startup files are read.
.PP
.B 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 \fIrshd\fP,
or the secure shell daemon \fIsshd\fP.
If
.B bash
determines it is being run non-interactively in this fashion,
it reads and executes commands from \fI~/.bashrc\fP,
if that file exists and is readable.
It will not do this if invoked as \fBsh\fP.
The
.B \-\-norc
option may be used to inhibit this behavior, and the
.B \-\-rcfile
option may be used to force another file to be read, but neither
\fIrshd\fP nor \fIsshd\fP generally invoke the shell with those options
or allow them to be specified.
.PP
If the shell is started with the effective user (group) id not equal to the
real user (group) id, and the \fB\-p\fP option is not supplied, no startup
files are read, shell functions are not inherited from the environment, the
.SM
.BR SHELLOPTS ,
.SM
.BR BASHOPTS ,
.SM
.BR CDPATH ,
and
.SM
.B GLOBIGNORE
variables, if they appear in the environment, are ignored,
and the effective user id is set to the real user id.
If the \fB\-p\fP option is supplied at invocation, the startup behavior is
the same, but the effective user id is not reset.
.SH DEFINITIONS
The following definitions are used throughout the rest of this
document.
.PD 0
.TP
.B blank
A space or tab.
.TP
.B word
A sequence of characters considered as a single unit by the shell.
Also known as a
.BR token .
.TP
.B name
A
.I word
consisting only of alphanumeric characters and underscores, and
beginning with an alphabetic character or an underscore.  Also
referred to as an
.BR identifier .
.TP
.B metacharacter
A character that, when unquoted, separates words.  One of the following:
.br
.RS
.PP
.if t \fB|  &  ;  (  )  <  >  space  tab  newline\fP
.if n \fB|  & ; ( ) < > space tab newline\fP
.RE
.TP
.B control operator
A \fItoken\fP that performs a control function.  It is one of the following
symbols:
.RS
.PP
.if t \fB||  &  &&  ;  ;;  ;&  ;;&  (  )  |  |&    <newline>\fP
.if n \fB|| & && ; ;; ;& ;;& ( ) | |& <newline>\fP
.RE
.PD
.SH "RESERVED WORDS"
\fIReserved words\fP are words that have a special meaning to the shell.
The following words are recognized as reserved when unquoted and either
the first word of a command (see
.SM
.B SHELL GRAMMAR
below), the third word of a
.B case
or
.B select
command
(only \fBin\fP is valid), or the third word of a
.B for
command (only \fBin\fP and \fBdo\fP are valid):
.if t .RS
.PP
.B
.if n ! case  coproc  do done elif else esac fi for function if in select then until while { } time [[ ]]
.if t !    case    coproc    do    done    elif    else    esac    fi    for    function    if    in    select    then    until    while    {    }    time    [[    ]]
.if t .RE
.SH "SHELL GRAMMAR"
This section describes the syntax of the various forms of shell commands.
.SS Simple Commands
A \fIsimple command\fP is a sequence of optional variable assignments
followed by \fBblank\fP-separated words and redirections, and
terminated by a \fIcontrol operator\fP.  The first word
specifies the command to be executed, and is passed as argument zero.
The remaining words are passed as arguments to the invoked command.
.PP
The return value of a \fIsimple command\fP is its exit status, or
128+\fIn\^\fP if the command is terminated by signal
.IR n .
.SS Pipelines
A \fIpipeline\fP is a sequence of one or more commands separated by
one of the control operators
.B |
or \fB|&\fP.
The format for a pipeline is:
.RS
.PP
[\fBtime\fP [\fB\-p\fP]] [ ! ] \fIcommand1\fP [ [\fB|\fP\(bv\fB|&\fP] \fIcommand2\fP ... ]
.RE
.PP
The standard output of
.I command1
is connected via a pipe to the standard input of
.IR command2 .
This connection is performed before any redirections specified by the
.IR command1 (see
.SM
.B REDIRECTION
below).
If \fB|&\fP is used, \fIcommand1\fP's standard error, in addition to its
standard output, is connected to
\fIcommand2\fP's standard input through the pipe;
it is shorthand for \fB2>&1 |\fP.
This implicit redirection of the standard error to the standard output is
performed after any redirections specified by \fIcommand1\fP.
.PP
The return status of a pipeline is the exit status of the last
command, unless the \fBpipefail\fP option is enabled.
If \fBpipefail\fP is enabled, the pipeline'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
.B !
precedes a pipeline, the exit status of that pipeline 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.
.PP
If the
.B time
reserved word precedes a pipeline, the elapsed as well as user and
system time consumed by its execution are reported when the pipeline
terminates.
The \fB\-p\fP option changes the output format to that specified by POSIX.
When the shell is in \fIposix mode\fP, it does not recognize
\fBtime\fP as a reserved word if the next token begins with a `-'.
The
.SM
.B TIMEFORMAT
variable may be set to a format string that specifies how the timing
information should be displayed; see the description of
.SM
.B TIMEFORMAT
under
.B "Shell Variables"
below.
.PP
When the shell is in \fIposix mode\fP, \fBtime\fP
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
.SM
.B TIMEFORMAT
variable may be used to specify the format of
the time information.
.PP
Each command in a multi-command pipeline,
where pipes are created,
is executed in a \fIsubshell\fP, which is a
separate process.
See
.SM
\fBCOMMAND EXECUTION ENVIRONMENT\fP
for a description of subshells and a subshell environment.
If the \fBlastpipe\fP option is enabled using the \fBshopt\fP builtin
(see the description of \fBshopt\fP below),
the last element of a pipeline may be run by the shell process
when job control is not active.
.SS Lists
A \fIlist\fP is a sequence of one or more pipelines separated by one
of the operators
.BR ; ,
.BR & ,
.BR && ,
or
.BR || ,
and optionally terminated by one of
.BR ; ,
.BR & ,
or
.BR <newline> .
.PP
Of these list operators,
.B &&
and
.B ||
have equal precedence, followed by
.B ;
and
.BR & ,
which have equal precedence.
.PP
A sequence of one or more newlines may appear in a \fIlist\fP instead
of a semicolon to delimit commands.
.PP
If a command is terminated by the control operator
.BR & ,
the shell executes the command in the \fIbackground\fP
in a subshell.
The shell does not wait for the command to
finish, and the return status is 0.
These are referred to as \fIasynchronous\fP commands.
Commands separated by a
.B ;
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.
.PP
AND and OR lists are sequences of one or more pipelines separated by the
\fB&&\fP and \fB||\fP control operators, respectively.
AND and OR lists are executed with left associativity.
An AND list has the form
.RS
.PP
\fIcommand1\fP \fB&&\fP \fIcommand2\fP
.RE
.PP
.I command2
is executed if, and only if,
.I command1
returns an exit status of zero (success).
.PP
An OR list has the form
.RS
.PP
\fIcommand1\fP \fB||\fP \fIcommand2\fP
.RE
.PP
.I command2
is executed if, and only if,
.I command1
returns a non-zero exit status.
The return status of
AND and OR lists is the exit status of the last command
executed in the list.
.SS Compound Commands
A \fIcompound command\fP is one of the following.
In most cases a \fIlist\fP in a command'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.
.TP
(\fIlist\fP)
\fIlist\fP is executed in a subshell (see
.SM
\fBCOMMAND EXECUTION ENVIRONMENT\fP
below for a description of a subshell environment).
Variable assignments and builtin
commands that affect the shell's environment do not remain in effect
after the command completes.  The return status is the exit status of
\fIlist\fP.
.TP
{ \fIlist\fP; }
\fIlist\fP is simply executed in the current shell environment.
\fIlist\fP must be terminated with a newline or semicolon.
This is known as a \fIgroup command\fP.
The return status is the exit status of
\fIlist\fP.
Note that unlike the metacharacters \fB(\fP and \fB)\fP, \fB{\fP and
\fB}\fP are \fIreserved words\fP and must occur where a reserved
word is permitted to be recognized.  Since they do not cause a word
break, they must be separated from \fIlist\fP by whitespace or another
shell metacharacter.
.TP
((\fIexpression\fP))
The \fIexpression\fP is evaluated according to the rules described
below under
.SM
.BR "ARITHMETIC EVALUATION" .
If the value of the expression is non-zero, the return status is 0;
otherwise the return status is 1.
The \fIexpression\fP
undergoes the same expansions
as if it were within double quotes,
but double quote characters in \fIexpression\fP are not treated specially
and are removed.
.TP
\fB[[\fP \fIexpression\fP \fB]]\fP
Return a status of 0 or 1 depending on the evaluation of
the conditional expression \fIexpression\fP.
Expressions are composed of the primaries described below under
.SM
.BR "CONDITIONAL EXPRESSIONS" .
The words between the \fB[[\fP and \fB]]\fP do not undergo word splitting
and pathname 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 \fB\-f\fP must be unquoted to be recognized
as primaries.
.if t .sp 0.5
.if n .sp 1
When used with \fB[[\fP, the \fB<\fP and \fB>\fP operators sort
lexicographically using the current locale.
.if t .sp 0.5
.if n .sp 1
When the \fB==\fP and \fB!=\fP operators are used, the string to the
right of the operator is considered a pattern and matched according
to the rules described below under \fBPattern Matching\fP,
as if the \fBextglob\fP shell option were enabled.
The \fB=\fP operator is equivalent to \fB==\fP.
If the
.B nocasematch
shell option is enabled, the match is performed without regard to the case
of alphabetic characters.
The return value is 0 if the string matches (\fB==\fP) or does not match
(\fB!=\fP) the pattern, and 1 otherwise.
Any part of the pattern may be quoted to force the quoted portion
to be matched as a string.
.if t .sp 0.5
.if n .sp 1
An additional binary operator, \fB=~\fP, is available, with the same
precedence as \fB==\fP and \fB!=\fP.
When it is used, the string to the right of the operator is considered
a POSIX extended regular expression and matched accordingly
(using the POSIX \fIregcomp\fP and \fIregexec\fP interfaces
usually described in \fIregex\fP(3)).
The return value is 0 if the string matches
the pattern, and 1 otherwise.
If the regular expression is syntactically incorrect, the conditional
expression's return value is 2.
If the
.B nocasematch
shell option is enabled, the match is performed without regard to the case
of alphabetic characters.
If any part of the pattern is quoted, the quoted portion is matched literally.
This means every character in the quoted portion matches itself,
instead of having any special pattern matching meaning.
If the pattern is stored in a shell variable, quoting the variable
expansion forces the entire pattern to be matched literally.
Treat bracket expressions in regular expressions carefully,
since normal quoting and pattern characters lose their meanings
between brackets.
.if t .sp 0.5
.if n .sp 1
The pattern will match if it matches any part of the string.
Anchor the pattern using the \fB^\fP and \fB$\fP regular expression
operators to force it to match the entire string.
The array variable
.SM
.B BASH_REMATCH
records which parts of the string matched the pattern.
The element of
.SM
.B BASH_REMATCH
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
.SM
.B BASH_REMATCH
indices. The element of
.SM
.B BASH_REMATCH
with index \fIn\fP is the portion of the
string matching the \fIn\fPth parenthesized subexpression.
Bash sets
.SM
.B BASH_REMATCH
in the global scope; declaring it as a local variable will lead to
unexpected results.
.if t .sp 0.5
.if n .sp 1
Expressions may be combined using the following operators, listed
in decreasing order of precedence:
.if t .sp 0.5
.if n .sp 1
.RS
.PD 0
.TP
.B ( \fIexpression\fP )
Returns the value of \fIexpression\fP.
This may be used to override the normal precedence of operators.
.TP
.B ! \fIexpression\fP
True if
.I expression
is false.
.TP
\fIexpression1\fP \fB&&\fP \fIexpression2\fP
True if both
.I expression1
and
.I expression2
are true.
.TP
\fIexpression1\fP \fB||\fP \fIexpression2\fP
True if either
.I expression1
or
.I expression2
is true.
.PD
.LP
The \fB&&\fP and \fB||\fP
operators do not evaluate \fIexpression2\fP if the value of
\fIexpression1\fP is sufficient to determine the return value of
the entire conditional expression.
.RE
.TP
\fBfor\fP \fIname\fP [ [ \fBin\fP [ \fIword ...\fP ] ] ; ] \fBdo\fP \fIlist\fP ; \fBdone\fP
The list of words following \fBin\fP is expanded, generating a list
of items.
The variable \fIname\fP is set to each element of this list
in turn, and \fIlist\fP is executed each time.
If the \fBin\fP \fIword\fP is omitted, the \fBfor\fP command executes
\fIlist\fP once for each positional parameter that is set (see
.SM
.B PARAMETERS
below).
The return status is the exit status of the last command that executes.
If the expansion of the items following \fBin\fP results in an empty
list, no commands are executed, and the return status is 0.
.TP
\fBfor\fP (( \fIexpr1\fP ; \fIexpr2\fP ; \fIexpr3\fP )) ; \fBdo\fP \fIlist\fP ; \fBdone\fP
First, the arithmetic expression \fIexpr1\fP is evaluated according
to the rules described below under
.SM
.BR "ARITHMETIC EVALUATION" .
The arithmetic expression \fIexpr2\fP is then evaluated repeatedly
until it evaluates to zero.
Each time \fIexpr2\fP evaluates to a non-zero value, \fIlist\fP is
executed and the arithmetic expression \fIexpr3\fP 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 \fIlist\fP
that is executed, or false if any of the expressions is invalid.
.TP
\fBselect\fP \fIname\fP [ \fBin\fP \fIword\fP ] ; \fBdo\fP \fIlist\fP ; \fBdone\fP
The list of words following \fBin\fP is expanded, generating a list
of items, and the set of expanded words is printed on the standard
error, each preceded by a number.  If the \fBin\fP
\fIword\fP is omitted, the positional parameters are printed (see
.SM
.B PARAMETERS
below).
.B select
then displays the
.SM
.B PS3
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
.I name
is set to that word.
If the line is empty, the words and prompt are displayed again.
If EOF is read, the \fBselect\fP command completes and returns 1.
Any other value read causes
.I name
to be set to null.  The line read is saved in the variable
.SM
.BR REPLY .
The
.I list
is executed after each selection until a
.B break
command is executed.
The exit status of
.B select
is the exit status of the last command executed in
.IR list ,
or zero if no commands were executed.
.TP
\fBcase\fP \fIword\fP \fBin\fP [ [(] \fIpattern\fP [ \fB|\fP \fIpattern\fP ] \
... ) \fIlist\fP ;; ] ... \fBesac\fP
A \fBcase\fP command first expands \fIword\fP, and tries to match
it against each \fIpattern\fP in turn, using the matching rules
described under
.B Pattern Matching
below.
The \fIword\fP is expanded using tilde
expansion, parameter and variable expansion, arithmetic expansion,
command substitution, process substitution and quote removal.
Each \fIpattern\fP examined is expanded using tilde
expansion, parameter and variable expansion, arithmetic expansion,
command substitution, process substitution, and quote removal.
If the
.B nocasematch
shell option is enabled, the match is performed without regard to the case
of alphabetic characters.
When a match is found, the corresponding \fIlist\fP is executed.
If the \fB;;\fP operator is used, no subsequent matches are attempted after
the first pattern match.
Using \fB;&\fP in place of \fB;;\fP causes execution to continue with
the \fIlist\fP associated with the next set of patterns.
Using \fB;;&\fP in place of \fB;;\fP causes the shell to test the next
pattern list in the statement, if any, and execute any associated \fIlist\fP
on a successful match,
continuing the case statement execution as if the pattern list had not matched.
The exit status is zero if no
pattern matches.  Otherwise, it is the exit status of the
last command executed in \fIlist\fP.
.TP
\fBif\fP \fIlist\fP; \fBthen\fP \fIlist\fP; \
[ \fBelif\fP \fIlist\fP; \fBthen\fP \fIlist\fP; ] ... \
[ \fBelse\fP \fIlist\fP; ] \fBfi\fP
The
.B if
.I list
is executed.  If its exit status is zero, the
\fBthen\fP \fIlist\fP is executed.  Otherwise, each \fBelif\fP
\fIlist\fP is executed in turn, and if its exit status is zero,
the corresponding \fBthen\fP \fIlist\fP is executed and the
command completes.  Otherwise, the \fBelse\fP \fIlist\fP is
executed, if present.  The exit status is the exit status of the
last command executed, or zero if no condition tested true.
.TP
\fBwhile\fP \fIlist-1\fP; \fBdo\fP \fIlist-2\fP; \fBdone\fP
.PD 0
.TP
\fBuntil\fP \fIlist-1\fP; \fBdo\fP \fIlist-2\fP; \fBdone\fP
.PD
The \fBwhile\fP command continuously executes the list
\fIlist-2\fP as long as the last command in the list \fIlist-1\fP returns
an exit status of zero.  The \fBuntil\fP command is identical
to the \fBwhile\fP command, except that the test is negated:
.I list-2
is executed as long as the last command in
.I list-1
returns a non-zero exit status.
The exit status of the \fBwhile\fP and \fBuntil\fP commands
is the exit status
of the last command executed in \fIlist-2\fP, or zero if
none was executed.
.SS Coprocesses
A \fIcoprocess\fP is a shell command preceded by the \fBcoproc\fP reserved
word.
A coprocess is executed asynchronously in a subshell, as if the command
had been terminated with the \fB&\fP control operator, with a two-way pipe
established between the executing shell and the coprocess.
.PP
The syntax for a coprocess is:
.RS
.PP
\fBcoproc\fP [\fINAME\fP] \fIcommand\fP [\fIredirections\fP]
.RE
.PP
This creates a coprocess named \fINAME\fP.
\fIcommand\fP may be either a simple command or a compound
command (see above).
\fINAME\fP is a shell variable name.
If \fINAME\fP is not supplied, the default name is \fBCOPROC\fP.
.PP
The recommended form to use for a coprocess is
.RS
.PP
\fBcoproc\fP \fINAME\fP { \fIcommand\fP [\fIredirections\fP]; }
.RE
.PP
This form is recommended because simple commands result in the coprocess
always being named \fBCOPROC\fP, and it is simpler to use and more complete
than the other compound commands.
.PP
If \fIcommand\fP is a compound command, \fINAME\fP is optional. The
word following \fBcoproc\fP determines whether that word is interpreted
as a variable name: it is interpreted as \fINAME\fP if it is not a
reserved word that introduces a compound command.
If \fIcommand\fP is a simple command, \fINAME\fP is not allowed; this
is to avoid confusion between \fINAME\fP and the first word of the simple
command.
.PP
When the coprocess is executed, the shell creates an array variable (see
.B Arrays
below) named \fINAME\fP in the context of the executing shell.
The standard output of
.I command
is connected via a pipe to a file descriptor in the executing shell,
and that file descriptor is assigned to \fINAME\fP[0].
The standard input of
.I command
is connected via a pipe to a file descriptor in the executing shell,
and that file descriptor is assigned to \fINAME\fP[1].
This pipe is established before any redirections specified by the
command (see
.SM
.B REDIRECTION
below).
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.
.PP
The process ID of the shell spawned to execute the coprocess is
available as the value of the variable \fINAME\fP_PID.
The \fBwait\fP
builtin command may be used to wait for the coprocess to terminate.
.PP
Since the coprocess is created as an asynchronous command,
the \fBcoproc\fP command always returns success.
The return status of a coprocess is the exit status of \fIcommand\fP.
.SS Shell Function Definitions
A shell function is an object that is called like a simple command and
executes a compound command with a new set of positional parameters.
Shell functions are declared as follows:
.TP
\fIfname\fP () \fIcompound\-command\fP [\fIredirection\fP]
.PD 0
.TP
\fBfunction\fP \fIfname\fP [()] \fIcompound\-command\fP [\fIredirection\fP]
.PD
This defines a function named \fIfname\fP.
The reserved word \fBfunction\fP is optional.
If the \fBfunction\fP reserved word is supplied, the parentheses are optional.
The \fIbody\fP of the function is the compound command
.I compound\-command
(see \fBCompound Commands\fP above).
That command is usually a \fIlist\fP of commands between { and }, but
may be any command listed under \fBCompound Commands\fP above.
If the \fBfunction\fP reserved word is used, but the
parentheses are not supplied, the braces are recommended.
\fIcompound\-command\fP is executed whenever \fIfname\fP is specified as the
name of a simple command.
When in \fIposix mode\fP, \fIfname\fP must be a valid shell \fIname\fP
and may not be the name of one of the
POSIX \fIspecial builtins\fP.
In default mode, a function name can be any unquoted shell word that does
not contain \fB$\fP.
Any redirections (see
.SM
.B REDIRECTION
below) specified when a function is defined are performed
when the function is executed.
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.  (See
.SM
.B FUNCTIONS
below.)
.SH COMMENTS
In a non-interactive shell, or an interactive shell in which the
.B interactive_comments
option to the
.B shopt
builtin is enabled (see
.SM
.B "SHELL BUILTIN COMMANDS"
below), a word beginning with
.B #
causes that word and all remaining characters on that line to
be ignored.  An interactive shell without the
.B interactive_comments
option enabled does not allow comments.  The
.B interactive_comments
option is on by default in interactive shells.
.SH QUOTING
\fIQuoting\fP 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.
.PP
Each of the \fImetacharacters\fP listed above under
.SM
.B DEFINITIONS
has special meaning to the shell and must be quoted if it is to
represent itself.
.PP
When the command history expansion facilities are being used
(see
.SM
.B HISTORY EXPANSION
below), the
\fIhistory expansion\fP character, usually \fB!\fP, must be quoted
to prevent history expansion.
.PP
There are three quoting mechanisms: the
.IR "escape character" ,
single quotes, and double quotes.
.PP
A non-quoted backslash (\fB\e\fP) is the
.IR "escape character" .
It preserves the literal value of the next character that follows,
with the exception of <newline>.  If a \fB\e\fP<newline> pair
appears, and the backslash is not itself quoted, the \fB\e\fP<newline>
is treated as a line continuation (that is, it is removed from the
input stream and effectively ignored).
.PP
Enclosing characters in single quotes 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.
.PP
Enclosing characters in double quotes preserves the literal value
of all characters within the quotes, with the exception of
.BR $ ,
.BR \` ,
.BR \e ,
and, when history expansion is enabled,
.BR ! .
When the shell is in \fIposix mode\fP, the \fB!\fP has no special meaning
within double quotes, even when history expansion is enabled.
The characters
.B $
and
.B \`
retain their special meaning within double quotes.  The backslash
retains its special meaning only when followed by one of the following
characters:
.BR $ ,
.BR \` ,
\^\fB"\fP\^,
.BR \e ,
or
.BR <newline> .
A double quote may be quoted within double quotes by preceding it with
a backslash.
If enabled, history expansion will be performed unless an
.B !
appearing in double quotes is escaped using a backslash.
The backslash preceding the
.B !
is not removed.
.PP
The special parameters
.B *
and
.B @
have special meaning when in double
quotes (see
.SM
.B PARAMETERS
below).
.PP
Character sequences of the form \fB$\fP\(aq\fIstring\fP\(aq are treated
as a special variant of single quotes.
The sequence expands to \fIstring\fP, with backslash-escaped characters
in \fIstring\fP replaced as specified by the ANSI C standard.
Backslash escape sequences, if present, are decoded as follows:
.RS
.PD 0
.TP
.B \ea
alert (bell)
.TP
.B \eb
backspace
.TP
.B \ee
.TP
.B \eE
an escape character
.TP
.B \ef
form feed
.TP
.B \en
new line
.TP
.B \er
carriage return
.TP
.B \et
horizontal tab
.TP
.B \ev
vertical tab
.TP
.B \e\e
backslash
.TP
.B \e\(aq
single quote
.TP
.B \e\(dq
double quote
.TP
.B \e?
question mark
.TP
.B \e\fInnn\fP
the eight-bit character whose value is the octal value \fInnn\fP
(one to three octal digits)
.TP
.B \ex\fIHH\fP
the eight-bit character whose value is the hexadecimal value \fIHH\fP
(one or two hex digits)
.TP
.B \eu\fIHHHH\fP
the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value
\fIHHHH\fP (one to four hex digits)
.TP
.B \eU\fIHHHHHHHH\fP
the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value
\fIHHHHHHHH\fP (one to eight hex digits)
.TP
.B \ec\fIx\fP
a control-\fIx\fP character
.PD
.RE
.LP
The expanded result is single-quoted, as if the dollar sign had
not been present.
.PP
A double-quoted string preceded by a dollar sign (\fB$\fP\(dq\fIstring\fP\(dq)
will cause the string to be translated according to the current locale.
The \fIgettext\fP infrastructure performs the lookup and
translation, using the \fBLC_MESSAGES\fP, \fBTEXTDOMAINDIR\fP,
and \fBTEXTDOMAIN\fP shell variables.
If the current locale is \fBC\fP or \fBPOSIX\fP,
if there are no translations available,
or if the string is not translated,
the dollar sign is ignored.
This is a form of double quoting, so the string remains double-quoted
by default, whether or not it is translated and replaced.
If the \fBnoexpand_translation\fP option is enabled
using the \fBshopt\fP builtin,
translated strings are single-quoted instead of double-quoted.
See the description of
.B shopt
below under
.SM
.BR SHELL BUILTIN COMMANDS .
.SH PARAMETERS
A
.I parameter
is an entity that stores values.
It can be a
.IR name ,
a number, or one of the special characters listed below under
.BR "Special Parameters" .
A
.I variable
is a parameter denoted by a
.IR name .
A variable has a \fIvalue\fP and zero or more \fIattributes\fP.
Attributes are assigned using the
.B declare
builtin command (see
.B declare
below in
.SM
.BR "SHELL BUILTIN COMMANDS" ).
.PP
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
.B unset
builtin command (see
.SM
.B SHELL BUILTIN COMMANDS
below).
.PP
A
.I variable
may be assigned to by a statement of the form
.RS
.PP
\fIname\fP=[\fIvalue\fP]
.RE
.PP
If
.I value
is not given, the variable is assigned the null string.  All
.I values
undergo tilde expansion, parameter and variable expansion,
command substitution, arithmetic expansion, and quote
removal (see
.SM
.B EXPANSION
below).  If the variable has its
.B integer
attribute set, then
.I value
is evaluated as an arithmetic expression even if the $((...)) expansion is
not used (see
.B "Arithmetic Expansion"
below).
Word splitting and pathname expansion are not performed.
Assignment statements may also appear as arguments to the
.BR alias ,
.BR declare ,
.BR typeset ,
.BR export ,
.BR readonly ,
and
.B local
builtin commands (\fIdeclaration\fP commands).
When in \fIposix mode\fP, these builtins may appear in a command after
one or more instances of the \fBcommand\fP builtin and retain these
assignment statement properties.
.PP
In the context where an assignment statement is assigning a value
to a shell variable or array index, the += operator can be used to
append to or add to the variable's previous value.
This includes arguments to builtin commands such as \fBdeclare\fP that
accept assignment statements (\fIdeclaration\fP commands).
When += is applied to a variable for which the \fBinteger\fP attribute has been
set, \fIvalue\fP is evaluated as an arithmetic expression and added to the
variable's current value, which is also evaluated.
When += is applied to an array variable using compound assignment (see
.B Arrays
below), the
variable's value is not unset (as it is when using =), and new values are
appended to the array beginning at one greater than the array's maximum index
(for indexed arrays) or added as additional key\-value pairs in an
associative array.
When applied to a string-valued variable, \fIvalue\fP is expanded and
appended to the variable's value.
.PP
A variable can be assigned the \fInameref\fP attribute using the
\fB\-n\fP option to the \fBdeclare\fP or \fBlocal\fP builtin commands
(see the descriptions of \fBdeclare\fP and \fBlocal\fP below)
to create a \fInameref\fP, 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 \fInameref\fP
attribute itself), the
operation is actually performed on the variable specified by the nameref
variable'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
.sp .5
.RS
.if t \f(CWdeclare -n ref=$1\fP
.if n declare -n ref=$1
.RE
.sp .5
inside the function creates a nameref variable \fBref\fP whose value is
the variable name passed as the first argument.
References and assignments to \fBref\fP, and changes to its attributes,
are treated as references, assignments, and attribute modifications
to the variable whose name was passed as \fB$1\fP.
If the control variable in a \fBfor\fP loop has the nameref attribute,
the list of words can be a list of shell variables, and a name reference
will be established for each word in the list, in turn, when the loop is
executed.
Array variables cannot be given the \fBnameref\fP attribute.
However, nameref variables can reference array variables and subscripted
array variables.
Namerefs can be unset using the \fB\-n\fP option to the \fBunset\fP builtin.
Otherwise, if \fBunset\fP is executed with the name of a nameref variable
as an argument, the variable referenced by the nameref variable will be unset.
.SS Positional Parameters
A
.I positional parameter
is a parameter denoted by one or more
digits, other than the single digit 0.  Positional parameters are
assigned from the shell's arguments when it is invoked,
and may be reassigned using the
.B set
builtin command.  Positional parameters may not be assigned to
with assignment statements.  The positional parameters are
temporarily replaced when a shell function is executed (see
.SM
.B FUNCTIONS
below).
.PP
When a positional parameter consisting of more than a single
digit is expanded, it must be enclosed in braces (see
.SM
.B EXPANSION
below).
.SS Special Parameters
The shell treats several parameters specially.  These parameters may
only be referenced; assignment to them is not allowed.
.PD 0
.TP
.B *
Expands to the positional parameters, starting from one.
When the expansion is not within double quotes, each positional parameter
expands to a separate word.
In contexts where it is performed, those words
are subject to further word splitting and pathname expansion.
When the expansion occurs within double quotes, it expands to a single word
with the value of each parameter separated by the first character of the
.SM
.B IFS
special variable.  That is, "\fB$*\fP" is equivalent
to "\fB$1\fP\fIc\fP\fB$2\fP\fIc\fP\fB...\fP", where
.I c
is the first character of the value of the
.SM
.B IFS
variable.  If
.SM
.B IFS
is unset, the parameters are separated by spaces.
If
.SM
.B IFS
is null, the parameters are joined without intervening separators.
.TP
.B @
Expands to the positional parameters, starting from one.
In contexts where word splitting is performed, this expands each
positional parameter to a separate word; if not within double
quotes, these words are subject to word splitting.
In contexts where word splitting is not performed,
this expands to a single word
with each positional parameter separated by a space.
When the
expansion occurs within double quotes, each parameter expands to a
separate word.  That is, "\fB$@\fP" is equivalent to
"\fB$1\fP" "\fB$2\fP" ...
If the double-quoted expansion occurs within a word, the expansion of
the first parameter is joined with the beginning part of the original
word, and the expansion of the last parameter is joined with the last
part of the original word.
When there are no positional parameters, "\fB$@\fP" and
.B $@
expand to nothing (i.e., they are removed).
.TP
.B #
Expands to the number of positional parameters in decimal.
.TP
.B ?
Expands to the exit status of the most recently executed foreground
pipeline.
.TP
.B \-
Expands to the current option flags as specified upon invocation,
by the
.B set
builtin command, or those set by the shell itself
(such as the
.B \-i
option).
.TP
.B $
Expands to the process ID of the shell. In a subshell, it
expands to the process ID of the current shell, not the
subshell.
.TP
.B !
Expands to the process ID of the job most recently placed into the
background, whether executed as an asynchronous command or using
the \fBbg\fP builtin (see
.SM
.B "JOB CONTROL"
below).
.TP
.B 0
Expands to the name of the shell or shell script.  This is set at
shell initialization.  If
.B bash
is invoked with a file of commands,
.B $0
is set to the name of that file.  If
.B bash
is started with the
.B \-c
option, then
.B $0
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
.BR bash ,
as given by argument zero.
.PD
.SS Shell Variables
The following variables are set by the shell:
.PP
.PD 0
.TP
.B _
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
currently being checked.
.TP
.B BASH
Expands to the full filename used to invoke this instance of
.BR bash .
.TP
.B BASHOPTS
A colon-separated list of enabled shell options.  Each word in
the list is a valid argument for the
.B \-s
option to the
.B shopt
builtin command (see
.SM
.B "SHELL BUILTIN COMMANDS"
below).  The options appearing in
.SM
.B BASHOPTS
are those reported as
.I on
by \fBshopt\fP.
If this variable is in the environment when
.B bash
starts up, each shell option in the list will be enabled before
reading any startup files.
This variable is read-only.
.TP
.B BASHPID
Expands to the process ID of the current \fBbash\fP process.
This differs from \fB$$\fP under certain circumstances, such as subshells
that do not require \fBbash\fP to be re-initialized.
Assignments to
.SM
.B BASHPID
have no effect.
If
.B BASHPID
is unset, it loses its special properties, even if it is
subsequently reset.
.TP
.B BASH_ALIASES
An associative array variable whose members correspond to the internal
list of aliases as maintained by the \fBalias\fP builtin.
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
.B BASH_ALIASES
is unset, it loses its special properties, even if it is
subsequently reset.
.TP
.B BASH_ARGC
An array variable whose values are the number of parameters in each
frame of the current \fBbash\fP execution call stack.
The number of
parameters to the current subroutine (shell function or script executed
with \fB.\fP or \fBsource\fP) is at the top of the stack.
When a subroutine is executed, the number of parameters passed is pushed onto
.SM
.BR BASH_ARGC .
The shell sets
.SM
.B BASH_ARGC
only when in extended debugging mode (see the description of the
.B extdebug
option to the
.B shopt
builtin below).
Setting \fBextdebug\fP after the shell has started to execute a script,
or referencing this variable when \fBextdebug\fP is not set,
may result in inconsistent values.
.TP
.B BASH_ARGV
An array variable containing all of the parameters in the current \fBbash\fP
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
.SM
.BR BASH_ARGV .
The shell sets
.SM
.B BASH_ARGV
only when in extended debugging mode
(see the description of the
.B extdebug
option to the
.B shopt
builtin below).
Setting \fBextdebug\fP after the shell has started to execute a script,
or referencing this variable when \fBextdebug\fP is not set,
may result in inconsistent values.
.TP
.B BASH_ARGV0
When referenced, this variable expands to the name of the shell or shell
script (identical to
.BR $0 ;
see the description of special parameter 0 above).
Assignment to
.B BASH_ARGV0
causes the value assigned to also be assigned to \fB$0\fP.
If
.B BASH_ARGV0
is unset, it loses its special properties, even if it is
subsequently reset.
.TP
.B BASH_CMDS
An associative array variable whose members correspond to the internal
hash table of commands as maintained by the \fBhash\fP builtin.
Elements added to this array appear in the hash table; however,
unsetting array elements currently does not cause command names to be removed
from the hash table.
If
.B BASH_CMDS
is unset, it loses its special properties, even if it is
subsequently reset.
.TP
.B BASH_COMMAND
The command currently being executed or about to be executed, unless the
shell is executing a command as the result of a trap,
in which case it is the command executing at the time of the trap.
If
.B BASH_COMMAND
is unset, it loses its special properties, even if it is
subsequently reset.
.TP
.B BASH_EXECUTION_STRING
The command argument to the \fB\-c\fP invocation option.
.TP
.B BASH_LINENO
An array variable whose members are the line numbers in source files
where each corresponding member of
.SM
.B FUNCNAME
was invoked.
\fB${BASH_LINENO[\fP\fI$i\fP\fB]}\fP is the line number in the source
file (\fB${BASH_SOURCE[\fP\fI$i+1\fP\fB]}\fP) where
\fB${FUNCNAME[\fP\fI$i\fP\fB]}\fP was called
(or \fB${BASH_LINENO[\fP\fI$i-1\fP\fB]}\fP if referenced within another
shell function).
Use
.SM
.B LINENO
to obtain the current line number.
.TP
.B BASH_LOADABLES_PATH
A colon-separated list of directories in which the shell looks for
dynamically loadable builtins specified by the
.B enable
command.
.TP
.B BASH_REMATCH
An array variable whose members are assigned by the \fB=~\fP binary
operator to the \fB[[\fP conditional command.
The element with index 0 is the portion of the string
matching the entire regular expression.
The element with index \fIn\fP is the portion of the
string matching the \fIn\fPth parenthesized subexpression.
.TP
.B BASH_SOURCE
An array variable whose members are the source filenames
where the corresponding shell function names in the
.SM
.B FUNCNAME
array variable are defined.
The shell function
\fB${FUNCNAME[\fP\fI$i\fP\fB]}\fP is defined in the file
\fB${BASH_SOURCE[\fP\fI$i\fP\fB]}\fP and called from
\fB${BASH_SOURCE[\fP\fI$i+1\fP\fB]}\fP.
.TP
.B BASH_SUBSHELL
Incremented by one within each subshell or subshell environment when
the shell begins executing in that environment.
The initial value is 0.
If
.B BASH_SUBSHELL
is unset, it loses its special properties, even if it is
subsequently reset.
.TP
.B BASH_VERSINFO
A readonly array variable whose members hold version information for
this instance of
.BR bash .
The values assigned to the array members are as follows:
.sp .5
.RS
.TP 24
.B BASH_VERSINFO[\fR0\fP]
The major version number (the \fIrelease\fP).
.TP
.B BASH_VERSINFO[\fR1\fP]
The minor version number (the \fIversion\fP).
.TP
.B BASH_VERSINFO[\fR2\fP]
The patch level.
.TP
.B BASH_VERSINFO[\fR3\fP]
The build version.
.TP
.B BASH_VERSINFO[\fR4\fP]
The release status (e.g., \fIbeta1\fP).
.TP
.B BASH_VERSINFO[\fR5\fP]
The value of
.SM
.BR MACHTYPE .
.RE
.TP
.B BASH_VERSION
Expands to a string describing the version of this instance of
.BR bash .
.TP
.B COMP_CWORD
An index into \fB${COMP_WORDS}\fP of the word containing the current
cursor position.
This variable is available only in shell functions invoked by the
programmable completion facilities (see \fBProgrammable Completion\fP
below).
.TP
.B COMP_KEY
The key (or final key of a key sequence) used to invoke the current
completion function.
.TP
.B COMP_LINE
The current command line.
This variable is available only in shell functions and external
commands invoked by the
programmable completion facilities (see \fBProgrammable Completion\fP
below).
.TP
.B COMP_POINT
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 \fB${#COMP_LINE}\fP.
This variable is available only in shell functions and external
commands invoked by the
programmable completion facilities (see \fBProgrammable Completion\fP
below).
.TP
.B COMP_TYPE
Set to an integer value corresponding to the type of completion attempted
that caused a completion function to be called:
\fITAB\fP, for normal completion,
\fI?\fP, for listing completions after successive tabs,
\fI!\fP, for listing alternatives on partial word completion,
\fI@\fP, to list completions if the word is not unmodified,
or
\fI%\fP, for menu completion.
This variable is available only in shell functions and external
commands invoked by the
programmable completion facilities (see \fBProgrammable Completion\fP
below).
.TP
.B COMP_WORDBREAKS
The set of characters that the \fBreadline\fP library treats as word
separators when performing word completion.
If
.SM
.B COMP_WORDBREAKS
is unset, it loses its special properties, even if it is
subsequently reset.
.TP
.B COMP_WORDS
An array variable (see \fBArrays\fP below) consisting of the individual
words in the current command line.
The line is split into words as \fBreadline\fP would split it, using
.SM
.B COMP_WORDBREAKS
as described above.
This variable is available only in shell functions invoked by the
programmable completion facilities (see \fBProgrammable Completion\fP
below).
.TP
.B COPROC
An array variable (see \fBArrays\fP below) created to hold the file descriptors
for output from and input to an unnamed coprocess (see \fBCoprocesses\fP
above).
.TP
.B DIRSTACK
An array variable (see
.B Arrays
below) containing the current contents of the directory stack.
Directories appear in the stack in the order they are displayed by the
.B dirs
builtin.
Assigning to members of this array variable may be used to modify
directories already in the stack, but the
.B pushd
and
.B popd
builtins must be used to add and remove directories.
Assignment to this variable will not change the current directory.
If
.SM
.B DIRSTACK
is unset, it loses its special properties, even if it is
subsequently reset.
.TP
.B EPOCHREALTIME
Each time this parameter is referenced, it expands to the number of seconds
since the Unix Epoch (see \fItime\fP\fR(3)\fP) as a floating point value
with micro-second granularity.
Assignments to
.SM
.B EPOCHREALTIME
are ignored.
If
.SM
.B EPOCHREALTIME
is unset, it loses its special properties, even if it is
subsequently reset.
.TP
.B EPOCHSECONDS
Each time this parameter is referenced, it expands to the number of seconds
since the Unix Epoch (see \fItime\fP\fR(3)\fP).
Assignments to
.SM
.B EPOCHSECONDS
are ignored.
If
.SM
.B EPOCHSECONDS
is unset, it loses its special properties, even if it is
subsequently reset.
.TP
.B EUID
Expands to the effective user ID of the current user, initialized at
shell startup.  This variable is readonly.
.TP
.B FUNCNAME
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
.if t \f(CW"main"\fP.
.if n "main".
This variable exists only when a shell function is executing.
Assignments to
.SM
.B FUNCNAME
have no effect.
If
.SM
.B FUNCNAME
is unset, it loses its special properties, even if it is
subsequently reset.
.if t .sp 0.5
.if n .sp 1
This variable can be used with \fBBASH_LINENO\fP and \fBBASH_SOURCE\fP.
Each element of \fBFUNCNAME\fP has corresponding elements in
\fBBASH_LINENO\fP and \fBBASH_SOURCE\fP to describe the call stack.
For instance, \fB${FUNCNAME[\fP\fI$i\fP\fB]}\fP was called from the file
\fB${BASH_SOURCE[\fP\fI$i+1\fP\fB]}\fP at line number
\fB${BASH_LINENO[\fP\fI$i\fP\fB]}\fP.
The \fBcaller\fP builtin displays the current call stack using this
information.
.TP
.B GROUPS
An array variable containing the list of groups of which the current
user is a member.
Assignments to
.SM
.B GROUPS
have no effect.
If
.SM
.B GROUPS
is unset, it loses its special properties, even if it is
subsequently reset.
.TP
.B HISTCMD
The history number, or index in the history list, of the current
command.
Assignments to
.SM
.B HISTCMD
are ignored.
If
.SM
.B HISTCMD
is unset, it loses its special properties, even if it is
subsequently reset.
.TP
.B HOSTNAME
Automatically set to the name of the current host.
.TP
.B HOSTTYPE
Automatically set to a string that uniquely
describes the type of machine on which
.B bash
is executing.
The default is system-dependent.
.TP
.B LINENO
Each time this parameter is referenced, the shell substitutes
a decimal number representing the current sequential line number
(starting with 1) within a script or function.  When not in a
script or function, the value substituted is not guaranteed to
be meaningful.
If
.SM
.B LINENO
is unset, it loses its special properties, even if it is
subsequently reset.
.TP
.B MACHTYPE
Automatically set to a string that fully describes the system
type on which
.B bash
is executing, in the standard GNU \fIcpu-company-system\fP format.
The default is system-dependent.
.TP
.B MAPFILE
An array variable (see \fBArrays\fP below) created to hold the text
read by the \fBmapfile\fP builtin when no variable name is supplied.
.TP
.B OLDPWD
The previous working directory as set by the
.B cd
command.
.TP
.B OPTARG
The value of the last option argument processed by the
.B getopts
builtin command (see
.SM
.B SHELL BUILTIN COMMANDS
below).
.TP
.B OPTIND
The index of the next argument to be processed by the
.B getopts
builtin command (see
.SM
.B SHELL BUILTIN COMMANDS
below).
.TP
.B OSTYPE
Automatically set to a string that
describes the operating system on which
.B bash
is executing.
The default is system-dependent.
.TP
.B PIPESTATUS
An array variable (see
.B Arrays
below) containing a list of exit status values from the processes
in the most-recently-executed foreground pipeline (which may
contain only a single command).
.TP
.B PPID
The process ID of the shell's parent.  This variable is readonly.
.TP
.B PWD
The current working directory as set by the
.B cd
command.
.TP
.B RANDOM
Each time this parameter is referenced, it expands to a random integer
between 0 and 32767.
Assigning
a value to
.SM
.BR RANDOM
initializes (seeds) the sequence of random numbers.
If
.SM
.B RANDOM
is unset, it loses its special properties, even if it is
subsequently reset.
.TP
.B READLINE_ARGUMENT
Any numeric argument given to a readline command that was defined using
.if t \f(CWbind -x\fP
.if n "bind -x"
(see
.SM
.B "SHELL BUILTIN COMMANDS"
below)
when it was invoked.
.TP
.B READLINE_LINE
The contents of the
.B readline
line buffer, for use with
.if t \f(CWbind -x\fP
.if n "bind -x"
(see
.SM
.B "SHELL BUILTIN COMMANDS"
below).
.TP
.B READLINE_MARK
The position of the mark (saved insertion point) in the
.B readline
line buffer, for use with
.if t \f(CWbind -x\fP
.if n "bind -x"
(see
.SM
.B "SHELL BUILTIN COMMANDS"
below).
The characters between the insertion point and the mark are often
called the \fIregion\fP.
.TP
.B READLINE_POINT
The position of the insertion point in the
.B readline
line buffer, for use with
.if t \f(CWbind -x\fP
.if n "bind -x"
(see
.SM
.B "SHELL BUILTIN COMMANDS"
below).
.TP
.B REPLY
Set to the line of input read by the
.B read
builtin command when no arguments are supplied.
.TP
.B SECONDS
Each time this parameter is
referenced, it expands to the number of seconds since shell invocation.
If a value is assigned to
.SM
.BR SECONDS ,
the value returned upon subsequent
references is
the number of seconds since the assignment plus the value assigned.
The number of seconds at shell invocation and the current time are always
determined by querying the system clock.
If
.SM
.B SECONDS
is unset, it loses its special properties, even if it is
subsequently reset.
.TP
.B SHELLOPTS
A colon-separated list of enabled shell options.  Each word in
the list is a valid argument for the
.B \-o
option to the
.B set
builtin command (see
.SM
.B "SHELL BUILTIN COMMANDS"
below).  The options appearing in
.SM
.B SHELLOPTS
are those reported as
.I on
by \fBset \-o\fP.
If this variable is in the environment when
.B bash
starts up, each shell option in the list will be enabled before
reading any startup files.
This variable is read-only.
.TP
.B SHLVL
Incremented by one each time an instance of
.B bash
is started.
.TP
.B SRANDOM
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 \f(CW/dev/urandom\fP or \fIarc4random\fP, 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
.SM
.B SRANDOM
is unset, it loses its special properties,
even if it is subsequently reset.
.TP
.B UID
Expands to the user ID of the current user, initialized at shell startup.
This variable is readonly.
.PD
.PP
The following variables are used by the shell.  In some cases,
.B bash
assigns a default value to a variable; these cases are noted
below.
.PP
.PD 0
.TP
.B BASH_COMPAT
The value is used to set the shell's compatibility level.
See
.SM
.B "SHELL COMPATIBILITY MODE"
below 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 \fBBASH_COMPAT\fP is unset or set to the empty string, the compatibility
level is set to the default for the current version.
If \fBBASH_COMPAT\fP 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 under
.SM
.BR "SHELL COMPATIBILITY MODE" .
For example, 4.2 and 42 are valid values that correspond
to the \fBcompat42\fP \fBshopt\fP option
and set the compatibility level to 42.
The current version is also a valid value.
.TP
.B BASH_ENV
If this parameter is set when \fBbash\fP is executing a shell script,
its value is interpreted as a filename containing commands to
initialize the shell, as in
.IR ~/.bashrc .
The value of
.SM
.B BASH_ENV
is subjected to parameter expansion, command substitution, and arithmetic
expansion before being interpreted as a filename.
.SM
.B PATH
is not used to search for the resultant filename.
.TP
.B BASH_XTRACEFD
If set to an integer corresponding to a valid file descriptor, \fBbash\fP
will write the trace output generated when
.if t \f(CWset -x\fP
.if n \fIset -x\fP
is enabled to that file descriptor.
The file descriptor is closed when
.SM
.B BASH_XTRACEFD
is unset or assigned a new value.
Unsetting
.SM
.B BASH_XTRACEFD
or assigning it the empty string causes the
trace output to be sent to the standard error.
Note that setting
.SM
.B BASH_XTRACEFD
to 2 (the standard error file
descriptor) and then unsetting it will result in the standard error
being closed.
.TP
.B CDPATH
The search path for the
.B cd
command.
This is a colon-separated list of directories in which the shell looks
for destination directories specified by the
.B cd
command.
A sample value is
.if t \f(CW".:~:/usr"\fP.
.if n ".:~:/usr".
.TP
.B CHILD_MAX
Set the number of exited child status values for the shell to remember.
Bash will not allow this value to be decreased below a POSIX-mandated
minimum, and there is a maximum value (currently 8192) that this may
not exceed.
The minimum value is system-dependent.
.TP
.B COLUMNS
Used by the \fBselect\fP compound command to determine the terminal width
when printing selection lists.
Automatically set if the
.B checkwinsize
option is enabled or in an interactive shell upon receipt of a
.SM
.BR SIGWINCH .
.TP
.B COMPREPLY
An array variable from which \fBbash\fP reads the possible completions
generated by a shell function invoked by the programmable completion
facility (see \fBProgrammable Completion\fP below).
Each array element contains one possible completion.
.TP
.B EMACS
If \fBbash\fP finds this variable in the environment when the shell starts
with value
.if t \f(CWt\fP,
.if n "t",
it assumes that the shell is running in an Emacs shell buffer and disables
line editing.
.TP
.B ENV
Expanded and executed similarly to
.SM
.B BASH_ENV
(see \fBINVOCATION\fP above)
when an interactive shell is invoked in \fIposix mode\fP.
.TP
.B EXECIGNORE
A colon-separated list of shell patterns (see \fBPattern Matching\fP)
defining the list of filenames to be ignored by command search using
\fBPATH\fP.
Files whose full pathnames match one of these patterns are not considered
executable files for the purposes of completion and command execution
via \fBPATH\fP lookup.
This does not affect the behavior of the \fB[\fP, \fBtest\fP, and \fB[[\fP
commands.
Full pathnames in the command hash table are not subject to \fBEXECIGNORE\fP.
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 \fBextglob\fP shell
option.
.TP
.B FCEDIT
The default editor for the
.B fc
builtin command.
.TP
.B FIGNORE
A colon-separated list of suffixes to ignore when performing
filename completion (see
.SM
.B READLINE
below).
A filename whose suffix matches one of the entries in
.SM
.B FIGNORE
is excluded from the list of matched filenames.
A sample value is
.if t \f(CW".o:~"\fP.
.if n ".o:~".
.TP
.B FUNCNEST
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.
.TP
.B GLOBIGNORE
A colon-separated list of patterns defining the set of file names to
be ignored by pathname expansion.
If a file name matched by a pathname expansion pattern also matches one
of the patterns in
.SM
.BR GLOBIGNORE ,
it is removed from the list of matches.
.TP
.B HISTCONTROL
A colon-separated list of values controlling how commands are saved on
the history list.
If the list of values includes
.IR ignorespace ,
lines which begin with a
.B space
character are not saved in the history list.
A value of
.I ignoredups
causes lines matching the previous history entry to not be saved.
A value of
.I ignoreboth
is shorthand for \fIignorespace\fP and \fIignoredups\fP.
A value of
.I erasedups
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
.SM
.B HISTCONTROL
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
.SM
.BR HISTIGNORE .
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
.SM
.BR HISTCONTROL .
.TP
.B HISTFILE
The name of the file in which command history is saved (see
.SM
.B HISTORY
below).  The default value is \fI~/.bash_history\fP.  If unset, the
command history is not saved when a shell exits.
.TP
.B HISTFILESIZE
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 \fBHISTSIZE\fP
after reading any startup files.
.TP
.B HISTIGNORE
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
`\fB*\fP' is appended).  Each pattern is tested against the line
after the checks specified by
.SM
.B HISTCONTROL
are applied.
In addition to the normal shell pattern matching characters, `\fB&\fP'
matches the previous history line.  `\fB&\fP' 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
.SM
.BR HISTIGNORE .
The pattern matching honors the setting of the \fBextglob\fP shell
option.
.TP
.B HISTSIZE
The number of commands to remember in the command history (see
.SM
.B HISTORY
below).
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.
.TP
.B HISTTIMEFORMAT
If this variable is set and not null, its value is used as a format string
for \fIstrftime\fP(3) to print the time stamp associated with each history
entry displayed by the \fBhistory\fP 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.
.TP
.B HOME
The home directory of the current user; the default argument for the
\fBcd\fP builtin command.
The value of this variable is also used when performing tilde expansion.
.TP
.B HOSTFILE
Contains the name of a file in the same format as
.FN /etc/hosts
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,
.B bash
adds the contents of the new file to the existing list.
If
.SM
.B HOSTFILE
is set, but has no value, or does not name a readable file,
\fBbash\fP attempts to read
.FN /etc/hosts
to obtain the list of possible hostname completions.
When
.SM
.B HOSTFILE
is unset, the hostname list is cleared.
.TP
.B IFS
The
.I Internal Field Separator
that is used
for word splitting after expansion and to
split lines into words with the
.B read
builtin command.  The default value is
``<space><tab><newline>''.
.TP
.B IGNOREEOF
Controls the
action of an interactive shell on receipt of an
.SM
.B EOF
character as the sole input.  If set, the value is the number of
consecutive
.SM
.B EOF
characters which must be
typed as the first characters on an input line before
.B bash
exits.  If the variable exists but does not have a numeric value, or
has no value, the default value is 10.  If it does not exist,
.SM
.B EOF
signifies the end of input to the shell.
.TP
.B INPUTRC
The filename for the
.B readline
startup file, overriding the default of
.FN ~/.inputrc
(see
.SM
.B READLINE
below).
.TP
.B INSIDE_EMACS
If this variable appears in the environment when the shell starts,
\fBbash\fP assumes that it is running inside an Emacs shell buffer
and may disable line editing, depending on the value of \fBTERM\fP.
.TP
.B LANG
Used to determine the locale category for any category not specifically
selected with a variable starting with \fBLC_\fP.
.TP
.B LC_ALL
This variable overrides the value of
.SM
.B LANG
and any other
\fBLC_\fP variable specifying a locale category.
.TP
.B LC_COLLATE
This variable determines the collation order used when sorting the
results of pathname expansion, and determines the behavior of range
expressions, equivalence classes, and collating sequences within
pathname expansion and pattern matching.
.TP
.B LC_CTYPE
This variable determines the interpretation of characters and the
behavior of character classes within pathname expansion and pattern
matching.
.TP
.B LC_MESSAGES
This variable determines the locale used to translate double-quoted
strings preceded by a \fB$\fP.
.TP
.B LC_NUMERIC
This variable determines the locale category used for number formatting.
.TP
.B LC_TIME
This variable determines the locale category used for data and time
formatting.
.TP
.B LINES
Used by the \fBselect\fP compound command to determine the column length
for printing selection lists.
Automatically set if the
.B checkwinsize
option is enabled or in an interactive shell upon receipt of a
.SM
.BR SIGWINCH .
.TP
.B MAIL
If this parameter is set to a file or directory name and the
.SM
.B MAILPATH
variable is not set,
.B bash
informs the user of the arrival of mail in the specified file or
Maildir-format directory.
.TP
.B MAILCHECK
Specifies how
often (in seconds)
.B bash
checks for mail.  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.
.TP
.B MAILPATH
A colon-separated list of filenames to be checked for mail.
The message to be printed when mail arrives in a particular file
may be specified by separating the filename from the message with a `?'.
When used in the text of the message, \fB$_\fP expands to the name of
the current mailfile.
Example:
.RS
.PP
\fBMAILPATH\fP=\(aq/var/mail/bfox?"You have mail":~/shell\-mail?"$_ has mail!"\(aq
.PP
.B Bash
can be configured to supply
a default value for this variable (there is no value by default),
but the location of the user
mail files that it uses is system dependent (e.g., /var/mail/\fB$USER\fP).
.RE
.TP
.B OPTERR
If set to the value 1,
.B bash
displays error messages generated by the
.B getopts
builtin command (see
.SM
.B SHELL BUILTIN COMMANDS
below).
.SM
.B OPTERR
is initialized to 1 each time the shell is invoked or a shell
script is executed.
.TP
.B PATH
The search path for commands.  It
is a colon-separated list of directories in which
the shell looks for commands (see
.SM
.B COMMAND EXECUTION
below).
A zero-length (null) directory name in the value of
.SM
.B PATH
indicates the current directory.
A null directory name may appear as two adjacent colons, or as an initial
or trailing colon.
The default path is system-dependent,
and is set by the administrator who installs
.BR bash .
A common value is
.na
.if t \f(CW/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin\fP.
.if n ``/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin''.
.ad
.TP
.B POSIXLY_CORRECT
If this variable is in the environment when \fBbash\fP starts, the shell
enters \fIposix mode\fP before reading the startup files, as if the
.B \-\-posix
invocation option had been supplied.  If it is set while the shell is
running, \fBbash\fP enables \fIposix mode\fP, as if the command
.if t \f(CWset -o posix\fP
.if n \fIset -o posix\fP
had been executed.
When the shell enters \fIposix mode\fP, it sets this variable if it was
not already set.
.TP
.B PROMPT_COMMAND
If this variable is set, and is an array,
the value of each set element is executed as a command
prior to issuing each primary prompt.
If this is set but not an array variable, 
its value is used as a command to execute instead.
.TP
.B PROMPT_DIRTRIM
If set to a number greater than zero, the value is used as the number of
trailing directory components to retain when expanding the \fB\ew\fP and
\fB\eW\fP prompt string escapes (see
.SM
.B PROMPTING
below).  Characters removed are replaced with an ellipsis.
.TP
.B PS0
The value of this parameter is expanded (see
.SM
.B PROMPTING
below) and displayed by interactive shells after reading a command
and before the command is executed.
.TP
.B PS1
The value of this parameter is expanded (see
.SM
.B PROMPTING
below) and used as the primary prompt string.  The default value is
``\fB\es\-\ev\e$ \fP''.
.TP
.B PS2
The value of this parameter is expanded as with
.SM
.B PS1
and used as the secondary prompt string.  The default is
``\fB> \fP''.
.TP
.B PS3
The value of this parameter is used as the prompt for the
.B select
command (see
.SM
.B SHELL GRAMMAR
above).
.TP
.B PS4
The value of this parameter is expanded as with
.SM
.B PS1
and the value is printed before each command
.B bash
displays during an execution trace.  The first character of
the expanded value of
.SM
.B PS4
is replicated multiple times, as necessary, to indicate multiple
levels of indirection.  The default is ``\fB+ \fP''.
.TP
.B SHELL
This variable expands to the full pathname to the shell.
If it is not set when the shell starts,
.B bash
assigns to it the full pathname of the current user's login shell.
.TP
.B TIMEFORMAT
The value of this parameter is used as a format string specifying
how the timing information for pipelines prefixed with the
.B time
reserved word should be displayed.
The \fB%\fP 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.
.sp .5
.RS
.PD 0
.TP 10
.B %%
A literal \fB%\fP.
.TP
.B %[\fIp\fP][l]R
The elapsed time in seconds.
.TP
.B %[\fIp\fP][l]U
The number of CPU seconds spent in user mode.
.TP
.B %[\fIp\fP][l]S
The number of CPU seconds spent in system mode.
.TP
.B %P
The CPU percentage, computed as (%U + %S) / %R.
.PD
.RE
.IP
The optional \fIp\fP is a digit specifying the \fIprecision\fP,
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 \fIp\fP greater than 3 are changed to 3.
If \fIp\fP is not specified, the value 3 is used.
.IP
The optional \fBl\fP specifies a longer format, including
minutes, of the form \fIMM\fPm\fISS\fP.\fIFF\fPs.
The value of \fIp\fP determines whether or not the fraction is
included.
.IP
If this variable is not set, \fBbash\fP acts as if it had the
value \fB$\(aq\enreal\et%3lR\enuser\et%3lU\ensys\et%3lS\(aq\fP.
If the value is null, no timing information is displayed.
A trailing newline is added when the format string is displayed.
.PD 0
.TP
.B TMOUT
If set to a value greater than zero,
.SM
.B TMOUT
is treated as the
default timeout for the \fBread\fP builtin.
The \fBselect\fP command terminates if input does not arrive
after
.SM
.B TMOUT
seconds when input is coming from a terminal.
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.
.B Bash
terminates after waiting for that number of seconds if a complete
line of input does not arrive.
.TP
.B TMPDIR
If set, \fBbash\fP uses its value as the name of a directory in which
\fBbash\fP creates temporary files for the shell's use.
.TP
.B auto_resume
This variable controls how the shell interacts with the user and
job control.  If this variable is set, single word simple
commands without redirections are treated as candidates for resumption
of an existing stopped job.  There is no ambiguity allowed; if there is
more than one job beginning with the string typed, the job most recently
accessed is selected.  The
.I name
of a stopped job, in this context, is the command line used to
start it.
If set to the value
.IR exact ,
the string supplied must match the name of a stopped job exactly;
if set to
.IR substring ,
the string supplied needs to match a substring of the name of a
stopped job.  The
.I substring
value provides functionality analogous to the
.B %?
job identifier (see
.SM
.B JOB CONTROL
below).  If set to any other value, the supplied string must
be a prefix of a stopped job's name; this provides functionality
analogous to the \fB%\fP\fIstring\fP job identifier.
.TP
.B histchars
The two or three characters which control history expansion
and tokenization (see
.SM
.B HISTORY EXPANSION
below).  The first character is the \fIhistory expansion\fP character,
the character which signals the start of a history
expansion, normally `\fB!\fP'.
The second character is the \fIquick substitution\fP
character, which is used as shorthand for re-running the previous
command entered, substituting one string for another in the command.
The default is `\fB^\fP'.
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, normally `\fB#\fP'.  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.
.PD
.SS Arrays
.B Bash
provides one-dimensional indexed and associative array variables.
Any variable may be used as an indexed array; the
.B declare
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) and are zero-based; associative arrays are referenced
using arbitrary strings.
Unless otherwise noted, indexed array indices must be non-negative integers.
.PP
An indexed array is created automatically if any variable is assigned to
using the syntax \fIname\fP[\fIsubscript\fP]=\fIvalue\fP.  The
.I subscript
is treated as an arithmetic expression that must evaluate to a number.
To explicitly declare an indexed array, use
.B declare \-a \fIname\fP
(see
.SM
.B SHELL BUILTIN COMMANDS
below).
.B declare \-a \fIname\fP[\fIsubscript\fP]
is also accepted; the \fIsubscript\fP is ignored.
.PP
Associative arrays are created using
.BR "declare \-A \fIname\fP" .
.PP
Attributes may be
specified for an array variable using the
.B declare
and
.B readonly
builtins.  Each attribute applies to all members of an array.
.PP
Arrays are assigned to using compound assignments of the form
\fIname\fP=\fB(\fPvalue\fI1\fP ... value\fIn\fP\fB)\fP, where each
\fIvalue\fP may be of the form [\fIsubscript\fP]=\fIstring\fP.
Indexed array assignments do not require anything but \fIstring\fP.
Each \fIvalue\fP in the list is expanded using all the shell expansions
described below under
.SM
.BR EXPANSION .
When assigning to indexed arrays, if the optional brackets and subscript
are 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.
.PP
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:
\fIname\fP=\fB( \fP\fIkey1 value1 key2 value2\fP ...\fB)\fP.
These are treated identically to
\fIname\fP=\fB(\fP [\fIkey1\fP]=\fIvalue1\fP [\fIkey2\fP]=\fIvalue2\fP ...\fB)\fP.
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.
.PP
This syntax is also accepted by the
.B declare
builtin.  Individual array elements may be assigned to using the
\fIname\fP[\fIsubscript\fP]=\fIvalue\fP syntax introduced above.
When assigning to an indexed array, if
.I name
is subscripted by a negative number, that number is
interpreted as relative to one greater than the maximum index of
\fIname\fP, so negative indices count back from the end of the
array, and an index of \-1 references the last element.
.PP
The += operator will append to an array variable when assigning
using the compound assignment syntax; see
.SM
.B PARAMETERS
above.
.PP
Any element of an array may be referenced using
${\fIname\fP[\fIsubscript\fP]}.  The braces are required to avoid
conflicts with pathname expansion.  If
\fIsubscript\fP is \fB@\fP or \fB*\fP, the word expands to
all members of \fIname\fP.  These subscripts differ only when the
word appears within double quotes.  If the word is double-quoted,
${\fIname\fP[*]} expands to a single
word with the value of each array member separated by the first
character of the
.SM
.B IFS
special variable, and ${\fIname\fP[@]} expands each element of
\fIname\fP to a separate word.  When there are no array members,
${\fIname\fP[@]} 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 \fB*\fP and \fB@\fP (see
.B Special Parameters
above).  ${#\fIname\fP[\fIsubscript\fP]} expands to the length of
${\fIname\fP[\fIsubscript\fP]}.  If \fIsubscript\fP is \fB*\fP or
\fB@\fP, the expansion is the number of elements in the array.
If the
.I subscript
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 references the last element.
.PP
Referencing an array variable without a subscript is equivalent to
referencing the array with a subscript of 0.
Any reference to a variable using a valid subscript is legal, and
.B bash
will create an array if necessary.
.PP
An array variable is considered set if a subscript has been assigned a
value.  The null string is a valid value.
.PP
It is possible to obtain the keys (indices) of an array as well as the values.
${\fB!\fP\fIname\fP[\fI@\fP]} and ${\fB!\fP\fIname\fP[\fI*\fP]}
expand to the indices assigned in array variable \fIname\fP.
The treatment when in double quotes is similar to the expansion of the
special parameters \fI@\fP and \fI*\fP within double quotes.
.PP
The
.B unset
builtin is used to destroy arrays.  \fBunset\fP \fIname\fP[\fIsubscript\fP]
destroys the array element at index \fIsubscript\fP,
for both indexed and associative arrays.
Negative subscripts to indexed arrays are interpreted as described above.
Unsetting the last element of an array variable does not unset the variable.
\fBunset\fP \fIname\fP, where \fIname\fP is an array,
removes the entire array.
\fBunset\fP \fIname\fP[\fIsubscript\fP], where
\fIsubscript\fP is \fB*\fP or \fB@\fP, behaves differently depending on
whether \fIname\fP is an indexed or associative array.
If \fIname\fP is an associative array, this unsets the element with
subscript \fB*\fP or \fB@\fP.
If \fIname\fP is an indexed array, unset removes all of the elements but
does not remove the array itself.
.PP
When using a variable name with a subscript as an argument to a command,
such as with \fBunset\fP, without using the word expansion syntax
described above, the argument is subject to pathname expansion.
If pathname expansion is not desired, the argument should be quoted.
.PP
The
.BR declare ,
.BR local ,
and
.B readonly
builtins each accept a
.B \-a
option to specify an indexed array and a
.B \-A
option to specify an associative array.
If both options are supplied,
.B \-A
takes precedence.
The
.B read
builtin accepts a
.B \-a
option to assign a list of words read from the standard input
to an array.  The
.B set
and
.B declare
builtins display array values in a way that allows them to be
reused as assignments.
.SH EXPANSION
Expansion is performed on the command line after it has been split into
words.  There are seven kinds of expansion performed:
.IR "brace expansion" ,
.IR "tilde expansion" ,
.IR "parameter and variable expansion" ,
.IR "command substitution" ,
.IR "arithmetic expansion" ,
.IR "word splitting" ,
and
.IR "pathname expansion" .
.PP
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 pathname expansion.
.PP
On systems that can support it, there is an additional expansion
available: \fIprocess substitution\fP.
This is performed at the
same time as tilde, parameter, variable, and arithmetic expansion and
command substitution.
.PP
After these expansions are performed, quote characters present in the
original word are removed unless they have been quoted themselves
(\fIquote removal\fP).
.PP
Only brace expansion, word splitting, and pathname 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
"\fB$@\fP" and "\fB${\fP\fIname\fP\fB[@]}\fP",
and, in most cases, \fB$*\fP and \fB${\fP\fIname\fP\fB[*]}\fP
as explained above (see
.SM
.BR PARAMETERS ).
.SS Brace Expansion
.I "Brace expansion"
is a mechanism by which arbitrary strings
may be generated.  This mechanism is similar to
\fIpathname expansion\fP, but the filenames generated
need not exist.  Patterns to be brace expanded take
the form of an optional
.IR preamble ,
followed by either a series of comma-separated strings or
a sequence expression between a pair of braces, followed by
an optional
.IR postscript .
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.
.PP
Brace expansions may be nested.  The results of each expanded
string are not sorted; left to right order is preserved.
For example, a\fB{\fPd,c,b\fB}\fPe expands into `ade ace abe'.
.PP
A sequence expression takes the form
\fB{\fP\fIx\fP\fB..\fP\fIy\fP\fB[..\fP\fIincr\fP\fB]}\fP,
where \fIx\fP and \fIy\fP are either integers or single letters,
and \fIincr\fP, an optional increment, is an integer.
When integers are supplied, the expression expands to each number between
\fIx\fP and \fIy\fP, inclusive.
Supplied integers may be prefixed with \fI0\fP to force each term to have the
same width.
When either \fIx\fP or \fPy\fP 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 \fIx\fP and \fIy\fP, inclusive,
using the default C locale.
Note that both \fIx\fP and \fIy\fP 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.
.PP
Brace expansion is performed before any other expansions,
and any characters special to other expansions are preserved
in the result.  It is strictly textual.
.B Bash
does not apply any syntactic interpretation to the context of the
expansion or the text between the braces.
.PP
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.
A \fB{\fP or \fB,\fP may be quoted with a backslash to prevent its
being considered part of a brace expression.
To avoid conflicts with parameter expansion, the string \fB${\fP
is not considered eligible for brace expansion, and inhibits brace
expansion until the closing \fB}\fP.
.PP
This construct is typically used as shorthand when the common
prefix of the strings to be generated is longer than in the
above example:
.RS
.PP
mkdir /usr/local/src/bash/{old,new,dist,bugs}
.RE
or
.RS
chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}
.RE
.PP
Brace expansion introduces a slight incompatibility with
historical versions of
.BR sh .
.B sh
does not treat opening or closing braces specially when they
appear as part of a word, and preserves them in the output.
.B Bash
removes braces from words as a consequence of brace
expansion.  For example, a word entered to
.B sh
as \fIfile{1,2}\fP
appears identically in the output.  The same word is
output as
.I file1 file2
after expansion by
.BR bash .
If strict compatibility with
.B sh
is desired, start
.B bash
with the
.B +B
option or disable brace expansion with the
.B +B
option to the
.B set
command (see
.SM
.B SHELL BUILTIN COMMANDS
below).
.SS Tilde Expansion
If a word begins with an unquoted tilde character (`\fB~\fP'), all of
the characters preceding the first unquoted slash (or all characters,
if there is no unquoted slash) are considered a \fItilde-prefix\fP.
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 \fIlogin name\fP.
If this login name is the null string, the tilde is replaced with the
value of the shell parameter
.SM
.BR HOME .
If
.SM
.B HOME
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.
.PP
If the tilde-prefix is a `~+', the value of the shell variable
.SM
.B PWD
replaces the tilde-prefix.
If the tilde-prefix is a `~\-', the value of the shell variable
.SM
.BR OLDPWD ,
if it is set, is substituted.
If the characters following the tilde in the tilde-prefix consist
of a number \fIN\fP, optionally prefixed
by a `+' or a `\-', the tilde-prefix is replaced with the corresponding
element from the directory stack, as it would be displayed by the
.B dirs
builtin invoked with the tilde-prefix as an argument.
If the characters following the tilde in the tilde-prefix consist of a
number without a leading `+' or `\-', `+' is assumed.
.PP
If the login name is invalid, or the tilde expansion fails, the word
is unchanged.
.PP
Each variable assignment is checked for unquoted tilde-prefixes immediately
following a
.B :
or the first
.BR = .
In these cases, tilde expansion is also performed.
Consequently, one may use filenames with tildes in assignments to
.SM
.BR PATH ,
.SM
.BR MAILPATH ,
and
.SM
.BR CDPATH ,
and the shell assigns the expanded value.
.PP
Bash also performs tilde expansion on words satisfying the conditions of
variable assignments (as described above under
.SM
.BR PARAMETERS )
when they appear as arguments to simple commands.
Bash does not do this, except for the \fIdeclaration\fP commands listed
above, when in \fIposix mode\fP.
.SS Parameter Expansion
The `\fB$\fP' 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.
.PP
When braces are used, the matching ending brace is the first `\fB}\fP'
not escaped by a backslash or within a quoted string, and not within an
embedded arithmetic expansion, command substitution, or parameter
expansion.
.PP
.PD 0
.TP
${\fIparameter\fP}
The value of \fIparameter\fP is substituted.  The braces are required
when
.I parameter
is a positional parameter with more than one digit,
or when
.I parameter
is followed by a character which is not to be
interpreted as part of its name.
The \fIparameter\fP is a shell parameter as described above
\fBPARAMETERS\fP) or an array reference (\fBArrays\fP).
.PD
.PP
If the first character of \fIparameter\fP is an exclamation point (\fB!\fP),
and \fIparameter\fP is not a \fInameref\fP,
it introduces a level of indirection.
\fBBash\fP uses the value formed by expanding the rest of
\fIparameter\fP as the new \fIparameter\fP; this is then
expanded and that value is used in the rest of the expansion, rather
than the expansion of the original \fIparameter\fP.
This is known as \fIindirect expansion\fP.
The value is subject to tilde expansion,
parameter expansion, command substitution, and arithmetic expansion.
If \fIparameter\fP is a nameref, this expands to the name of the
parameter referenced by \fIparameter\fP instead of performing the
complete indirect expansion.
The exceptions to this are the expansions of ${\fB!\fP\fIprefix\fP\fB*\fP} and
${\fB!\fP\fIname\fP[\fI@\fP]} described below.
The exclamation point must immediately follow the left brace in order to
introduce indirection.
.PP
In each of the cases below, \fIword\fP is subject to tilde expansion,
parameter expansion, command substitution, and arithmetic expansion.
.PP
When not performing substring expansion, using the forms documented below
(e.g., \fB:-\fP),
\fBbash\fP tests for a parameter that is unset or null.  Omitting the colon
results in a test only for a parameter that is unset.
.PP
.PD 0
.TP
${\fIparameter\fP\fB:\-\fP\fIword\fP}
\fBUse Default Values\fP.  If
.I parameter
is unset or null, the expansion of
.I word
is substituted.  Otherwise, the value of
.I parameter
is substituted.
.TP
${\fIparameter\fP\fB:=\fP\fIword\fP}
\fBAssign Default Values\fP.
If
.I parameter
is unset or null, the expansion of
.I word
is assigned to
.IR parameter .
The value of
.I parameter
is then substituted.  Positional parameters and special parameters may
not be assigned to in this way.
.TP
${\fIparameter\fP\fB:?\fP\fIword\fP}
\fBDisplay Error if Null or Unset\fP.
If
.I parameter
is null or unset, the expansion of \fIword\fP (or a message to that effect
if
.I word
is not present) is written to the standard error and the shell, if it
is not interactive, exits.  Otherwise, the value of \fIparameter\fP is
substituted.
.TP
${\fIparameter\fP\fB:+\fP\fIword\fP}
\fBUse Alternate Value\fP.
If
.I parameter
is null or unset, nothing is substituted, otherwise the expansion of
.I word
is substituted.
.TP
${\fIparameter\fP\fB:\fP\fIoffset\fP}
.PD 0
.TP
${\fIparameter\fP\fB:\fP\fIoffset\fP\fB:\fP\fIlength\fP}
.PD
\fBSubstring Expansion\fP.
Expands to up to \fIlength\fP characters of the value of \fIparameter\fP
starting at the character specified by \fIoffset\fP.
If \fIparameter\fP is \fB@\fP or \fB*\fP, an indexed array subscripted by
\fB@\fP or \fB*\fP, or an associative array name, the results differ as
described below.
If \fIlength\fP is omitted, expands to the substring of the value of
\fIparameter\fP starting at the character specified by \fIoffset\fP
and extending to the end of the value.
\fIlength\fP and \fIoffset\fP are arithmetic expressions (see
.SM
.B
ARITHMETIC EVALUATION
below).
.sp 1
If \fIoffset\fP evaluates to a number less than zero, the value
is used as an offset in characters
from the end of the value of \fIparameter\fP.
If \fIlength\fP evaluates to a number less than zero,
it is interpreted as an offset in characters
from the end of the value of \fIparameter\fP rather than
a number of characters, and the expansion is the characters between
\fIoffset\fP 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 \fB:-\fP expansion.
.sp 1
If \fIparameter\fP is \fB@\fP or \fB*\fP, the result is \fIlength\fP
positional parameters beginning at \fIoffset\fP.
A negative \fIoffset\fP 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 \fIlength\fP evaluates to a number less than
zero.
.sp 1
If \fIparameter\fP is an indexed array name subscripted by @ or *,
the result is the \fIlength\fP
members of the array beginning with ${\fIparameter\fP[\fIoffset\fP]}.
A negative \fIoffset\fP is taken relative to one greater than the maximum
index of the specified array.
It is an expansion error if \fIlength\fP evaluates to a number less than
zero.
.sp 1
Substring expansion applied to an associative array produces undefined
results.
.sp 1
Substring indexing is zero-based unless the positional parameters
are used, in which case the indexing starts at 1 by default.
If \fIoffset\fP is 0, and the positional parameters are used, \fB$0\fP is
prefixed to the list.
.TP
${\fB!\fP\fIprefix\fP\fB*\fP}
.PD 0
.TP
${\fB!\fP\fIprefix\fP\fB@\fP}
.PD
\fBNames matching prefix\fP.
Expands to the names of variables whose names begin with \fIprefix\fP,
separated by the first character of the
.SM
.B IFS
special variable.
When \fI@\fP is used and the expansion appears within double quotes, each
variable name expands to a separate word.
.TP
${\fB!\fP\fIname\fP[\fI@\fP]}
.PD 0
.TP
${\fB!\fP\fIname\fP[\fI*\fP]}
.PD
\fBList of array keys\fP.
If \fIname\fP is an array variable, expands to the list of array indices
(keys) assigned in \fIname\fP.
If \fIname\fP is not an array, expands to 0 if \fIname\fP is set and null
otherwise.
When \fI@\fP is used and the expansion appears within double quotes, each
key expands to a separate word.
.TP
${\fB#\fP\fIparameter\fP}
\fBParameter length\fP.
The length in characters of the value of \fIparameter\fP is substituted.
If
.I parameter
is
.B *
or
.BR @ ,
the value substituted is the number of positional parameters.
If
.I parameter
is an array name subscripted by
.B *
or
.BR @ ,
the value substituted is the number of elements in the array.
If
.I parameter
is an indexed array name subscripted by a negative number, that number is
interpreted as relative to one greater than the maximum index of
\fIparameter\fP, so negative indices count back from the end of the
array, and an index of \-1 references the last element.
.TP
${\fIparameter\fP\fB#\fP\fIword\fP}
.PD 0
.TP
${\fIparameter\fP\fB##\fP\fIword\fP}
.PD
\fBRemove matching prefix pattern\fP.
The
.I word
is expanded to produce a pattern just as in pathname
expansion, and matched against the expanded value of
.I parameter
using the rules described under
.B Pattern Matching
below.
If the pattern matches the beginning of
the value of
.IR parameter ,
then the result of the expansion is the expanded value of
.I parameter
with the shortest matching pattern (the ``\fB#\fP'' case) or the
longest matching pattern (the ``\fB##\fP'' case) deleted.
If
.I parameter
is
.B @
or
.BR * ,
the pattern removal operation is applied to each positional
parameter in turn, and the expansion is the resultant list.
If
.I parameter
is an array variable subscripted with
.B @
or
.BR * ,
the pattern removal operation is applied to each member of the
array in turn, and the expansion is the resultant list.
.TP
${\fIparameter\fP\fB%\fP\fIword\fP}
.PD 0
.TP
${\fIparameter\fP\fB%%\fP\fIword\fP}
.PD
\fBRemove matching suffix pattern\fP.
The \fIword\fP is expanded to produce a pattern just as in
pathname expansion, and matched against the expanded value of
.I parameter
using the rules described under
.B Pattern Matching
below.
If the pattern matches a trailing portion of the expanded value of
.IR parameter ,
then the result of the expansion is the expanded value of
.I parameter
with the shortest matching pattern (the ``\fB%\fP'' case) or the
longest matching pattern (the ``\fB%%\fP'' case) deleted.
If
.I parameter
is
.B @
or
.BR * ,
the pattern removal operation is applied to each positional
parameter in turn, and the expansion is the resultant list.
If
.I parameter
is an array variable subscripted with
.B @
or
.BR * ,
the pattern removal operation is applied to each member of the
array in turn, and the expansion is the resultant list.
.TP
${\fIparameter\fP\fB/\fP\fIpattern\fP\fB/\fP\fIstring\fP}
.PD 0
.TP
${\fIparameter\fP\fB//\fP\fIpattern\fP\fB/\fP\fIstring\fP}
.TP
${\fIparameter\fP\fB/#\fP\fIpattern\fP\fB/\fP\fIstring\fP}
.TP
${\fIparameter\fP\fB/%\fP\fIpattern\fP\fB/\fP\fIstring\fP}
.PD
\fBPattern substitution\fP.
The \fIpattern\fP is expanded to produce a pattern just as in
pathname expansion.
\fIParameter\fP is expanded and the longest match of \fIpattern\fP
against its value is replaced with \fIstring\fP.
\fIstring\fP undergoes tilde expansion, parameter and variable expansion,
arithmetic expansion, command and process substitution, and quote removal.
The match is performed using the rules described under
.B Pattern Matching
below.
In the first form above, only the first match is replaced.
If there are two slashes separating \fIparameter\fP and \fIpattern\fP 
(the second form above), all matches of \fIpattern\fP are
replaced with \fIstring\fP.
If \fIpattern\fP is preceded by \fB#\fP (the third form above),
it must match at the beginning of the expanded value of \fIparameter\fP.
If \fIpattern\fP is preceded by \fB%\fP (the fourth form above),
it must match at the end of the expanded value of \fIparameter\fP.
If the expansion of \fIstring\fP is null,
matches of \fIpattern\fP are deleted.
If \fIstring\fP is null,
matches of \fIpattern\fP are deleted
and the \fB/\fP following \fIpattern\fP may be omitted.
.sp 1
If the \fBpatsub_replacement\fP shell option is enabled using \fBshopt\fP,
any unquoted instances of \fB&\fP in \fIstring\fP are replaced with the
matching portion of \fIpattern\fP.
.sp 1
Quoting any part of \fIstring\fP inhibits replacement in the
expansion of the quoted portion, including replacement strings stored
in shell variables.
Backslash will escape \fB&\fP in \fIstring\fP; the backslash is removed
in order to permit a literal \fB&\fP in the replacement string.
Backslash can also be used to escape a backslash; \fB\e\e\fP results in
a literal backslash in the replacement.
Users should take care if \fIstring\fP 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 \fB&\fP after
expanding \fIstring\fP;
shell programmers should quote any occurrences of \fB&\fP
they want to be taken literally in the replacement
and ensure any instances of \fB&\fP they want to be replaced are unquoted.
.sp 1
If the
.B nocasematch
shell option is enabled, the match is performed without regard to the case
of alphabetic characters.
If
.I parameter
is
.B @
or
.BR * ,
the substitution operation is applied to each positional
parameter in turn, and the expansion is the resultant list.
If
.I parameter
is an array variable subscripted with
.B @
or
.BR * ,
the substitution operation is applied to each member of the
array in turn, and the expansion is the resultant list.
.TP
${\fIparameter\fP\fB^\fP\fIpattern\fP}
.PD 0
.TP
${\fIparameter\fP\fB^^\fP\fIpattern\fP}
.TP
${\fIparameter\fP\fB,\fP\fIpattern\fP}
.TP
${\fIparameter\fP\fB,,\fP\fIpattern\fP}
.PD
\fBCase modification\fP.
This expansion modifies the case of alphabetic characters in \fIparameter\fP.
The \fIpattern\fP is expanded to produce a pattern just as in
pathname expansion.
Each character in the expanded value of \fIparameter\fP is tested against
\fIpattern\fP, and, if it matches the pattern, its case is converted.
The pattern should not attempt to match more than one character.
The \fB^\fP operator converts lowercase letters matching \fIpattern\fP
to uppercase; the \fB,\fP operator converts matching uppercase letters
to lowercase.
The \fB^^\fP and \fB,,\fP expansions convert each matched character in the
expanded value; the \fB^\fP and \fB,\fP expansions match and convert only
the first character in the expanded value.
If \fIpattern\fP is omitted, it is treated like a \fB?\fP, which matches
every character.
If
.I parameter
is
.B @
or
.BR * ,
the case modification operation is applied to each positional
parameter in turn, and the expansion is the resultant list.
If
.I parameter
is an array variable subscripted with
.B @
or
.BR * ,
the case modification operation is applied to each member of the
array in turn, and the expansion is the resultant list.
.TP
${\fIparameter\fP\fB@\fP\fIoperator\fP}
\fBParameter transformation\fP.
The expansion is either a transformation of the value of \fIparameter\fP
or information about \fIparameter\fP itself, depending on the value of
\fIoperator\fP.  Each \fIoperator\fP is a single letter:
.sp 1
.RS
.PD 0
.TP
.B U
The expansion is a string that is the value of \fIparameter\fP with lowercase
alphabetic characters converted to uppercase.
.TP
.B u
The expansion is a string that is the value of \fIparameter\fP with the first
character converted to uppercase, if it is alphabetic.
.TP
.B L
The expansion is a string that is the value of \fIparameter\fP with uppercase
alphabetic characters converted to lowercase.
.TP
.B Q
The expansion is a string that is the value of \fIparameter\fP quoted in a
format that can be reused as input.
.TP
.B E
The expansion is a string that is the value of \fIparameter\fP with backslash
escape sequences expanded as with the \fB$\(aq...\(aq\fP quoting mechanism.
.TP
.B P
The expansion is a string that is the result of expanding the value of
\fIparameter\fP as if it were a prompt string (see \fBPROMPTING\fP below).
.TP
.B A
The expansion is a string in the form of
an assignment statement or \fBdeclare\fP command that, if
evaluated, will recreate \fIparameter\fP with its attributes and value.
.TP
.B K
Produces a possibly-quoted version of the value of \fIparameter\fP,
except that it prints the values of
indexed and associative arrays as a sequence of quoted key-value pairs
(see \fBArrays\fP above).
.TP
.B a
The expansion is a string consisting of flag values representing
\fIparameter\fP's attributes.
.TP
.B k
Like the K transformation, but expands the keys and values of
indexed and associative arrays to separate words after word splitting.
.PD
.PP
If
.I parameter
is
.B @
or
.BR * ,
the operation is applied to each positional
parameter in turn, and the expansion is the resultant list.
If
.I parameter
is an array variable subscripted with
.B @
or
.BR * ,
the operation is applied to each member of the
array in turn, and the expansion is the resultant list.
.sp 1
The result of the expansion is subject to word splitting and pathname
expansion as described below.
.RE
.SS Command Substitution
\fICommand substitution\fP allows the output of a command to replace
the command name.  There are two forms:
.RS
.PP
\fB$(\fP\fIcommand\fP\|\fB)\fP
.RE
or
.RS
\fB\`\fP\fIcommand\fP\fB\`\fP
.RE
.PP
.B Bash
performs the expansion by executing \fIcommand\fP in a subshell environment
and replacing the command substitution with the standard output of the
command, with any trailing newlines deleted.
Embedded newlines are not deleted, but they may be removed during
word splitting.
The command substitution \fB$(cat \fIfile\fP)\fR can be replaced by
the equivalent but faster \fB$(< \fIfile\fP)\fR.
.PP
When the old-style backquote form of substitution is used,
backslash retains its literal meaning except when followed by
.BR $ ,
.BR \` ,
or
.BR \e .
The first backquote not preceded by a backslash terminates the
command substitution.
When using the $(\^\fIcommand\fP\|) form, all characters between the
parentheses make up the command; none are treated specially.
.PP
Command substitutions may be nested.  To nest when using the backquoted form,
escape the inner backquotes with backslashes.
.PP
If the substitution appears within double quotes, word splitting and
pathname expansion are not performed on the results.
.SS Arithmetic Expansion
Arithmetic expansion allows the evaluation of an arithmetic expression
and the substitution of the result.  The format for arithmetic expansion is:
.RS
.PP
\fB$((\fP\fIexpression\fP\fB))\fP
.RE
.PP
The
.I expression
undergoes the same expansions
as if it were within double quotes,
but double quote characters in \fIexpression\fP 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.
.PP
The evaluation is performed according to the rules listed below under
.SM
.BR "ARITHMETIC EVALUATION" .
If
.I expression
is invalid,
.B bash
prints a message indicating failure and no substitution occurs.
.SS Process Substitution
\fIProcess substitution\fP allows a process's input or output to be
referred to using a filename.
It takes the form of
\fB<(\fP\fIlist\^\fP\fB)\fP
or
\fB>(\fP\fIlist\^\fP\fB)\fP.
The process \fIlist\fP 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 \fB>(\fP\fIlist\^\fP\fB)\fP form is used, writing to
the file will provide input for \fIlist\fP.  If the
\fB<(\fP\fIlist\^\fP\fB)\fP form is used, the file passed as an
argument should be read to obtain the output of \fIlist\fP.
Process substitution is supported on systems that support named
pipes (\fIFIFOs\fP) or the \fB/dev/fd\fP method of naming open files.
.PP
When available, process substitution is performed
simultaneously with parameter and variable expansion,
command substitution,
and arithmetic expansion.
.SS Word Splitting
The shell scans the results of
parameter expansion,
command substitution,
and
arithmetic expansion
that did not occur within double quotes for
.IR "word splitting" .
.PP
The shell treats each character of
.SM
.B IFS
as a delimiter, and splits the results of the other
expansions into words using these characters as field terminators.
If
.SM
.B IFS
is unset, or its
value is exactly
.BR <space><tab><newline> ,
the default, then
sequences of
.BR <space> ,
.BR <tab> ,
and
.B <newline>
at the beginning and end of the results of the previous
expansions are ignored, and
any sequence of
.SM
.B IFS
characters not at the beginning or end serves to delimit words.
If
.SM
.B IFS
has a value other than the default, then sequences of
the whitespace characters
.BR space ,
.BR tab ,
and
.B newline
are ignored at the beginning and end of the
word, as long as the whitespace character is in the
value of
.SM
.B IFS
(an
.SM
.B IFS
whitespace character).
Any character in
.SM
.B IFS
that is not
.SM
.B IFS
whitespace, along with any adjacent
.SM
.B IFS
whitespace characters, delimits a field.
A sequence of
.SM
.B IFS
whitespace characters is also treated as a delimiter.
If the value of
.SM
.B IFS
is null, no word splitting occurs.
.PP
Explicit null arguments (\^\f3"\^"\fP or \^\f3\(aq\^\(aq\fP\^) 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
\f(CW\-d\(aq\^\(aq\fP becomes \f(CW\-d\fP after word splitting and
null argument removal.
.PP
Note that if no expansion occurs, no splitting
is performed.
.SS Pathname Expansion
After word splitting,
unless the
.B \-f
option has been set,
.B bash
scans each word for the characters
.BR * ,
.BR ? ,
and
.BR [ .
If one of these characters appears, and is not quoted, then the word is
regarded as a
.IR pattern ,
and replaced with an alphabetically sorted list of
filenames matching the pattern
(see
.SM
.B "Pattern Matching"
below).
If no matching filenames are found,
and the shell option
.B nullglob
is not enabled, the word is left unchanged.
If the
.B nullglob
option is set, and no matches are found,
the word is removed.
If the
.B failglob
shell option is set, and no matches are found, an error message
is printed and the command is not executed.
If the shell option
.B nocaseglob
is enabled, the match is performed without regard to the case
of alphabetic characters.
When a pattern is used for pathname expansion,
the character
.B ``.''
at the start of a name or immediately following a slash
must be matched explicitly, unless the shell option
.B dotglob
is set.
In order to match the filenames
.B ``.''
and
.BR ``..'' ,
the pattern must begin with ``.'' (for example, ``.?''),
even if
.B dotglob
is set.
If the
.B globskipdots
shell option is enabled, the filenames
.B ``.''
and
.BR ``..''
are never matched, even if the pattern begins with a
.BR ``.'' .
When not matching pathnames, the
.B ``.''
character is not treated specially.
When matching a pathname, 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 under
.SM
.BR "Pattern Matching" .
See the description of
.B shopt
below under
.SM
.B SHELL BUILTIN COMMANDS
for a description of the
.BR nocaseglob ,
.BR nullglob ,
.BR globskipdots ,
.BR failglob ,
and
.B dotglob
shell options.
.PP
The
.SM
.B GLOBIGNORE
shell variable may be used to restrict the set of file names matching a
.IR pattern .
If
.SM
.B GLOBIGNORE
is set, each matching file name that also matches one of the patterns in
.SM
.B GLOBIGNORE
is removed from the list of matches.
If the \fBnocaseglob\fP option is set, the matching against the patterns in
.SM
.B GLOBIGNORE
is performed without regard to case.
The filenames
.B ``.''
and
.B ``..''
are always ignored when
.SM
.B GLOBIGNORE
is set and not null.  However, setting
.SM
.B GLOBIGNORE
to a non-null value has the effect of enabling the
.B dotglob
shell option, so all other filenames beginning with a
.B ``.''
will match.
To get the old behavior of ignoring filenames beginning with a
.BR ``.'' ,
make
.B ``.*''
one of the patterns in
.SM
.BR GLOBIGNORE .
The
.B dotglob
option is disabled when
.SM
.B GLOBIGNORE
is unset.
The pattern matching honors the setting of the \fBextglob\fP shell
option.
.PP
\fBPattern Matching\fP
.PP
Any character that appears in a pattern, other than the special pattern
characters described below, matches itself.  The NUL 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.
.PP
The special pattern characters have the following meanings:
.PP
.PD 0
.RS
.TP
.B *
Matches any string, including the null string.
When the \fBglobstar\fP shell option is enabled, and \fB*\fP is used in
a pathname expansion context, two adjacent \fB*\fPs used as a single
pattern will match all files and zero or more directories and
subdirectories.
If followed by a \fB/\fP, two adjacent \fB*\fPs will match only directories
and subdirectories.
.TP
.B ?
Matches any single character.
.TP
.B [...]
Matches any one of the enclosed characters.  A pair of characters
separated by a hyphen denotes a
\fIrange expression\fP;
any character that falls between those two characters, inclusive,
using the current locale's collating sequence and character set,
is matched.  If the first character following the
.B [
is a
.B !
or a
.B ^
then any character not enclosed is matched.
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
.SM
.B LC_COLLATE
or
.SM
.B LC_ALL
shell variables, if set.
To obtain the traditional interpretation of range expressions, where
.B [a\-d]
is equivalent to
.BR [abcd] ,
set value of the
.B LC_ALL
shell variable to
.BR C ,
or enable the
.B globasciiranges
shell option.
A
.B \-
may be matched by including it as the first or last character
in the set.
A
.B ]
may be matched by including it as the first character
in the set.
.br
.if t .sp 0.5
.if n .sp 1
Within
.B [
and
.BR ] ,
\fIcharacter classes\fP can be specified using the syntax
\fB[:\fP\fIclass\fP\fB:]\fP, where \fIclass\fP is one of the
following classes defined in the POSIX standard:
.PP
.RS
.B
.if n alnum alpha ascii blank cntrl digit graph lower print punct space upper word xdigit
.if t alnum   alpha   ascii   blank   cntrl   digit   graph   lower   print   punct   space   upper   word   xdigit
.br
A character class matches any character belonging to that class.
The \fBword\fP character class matches letters, digits, and the character _.
.br
.if t .sp 0.5
.if n .sp 1
Within
.B [
and
.BR ] ,
an \fIequivalence class\fP can be specified using the syntax
\fB[=\fP\fIc\fP\fB=]\fP, which matches all characters with the
same collation weight (as defined by the current locale) as
the character \fIc\fP.
.br
.if t .sp 0.5
.if n .sp 1
Within
.B [
and
.BR ] ,
the syntax \fB[.\fP\fIsymbol\fP\fB.]\fP matches the collating symbol
\fIsymbol\fP.
.RE
.RE
.PD
.PP
If the \fBextglob\fP shell option is enabled using the \fBshopt\fP
builtin, the shell recognizes several extended pattern matching operators.
In the following description, a \fIpattern-list\fP is a list of one
or more patterns separated by a \fB|\fP.
Composite patterns may be formed using one or more of the following
sub-patterns:
.sp 1
.PD 0
.RS
.TP
\fB?(\fP\^\fIpattern-list\^\fP\fB)\fP
Matches zero or one occurrence of the given patterns
.TP
\fB*(\fP\^\fIpattern-list\^\fP\fB)\fP
Matches zero or more occurrences of the given patterns
.TP
\fB+(\fP\^\fIpattern-list\^\fP\fB)\fP
Matches one or more occurrences of the given patterns
.TP
\fB@(\fP\^\fIpattern-list\^\fP\fB)\fP
Matches one of the given patterns
.TP
\fB!(\fP\^\fIpattern-list\^\fP\fB)\fP
Matches anything except one of the given patterns
.RE
.PD
.PP
The\fBextglob\fP 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 \fBextglob\fP is enabled before parsing constructs containing the
patterns, including shell functions and command substitutions.
.PP
When matching filenames, the \fBdotglob\fP shell option determines
the set of filenames that are tested:
when \fBdotglob\fP is enabled, the set of filenames includes all files
beginning with ``.'', but ``.'' and ``..'' 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 ``.'' unless the pattern
or sub-pattern begins with a ``.''.
As above, ``.'' only has a special meaning when matching filenames.
.PP
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.
.SS Quote Removal
After the preceding expansions, all unquoted occurrences of the
characters
.BR \e ,
.BR \(aq ,
and \^\f3"\fP\^ that did not result from one of the above
expansions are removed.
.SH REDIRECTION
Before a command is executed, its input and output
may be
.I redirected
using a special notation interpreted by the shell.
\fIRedirection\fP allows commands' 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
.I simple command
or may follow a
.IR command .
Redirections are processed in the order they appear, from
left to right.
.PP
Each redirection that may be preceded by a file descriptor number
may instead be preceded by a word of the form {\fIvarname\fP}.
In this case, for each redirection operator except
>&- and <&-, the shell will allocate a file descriptor greater
than or equal to 10 and assign it to \fIvarname\fP.
If >&- or <&- is preceded
by {\fIvarname\fP}, the value of \fIvarname\fP defines the file
descriptor to close.
If {\fIvarname\fP} is supplied, the redirection persists beyond
the scope of the command, allowing the shell programmer to manage
the file descriptor's lifetime manually.
The \fBvarredir_close\fP shell option manages this behavior.
.PP
In the following descriptions, if the file descriptor number is
omitted, and the first character of the redirection operator is
.BR < ,
the redirection refers to the standard input (file descriptor
0).  If the first character of the redirection operator is
.BR > ,
the redirection refers to the standard output (file descriptor
1).
.PP
The word following the redirection operator in the following
descriptions, unless otherwise noted, is subjected to
brace expansion, tilde expansion, parameter and variable expansion,
command substitution, arithmetic expansion, quote removal,
pathname expansion, and word splitting.
If it expands to more than one word,
.B bash
reports an error.
.PP
Note that the order of redirections is significant.  For example,
the command
.RS
.PP
ls \fB>\fP dirlist 2\fB>&\fP1
.RE
.PP
directs both standard output and standard error to the file
.IR dirlist ,
while the command
.RS
.PP
ls 2\fB>&\fP1 \fB>\fP dirlist
.RE
.PP
directs only the standard output to file
.IR dirlist ,
because the standard error was duplicated from the standard output
before the standard output was redirected to
.IR dirlist .
.PP
\fBBash\fP handles several filenames specially when they are used in
redirections, as described in the following table.
If the operating system on which \fBbash\fP is running provides these
special files, bash will use them; otherwise it will emulate them
internally with the behavior described below.
.RS
.PP
.PD 0
.TP
.B /dev/fd/\fIfd\fP
If \fIfd\fP is a valid integer, file descriptor \fIfd\fP is duplicated.
.TP
.B /dev/stdin
File descriptor 0 is duplicated.
.TP
.B /dev/stdout
File descriptor 1 is duplicated.
.TP
.B /dev/stderr
File descriptor 2 is duplicated.
.TP
.B /dev/tcp/\fIhost\fP/\fIport\fP
If \fIhost\fP is a valid hostname or Internet address, and \fIport\fP
is an integer port number or service name, \fBbash\fP attempts to open
the corresponding TCP socket.
.TP
.B /dev/udp/\fIhost\fP/\fIport\fP
If \fIhost\fP is a valid hostname or Internet address, and \fIport\fP
is an integer port number or service name, \fBbash\fP attempts to open
the corresponding UDP socket.
.PD
.RE
.PP
A failure to open or create a file causes the redirection to fail.
.PP
Redirections using file descriptors greater than 9 should be used with
care, as they may conflict with file descriptors the shell uses
internally.
.SS Redirecting Input
Redirection of input causes the file whose name results from
the expansion of
.I word
to be opened for reading on file descriptor
.IR n ,
or the standard input (file descriptor 0) if
.I n
is not specified.
.PP
The general format for redirecting input is:
.RS
.PP
[\fIn\fP]\fB<\fP\fIword\fP
.RE
.SS Redirecting Output
Redirection of output causes the file whose name results from
the expansion of
.I word
to be opened for writing on file descriptor
.IR n ,
or the standard output (file descriptor 1) if
.I n
is not specified.  If the file does not exist it is created;
if it does exist it is truncated to zero size.
.PP
The general format for redirecting output is:
.RS
.PP
[\fIn\fP]\fB>\fP\fIword\fP
.RE
.PP
If the redirection operator is
.BR > ,
and the
.B noclobber
option to the
.B set
builtin has been enabled, the redirection will fail if the file
whose name results from the expansion of \fIword\fP exists and is
a regular file.
If the redirection operator is
.BR >| ,
or the redirection operator is
.B >
and the
.B noclobber
option to the
.B set
builtin command is not enabled, the redirection is attempted even
if the file named by \fIword\fP exists.
.SS Appending Redirected Output
Redirection of output in this fashion
causes the file whose name results from
the expansion of
.I word
to be opened for appending on file descriptor
.IR n ,
or the standard output (file descriptor 1) if
.I n
is not specified.  If the file does not exist it is created.
.PP
The general format for appending output is:
.RS
.PP
[\fIn\fP]\fB>>\fP\fIword\fP
.RE
.SS Redirecting Standard Output and Standard Error
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
.IR word .
.PP
There are two formats for redirecting standard output and
standard error:
.RS
.PP
\fB&>\fP\fIword\fP
.RE
and
.RS
\fB>&\fP\fIword\fP
.RE
.PP
Of the two forms, the first is preferred.
This is semantically equivalent to
.RS
.PP
\fB>\fP\fIword\fP 2\fB>&\fP1
.RE
.PP
When using the second form, \fIword\fP may not expand to a number or
\fB\-\fP.  If it does, other redirection operators apply
(see \fBDuplicating File Descriptors\fP below) for compatibility
reasons.
.SS Appending Standard Output and Standard Error
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
.IR word .
.PP
The format for appending standard output and standard error is:
.RS
.PP
\fB&>>\fP\fIword\fP
.RE
.PP
This is semantically equivalent to
.RS
.PP
\fB>>\fP\fIword\fP 2\fB>&\fP1
.RE
.PP
(see \fBDuplicating File Descriptors\fP below).
.SS Here Documents
This type of redirection instructs the shell to read input from the
current source until a line containing only
.I delimiter
(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 \fIn\fP if \fIn\fP is specified) for a command.
.PP
The format of here-documents is:
.RS
.PP
.nf
[\fIn\fP]\fB<<\fP[\fB\-\fP]\fIword\fP
        \fIhere-document\fP
\fIdelimiter\fP
.fi
.RE
.PP
No parameter and variable expansion, command substitution,
arithmetic expansion, or pathname expansion is performed on
.IR word .
If any part of
.I word
is quoted, the
.I delimiter
is the result of quote removal on
.IR word ,
and the lines in the here-document are not expanded.
If \fIword\fP is unquoted,
all lines of the here-document are subjected to
parameter expansion, command substitution, and arithmetic expansion,
the character sequence
.B \e<newline>
is ignored, and
.B \e
must be used to quote the characters
.BR \e ,
.BR $ ,
and
.BR \` .
.PP
If the redirection operator is
.BR <<\- ,
then all leading tab characters are stripped from input lines and the
line containing
.IR delimiter .
This allows
here-documents within shell scripts to be indented in a
natural fashion.
.SS "Here Strings"
A variant of here documents, the format is:
.RS
.PP
.nf
[\fIn\fP]\fB<<<\fP\fIword\fP
.fi
.RE
.PP
The \fIword\fP undergoes
tilde expansion, parameter and variable expansion,
command substitution, arithmetic expansion, and quote removal.
Pathname 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 \fIn\fP if \fIn\fP is specified).
.SS "Duplicating File Descriptors"
The redirection operator
.RS
.PP
[\fIn\fP]\fB<&\fP\fIword\fP
.RE
.PP
is used to duplicate input file descriptors.
If
.I word
expands to one or more digits, the file descriptor denoted by
.I n
is made to be a copy of that file descriptor.
If the digits in
.I word
do not specify a file descriptor open for input, a redirection error occurs.
If
.I word
evaluates to
.BR \- ,
file descriptor
.I n
is closed.  If
.I n
is not specified, the standard input (file descriptor 0) is used.
.PP
The operator
.RS
.PP
[\fIn\fP]\fB>&\fP\fIword\fP
.RE
.PP
is used similarly to duplicate output file descriptors.  If
.I n
is not specified, the standard output (file descriptor 1) is used.
If the digits in
.I word
do not specify a file descriptor open for output, a redirection error occurs.
If
.I word
evaluates to
.BR \- ,
file descriptor
.I n
is closed.
As a special case, if \fIn\fP is omitted, and \fIword\fP does not
expand to one or more digits or \fB\-\fP, the standard output and standard
error are redirected as described previously.
.SS "Moving File Descriptors"
The redirection operator
.RS
.PP
[\fIn\fP]\fB<&\fP\fIdigit\fP\fB\-\fP
.RE
.PP
moves the file descriptor \fIdigit\fP to file descriptor
.IR n ,
or the standard input (file descriptor 0) if \fIn\fP is not specified.
\fIdigit\fP is closed after being duplicated to \fIn\fP.
.PP
Similarly, the redirection operator
.RS
.PP
[\fIn\fP]\fB>&\fP\fIdigit\fP\fB\-\fP
.RE
.PP
moves the file descriptor \fIdigit\fP to file descriptor
.IR n ,
or the standard output (file descriptor 1) if \fIn\fP is not specified.
.SS "Opening File Descriptors for Reading and Writing"
The redirection operator
.RS
.PP
[\fIn\fP]\fB<>\fP\fIword\fP
.RE
.PP
causes the file whose name is the expansion of
.I word
to be opened for both reading and writing on file descriptor
.IR n ,
or on file descriptor 0 if
.I n
is not specified.  If the file does not exist, it is created.
.SH ALIASES
\fIAliases\fP 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
.B alias
and
.B unalias
builtin commands (see
.SM
.B SHELL BUILTIN COMMANDS
below).
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 \fB/\fP, \fB$\fP, \fB\`\fP, and \fB=\fP and
any of the shell \fImetacharacters\fP 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
.B ls
to
.BR "ls \-F" ,
for instance, and
.B bash
does not try to recursively expand the replacement text.
If the last character of the alias value is a
.IR blank ,
then the next command
word following the alias is also checked for alias expansion.
.PP
Aliases are created and listed with the
.B alias
command, and removed with the
.B unalias
command.
.PP
There is no mechanism for using arguments in the replacement text.
If arguments are needed, use a shell function (see
.SM
.B FUNCTIONS
below).
.PP
Aliases are not expanded when the shell is not interactive, unless
the
.B expand_aliases
shell option is set using
.B shopt
(see the description of
.B shopt
under
.SM
\fBSHELL BUILTIN COMMANDS\fP
below).
.PP
The rules concerning the definition and use of aliases are
somewhat confusing.
.B 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
.B alias
in compound commands.
.PP
For almost every purpose, aliases are superseded by
shell functions.
.SH FUNCTIONS
A shell function, defined as described above under
.SM
.BR "SHELL GRAMMAR" ,
stores a series of commands for later execution.
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.
Functions are executed in the context of the
current shell; no new process is created to interpret
them (contrast this with the execution of a shell script).
When a function is executed, the arguments to the
function become the positional parameters
during its execution.
The special parameter
.B #
is updated to reflect the change.  Special parameter \fB0\fP
is unchanged.
The first element of the
.SM
.B FUNCNAME
variable is set to the name of the function while the function
is executing.
.PP
All other aspects of the shell execution
environment are identical between a function and its caller
with these exceptions: the
.SM
.B DEBUG
and
.B RETURN
traps (see the description of the
.B trap
builtin under
.SM
.B SHELL BUILTIN COMMANDS
below) are not inherited unless the function has been given the
\fBtrace\fP attribute (see the description of the
.SM
.B declare
builtin below) or the
\fB\-o functrace\fP shell option has been enabled with
the \fBset\fP builtin
(in which case all functions inherit the \fBDEBUG\fP and \fBRETURN\fP traps),
and the
.SM
.B ERR
trap is not inherited unless the \fB\-o errtrace\fP shell option has
been enabled.
.PP
Variables local to the function may be declared with the
.B local
builtin command (\fIlocal variables\fP).
Ordinarily, variables and their values
are shared between the function and its caller.
If a variable is declared \fBlocal\fP, the variable's visible scope
is restricted to that function and its children (including the functions
it calls).
.PP
In the following description, the \fIcurrent scope\fP is a currently-
executing function.
Previous scopes consist of that function's caller and so on,
back to the "global" scope, where the shell is not executing
any shell function.
Consequently, a local variable at the current scope is a variable
declared using the \fBlocal\fP or \fBdeclare\fP builtins in the
function that is currently executing.
.PP
Local variables "shadow" 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.
.PP
The shell uses \fIdynamic scoping\fP to control a variable'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 "global" scope or another shell function.
This is also the value that a local variable
declaration "shadows", and the value that is restored when the function
returns.
.PP
For example, if a variable \fIvar\fP is declared as local in function
\fIfunc1\fP, and \fIfunc1\fP calls another function \fIfunc2\fP,
references to \fIvar\fP made from within \fIfunc2\fP will resolve to the
local variable \fIvar\fP from \fIfunc1\fP, shadowing any global variable
named \fIvar\fP.
.PP
The \fBunset\fP builtin also acts using the same dynamic scope: if a
variable is local to the current scope, \fBunset\fP 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 the \fBlocalvar_unset\fP shell option changes this behavior).
.PP
The \fBFUNCNEST\fP 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.
.PP
If the builtin command
.B return
is executed in a function, the function completes and
execution resumes with the next command after the function
call.
Any command associated with the \fBRETURN\fP trap is executed
before execution resumes.
When a function completes, the values of the
positional parameters and the special parameter
.B #
are restored to the values they had prior to the function's
execution.
.PP
Function names and definitions may be listed with the
.B \-f
option to the
.B declare
or
.B typeset
builtin commands.  The
.B \-F
option to
.B declare
or
.B typeset
will list the function names only
(and optionally the source file and line number, if the \fBextdebug\fP
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
.B \-f
option to the
.B export
builtin.
A function definition may be deleted using the \fB\-f\fP option to
the
.B unset
builtin.
.PP
Functions may be recursive.
The \fBFUNCNEST\fP 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 imposed on the number of recursive calls.
.SH "ARITHMETIC EVALUATION"
The shell allows arithmetic expressions to be evaluated, under
certain circumstances (see the \fBlet\fP and \fBdeclare\fP builtin
commands, the \fB((\fP compound command, and \fBArithmetic Expansion\fP).
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.
.PP
.PD 0
.TP
.B \fIid\fP++ \fIid\fP\-\-
variable post-increment and post-decrement
.TP
.B \- +
unary minus and plus
.TP
.B ++\fIid\fP \-\-\fIid\fP
variable pre-increment and pre-decrement
.TP
.B ! ~
logical and bitwise negation
.TP
.B **
exponentiation
.TP
.B * / %
multiplication, division, remainder
.TP
.B + \-
addition, subtraction
.TP
.B << >>
left and right bitwise shifts
.TP
.B <= >= < >
comparison
.TP
.B == !=
equality and inequality
.TP
.B &
bitwise AND
.TP
.B ^
bitwise exclusive OR
.TP
.B |
bitwise OR
.TP
.B &&
logical AND
.TP
.B ||
logical OR
.TP
.B \fIexpr\fP?\fIexpr\fP:\fIexpr\fP
conditional operator
.TP
.B = *= /= %= += \-= <<= >>= &= ^= |=
assignment
.TP
.B \fIexpr1\fP , \fIexpr2\fP
comma
.PD
.PP
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
\fIinteger\fP attribute using \fBdeclare \-i\fP is assigned a value.
A null value evaluates to 0.
A shell variable need not have its \fIinteger\fP attribute
turned on to be used in an expression.
.PP
Integer constants follow the C language definition, without suffixes or
character constants.
Constants with a leading 0 are interpreted as octal numbers.
A leading 0x or 0X denotes hexadecimal.
Otherwise, numbers take the form [\fIbase#\fP]n, where the optional \fIbase\fP
is a decimal number between 2 and 64 representing the arithmetic
base, and \fIn\fP is a number in that base.
If \fIbase#\fP is omitted, then base 10 is used.
When specifying \fIn\fP,
if a non-digit is required,
the digits greater than 9 are represented by the lowercase letters,
the uppercase letters, @, and _, in that order.
If \fIbase\fP is less than or equal to 36, lowercase and uppercase
letters may be used interchangeably to represent numbers between 10
and 35.
.PP
Operators are evaluated in order of precedence.  Sub-expressions in
parentheses are evaluated first and may override the precedence
rules above.
.SH "CONDITIONAL EXPRESSIONS"
Conditional expressions are used by the \fB[[\fP compound command and
the \fBtest\fP and \fB[\fP builtin commands to test file attributes
and perform string and arithmetic comparisons.
The \fBtest\fP and \fB[\fP commands determine their behavior based on
the number of arguments; see the descriptions of those commands for any
other command-specific actions.
.PP
Expressions are formed from the following unary or binary primaries.
\fBBash\fP handles several filenames specially when they are used in
expressions.
If the operating system on which \fBbash\fP is running provides these
special files, bash will use them; otherwise it will emulate them
internally with this behavior:
If any \fIfile\fP argument to one of the primaries is of the form
\fI/dev/fd/n\fP, then file descriptor \fIn\fP is checked.
If the \fIfile\fP argument to one of the primaries is one of
\fI/dev/stdin\fP, \fI/dev/stdout\fP, or \fI/dev/stderr\fP, file
descriptor 0, 1, or 2, respectively, is checked.
.PP
Unless otherwise specified, primaries that operate on files follow symbolic
links and operate on the target of the link, rather than the link itself.
.if t .sp 0.5
.if n .sp 1
When used with \fB[[\fP, the \fB<\fP and \fB>\fP operators sort
lexicographically using the current locale.
The \fBtest\fP command sorts using ASCII ordering.
.sp 1
.PD 0
.TP
.B \-a \fIfile\fP
True if \fIfile\fP exists.
.TP
.B \-b \fIfile\fP
True if \fIfile\fP exists and is a block special file.
.TP
.B \-c \fIfile\fP
True if \fIfile\fP exists and is a character special file.
.TP
.B \-d \fIfile\fP
True if \fIfile\fP exists and is a directory.
.TP
.B \-e \fIfile\fP
True if \fIfile\fP exists.
.TP
.B \-f \fIfile\fP
True if \fIfile\fP exists and is a regular file.
.TP
.B \-g \fIfile\fP
True if \fIfile\fP exists and is set-group-id.
.TP
.B \-h \fIfile\fP
True if \fIfile\fP exists and is a symbolic link.
.TP
.B \-k \fIfile\fP
True if \fIfile\fP exists and its ``sticky'' bit is set.
.TP
.B \-p \fIfile\fP
True if \fIfile\fP exists and is a named pipe (FIFO).
.TP
.B \-r \fIfile\fP
True if \fIfile\fP exists and is readable.
.TP
.B \-s \fIfile\fP
True if \fIfile\fP exists and has a size greater than zero.
.TP
.B \-t \fIfd\fP
True if file descriptor
.I fd
is open and refers to a terminal.
.TP
.B \-u \fIfile\fP
True if \fIfile\fP exists and its set-user-id bit is set.
.TP
.B \-w \fIfile\fP
True if \fIfile\fP exists and is writable.
.TP
.B \-x \fIfile\fP
True if \fIfile\fP exists and is executable.
.TP
.B \-G \fIfile\fP
True if \fIfile\fP exists and is owned by the effective group id.
.TP
.B \-L \fIfile\fP
True if \fIfile\fP exists and is a symbolic link.
.TP
.B \-N \fIfile\fP
True if \fIfile\fP exists and has been modified since it was last read.
.TP
.B \-O \fIfile\fP
True if \fIfile\fP exists and is owned by the effective user id.
.TP
.B \-S \fIfile\fP
True if \fIfile\fP exists and is a socket.
.TP
\fIfile1\fP \fB\-ef\fP \fIfile2\fP
True if \fIfile1\fP and \fIfile2\fP refer to the same device and
inode numbers.
.TP
\fIfile1\fP \-\fBnt\fP \fIfile2\fP
True if \fIfile1\fP is newer (according to modification date) than \fIfile2\fP,
or if \fIfile1\fP exists and \fPfile2\fP does not.
.TP
\fIfile1\fP \-\fBot\fP \fIfile2\fP
True if \fIfile1\fP is older than \fIfile2\fP, or if \fIfile2\fP exists
and \fIfile1\fP does not.
.TP
.B \-o \fIoptname\fP
True if the shell option
.I optname
is enabled.
See the list of options under the description of the
.B \-o
option to the
.B set
builtin below.
.TP
.B \-v \fIvarname\fP
True if the shell variable
.I varname
is set (has been assigned a value).
.TP
.B \-R \fIvarname\fP
True if the shell variable
.I varname
is set and is a name reference.
.TP
.B \-z \fIstring\fP
True if the length of \fIstring\fP is zero.
.TP
\fIstring\fP
.PD 0
.TP
.B \-n \fIstring\fP
.PD
True if the length of
.I string
is non-zero.
.TP
\fIstring1\fP \fB==\fP \fIstring2\fP
.PD 0
.TP
\fIstring1\fP \fB=\fP \fIstring2\fP
.PD
True if the strings are equal.  \fB=\fP should be used
with the \fBtest\fP command for POSIX conformance.
When used with the \fB[[\fP command, this performs pattern matching as
described above (\fBCompound Commands\fP).
.TP
\fIstring1\fP \fB!=\fP \fIstring2\fP
True if the strings are not equal.
.TP
\fIstring1\fP \fB<\fP \fIstring2\fP
True if \fIstring1\fP sorts before \fIstring2\fP lexicographically.
.TP
\fIstring1\fP \fB>\fP \fIstring2\fP
True if \fIstring1\fP sorts after \fIstring2\fP lexicographically.
.TP
.I \fIarg1\fP \fBOP\fP \fIarg2\fP
.SM
.B OP
is one of
.BR \-eq ,
.BR \-ne ,
.BR \-lt ,
.BR \-le ,
.BR \-gt ,
or
.BR \-ge .
These arithmetic binary operators return true if \fIarg1\fP
is equal to, not equal to, less than, less than or equal to,
greater than, or greater than or equal to \fIarg2\fP, respectively.
.I Arg1
and
.I arg2
may be positive or negative integers.
When used with the \fB[[\fP command,
.I Arg1
and
.I Arg2
are evaluated as arithmetic expressions (see
.SM
.B "ARITHMETIC EVALUATION"
above).
.PD
.SH "SIMPLE COMMAND EXPANSION"
When a simple command is executed, the shell performs the following
expansions, assignments, and redirections, from left to right, in
the following order.
.IP 1.
The words that the parser has marked as variable assignments (those
preceding the command name) and redirections are saved for later
processing.
.IP 2.
The words that are not variable assignments or redirections are
expanded.  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.
.IP 3.
Redirections are performed as described above under
.SM
.BR REDIRECTION .
.IP 4.
The text after the \fB=\fP in each variable assignment undergoes tilde
expansion, parameter expansion, command substitution, arithmetic expansion,
and quote removal before being assigned to the variable.
.PP
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.
.PP
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.
.PP
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.
.SH "COMMAND EXECUTION"
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.
.PP
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 above in
.SM
.BR FUNCTIONS .
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.
.PP
If the name is neither a shell function nor a builtin,
and contains no slashes,
.B bash
searches each element of the
.SM
.B PATH
for a directory containing an executable file by that name.
.B Bash
uses a hash table to remember the full pathnames of executable
files (see
.B hash
under
.SM
.B "SHELL BUILTIN COMMANDS"
below).
A full search of the directories in
.SM
.B PATH
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 \fBcommand_not_found_handle\fP.
If that function exists, it is invoked in a separate execution environment
with the original command and
the original command's arguments as its arguments, and the function'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.
.PP
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 given, if any.
.PP
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 \fIshell script\fP, a file
containing shell commands, and the shell creates a
new instance of itself
to execute it.
This subshell reinitializes itself, so
that the effect is as if a new shell had been invoked
to handle the script, with the exception that the locations of
commands remembered by the parent (see
.B hash
below under
.SM
\fBSHELL BUILTIN COMMANDS\fP)
are retained by the child.
.PP
If the program is a file beginning with
.BR #! ,
the remainder of the first line specifies an interpreter
for the program.  The shell executes the
specified interpreter on operating systems that do not
handle this executable format themselves.  The arguments to the
interpreter consist of a single optional argument following the
interpreter name on the first line of the program, followed
by the name of the program, followed by the command
arguments, if any.
.SH COMMAND EXECUTION ENVIRONMENT
The shell has an \fIexecution environment\fP, which consists of the
following:
.IP \(bu
open files inherited by the shell at invocation, as modified by
redirections supplied to the \fBexec\fP builtin
.IP \(bu
the current working directory as set by \fBcd\fP, \fBpushd\fP, or
\fBpopd\fP, or inherited by the shell at invocation
.IP \(bu
the file creation mode mask as set by \fBumask\fP or inherited from
the shell's parent
.IP \(bu
current traps set by \fBtrap\fP
.IP \(bu
shell parameters that are set by variable assignment or with \fBset\fP
or inherited from the shell's parent in the environment
.IP \(bu
shell functions defined during execution or inherited from the shell's
parent in the environment
.IP \(bu
options enabled at invocation (either by default or with command-line
arguments) or by \fBset\fP
.IP \(bu
options enabled by \fBshopt\fP
.IP \(bu
shell aliases defined with \fBalias\fP
.IP \(bu
various process IDs, including those of background jobs, the value
of \fB$$\fP, and the value of
.SM
.B PPID
.PP
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.
.if n .sp 1
.IP \(bu
the shell's open files, plus any modifications and additions specified
by redirections to the command
.IP \(bu
the current working directory
.IP \(bu
the file creation mode mask
.IP \(bu
shell variables and functions marked for export, along with variables
exported for the command, passed in the environment
.IP \(bu
traps caught by the shell are reset to the values inherited from the
shell's parent, and traps ignored by the shell are ignored
.PP
A command invoked in this separate environment cannot affect the
shell's execution environment.
.PP
A \fIsubshell\fP is a copy of the shell process.
.PP
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's execution environment.
.PP
Subshells spawned to execute command substitutions inherit the value of
the \fB\-e\fP option from the parent shell.  When not in \fIposix mode\fP,
\fBbash\fP clears the \fB\-e\fP option in such subshells.
.PP
If a command is followed by a \fB&\fP and job control is not active, the
default standard input for the command is the empty file \fI/dev/null\fP.
Otherwise, the invoked command inherits the file descriptors of the calling
shell as modified by redirections.
.SH ENVIRONMENT
When a program is invoked it is given an array of strings
called the
.IR environment .
This is a list of
\fIname\fP\-\fIvalue\fP pairs, of the form
.IR "name\fR=\fPvalue" .
.PP
The shell 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
.I export
to child processes.  Executed commands inherit the environment.
The
.B export
and
.B declare \-x
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's
initial environment, whose values may be modified in the shell,
less any pairs removed by the
.B unset
command, plus any additions via the
.B export
and
.B declare \-x
commands.
.PP
The environment for any
.I simple command
or function may be augmented temporarily by prefixing it with
parameter assignments, as described above in
.SM
.BR PARAMETERS .
These assignment statements affect only the environment seen
by that command.
.PP
If the
.B \-k
option is set (see the
.B set
builtin command below), then
.I all
parameter assignments are placed in the environment for a command,
not just those that precede the command name.
.PP
When
.B bash
invokes an external command, the variable
.B _
is set to the full filename of the command and passed to that
command in its environment.
.SH "EXIT STATUS"
The exit status of an executed command is the value returned by the
\fIwaitpid\fP 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.
.PP
For the shell's purposes, a command which exits with a
zero exit status has succeeded.  An exit status of zero
indicates success.  A non-zero exit status indicates failure.
When a command terminates on a fatal signal \fIN\fP, \fBbash\fP uses
the value of 128+\fIN\fP as the exit status.
.PP
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.
.PP
If a command fails because of an error during expansion or redirection,
the exit status is greater than zero.
.PP
Shell builtin commands return a status of 0 (\fItrue\fP) if
successful, and non-zero (\fIfalse\fP) if an error occurs
while they execute.
All builtins return an exit status of 2 to indicate incorrect usage,
generally invalid options or missing arguments.
.PP
The exit status of the last command is available in the special
parameter $?.
.PP
\fBBash\fP itself returns the exit status of the last command
executed, unless a syntax error occurs, in which case it exits
with a non-zero value.  See also the \fBexit\fP builtin
command below.
.SH SIGNALS
When \fBbash\fP is interactive, in the absence of any traps, it ignores
.SM
.B SIGTERM
(so that \fBkill 0\fP does not kill an interactive shell),
and
.SM
.B SIGINT
is caught and handled (so that the \fBwait\fP builtin is interruptible).
In all cases, \fBbash\fP ignores
.SM
.BR SIGQUIT .
If job control is in effect,
.B bash
ignores
.SM
.BR SIGTTIN ,
.SM
.BR SIGTTOU ,
and
.SM
.BR SIGTSTP .
.PP
Non-builtin commands run by \fBbash\fP have signal handlers
set to the values inherited by the shell from its parent.
When job control is not in effect, asynchronous commands
ignore
.SM
.B SIGINT
and
.SM
.B SIGQUIT
in addition to these inherited handlers.
Commands run as a result of command substitution ignore the
keyboard-generated job control signals
.SM
.BR SIGTTIN ,
.SM
.BR SIGTTOU ,
and
.SM
.BR SIGTSTP .
.PP
The shell exits by default upon receipt of a
.SM
.BR SIGHUP .
Before exiting, an interactive shell resends the
.SM
.B SIGHUP
to all jobs, running or stopped.
Stopped jobs are sent
.SM
.B SIGCONT
to ensure that they receive the
.SM
.BR SIGHUP .
To prevent the shell from
sending the signal to a particular job, it should be removed from the
jobs table with the
.B disown
builtin (see
.SM
.B "SHELL BUILTIN COMMANDS"
below) or marked
to not receive
.SM
.B SIGHUP
using
.BR "disown \-h" .
.PP
If the
.B huponexit
shell option has been set with
.BR shopt ,
.B bash
sends a
.SM
.B SIGHUP
to all jobs when an interactive login shell exits.
.PP
If \fBbash\fP 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 \fBbash\fP is waiting for an asynchronous command via the \fBwait\fP
builtin, the reception of a signal for which a trap has been set will
cause the \fBwait\fP builtin to return immediately with an exit status
greater than 128, immediately after which the trap is executed.
.PP
When job control is not enabled, and \fBbash\fP is waiting for a foreground
command to complete, the shell receives keyboard-generated signals
such as
.SM
.B SIGINT
(usually generated by \fB^C\fP) 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 \fB^C\fP sends
.SM
.B SIGINT
to all processes in that process group.
.PP
When \fBbash\fP is running without job control enabled and receives 
.SM
.B SIGINT
while waiting for a foreground command, it waits until that foreground
command terminates and then decides what to do about the
.SM
.BR SIGINT :
.IP 1.
If the command terminates due to the
.SM
.BR SIGINT ,
\fBbash\fP concludes
that the user meant to end the entire script, and acts on the
.SM
.B SIGINT
(e.g., by running a
.SM
.B SIGINT
trap or exiting itself);
.IP 2.
If the command does not terminate due to
.SM
.BR SIGINT ,
the program handled the
.SM
.B SIGINT
itself and did not treat it as a fatal signal.
In that case, \fBbash\fP does not treat
.SM
.B SIGINT
as a fatal signal, either, instead assuming that the
.SM
.B SIGINT
was used as part of the program's normal operation
(e.g., emacs uses it to abort editing
commands) or deliberately discarded.
However, \fBbash\fP will run any
trap set on
.SM
.BR SIGINT ,
as it does with any other trapped signal it
receives while it is waiting for the foreground command to
complete, for compatibility.
.SH "JOB CONTROL"
.I Job control
refers to the ability to selectively stop (\fIsuspend\fP)
the execution of processes and continue (\fIresume\fP)
their execution at a later point.  A user typically employs
this facility via an interactive interface supplied jointly
by the operating system kernel's terminal driver and
.BR bash .
.PP
The shell associates a
.I job
with each pipeline.  It keeps a table of currently executing
jobs, which may be listed with the
.B jobs
command.  When
.B bash
starts a job asynchronously (in the
.IR background ),
it prints a line that looks like:
.RS
.PP
[1] 25647
.RE
.PP
indicating that this job is job number 1 and that the process ID
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.
.B Bash
uses the
.I job
abstraction as the basis for job control.
.PP
To facilitate the implementation of the user interface to job
control, the operating system maintains the notion of a \fIcurrent terminal
process group ID\fP.  Members of this process group (processes whose
process group ID is equal to the current terminal process group ID)
receive keyboard-generated signals such as
.SM
.BR SIGINT .
These processes are said to be in the
.IR foreground .
.I Background
processes are those whose process group ID differs from the terminal's;
such processes are immune to keyboard-generated signals.
Only foreground processes are allowed to read from or, if the
user so specifies with \f(CWstty tostop\fP, write to the
terminal.
Background processes which attempt to read from (write to when
\f(CWstty tostop\fP is in effect) the
terminal are sent a
.SM
.B SIGTTIN (SIGTTOU)
signal by the kernel's terminal driver,
which, unless caught, suspends the process.
.PP
If the operating system on which
.B bash
is running supports
job control,
.B bash
contains facilities to use it.
Typing the
.I suspend
character (typically
.BR ^Z ,
Control-Z) while a process is running
causes that process to be stopped and returns control to
.BR bash .
Typing the
.I "delayed suspend"
character (typically
.BR ^Y ,
Control-Y) causes the process to be stopped when it
attempts to read input from the terminal, and control to
be returned to
.BR bash .
The user may then manipulate the state of this job, using the
.B bg
command to continue it in the background, the
.B fg
command to continue it in the foreground, or
the
.B kill
command to kill it.  A \fB^Z\fP takes effect immediately,
and has the additional side effect of causing pending output
and typeahead to be discarded.
.PP
There are a number of ways to refer to a job in the shell.
The character
.B %
introduces a job specification (\fIjobspec\fP).  Job number
.I n
may be referred to as
.BR %n .
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,
.B %ce
refers to a stopped
job whose command name begins with
.BR ce .
If a prefix matches more than one job,
.B bash
reports an error.  Using
.BR %?ce ,
on the other hand, refers to any job containing the string
.B ce
in its command line.  If the substring matches more than one job,
.B bash
reports an error.  The symbols
.B %%
and
.B %+
refer to the shell's notion of the
.IR "current job" ,
which is the last job stopped while it was in
the foreground or started in the background.
The
.I "previous job"
may be referenced using
.BR %\- .
If there is only a single job, \fB%+\fP and \fB%\-\fP can both be used
to refer to that job.
In output pertaining to jobs (e.g., the output of the
.B jobs
command), the current job is always flagged with a
.BR + ,
and the previous job with a
.BR \- .
A single % (with no accompanying job specification) also refers to the
current job.
.PP
Simply naming a job can be used to bring it into the
foreground:
.B %1
is a synonym for
\fB``fg %1''\fP,
bringing job 1 from the background into the foreground.
Similarly,
.B ``%1 &''
resumes job 1 in the background, equivalent to
\fB``bg %1''\fP.
.PP
The shell learns immediately whenever a job changes state.
Normally,
.B bash
waits until it is about to print a prompt before reporting
changes in a job's status so as to not interrupt
any other output.  If the
.B \-b
option to the
.B set
builtin command
is enabled,
.B bash
reports such changes immediately.
Any trap on
.SM
.B SIGCHLD
is executed for each child that exits.
.PP
If an attempt to exit
.B bash
is made while jobs are stopped (or, if the \fBcheckjobs\fP shell option has
been enabled using the \fBshopt\fP builtin, running), the shell prints a
warning message, and, if the \fBcheckjobs\fP option is enabled, lists the
jobs and their statuses.
The
.B jobs
command may then be used to inspect their status.
If a second attempt to exit is made without an intervening command,
the shell does not print another warning, and any stopped
jobs are terminated.
.PP
When the shell is waiting for a job or process using the \fBwait\fP
builtin, and job control is enabled, \fBwait\fP will return when the
job changes state. The \fB\-f\fP option causes \fBwait\fP to wait
until the job or process terminates before returning.
.SH PROMPTING
When executing interactively,
.B bash
displays the primary prompt
.SM
.B PS1
when it is ready to read a command, and the secondary prompt
.SM
.B PS2
when it needs more input to complete a command.
.B Bash
displays
.SM
.B PS0
after it reads a command but before executing it.
.B Bash
displays
.SM
.B PS4
as described above
before tracing each command when the \fB\-x\fP option is enabled.
.B Bash
allows these prompt strings to be customized by inserting a number of
backslash-escaped special characters that are decoded as follows:
.RS
.PD 0
.TP
.B \ea
an ASCII bell character (07)
.TP
.B \ed
the date in "Weekday Month Date" format (e.g., "Tue May 26")
.TP
.B \eD{\fIformat\fP}
the \fIformat\fP is passed to \fIstrftime\fP(3) and the result is inserted
into the prompt string; an empty \fIformat\fP results in a locale-specific
time representation.  The braces are required
.TP
.B \ee
an ASCII escape character (033)
.TP
.B \eh
the hostname up to the first `.'
.TP
.B \eH
the hostname
.TP
.B \ej
the number of jobs currently managed by the shell
.TP
.B \el
the basename of the shell's terminal device name
.TP
.B \en
newline
.TP
.B \er
carriage return
.TP
.B \es
the name of the shell, the basename of
.B $0
(the portion following the final slash)
.TP
.B \et
the current time in 24-hour HH:MM:SS format
.TP
.B \eT
the current time in 12-hour HH:MM:SS format
.TP
.B \e@
the current time in 12-hour am/pm format
.TP
.B \eA
the current time in 24-hour HH:MM format
.TP
.B \eu
the username of the current user
.TP
.B \ev
the version of \fBbash\fP (e.g., 2.00)
.TP
.B \eV
the release of \fBbash\fP, version + patch level (e.g., 2.00.0)
.TP
.B \ew
the value of the \fBPWD\fP shell variable (\fB$PWD\fP),
with
.SM
.B $HOME
abbreviated with a tilde
(uses the value of the
.SM
.B PROMPT_DIRTRIM
variable)
.TP
.B \eW
the basename of \fB$PWD\fP,
with
.SM
.B $HOME
abbreviated with a tilde
.TP
.B \e!
the history number of this command
.TP
.B \e#
the command number of this command
.TP
.B \e$
if the effective UID is 0, a
.BR # ,
otherwise a
.B $
.TP
.B \e\fInnn\fP
the character corresponding to the octal number \fInnn\fP
.TP
.B \e\e
a backslash
.TP
.B \e[
begin a sequence of non-printing characters, which could be used to
embed a terminal control sequence into the prompt
.TP
.B \e]
end a sequence of non-printing characters
.PD
.RE
.PP
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
.SM
.B HISTORY
below), while the command number is the position in the sequence
of commands executed during the current shell session.
After the string is decoded, it is expanded via
parameter expansion, command substitution, arithmetic
expansion, and quote removal, subject to the value of the
.B promptvars
shell option (see the description of the
.B shopt
command under
.SM
.B "SHELL BUILTIN COMMANDS"
below).
This can have unwanted side effects if escaped portions of the string
appear within command substitution or contain characters special to
word expansion.
.SH READLINE
This is the library that handles reading input when using an interactive
shell, unless the
.B \-\-noediting
option is given at shell invocation.
Line editing is also used when using the \fB\-e\fP option to the
\fBread\fP builtin.
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
.B \-o emacs
or
.B \-o vi
options to the
.B set
builtin (see
.SM
.B SHELL BUILTIN COMMANDS
below).
To turn off line editing after the shell is running, use the
.B +o emacs
or
.B +o vi
options to the
.B set
builtin.
.SS "Readline Notation"
In this section, the Emacs-style notation is used to denote
keystrokes.  Control keys are denoted by C\-\fIkey\fR, e.g., C\-n
means Control\-N.  Similarly,
.I meta
keys are denoted by M\-\fIkey\fR, so M\-x means Meta\-X.  (On keyboards
without a
.I meta
key, M\-\fIx\fP means ESC \fIx\fP, i.e., press the Escape key
then the
.I x
key.  This makes ESC the \fImeta prefix\fP.
The combination M\-C\-\fIx\fP means ESC\-Control\-\fIx\fP,
or press the Escape key
then hold the Control key while pressing the
.I x
key.)
.PP
Readline commands may be given numeric
.IR arguments ,
which normally act as a repeat count.
Sometimes, however, it is the sign of the argument that is significant.
Passing a negative argument to a command that acts in the forward
direction (e.g., \fBkill\-line\fP) causes that command to act in a
backward direction.
Commands whose behavior with arguments deviates from this are noted
below.
.PP
When a command is described as \fIkilling\fP text, the text
deleted is saved for possible future retrieval
(\fIyanking\fP).  The killed text is saved in a
\fIkill ring\fP.  Consecutive kills cause the text to be
accumulated into one unit, which can be yanked all at once.
Commands which do not kill text separate the chunks of text
on the kill ring.
.SS "Readline Initialization"
Readline is customized by putting commands in an initialization
file (the \fIinputrc\fP file).
The name of this file is taken from the value of the
.SM
.B INPUTRC
variable.  If that variable is unset, the default is
.IR ~/.inputrc .
If that file  does not exist or cannot be read, the ultimate default is
.IR /etc/inputrc .
When a program which uses the readline library starts up, the
initialization file is read, and the key bindings and variables
are set.
There are only a few basic constructs allowed in the
readline initialization file.
Blank lines are ignored.
Lines beginning with a \fB#\fP are comments.
Lines beginning with a \fB$\fP indicate conditional constructs.
Other lines denote key bindings and variable settings.
.PP
The default key-bindings may be changed with an
.I inputrc
file.
Other programs that use this library may add their own commands
and bindings.
.PP
For example, placing
.RS
.PP
M\-Control\-u: universal\-argument
.RE
or
.RS
C\-Meta\-u: universal\-argument
.RE
into the
.I inputrc
would make M\-C\-u execute the readline command
.IR universal\-argument .
.PP
The following symbolic character names are recognized:
.IR RUBOUT ,
.IR DEL ,
.IR ESC ,
.IR LFD ,
.IR NEWLINE ,
.IR RET ,
.IR RETURN ,
.IR SPC ,
.IR SPACE ,
and
.IR TAB .
.PP
In addition to command names, readline allows keys to be bound
to a string that is inserted when the key is pressed (a \fImacro\fP).
.SS "Readline Key Bindings"
The syntax for controlling key bindings in the
.I inputrc
file is simple.  All that is required is the name of the
command or the text of a macro and a key sequence to which
it should be bound.  The name may be specified in one of two ways:
as a symbolic key name, possibly with \fIMeta\-\fP or \fIControl\-\fP
prefixes, or as a key sequence.
.PP
When using the form \fBkeyname\fP:\^\fIfunction\-name\fP or \fImacro\fP,
.I keyname
is the name of a key spelled out in English.  For example:
.sp
.RS
Control-u: universal\-argument
.br
Meta-Rubout: backward-kill-word
.br
Control-o: "> output"
.RE
.LP
In the above example,
.I C\-u
is bound to the function
.BR universal\-argument ,
.I M\-DEL
is bound to the function
.BR backward\-kill\-word ,
and
.I C\-o
is bound to run the macro
expressed on the right hand side (that is, to insert the text
.if t \f(CW> output\fP
.if n ``> output''
into the line).
.PP
In the second form, \fB"keyseq"\fP:\^\fIfunction\-name\fP or \fImacro\fP,
.B keyseq
differs from
.B keyname
above in that strings denoting
an entire key sequence may be specified by placing the sequence
within double quotes.  Some GNU Emacs style key escapes can be
used, as in the following example, but the symbolic character names
are not recognized.
.sp
.RS
"\eC\-u": universal\-argument
.br
"\eC\-x\eC\-r": re\-read\-init\-file
.br
"\ee[11~": "Function Key 1"
.RE
.PP
In this example,
.I C\-u
is again bound to the function
.BR universal\-argument .
.I "C\-x C\-r"
is bound to the function
.BR re\-read\-init\-file ,
and
.I "ESC [ 1 1 ~"
is bound to insert the text
.if t \f(CWFunction Key 1\fP.
.if n ``Function Key 1''.
.PP
The full set of GNU Emacs style escape sequences is
.RS
.PD 0
.TP
.B \eC\-
control prefix
.TP
.B \eM\-
meta prefix
.TP
.B \ee
an escape character
.TP
.B \e\e
backslash
.TP
.B \e"
literal "
.TP
.B \e\(aq
literal \(aq
.RE
.PD
.PP
In addition to the GNU Emacs style escape sequences, a second
set of backslash escapes is available:
.RS
.PD 0
.TP
.B \ea
alert (bell)
.TP
.B \eb
backspace
.TP
.B \ed
delete
.TP
.B \ef
form feed
.TP
.B \en
newline
.TP
.B \er
carriage return
.TP
.B \et
horizontal tab
.TP
.B \ev
vertical tab
.TP
.B \e\fInnn\fP
the eight-bit character whose value is the octal value \fInnn\fP
(one to three digits)
.TP
.B \ex\fIHH\fP
the eight-bit character whose value is the hexadecimal value \fIHH\fP
(one or two hex digits)
.RE
.PD
.PP
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 " and \(aq.
.PP
.B Bash
allows the current readline key bindings to be displayed or modified
with the
.B bind
builtin command.  The editing mode may be switched during interactive
use by using the
.B \-o
option to the
.B set
builtin command (see
.SM
.B SHELL BUILTIN COMMANDS
below).
.SS "Readline Variables"
Readline has variables that can be used to further customize its
behavior.  A variable may be set in the
.I inputrc
file with a statement of the form
.RS
.PP
\fBset\fP \fIvariable\-name\fP \fIvalue\fP
.RE
or using the \fBbind\fP builtin command (see
.SM
.B SHELL BUILTIN COMMANDS
below).
.PP
Except where noted, readline variables can take the values
.B On
or
.B Off
(without regard to case).
Unrecognized variable names are ignored.
When a variable value is read, empty or null values, "on" (case-insensitive),
and "1" are equivalent to \fBOn\fP.  All other values are equivalent to
\fBOff\fP.
The variables and their default values are:
.PP
.PD 0
.TP
.B active\-region\-start\-color   
A string variable that controls the text color and background when displaying
the text in the active region (see the description of
\fBenable\-active\-region\fP 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's terminfo description.
A sample value might be \f(CW"\ee[01;33m"\fP.
.TP
.B active\-region\-end\-color     
A string variable that "undoes" the effects of \fBactive\-region\-start\-color\fP 
and restores "normal" 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's terminfo description.
A sample value might be \f(CW"\ee[0m"\fP.
.TP
.B bell\-style (audible)
Controls what happens when readline wants to ring the terminal bell.
If set to \fBnone\fP, readline never rings the bell.  If set to
\fBvisible\fP, readline uses a visible bell if one is available.
If set to \fBaudible\fP, readline attempts to ring the terminal's bell.
.TP
.B bind\-tty\-special\-chars (On)
If set to \fBOn\fP, readline attempts to bind the control characters
treated specially by the kernel's terminal driver to their readline
equivalents.
.TP
.B blink\-matching\-paren (Off)
If set to \fBOn\fP, readline attempts to briefly move the cursor to an
opening parenthesis when a closing parenthesis is inserted.
.TP
.B colored\-completion\-prefix (Off)
If set to \fBOn\fP, 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 \fBLS_COLORS\fP
environment variable.
If there is a color definition in \fB$LS_COLORS\fP for the custom suffix
"readline-colored-completion-prefix", readline uses this color for
the common prefix instead of its default.
.TP
.B colored\-stats (Off)
If set to \fBOn\fP, readline displays possible completions using different
colors to indicate their file type.
The color definitions are taken from the value of the \fBLS_COLORS\fP
environment variable.
.TP
.B comment\-begin (``#'')
The string that is inserted when the readline
.B insert\-comment
command is executed.
This command is bound to
.B M\-#
in emacs mode and to
.B #
in vi command mode.
.TP
.B completion\-display\-width (\-1)
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.
.TP
.B completion\-ignore\-case (Off)
If set to \fBOn\fP, readline performs filename matching and completion
in a case\-insensitive fashion.
.TP
.B completion\-map\-case (Off)
If set to \fBOn\fP, and \fBcompletion\-ignore\-case\fP is enabled, readline
treats hyphens (\fI\-\fP) and underscores (\fI_\fP) as equivalent when
performing case\-insensitive filename matching and completion.
.TP
.B completion\-prefix\-display\-length (0)
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.
.TP
.B completion\-query\-items (100)
This determines when the user is queried about viewing
the number of possible completions
generated by the \fBpossible\-completions\fP command.
It may be set to any integer value greater than or equal to zero.
If the number of possible completions is greater than
or equal to the value of this variable,
readline will ask whether or not the user wishes to view them;
otherwise they are simply listed on the terminal.
A zero value means readline should never ask; negative values are
treated as zero.
.TP
.B convert\-meta (On)
If set to \fBOn\fP, readline will convert characters with the
eighth bit set to an ASCII key sequence
by stripping the eighth bit and prefixing an
escape character (in effect, using escape as the \fImeta prefix\fP).
The default is \fIOn\fP, but readline will set it to \fIOff\fP if the
locale contains eight-bit characters.
This variable is dependent on the \fBLC_CTYPE\fP locale category, and 
may change if the locale is changed.
.TP
.B disable\-completion (Off)
If set to \fBOn\fP, readline will inhibit word completion.  Completion
characters will be inserted into the line as if they had been
mapped to \fBself-insert\fP.
.TP
.B echo\-control\-characters (On)
When set to \fBOn\fP, on operating systems that indicate they support it,
readline echoes a character corresponding to a signal generated from the
keyboard.
.TP
.B editing\-mode (emacs)
Controls whether readline begins with a set of key bindings similar
to \fIEmacs\fP or \fIvi\fP.
.B editing\-mode
can be set to either
.B emacs
or
.BR vi .
.TP
.B emacs\-mode\-string (@)
If the \fIshow\-mode\-in\-prompt\fP 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 \e1 and \e2 escapes to begin and end sequences of
non-printing characters, which can be used to embed a terminal control
sequence into the mode string.
.TP
.B enable\-active\-region (On)
The \fIpoint\fP is the current cursor position, and \fImark\fP refers  
to a saved cursor position.   
The text between the point and mark is referred to as the \fIregion\fP.  
When this variable is set to \fIOn\fP, readline allows certain commands
to designate the region as \fIactive\fP.  
When the region is active, readline highlights the text in the region using
the value of the \fBactive\-region\-start\-color\fP, which defaults to the
string that enables
the terminal'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.
.TP
.B enable\-bracketed\-paste (On)
When set to \fBOn\fP, 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 prevents readline from executing any editing commands bound to key
sequences appearing in the pasted text.
.TP
.B enable\-keypad (Off)
When set to \fBOn\fP, readline will try to enable the application
keypad when it is called.  Some systems need this to enable the
arrow keys.
.TP
.B enable\-meta\-key (On)
When set to \fBOn\fP, 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.
.TP
.B expand\-tilde (Off)
If set to \fBOn\fP, tilde expansion is performed when readline
attempts word completion.
.TP
.B history\-preserve\-point (Off)
If set to \fBOn\fP, the history code attempts to place point at the
same location on each history line retrieved with \fBprevious-history\fP
or \fBnext-history\fP.
.TP
.B history\-size (unset)
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 set to the value of the
\fBHISTSIZE\fP shell variable.
If an attempt is made to set \fIhistory\-size\fP to a non-numeric value,
the maximum number of history entries will be set to 500.
.TP
.B horizontal\-scroll\-mode (Off)
When set to \fBOn\fP, makes readline use a single line for display,
scrolling the input horizontally on a single screen line when it
becomes longer than the screen width rather than wrapping to a new line.
This setting is automatically enabled for terminals of height 1.
.TP
.B input\-meta (Off)
If set to \fBOn\fP, readline will enable eight-bit input (that is,
it will not strip the eighth bit from the characters it reads),
regardless of what the terminal claims it can support.  The name
.B meta\-flag
is a synonym for this variable.
The default is \fIOff\fP, but readline will set it to \fIOn\fP if the
locale contains eight-bit characters.
This variable is dependent on the \fBLC_CTYPE\fP locale category, and 
may change if the locale is changed.
.TP
.B isearch\-terminators (``C\-[C\-J'')
The string of characters that should terminate an incremental
search without subsequently executing the character as a command.
If this variable has not been given a value, the characters
\fIESC\fP and \fIC\-J\fP will terminate an incremental search.
.TP
.B keymap (emacs)
Set the current readline keymap.  The set of valid keymap names is
\fIemacs, emacs\-standard, emacs\-meta, emacs\-ctlx, vi,
vi\-command\fP, and
.IR vi\-insert .
\fIvi\fP is equivalent to \fIvi\-command\fP; \fIemacs\fP is
equivalent to \fIemacs\-standard\fP.  The default value is
.IR emacs ;
the value of
.B editing\-mode
also affects the default keymap.
.TP
.B keyseq\-timeout (500)
Specifies the duration \fIreadline\fP 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, \fIreadline\fP will use the shorter
but complete key sequence.
The value is specified in milliseconds, so a value of 1000 means that
\fIreadline\fP 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, \fIreadline\fP will wait until another key is pressed to
decide which key sequence to complete.
.TP
.B mark\-directories (On)
If set to \fBOn\fP, completed directory names have a slash
appended.
.TP
.B mark\-modified\-lines (Off)
If set to \fBOn\fP, history lines that have been modified are displayed
with a preceding asterisk (\fB*\fP).
.TP
.B mark\-symlinked\-directories (Off)
If set to \fBOn\fP, completed names which are symbolic links to directories
have a slash appended (subject to the value of
\fBmark\-directories\fP).
.TP
.B match\-hidden\-files (On)
This variable, when set to \fBOn\fP, causes readline to match files whose
names begin with a `.' (hidden files) when performing filename
completion.
If set to \fBOff\fP, the leading `.' must be
supplied by the user in the filename to be completed.
.TP
.B menu\-complete\-display\-prefix (Off)
If set to \fBOn\fP, menu completion displays the common prefix of the
list of possible completions (which may be empty) before cycling through
the list.
.TP
.B output\-meta (Off)
If set to \fBOn\fP, readline will display characters with the
eighth bit set directly rather than as a meta-prefixed escape
sequence.
The default is \fIOff\fP, but readline will set it to \fIOn\fP if the
locale contains eight-bit characters.
This variable is dependent on the \fBLC_CTYPE\fP locale category, and 
may change if the locale is changed.
.TP
.B page\-completions (On)
If set to \fBOn\fP, readline uses an internal \fImore\fP-like pager
to display a screenful of possible completions at a time.
.TP
.B print\-completions\-horizontally (Off)
If set to \fBOn\fP, readline will display completions with matches
sorted horizontally in alphabetical order, rather than down the screen.
.TP
.B revert\-all\-at\-newline (Off)
If set to \fBOn\fP, readline will undo all changes to history lines
before returning when \fBaccept\-line\fP is executed.  By default,
history lines may be modified and retain individual undo lists across
calls to \fBreadline\fP.
.TP
.B show\-all\-if\-ambiguous (Off)
This alters the default behavior of the completion functions.  If
set to
.BR On ,
words which have more than one possible completion cause the
matches to be listed immediately instead of ringing the bell.
.TP
.B show\-all\-if\-unmodified (Off)
This alters the default behavior of the completion functions in
a fashion similar to \fBshow\-all\-if\-ambiguous\fP.
If set to
.BR On ,
words which have more than one possible completion without any
possible partial completion (the possible completions don't share
a common prefix) cause the matches to be listed immediately instead
of ringing the bell.
.TP
.B show\-mode\-in\-prompt (Off)
If set to \fBOn\fP, 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., \fIemacs\-mode\-string\fP).
.TP
.B skip\-completed\-text (Off)
If set to \fBOn\fP, this alters the default completion behavior when
inserting a single match into the line.  It'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.
.TP
.B vi\-cmd\-mode\-string ((cmd))
If the \fIshow\-mode\-in\-prompt\fP 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 \e1 and \e2 escapes to begin and end sequences of
non-printing characters, which can be used to embed a terminal control
sequence into the mode string.
.TP
.B vi\-ins\-mode\-string ((ins))
If the \fIshow\-mode\-in\-prompt\fP 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 \e1 and \e2 escapes to begin and end sequences of
non-printing characters, which can be used to embed a terminal control
sequence into the mode string.
.TP
.B visible\-stats (Off)
If set to \fBOn\fP, a character denoting a file's type as reported
by \fIstat\fP(2) is appended to the filename when listing possible
completions.
.PD
.SS "Readline Conditional Constructs"
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.
.IP \fB$if\fP
The
.B $if
construct allows bindings to be made based on the
editing mode, the terminal being used, or the application using
readline.  The text of the test, after any comparison operator,
 extends to the end of the line;
unless otherwise noted, no characters are required to isolate it.
.RS
.IP \fBmode\fP
The \fBmode=\fP form of the \fB$if\fP directive is used to test
whether readline is in emacs or vi mode.
This may be used in conjunction
with the \fBset keymap\fP command, for instance, to set bindings in
the \fIemacs\-standard\fP and \fIemacs\-ctlx\fP keymaps only if
readline is starting out in emacs mode.
.IP \fBterm\fP
The \fBterm=\fP form may be used to include terminal-specific
key bindings, perhaps to bind the key sequences output by the
terminal's function keys.  The word on the right side of the
.B =
is tested against both the full name of the terminal and the portion
of the terminal name before the first \fB\-\fP.  This allows
.I sun
to match both
.I sun
and
.IR sun\-cmd ,
for instance.
.IP \fBversion\fP
The \fBversion\fP test may be used to perform comparisons against
specific readline versions.
The \fBversion\fP expands to the current readline version.
The set of comparison operators includes
.BR = ,
(and
.BR == ),
.BR != ,
.BR <= ,
.BR >= ,
.BR < ,
and
.BR > .
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., \fB7.1\fP). If the minor version is omitted, it
is assumed to be \fB0\fP.
The operator may be separated from the string \fBversion\fP
and from the version number argument by whitespace.
.IP \fBapplication\fP
The \fBapplication\fP construct is used to include
application-specific settings.  Each program using the readline
library sets the \fIapplication name\fP, and an initialization
file 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 \fBbash\fP:
.sp 1
.RS
.nf
\fB$if\fP Bash
# Quote the current or previous word
"\eC\-xq": "\eeb\e"\eef\e""
\fB$endif\fP
.fi
.RE
.IP \fIvariable\fP
The \fIvariable\fP construct provides simple equality tests for readline
variables and values.
The permitted comparison operators are \fI=\fP, \fI==\fP, and \fI!=\fP.
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 \fIon\fP and \fIoff\fP.
.RE
.IP \fB$endif\fP
This command, as seen in the previous example, terminates an
\fB$if\fP command.
.IP \fB$else\fP
Commands in this branch of the \fB$if\fP directive are executed if
the test fails.
.IP \fB$include\fP
This directive takes a single filename as an argument and reads commands
and bindings from that file.  For example, the following directive
would read \fI/etc/inputrc\fP:
.sp 1
.RS
.nf
\fB$include\fP \^ \fI/etc/inputrc\fP
.fi
.RE
.SS Searching
Readline provides commands for searching through the command history
(see
.SM
.B HISTORY
below) for lines containing a specified string.
There are two search modes:
.I incremental
and
.IR non-incremental .
.PP
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.
The characters present in the value of the \fBisearch-terminators\fP
variable are used to terminate an incremental search.
If that variable has not been assigned a value the Escape and
Control-J characters will terminate an incremental search.
Control-G 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.
.PP
To find other matching entries in the history list, type Control-S or
Control-R 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 \fInewline\fP will terminate the search and accept
the line, thereby executing the command from the history list.
.PP
Readline remembers the last incremental search string.  If two
Control-Rs are typed without any intervening characters defining a
new search string, any remembered search string is used.
.PP
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.
.SS "Readline Command Names"
The following is a list of the names of the commands and the default
key sequences to which they are bound.
Command names without an accompanying key sequence are unbound by default.
In the following descriptions, \fIpoint\fP refers to the current cursor
position, and \fImark\fP refers to a cursor position saved by the
\fBset\-mark\fP command.
The text between the point and mark is referred to as the \fIregion\fP.
.SS Commands for Moving
.PD 0
.TP
.B beginning\-of\-line (C\-a)
Move to the start of the current line.
.TP
.B end\-of\-line (C\-e)
Move to the end of the line.
.TP
.B forward\-char (C\-f)
Move forward a character.
.TP
.B backward\-char (C\-b)
Move back a character.
.TP
.B forward\-word (M\-f)
Move forward to the end of the next word.  Words are composed of
alphanumeric characters (letters and digits).
.TP
.B backward\-word (M\-b)
Move back to the start of the current or previous word.
Words are composed of alphanumeric characters (letters and digits).
.TP
.B shell\-forward\-word
Move forward to the end of the next word.
Words are delimited by non-quoted shell metacharacters.
.TP
.B shell\-backward\-word
Move back to the start of the current or previous word.
Words are delimited by non-quoted shell metacharacters.
.TP
.B previous\-screen\-line
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.
.TP
.B next\-screen\-line
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.
.TP
.B clear\-display (M\-C\-l)
Clear the screen and, if possible, the terminal's scrollback buffer,
then redraw the current line,
leaving the current line at the top of the screen.
.TP
.B clear\-screen (C\-l)
Clear the screen,
then redraw the current line,
leaving the current line at the top of the screen.
With an argument, refresh the current line without clearing the
screen.
.TP
.B redraw\-current\-line
Refresh the current line.
.PD
.SS Commands for Manipulating the History
.PD 0
.TP
.B accept\-line (Newline, Return)
Accept the line regardless of where the cursor is.  If this line is
non-empty, add it to the history list according to the state of the
.SM
.B HISTCONTROL
variable.  If the line is a modified history
line, then restore the history line to its original state.
.TP
.B previous\-history (C\-p)
Fetch the previous command from the history list, moving back in
the list.
.TP
.B next\-history (C\-n)
Fetch the next command from the history list, moving forward in the
list.
.TP
.B beginning\-of\-history (M\-<)
Move to the first line in the history.
.TP
.B end\-of\-history (M\->)
Move to the end of the input history, i.e., the line currently being
entered.
.TP
.B operate\-and\-get\-next (C\-o)
Accept the current line for execution 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.
.TP
.B
fetch\-history
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.
.TP
.B reverse\-search\-history (C\-r)
Search backward starting at the current line and moving `up' through
the history as necessary.  This is an incremental search.
.TP
.B forward\-search\-history (C\-s)
Search forward starting at the current line and moving `down' through
the history as necessary.  This is an incremental search.
.TP
.B non\-incremental\-reverse\-search\-history (M\-p)
Search backward through the history starting at the current line
using a non-incremental search for a string supplied by the user.
.TP
.B non\-incremental\-forward\-search\-history (M\-n)
Search forward through the history using a non-incremental search for
a string supplied by the user.
.TP
.B history\-search\-forward
Search forward through the history for the string of characters
between the start of the current line and the point.
This is a non-incremental search.
.TP
.B history\-search\-backward
Search backward through the history for the string of characters
between the start of the current line and the point.
This is a non-incremental search.
.TP
.B history\-substring\-search\-backward
Search backward through the history for the string of characters
between the start of the current line and the current cursor
position (the \fIpoint\fP).
The search string may match anywhere in a history line.
This is a non-incremental search.
.TP
.B history\-substring\-search\-forward
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.
.TP
.B yank\-nth\-arg (M\-C\-y)
Insert the first argument to the previous command (usually
the second word on the previous line) at point.
With an argument
.IR n ,
insert the \fIn\fPth word from the previous command (the words
in the previous command begin with word 0).  A negative argument
inserts the \fIn\fPth word from the end of the previous command.
Once the argument \fIn\fP is computed, the argument is extracted
as if the "!\fIn\fP" history expansion had been specified.
.TP
.B
yank\-last\-arg (M\-.\^, M\-_\^)
Insert the last argument to the previous command (the last word of
the previous history entry).
With a numeric argument, behave exactly like \fByank\-nth\-arg\fP.
Successive calls to \fByank\-last\-arg\fP 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 word,
as if the "!$" history expansion had been specified.
.TP
.B shell\-expand\-line (M\-C\-e)
Expand the line as the shell does.  This
performs alias and history expansion as well as all of the shell
word expansions.  See
.SM
.B HISTORY EXPANSION
below for a description of history expansion.
.TP
.B history\-expand\-line (M\-^)
Perform history expansion on the current line.
See
.SM
.B HISTORY EXPANSION
below for a description of history expansion.
.TP
.B magic\-space
Perform history expansion on the current line and insert a space.
See
.SM
.B HISTORY EXPANSION
below for a description of history expansion.
.TP
.B alias\-expand\-line
Perform alias expansion on the current line.
See
.SM
.B ALIASES
above for a description of alias expansion.
.TP
.B history\-and\-alias\-expand\-line
Perform history and alias expansion on the current line.
.TP
.B insert\-last\-argument (M\-.\^, M\-_\^)
A synonym for \fByank\-last\-arg\fP.
.TP
.B edit\-and\-execute\-command (C\-x C\-e)
Invoke an editor on the current command line, and execute the result as shell
commands.
\fBBash\fP attempts to invoke
.SM
.BR $VISUAL ,
.SM
.BR $EDITOR ,
and \fIemacs\fP as the editor, in that order.
.PD
.SS Commands for Changing Text
.PD 0
.TP
.B \fIend\-of\-file\fP (usually C\-d)
The character indicating end-of-file as set, for example, by
.if t \f(CWstty\fP.
.if n ``stty''.
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
.SM
.BR EOF .
.TP
.B delete\-char (C\-d)
Delete the character at point.
If this function is bound to the
same character as the tty \fBEOF\fP character, as \fBC\-d\fP
commonly is, see above for the effects.
.TP
.B backward\-delete\-char (Rubout)
Delete the character behind the cursor.  When given a numeric argument,
save the deleted text on the kill ring.
.TP
.B forward\-backward\-delete\-char
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.
.TP
.B quoted\-insert (C\-q, C\-v)
Add the next character typed to the line verbatim.  This is
how to insert characters like \fBC\-q\fP, for example.
.TP
.B tab\-insert (C\-v TAB)
Insert a tab character.
.TP
.B self\-insert (a,\ b,\ A,\ 1,\ !,\ ...)
Insert the character typed.
.TP
.B transpose\-chars (C\-t)
Drag the character before point forward over the character at point,
moving point forward as well.
If point is at the end of the line, then this transposes
the two characters before point.
Negative arguments have no effect.
.TP
.B transpose\-words (M\-t)
Drag the word before point past the word after point,
moving point over that word as well.
If point is at the end of the line, this transposes
the last two words on the line.
.TP
.B upcase\-word (M\-u)
Uppercase the current (or following) word.  With a negative argument,
uppercase the previous word, but do not move point.
.TP
.B downcase\-word (M\-l)
Lowercase the current (or following) word.  With a negative argument,
lowercase the previous word, but do not move point.
.TP
.B capitalize\-word (M\-c)
Capitalize the current (or following) word.  With a negative argument,
capitalize the previous word, but do not move point.
.TP
.B overwrite\-mode
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
\fBemacs\fP mode; \fBvi\fP mode does overwrite differently.
Each call to \fIreadline()\fP starts in insert mode.
In overwrite mode, characters bound to \fBself\-insert\fP replace
the text at point rather than pushing the text to the right.
Characters bound to \fBbackward\-delete\-char\fP replace the character
before point with a space.  By default, this command is unbound.
.PD
.SS Killing and Yanking
.PD 0
.TP
.B kill\-line (C\-k)
Kill the text from point to the end of the line.
.TP
.B backward\-kill\-line (C\-x Rubout)
Kill backward to the beginning of the line.
.TP
.B unix\-line\-discard (C\-u)
Kill backward from point to the beginning of the line.
The killed text is saved on the kill-ring.
.\" There is no real difference between this and backward-kill-line
.TP
.B kill\-whole\-line
Kill all characters on the current line, no matter where point is.
.TP
.B kill\-word (M\-d)
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 those used by \fBforward\-word\fP.
.TP
.B backward\-kill\-word (M\-Rubout)
Kill the word behind point.
Word boundaries are the same as those used by \fBbackward\-word\fP.
.TP
.B shell\-kill\-word
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 those used by \fBshell\-forward\-word\fP.
.TP
.B shell\-backward\-kill\-word
Kill the word behind point.
Word boundaries are the same as those used by \fBshell\-backward\-word\fP.
.TP
.B unix\-word\-rubout (C\-w)
Kill the word behind point, using white space as a word boundary.
The killed text is saved on the kill-ring.
.TP
.B unix\-filename\-rubout
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.
.TP
.B delete\-horizontal\-space (M\-\e)
Delete all spaces and tabs around point.
.TP
.B kill\-region
Kill the text in the current region.
.TP
.B copy\-region\-as\-kill
Copy the text in the region to the kill buffer.
.TP
.B copy\-backward\-word
Copy the word before point to the kill buffer.
The word boundaries are the same as \fBbackward\-word\fP.
.TP
.B copy\-forward\-word
Copy the word following point to the kill buffer.
The word boundaries are the same as \fBforward\-word\fP.
.TP
.B yank (C\-y)
Yank the top of the kill ring into the buffer at point.
.TP
.B yank\-pop (M\-y)
Rotate the kill ring, and yank the new top.  Only works following
.B yank
or
.BR yank\-pop .
.PD
.SS Numeric Arguments
.PD 0
.TP
.B digit\-argument (M\-0, M\-1, ..., M\-\-)
Add this digit to the argument already accumulating, or start a new
argument.  M\-\- starts a negative argument.
.TP
.B universal\-argument
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
.B universal\-argument
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.
.PD
.SS Completing
.PD 0
.TP
.B complete (TAB)
Attempt to perform completion on the text before point.
.B Bash
attempts completion treating the text as a variable (if the
text begins with \fB$\fP), username (if the text begins with
\fB~\fP), hostname (if the text begins with \fB@\fP), or
command (including aliases and functions) in turn.  If none
of these produces a match, filename completion is attempted.
.TP
.B possible\-completions (M\-?)
List the possible completions of the text before point.
.TP
.B insert\-completions (M\-*)
Insert all completions of the text before point
that would have been generated by
\fBpossible\-completions\fP.
.TP
.B menu\-complete
Similar to \fBcomplete\fP, but replaces the word to be completed
with a single match from the list of possible completions.
Repeated execution of \fBmenu\-complete\fP 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 \fBbell\-style\fP)
and the original text is restored.
An argument of \fIn\fP moves \fIn\fP 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 \fBTAB\fP, but is unbound
by default.
.TP
.B menu\-complete\-backward
Identical to \fBmenu\-complete\fP, but moves backward through the list
of possible completions, as if \fBmenu\-complete\fP had been given a
negative argument.  This command is unbound by default.
.TP
.B delete\-char\-or\-list
Deletes the character under the cursor if not at the beginning or
end of the line (like \fBdelete\-char\fP).
If at the end of the line, behaves identically to
\fBpossible\-completions\fP.
This command is unbound by default.
.TP
.B complete\-filename (M\-/)
Attempt filename completion on the text before point.
.TP
.B possible\-filename\-completions (C\-x /)
List the possible completions of the text before point,
treating it as a filename.
.TP
.B complete\-username (M\-~)
Attempt completion on the text before point, treating
it as a username.
.TP
.B possible\-username\-completions (C\-x ~)
List the possible completions of the text before point,
treating it as a username.
.TP
.B complete\-variable (M\-$)
Attempt completion on the text before point, treating
it as a shell variable.
.TP
.B possible\-variable\-completions (C\-x $)
List the possible completions of the text before point,
treating it as a shell variable.
.TP
.B complete\-hostname (M\-@)
Attempt completion on the text before point, treating
it as a hostname.
.TP
.B possible\-hostname\-completions (C\-x @)
List the possible completions of the text before point,
treating it as a hostname.
.TP
.B complete\-command (M\-!)
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.
.TP
.B possible\-command\-completions (C\-x !)
List the possible completions of the text before point,
treating it as a command name.
.TP
.B dynamic\-complete\-history (M\-TAB)
Attempt completion on the text before point, comparing
the text against lines from the history list for possible
completion matches.
.TP
.B dabbrev\-expand
Attempt menu completion on the text before point, comparing
the text against lines from the history list for possible
completion matches.
.TP
.B complete\-into\-braces (M\-{)
Perform filename completion and insert the list of possible completions
enclosed within braces so the list is available to the shell (see
.B Brace Expansion
above).
.PD
.SS Keyboard Macros
.PD 0
.TP
.B start\-kbd\-macro (C\-x (\^)
Begin saving the characters typed into the current keyboard macro.
.TP
.B end\-kbd\-macro (C\-x )\^)
Stop saving the characters typed into the current keyboard macro
and store the definition.
.TP
.B call\-last\-kbd\-macro (C\-x e)
Re-execute the last keyboard macro defined, by making the characters
in the macro appear as if typed at the keyboard.
.TP
.B print\-last\-kbd\-macro ()
Print the last keyboard macro defined in a format suitable for the
\fIinputrc\fP file.
.PD
.SS Miscellaneous
.PD 0
.TP
.B re\-read\-init\-file (C\-x C\-r)
Read in the contents of the \fIinputrc\fP file, and incorporate
any bindings or variable assignments found there.
.TP
.B abort (C\-g)
Abort the current editing command and
ring the terminal's bell (subject to the setting of
.BR bell\-style ).
.TP
.B do\-lowercase\-version (M\-A, M\-B, M\-\fIx\fP, ...)
If the metafied character \fIx\fP is uppercase, run the command
that is bound to the corresponding metafied lowercase character.
The behavior is undefined if \fIx\fP is already lowercase.
.TP
.B prefix\-meta (ESC)
Metafy the next character typed.
.SM
.B ESC
.B f
is equivalent to
.BR Meta\-f .
.TP
.B undo (C\-_, C\-x C\-u)
Incremental undo, separately remembered for each line.
.TP
.B revert\-line (M\-r)
Undo all changes made to this line.  This is like executing the
.B undo
command enough times to return the line to its initial state.
.TP
.B tilde\-expand (M\-&)
Perform tilde expansion on the current word.
.TP
.B set\-mark (C\-@, M\-<space>)
Set the mark to the point.  If a
numeric argument is supplied, the mark is set to that position.
.TP
.B exchange\-point\-and\-mark (C\-x C\-x)
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.
.TP
.B character\-search (C\-])
A character is read and point is moved to the next occurrence of that
character.  A negative argument searches for previous occurrences.
.TP
.B character\-search\-backward (M\-C\-])
A character is read and point is moved to the previous occurrence of that
character.  A negative argument searches for subsequent occurrences.
.TP
.B skip\-csi\-sequence
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 "\e[", 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\-[.
.TP
.B insert\-comment (M\-#)
Without a numeric argument, the value of the readline
.B comment\-begin
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 \fBcomment\-begin\fP, the value is inserted, otherwise
the characters in \fBcomment\-begin\fP 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
\fBcomment\-begin\fP 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.
.TP
.B spell\-correct\-word (C\-x s)
Perform spelling correction on the current word, treating it as a directory
or filename, in the same way as the \fBcdspell\fP shell option.
Word boundaries are the same as those used by \fBshell\-forward\-word\fP.
.TP
.B glob\-complete\-word (M\-g)
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 filenames for possible completions.
.TP
.B glob\-expand\-word (C\-x *)
The word before point is treated as a pattern for pathname expansion,
and the list of matching filenames is inserted, replacing the word.
If a numeric argument is supplied, an asterisk is appended before
pathname expansion.
.TP
.B glob\-list\-expansions (C\-x g)
The list of expansions that would have been generated by
.B glob\-expand\-word
is displayed, and the line is redrawn.
If a numeric argument is supplied, an asterisk is appended before
pathname expansion.
.TP
.B dump\-functions
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 \fIinputrc\fP file.
.TP
.B dump\-variables
Print all of the settable readline 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 \fIinputrc\fP file.
.TP
.B dump\-macros
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 \fIinputrc\fP file.
.TP
.B display\-shell\-version (C\-x C\-v)
Display version information about the current instance of
.BR bash .
.PD
.SS Programmable Completion
When word completion is attempted for an argument to a command for
which a completion specification (a \fIcompspec\fP) has been defined
using the \fBcomplete\fP builtin (see
.SM
.B "SHELL BUILTIN COMMANDS"
below), the programmable completion facilities are invoked.
.PP
First, the command name is identified.
If the command word is the empty string (completion attempted at the
beginning of an empty line), any compspec defined with
the \fB\-E\fP option to \fBcomplete\fP is used.
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 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 \fB\-D\fP option to \fBcomplete\fP is used as the default.
If there is no default compspec, \fBbash\fP 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.
.PP
Once a compspec has been found, it is used to generate the list of
matching words.
If a compspec is not found, the default \fBbash\fP completion as
described above under \fBCompleting\fP is performed.
.PP
First, the actions specified by the compspec are used.
Only matches which are prefixed by the word being completed are
returned.
When the
.B \-f
or
.B \-d
option is used for filename or directory name completion, the shell
variable
.SM
.B FIGNORE
is used to filter the matches.
.PP
Any completions specified by a pathname expansion pattern to the
\fB\-G\fP option are generated next.
The words generated by the pattern need not match the word
being completed.
The
.SM
.B GLOBIGNORE
shell variable is not used to filter the matches, but the
.SM
.B FIGNORE
variable is used.
.PP
Next, the string specified as the argument to the \fB\-W\fP option
is considered.
The string is first split using the characters in the
.SM
.B IFS
special variable as delimiters.
Shell quoting is honored.
Each word is then expanded using
brace expansion, tilde expansion, parameter and variable expansion,
command substitution, and arithmetic expansion,
as described above under
.SM
.BR EXPANSION .
The results are split using the rules described above under
\fBWord Splitting\fP.
The results of the expansion are prefix-matched against the word being
completed, and the matching words become the possible completions.
.PP
After these matches have been generated, any shell function or command
specified with the \fB\-F\fP and \fB\-C\fP options is invoked.
When the command or function is invoked, the
.SM
.BR COMP_LINE ,
.SM
.BR COMP_POINT ,
.SM
.BR COMP_KEY ,
and
.SM
.B COMP_TYPE
variables are assigned values as described above under
\fBShell Variables\fP.
If a shell function is being invoked, the
.SM
.B COMP_WORDS
and
.SM
.B COMP_CWORD
variables are also set.
When the function or command is invoked,
the first argument (\fB$1\fP) is the name of the command whose arguments are
being completed,
the second argument (\fB$2\fP) is the word being completed,
and the third argument (\fB$3\fP) 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.
.PP
Any function specified with \fB\-F\fP is invoked first.
The function may use any of the shell facilities, including the
\fBcompgen\fP builtin described below, to generate the matches.
It must put the possible completions in the
.SM
.B COMPREPLY
array variable, one per array element.
.PP
Next, any command specified with the \fB\-C\fP 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.
.PP
After all of the possible completions are generated, any filter
specified with the \fB\-X\fP option is applied to the list.
The filter is a pattern as used for pathname expansion; a \fB&\fP
in the pattern is replaced with the text of the word being completed.
A literal \fB&\fP 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 \fB!\fP negates the pattern; in this case any completion
not matching the pattern will be removed.
If the
.B nocasematch
shell option is enabled, the match is performed without regard to the case
of alphabetic characters.
.PP
Finally, any prefix and suffix specified with the \fB\-P\fP and \fB\-S\fP
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.
.PP
If the previously-applied actions do not generate any matches, and the
\fB\-o dirnames\fP option was supplied to \fBcomplete\fP when the
compspec was defined, directory name completion is attempted.
.PP
If the \fB\-o plusdirs\fP option was supplied to \fBcomplete\fP when the
compspec was defined, directory name completion is attempted and any
matches are added to the results of the other actions.
.PP
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 \fBbash\fP completions are not attempted, and the readline
default of filename completion is disabled.
If the \fB\-o bashdefault\fP option was supplied to \fBcomplete\fP when
the compspec was defined, the \fBbash\fP default completions are attempted
if the compspec generates no matches.
If the \fB\-o default\fP option was supplied to \fBcomplete\fP when the
compspec was defined, readline's default completion will be performed
if the compspec (and, if attempted, the default \fBbash\fP completions)
generate no matches.
.PP
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 \fBmark\-directories\fP readline variable, regardless
of the setting of the \fBmark-symlinked\-directories\fP readline variable.
.PP
There is some support for dynamically modifying completions.  This is
most useful when used in combination with a default completion specified
with \fBcomplete \-D\fP.
It'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.
.PP
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:
.PP
\f(CW_completion_loader()
.br
{
.br
	. "/etc/bash_completion.d/$1.sh" >/dev/null 2>&1 && return 124
.br
}
.br
complete -D -F _completion_loader -o bashdefault -o default
.br
\fP
.SH HISTORY
When the
.B \-o history
option to the
.B set
builtin is enabled, the shell provides access to the
\fIcommand history\fP,
the list of commands previously typed.
The value of the
.SM
.B HISTSIZE
variable is used as the
number of commands to save in a history list.
The text of the last
.SM
.B HISTSIZE
commands (default 500) is saved.  The shell
stores each command in the history list prior to parameter and
variable expansion (see
.SM
.B EXPANSION
above) but after history expansion is performed, subject to the
values of the shell variables
.SM
.B HISTIGNORE
and
.SM
.BR HISTCONTROL .
.PP
On startup, the history is initialized from the file named by
the variable
.SM
.B HISTFILE
(default \fI~/.bash_history\fP).
The file named by the value of
.SM
.B HISTFILE
is truncated, if necessary, to contain no more than
the number of lines specified by the value of
.SM
.BR HISTFILESIZE .
If \fBHISTFILESIZE\fP is unset, or set to null, a non-numeric value,
or a numeric value less than zero, the history file is not truncated.
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 line.
These timestamps are optionally displayed depending on the value of the
.SM
.B HISTTIMEFORMAT
variable.
When a shell with history enabled exits, the last
.SM
.B $HISTSIZE
lines are copied from the history list to
.SM
.BR $HISTFILE .
If the
.B histappend
shell option is enabled
(see the description of
.B shopt
under
.SM
.B "SHELL BUILTIN COMMANDS"
below), the lines are appended to the history file,
otherwise the history file is overwritten.
If
.SM
.B HISTFILE
is unset, or if the history file is unwritable, the history is
not saved.
If the
.SM
.B HISTTIMEFORMAT
variable is set, time stamps are written to the history file, marked
with the history comment character, so
they may be preserved across shell sessions.
This uses the history comment character to distinguish timestamps from
other history lines.
After saving the history, the history file is truncated
to contain no more than
.SM
.B HISTFILESIZE
lines.  If
.SM
.B HISTFILESIZE
is unset, or set to null, a non-numeric value,
or a numeric value less than zero, the history file is not truncated.
.PP
The builtin command
.B fc
(see
.SM
.B SHELL BUILTIN COMMANDS
below) may be used to list or edit and re-execute a portion of
the history list.
The
.B history
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.
.PP
The shell allows control over which commands are saved on the history
list.  The
.SM
.B HISTCONTROL
and
.SM
.B HISTIGNORE
variables may be set to cause the shell to save only a subset of the
commands entered.
The
.B cmdhist
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
.B lithist
shell option causes the shell to save the command with embedded newlines
instead of semicolons.  See the description of the
.B shopt
builtin below under
.SM
.B "SHELL BUILTIN COMMANDS"
for information on setting and unsetting shell options.
.SH "HISTORY EXPANSION"
The shell supports a history expansion feature that
is similar to the history expansion in
.BR csh .
This section describes what syntax features are available.  This
feature is enabled by default for interactive shells, and can be
disabled using the
.B +H
option to the
.B set
builtin command (see
.SM
.B SHELL BUILTIN COMMANDS
below).  Non-interactive shells do not perform history expansion
by default.
.PP
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.
.PP
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 without taking quoting on previous lines into
account.
It takes place in two parts.
The first is to determine which line from the history list
to use during substitution.
The second is to select portions of that line for inclusion into
the current one.
The line selected from the history is the \fIevent\fP,
and the portions of that line that are acted upon are \fIwords\fP.
Various \fImodifiers\fP are available to manipulate the selected words.
The line is broken into words in the same fashion as when reading input,
so that several \fImetacharacter\fP-separated words surrounded by
quotes are considered one word.
History expansions are introduced by the appearance of the
history expansion character, which is \^\fB!\fP\^ by default.
Only backslash (\^\fB\e\fP\^) and single quotes can quote
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.
.PP
Several characters inhibit history expansion if found immediately
following the history expansion character, even if it is unquoted:
space, tab, newline, carriage return, and \fB=\fP.
If the \fBextglob\fP shell option is enabled, \fB(\fP will also
inhibit expansion.
.PP
Several shell options settable with the
.B shopt
builtin may be used to tailor the behavior of history expansion.
If the
.B histverify
shell option is enabled (see the description of the
.B shopt
builtin below), and
.B readline
is being used, history substitutions are not immediately passed to
the shell parser.
Instead, the expanded line is reloaded into the
.B readline
editing buffer for further modification.
If
.B readline
is being used, and the
.B histreedit
shell option is enabled, a failed history substitution will be reloaded
into the
.B readline
editing buffer for correction.
The
.B \-p
option to the
.B history
builtin command may be used to see what a history expansion will
do before using it.
The
.B \-s
option to the
.B history
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.
.PP
The shell allows control of the various characters used by the
history expansion mechanism (see the description of
.B histchars
above under
.BR "Shell Variables" ).
The shell uses
the history comment character to mark history timestamps when
writing the history file.
.SS Event Designators
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.
.PP
.PD 0
.TP
.B !
Start a history substitution, except when followed by a
.BR blank ,
newline, carriage return, =
or ( (when the \fBextglob\fP shell option is enabled using
the \fBshopt\fP builtin).
.TP
.B !\fIn\fR
Refer to command line
.IR n .
.TP
.B !\-\fIn\fR
Refer to the current command minus
.IR n .
.TP
.B !!
Refer to the previous command.  This is a synonym for `!\-1'.
.TP
.B !\fIstring\fR
Refer to the most recent command preceding the current position in the
history list starting with
.IR string .
.TP
.B !?\fIstring\fR\fB[?]\fR
Refer to the most recent command preceding the current position in the
history list containing
.IR string .
The trailing \fB?\fP may be omitted if
.I string
is followed immediately by a newline.
If \fIstring\fP is missing, the string from the most recent search is used;
it is an error if there is no previous search string.
.TP
.B \d\s+2^\s-2\u\fIstring1\fP\d\s+2^\s-2\u\fIstring2\fP\d\s+2^\s-2\u
Quick substitution.  Repeat the previous command, replacing
.I string1
with
.IR string2 .
Equivalent to
``!!:s\d\s+2^\s-2\u\fIstring1\fP\d\s+2^\s-2\u\fIstring2\fP\d\s+2^\s-2\u''
(see \fBModifiers\fP below).
.TP
.B !#
The entire command line typed so far.
.PD
.SS Word Designators
Word designators are used to select desired words from the event.
A
.B :
separates the event specification from the word designator.
It may be omitted if the word designator begins with a
.BR ^ ,
.BR $ ,
.BR * ,
.BR \- ,
or
.BR % .
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.
.PP
.PD 0
.TP
.B 0 (zero)
The zeroth word.  For the shell, this is the command
word.
.TP
.I n
The \fIn\fRth word.
.TP
.B ^
The first argument.  That is, word 1.
.TP
.B $
The last word.  This is usually the last argument, but will expand to the
zeroth word if there is only one word in the line.
.TP
.B %
The first word matched by the most recent `?\fIstring\fR?' search,
if the search string begins with a character that is part of a word.
.TP
.I x\fB\-\fPy
A range of words; `\-\fIy\fR' abbreviates `0\-\fIy\fR'.
.TP
.B *
All of the words but the zeroth.  This is a synonym
for `\fI1\-$\fP'.  It is not an error to use
.B *
if there is just one
word in the event; the empty string is returned in that case.
.TP
.B x*
Abbreviates \fIx\-$\fP.
.TP
.B x\-
Abbreviates \fIx\-$\fP like \fBx*\fP, but omits the last word.
If \fBx\fP is missing, it defaults to 0.
.PD
.PP
If a word designator is supplied without an event specification, the
previous command is used as the event.
.SS Modifiers
After the optional word designator, there may appear a sequence of
one or more of the following modifiers, each preceded by a `:'.
These modify, or edit, the word or words selected from the history event.
.PP
.PD 0
.TP
.B h
Remove a trailing filename component, leaving only the head.
.TP
.B t
Remove all leading filename components, leaving the tail.
.TP
.B r
Remove a trailing suffix of the form \fI.xxx\fP, leaving the
basename.
.TP
.B e
Remove all but the trailing suffix.
.TP
.B p
Print the new command but do not execute it.
.TP
.B q
Quote the substituted words, escaping further substitutions.
.TP
.B x
Quote the substituted words as with
.BR q ,
but break into words at
.B blanks
and newlines.
The \fBq\fP and \fBx\fP modifiers are mutually exclusive; the last one
supplied is used.
.TP
.B s/\fIold\fP/\fInew\fP/
Substitute
.I new
for the first occurrence of
.I old
in the event line.
Any character may be used as the delimiter in place of /.
The final delimiter is optional if it is the last character of the
event line.
The delimiter may be quoted in
.I old
and
.I new
with a single backslash.  If & appears in
.IR new ,
it is replaced by
.IR old .
A single backslash will quote the &.
If
.I old
is null, it is set to the last
.I old
substituted, or, if no previous history substitutions took place,
the last
.I string
in a
.B !?\fIstring\fR\fB[?]\fR
search.
If
.I new
is null, each matching
.I old
is deleted.
.TP
.B &
Repeat the previous substitution.
.TP
.B g
Cause changes to be applied over the entire event line.  This is
used in conjunction with `\fB:s\fP' (e.g., `\fB:gs/\fIold\fP/\fInew\fP/\fR')
or `\fB:&\fP'.  If used with
`\fB:s\fP', any delimiter can be used
in place of /, and the final delimiter is optional
if it is the last character of the event line.
An \fBa\fP may be used as a synonym for \fBg\fP.
.TP
.B G
Apply the following `\fBs\fP' or `\fB&\fP' modifier once to each word
in the event line.
.PD
.SH "SHELL BUILTIN COMMANDS"
.\" start of bash_builtins
.zZ
.PP
Unless otherwise noted, each builtin command documented in this
section as accepting options preceded by
.B \-
accepts
.B \-\-
to signify the end of the options.
The \fB:\fP, \fBtrue\fP, \fBfalse\fP, and \fBtest\fP/\fB[\fP builtins
do not accept options and do not treat \fB\-\-\fP specially.
The \fBexit\fP, \fBlogout\fP, \fBreturn\fP,
\fBbreak\fP, \fBcontinue\fP, \fBlet\fP,
and \fBshift\fP builtins accept and process arguments beginning with
\fB\-\fP without requiring \fB\-\-\fP.
Other builtins that accept arguments but are not specified as accepting
options interpret arguments beginning with \fB\-\fP as invalid options and
require \fB\-\-\fP to prevent this interpretation.
.sp .5
.PD 0
.TP
\fB:\fP [\fIarguments\fP]
.PD
No effect; the command does nothing beyond expanding
.I arguments
and performing any specified
redirections.
The return status is zero.
.TP
\fB .\| \fP \fIfilename\fP [\fIarguments\fP]
.PD 0
.TP
\fBsource\fP \fIfilename\fP [\fIarguments\fP]
.PD
Read and execute commands from
.I filename
in the current
shell environment and return the exit status of the last command
executed from
.IR filename .
If
.I filename
does not contain a slash, filenames in
.SM
.B PATH
are used to find the directory containing
.IR filename ,
but \fIfilename\fP does not need to be executable.
The file searched for in
.SM
.B PATH
need not be executable.
When \fBbash\fP is not in \fIposix mode\fP, it searches
the current directory if no file is found in
.SM
.BR PATH .
If the
.B sourcepath
option to the
.B shopt
builtin command is turned off, the
.SM
.B PATH
is not searched.
If any \fIarguments\fP are supplied, they become the positional
parameters when \fIfilename\fP is executed.  Otherwise the positional
parameters are unchanged.
If the \fB\-T\fP option is enabled, \fB.\fP inherits any trap on
\fBDEBUG\fP; if it is not, any \fBDEBUG\fP trap string is saved and
restored around the call to \fB.\fP, and \fB.\fP unsets the
\fBDEBUG\fP trap while it executes.
If \fB\-T\fP is not set, and the sourced file changes
the \fBDEBUG\fP trap, the new value is retained when \fB.\fP completes.
The return status is the status of the last command exited within
the script (0 if no commands are executed), and false if
.I filename
is not found or cannot be read.
.TP
\fBalias\fP [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP] ...]
\fBAlias\fP with no arguments or with the
.B \-p
option prints the list of aliases in the form
\fBalias\fP \fIname\fP=\fIvalue\fP on standard output.
When arguments are supplied, an alias is defined for
each \fIname\fP whose \fIvalue\fP is given.
A trailing space in \fIvalue\fP causes the next word to be
checked for alias substitution when the alias is expanded.
For each \fIname\fP in the argument list for which no \fIvalue\fP
is supplied, the name and value of the alias is printed.
\fBAlias\fP returns true unless a \fIname\fP is given for which
no alias has been defined.
.TP
\fBbg\fP [\fIjobspec\fP ...]
Resume each suspended job \fIjobspec\fP in the background, as if it
had been started with
.BR & .
If
.I jobspec
is not present, the shell's notion of the \fIcurrent job\fP is used.
.B bg
.I jobspec
returns 0 unless run when job control is disabled or, when run with
job control enabled, any specified \fIjobspec\fP was not found
or was started without job control.
.TP
\fBbind\fP [\fB\-m\fP \fIkeymap\fP] [\fB\-lpsvPSVX\fP]
.PD 0
.TP
\fBbind\fP [\fB\-m\fP \fIkeymap\fP] [\fB\-q\fP \fIfunction\fP] [\fB\-u\fP \fIfunction\fP] [\fB\-r\fP \fIkeyseq\fP]
.TP
\fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fB\-f\fP \fIfilename\fP
.TP
\fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fB\-x\fP \fIkeyseq\fP:\fIshell\-command\fP
.TP
\fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fIkeyseq\fP:\fIfunction\-name\fP
.TP
\fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fIkeyseq\fP:\fIreadline\-command\fP
.TP
\fBbind\fP \fIreadline-command-line\fP
.PD
Display current
.B readline
key and function bindings, bind a key sequence to a
.B readline
function or macro, or set a
.B readline
variable.
Each non-option argument is a command as it would appear in a
.B readline
initialization file such as
.IR .inputrc ,
but each binding or command must be passed as a separate argument;
e.g., '"\eC\-x\eC\-r": re\-read\-init\-file'.
Options, if supplied, have the following meanings:
.RS
.PD 0
.TP
.B \-m \fIkeymap\fP
Use
.I keymap
as the keymap to be affected by the subsequent bindings.
Acceptable
.I keymap
names are
\fIemacs, emacs\-standard, emacs\-meta, emacs\-ctlx, vi,
vi\-move, vi\-command\fP, and
.IR vi\-insert .
\fIvi\fP is equivalent to \fIvi\-command\fP (\fIvi\-move\fP is also
a synonym); \fIemacs\fP is
equivalent to \fIemacs\-standard\fP.
.TP
.B \-l
List the names of all \fBreadline\fP functions.
.TP
.B \-p
Display \fBreadline\fP function names and bindings in such a way
that they can be re-read.
.TP
.B \-P
List current \fBreadline\fP function names and bindings.
.TP
.B \-s
Display \fBreadline\fP key sequences bound to macros and the strings
they output in such a way that they can be re-read.
.TP
.B \-S
Display \fBreadline\fP key sequences bound to macros and the strings
they output.
.TP
.B \-v
Display \fBreadline\fP variable names and values in such a way that they
can be re-read.
.TP
.B \-V
List current \fBreadline\fP variable names and values.
.TP
.B \-f \fIfilename\fP
Read key bindings from \fIfilename\fP.
.TP
.B \-q \fIfunction\fP
Query about which keys invoke the named \fIfunction\fP.
.TP
.B \-u \fIfunction\fP
Unbind all keys bound to the named \fIfunction\fP.
.TP
.B \-r \fIkeyseq\fP
Remove any current binding for \fIkeyseq\fP.
.TP
.B \-x \fIkeyseq\fP:\fIshell\-command\fP
Cause \fIshell\-command\fP to be executed whenever \fIkeyseq\fP is
entered.
When \fIshell\-command\fP is executed, the shell sets the
.SM
.B READLINE_LINE
variable to the contents of the \fBreadline\fP line buffer and the
.SM
.B READLINE_POINT
and
.SM
.B READLINE_MARK
variables to the current location of the insertion point and the saved
insertion point (the mark), respectively.
The shell assigns any numeric argument the user supplied to the     
.SM
.B READLINE_ARGUMENT
variable.
If there was no argument, that variable is not set.
If the executed command changes the value of any of
.SM
.BR READLINE_LINE ,
.SM
.BR READLINE_POINT ,
or
.SM
.BR READLINE_MARK ,
those new values will be reflected in the editing state.
.TP
.B \-X
List all key sequences bound to shell commands and the associated commands
in a format that can be reused as input.
.PD
.PP
The return value is 0 unless an unrecognized option is given or an
error occurred.
.RE
.TP
\fBbreak\fP [\fIn\fP]
Exit from within a
.BR for ,
.BR while ,
.BR until ,
or
.B select
loop.  If \fIn\fP is specified, break \fIn\fP levels.
.I n
must be \(>= 1.  If
.I n
is greater than the number of enclosing loops, all enclosing loops
are exited.
The return value is 0 unless \fIn\fP is not greater than or equal to 1.
.TP
\fBbuiltin\fP \fIshell\-builtin\fP [\fIarguments\fP]
Execute the specified shell builtin, passing it
.IR arguments ,
and return its exit status.
This is useful when defining a
function whose name is the same as a shell builtin,
retaining the functionality of the builtin within the function.
The \fBcd\fP builtin is commonly redefined this way.
The return status is false if
.I shell\-builtin
is not a shell builtin command.
.TP
\fBcaller\fP [\fIexpr\fP]
Returns the context of any active subroutine call (a shell function or
a script executed with the \fB.\fP or \fBsource\fP builtins).
Without \fIexpr\fP, \fBcaller\fP displays the line number and source
filename of the current subroutine call.
If a non-negative integer is supplied as \fIexpr\fP, \fBcaller\fP
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.
The return value is 0 unless the shell is not executing a subroutine
call or \fIexpr\fP does not correspond to a valid position in the
call stack.
.TP
\fBcd\fP [\fB\-L\fP|[\fB\-P\fP [\fB\-e\fP]] [\-@]] [\fIdir\fP]
Change the current directory to \fIdir\fP.
if \fIdir\fP is not supplied, the value of the
.SM
.B HOME
shell variable is the default.
The variable
.SM
.B CDPATH
defines the search path for the directory containing
.IR dir :
each directory name in
.SM
.B CDPATH
is searched for \fIdir\fP.
Alternative directory names in
.SM
.B CDPATH
are separated by a colon (:).  A null directory name in
.SM
.B CDPATH
is the same as the current directory, i.e., ``\fB.\fP''.  If
.I dir
begins with a slash (/),
then
.SM
.B CDPATH
is not used.  The
.B \-P
option causes \fBcd\fP to use the physical directory structure
by resolving symbolic links while traversing \fIdir\fP and
before processing instances of \fI..\fP in \fIdir\fP (see also the
.B \-P
option to the
.B set
builtin command); the
.B \-L
option forces symbolic links to be followed by resolving the link
after processing instances of \fI..\fP in \fIdir\fP.
If \fI..\fP appears in \fIdir\fP, it is processed by removing the
immediately previous pathname component from \fIdir\fP, back to a slash
or the beginning of \fIdir\fP.
If the
.B \-e
option is supplied with
.BR \-P ,
and the current working directory cannot be successfully determined
after a successful directory change, \fBcd\fP will return an unsuccessful
status.
On systems that support it, the \fB\-@\fP option presents the extended
attributes associated with a file as a directory.
An argument of
.B \-
is converted to
.SM
.B $OLDPWD
before the directory change is attempted.
If a non-empty directory name from
.SM
.B CDPATH
is used, or if
\fB\-\fP is the first argument, and the directory change is
successful, the absolute pathname of the new working directory is
written to the standard output.
If the directory change is successful, \fBcd\fP sets the value of the
\fBPWD\fP environment variable to the new directory name, and sets the
\fBOLDPWD\fP environment variable to the value of the current working
directory before the change.
The return value is true if the directory was successfully changed;
false otherwise.
.TP
\fBcommand\fP [\fB\-pVv\fP] \fIcommand\fP [\fIarg\fP ...]
Run
.I command
with
.I args
suppressing the normal shell function lookup.
Only builtin commands or commands found in the
.SM
.B PATH
are executed.  If the
.B \-p
option is given, the search for
.I command
is performed using a default value for
.SM
.B PATH
that is guaranteed to find all of the standard utilities.
If either the
.B \-V
or
.B \-v
option is supplied, a description of
.I command
is printed.  The
.B \-v
option causes a single word indicating the command or filename
used to invoke
.I command
to be displayed; the
.B \-V
option produces a more verbose description.
If the
.B \-V
or
.B \-v
option is supplied, the exit status is 0 if
.I command
was found, and 1 if not.  If neither option is supplied and
an error occurred or
.I command
cannot be found, the exit status is 127.  Otherwise, the exit status of the
.B command
builtin is the exit status of
.IR command .
.TP
\fBcompgen\fP [\fIoption\fP] [\fIword\fP]
Generate possible completion matches for \fIword\fP according to
the \fIoption\fPs, which may be any option accepted by the
.B complete
builtin with the exception of \fB\-p\fP and \fB\-r\fP, and write
the matches to the standard output.
When using the \fB\-F\fP or \fB\-C\fP options, the various shell variables
set by the programmable completion facilities, while available, will not
have useful values.
.sp 1
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 \fIword\fP is specified, only those completions matching \fIword\fP
will be displayed.
.sp 1
The return value is true unless an invalid option is supplied, or no
matches were generated.
.TP
\fBcomplete\fP [\fB\-abcdefgjksuv\fP] [\fB\-o\fP \fIcomp-option\fP] [\fB\-DEI\fP] [\fB\-A\fP \fIaction\fP] [\fB\-G\fP \fIglobpat\fP] [\fB\-W\fP \fIwordlist\fP]
.br
[\fB\-F\fP \fIfunction\fP] [\fB\-C\fP \fIcommand\fP] [\fB\-X\fP \fIfilterpat\fP] [\fB\-P\fP \fIprefix\fP] [\fB\-S\fP \fIsuffix\fP] \fIname\fP [\fIname ...\fP]
.PD 0
.TP
\fBcomplete\fP \fB\-pr\fP [\fB\-DEI\fP] [\fIname\fP ...]
.PD
Specify how arguments to each \fIname\fP should be completed.
If the \fB\-p\fP 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 \fB\-r\fP option removes a completion specification for
each \fIname\fP, or, if no \fIname\fPs are supplied, all
completion specifications.
The \fB\-D\fP option indicates that other supplied options and actions should
apply to the ``default'' command completion; that is, completion attempted
on a command for which no completion has previously been defined.
The \fB\-E\fP option indicates that other supplied options and actions should
apply to ``empty'' command completion; that is, completion attempted on a
blank line.
The \fB\-I\fP 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 \fB;\fP or \fB|\fP, which is usually command
name completion.
If multiple options are supplied, the \fB\-D\fP option takes precedence
over \fB\-E\fP, and both take precedence over \fB\-I\fP.
If any of \fB\-D\fP, \fB\-E\fP, or \fB\-I\fP are supplied, any other
\fIname\fP arguments are ignored; these completions only apply to the case
specified by the option.
.sp 1
The process of applying these completion specifications when word completion
is attempted is described
.ie \n(zZ=1 in \fIbash(1)\fP.
.el above under \fBProgrammable Completion\fP.
.sp 1
Other options, if specified, have the following meanings.
The arguments to the \fB\-G\fP, \fB\-W\fP, and \fB\-X\fP options
(and, if necessary, the \fB\-P\fP and \fB\-S\fP options)
should be quoted to protect them from expansion before the
.B complete
builtin is invoked.
.RS
.PD 0
.TP 8
\fB\-o\fP \fIcomp-option\fP
The \fIcomp-option\fP controls several aspects of the compspec's behavior
beyond the simple generation of completions.
\fIcomp-option\fP may be one of:
.RS
.TP 8
.B bashdefault
Perform the rest of the default \fBbash\fP completions if the compspec
generates no matches.
.TP 8
.B default
Use readline's default filename completion if the compspec generates
no matches.
.TP 8
.B dirnames
Perform directory name completion if the compspec generates no matches.
.TP 8
.B filenames
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).
Intended to be used with shell functions.
.TP 8
.B noquote
Tell readline not to quote the completed words if they are filenames
(quoting filenames is the default).
.TP 8
.B nosort
Tell readline not to sort the list of possible completions alphabetically.
.TP 8
.B nospace
Tell readline not to append a space (the default) to words completed at
the end of the line.
.TP 8
.B plusdirs
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.
.RE
.TP 8
\fB\-A\fP \fIaction\fP
The \fIaction\fP may be one of the following to generate a list of possible
completions:
.RS
.TP 8
.B alias
Alias names.  May also be specified as \fB\-a\fP.
.TP 8
.B arrayvar
Array variable names.
.TP 8
.B binding
\fBReadline\fP key binding names.
.TP 8
.B builtin
Names of shell builtin commands.  May also be specified as \fB\-b\fP.
.TP 8
.B command
Command names.  May also be specified as \fB\-c\fP.
.TP 8
.B directory
Directory names.  May also be specified as \fB\-d\fP.
.TP 8
.B disabled
Names of disabled shell builtins.
.TP 8
.B enabled
Names of enabled shell builtins.
.TP 8
.B export
Names of exported shell variables.  May also be specified as \fB\-e\fP.
.TP 8
.B file
File names.  May also be specified as \fB\-f\fP.
.TP 8
.B function
Names of shell functions.
.TP 8
.B group
Group names.  May also be specified as \fB\-g\fP.
.TP 8
.B helptopic
Help topics as accepted by the \fBhelp\fP builtin.
.TP 8
.B hostname
Hostnames, as taken from the file specified by the
.SM
.B HOSTFILE
shell variable.
.TP 8
.B job
Job names, if job control is active.  May also be specified as \fB\-j\fP.
.TP 8
.B keyword
Shell reserved words.  May also be specified as \fB\-k\fP.
.TP 8
.B running
Names of running jobs, if job control is active.
.TP 8
.B service
Service names.  May also be specified as \fB\-s\fP.
.TP 8
.B setopt
Valid arguments for the \fB\-o\fP option to the \fBset\fP builtin.
.TP 8
.B shopt
Shell option names as accepted by the \fBshopt\fP builtin.
.TP 8
.B signal
Signal names.
.TP 8
.B stopped
Names of stopped jobs, if job control is active.
.TP 8
.B user
User names.  May also be specified as \fB\-u\fP.
.TP 8
.B variable
Names of all shell variables.  May also be specified as \fB\-v\fP.
.RE
.TP 8
\fB\-C\fP \fIcommand\fP
\fIcommand\fP is executed in a subshell environment, and its output is
used as the possible completions.
Arguments are passed as with the \fB\-F\fP option.
.TP 8
\fB\-F\fP \fIfunction\fP
The shell function \fIfunction\fP is executed in the current shell
environment.
When the function is executed,
the first argument (\fB$1\fP) is the name of the command whose arguments are
being completed,
the second argument (\fB$2\fP) is the word being completed,
and the third argument (\fB$3\fP) is the word preceding the word being
completed on the current command line.
When it finishes, the possible completions are retrieved from the value
of the
.SM
.B COMPREPLY
array variable.
.TP 8
\fB\-G\fP \fIglobpat\fP
The pathname expansion pattern \fIglobpat\fP is expanded to generate
the possible completions.
.TP 8
\fB\-P\fP \fIprefix\fP
\fIprefix\fP is added at the beginning of each possible completion
after all other options have been applied.
.TP 8
\fB\-S\fP \fIsuffix\fP
\fIsuffix\fP is appended to each possible completion
after all other options have been applied.
.TP 8
\fB\-W\fP \fIwordlist\fP
The \fIwordlist\fP is split using the characters in the
.SM
.B IFS
special variable as delimiters, and each resultant word is expanded.
Shell quoting is honored within \fIwordlist\fP,
in order to provide a
mechanism for the words to contain shell metacharacters or characters
in the value of
.SM
.BR IFS .
The possible completions are the members of the resultant list which
match the word being completed.
.TP 8
\fB\-X\fP \fIfilterpat\fP
\fIfilterpat\fP is a pattern as used for pathname expansion.
It is applied to the list of possible completions generated by the
preceding options and arguments, and each completion matching
\fIfilterpat\fP is removed from the list.
A leading \fB!\fP in \fIfilterpat\fP negates the pattern; in this
case, any completion not matching \fIfilterpat\fP is removed.
.PD
.PP
The return value is true unless an invalid option is supplied, an option
other than \fB\-p\fP or \fB\-r\fP is supplied without a \fIname\fP
argument, an attempt is made to remove a completion specification for
a \fIname\fP for which no specification exists, or
an error occurs adding a completion specification.
.RE
.TP
\fBcompopt\fP [\fB\-o\fP \fIoption\fP] [\fB\-DEI\fP] [\fB+o\fP \fIoption\fP] [\fIname\fP]
Modify completion options for each \fIname\fP according to the
\fIoption\fPs, or for the
currently-executing completion if no \fIname\fPs are supplied.
If no \fIoption\fPs are given, display the completion options for each
\fIname\fP or the current completion.
The possible values of \fIoption\fP are those valid for the \fBcomplete\fP
builtin described above.
The \fB\-D\fP option indicates that other supplied options should
apply to the ``default'' command completion; that is, completion attempted
on a command for which no completion has previously been defined.
The \fB\-E\fP option indicates that other supplied options should
apply to ``empty'' command completion; that is, completion attempted on a
blank line.
The \fB\-I\fP 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 \fB;\fP or \fB|\fP, which is usually
command name completion.
.sp 1
The return value is true unless an invalid option is supplied, an attempt
is made to modify the options for a \fIname\fP for which no completion
specification exists, or an output error occurs.
.TP
\fBcontinue\fP [\fIn\fP]
Resume the next iteration of the enclosing
.BR for ,
.BR while ,
.BR until ,
or
.B select
loop.
If
.I n
is specified, resume at the \fIn\fPth enclosing loop.
.I n
must be \(>= 1.  If
.I n
is greater than the number of enclosing loops, the last enclosing loop
(the ``top-level'' loop) is resumed.
The return value is 0 unless \fIn\fP is not greater than or equal to 1.
.TP
\fBdeclare\fP [\fB\-aAfFgiIlnrtux\fP] [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP] ...]
.PD 0
.TP
\fBtypeset\fP [\fB\-aAfFgiIlnrtux\fP] [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP] ...]
.PD
Declare variables and/or give them attributes.
If no \fIname\fPs are given then display the values of variables.
The
.B \-p
option will display the attributes and values of each
.IR name .
When
.B \-p
is used with \fIname\fP arguments, additional options,
other than \fB\-f\fP and \fB\-F\fP, are ignored.
When
.B \-p
is supplied without \fIname\fP arguments, it will display the attributes
and values of all variables having the attributes specified by the
additional options.
If no other options are supplied with \fB\-p\fP, \fBdeclare\fP will display
the attributes and values of all shell variables.  The \fB\-f\fP option
will restrict the display to shell functions.
The
.B \-F
option inhibits the display of function definitions; only the
function name and attributes are printed.
If the \fBextdebug\fP shell option is enabled using \fBshopt\fP,
the source file name and line number where each \fIname\fP
is defined are displayed as well.  The
.B \-F
option implies
.BR \-f .
The
.B \-g
option forces variables to be created or modified at the global scope,
even when \fBdeclare\fP is executed in a shell function.
It is ignored in all other cases.
The
.B \-I
option causes local variables to inherit the attributes
(except the \fInameref\fP attribute) 
and value of any existing variable with the same
\fIname\fP at a surrounding scope.
If there is no existing variable, the local variable is initially unset.
The following options can
be used to restrict output to variables with the specified attribute or
to give variables attributes:
.RS
.PD 0
.TP
.B \-a
Each \fIname\fP is an indexed array variable (see
.B Arrays
.ie \n(zZ=1 in \fIbash(1)\fP).
.el above).
.TP
.B \-A
Each \fIname\fP is an associative array variable (see
.B Arrays
.ie \n(zZ=1 in \fIbash(1)\fP).
.el above).
.TP
.B \-f
Use function names only.
.TP
.B \-i
The variable is treated as an integer; arithmetic evaluation (see
.SM
.B "ARITHMETIC EVALUATION"
.ie \n(zZ=1 in \fIbash(1)\fP)
.el above)
is performed when the variable is assigned a value.
.TP
.B \-l
When the variable is assigned a value, all upper-case characters are
converted to lower-case.
The upper-case attribute is disabled.
.TP
.B \-n
Give each \fIname\fP the \fInameref\fP attribute, making
it a name reference to another variable.
That other variable is defined by the value of \fIname\fP.
All references, assignments, and attribute modifications
to \fIname\fP, except those using or changing the
\fB\-n\fP attribute itself, are performed on the variable referenced by
\fIname\fP's value.
The nameref attribute cannot be applied to array variables.
.TP
.B \-r
Make \fIname\fPs readonly.  These names cannot then be assigned values
by subsequent assignment statements or unset.
.TP
.B \-t
Give each \fIname\fP the \fItrace\fP attribute.
Traced functions inherit the \fBDEBUG\fP and \fBRETURN\fP traps from
the calling shell.
The trace attribute has no special meaning for variables.
.TP
.B \-u
When the variable is assigned a value, all lower-case characters are
converted to upper-case.
The lower-case attribute is disabled.
.TP
.B \-x
Mark \fIname\fPs for export to subsequent commands via the environment.
.PD
.PP
Using `+' instead of `\-'
turns off the attribute instead,
with the exceptions that \fB+a\fP and \fB+A\fP
may not be used to destroy array variables and \fB+r\fP will not
remove the readonly attribute.
When used in a function,
.B declare
and
.B typeset
make each
\fIname\fP local, as with the
.B local
command,
unless the \fB\-g\fP option is supplied.
If a variable name is followed by =\fIvalue\fP, the value of
the variable is set to \fIvalue\fP.
When using \fB\-a\fP or \fB\-A\fP and the compound assignment syntax to
create array variables, additional attributes do not take effect until
subsequent assignments.
The return value is 0 unless an invalid option is encountered,
an attempt is made to define a function using
.if n ``\-f foo=bar'',
.if t \f(CW\-f foo=bar\fP,
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
.B Arrays
.ie \n(zZ=1 in \fIbash(1)\fP),
.el above),
one of the \fInames\fP 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 \fB\-f\fP.
.RE
.TP
.B dirs [\fB\-clpv\fP] [+\fIn\fP] [\-\fIn\fP]
Without options, displays the list of currently remembered directories.
The default display is on a single line with directory names separated
by spaces.
Directories are added to the list with the
.B pushd
command; the
.B popd
command removes entries from the list.
The current directory is always the first directory in the stack.
.RS
.PD 0
.TP
.B \-c
Clears the directory stack by deleting all of the entries.
.TP
.B \-l
Produces a listing using full pathnames;
the default listing format uses a tilde to denote the home directory.
.TP
.B \-p
Print the directory stack with one entry per line.
.TP
.B \-v
Print the directory stack with one entry per line,
prefixing each entry with its index in the stack.
.TP
\fB+\fP\fIn\fP
Displays the \fIn\fPth entry counting from the left of the list
shown by
.B dirs
when invoked without options, starting with zero.
.TP
\fB\-\fP\fIn\fP
Displays the \fIn\fPth entry counting from the right of the list
shown by
.B dirs
when invoked without options, starting with zero.
.PD
.PP
The return value is 0 unless an
invalid option is supplied or \fIn\fP indexes beyond the end
of the directory stack.
.RE
.TP
\fBdisown\fP [\fB\-ar\fP] [\fB\-h\fP] [\fIjobspec\fP ... | \fIpid\fP ... ]
Without options, remove each
.I jobspec
from the table of active jobs.
If
.I jobspec
is not present, and neither the \fB\-a\fP nor the \fB\-r\fP option
is supplied, the \fIcurrent job\fP is used.
If the \fB\-h\fP option is given, each
.I jobspec
is not removed from the table, but is marked so that
.SM
.B SIGHUP
is not sent to the job if the shell receives a
.SM
.BR SIGHUP .
If no
.I jobspec
is supplied, the
.B \-a
option means to remove or mark all jobs; the
.B \-r
option without a
.I jobspec
argument restricts operation to running jobs.
The return value is 0 unless a
.I jobspec
does not specify a valid job.
.TP
\fBecho\fP [\fB\-neE\fP] [\fIarg\fP ...]
Output the \fIarg\fPs, separated by spaces, followed by a newline.
The return status is 0 unless a write error occurs.
If \fB\-n\fP is specified, the trailing newline is
suppressed.  If the \fB\-e\fP option is given, interpretation of
the following backslash-escaped characters is enabled.  The
.B \-E
option disables the interpretation of these escape characters,
even on systems where they are interpreted by default.
The \fBxpg_echo\fP shell option may be used to
dynamically determine whether or not \fBecho\fP expands these
escape characters by default.
.B echo
does not interpret \fB\-\-\fP to mean the end of options.
.B echo
interprets the following escape sequences:
.RS
.PD 0
.TP
.B \ea
alert (bell)
.TP
.B \eb
backspace
.TP
.B \ec
suppress further output
.TP
.B \ee
.TP
.B \eE
an escape character
.TP
.B \ef
form feed
.TP
.B \en
new line
.TP
.B \er
carriage return
.TP
.B \et
horizontal tab
.TP
.B \ev
vertical tab
.TP
.B \e\e
backslash
.TP
.B \e0\fInnn\fP
the eight-bit character whose value is the octal value \fInnn\fP
(zero to three octal digits)
.TP
.B \ex\fIHH\fP
the eight-bit character whose value is the hexadecimal value \fIHH\fP
(one or two hex digits)
.TP
.B \eu\fIHHHH\fP
the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value
\fIHHHH\fP (one to four hex digits)
.TP
.B \eU\fIHHHHHHHH\fP
the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value
\fIHHHHHHHH\fP (one to eight hex digits)
.PD
.RE
.TP
\fBenable\fP [\fB\-a\fP] [\fB\-dnps\fP] [\fB\-f\fP \fIfilename\fP] [\fIname\fP ...]
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 \fB\-n\fP is used, each \fIname\fP
is disabled; otherwise,
\fInames\fP are enabled.  For example, to use the
.B test
binary found via the
.SM
.B PATH
instead of the shell builtin version, run
.if t \f(CWenable -n test\fP.
.if n ``enable -n test''.
The
.B \-f
option means to load the new builtin command
.I name
from shared object
.IR filename ,
on systems that support dynamic loading.
Bash will use the value of the \fBBASH_LOADABLES_PATH\fP variable as a
colon-separated list of directories in which to search for \fIfilename\fP.
The default is system-dependent.
The
.B \-d
option will delete a builtin previously loaded with
.BR \-f .
If no \fIname\fP arguments are given, or if the
.B \-p
option is supplied, a list of shell builtins is printed.
With no other option arguments, the list consists of all enabled
shell builtins.
If \fB\-n\fP is supplied, only disabled builtins are printed.
If \fB\-a\fP is supplied, the list printed includes all builtins, with an
indication of whether or not each is enabled.
If \fB\-s\fP is supplied, the output is restricted to the POSIX
\fIspecial\fP builtins.
If no options are supplied and a \fIname\fP is not a shell builtin,
\fBenable\fP will attempt to load \fIname\fP from a shared object named
\fIname\fP, as if the command were
.if t \f(CWenable \-f\fP \fIname name\fP .
.if n ``enable -f \fIname name\fP .
The return value is 0 unless a
.I name
is not a shell builtin or there is an error loading a new builtin
from a shared object.
.TP
\fBeval\fP [\fIarg\fP ...]
The \fIarg\fPs are read and concatenated together into a single
command.  This command is then read and executed by the shell, and
its exit status is returned as the value of
.BR eval .
If there are no
.IR args ,
or only null arguments,
.B eval
returns 0.
.TP
\fBexec\fP [\fB\-cl\fP] [\fB\-a\fP \fIname\fP] [\fIcommand\fP [\fIarguments\fP]]
If
.I command
is specified, it replaces the shell.
No new process is created.  The
.I arguments
become the arguments to \fIcommand\fP.
If the
.B \-l
option is supplied,
the shell places a dash at the beginning of the zeroth argument passed to
.IR command .
This is what
.IR login (1)
does.  The
.B \-c
option causes
.I command
to be executed with an empty environment.  If
.B \-a
is supplied, the shell passes
.I name
as the zeroth argument to the executed command.
If
.I command
cannot be executed for some reason, a non-interactive shell exits,
unless the
.B execfail
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 \fBexec\fP fails.
If
.I command
is not specified, any redirections take effect in the current shell,
and the return status is 0.  If there is a redirection error, the
return status is 1.
.TP
\fBexit\fP [\fIn\fP]
Cause the shell to exit
with a status of \fIn\fP.  If
.I n
is omitted, the exit status
is that of the last command executed.
A trap on
.SM
.B EXIT
is executed before the shell terminates.
.TP
\fBexport\fP [\fB\-fn\fP\^] [\fIname\fP[=\fIword\fP]] ...
.PD 0
.TP
.B export \-p
.PD
The supplied
.I names
are marked for automatic export to the environment of
subsequently executed commands.  If the
.B \-f
option is given, the
.I names
refer to functions.
If no
.I names
are given, or if the
.B \-p
option is supplied, a list
of names of all exported variables is printed.
The
.B \-n
option causes the export property to be removed from each
\fIname\fP.
If a variable name is followed by =\fIword\fP, the value of
the variable is set to \fIword\fP.
.B export
returns an exit status of 0 unless an invalid option is
encountered,
one of the \fInames\fP is not a valid shell variable name, or
.B \-f
is supplied with a
.I name
that is not a function.
.TP
\fBfc\fP [\fB\-e\fP \fIename\fP] [\fB\-lnr\fP] [\fIfirst\fP] [\fIlast\fP]
.PD 0
.TP
\fBfc\fP \fB\-s\fP [\fIpat\fP=\fIrep\fP] [\fIcmd\fP]
.PD
The first form selects a range of commands from
.I first
to
.I last
from the history list and displays or edits and re-executes them.
.I First
and
.I last
may be specified as a string (to locate the last 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).
When listing, a \fIfirst\fP or \fIlast\fP of
0 is equivalent to \-1 and \-0 is equivalent to the current
command (usually the \fBfc\fP command); otherwise 0 is equivalent to \-1
and \-0 is invalid.
If
.I last
is not specified, it is set to
the current command for listing (so that
.if n ``fc \-l \-10''
.if t \f(CWfc \-l \-10\fP
prints the last 10 commands) and to
.I first
otherwise.
If
.I first
is not specified, it is set to the previous
command for editing and \-16 for listing.
.sp 1
The
.B \-n
option suppresses
the command numbers when listing.  The
.B \-r
option reverses the order of
the commands.  If the
.B \-l
option is given,
the commands are listed on
standard output.  Otherwise, the editor given by
.I ename
is invoked
on a file containing those commands.  If
.I ename
is not given, the
value of the
.SM
.B FCEDIT
variable is used, and
the value of
.SM
.B EDITOR
if
.SM
.B FCEDIT
is not set.  If neither variable is set,
.FN vi
is used.  When editing is complete, the edited commands are
echoed and executed.
.sp 1
In the second form, \fIcommand\fP is re-executed after each instance
of \fIpat\fP is replaced by \fIrep\fP.
\fICommand\fP is interpreted the same as \fIfirst\fP above.
A useful alias to use with this is
.if n ``r="fc -s"'',
.if t \f(CWr='fc \-s'\fP,
so that typing
.if n ``r cc''
.if t \f(CWr cc\fP
runs the last command beginning with
.if n ``cc''
.if t \f(CWcc\fP
and typing
.if n ``r''
.if t \f(CWr\fP
re-executes the last command.
.sp 1
If the first form is used, the return value is 0 unless an invalid
option is encountered or
.I first
or
.I last
specify history lines out of range.
If the
.B \-e
option is supplied, the return value is the value of the last
command executed or failure if an error occurs with the temporary
file of commands.  If the second form is used, the return status
is that of the command re-executed, unless
.I cmd
does not specify a valid history line, in which case
.B fc
returns failure.
.TP
\fBfg\fP [\fIjobspec\fP]
Resume
.I jobspec
in the foreground, and make it the current job.
If
.I jobspec
is not present, the shell's notion of the \fIcurrent job\fP is used.
The return value is that of the command placed into the foreground,
or failure if run when job control is disabled or, when run with
job control enabled, if
.I jobspec
does not specify a valid job or
.I jobspec
specifies a job that was started without job control.
.TP
\fBgetopts\fP \fIoptstring\fP \fIname\fP [\fIarg ...\fP]
.B getopts
is used by shell procedures to parse positional parameters.
.I optstring
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 white space.
The colon and question mark characters may not be used as
option characters.
Each time it is invoked,
.B getopts
places the next option in the shell variable
.IR name ,
initializing
.I name
if it does not exist,
and the index of the next argument to be processed into the
variable
.SM
.BR OPTIND .
.SM
.B OPTIND
is initialized to 1 each time the shell or a shell script
is invoked.  When an option requires an argument,
.B getopts
places that argument into the variable
.SM
.BR OPTARG .
The shell does not reset
.SM
.B OPTIND
automatically; it must be manually reset between multiple
calls to
.B getopts
within the same shell invocation if a new set of parameters
is to be used.
.sp 1
When the end of options is encountered, \fBgetopts\fP exits with a
return value greater than zero.
.SM
.B OPTIND
is set to the index of the first non-option argument,
and \fIname\fP is set to ?.
.sp 1
.B getopts
normally parses the positional parameters, but if more arguments are
supplied as
.I arg
values,
.B getopts
parses those instead.
.sp 1
.B getopts
can report errors in two ways.  If the first character of
.I optstring
is a colon,
.I silent
error reporting is used.  In normal operation, diagnostic messages
are printed when invalid options or missing option arguments are
encountered.
If the variable
.SM
.B OPTERR
is set to 0, no error messages will be displayed, even if the first
character of
.I optstring
is not a colon.
.sp 1
If an invalid option is seen,
.B getopts
places ? into
.I name
and, if not silent,
prints an error message and unsets
.SM
.BR OPTARG .
If
.B getopts
is silent,
the option character found is placed in
.SM
.B OPTARG
and no diagnostic message is printed.
.sp 1
If a required argument is not found, and
.B getopts
is not silent,
a question mark (\^\fB?\fP\^) is placed in
.IR name ,
.SM
.B OPTARG
is unset, and a diagnostic message is printed.
If
.B getopts
is silent, then a colon (\^\fB:\fP\^) is placed in
.I name
and
.SM
.B OPTARG
is set to the option character found.
.sp 1
.B getopts
returns true if an option, specified or unspecified, is found.
It returns false if the end of options is encountered or an
error occurs.
.TP
\fBhash\fP [\fB\-lr\fP] [\fB\-p\fP \fIfilename\fP] [\fB\-dt\fP] [\fIname\fP]
Each time \fBhash\fP is invoked,
the full pathname of the command
.I name
is determined by searching
the directories in
.B $PATH
and remembered.  Any previously-remembered pathname is discarded.
If the
.B \-p
option is supplied, no path search is performed, and
.I filename
is used as the full filename of the command.
The
.B \-r
option causes the shell to forget all
remembered locations.
The
.B \-d
option causes the shell to forget the remembered location of each \fIname\fP.
If the
.B \-t
option is supplied, the full pathname to which each \fIname\fP corresponds
is printed.  If multiple \fIname\fP arguments are supplied with \fB\-t\fP,
the \fIname\fP is printed before the hashed full pathname.
The
.B \-l
option causes output to be displayed in a format that may be reused as input.
If no arguments are given, or if only \fB\-l\fP is supplied,
information about remembered commands is printed.
The return status is true unless a
.I name
is not found or an invalid option is supplied.
.TP
\fBhelp\fP [\fB\-dms\fP] [\fIpattern\fP]
Display helpful information about builtin commands.  If
.I pattern
is specified,
.B help
gives detailed help on all commands matching
.IR pattern ;
otherwise help for all the builtins and shell control structures
is printed.
.RS
.PD 0
.TP
.B \-d
Display a short description of each \fIpattern\fP
.TP
.B \-m
Display the description of each \fIpattern\fP in a manpage-like format
.TP
.B \-s
Display only a short usage synopsis for each \fIpattern\fP
.PD
.PP
The return status is 0 unless no command matches
.IR pattern .
.RE
.TP
\fBhistory [\fIn\fP]
.PD 0
.TP
\fBhistory\fP \fB\-c\fP
.TP
\fBhistory \-d\fP \fIoffset\fP
.TP
\fBhistory \-d\fP \fIstart\fP\-\fIend\fP
.TP
\fBhistory\fP \fB\-anrw\fP [\fIfilename\fP]
.TP
\fBhistory\fP \fB\-p\fP \fIarg\fP [\fIarg ...\fP]
.TP
\fBhistory\fP \fB\-s\fP \fIarg\fP [\fIarg ...\fP]
.PD
With no options, display the command
history list with line numbers.  Lines listed
with a
.B *
have been modified.  An argument of
.I n
lists only the last
.I n
lines.
If the shell variable
.SM
.B HISTTIMEFORMAT
is set and not null,
it is used as a format string for \fIstrftime\fP(3) 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.
If \fIfilename\fP is supplied, it is used as the
name of the history file; if not, the value of
.SM
.B HISTFILE
is used.  Options, if supplied, have the following meanings:
.RS
.PD 0
.TP
.B \-c
Clear the history list by deleting all the entries.
.TP
\fB\-d\fP \fIoffset\fP
Delete the history entry at position \fIoffset\fP.
If \fIoffset\fP 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 \-1 refers to the current
\fBhistory -d\fP command.
.TP
\fB\-d\fP \fIstart\fP\-\fIend\fP
Delete the range of history entries between positions \fIstart\fP and
\fIend\fP, inclusive.
Positive and negative values for \fIstart\fP and \fIend\fP
are interpreted as described above.
.TP
.B \-a
Append the ``new'' history lines to the history file.
These are history lines entered since the beginning of the current
\fBbash\fP session, but not already appended to the history file.
.TP
.B \-n
Read the history lines not already read from the history
file into the current history list.  These are lines
appended to the history file since the beginning of the
current \fBbash\fP session.
.TP
.B \-r
Read the contents of the history file
and append them to the current history list.
.TP
.B \-w
Write the current history list to the history file, overwriting the
history file's contents.
.TP
.B \-p
Perform history substitution on the following \fIargs\fP and display
the result on the standard output.
Does not store the results in the history list.
Each \fIarg\fP must be quoted to disable normal history expansion.
.TP
.B \-s
Store the
.I args
in the history list as a single entry.  The last command in the
history list is removed before the
.I args
are added.
.PD
.PP
If the
.SM
.B HISTTIMEFORMAT
variable 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.
The return value is 0 unless an invalid option is encountered, an
error occurs while reading or writing the history file, an invalid
\fIoffset\fP or range is supplied as an argument to \fB\-d\fP, or the
history expansion supplied as an argument to \fB\-p\fP fails.
.RE
.TP
\fBjobs\fP [\fB\-lnprs\fP] [ \fIjobspec\fP ... ]
.PD 0
.TP
\fBjobs\fP \fB\-x\fP \fIcommand\fP [ \fIargs\fP ... ]
.PD
The first form lists the active jobs.  The options have the following
meanings:
.RS
.PD 0
.TP
.B \-l
List process IDs
in addition to the normal information.
.TP
.B \-n
Display information only about jobs that have changed status since
the user was last notified of their status.
.TP
.B \-p
List only the process ID of the job's process group
leader.
.TP
.B \-r
Display only running jobs.
.TP
.B \-s
Display only stopped jobs.
.PD
.PP
If
.I jobspec
is given, output is restricted to information about that job.
The return status is 0 unless an invalid option is encountered
or an invalid
.I jobspec
is supplied.
.PP
If the
.B \-x
option is supplied,
.B jobs
replaces any
.I jobspec
found in
.I command
or
.I args
with the corresponding process group ID, and executes
.I command
passing it
.IR args ,
returning its exit status.
.RE
.TP
\fBkill\fP [\fB\-s\fP \fIsigspec\fP | \fB\-n\fP \fIsignum\fP | \fB\-\fP\fIsigspec\fP] [\fIpid\fP | \fIjobspec\fP] ...
.PD 0
.TP
\fBkill\fP \fB\-l\fP|\fB\-L\fP [\fIsigspec\fP | \fIexit_status\fP]
.PD
Send the signal named by
.I sigspec
or
.I signum
to the processes named by
.I pid
or
.IR jobspec .
.I sigspec
is either a case-insensitive signal name such as
.SM
.B SIGKILL
(with or without the
.SM
.B SIG
prefix) or a signal number;
.I signum
is a signal number.
If
.I sigspec
is not present, then
.SM
.B SIGTERM
is assumed.
An argument of
.B \-l
lists the signal names.
If any arguments are supplied when
.B \-l
is given, the names of the signals corresponding to the arguments are
listed, and the return status is 0.
The \fIexit_status\fP argument to
.B \-l
is a number specifying either a signal number or the exit status of
a process terminated by a signal.
The
.B \-L
option is equivalent to \fB\-l\fP.
.B kill
returns true if at least one signal was successfully sent, or false
if an error occurs or an invalid option is encountered.
.TP
\fBlet\fP \fIarg\fP [\fIarg\fP ...]
Each
.I arg
is an arithmetic expression to be evaluated (see
.SM
.B "ARITHMETIC EVALUATION"
.ie \n(zZ=1 in \fIbash(1)\fP).
.el above).
If the last
.I arg
evaluates to 0,
.B let
returns 1; 0 is returned otherwise.
.TP
\fBlocal\fP [\fIoption\fP] [\fIname\fP[=\fIvalue\fP] ... | \- ]
For each argument, a local variable named
.I name
is created, and assigned
.IR value .
The \fIoption\fP can be any of the options accepted by \fBdeclare\fP.
When
.B local
is used within a function, it causes the variable
.I name
to have a visible scope restricted to that function and its children.
If \fIname\fP is \-, the set of shell options is made local to the function
in which \fBlocal\fP is invoked: shell options changed using the
\fBset\fP builtin inside the function are restored to their original values
when the function returns.
The restore is effected as if a series of \fBset\fP commands were executed
to restore the values that were in place before the function.
With no operands,
.B local
writes a list of local variables to the standard output.  It is
an error to use
.B local
when not within a function.  The return status is 0 unless
.B local
is used outside a function, an invalid
.I name
is supplied, or
\fIname\fP is a readonly variable.
.TP
.B logout
Exit a login shell.
.TP
\fBmapfile\fP [\fB\-d\fP \fIdelim\fP] [\fB\-n\fP \fIcount\fP] [\fB\-O\fP \fIorigin\fP] [\fB\-s\fP \fIcount\fP] [\fB\-t\fP] [\fB\-u\fP \fIfd\fP] [\fB\-C\fP \fIcallback\fP] [\fB\-c\fP \fIquantum\fP] [\fIarray\fP]
.PD 0
.TP
\fBreadarray\fP [\fB\-d\fP \fIdelim\fP] [\fB\-n\fP \fIcount\fP] [\fB\-O\fP \fIorigin\fP] [\fB\-s\fP \fIcount\fP] [\fB\-t\fP] [\fB\-u\fP \fIfd\fP] [\fB\-C\fP \fIcallback\fP] [\fB\-c\fP \fIquantum\fP] [\fIarray\fP]
.PD
Read lines from the standard input into the indexed array variable
.IR array ,
or from file descriptor
.I fd
if the
.B \-u
option is supplied.
The variable
.SM
.B MAPFILE
is the default \fIarray\fP.
Options, if supplied, have the following meanings:
.RS
.PD 0
.TP
.B \-d
The first character of \fIdelim\fP is used to terminate each input line,
rather than newline.
If \fIdelim\fP is the empty string, \fBmapfile\fP will terminate a line
when it reads a NUL character.
.TP
.B \-n
Copy at most
.I count
lines.  If \fIcount\fP is 0, all lines are copied.
.TP
.B \-O
Begin assigning to
.I array
at index
.IR origin .
The default index is 0.
.TP
.B \-s
Discard the first \fIcount\fP lines read.
.TP
.B \-t
Remove a trailing \fIdelim\fP (default newline) from each line read.
.TP
.B \-u
Read lines from file descriptor \fIfd\fP instead of the standard input.
.TP
.B \-C
Evaluate
.I callback
each time \fIquantum\fP lines are read.  The \fB\-c\fP option specifies
.IR quantum .
.TP
.B \-c
Specify the number of lines read between each call to
.IR callback .
.PD
.PP
If
.B \-C
is specified without
.BR \-c ,
the default quantum is 5000.
When \fIcallback\fP 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.
\fIcallback\fP is evaluated after the line is read but before the
array element is assigned.
.PP
If not supplied with an explicit origin, \fBmapfile\fP will clear \fIarray\fP
before assigning to it.
.PP
\fBmapfile\fP returns successfully unless an invalid option or option
argument is supplied, \fIarray\fP is invalid or unassignable, or if
\fIarray\fP is not an indexed array.
.RE
.TP
\fBpopd\fP [\-\fBn\fP] [+\fIn\fP] [\-\fIn\fP]
Removes entries from the directory stack.
The elements are numbered from 0 starting at the first directory
listed by \fBdirs\fP.
With no arguments, \fBpopd\fP
removes the top directory from the stack, and
changes to the new top directory.
Arguments, if supplied, have the following meanings:
.RS
.PD 0
.TP
.B \-n
Suppresses the normal change of directory when removing directories
from the stack, so that only the stack is manipulated.
.TP
\fB+\fP\fIn\fP
Removes the \fIn\fPth entry counting from the left of the list
shown by
.BR dirs ,
starting with zero, from the stack.
For example:
.if n ``popd +0''
.if t \f(CWpopd +0\fP
removes the first directory,
.if n ``popd +1''
.if t \f(CWpopd +1\fP
the second.
.TP
\fB\-\fP\fIn\fP
Removes the \fIn\fPth entry counting from the right of the list
shown by
.BR dirs ,
starting with zero.  For example:
.if n ``popd -0''
.if t \f(CWpopd -0\fP
removes the last directory,
.if n ``popd -1''
.if t \f(CWpopd -1\fP
the next to last.
.PD
.PP
If the top element of the directory stack is modified, and
the \fI-n\fP option was not supplied, \fBpopd\fP uses the \fBcd\fP
builtin to change to the directory at the top of the stack.
If the \fBcd\fP fails, \fBpopd\fP returns a non-zero value.
.PP
Otherwise,
.B popd
returns false if an invalid option is encountered, the directory stack
is empty, or a non-existent directory stack entry is specified.
.PP
If the
.B popd
command is successful,
bash runs
.B dirs
to show the final contents of the directory stack,
and the return status is 0.
.RE
.TP
\fBprintf\fP [\fB\-v\fP \fIvar\fP] \fIformat\fP [\fIarguments\fP]
Write the formatted \fIarguments\fP to the standard output under the
control of the \fIformat\fP.
The \fB\-v\fP option causes the output to be assigned to the variable
\fIvar\fP rather than being printed to the standard output.
.sp 1
The \fIformat\fP 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
\fIargument\fP.
In addition to the standard \fIprintf\fP(1) format specifications,
\fBprintf\fP interprets the following extensions:
.RS
.PD 0
.TP
.B %b
causes
\fBprintf\fP to expand backslash escape sequences in the corresponding
\fIargument\fP
in the same way as \fBecho \-e\fP.
.TP
.B %q
causes \fBprintf\fP to output the corresponding
\fIargument\fP in a format that can be reused as shell input.
.TP
.B %Q
like \fB%q\fP, but applies any supplied precision to the \fIargument\fP
before quoting it.
.TP
.B %(\fIdatefmt\fP)T
causes \fBprintf\fP to output the date-time string resulting from using
\fIdatefmt\fP as a format string for \fIstrftime\fP(3).
The corresponding \fIargument\fP 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 \fBprintf\fP behavior.
.PD
.PP
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.
.PP
Arguments to non-string format specifiers are treated as C 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.
.PP
The \fIformat\fP is reused as necessary to consume all of the \fIarguments\fP.
If the \fIformat\fP requires more \fIarguments\fP 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.
.RE
.TP
\fBpushd\fP [\fB\-n\fP] [+\fIn\fP] [\-\fIn\fP]
.PD 0
.TP
\fBpushd\fP [\fB\-n\fP] [\fIdir\fP]
.PD
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, \fBpushd\fP exchanges the top two elements of
the directory stack.
Arguments, if supplied, have the following meanings:
.RS
.PD 0
.TP
.B \-n
Suppresses the normal change of directory when rotating or
adding directories to the stack, so that only the stack is manipulated.
.TP
\fB+\fP\fIn\fP
Rotates the stack so that the \fIn\fPth directory
(counting from the left of the list shown by
.BR dirs ,
starting with zero)
is at the top.
.TP
\fB\-\fP\fIn\fP
Rotates the stack so that the \fIn\fPth directory
(counting from the right of the list shown by
.BR dirs ,
starting with zero) is at the top.
.TP
.I dir
Adds
.I dir
to the directory stack at the top
.PD
.PP
After the stack has been modified, if the \fB\-n\fP option was not
supplied, \fBpushd\fP uses the \fBcd\fP builtin to change to the
directory at the top of the stack.
If the \fBcd\fP fails, \fBpushd\fP returns a non-zero value.
.PP
Otherwise, if no arguments are supplied,
.B pushd
returns 0 unless the directory stack is empty.
When rotating the directory stack,
.B pushd
returns 0 unless the directory stack is empty or
a non-existent directory stack element is specified.
.PP
If the
.B pushd
command is successful,
bash runs
.B dirs
to show the final contents of the directory stack.
.RE
.TP
\fBpwd\fP [\fB\-LP\fP]
Print the absolute pathname of the current working directory.
The pathname printed contains no symbolic links if the
.B \-P
option is supplied or the
.B \-o physical
option to the
.B set
builtin command is enabled.
If the
.B \-L
option is used, the pathname printed may contain symbolic links.
The return status is 0 unless an error occurs while
reading the name of the current directory or an
invalid option is supplied.
.TP
\fBread\fP [\fB\-ers\fP] [\fB\-a\fP \fIaname\fP] [\fB\-d\fP \fIdelim\fP] [\fB\-i\fP \fItext\fP] [\fB\-n\fP \fInchars\fP] [\fB\-N\fP \fInchars\fP] [\fB\-p\fP \fIprompt\fP] [\fB\-t\fP \fItimeout\fP] [\fB\-u\fP \fIfd\fP] [\fIname\fP ...]
One line is read from the standard input, or from the file descriptor
\fIfd\fP supplied as an argument to the \fB\-u\fP option,
split into words as described
.ie \n(zZ=1 in \fIbash(1)\fP
.el above
under \fBWord Splitting\fP,
and the first word
is assigned to the first
.IR name ,
the second word to the second
.IR name ,
and so on.
If there are more words than names, the remaining words and their
intervening delimiters are assigned to the last
.IR name .
If there are fewer words read from the input stream than names,
the remaining names are assigned empty values.
The characters in
.SM
.B IFS
are used to split the line into words using the same rules the shell
uses for expansion (described
.ie \n(zZ=1 in \fIbash(1)\fP
.el above
under \fBWord Splitting\fP).
The backslash character (\fB\e\fP) may be used to remove any special
meaning for the next character read and for line continuation.
Options, if supplied, have the following meanings:
.RS
.PD 0
.TP
.B \-a \fIaname\fP
The words are assigned to sequential indices
of the array variable
.IR aname ,
starting at 0.
.I aname
is unset before any new values are assigned.
Other \fIname\fP arguments are ignored.
.TP
.B \-d \fIdelim\fP
The first character of \fIdelim\fP is used to terminate the input line,
rather than newline.
If \fIdelim\fP is the empty string, \fBread\fP will terminate a line
when it reads a NUL character.
.TP
.B \-e
If the standard input
is coming from a terminal,
.B readline
(see
.SM
.B READLINE
.ie \n(zZ=1 in \fIbash(1)\fP)
.el above)
is used to obtain the line.
Readline uses the current (or default, if line editing was not previously
active) editing settings, but uses readline's default filename completion.
.TP
.B \-i \fItext\fP
If
.B readline
is being used to read the line, \fItext\fP is placed into the editing
buffer before editing begins.
.TP
.B \-n \fInchars\fP
\fBread\fP returns after reading \fInchars\fP characters rather than
waiting for a complete line of input, but honors a delimiter if fewer
than \fInchars\fP characters are read before the delimiter.
.TP
.B \-N \fInchars\fP
\fBread\fP returns after reading exactly \fInchars\fP characters rather
than waiting for a complete line of input, unless EOF is encountered or
\fBread\fP times out.
Delimiter characters encountered in the input are
not treated specially and do not cause \fBread\fP to return until
\fInchars\fP characters are read.
The result is not split on the characters in \fBIFS\fP; the intent is
that the variable is assigned exactly the characters read
(with the exception of backslash; see the \fB\-r\fP option below).
.TP
.B \-p \fIprompt\fP
Display \fIprompt\fP on standard error, without a
trailing newline, before attempting to read any input.  The prompt
is displayed only if input is coming from a terminal.
.TP
.B \-r
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.
.TP
.B \-s
Silent mode.  If input is coming from a terminal, characters are
not echoed.
.TP
.B \-t \fItimeout\fP
Cause \fBread\fP to time out and return failure if a complete line of
input (or a specified number of characters)
is not read within \fItimeout\fP seconds.
\fItimeout\fP may be a decimal number with a fractional portion following
the decimal point.
This option is only effective if \fBread\fP is reading input from a
terminal, pipe, or other special file; it has no effect when reading
from regular files.
If \fBread\fP times out, \fBread\fP saves any partial input read into
the specified variable \fIname\fP.
If \fItimeout\fP is 0, \fBread\fP 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.
.TP
.B \-u \fIfd\fP
Read input from file descriptor \fIfd\fP.
.PD
.PP
If no
.I names
are supplied, the line read,
without the ending delimiter but otherwise unmodified,
is assigned to the variable
.SM
.BR REPLY .
The exit status is zero, unless end-of-file is encountered, \fBread\fP
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 \fB\-u\fP.
.RE
.TP
\fBreadonly\fP [\fB\-aAf\fP] [\fB\-p\fP] [\fIname\fP[=\fIword\fP] ...]
.PD
The given
\fInames\fP are marked readonly; the values of these
.I names
may not be changed by subsequent assignment.
If the
.B \-f
option is supplied, the functions corresponding to the
\fInames\fP are so
marked.
The
.B \-a
option restricts the variables to indexed arrays; the
.B \-A
option restricts the variables to associative arrays.
If both options are supplied,
.B \-A
takes precedence.
If no
.I name
arguments are given, or if the
.B \-p
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
.B \-p
option causes output to be displayed in a format that
may be reused as input.
If a variable name is followed by =\fIword\fP, the value of
the variable is set to \fIword\fP.
The return status is 0 unless an invalid option is encountered,
one of the
.I names
is not a valid shell variable name, or
.B \-f
is supplied with a
.I name
that is not a function.
.TP
\fBreturn\fP [\fIn\fP]
Causes a function to stop executing and return the value specified by
.I n
to its caller.
If
.I n
is omitted, the return status is that of the last command
executed in the function body.
If \fBreturn\fP is executed by a trap handler, the last command used to
determine the status is the last command executed before the trap handler.
If \fBreturn\fP is executed during a \fBDEBUG\fP trap, the last command
used to determine the status is the last command executed by the trap
handler before \fBreturn\fP was invoked.
If
.B return
is used outside a function,
but during execution of a script by the
.B .
(\fBsource\fP) command, it causes the shell to stop executing
that script and return either
.I n
or the exit status of the last command executed within the
script as the exit status of the script.
If \fIn\fP is supplied, the return value is its least significant
8 bits.
The return status is non-zero if
.B return
is supplied a non-numeric argument, or
is used outside a
function and not during execution of a script by \fB.\fP\^ or \fBsource\fP.
Any command associated with the \fBRETURN\fP trap is executed
before execution resumes after the function or script.
.TP
\fBset\fP [\fB\-abefhkmnptuvxBCEHPT\fP] [\fB\-o\fP \fIoption\-name\fP] [\fB\-\-\fP] [\fB\-\fP] [\fIarg\fP ...]
.PD 0
.TP
\fBset\fP [\fB+abefhkmnptuvxBCEHPT\fP] [\fB+o\fP \fIoption\-name\fP] [\fB\-\-\fP] [\fB\-\fP] [\fIarg\fP ...]
.PD
Without options, display the name and value of each shell variable
in a format that can be reused as input
for setting or resetting the currently-set variables.
Read-only variables cannot be reset.
In \fIposix mode\fP, only shell variables are listed.
The output is sorted according to the current locale.
When options are specified, they set or unset shell attributes.
Any arguments remaining after option processing are treated
as values for the positional parameters and are assigned, in order, to
.BR $1 ,
.BR $2 ,
.B ...
.BR $\fIn\fP .
Options, if specified, have the following meanings:
.RS
.PD 0
.TP 8
.B \-a
Each variable or function that is created or modified is given the
export attribute and marked for export to the environment of
subsequent commands.
.TP 8
.B \-b
Report the status of terminated background jobs
immediately, rather than before the next primary prompt.  This is
effective only when job control is enabled.
.TP 8
.B \-e
Exit immediately if a
\fIpipeline\fP (which may consist of a single \fIsimple command\fP),
a \fIlist\fP,
or a \fIcompound command\fP
(see
.SM
.B SHELL GRAMMAR
.ie \n(zZ=1 in \fIbash(1)\fP),
.el above),
exits with a non-zero status.
The shell does not exit if the
command that fails is part of the command list immediately following a
.B while
or
.B until
keyword,
part of the test following the
.B if
or
.B elif
reserved words, part of any command executed in a
.B &&
or
.B ||
list except the command following the final \fB&&\fP or \fB||\fP,
any command in a pipeline but the last,
or if the command's return value is
being inverted with
.BR ! .
If a compound command other than a subshell
returns a non-zero status because a command failed
while \fB\-e\fP was being ignored, the shell does not exit.
A trap on \fBERR\fP, if set, is executed before the shell exits.
This option applies to the shell environment and each subshell environment
separately (see
.SM
.B "COMMAND EXECUTION ENVIRONMENT"
.ie \n(zZ=1 in \fIbash(1)\fP),
.el above),
and may cause
subshells to exit before executing all the commands in the subshell.
.if t .sp 0.5
.if n .sp 1
If a compound command or shell function executes in a context
where \fB\-e\fP is being ignored,
none of the commands executed within the compound command or function body
will be affected by the \fB\-e\fP setting, even if \fB\-e\fP is set
and a command returns a failure status.
If a compound command or shell function sets \fB\-e\fP while executing in
a context where \fB\-e\fP is ignored, that setting will not have any
effect until the compound command or the command containing the function
call completes.
.TP 8
.B \-f
Disable pathname expansion.
.TP 8
.B \-h
Remember the location of commands as they are looked up for execution.
This is enabled by default.
.TP 8
.B \-k
All arguments in the form of assignment statements
are placed in the environment for a command, not just
those that precede the command name.
.TP 8
.B \-m
Monitor mode.  Job control is enabled.  This option is on
by default for interactive shells on systems that support
it (see
.SM
.B JOB CONTROL
.ie \n(zZ=1 in \fIbash(1)\fP).
.el above).
All processes run in a separate process group.
When a background job completes, the shell prints a line
containing its exit status.
.TP 8
.B \-n
Read commands but do not execute them.
This may be used to check a shell script for syntax errors.
This is ignored by interactive shells.
.TP 8
.B \-o \fIoption\-name\fP
The \fIoption\-name\fP can be one of the following:
.RS
.TP 8
.B allexport
Same as
.BR \-a .
.TP 8
.B braceexpand
Same as
.BR \-B .
.TP 8
.B emacs
Use an emacs-style command line editing interface.  This is enabled
by default when the shell is interactive, unless the shell is started
with the
.B \-\-noediting
option.
This also affects the editing interface used for \fBread \-e\fP.
.TP 8
.B errexit
Same as
.BR \-e .
.TP 8
.B errtrace
Same as
.BR \-E .
.TP 8
.B functrace
Same as
.BR \-T .
.TP 8
.B hashall
Same as
.BR \-h .
.TP 8
.B histexpand
Same as
.BR \-H .
.TP 8
.B history
Enable command history, as described
.ie \n(zZ=1 in \fIbash(1)\fP
.el above
under
.SM
.BR HISTORY .
This option is on by default in interactive shells.
.TP 8
.B ignoreeof
The effect is as if the shell command
.if t \f(CWIGNOREEOF=10\fP
.if n ``IGNOREEOF=10''
had been executed
(see
.B Shell Variables
.ie \n(zZ=1 in \fIbash(1)\fP).
.el above).
.TP 8
.B keyword
Same as
.BR \-k .
.TP 8
.B monitor
Same as
.BR \-m .
.TP 8
.B noclobber
Same as
.BR \-C .
.TP 8
.B noexec
Same as
.BR \-n .
.TP 8
.B noglob
Same as
.BR \-f .
.TP 8
.B nolog
Currently ignored.
.TP 8
.B notify
Same as
.BR \-b .
.TP 8
.B nounset
Same as
.BR \-u .
.TP 8
.B onecmd
Same as
.BR \-t .
.TP 8
.B physical
Same as
.BR \-P .
.TP 8
.B pipefail
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.
.TP 8
.B posix
Change the behavior of
.B bash
where the default operation differs
from the POSIX standard to match the standard (\fIposix mode\fP).
See
.SM
.B "SEE ALSO"
.ie \n(zZ=1 in \fIbash(1)\fP
.el below
for a reference to a document that details how posix mode affects
bash's behavior.
.TP 8
.B privileged
Same as
.BR \-p .
.TP 8
.B verbose
Same as
.BR \-v .
.TP 8
.B vi
Use a vi-style command line editing interface.
This also affects the editing interface used for \fBread \-e\fP.
.TP 8
.B xtrace
Same as
.BR \-x .
.sp .5
.PP
If
.B \-o
is supplied with no \fIoption\-name\fP, the values of the current options are
printed.
If
.B +o
is supplied with no \fIoption\-name\fP, a series of
.B set
commands to recreate the current option settings is displayed on
the standard output.
.RE
.TP 8
.B \-p
Turn on
.I privileged
mode.  In this mode, the
.SM
.B $ENV
and
.SM
.B $BASH_ENV
files are not processed, shell functions are not inherited from the
environment, and the
.SM
.BR SHELLOPTS ,
.SM
.BR BASHOPTS ,
.SM
.BR CDPATH ,
and
.SM
.B GLOBIGNORE
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 \fB\-p\fP option is not supplied, these actions
are taken and the effective user id is set to the real user id.
If the \fB\-p\fP 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.
.TP 8
.B \-r
Enable restricted shell mode.
This option cannot be unset once it has been set.
.TP 8
.B \-t
Exit after reading and executing one command.
.TP 8
.B \-u
Treat unset variables and parameters other than the special
parameters "@" and "*",
or array variables subscripted with "@" or "*",
as an error when performing
parameter expansion.  If expansion is attempted on an
unset variable or parameter, the shell prints an error message, and,
if not interactive, exits with a non-zero status.
.TP 8
.B \-v
Print shell input lines as they are read.
.TP 8
.B \-x
After expanding each \fIsimple command\fP,
\fBfor\fP command, \fBcase\fP command, \fBselect\fP command, or
arithmetic \fBfor\fP command, display the expanded value of
.SM
.BR PS4 ,
followed by the command and its expanded arguments
or associated word list.
.TP 8
.B \-B
The shell performs brace expansion (see
.B Brace Expansion
.ie \n(zZ=1 in \fIbash(1)\fP).
.el above).
This is on by default.
.TP 8
.B \-C
If set,
.B bash
does not overwrite an existing file with the
.BR > ,
.BR >& ,
and
.B <>
redirection operators.  This may be overridden when
creating output files by using the redirection operator
.B >|
instead of
.BR > .
.TP 8
.B \-E
If set, any trap on \fBERR\fP is inherited by shell functions, command
substitutions, and commands executed in a subshell environment.
The \fBERR\fP trap is normally not inherited in such cases.
.TP 8
.B \-H
Enable
.B !
style history substitution.  This option is on by
default when the shell is interactive.
.TP 8
.B \-P
If set, the shell does not resolve symbolic links when executing
commands such as
.B cd
that change the current working directory.  It uses the
physical directory structure instead.  By default,
.B bash
follows the logical chain of directories when performing commands
which change the current directory.
.TP 8
.B \-T
If set, any traps on \fBDEBUG\fP and \fBRETURN\fP are inherited by shell
functions, command substitutions, and commands executed in a
subshell environment.
The \fBDEBUG\fP and \fBRETURN\fP traps are normally not inherited
in such cases.
.TP 8
.B \-\-
If no arguments follow this option, then the positional parameters are
unset.  Otherwise, the positional parameters are set to the
\fIarg\fPs, even if some of them begin with a
.BR \- .
.TP 8
.B \-
Signal the end of options, cause all remaining \fIarg\fPs to be
assigned to the positional parameters.  The
.B \-x
and
.B \-v
options are turned off.
If there are no \fIarg\fPs,
the positional parameters remain unchanged.
.PD
.PP
The options are off by default unless otherwise noted.
Using + rather than \- causes these options to be turned off.
The options can also be specified as arguments to an invocation of
the shell.
The current set of options may be found in
.BR $\- .
The return status is always true unless an invalid option is encountered.
.RE
.TP
\fBshift\fP [\fIn\fP]
The positional parameters from \fIn\fP+1 ... are renamed to
.B $1
.B ....
Parameters represented by the numbers \fB$#\fP
down to \fB$#\fP\-\fIn\fP+1 are unset.
.I n
must be a non-negative number less than or equal to \fB$#\fP.
If
.I n
is 0, no parameters are changed.
If
.I n
is not given, it is assumed to be 1.
If
.I n
is greater than \fB$#\fP, the positional parameters are not changed.
The return status is greater than zero if
.I n
is greater than
.B $#
or less than zero; otherwise 0.
.TP
\fBshopt\fP [\fB\-pqsu\fP] [\fB\-o\fP] [\fIoptname\fP ...]
Toggle the values of settings controlling optional shell behavior.
The settings can be either those listed below, or, if the
.B \-o
option is used, those available with the
.B \-o
option to the \fBset\fP builtin command.
With no options, or with the
.B \-p
option, a list of all settable options is displayed, with
an indication of whether or not each is set;
if \fIoptnames\fP are supplied, the output is restricted to those options.
The \fB\-p\fP option causes output to be displayed in a form that
may be reused as input.
Other options have the following meanings:
.RS
.PD 0
.TP
.B \-s
Enable (set) each \fIoptname\fP.
.TP
.B \-u
Disable (unset) each \fIoptname\fP.
.TP
.B \-q
Suppresses normal output (quiet mode); the return status indicates
whether the \fIoptname\fP is set or unset.
If multiple \fIoptname\fP arguments are given with
.BR \-q ,
the return status is zero if all \fIoptnames\fP are enabled; non-zero
otherwise.
.TP
.B \-o
Restricts the values of \fIoptname\fP to be those defined for the
.B \-o
option to the
.B set
builtin.
.PD
.PP
If either
.B \-s
or
.B \-u
is used with no \fIoptname\fP arguments,
.B shopt
shows only those options which are set or unset, respectively.
Unless otherwise noted, the \fBshopt\fP options are disabled (unset)
by default.
.PP
The return status when listing options is zero if all \fIoptnames\fP
are enabled, non-zero otherwise.  When setting or unsetting options,
the return status is zero unless an \fIoptname\fP is not a valid shell
option.
.PP
The list of \fBshopt\fP options is:
.if t .sp .5v
.if n .sp 1v
.PD 0
.TP 8
.B assoc_expand_once
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.
.TP 8
.B autocd
If set, a command name that is the name of a directory is executed as if
it were the argument to the \fBcd\fP command.
This option is only used by interactive shells.
.TP 8
.B cdable_vars
If set, an argument to the
.B cd
builtin command that
is not a directory is assumed to be the name of a variable whose
value is the directory to change to.
.TP 8
.B cdspell
If set, minor errors in the spelling of a directory component in a
.B cd
command will be corrected.
The errors checked for are transposed characters,
a missing character, and one character too many.
If a correction is found, the corrected filename is printed,
and the command proceeds.
This option is only used by interactive shells.
.TP 8
.B checkhash
If set, \fBbash\fP 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.
.TP 8
.B checkjobs
If set, \fBbash\fP 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
.SM
.B "JOB CONTROL"
.ie \n(zZ=1 in \fIbash(1)\fP).
.el above).
The shell always postpones exiting if any jobs are stopped.
.TP 8
.B checkwinsize
If set, \fBbash\fP checks the window size after each external (non-builtin)
command and, if necessary, updates the values of
.SM
.B LINES
and
.SM
.BR COLUMNS .
This option is enabled by default.
.TP 8
.B cmdhist
If set,
.B 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, as described
.ie \n(zZ=1 in \fIbash(1)\fP
.el above
under
.SM
.BR HISTORY .
.PD 0
.TP 8
.B compat31
.TP 8
.B compat32
.TP 8
.B compat40
.TP 8
.B compat41
.TP 8
.B compat42
.TP 8
.B compat43
.TP 8
.B compat44
.TP 8
.B compat50
.PD
These control aspects of the shell's compatibility mode
(see
.SM
.B "SHELL COMPATIBILITY MODE"
.ie \n(zZ=1 in \fIbash(1)\fP).
.el below).
.TP 8
.B complete_fullquote
If set,
.B bash
quotes all shell metacharacters in filenames and directory names when
performing completion.
If not set,
.B 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.
.TP 8
.B direxpand
If set,
.B 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,
.B bash
attempts to preserve what the user typed.
.TP 8
.B dirspell
If set,
.B bash
attempts spelling correction on directory names during word completion
if the directory name initially supplied does not exist.
.TP 8
.B dotglob
If set,
.B bash
includes filenames beginning with a `.' in the results of pathname
expansion.
The filenames
.B ``.''
and
.B ``..''
must always be matched explicitly, even if
.B dotglob
is set.
.TP 8
.B execfail
If set, a non-interactive shell will not exit if
it cannot execute the file specified as an argument to the
.B exec
builtin command.  An interactive shell does not exit if
.B exec
fails.
.TP 8
.B expand_aliases
If set, aliases are expanded as described
.ie \n(zZ=1 in \fIbash(1)\fP
.el above
under
.SM
.BR ALIASES .
This option is enabled by default for interactive shells.
.TP 8
.B extdebug
If set at shell invocation,
or in a shell startup file,
arrange to execute the debugger profile
before the shell starts, identical to the \fB\-\-debugger\fP option.
If set after invocation, behavior intended for use by debuggers is enabled:
.RS
.TP
.B 1.
The \fB\-F\fP option to the \fBdeclare\fP builtin displays the source
file name and line number corresponding to each function name supplied
as an argument.
.TP
.B 2.
If the command run by the \fBDEBUG\fP trap returns a non-zero value, the
next command is skipped and not executed.
.TP
.B 3.
If the command run by the \fBDEBUG\fP trap returns a value of 2, and the
shell is executing in a subroutine (a shell function or a shell script
executed by the \fB.\fP or \fBsource\fP builtins), the shell simulates
a call to \fBreturn\fP.
.TP
.B 4.
.SM
.B BASH_ARGC
and
.SM
.B BASH_ARGV
are updated as described in their descriptions
.ie \n(zZ=1 in \fIbash(1)\fP).
.el above).
.TP
.B 5.
Function tracing is enabled: command substitution, shell functions, and
subshells invoked with \fB(\fP \fIcommand\fP \fB)\fP inherit the
\fBDEBUG\fP and \fBRETURN\fP traps.
.TP
.B 6.
Error tracing is enabled: command substitution, shell functions, and
subshells invoked with \fB(\fP \fIcommand\fP \fB)\fP inherit the
\fBERR\fP trap.
.RE
.TP 8
.B extglob
If set, the extended pattern matching features described
.ie \n(zZ=1 in \fIbash(1)\fP
.el above
under
\fBPathname Expansion\fP are enabled.
.TP 8
.B extquote
If set, \fB$\fP\(aq\fIstring\fP\(aq and \fB$\fP"\fIstring\fP" quoting is
performed within \fB${\fP\fIparameter\fP\fB}\fP expansions
enclosed in double quotes.  This option is enabled by default.
.TP 8
.B failglob
If set, patterns which fail to match filenames during pathname expansion
result in an expansion error.
.TP 8
.B force_fignore
If set, the suffixes specified by the
.SM
.B FIGNORE
shell variable
cause words to be ignored when performing word completion even if
the ignored words are the only possible completions.
See
.SM
\fBSHELL VARIABLES\fP
.ie \n(zZ=1 in \fIbash(1)\fP
.el above
for a description of
.SM
.BR FIGNORE .
This option is enabled by default.
.TP 8
.B globasciiranges
If set, range expressions used in pattern matching bracket expressions (see
.SM
.B Pattern Matching
.ie \n(zZ=1 in \fIbash(1)\fP)
.el above)
behave as if in the traditional C locale when performing
comparisons.  That is, the current locale's collating sequence
is not taken into account, so
.B b
will not collate between
.B A
and
.BR B ,
and upper-case and lower-case ASCII characters will collate together.
.TP 8
.B globskipdots
If set, pathname expansion will never match the filenames
.B ``.''
and
.BR ``..'' ,
even if the pattern begins with a
.BR ``.'' .
This option is enabled by default.
.TP 8
.B globstar
If set, the pattern \fB**\fP used in a pathname expansion context will
match all files and zero or more directories and subdirectories.
If the pattern is followed by a \fB/\fP, only directories and
subdirectories match.
.TP 8
.B gnu_errfmt
If set, shell error messages are written in the standard GNU error
message format.
.TP 8
.B histappend
If set, the history list is appended to the file named by the value
of the
.SM
.B HISTFILE
variable when the shell exits, rather than overwriting the file.
.TP 8
.B histreedit
If set, and
.B readline
is being used, a user is given the opportunity to re-edit a
failed history substitution.
.TP 8
.B histverify
If set, and
.B 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 \fBreadline\fP editing buffer, allowing further modification.
.TP 8
.B hostcomplete
If set, and
.B readline
is being used, \fBbash\fP will attempt to perform hostname completion when a
word containing a \fB@\fP is being completed (see
.B Completing
under
.SM
.B READLINE
.ie \n(zZ=1 in \fIbash(1)\fP).
.el above).
This is enabled by default.
.TP 8
.B huponexit
If set, \fBbash\fP will send
.SM
.B SIGHUP
to all jobs when an interactive login shell exits.
.TP 8
.B inherit_errexit
If set, command substitution inherits the value of the \fBerrexit\fP option,
instead of unsetting it in the subshell environment.
This option is enabled when \fIposix mode\fP is enabled.
.TP 8
.B interactive_comments
If set, allow a word beginning with
.B #
to cause that word and all remaining characters on that
line to be ignored in an interactive shell (see
.SM
.B COMMENTS
.ie \n(zZ=1 in \fIbash(1)\fP).
.el above).
This option is enabled by default.
.TP 8
.B lastpipe
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.
.TP 8
.B lithist
If set, and the
.B cmdhist
option is enabled, multi-line commands are saved to the history with
embedded newlines rather than using semicolon separators where possible.
.TP 8
.B localvar_inherit
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 nameref attribute is not inherited.
.TP 8
.B localvar_unset
If set, calling \fBunset\fP 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.
.TP 8
.B login_shell
The shell sets this option if it is started as a login shell (see
.SM
.B "INVOCATION"
.ie \n(zZ=1 in \fIbash(1)\fP).
.el above).
The value may not be changed.
.TP 8
.B mailwarn
If set, and a file that \fBbash\fP is checking for mail has been
accessed since the last time it was checked, the message ``The mail in
\fImailfile\fP has been read'' is displayed.
.TP 8
.B no_empty_cmd_completion
If set, and
.B readline
is being used,
.B bash
will not attempt to search the
.SM
.B PATH
for possible completions when
completion is attempted on an empty line.
.TP 8
.B nocaseglob
If set,
.B bash
matches filenames in a case\-insensitive fashion when performing pathname
expansion (see
.B Pathname Expansion
.ie \n(zZ=1 in \fIbash(1)\fP).
.el above).
.TP 8
.B nocasematch
If set,
.B bash
matches patterns in a case\-insensitive fashion when performing matching
while executing \fBcase\fP or \fB[[\fP conditional commands,
when performing pattern substitution word expansions,
or when filtering possible completions as part of programmable completion.
.TP 8
.B noexpand_translation
If set,
.B bash
encloses the translated results of $"..." quoting in single quotes
instead of double quotes.
If the string is not translated, this has no effect.
.TP 8
.B nullglob
If set,
.B bash
allows patterns which match no
files (see
.B Pathname Expansion
.ie \n(zZ=1 in \fIbash(1)\fP)
.el above)
to expand to a null string, rather than themselves.
.TP 8
.B patsub_replacement
If set, \fBbash\fP
expands occurrences of \fB&\fP in the replacement string of pattern
substitution to the text matched by the pattern, as described
under \fBParameter Expansion\fP
.ie \n(zZ=1 in \fIbash(1)\fP.
.el above.
This option is enabled by default.
.TP 8
.B progcomp
If set, the programmable completion facilities (see
\fBProgrammable Completion\fP
.ie \n(zZ=1 in \fIbash(1)\fP)
.el above)
are enabled.
This option is enabled by default.
.TP 8
.B progcomp_alias
If set, and programmable completion is enabled, \fBbash\fP treats a command
name that doesn't have any completions as a possible alias and attempts
alias expansion. If it has an alias, \fBbash\fP attempts programmable
completion using the command word resulting from the expanded alias.
.TP 8
.B promptvars
If set, prompt strings undergo
parameter expansion, command substitution, arithmetic
expansion, and quote removal after being expanded as described in
.SM
.B PROMPTING
.ie \n(zZ=1 in \fIbash(1)\fP.
.el above.
This option is enabled by default.
.TP 8
.B restricted_shell
The shell sets this option if it is started in restricted mode
(see
.SM
.B "RESTRICTED SHELL"
.ie \n(zZ=1 in \fIbash(1)\fP).
.el below).
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.
.TP 8
.B shift_verbose
If set, the
.B shift
builtin prints an error message when the shift count exceeds the
number of positional parameters.
.TP 8
.B sourcepath
If set, the
\fB.\fP (\fBsource\fP) builtin uses the value of
.SM
.B PATH
to find the directory containing the file supplied as an argument.
This option is enabled by default.
.TP 8
.B varredir_close
If set, the shell automatically closes file descriptors assigned using the
\fI{varname}\fP redirection syntax (see
.SM
.B REDIRECTION
.ie \n(zZ=1 in \fIbash(1)\fP)
.el above)
instead of leaving them open when the command completes.
.TP 8
.B xpg_echo
If set, the \fBecho\fP builtin expands backslash-escape sequences
by default.
.RE
.PD
.TP
\fBsuspend\fP [\fB\-f\fP]
Suspend the execution of this shell until it receives a
.SM
.B SIGCONT
signal.  A login shell,
or a shell without job control enabled,
cannot be suspended; the
.B \-f
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
.B \-f
is not supplied.
.TP
\fBtest\fP \fIexpr\fP
.PD 0
.TP
\fB[\fP \fIexpr\fP \fB]\fP
Return a status of 0 (true) or 1 (false) depending on
the evaluation of the conditional expression
.IR expr .
Each operator and operand must be a separate argument.
Expressions are composed of the primaries described 
.ie \n(zZ=1 in \fIbash(1)\fP
.el above
under
.SM
.BR "CONDITIONAL EXPRESSIONS" .
\fBtest\fP does not accept any options, nor does it accept and ignore
an argument of \fB\-\-\fP as signifying the end of options.
.if t .sp 0.5
.if n .sp 1
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.
.RS
.PD 0
.TP
.B ! \fIexpr\fP
True if
.I expr
is false.
.TP
.B ( \fIexpr\fP )
Returns the value of \fIexpr\fP.
This may be used to override the normal precedence of operators.
.TP
\fIexpr1\fP \-\fBa\fP \fIexpr2\fP
True if both
.I expr1
and
.I expr2
are true.
.TP
\fIexpr1\fP \-\fBo\fP \fIexpr2\fP
True if either
.I expr1
or
.I expr2
is true.
.PD
.PP
\fBtest\fP and \fB[\fP evaluate conditional
expressions using a set of rules based on the number of arguments.
.if t .sp 0.5
.if n .sp 1
.PD 0
.TP
0 arguments
The expression is false.
.TP
1 argument
The expression is true if and only if the argument is not null.
.TP
2 arguments
If the first argument is \fB!\fP, the expression is true if and
only if the second argument is null.
If the first argument is one of the unary conditional operators listed
.ie \n(zZ=1 in \fIbash(1)\fP
.el above
under
.SM
.BR "CONDITIONAL EXPRESSIONS" ,
the expression is true if the unary test is true.
If the first argument is not a valid unary conditional operator, the expression
is false.
.TP
3 arguments
The following conditions are applied in the order listed.
If the second argument is one of the binary conditional operators listed
.ie \n(zZ=1 in \fIbash(1)\fP
.el above
under
.SM
.BR "CONDITIONAL EXPRESSIONS" ,
the result of the expression is the result of the binary test using
the first and third arguments as operands.
The \fB\-a\fP and \fB\-o\fP operators are considered binary operators
when there are three arguments.
If the first argument is \fB!\fP, the value is the negation of
the two-argument test using the second and third arguments.
If the first argument is exactly \fB(\fP and the third argument is
exactly \fB)\fP, the result is the one-argument test of the second
argument.
Otherwise, the expression is false.
.TP
4 arguments
The following conditions are applied in the order listed.
If the first argument is \fB!\fP, the result is the negation of
the three-argument expression composed of the remaining arguments.
the two-argument test using the second and third arguments.
If the first argument is exactly \fB(\fP and the fourth argument is
exactly \fB)\fP, the result is the two-argument test of the second
and third arguments.
Otherwise, the expression is parsed and evaluated according to
precedence using the rules listed above.
.TP
5 or more arguments
The expression is parsed and evaluated according to precedence
using the rules listed above.
.if t .sp 0.5
.if n .sp 1
.LP
When used with \fBtest\fP or \fB[\fP, the \fB<\fP and \fB>\fP operators
sort lexicographically using ASCII ordering.
.RE
.PD
.TP
.B times
Print the accumulated user and system times for the shell and
for processes run from the shell.  The return status is 0.
.TP
\fBtrap\fP [\fB\-lp\fP] [[\fIarg\fP] \fIsigspec\fP ...]
The command
.I arg
is to be read and executed when the shell receives
signal(s)
.IR sigspec .
If
.I arg
is absent (and there is a single \fIsigspec\fP) or
.BR \- ,
each specified signal is
reset to its original disposition (the value it had
upon entrance to the shell).
If
.I arg
is the null string the signal specified by each
.I sigspec
is ignored by the shell and by the commands it invokes.
If
.I arg
is not present and
.B \-p
has been supplied, then the trap commands associated with each
.I sigspec
are displayed.
If no arguments are supplied or if only
.B \-p
is given,
.B trap
prints the list of commands associated with each signal.
The
.B \-l
option causes the shell to print a list of signal names and
their corresponding numbers.
Each
.I sigspec
is either
a signal name defined in <\fIsignal.h\fP>, or a signal number.
Signal names are case insensitive and the
.SM
.B SIG
prefix is optional.
.if t .sp 0.5
.if n .sp 1
If a
.I sigspec
is
.SM
.B EXIT
(0) the command
.I arg
is executed on exit from the shell.
If a
.I sigspec
is
.SM
.BR DEBUG ,
the command
.I arg
is executed before every \fIsimple command\fP, \fIfor\fP command,
\fIcase\fP command, \fIselect\fP command, every arithmetic \fIfor\fP
command, and before the first command executes in a shell function (see
.SM
.B SHELL GRAMMAR
.ie \n(zZ=1 in \fIbash(1)\fP).
.el above).
Refer to the description of the \fBextdebug\fP option to the
\fBshopt\fP builtin for details of its effect on the \fBDEBUG\fP trap.
If a
.I sigspec
is
.SM
.BR RETURN ,
the command
.I arg
is executed each time a shell function or a script executed with
the \fB.\fP or \fBsource\fP builtins finishes executing.
.if t .sp 0.5
.if n .sp 1
If a
.I sigspec
is
.SM
.BR ERR ,
the command
.I arg
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
.SM
.B ERR
trap is not executed if the failed
command is part of the command list immediately following a
.B while
or
.B until
keyword,
part of the test in an
.I if
statement, part of a command executed in a
.B &&
or
.B ||
list except the command following the final \fB&&\fP or \fB||\fP,
any command in a pipeline but the last,
or if the command's return value is
being inverted using
.BR ! .
These are the same conditions obeyed by the \fBerrexit\fP (\fB\-e\fP) option.
.if t .sp 0.5
.if n .sp 1
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.
The return status is false if any
.I sigspec
is invalid; otherwise
.B trap
returns true.
.TP
\fBtype\fP [\fB\-aftpP\fP] \fIname\fP [\fIname\fP ...]
With no options,
indicate how each
.I name
would be interpreted if used as a command name.
If the
.B \-t
option is used,
.B type
prints a string which is one of
.IR alias ,
.IR keyword ,
.IR function ,
.IR builtin ,
or
.I file
if
.I name
is an alias, shell reserved word, function, builtin, or disk file,
respectively.
If the
.I name
is not found, then nothing is printed, and an exit status of false
is returned.
If the
.B \-p
option is used,
.B type
either returns the name of the disk file
that would be executed if
.I name
were specified as a command name,
or nothing if
.if t \f(CWtype -t name\fP
.if n ``type -t name''
would not return
.IR file .
The
.B \-P
option forces a
.SM
.B PATH
search for each \fIname\fP, even if
.if t \f(CWtype -t name\fP
.if n ``type -t name''
would not return
.IR file .
If a command is hashed,
.B \-p
and
.B \-P
print the hashed value, which is not necessarily the file that appears
first in
.SM
.BR PATH .
If the
.B \-a
option is used,
.B type
prints all of the places that contain
an executable named
.IR name .
This includes aliases and functions,
if and only if the
.B \-p
option is not also used.
The table of hashed commands is not consulted
when using
.BR \-a .
The
.B \-f
option suppresses shell function lookup, as with the \fBcommand\fP builtin.
.B type
returns true if all of the arguments are found, false if
any are not found.
.TP
\fBulimit\fP [\fB\-HS\fP] \fB\-a\fP
.PD 0
.TP
\fBulimit\fP [\fB\-HS\fP] [\fB\-bcdefiklmnpqrstuvxPRT\fP [\fIlimit\fP]]
.PD
Provides control over the resources available to the shell and to
processes started by it, on systems that allow such control.
The \fB\-H\fP and \fB\-S\fP options specify that the hard or soft limit is
set for the given resource.
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.
If neither \fB\-H\fP nor \fB\-S\fP is specified, both the soft and hard
limits are set.
The value of
.I limit
can be a number in the unit specified for the resource
or one of the special values
.BR hard ,
.BR soft ,
or
.BR unlimited ,
which stand for the current hard limit, the current soft limit, and
no limit, respectively.
If
.I limit
is omitted, the current value of the soft limit of the resource is
printed, unless the \fB\-H\fP option is given.  When more than one
resource is specified, the limit name and unit, if appropriate,
are printed before the value.
Other options are interpreted as follows:
.RS
.PD 0
.TP
.B \-a
All current limits are reported; no limits are set
.TP
.B \-b
The maximum socket buffer size
.TP
.B \-c
The maximum size of core files created
.TP
.B \-d
The maximum size of a process's data segment
.TP
.B \-e
The maximum scheduling priority ("nice")
.TP
.B \-f
The maximum size of files written by the shell and its children
.TP
.B \-i
The maximum number of pending signals
.TP
.B \-k
The maximum number of kqueues that may be allocated
.TP
.B \-l
The maximum size that may be locked into memory
.TP
.B \-m
The maximum resident set size (many systems do not honor this limit)
.TP
.B \-n
The maximum number of open file descriptors (most systems do not
allow this value to be set)
.TP
.B \-p
The pipe size in 512-byte blocks (this may not be set)
.TP
.B \-q
The maximum number of bytes in POSIX message queues
.TP
.B \-r
The maximum real-time scheduling priority
.TP
.B \-s
The maximum stack size
.TP
.B \-t
The maximum amount of cpu time in seconds
.TP
.B \-u
The maximum number of processes available to a single user
.TP
.B \-v
The maximum amount of virtual memory available to the shell and, on
some systems, to its children
.TP
.B \-x
The maximum number of file locks
.TP
.B \-P
The maximum number of pseudoterminals
.TP
.B \-R
The maximum time a real-time process can run before blocking, in microseconds
.TP
.B \-T
The maximum number of threads
.PD
.PP
If
.I limit
is given, and the
.B \-a
option is not used,
\fIlimit\fP is the new value of the specified resource.
If no option is given, then
.B \-f
is assumed.  Values are in 1024-byte increments, except for
.BR \-t ,
which is in seconds;
.BR \-R ,
which is in microseconds;
.BR \-p ,
which is in units of 512-byte blocks;
.BR \-P ,
.BR \-T ,
.BR \-b ,
.BR \-k ,
.BR \-n ,
and
.BR \-u ,
which are unscaled values;
and, when in posix mode,
.B \-c
and
.BR \-f ,
which are in 512-byte increments.
The return status is 0 unless an invalid option or argument is supplied,
or an error occurs while setting a new limit.
.RE
.TP
\fBumask\fP [\fB\-p\fP] [\fB\-S\fP] [\fImode\fP]
The user file-creation mask is set to
.IR mode .
If
.I mode
begins with a digit, it
is interpreted as an octal number; otherwise
it is interpreted as a symbolic mode mask similar
to that accepted by
.IR chmod (1).
If
.I mode
is omitted, the current value of the mask is printed.
The
.B \-S
option causes the mask to be printed in symbolic form; the
default output is an octal number.
If the
.B \-p
option is supplied, and
.I mode
is omitted, the output is in a form that may be reused as input.
The return status is 0 if the mode was successfully changed or if
no \fImode\fP argument was supplied, and false otherwise.
.TP
\fBunalias\fP [\-\fBa\fP] [\fIname\fP ...]
Remove each \fIname\fP from the list of defined aliases.  If
.B \-a
is supplied, all alias definitions are removed.  The return
value is true unless a supplied
.I name
is not a defined alias.
.TP
\fBunset\fP [\-\fBfv\fP] [\-\fBn\fP] [\fIname\fP ...]
For each
.IR name ,
remove the corresponding variable or function.
If the
.B \-v
option is given, each
.I name
refers to a shell variable, and that variable is removed.
Read-only variables may not be unset.
If
.B \-f
is specified, each
.I name
refers to a shell function, and the function definition
is removed.
If the
.B \-n
option is supplied, and \fIname\fP is a variable with the \fInameref\fP
attribute, \fIname\fP will be unset rather than the variable it
references.
\fB\-n\fP has no effect if the \fB\-f\fP option is supplied.
If no options are supplied, each \fIname\fP refers to a variable; if
there is no variable by that name, a function with that name, if any, is
unset.
Each unset variable or function is removed from the environment
passed to subsequent commands.
If any of
.SM
.BR BASH_ALIASES ,
.SM
.BR BASH_ARGV0 ,
.SM
.BR BASH_CMDS ,
.SM
.BR BASH_COMMAND ,
.SM
.BR BASH_SUBSHELL ,
.SM
.BR BASHPID ,
.SM
.BR COMP_WORDBREAKS ,
.SM
.BR DIRSTACK ,
.SM
.BR EPOCHREALTIME ,
.SM
.BR EPOCHSECONDS ,
.SM
.BR FUNCNAME ,
.SM
.BR GROUPS ,
.SM
.BR HISTCMD ,
.SM
.BR LINENO ,
.SM
.BR RANDOM ,
.SM
.BR SECONDS ,
or
.SM
.B SRANDOM
are unset, they lose their special properties, even if they are
subsequently reset.  The exit status is true unless a
.I name
is readonly or may not be unset.
.TP
\fBwait\fP [\fB\-fn\fP] [\fP\-p\fP \fIvarname\fP] [\fIid ...\fP]
Wait for each specified child process and return its termination status.
Each
.I id
may be a process
ID or a job specification; if a job spec is given, all processes
in that job's pipeline are waited for.  If
.I id
is not given,
\fBwait\fP waits for all running background jobs and
the last-executed process substitution, if its process id is the same as
\fB$!\fP,
and the return status is zero.
If the \fB\-n\fP option is supplied,
\fBwait\fP waits for a single job
from the list of \fIid\fPs or, if no \fIid\fPs 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 \fB\-p\fP option is supplied, the process or job identifier of the job
for which the exit status is returned is assigned to the variable
\fIvarname\fP named by the option argument.
The variable will be unset initially, before any assignment.
This is useful only when the \fB\-n\fP option is supplied.
Supplying the \fB\-f\fP option, when job control is enabled,
forces \fBwait\fP to wait for \fIid\fP to terminate before returning
its status, instead of returning when it changes status.
If
.I id
specifies a non-existent process or job, the return status is 127.
If \fBwait\fP is interrupted by a signal, the return status will be greater
than 128, as described under
.B SIGNALS
.ie \n(zZ=1 in \fIbash(1)\fP.
.el above.
Otherwise, the return status is the exit status of the last
process or job waited for.
.SH "SHELL COMPATIBILITY MODE"
Bash-4.0 introduced the concept of a \fIshell compatibility level\fP,
specified as a set of options to the shopt builtin (
.BR compat31 ,
.BR compat32 ,
.BR compat40 ,
.BR compat41 ,
and so on).
There is only one current
compatibility level -- 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's intended to be a temporary solution.
.PP
This section does not mention behavior that is standard for a particular
version (e.g., setting \fBcompat32\fP 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). 
.PP
If a user enables, say, \fBcompat32\fP, 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 \fBbash\fP,
but that behavior may have been present in earlier versions.
For instance, the change to use locale-based comparisons with the \fB[[\fP
command came in bash-4.1, and earlier versions used ASCII-based comparisons,
so enabling \fBcompat32\fP 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.
.PP
Bash-4.3 introduced a new shell variable:
.SM
.BR BASH_COMPAT .
The value assigned
to this variable (a decimal version number like 4.2, or an integer
corresponding to the \fBcompat\fP\fINN\fP option, like 42) determines the
compatibility level.
.PP
Starting with bash-4.4, Bash has begun deprecating older compatibility
levels.
Eventually, the options will be removed in favor of
.SM
.BR BASH_COMPAT .
.PP
Bash-5.0 is the final version for which there will be an individual shopt
option for the previous version. Users should use
.SM
.B BASH_COMPAT
on bash-5.0 and later versions.
.PP
The following table describes the behavior changes controlled by each
compatibility level setting.
The \fBcompat\fP\fINN\fP tag is used as shorthand for setting the
compatibility level
to \fINN\fP using one of the following mechanisms.
For versions prior to bash-5.0, the compatibility level may be set using
the corresponding \fBcompat\fP\fINN\fP shopt option.
For bash-4.3 and later versions, the
.SM
.B BASH_COMPAT
variable is preferred,
and it is required for bash-5.1 and later versions.
.TP
\fBcompat31\fP
.PD 0
.RS
.IP \(bu
quoting the rhs of the \fB[[\fP command's regexp matching operator (=~)
has no special effect
.RE
.PD
.TP
\fBcompat32\fP
.PD 0
.RS
.IP \(bu
interrupting a command list such as "a ; b ; c" 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)
.RE
.PD
.TP
\fBcompat40\fP
.PD 0
.RS
.IP \(bu
the \fB<\fP and \fB>\fP operators to the \fB[[\fP 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
.IR strcmp (3);
bash-4.1 and later use the current locale's collation sequence and
.IR strcoll (3).
.RE
.PD
.TP
\fBcompat41\fP
.PD 0
.RS
.IP \(bu
in \fIposix\fP mode, \fBtime\fP may be followed by options and still be
recognized as a reserved word (this is POSIX interpretation 267)
.IP \(bu
in \fIposix\fP mode, the parser requires that an even number of single
quotes occur in the \fIword\fP portion of a double-quoted
parameter expansion and treats them specially, so that characters within
the single quotes are considered quoted
(this is POSIX interpretation 221)
.RE
.PD
.TP
\fBcompat42\fP
.PD 0
.RS
.IP \(bu
the replacement string in double-quoted pattern substitution does not
undergo quote removal, as it does in versions after bash-4.2
.IP \(bu
in posix mode, single quotes are considered special when expanding
the \fIword\fP portion of a double-quoted parameter expansion
and can be used to quote a closing brace or other special character
(this is part of POSIX interpretation 221);
in later versions, single quotes
are not special within double-quoted word expansions
.RE
.PD
.TP
\fBcompat43\fP
.PD 0
.RS
.IP \(bu
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=\(aq(1 2)\(aq). Later versions warn that this usage is
deprecated
.IP \(bu
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)
.IP \(bu
when executing a shell function, the loop state (while/until/etc.)
is not reset, so \fBbreak\fP or \fBcontinue\fP in that function will break
or continue loops in the calling context. Bash-4.4 and later reset
the loop state to prevent this
.RE
.PD
.TP
\fBcompat44\fP
.PD 0
.RS
.IP \(bu
the shell sets up the values used by
.SM
.B BASH_ARGV
and
.SM
.B BASH_ARGC
so they can expand to the shell's positional parameters even if extended
debugging mode is not enabled
.IP \(bu
a subshell inherits loops from its parent context, so \fBbreak\fP
or \fBcontinue\fP will cause the subshell to exit.
Bash-5.0 and later reset the loop state to prevent the exit
.IP \(bu
variable assignments preceding builtins like \fBexport\fP and \fBreadonly\fP
that set attributes continue to affect variables with the same
name in the calling environment even if the shell is not in posix
mode
.RE
.PD
.TP
\fBcompat50\fP
.PD 0
.RS
.IP \(bu
Bash-5.1 changed the way
.SM
.B $RANDOM
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
.SM
.B RANDOM
will produce the same sequence as in bash-5.0
.IP \(bu
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 \fB\-l\fP option is supplied.
.RE
.PD
.TP
\fBcompat51\fP
.PD 0
.RS
.IP \(bu
The \fBunset\fP builtin treats attempts to unset array subscripts \fB@\fP
and \fB*\fP differently depending on whether the array is indexed or
associative, and differently than in previous versions.
.RE
.PD
.\" bash_builtins
.if \n(zZ=1 .ig zZ
.SH "RESTRICTED SHELL"
.\" rbash.1
.zY
.PP
If
.B bash
is started with the name
.BR rbash ,
or the
.B \-r
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.
It behaves identically to
.B bash
with the exception that the following are disallowed or not performed:
.IP \(bu
changing directories with \fBcd\fP
.IP \(bu
setting or unsetting the values of
.SM
.BR SHELL ,
.SM
.BR PATH ,
.SM
.BR HISTFILE ,
.SM
.BR ENV ,
or
.SM
.B BASH_ENV
.IP \(bu
specifying command names containing
.B /
.IP \(bu
specifying a filename containing a
.B /
as an argument to the
.B .
builtin command
.IP \(bu
specifying a filename containing a slash as an argument to the
.B history
builtin command
.IP \(bu
specifying a filename containing a slash as an argument to the
.B \-p
option to the
.B hash
builtin command
.IP \(bu
importing function definitions from the shell environment at startup
.IP \(bu
parsing the value of
.SM
.B SHELLOPTS
from the shell environment at startup
.IP \(bu
redirecting output using the >, >|, <>, >&, &>, and >> redirection operators
.IP \(bu
using the
.B exec
builtin command to replace the shell with another command
.IP \(bu
adding or deleting builtin commands with the
.B \-f
and
.B \-d
options to the
.B enable
builtin command
.IP \(bu
using the \fBenable\fP builtin command to enable disabled shell builtins
.IP \(bu
specifying the
.B \-p
option to the
.B command
builtin command
.IP \(bu
turning off restricted mode with
\fBset +r\fP or \fBshopt -u restricted_shell\fP.
.PP
These restrictions are enforced after any startup files are read.
.PP
.ie \n(zY=1 When a command that is found to be a shell script is executed,
.el \{ When a command that is found to be a shell script is executed
(see
.SM
.B "COMMAND EXECUTION"
above),
\}
.B rbash
turns off any restrictions in the shell spawned to execute the
script.
.\" end of rbash.1
.if \n(zY=1 .ig zY
.SH "SEE ALSO"
.PD 0
.TP
\fIBash Reference Manual\fP, Brian Fox and Chet Ramey
.TP
\fIThe Gnu Readline Library\fP, Brian Fox and Chet Ramey
.TP
\fIThe Gnu History Library\fP, Brian Fox and Chet Ramey
.TP
\fIPortable Operating System Interface (POSIX) Part 2: Shell and Utilities\fP, IEEE --
http://pubs.opengroup.org/onlinepubs/9699919799/
.TP
http://tiswww.case.edu/~chet/bash/POSIX -- a description of posix mode
.TP
\fIsh\fP(1), \fIksh\fP(1), \fIcsh\fP(1)
.TP
\fIemacs\fP(1), \fIvi\fP(1)
.TP
\fIreadline\fP(3)
.PD
.SH FILES
.PD 0
.TP
.FN /bin/bash
The \fBbash\fP executable
.TP
.FN /etc/profile
The systemwide initialization file, executed for login shells
.TP
.FN ~/.bash_profile
The personal initialization file, executed for login shells
.TP
.FN ~/.bashrc
The individual per-interactive-shell startup file
.TP
.FN ~/.bash_logout
The individual login shell cleanup file, executed when a login shell exits
.TP
.FN ~/.bash_history
The default value of \fBHISTFILE\fP, the file in which bash saves the
command history
.TP
.FN ~/.inputrc
Individual \fIreadline\fP initialization file
.PD
.SH AUTHORS
Brian Fox, Free Software Foundation
.br
bfox@gnu.org
.PP
Chet Ramey, Case Western Reserve University
.br
chet.ramey@case.edu
.SH BUG REPORTS
If you find a bug in
.B bash,
you should report it.  But first, you should
make sure that it really is a bug, and that it appears in the latest
version of
.BR bash .
The latest version is always available from
\fIftp://ftp.gnu.org/pub/gnu/bash/\fP and
\fIhttp://git.savannah.gnu.org/cgit/bash.git/snapshot/bash-master.tar.gz\fP.
.PP
Once you have determined that a bug actually exists, use the
.I bashbug
command to submit a bug report.
If you have a fix, you are encouraged to mail that as well!
Suggestions and `philosophical' bug reports may be mailed
to \fIbug-bash@gnu.org\fP or posted to the Usenet
newsgroup
.BR gnu.bash.bug .
.PP
ALL bug reports should include:
.PP
.PD 0
.TP 20
The version number of \fBbash\fR
.TP
The hardware and operating system
.TP
The compiler used to compile
.TP
A description of the bug behaviour
.TP
A short script or `recipe' which exercises the bug
.PD
.PP
.I bashbug
inserts the first three items automatically into the template
it provides for filing a bug report.
.PP
Comments and bug reports concerning
this manual page should be directed to
.IR chet.ramey@case.edu .
.SH BUGS
It's too big and too slow.
.PP
There are some subtle differences between
.B bash
and traditional versions of
.BR sh ,
mostly because of the
.SM
.B POSIX
specification.
.PP
Aliases are confusing in some uses.
.PP
Shell builtin commands and functions are not stoppable/restartable.
.PP
Compound commands and command sequences of the form `a ; b ; c'
are not handled gracefully when process suspension is attempted.
When a process is stopped, the shell immediately executes the next
command in the sequence.
It suffices to place the sequence of commands between
parentheses to force it into a subshell, which may be stopped as
a unit.
.PP
Array variables may not (yet) be exported.
.PP
There may be only one active coprocess at a time.
.zZ
.zY