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| author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 15:38:56 +0000 |
|---|---|---|
| committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 15:38:56 +0000 |
| commit | 6c20c8ed2cb9ab69a1a57ccb2b9b79969a808321 (patch) | |
| tree | f63ce19d57fad3ac4a15bc26dbfbfa2b834111b5 /doc/bash.0 | |
| parent | Initial commit. (diff) | |
| download | bash-upstream.tar.xz bash-upstream.zip | |
Adding upstream version 5.2.15.upstream/5.2.15upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'doc/bash.0')
| -rw-r--r-- | doc/bash.0 | 6664 |
1 files changed, 6664 insertions, 0 deletions
diff --git a/doc/bash.0 b/doc/bash.0 new file mode 100644 index 0000000..1580b77 --- /dev/null +++ b/doc/bash.0 @@ -0,0 +1,6664 @@ +BASH(1) General Commands Manual BASH(1) + + + +NNAAMMEE + bash - GNU Bourne-Again SHell + +SSYYNNOOPPSSIISS + bbaasshh [options] [command_string | file] + +CCOOPPYYRRIIGGHHTT + Bash is Copyright (C) 1989-2022 by the Free Software Foundation, Inc. + +DDEESSCCRRIIPPTTIIOONN + BBaasshh is an sshh-compatible command language interpreter that executes + commands read from the standard input or from a file. BBaasshh also incor- + porates useful features from the _K_o_r_n and _C shells (kksshh and ccsshh). + + BBaasshh is intended to be a conformant implementation of the Shell and + Utilities portion of the IEEE POSIX specification (IEEE Standard + 1003.1). BBaasshh can be configured to be POSIX-conformant by default. + +OOPPTTIIOONNSS + All of the single-character shell options documented in the description + of the sseett builtin command, including --oo, can be used as options when + the shell is invoked. In addition, bbaasshh interprets the following op- + tions when it is invoked: + + --cc If the --cc option is present, then commands are read from the + first non-option argument _c_o_m_m_a_n_d___s_t_r_i_n_g. If there are argu- + ments after the _c_o_m_m_a_n_d___s_t_r_i_n_g, the first argument is as- + signed to $$00 and any remaining arguments are assigned to the + positional parameters. The assignment to $$00 sets the name of + the shell, which is used in warning and error messages. + --ii If the --ii option is present, the shell is _i_n_t_e_r_a_c_t_i_v_e. + --ll Make bbaasshh act as if it had been invoked as a login shell (see + IINNVVOOCCAATTIIOONN below). + --rr If the --rr option is present, the shell becomes _r_e_s_t_r_i_c_t_e_d + (see RREESSTTRRIICCTTEEDD SSHHEELLLL below). + --ss If the --ss 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. + --DD A list of all double-quoted strings preceded by $$ is printed + on the standard output. These are the strings that are sub- + ject to language translation when the current locale is not CC + or PPOOSSIIXX. This implies the --nn option; no commands will be + executed. + [[--++]]OO [[_s_h_o_p_t___o_p_t_i_o_n]] + _s_h_o_p_t___o_p_t_i_o_n is one of the shell options accepted by the + sshhoopptt builtin (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below). If + _s_h_o_p_t___o_p_t_i_o_n is present, --OO sets the value of that option; ++OO + unsets it. If _s_h_o_p_t___o_p_t_i_o_n is not supplied, the names and + values of the shell options accepted by sshhoopptt are printed on + the standard output. If the invocation option is ++OO, the + output is displayed in a format that may be reused as input. + ---- A ---- signals the end of options and disables further option + processing. Any arguments after the ---- are treated as file- + names and arguments. An argument of -- is equivalent to ----. + + BBaasshh also interprets a number of multi-character options. These op- + tions must appear on the command line before the single-character op- + tions to be recognized. + + ----ddeebbuuggggeerr + Arrange for the debugger profile to be executed before the shell + starts. Turns on extended debugging mode (see the description + of the eexxttddeebbuugg option to the sshhoopptt builtin below). + ----dduummpp--ppoo--ssttrriinnggss + Equivalent to --DD, but the output is in the GNU _g_e_t_t_e_x_t ppoo (por- + table object) file format. + ----dduummpp--ssttrriinnggss + Equivalent to --DD. + ----hheellpp Display a usage message on standard output and exit success- + fully. + ----iinniitt--ffiillee _f_i_l_e + ----rrccffiillee _f_i_l_e + Execute commands from _f_i_l_e instead of the standard personal ini- + tialization file _~_/_._b_a_s_h_r_c if the shell is interactive (see IINN-- + VVOOCCAATTIIOONN below). + + ----llooggiinn + Equivalent to --ll. + + ----nnooeeddiittiinngg + Do not use the GNU rreeaaddlliinnee library to read command lines when + the shell is interactive. + + ----nnoopprrooffiillee + Do not read either the system-wide startup file _/_e_t_c_/_p_r_o_f_i_l_e or + any of the personal initialization files _~_/_._b_a_s_h___p_r_o_f_i_l_e, + _~_/_._b_a_s_h___l_o_g_i_n, or _~_/_._p_r_o_f_i_l_e. By default, bbaasshh reads these + files when it is invoked as a login shell (see IINNVVOOCCAATTIIOONN be- + low). + + ----nnoorrcc Do not read and execute the personal initialization file + _~_/_._b_a_s_h_r_c if the shell is interactive. This option is on by de- + fault if the shell is invoked as sshh. + + ----ppoossiixx + Change the behavior of bbaasshh where the default operation differs + from the POSIX standard to match the standard (_p_o_s_i_x _m_o_d_e). See + SSEEEE AALLSSOO below for a reference to a document that details how + posix mode affects bash's behavior. + + ----rreessttrriicctteedd + The shell becomes restricted (see RREESSTTRRIICCTTEEDD SSHHEELLLL below). + + ----vveerrbboossee + Equivalent to --vv. + + ----vveerrssiioonn + Show version information for this instance of bbaasshh on the stan- + dard output and exit successfully. + +AARRGGUUMMEENNTTSS + If arguments remain after option processing, and neither the --cc nor the + --ss option has been supplied, the first argument is assumed to be the + name of a file containing shell commands. If bbaasshh is invoked in this + fashion, $$00 is set to the name of the file, and the positional parame- + ters are set to the remaining arguments. BBaasshh reads and executes com- + mands from this file, then exits. BBaasshh's exit status is the exit sta- + tus of the last command executed in the script. If no commands are ex- + ecuted, 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 PPAATTHH for the script. + +IINNVVOOCCAATTIIOONN + A _l_o_g_i_n _s_h_e_l_l is one whose first character of argument zero is a --, or + one started with the ----llooggiinn option. + + An _i_n_t_e_r_a_c_t_i_v_e shell is one started without non-option arguments (un- + less --ss is specified) and without the --cc option, whose standard input + and error are both connected to terminals (as determined by _i_s_a_t_t_y(3)), + or one started with the --ii option. PPSS11 is set and $$-- includes ii if + bbaasshh is interactive, allowing a shell script or a startup file to test + this state. + + The following paragraphs describe how bbaasshh executes its startup files. + If any of the files exist but cannot be read, bbaasshh reports an error. + Tildes are expanded in filenames as described below under TTiillddee EExxppaann-- + ssiioonn in the EEXXPPAANNSSIIOONN section. + + When bbaasshh is invoked as an interactive login shell, or as a non-inter- + active shell with the ----llooggiinn option, it first reads and executes com- + mands from the file _/_e_t_c_/_p_r_o_f_i_l_e, if that file exists. After reading + that file, it looks for _~_/_._b_a_s_h___p_r_o_f_i_l_e, _~_/_._b_a_s_h___l_o_g_i_n, and _~_/_._p_r_o_f_i_l_e, + in that order, and reads and executes commands from the first one that + exists and is readable. The ----nnoopprrooffiillee option may be used when the + shell is started to inhibit this behavior. + + When an interactive login shell exits, or a non-interactive login shell + executes the eexxiitt builtin command, bbaasshh reads and executes commands + from the file _~_/_._b_a_s_h___l_o_g_o_u_t, if it exists. + + When an interactive shell that is not a login shell is started, bbaasshh + reads and executes commands from _~_/_._b_a_s_h_r_c, if that file exists. This + may be inhibited by using the ----nnoorrcc option. The ----rrccffiillee _f_i_l_e option + will force bbaasshh to read and execute commands from _f_i_l_e instead of + _~_/_._b_a_s_h_r_c. + + When bbaasshh is started non-interactively, to run a shell script, for ex- + ample, it looks for the variable BBAASSHH__EENNVV 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. BBaasshh behaves as if the following com- + mand were executed: + if [ -n "$BASH_ENV" ]; then . "$BASH_ENV"; fi + but the value of the PPAATTHH variable is not used to search for the file- + name. + + If bbaasshh is invoked with the name sshh, it tries to mimic the startup be- + havior of historical versions of sshh as closely as possible, while con- + forming to the POSIX standard as well. When invoked as an interactive + login shell, or a non-interactive shell with the ----llooggiinn option, it + first attempts to read and execute commands from _/_e_t_c_/_p_r_o_f_i_l_e and + _~_/_._p_r_o_f_i_l_e, in that order. The ----nnoopprrooffiillee option may be used to in- + hibit this behavior. When invoked as an interactive shell with the + name sshh, bbaasshh looks for the variable EENNVV, 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 sshh does not attempt to read and exe- + cute commands from any other startup files, the ----rrccffiillee option has no + effect. A non-interactive shell invoked with the name sshh does not at- + tempt to read any other startup files. When invoked as sshh, bbaasshh enters + _p_o_s_i_x mode after the startup files are read. + + When bbaasshh is started in _p_o_s_i_x mode, as with the ----ppoossiixx command line + option, it follows the POSIX standard for startup files. In this mode, + interactive shells expand the EENNVV variable and commands are read and + executed from the file whose name is the expanded value. No other + startup files are read. + + BBaasshh 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 _r_s_h_d, or the secure shell daemon _s_s_h_d. If + bbaasshh determines it is being run non-interactively in this fashion, it + reads and executes commands from _~_/_._b_a_s_h_r_c, if that file exists and is + readable. It will not do this if invoked as sshh. The ----nnoorrcc option may + be used to inhibit this behavior, and the ----rrccffiillee option may be used + to force another file to be read, but neither _r_s_h_d nor _s_s_h_d generally + invoke the shell with those options or allow them to be specified. + + If the shell is started with the effective user (group) id not equal to + the real user (group) id, and the --pp option is not supplied, no startup + files are read, shell functions are not inherited from the environment, + the SSHHEELLLLOOPPTTSS, BBAASSHHOOPPTTSS, CCDDPPAATTHH, and GGLLOOBBIIGGNNOORREE variables, if they ap- + pear in the environment, are ignored, and the effective user id is set + to the real user id. If the --pp option is supplied at invocation, the + startup behavior is the same, but the effective user id is not reset. + +DDEEFFIINNIITTIIOONNSS + The following definitions are used throughout the rest of this docu- + ment. + bbllaannkk A space or tab. + wwoorrdd A sequence of characters considered as a single unit by the + shell. Also known as a ttookkeenn. + nnaammee A _w_o_r_d consisting only of alphanumeric characters and under- + scores, and beginning with an alphabetic character or an under- + score. Also referred to as an iiddeennttiiffiieerr. + mmeettaacchhaarraacctteerr + A character that, when unquoted, separates words. One of the + following: + || && ;; (( )) << >> ssppaaccee ttaabb nneewwlliinnee + ccoonnttrrooll ooppeerraattoorr + A _t_o_k_e_n that performs a control function. It is one of the fol- + lowing symbols: + |||| && &&&& ;; ;;;; ;;&& ;;;;&& (( )) || ||&& <<nneewwlliinnee>> + +RREESSEERRVVEEDD WWOORRDDSS + _R_e_s_e_r_v_e_d _w_o_r_d_s 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 SSHHEELLLL GGRRAAMMMMAARR below), the third word of a + ccaassee or sseelleecctt command (only iinn is valid), or the third word of a ffoorr + command (only iinn and ddoo are valid): + + !! ccaassee ccoopprroocc ddoo ddoonnee eelliiff eellssee eessaacc ffii ffoorr ffuunnccttiioonn iiff iinn sseelleecctt + tthheenn uunnttiill wwhhiillee {{ }} ttiimmee [[[[ ]]]] + +SSHHEELLLL GGRRAAMMMMAARR + This section describes the syntax of the various forms of shell com- + mands. + + SSiimmppllee CCoommmmaannddss + A _s_i_m_p_l_e _c_o_m_m_a_n_d is a sequence of optional variable assignments fol- + lowed by bbllaannkk-separated words and redirections, and terminated by a + _c_o_n_t_r_o_l _o_p_e_r_a_t_o_r. The first word specifies the command to be executed, + and is passed as argument zero. The remaining words are passed as ar- + guments to the invoked command. + + The return value of a _s_i_m_p_l_e _c_o_m_m_a_n_d is its exit status, or 128+_n if + the command is terminated by signal _n. + + PPiippeelliinneess + A _p_i_p_e_l_i_n_e is a sequence of one or more commands separated by one of + the control operators || or ||&&. The format for a pipeline is: + + [ttiimmee [--pp]] [ ! ] _c_o_m_m_a_n_d_1 [ [|||||&&] _c_o_m_m_a_n_d_2 ... ] + + The standard output of _c_o_m_m_a_n_d_1 is connected via a pipe to the standard + input of _c_o_m_m_a_n_d_2. This connection is performed before any redirec- + tions specified by the _c_o_m_m_a_n_d_1(see RREEDDIIRREECCTTIIOONN below). If ||&& is used, + _c_o_m_m_a_n_d_1's standard error, in addition to its standard output, is con- + nected to _c_o_m_m_a_n_d_2's standard input through the pipe; it is shorthand + for 22>>&&11 ||. This implicit redirection of the standard error to the + standard output is performed after any redirections specified by _c_o_m_- + _m_a_n_d_1. + + The return status of a pipeline is the exit status of the last command, + unless the ppiippeeffaaiill option is enabled. If ppiippeeffaaiill 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 success- + fully. If the reserved word !! 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. + + If the ttiimmee 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 --pp option changes the output format to that + specified by POSIX. When the shell is in _p_o_s_i_x _m_o_d_e, it does not rec- + ognize ttiimmee as a reserved word if the next token begins with a `-'. + The TTIIMMEEFFOORRMMAATT variable may be set to a format string that specifies + how the timing information should be displayed; see the description of + TTIIMMEEFFOORRMMAATT under SShheellll VVaarriiaabblleess below. + + When the shell is in _p_o_s_i_x _m_o_d_e, ttiimmee 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 TTIIMMEEFFOORRMMAATT variable may be used to + specify the format of the time information. + + Each command in a multi-command pipeline, where pipes are created, is + executed in a _s_u_b_s_h_e_l_l, which is a separate process. See CCOOMMMMAANNDD EEXXEE-- + CCUUTTIIOONN EENNVVIIRROONNMMEENNTT for a description of subshells and a subshell envi- + ronment. If the llaassttppiippee option is enabled using the sshhoopptt builtin + (see the description of sshhoopptt below), the last element of a pipeline + may be run by the shell process when job control is not active. + + LLiissttss + A _l_i_s_t is a sequence of one or more pipelines separated by one of the + operators ;;, &&, &&&&, or ||||, and optionally terminated by one of ;;, &&, or + <<nneewwlliinnee>>. + + Of these list operators, &&&& and |||| have equal precedence, followed by ;; + and &&, which have equal precedence. + + A sequence of one or more newlines may appear in a _l_i_s_t instead of a + semicolon to delimit commands. + + If a command is terminated by the control operator &&, the shell exe- + cutes the command in the _b_a_c_k_g_r_o_u_n_d in a subshell. The shell does not + wait for the command to finish, and the return status is 0. These are + referred to as _a_s_y_n_c_h_r_o_n_o_u_s commands. Commands separated by a ;; are + executed sequentially; the shell waits for each command to terminate in + turn. The return status is the exit status of the last command exe- + cuted. + + AND and OR lists are sequences of one or more pipelines separated by + the &&&& and |||| control operators, respectively. AND and OR lists are + executed with left associativity. An AND list has the form + + _c_o_m_m_a_n_d_1 &&&& _c_o_m_m_a_n_d_2 + + _c_o_m_m_a_n_d_2 is executed if, and only if, _c_o_m_m_a_n_d_1 returns an exit status + of zero (success). + + An OR list has the form + + _c_o_m_m_a_n_d_1 |||| _c_o_m_m_a_n_d_2 + + _c_o_m_m_a_n_d_2 is executed if, and only if, _c_o_m_m_a_n_d_1 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. + + CCoommppoouunndd CCoommmmaannddss + A _c_o_m_p_o_u_n_d _c_o_m_m_a_n_d is one of the following. In most cases a _l_i_s_t 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. + + (_l_i_s_t) _l_i_s_t is executed in a subshell (see CCOOMMMMAANNDD EEXXEECCUUTTIIOONN EENNVVIIRROONN-- + MMEENNTT below for a description of a subshell environment). Vari- + able 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 _l_i_s_t. + + { _l_i_s_t; } + _l_i_s_t is simply executed in the current shell environment. _l_i_s_t + must be terminated with a newline or semicolon. This is known + as a _g_r_o_u_p _c_o_m_m_a_n_d. The return status is the exit status of + _l_i_s_t. Note that unlike the metacharacters (( and )), {{ and }} are + _r_e_s_e_r_v_e_d _w_o_r_d_s 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 _l_i_s_t by whitespace or another shell + metacharacter. + + ((_e_x_p_r_e_s_s_i_o_n)) + The _e_x_p_r_e_s_s_i_o_n is evaluated according to the rules described be- + low under AARRIITTHHMMEETTIICC EEVVAALLUUAATTIIOONN. If the value of the expression + is non-zero, the return status is 0; otherwise the return status + is 1. The _e_x_p_r_e_s_s_i_o_n undergoes the same expansions as if it + were within double quotes, but double quote characters in _e_x_- + _p_r_e_s_s_i_o_n are not treated specially and are removed. + + [[[[ _e_x_p_r_e_s_s_i_o_n ]]]] + Return a status of 0 or 1 depending on the evaluation of the + conditional expression _e_x_p_r_e_s_s_i_o_n. Expressions are composed of + the primaries described below under CCOONNDDIITTIIOONNAALL EEXXPPRREESSSSIIOONNSS. + The words between the [[[[ and ]]]] do not undergo word splitting + and pathname expansion. The shell performs tilde expansion, pa- + rameter and variable expansion, arithmetic expansion, command + substitution, process substitution, and quote removal on those + words (the expansions that would occur if the words were en- + closed in double quotes). Conditional operators such as --ff must + be unquoted to be recognized as primaries. + + When used with [[[[, the << and >> operators sort lexicographically + using the current locale. + + When the ==== and !!== operators are used, the string to the right + of the operator is considered a pattern and matched according to + the rules described below under PPaatttteerrnn MMaattcchhiinngg, as if the eexxtt-- + gglloobb shell option were enabled. The == operator is equivalent to + ====. If the nnooccaasseemmaattcchh 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 (====) or does not + match (!!==) the pattern, and 1 otherwise. Any part of the pat- + tern may be quoted to force the quoted portion to be matched as + a string. + + An additional binary operator, ==~~, is available, with the same + precedence as ==== and !!==. When it is used, the string to the + right of the operator is considered a POSIX extended regular ex- + pression and matched accordingly (using the POSIX _r_e_g_c_o_m_p and + _r_e_g_e_x_e_c interfaces usually described in _r_e_g_e_x(3)). The return + value is 0 if the string matches the pattern, and 1 otherwise. + If the regular expression is syntactically incorrect, the condi- + tional expression's return value is 2. If the nnooccaasseemmaattcchh 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 ev- + ery 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 nor- + mal quoting and pattern characters lose their meanings between + brackets. + + The pattern will match if it matches any part of the string. + Anchor the pattern using the ^^ and $$ regular expression opera- + tors to force it to match the entire string. The array variable + BBAASSHH__RREEMMAATTCCHH records which parts of the string matched the pat- + tern. The element of BBAASSHH__RREEMMAATTCCHH 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 BBAASSHH__RREEMMAATTCCHH in- + dices. The element of BBAASSHH__RREEMMAATTCCHH with index _n is the portion + of the string matching the _nth parenthesized subexpression. + Bash sets BBAASSHH__RREEMMAATTCCHH in the global scope; declaring it as a + local variable will lead to unexpected results. + + Expressions may be combined using the following operators, + listed in decreasing order of precedence: + + (( _e_x_p_r_e_s_s_i_o_n )) + Returns the value of _e_x_p_r_e_s_s_i_o_n. This may be used to + override the normal precedence of operators. + !! _e_x_p_r_e_s_s_i_o_n + True if _e_x_p_r_e_s_s_i_o_n is false. + _e_x_p_r_e_s_s_i_o_n_1 &&&& _e_x_p_r_e_s_s_i_o_n_2 + True if both _e_x_p_r_e_s_s_i_o_n_1 and _e_x_p_r_e_s_s_i_o_n_2 are true. + _e_x_p_r_e_s_s_i_o_n_1 |||| _e_x_p_r_e_s_s_i_o_n_2 + True if either _e_x_p_r_e_s_s_i_o_n_1 or _e_x_p_r_e_s_s_i_o_n_2 is true. + + The &&&& and |||| operators do not evaluate _e_x_p_r_e_s_s_i_o_n_2 if the value + of _e_x_p_r_e_s_s_i_o_n_1 is sufficient to determine the return value of + the entire conditional expression. + + ffoorr _n_a_m_e [ [ iinn [ _w_o_r_d _._._. ] ] ; ] ddoo _l_i_s_t ; ddoonnee + The list of words following iinn is expanded, generating a list of + items. The variable _n_a_m_e is set to each element of this list in + turn, and _l_i_s_t is executed each time. If the iinn _w_o_r_d is omit- + ted, the ffoorr command executes _l_i_s_t once for each positional pa- + rameter that is set (see PPAARRAAMMEETTEERRSS below). The return status + is the exit status of the last command that executes. If the + expansion of the items following iinn results in an empty list, no + commands are executed, and the return status is 0. + + ffoorr (( _e_x_p_r_1 ; _e_x_p_r_2 ; _e_x_p_r_3 )) ; ddoo _l_i_s_t ; ddoonnee + First, the arithmetic expression _e_x_p_r_1 is evaluated according to + the rules described below under AARRIITTHHMMEETTIICC EEVVAALLUUAATTIIOONN. The + arithmetic expression _e_x_p_r_2 is then evaluated repeatedly until + it evaluates to zero. Each time _e_x_p_r_2 evaluates to a non-zero + value, _l_i_s_t is executed and the arithmetic expression _e_x_p_r_3 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 _l_i_s_t that is executed, or false if any of the expres- + sions is invalid. + + sseelleecctt _n_a_m_e [ iinn _w_o_r_d ] ; ddoo _l_i_s_t ; ddoonnee + The list of words following iinn 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 iinn _w_o_r_d is omitted, + the positional parameters are printed (see PPAARRAAMMEETTEERRSS below). + sseelleecctt then displays the PPSS33 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 _n_a_m_e is set to + that word. If the line is empty, the words and prompt are dis- + played again. If EOF is read, the sseelleecctt command completes and + returns 1. Any other value read causes _n_a_m_e to be set to null. + The line read is saved in the variable RREEPPLLYY. The _l_i_s_t is exe- + cuted after each selection until a bbrreeaakk command is executed. + The exit status of sseelleecctt is the exit status of the last command + executed in _l_i_s_t, or zero if no commands were executed. + + ccaassee _w_o_r_d iinn [ [(] _p_a_t_t_e_r_n [ || _p_a_t_t_e_r_n ] ... ) _l_i_s_t ;; ] ... eessaacc + A ccaassee command first expands _w_o_r_d, and tries to match it against + each _p_a_t_t_e_r_n in turn, using the matching rules described under + PPaatttteerrnn MMaattcchhiinngg below. The _w_o_r_d is expanded using tilde expan- + sion, parameter and variable expansion, arithmetic expansion, + command substitution, process substitution and quote removal. + Each _p_a_t_t_e_r_n examined is expanded using tilde expansion, parame- + ter and variable expansion, arithmetic expansion, command sub- + stitution, process substitution, and quote removal. If the nnoo-- + ccaasseemmaattcchh shell option is enabled, the match is performed with- + out regard to the case of alphabetic characters. When a match + is found, the corresponding _l_i_s_t is executed. If the ;;;; opera- + tor is used, no subsequent matches are attempted after the first + pattern match. Using ;;&& in place of ;;;; causes execution to con- + tinue with the _l_i_s_t associated with the next set of patterns. + Using ;;;;&& in place of ;;;; causes the shell to test the next pat- + tern list in the statement, if any, and execute any associated + _l_i_s_t on a successful match, continuing the case statement execu- + tion 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 _l_i_s_t. + + iiff _l_i_s_t; tthheenn _l_i_s_t; [ eelliiff _l_i_s_t; tthheenn _l_i_s_t; ] ... [ eellssee _l_i_s_t; ] ffii + The iiff _l_i_s_t is executed. If its exit status is zero, the tthheenn + _l_i_s_t is executed. Otherwise, each eelliiff _l_i_s_t is executed in + turn, and if its exit status is zero, the corresponding tthheenn + _l_i_s_t is executed and the command completes. Otherwise, the eellssee + _l_i_s_t is executed, if present. The exit status is the exit sta- + tus of the last command executed, or zero if no condition tested + true. + + wwhhiillee _l_i_s_t_-_1; ddoo _l_i_s_t_-_2; ddoonnee + uunnttiill _l_i_s_t_-_1; ddoo _l_i_s_t_-_2; ddoonnee + The wwhhiillee command continuously executes the list _l_i_s_t_-_2 as long + as the last command in the list _l_i_s_t_-_1 returns an exit status of + zero. The uunnttiill command is identical to the wwhhiillee command, ex- + cept that the test is negated: _l_i_s_t_-_2 is executed as long as the + last command in _l_i_s_t_-_1 returns a non-zero exit status. The exit + status of the wwhhiillee and uunnttiill commands is the exit status of the + last command executed in _l_i_s_t_-_2, or zero if none was executed. + + CCoopprroocceesssseess + A _c_o_p_r_o_c_e_s_s is a shell command preceded by the ccoopprroocc reserved word. A + coprocess is executed asynchronously in a subshell, as if the command + had been terminated with the && control operator, with a two-way pipe + established between the executing shell and the coprocess. + + The syntax for a coprocess is: + + ccoopprroocc [_N_A_M_E] _c_o_m_m_a_n_d [_r_e_d_i_r_e_c_t_i_o_n_s] + + This creates a coprocess named _N_A_M_E. _c_o_m_m_a_n_d may be either a simple + command or a compound command (see above). _N_A_M_E is a shell variable + name. If _N_A_M_E is not supplied, the default name is CCOOPPRROOCC. + + The recommended form to use for a coprocess is + + ccoopprroocc _N_A_M_E { _c_o_m_m_a_n_d [_r_e_d_i_r_e_c_t_i_o_n_s]; } + + This form is recommended because simple commands result in the copro- + cess always being named CCOOPPRROOCC, and it is simpler to use and more com- + plete than the other compound commands. + + If _c_o_m_m_a_n_d is a compound command, _N_A_M_E is optional. The word following + ccoopprroocc determines whether that word is interpreted as a variable name: + it is interpreted as _N_A_M_E if it is not a reserved word that introduces + a compound command. If _c_o_m_m_a_n_d is a simple command, _N_A_M_E is not al- + lowed; this is to avoid confusion between _N_A_M_E and the first word of + the simple command. + + When the coprocess is executed, the shell creates an array variable + (see AArrrraayyss below) named _N_A_M_E in the context of the executing shell. + The standard output of _c_o_m_m_a_n_d is connected via a pipe to a file de- + scriptor in the executing shell, and that file descriptor is assigned + to _N_A_M_E[0]. The standard input of _c_o_m_m_a_n_d is connected via a pipe to a + file descriptor in the executing shell, and that file descriptor is as- + signed to _N_A_M_E[1]. This pipe is established before any redirections + specified by the command (see RREEDDIIRREECCTTIIOONN 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. + + The process ID of the shell spawned to execute the coprocess is avail- + able as the value of the variable _N_A_M_E_PID. The wwaaiitt builtin command + may be used to wait for the coprocess to terminate. + + Since the coprocess is created as an asynchronous command, the ccoopprroocc + command always returns success. The return status of a coprocess is + the exit status of _c_o_m_m_a_n_d. + + SShheellll FFuunnccttiioonn DDeeffiinniittiioonnss + 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: + + _f_n_a_m_e () _c_o_m_p_o_u_n_d_-_c_o_m_m_a_n_d [_r_e_d_i_r_e_c_t_i_o_n] + ffuunnccttiioonn _f_n_a_m_e [()] _c_o_m_p_o_u_n_d_-_c_o_m_m_a_n_d [_r_e_d_i_r_e_c_t_i_o_n] + This defines a function named _f_n_a_m_e. The reserved word ffuunnccttiioonn + is optional. If the ffuunnccttiioonn reserved word is supplied, the + parentheses are optional. The _b_o_d_y of the function is the com- + pound command _c_o_m_p_o_u_n_d_-_c_o_m_m_a_n_d (see CCoommppoouunndd CCoommmmaannddss above). + That command is usually a _l_i_s_t of commands between { and }, but + may be any command listed under CCoommppoouunndd CCoommmmaannddss above. If the + ffuunnccttiioonn reserved word is used, but the parentheses are not sup- + plied, the braces are recommended. _c_o_m_p_o_u_n_d_-_c_o_m_m_a_n_d is executed + whenever _f_n_a_m_e is specified as the name of a simple command. + When in _p_o_s_i_x _m_o_d_e, _f_n_a_m_e must be a valid shell _n_a_m_e and may not + be the name of one of the POSIX _s_p_e_c_i_a_l _b_u_i_l_t_i_n_s. In default + mode, a function name can be any unquoted shell word that does + not contain $$. Any redirections (see RREEDDIIRREECCTTIIOONN below) speci- + fied 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 FFUUNNCCTTIIOONNSS below.) + +CCOOMMMMEENNTTSS + In a non-interactive shell, or an interactive shell in which the iinntteerr-- + aaccttiivvee__ccoommmmeennttss option to the sshhoopptt builtin is enabled (see SSHHEELLLL + BBUUIILLTTIINN CCOOMMMMAANNDDSS below), a word beginning with ## causes that word and + all remaining characters on that line to be ignored. An interactive + shell without the iinntteerraaccttiivvee__ccoommmmeennttss option enabled does not allow + comments. The iinntteerraaccttiivvee__ccoommmmeennttss option is on by default in interac- + tive shells. + +QQUUOOTTIINNGG + _Q_u_o_t_i_n_g 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. + + Each of the _m_e_t_a_c_h_a_r_a_c_t_e_r_s listed above under DDEEFFIINNIITTIIOONNSS has special + meaning to the shell and must be quoted if it is to represent itself. + + When the command history expansion facilities are being used (see HHIISS-- + TTOORRYY EEXXPPAANNSSIIOONN below), the _h_i_s_t_o_r_y _e_x_p_a_n_s_i_o_n character, usually !!, must + be quoted to prevent history expansion. + + There are three quoting mechanisms: the _e_s_c_a_p_e _c_h_a_r_a_c_t_e_r, single + quotes, and double quotes. + + A non-quoted backslash (\\) is the _e_s_c_a_p_e _c_h_a_r_a_c_t_e_r. It preserves the + literal value of the next character that follows, with the exception of + <newline>. If a \\<newline> pair appears, and the backslash is not it- + self quoted, the \\<newline> is treated as a line continuation (that is, + it is removed from the input stream and effectively ignored). + + 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. + + Enclosing characters in double quotes preserves the literal value of + all characters within the quotes, with the exception of $$, ``, \\, and, + when history expansion is enabled, !!. When the shell is in _p_o_s_i_x _m_o_d_e, + the !! has no special meaning within double quotes, even when history + expansion is enabled. The characters $$ and `` retain their special + meaning within double quotes. The backslash retains its special mean- + ing only when followed by one of the following characters: $$, ``, "", \\, + or <<nneewwlliinnee>>. A double quote may be quoted within double quotes by + preceding it with a backslash. If enabled, history expansion will be + performed unless an !! appearing in double quotes is escaped using a + backslash. The backslash preceding the !! is not removed. + + The special parameters ** and @@ have special meaning when in double + quotes (see PPAARRAAMMEETTEERRSS below). + + Character sequences of the form $$'_s_t_r_i_n_g' are treated as a special + variant of single quotes. The sequence expands to _s_t_r_i_n_g, with back- + slash-escaped characters in _s_t_r_i_n_g replaced as specified by the ANSI C + standard. Backslash escape sequences, if present, are decoded as fol- + lows: + \\aa alert (bell) + \\bb backspace + \\ee + \\EE an escape character + \\ff form feed + \\nn new line + \\rr carriage return + \\tt horizontal tab + \\vv vertical tab + \\\\ backslash + \\'' single quote + \\"" double quote + \\?? question mark + \\_n_n_n the eight-bit character whose value is the octal value + _n_n_n (one to three octal digits) + \\xx_H_H the eight-bit character whose value is the hexadecimal + value _H_H (one or two hex digits) + \\uu_H_H_H_H the Unicode (ISO/IEC 10646) character whose value is the + hexadecimal value _H_H_H_H (one to four hex digits) + \\UU_H_H_H_H_H_H_H_H + the Unicode (ISO/IEC 10646) character whose value is the + hexadecimal value _H_H_H_H_H_H_H_H (one to eight hex digits) + \\cc_x a control-_x character + + The expanded result is single-quoted, as if the dollar sign had not + been present. + + A double-quoted string preceded by a dollar sign ($$"_s_t_r_i_n_g") will cause + the string to be translated according to the current locale. The _g_e_t_- + _t_e_x_t infrastructure performs the lookup and translation, using the + LLCC__MMEESSSSAAGGEESS, TTEEXXTTDDOOMMAAIINNDDIIRR, and TTEEXXTTDDOOMMAAIINN shell variables. If the + current locale is CC or PPOOSSIIXX, 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 de- + fault, whether or not it is translated and replaced. If the nnooeexx-- + ppaanndd__ttrraannssllaattiioonn option is enabled using the sshhoopptt builtin, translated + strings are single-quoted instead of double-quoted. See the descrip- + tion of sshhoopptt below under SSHHEELLLLBUILTINCCOOMMMMAANNDDSS. + +PPAARRAAMMEETTEERRSS + A _p_a_r_a_m_e_t_e_r is an entity that stores values. It can be a _n_a_m_e, a num- + ber, or one of the special characters listed below under SSppeecciiaall PPaarraamm-- + eetteerrss. A _v_a_r_i_a_b_l_e is a parameter denoted by a _n_a_m_e. A variable has a + _v_a_l_u_e and zero or more _a_t_t_r_i_b_u_t_e_s. Attributes are assigned using the + ddeeccllaarree builtin command (see ddeeccllaarree below in SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS). + + 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 uunnsseett builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below). + + A _v_a_r_i_a_b_l_e may be assigned to by a statement of the form + + _n_a_m_e=[_v_a_l_u_e] + + If _v_a_l_u_e is not given, the variable is assigned the null string. All + _v_a_l_u_e_s undergo tilde expansion, parameter and variable expansion, com- + mand substitution, arithmetic expansion, and quote removal (see EEXXPPAANN-- + SSIIOONN below). If the variable has its iinntteeggeerr attribute set, then _v_a_l_u_e + is evaluated as an arithmetic expression even if the $((...)) expansion + is not used (see AArriitthhmmeettiicc EExxppaannssiioonn below). Word splitting and path- + name expansion are not performed. Assignment statements may also ap- + pear as arguments to the aalliiaass, ddeeccllaarree, ttyyppeesseett, eexxppoorrtt, rreeaaddoonnllyy, and + llooccaall builtin commands (_d_e_c_l_a_r_a_t_i_o_n commands). When in _p_o_s_i_x _m_o_d_e, + these builtins may appear in a command after one or more instances of + the ccoommmmaanndd builtin and retain these assignment statement properties. + + 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 ddeeccllaarree that accept assignment statements + (_d_e_c_l_a_r_a_t_i_o_n commands). When += is applied to a variable for which the + iinntteeggeerr attribute has been set, _v_a_l_u_e is evaluated as an arithmetic ex- + pression and added to the variable's current value, which is also eval- + uated. When += is applied to an array variable using compound assign- + ment (see AArrrraayyss 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 ap- + plied to a string-valued variable, _v_a_l_u_e is expanded and appended to + the variable's value. + + A variable can be assigned the _n_a_m_e_r_e_f attribute using the --nn option to + the ddeeccllaarree or llooccaall builtin commands (see the descriptions of ddeeccllaarree + and llooccaall below) to create a _n_a_m_e_r_e_f, or a reference to another vari- + able. This allows variables to be manipulated indirectly. Whenever + the nameref variable is referenced, assigned to, unset, or has its at- + tributes modified (other than using or changing the _n_a_m_e_r_e_f 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 argu- + ment to the function. For instance, if a variable name is passed to a + shell function as its first argument, running + declare -n ref=$1 + inside the function creates a nameref variable rreeff whose value is the + variable name passed as the first argument. References and assignments + to rreeff, and changes to its attributes, are treated as references, as- + signments, and attribute modifications to the variable whose name was + passed as $$11. If the control variable in a ffoorr loop has the nameref + attribute, the list of words can be a list of shell variables, and a + name reference will be established for each word in the list, in turn, + when the loop is executed. Array variables cannot be given the nnaammeerreeff + attribute. However, nameref variables can reference array variables + and subscripted array variables. Namerefs can be unset using the --nn + option to the uunnsseett builtin. Otherwise, if uunnsseett is executed with the + name of a nameref variable as an argument, the variable referenced by + the nameref variable will be unset. + + PPoossiittiioonnaall PPaarraammeetteerrss + A _p_o_s_i_t_i_o_n_a_l _p_a_r_a_m_e_t_e_r is a parameter denoted by one or more digits, + other than the single digit 0. Positional parameters are assigned from + the shell's arguments when it is invoked, and may be reassigned using + the sseett builtin command. Positional parameters may not be assigned to + with assignment statements. The positional parameters are temporarily + replaced when a shell function is executed (see FFUUNNCCTTIIOONNSS below). + + When a positional parameter consisting of more than a single digit is + expanded, it must be enclosed in braces (see EEXXPPAANNSSIIOONN below). + + SSppeecciiaall PPaarraammeetteerrss + The shell treats several parameters specially. These parameters may + only be referenced; assignment to them is not allowed. + ** Expands to the positional parameters, starting from one. When + the expansion is not within double quotes, each positional pa- + rameter expands to a separate word. In contexts where it is + performed, those words are subject to further word splitting and + pathname expansion. When the expansion occurs within double + quotes, it expands to a single word with the value of each pa- + rameter separated by the first character of the IIFFSS special + variable. That is, "$$**" is equivalent to "$$11_c$$22_c......", where _c + is the first character of the value of the IIFFSS variable. If IIFFSS + is unset, the parameters are separated by spaces. If IIFFSS is + null, the parameters are joined without intervening separators. + @@ 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 ex- + pands to a separate word. That is, "$$@@" is equivalent to "$$11" + "$$22" ... If the double-quoted expansion occurs within a word, + the expansion of the first parameter is joined with the begin- + ning part of the original word, and the expansion of the last + parameter is joined with the last part of the original word. + When there are no positional parameters, "$$@@" and $$@@ expand to + nothing (i.e., they are removed). + ## Expands to the number of positional parameters in decimal. + ?? Expands to the exit status of the most recently executed fore- + ground pipeline. + -- Expands to the current option flags as specified upon invoca- + tion, by the sseett builtin command, or those set by the shell it- + self (such as the --ii option). + $$ Expands to the process ID of the shell. In a subshell, it ex- + pands to the process ID of the current shell, not the subshell. + !! Expands to the process ID of the job most recently placed into + the background, whether executed as an asynchronous command or + using the bbgg builtin (see JJOOBB CCOONNTTRROOLL below). + 00 Expands to the name of the shell or shell script. This is set + at shell initialization. If bbaasshh is invoked with a file of com- + mands, $$00 is set to the name of that file. If bbaasshh is started + with the --cc option, then $$00 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 bbaasshh, as given by argument + zero. + + SShheellll VVaarriiaabblleess + The following variables are set by the shell: + + __ 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. + BBAASSHH Expands to the full filename used to invoke this instance of + bbaasshh. + BBAASSHHOOPPTTSS + A colon-separated list of enabled shell options. Each word in + the list is a valid argument for the --ss option to the sshhoopptt + builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below). The options + appearing in BBAASSHHOOPPTTSS are those reported as _o_n by sshhoopptt. If + this variable is in the environment when bbaasshh starts up, each + shell option in the list will be enabled before reading any + startup files. This variable is read-only. + BBAASSHHPPIIDD + Expands to the process ID of the current bbaasshh process. This + differs from $$$$ under certain circumstances, such as subshells + that do not require bbaasshh to be re-initialized. Assignments to + BBAASSHHPPIIDD have no effect. If BBAASSHHPPIIDD is unset, it loses its spe- + cial properties, even if it is subsequently reset. + BBAASSHH__AALLIIAASSEESS + An associative array variable whose members correspond to the + internal list of aliases as maintained by the aalliiaass 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 BBAASSHH__AALLIIAASSEESS is unset, it loses + its special properties, even if it is subsequently reset. + BBAASSHH__AARRGGCC + An array variable whose values are the number of parameters in + each frame of the current bbaasshh execution call stack. The number + of parameters to the current subroutine (shell function or + script executed with .. or ssoouurrccee) is at the top of the stack. + When a subroutine is executed, the number of parameters passed + is pushed onto BBAASSHH__AARRGGCC. The shell sets BBAASSHH__AARRGGCC only when in + extended debugging mode (see the description of the eexxttddeebbuugg op- + tion to the sshhoopptt builtin below). Setting eexxttddeebbuugg after the + shell has started to execute a script, or referencing this vari- + able when eexxttddeebbuugg is not set, may result in inconsistent val- + ues. + BBAASSHH__AARRGGVV + An array variable containing all of the parameters in the cur- + rent bbaasshh 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 exe- + cuted, the parameters supplied are pushed onto BBAASSHH__AARRGGVV. The + shell sets BBAASSHH__AARRGGVV only when in extended debugging mode (see + the description of the eexxttddeebbuugg option to the sshhoopptt builtin be- + low). Setting eexxttddeebbuugg after the shell has started to execute a + script, or referencing this variable when eexxttddeebbuugg is not set, + may result in inconsistent values. + BBAASSHH__AARRGGVV00 + When referenced, this variable expands to the name of the shell + or shell script (identical to $$00; see the description of special + parameter 0 above). Assignment to BBAASSHH__AARRGGVV00 causes the value + assigned to also be assigned to $$00. If BBAASSHH__AARRGGVV00 is unset, it + loses its special properties, even if it is subsequently reset. + BBAASSHH__CCMMDDSS + An associative array variable whose members correspond to the + internal hash table of commands as maintained by the hhaasshh + builtin. Elements added to this array appear in the hash table; + however, unsetting array elements currently does not cause com- + mand names to be removed from the hash table. If BBAASSHH__CCMMDDSS is + unset, it loses its special properties, even if it is subse- + quently reset. + BBAASSHH__CCOOMMMMAANNDD + The command currently being executed or about to be executed, + unless the shell is executing a command as the result of a trap, + in which case it is the command executing at the time of the + trap. If BBAASSHH__CCOOMMMMAANNDD is unset, it loses its special proper- + ties, even if it is subsequently reset. + BBAASSHH__EEXXEECCUUTTIIOONN__SSTTRRIINNGG + The command argument to the --cc invocation option. + BBAASSHH__LLIINNEENNOO + An array variable whose members are the line numbers in source + files where each corresponding member of FFUUNNCCNNAAMMEE was invoked. + $${{BBAASSHH__LLIINNEENNOO[[_$_i]]}} is the line number in the source file + ($${{BBAASSHH__SSOOUURRCCEE[[_$_i_+_1]]}}) where $${{FFUUNNCCNNAAMMEE[[_$_i]]}} was called (or + $${{BBAASSHH__LLIINNEENNOO[[_$_i_-_1]]}} if referenced within another shell func- + tion). Use LLIINNEENNOO to obtain the current line number. + BBAASSHH__LLOOAADDAABBLLEESS__PPAATTHH + A colon-separated list of directories in which the shell looks + for dynamically loadable builtins specified by the eennaabbllee com- + mand. + BBAASSHH__RREEMMAATTCCHH + An array variable whose members are assigned by the ==~~ binary + operator to the [[[[ conditional command. The element with index + 0 is the portion of the string matching the entire regular ex- + pression. The element with index _n is the portion of the string + matching the _nth parenthesized subexpression. + BBAASSHH__SSOOUURRCCEE + An array variable whose members are the source filenames where + the corresponding shell function names in the FFUUNNCCNNAAMMEE array + variable are defined. The shell function $${{FFUUNNCCNNAAMMEE[[_$_i]]}} is de- + fined in the file $${{BBAASSHH__SSOOUURRCCEE[[_$_i]]}} and called from + $${{BBAASSHH__SSOOUURRCCEE[[_$_i_+_1]]}}. + BBAASSHH__SSUUBBSSHHEELLLL + Incremented by one within each subshell or subshell environment + when the shell begins executing in that environment. The ini- + tial value is 0. If BBAASSHH__SSUUBBSSHHEELLLL is unset, it loses its spe- + cial properties, even if it is subsequently reset. + BBAASSHH__VVEERRSSIINNFFOO + A readonly array variable whose members hold version information + for this instance of bbaasshh. The values assigned to the array + members are as follows: + BBAASSHH__VVEERRSSIINNFFOO[[0]] The major version number (the _r_e_l_e_a_s_e). + BBAASSHH__VVEERRSSIINNFFOO[[1]] The minor version number (the _v_e_r_s_i_o_n). + BBAASSHH__VVEERRSSIINNFFOO[[2]] The patch level. + BBAASSHH__VVEERRSSIINNFFOO[[3]] The build version. + BBAASSHH__VVEERRSSIINNFFOO[[4]] The release status (e.g., _b_e_t_a_1). + BBAASSHH__VVEERRSSIINNFFOO[[5]] The value of MMAACCHHTTYYPPEE. + BBAASSHH__VVEERRSSIIOONN + Expands to a string describing the version of this instance of + bbaasshh. + CCOOMMPP__CCWWOORRDD + An index into $${{CCOOMMPP__WWOORRDDSS}} of the word containing the current + cursor position. This variable is available only in shell func- + tions invoked by the programmable completion facilities (see + PPrrooggrraammmmaabbllee CCoommpplleettiioonn below). + CCOOMMPP__KKEEYY + The key (or final key of a key sequence) used to invoke the cur- + rent completion function. + CCOOMMPP__LLIINNEE + The current command line. This variable is available only in + shell functions and external commands invoked by the program- + mable completion facilities (see PPrrooggrraammmmaabbllee CCoommpplleettiioonn below). + CCOOMMPP__PPOOIINNTT + The index of the current cursor position relative to the begin- + ning of the current command. If the current cursor position is + at the end of the current command, the value of this variable is + equal to $${{##CCOOMMPP__LLIINNEE}}. This variable is available only in + shell functions and external commands invoked by the program- + mable completion facilities (see PPrrooggrraammmmaabbllee CCoommpplleettiioonn below). + CCOOMMPP__TTYYPPEE + Set to an integer value corresponding to the type of completion + attempted that caused a completion function to be called: _T_A_B, + for normal completion, _?, for listing completions after succes- + sive tabs, _!, for listing alternatives on partial word comple- + tion, _@, to list completions if the word is not unmodified, or + _%, for menu completion. This variable is available only in + shell functions and external commands invoked by the program- + mable completion facilities (see PPrrooggrraammmmaabbllee CCoommpplleettiioonn below). + CCOOMMPP__WWOORRDDBBRREEAAKKSS + The set of characters that the rreeaaddlliinnee library treats as word + separators when performing word completion. If CCOOMMPP__WWOORRDDBBRREEAAKKSS + is unset, it loses its special properties, even if it is subse- + quently reset. + CCOOMMPP__WWOORRDDSS + An array variable (see AArrrraayyss below) consisting of the individ- + ual words in the current command line. The line is split into + words as rreeaaddlliinnee would split it, using CCOOMMPP__WWOORRDDBBRREEAAKKSS as de- + scribed above. This variable is available only in shell func- + tions invoked by the programmable completion facilities (see + PPrrooggrraammmmaabbllee CCoommpplleettiioonn below). + CCOOPPRROOCC An array variable (see AArrrraayyss below) created to hold the file + descriptors for output from and input to an unnamed coprocess + (see CCoopprroocceesssseess above). + DDIIRRSSTTAACCKK + An array variable (see AArrrraayyss below) containing the current con- + tents of the directory stack. Directories appear in the stack + in the order they are displayed by the ddiirrss builtin. Assigning + to members of this array variable may be used to modify directo- + ries already in the stack, but the ppuusshhdd and ppooppdd builtins must + be used to add and remove directories. Assignment to this vari- + able will not change the current directory. If DDIIRRSSTTAACCKK is un- + set, it loses its special properties, even if it is subsequently + reset. + EEPPOOCCHHRREEAALLTTIIMMEE + Each time this parameter is referenced, it expands to the number + of seconds since the Unix Epoch (see _t_i_m_e(3)) as a floating + point value with micro-second granularity. Assignments to + EEPPOOCCHHRREEAALLTTIIMMEE are ignored. If EEPPOOCCHHRREEAALLTTIIMMEE is unset, it loses + its special properties, even if it is subsequently reset. + EEPPOOCCHHSSEECCOONNDDSS + Each time this parameter is referenced, it expands to the number + of seconds since the Unix Epoch (see _t_i_m_e(3)). Assignments to + EEPPOOCCHHSSEECCOONNDDSS are ignored. If EEPPOOCCHHSSEECCOONNDDSS is unset, it loses + its special properties, even if it is subsequently reset. + EEUUIIDD Expands to the effective user ID of the current user, initial- + ized at shell startup. This variable is readonly. + FFUUNNCCNNAAMMEE + 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 bot- + tom-most element (the one with the highest index) is "main". + This variable exists only when a shell function is executing. + Assignments to FFUUNNCCNNAAMMEE have no effect. If FFUUNNCCNNAAMMEE is unset, + it loses its special properties, even if it is subsequently re- + set. + + This variable can be used with BBAASSHH__LLIINNEENNOO and BBAASSHH__SSOOUURRCCEE. + Each element of FFUUNNCCNNAAMMEE has corresponding elements in + BBAASSHH__LLIINNEENNOO and BBAASSHH__SSOOUURRCCEE to describe the call stack. For in- + stance, $${{FFUUNNCCNNAAMMEE[[_$_i]]}} was called from the file + $${{BBAASSHH__SSOOUURRCCEE[[_$_i_+_1]]}} at line number $${{BBAASSHH__LLIINNEENNOO[[_$_i]]}}. The + ccaalllleerr builtin displays the current call stack using this infor- + mation. + GGRROOUUPPSS An array variable containing the list of groups of which the + current user is a member. Assignments to GGRROOUUPPSS have no effect. + If GGRROOUUPPSS is unset, it loses its special properties, even if it + is subsequently reset. + HHIISSTTCCMMDD + The history number, or index in the history list, of the current + command. Assignments to HHIISSTTCCMMDD are ignored. If HHIISSTTCCMMDD is un- + set, it loses its special properties, even if it is subsequently + reset. + HHOOSSTTNNAAMMEE + Automatically set to the name of the current host. + HHOOSSTTTTYYPPEE + Automatically set to a string that uniquely describes the type + of machine on which bbaasshh is executing. The default is system- + dependent. + LLIINNEENNOO 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 LLIINNEENNOO is unset, it loses its special proper- + ties, even if it is subsequently reset. + MMAACCHHTTYYPPEE + Automatically set to a string that fully describes the system + type on which bbaasshh is executing, in the standard GNU _c_p_u_-_c_o_m_- + _p_a_n_y_-_s_y_s_t_e_m format. The default is system-dependent. + MMAAPPFFIILLEE + An array variable (see AArrrraayyss below) created to hold the text + read by the mmaappffiillee builtin when no variable name is supplied. + OOLLDDPPWWDD The previous working directory as set by the ccdd command. + OOPPTTAARRGG The value of the last option argument processed by the ggeettooppttss + builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below). + OOPPTTIINNDD The index of the next argument to be processed by the ggeettooppttss + builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below). + OOSSTTYYPPEE Automatically set to a string that describes the operating sys- + tem on which bbaasshh is executing. The default is system-depen- + dent. + PPIIPPEESSTTAATTUUSS + An array variable (see AArrrraayyss 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). + PPPPIIDD The process ID of the shell's parent. This variable is read- + only. + PPWWDD The current working directory as set by the ccdd command. + RRAANNDDOOMM Each time this parameter is referenced, it expands to a random + integer between 0 and 32767. Assigning a value to RRAANNDDOOMM ini- + tializes (seeds) the sequence of random numbers. If RRAANNDDOOMM is + unset, it loses its special properties, even if it is subse- + quently reset. + RREEAADDLLIINNEE__AARRGGUUMMEENNTT + Any numeric argument given to a readline command that was de- + fined using "bind -x" (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below) when it + was invoked. + RREEAADDLLIINNEE__LLIINNEE + The contents of the rreeaaddlliinnee line buffer, for use with "bind -x" + (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below). + RREEAADDLLIINNEE__MMAARRKK + The position of the mark (saved insertion point) in the rreeaaddlliinnee + line buffer, for use with "bind -x" (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS + below). The characters between the insertion point and the mark + are often called the _r_e_g_i_o_n. + RREEAADDLLIINNEE__PPOOIINNTT + The position of the insertion point in the rreeaaddlliinnee line buffer, + for use with "bind -x" (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below). + RREEPPLLYY Set to the line of input read by the rreeaadd builtin command when + no arguments are supplied. + SSEECCOONNDDSS + Each time this parameter is referenced, it expands to the number + of seconds since shell invocation. If a value is assigned to + SSEECCOONNDDSS, 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 SSEECCOONNDDSS + is unset, it loses its special properties, even if it is subse- + quently reset. + SSHHEELLLLOOPPTTSS + A colon-separated list of enabled shell options. Each word in + the list is a valid argument for the --oo option to the sseett + builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below). The options + appearing in SSHHEELLLLOOPPTTSS are those reported as _o_n by sseett --oo. If + this variable is in the environment when bbaasshh starts up, each + shell option in the list will be enabled before reading any + startup files. This variable is read-only. + SSHHLLVVLL Incremented by one each time an instance of bbaasshh is started. + SSRRAANNDDOOMM + 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 /dev/urandom or _a_r_c_4_r_a_n_d_o_m, so each re- + turned 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 SSRRAANNDDOOMM is unset, it loses its + special properties, even if it is subsequently reset. + UUIIDD Expands to the user ID of the current user, initialized at shell + startup. This variable is readonly. + + The following variables are used by the shell. In some cases, bbaasshh as- + signs a default value to a variable; these cases are noted below. + + BBAASSHH__CCOOMMPPAATT + The value is used to set the shell's compatibility level. See + SSHHEELLLL CCOOMMPPAATTIIBBIILLIITTYY MMOODDEE below for a description of the various + compatibility levels and their effects. The value may be a dec- + imal number (e.g., 4.2) or an integer (e.g., 42) corresponding + to the desired compatibility level. If BBAASSHH__CCOOMMPPAATT is unset or + set to the empty string, the compatibility level is set to the + default for the current version. If BBAASSHH__CCOOMMPPAATT 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 corre- + spond to the compatibility levels described below under SSHHEELLLL + CCOOMMPPAATTIIBBIILLIITTYY MMOODDEE. For example, 4.2 and 42 are valid values + that correspond to the ccoommppaatt4422 sshhoopptt option and set the compat- + ibility level to 42. The current version is also a valid value. + BBAASSHH__EENNVV + If this parameter is set when bbaasshh is executing a shell script, + its value is interpreted as a filename containing commands to + initialize the shell, as in _~_/_._b_a_s_h_r_c. The value of BBAASSHH__EENNVV is + subjected to parameter expansion, command substitution, and + arithmetic expansion before being interpreted as a filename. + PPAATTHH is not used to search for the resultant filename. + BBAASSHH__XXTTRRAACCEEFFDD + If set to an integer corresponding to a valid file descriptor, + bbaasshh will write the trace output generated when _s_e_t _-_x is en- + abled to that file descriptor. The file descriptor is closed + when BBAASSHH__XXTTRRAACCEEFFDD is unset or assigned a new value. Unsetting + BBAASSHH__XXTTRRAACCEEFFDD or assigning it the empty string causes the trace + output to be sent to the standard error. Note that setting + BBAASSHH__XXTTRRAACCEEFFDD to 2 (the standard error file descriptor) and then + unsetting it will result in the standard error being closed. + CCDDPPAATTHH The search path for the ccdd command. This is a colon-separated + list of directories in which the shell looks for destination di- + rectories specified by the ccdd command. A sample value is + ".:~:/usr". + CCHHIILLDD__MMAAXX + 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 (cur- + rently 8192) that this may not exceed. The minimum value is + system-dependent. + CCOOLLUUMMNNSS + Used by the sseelleecctt compound command to determine the terminal + width when printing selection lists. Automatically set if the + cchheecckkwwiinnssiizzee option is enabled or in an interactive shell upon + receipt of a SSIIGGWWIINNCCHH. + CCOOMMPPRREEPPLLYY + An array variable from which bbaasshh reads the possible completions + generated by a shell function invoked by the programmable com- + pletion facility (see PPrrooggrraammmmaabbllee CCoommpplleettiioonn below). Each ar- + ray element contains one possible completion. + EEMMAACCSS If bbaasshh finds this variable in the environment when the shell + starts with value "t", it assumes that the shell is running in + an Emacs shell buffer and disables line editing. + EENNVV Expanded and executed similarly to BBAASSHH__EENNVV (see IINNVVOOCCAATTIIOONN + above) when an interactive shell is invoked in _p_o_s_i_x _m_o_d_e. + EEXXEECCIIGGNNOORREE + A colon-separated list of shell patterns (see PPaatttteerrnn MMaattcchhiinngg) + defining the list of filenames to be ignored by command search + using PPAATTHH. Files whose full pathnames match one of these pat- + terns are not considered executable files for the purposes of + completion and command execution via PPAATTHH lookup. This does not + affect the behavior of the [[, tteesstt, and [[[[ commands. Full path- + names in the command hash table are not subject to EEXXEECCIIGGNNOORREE. + 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 eexxttgglloobb shell option. + FFCCEEDDIITT The default editor for the ffcc builtin command. + FFIIGGNNOORREE + A colon-separated list of suffixes to ignore when performing + filename completion (see RREEAADDLLIINNEE below). A filename whose suf- + fix matches one of the entries in FFIIGGNNOORREE is excluded from the + list of matched filenames. A sample value is ".o:~". + FFUUNNCCNNEESSTT + 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. + GGLLOOBBIIGGNNOORREE + 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 GGLLOOBBIIGGNNOORREE, it is removed from the list of matches. + HHIISSTTCCOONNTTRROOLL + A colon-separated list of values controlling how commands are + saved on the history list. If the list of values includes _i_g_- + _n_o_r_e_s_p_a_c_e, lines which begin with a ssppaaccee character are not + saved in the history list. A value of _i_g_n_o_r_e_d_u_p_s causes lines + matching the previous history entry to not be saved. A value of + _i_g_n_o_r_e_b_o_t_h is shorthand for _i_g_n_o_r_e_s_p_a_c_e and _i_g_n_o_r_e_d_u_p_s. A value + of _e_r_a_s_e_d_u_p_s 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 HHIISSTTCCOONNTTRROOLL 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 HHIISSTTIIGGNNOORREE. 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 HHIISSTTCCOONNTTRROOLL. + HHIISSTTFFIILLEE + The name of the file in which command history is saved (see HHIISS-- + TTOORRYY below). The default value is _~_/_._b_a_s_h___h_i_s_t_o_r_y. If unset, + the command history is not saved when a shell exits. + HHIISSTTFFIILLEESSIIZZEE + The maximum number of lines contained in the history file. When + this variable is assigned a value, the history file is trun- + cated, 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 + HHIISSTTSSIIZZEE after reading any startup files. + HHIISSTTIIGGNNOORREE + A colon-separated list of patterns used to decide which command + lines should be saved on the history list. Each pattern is an- + chored at the beginning of the line and must match the complete + line (no implicit `**' is appended). Each pattern is tested + against the line after the checks specified by HHIISSTTCCOONNTTRROOLL are + applied. In addition to the normal shell pattern matching char- + acters, `&&' matches the previous history line. `&&' may be es- + caped using a backslash; the backslash is removed before at- + tempting a match. The second and subsequent lines of a multi- + line compound command are not tested, and are added to the his- + tory regardless of the value of HHIISSTTIIGGNNOORREE. The pattern match- + ing honors the setting of the eexxttgglloobb shell option. + HHIISSTTSSIIZZEE + The number of commands to remember in the command history (see + HHIISSTTOORRYY 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. + HHIISSTTTTIIMMEEFFOORRMMAATT + If this variable is set and not null, its value is used as a + format string for _s_t_r_f_t_i_m_e(3) to print the time stamp associated + with each history entry displayed by the hhiissttoorryy 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. + HHOOMMEE The home directory of the current user; the default argument for + the ccdd builtin command. The value of this variable is also used + when performing tilde expansion. + HHOOSSTTFFIILLEE + Contains the name of a file in the same format as _/_e_t_c_/_h_o_s_t_s + 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 at- + tempted after the value is changed, bbaasshh adds the contents of + the new file to the existing list. If HHOOSSTTFFIILLEE is set, but has + no value, or does not name a readable file, bbaasshh attempts to + read _/_e_t_c_/_h_o_s_t_s to obtain the list of possible hostname comple- + tions. When HHOOSSTTFFIILLEE is unset, the hostname list is cleared. + IIFFSS The _I_n_t_e_r_n_a_l _F_i_e_l_d _S_e_p_a_r_a_t_o_r that is used for word splitting af- + ter expansion and to split lines into words with the rreeaadd + builtin command. The default value is ``<space><tab><new- + line>''. + IIGGNNOORREEEEOOFF + Controls the action of an interactive shell on receipt of an EEOOFF + character as the sole input. If set, the value is the number of + consecutive EEOOFF characters which must be typed as the first + characters on an input line before bbaasshh 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, EEOOFF signifies the + end of input to the shell. + IINNPPUUTTRRCC + The filename for the rreeaaddlliinnee startup file, overriding the de- + fault of _~_/_._i_n_p_u_t_r_c (see RREEAADDLLIINNEE below). + IINNSSIIDDEE__EEMMAACCSS + If this variable appears in the environment when the shell + starts, bbaasshh assumes that it is running inside an Emacs shell + buffer and may disable line editing, depending on the value of + TTEERRMM. + LLAANNGG Used to determine the locale category for any category not + specifically selected with a variable starting with LLCC__. + LLCC__AALLLL This variable overrides the value of LLAANNGG and any other LLCC__ + variable specifying a locale category. + LLCC__CCOOLLLLAATTEE + 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 se- + quences within pathname expansion and pattern matching. + LLCC__CCTTYYPPEE + This variable determines the interpretation of characters and + the behavior of character classes within pathname expansion and + pattern matching. + LLCC__MMEESSSSAAGGEESS + This variable determines the locale used to translate double- + quoted strings preceded by a $$. + LLCC__NNUUMMEERRIICC + This variable determines the locale category used for number + formatting. + LLCC__TTIIMMEE + This variable determines the locale category used for data and + time formatting. + LLIINNEESS Used by the sseelleecctt compound command to determine the column + length for printing selection lists. Automatically set if the + cchheecckkwwiinnssiizzee option is enabled or in an interactive shell upon + receipt of a SSIIGGWWIINNCCHH. + MMAAIILL If this parameter is set to a file or directory name and the + MMAAIILLPPAATTHH variable is not set, bbaasshh informs the user of the ar- + rival of mail in the specified file or Maildir-format directory. + MMAAIILLCCHHEECCKK + Specifies how often (in seconds) bbaasshh checks for mail. The de- + fault 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. + MMAAIILLPPAATTHH + 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, $$__ expands to the + name of the current mailfile. Example: + MMAAIILLPPAATTHH='/var/mail/bfox?"You have mail":~/shell-mail?"$_ has + mail!"' + BBaasshh can be configured to supply a default value for this vari- + able (there is no value by default), but the location of the + user mail files that it uses is system dependent (e.g., + /var/mail/$$UUSSEERR). + OOPPTTEERRRR If set to the value 1, bbaasshh displays error messages generated by + the ggeettooppttss builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below). + OOPPTTEERRRR is initialized to 1 each time the shell is invoked or a + shell script is executed. + PPAATTHH The search path for commands. It is a colon-separated list of + directories in which the shell looks for commands (see CCOOMMMMAANNDD + EEXXEECCUUTTIIOONN below). A zero-length (null) directory name in the + value of PPAATTHH 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 bbaasshh. A common value is + ``/usr/local/bin:/usr/lo- + cal/sbin:/usr/bin:/usr/sbin:/bin:/sbin''. + PPOOSSIIXXLLYY__CCOORRRREECCTT + If this variable is in the environment when bbaasshh starts, the + shell enters _p_o_s_i_x _m_o_d_e before reading the startup files, as if + the ----ppoossiixx invocation option had been supplied. If it is set + while the shell is running, bbaasshh enables _p_o_s_i_x _m_o_d_e, as if the + command _s_e_t _-_o _p_o_s_i_x had been executed. When the shell enters + _p_o_s_i_x _m_o_d_e, it sets this variable if it was not already set. + PPRROOMMPPTT__CCOOMMMMAANNDD + 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. + PPRROOMMPPTT__DDIIRRTTRRIIMM + If set to a number greater than zero, the value is used as the + number of trailing directory components to retain when expanding + the \\ww and \\WW prompt string escapes (see PPRROOMMPPTTIINNGG below). + Characters removed are replaced with an ellipsis. + PPSS00 The value of this parameter is expanded (see PPRROOMMPPTTIINNGG below) + and displayed by interactive shells after reading a command and + before the command is executed. + PPSS11 The value of this parameter is expanded (see PPRROOMMPPTTIINNGG below) + and used as the primary prompt string. The default value is + ``\\ss--\\vv\\$$ ''. + PPSS22 The value of this parameter is expanded as with PPSS11 and used as + the secondary prompt string. The default is ``>> ''. + PPSS33 The value of this parameter is used as the prompt for the sseelleecctt + command (see SSHHEELLLL GGRRAAMMMMAARR above). + PPSS44 The value of this parameter is expanded as with PPSS11 and the + value is printed before each command bbaasshh displays during an ex- + ecution trace. The first character of the expanded value of PPSS44 + is replicated multiple times, as necessary, to indicate multiple + levels of indirection. The default is ``++ ''. + SSHHEELLLL This variable expands to the full pathname to the shell. If it + is not set when the shell starts, bbaasshh assigns to it the full + pathname of the current user's login shell. + TTIIMMEEFFOORRMMAATT + The value of this parameter is used as a format string specify- + ing how the timing information for pipelines prefixed with the + ttiimmee reserved word should be displayed. The %% character intro- + duces 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. + %%%% A literal %%. + %%[[_p]][[ll]]RR The elapsed time in seconds. + %%[[_p]][[ll]]UU The number of CPU seconds spent in user mode. + %%[[_p]][[ll]]SS The number of CPU seconds spent in system mode. + %%PP The CPU percentage, computed as (%U + %S) / %R. + + The optional _p is a digit specifying the _p_r_e_c_i_s_i_o_n, 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 _p greater + than 3 are changed to 3. If _p is not specified, the value 3 is + used. + + The optional ll specifies a longer format, including minutes, of + the form _M_Mm_S_S._F_Fs. The value of _p determines whether or not + the fraction is included. + + If this variable is not set, bbaasshh acts as if it had the value + $$''\\nnrreeaall\\tt%%33llRR\\nnuusseerr\\tt%%33llUU\\nnssyyss\\tt%%33llSS''. If the value is null, + no timing information is displayed. A trailing newline is added + when the format string is displayed. + TTMMOOUUTT If set to a value greater than zero, TTMMOOUUTT is treated as the de- + fault timeout for the rreeaadd builtin. The sseelleecctt command termi- + nates if input does not arrive after TTMMOOUUTT 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. BBaasshh terminates after waiting + for that number of seconds if a complete line of input does not + arrive. + TTMMPPDDIIRR If set, bbaasshh uses its value as the name of a directory in which + bbaasshh creates temporary files for the shell's use. + aauuttoo__rreessuummee + This variable controls how the shell interacts with the user and + job control. If this variable is set, single word simple com- + mands without redirections are treated as candidates for resump- + tion 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 _n_a_m_e of a + stopped job, in this context, is the command line used to start + it. If set to the value _e_x_a_c_t, the string supplied must match + the name of a stopped job exactly; if set to _s_u_b_s_t_r_i_n_g, the + string supplied needs to match a substring of the name of a + stopped job. The _s_u_b_s_t_r_i_n_g value provides functionality analo- + gous to the %%?? job identifier (see JJOOBB CCOONNTTRROOLL 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 + %%_s_t_r_i_n_g job identifier. + hhiissttcchhaarrss + The two or three characters which control history expansion and + tokenization (see HHIISSTTOORRYY EEXXPPAANNSSIIOONN below). The first character + is the _h_i_s_t_o_r_y _e_x_p_a_n_s_i_o_n character, the character which signals + the start of a history expansion, normally `!!'. The second + character is the _q_u_i_c_k _s_u_b_s_t_i_t_u_t_i_o_n character, which is used as + shorthand for re-running the previous command entered, substi- + tuting one string for another in the command. The default is + `^^'. The optional third character is the character which indi- + cates that the remainder of the line is a comment when found as + the first character of a word, normally `##'. The history com- + ment 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. + + AArrrraayyss + BBaasshh provides one-dimensional indexed and associative array variables. + Any variable may be used as an indexed array; the ddeeccllaarree 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 con- + tiguously. Indexed arrays are referenced using integers (including + arithmetic expressions) and are zero-based; associative arrays are ref- + erenced using arbitrary strings. Unless otherwise noted, indexed array + indices must be non-negative integers. + + An indexed array is created automatically if any variable is assigned + to using the syntax _n_a_m_e[_s_u_b_s_c_r_i_p_t]=_v_a_l_u_e. The _s_u_b_s_c_r_i_p_t is treated as + an arithmetic expression that must evaluate to a number. To explicitly + declare an indexed array, use ddeeccllaarree --aa _n_a_m_e (see SSHHEELLLL BBUUIILLTTIINN CCOOMM-- + MMAANNDDSS below). ddeeccllaarree --aa _n_a_m_e[[_s_u_b_s_c_r_i_p_t]] is also accepted; the _s_u_b_- + _s_c_r_i_p_t is ignored. + + Associative arrays are created using ddeeccllaarree --AA _n_a_m_e. + + Attributes may be specified for an array variable using the ddeeccllaarree and + rreeaaddoonnllyy builtins. Each attribute applies to all members of an array. + + Arrays are assigned to using compound assignments of the form + _n_a_m_e=((value_1 ... value_n)), where each _v_a_l_u_e may be of the form [_s_u_b_- + _s_c_r_i_p_t]=_s_t_r_i_n_g. Indexed array assignments do not require anything but + _s_t_r_i_n_g. Each _v_a_l_u_e in the list is expanded using all the shell expan- + sions described below under EEXXPPAANNSSIIOONN. When assigning to indexed ar- + rays, 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. + + When assigning to an associative array, the words in a compound assign- + ment may be either assignment statements, for which the subscript is + required, or a list of words that is interpreted as a sequence of al- + ternating keys and values: _n_a_m_e=(( _k_e_y_1 _v_a_l_u_e_1 _k_e_y_2 _v_a_l_u_e_2 ...)). These + are treated identically to _n_a_m_e=(( [_k_e_y_1]=_v_a_l_u_e_1 [_k_e_y_2]=_v_a_l_u_e_2 ...)). + The first word in the list determines how the remaining words are in- + terpreted; 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. + + This syntax is also accepted by the ddeeccllaarree builtin. Individual array + elements may be assigned to using the _n_a_m_e[_s_u_b_s_c_r_i_p_t]=_v_a_l_u_e syntax in- + troduced above. When assigning to an indexed array, if _n_a_m_e is sub- + scripted by a negative number, that number is interpreted as relative + to one greater than the maximum index of _n_a_m_e, so negative indices + count back from the end of the array, and an index of -1 references the + last element. + + The += operator will append to an array variable when assigning using + the compound assignment syntax; see PPAARRAAMMEETTEERRSS above. + + Any element of an array may be referenced using ${_n_a_m_e[_s_u_b_s_c_r_i_p_t]}. + The braces are required to avoid conflicts with pathname expansion. If + _s_u_b_s_c_r_i_p_t is @@ or **, the word expands to all members of _n_a_m_e. These + subscripts differ only when the word appears within double quotes. If + the word is double-quoted, ${_n_a_m_e[*]} expands to a single word with the + value of each array member separated by the first character of the IIFFSS + special variable, and ${_n_a_m_e[@]} expands each element of _n_a_m_e to a sep- + arate word. When there are no array members, ${_n_a_m_e[@]} expands to + nothing. If the double-quoted expansion occurs within a word, the ex- + pansion 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 ** and @@ (see SSppeecciiaall PPaarraammeetteerrss above). + ${#_n_a_m_e[_s_u_b_s_c_r_i_p_t]} expands to the length of ${_n_a_m_e[_s_u_b_s_c_r_i_p_t]}. If + _s_u_b_s_c_r_i_p_t is ** or @@, the expansion is the number of elements in the ar- + ray. If the _s_u_b_s_c_r_i_p_t 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. + + Referencing an array variable without a subscript is equivalent to ref- + erencing the array with a subscript of 0. Any reference to a variable + using a valid subscript is legal, and bbaasshh will create an array if nec- + essary. + + An array variable is considered set if a subscript has been assigned a + value. The null string is a valid value. + + It is possible to obtain the keys (indices) of an array as well as the + values. ${!!_n_a_m_e[_@]} and ${!!_n_a_m_e[_*]} expand to the indices assigned in + array variable _n_a_m_e. The treatment when in double quotes is similar to + the expansion of the special parameters _@ and _* within double quotes. + + The uunnsseett builtin is used to destroy arrays. uunnsseett _n_a_m_e[_s_u_b_s_c_r_i_p_t] de- + stroys the array element at index _s_u_b_s_c_r_i_p_t, for both indexed and asso- + ciative arrays. Negative subscripts to indexed arrays are interpreted + as described above. Unsetting the last element of an array variable + does not unset the variable. uunnsseett _n_a_m_e, where _n_a_m_e is an array, re- + moves the entire array. uunnsseett _n_a_m_e[_s_u_b_s_c_r_i_p_t], where _s_u_b_s_c_r_i_p_t is ** or + @@, behaves differently depending on whether _n_a_m_e is an indexed or asso- + ciative array. If _n_a_m_e is an associative array, this unsets the ele- + ment with subscript ** or @@. If _n_a_m_e is an indexed array, unset removes + all of the elements but does not remove the array itself. + + When using a variable name with a subscript as an argument to a com- + mand, such as with uunnsseett, without using the word expansion syntax de- + scribed above, the argument is subject to pathname expansion. If path- + name expansion is not desired, the argument should be quoted. + + The ddeeccllaarree, llooccaall, and rreeaaddoonnllyy builtins each accept a --aa option to + specify an indexed array and a --AA option to specify an associative ar- + ray. If both options are supplied, --AA takes precedence. The rreeaadd + builtin accepts a --aa option to assign a list of words read from the + standard input to an array. The sseett and ddeeccllaarree builtins display array + values in a way that allows them to be reused as assignments. + +EEXXPPAANNSSIIOONN + Expansion is performed on the command line after it has been split into + words. There are seven kinds of expansion performed: _b_r_a_c_e _e_x_p_a_n_s_i_o_n, + _t_i_l_d_e _e_x_p_a_n_s_i_o_n, _p_a_r_a_m_e_t_e_r _a_n_d _v_a_r_i_a_b_l_e _e_x_p_a_n_s_i_o_n, _c_o_m_m_a_n_d _s_u_b_s_t_i_t_u_- + _t_i_o_n, _a_r_i_t_h_m_e_t_i_c _e_x_p_a_n_s_i_o_n, _w_o_r_d _s_p_l_i_t_t_i_n_g, and _p_a_t_h_n_a_m_e _e_x_p_a_n_s_i_o_n. + + 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 expan- + sion. + + On systems that can support it, there is an additional expansion avail- + able: _p_r_o_c_e_s_s _s_u_b_s_t_i_t_u_t_i_o_n. This is performed at the same time as + tilde, parameter, variable, and arithmetic expansion and command sub- + stitution. + + After these expansions are performed, quote characters present in the + original word are removed unless they have been quoted themselves + (_q_u_o_t_e _r_e_m_o_v_a_l). + + Only brace expansion, word splitting, and pathname expansion can in- + crease the number of words of the expansion; other expansions expand a + single word to a single word. The only exceptions to this are the ex- + pansions of "$$@@" and "$${{_n_a_m_e[[@@]]}}", and, in most cases, $$** and + $${{_n_a_m_e[[**]]}} as explained above (see PPAARRAAMMEETTEERRSS). + + BBrraaccee EExxppaannssiioonn + _B_r_a_c_e _e_x_p_a_n_s_i_o_n is a mechanism by which arbitrary strings may be gener- + ated. This mechanism is similar to _p_a_t_h_n_a_m_e _e_x_p_a_n_s_i_o_n, but the file- + names generated need not exist. Patterns to be brace expanded take the + form of an optional _p_r_e_a_m_b_l_e, followed by either a series of comma-sep- + arated strings or a sequence expression between a pair of braces, fol- + lowed by an optional _p_o_s_t_s_c_r_i_p_t. 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. + + Brace expansions may be nested. The results of each expanded string + are not sorted; left to right order is preserved. For example, + a{{d,c,b}}e expands into `ade ace abe'. + + A sequence expression takes the form {{_x...._y[[...._i_n_c_r]]}}, where _x and _y are + either integers or single letters, and _i_n_c_r, an optional increment, is + an integer. When integers are supplied, the expression expands to each + number between _x and _y, inclusive. Supplied integers may be prefixed + with _0 to force each term to have the same width. When either _x or _y + 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 lexico- + graphically between _x and _y, inclusive, using the default C locale. + Note that both _x and _y 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. + + Brace expansion is performed before any other expansions, and any char- + acters special to other expansions are preserved in the result. It is + strictly textual. BBaasshh does not apply any syntactic interpretation to + the context of the expansion or the text between the braces. + + A correctly-formed brace expansion must contain unquoted opening and + closing braces, and at least one unquoted comma or a valid sequence ex- + pression. Any incorrectly formed brace expansion is left unchanged. A + {{ or ,, may be quoted with a backslash to prevent its being considered + part of a brace expression. To avoid conflicts with parameter expan- + sion, the string $${{ is not considered eligible for brace expansion, and + inhibits brace expansion until the closing }}. + + This construct is typically used as shorthand when the common prefix of + the strings to be generated is longer than in the above example: + + mkdir /usr/local/src/bash/{old,new,dist,bugs} + or + chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}} + + Brace expansion introduces a slight incompatibility with historical + versions of sshh. sshh does not treat opening or closing braces specially + when they appear as part of a word, and preserves them in the output. + BBaasshh removes braces from words as a consequence of brace expansion. + For example, a word entered to sshh as _f_i_l_e_{_1_,_2_} appears identically in + the output. The same word is output as _f_i_l_e_1 _f_i_l_e_2 after expansion by + bbaasshh. If strict compatibility with sshh is desired, start bbaasshh with the + ++BB option or disable brace expansion with the ++BB option to the sseett com- + mand (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below). + + TTiillddee EExxppaannssiioonn + If a word begins with an unquoted tilde character (`~~'), all of the + characters preceding the first unquoted slash (or all characters, if + there is no unquoted slash) are considered a _t_i_l_d_e_-_p_r_e_f_i_x. 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 _l_o_g_i_n _n_a_m_e. + If this login name is the null string, the tilde is replaced with the + value of the shell parameter HHOOMMEE. If HHOOMMEE is unset, the home direc- + tory of the user executing the shell is substituted instead. Other- + wise, the tilde-prefix is replaced with the home directory associated + with the specified login name. + + If the tilde-prefix is a `~+', the value of the shell variable PPWWDD re- + places the tilde-prefix. If the tilde-prefix is a `~-', the value of + the shell variable OOLLDDPPWWDD, if it is set, is substituted. If the char- + acters following the tilde in the tilde-prefix consist of a number _N, + 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 ddiirrss builtin invoked with the tilde-prefix as an argu- + ment. If the characters following the tilde in the tilde-prefix con- + sist of a number without a leading `+' or `-', `+' is assumed. + + If the login name is invalid, or the tilde expansion fails, the word is + unchanged. + + Each variable assignment is checked for unquoted tilde-prefixes immedi- + ately following a :: or the first ==. In these cases, tilde expansion is + also performed. Consequently, one may use filenames with tildes in as- + signments to PPAATTHH, MMAAIILLPPAATTHH, and CCDDPPAATTHH, and the shell assigns the ex- + panded value. + + Bash also performs tilde expansion on words satisfying the conditions + of variable assignments (as described above under PPAARRAAMMEETTEERRSS) when they + appear as arguments to simple commands. Bash does not do this, except + for the _d_e_c_l_a_r_a_t_i_o_n commands listed above, when in _p_o_s_i_x _m_o_d_e. + + PPaarraammeetteerr EExxppaannssiioonn + The `$$' 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. + + When braces are used, the matching ending brace is the first `}}' not + escaped by a backslash or within a quoted string, and not within an em- + bedded arithmetic expansion, command substitution, or parameter expan- + sion. + + ${_p_a_r_a_m_e_t_e_r} + The value of _p_a_r_a_m_e_t_e_r is substituted. The braces are required + when _p_a_r_a_m_e_t_e_r is a positional parameter with more than one + digit, or when _p_a_r_a_m_e_t_e_r is followed by a character which is not + to be interpreted as part of its name. The _p_a_r_a_m_e_t_e_r is a shell + parameter as described above PPAARRAAMMEETTEERRSS) or an array reference + (AArrrraayyss). + + If the first character of _p_a_r_a_m_e_t_e_r is an exclamation point (!!), and + _p_a_r_a_m_e_t_e_r is not a _n_a_m_e_r_e_f, it introduces a level of indirection. BBaasshh + uses the value formed by expanding the rest of _p_a_r_a_m_e_t_e_r as the new _p_a_- + _r_a_m_e_t_e_r; this is then expanded and that value is used in the rest of + the expansion, rather than the expansion of the original _p_a_r_a_m_e_t_e_r. + This is known as _i_n_d_i_r_e_c_t _e_x_p_a_n_s_i_o_n. The value is subject to tilde ex- + pansion, parameter expansion, command substitution, and arithmetic ex- + pansion. If _p_a_r_a_m_e_t_e_r is a nameref, this expands to the name of the + parameter referenced by _p_a_r_a_m_e_t_e_r instead of performing the complete + indirect expansion. The exceptions to this are the expansions of + ${!!_p_r_e_f_i_x**} and ${!!_n_a_m_e[_@]} described below. The exclamation point + must immediately follow the left brace in order to introduce indirec- + tion. + + In each of the cases below, _w_o_r_d is subject to tilde expansion, parame- + ter expansion, command substitution, and arithmetic expansion. + + When not performing substring expansion, using the forms documented be- + low (e.g., ::--), bbaasshh tests for a parameter that is unset or null. + Omitting the colon results in a test only for a parameter that is un- + set. + + ${_p_a_r_a_m_e_t_e_r::--_w_o_r_d} + UUssee DDeeffaauulltt VVaalluueess. If _p_a_r_a_m_e_t_e_r is unset or null, the expan- + sion of _w_o_r_d is substituted. Otherwise, the value of _p_a_r_a_m_e_t_e_r + is substituted. + ${_p_a_r_a_m_e_t_e_r::==_w_o_r_d} + AAssssiiggnn DDeeffaauulltt VVaalluueess. If _p_a_r_a_m_e_t_e_r is unset or null, the ex- + pansion of _w_o_r_d is assigned to _p_a_r_a_m_e_t_e_r. The value of _p_a_r_a_m_e_- + _t_e_r is then substituted. Positional parameters and special pa- + rameters may not be assigned to in this way. + ${_p_a_r_a_m_e_t_e_r::??_w_o_r_d} + DDiissppllaayy EErrrroorr iiff NNuullll oorr UUnnsseett. If _p_a_r_a_m_e_t_e_r is null or unset, + the expansion of _w_o_r_d (or a message to that effect if _w_o_r_d is + not present) is written to the standard error and the shell, if + it is not interactive, exits. Otherwise, the value of _p_a_r_a_m_e_t_e_r + is substituted. + ${_p_a_r_a_m_e_t_e_r::++_w_o_r_d} + UUssee AAlltteerrnnaattee VVaalluuee. If _p_a_r_a_m_e_t_e_r is null or unset, nothing is + substituted, otherwise the expansion of _w_o_r_d is substituted. + ${_p_a_r_a_m_e_t_e_r::_o_f_f_s_e_t} + ${_p_a_r_a_m_e_t_e_r::_o_f_f_s_e_t::_l_e_n_g_t_h} + SSuubbssttrriinngg EExxppaannssiioonn. Expands to up to _l_e_n_g_t_h characters of the + value of _p_a_r_a_m_e_t_e_r starting at the character specified by _o_f_f_- + _s_e_t. If _p_a_r_a_m_e_t_e_r is @@ or **, an indexed array subscripted by @@ + or **, or an associative array name, the results differ as de- + scribed below. If _l_e_n_g_t_h is omitted, expands to the substring + of the value of _p_a_r_a_m_e_t_e_r starting at the character specified by + _o_f_f_s_e_t and extending to the end of the value. _l_e_n_g_t_h and _o_f_f_s_e_t + are arithmetic expressions (see AARRIITTHHMMEETTIICC EEVVAALLUUAATTIIOONN below). + + If _o_f_f_s_e_t evaluates to a number less than zero, the value is + used as an offset in characters from the end of the value of _p_a_- + _r_a_m_e_t_e_r. If _l_e_n_g_t_h evaluates to a number less than zero, it is + interpreted as an offset in characters from the end of the value + of _p_a_r_a_m_e_t_e_r rather than a number of characters, and the expan- + sion is the characters between _o_f_f_s_e_t 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 ::-- expansion. + + If _p_a_r_a_m_e_t_e_r is @@ or **, the result is _l_e_n_g_t_h positional parame- + ters beginning at _o_f_f_s_e_t. A negative _o_f_f_s_e_t 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 _l_e_n_g_t_h evaluates to a number less than + zero. + + If _p_a_r_a_m_e_t_e_r is an indexed array name subscripted by @ or *, the + result is the _l_e_n_g_t_h members of the array beginning with ${_p_a_- + _r_a_m_e_t_e_r[_o_f_f_s_e_t]}. A negative _o_f_f_s_e_t is taken relative to one + greater than the maximum index of the specified array. It is an + expansion error if _l_e_n_g_t_h evaluates to a number less than zero. + + Substring expansion applied to an associative array produces un- + defined results. + + Substring indexing is zero-based unless the positional parame- + ters are used, in which case the indexing starts at 1 by de- + fault. If _o_f_f_s_e_t is 0, and the positional parameters are used, + $$00 is prefixed to the list. + + ${!!_p_r_e_f_i_x**} + ${!!_p_r_e_f_i_x@@} + NNaammeess mmaattcchhiinngg pprreeffiixx. Expands to the names of variables whose + names begin with _p_r_e_f_i_x, separated by the first character of the + IIFFSS special variable. When _@ is used and the expansion appears + within double quotes, each variable name expands to a separate + word. + + ${!!_n_a_m_e[_@]} + ${!!_n_a_m_e[_*]} + LLiisstt ooff aarrrraayy kkeeyyss. If _n_a_m_e is an array variable, expands to + the list of array indices (keys) assigned in _n_a_m_e. If _n_a_m_e is + not an array, expands to 0 if _n_a_m_e is set and null otherwise. + When _@ is used and the expansion appears within double quotes, + each key expands to a separate word. + + ${##_p_a_r_a_m_e_t_e_r} + PPaarraammeetteerr lleennggtthh. The length in characters of the value of _p_a_- + _r_a_m_e_t_e_r is substituted. If _p_a_r_a_m_e_t_e_r is ** or @@, the value sub- + stituted is the number of positional parameters. If _p_a_r_a_m_e_t_e_r + is an array name subscripted by ** or @@, the value substituted is + the number of elements in the array. If _p_a_r_a_m_e_t_e_r is an indexed + array name subscripted by a negative number, that number is in- + terpreted as relative to one greater than the maximum index of + _p_a_r_a_m_e_t_e_r, so negative indices count back from the end of the + array, and an index of -1 references the last element. + + ${_p_a_r_a_m_e_t_e_r##_w_o_r_d} + ${_p_a_r_a_m_e_t_e_r####_w_o_r_d} + RReemmoovvee mmaattcchhiinngg pprreeffiixx ppaatttteerrnn. The _w_o_r_d is expanded to produce + a pattern just as in pathname expansion, and matched against the + expanded value of _p_a_r_a_m_e_t_e_r using the rules described under PPaatt-- + tteerrnn MMaattcchhiinngg below. If the pattern matches the beginning of + the value of _p_a_r_a_m_e_t_e_r, then the result of the expansion is the + expanded value of _p_a_r_a_m_e_t_e_r with the shortest matching pattern + (the ``##'' case) or the longest matching pattern (the ``####'' + case) deleted. If _p_a_r_a_m_e_t_e_r is @@ or **, the pattern removal op- + eration is applied to each positional parameter in turn, and the + expansion is the resultant list. If _p_a_r_a_m_e_t_e_r is an array vari- + able subscripted with @@ or **, the pattern removal operation is + applied to each member of the array in turn, and the expansion + is the resultant list. + + ${_p_a_r_a_m_e_t_e_r%%_w_o_r_d} + ${_p_a_r_a_m_e_t_e_r%%%%_w_o_r_d} + RReemmoovvee mmaattcchhiinngg ssuuffffiixx ppaatttteerrnn. The _w_o_r_d is expanded to produce + a pattern just as in pathname expansion, and matched against the + expanded value of _p_a_r_a_m_e_t_e_r using the rules described under PPaatt-- + tteerrnn MMaattcchhiinngg below. If the pattern matches a trailing portion + of the expanded value of _p_a_r_a_m_e_t_e_r, then the result of the ex- + pansion is the expanded value of _p_a_r_a_m_e_t_e_r with the shortest + matching pattern (the ``%%'' case) or the longest matching pat- + tern (the ``%%%%'' case) deleted. If _p_a_r_a_m_e_t_e_r is @@ or **, the + pattern removal operation is applied to each positional parame- + ter in turn, and the expansion is the resultant list. If _p_a_r_a_m_- + _e_t_e_r is an array variable subscripted with @@ or **, the pattern + removal operation is applied to each member of the array in + turn, and the expansion is the resultant list. + + ${_p_a_r_a_m_e_t_e_r//_p_a_t_t_e_r_n//_s_t_r_i_n_g} + ${_p_a_r_a_m_e_t_e_r////_p_a_t_t_e_r_n//_s_t_r_i_n_g} + ${_p_a_r_a_m_e_t_e_r//##_p_a_t_t_e_r_n//_s_t_r_i_n_g} + ${_p_a_r_a_m_e_t_e_r//%%_p_a_t_t_e_r_n//_s_t_r_i_n_g} + PPaatttteerrnn ssuubbssttiittuuttiioonn. The _p_a_t_t_e_r_n is expanded to produce a pat- + tern just as in pathname expansion. _P_a_r_a_m_e_t_e_r is expanded and + the longest match of _p_a_t_t_e_r_n against its value is replaced with + _s_t_r_i_n_g. _s_t_r_i_n_g undergoes tilde expansion, parameter and vari- + able expansion, arithmetic expansion, command and process sub- + stitution, and quote removal. The match is performed using the + rules described under PPaatttteerrnn MMaattcchhiinngg below. In the first form + above, only the first match is replaced. If there are two + slashes separating _p_a_r_a_m_e_t_e_r and _p_a_t_t_e_r_n (the second form + above), all matches of _p_a_t_t_e_r_n are replaced with _s_t_r_i_n_g. If + _p_a_t_t_e_r_n is preceded by ## (the third form above), it must match + at the beginning of the expanded value of _p_a_r_a_m_e_t_e_r. If _p_a_t_t_e_r_n + is preceded by %% (the fourth form above), it must match at the + end of the expanded value of _p_a_r_a_m_e_t_e_r. If the expansion of + _s_t_r_i_n_g is null, matches of _p_a_t_t_e_r_n are deleted. If _s_t_r_i_n_g is + null, matches of _p_a_t_t_e_r_n are deleted and the // following _p_a_t_t_e_r_n + may be omitted. + + If the ppaattssuubb__rreeppllaacceemmeenntt shell option is enabled using sshhoopptt, + any unquoted instances of && in _s_t_r_i_n_g are replaced with the + matching portion of _p_a_t_t_e_r_n. + + Quoting any part of _s_t_r_i_n_g inhibits replacement in the expansion + of the quoted portion, including replacement strings stored in + shell variables. Backslash will escape && in _s_t_r_i_n_g; the back- + slash is removed in order to permit a literal && in the replace- + ment string. Backslash can also be used to escape a backslash; + \\\\ results in a literal backslash in the replacement. Users + should take care if _s_t_r_i_n_g 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 && after expanding + _s_t_r_i_n_g; shell programmers should quote any occurrences of && they + want to be taken literally in the replacement and ensure any in- + stances of && they want to be replaced are unquoted. + + If the nnooccaasseemmaattcchh shell option is enabled, the match is per- + formed without regard to the case of alphabetic characters. If + _p_a_r_a_m_e_t_e_r is @@ or **, the substitution operation is applied to + each positional parameter in turn, and the expansion is the re- + sultant list. If _p_a_r_a_m_e_t_e_r is an array variable subscripted + with @@ or **, the substitution operation is applied to each mem- + ber of the array in turn, and the expansion is the resultant + list. + + ${_p_a_r_a_m_e_t_e_r^^_p_a_t_t_e_r_n} + ${_p_a_r_a_m_e_t_e_r^^^^_p_a_t_t_e_r_n} + ${_p_a_r_a_m_e_t_e_r,,_p_a_t_t_e_r_n} + ${_p_a_r_a_m_e_t_e_r,,,,_p_a_t_t_e_r_n} + CCaassee mmooddiiffiiccaattiioonn. This expansion modifies the case of alpha- + betic characters in _p_a_r_a_m_e_t_e_r. The _p_a_t_t_e_r_n is expanded to pro- + duce a pattern just as in pathname expansion. Each character in + the expanded value of _p_a_r_a_m_e_t_e_r is tested against _p_a_t_t_e_r_n, and, + if it matches the pattern, its case is converted. The pattern + should not attempt to match more than one character. The ^^ op- + erator converts lowercase letters matching _p_a_t_t_e_r_n to uppercase; + the ,, operator converts matching uppercase letters to lowercase. + The ^^^^ and ,,,, expansions convert each matched character in the + expanded value; the ^^ and ,, expansions match and convert only + the first character in the expanded value. If _p_a_t_t_e_r_n is omit- + ted, it is treated like a ??, which matches every character. If + _p_a_r_a_m_e_t_e_r is @@ or **, the case modification operation is applied + to each positional parameter in turn, and the expansion is the + resultant list. If _p_a_r_a_m_e_t_e_r is an array variable subscripted + with @@ or **, the case modification operation is applied to each + member of the array in turn, and the expansion is the resultant + list. + + ${_p_a_r_a_m_e_t_e_r@@_o_p_e_r_a_t_o_r} + PPaarraammeetteerr ttrraannssffoorrmmaattiioonn. The expansion is either a transforma- + tion of the value of _p_a_r_a_m_e_t_e_r or information about _p_a_r_a_m_e_t_e_r + itself, depending on the value of _o_p_e_r_a_t_o_r. Each _o_p_e_r_a_t_o_r is a + single letter: + + UU The expansion is a string that is the value of _p_a_r_a_m_e_t_e_r + with lowercase alphabetic characters converted to upper- + case. + uu The expansion is a string that is the value of _p_a_r_a_m_e_t_e_r + with the first character converted to uppercase, if it is + alphabetic. + LL The expansion is a string that is the value of _p_a_r_a_m_e_t_e_r + with uppercase alphabetic characters converted to lower- + case. + QQ The expansion is a string that is the value of _p_a_r_a_m_e_t_e_r + quoted in a format that can be reused as input. + EE The expansion is a string that is the value of _p_a_r_a_m_e_t_e_r + with backslash escape sequences expanded as with the + $$''......'' quoting mechanism. + PP The expansion is a string that is the result of expanding + the value of _p_a_r_a_m_e_t_e_r as if it were a prompt string (see + PPRROOMMPPTTIINNGG below). + AA The expansion is a string in the form of an assignment + statement or ddeeccllaarree command that, if evaluated, will + recreate _p_a_r_a_m_e_t_e_r with its attributes and value. + KK Produces a possibly-quoted version of the value of _p_a_r_a_m_- + _e_t_e_r, except that it prints the values of indexed and as- + sociative arrays as a sequence of quoted key-value pairs + (see AArrrraayyss above). + aa The expansion is a string consisting of flag values rep- + resenting _p_a_r_a_m_e_t_e_r's attributes. + kk Like the K transformation, but expands the keys and val- + ues of indexed and associative arrays to separate words + after word splitting. + + If _p_a_r_a_m_e_t_e_r is @@ or **, the operation is applied to each posi- + tional parameter in turn, and the expansion is the resultant + list. If _p_a_r_a_m_e_t_e_r is an array variable subscripted with @@ or + **, the operation is applied to each member of the array in turn, + and the expansion is the resultant list. + + The result of the expansion is subject to word splitting and + pathname expansion as described below. + + CCoommmmaanndd SSuubbssttiittuuttiioonn + _C_o_m_m_a_n_d _s_u_b_s_t_i_t_u_t_i_o_n allows the output of a command to replace the com- + mand name. There are two forms: + + $$((_c_o_m_m_a_n_d)) + or + ``_c_o_m_m_a_n_d`` + + BBaasshh performs the expansion by executing _c_o_m_m_a_n_d in a subshell environ- + ment 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 com- + mand substitution $$((ccaatt _f_i_l_e)) can be replaced by the equivalent but + faster $$((<< _f_i_l_e)). + + When the old-style backquote form of substitution is used, backslash + retains its literal meaning except when followed by $$, ``, or \\. The + first backquote not preceded by a backslash terminates the command sub- + stitution. When using the $(_c_o_m_m_a_n_d) form, all characters between the + parentheses make up the command; none are treated specially. + + Command substitutions may be nested. To nest when using the backquoted + form, escape the inner backquotes with backslashes. + + If the substitution appears within double quotes, word splitting and + pathname expansion are not performed on the results. + + AArriitthhmmeettiicc EExxppaannssiioonn + Arithmetic expansion allows the evaluation of an arithmetic expression + and the substitution of the result. The format for arithmetic expan- + sion is: + + $$((((_e_x_p_r_e_s_s_i_o_n)))) + + The _e_x_p_r_e_s_s_i_o_n undergoes the same expansions as if it were within dou- + ble quotes, but double quote characters in _e_x_p_r_e_s_s_i_o_n are not treated + specially and are removed. All tokens in the expression undergo param- + eter and variable expansion, command substitution, and quote removal. + The result is treated as the arithmetic expression to be evaluated. + Arithmetic expansions may be nested. + + The evaluation is performed according to the rules listed below under + AARRIITTHHMMEETTIICC EEVVAALLUUAATTIIOONN. If _e_x_p_r_e_s_s_i_o_n is invalid, bbaasshh prints a message + indicating failure and no substitution occurs. + + PPrroocceessss SSuubbssttiittuuttiioonn + _P_r_o_c_e_s_s _s_u_b_s_t_i_t_u_t_i_o_n allows a process's input or output to be referred + to using a filename. It takes the form of <<((_l_i_s_t)) or >>((_l_i_s_t)). The + process _l_i_s_t is run asynchronously, and its input or output appears as + a filename. This filename is passed as an argument to the current com- + mand as the result of the expansion. If the >>((_l_i_s_t)) form is used, + writing to the file will provide input for _l_i_s_t. If the <<((_l_i_s_t)) form + is used, the file passed as an argument should be read to obtain the + output of _l_i_s_t. Process substitution is supported on systems that sup- + port named pipes (_F_I_F_O_s) or the //ddeevv//ffdd method of naming open files. + + When available, process substitution is performed simultaneously with + parameter and variable expansion, command substitution, and arithmetic + expansion. + + WWoorrdd SSpplliittttiinngg + The shell scans the results of parameter expansion, command substitu- + tion, and arithmetic expansion that did not occur within double quotes + for _w_o_r_d _s_p_l_i_t_t_i_n_g. + + The shell treats each character of IIFFSS as a delimiter, and splits the + results of the other expansions into words using these characters as + field terminators. If IIFFSS is unset, or its value is exactly + <<ssppaaccee>><<ttaabb>><<nneewwlliinnee>>, the default, then sequences of <<ssppaaccee>>, <<ttaabb>>, + and <<nneewwlliinnee>> at the beginning and end of the results of the previous + expansions are ignored, and any sequence of IIFFSS characters not at the + beginning or end serves to delimit words. If IIFFSS has a value other + than the default, then sequences of the whitespace characters ssppaaccee, + ttaabb, and nneewwlliinnee are ignored at the beginning and end of the word, as + long as the whitespace character is in the value of IIFFSS (an IIFFSS white- + space character). Any character in IIFFSS that is not IIFFSS whitespace, + along with any adjacent IIFFSS whitespace characters, delimits a field. A + sequence of IIFFSS whitespace characters is also treated as a delimiter. + If the value of IIFFSS is null, no word splitting occurs. + + Explicit null arguments ("""" or '''') 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 parame- + ter with no value is expanded within double quotes, a null argument re- + sults 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 -d'' becomes + -d after word splitting and null argument removal. + + Note that if no expansion occurs, no splitting is performed. + + PPaatthhnnaammee EExxppaannssiioonn + After word splitting, unless the --ff option has been set, bbaasshh scans + each word for the characters **, ??, and [[. If one of these characters + appears, and is not quoted, then the word is regarded as a _p_a_t_t_e_r_n, and + replaced with an alphabetically sorted list of filenames matching the + pattern (see PPaatttteerrnn MMaattcchhiinngg below). If no matching filenames are + found, and the shell option nnuullllgglloobb is not enabled, the word is left + unchanged. If the nnuullllgglloobb option is set, and no matches are found, + the word is removed. If the ffaaiillgglloobb shell option is set, and no + matches are found, an error message is printed and the command is not + executed. If the shell option nnooccaasseegglloobb is enabled, the match is per- + formed without regard to the case of alphabetic characters. When a + pattern is used for pathname expansion, the character ````..'''' at the + start of a name or immediately following a slash must be matched ex- + plicitly, unless the shell option ddoottgglloobb is set. In order to match + the filenames ````..'''' and ````....'''', the pattern must begin with ``.'' (for + example, ``.?''), even if ddoottgglloobb is set. If the gglloobbsskkiippddoottss shell + option is enabled, the filenames ````..'''' and ````....'''' are never matched, + even if the pattern begins with a ````..''''. When not matching pathnames, + the ````..'''' character is not treated specially. When matching a path- + name, 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 PPaatttteerrnn MMaattcchhiinngg. + See the description of sshhoopptt below under SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS for a + description of the nnooccaasseegglloobb, nnuullllgglloobb, gglloobbsskkiippddoottss, ffaaiillgglloobb, and + ddoottgglloobb shell options. + + The GGLLOOBBIIGGNNOORREE shell variable may be used to restrict the set of file + names matching a _p_a_t_t_e_r_n. If GGLLOOBBIIGGNNOORREE is set, each matching file + name that also matches one of the patterns in GGLLOOBBIIGGNNOORREE is removed + from the list of matches. If the nnooccaasseegglloobb option is set, the match- + ing against the patterns in GGLLOOBBIIGGNNOORREE is performed without regard to + case. The filenames ````..'''' and ````....'''' are always ignored when GGLLOOBBIIGG-- + NNOORREE is set and not null. However, setting GGLLOOBBIIGGNNOORREE to a non-null + value has the effect of enabling the ddoottgglloobb shell option, so all other + filenames beginning with a ````..'''' will match. To get the old behavior + of ignoring filenames beginning with a ````..'''', make ````..**'''' one of the + patterns in GGLLOOBBIIGGNNOORREE. The ddoottgglloobb option is disabled when GGLLOOBBIIGGNNOORREE + is unset. The pattern matching honors the setting of the eexxttgglloobb shell + option. + + PPaatttteerrnn MMaattcchhiinngg + + 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. + + The special pattern characters have the following meanings: + + ** Matches any string, including the null string. When the + gglloobbssttaarr shell option is enabled, and ** is used in a + pathname expansion context, two adjacent **s used as a + single pattern will match all files and zero or more di- + rectories and subdirectories. If followed by a //, two + adjacent **s will match only directories and subdirecto- + ries. + ?? Matches any single character. + [[......]] Matches any one of the enclosed characters. A pair of + characters separated by a hyphen denotes a _r_a_n_g_e _e_x_p_r_e_s_- + _s_i_o_n; any character that falls between those two charac- + ters, inclusive, using the current locale's collating se- + quence and character set, is matched. If the first char- + acter following the [[ is a !! or a ^^ 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 val- + ues of the LLCC__CCOOLLLLAATTEE or LLCC__AALLLL shell variables, if set. + To obtain the traditional interpretation of range expres- + sions, where [[aa--dd]] is equivalent to [[aabbccdd]], set value of + the LLCC__AALLLL shell variable to CC, or enable the gglloobbaassccii-- + iirraannggeess shell option. A -- may be matched by including it + as the first or last character in the set. A ]] may be + matched by including it as the first character in the + set. + + Within [[ and ]], _c_h_a_r_a_c_t_e_r _c_l_a_s_s_e_s can be specified using + the syntax [[::_c_l_a_s_s::]], where _c_l_a_s_s is one of the following + classes defined in the POSIX standard: + aallnnuumm aallpphhaa aasscciiii bbllaannkk ccnnttrrll ddiiggiitt ggrraapphh lloowweerr pprriinntt + ppuunncctt ssppaaccee uuppppeerr wwoorrdd xxddiiggiitt + A character class matches any character belonging to that + class. The wwoorrdd character class matches letters, digits, + and the character _. + + Within [[ and ]], an _e_q_u_i_v_a_l_e_n_c_e _c_l_a_s_s can be specified us- + ing the syntax [[==_c==]], which matches all characters with + the same collation weight (as defined by the current lo- + cale) as the character _c. + + Within [[ and ]], the syntax [[.._s_y_m_b_o_l..]] matches the collat- + ing symbol _s_y_m_b_o_l. + + If the eexxttgglloobb shell option is enabled using the sshhoopptt builtin, the + shell recognizes several extended pattern matching operators. In the + following description, a _p_a_t_t_e_r_n_-_l_i_s_t is a list of one or more patterns + separated by a ||. Composite patterns may be formed using one or more + of the following sub-patterns: + + ??((_p_a_t_t_e_r_n_-_l_i_s_t)) + Matches zero or one occurrence of the given patterns + **((_p_a_t_t_e_r_n_-_l_i_s_t)) + Matches zero or more occurrences of the given patterns + ++((_p_a_t_t_e_r_n_-_l_i_s_t)) + Matches one or more occurrences of the given patterns + @@((_p_a_t_t_e_r_n_-_l_i_s_t)) + Matches one of the given patterns + !!((_p_a_t_t_e_r_n_-_l_i_s_t)) + Matches anything except one of the given patterns + + Theeexxttgglloobb option changes the behavior of the parser, since the paren- + theses are normally treated as operators with syntactic meaning. To + ensure that extended matching patterns are parsed correctly, make sure + that eexxttgglloobb is enabled before parsing constructs containing the pat- + terns, including shell functions and command substitutions. + + When matching filenames, the ddoottgglloobb shell option determines the set of + filenames that are tested: when ddoottgglloobb is enabled, the set of file- + names 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. + + Complicated extended pattern matching against long strings is slow, es- + pecially 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. + + QQuuoottee RReemmoovvaall + After the preceding expansions, all unquoted occurrences of the charac- + ters \\, '', and "" that did not result from one of the above expansions + are removed. + +RREEDDIIRREECCTTIIOONN + Before a command is executed, its input and output may be _r_e_d_i_r_e_c_t_e_d + using a special notation interpreted by the shell. _R_e_d_i_r_e_c_t_i_o_n 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 opera- + tors may precede or appear anywhere within a _s_i_m_p_l_e _c_o_m_m_a_n_d or may fol- + low a _c_o_m_m_a_n_d. Redirections are processed in the order they appear, + from left to right. + + Each redirection that may be preceded by a file descriptor number may + instead be preceded by a word of the form {_v_a_r_n_a_m_e}. 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 _v_a_r_n_a_m_e. + If >&- or <&- is preceded by {_v_a_r_n_a_m_e}, the value of _v_a_r_n_a_m_e defines + the file descriptor to close. If {_v_a_r_n_a_m_e} is supplied, the redirect- + ion persists beyond the scope of the command, allowing the shell pro- + grammer to manage the file descriptor's lifetime manually. The + vvaarrrreeddiirr__cclloossee shell option manages this behavior. + + In the following descriptions, if the file descriptor number is omit- + ted, and the first character of the redirection operator is <<, the re- + direction refers to the standard input (file descriptor 0). If the + first character of the redirection operator is >>, the redirection + refers to the standard output (file descriptor 1). + + The word following the redirection operator in the following descrip- + tions, 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, bbaasshh reports an error. + + Note that the order of redirections is significant. For example, the + command + + ls >> dirlist 2>>&&1 + + directs both standard output and standard error to the file _d_i_r_l_i_s_t, + while the command + + ls 2>>&&1 >> dirlist + + directs only the standard output to file _d_i_r_l_i_s_t, because the standard + error was duplicated from the standard output before the standard out- + put was redirected to _d_i_r_l_i_s_t. + + BBaasshh handles several filenames specially when they are used in redirec- + tions, as described in the following table. If the operating system on + which bbaasshh is running provides these special files, bash will use them; + otherwise it will emulate them internally with the behavior described + below. + + //ddeevv//ffdd//_f_d + If _f_d is a valid integer, file descriptor _f_d is dupli- + cated. + //ddeevv//ssttddiinn + File descriptor 0 is duplicated. + //ddeevv//ssttddoouutt + File descriptor 1 is duplicated. + //ddeevv//ssttddeerrrr + File descriptor 2 is duplicated. + //ddeevv//ttccpp//_h_o_s_t//_p_o_r_t + If _h_o_s_t is a valid hostname or Internet address, and _p_o_r_t + is an integer port number or service name, bbaasshh attempts + to open the corresponding TCP socket. + //ddeevv//uuddpp//_h_o_s_t//_p_o_r_t + If _h_o_s_t is a valid hostname or Internet address, and _p_o_r_t + is an integer port number or service name, bbaasshh attempts + to open the corresponding UDP socket. + + A failure to open or create a file causes the redirection to fail. + + Redirections using file descriptors greater than 9 should be used with + care, as they may conflict with file descriptors the shell uses inter- + nally. + + RReeddiirreeccttiinngg IInnppuutt + Redirection of input causes the file whose name results from the expan- + sion of _w_o_r_d to be opened for reading on file descriptor _n, or the + standard input (file descriptor 0) if _n is not specified. + + The general format for redirecting input is: + + [_n]<<_w_o_r_d + + RReeddiirreeccttiinngg OOuuttppuutt + Redirection of output causes the file whose name results from the ex- + pansion of _w_o_r_d to be opened for writing on file descriptor _n, or the + standard output (file descriptor 1) if _n is not specified. If the file + does not exist it is created; if it does exist it is truncated to zero + size. + + The general format for redirecting output is: + + [_n]>>_w_o_r_d + + If the redirection operator is >>, and the nnoocclloobbbbeerr option to the sseett + builtin has been enabled, the redirection will fail if the file whose + name results from the expansion of _w_o_r_d exists and is a regular file. + If the redirection operator is >>||, or the redirection operator is >> and + the nnoocclloobbbbeerr option to the sseett builtin command is not enabled, the re- + direction is attempted even if the file named by _w_o_r_d exists. + + AAppppeennddiinngg RReeddiirreecctteedd OOuuttppuutt + Redirection of output in this fashion causes the file whose name re- + sults from the expansion of _w_o_r_d to be opened for appending on file de- + scriptor _n, or the standard output (file descriptor 1) if _n is not + specified. If the file does not exist it is created. + + The general format for appending output is: + + [_n]>>>>_w_o_r_d + + RReeddiirreeccttiinngg SSttaannddaarrdd OOuuttppuutt aanndd SSttaannddaarrdd EErrrroorr + 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 _w_o_r_d. + + There are two formats for redirecting standard output and standard er- + ror: + + &&>>_w_o_r_d + and + >>&&_w_o_r_d + + Of the two forms, the first is preferred. This is semantically equiva- + lent to + + >>_w_o_r_d 2>>&&1 + + When using the second form, _w_o_r_d may not expand to a number or --. If + it does, other redirection operators apply (see DDuupplliiccaattiinngg FFiillee DDee-- + ssccrriippttoorrss below) for compatibility reasons. + + AAppppeennddiinngg SSttaannddaarrdd OOuuttppuutt aanndd SSttaannddaarrdd EErrrroorr + 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 _w_o_r_d. + + The format for appending standard output and standard error is: + + &&>>>>_w_o_r_d + + This is semantically equivalent to + + >>>>_w_o_r_d 2>>&&1 + + (see DDuupplliiccaattiinngg FFiillee DDeessccrriippttoorrss below). + + HHeerree DDooccuummeennttss + This type of redirection instructs the shell to read input from the + current source until a line containing only _d_e_l_i_m_i_t_e_r (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 _n if _n is specified) for a + command. + + The format of here-documents is: + + [_n]<<<<[--]_w_o_r_d + _h_e_r_e_-_d_o_c_u_m_e_n_t + _d_e_l_i_m_i_t_e_r + + No parameter and variable expansion, command substitution, arithmetic + expansion, or pathname expansion is performed on _w_o_r_d. If any part of + _w_o_r_d is quoted, the _d_e_l_i_m_i_t_e_r is the result of quote removal on _w_o_r_d, + and the lines in the here-document are not expanded. If _w_o_r_d is un- + quoted, all lines of the here-document are subjected to parameter ex- + pansion, command substitution, and arithmetic expansion, the character + sequence \\<<nneewwlliinnee>> is ignored, and \\ must be used to quote the charac- + ters \\, $$, and ``. + + If the redirection operator is <<<<--, then all leading tab characters are + stripped from input lines and the line containing _d_e_l_i_m_i_t_e_r. This al- + lows here-documents within shell scripts to be indented in a natural + fashion. + + HHeerree SSttrriinnggss + A variant of here documents, the format is: + + [_n]<<<<<<_w_o_r_d + + The _w_o_r_d undergoes tilde expansion, parameter and variable expansion, + command substitution, arithmetic expansion, and quote removal. Path- + name 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 _n if _n is specified). + + DDuupplliiccaattiinngg FFiillee DDeessccrriippttoorrss + The redirection operator + + [_n]<<&&_w_o_r_d + + is used to duplicate input file descriptors. If _w_o_r_d expands to one or + more digits, the file descriptor denoted by _n is made to be a copy of + that file descriptor. If the digits in _w_o_r_d do not specify a file de- + scriptor open for input, a redirection error occurs. If _w_o_r_d evaluates + to --, file descriptor _n is closed. If _n is not specified, the standard + input (file descriptor 0) is used. + + The operator + + [_n]>>&&_w_o_r_d + + is used similarly to duplicate output file descriptors. If _n is not + specified, the standard output (file descriptor 1) is used. If the + digits in _w_o_r_d do not specify a file descriptor open for output, a re- + direction error occurs. If _w_o_r_d evaluates to --, file descriptor _n is + closed. As a special case, if _n is omitted, and _w_o_r_d does not expand + to one or more digits or --, the standard output and standard error are + redirected as described previously. + + MMoovviinngg FFiillee DDeessccrriippttoorrss + The redirection operator + + [_n]<<&&_d_i_g_i_t-- + + moves the file descriptor _d_i_g_i_t to file descriptor _n, or the standard + input (file descriptor 0) if _n is not specified. _d_i_g_i_t is closed after + being duplicated to _n. + + Similarly, the redirection operator + + [_n]>>&&_d_i_g_i_t-- + + moves the file descriptor _d_i_g_i_t to file descriptor _n, or the standard + output (file descriptor 1) if _n is not specified. + + OOppeenniinngg FFiillee DDeessccrriippttoorrss ffoorr RReeaaddiinngg aanndd WWrriittiinngg + The redirection operator + + [_n]<<>>_w_o_r_d + + causes the file whose name is the expansion of _w_o_r_d to be opened for + both reading and writing on file descriptor _n, or on file descriptor 0 + if _n is not specified. If the file does not exist, it is created. + +AALLIIAASSEESS + _A_l_i_a_s_e_s 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 aalliiaass and uunnaalliiaass builtin + commands (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS 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 //, + $$, ``, and == and any of the shell _m_e_t_a_c_h_a_r_a_c_t_e_r_s 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 llss to llss --FF, for instance, and + bbaasshh does not try to recursively expand the replacement text. If the + last character of the alias value is a _b_l_a_n_k, then the next command + word following the alias is also checked for alias expansion. + + Aliases are created and listed with the aalliiaass command, and removed with + the uunnaalliiaass command. + + There is no mechanism for using arguments in the replacement text. If + arguments are needed, use a shell function (see FFUUNNCCTTIIOONNSS below). + + Aliases are not expanded when the shell is not interactive, unless the + eexxppaanndd__aalliiaasseess shell option is set using sshhoopptt (see the description of + sshhoopptt under SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below). + + The rules concerning the definition and use of aliases are somewhat + confusing. BBaasshh 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 af- + ter that function is executed. To be safe, always put alias defini- + tions on a separate line, and do not use aalliiaass in compound commands. + + For almost every purpose, aliases are superseded by shell functions. + +FFUUNNCCTTIIOONNSS + A shell function, defined as described above under SSHHEELLLL GGRRAAMMMMAARR, + 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 in- + terpret 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 ## is + updated to reflect the change. Special parameter 00 is unchanged. The + first element of the FFUUNNCCNNAAMMEE variable is set to the name of the func- + tion while the function is executing. + + All other aspects of the shell execution environment are identical be- + tween a function and its caller with these exceptions: the DDEEBBUUGG and + RREETTUURRNN traps (see the description of the ttrraapp builtin under SSHHEELLLL + BBUUIILLTTIINN CCOOMMMMAANNDDSS below) are not inherited unless the function has been + given the ttrraaccee attribute (see the description of the ddeeccllaarree builtin + below) or the --oo ffuunnccttrraaccee shell option has been enabled with the sseett + builtin (in which case all functions inherit the DDEEBBUUGG and RREETTUURRNN + traps), and the EERRRR trap is not inherited unless the --oo eerrrrttrraaccee shell + option has been enabled. + + Variables local to the function may be declared with the llooccaall builtin + command (_l_o_c_a_l _v_a_r_i_a_b_l_e_s). Ordinarily, variables and their values are + shared between the function and its caller. If a variable is declared + llooccaall, the variable's visible scope is restricted to that function and + its children (including the functions it calls). + + In the following description, the _c_u_r_r_e_n_t _s_c_o_p_e is a currently- execut- + ing 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 llooccaall or ddeeccllaarree builtins in the function + that is currently executing. + + Local variables "shadow" variables with the same name declared at pre- + vious 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. + + The shell uses _d_y_n_a_m_i_c _s_c_o_p_i_n_g 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 exe- + cution 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. + + For example, if a variable _v_a_r is declared as local in function _f_u_n_c_1, + and _f_u_n_c_1 calls another function _f_u_n_c_2, references to _v_a_r made from + within _f_u_n_c_2 will resolve to the local variable _v_a_r from _f_u_n_c_1, shadow- + ing any global variable named _v_a_r. + + The uunnsseett builtin also acts using the same dynamic scope: if a variable + is local to the current scope, uunnsseett 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 re- + main 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 lloo-- + ccaallvvaarr__uunnsseett shell option changes this behavior). + + The FFUUNNCCNNEESSTT variable, if set to a numeric value greater than 0, de- + fines a maximum function nesting level. Function invocations that ex- + ceed the limit cause the entire command to abort. + + If the builtin command rreettuurrnn is executed in a function, the function + completes and execution resumes with the next command after the func- + tion call. Any command associated with the RREETTUURRNN trap is executed be- + fore execution resumes. When a function completes, the values of the + positional parameters and the special parameter ## are restored to the + values they had prior to the function's execution. + + Function names and definitions may be listed with the --ff option to the + ddeeccllaarree or ttyyppeesseett builtin commands. The --FF option to ddeeccllaarree or ttyyppee-- + sseett will list the function names only (and optionally the source file + and line number, if the eexxttddeebbuugg shell option is enabled). Functions + may be exported so that child shell processes (those created when exe- + cuting a separate shell invocation) automatically have them defined + with the --ff option to the eexxppoorrtt builtin. A function definition may be + deleted using the --ff option to the uunnsseett builtin. + + Functions may be recursive. The FFUUNNCCNNEESSTT variable may be used to limit + the depth of the function call stack and restrict the number of func- + tion invocations. By default, no limit is imposed on the number of re- + cursive calls. + +AARRIITTHHMMEETTIICC EEVVAALLUUAATTIIOONN + The shell allows arithmetic expressions to be evaluated, under certain + circumstances (see the lleett and ddeeccllaarree builtin commands, the (((( com- + pound command, and AArriitthhmmeettiicc EExxppaannssiioonn). 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 fol- + lowing list of operators is grouped into levels of equal-precedence op- + erators. The levels are listed in order of decreasing precedence. + + _i_d++++ _i_d---- + variable post-increment and post-decrement + -- ++ unary minus and plus + ++++_i_d ----_i_d + variable pre-increment and pre-decrement + !! ~~ logical and bitwise negation + **** exponentiation + ** // %% multiplication, division, remainder + ++ -- addition, subtraction + <<<< >>>> left and right bitwise shifts + <<== >>== << >> + comparison + ==== !!== equality and inequality + && bitwise AND + ^^ bitwise exclusive OR + || bitwise OR + &&&& logical AND + |||| logical OR + _e_x_p_r??_e_x_p_r::_e_x_p_r + conditional operator + == **== //== %%== ++== --== <<<<== >>>>== &&== ^^== ||== + assignment + _e_x_p_r_1 ,, _e_x_p_r_2 + comma + + Shell variables are allowed as operands; parameter expansion is per- + formed 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 _i_n_t_e_g_e_r + attribute using ddeeccllaarree --ii is assigned a value. A null value evaluates + to 0. A shell variable need not have its _i_n_t_e_g_e_r attribute turned on + to be used in an expression. + + Integer constants follow the C language definition, without suffixes or + character constants. Constants with a leading 0 are interpreted as oc- + tal numbers. A leading 0x or 0X denotes hexadecimal. Otherwise, num- + bers take the form [_b_a_s_e_#]n, where the optional _b_a_s_e is a decimal num- + ber between 2 and 64 representing the arithmetic base, and _n is a num- + ber in that base. If _b_a_s_e_# is omitted, then base 10 is used. When + specifying _n, 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 _b_a_s_e is less than or equal to 36, lowercase and up- + percase letters may be used interchangeably to represent numbers be- + tween 10 and 35. + + Operators are evaluated in order of precedence. Sub-expressions in + parentheses are evaluated first and may override the precedence rules + above. + +CCOONNDDIITTIIOONNAALL EEXXPPRREESSSSIIOONNSS + Conditional expressions are used by the [[[[ compound command and the + tteesstt and [[ builtin commands to test file attributes and perform string + and arithmetic comparisons. The tteesstt and [[ commands determine their + behavior based on the number of arguments; see the descriptions of + those commands for any other command-specific actions. + + Expressions are formed from the following unary or binary primaries. + BBaasshh handles several filenames specially when they are used in expres- + sions. If the operating system on which bbaasshh is running provides these + special files, bash will use them; otherwise it will emulate them in- + ternally with this behavior: If any _f_i_l_e argument to one of the pri- + maries is of the form _/_d_e_v_/_f_d_/_n, then file descriptor _n is checked. If + the _f_i_l_e argument to one of the primaries is one of _/_d_e_v_/_s_t_d_i_n, + _/_d_e_v_/_s_t_d_o_u_t, or _/_d_e_v_/_s_t_d_e_r_r, file descriptor 0, 1, or 2, respectively, + is checked. + + Unless otherwise specified, primaries that operate on files follow sym- + bolic links and operate on the target of the link, rather than the link + itself. + + When used with [[[[, the << and >> operators sort lexicographically using + the current locale. The tteesstt command sorts using ASCII ordering. + + --aa _f_i_l_e + True if _f_i_l_e exists. + --bb _f_i_l_e + True if _f_i_l_e exists and is a block special file. + --cc _f_i_l_e + True if _f_i_l_e exists and is a character special file. + --dd _f_i_l_e + True if _f_i_l_e exists and is a directory. + --ee _f_i_l_e + True if _f_i_l_e exists. + --ff _f_i_l_e + True if _f_i_l_e exists and is a regular file. + --gg _f_i_l_e + True if _f_i_l_e exists and is set-group-id. + --hh _f_i_l_e + True if _f_i_l_e exists and is a symbolic link. + --kk _f_i_l_e + True if _f_i_l_e exists and its ``sticky'' bit is set. + --pp _f_i_l_e + True if _f_i_l_e exists and is a named pipe (FIFO). + --rr _f_i_l_e + True if _f_i_l_e exists and is readable. + --ss _f_i_l_e + True if _f_i_l_e exists and has a size greater than zero. + --tt _f_d True if file descriptor _f_d is open and refers to a terminal. + --uu _f_i_l_e + True if _f_i_l_e exists and its set-user-id bit is set. + --ww _f_i_l_e + True if _f_i_l_e exists and is writable. + --xx _f_i_l_e + True if _f_i_l_e exists and is executable. + --GG _f_i_l_e + True if _f_i_l_e exists and is owned by the effective group id. + --LL _f_i_l_e + True if _f_i_l_e exists and is a symbolic link. + --NN _f_i_l_e + True if _f_i_l_e exists and has been modified since it was last + read. + --OO _f_i_l_e + True if _f_i_l_e exists and is owned by the effective user id. + --SS _f_i_l_e + True if _f_i_l_e exists and is a socket. + _f_i_l_e_1 --eeff _f_i_l_e_2 + True if _f_i_l_e_1 and _f_i_l_e_2 refer to the same device and inode num- + bers. + _f_i_l_e_1 -nntt _f_i_l_e_2 + True if _f_i_l_e_1 is newer (according to modification date) than + _f_i_l_e_2, or if _f_i_l_e_1 exists and _f_i_l_e_2 does not. + _f_i_l_e_1 -oott _f_i_l_e_2 + True if _f_i_l_e_1 is older than _f_i_l_e_2, or if _f_i_l_e_2 exists and _f_i_l_e_1 + does not. + --oo _o_p_t_n_a_m_e + True if the shell option _o_p_t_n_a_m_e is enabled. See the list of + options under the description of the --oo option to the sseett + builtin below. + --vv _v_a_r_n_a_m_e + True if the shell variable _v_a_r_n_a_m_e is set (has been assigned a + value). + --RR _v_a_r_n_a_m_e + True if the shell variable _v_a_r_n_a_m_e is set and is a name refer- + ence. + --zz _s_t_r_i_n_g + True if the length of _s_t_r_i_n_g is zero. + _s_t_r_i_n_g + --nn _s_t_r_i_n_g + True if the length of _s_t_r_i_n_g is non-zero. + + _s_t_r_i_n_g_1 ==== _s_t_r_i_n_g_2 + _s_t_r_i_n_g_1 == _s_t_r_i_n_g_2 + True if the strings are equal. == should be used with the tteesstt + command for POSIX conformance. When used with the [[[[ command, + this performs pattern matching as described above (CCoommppoouunndd CCoomm-- + mmaannddss). + + _s_t_r_i_n_g_1 !!== _s_t_r_i_n_g_2 + True if the strings are not equal. + + _s_t_r_i_n_g_1 << _s_t_r_i_n_g_2 + True if _s_t_r_i_n_g_1 sorts before _s_t_r_i_n_g_2 lexicographically. + + _s_t_r_i_n_g_1 >> _s_t_r_i_n_g_2 + True if _s_t_r_i_n_g_1 sorts after _s_t_r_i_n_g_2 lexicographically. + + _a_r_g_1 OOPP _a_r_g_2 + OOPP is one of --eeqq, --nnee, --lltt, --llee, --ggtt, or --ggee. These arithmetic + binary operators return true if _a_r_g_1 is equal to, not equal to, + less than, less than or equal to, greater than, or greater than + or equal to _a_r_g_2, respectively. _A_r_g_1 and _a_r_g_2 may be positive + or negative integers. When used with the [[[[ command, _A_r_g_1 and + _A_r_g_2 are evaluated as arithmetic expressions (see AARRIITTHHMMEETTIICC + EEVVAALLUUAATTIIOONN above). + +SSIIMMPPLLEE CCOOMMMMAANNDD EEXXPPAANNSSIIOONN + When a simple command is executed, the shell performs the following ex- + pansions, assignments, and redirections, from left to right, in the + following order. + + 1. The words that the parser has marked as variable assignments + (those preceding the command name) and redirections are saved + for later processing. + + 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. + + 3. Redirections are performed as described above under RREEDDIIRREECCTTIIOONN. + + 4. The text after the == in each variable assignment undergoes tilde + expansion, parameter expansion, command substitution, arithmetic + expansion, and quote removal before being assigned to the vari- + able. + + 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 cur- + rent 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. + + If no command name results, redirections are performed, but do not af- + fect the current shell environment. A redirection error causes the + command to exit with a non-zero status. + + If there is a command name left after expansion, execution proceeds as + described below. Otherwise, the command exits. If one of the expan- + sions 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. + +CCOOMMMMAANNDD EEXXEECCUUTTIIOONN + 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. + + 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 FFUUNNCCTTIIOONNSS. 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. + + If the name is neither a shell function nor a builtin, and contains no + slashes, bbaasshh searches each element of the PPAATTHH for a directory con- + taining an executable file by that name. BBaasshh uses a hash table to re- + member the full pathnames of executable files (see hhaasshh under SSHHEELLLL + BBUUIILLTTIINN CCOOMMMMAANNDDSS below). A full search of the directories in PPAATTHH 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 ccoommmmaanndd__nnoott__ffoouunndd__hhaannddllee. 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 sta- + tus of 127. + + If the search is successful, or if the command name contains one or + more slashes, the shell executes the named program in a separate execu- + tion environment. Argument 0 is set to the name given, and the remain- + ing arguments to the command are set to the arguments given, if any. + + 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 _s_h_e_l_l _s_c_r_i_p_t, 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 hhaasshh below under SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS) are retained by the + child. + + If the program is a file beginning with ##!!, 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 exe- + cutable 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. + +CCOOMMMMAANNDD EEXXEECCUUTTIIOONN EENNVVIIRROONNMMEENNTT + The shell has an _e_x_e_c_u_t_i_o_n _e_n_v_i_r_o_n_m_e_n_t, which consists of the follow- + ing: + + +o open files inherited by the shell at invocation, as modified by + redirections supplied to the eexxeecc builtin + + +o the current working directory as set by ccdd, ppuusshhdd, or ppooppdd, or + inherited by the shell at invocation + + +o the file creation mode mask as set by uummaasskk or inherited from + the shell's parent + + +o current traps set by ttrraapp + + +o shell parameters that are set by variable assignment or with sseett + or inherited from the shell's parent in the environment + + +o shell functions defined during execution or inherited from the + shell's parent in the environment + + +o options enabled at invocation (either by default or with com- + mand-line arguments) or by sseett + + +o options enabled by sshhoopptt + + +o shell aliases defined with aalliiaass + + +o various process IDs, including those of background jobs, the + value of $$$$, and the value of PPPPIIDD + + When a simple command other than a builtin or shell function is to be + executed, it is invoked in a separate execution environment that con- + sists of the following. Unless otherwise noted, the values are inher- + ited from the shell. + + + +o the shell's open files, plus any modifications and additions + specified by redirections to the command + + +o the current working directory + + +o the file creation mode mask + + +o shell variables and functions marked for export, along with + variables exported for the command, passed in the environment + + +o traps caught by the shell are reset to the values inherited from + the shell's parent, and traps ignored by the shell are ignored + + A command invoked in this separate environment cannot affect the + shell's execution environment. + + A _s_u_b_s_h_e_l_l is a copy of the shell process. + + Command substitution, commands grouped with parentheses, and asynchro- + nous commands are invoked in a subshell environment that is a duplicate + of the shell environment, except that traps caught by the shell are re- + set to the values that the shell inherited from its parent at invoca- + tion. Builtin commands that are invoked as part of a pipeline are also + executed in a subshell environment. Changes made to the subshell envi- + ronment cannot affect the shell's execution environment. + + Subshells spawned to execute command substitutions inherit the value of + the --ee option from the parent shell. When not in _p_o_s_i_x _m_o_d_e, bbaasshh + clears the --ee option in such subshells. + + If a command is followed by a && and job control is not active, the de- + fault standard input for the command is the empty file _/_d_e_v_/_n_u_l_l. Oth- + erwise, the invoked command inherits the file descriptors of the call- + ing shell as modified by redirections. + +EENNVVIIRROONNMMEENNTT + When a program is invoked it is given an array of strings called the + _e_n_v_i_r_o_n_m_e_n_t. This is a list of _n_a_m_e-_v_a_l_u_e pairs, of the form + _n_a_m_e=_v_a_l_u_e. + + The shell provides several ways to manipulate the environment. On in- + vocation, the shell scans its own environment and creates a parameter + for each name found, automatically marking it for _e_x_p_o_r_t to child pro- + cesses. Executed commands inherit the environment. The eexxppoorrtt and ddee-- + ccllaarree --xx commands allow parameters and functions to be added to and + deleted from the environment. If the value of a parameter in the envi- + ronment is modified, the new value becomes part of the environment, re- + placing the old. The environment inherited by any executed command + consists of the shell's initial environment, whose values may be modi- + fied in the shell, less any pairs removed by the uunnsseett command, plus + any additions via the eexxppoorrtt and ddeeccllaarree --xx commands. + + The environment for any _s_i_m_p_l_e _c_o_m_m_a_n_d or function may be augmented + temporarily by prefixing it with parameter assignments, as described + above in PPAARRAAMMEETTEERRSS. These assignment statements affect only the envi- + ronment seen by that command. + + If the --kk option is set (see the sseett builtin command below), then _a_l_l + parameter assignments are placed in the environment for a command, not + just those that precede the command name. + + When bbaasshh invokes an external command, the variable __ is set to the + full filename of the command and passed to that command in its environ- + ment. + +EEXXIITT SSTTAATTUUSS + The exit status of an executed command is the value returned by the + _w_a_i_t_p_i_d 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. + + 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 _N, bbaasshh uses the value of 128+_N as the exit status. + + If a command is not found, the child process created to execute it re- + turns a status of 127. If a command is found but is not executable, + the return status is 126. + + If a command fails because of an error during expansion or redirection, + the exit status is greater than zero. + + Shell builtin commands return a status of 0 (_t_r_u_e) if successful, and + non-zero (_f_a_l_s_e) if an error occurs while they execute. All builtins + return an exit status of 2 to indicate incorrect usage, generally in- + valid options or missing arguments. + + The exit status of the last command is available in the special parame- + ter $?. + + BBaasshh itself returns the exit status of the last command executed, un- + less a syntax error occurs, in which case it exits with a non-zero + value. See also the eexxiitt builtin command below. + +SSIIGGNNAALLSS + When bbaasshh is interactive, in the absence of any traps, it ignores + SSIIGGTTEERRMM (so that kkiillll 00 does not kill an interactive shell), and SSIIGGIINNTT + is caught and handled (so that the wwaaiitt builtin is interruptible). In + all cases, bbaasshh ignores SSIIGGQQUUIITT. If job control is in effect, bbaasshh ig- + nores SSIIGGTTTTIINN, SSIIGGTTTTOOUU, and SSIIGGTTSSTTPP. + + Non-builtin commands run by bbaasshh have signal handlers set to the values + inherited by the shell from its parent. When job control is not in ef- + fect, asynchronous commands ignore SSIIGGIINNTT and SSIIGGQQUUIITT in addition to + these inherited handlers. Commands run as a result of command substi- + tution ignore the keyboard-generated job control signals SSIIGGTTTTIINN, SSIIGGTT-- + TTOOUU, and SSIIGGTTSSTTPP. + + The shell exits by default upon receipt of a SSIIGGHHUUPP. Before exiting, + an interactive shell resends the SSIIGGHHUUPP to all jobs, running or + stopped. Stopped jobs are sent SSIIGGCCOONNTT to ensure that they receive the + SSIIGGHHUUPP. To prevent the shell from sending the signal to a particular + job, it should be removed from the jobs table with the ddiissoowwnn builtin + (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below) or marked to not receive SSIIGGHHUUPP us- + ing ddiissoowwnn --hh. + + If the hhuuppoonneexxiitt shell option has been set with sshhoopptt, bbaasshh sends a + SSIIGGHHUUPP to all jobs when an interactive login shell exits. + + If bbaasshh 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 com- + mand completes. When bbaasshh is waiting for an asynchronous command via + the wwaaiitt builtin, the reception of a signal for which a trap has been + set will cause the wwaaiitt builtin to return immediately with an exit sta- + tus greater than 128, immediately after which the trap is executed. + + When job control is not enabled, and bbaasshh is waiting for a foreground + command to complete, the shell receives keyboard-generated signals such + as SSIIGGIINNTT (usually generated by ^^CC) 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 ^^CC sends SSIIGGIINNTT to all pro- + cesses in that process group. + + When bbaasshh is running without job control enabled and receives SSIIGGIINNTT + while waiting for a foreground command, it waits until that foreground + command terminates and then decides what to do about the SSIIGGIINNTT: + + 1. If the command terminates due to the SSIIGGIINNTT, bbaasshh concludes that + the user meant to end the entire script, and acts on the SSIIGGIINNTT + (e.g., by running a SSIIGGIINNTT trap or exiting itself); + + 2. If the command does not terminate due to SSIIGGIINNTT, the program + handled the SSIIGGIINNTT itself and did not treat it as a fatal sig- + nal. In that case, bbaasshh does not treat SSIIGGIINNTT as a fatal sig- + nal, either, instead assuming that the SSIIGGIINNTT was used as part + of the program's normal operation (e.g., emacs uses it to abort + editing commands) or deliberately discarded. However, bbaasshh will + run any trap set on SSIIGGIINNTT, as it does with any other trapped + signal it receives while it is waiting for the foreground com- + mand to complete, for compatibility. + +JJOOBB CCOONNTTRROOLL + _J_o_b _c_o_n_t_r_o_l refers to the ability to selectively stop (_s_u_s_p_e_n_d) the ex- + ecution of processes and continue (_r_e_s_u_m_e) their execution at a later + point. A user typically employs this facility via an interactive in- + terface supplied jointly by the operating system kernel's terminal + driver and bbaasshh. + + The shell associates a _j_o_b with each pipeline. It keeps a table of + currently executing jobs, which may be listed with the jjoobbss command. + When bbaasshh starts a job asynchronously (in the _b_a_c_k_g_r_o_u_n_d), it prints a + line that looks like: + + [1] 25647 + + 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. BBaasshh + uses the _j_o_b abstraction as the basis for job control. + + To facilitate the implementation of the user interface to job control, + the operating system maintains the notion of a _c_u_r_r_e_n_t _t_e_r_m_i_n_a_l _p_r_o_c_e_s_s + _g_r_o_u_p _I_D. 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 SSIIGGIINNTT. These processes are said to be in + the _f_o_r_e_g_r_o_u_n_d. _B_a_c_k_g_r_o_u_n_d processes are those whose process group ID + differs from the terminal's; such processes are immune to keyboard-gen- + erated signals. Only foreground processes are allowed to read from or, + if the user so specifies with stty tostop, write to the terminal. + Background processes which attempt to read from (write to when stty + tostop is in effect) the terminal are sent a SSIIGGTTTTIINN ((SSIIGGTTTTOOUU)) signal + by the kernel's terminal driver, which, unless caught, suspends the + process. + + If the operating system on which bbaasshh is running supports job control, + bbaasshh contains facilities to use it. Typing the _s_u_s_p_e_n_d character (typ- + ically ^^ZZ, Control-Z) while a process is running causes that process to + be stopped and returns control to bbaasshh. Typing the _d_e_l_a_y_e_d _s_u_s_p_e_n_d + character (typically ^^YY, Control-Y) causes the process to be stopped + when it attempts to read input from the terminal, and control to be re- + turned to bbaasshh. The user may then manipulate the state of this job, + using the bbgg command to continue it in the background, the ffgg command + to continue it in the foreground, or the kkiillll command to kill it. A ^^ZZ + takes effect immediately, and has the additional side effect of causing + pending output and typeahead to be discarded. + + There are a number of ways to refer to a job in the shell. The charac- + ter %% introduces a job specification (_j_o_b_s_p_e_c). Job number _n may be + referred to as %%nn. 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, %%ccee refers to a stopped job whose command name be- + gins with ccee. If a prefix matches more than one job, bbaasshh reports an + error. Using %%??ccee, on the other hand, refers to any job containing the + string ccee in its command line. If the substring matches more than one + job, bbaasshh reports an error. The symbols %%%% and %%++ refer to the shell's + notion of the _c_u_r_r_e_n_t _j_o_b, which is the last job stopped while it was + in the foreground or started in the background. The _p_r_e_v_i_o_u_s _j_o_b may + be referenced using %%--. If there is only a single job, %%++ and %%-- can + both be used to refer to that job. In output pertaining to jobs (e.g., + the output of the jjoobbss command), the current job is always flagged with + a ++, and the previous job with a --. A single % (with no accompanying + job specification) also refers to the current job. + + Simply naming a job can be used to bring it into the foreground: %%11 is + a synonym for ````ffgg %%11'''', bringing job 1 from the background into the + foreground. Similarly, ````%%11 &&'''' resumes job 1 in the background, + equivalent to ````bbgg %%11''''. + + The shell learns immediately whenever a job changes state. Normally, + bbaasshh 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 --bb + option to the sseett builtin command is enabled, bbaasshh reports such changes + immediately. Any trap on SSIIGGCCHHLLDD is executed for each child that ex- + its. + + If an attempt to exit bbaasshh is made while jobs are stopped (or, if the + cchheecckkjjoobbss shell option has been enabled using the sshhoopptt builtin, run- + ning), the shell prints a warning message, and, if the cchheecckkjjoobbss option + is enabled, lists the jobs and their statuses. The jjoobbss 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. + + When the shell is waiting for a job or process using the wwaaiitt builtin, + and job control is enabled, wwaaiitt will return when the job changes + state. The --ff option causes wwaaiitt to wait until the job or process ter- + minates before returning. + +PPRROOMMPPTTIINNGG + When executing interactively, bbaasshh displays the primary prompt PPSS11 when + it is ready to read a command, and the secondary prompt PPSS22 when it + needs more input to complete a command. BBaasshh displays PPSS00 after it + reads a command but before executing it. BBaasshh displays PPSS44 as de- + scribed above before tracing each command when the --xx option is en- + abled. BBaasshh allows these prompt strings to be customized by inserting + a number of backslash-escaped special characters that are decoded as + follows: + \\aa an ASCII bell character (07) + \\dd the date in "Weekday Month Date" format (e.g., "Tue May + 26") + \\DD{{_f_o_r_m_a_t}} + the _f_o_r_m_a_t is passed to _s_t_r_f_t_i_m_e(3) and the result is in- + serted into the prompt string; an empty _f_o_r_m_a_t results in + a locale-specific time representation. The braces are + required + \\ee an ASCII escape character (033) + \\hh the hostname up to the first `.' + \\HH the hostname + \\jj the number of jobs currently managed by the shell + \\ll the basename of the shell's terminal device name + \\nn newline + \\rr carriage return + \\ss the name of the shell, the basename of $$00 (the portion + following the final slash) + \\tt the current time in 24-hour HH:MM:SS format + \\TT the current time in 12-hour HH:MM:SS format + \\@@ the current time in 12-hour am/pm format + \\AA the current time in 24-hour HH:MM format + \\uu the username of the current user + \\vv the version of bbaasshh (e.g., 2.00) + \\VV the release of bbaasshh, version + patch level (e.g., 2.00.0) + \\ww the value of the PPWWDD shell variable ($$PPWWDD), with $$HHOOMMEE + abbreviated with a tilde (uses the value of the + PPRROOMMPPTT__DDIIRRTTRRIIMM variable) + \\WW the basename of $$PPWWDD, with $$HHOOMMEE abbreviated with a tilde + \\!! the history number of this command + \\## the command number of this command + \\$$ if the effective UID is 0, a ##, otherwise a $$ + \\_n_n_n the character corresponding to the octal number _n_n_n + \\\\ a backslash + \\[[ begin a sequence of non-printing characters, which could + be used to embed a terminal control sequence into the + prompt + \\]] end a sequence of non-printing characters + + 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 HHIISSTTOORRYY be- + low), while the command number is the position in the sequence of com- + mands 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 + pprroommppttvvaarrss shell option (see the description of the sshhoopptt command under + SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below). This can have unwanted side effects if + escaped portions of the string appear within command substitution or + contain characters special to word expansion. + +RREEAADDLLIINNEE + This is the library that handles reading input when using an interac- + tive shell, unless the ----nnooeeddiittiinngg option is given at shell invocation. + Line editing is also used when using the --ee option to the rreeaadd 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 --oo eemmaaccss or --oo vvii options to the sseett + builtin (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below). To turn off line editing + after the shell is running, use the ++oo eemmaaccss or ++oo vvii options to the + sseett builtin. + + RReeaaddlliinnee NNoottaattiioonn + In this section, the Emacs-style notation is used to denote keystrokes. + Control keys are denoted by C-_k_e_y, e.g., C-n means Control-N. Simi- + larly, _m_e_t_a keys are denoted by M-_k_e_y, so M-x means Meta-X. (On key- + boards without a _m_e_t_a key, M-_x means ESC _x, i.e., press the Escape key + then the _x key. This makes ESC the _m_e_t_a _p_r_e_f_i_x. The combination M-C-_x + means ESC-Control-_x, or press the Escape key then hold the Control key + while pressing the _x key.) + + Readline commands may be given numeric _a_r_g_u_m_e_n_t_s, 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., kkiillll--lliinnee) causes that command to + act in a backward direction. Commands whose behavior with arguments + deviates from this are noted below. + + When a command is described as _k_i_l_l_i_n_g text, the text deleted is saved + for possible future retrieval (_y_a_n_k_i_n_g). The killed text is saved in a + _k_i_l_l _r_i_n_g. 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. + + RReeaaddlliinnee IInniittiiaalliizzaattiioonn + Readline is customized by putting commands in an initialization file + (the _i_n_p_u_t_r_c file). The name of this file is taken from the value of + the IINNPPUUTTRRCC variable. If that variable is unset, the default is _~_/_._i_n_- + _p_u_t_r_c. If that file does not exist or cannot be read, the ultimate + default is _/_e_t_c_/_i_n_p_u_t_r_c. When a program which uses the readline li- + brary 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 ## are comments. Lines beginning with a $$ indicate + conditional constructs. Other lines denote key bindings and variable + settings. + + The default key-bindings may be changed with an _i_n_p_u_t_r_c file. Other + programs that use this library may add their own commands and bindings. + + For example, placing + + M-Control-u: universal-argument + or + C-Meta-u: universal-argument + into the _i_n_p_u_t_r_c would make M-C-u execute the readline command _u_n_i_v_e_r_- + _s_a_l_-_a_r_g_u_m_e_n_t. + + The following symbolic character names are recognized: _R_U_B_O_U_T, _D_E_L, + _E_S_C, _L_F_D, _N_E_W_L_I_N_E, _R_E_T, _R_E_T_U_R_N, _S_P_C, _S_P_A_C_E, and _T_A_B. + + In addition to command names, readline allows keys to be bound to a + string that is inserted when the key is pressed (a _m_a_c_r_o). + + RReeaaddlliinnee KKeeyy BBiinnddiinnggss + The syntax for controlling key bindings in the _i_n_p_u_t_r_c 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 speci- + fied in one of two ways: as a symbolic key name, possibly with _M_e_t_a_- or + _C_o_n_t_r_o_l_- prefixes, or as a key sequence. + + When using the form kkeeyynnaammee:_f_u_n_c_t_i_o_n_-_n_a_m_e or _m_a_c_r_o, _k_e_y_n_a_m_e is the name + of a key spelled out in English. For example: + + Control-u: universal-argument + Meta-Rubout: backward-kill-word + Control-o: "> output" + + In the above example, _C_-_u is bound to the function uunniivveerrssaall--aarrgguummeenntt, + _M_-_D_E_L is bound to the function bbaacckkwwaarrdd--kkiillll--wwoorrdd, and _C_-_o is bound to + run the macro expressed on the right hand side (that is, to insert the + text ``> output'' into the line). + + In the second form, ""kkeeyysseeqq"":_f_u_n_c_t_i_o_n_-_n_a_m_e or _m_a_c_r_o, kkeeyysseeqq differs + from kkeeyynnaammee 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. + + "\C-u": universal-argument + "\C-x\C-r": re-read-init-file + "\e[11~": "Function Key 1" + + In this example, _C_-_u is again bound to the function uunniivveerrssaall--aarrgguummeenntt. + _C_-_x _C_-_r is bound to the function rree--rreeaadd--iinniitt--ffiillee, and _E_S_C _[ _1 _1 _~ is + bound to insert the text ``Function Key 1''. + + The full set of GNU Emacs style escape sequences is + \\CC-- control prefix + \\MM-- meta prefix + \\ee an escape character + \\\\ backslash + \\"" literal " + \\'' literal ' + + In addition to the GNU Emacs style escape sequences, a second set of + backslash escapes is available: + \\aa alert (bell) + \\bb backspace + \\dd delete + \\ff form feed + \\nn newline + \\rr carriage return + \\tt horizontal tab + \\vv vertical tab + \\_n_n_n the eight-bit character whose value is the octal value + _n_n_n (one to three digits) + \\xx_H_H the eight-bit character whose value is the hexadecimal + value _H_H (one or two hex digits) + + 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 func- + tion name. In the macro body, the backslash escapes described above + are expanded. Backslash will quote any other character in the macro + text, including " and '. + + BBaasshh allows the current readline key bindings to be displayed or modi- + fied with the bbiinndd builtin command. The editing mode may be switched + during interactive use by using the --oo option to the sseett builtin com- + mand (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below). + + RReeaaddlliinnee VVaarriiaabblleess + Readline has variables that can be used to further customize its behav- + ior. A variable may be set in the _i_n_p_u_t_r_c file with a statement of the + form + + sseett _v_a_r_i_a_b_l_e_-_n_a_m_e _v_a_l_u_e + or using the bbiinndd builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below). + + Except where noted, readline variables can take the values OOnn or OOffff + (without regard to case). Unrecognized variable names are ignored. + When a variable value is read, empty or null values, "on" (case-insen- + sitive), and "1" are equivalent to OOnn. All other values are equivalent + to OOffff. The variables and their default values are: + + aaccttiivvee--rreeggiioonn--ssttaarrtt--ccoolloorr + A string variable that controls the text color and background + when displaying the text in the active region (see the descrip- + tion of eennaabbllee--aaccttiivvee--rreeggiioonn 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 ter- + minfo description. A sample value might be "\e[01;33m". + aaccttiivvee--rreeggiioonn--eenndd--ccoolloorr + A string variable that "undoes" the effects of aaccttiivvee--rree-- + ggiioonn--ssttaarrtt--ccoolloorr and restores "normal" terminal display appear- + ance after displaying text in the active region. This string + must not take up any physical character positions on the dis- + play, 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 ob- + tained from the terminal's terminfo description. A sample value + might be "\e[0m". + bbeellll--ssttyyllee ((aauuddiibbllee)) + Controls what happens when readline wants to ring the terminal + bell. If set to nnoonnee, readline never rings the bell. If set to + vviissiibbllee, readline uses a visible bell if one is available. If + set to aauuddiibbllee, readline attempts to ring the terminal's bell. + bbiinndd--ttttyy--ssppeecciiaall--cchhaarrss ((OOnn)) + If set to OOnn, readline attempts to bind the control characters + treated specially by the kernel's terminal driver to their read- + line equivalents. + bblliinnkk--mmaattcchhiinngg--ppaarreenn ((OOffff)) + If set to OOnn, readline attempts to briefly move the cursor to an + opening parenthesis when a closing parenthesis is inserted. + ccoolloorreedd--ccoommpplleettiioonn--pprreeffiixx ((OOffff)) + If set to OOnn, when listing completions, readline displays the + common prefix of the set of possible completions using a differ- + ent color. The color definitions are taken from the value of + the LLSS__CCOOLLOORRSS environment variable. If there is a color defini- + tion in $$LLSS__CCOOLLOORRSS for the custom suffix "readline-colored-com- + pletion-prefix", readline uses this color for the common prefix + instead of its default. + ccoolloorreedd--ssttaattss ((OOffff)) + If set to OOnn, readline displays possible completions using dif- + ferent colors to indicate their file type. The color defini- + tions are taken from the value of the LLSS__CCOOLLOORRSS environment + variable. + ccoommmmeenntt--bbeeggiinn ((````##'''')) + The string that is inserted when the readline iinnsseerrtt--ccoommmmeenntt + command is executed. This command is bound to MM--## in emacs mode + and to ## in vi command mode. + ccoommpplleettiioonn--ddiissppllaayy--wwiiddtthh ((--11)) + 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. + ccoommpplleettiioonn--iiggnnoorree--ccaassee ((OOffff)) + If set to OOnn, readline performs filename matching and completion + in a case-insensitive fashion. + ccoommpplleettiioonn--mmaapp--ccaassee ((OOffff)) + If set to OOnn, and ccoommpplleettiioonn--iiggnnoorree--ccaassee is enabled, readline + treats hyphens (_-) and underscores (__) as equivalent when per- + forming case-insensitive filename matching and completion. + ccoommpplleettiioonn--pprreeffiixx--ddiissppllaayy--lleennggtthh ((00)) + The length in characters of the common prefix of a list of pos- + sible 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 possi- + ble completions. + ccoommpplleettiioonn--qquueerryy--iitteemmss ((110000)) + This determines when the user is queried about viewing the num- + ber of possible completions generated by the ppoossssiibbllee--ccoommppllee-- + ttiioonnss 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. + ccoonnvveerrtt--mmeettaa ((OOnn)) + If set to OOnn, 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 + _m_e_t_a _p_r_e_f_i_x). The default is _O_n, but readline will set it to + _O_f_f if the locale contains eight-bit characters. This variable + is dependent on the LLCC__CCTTYYPPEE locale category, and may change if + the locale is changed. + ddiissaabbllee--ccoommpplleettiioonn ((OOffff)) + If set to OOnn, readline will inhibit word completion. Completion + characters will be inserted into the line as if they had been + mapped to sseellff--iinnsseerrtt. + eecchhoo--ccoonnttrrooll--cchhaarraacctteerrss ((OOnn)) + When set to OOnn, on operating systems that indicate they support + it, readline echoes a character corresponding to a signal gener- + ated from the keyboard. + eeddiittiinngg--mmooddee ((eemmaaccss)) + Controls whether readline begins with a set of key bindings sim- + ilar to _E_m_a_c_s or _v_i. eeddiittiinngg--mmooddee can be set to either eemmaaccss or + vvii. + eemmaaccss--mmooddee--ssttrriinngg ((@@)) + If the _s_h_o_w_-_m_o_d_e_-_i_n_-_p_r_o_m_p_t 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 \1 and \2 + escapes to begin and end sequences of non-printing characters, + which can be used to embed a terminal control sequence into the + mode string. + eennaabbllee--aaccttiivvee--rreeggiioonn ((OOnn)) + The _p_o_i_n_t is the current cursor position, and _m_a_r_k refers to a + saved cursor position. The text between the point and mark is + referred to as the _r_e_g_i_o_n. When this variable is set to _O_n, + readline allows certain commands to designate the region as _a_c_- + _t_i_v_e. When the region is active, readline highlights the text + in the region using the value of the aaccttiivvee--rreeggiioonn--ssttaarrtt--ccoolloorr, + which defaults to the string that enables the terminal's stand- + out mode. The active region shows the text inserted by brack- + eted-paste and any matching text found by incremental and non- + incremental history searches. + eennaabbllee--bbrraacckkeetteedd--ppaassttee ((OOnn)) + When set to OOnn, 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. + eennaabbllee--kkeeyyppaadd ((OOffff)) + When set to OOnn, readline will try to enable the application key- + pad when it is called. Some systems need this to enable the ar- + row keys. + eennaabbllee--mmeettaa--kkeeyy ((OOnn)) + When set to OOnn, 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. + eexxppaanndd--ttiillddee ((OOffff)) + If set to OOnn, tilde expansion is performed when readline at- + tempts word completion. + hhiissttoorryy--pprreesseerrvvee--ppooiinntt ((OOffff)) + If set to OOnn, the history code attempts to place point at the + same location on each history line retrieved with pprreevviioouuss--hhiiss-- + ttoorryy or nneexxtt--hhiissttoorryy. + hhiissttoorryy--ssiizzee ((uunnsseett)) + 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 HHIISSTTSSIIZZEE + shell variable. If an attempt is made to set _h_i_s_t_o_r_y_-_s_i_z_e to a + non-numeric value, the maximum number of history entries will be + set to 500. + hhoorriizzoonnttaall--ssccrroollll--mmooddee ((OOffff)) + When set to OOnn, 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. + iinnppuutt--mmeettaa ((OOffff)) + If set to OOnn, readline will enable eight-bit input (that is, it + will not strip the eighth bit from the characters it reads), re- + gardless of what the terminal claims it can support. The name + mmeettaa--ffllaagg is a synonym for this variable. The default is _O_f_f, + but readline will set it to _O_n if the locale contains eight-bit + characters. This variable is dependent on the LLCC__CCTTYYPPEE locale + category, and may change if the locale is changed. + iisseeaarrcchh--tteerrmmiinnaattoorrss ((````CC--[[CC--JJ'''')) + The string of characters that should terminate an incremental + search without subsequently executing the character as a com- + mand. If this variable has not been given a value, the charac- + ters _E_S_C and _C_-_J will terminate an incremental search. + kkeeyymmaapp ((eemmaaccss)) + Set the current readline keymap. The set of valid keymap names + is _e_m_a_c_s_, _e_m_a_c_s_-_s_t_a_n_d_a_r_d_, _e_m_a_c_s_-_m_e_t_a_, _e_m_a_c_s_-_c_t_l_x_, _v_i_, _v_i_-_c_o_m_- + _m_a_n_d, and _v_i_-_i_n_s_e_r_t. _v_i is equivalent to _v_i_-_c_o_m_m_a_n_d; _e_m_a_c_s is + equivalent to _e_m_a_c_s_-_s_t_a_n_d_a_r_d. The default value is _e_m_a_c_s; the + value of eeddiittiinngg--mmooddee also affects the default keymap. + kkeeyysseeqq--ttiimmeeoouutt ((550000)) + Specifies the duration _r_e_a_d_l_i_n_e 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 re- + ceived within the timeout, _r_e_a_d_l_i_n_e will use the shorter but + complete key sequence. The value is specified in milliseconds, + so a value of 1000 means that _r_e_a_d_l_i_n_e 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, _r_e_a_d_l_i_n_e will wait + until another key is pressed to decide which key sequence to + complete. + mmaarrkk--ddiirreeccttoorriieess ((OOnn)) + If set to OOnn, completed directory names have a slash appended. + mmaarrkk--mmooddiiffiieedd--lliinneess ((OOffff)) + If set to OOnn, history lines that have been modified are dis- + played with a preceding asterisk (**). + mmaarrkk--ssyymmlliinnkkeedd--ddiirreeccttoorriieess ((OOffff)) + If set to OOnn, completed names which are symbolic links to direc- + tories have a slash appended (subject to the value of mmaarrkk--ddii-- + rreeccttoorriieess). + mmaattcchh--hhiiddddeenn--ffiilleess ((OOnn)) + This variable, when set to OOnn, causes readline to match files + whose names begin with a `.' (hidden files) when performing + filename completion. If set to OOffff, the leading `.' must be + supplied by the user in the filename to be completed. + mmeennuu--ccoommpplleettee--ddiissppllaayy--pprreeffiixx ((OOffff)) + If set to OOnn, menu completion displays the common prefix of the + list of possible completions (which may be empty) before cycling + through the list. + oouuttppuutt--mmeettaa ((OOffff)) + If set to OOnn, readline will display characters with the eighth + bit set directly rather than as a meta-prefixed escape sequence. + The default is _O_f_f, but readline will set it to _O_n if the locale + contains eight-bit characters. This variable is dependent on + the LLCC__CCTTYYPPEE locale category, and may change if the locale is + changed. + ppaaggee--ccoommpplleettiioonnss ((OOnn)) + If set to OOnn, readline uses an internal _m_o_r_e-like pager to dis- + play a screenful of possible completions at a time. + pprriinntt--ccoommpplleettiioonnss--hhoorriizzoonnttaallllyy ((OOffff)) + If set to OOnn, readline will display completions with matches + sorted horizontally in alphabetical order, rather than down the + screen. + rreevveerrtt--aallll--aatt--nneewwlliinnee ((OOffff)) + If set to OOnn, readline will undo all changes to history lines + before returning when aacccceepptt--lliinnee is executed. By default, his- + tory lines may be modified and retain individual undo lists + across calls to rreeaaddlliinnee. + sshhooww--aallll--iiff--aammbbiigguuoouuss ((OOffff)) + This alters the default behavior of the completion functions. + If set to OOnn, words which have more than one possible completion + cause the matches to be listed immediately instead of ringing + the bell. + sshhooww--aallll--iiff--uunnmmooddiiffiieedd ((OOffff)) + This alters the default behavior of the completion functions in + a fashion similar to sshhooww--aallll--iiff--aammbbiigguuoouuss. If set to OOnn, words + which have more than one possible completion without any possi- + ble partial completion (the possible completions don't share a + common prefix) cause the matches to be listed immediately in- + stead of ringing the bell. + sshhooww--mmooddee--iinn--pprroommpptt ((OOffff)) + If set to OOnn, add a string to the beginning of the prompt indi- + cating the editing mode: emacs, vi command, or vi insertion. + The mode strings are user-settable (e.g., _e_m_a_c_s_-_m_o_d_e_-_s_t_r_i_n_g). + sskkiipp--ccoommpplleetteedd--tteexxtt ((OOffff)) + If set to OOnn, 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. + vvii--ccmmdd--mmooddee--ssttrriinngg ((((ccmmdd)))) + If the _s_h_o_w_-_m_o_d_e_-_i_n_-_p_r_o_m_p_t 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 \1 and \2 escapes to begin and end sequences of non- + printing characters, which can be used to embed a terminal con- + trol sequence into the mode string. + vvii--iinnss--mmooddee--ssttrriinngg ((((iinnss)))) + If the _s_h_o_w_-_m_o_d_e_-_i_n_-_p_r_o_m_p_t 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 \1 and \2 escapes to begin and end sequences of non- + printing characters, which can be used to embed a terminal con- + trol sequence into the mode string. + vviissiibbllee--ssttaattss ((OOffff)) + If set to OOnn, a character denoting a file's type as reported by + _s_t_a_t(2) is appended to the filename when listing possible com- + pletions. + + RReeaaddlliinnee CCoonnddiittiioonnaall CCoonnssttrruuccttss + 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. + + $$iiff The $$iiff construct allows bindings to be made based on the edit- + ing mode, the terminal being used, or the application using + readline. The text of the test, after any comparison operator, + extends to the end of the line; unless otherwise noted, no + characters are required to isolate it. + + mmooddee The mmooddee== form of the $$iiff directive is used to test + whether readline is in emacs or vi mode. This may be + used in conjunction with the sseett kkeeyymmaapp command, for in- + stance, to set bindings in the _e_m_a_c_s_-_s_t_a_n_d_a_r_d and + _e_m_a_c_s_-_c_t_l_x keymaps only if readline is starting out in + emacs mode. + + tteerrmm The tteerrmm== 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 == is tested against both the full name of the ter- + minal and the portion of the terminal name before the + first --. This allows _s_u_n to match both _s_u_n and _s_u_n_-_c_m_d, + for instance. + + vveerrssiioonn + The vveerrssiioonn test may be used to perform comparisons + against specific readline versions. The vveerrssiioonn expands + to the current readline version. The set of comparison + operators includes ==, (and ====), !!==, <<==, >>==, <<, and >>. + The version number supplied on the right side of the op- + erator consists of a major version number, an optional + decimal point, and an optional minor version (e.g., 77..11). + If the minor version is omitted, it is assumed to be 00. + The operator may be separated from the string vveerrssiioonn and + from the version number argument by whitespace. + + aapppplliiccaattiioonn + The aapppplliiccaattiioonn construct is used to include application- + specific settings. Each program using the readline li- + brary sets the _a_p_p_l_i_c_a_t_i_o_n _n_a_m_e, 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 + bbaasshh: + + $$iiff Bash + # Quote the current or previous word + "\C-xq": "\eb\"\ef\"" + $$eennddiiff + + _v_a_r_i_a_b_l_e + The _v_a_r_i_a_b_l_e construct provides simple equality tests for + readline variables and values. The permitted comparison + operators are _=, _=_=, and _!_=. 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 vari- + ables may be tested. Boolean variables must be tested + against the values _o_n and _o_f_f. + + $$eennddiiff This command, as seen in the previous example, terminates an $$iiff + command. + + $$eellssee Commands in this branch of the $$iiff directive are executed if the + test fails. + + $$iinncclluuddee + This directive takes a single filename as an argument and reads + commands and bindings from that file. For example, the follow- + ing directive would read _/_e_t_c_/_i_n_p_u_t_r_c: + + $$iinncclluuddee _/_e_t_c_/_i_n_p_u_t_r_c + + SSeeaarrcchhiinngg + Readline provides commands for searching through the command history + (see HHIISSTTOORRYY below) for lines containing a specified string. There are + two search modes: _i_n_c_r_e_m_e_n_t_a_l and _n_o_n_-_i_n_c_r_e_m_e_n_t_a_l. + + Incremental searches begin before the user has finished typing the + search string. As each character of the search string is typed, read- + line 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 iisseeaarrcchh--tteerrmmiinnaattoorrss 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. + + 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 _n_e_w_l_i_n_e will termi- + nate the search and accept the line, thereby executing the command from + the history list. + + 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. + + 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. + + RReeaaddlliinnee CCoommmmaanndd NNaammeess + 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 accom- + panying key sequence are unbound by default. In the following descrip- + tions, _p_o_i_n_t refers to the current cursor position, and _m_a_r_k refers to + a cursor position saved by the sseett--mmaarrkk command. The text between the + point and mark is referred to as the _r_e_g_i_o_n. + + CCoommmmaannddss ffoorr MMoovviinngg + bbeeggiinnnniinngg--ooff--lliinnee ((CC--aa)) + Move to the start of the current line. + eenndd--ooff--lliinnee ((CC--ee)) + Move to the end of the line. + ffoorrwwaarrdd--cchhaarr ((CC--ff)) + Move forward a character. + bbaacckkwwaarrdd--cchhaarr ((CC--bb)) + Move back a character. + ffoorrwwaarrdd--wwoorrdd ((MM--ff)) + Move forward to the end of the next word. Words are composed of + alphanumeric characters (letters and digits). + bbaacckkwwaarrdd--wwoorrdd ((MM--bb)) + Move back to the start of the current or previous word. Words + are composed of alphanumeric characters (letters and digits). + sshheellll--ffoorrwwaarrdd--wwoorrdd + Move forward to the end of the next word. Words are delimited + by non-quoted shell metacharacters. + sshheellll--bbaacckkwwaarrdd--wwoorrdd + Move back to the start of the current or previous word. Words + are delimited by non-quoted shell metacharacters. + pprreevviioouuss--ssccrreeeenn--lliinnee + 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. + nneexxtt--ssccrreeeenn--lliinnee + 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. + cclleeaarr--ddiissppllaayy ((MM--CC--ll)) + 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. + cclleeaarr--ssccrreeeenn ((CC--ll)) + Clear the screen, then redraw the current line, leaving the cur- + rent line at the top of the screen. With an argument, refresh + the current line without clearing the screen. + rreeddrraaww--ccuurrrreenntt--lliinnee + Refresh the current line. + + CCoommmmaannddss ffoorr MMaanniippuullaattiinngg tthhee HHiissttoorryy + aacccceepptt--lliinnee ((NNeewwlliinnee,, RReettuurrnn)) + 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 HHIISSTTCCOONNTTRROOLL variable. If the line is a modified history + line, then restore the history line to its original state. + pprreevviioouuss--hhiissttoorryy ((CC--pp)) + Fetch the previous command from the history list, moving back in + the list. + nneexxtt--hhiissttoorryy ((CC--nn)) + Fetch the next command from the history list, moving forward in + the list. + bbeeggiinnnniinngg--ooff--hhiissttoorryy ((MM--<<)) + Move to the first line in the history. + eenndd--ooff--hhiissttoorryy ((MM-->>)) + Move to the end of the input history, i.e., the line currently + being entered. + ooppeerraattee--aanndd--ggeett--nneexxtt ((CC--oo)) + 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. + ffeettcchh--hhiissttoorryy + 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. + rreevveerrssee--sseeaarrcchh--hhiissttoorryy ((CC--rr)) + Search backward starting at the current line and moving `up' + through the history as necessary. This is an incremental + search. + ffoorrwwaarrdd--sseeaarrcchh--hhiissttoorryy ((CC--ss)) + Search forward starting at the current line and moving `down' + through the history as necessary. This is an incremental + search. + nnoonn--iinnccrreemmeennttaall--rreevveerrssee--sseeaarrcchh--hhiissttoorryy ((MM--pp)) + Search backward through the history starting at the current line + using a non-incremental search for a string supplied by the + user. + nnoonn--iinnccrreemmeennttaall--ffoorrwwaarrdd--sseeaarrcchh--hhiissttoorryy ((MM--nn)) + Search forward through the history using a non-incremental + search for a string supplied by the user. + hhiissttoorryy--sseeaarrcchh--ffoorrwwaarrdd + 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. + hhiissttoorryy--sseeaarrcchh--bbaacckkwwaarrdd + 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. + hhiissttoorryy--ssuubbssttrriinngg--sseeaarrcchh--bbaacckkwwaarrdd + Search backward through the history for the string of characters + between the start of the current line and the current cursor po- + sition (the _p_o_i_n_t). The search string may match anywhere in a + history line. This is a non-incremental search. + hhiissttoorryy--ssuubbssttrriinngg--sseeaarrcchh--ffoorrwwaarrdd + 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-in- + cremental search. + yyaannkk--nntthh--aarrgg ((MM--CC--yy)) + Insert the first argument to the previous command (usually the + second word on the previous line) at point. With an argument _n, + insert the _nth word from the previous command (the words in the + previous command begin with word 0). A negative argument in- + serts the _nth word from the end of the previous command. Once + the argument _n is computed, the argument is extracted as if the + "!_n" history expansion had been specified. + yyaannkk--llaasstt--aarrgg ((MM--..,, MM--__)) + Insert the last argument to the previous command (the last word + of the previous history entry). With a numeric argument, behave + exactly like yyaannkk--nntthh--aarrgg. Successive calls to yyaannkk--llaasstt--aarrgg + 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. + sshheellll--eexxppaanndd--lliinnee ((MM--CC--ee)) + Expand the line as the shell does. This performs alias and his- + tory expansion as well as all of the shell word expansions. See + HHIISSTTOORRYY EEXXPPAANNSSIIOONN below for a description of history expansion. + hhiissttoorryy--eexxppaanndd--lliinnee ((MM--^^)) + Perform history expansion on the current line. See HHIISSTTOORRYY EEXX-- + PPAANNSSIIOONN below for a description of history expansion. + mmaaggiicc--ssppaaccee + Perform history expansion on the current line and insert a + space. See HHIISSTTOORRYY EEXXPPAANNSSIIOONN below for a description of history + expansion. + aalliiaass--eexxppaanndd--lliinnee + Perform alias expansion on the current line. See AALLIIAASSEESS above + for a description of alias expansion. + hhiissttoorryy--aanndd--aalliiaass--eexxppaanndd--lliinnee + Perform history and alias expansion on the current line. + iinnsseerrtt--llaasstt--aarrgguummeenntt ((MM--..,, MM--__)) + A synonym for yyaannkk--llaasstt--aarrgg. + eeddiitt--aanndd--eexxeeccuuttee--ccoommmmaanndd ((CC--xx CC--ee)) + Invoke an editor on the current command line, and execute the + result as shell commands. BBaasshh attempts to invoke $$VVIISSUUAALL, $$EEDD-- + IITTOORR, and _e_m_a_c_s as the editor, in that order. + + CCoommmmaannddss ffoorr CChhaannggiinngg TTeexxtt + _e_n_d_-_o_f_-_f_i_l_e ((uussuuaallllyy CC--dd)) + The character indicating end-of-file as set, for example, by + ``stty''. If this character is read when there are no charac- + ters on the line, and point is at the beginning of the line, + readline interprets it as the end of input and returns EEOOFF. + ddeelleettee--cchhaarr ((CC--dd)) + Delete the character at point. If this function is bound to the + same character as the tty EEOOFF character, as CC--dd commonly is, see + above for the effects. + bbaacckkwwaarrdd--ddeelleettee--cchhaarr ((RRuubboouutt)) + Delete the character behind the cursor. When given a numeric + argument, save the deleted text on the kill ring. + ffoorrwwaarrdd--bbaacckkwwaarrdd--ddeelleettee--cchhaarr + Delete the character under the cursor, unless the cursor is at + the end of the line, in which case the character behind the cur- + sor is deleted. + qquuootteedd--iinnsseerrtt ((CC--qq,, CC--vv)) + Add the next character typed to the line verbatim. This is how + to insert characters like CC--qq, for example. + ttaabb--iinnsseerrtt ((CC--vv TTAABB)) + Insert a tab character. + sseellff--iinnsseerrtt ((aa,, bb,, AA,, 11,, !!,, ......)) + Insert the character typed. + ttrraannssppoossee--cchhaarrss ((CC--tt)) + 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. + ttrraannssppoossee--wwoorrddss ((MM--tt)) + 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. + uuppccaassee--wwoorrdd ((MM--uu)) + Uppercase the current (or following) word. With a negative ar- + gument, uppercase the previous word, but do not move point. + ddoowwnnccaassee--wwoorrdd ((MM--ll)) + Lowercase the current (or following) word. With a negative ar- + gument, lowercase the previous word, but do not move point. + ccaappiittaalliizzee--wwoorrdd ((MM--cc)) + Capitalize the current (or following) word. With a negative ar- + gument, capitalize the previous word, but do not move point. + oovveerrwwrriittee--mmooddee + Toggle overwrite mode. With an explicit positive numeric argu- + ment, switches to overwrite mode. With an explicit non-positive + numeric argument, switches to insert mode. This command affects + only eemmaaccss mode; vvii mode does overwrite differently. Each call + to _r_e_a_d_l_i_n_e_(_) starts in insert mode. In overwrite mode, charac- + ters bound to sseellff--iinnsseerrtt replace the text at point rather than + pushing the text to the right. Characters bound to bbaacckk-- + wwaarrdd--ddeelleettee--cchhaarr replace the character before point with a + space. By default, this command is unbound. + + KKiilllliinngg aanndd YYaannkkiinngg + kkiillll--lliinnee ((CC--kk)) + Kill the text from point to the end of the line. + bbaacckkwwaarrdd--kkiillll--lliinnee ((CC--xx RRuubboouutt)) + Kill backward to the beginning of the line. + uunniixx--lliinnee--ddiissccaarrdd ((CC--uu)) + Kill backward from point to the beginning of the line. The + killed text is saved on the kill-ring. + kkiillll--wwhhoollee--lliinnee + Kill all characters on the current line, no matter where point + is. + kkiillll--wwoorrdd ((MM--dd)) + 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 ffoorrwwaarrdd--wwoorrdd. + bbaacckkwwaarrdd--kkiillll--wwoorrdd ((MM--RRuubboouutt)) + Kill the word behind point. Word boundaries are the same as + those used by bbaacckkwwaarrdd--wwoorrdd. + sshheellll--kkiillll--wwoorrdd + 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 sshheellll--ffoorrwwaarrdd--wwoorrdd. + sshheellll--bbaacckkwwaarrdd--kkiillll--wwoorrdd + Kill the word behind point. Word boundaries are the same as + those used by sshheellll--bbaacckkwwaarrdd--wwoorrdd. + uunniixx--wwoorrdd--rruubboouutt ((CC--ww)) + Kill the word behind point, using white space as a word bound- + ary. The killed text is saved on the kill-ring. + uunniixx--ffiilleennaammee--rruubboouutt + 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. + ddeelleettee--hhoorriizzoonnttaall--ssppaaccee ((MM--\\)) + Delete all spaces and tabs around point. + kkiillll--rreeggiioonn + Kill the text in the current region. + ccooppyy--rreeggiioonn--aass--kkiillll + Copy the text in the region to the kill buffer. + ccooppyy--bbaacckkwwaarrdd--wwoorrdd + Copy the word before point to the kill buffer. The word bound- + aries are the same as bbaacckkwwaarrdd--wwoorrdd. + ccooppyy--ffoorrwwaarrdd--wwoorrdd + Copy the word following point to the kill buffer. The word + boundaries are the same as ffoorrwwaarrdd--wwoorrdd. + yyaannkk ((CC--yy)) + Yank the top of the kill ring into the buffer at point. + yyaannkk--ppoopp ((MM--yy)) + Rotate the kill ring, and yank the new top. Only works follow- + ing yyaannkk or yyaannkk--ppoopp. + + NNuummeerriicc AArrgguummeennttss + ddiiggiitt--aarrgguummeenntt ((MM--00,, MM--11,, ......,, MM----)) + Add this digit to the argument already accumulating, or start a + new argument. M-- starts a negative argument. + uunniivveerrssaall--aarrgguummeenntt + 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 fol- + lowed by digits, executing uunniivveerrssaall--aarrgguummeenntt again ends the nu- + meric argument, but is otherwise ignored. As a special case, if + this command is immediately followed by a character that is nei- + ther 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 argu- + ment count four, a second time makes the argument count sixteen, + and so on. + + CCoommpplleettiinngg + ccoommpplleettee ((TTAABB)) + Attempt to perform completion on the text before point. BBaasshh + attempts completion treating the text as a variable (if the text + begins with $$), username (if the text begins with ~~), hostname + (if the text begins with @@), or command (including aliases and + functions) in turn. If none of these produces a match, filename + completion is attempted. + ppoossssiibbllee--ccoommpplleettiioonnss ((MM--??)) + List the possible completions of the text before point. + iinnsseerrtt--ccoommpplleettiioonnss ((MM--**)) + Insert all completions of the text before point that would have + been generated by ppoossssiibbllee--ccoommpplleettiioonnss. + mmeennuu--ccoommpplleettee + Similar to ccoommpplleettee, but replaces the word to be completed with + a single match from the list of possible completions. Repeated + execution of mmeennuu--ccoommpplleettee 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 + bbeellll--ssttyyllee) and the original text is restored. An argument of _n + moves _n positions forward in the list of matches; a negative ar- + gument may be used to move backward through the list. This com- + mand is intended to be bound to TTAABB, but is unbound by default. + mmeennuu--ccoommpplleettee--bbaacckkwwaarrdd + Identical to mmeennuu--ccoommpplleettee, but moves backward through the list + of possible completions, as if mmeennuu--ccoommpplleettee had been given a + negative argument. This command is unbound by default. + ddeelleettee--cchhaarr--oorr--lliisstt + Deletes the character under the cursor if not at the beginning + or end of the line (like ddeelleettee--cchhaarr). If at the end of the + line, behaves identically to ppoossssiibbllee--ccoommpplleettiioonnss. This command + is unbound by default. + ccoommpplleettee--ffiilleennaammee ((MM--//)) + Attempt filename completion on the text before point. + ppoossssiibbllee--ffiilleennaammee--ccoommpplleettiioonnss ((CC--xx //)) + List the possible completions of the text before point, treating + it as a filename. + ccoommpplleettee--uusseerrnnaammee ((MM--~~)) + Attempt completion on the text before point, treating it as a + username. + ppoossssiibbllee--uusseerrnnaammee--ccoommpplleettiioonnss ((CC--xx ~~)) + List the possible completions of the text before point, treating + it as a username. + ccoommpplleettee--vvaarriiaabbllee ((MM--$$)) + Attempt completion on the text before point, treating it as a + shell variable. + ppoossssiibbllee--vvaarriiaabbllee--ccoommpplleettiioonnss ((CC--xx $$)) + List the possible completions of the text before point, treating + it as a shell variable. + ccoommpplleettee--hhoossttnnaammee ((MM--@@)) + Attempt completion on the text before point, treating it as a + hostname. + ppoossssiibbllee--hhoossttnnaammee--ccoommpplleettiioonnss ((CC--xx @@)) + List the possible completions of the text before point, treating + it as a hostname. + ccoommpplleettee--ccoommmmaanndd ((MM--!!)) + 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. + ppoossssiibbllee--ccoommmmaanndd--ccoommpplleettiioonnss ((CC--xx !!)) + List the possible completions of the text before point, treating + it as a command name. + ddyynnaammiicc--ccoommpplleettee--hhiissttoorryy ((MM--TTAABB)) + Attempt completion on the text before point, comparing the text + against lines from the history list for possible completion + matches. + ddaabbbbrreevv--eexxppaanndd + Attempt menu completion on the text before point, comparing the + text against lines from the history list for possible completion + matches. + ccoommpplleettee--iinnttoo--bbrraacceess ((MM--{{)) + Perform filename completion and insert the list of possible com- + pletions enclosed within braces so the list is available to the + shell (see BBrraaccee EExxppaannssiioonn above). + + KKeeyybbooaarrdd MMaaccrrooss + ssttaarrtt--kkbbdd--mmaaccrroo ((CC--xx (()) + Begin saving the characters typed into the current keyboard + macro. + eenndd--kkbbdd--mmaaccrroo ((CC--xx )))) + Stop saving the characters typed into the current keyboard macro + and store the definition. + ccaallll--llaasstt--kkbbdd--mmaaccrroo ((CC--xx ee)) + Re-execute the last keyboard macro defined, by making the char- + acters in the macro appear as if typed at the keyboard. + pprriinntt--llaasstt--kkbbdd--mmaaccrroo (()) + Print the last keyboard macro defined in a format suitable for + the _i_n_p_u_t_r_c file. + + MMiisscceellllaanneeoouuss + rree--rreeaadd--iinniitt--ffiillee ((CC--xx CC--rr)) + Read in the contents of the _i_n_p_u_t_r_c file, and incorporate any + bindings or variable assignments found there. + aabboorrtt ((CC--gg)) + Abort the current editing command and ring the terminal's bell + (subject to the setting of bbeellll--ssttyyllee). + ddoo--lloowweerrccaassee--vveerrssiioonn ((MM--AA,, MM--BB,, MM--_x,, ......)) + If the metafied character _x is uppercase, run the command that + is bound to the corresponding metafied lowercase character. The + behavior is undefined if _x is already lowercase. + pprreeffiixx--mmeettaa ((EESSCC)) + Metafy the next character typed. EESSCC ff is equivalent to MMeettaa--ff. + uunnddoo ((CC--__,, CC--xx CC--uu)) + Incremental undo, separately remembered for each line. + rreevveerrtt--lliinnee ((MM--rr)) + Undo all changes made to this line. This is like executing the + uunnddoo command enough times to return the line to its initial + state. + ttiillddee--eexxppaanndd ((MM--&&)) + Perform tilde expansion on the current word. + sseett--mmaarrkk ((CC--@@,, MM--<<ssppaaccee>>)) + Set the mark to the point. If a numeric argument is supplied, + the mark is set to that position. + eexxcchhaannggee--ppooiinntt--aanndd--mmaarrkk ((CC--xx CC--xx)) + 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. + cchhaarraacctteerr--sseeaarrcchh ((CC--]])) + A character is read and point is moved to the next occurrence of + that character. A negative argument searches for previous oc- + currences. + cchhaarraacctteerr--sseeaarrcchh--bbaacckkwwaarrdd ((MM--CC--]])) + A character is read and point is moved to the previous occur- + rence of that character. A negative argument searches for sub- + sequent occurrences. + sskkiipp--ccssii--sseeqquueennccee + 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 "\[", 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-[. + iinnsseerrtt--ccoommmmeenntt ((MM--##)) + Without a numeric argument, the value of the readline ccoomm-- + mmeenntt--bbeeggiinn 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 ccoommmmeenntt--bbeeggiinn, the value is inserted, other- + wise the characters in ccoommmmeenntt--bbeeggiinn are deleted from the begin- + ning of the line. In either case, the line is accepted as if a + newline had been typed. The default value of ccoommmmeenntt--bbeeggiinn + causes this command to make the current line a shell comment. + If a numeric argument causes the comment character to be re- + moved, the line will be executed by the shell. + ssppeellll--ccoorrrreecctt--wwoorrdd ((CC--xx ss)) + Perform spelling correction on the current word, treating it as + a directory or filename, in the same way as the ccddssppeellll shell + option. Word boundaries are the same as those used by + sshheellll--ffoorrwwaarrdd--wwoorrdd. + gglloobb--ccoommpplleettee--wwoorrdd ((MM--gg)) + The word before point is treated as a pattern for pathname ex- + pansion, with an asterisk implicitly appended. This pattern is + used to generate a list of matching filenames for possible com- + pletions. + gglloobb--eexxppaanndd--wwoorrdd ((CC--xx **)) + The word before point is treated as a pattern for pathname ex- + pansion, and the list of matching filenames is inserted, replac- + ing the word. If a numeric argument is supplied, an asterisk is + appended before pathname expansion. + gglloobb--lliisstt--eexxppaannssiioonnss ((CC--xx gg)) + The list of expansions that would have been generated by + gglloobb--eexxppaanndd--wwoorrdd is displayed, and the line is redrawn. If a + numeric argument is supplied, an asterisk is appended before + pathname expansion. + dduummpp--ffuunnccttiioonnss + Print all of the functions and their key bindings to the read- + line output stream. If a numeric argument is supplied, the out- + put is formatted in such a way that it can be made part of an + _i_n_p_u_t_r_c file. + dduummpp--vvaarriiaabblleess + 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 _i_n_p_u_t_r_c file. + dduummpp--mmaaccrrooss + 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 + _i_n_p_u_t_r_c file. + ddiissppllaayy--sshheellll--vveerrssiioonn ((CC--xx CC--vv)) + Display version information about the current instance of bbaasshh. + + PPrrooggrraammmmaabbllee CCoommpplleettiioonn + When word completion is attempted for an argument to a command for + which a completion specification (a _c_o_m_p_s_p_e_c) has been defined using + the ccoommpplleettee builtin (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below), the program- + mable completion facilities are invoked. + + 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 --EE option to ccoommpplleettee 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 --DD option to ccoommpplleettee is used as the default. If there is no + default compspec, bbaasshh 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. + + Once a compspec has been found, it is used to generate the list of + matching words. If a compspec is not found, the default bbaasshh comple- + tion as described above under CCoommpplleettiinngg is performed. + + First, the actions specified by the compspec are used. Only matches + which are prefixed by the word being completed are returned. When the + --ff or --dd option is used for filename or directory name completion, the + shell variable FFIIGGNNOORREE is used to filter the matches. + + Any completions specified by a pathname expansion pattern to the --GG op- + tion are generated next. The words generated by the pattern need not + match the word being completed. The GGLLOOBBIIGGNNOORREE shell variable is not + used to filter the matches, but the FFIIGGNNOORREE variable is used. + + Next, the string specified as the argument to the --WW option is consid- + ered. The string is first split using the characters in the IIFFSS spe- + cial 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 EEXXPPAANNSSIIOONN. The results are split using the rules + described above under WWoorrdd SSpplliittttiinngg. The results of the expansion are + prefix-matched against the word being completed, and the matching words + become the possible completions. + + After these matches have been generated, any shell function or command + specified with the --FF and --CC options is invoked. When the command or + function is invoked, the CCOOMMPP__LLIINNEE, CCOOMMPP__PPOOIINNTT, CCOOMMPP__KKEEYY, and CCOOMMPP__TTYYPPEE + variables are assigned values as described above under SShheellll VVaarriiaabblleess. + If a shell function is being invoked, the CCOOMMPP__WWOORRDDSS and CCOOMMPP__CCWWOORRDD + variables are also set. When the function or command is invoked, the + first argument ($$11) is the name of the command whose arguments are be- + ing completed, the second argument ($$22) is the word being completed, + and the third argument ($$33) is the word preceding the word being com- + pleted on the current command line. No filtering of the generated com- + pletions against the word being completed is performed; the function or + command has complete freedom in generating the matches. + + Any function specified with --FF is invoked first. The function may use + any of the shell facilities, including the ccoommppggeenn builtin described + below, to generate the matches. It must put the possible completions + in the CCOOMMPPRREEPPLLYY array variable, one per array element. + + Next, any command specified with the --CC option is invoked in an envi- + ronment 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. + + After all of the possible completions are generated, any filter speci- + fied with the --XX option is applied to the list. The filter is a pat- + tern as used for pathname expansion; a && in the pattern is replaced + with the text of the word being completed. A literal && 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 !! negates the pattern; in this case any completion not match- + ing the pattern will be removed. If the nnooccaasseemmaattcchh shell option is + enabled, the match is performed without regard to the case of alpha- + betic characters. + + Finally, any prefix and suffix specified with the --PP and --SS 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. + + If the previously-applied actions do not generate any matches, and the + --oo ddiirrnnaammeess option was supplied to ccoommpplleettee when the compspec was de- + fined, directory name completion is attempted. + + If the --oo pplluussddiirrss option was supplied to ccoommpplleettee when the compspec + was defined, directory name completion is attempted and any matches are + added to the results of the other actions. + + 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 bbaasshh completions are not attempted, and the readline default of + filename completion is disabled. If the --oo bbaasshhddeeffaauulltt option was sup- + plied to ccoommpplleettee when the compspec was defined, the bbaasshh default com- + pletions are attempted if the compspec generates no matches. If the --oo + ddeeffaauulltt option was supplied to ccoommpplleettee when the compspec was defined, + readline's default completion will be performed if the compspec (and, + if attempted, the default bbaasshh completions) generate no matches. + + 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 mmaarrkk--ddiirreeccttoorriieess readline variable, regardless of the + setting of the mmaarrkk--ssyymmlliinnkkeedd--ddiirreeccttoorriieess readline variable. + + There is some support for dynamically modifying completions. This is + most useful when used in combination with a default completion speci- + fied with ccoommpplleettee --DD. 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. + + For instance, assuming that there is a library of compspecs, each kept + in a file corresponding to the name of the command, the following de- + fault completion function would load completions dynamically: + + _completion_loader() + { + . "/etc/bash_completion.d/$1.sh" >/dev/null 2>&1 && return 124 + } + complete -D -F _completion_loader -o bashdefault -o default + + +HHIISSTTOORRYY + When the --oo hhiissttoorryy option to the sseett builtin is enabled, the shell + provides access to the _c_o_m_m_a_n_d _h_i_s_t_o_r_y, the list of commands previously + typed. The value of the HHIISSTTSSIIZZEE variable is used as the number of + commands to save in a history list. The text of the last HHIISSTTSSIIZZEE com- + mands (default 500) is saved. The shell stores each command in the + history list prior to parameter and variable expansion (see EEXXPPAANNSSIIOONN + above) but after history expansion is performed, subject to the values + of the shell variables HHIISSTTIIGGNNOORREE and HHIISSTTCCOONNTTRROOLL. + + On startup, the history is initialized from the file named by the vari- + able HHIISSTTFFIILLEE (default _~_/_._b_a_s_h___h_i_s_t_o_r_y). The file named by the value + of HHIISSTTFFIILLEE is truncated, if necessary, to contain no more than the + number of lines specified by the value of HHIISSTTFFIILLEESSIIZZEE. If HHIISSTTFFIILLEE-- + SSIIZZEE 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 fol- + lowed immediately by a digit are interpreted as timestamps for the fol- + lowing history line. These timestamps are optionally displayed depend- + ing on the value of the HHIISSTTTTIIMMEEFFOORRMMAATT variable. When a shell with + history enabled exits, the last $$HHIISSTTSSIIZZEE lines are copied from the + history list to $$HHIISSTTFFIILLEE. If the hhiissttaappppeenndd shell option is enabled + (see the description of sshhoopptt under SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below), the + lines are appended to the history file, otherwise the history file is + overwritten. If HHIISSTTFFIILLEE is unset, or if the history file is un- + writable, the history is not saved. If the HHIISSTTTTIIMMEEFFOORRMMAATT variable is + set, time stamps are written to the history file, marked with the his- + tory 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 HHIISSTTFFIILLEESSIIZZEE lines. If HHIISSTTFFIILLEESSIIZZEE + is unset, or set to null, a non-numeric value, or a numeric value less + than zero, the history file is not truncated. + + The builtin command ffcc (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below) may be used + to list or edit and re-execute a portion of the history list. The hhiiss-- + ttoorryy builtin may be used to display or modify the history list and ma- + nipulate the history file. When using command-line editing, search + commands are available in each editing mode that provide access to the + history list. + + The shell allows control over which commands are saved on the history + list. The HHIISSTTCCOONNTTRROOLL and HHIISSTTIIGGNNOORREE variables may be set to cause the + shell to save only a subset of the commands entered. The ccmmddhhiisstt 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 lliitthhiisstt shell option + causes the shell to save the command with embedded newlines instead of + semicolons. See the description of the sshhoopptt builtin below under SSHHEELLLL + BBUUIILLTTIINN CCOOMMMMAANNDDSS for information on setting and unsetting shell op- + tions. + +HHIISSTTOORRYY EEXXPPAANNSSIIOONN + The shell supports a history expansion feature that is similar to the + history expansion in ccsshh. This section describes what syntax features + are available. This feature is enabled by default for interactive + shells, and can be disabled using the ++HH option to the sseett builtin com- + mand (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below). Non-interactive shells do not + perform history expansion by default. + + 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. + + 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 ac- + count. 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 _e_v_e_n_t, and the portions of + that line that are acted upon are _w_o_r_d_s. Various _m_o_d_i_f_i_e_r_s are avail- + able to manipulate the selected words. The line is broken into words + in the same fashion as when reading input, so that several _m_e_t_a_c_h_a_r_a_c_- + _t_e_r-separated words surrounded by quotes are considered one word. His- + tory expansions are introduced by the appearance of the history expan- + sion character, which is !! by default. Only backslash (\\) and single + quotes can quote the history expansion character, but the history ex- + pansion character is also treated as quoted if it immediately precedes + the closing double quote in a double-quoted string. + + Several characters inhibit history expansion if found immediately fol- + lowing the history expansion character, even if it is unquoted: space, + tab, newline, carriage return, and ==. If the eexxttgglloobb shell option is + enabled, (( will also inhibit expansion. + + Several shell options settable with the sshhoopptt builtin may be used to + tailor the behavior of history expansion. If the hhiissttvveerriiffyy shell op- + tion is enabled (see the description of the sshhoopptt builtin below), and + rreeaaddlliinnee is being used, history substitutions are not immediately + passed to the shell parser. Instead, the expanded line is reloaded + into the rreeaaddlliinnee editing buffer for further modification. If rreeaaddlliinnee + is being used, and the hhiissttrreeeeddiitt shell option is enabled, a failed + history substitution will be reloaded into the rreeaaddlliinnee editing buffer + for correction. The --pp option to the hhiissttoorryy builtin command may be + used to see what a history expansion will do before using it. The --ss + option to the hhiissttoorryy 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. + + The shell allows control of the various characters used by the history + expansion mechanism (see the description of hhiissttcchhaarrss above under SShheellll + VVaarriiaabblleess). The shell uses the history comment character to mark his- + tory timestamps when writing the history file. + + EEvveenntt DDeessiiggnnaattoorrss + An event designator is a reference to a command line entry in the his- + tory list. Unless the reference is absolute, events are relative to + the current position in the history list. + + !! Start a history substitution, except when followed by a bbllaannkk, + newline, carriage return, = or ( (when the eexxttgglloobb shell option + is enabled using the sshhoopptt builtin). + !!_n Refer to command line _n. + !!--_n Refer to the current command minus _n. + !!!! Refer to the previous command. This is a synonym for `!-1'. + !!_s_t_r_i_n_g + Refer to the most recent command preceding the current position + in the history list starting with _s_t_r_i_n_g. + !!??_s_t_r_i_n_g[[??]] + Refer to the most recent command preceding the current position + in the history list containing _s_t_r_i_n_g. The trailing ?? may be + omitted if _s_t_r_i_n_g is followed immediately by a newline. If + _s_t_r_i_n_g is missing, the string from the most recent search is + used; it is an error if there is no previous search string. + ^^_s_t_r_i_n_g_1^^_s_t_r_i_n_g_2^^ + Quick substitution. Repeat the previous command, replacing + _s_t_r_i_n_g_1 with _s_t_r_i_n_g_2. Equivalent to ``!!:s^_s_t_r_i_n_g_1^_s_t_r_i_n_g_2^'' + (see MMooddiiffiieerrss below). + !!## The entire command line typed so far. + + WWoorrdd DDeessiiggnnaattoorrss + Word designators are used to select desired words from the event. A :: + separates the event specification from the word designator. It may be + omitted if the word designator begins with a ^^, $$, **, --, or %%. 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 sepa- + rated by single spaces. + + 00 ((zzeerroo)) + The zeroth word. For the shell, this is the command word. + _n The _nth word. + ^^ The first argument. That is, word 1. + $$ The last word. This is usually the last argument, but will ex- + pand to the zeroth word if there is only one word in the line. + %% The first word matched by the most recent `?_s_t_r_i_n_g?' search, if + the search string begins with a character that is part of a + word. + _x--_y A range of words; `-_y' abbreviates `0-_y'. + ** All of the words but the zeroth. This is a synonym for `_1_-_$'. + It is not an error to use ** if there is just one word in the + event; the empty string is returned in that case. + xx** Abbreviates _x_-_$. + xx-- Abbreviates _x_-_$ like xx**, but omits the last word. If xx is miss- + ing, it defaults to 0. + + If a word designator is supplied without an event specification, the + previous command is used as the event. + + MMooddiiffiieerrss + After the optional word designator, there may appear a sequence of one + or more of the following modifiers, each preceded by a `:'. These mod- + ify, or edit, the word or words selected from the history event. + + hh Remove a trailing filename component, leaving only the head. + tt Remove all leading filename components, leaving the tail. + rr Remove a trailing suffix of the form _._x_x_x, leaving the basename. + ee Remove all but the trailing suffix. + pp Print the new command but do not execute it. + qq Quote the substituted words, escaping further substitutions. + xx Quote the substituted words as with qq, but break into words at + bbllaannkkss and newlines. The qq and xx modifiers are mutually exclu- + sive; the last one supplied is used. + ss//_o_l_d//_n_e_w// + Substitute _n_e_w for the first occurrence of _o_l_d 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 _o_l_d and _n_e_w with + a single backslash. If & appears in _n_e_w, it is replaced by _o_l_d. + A single backslash will quote the &. If _o_l_d is null, it is set + to the last _o_l_d substituted, or, if no previous history substi- + tutions took place, the last _s_t_r_i_n_g in a !!??_s_t_r_i_n_g[[??]] search. + If _n_e_w is null, each matching _o_l_d is deleted. + && Repeat the previous substitution. + gg Cause changes to be applied over the entire event line. This is + used in conjunction with `::ss' (e.g., `::ggss//_o_l_d//_n_e_w//') or `::&&'. + If used with `::ss', 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 aa may be used as a synonym for gg. + GG Apply the following `ss' or `&&' modifier once to each word in the + event line. + +SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS + Unless otherwise noted, each builtin command documented in this section + as accepting options preceded by -- accepts ---- to signify the end of the + options. The ::, ttrruuee, ffaallssee, and tteesstt/[[ builtins do not accept options + and do not treat ---- specially. The eexxiitt, llooggoouutt, rreettuurrnn, bbrreeaakk, ccoonn-- + ttiinnuuee, lleett, and sshhiifftt builtins accept and process arguments beginning + with -- without requiring ----. Other builtins that accept arguments but + are not specified as accepting options interpret arguments beginning + with -- as invalid options and require ---- to prevent this interpreta- + tion. + :: [_a_r_g_u_m_e_n_t_s] + No effect; the command does nothing beyond expanding _a_r_g_u_m_e_n_t_s + and performing any specified redirections. The return status is + zero. + + .. _f_i_l_e_n_a_m_e [_a_r_g_u_m_e_n_t_s] + ssoouurrccee _f_i_l_e_n_a_m_e [_a_r_g_u_m_e_n_t_s] + Read and execute commands from _f_i_l_e_n_a_m_e in the current shell en- + vironment and return the exit status of the last command exe- + cuted from _f_i_l_e_n_a_m_e. If _f_i_l_e_n_a_m_e does not contain a slash, + filenames in PPAATTHH are used to find the directory containing + _f_i_l_e_n_a_m_e, but _f_i_l_e_n_a_m_e does not need to be executable. The file + searched for in PPAATTHH need not be executable. When bbaasshh is not + in _p_o_s_i_x _m_o_d_e, it searches the current directory if no file is + found in PPAATTHH. If the ssoouurrcceeppaatthh option to the sshhoopptt builtin + command is turned off, the PPAATTHH is not searched. If any _a_r_g_u_- + _m_e_n_t_s are supplied, they become the positional parameters when + _f_i_l_e_n_a_m_e is executed. Otherwise the positional parameters are + unchanged. If the --TT option is enabled, .. inherits any trap on + DDEEBBUUGG; if it is not, any DDEEBBUUGG trap string is saved and restored + around the call to .., and .. unsets the DDEEBBUUGG trap while it exe- + cutes. If --TT is not set, and the sourced file changes the DDEEBBUUGG + trap, the new value is retained when .. completes. The return + status is the status of the last command exited within the + script (0 if no commands are executed), and false if _f_i_l_e_n_a_m_e is + not found or cannot be read. + + aalliiaass [--pp] [_n_a_m_e[=_v_a_l_u_e] ...] + AAlliiaass with no arguments or with the --pp option prints the list of + aliases in the form aalliiaass _n_a_m_e=_v_a_l_u_e on standard output. When + arguments are supplied, an alias is defined for each _n_a_m_e whose + _v_a_l_u_e is given. A trailing space in _v_a_l_u_e causes the next word + to be checked for alias substitution when the alias is expanded. + For each _n_a_m_e in the argument list for which no _v_a_l_u_e is sup- + plied, the name and value of the alias is printed. AAlliiaass re- + turns true unless a _n_a_m_e is given for which no alias has been + defined. + + bbgg [_j_o_b_s_p_e_c ...] + Resume each suspended job _j_o_b_s_p_e_c in the background, as if it + had been started with &&. If _j_o_b_s_p_e_c is not present, the shell's + notion of the _c_u_r_r_e_n_t _j_o_b is used. bbgg _j_o_b_s_p_e_c returns 0 unless + run when job control is disabled or, when run with job control + enabled, any specified _j_o_b_s_p_e_c was not found or was started + without job control. + + bbiinndd [--mm _k_e_y_m_a_p] [--llppssvvPPSSVVXX] + bbiinndd [--mm _k_e_y_m_a_p] [--qq _f_u_n_c_t_i_o_n] [--uu _f_u_n_c_t_i_o_n] [--rr _k_e_y_s_e_q] + bbiinndd [--mm _k_e_y_m_a_p] --ff _f_i_l_e_n_a_m_e + bbiinndd [--mm _k_e_y_m_a_p] --xx _k_e_y_s_e_q:_s_h_e_l_l_-_c_o_m_m_a_n_d + bbiinndd [--mm _k_e_y_m_a_p] _k_e_y_s_e_q:_f_u_n_c_t_i_o_n_-_n_a_m_e + bbiinndd [--mm _k_e_y_m_a_p] _k_e_y_s_e_q:_r_e_a_d_l_i_n_e_-_c_o_m_m_a_n_d + bbiinndd _r_e_a_d_l_i_n_e_-_c_o_m_m_a_n_d_-_l_i_n_e + Display current rreeaaddlliinnee key and function bindings, bind a key + sequence to a rreeaaddlliinnee function or macro, or set a rreeaaddlliinnee + variable. Each non-option argument is a command as it would ap- + pear in a rreeaaddlliinnee initialization file such as _._i_n_p_u_t_r_c, but + each binding or command must be passed as a separate argument; + e.g., '"\C-x\C-r": re-read-init-file'. Options, if supplied, + have the following meanings: + --mm _k_e_y_m_a_p + Use _k_e_y_m_a_p as the keymap to be affected by the subsequent + bindings. Acceptable _k_e_y_m_a_p names are _e_m_a_c_s_, _e_m_a_c_s_-_s_t_a_n_- + _d_a_r_d_, _e_m_a_c_s_-_m_e_t_a_, _e_m_a_c_s_-_c_t_l_x_, _v_i_, _v_i_-_m_o_v_e_, _v_i_-_c_o_m_m_a_n_d, + and _v_i_-_i_n_s_e_r_t. _v_i is equivalent to _v_i_-_c_o_m_m_a_n_d (_v_i_-_m_o_v_e + is also a synonym); _e_m_a_c_s is equivalent to _e_m_a_c_s_-_s_t_a_n_- + _d_a_r_d. + --ll List the names of all rreeaaddlliinnee functions. + --pp Display rreeaaddlliinnee function names and bindings in such a + way that they can be re-read. + --PP List current rreeaaddlliinnee function names and bindings. + --ss Display rreeaaddlliinnee key sequences bound to macros and the + strings they output in such a way that they can be re- + read. + --SS Display rreeaaddlliinnee key sequences bound to macros and the + strings they output. + --vv Display rreeaaddlliinnee variable names and values in such a way + that they can be re-read. + --VV List current rreeaaddlliinnee variable names and values. + --ff _f_i_l_e_n_a_m_e + Read key bindings from _f_i_l_e_n_a_m_e. + --qq _f_u_n_c_t_i_o_n + Query about which keys invoke the named _f_u_n_c_t_i_o_n. + --uu _f_u_n_c_t_i_o_n + Unbind all keys bound to the named _f_u_n_c_t_i_o_n. + --rr _k_e_y_s_e_q + Remove any current binding for _k_e_y_s_e_q. + --xx _k_e_y_s_e_q::_s_h_e_l_l_-_c_o_m_m_a_n_d + Cause _s_h_e_l_l_-_c_o_m_m_a_n_d to be executed whenever _k_e_y_s_e_q is en- + tered. When _s_h_e_l_l_-_c_o_m_m_a_n_d is executed, the shell sets + the RREEAADDLLIINNEE__LLIINNEE variable to the contents of the rreeaadd-- + lliinnee line buffer and the RREEAADDLLIINNEE__PPOOIINNTT and RREEAADDLLIINNEE__MMAARRKK + 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 RREEAADDLLIINNEE__AARRGGUUMMEENNTT variable. If there was no argu- + ment, that variable is not set. If the executed command + changes the value of any of RREEAADDLLIINNEE__LLIINNEE, RREEAADD-- + LLIINNEE__PPOOIINNTT, or RREEAADDLLIINNEE__MMAARRKK, those new values will be + reflected in the editing state. + --XX List all key sequences bound to shell commands and the + associated commands in a format that can be reused as in- + put. + + The return value is 0 unless an unrecognized option is given or + an error occurred. + + bbrreeaakk [_n] + Exit from within a ffoorr, wwhhiillee, uunnttiill, or sseelleecctt loop. If _n is + specified, break _n levels. _n must be >= 1. If _n is greater + than the number of enclosing loops, all enclosing loops are ex- + ited. The return value is 0 unless _n is not greater than or + equal to 1. + + bbuuiillttiinn _s_h_e_l_l_-_b_u_i_l_t_i_n [_a_r_g_u_m_e_n_t_s] + Execute the specified shell builtin, passing it _a_r_g_u_m_e_n_t_s, and + return its exit status. This is useful when defining a function + whose name is the same as a shell builtin, retaining the func- + tionality of the builtin within the function. The ccdd builtin is + commonly redefined this way. The return status is false if + _s_h_e_l_l_-_b_u_i_l_t_i_n is not a shell builtin command. + + ccaalllleerr [_e_x_p_r] + Returns the context of any active subroutine call (a shell func- + tion or a script executed with the .. or ssoouurrccee builtins). With- + out _e_x_p_r, ccaalllleerr displays the line number and source filename of + the current subroutine call. If a non-negative integer is sup- + plied as _e_x_p_r, ccaalllleerr 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 sub- + routine call or _e_x_p_r does not correspond to a valid position in + the call stack. + + ccdd [--LL|[--PP [--ee]] [-@]] [_d_i_r] + Change the current directory to _d_i_r. if _d_i_r is not supplied, + the value of the HHOOMMEE shell variable is the default. The vari- + able CCDDPPAATTHH defines the search path for the directory containing + _d_i_r: each directory name in CCDDPPAATTHH is searched for _d_i_r. Alter- + native directory names in CCDDPPAATTHH are separated by a colon (:). + A null directory name in CCDDPPAATTHH is the same as the current di- + rectory, i.e., ``..''. If _d_i_r begins with a slash (/), then CCDD-- + PPAATTHH is not used. The --PP option causes ccdd to use the physical + directory structure by resolving symbolic links while traversing + _d_i_r and before processing instances of _._. in _d_i_r (see also the + --PP option to the sseett builtin command); the --LL option forces sym- + bolic links to be followed by resolving the link after process- + ing instances of _._. in _d_i_r. If _._. appears in _d_i_r, it is pro- + cessed by removing the immediately previous pathname component + from _d_i_r, back to a slash or the beginning of _d_i_r. If the --ee + option is supplied with --PP, and the current working directory + cannot be successfully determined after a successful directory + change, ccdd will return an unsuccessful status. On systems that + support it, the --@@ option presents the extended attributes asso- + ciated with a file as a directory. An argument of -- is con- + verted to $$OOLLDDPPWWDD before the directory change is attempted. If + a non-empty directory name from CCDDPPAATTHH is used, or if -- is the + first argument, and the directory change is successful, the ab- + solute pathname of the new working directory is written to the + standard output. If the directory change is successful, ccdd sets + the value of the PPWWDD environment variable to the new directory + name, and sets the OOLLDDPPWWDD 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. + + ccoommmmaanndd [--ppVVvv] _c_o_m_m_a_n_d [_a_r_g ...] + Run _c_o_m_m_a_n_d with _a_r_g_s suppressing the normal shell function + lookup. Only builtin commands or commands found in the PPAATTHH are + executed. If the --pp option is given, the search for _c_o_m_m_a_n_d is + performed using a default value for PPAATTHH that is guaranteed to + find all of the standard utilities. If either the --VV or --vv op- + tion is supplied, a description of _c_o_m_m_a_n_d is printed. The --vv + option causes a single word indicating the command or filename + used to invoke _c_o_m_m_a_n_d to be displayed; the --VV option produces a + more verbose description. If the --VV or --vv option is supplied, + the exit status is 0 if _c_o_m_m_a_n_d was found, and 1 if not. If + neither option is supplied and an error occurred or _c_o_m_m_a_n_d can- + not be found, the exit status is 127. Otherwise, the exit sta- + tus of the ccoommmmaanndd builtin is the exit status of _c_o_m_m_a_n_d. + + ccoommppggeenn [_o_p_t_i_o_n] [_w_o_r_d] + Generate possible completion matches for _w_o_r_d according to the + _o_p_t_i_o_ns, which may be any option accepted by the ccoommpplleettee + builtin with the exception of --pp and --rr, and write the matches + to the standard output. When using the --FF or --CC options, the + various shell variables set by the programmable completion fa- + cilities, while available, will not have useful values. + + The matches will be generated in the same way as if the program- + mable completion code had generated them directly from a comple- + tion specification with the same flags. If _w_o_r_d is specified, + only those completions matching _w_o_r_d will be displayed. + + The return value is true unless an invalid option is supplied, + or no matches were generated. + + ccoommpplleettee [--aabbccddeeffggjjkkssuuvv] [--oo _c_o_m_p_-_o_p_t_i_o_n] [--DDEEII] [--AA _a_c_t_i_o_n] [--GG _g_l_o_b_- + _p_a_t] [--WW _w_o_r_d_l_i_s_t] + [--FF _f_u_n_c_t_i_o_n] [--CC _c_o_m_m_a_n_d] [--XX _f_i_l_t_e_r_p_a_t] [--PP _p_r_e_f_i_x] [--SS _s_u_f_- + _f_i_x] _n_a_m_e [_n_a_m_e _._._.] + ccoommpplleettee --pprr [--DDEEII] [_n_a_m_e ...] + Specify how arguments to each _n_a_m_e should be completed. If the + --pp 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 --rr option removes a completion spec- + ification for each _n_a_m_e, or, if no _n_a_m_es are supplied, all com- + pletion specifications. The --DD option indicates that other sup- + plied options and actions should apply to the ``default'' com- + mand completion; that is, completion attempted on a command for + which no completion has previously been defined. The --EE option + indicates that other supplied options and actions should apply + to ``empty'' command completion; that is, completion attempted + on a blank line. The --II 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 ;; or ||, which is usually command name completion. If + multiple options are supplied, the --DD option takes precedence + over --EE, and both take precedence over --II. If any of --DD, --EE, or + --II are supplied, any other _n_a_m_e arguments are ignored; these + completions only apply to the case specified by the option. + + The process of applying these completion specifications when + word completion is attempted is described above under PPrrooggrraamm-- + mmaabbllee CCoommpplleettiioonn. + + Other options, if specified, have the following meanings. The + arguments to the --GG, --WW, and --XX options (and, if necessary, the + --PP and --SS options) should be quoted to protect them from expan- + sion before the ccoommpplleettee builtin is invoked. + --oo _c_o_m_p_-_o_p_t_i_o_n + The _c_o_m_p_-_o_p_t_i_o_n controls several aspects of the comp- + spec's behavior beyond the simple generation of comple- + tions. _c_o_m_p_-_o_p_t_i_o_n may be one of: + bbaasshhddeeffaauulltt + Perform the rest of the default bbaasshh completions + if the compspec generates no matches. + ddeeffaauulltt Use readline's default filename completion if + the compspec generates no matches. + ddiirrnnaammeess + Perform directory name completion if the comp- + spec generates no matches. + ffiilleennaammeess + Tell readline that the compspec generates file- + names, so it can perform any filename-specific + processing (like adding a slash to directory + names, quoting special characters, or suppress- + ing trailing spaces). Intended to be used with + shell functions. + nnooqquuoottee Tell readline not to quote the completed words + if they are filenames (quoting filenames is the + default). + nnoossoorrtt Tell readline not to sort the list of possible + completions alphabetically. + nnoossppaaccee Tell readline not to append a space (the de- + fault) to words completed at the end of the + line. + pplluussddiirrss + After any matches defined by the compspec are + generated, directory name completion is at- + tempted and any matches are added to the results + of the other actions. + --AA _a_c_t_i_o_n + The _a_c_t_i_o_n may be one of the following to generate a + list of possible completions: + aalliiaass Alias names. May also be specified as --aa. + aarrrraayyvvaarr + Array variable names. + bbiinnddiinngg RReeaaddlliinnee key binding names. + bbuuiillttiinn Names of shell builtin commands. May also be + specified as --bb. + ccoommmmaanndd Command names. May also be specified as --cc. + ddiirreeccttoorryy + Directory names. May also be specified as --dd. + ddiissaabblleedd + Names of disabled shell builtins. + eennaabblleedd Names of enabled shell builtins. + eexxppoorrtt Names of exported shell variables. May also be + specified as --ee. + ffiillee File names. May also be specified as --ff. + ffuunnccttiioonn + Names of shell functions. + ggrroouupp Group names. May also be specified as --gg. + hheellppttooppiicc + Help topics as accepted by the hheellpp builtin. + hhoossttnnaammee + Hostnames, as taken from the file specified by + the HHOOSSTTFFIILLEE shell variable. + jjoobb Job names, if job control is active. May also + be specified as --jj. + kkeeyywwoorrdd Shell reserved words. May also be specified as + --kk. + rruunnnniinngg Names of running jobs, if job control is active. + sseerrvviiccee Service names. May also be specified as --ss. + sseettoopptt Valid arguments for the --oo option to the sseett + builtin. + sshhoopptt Shell option names as accepted by the sshhoopptt + builtin. + ssiiggnnaall Signal names. + ssttooppppeedd Names of stopped jobs, if job control is active. + uusseerr User names. May also be specified as --uu. + vvaarriiaabbllee + Names of all shell variables. May also be spec- + ified as --vv. + --CC _c_o_m_m_a_n_d + _c_o_m_m_a_n_d is executed in a subshell environment, and its + output is used as the possible completions. Arguments + are passed as with the --FF option. + --FF _f_u_n_c_t_i_o_n + The shell function _f_u_n_c_t_i_o_n is executed in the current + shell environment. When the function is executed, the + first argument ($$11) is the name of the command whose ar- + guments are being completed, the second argument ($$22) is + the word being completed, and the third argument ($$33) is + the word preceding the word being completed on the cur- + rent command line. When it finishes, the possible com- + pletions are retrieved from the value of the CCOOMMPPRREEPPLLYY + array variable. + --GG _g_l_o_b_p_a_t + The pathname expansion pattern _g_l_o_b_p_a_t is expanded to + generate the possible completions. + --PP _p_r_e_f_i_x + _p_r_e_f_i_x is added at the beginning of each possible com- + pletion after all other options have been applied. + --SS _s_u_f_f_i_x + _s_u_f_f_i_x is appended to each possible completion after all + other options have been applied. + --WW _w_o_r_d_l_i_s_t + The _w_o_r_d_l_i_s_t is split using the characters in the IIFFSS + special variable as delimiters, and each resultant word + is expanded. Shell quoting is honored within _w_o_r_d_l_i_s_t, + in order to provide a mechanism for the words to contain + shell metacharacters or characters in the value of IIFFSS. + The possible completions are the members of the resul- + tant list which match the word being completed. + --XX _f_i_l_t_e_r_p_a_t + _f_i_l_t_e_r_p_a_t is a pattern as used for pathname expansion. + It is applied to the list of possible completions gener- + ated by the preceding options and arguments, and each + completion matching _f_i_l_t_e_r_p_a_t is removed from the list. + A leading !! in _f_i_l_t_e_r_p_a_t negates the pattern; in this + case, any completion not matching _f_i_l_t_e_r_p_a_t is removed. + + The return value is true unless an invalid option is supplied, + an option other than --pp or --rr is supplied without a _n_a_m_e argu- + ment, an attempt is made to remove a completion specification + for a _n_a_m_e for which no specification exists, or an error occurs + adding a completion specification. + + ccoommppoopptt [--oo _o_p_t_i_o_n] [--DDEEII] [++oo _o_p_t_i_o_n] [_n_a_m_e] + Modify completion options for each _n_a_m_e according to the _o_p_- + _t_i_o_ns, or for the currently-executing completion if no _n_a_m_es are + supplied. If no _o_p_t_i_o_ns are given, display the completion op- + tions for each _n_a_m_e or the current completion. The possible + values of _o_p_t_i_o_n are those valid for the ccoommpplleettee builtin de- + scribed above. The --DD option indicates that other supplied op- + tions should apply to the ``default'' command completion; that + is, completion attempted on a command for which no completion + has previously been defined. The --EE option indicates that other + supplied options should apply to ``empty'' command completion; + that is, completion attempted on a blank line. The --II option + indicates that other supplied options should apply to completion + on the initial non-assignment word on the line, or after a com- + mand delimiter such as ;; or ||, which is usually command name + completion. + + The return value is true unless an invalid option is supplied, + an attempt is made to modify the options for a _n_a_m_e for which no + completion specification exists, or an output error occurs. + + ccoonnttiinnuuee [_n] + Resume the next iteration of the enclosing ffoorr, wwhhiillee, uunnttiill, or + sseelleecctt loop. If _n is specified, resume at the _nth enclosing + loop. _n must be >= 1. If _n is greater than the number of en- + closing loops, the last enclosing loop (the ``top-level'' loop) + is resumed. The return value is 0 unless _n is not greater than + or equal to 1. + + ddeeccllaarree [--aaAAffFFggiiIIllnnrrttuuxx] [--pp] [_n_a_m_e[=_v_a_l_u_e] ...] + ttyyppeesseett [--aaAAffFFggiiIIllnnrrttuuxx] [--pp] [_n_a_m_e[=_v_a_l_u_e] ...] + Declare variables and/or give them attributes. If no _n_a_m_es are + given then display the values of variables. The --pp option will + display the attributes and values of each _n_a_m_e. When --pp is used + with _n_a_m_e arguments, additional options, other than --ff and --FF, + are ignored. When --pp is supplied without _n_a_m_e 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 --pp, ddeeccllaarree will display the at- + tributes and values of all shell variables. The --ff option will + restrict the display to shell functions. The --FF option inhibits + the display of function definitions; only the function name and + attributes are printed. If the eexxttddeebbuugg shell option is enabled + using sshhoopptt, the source file name and line number where each + _n_a_m_e is defined are displayed as well. The --FF option implies + --ff. The --gg option forces variables to be created or modified at + the global scope, even when ddeeccllaarree is executed in a shell func- + tion. It is ignored in all other cases. The --II option causes + local variables to inherit the attributes (except the _n_a_m_e_r_e_f + attribute) and value of any existing variable with the same _n_a_m_e + 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 attri- + bute or to give variables attributes: + --aa Each _n_a_m_e is an indexed array variable (see AArrrraayyss + above). + --AA Each _n_a_m_e is an associative array variable (see AArrrraayyss + above). + --ff Use function names only. + --ii The variable is treated as an integer; arithmetic evalua- + tion (see AARRIITTHHMMEETTIICC EEVVAALLUUAATTIIOONN above) is performed when + the variable is assigned a value. + --ll When the variable is assigned a value, all upper-case + characters are converted to lower-case. The upper-case + attribute is disabled. + --nn Give each _n_a_m_e the _n_a_m_e_r_e_f attribute, making it a name + reference to another variable. That other variable is + defined by the value of _n_a_m_e. All references, assign- + ments, and attribute modifications to _n_a_m_e, except those + using or changing the --nn attribute itself, are performed + on the variable referenced by _n_a_m_e's value. The nameref + attribute cannot be applied to array variables. + --rr Make _n_a_m_es readonly. These names cannot then be assigned + values by subsequent assignment statements or unset. + --tt Give each _n_a_m_e the _t_r_a_c_e attribute. Traced functions in- + herit the DDEEBBUUGG and RREETTUURRNN traps from the calling shell. + The trace attribute has no special meaning for variables. + --uu When the variable is assigned a value, all lower-case + characters are converted to upper-case. The lower-case + attribute is disabled. + --xx Mark _n_a_m_es for export to subsequent commands via the en- + vironment. + + Using `+' instead of `-' turns off the attribute instead, with + the exceptions that ++aa and ++AA may not be used to destroy array + variables and ++rr will not remove the readonly attribute. When + used in a function, ddeeccllaarree and ttyyppeesseett make each _n_a_m_e local, as + with the llooccaall command, unless the --gg option is supplied. If a + variable name is followed by =_v_a_l_u_e, the value of the variable + is set to _v_a_l_u_e. When using --aa or --AA and the compound assign- + ment 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 ``-f foo=bar'', an attempt is made to + assign a value to a readonly variable, an attempt is made to as- + sign a value to an array variable without using the compound as- + signment syntax (see AArrrraayyss above), one of the _n_a_m_e_s is not a + valid shell variable name, an attempt is made to turn off read- + only 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 --ff. + + ddiirrss [[--ccllppvv]] [[++_n]] [[--_n]] + Without options, displays the list of currently remembered di- + rectories. The default display is on a single line with direc- + tory names separated by spaces. Directories are added to the + list with the ppuusshhdd command; the ppooppdd command removes entries + from the list. The current directory is always the first direc- + tory in the stack. + --cc Clears the directory stack by deleting all of the en- + tries. + --ll Produces a listing using full pathnames; the default + listing format uses a tilde to denote the home directory. + --pp Print the directory stack with one entry per line. + --vv Print the directory stack with one entry per line, pre- + fixing each entry with its index in the stack. + ++_n Displays the _nth entry counting from the left of the list + shown by ddiirrss when invoked without options, starting with + zero. + --_n Displays the _nth entry counting from the right of the + list shown by ddiirrss when invoked without options, starting + with zero. + + The return value is 0 unless an invalid option is supplied or _n + indexes beyond the end of the directory stack. + + ddiissoowwnn [--aarr] [--hh] [_j_o_b_s_p_e_c ... | _p_i_d ... ] + Without options, remove each _j_o_b_s_p_e_c from the table of active + jobs. If _j_o_b_s_p_e_c is not present, and neither the --aa nor the --rr + option is supplied, the _c_u_r_r_e_n_t _j_o_b is used. If the --hh option + is given, each _j_o_b_s_p_e_c is not removed from the table, but is + marked so that SSIIGGHHUUPP is not sent to the job if the shell re- + ceives a SSIIGGHHUUPP. If no _j_o_b_s_p_e_c is supplied, the --aa option means + to remove or mark all jobs; the --rr option without a _j_o_b_s_p_e_c ar- + gument restricts operation to running jobs. The return value is + 0 unless a _j_o_b_s_p_e_c does not specify a valid job. + + eecchhoo [--nneeEE] [_a_r_g ...] + Output the _a_r_gs, separated by spaces, followed by a newline. + The return status is 0 unless a write error occurs. If --nn is + specified, the trailing newline is suppressed. If the --ee option + is given, interpretation of the following backslash-escaped + characters is enabled. The --EE option disables the interpreta- + tion of these escape characters, even on systems where they are + interpreted by default. The xxppgg__eecchhoo shell option may be used + to dynamically determine whether or not eecchhoo expands these es- + cape characters by default. eecchhoo does not interpret ---- to mean + the end of options. eecchhoo interprets the following escape se- + quences: + \\aa alert (bell) + \\bb backspace + \\cc suppress further output + \\ee + \\EE an escape character + \\ff form feed + \\nn new line + \\rr carriage return + \\tt horizontal tab + \\vv vertical tab + \\\\ backslash + \\00_n_n_n the eight-bit character whose value is the octal value + _n_n_n (zero to three octal digits) + \\xx_H_H the eight-bit character whose value is the hexadecimal + value _H_H (one or two hex digits) + \\uu_H_H_H_H the Unicode (ISO/IEC 10646) character whose value is the + hexadecimal value _H_H_H_H (one to four hex digits) + \\UU_H_H_H_H_H_H_H_H + the Unicode (ISO/IEC 10646) character whose value is the + hexadecimal value _H_H_H_H_H_H_H_H (one to eight hex digits) + + eennaabbllee [--aa] [--ddnnppss] [--ff _f_i_l_e_n_a_m_e] [_n_a_m_e ...] + 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 --nn is used, each _n_a_m_e is disabled; otherwise, _n_a_m_e_s are en- + abled. For example, to use the tteesstt binary found via the PPAATTHH + instead of the shell builtin version, run ``enable -n test''. + The --ff option means to load the new builtin command _n_a_m_e from + shared object _f_i_l_e_n_a_m_e, on systems that support dynamic loading. + Bash will use the value of the BBAASSHH__LLOOAADDAABBLLEESS__PPAATTHH variable as a + colon-separated list of directories in which to search for _f_i_l_e_- + _n_a_m_e. The default is system-dependent. The --dd option will + delete a builtin previously loaded with --ff. If no _n_a_m_e argu- + ments are given, or if the --pp option is supplied, a list of + shell builtins is printed. With no other option arguments, the + list consists of all enabled shell builtins. If --nn is supplied, + only disabled builtins are printed. If --aa is supplied, the list + printed includes all builtins, with an indication of whether or + not each is enabled. If --ss is supplied, the output is re- + stricted to the POSIX _s_p_e_c_i_a_l builtins. If no options are sup- + plied and a _n_a_m_e is not a shell builtin, eennaabbllee will attempt to + load _n_a_m_e from a shared object named _n_a_m_e, as if the command + were ``enable -f _n_a_m_e _n_a_m_e . The return value is 0 unless a + _n_a_m_e is not a shell builtin or there is an error loading a new + builtin from a shared object. + + eevvaall [_a_r_g ...] + The _a_r_gs are read and concatenated together into a single com- + mand. This command is then read and executed by the shell, and + its exit status is returned as the value of eevvaall. If there are + no _a_r_g_s, or only null arguments, eevvaall returns 0. + + eexxeecc [--ccll] [--aa _n_a_m_e] [_c_o_m_m_a_n_d [_a_r_g_u_m_e_n_t_s]] + If _c_o_m_m_a_n_d is specified, it replaces the shell. No new process + is created. The _a_r_g_u_m_e_n_t_s become the arguments to _c_o_m_m_a_n_d. If + the --ll option is supplied, the shell places a dash at the begin- + ning of the zeroth argument passed to _c_o_m_m_a_n_d. This is what _l_o_- + _g_i_n(1) does. The --cc option causes _c_o_m_m_a_n_d to be executed with + an empty environment. If --aa is supplied, the shell passes _n_a_m_e + as the zeroth argument to the executed command. If _c_o_m_m_a_n_d can- + not be executed for some reason, a non-interactive shell exits, + unless the eexxeeccffaaiill 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 + eexxeecc fails. If _c_o_m_m_a_n_d 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. + + eexxiitt [_n] + Cause the shell to exit with a status of _n. If _n is omitted, + the exit status is that of the last command executed. A trap on + EEXXIITT is executed before the shell terminates. + + eexxppoorrtt [--ffnn] [_n_a_m_e[=_w_o_r_d]] ... + eexxppoorrtt --pp + The supplied _n_a_m_e_s are marked for automatic export to the envi- + ronment of subsequently executed commands. If the --ff option is + given, the _n_a_m_e_s refer to functions. If no _n_a_m_e_s are given, or + if the --pp option is supplied, a list of names of all exported + variables is printed. The --nn option causes the export property + to be removed from each _n_a_m_e. If a variable name is followed by + =_w_o_r_d, the value of the variable is set to _w_o_r_d. eexxppoorrtt returns + an exit status of 0 unless an invalid option is encountered, one + of the _n_a_m_e_s is not a valid shell variable name, or --ff is sup- + plied with a _n_a_m_e that is not a function. + + ffcc [--ee _e_n_a_m_e] [--llnnrr] [_f_i_r_s_t] [_l_a_s_t] + ffcc --ss [_p_a_t=_r_e_p] [_c_m_d] + The first form selects a range of commands from _f_i_r_s_t to _l_a_s_t + from the history list and displays or edits and re-executes + them. _F_i_r_s_t and _l_a_s_t 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 + _f_i_r_s_t or _l_a_s_t of 0 is equivalent to -1 and -0 is equivalent to + the current command (usually the ffcc command); otherwise 0 is + equivalent to -1 and -0 is invalid. If _l_a_s_t is not specified, + it is set to the current command for listing (so that ``fc -l + -10'' prints the last 10 commands) and to _f_i_r_s_t otherwise. If + _f_i_r_s_t is not specified, it is set to the previous command for + editing and -16 for listing. + + The --nn option suppresses the command numbers when listing. The + --rr option reverses the order of the commands. If the --ll option + is given, the commands are listed on standard output. Other- + wise, the editor given by _e_n_a_m_e is invoked on a file containing + those commands. If _e_n_a_m_e is not given, the value of the FFCCEEDDIITT + variable is used, and the value of EEDDIITTOORR if FFCCEEDDIITT is not set. + If neither variable is set, _v_i is used. When editing is com- + plete, the edited commands are echoed and executed. + + In the second form, _c_o_m_m_a_n_d is re-executed after each instance + of _p_a_t is replaced by _r_e_p. _C_o_m_m_a_n_d is interpreted the same as + _f_i_r_s_t above. A useful alias to use with this is ``r="fc -s"'', + so that typing ``r cc'' runs the last command beginning with + ``cc'' and typing ``r'' re-executes the last command. + + If the first form is used, the return value is 0 unless an in- + valid option is encountered or _f_i_r_s_t or _l_a_s_t specify history + lines out of range. If the --ee 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-exe- + cuted, unless _c_m_d does not specify a valid history line, in + which case ffcc returns failure. + + ffgg [_j_o_b_s_p_e_c] + Resume _j_o_b_s_p_e_c in the foreground, and make it the current job. + If _j_o_b_s_p_e_c is not present, the shell's notion of the _c_u_r_r_e_n_t _j_o_b + 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 _j_o_b_s_p_e_c does not spec- + ify a valid job or _j_o_b_s_p_e_c specifies a job that was started + without job control. + + ggeettooppttss _o_p_t_s_t_r_i_n_g _n_a_m_e [_a_r_g _._._.] + ggeettooppttss is used by shell procedures to parse positional parame- + ters. _o_p_t_s_t_r_i_n_g contains the option characters to be recog- + nized; if a character is followed by a colon, the option is ex- + pected 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, ggeettooppttss + places the next option in the shell variable _n_a_m_e, initializing + _n_a_m_e if it does not exist, and the index of the next argument to + be processed into the variable OOPPTTIINNDD. OOPPTTIINNDD is initialized to + 1 each time the shell or a shell script is invoked. When an op- + tion requires an argument, ggeettooppttss places that argument into the + variable OOPPTTAARRGG. The shell does not reset OOPPTTIINNDD automatically; + it must be manually reset between multiple calls to ggeettooppttss + within the same shell invocation if a new set of parameters is + to be used. + + When the end of options is encountered, ggeettooppttss exits with a re- + turn value greater than zero. OOPPTTIINNDD is set to the index of the + first non-option argument, and _n_a_m_e is set to ?. + + ggeettooppttss normally parses the positional parameters, but if more + arguments are supplied as _a_r_g values, ggeettooppttss parses those in- + stead. + + ggeettooppttss can report errors in two ways. If the first character + of _o_p_t_s_t_r_i_n_g is a colon, _s_i_l_e_n_t error reporting is used. In + normal operation, diagnostic messages are printed when invalid + options or missing option arguments are encountered. If the + variable OOPPTTEERRRR is set to 0, no error messages will be dis- + played, even if the first character of _o_p_t_s_t_r_i_n_g is not a colon. + + If an invalid option is seen, ggeettooppttss places ? into _n_a_m_e and, if + not silent, prints an error message and unsets OOPPTTAARRGG. If + ggeettooppttss is silent, the option character found is placed in OOPP-- + TTAARRGG and no diagnostic message is printed. + + If a required argument is not found, and ggeettooppttss is not silent, + a question mark (??) is placed in _n_a_m_e, OOPPTTAARRGG is unset, and a + diagnostic message is printed. If ggeettooppttss is silent, then a + colon (::) is placed in _n_a_m_e and OOPPTTAARRGG is set to the option + character found. + + ggeettooppttss returns true if an option, specified or unspecified, is + found. It returns false if the end of options is encountered or + an error occurs. + + hhaasshh [--llrr] [--pp _f_i_l_e_n_a_m_e] [--ddtt] [_n_a_m_e] + Each time hhaasshh is invoked, the full pathname of the command _n_a_m_e + is determined by searching the directories in $$PPAATTHH and remem- + bered. Any previously-remembered pathname is discarded. If the + --pp option is supplied, no path search is performed, and _f_i_l_e_n_a_m_e + is used as the full filename of the command. The --rr option + causes the shell to forget all remembered locations. The --dd op- + tion causes the shell to forget the remembered location of each + _n_a_m_e. If the --tt option is supplied, the full pathname to which + each _n_a_m_e corresponds is printed. If multiple _n_a_m_e arguments + are supplied with --tt, the _n_a_m_e is printed before the hashed full + pathname. The --ll option causes output to be displayed in a for- + mat that may be reused as input. If no arguments are given, or + if only --ll is supplied, information about remembered commands is + printed. The return status is true unless a _n_a_m_e is not found + or an invalid option is supplied. + + hheellpp [--ddmmss] [_p_a_t_t_e_r_n] + Display helpful information about builtin commands. If _p_a_t_t_e_r_n + is specified, hheellpp gives detailed help on all commands matching + _p_a_t_t_e_r_n; otherwise help for all the builtins and shell control + structures is printed. + --dd Display a short description of each _p_a_t_t_e_r_n + --mm Display the description of each _p_a_t_t_e_r_n in a manpage-like + format + --ss Display only a short usage synopsis for each _p_a_t_t_e_r_n + + The return status is 0 unless no command matches _p_a_t_t_e_r_n. + + hhiissttoorryy [[_n]] + hhiissttoorryy --cc + hhiissttoorryy --dd _o_f_f_s_e_t + hhiissttoorryy --dd _s_t_a_r_t-_e_n_d + hhiissttoorryy --aannrrww [_f_i_l_e_n_a_m_e] + hhiissttoorryy --pp _a_r_g [_a_r_g _._._.] + hhiissttoorryy --ss _a_r_g [_a_r_g _._._.] + With no options, display the command history list with line num- + bers. Lines listed with a ** have been modified. An argument of + _n lists only the last _n lines. If the shell variable HHIISSTTTTIIMMEE-- + FFOORRMMAATT is set and not null, it is used as a format string for + _s_t_r_f_t_i_m_e(3) to display the time stamp associated with each dis- + played history entry. No intervening blank is printed between + the formatted time stamp and the history line. If _f_i_l_e_n_a_m_e is + supplied, it is used as the name of the history file; if not, + the value of HHIISSTTFFIILLEE is used. Options, if supplied, have the + following meanings: + --cc Clear the history list by deleting all the entries. + --dd _o_f_f_s_e_t + Delete the history entry at position _o_f_f_s_e_t. If _o_f_f_s_e_t + 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 hhiissttoorryy --dd command. + --dd _s_t_a_r_t-_e_n_d + Delete the range of history entries between positions + _s_t_a_r_t and _e_n_d, inclusive. Positive and negative values + for _s_t_a_r_t and _e_n_d are interpreted as described above. + --aa Append the ``new'' history lines to the history file. + These are history lines entered since the beginning of + the current bbaasshh session, but not already appended to the + history file. + --nn Read the history lines not already read from the history + file into the current history list. These are lines ap- + pended to the history file since the beginning of the + current bbaasshh session. + --rr Read the contents of the history file and append them to + the current history list. + --ww Write the current history list to the history file, over- + writing the history file's contents. + --pp Perform history substitution on the following _a_r_g_s and + display the result on the standard output. Does not + store the results in the history list. Each _a_r_g must be + quoted to disable normal history expansion. + --ss Store the _a_r_g_s in the history list as a single entry. + The last command in the history list is removed before + the _a_r_g_s are added. + + If the HHIISSTTTTIIMMEEFFOORRMMAATT variable is set, the time stamp informa- + tion associated with each history entry is written to the his- + tory 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 _o_f_f_s_e_t or range + is supplied as an argument to --dd, or the history expansion sup- + plied as an argument to --pp fails. + + jjoobbss [--llnnpprrss] [ _j_o_b_s_p_e_c ... ] + jjoobbss --xx _c_o_m_m_a_n_d [ _a_r_g_s ... ] + The first form lists the active jobs. The options have the fol- + lowing meanings: + --ll List process IDs in addition to the normal information. + --nn Display information only about jobs that have changed + status since the user was last notified of their status. + --pp List only the process ID of the job's process group + leader. + --rr Display only running jobs. + --ss Display only stopped jobs. + + If _j_o_b_s_p_e_c is given, output is restricted to information about + that job. The return status is 0 unless an invalid option is + encountered or an invalid _j_o_b_s_p_e_c is supplied. + + If the --xx option is supplied, jjoobbss replaces any _j_o_b_s_p_e_c found in + _c_o_m_m_a_n_d or _a_r_g_s with the corresponding process group ID, and ex- + ecutes _c_o_m_m_a_n_d passing it _a_r_g_s, returning its exit status. + + kkiillll [--ss _s_i_g_s_p_e_c | --nn _s_i_g_n_u_m | --_s_i_g_s_p_e_c] [_p_i_d | _j_o_b_s_p_e_c] ... + kkiillll --ll|--LL [_s_i_g_s_p_e_c | _e_x_i_t___s_t_a_t_u_s] + Send the signal named by _s_i_g_s_p_e_c or _s_i_g_n_u_m to the processes + named by _p_i_d or _j_o_b_s_p_e_c. _s_i_g_s_p_e_c is either a case-insensitive + signal name such as SSIIGGKKIILLLL (with or without the SSIIGG prefix) or + a signal number; _s_i_g_n_u_m is a signal number. If _s_i_g_s_p_e_c is not + present, then SSIIGGTTEERRMM is assumed. An argument of --ll lists the + signal names. If any arguments are supplied when --ll is given, + the names of the signals corresponding to the arguments are + listed, and the return status is 0. The _e_x_i_t___s_t_a_t_u_s argument to + --ll is a number specifying either a signal number or the exit + status of a process terminated by a signal. The --LL option is + equivalent to --ll. kkiillll returns true if at least one signal was + successfully sent, or false if an error occurs or an invalid op- + tion is encountered. + + lleett _a_r_g [_a_r_g ...] + Each _a_r_g is an arithmetic expression to be evaluated (see AARRIITTHH-- + MMEETTIICC EEVVAALLUUAATTIIOONN above). If the last _a_r_g evaluates to 0, lleett + returns 1; 0 is returned otherwise. + + llooccaall [_o_p_t_i_o_n] [_n_a_m_e[=_v_a_l_u_e] ... | - ] + For each argument, a local variable named _n_a_m_e is created, and + assigned _v_a_l_u_e. The _o_p_t_i_o_n can be any of the options accepted + by ddeeccllaarree. When llooccaall is used within a function, it causes the + variable _n_a_m_e to have a visible scope restricted to that func- + tion and its children. If _n_a_m_e is -, the set of shell options + is made local to the function in which llooccaall is invoked: shell + options changed using the sseett builtin inside the function are + restored to their original values when the function returns. + The restore is effected as if a series of sseett commands were exe- + cuted to restore the values that were in place before the func- + tion. With no operands, llooccaall writes a list of local variables + to the standard output. It is an error to use llooccaall when not + within a function. The return status is 0 unless llooccaall is used + outside a function, an invalid _n_a_m_e is supplied, or _n_a_m_e is a + readonly variable. + + llooggoouutt Exit a login shell. + + mmaappffiillee [--dd _d_e_l_i_m] [--nn _c_o_u_n_t] [--OO _o_r_i_g_i_n] [--ss _c_o_u_n_t] [--tt] [--uu _f_d] [--CC + _c_a_l_l_b_a_c_k] [--cc _q_u_a_n_t_u_m] [_a_r_r_a_y] + rreeaaddaarrrraayy [--dd _d_e_l_i_m] [--nn _c_o_u_n_t] [--OO _o_r_i_g_i_n] [--ss _c_o_u_n_t] [--tt] [--uu _f_d] [--CC + _c_a_l_l_b_a_c_k] [--cc _q_u_a_n_t_u_m] [_a_r_r_a_y] + Read lines from the standard input into the indexed array vari- + able _a_r_r_a_y, or from file descriptor _f_d if the --uu option is sup- + plied. The variable MMAAPPFFIILLEE is the default _a_r_r_a_y. Options, if + supplied, have the following meanings: + --dd The first character of _d_e_l_i_m is used to terminate each + input line, rather than newline. If _d_e_l_i_m is the empty + string, mmaappffiillee will terminate a line when it reads a NUL + character. + --nn Copy at most _c_o_u_n_t lines. If _c_o_u_n_t is 0, all lines are + copied. + --OO Begin assigning to _a_r_r_a_y at index _o_r_i_g_i_n. The default + index is 0. + --ss Discard the first _c_o_u_n_t lines read. + --tt Remove a trailing _d_e_l_i_m (default newline) from each line + read. + --uu Read lines from file descriptor _f_d instead of the stan- + dard input. + --CC Evaluate _c_a_l_l_b_a_c_k each time _q_u_a_n_t_u_m lines are read. The + --cc option specifies _q_u_a_n_t_u_m. + --cc Specify the number of lines read between each call to + _c_a_l_l_b_a_c_k. + + If --CC is specified without --cc, the default quantum is 5000. + When _c_a_l_l_b_a_c_k 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. _c_a_l_l_b_a_c_k is evaluated after + the line is read but before the array element is assigned. + + If not supplied with an explicit origin, mmaappffiillee will clear _a_r_- + _r_a_y before assigning to it. + + mmaappffiillee returns successfully unless an invalid option or option + argument is supplied, _a_r_r_a_y is invalid or unassignable, or if + _a_r_r_a_y is not an indexed array. + + ppooppdd [-nn] [+_n] [-_n] + Removes entries from the directory stack. The elements are num- + bered from 0 starting at the first directory listed by ddiirrss. + With no arguments, ppooppdd removes the top directory from the + stack, and changes to the new top directory. Arguments, if sup- + plied, have the following meanings: + --nn Suppresses the normal change of directory when removing + directories from the stack, so that only the stack is ma- + nipulated. + ++_n Removes the _nth entry counting from the left of the list + shown by ddiirrss, starting with zero, from the stack. For + example: ``popd +0'' removes the first directory, ``popd + +1'' the second. + --_n Removes the _nth entry counting from the right of the list + shown by ddiirrss, starting with zero. For example: ``popd + -0'' removes the last directory, ``popd -1'' the next to + last. + + If the top element of the directory stack is modified, and the + _-_n option was not supplied, ppooppdd uses the ccdd builtin to change + to the directory at the top of the stack. If the ccdd fails, ppooppdd + returns a non-zero value. + + Otherwise, ppooppdd returns false if an invalid option is encoun- + tered, the directory stack is empty, or a non-existent directory + stack entry is specified. + + If the ppooppdd command is successful, bash runs ddiirrss to show the + final contents of the directory stack, and the return status is + 0. + + pprriinnttff [--vv _v_a_r] _f_o_r_m_a_t [_a_r_g_u_m_e_n_t_s] + Write the formatted _a_r_g_u_m_e_n_t_s to the standard output under the + control of the _f_o_r_m_a_t. The --vv option causes the output to be + assigned to the variable _v_a_r rather than being printed to the + standard output. + + The _f_o_r_m_a_t 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 _a_r_g_u_m_e_n_t. In + addition to the standard _p_r_i_n_t_f(1) format specifications, pprriinnttff + interprets the following extensions: + %%bb causes pprriinnttff to expand backslash escape sequences in the + corresponding _a_r_g_u_m_e_n_t in the same way as eecchhoo --ee. + %%qq causes pprriinnttff to output the corresponding _a_r_g_u_m_e_n_t in a + format that can be reused as shell input. + %%QQ like %%qq, but applies any supplied precision to the _a_r_g_u_- + _m_e_n_t before quoting it. + %%((_d_a_t_e_f_m_t))TT + causes pprriinnttff to output the date-time string resulting + from using _d_a_t_e_f_m_t as a format string for _s_t_r_f_t_i_m_e(3). + The corresponding _a_r_g_u_m_e_n_t 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 ar- + gument is specified, conversion behaves as if -1 had been + given. This is an exception to the usual pprriinnttff behav- + ior. + + The %b, %q, and %T directives all use the field width and preci- + sion 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. + + Arguments to non-string format specifiers are treated as C con- + stants, 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. + + The _f_o_r_m_a_t is reused as necessary to consume all of the _a_r_g_u_- + _m_e_n_t_s. If the _f_o_r_m_a_t requires more _a_r_g_u_m_e_n_t_s 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. + + ppuusshhdd [--nn] [+_n] [-_n] + ppuusshhdd [--nn] [_d_i_r] + 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, ppuusshhdd exchanges the top two ele- + ments of the directory stack. Arguments, if supplied, have the + following meanings: + --nn Suppresses the normal change of directory when rotating + or adding directories to the stack, so that only the + stack is manipulated. + ++_n Rotates the stack so that the _nth directory (counting + from the left of the list shown by ddiirrss, starting with + zero) is at the top. + --_n Rotates the stack so that the _nth directory (counting + from the right of the list shown by ddiirrss, starting with + zero) is at the top. + _d_i_r Adds _d_i_r to the directory stack at the top + + After the stack has been modified, if the --nn option was not sup- + plied, ppuusshhdd uses the ccdd builtin to change to the directory at + the top of the stack. If the ccdd fails, ppuusshhdd returns a non-zero + value. + + Otherwise, if no arguments are supplied, ppuusshhdd returns 0 unless + the directory stack is empty. When rotating the directory + stack, ppuusshhdd returns 0 unless the directory stack is empty or a + non-existent directory stack element is specified. + + If the ppuusshhdd command is successful, bash runs ddiirrss to show the + final contents of the directory stack. + + ppwwdd [--LLPP] + Print the absolute pathname of the current working directory. + The pathname printed contains no symbolic links if the --PP option + is supplied or the --oo pphhyyssiiccaall option to the sseett builtin command + is enabled. If the --LL 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 in- + valid option is supplied. + + rreeaadd [--eerrss] [--aa _a_n_a_m_e] [--dd _d_e_l_i_m] [--ii _t_e_x_t] [--nn _n_c_h_a_r_s] [--NN _n_c_h_a_r_s] [--pp + _p_r_o_m_p_t] [--tt _t_i_m_e_o_u_t] [--uu _f_d] [_n_a_m_e ...] + One line is read from the standard input, or from the file de- + scriptor _f_d supplied as an argument to the --uu option, split into + words as described above under WWoorrdd SSpplliittttiinngg, and the first + word is assigned to the first _n_a_m_e, the second word to the sec- + ond _n_a_m_e, and so on. If there are more words than names, the + remaining words and their intervening delimiters are assigned to + the last _n_a_m_e. If there are fewer words read from the input + stream than names, the remaining names are assigned empty val- + ues. The characters in IIFFSS are used to split the line into + words using the same rules the shell uses for expansion (de- + scribed above under WWoorrdd SSpplliittttiinngg). The backslash character + (\\) may be used to remove any special meaning for the next char- + acter read and for line continuation. Options, if supplied, + have the following meanings: + --aa _a_n_a_m_e + The words are assigned to sequential indices of the array + variable _a_n_a_m_e, starting at 0. _a_n_a_m_e is unset before any + new values are assigned. Other _n_a_m_e arguments are ig- + nored. + --dd _d_e_l_i_m + The first character of _d_e_l_i_m is used to terminate the in- + put line, rather than newline. If _d_e_l_i_m is the empty + string, rreeaadd will terminate a line when it reads a NUL + character. + --ee If the standard input is coming from a terminal, rreeaaddlliinnee + (see RREEAADDLLIINNEE above) is used to obtain the line. Read- + line uses the current (or default, if line editing was + not previously active) editing settings, but uses read- + line's default filename completion. + --ii _t_e_x_t + If rreeaaddlliinnee is being used to read the line, _t_e_x_t is + placed into the editing buffer before editing begins. + --nn _n_c_h_a_r_s + rreeaadd returns after reading _n_c_h_a_r_s characters rather than + waiting for a complete line of input, but honors a delim- + iter if fewer than _n_c_h_a_r_s characters are read before the + delimiter. + --NN _n_c_h_a_r_s + rreeaadd returns after reading exactly _n_c_h_a_r_s characters + rather than waiting for a complete line of input, unless + EOF is encountered or rreeaadd times out. Delimiter charac- + ters encountered in the input are not treated specially + and do not cause rreeaadd to return until _n_c_h_a_r_s characters + are read. The result is not split on the characters in + IIFFSS; the intent is that the variable is assigned exactly + the characters read (with the exception of backslash; see + the --rr option below). + --pp _p_r_o_m_p_t + Display _p_r_o_m_p_t on standard error, without a trailing new- + line, before attempting to read any input. The prompt is + displayed only if input is coming from a terminal. + --rr Backslash does not act as an escape character. The back- + slash is considered to be part of the line. In particu- + lar, a backslash-newline pair may not then be used as a + line continuation. + --ss Silent mode. If input is coming from a terminal, charac- + ters are not echoed. + --tt _t_i_m_e_o_u_t + Cause rreeaadd to time out and return failure if a complete + line of input (or a specified number of characters) is + not read within _t_i_m_e_o_u_t seconds. _t_i_m_e_o_u_t may be a deci- + mal number with a fractional portion following the deci- + mal point. This option is only effective if rreeaadd is + reading input from a terminal, pipe, or other special + file; it has no effect when reading from regular files. + If rreeaadd times out, rreeaadd saves any partial input read into + the specified variable _n_a_m_e. If _t_i_m_e_o_u_t is 0, rreeaadd re- + turns 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. + --uu _f_d Read input from file descriptor _f_d. + + If no _n_a_m_e_s are supplied, the line read, without the ending de- + limiter but otherwise unmodified, is assigned to the variable + RREEPPLLYY. The exit status is zero, unless end-of-file is encoun- + tered, rreeaadd times out (in which case the status is greater than + 128), a variable assignment error (such as assigning to a read- + only variable) occurs, or an invalid file descriptor is supplied + as the argument to --uu. + + rreeaaddoonnllyy [--aaAAff] [--pp] [_n_a_m_e[=_w_o_r_d] ...] + The given _n_a_m_e_s are marked readonly; the values of these _n_a_m_e_s + may not be changed by subsequent assignment. If the --ff option + is supplied, the functions corresponding to the _n_a_m_e_s are so + marked. The --aa option restricts the variables to indexed ar- + rays; the --AA option restricts the variables to associative ar- + rays. If both options are supplied, --AA takes precedence. If no + _n_a_m_e arguments are given, or if the --pp 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 --pp option causes output to be displayed in a format + that may be reused as input. If a variable name is followed by + =_w_o_r_d, the value of the variable is set to _w_o_r_d. The return + status is 0 unless an invalid option is encountered, one of the + _n_a_m_e_s is not a valid shell variable name, or --ff is supplied with + a _n_a_m_e that is not a function. + + rreettuurrnn [_n] + Causes a function to stop executing and return the value speci- + fied by _n to its caller. If _n is omitted, the return status is + that of the last command executed in the function body. If rree-- + ttuurrnn is executed by a trap handler, the last command used to de- + termine the status is the last command executed before the trap + handler. If rreettuurrnn is executed during a DDEEBBUUGG trap, the last + command used to determine the status is the last command exe- + cuted by the trap handler before rreettuurrnn was invoked. If rreettuurrnn + is used outside a function, but during execution of a script by + the .. (ssoouurrccee) command, it causes the shell to stop executing + that script and return either _n or the exit status of the last + command executed within the script as the exit status of the + script. If _n is supplied, the return value is its least signif- + icant 8 bits. The return status is non-zero if rreettuurrnn is sup- + plied a non-numeric argument, or is used outside a function and + not during execution of a script by .. or ssoouurrccee. Any command + associated with the RREETTUURRNN trap is executed before execution re- + sumes after the function or script. + + sseett [--aabbeeffhhkkmmnnppttuuvvxxBBCCEEHHPPTT] [--oo _o_p_t_i_o_n_-_n_a_m_e] [----] [--] [_a_r_g ...] + sseett [++aabbeeffhhkkmmnnppttuuvvxxBBCCEEHHPPTT] [++oo _o_p_t_i_o_n_-_n_a_m_e] [----] [--] [_a_r_g ...] + Without options, display the name and value of each shell vari- + able in a format that can be reused as input for setting or re- + setting the currently-set variables. Read-only variables cannot + be reset. In _p_o_s_i_x _m_o_d_e, 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 argu- + ments remaining after option processing are treated as values + for the positional parameters and are assigned, in order, to $$11, + $$22, ...... $$_n. Options, if specified, have the following mean- + ings: + --aa Each variable or function that is created or modified is + given the export attribute and marked for export to the + environment of subsequent commands. + --bb Report the status of terminated background jobs immedi- + ately, rather than before the next primary prompt. This + is effective only when job control is enabled. + --ee Exit immediately if a _p_i_p_e_l_i_n_e (which may consist of a + single _s_i_m_p_l_e _c_o_m_m_a_n_d), a _l_i_s_t, or a _c_o_m_p_o_u_n_d _c_o_m_m_a_n_d + (see SSHHEELLLL GGRRAAMMMMAARR 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 wwhhiillee + or uunnttiill keyword, part of the test following the iiff or + eelliiff reserved words, part of any command executed in a + &&&& or |||| list except the command following the final &&&& + or ||||, any command in a pipeline but the last, or if the + command's return value is being inverted with !!. If a + compound command other than a subshell returns a non- + zero status because a command failed while --ee was being + ignored, the shell does not exit. A trap on EERRRR, if + set, is executed before the shell exits. This option + applies to the shell environment and each subshell envi- + ronment separately (see CCOOMMMMAANNDD EEXXEECCUUTTIIOONN EENNVVIIRROONNMMEENNTT + above), and may cause subshells to exit before executing + all the commands in the subshell. + + If a compound command or shell function executes in a + context where --ee is being ignored, none of the commands + executed within the compound command or function body + will be affected by the --ee setting, even if --ee is set + and a command returns a failure status. If a compound + command or shell function sets --ee while executing in a + context where --ee is ignored, that setting will not have + any effect until the compound command or the command + containing the function call completes. + --ff Disable pathname expansion. + --hh Remember the location of commands as they are looked up + for execution. This is enabled by default. + --kk All arguments in the form of assignment statements are + placed in the environment for a command, not just those + that precede the command name. + --mm Monitor mode. Job control is enabled. This option is + on by default for interactive shells on systems that + support it (see JJOOBB CCOONNTTRROOLL above). All processes run + in a separate process group. When a background job com- + pletes, the shell prints a line containing its exit sta- + tus. + --nn Read commands but do not execute them. This may be used + to check a shell script for syntax errors. This is ig- + nored by interactive shells. + --oo _o_p_t_i_o_n_-_n_a_m_e + The _o_p_t_i_o_n_-_n_a_m_e can be one of the following: + aalllleexxppoorrtt + Same as --aa. + bbrraacceeeexxppaanndd + Same as --BB. + eemmaaccss Use an emacs-style command line editing inter- + face. This is enabled by default when the shell + is interactive, unless the shell is started with + the ----nnooeeddiittiinngg option. This also affects the + editing interface used for rreeaadd --ee. + eerrrreexxiitt Same as --ee. + eerrrrttrraaccee + Same as --EE. + ffuunnccttrraaccee + Same as --TT. + hhaasshhaallll Same as --hh. + hhiisstteexxppaanndd + Same as --HH. + hhiissttoorryy Enable command history, as described above under + HHIISSTTOORRYY. This option is on by default in inter- + active shells. + iiggnnoorreeeeooff + The effect is as if the shell command ``IG- + NOREEOF=10'' had been executed (see SShheellll VVaarrii-- + aabblleess above). + kkeeyywwoorrdd Same as --kk. + mmoonniittoorr Same as --mm. + nnoocclloobbbbeerr + Same as --CC. + nnooeexxeecc Same as --nn. + nnoogglloobb Same as --ff. + nnoolloogg Currently ignored. + nnoottiiffyy Same as --bb. + nnoouunnsseett Same as --uu. + oonneeccmmdd Same as --tt. + pphhyyssiiccaall + Same as --PP. + ppiippeeffaaiill + 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. + ppoossiixx Change the behavior of bbaasshh where the default + operation differs from the POSIX standard to + match the standard (_p_o_s_i_x _m_o_d_e). See SSEEEE AALLSSOO + below for a reference to a document that details + how posix mode affects bash's behavior. + pprriivviilleeggeedd + Same as --pp. + vveerrbboossee Same as --vv. + vvii Use a vi-style command line editing interface. + This also affects the editing interface used for + rreeaadd --ee. + xxttrraaccee Same as --xx. + If --oo is supplied with no _o_p_t_i_o_n_-_n_a_m_e, the values of the + current options are printed. If ++oo is supplied with no + _o_p_t_i_o_n_-_n_a_m_e, a series of sseett commands to recreate the + current option settings is displayed on the standard + output. + --pp Turn on _p_r_i_v_i_l_e_g_e_d mode. In this mode, the $$EENNVV and + $$BBAASSHH__EENNVV files are not processed, shell functions are + not inherited from the environment, and the SSHHEELLLLOOPPTTSS, + BBAASSHHOOPPTTSS, CCDDPPAATTHH, and GGLLOOBBIIGGNNOORREE variables, if they ap- + pear 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 --pp option is not sup- + plied, these actions are taken and the effective user id + is set to the real user id. If the --pp option is sup- + plied 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. + --rr Enable restricted shell mode. This option cannot be un- + set once it has been set. + --tt Exit after reading and executing one command. + --uu Treat unset variables and parameters other than the spe- + cial parameters "@" and "*", or array variables sub- + scripted 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. + --vv Print shell input lines as they are read. + --xx After expanding each _s_i_m_p_l_e _c_o_m_m_a_n_d, ffoorr command, ccaassee + command, sseelleecctt command, or arithmetic ffoorr command, dis- + play the expanded value of PPSS44, followed by the command + and its expanded arguments or associated word list. + --BB The shell performs brace expansion (see BBrraaccee EExxppaannssiioonn + above). This is on by default. + --CC If set, bbaasshh does not overwrite an existing file with + the >>, >>&&, and <<>> redirection operators. This may be + overridden when creating output files by using the redi- + rection operator >>|| instead of >>. + --EE If set, any trap on EERRRR is inherited by shell functions, + command substitutions, and commands executed in a sub- + shell environment. The EERRRR trap is normally not inher- + ited in such cases. + --HH Enable !! style history substitution. This option is on + by default when the shell is interactive. + --PP If set, the shell does not resolve symbolic links when + executing commands such as ccdd that change the current + working directory. It uses the physical directory + structure instead. By default, bbaasshh follows the logical + chain of directories when performing commands which + change the current directory. + --TT If set, any traps on DDEEBBUUGG and RREETTUURRNN are inherited by + shell functions, command substitutions, and commands ex- + ecuted in a subshell environment. The DDEEBBUUGG and RREETTUURRNN + traps are normally not inherited in such cases. + ---- If no arguments follow this option, then the positional + parameters are unset. Otherwise, the positional parame- + ters are set to the _a_r_gs, even if some of them begin + with a --. + -- Signal the end of options, cause all remaining _a_r_gs to + be assigned to the positional parameters. The --xx and --vv + options are turned off. If there are no _a_r_gs, the posi- + tional parameters remain unchanged. + + The options are off by default unless otherwise noted. Using + + rather than - causes these options to be turned off. The op- + tions can also be specified as arguments to an invocation of the + shell. The current set of options may be found in $$--. The re- + turn status is always true unless an invalid option is encoun- + tered. + + sshhiifftt [_n] + The positional parameters from _n+1 ... are renamed to $$11 ........ + Parameters represented by the numbers $$## down to $$##-_n+1 are un- + set. _n must be a non-negative number less than or equal to $$##. + If _n is 0, no parameters are changed. If _n is not given, it is + assumed to be 1. If _n is greater than $$##, the positional param- + eters are not changed. The return status is greater than zero + if _n is greater than $$## or less than zero; otherwise 0. + + sshhoopptt [--ppqqssuu] [--oo] [_o_p_t_n_a_m_e ...] + Toggle the values of settings controlling optional shell behav- + ior. The settings can be either those listed below, or, if the + --oo option is used, those available with the --oo option to the sseett + builtin command. With no options, or with the --pp option, a list + of all settable options is displayed, with an indication of + whether or not each is set; if _o_p_t_n_a_m_e_s are supplied, the output + is restricted to those options. The --pp option causes output to + be displayed in a form that may be reused as input. Other op- + tions have the following meanings: + --ss Enable (set) each _o_p_t_n_a_m_e. + --uu Disable (unset) each _o_p_t_n_a_m_e. + --qq Suppresses normal output (quiet mode); the return status + indicates whether the _o_p_t_n_a_m_e is set or unset. If multi- + ple _o_p_t_n_a_m_e arguments are given with --qq, the return sta- + tus is zero if all _o_p_t_n_a_m_e_s are enabled; non-zero other- + wise. + --oo Restricts the values of _o_p_t_n_a_m_e to be those defined for + the --oo option to the sseett builtin. + + If either --ss or --uu is used with no _o_p_t_n_a_m_e arguments, sshhoopptt + shows only those options which are set or unset, respectively. + Unless otherwise noted, the sshhoopptt options are disabled (unset) + by default. + + The return status when listing options is zero if all _o_p_t_n_a_m_e_s + are enabled, non-zero otherwise. When setting or unsetting op- + tions, the return status is zero unless an _o_p_t_n_a_m_e is not a + valid shell option. + + The list of sshhoopptt options is: + + aassssoocc__eexxppaanndd__oonnccee + If set, the shell suppresses multiple evaluation of as- + sociative array subscripts during arithmetic expression + evaluation, while executing builtins that can perform + variable assignments, and while executing builtins that + perform array dereferencing. + aauuttooccdd If set, a command name that is the name of a directory + is executed as if it were the argument to the ccdd com- + mand. This option is only used by interactive shells. + ccddaabbllee__vvaarrss + If set, an argument to the ccdd builtin command that is + not a directory is assumed to be the name of a variable + whose value is the directory to change to. + ccddssppeellll If set, minor errors in the spelling of a directory com- + ponent in a ccdd command will be corrected. The errors + checked for are transposed characters, a missing charac- + ter, and one character too many. If a correction is + found, the corrected filename is printed, and the com- + mand proceeds. This option is only used by interactive + shells. + cchheecckkhhaasshh + If set, bbaasshh checks that a command found in the hash ta- + ble exists before trying to execute it. If a hashed + command no longer exists, a normal path search is per- + formed. + cchheecckkjjoobbss + If set, bbaasshh 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 JJOOBB CCOONNTTRROOLL above). The shell always postpones ex- + iting if any jobs are stopped. + cchheecckkwwiinnssiizzee + If set, bbaasshh checks the window size after each external + (non-builtin) command and, if necessary, updates the + values of LLIINNEESS and CCOOLLUUMMNNSS. This option is enabled by + default. + ccmmddhhiisstt If set, bbaasshh 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 above under HHIISSTTOORRYY. + ccoommppaatt3311 + ccoommppaatt3322 + ccoommppaatt4400 + ccoommppaatt4411 + ccoommppaatt4422 + ccoommppaatt4433 + ccoommppaatt4444 + ccoommppaatt5500 + These control aspects of the shell's compatibility mode + (see SSHHEELLLL CCOOMMPPAATTIIBBIILLIITTYY MMOODDEE below). + + ccoommpplleettee__ffuullllqquuoottee + If set, bbaasshh quotes all shell metacharacters in file- + names and directory names when performing completion. + If not set, bbaasshh removes metacharacters such as the dol- + lar 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 ex- + pand 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 back- + slashes to quote completed filenames. This variable is + set by default, which is the default bash behavior in + versions through 4.2. + + ddiirreexxppaanndd + If set, bbaasshh replaces directory names with the results + of word expansion when performing filename completion. + This changes the contents of the readline editing buf- + fer. If not set, bbaasshh attempts to preserve what the + user typed. + + ddiirrssppeellll + If set, bbaasshh attempts spelling correction on directory + names during word completion if the directory name ini- + tially supplied does not exist. + + ddoottgglloobb If set, bbaasshh includes filenames beginning with a `.' in + the results of pathname expansion. The filenames ````..'''' + and ````....'''' must always be matched explicitly, even if + ddoottgglloobb is set. + + eexxeeccffaaiill + If set, a non-interactive shell will not exit if it can- + not execute the file specified as an argument to the + eexxeecc builtin command. An interactive shell does not + exit if eexxeecc fails. + + eexxppaanndd__aalliiaasseess + If set, aliases are expanded as described above under + AALLIIAASSEESS. This option is enabled by default for interac- + tive shells. + + eexxttddeebbuugg + If set at shell invocation, or in a shell startup file, + arrange to execute the debugger profile before the shell + starts, identical to the ----ddeebbuuggggeerr option. If set af- + ter invocation, behavior intended for use by debuggers + is enabled: + + 11.. The --FF option to the ddeeccllaarree builtin displays the + source file name and line number corresponding to + each function name supplied as an argument. + + 22.. If the command run by the DDEEBBUUGG trap returns a + non-zero value, the next command is skipped and + not executed. + + 33.. If the command run by the DDEEBBUUGG trap returns a + value of 2, and the shell is executing in a sub- + routine (a shell function or a shell script exe- + cuted by the .. or ssoouurrccee builtins), the shell + simulates a call to rreettuurrnn. + + 44.. BBAASSHH__AARRGGCC and BBAASSHH__AARRGGVV are updated as described + in their descriptions above). + + 55.. Function tracing is enabled: command substitu- + tion, shell functions, and subshells invoked with + (( _c_o_m_m_a_n_d )) inherit the DDEEBBUUGG and RREETTUURRNN traps. + + 66.. Error tracing is enabled: command substitution, + shell functions, and subshells invoked with (( + _c_o_m_m_a_n_d )) inherit the EERRRR trap. + + eexxttgglloobb If set, the extended pattern matching features described + above under PPaatthhnnaammee EExxppaannssiioonn are enabled. + + eexxttqquuoottee + If set, $$'_s_t_r_i_n_g' and $$"_s_t_r_i_n_g" quoting is performed + within $${{_p_a_r_a_m_e_t_e_r}} expansions enclosed in double + quotes. This option is enabled by default. + + ffaaiillgglloobb + If set, patterns which fail to match filenames during + pathname expansion result in an expansion error. + + ffoorrccee__ffiiggnnoorree + If set, the suffixes specified by the FFIIGGNNOORREE shell + variable cause words to be ignored when performing word + completion even if the ignored words are the only possi- + ble completions. See SSHHEELLLL VVAARRIIAABBLLEESS above for a de- + scription of FFIIGGNNOORREE. This option is enabled by de- + fault. + + gglloobbaasscciiiirraannggeess + If set, range expressions used in pattern matching + bracket expressions (see PPaatttteerrnn MMaattcchhiinngg above) behave + as if in the traditional C locale when performing com- + parisons. That is, the current locale's collating se- + quence is not taken into account, so bb will not collate + between AA and BB, and upper-case and lower-case ASCII + characters will collate together. + + gglloobbsskkiippddoottss + If set, pathname expansion will never match the file- + names ````..'''' and ````....'''', even if the pattern begins with + a ````..''''. This option is enabled by default. + + gglloobbssttaarr + If set, the pattern **** used in a pathname expansion con- + text will match all files and zero or more directories + and subdirectories. If the pattern is followed by a //, + only directories and subdirectories match. + + ggnnuu__eerrrrffmmtt + If set, shell error messages are written in the standard + GNU error message format. + + hhiissttaappppeenndd + If set, the history list is appended to the file named + by the value of the HHIISSTTFFIILLEE variable when the shell ex- + its, rather than overwriting the file. + + hhiissttrreeeeddiitt + If set, and rreeaaddlliinnee is being used, a user is given the + opportunity to re-edit a failed history substitution. + + hhiissttvveerriiffyy + If set, and rreeaaddlliinnee is being used, the results of his- + tory substitution are not immediately passed to the + shell parser. Instead, the resulting line is loaded + into the rreeaaddlliinnee editing buffer, allowing further modi- + fication. + + hhoossttccoommpplleettee + If set, and rreeaaddlliinnee is being used, bbaasshh will attempt to + perform hostname completion when a word containing a @@ + is being completed (see CCoommpplleettiinngg under RREEAADDLLIINNEE + above). This is enabled by default. + + hhuuppoonneexxiitt + If set, bbaasshh will send SSIIGGHHUUPP to all jobs when an inter- + active login shell exits. + + iinnhheerriitt__eerrrreexxiitt + If set, command substitution inherits the value of the + eerrrreexxiitt option, instead of unsetting it in the subshell + environment. This option is enabled when _p_o_s_i_x _m_o_d_e is + enabled. + + iinntteerraaccttiivvee__ccoommmmeennttss + If set, allow a word beginning with ## to cause that word + and all remaining characters on that line to be ignored + in an interactive shell (see CCOOMMMMEENNTTSS above). This op- + tion is enabled by default. + + llaassttppiippee + If set, and job control is not active, the shell runs + the last command of a pipeline not executed in the back- + ground in the current shell environment. + + lliitthhiisstt If set, and the ccmmddhhiisstt option is enabled, multi-line + commands are saved to the history with embedded newlines + rather than using semicolon separators where possible. + + llooccaallvvaarr__iinnhheerriitt + 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 at- + tribute is not inherited. + + llooccaallvvaarr__uunnsseett + If set, calling uunnsseett on local variables in previous + function scopes marks them so subsequent lookups find + them unset until that function returns. This is identi- + cal to the behavior of unsetting local variables at the + current function scope. + + llooggiinn__sshheellll + The shell sets this option if it is started as a login + shell (see IINNVVOOCCAATTIIOONN above). The value may not be + changed. + + mmaaiillwwaarrnn + If set, and a file that bbaasshh is checking for mail has + been accessed since the last time it was checked, the + message ``The mail in _m_a_i_l_f_i_l_e has been read'' is dis- + played. + + nnoo__eemmppttyy__ccmmdd__ccoommpplleettiioonn + If set, and rreeaaddlliinnee is being used, bbaasshh will not at- + tempt to search the PPAATTHH for possible completions when + completion is attempted on an empty line. + + nnooccaasseegglloobb + If set, bbaasshh matches filenames in a case-insensitive + fashion when performing pathname expansion (see PPaatthhnnaammee + EExxppaannssiioonn above). + + nnooccaasseemmaattcchh + If set, bbaasshh matches patterns in a case-insensitive + fashion when performing matching while executing ccaassee or + [[[[ conditional commands, when performing pattern substi- + tution word expansions, or when filtering possible com- + pletions as part of programmable completion. + + nnooeexxppaanndd__ttrraannssllaattiioonn + If set, bbaasshh encloses the translated results of $"..." + quoting in single quotes instead of double quotes. If + the string is not translated, this has no effect. + + nnuullllgglloobb + If set, bbaasshh allows patterns which match no files (see + PPaatthhnnaammee EExxppaannssiioonn above) to expand to a null string, + rather than themselves. + + ppaattssuubb__rreeppllaacceemmeenntt + If set, bbaasshh expands occurrences of && in the replacement + string of pattern substitution to the text matched by + the pattern, as described under PPaarraammeetteerr EExxppaannssiioonn + above. This option is enabled by default. + + pprrooggccoommpp + If set, the programmable completion facilities (see PPrroo-- + ggrraammmmaabbllee CCoommpplleettiioonn above) are enabled. This option is + enabled by default. + + pprrooggccoommpp__aalliiaass + If set, and programmable completion is enabled, bbaasshh + treats a command name that doesn't have any completions + as a possible alias and attempts alias expansion. If it + has an alias, bbaasshh attempts programmable completion us- + ing the command word resulting from the expanded alias. + + pprroommppttvvaarrss + If set, prompt strings undergo parameter expansion, com- + mand substitution, arithmetic expansion, and quote re- + moval after being expanded as described in PPRROOMMPPTTIINNGG + above. This option is enabled by default. + + rreessttrriicctteedd__sshheellll + The shell sets this option if it is started in re- + stricted mode (see RREESSTTRRIICCTTEEDD SSHHEELLLL below). The value + may not be changed. This is not reset when the startup + files are executed, allowing the startup files to dis- + cover whether or not a shell is restricted. + + sshhiifftt__vveerrbboossee + If set, the sshhiifftt builtin prints an error message when + the shift count exceeds the number of positional parame- + ters. + + ssoouurrcceeppaatthh + If set, the .. (ssoouurrccee) builtin uses the value of PPAATTHH to + find the directory containing the file supplied as an + argument. This option is enabled by default. + + vvaarrrreeddiirr__cclloossee + If set, the shell automatically closes file descriptors + assigned using the _{_v_a_r_n_a_m_e_} redirection syntax (see RREE-- + DDIIRREECCTTIIOONN above) instead of leaving them open when the + command completes. + + xxppgg__eecchhoo + If set, the eecchhoo builtin expands backslash-escape se- + quences by default. + + ssuussppeenndd [--ff] + Suspend the execution of this shell until it receives a SSIIGGCCOONNTT + signal. A login shell, or a shell without job control enabled, + cannot be suspended; the --ff 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 --ff is + not supplied. + + tteesstt _e_x_p_r + [[ _e_x_p_r ]] + Return a status of 0 (true) or 1 (false) depending on the evalu- + ation of the conditional expression _e_x_p_r. Each operator and op- + erand must be a separate argument. Expressions are composed of + the primaries described above under CCOONNDDIITTIIOONNAALL EEXXPPRREESSSSIIOONNSS. + tteesstt does not accept any options, nor does it accept and ignore + an argument of ---- as signifying the end of options. + + Expressions may be combined using the following operators, + listed in decreasing order of precedence. The evaluation de- + pends on the number of arguments; see below. Operator prece- + dence is used when there are five or more arguments. + !! _e_x_p_r True if _e_x_p_r is false. + (( _e_x_p_r )) + Returns the value of _e_x_p_r. This may be used to override + the normal precedence of operators. + _e_x_p_r_1 -aa _e_x_p_r_2 + True if both _e_x_p_r_1 and _e_x_p_r_2 are true. + _e_x_p_r_1 -oo _e_x_p_r_2 + True if either _e_x_p_r_1 or _e_x_p_r_2 is true. + + tteesstt and [[ evaluate conditional expressions using a set of rules + based on the number of arguments. + + 0 arguments + The expression is false. + 1 argument + The expression is true if and only if the argument is not + null. + 2 arguments + If the first argument is !!, the expression is true if and + only if the second argument is null. If the first argu- + ment is one of the unary conditional operators listed + above under CCOONNDDIITTIIOONNAALL EEXXPPRREESSSSIIOONNSS, 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. + 3 arguments + The following conditions are applied in the order listed. + If the second argument is one of the binary conditional + operators listed above under CCOONNDDIITTIIOONNAALL EEXXPPRREESSSSIIOONNSS, the + result of the expression is the result of the binary test + using the first and third arguments as operands. The --aa + and --oo operators are considered binary operators when + there are three arguments. If the first argument is !!, + the value is the negation of the two-argument test using + the second and third arguments. If the first argument is + exactly (( and the third argument is exactly )), the result + is the one-argument test of the second argument. Other- + wise, the expression is false. + 4 arguments + The following conditions are applied in the order listed. + If the first argument is !!, 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 (( and + the fourth argument is exactly )), the result is the two- + argument test of the second and third arguments. Other- + wise, the expression is parsed and evaluated according to + precedence using the rules listed above. + 5 or more arguments + The expression is parsed and evaluated according to + precedence using the rules listed above. + + When used with tteesstt or [[, the << and >> operators sort lexico- + graphically using ASCII ordering. + + ttiimmeess Print the accumulated user and system times for the shell and + for processes run from the shell. The return status is 0. + + ttrraapp [--llpp] [[_a_r_g] _s_i_g_s_p_e_c ...] + The command _a_r_g is to be read and executed when the shell re- + ceives signal(s) _s_i_g_s_p_e_c. If _a_r_g is absent (and there is a sin- + gle _s_i_g_s_p_e_c) or --, each specified signal is reset to its origi- + nal disposition (the value it had upon entrance to the shell). + If _a_r_g is the null string the signal specified by each _s_i_g_s_p_e_c + is ignored by the shell and by the commands it invokes. If _a_r_g + is not present and --pp has been supplied, then the trap commands + associated with each _s_i_g_s_p_e_c are displayed. If no arguments are + supplied or if only --pp is given, ttrraapp prints the list of com- + mands associated with each signal. The --ll option causes the + shell to print a list of signal names and their corresponding + numbers. Each _s_i_g_s_p_e_c is either a signal name defined in <_s_i_g_- + _n_a_l_._h>, or a signal number. Signal names are case insensitive + and the SSIIGG prefix is optional. + + If a _s_i_g_s_p_e_c is EEXXIITT (0) the command _a_r_g is executed on exit + from the shell. If a _s_i_g_s_p_e_c is DDEEBBUUGG, the command _a_r_g is exe- + cuted before every _s_i_m_p_l_e _c_o_m_m_a_n_d, _f_o_r command, _c_a_s_e command, + _s_e_l_e_c_t command, every arithmetic _f_o_r command, and before the + first command executes in a shell function (see SSHHEELLLL GGRRAAMMMMAARR + above). Refer to the description of the eexxttddeebbuugg option to the + sshhoopptt builtin for details of its effect on the DDEEBBUUGG trap. If a + _s_i_g_s_p_e_c is RREETTUURRNN, the command _a_r_g is executed each time a shell + function or a script executed with the .. or ssoouurrccee builtins fin- + ishes executing. + + If a _s_i_g_s_p_e_c is EERRRR, the command _a_r_g 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 EERRRR trap is not executed if the + failed command is part of the command list immediately following + a wwhhiillee or uunnttiill keyword, part of the test in an _i_f statement, + part of a command executed in a &&&& or |||| list except the command + following the final &&&& or ||||, any command in a pipeline but the + last, or if the command's return value is being inverted using + !!. These are the same conditions obeyed by the eerrrreexxiitt (--ee) op- + tion. + + Signals ignored upon entry to the shell cannot be trapped or re- + set. 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 _s_i_g_s_p_e_c is + invalid; otherwise ttrraapp returns true. + + ttyyppee [--aaffttppPP] _n_a_m_e [_n_a_m_e ...] + With no options, indicate how each _n_a_m_e would be interpreted if + used as a command name. If the --tt option is used, ttyyppee prints a + string which is one of _a_l_i_a_s, _k_e_y_w_o_r_d, _f_u_n_c_t_i_o_n, _b_u_i_l_t_i_n, or + _f_i_l_e if _n_a_m_e is an alias, shell reserved word, function, + builtin, or disk file, respectively. If the _n_a_m_e is not found, + then nothing is printed, and an exit status of false is re- + turned. If the --pp option is used, ttyyppee either returns the name + of the disk file that would be executed if _n_a_m_e were specified + as a command name, or nothing if ``type -t name'' would not re- + turn _f_i_l_e. The --PP option forces a PPAATTHH search for each _n_a_m_e, + even if ``type -t name'' would not return _f_i_l_e. If a command is + hashed, --pp and --PP print the hashed value, which is not necessar- + ily the file that appears first in PPAATTHH. If the --aa option is + used, ttyyppee prints all of the places that contain an executable + named _n_a_m_e. This includes aliases and functions, if and only if + the --pp option is not also used. The table of hashed commands is + not consulted when using --aa. The --ff option suppresses shell + function lookup, as with the ccoommmmaanndd builtin. ttyyppee returns true + if all of the arguments are found, false if any are not found. + + uulliimmiitt [--HHSS] --aa + uulliimmiitt [--HHSS] [--bbccddeeffiikkllmmnnppqqrrssttuuvvxxPPRRTT [_l_i_m_i_t]] + Provides control over the resources available to the shell and + to processes started by it, on systems that allow such control. + The --HH and --SS 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 --HH nor --SS is speci- + fied, both the soft and hard limits are set. The value of _l_i_m_i_t + can be a number in the unit specified for the resource or one of + the special values hhaarrdd, ssoofftt, or uunnlliimmiitteedd, which stand for the + current hard limit, the current soft limit, and no limit, re- + spectively. If _l_i_m_i_t is omitted, the current value of the soft + limit of the resource is printed, unless the --HH option is given. + When more than one resource is specified, the limit name and + unit, if appropriate, are printed before the value. Other op- + tions are interpreted as follows: + --aa All current limits are reported; no limits are set + --bb The maximum socket buffer size + --cc The maximum size of core files created + --dd The maximum size of a process's data segment + --ee The maximum scheduling priority ("nice") + --ff The maximum size of files written by the shell and its + children + --ii The maximum number of pending signals + --kk The maximum number of kqueues that may be allocated + --ll The maximum size that may be locked into memory + --mm The maximum resident set size (many systems do not honor + this limit) + --nn The maximum number of open file descriptors (most systems + do not allow this value to be set) + --pp The pipe size in 512-byte blocks (this may not be set) + --qq The maximum number of bytes in POSIX message queues + --rr The maximum real-time scheduling priority + --ss The maximum stack size + --tt The maximum amount of cpu time in seconds + --uu The maximum number of processes available to a single + user + --vv The maximum amount of virtual memory available to the + shell and, on some systems, to its children + --xx The maximum number of file locks + --PP The maximum number of pseudoterminals + --RR The maximum time a real-time process can run before + blocking, in microseconds + --TT The maximum number of threads + + If _l_i_m_i_t is given, and the --aa option is not used, _l_i_m_i_t is the + new value of the specified resource. If no option is given, + then --ff is assumed. Values are in 1024-byte increments, except + for --tt, which is in seconds; --RR, which is in microseconds; --pp, + which is in units of 512-byte blocks; --PP, --TT, --bb, --kk, --nn, and + --uu, which are unscaled values; and, when in posix mode, --cc and + --ff, 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. + + uummaasskk [--pp] [--SS] [_m_o_d_e] + The user file-creation mask is set to _m_o_d_e. If _m_o_d_e 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 + _c_h_m_o_d(1). If _m_o_d_e is omitted, the current value of the mask is + printed. The --SS option causes the mask to be printed in sym- + bolic form; the default output is an octal number. If the --pp + option is supplied, and _m_o_d_e 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 _m_o_d_e argument was supplied, + and false otherwise. + + uunnaalliiaass [-aa] [_n_a_m_e ...] + Remove each _n_a_m_e from the list of defined aliases. If --aa is + supplied, all alias definitions are removed. The return value + is true unless a supplied _n_a_m_e is not a defined alias. + + uunnsseett [-ffvv] [-nn] [_n_a_m_e ...] + For each _n_a_m_e, remove the corresponding variable or function. + If the --vv option is given, each _n_a_m_e refers to a shell variable, + and that variable is removed. Read-only variables may not be + unset. If --ff is specified, each _n_a_m_e refers to a shell func- + tion, and the function definition is removed. If the --nn option + is supplied, and _n_a_m_e is a variable with the _n_a_m_e_r_e_f attribute, + _n_a_m_e will be unset rather than the variable it references. --nn + has no effect if the --ff option is supplied. If no options are + supplied, each _n_a_m_e refers to a variable; if there is no vari- + able 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 BBAASSHH__AALLIIAASSEESS, + BBAASSHH__AARRGGVV00, BBAASSHH__CCMMDDSS, BBAASSHH__CCOOMMMMAANNDD, BBAASSHH__SSUUBBSSHHEELLLL, BBAASSHHPPIIDD, + CCOOMMPP__WWOORRDDBBRREEAAKKSS, DDIIRRSSTTAACCKK, EEPPOOCCHHRREEAALLTTIIMMEE, EEPPOOCCHHSSEECCOONNDDSS, FFUUNNCC-- + NNAAMMEE, GGRROOUUPPSS, HHIISSTTCCMMDD, LLIINNEENNOO, RRAANNDDOOMM, SSEECCOONNDDSS, or SSRRAANNDDOOMM are + unset, they lose their special properties, even if they are sub- + sequently reset. The exit status is true unless a _n_a_m_e is read- + only or may not be unset. + + wwaaiitt [--ffnn] [--pp _v_a_r_n_a_m_e] [_i_d _._._.] + Wait for each specified child process and return its termination + status. Each _i_d 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_d is not given, wwaaiitt waits for all running + background jobs and the last-executed process substitution, if + its process id is the same as $$!!, and the return status is zero. + If the --nn option is supplied, wwaaiitt waits for a single job from + the list of _i_ds or, if no _i_ds 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 --pp option is supplied, the process or job identifier of the + job for which the exit status is returned is assigned to the + variable _v_a_r_n_a_m_e named by the option argument. The variable + will be unset initially, before any assignment. This is useful + only when the --nn option is supplied. Supplying the --ff option, + when job control is enabled, forces wwaaiitt to wait for _i_d to ter- + minate before returning its status, instead of returning when it + changes status. If _i_d specifies a non-existent process or job, + the return status is 127. If wwaaiitt is interrupted by a signal, + the return status will be greater than 128, as described under + SSIIGGNNAALLSS above. Otherwise, the return status is the exit status + of the last process or job waited for. + +SSHHEELLLL CCOOMMPPAATTIIBBIILLIITTYY MMOODDEE + Bash-4.0 introduced the concept of a _s_h_e_l_l _c_o_m_p_a_t_i_b_i_l_i_t_y _l_e_v_e_l, speci- + fied as a set of options to the shopt builtin ( ccoommppaatt3311, ccoommppaatt3322, + ccoommppaatt4400, ccoommppaatt4411, and so on). There is only one current compatibil- + ity level -- each option is mutually exclusive. The compatibility + level is intended to allow users to select behavior from previous ver- + sions that is incompatible with newer versions while they migrate + scripts to use current features and behavior. It's intended to be a + temporary solution. + + This section does not mention behavior that is standard for a particu- + lar version (e.g., setting ccoommppaatt3322 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). + + If a user enables, say, ccoommppaatt3322, 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 bbaasshh, but that behavior may have been + present in earlier versions. For instance, the change to use locale- + based comparisons with the [[[[ command came in bash-4.1, and earlier + versions used ASCII-based comparisons, so enabling ccoommppaatt3322 will enable + ASCII-based comparisons as well. That granularity may not be suffi- + cient 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. + + Bash-4.3 introduced a new shell variable: BBAASSHH__CCOOMMPPAATT. The value as- + signed to this variable (a decimal version number like 4.2, or an inte- + ger corresponding to the ccoommppaatt_N_N option, like 42) determines the com- + patibility level. + + Starting with bash-4.4, Bash has begun deprecating older compatibility + levels. Eventually, the options will be removed in favor of BBAASSHH__CCOOMM-- + PPAATT. + + Bash-5.0 is the final version for which there will be an individual + shopt option for the previous version. Users should use BBAASSHH__CCOOMMPPAATT on + bash-5.0 and later versions. + + The following table describes the behavior changes controlled by each + compatibility level setting. The ccoommppaatt_N_N tag is used as shorthand for + setting the compatibility level to _N_N using one of the following mecha- + nisms. For versions prior to bash-5.0, the compatibility level may be + set using the corresponding ccoommppaatt_N_N shopt option. For bash-4.3 and + later versions, the BBAASSHH__CCOOMMPPAATT variable is preferred, and it is re- + quired for bash-5.1 and later versions. + + ccoommppaatt3311 + +o quoting the rhs of the [[[[ command's regexp matching oper- + ator (=~) has no special effect + + ccoommppaatt3322 + +o 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 re- + ceived the interrupt, so interrupting one command in a + list aborts the execution of the entire list) + + ccoommppaatt4400 + +o the << and >> operators to the [[[[ command do not consider + the current locale when comparing strings; they use ASCII + ordering. Bash versions prior to bash-4.1 use ASCII col- + lation and _s_t_r_c_m_p(3); bash-4.1 and later use the current + locale's collation sequence and _s_t_r_c_o_l_l(3). + + ccoommppaatt4411 + +o in _p_o_s_i_x mode, ttiimmee may be followed by options and still + be recognized as a reserved word (this is POSIX interpre- + tation 267) + +o in _p_o_s_i_x mode, the parser requires that an even number of + single quotes occur in the _w_o_r_d 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) + + ccoommppaatt4422 + +o the replacement string in double-quoted pattern substitu- + tion does not undergo quote removal, as it does in ver- + sions after bash-4.2 + +o in posix mode, single quotes are considered special when + expanding the _w_o_r_d 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 interpre- + tation 221); in later versions, single quotes are not + special within double-quoted word expansions + + ccoommppaatt4433 + +o the shell does not print a warning message if an attempt + is made to use a quoted compound assignment as an argu- + ment to declare (e.g., declare -a foo='(1 2)'). Later + versions warn that this usage is deprecated + +o 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) + +o when executing a shell function, the loop state + (while/until/etc.) is not reset, so bbrreeaakk or ccoonnttiinnuuee in + that function will break or continue loops in the calling + context. Bash-4.4 and later reset the loop state to pre- + vent this + + ccoommppaatt4444 + +o the shell sets up the values used by BBAASSHH__AARRGGVV and + BBAASSHH__AARRGGCC so they can expand to the shell's positional + parameters even if extended debugging mode is not enabled + +o a subshell inherits loops from its parent context, so + bbrreeaakk or ccoonnttiinnuuee will cause the subshell to exit. + Bash-5.0 and later reset the loop state to prevent the + exit + +o variable assignments preceding builtins like eexxppoorrtt and + rreeaaddoonnllyy that set attributes continue to affect variables + with the same name in the calling environment even if the + shell is not in posix mode + + ccoommppaatt5500 + +o Bash-5.1 changed the way $$RRAANNDDOOMM is generated to intro- + duce 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 ran- + dom number generator by assigning a value to RRAANNDDOOMM will + produce the same sequence as in bash-5.0 + +o If the command hash table is empty, bash versions prior + to bash-5.1 printed an informational message to that ef- + fect, even when producing output that can be reused as + input. Bash-5.1 suppresses that message when the --ll op- + tion is supplied. + + ccoommppaatt5511 + +o The uunnsseett builtin treats attempts to unset array sub- + scripts @@ and ** differently depending on whether the ar- + ray is indexed or associative, and differently than in + previous versions. + +RREESSTTRRIICCTTEEDD SSHHEELLLL + If bbaasshh is started with the name rrbbaasshh, or the --rr 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 bbaasshh with the exception that the following are + disallowed or not performed: + + +o changing directories with ccdd + + +o setting or unsetting the values of SSHHEELLLL, PPAATTHH, HHIISSTTFFIILLEE, EENNVV, + or BBAASSHH__EENNVV + + +o specifying command names containing // + + +o specifying a filename containing a // as an argument to the .. + builtin command + + +o specifying a filename containing a slash as an argument to the + hhiissttoorryy builtin command + + +o specifying a filename containing a slash as an argument to the + --pp option to the hhaasshh builtin command + + +o importing function definitions from the shell environment at + startup + + +o parsing the value of SSHHEELLLLOOPPTTSS from the shell environment at + startup + + +o redirecting output using the >, >|, <>, >&, &>, and >> redirect- + ion operators + + +o using the eexxeecc builtin command to replace the shell with another + command + + +o adding or deleting builtin commands with the --ff and --dd options + to the eennaabbllee builtin command + + +o using the eennaabbllee builtin command to enable disabled shell + builtins + + +o specifying the --pp option to the ccoommmmaanndd builtin command + + +o turning off restricted mode with sseett ++rr or sshhoopptt --uu rree-- + ssttrriicctteedd__sshheellll. + + These restrictions are enforced after any startup files are read. + + When a command that is found to be a shell script is executed (see CCOOMM-- + MMAANNDD EEXXEECCUUTTIIOONN above), rrbbaasshh turns off any restrictions in the shell + spawned to execute the script. + +SSEEEE AALLSSOO + _B_a_s_h _R_e_f_e_r_e_n_c_e _M_a_n_u_a_l, Brian Fox and Chet Ramey + _T_h_e _G_n_u _R_e_a_d_l_i_n_e _L_i_b_r_a_r_y, Brian Fox and Chet Ramey + _T_h_e _G_n_u _H_i_s_t_o_r_y _L_i_b_r_a_r_y, Brian Fox and Chet Ramey + _P_o_r_t_a_b_l_e _O_p_e_r_a_t_i_n_g _S_y_s_t_e_m _I_n_t_e_r_f_a_c_e _(_P_O_S_I_X_) _P_a_r_t _2_: _S_h_e_l_l _a_n_d _U_t_i_l_i_- + _t_i_e_s, IEEE -- + http://pubs.opengroup.org/onlinepubs/9699919799/ + http://tiswww.case.edu/~chet/bash/POSIX -- a description of posix mode + _s_h(1), _k_s_h(1), _c_s_h(1) + _e_m_a_c_s(1), _v_i(1) + _r_e_a_d_l_i_n_e(3) + +FFIILLEESS + _/_b_i_n_/_b_a_s_h + The bbaasshh executable + _/_e_t_c_/_p_r_o_f_i_l_e + The systemwide initialization file, executed for login shells + _~_/_._b_a_s_h___p_r_o_f_i_l_e + The personal initialization file, executed for login shells + _~_/_._b_a_s_h_r_c + The individual per-interactive-shell startup file + _~_/_._b_a_s_h___l_o_g_o_u_t + The individual login shell cleanup file, executed when a login + shell exits + _~_/_._b_a_s_h___h_i_s_t_o_r_y + The default value of HHIISSTTFFIILLEE, the file in which bash saves the + command history + _~_/_._i_n_p_u_t_r_c + Individual _r_e_a_d_l_i_n_e initialization file + +AAUUTTHHOORRSS + Brian Fox, Free Software Foundation + bfox@gnu.org + + Chet Ramey, Case Western Reserve University + chet.ramey@case.edu + +BBUUGG RREEPPOORRTTSS + If you find a bug in bbaasshh,, 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 bbaasshh. The latest version is always available from + _f_t_p_:_/_/_f_t_p_._g_n_u_._o_r_g_/_p_u_b_/_g_n_u_/_b_a_s_h_/ and _h_t_t_p_:_/_/_g_i_t_._s_a_v_a_n_- + _n_a_h_._g_n_u_._o_r_g_/_c_g_i_t_/_b_a_s_h_._g_i_t_/_s_n_a_p_s_h_o_t_/_b_a_s_h_-_m_a_s_t_e_r_._t_a_r_._g_z. + + Once you have determined that a bug actually exists, use the _b_a_s_h_b_u_g + 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 _b_u_g_-_b_a_s_h_@_g_n_u_._o_r_g or posted to the Usenet newsgroup + ggnnuu..bbaasshh..bbuugg. + + ALL bug reports should include: + + The version number of bbaasshh + The hardware and operating system + The compiler used to compile + A description of the bug behaviour + A short script or `recipe' which exercises the bug + + _b_a_s_h_b_u_g inserts the first three items automatically into the template + it provides for filing a bug report. + + Comments and bug reports concerning this manual page should be directed + to _c_h_e_t_._r_a_m_e_y_@_c_a_s_e_._e_d_u. + +BBUUGGSS + It's too big and too slow. + + There are some subtle differences between bbaasshh and traditional versions + of sshh, mostly because of the PPOOSSIIXX specification. + + Aliases are confusing in some uses. + + Shell builtin commands and functions are not stoppable/restartable. + + 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. + + Array variables may not (yet) be exported. + + There may be only one active coprocess at a time. + + + +GNU Bash 5.2 2022 September 19 BASH(1) |