2 .\" MAN PAGE COMMENTS to
5 .\" Case Western Reserve University
6 .\" chet.ramey@case.edu
8 .\" Last Change: Fri Aug 26 09:45:10 EDT 2016
10 .\" bash_builtins, strip all but Built-Ins section
13 .TH BASH 1 "2016 August 26" "GNU Bash 4.4"
15 .\" There's some problem with having a `@'
16 .\" in a tagged paragraph with the BSD man macros.
17 .\" It has to do with `@' appearing in the }1 macro.
18 .\" This is a problem on 4.3 BSD and Ultrix, but Sun
19 .\" appears to have fixed it.
20 .\" If you're seeing the characters
21 .\" `@u-3p' appearing before the lines reading
22 .\" `possible-hostname-completions
23 .\" and `complete-hostname' down in READLINE,
24 .\" then uncomment this redefinition.
29 .if !"\\$1"" .nr )I \\$1n
32 .in \\n()Ru+\\n(INu+\\n()Iu
34 .ie !\\n()Iu+\\n()Ru-\w
\a\\*(]X
\au-3p \{\\*(]X
36 .el \\*(]X\h
\a|\\n()Iu+\\n()Ru
\a\c
40 .\" File Name macro. This used to be `.PN', for Path Name,
41 .\" but Sun doesn't seem to like that very much.
47 bash \- GNU Bourne-Again SHell
51 [command_string | file]
53 .if n Bash is Copyright (C) 1989-2016 by the Free Software Foundation, Inc.
54 .if t Bash is Copyright \(co 1989-2016 by the Free Software Foundation, Inc.
57 is an \fBsh\fR-compatible command language interpreter that
58 executes commands read from the standard input or from a file.
60 also incorporates useful features from the \fIKorn\fP and \fIC\fP
61 shells (\fBksh\fP and \fBcsh\fP).
64 is intended to be a conformant implementation of the
65 Shell and Utilities portion of the IEEE POSIX specification
66 (IEEE Standard 1003.1).
68 can be configured to be POSIX-conformant by default.
70 All of the single-character shell options documented in the
71 description of the \fBset\fR builtin command can be used as options
72 when the shell is invoked.
73 In addition, \fBbash\fR
74 interprets the following options when it is invoked:
81 option is present, then commands are read from the first non-option argument
83 If there are arguments after the
85 the first argument is assigned to
87 and any remaining arguments are assigned to the positional parameters.
90 sets the name of the shell, which is used in warning and error messages.
95 option is present, the shell is
101 act as if it had been invoked as a login shell (see
109 option is present, the shell becomes
113 .B "RESTRICTED SHELL"
119 option is present, or if no arguments remain after option
120 processing, then commands are read from the standard input.
121 This option allows the positional parameters to be set
122 when invoking an interactive shell.
125 A list of all double-quoted strings preceded by \fB$\fP
126 is printed on the standard output.
127 These are the strings that
128 are subject to language translation when the current locale
129 is not \fBC\fP or \fBPOSIX\fP.
130 This implies the \fB\-n\fP option; no commands will be executed.
132 .B [\-+]O [\fIshopt_option\fP]
133 \fIshopt_option\fP is one of the shell options accepted by the
134 \fBshopt\fP builtin (see
136 .B SHELL BUILTIN COMMANDS
138 If \fIshopt_option\fP is present, \fB\-O\fP sets the value of that option;
140 If \fIshopt_option\fP is not supplied, the names and values of the shell
141 options accepted by \fBshopt\fP are printed on the standard output.
142 If the invocation option is \fB+O\fP, the output is displayed in a format
143 that may be reused as input.
148 signals the end of options and disables further option processing.
149 Any arguments after the
151 are treated as filenames and arguments. An argument of
153 is equivalent to \fB\-\-\fP.
157 also interprets a number of multi-character options.
158 These options must appear on the command line before the
159 single-character options to be recognized.
164 Arrange for the debugger profile to be executed before the shell
166 Turns on extended debugging mode (see the description of the
172 .B \-\-dump\-po\-strings
173 Equivalent to \fB\-D\fP, but the output is in the GNU \fIgettext\fP
174 \fBpo\fP (portable object) file format.
177 Equivalent to \fB\-D\fP.
180 Display a usage message on standard output and exit successfully.
182 \fB\-\-init\-file\fP \fIfile\fP
185 \fB\-\-rcfile\fP \fIfile\fP
187 Execute commands from
189 instead of the standard personal initialization file
191 if the shell is interactive (see
197 Equivalent to \fB\-l\fP.
202 library to read command lines when the shell is interactive.
205 Do not read either the system-wide startup file
207 or any of the personal initialization files
208 .IR ~/.bash_profile ,
214 reads these files when it is invoked as a login shell (see
220 Do not read and execute the personal initialization file
222 if the shell is interactive.
223 This option is on by default if the shell is invoked as
227 Change the behavior of \fBbash\fP where the default operation differs
228 from the POSIX standard to match the standard (\fIposix mode\fP).
232 below for a reference to a document that details how posix mode affects
236 The shell becomes restricted (see
238 .B "RESTRICTED SHELL"
242 Equivalent to \fB\-v\fP.
245 Show version information for this instance of
247 on the standard output and exit successfully.
250 If arguments remain after option processing, and neither the
254 option has been supplied, the first argument is assumed to
255 be the name of a file containing shell commands.
258 is invoked in this fashion,
260 is set to the name of the file, and the positional parameters
261 are set to the remaining arguments.
263 reads and executes commands from this file, then exits.
264 \fBBash\fP's exit status is the exit status of the last command
265 executed in the script.
266 If no commands are executed, the exit status is 0.
267 An attempt is first made to open the file in the current directory, and,
268 if no file is found, then the shell searches the directories in
273 A \fIlogin shell\fP is one whose first character of argument zero is a
275 or one started with the
279 An \fIinteractive\fP shell is one started without non-option arguments
280 (unless \fB\-s\fP is specified)
284 whose standard input and error are
285 both connected to terminals (as determined by
287 or one started with the
299 allowing a shell script or a startup file to test this state.
301 The following paragraphs describe how
303 executes its startup files.
304 If any of the files exist but cannot be read,
307 Tildes are expanded in filenames as described below under
316 is invoked as an interactive login shell, or as a non-interactive shell
317 with the \fB\-\-login\fP option, it first reads and
318 executes commands from the file \fI/etc/profile\fP, if that
320 After reading that file, it looks for \fI~/.bash_profile\fP,
321 \fI~/.bash_login\fP, and \fI~/.profile\fP, in that order, and reads
322 and executes commands from the first one that exists and is readable.
325 option may be used when the shell is started to inhibit this behavior.
327 When an interactive login shell exits,
328 or a non-interactive login shell executes the \fBexit\fP builtin command,
330 reads and executes commands from the file \fI~/.bash_logout\fP, if it
333 When an interactive shell that is not a login shell is started,
335 reads and executes commands from \fI~/.bashrc\fP, if that file exists.
336 This may be inhibited by using the
339 The \fB\-\-rcfile\fP \fIfile\fP option will force
341 to read and execute commands from \fIfile\fP instead of \fI~/.bashrc\fP.
345 is started non-interactively, to run a shell script, for example, it
346 looks for the variable
349 in the environment, expands its value if it appears there, and uses the
350 expanded value as the name of a file to read and execute.
352 behaves as if the following command were executed:
355 .if t \f(CWif [ \-n "$BASH_ENV" ]; then . "$BASH_ENV"; fi\fP
356 .if n if [ \-n "$BASH_ENV" ]; then . "$BASH_ENV"; fi
362 variable is not used to search for the filename.
366 is invoked with the name
368 it tries to mimic the startup behavior of historical versions of
370 as closely as possible,
371 while conforming to the POSIX standard as well.
372 When invoked as an interactive login shell, or a non-interactive
373 shell with the \fB\-\-login\fP option, it first attempts to
374 read and execute commands from
381 option may be used to inhibit this behavior.
382 When invoked as an interactive shell with the name
385 looks for the variable
388 expands its value if it is defined, and uses the
389 expanded value as the name of a file to read and execute.
390 Since a shell invoked as
392 does not attempt to read and execute commands from any other startup
395 option has no effect.
396 A non-interactive shell invoked with the name
398 does not attempt to read any other startup files.
404 mode after the startup files are read.
412 command line option, it follows the POSIX standard for startup files.
413 In this mode, interactive shells expand the
416 variable and commands are read and executed from the file
417 whose name is the expanded value.
418 No other startup files are read.
421 attempts to determine when it is being run with its standard input
422 connected to a network connection, as when executed by the remote shell
423 daemon, usually \fIrshd\fP, or the secure shell daemon \fIsshd\fP.
426 determines it is being run in this fashion, it reads and executes
427 commands from \fI~/.bashrc\fP, if that file exists and is readable.
428 It will not do this if invoked as \fBsh\fP.
431 option may be used to inhibit this behavior, and the
433 option may be used to force another file to be read, but neither
434 \fIrshd\fP nor \fIsshd\fP generally invoke the shell with those options
435 or allow them to be specified.
437 If the shell is started with the effective user (group) id not equal to the
438 real user (group) id, and the \fB\-p\fP option is not supplied, no startup
439 files are read, shell functions are not inherited from the environment, the
449 variables, if they appear in the environment, are ignored,
450 and the effective user id is set to the real user id.
451 If the \fB\-p\fP option is supplied at invocation, the startup behavior is
452 the same, but the effective user id is not reset.
455 The following definitions are used throughout the rest of this
463 A sequence of characters considered as a single unit by the shell.
470 consisting only of alphanumeric characters and underscores, and
471 beginning with an alphabetic character or an underscore. Also
476 A character that, when unquoted, separates words. One of the following:
480 .if t \fB| & ; ( ) < > space tab newline\fP
481 .if n \fB| & ; ( ) < > space tab newline\fP
486 A \fItoken\fP that performs a control function. It is one of the following
490 .if t \fB|| & && ; ;; ;& ;;& ( ) | |& <newline>\fP
491 .if n \fB|| & && ; ;; ;& ;;& ( ) | |& <newline>\fP
495 \fIReserved words\fP are words that have a special meaning to the shell.
496 The following words are recognized as reserved when unquoted and either
497 the first word of a simple command (see
500 below) or the third word of a
508 .if n ! case coproc do done elif else esac fi for function if in select then until while { } time [[ ]]
509 .if t ! case coproc do done elif else esac fi for function if in select then until while { } time [[ ]]
514 A \fIsimple command\fP is a sequence of optional variable assignments
515 followed by \fBblank\fP-separated words and redirections, and
516 terminated by a \fIcontrol operator\fP. The first word
517 specifies the command to be executed, and is passed as argument zero.
518 The remaining words are passed as arguments to the invoked command.
520 The return value of a \fIsimple command\fP is its exit status, or
521 128+\fIn\^\fP if the command is terminated by signal
525 A \fIpipeline\fP is a sequence of one or more commands separated by
526 one of the control operators
529 The format for a pipeline is:
532 [\fBtime\fP [\fB\-p\fP]] [ ! ] \fIcommand\fP [ [\fB|\fP\(bv\fB|&\fP] \fIcommand2\fP ... ]
535 The standard output of
537 is connected via a pipe to the standard input of
539 This connection is performed before any redirections specified by the
544 If \fB|&\fP is used, \fIcommand\fP's standard error, in addition to its
545 standard output, is connected to
546 \fIcommand2\fP's standard input through the pipe;
547 it is shorthand for \fB2>&1 |\fP.
548 This implicit redirection of the standard error to the standard output is
549 performed after any redirections specified by the command.
551 The return status of a pipeline is the exit status of the last
552 command, unless the \fBpipefail\fP option is enabled.
553 If \fBpipefail\fP is enabled, the pipeline's return status is the
554 value of the last (rightmost) command to exit with a non-zero status,
555 or zero if all commands exit successfully.
558 precedes a pipeline, the exit status of that pipeline is the logical
559 negation of the exit status as described above.
560 The shell waits for all commands in the pipeline to
561 terminate before returning a value.
565 reserved word precedes a pipeline, the elapsed as well as user and
566 system time consumed by its execution are reported when the pipeline
568 The \fB\-p\fP option changes the output format to that specified by POSIX.
569 When the shell is in \fIposix mode\fP, it does not recognize
570 \fBtime\fP as a reserved word if the next token begins with a `-'.
574 variable may be set to a format string that specifies how the timing
575 information should be displayed; see the description of
582 When the shell is in \fIposix mode\fP, \fBtime\fP
583 may be followed by a newline. In this case, the shell displays the
584 total user and system time consumed by the shell and its children.
588 variable may be used to specify the format of
589 the time information.
591 Each command in a pipeline is executed as a separate process (i.e., in a
595 A \fIlist\fP is a sequence of one or more pipelines separated by one
602 and optionally terminated by one of
608 Of these list operators,
612 have equal precedence, followed by
616 which have equal precedence.
618 A sequence of one or more newlines may appear in a \fIlist\fP instead
619 of a semicolon to delimit commands.
621 If a command is terminated by the control operator
623 the shell executes the command in the \fIbackground\fP
624 in a subshell. The shell does not wait for the command to
625 finish, and the return status is 0. Commands separated by a
627 are executed sequentially; the shell waits for each
628 command to terminate in turn. The return status is the
629 exit status of the last command executed.
631 AND and OR lists are sequences of one or more pipelines separated by the
632 \fB&&\fP and \fB||\fP control operators, respectively.
633 AND and OR lists are executed with left associativity.
634 An AND list has the form
637 \fIcommand1\fP \fB&&\fP \fIcommand2\fP
641 is executed if, and only if,
643 returns an exit status of zero.
645 An OR list has the form
648 \fIcommand1\fP \fB||\fP \fIcommand2\fP
653 is executed if and only if
655 returns a non-zero exit status.
657 AND and OR lists is the exit status of the last command
658 executed in the list.
659 .SS Compound Commands
661 A \fIcompound command\fP is one of the following.
662 In most cases a \fIlist\fP in a command's description may be separated from
663 the rest of the command by one or more newlines, and may be followed by a
664 newline in place of a semicolon.
667 \fIlist\fP is executed in a subshell environment (see
669 \fBCOMMAND EXECUTION ENVIRONMENT\fP
671 Variable assignments and builtin
672 commands that affect the shell's environment do not remain in effect
673 after the command completes. The return status is the exit status of
677 \fIlist\fP is simply executed in the current shell environment.
678 \fIlist\fP must be terminated with a newline or semicolon.
679 This is known as a \fIgroup command\fP.
680 The return status is the exit status of
682 Note that unlike the metacharacters \fB(\fP and \fB)\fP, \fB{\fP and
683 \fB}\fP are \fIreserved words\fP and must occur where a reserved
684 word is permitted to be recognized. Since they do not cause a word
685 break, they must be separated from \fIlist\fP by whitespace or another
689 The \fIexpression\fP is evaluated according to the rules described
692 .BR "ARITHMETIC EVALUATION" .
693 If the value of the expression is non-zero, the return status is 0;
694 otherwise the return status is 1. This is exactly equivalent to
695 \fBlet "\fIexpression\fP"\fR.
697 \fB[[\fP \fIexpression\fP \fB]]\fP
698 Return a status of 0 or 1 depending on the evaluation of
699 the conditional expression \fIexpression\fP.
700 Expressions are composed of the primaries described below under
702 .BR "CONDITIONAL EXPRESSIONS" .
703 Word splitting and pathname expansion are not performed on the words
704 between the \fB[[\fP and \fB]]\fP; tilde expansion,
705 parameter and variable expansion,
706 arithmetic expansion, command substitution, process
707 substitution, and quote removal are performed.
708 Conditional operators such as \fB\-f\fP must be unquoted to be recognized
712 When used with \fB[[\fP, the \fB<\fP and \fB>\fP operators sort
713 lexicographically using the current locale.
716 When the \fB==\fP and \fB!=\fP operators are used, the string to the
717 right of the operator is considered a pattern and matched according
718 to the rules described below under \fBPattern Matching\fP,
719 as if the \fBextglob\fP shell option were enabled.
720 The \fB=\fP operator is equivalent to \fB==\fP.
723 shell option is enabled, the match is performed without regard to the case
724 of alphabetic characters.
725 The return value is 0 if the string matches (\fB==\fP) or does not match
726 (\fB!=\fP) the pattern, and 1 otherwise.
727 Any part of the pattern may be quoted to force the quoted portion
728 to be matched as a string.
731 An additional binary operator, \fB=~\fP, is available, with the same
732 precedence as \fB==\fP and \fB!=\fP.
733 When it is used, the string to the right of the operator is considered
734 an extended regular expression and matched accordingly (as in \fIregex\fP(3)).
735 The return value is 0 if the string matches
736 the pattern, and 1 otherwise.
737 If the regular expression is syntactically incorrect, the conditional
738 expression's return value is 2.
741 shell option is enabled, the match is performed without regard to the case
742 of alphabetic characters.
743 Any part of the pattern may be quoted to force the quoted portion
744 to be matched as a string.
745 Bracket expressions in regular expressions must be treated carefully,
746 since normal quoting characters lose their meanings between brackets.
747 If the pattern is stored in a shell variable, quoting the variable
748 expansion forces the entire pattern to be matched as a string.
749 Substrings matched by parenthesized subexpressions within the regular
750 expression are saved in the array variable
756 with index 0 is the portion of the string
757 matching the entire regular expression.
761 with index \fIn\fP is the portion of the
762 string matching the \fIn\fPth parenthesized subexpression.
765 Expressions may be combined using the following operators, listed
766 in decreasing order of precedence:
772 .B ( \fIexpression\fP )
773 Returns the value of \fIexpression\fP.
774 This may be used to override the normal precedence of operators.
776 .B ! \fIexpression\fP
781 \fIexpression1\fP \fB&&\fP \fIexpression2\fP
788 \fIexpression1\fP \fB||\fP \fIexpression2\fP
796 The \fB&&\fP and \fB||\fP
797 operators do not evaluate \fIexpression2\fP if the value of
798 \fIexpression1\fP is sufficient to determine the return value of
799 the entire conditional expression.
802 \fBfor\fP \fIname\fP [ [ \fBin\fP [ \fIword ...\fP ] ] ; ] \fBdo\fP \fIlist\fP ; \fBdone\fP
803 The list of words following \fBin\fP is expanded, generating a list
805 The variable \fIname\fP is set to each element of this list
806 in turn, and \fIlist\fP is executed each time.
807 If the \fBin\fP \fIword\fP is omitted, the \fBfor\fP command executes
808 \fIlist\fP once for each positional parameter that is set (see
812 The return status is the exit status of the last command that executes.
813 If the expansion of the items following \fBin\fP results in an empty
814 list, no commands are executed, and the return status is 0.
816 \fBfor\fP (( \fIexpr1\fP ; \fIexpr2\fP ; \fIexpr3\fP )) ; \fBdo\fP \fIlist\fP ; \fBdone\fP
817 First, the arithmetic expression \fIexpr1\fP is evaluated according
818 to the rules described below under
820 .BR "ARITHMETIC EVALUATION" .
821 The arithmetic expression \fIexpr2\fP is then evaluated repeatedly
822 until it evaluates to zero.
823 Each time \fIexpr2\fP evaluates to a non-zero value, \fIlist\fP is
824 executed and the arithmetic expression \fIexpr3\fP is evaluated.
825 If any expression is omitted, it behaves as if it evaluates to 1.
826 The return value is the exit status of the last command in \fIlist\fP
827 that is executed, or false if any of the expressions is invalid.
829 \fBselect\fP \fIname\fP [ \fBin\fP \fIword\fP ] ; \fBdo\fP \fIlist\fP ; \fBdone\fP
830 The list of words following \fBin\fP is expanded, generating a list
831 of items. The set of expanded words is printed on the standard
832 error, each preceded by a number. If the \fBin\fP
833 \fIword\fP is omitted, the positional parameters are printed (see
839 prompt is then displayed and a line read from the standard input.
840 If the line consists of a number corresponding to one of
841 the displayed words, then the value of
843 is set to that word. If the line is empty, the words and prompt
844 are displayed again. If EOF is read, the command completes. Any
845 other value read causes
847 to be set to null. The line read is saved in the variable
852 is executed after each selection until a
857 is the exit status of the last command executed in
859 or zero if no commands were executed.
861 \fBcase\fP \fIword\fP \fBin\fP [ [(] \fIpattern\fP [ \fB|\fP \fIpattern\fP ] \
862 ... ) \fIlist\fP ;; ] ... \fBesac\fP
863 A \fBcase\fP command first expands \fIword\fP, and tries to match
864 it against each \fIpattern\fP in turn, using the same matching rules
865 as for pathname expansion (see
866 .B Pathname Expansion
868 The \fIword\fP is expanded using tilde
869 expansion, parameter and variable expansion, arithmetic expansion,
870 command substitution, process substitution and quote removal.
871 Each \fIpattern\fP examined is expanded using tilde
872 expansion, parameter and variable expansion, arithmetic expansion,
873 command substitution, and process substitution.
876 shell option is enabled, the match is performed without regard to the case
877 of alphabetic characters.
878 When a match is found, the corresponding \fIlist\fP is executed.
879 If the \fB;;\fP operator is used, no subsequent matches are attempted after
880 the first pattern match.
881 Using \fB;&\fP in place of \fB;;\fP causes execution to continue with
882 the \fIlist\fP associated with the next set of patterns.
883 Using \fB;;&\fP in place of \fB;;\fP causes the shell to test the next
884 pattern list in the statement, if any, and execute any associated \fIlist\fP
885 on a successful match.
886 The exit status is zero if no
887 pattern matches. Otherwise, it is the exit status of the
888 last command executed in \fIlist\fP.
890 \fBif\fP \fIlist\fP; \fBthen\fP \fIlist\fP; \
891 [ \fBelif\fP \fIlist\fP; \fBthen\fP \fIlist\fP; ] ... \
892 [ \fBelse\fP \fIlist\fP; ] \fBfi\fP
896 is executed. If its exit status is zero, the
897 \fBthen\fP \fIlist\fP is executed. Otherwise, each \fBelif\fP
898 \fIlist\fP is executed in turn, and if its exit status is zero,
899 the corresponding \fBthen\fP \fIlist\fP is executed and the
900 command completes. Otherwise, the \fBelse\fP \fIlist\fP is
901 executed, if present. The exit status is the exit status of the
902 last command executed, or zero if no condition tested true.
904 \fBwhile\fP \fIlist-1\fP; \fBdo\fP \fIlist-2\fP; \fBdone\fP
907 \fBuntil\fP \fIlist-1\fP; \fBdo\fP \fIlist-2\fP; \fBdone\fP
909 The \fBwhile\fP command continuously executes the list
910 \fIlist-2\fP as long as the last command in the list \fIlist-1\fP returns
911 an exit status of zero. The \fBuntil\fP command is identical
912 to the \fBwhile\fP command, except that the test is negated:
914 is executed as long as the last command in
916 returns a non-zero exit status.
917 The exit status of the \fBwhile\fP and \fBuntil\fP commands
919 of the last command executed in \fIlist-2\fP, or zero if
923 A \fIcoprocess\fP is a shell command preceded by the \fBcoproc\fP reserved
925 A coprocess is executed asynchronously in a subshell, as if the command
926 had been terminated with the \fB&\fP control operator, with a two-way pipe
927 established between the executing shell and the coprocess.
929 The format for a coprocess is:
932 \fBcoproc\fP [\fINAME\fP] \fIcommand\fP [\fIredirections\fP]
935 This creates a coprocess named \fINAME\fP.
936 If \fINAME\fP is not supplied, the default name is \fBCOPROC\fP.
937 \fINAME\fP must not be supplied if \fIcommand\fP is a \fIsimple
938 command\fP (see above); otherwise, it is interpreted as the first word
939 of the simple command.
940 When the coprocess is executed, the shell creates an array variable (see
942 below) named \fINAME\fP in the context of the executing shell.
943 The standard output of
945 is connected via a pipe to a file descriptor in the executing shell,
946 and that file descriptor is assigned to \fINAME\fP[0].
947 The standard input of
949 is connected via a pipe to a file descriptor in the executing shell,
950 and that file descriptor is assigned to \fINAME\fP[1].
951 This pipe is established before any redirections specified by the
956 The file descriptors can be utilized as arguments to shell commands
957 and redirections using standard word expansions.
958 The file descriptors are not available in subshells.
959 The process ID of the shell spawned to execute the coprocess is
960 available as the value of the variable \fINAME\fP_PID.
962 builtin command may be used to wait for the coprocess to terminate.
964 Since the coprocess is created as an asynchronous command,
965 the \fBcoproc\fP command always returns success.
966 The return status of a coprocess is the exit status of \fIcommand\fP.
967 .SS Shell Function Definitions
969 A shell function is an object that is called like a simple command and
970 executes a compound command with a new set of positional parameters.
971 Shell functions are declared as follows:
973 \fIname\fP () \fIcompound\-command\fP [\fIredirection\fP]
976 \fBfunction\fP \fIname\fP [()] \fIcompound\-command\fP [\fIredirection\fP]
978 This defines a function named \fIname\fP.
979 The reserved word \fBfunction\fP is optional.
980 If the \fBfunction\fP reserved word is supplied, the parentheses are optional.
981 The \fIbody\fP of the function is the compound command
983 (see \fBCompound Commands\fP above).
984 That command is usually a \fIlist\fP of commands between { and }, but
985 may be any command listed under \fBCompound Commands\fP above,
986 with one exception: If the \fBfunction\fP reserved word is used, but the
987 parentheses are not supplied, the braces are required.
988 \fIcompound\-command\fP is executed whenever \fIname\fP is specified as the
989 name of a simple command.
990 When in \fIposix mode\fP, \fIname\fP may not be the name of one of the
991 POSIX \fIspecial builtins\fP.
992 Any redirections (see
995 below) specified when a function is defined are performed
996 when the function is executed.
997 The exit status of a function definition is zero unless a syntax error
998 occurs or a readonly function with the same name already exists.
999 When executed, the exit status of a function is the exit status of the
1000 last command executed in the body. (See
1005 In a non-interactive shell, or an interactive shell in which the
1006 .B interactive_comments
1009 builtin is enabled (see
1011 .B "SHELL BUILTIN COMMANDS"
1012 below), a word beginning with
1014 causes that word and all remaining characters on that line to
1015 be ignored. An interactive shell without the
1016 .B interactive_comments
1017 option enabled does not allow comments. The
1018 .B interactive_comments
1019 option is on by default in interactive shells.
1021 \fIQuoting\fP is used to remove the special meaning of certain
1022 characters or words to the shell. Quoting can be used to
1023 disable special treatment for special characters, to prevent
1024 reserved words from being recognized as such, and to prevent
1025 parameter expansion.
1027 Each of the \fImetacharacters\fP listed above under
1030 has special meaning to the shell and must be quoted if it is to
1033 When the command history expansion facilities are being used
1036 .B HISTORY EXPANSION
1038 \fIhistory expansion\fP character, usually \fB!\fP, must be quoted
1039 to prevent history expansion.
1041 There are three quoting mechanisms: the
1042 .IR "escape character" ,
1043 single quotes, and double quotes.
1045 A non-quoted backslash (\fB\e\fP) is the
1046 .IR "escape character" .
1047 It preserves the literal value of the next character that follows,
1048 with the exception of <newline>. If a \fB\e\fP<newline> pair
1049 appears, and the backslash is not itself quoted, the \fB\e\fP<newline>
1050 is treated as a line continuation (that is, it is removed from the
1051 input stream and effectively ignored).
1053 Enclosing characters in single quotes preserves the literal value
1054 of each character within the quotes. A single quote may not occur
1055 between single quotes, even when preceded by a backslash.
1057 Enclosing characters in double quotes preserves the literal value
1058 of all characters within the quotes, with the exception of
1062 and, when history expansion is enabled,
1064 When the shell is in \fIposix mode\fP, the \fB!\fP has no special meaning
1065 within double quotes, even when history expansion is enabled.
1070 retain their special meaning within double quotes. The backslash
1071 retains its special meaning only when followed by one of the following
1079 A double quote may be quoted within double quotes by preceding it with
1081 If enabled, history expansion will be performed unless an
1083 appearing in double quotes is escaped using a backslash.
1084 The backslash preceding the
1088 The special parameters
1092 have special meaning when in double
1098 Words of the form \fB$\fP\(aq\fIstring\fP\(aq are treated specially. The
1099 word expands to \fIstring\fP, with backslash-escaped characters replaced
1100 as specified by the ANSI C standard. Backslash escape sequences, if
1101 present, are decoded as follows:
1144 the eight-bit character whose value is the octal value \fInnn\fP
1145 (one to three digits)
1148 the eight-bit character whose value is the hexadecimal value \fIHH\fP
1149 (one or two hex digits)
1152 the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value
1153 \fIHHHH\fP (one to four hex digits)
1155 .B \eU\fIHHHHHHHH\fP
1156 the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value
1157 \fIHHHHHHHH\fP (one to eight hex digits)
1160 a control-\fIx\fP character
1164 The expanded result is single-quoted, as if the dollar sign had
1167 A double-quoted string preceded by a dollar sign (\fB$\fP\(dq\fIstring\fP\(dq)
1168 will cause the string to be translated according to the current locale.
1169 If the current locale is \fBC\fP or \fBPOSIX\fP, the dollar sign
1171 If the string is translated and replaced, the replacement is
1176 is an entity that stores values.
1179 a number, or one of the special characters listed below under
1180 .BR "Special Parameters" .
1183 is a parameter denoted by a
1185 A variable has a \fIvalue\fP and zero or more \fIattributes\fP.
1186 Attributes are assigned using the
1188 builtin command (see
1192 .BR "SHELL BUILTIN COMMANDS" ).
1194 A parameter is set if it has been assigned a value. The null string is
1195 a valid value. Once a variable is set, it may be unset only by using
1198 builtin command (see
1200 .B SHELL BUILTIN COMMANDS
1205 may be assigned to by a statement of the form
1208 \fIname\fP=[\fIvalue\fP]
1213 is not given, the variable is assigned the null string. All
1215 undergo tilde expansion, parameter and variable expansion,
1216 command substitution, arithmetic expansion, and quote
1220 below). If the variable has its
1224 is evaluated as an arithmetic expression even if the $((...)) expansion is
1226 .B "Arithmetic Expansion"
1228 Word splitting is not performed, with the exception
1229 of \fB"$@"\fP as explained below under
1230 .BR "Special Parameters" .
1231 Pathname expansion is not performed.
1232 Assignment statements may also appear as arguments to the
1240 builtin commands (\fIdeclaration\fP commands).
1241 When in \fIposix mode\fP, these builtins may appear in a command after
1242 one or more instances of the \fBcommand\fP builtin and retain these
1243 assignment statement properties.
1245 In the context where an assignment statement is assigning a value
1246 to a shell variable or array index, the += operator can be used to
1247 append to or add to the variable's previous value.
1248 This includes arguments to builtin commands such as \fBdeclare\fP that
1249 accept assignment statements (\fIdeclaration\fP commands).
1250 When += is applied to a variable for which the \fIinteger\fP attribute has been
1251 set, \fIvalue\fP is evaluated as an arithmetic expression and added to the
1252 variable's current value, which is also evaluated.
1253 When += is applied to an array variable using compound assignment (see
1256 variable's value is not unset (as it is when using =), and new values are
1257 appended to the array beginning at one greater than the array's maximum index
1258 (for indexed arrays) or added as additional key\-value pairs in an
1260 When applied to a string-valued variable, \fIvalue\fP is expanded and
1261 appended to the variable's value.
1263 A variable can be assigned the \fInameref\fP attribute using the
1264 \fB\-n\fP option to the \fBdeclare\fP or \fBlocal\fP builtin commands
1265 (see the descriptions of \fBdeclare\fP and \fBlocal\fP below)
1266 to create a \fInameref\fP, or a reference to another variable.
1267 This allows variables to be manipulated indirectly.
1268 Whenever the nameref variable is referenced, assigned to, unset, or has
1269 its attributes modified (other than using or changing the \fInameref\fP
1270 attribute itself), the
1271 operation is actually performed on the variable specified by the nameref
1273 A nameref is commonly used within shell functions to refer to a variable
1274 whose name is passed as an argument to the function.
1275 For instance, if a variable name is passed to a shell function as its first
1279 .if t \f(CWdeclare -n ref=$1\fP
1280 .if n declare -n ref=$1
1283 inside the function creates a nameref variable \fBref\fP whose value is
1284 the variable name passed as the first argument.
1285 References and assignments to \fBref\fP, and changes to its attributes,
1286 are treated as references, assignments, and attribute modifications
1287 to the variable whose name was passed as \fB$1\fP.
1288 If the control variable in a \fBfor\fP loop has the nameref attribute,
1289 the list of words can be a list of shell variables, and a name reference
1290 will be established for each word in the list, in turn, when the loop is
1292 Array variables cannot be given the \fBnameref\fP attribute.
1293 However, nameref variables can reference array variables and subscripted
1295 Namerefs can be unset using the \fB\-n\fP option to the \fBunset\fP builtin.
1296 Otherwise, if \fBunset\fP is executed with the name of a nameref variable
1297 as an argument, the variable referenced by the nameref variable will be unset.
1298 .SS Positional Parameters
1301 .I positional parameter
1302 is a parameter denoted by one or more
1303 digits, other than the single digit 0. Positional parameters are
1304 assigned from the shell's arguments when it is invoked,
1305 and may be reassigned using the
1307 builtin command. Positional parameters may not be assigned to
1308 with assignment statements. The positional parameters are
1309 temporarily replaced when a shell function is executed (see
1314 When a positional parameter consisting of more than a single
1315 digit is expanded, it must be enclosed in braces (see
1319 .SS Special Parameters
1321 The shell treats several parameters specially. These parameters may
1322 only be referenced; assignment to them is not allowed.
1326 Expands to the positional parameters, starting from one.
1327 When the expansion is not within double quotes, each positional parameter
1328 expands to a separate word.
1329 In contexts where it is performed, those words
1330 are subject to further word splitting and pathname expansion.
1331 When the expansion occurs within double quotes, it expands to a single word
1332 with the value of each parameter separated by the first character of the
1335 special variable. That is, "\fB$*\fP" is equivalent
1336 to "\fB$1\fP\fIc\fP\fB$2\fP\fIc\fP\fB...\fP", where
1338 is the first character of the value of the
1344 is unset, the parameters are separated by spaces.
1348 is null, the parameters are joined without intervening separators.
1351 Expands to the positional parameters, starting from one. When the
1352 expansion occurs within double quotes, each parameter expands to a
1353 separate word. That is, "\fB$@\fP" is equivalent to
1354 "\fB$1\fP" "\fB$2\fP" ...
1355 If the double-quoted expansion occurs within a word, the expansion of
1356 the first parameter is joined with the beginning part of the original
1357 word, and the expansion of the last parameter is joined with the last
1358 part of the original word.
1359 When there are no positional parameters, "\fB$@\fP" and
1361 expand to nothing (i.e., they are removed).
1364 Expands to the number of positional parameters in decimal.
1367 Expands to the exit status of the most recently executed foreground
1371 Expands to the current option flags as specified upon invocation,
1374 builtin command, or those set by the shell itself
1380 Expands to the process ID of the shell. In a () subshell, it
1381 expands to the process ID of the current shell, not the
1385 Expands to the process ID of the job most recently placed into the
1386 background, whether executed as an asynchronous command or using
1387 the \fBbg\fP builtin (see
1393 Expands to the name of the shell or shell script. This is set at
1394 shell initialization. If
1396 is invoked with a file of commands,
1398 is set to the name of that file. If
1404 is set to the first argument after the string to be
1405 executed, if one is present. Otherwise, it is set
1406 to the filename used to invoke
1408 as given by argument zero.
1411 At shell startup, set to the absolute pathname used to invoke the
1412 shell or shell script being executed as passed in the environment
1414 Subsequently, expands to the last argument to the previous command,
1416 Also set to the full pathname used to invoke each command executed
1417 and placed in the environment exported to that command.
1418 When checking mail, this parameter holds the name of the mail file
1419 currently being checked.
1423 The following variables are set by the shell:
1428 Expands to the full filename used to invoke this instance of
1432 A colon-separated list of enabled shell options. Each word in
1433 the list is a valid argument for the
1437 builtin command (see
1439 .B "SHELL BUILTIN COMMANDS"
1440 below). The options appearing in
1443 are those reported as
1446 If this variable is in the environment when
1448 starts up, each shell option in the list will be enabled before
1449 reading any startup files.
1450 This variable is read-only.
1453 Expands to the process ID of the current \fBbash\fP process.
1454 This differs from \fB$$\fP under certain circumstances, such as subshells
1455 that do not require \fBbash\fP to be re-initialized.
1458 An associative array variable whose members correspond to the internal
1459 list of aliases as maintained by the \fBalias\fP builtin.
1460 Elements added to this array appear in the alias list; however,
1461 unsetting array elements currently does not cause aliases to be removed
1462 from the alias list.
1465 is unset, it loses its special properties, even if it is
1469 An array variable whose values are the number of parameters in each
1470 frame of the current \fBbash\fP execution call stack.
1472 parameters to the current subroutine (shell function or script executed
1473 with \fB.\fP or \fBsource\fP) is at the top of the stack.
1474 When a subroutine is executed, the number of parameters passed is pushed onto
1480 only when in extended debugging mode (see the description of the
1487 An array variable containing all of the parameters in the current \fBbash\fP
1488 execution call stack. The final parameter of the last subroutine call
1489 is at the top of the stack; the first parameter of the initial call is
1490 at the bottom. When a subroutine is executed, the parameters supplied
1497 only when in extended debugging mode
1498 (see the description of the
1505 An associative array variable whose members correspond to the internal
1506 hash table of commands as maintained by the \fBhash\fP builtin.
1507 Elements added to this array appear in the hash table; however,
1508 unsetting array elements currently does not cause command names to be removed
1509 from the hash table.
1512 is unset, it loses its special properties, even if it is
1516 The command currently being executed or about to be executed, unless the
1517 shell is executing a command as the result of a trap,
1518 in which case it is the command executing at the time of the trap.
1520 .B BASH_EXECUTION_STRING
1521 The command argument to the \fB\-c\fP invocation option.
1524 An array variable whose members are the line numbers in source files
1525 where each corresponding member of
1529 \fB${BASH_LINENO[\fP\fI$i\fP\fB]}\fP is the line number in the source
1530 file (\fB${BASH_SOURCE[\fP\fI$i+1\fP\fB]}\fP) where
1531 \fB${FUNCNAME[\fP\fI$i\fP\fB]}\fP was called
1532 (or \fB${BASH_LINENO[\fP\fI$i-1\fP\fB]}\fP if referenced within another
1537 to obtain the current line number.
1539 .B BASH_LOADABLES_PATH
1540 A colon-separated list of directories in which the shell looks for
1541 dynamically loadable builtins specified by the
1546 An array variable whose members are assigned by the \fB=~\fP binary
1547 operator to the \fB[[\fP conditional command.
1548 The element with index 0 is the portion of the string
1549 matching the entire regular expression.
1550 The element with index \fIn\fP is the portion of the
1551 string matching the \fIn\fPth parenthesized subexpression.
1552 This variable is read-only.
1555 An array variable whose members are the source filenames
1556 where the corresponding shell function names in the
1559 array variable are defined.
1561 \fB${FUNCNAME[\fP\fI$i\fP\fB]}\fP is defined in the file
1562 \fB${BASH_SOURCE[\fP\fI$i\fP\fB]}\fP and called from
1563 \fB${BASH_SOURCE[\fP\fI$i+1\fP\fB]}\fP.
1566 Incremented by one within each subshell or subshell environment when
1567 the shell begins executing in that environment.
1568 The initial value is 0.
1571 A readonly array variable whose members hold version information for
1574 The values assigned to the array members are as follows:
1578 .B BASH_VERSINFO[\fR0\fP]
1579 The major version number (the \fIrelease\fP).
1581 .B BASH_VERSINFO[\fR1\fP]
1582 The minor version number (the \fIversion\fP).
1584 .B BASH_VERSINFO[\fR2\fP]
1587 .B BASH_VERSINFO[\fR3\fP]
1590 .B BASH_VERSINFO[\fR4\fP]
1591 The release status (e.g., \fIbeta1\fP).
1593 .B BASH_VERSINFO[\fR5\fP]
1600 Expands to a string describing the version of this instance of
1604 An index into \fB${COMP_WORDS}\fP of the word containing the current
1606 This variable is available only in shell functions invoked by the
1607 programmable completion facilities (see \fBProgrammable Completion\fP
1611 The key (or final key of a key sequence) used to invoke the current
1612 completion function.
1615 The current command line.
1616 This variable is available only in shell functions and external
1617 commands invoked by the
1618 programmable completion facilities (see \fBProgrammable Completion\fP
1622 The index of the current cursor position relative to the beginning of
1623 the current command.
1624 If the current cursor position is at the end of the current command,
1625 the value of this variable is equal to \fB${#COMP_LINE}\fP.
1626 This variable is available only in shell functions and external
1627 commands invoked by the
1628 programmable completion facilities (see \fBProgrammable Completion\fP
1632 Set to an integer value corresponding to the type of completion attempted
1633 that caused a completion function to be called:
1634 \fITAB\fP, for normal completion,
1635 \fI?\fP, for listing completions after successive tabs,
1636 \fI!\fP, for listing alternatives on partial word completion,
1637 \fI@\fP, to list completions if the word is not unmodified,
1639 \fI%\fP, for menu completion.
1640 This variable is available only in shell functions and external
1641 commands invoked by the
1642 programmable completion facilities (see \fBProgrammable Completion\fP
1646 The set of characters that the \fBreadline\fP library treats as word
1647 separators when performing word completion.
1651 is unset, it loses its special properties, even if it is
1655 An array variable (see \fBArrays\fP below) consisting of the individual
1656 words in the current command line.
1657 The line is split into words as \fBreadline\fP would split it, using
1661 This variable is available only in shell functions invoked by the
1662 programmable completion facilities (see \fBProgrammable Completion\fP
1666 An array variable (see \fBArrays\fP below) created to hold the file descriptors
1667 for output from and input to an unnamed coprocess (see \fBCoprocesses\fP
1671 An array variable (see
1673 below) containing the current contents of the directory stack.
1674 Directories appear in the stack in the order they are displayed by the
1677 Assigning to members of this array variable may be used to modify
1678 directories already in the stack, but the
1682 builtins must be used to add and remove directories.
1683 Assignment to this variable will not change the current directory.
1687 is unset, it loses its special properties, even if it is
1691 Expands to the effective user ID of the current user, initialized at
1692 shell startup. This variable is readonly.
1695 An array variable containing the names of all shell functions
1696 currently in the execution call stack.
1697 The element with index 0 is the name of any currently-executing
1699 The bottom-most element (the one with the highest index) is
1700 .if t \f(CW"main"\fP.
1702 This variable exists only when a shell function is executing.
1710 is unset, it loses its special properties, even if it is
1714 This variable can be used with \fBBASH_LINENO\fP and \fBBASH_SOURCE\fP.
1715 Each element of \fBFUNCNAME\fP has corresponding elements in
1716 \fBBASH_LINENO\fP and \fBBASH_SOURCE\fP to describe the call stack.
1717 For instance, \fB${FUNCNAME[\fP\fI$i\fP\fB]}\fP was called from the file
1718 \fB${BASH_SOURCE[\fP\fI$i+1\fP\fB]}\fP at line number
1719 \fB${BASH_LINENO[\fP\fI$i\fP\fB]}\fP.
1720 The \fBcaller\fP builtin displays the current call stack using this
1724 An array variable containing the list of groups of which the current
1733 is unset, it loses its special properties, even if it is
1737 The history number, or index in the history list, of the current
1742 is unset, it loses its special properties, even if it is
1746 Automatically set to the name of the current host.
1749 Automatically set to a string that uniquely
1750 describes the type of machine on which
1753 The default is system-dependent.
1756 Each time this parameter is referenced, the shell substitutes
1757 a decimal number representing the current sequential line number
1758 (starting with 1) within a script or function. When not in a
1759 script or function, the value substituted is not guaranteed to
1764 is unset, it loses its special properties, even if it is
1768 Automatically set to a string that fully describes the system
1771 is executing, in the standard GNU \fIcpu-company-system\fP format.
1772 The default is system-dependent.
1775 An array variable (see \fBArrays\fP below) created to hold the text
1776 read by the \fBmapfile\fP builtin when no variable name is supplied.
1779 The previous working directory as set by the
1784 The value of the last option argument processed by the
1786 builtin command (see
1788 .B SHELL BUILTIN COMMANDS
1792 The index of the next argument to be processed by the
1794 builtin command (see
1796 .B SHELL BUILTIN COMMANDS
1800 Automatically set to a string that
1801 describes the operating system on which
1804 The default is system-dependent.
1807 An array variable (see
1809 below) containing a list of exit status values from the processes
1810 in the most-recently-executed foreground pipeline (which may
1811 contain only a single command).
1814 The process ID of the shell's parent. This variable is readonly.
1817 The current working directory as set by the
1822 Each time this parameter is referenced, a random integer between
1824 generated. The sequence of random numbers may be initialized by assigning
1831 is unset, it loses its special properties, even if it is
1837 line buffer, for use with
1838 .if t \f(CWbind -x\fP
1842 .B "SHELL BUILTIN COMMANDS"
1846 The position of the insertion point in the
1848 line buffer, for use with
1849 .if t \f(CWbind -x\fP
1853 .B "SHELL BUILTIN COMMANDS"
1857 Set to the line of input read by the
1859 builtin command when no arguments are supplied.
1862 Each time this parameter is
1863 referenced, the number of seconds since shell invocation is returned. If a
1864 value is assigned to
1867 the value returned upon subsequent
1869 the number of seconds since the assignment plus the value assigned.
1873 is unset, it loses its special properties, even if it is
1877 A colon-separated list of enabled shell options. Each word in
1878 the list is a valid argument for the
1882 builtin command (see
1884 .B "SHELL BUILTIN COMMANDS"
1885 below). The options appearing in
1888 are those reported as
1891 If this variable is in the environment when
1893 starts up, each shell option in the list will be enabled before
1894 reading any startup files.
1895 This variable is read-only.
1898 Incremented by one each time an instance of
1903 Expands to the user ID of the current user, initialized at shell startup.
1904 This variable is readonly.
1907 The following variables are used by the shell. In some cases,
1909 assigns a default value to a variable; these cases are noted
1915 The value is used to set the shell's compatibility level.
1916 See the description of the \fBshopt\fP builtin below under
1917 \fBSHELL BUILTIN COMMANDS\fP
1918 for a description of the various compatibility
1919 levels and their effects.
1920 The value may be a decimal number (e.g., 4.2) or an integer (e.g., 42)
1921 corresponding to the desired compatibility level.
1922 If \fBBASH_COMPAT\fP is unset or set to the empty string, the compatibility
1923 level is set to the default for the current version.
1924 If \fBBASH_COMPAT\fP is set to a value that is not one of the valid
1925 compatibility levels, the shell prints an error message and sets the
1926 compatibility level to the default for the current version.
1927 The valid compatibility levels correspond to the compatibility options
1928 accepted by the \fBshopt\fP builtin described below (for example,
1929 \fBcompat42\fP means that 4.2 and 42 are valid values).
1930 The current version is also a valid value.
1933 If this parameter is set when \fBbash\fP is executing a shell script,
1934 its value is interpreted as a filename containing commands to
1935 initialize the shell, as in
1940 is subjected to parameter expansion, command substitution, and arithmetic
1941 expansion before being interpreted as a filename.
1944 is not used to search for the resultant filename.
1947 If set to an integer corresponding to a valid file descriptor, \fBbash\fP
1948 will write the trace output generated when
1949 .if t \f(CWset -x\fP
1951 is enabled to that file descriptor.
1952 The file descriptor is closed when
1955 is unset or assigned a new value.
1959 or assigning it the empty string causes the
1960 trace output to be sent to the standard error.
1964 to 2 (the standard error file
1965 descriptor) and then unsetting it will result in the standard error
1969 The search path for the
1972 This is a colon-separated list of directories in which the shell looks
1973 for destination directories specified by the
1977 .if t \f(CW".:~:/usr"\fP.
1981 Set the number of exited child status values for the shell to remember.
1982 Bash will not allow this value to be decreased below a POSIX-mandated
1983 minimum, and there is a maximum value (currently 8192) that this may
1985 The minimum value is system-dependent.
1988 Used by the \fBselect\fP compound command to determine the terminal width
1989 when printing selection lists.
1990 Automatically set if the
1992 option is enabled or in an interactive shell upon receipt of a
1997 An array variable from which \fBbash\fP reads the possible completions
1998 generated by a shell function invoked by the programmable completion
1999 facility (see \fBProgrammable Completion\fP below).
2000 Each array element contains one possible completion.
2003 If \fBbash\fP finds this variable in the environment when the shell starts
2007 it assumes that the shell is running in an Emacs shell buffer and disables
2014 used when the shell is invoked in POSIX mode.
2017 A colon-separated list of shell patterns (see \fBPattern Matching\fP)
2018 defining the list of filenames to be ignored by command search using
2020 Files whose full pathnames match one of these patterns are not considered
2021 executable files for the purposes of completion and command execution
2022 via \fBPATH\fP lookup.
2023 This does not affect the behavior of the \fB[\fP, \fBtest\fP, and \fB[[\fP
2025 Full pathnames in the command hash table are not subject to \fBEXECIGNORE\fP.
2026 Use this variable to ignore shared library files that have the executable
2027 bit set, but are not executable files.
2028 The pattern matching honors the setting of the \fBextglob\fP shell
2032 The default editor for the
2037 A colon-separated list of suffixes to ignore when performing
2038 filename completion (see
2042 A filename whose suffix matches one of the entries in
2045 is excluded from the list of matched filenames.
2047 .if t \f(CW".o:~"\fP.
2051 If set to a numeric value greater than 0, defines a maximum function
2052 nesting level. Function invocations that exceed this nesting level
2053 will cause the current command to abort.
2056 A colon-separated list of patterns defining the set of filenames to
2057 be ignored by pathname expansion.
2058 If a filename matched by a pathname expansion pattern also matches one
2062 it is removed from the list of matches.
2065 A colon-separated list of values controlling how commands are saved on
2067 If the list of values includes
2069 lines which begin with a
2071 character are not saved in the history list.
2074 causes lines matching the previous history entry to not be saved.
2077 is shorthand for \fIignorespace\fP and \fIignoredups\fP.
2080 causes all previous lines matching the current line to be removed from
2081 the history list before that line is saved.
2082 Any value not in the above list is ignored.
2086 is unset, or does not include a valid value,
2087 all lines read by the shell parser are saved on the history list,
2088 subject to the value of
2091 The second and subsequent lines of a multi-line compound command are
2092 not tested, and are added to the history regardless of the value of
2097 The name of the file in which command history is saved (see
2100 below). The default value is \fI~/.bash_history\fP. If unset, the
2101 command history is not saved when a shell exits.
2104 The maximum number of lines contained in the history file. When this
2105 variable is assigned a value, the history file is truncated, if
2107 to contain no more than that number of lines by removing the oldest entries.
2108 The history file is also truncated to this size after
2109 writing it when a shell exits.
2110 If the value is 0, the history file is truncated to zero size.
2111 Non-numeric values and numeric values less than zero inhibit truncation.
2112 The shell sets the default value to the value of \fBHISTSIZE\fP
2113 after reading any startup files.
2116 A colon-separated list of patterns used to decide which command lines
2117 should be saved on the history list. Each pattern is anchored at the
2118 beginning of the line and must match the complete line (no implicit
2119 `\fB*\fP' is appended). Each pattern is tested against the line
2120 after the checks specified by
2124 In addition to the normal shell pattern matching characters, `\fB&\fP'
2125 matches the previous history line. `\fB&\fP' may be escaped using a
2126 backslash; the backslash is removed before attempting a match.
2127 The second and subsequent lines of a multi-line compound command are
2128 not tested, and are added to the history regardless of the value of
2131 The pattern matching honors the setting of the \fBextglob\fP shell
2135 The number of commands to remember in the command history (see
2139 If the value is 0, commands are not saved in the history list.
2140 Numeric values less than zero result in every command being saved
2141 on the history list (there is no limit).
2142 The shell sets the default value to 500 after reading any startup files.
2145 If this variable is set and not null, its value is used as a format string
2146 for \fIstrftime\fP(3) to print the time stamp associated with each history
2147 entry displayed by the \fBhistory\fP builtin.
2148 If this variable is set, time stamps are written to the history file so
2149 they may be preserved across shell sessions.
2150 This uses the history comment character to distinguish timestamps from
2151 other history lines.
2154 The home directory of the current user; the default argument for the
2155 \fBcd\fP builtin command.
2156 The value of this variable is also used when performing tilde expansion.
2159 Contains the name of a file in the same format as
2161 that should be read when the shell needs to complete a
2163 The list of possible hostname completions may be changed while the
2165 the next time hostname completion is attempted after the
2168 adds the contents of the new file to the existing list.
2172 is set, but has no value, or does not name a readable file,
2173 \fBbash\fP attempts to read
2175 to obtain the list of possible hostname completions.
2179 is unset, the hostname list is cleared.
2183 .I Internal Field Separator
2185 for word splitting after expansion and to
2186 split lines into words with the
2188 builtin command. The default value is
2189 ``<space><tab><newline>''.
2193 action of an interactive shell on receipt of an
2196 character as the sole input. If set, the value is the number of
2200 characters which must be
2201 typed as the first characters on an input line before
2203 exits. If the variable exists but does not have a numeric value, or
2204 has no value, the default value is 10. If it does not exist,
2207 signifies the end of input to the shell.
2210 The filename for the
2212 startup file, overriding the default of
2220 Used to determine the locale category for any category not specifically
2221 selected with a variable starting with \fBLC_\fP.
2224 This variable overrides the value of
2228 \fBLC_\fP variable specifying a locale category.
2231 This variable determines the collation order used when sorting the
2232 results of pathname expansion, and determines the behavior of range
2233 expressions, equivalence classes, and collating sequences within
2234 pathname expansion and pattern matching.
2237 This variable determines the interpretation of characters and the
2238 behavior of character classes within pathname expansion and pattern
2242 This variable determines the locale used to translate double-quoted
2243 strings preceded by a \fB$\fP.
2246 This variable determines the locale category used for number formatting.
2249 This variable determines the locale category used for data and time
2253 Used by the \fBselect\fP compound command to determine the column length
2254 for printing selection lists.
2255 Automatically set if the
2257 option is enabled or in an interactive shell upon receipt of a
2262 If this parameter is set to a file or directory name and the
2265 variable is not set,
2267 informs the user of the arrival of mail in the specified file or
2268 Maildir-format directory.
2274 checks for mail. The default is 60 seconds. When it is time to check
2275 for mail, the shell does so before displaying the primary prompt.
2276 If this variable is unset, or set to a value that is not a number
2277 greater than or equal to zero, the shell disables mail checking.
2280 A colon-separated list of filenames to be checked for mail.
2281 The message to be printed when mail arrives in a particular file
2282 may be specified by separating the filename from the message with a `?'.
2283 When used in the text of the message, \fB$_\fP expands to the name of
2284 the current mailfile.
2288 \fBMAILPATH\fP=\(aq/var/mail/bfox?"You have mail":~/shell\-mail?"$_ has mail!"\(aq
2291 can be configured to supply
2292 a default value for this variable (there is no value by default),
2293 but the location of the user
2294 mail files that it uses is system dependent (e.g., /var/mail/\fB$USER\fP).
2298 If set to the value 1,
2300 displays error messages generated by the
2302 builtin command (see
2304 .B SHELL BUILTIN COMMANDS
2308 is initialized to 1 each time the shell is invoked or a shell
2312 The search path for commands. It
2313 is a colon-separated list of directories in which
2314 the shell looks for commands (see
2316 .B COMMAND EXECUTION
2318 A zero-length (null) directory name in the value of
2321 indicates the current directory.
2322 A null directory name may appear as two adjacent colons, or as an initial
2324 The default path is system-dependent,
2325 and is set by the administrator who installs
2329 .if t \f(CW/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin\fP.
2330 .if n ``/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin''.
2334 If this variable is in the environment when \fBbash\fP starts, the shell
2335 enters \fIposix mode\fP before reading the startup files, as if the
2337 invocation option had been supplied. If it is set while the shell is
2338 running, \fBbash\fP enables \fIposix mode\fP, as if the command
2339 .if t \f(CWset -o posix\fP
2340 .if n \fIset -o posix\fP
2344 If set, the value is executed as a command prior to issuing each primary
2348 If set to a number greater than zero, the value is used as the number of
2349 trailing directory components to retain when expanding the \fB\ew\fP and
2350 \fB\eW\fP prompt string escapes (see
2353 below). Characters removed are replaced with an ellipsis.
2356 The value of this parameter is expanded (see
2359 below) and displayed by interactive shells after reading a command
2360 and before the command is executed.
2363 The value of this parameter is expanded (see
2366 below) and used as the primary prompt string. The default value is
2367 ``\fB\es\-\ev\e$ \fP''.
2370 The value of this parameter is expanded as with
2373 and used as the secondary prompt string. The default is
2377 The value of this parameter is used as the prompt for the
2385 The value of this parameter is expanded as with
2388 and the value is printed before each command
2390 displays during an execution trace. The first character of
2393 is replicated multiple times, as necessary, to indicate multiple
2394 levels of indirection. The default is ``\fB+ \fP''.
2397 The full pathname to the shell is kept in this environment variable.
2398 If it is not set when the shell starts,
2400 assigns to it the full pathname of the current user's login shell.
2403 The value of this parameter is used as a format string specifying
2404 how the timing information for pipelines prefixed with the
2406 reserved word should be displayed.
2407 The \fB%\fP character introduces an escape sequence that is
2408 expanded to a time value or other information.
2409 The escape sequences and their meanings are as follows; the
2410 braces denote optional portions.
2419 The elapsed time in seconds.
2422 The number of CPU seconds spent in user mode.
2425 The number of CPU seconds spent in system mode.
2428 The CPU percentage, computed as (%U + %S) / %R.
2432 The optional \fIp\fP is a digit specifying the \fIprecision\fP,
2433 the number of fractional digits after a decimal point.
2434 A value of 0 causes no decimal point or fraction to be output.
2435 At most three places after the decimal point may be specified;
2436 values of \fIp\fP greater than 3 are changed to 3.
2437 If \fIp\fP is not specified, the value 3 is used.
2439 The optional \fBl\fP specifies a longer format, including
2440 minutes, of the form \fIMM\fPm\fISS\fP.\fIFF\fPs.
2441 The value of \fIp\fP determines whether or not the fraction is
2444 If this variable is not set, \fBbash\fP acts as if it had the
2445 value \fB$\(aq\enreal\et%3lR\enuser\et%3lU\ensys\et%3lS\(aq\fP.
2446 If the value is null, no timing information is displayed.
2447 A trailing newline is added when the format string is displayed.
2451 If set to a value greater than zero,
2455 default timeout for the \fBread\fP builtin.
2456 The \fBselect\fP command terminates if input does not arrive
2460 seconds when input is coming from a terminal.
2461 In an interactive shell, the value is interpreted as the
2462 number of seconds to wait for a line of input after issuing the
2465 terminates after waiting for that number of seconds if a complete
2466 line of input does not arrive.
2469 If set, \fBbash\fP uses its value as the name of a directory in which
2470 \fBbash\fP creates temporary files for the shell's use.
2473 This variable controls how the shell interacts with the user and
2474 job control. If this variable is set, single word simple
2475 commands without redirections are treated as candidates for resumption
2476 of an existing stopped job. There is no ambiguity allowed; if there is
2477 more than one job beginning with the string typed, the job most recently
2478 accessed is selected. The
2480 of a stopped job, in this context, is the command line used to
2484 the string supplied must match the name of a stopped job exactly;
2487 the string supplied needs to match a substring of the name of a
2490 value provides functionality analogous to the
2495 below). If set to any other value, the supplied string must
2496 be a prefix of a stopped job's name; this provides functionality
2497 analogous to the \fB%\fP\fIstring\fP job identifier.
2500 The two or three characters which control history expansion
2501 and tokenization (see
2503 .B HISTORY EXPANSION
2504 below). The first character is the \fIhistory expansion\fP character,
2505 the character which signals the start of a history
2506 expansion, normally `\fB!\fP'.
2507 The second character is the \fIquick substitution\fP
2508 character, which is used as shorthand for re-running the previous
2509 command entered, substituting one string for another in the command.
2510 The default is `\fB^\fP'.
2511 The optional third character is the character
2512 which indicates that the remainder of the line is a comment when found
2513 as the first character of a word, normally `\fB#\fP'. The history
2514 comment character causes history substitution to be skipped for the
2515 remaining words on the line. It does not necessarily cause the shell
2516 parser to treat the rest of the line as a comment.
2520 provides one-dimensional indexed and associative array variables.
2521 Any variable may be used as an indexed array; the
2523 builtin will explicitly declare an array.
2525 limit on the size of an array, nor any requirement that members
2526 be indexed or assigned contiguously.
2527 Indexed arrays are referenced using integers (including arithmetic
2528 expressions) and are zero-based; associative arrays are referenced
2529 using arbitrary strings.
2530 Unless otherwise noted, indexed array indices must be non-negative integers.
2532 An indexed array is created automatically if any variable is assigned to
2533 using the syntax \fIname\fP[\fIsubscript\fP]=\fIvalue\fP. The
2535 is treated as an arithmetic expression that must evaluate to a number.
2536 To explicitly declare an indexed array, use
2537 .B declare \-a \fIname\fP
2540 .B SHELL BUILTIN COMMANDS
2542 .B declare \-a \fIname\fP[\fIsubscript\fP]
2543 is also accepted; the \fIsubscript\fP is ignored.
2545 Associative arrays are created using
2546 .BR "declare \-A \fIname\fP" .
2549 specified for an array variable using the
2553 builtins. Each attribute applies to all members of an array.
2555 Arrays are assigned to using compound assignments of the form
2556 \fIname\fP=\fB(\fPvalue\fI1\fP ... value\fIn\fP\fB)\fP, where each
2557 \fIvalue\fP is of the form [\fIsubscript\fP]=\fIstring\fP.
2558 Indexed array assignments do not require anything but \fIstring\fP.
2559 When assigning to indexed arrays, if the optional brackets and subscript
2560 are supplied, that index is assigned to;
2561 otherwise the index of the element assigned is the last index assigned
2562 to by the statement plus one. Indexing starts at zero.
2564 When assigning to an associative array, the subscript is required.
2566 This syntax is also accepted by the
2568 builtin. Individual array elements may be assigned to using the
2569 \fIname\fP[\fIsubscript\fP]=\fIvalue\fP syntax introduced above.
2570 When assigning to an indexed array, if
2572 is subscripted by a negative number, that number is
2573 interpreted as relative to one greater than the maximum index of
2574 \fIname\fP, so negative indices count back from the end of the
2575 array, and an index of \-1 references the last element.
2577 Any element of an array may be referenced using
2578 ${\fIname\fP[\fIsubscript\fP]}. The braces are required to avoid
2579 conflicts with pathname expansion. If
2580 \fIsubscript\fP is \fB@\fP or \fB*\fP, the word expands to
2581 all members of \fIname\fP. These subscripts differ only when the
2582 word appears within double quotes. If the word is double-quoted,
2583 ${\fIname\fP[*]} expands to a single
2584 word with the value of each array member separated by the first
2588 special variable, and ${\fIname\fP[@]} expands each element of
2589 \fIname\fP to a separate word. When there are no array members,
2590 ${\fIname\fP[@]} expands to nothing.
2591 If the double-quoted expansion occurs within a word, the expansion of
2592 the first parameter is joined with the beginning part of the original
2593 word, and the expansion of the last parameter is joined with the last
2594 part of the original word.
2595 This is analogous to the expansion
2596 of the special parameters \fB*\fP and \fB@\fP (see
2597 .B Special Parameters
2598 above). ${#\fIname\fP[\fIsubscript\fP]} expands to the length of
2599 ${\fIname\fP[\fIsubscript\fP]}. If \fIsubscript\fP is \fB*\fP or
2600 \fB@\fP, the expansion is the number of elements in the array.
2603 used to reference an element of an indexed array
2604 evaluates to a number less than zero, it is
2605 interpreted as relative to one greater than the maximum index of the array,
2606 so negative indices count back from the end of the
2607 array, and an index of \-1 references the last element.
2609 Referencing an array variable without a subscript is equivalent to
2610 referencing the array with a subscript of 0.
2611 Any reference to a variable using a valid subscript is legal, and
2613 will create an array if necessary.
2615 An array variable is considered set if a subscript has been assigned a
2616 value. The null string is a valid value.
2618 It is possible to obtain the keys (indices) of an array as well as the values.
2619 ${\fB!\fP\fIname\fP[\fI@\fP]} and ${\fB!\fP\fIname\fP[\fI*\fP]}
2620 expand to the indices assigned in array variable \fIname\fP.
2621 The treatment when in double quotes is similar to the expansion of the
2622 special parameters \fI@\fP and \fI*\fP within double quotes.
2626 builtin is used to destroy arrays. \fBunset\fP \fIname\fP[\fIsubscript\fP]
2627 destroys the array element at index \fIsubscript\fP.
2628 Negative subscripts to indexed arrays are interpreted as described above.
2629 Care must be taken to avoid unwanted side effects caused by pathname
2631 \fBunset\fP \fIname\fP, where \fIname\fP is an array, or
2632 \fBunset\fP \fIname\fP[\fIsubscript\fP], where
2633 \fIsubscript\fP is \fB*\fP or \fB@\fP, removes the entire array.
2640 builtins each accept a
2642 option to specify an indexed array and a
2644 option to specify an associative array.
2645 If both options are supplied,
2652 option to assign a list of words read from the standard input
2657 builtins display array values in a way that allows them to be
2658 reused as assignments.
2660 Expansion is performed on the command line after it has been split into
2661 words. There are seven kinds of expansion performed:
2662 .IR "brace expansion" ,
2663 .IR "tilde expansion" ,
2664 .IR "parameter and variable expansion" ,
2665 .IR "command substitution" ,
2666 .IR "arithmetic expansion" ,
2667 .IR "word splitting" ,
2669 .IR "pathname expansion" .
2671 The order of expansions is:
2673 tilde expansion, parameter and variable expansion, arithmetic expansion,
2674 and command substitution (done in a left-to-right fashion);
2676 and pathname expansion.
2678 On systems that can support it, there is an additional expansion
2679 available: \fIprocess substitution\fP.
2680 This is performed at the
2681 same time as tilde, parameter, variable, and arithmetic expansion and
2682 command substitution.
2684 After these expansions are performed, quote characters present in the
2685 original word are removed unless they have been quoted themselves
2686 (\fIquote removal\fP).
2688 Only brace expansion, word splitting, and pathname expansion
2689 can change the number of words of the expansion; other expansions
2690 expand a single word to a single word.
2691 The only exceptions to this are the expansions of
2692 "\fB$@\fP" and "\fB${\fP\fIname\fP\fB[@]}\fP"
2693 as explained above (see
2698 .I "Brace expansion"
2699 is a mechanism by which arbitrary strings
2700 may be generated. This mechanism is similar to
2701 \fIpathname expansion\fP, but the filenames generated
2702 need not exist. Patterns to be brace expanded take
2703 the form of an optional
2705 followed by either a series of comma-separated strings or
2706 a sequence expression between a pair of braces, followed by
2709 The preamble is prefixed to each string contained
2710 within the braces, and the postscript is then appended
2711 to each resulting string, expanding left to right.
2713 Brace expansions may be nested. The results of each expanded
2714 string are not sorted; left to right order is preserved.
2715 For example, a\fB{\fPd,c,b\fB}\fPe expands into `ade ace abe'.
2717 A sequence expression takes the form
2718 \fB{\fP\fIx\fP\fB..\fP\fIy\fP\fB[..\fP\fIincr\fP\fB]}\fP,
2719 where \fIx\fP and \fIy\fP are either integers or single characters,
2720 and \fIincr\fP, an optional increment, is an integer.
2721 When integers are supplied, the expression expands to each number between
2722 \fIx\fP and \fIy\fP, inclusive.
2723 Supplied integers may be prefixed with \fI0\fP to force each term to have the
2725 When either \fIx\fP or \fPy\fP begins with a zero, the shell
2726 attempts to force all generated terms to contain the same number of digits,
2727 zero-padding where necessary.
2728 When characters are supplied, the expression expands to each character
2729 lexicographically between \fIx\fP and \fIy\fP, inclusive,
2730 using the default C locale.
2731 Note that both \fIx\fP and \fIy\fP must be of the same type.
2732 When the increment is supplied, it is used as the difference between
2733 each term. The default increment is 1 or -1 as appropriate.
2735 Brace expansion is performed before any other expansions,
2736 and any characters special to other expansions are preserved
2737 in the result. It is strictly textual.
2739 does not apply any syntactic interpretation to the context of the
2740 expansion or the text between the braces.
2742 A correctly-formed brace expansion must contain unquoted opening
2743 and closing braces, and at least one unquoted comma or a valid
2744 sequence expression.
2745 Any incorrectly formed brace expansion is left unchanged.
2746 A \fB{\fP or \fB,\fP may be quoted with a backslash to prevent its
2747 being considered part of a brace expression.
2748 To avoid conflicts with parameter expansion, the string \fB${\fP
2749 is not considered eligible for brace expansion.
2751 This construct is typically used as shorthand when the common
2752 prefix of the strings to be generated is longer than in the
2756 mkdir /usr/local/src/bash/{old,new,dist,bugs}
2760 chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}
2763 Brace expansion introduces a slight incompatibility with
2764 historical versions of
2767 does not treat opening or closing braces specially when they
2768 appear as part of a word, and preserves them in the output.
2770 removes braces from words as a consequence of brace
2771 expansion. For example, a word entered to
2774 appears identically in the output. The same word is
2779 If strict compatibility with
2785 option or disable brace expansion with the
2791 .B SHELL BUILTIN COMMANDS
2795 If a word begins with an unquoted tilde character (`\fB~\fP'), all of
2796 the characters preceding the first unquoted slash (or all characters,
2797 if there is no unquoted slash) are considered a \fItilde-prefix\fP.
2798 If none of the characters in the tilde-prefix are quoted, the
2799 characters in the tilde-prefix following the tilde are treated as a
2800 possible \fIlogin name\fP.
2801 If this login name is the null string, the tilde is replaced with the
2802 value of the shell parameter
2808 is unset, the home directory of the user executing the shell is
2809 substituted instead.
2810 Otherwise, the tilde-prefix is replaced with the home directory
2811 associated with the specified login name.
2813 If the tilde-prefix is a `~+', the value of the shell variable
2816 replaces the tilde-prefix.
2817 If the tilde-prefix is a `~\-', the value of the shell variable
2820 if it is set, is substituted.
2821 If the characters following the tilde in the tilde-prefix consist
2822 of a number \fIN\fP, optionally prefixed
2823 by a `+' or a `\-', the tilde-prefix is replaced with the corresponding
2824 element from the directory stack, as it would be displayed by the
2826 builtin invoked with the tilde-prefix as an argument.
2827 If the characters following the tilde in the tilde-prefix consist of a
2828 number without a leading `+' or `\-', `+' is assumed.
2830 If the login name is invalid, or the tilde expansion fails, the word
2833 Each variable assignment is checked for unquoted tilde-prefixes immediately
2838 In these cases, tilde expansion is also performed.
2839 Consequently, one may use filenames with tildes in assignments to
2847 and the shell assigns the expanded value.
2848 .SS Parameter Expansion
2850 The `\fB$\fP' character introduces parameter expansion,
2851 command substitution, or arithmetic expansion. The parameter name
2852 or symbol to be expanded may be enclosed in braces, which
2853 are optional but serve to protect the variable to be expanded from
2854 characters immediately following it which could be
2855 interpreted as part of the name.
2857 When braces are used, the matching ending brace is the first `\fB}\fP'
2858 not escaped by a backslash or within a quoted string, and not within an
2859 embedded arithmetic expansion, command substitution, or parameter
2865 The value of \fIparameter\fP is substituted. The braces are required
2868 is a positional parameter with more than one digit,
2871 is followed by a character which is not to be
2872 interpreted as part of its name.
2873 The \fIparameter\fP is a shell parameter as described above
2874 \fBPARAMETERS\fP) or an array reference (\fBArrays\fP).
2877 If the first character of \fIparameter\fP is an exclamation point (\fB!\fP),
2878 and \fIparameter\fP is not a \fInameref\fP,
2879 it introduces a level of variable indirection.
2880 \fBBash\fP uses the value of the variable formed from the rest of
2881 \fIparameter\fP as the name of the variable; this variable is then
2882 expanded and that value is used in the rest of the substitution, rather
2883 than the value of \fIparameter\fP itself.
2884 This is known as \fIindirect expansion\fP.
2885 If \fIparameter\fP is a nameref, this expands to the name of the
2886 variable referenced by \fIparameter\fP instead of performing the
2887 complete indirect expansion.
2888 The exceptions to this are the expansions of ${\fB!\fP\fIprefix\fP\fB*\fP} and
2889 ${\fB!\fP\fIname\fP[\fI@\fP]} described below.
2890 The exclamation point must immediately follow the left brace in order to
2891 introduce indirection.
2893 In each of the cases below, \fIword\fP is subject to tilde expansion,
2894 parameter expansion, command substitution, and arithmetic expansion.
2896 When not performing substring expansion, using the forms documented below
2898 \fBbash\fP tests for a parameter that is unset or null. Omitting the colon
2899 results in a test only for a parameter that is unset.
2903 ${\fIparameter\fP\fB:\-\fP\fIword\fP}
2904 \fBUse Default Values\fP. If
2906 is unset or null, the expansion of
2908 is substituted. Otherwise, the value of
2912 ${\fIparameter\fP\fB:=\fP\fIword\fP}
2913 \fBAssign Default Values\fP.
2916 is unset or null, the expansion of
2922 is then substituted. Positional parameters and special parameters may
2923 not be assigned to in this way.
2925 ${\fIparameter\fP\fB:?\fP\fIword\fP}
2926 \fBDisplay Error if Null or Unset\fP.
2929 is null or unset, the expansion of \fIword\fP (or a message to that effect
2932 is not present) is written to the standard error and the shell, if it
2933 is not interactive, exits. Otherwise, the value of \fIparameter\fP is
2936 ${\fIparameter\fP\fB:+\fP\fIword\fP}
2937 \fBUse Alternate Value\fP.
2940 is null or unset, nothing is substituted, otherwise the expansion of
2944 ${\fIparameter\fP\fB:\fP\fIoffset\fP}
2947 ${\fIparameter\fP\fB:\fP\fIoffset\fP\fB:\fP\fIlength\fP}
2949 \fBSubstring Expansion\fP.
2950 Expands to up to \fIlength\fP characters of the value of \fIparameter\fP
2951 starting at the character specified by \fIoffset\fP.
2952 If \fIparameter\fP is \fB@\fP, an indexed array subscripted by
2953 \fB@\fP or \fB*\fP, or an associative array name, the results differ as
2955 If \fIlength\fP is omitted, expands to the substring of the value of
2956 \fIparameter\fP starting at the character specified by \fIoffset\fP
2957 and extending to the end of the value.
2958 \fIlength\fP and \fIoffset\fP are arithmetic expressions (see
2961 ARITHMETIC EVALUATION
2964 If \fIoffset\fP evaluates to a number less than zero, the value
2965 is used as an offset in characters
2966 from the end of the value of \fIparameter\fP.
2967 If \fIlength\fP evaluates to a number less than zero,
2968 it is interpreted as an offset in characters
2969 from the end of the value of \fIparameter\fP rather than
2970 a number of characters, and the expansion is the characters between
2971 \fIoffset\fP and that result.
2972 Note that a negative offset must be separated from the colon by at least
2973 one space to avoid being confused with the \fB:-\fP expansion.
2975 If \fIparameter\fP is \fB@\fP, the result is \fIlength\fP positional
2976 parameters beginning at \fIoffset\fP.
2977 A negative \fIoffset\fP is taken relative to one greater than the greatest
2978 positional parameter, so an offset of -1 evaluates to the last positional
2980 It is an expansion error if \fIlength\fP evaluates to a number less than
2983 If \fIparameter\fP is an indexed array name subscripted by @ or *,
2984 the result is the \fIlength\fP
2985 members of the array beginning with ${\fIparameter\fP[\fIoffset\fP]}.
2986 A negative \fIoffset\fP is taken relative to one greater than the maximum
2987 index of the specified array.
2988 It is an expansion error if \fIlength\fP evaluates to a number less than
2991 Substring expansion applied to an associative array produces undefined
2994 Substring indexing is zero-based unless the positional parameters
2995 are used, in which case the indexing starts at 1 by default.
2996 If \fIoffset\fP is 0, and the positional parameters are used, \fB$0\fP is
2997 prefixed to the list.
2999 ${\fB!\fP\fIprefix\fP\fB*\fP}
3002 ${\fB!\fP\fIprefix\fP\fB@\fP}
3004 \fBNames matching prefix\fP.
3005 Expands to the names of variables whose names begin with \fIprefix\fP,
3006 separated by the first character of the
3010 When \fI@\fP is used and the expansion appears within double quotes, each
3011 variable name expands to a separate word.
3013 ${\fB!\fP\fIname\fP[\fI@\fP]}
3016 ${\fB!\fP\fIname\fP[\fI*\fP]}
3018 \fBList of array keys\fP.
3019 If \fIname\fP is an array variable, expands to the list of array indices
3020 (keys) assigned in \fIname\fP.
3021 If \fIname\fP is not an array, expands to 0 if \fIname\fP is set and null
3023 When \fI@\fP is used and the expansion appears within double quotes, each
3024 key expands to a separate word.
3026 ${\fB#\fP\fIparameter\fP}
3027 \fBParameter length\fP.
3028 The length in characters of the value of \fIparameter\fP is substituted.
3035 the value substituted is the number of positional parameters.
3038 is an array name subscripted by
3042 the value substituted is the number of elements in the array.
3045 is an indexed array name subscripted by a negative number, that number is
3046 interpreted as relative to one greater than the maximum index of
3047 \fIparameter\fP, so negative indices count back from the end of the
3048 array, and an index of \-1 references the last element.
3050 ${\fIparameter\fP\fB#\fP\fIword\fP}
3053 ${\fIparameter\fP\fB##\fP\fIword\fP}
3055 \fBRemove matching prefix pattern\fP.
3058 is expanded to produce a pattern just as in pathname
3059 expansion. If the pattern matches the beginning of
3062 then the result of the expansion is the expanded value of
3064 with the shortest matching pattern (the ``\fB#\fP'' case) or the
3065 longest matching pattern (the ``\fB##\fP'' case) deleted.
3072 the pattern removal operation is applied to each positional
3073 parameter in turn, and the expansion is the resultant list.
3076 is an array variable subscripted with
3080 the pattern removal operation is applied to each member of the
3081 array in turn, and the expansion is the resultant list.
3083 ${\fIparameter\fP\fB%\fP\fIword\fP}
3086 ${\fIparameter\fP\fB%%\fP\fIword\fP}
3088 \fBRemove matching suffix pattern\fP.
3089 The \fIword\fP is expanded to produce a pattern just as in
3091 If the pattern matches a trailing portion of the expanded value of
3093 then the result of the expansion is the expanded value of
3095 with the shortest matching pattern (the ``\fB%\fP'' case) or the
3096 longest matching pattern (the ``\fB%%\fP'' case) deleted.
3103 the pattern removal operation is applied to each positional
3104 parameter in turn, and the expansion is the resultant list.
3107 is an array variable subscripted with
3111 the pattern removal operation is applied to each member of the
3112 array in turn, and the expansion is the resultant list.
3114 ${\fIparameter\fP\fB/\fP\fIpattern\fP\fB/\fP\fIstring\fP}
3115 \fBPattern substitution\fP.
3116 The \fIpattern\fP is expanded to produce a pattern just as in
3118 \fIParameter\fP is expanded and the longest match of \fIpattern\fP
3119 against its value is replaced with \fIstring\fP.
3120 If \fIpattern\fP begins with \fB/\fP, all matches of \fIpattern\fP are
3121 replaced with \fIstring\fP. Normally only the first match is replaced.
3122 If \fIpattern\fP begins with \fB#\fP, it must match at the beginning
3123 of the expanded value of \fIparameter\fP.
3124 If \fIpattern\fP begins with \fB%\fP, it must match at the end
3125 of the expanded value of \fIparameter\fP.
3126 If \fIstring\fP is null, matches of \fIpattern\fP are deleted
3127 and the \fB/\fP following \fIpattern\fP may be omitted.
3130 shell option is enabled, the match is performed without regard to the case
3131 of alphabetic characters.
3138 the substitution operation is applied to each positional
3139 parameter in turn, and the expansion is the resultant list.
3142 is an array variable subscripted with
3146 the substitution operation is applied to each member of the
3147 array in turn, and the expansion is the resultant list.
3149 ${\fIparameter\fP\fB^\fP\fIpattern\fP}
3152 ${\fIparameter\fP\fB^^\fP\fIpattern\fP}
3154 ${\fIparameter\fP\fB,\fP\fIpattern\fP}
3156 ${\fIparameter\fP\fB,,\fP\fIpattern\fP}
3158 \fBCase modification\fP.
3159 This expansion modifies the case of alphabetic characters in \fIparameter\fP.
3160 The \fIpattern\fP is expanded to produce a pattern just as in
3162 Each character in the expanded value of \fIparameter\fP is tested against
3163 \fIpattern\fP, and, if it matches the pattern, its case is converted.
3164 The pattern should not attempt to match more than one character.
3165 The \fB^\fP operator converts lowercase letters matching \fIpattern\fP
3166 to uppercase; the \fB,\fP operator converts matching uppercase letters
3168 The \fB^^\fP and \fB,,\fP expansions convert each matched character in the
3169 expanded value; the \fB^\fP and \fB,\fP expansions match and convert only
3170 the first character in the expanded value.
3171 If \fIpattern\fP is omitted, it is treated like a \fB?\fP, which matches
3179 the case modification operation is applied to each positional
3180 parameter in turn, and the expansion is the resultant list.
3183 is an array variable subscripted with
3187 the case modification operation is applied to each member of the
3188 array in turn, and the expansion is the resultant list.
3190 ${\fIparameter\fP\fB@\fP\fIoperator\fP}
3191 \fBParameter transformation\fP.
3192 The expansion is either a transformation of the value of \fIparameter\fP
3193 or information about \fIparameter\fP itself, depending on the value of
3194 \fIoperator\fP. Each \fIoperator\fP is a single letter:
3200 The expansion is a string that is the value of \fIparameter\fP quoted in a
3201 format that can be reused as input.
3204 The expansion is a string that is the value of \fIparameter\fP with backslash
3205 escape sequences expanded as with the \fB$'...'\fP quoting mechansim.
3208 The expansion is a string that is the result of expanding the value of
3209 \fIparameter\fP as if it were a prompt string (see \fBPROMPTING\fP below).
3212 The expansion is a string in the form of
3213 an assignment statement or \fBdeclare\fP command that, if
3214 evaluated, will recreate \fIparameter\fP with its attributes and value.
3217 The expansion is a string consisting of flag values representing
3218 \fIparameter\fP's attributes.
3227 the operation is applied to each positional
3228 parameter in turn, and the expansion is the resultant list.
3231 is an array variable subscripted with
3235 the case modification operation is applied to each member of the
3236 array in turn, and the expansion is the resultant list.
3238 The result of the expansion is subject to word splitting and pathname
3239 expansion as described below.
3241 .SS Command Substitution
3243 \fICommand substitution\fP allows the output of a command to replace
3244 the command name. There are two forms:
3247 \fB$(\fP\fIcommand\fP\|\fB)\fP
3251 \fB\`\fP\fIcommand\fP\fB\`\fP
3255 performs the expansion by executing \fIcommand\fP in a subshell environment
3256 and replacing the command substitution with the standard output of the
3257 command, with any trailing newlines deleted.
3258 Embedded newlines are not deleted, but they may be removed during
3260 The command substitution \fB$(cat \fIfile\fP)\fR can be replaced by
3261 the equivalent but faster \fB$(< \fIfile\fP)\fR.
3263 When the old-style backquote form of substitution is used,
3264 backslash retains its literal meaning except when followed by
3269 The first backquote not preceded by a backslash terminates the
3270 command substitution.
3271 When using the $(\^\fIcommand\fP\|) form, all characters between the
3272 parentheses make up the command; none are treated specially.
3274 Command substitutions may be nested. To nest when using the backquoted form,
3275 escape the inner backquotes with backslashes.
3277 If the substitution appears within double quotes, word splitting and
3278 pathname expansion are not performed on the results.
3279 .SS Arithmetic Expansion
3281 Arithmetic expansion allows the evaluation of an arithmetic expression
3282 and the substitution of the result. The format for arithmetic expansion is:
3285 \fB$((\fP\fIexpression\fP\fB))\fP
3290 is treated as if it were within double quotes, but a double quote
3291 inside the parentheses is not treated specially.
3292 All tokens in the expression undergo parameter and variable expansion,
3293 command substitution, and quote removal.
3294 The result is treated as the arithmetic expression to be evaluated.
3295 Arithmetic expansions may be nested.
3297 The evaluation is performed according to the rules listed below under
3299 .BR "ARITHMETIC EVALUATION" .
3304 prints a message indicating failure and no substitution occurs.
3305 .SS Process Substitution
3307 \fIProcess substitution\fP allows a process's input or output to be
3308 referred to using a filename.
3309 It takes the form of
3310 \fB<(\fP\fIlist\^\fP\fB)\fP
3312 \fB>(\fP\fIlist\^\fP\fB)\fP.
3313 The process \fIlist\fP is run asynchronously, and its input or output
3314 appears as a filename.
3316 passed as an argument to the current command as the result of the
3318 If the \fB>(\fP\fIlist\^\fP\fB)\fP form is used, writing to
3319 the file will provide input for \fIlist\fP. If the
3320 \fB<(\fP\fIlist\^\fP\fB)\fP form is used, the file passed as an
3321 argument should be read to obtain the output of \fIlist\fP.
3322 Process substitution is supported on systems that support named
3323 pipes (\fIFIFOs\fP) or the \fB/dev/fd\fP method of naming open files.
3325 When available, process substitution is performed
3326 simultaneously with parameter and variable expansion,
3327 command substitution,
3328 and arithmetic expansion.
3331 The shell scans the results of
3332 parameter expansion,
3333 command substitution,
3335 arithmetic expansion
3336 that did not occur within double quotes for
3337 .IR "word splitting" .
3339 The shell treats each character of
3342 as a delimiter, and splits the results of the other
3343 expansions into words using these characters as field terminators.
3349 .BR <space><tab><newline> ,
3356 at the beginning and end of the results of the previous
3357 expansions are ignored, and
3361 characters not at the beginning or end serves to delimit words.
3365 has a value other than the default, then sequences of
3366 the whitespace characters
3371 are ignored at the beginning and end of the
3372 word, as long as the whitespace character is in the
3379 whitespace character).
3386 whitespace, along with any adjacent
3389 whitespace characters, delimits a field.
3393 whitespace characters is also treated as a delimiter.
3397 is null, no word splitting occurs.
3399 Explicit null arguments (\^\f3"\^"\fP or \^\f3\(aq\^\(aq\fP\^) are retained
3400 and passed to commands as empty strings.
3401 Unquoted implicit null arguments, resulting from the expansion of
3402 parameters that have no values, are removed.
3403 If a parameter with no value is expanded within double quotes, a
3404 null argument results and is retained
3405 and passed to a command as an empty string.
3406 When a quoted null argument appears as part of a word whose expansion is
3407 non-null, the null argument is removed.
3409 \f(CW\-d\(aq\^\(aq\fP becomes \f(CW\-d\fP after word splitting and
3410 null argument removal.
3412 Note that if no expansion occurs, no splitting
3414 .SS Pathname Expansion
3416 After word splitting,
3419 option has been set,
3421 scans each word for the characters
3426 If one of these characters appears, then the word is
3429 and replaced with an alphabetically sorted list of
3430 filenames matching the pattern
3433 .B "Pattern Matching"
3435 If no matching filenames are found,
3436 and the shell option
3438 is not enabled, the word is left unchanged.
3441 option is set, and no matches are found,
3442 the word is removed.
3445 shell option is set, and no matches are found, an error message
3446 is printed and the command is not executed.
3449 is enabled, the match is performed without regard to the case
3450 of alphabetic characters.
3451 When a pattern is used for pathname expansion,
3454 at the start of a name or immediately following a slash
3455 must be matched explicitly, unless the shell option
3458 When matching a pathname, the slash character must always be
3462 character is not treated specially.
3463 See the description of
3467 .B SHELL BUILTIN COMMANDS
3468 for a description of the
3479 shell variable may be used to restrict the set of filenames matching a
3484 is set, each matching filename that also matches one of the patterns in
3487 is removed from the list of matches.
3488 If the \fBnocaseglob\fP option is set, the matching against the patterns in
3491 is performed without regard to case.
3496 are always ignored when
3499 is set and not null. However, setting
3502 to a non-null value has the effect of enabling the
3504 shell option, so all other filenames beginning with a
3507 To get the old behavior of ignoring filenames beginning with a
3511 one of the patterns in
3516 option is disabled when
3520 The pattern matching honors the setting of the \fBextglob\fP shell
3523 \fBPattern Matching\fP
3525 Any character that appears in a pattern, other than the special pattern
3526 characters described below, matches itself. The NUL character may not
3527 occur in a pattern. A backslash escapes the following character; the
3528 escaping backslash is discarded when matching.
3529 The special pattern characters must be quoted if
3530 they are to be matched literally.
3532 The special pattern characters have the following meanings:
3538 Matches any string, including the null string.
3539 When the \fBglobstar\fP shell option is enabled, and \fB*\fP is used in
3540 a pathname expansion context, two adjacent \fB*\fPs used as a single
3541 pattern will match all files and zero or more directories and
3543 If followed by a \fB/\fP, two adjacent \fB*\fPs will match only directories
3547 Matches any single character.
3550 Matches any one of the enclosed characters. A pair of characters
3551 separated by a hyphen denotes a
3552 \fIrange expression\fP;
3553 any character that falls between those two characters, inclusive,
3554 using the current locale's collating sequence and character set,
3555 is matched. If the first character following the
3561 then any character not enclosed is matched.
3562 The sorting order of characters in range expressions is determined by
3563 the current locale and the values of the
3569 shell variables, if set.
3570 To obtain the traditional interpretation of range expressions, where
3583 may be matched by including it as the first or last character
3587 may be matched by including it as the first character
3596 \fIcharacter classes\fP can be specified using the syntax
3597 \fB[:\fP\fIclass\fP\fB:]\fP, where \fIclass\fP is one of the
3598 following classes defined in the POSIX standard:
3602 .if n alnum alpha ascii blank cntrl digit graph lower print punct space upper word xdigit
3603 .if t alnum alpha ascii blank cntrl digit graph lower print punct space upper word xdigit
3605 A character class matches any character belonging to that class.
3606 The \fBword\fP character class matches letters, digits, and the character _.
3614 an \fIequivalence class\fP can be specified using the syntax
3615 \fB[=\fP\fIc\fP\fB=]\fP, which matches all characters with the
3616 same collation weight (as defined by the current locale) as
3617 the character \fIc\fP.
3625 the syntax \fB[.\fP\fIsymbol\fP\fB.]\fP matches the collating symbol
3631 If the \fBextglob\fP shell option is enabled using the \fBshopt\fP
3632 builtin, several extended pattern matching operators are recognized.
3633 In the following description, a \fIpattern-list\fP is a list of one
3634 or more patterns separated by a \fB|\fP.
3635 Composite patterns may be formed using one or more of the following
3641 \fB?(\fP\^\fIpattern-list\^\fP\fB)\fP
3642 Matches zero or one occurrence of the given patterns
3644 \fB*(\fP\^\fIpattern-list\^\fP\fB)\fP
3645 Matches zero or more occurrences of the given patterns
3647 \fB+(\fP\^\fIpattern-list\^\fP\fB)\fP
3648 Matches one or more occurrences of the given patterns
3650 \fB@(\fP\^\fIpattern-list\^\fP\fB)\fP
3651 Matches one of the given patterns
3653 \fB!(\fP\^\fIpattern-list\^\fP\fB)\fP
3654 Matches anything except one of the given patterns
3659 After the preceding expansions, all unquoted occurrences of the
3663 and \^\f3"\fP\^ that did not result from one of the above
3664 expansions are removed.
3666 Before a command is executed, its input and output
3669 using a special notation interpreted by the shell.
3670 Redirection allows commands' file handles to be
3671 duplicated, opened, closed,
3672 made to refer to different files,
3673 and can change the files the command reads from and writes to.
3674 Redirection may also be used to modify file handles in the
3675 current shell execution environment.
3676 The following redirection
3677 operators may precede or appear anywhere within a
3681 Redirections are processed in the order they appear, from
3684 Each redirection that may be preceded by a file descriptor number
3685 may instead be preceded by a word of the form {\fIvarname\fP}.
3686 In this case, for each redirection operator except
3687 >&- and <&-, the shell will allocate a file descriptor greater
3688 than or equal to 10 and assign it to \fIvarname\fP.
3689 If >&- or <&- is preceded
3690 by {\fIvarname\fP}, the value of \fIvarname\fP defines the file
3691 descriptor to close.
3693 In the following descriptions, if the file descriptor number is
3694 omitted, and the first character of the redirection operator is
3696 the redirection refers to the standard input (file descriptor
3697 0). If the first character of the redirection operator is
3699 the redirection refers to the standard output (file descriptor
3702 The word following the redirection operator in the following
3703 descriptions, unless otherwise noted, is subjected to
3704 brace expansion, tilde expansion, parameter and variable expansion,
3705 command substitution, arithmetic expansion, quote removal,
3706 pathname expansion, and word splitting.
3707 If it expands to more than one word,
3711 Note that the order of redirections is significant. For example,
3715 ls \fB>\fP dirlist 2\fB>&\fP1
3718 directs both standard output and standard error to the file
3723 ls 2\fB>&\fP1 \fB>\fP dirlist
3726 directs only the standard output to file
3728 because the standard error was duplicated from the standard output
3729 before the standard output was redirected to
3732 \fBBash\fP handles several filenames specially when they are used in
3733 redirections, as described in the following table.
3734 If the operating system on which \fBbash\fP is running provides these
3735 special files, bash will use them; otherwise it will emulate them
3736 internally with the behavior described below.
3742 If \fIfd\fP is a valid integer, file descriptor \fIfd\fP is duplicated.
3745 File descriptor 0 is duplicated.
3748 File descriptor 1 is duplicated.
3751 File descriptor 2 is duplicated.
3753 .B /dev/tcp/\fIhost\fP/\fIport\fP
3754 If \fIhost\fP is a valid hostname or Internet address, and \fIport\fP
3755 is an integer port number or service name, \fBbash\fP attempts to open
3756 the corresponding TCP socket.
3758 .B /dev/udp/\fIhost\fP/\fIport\fP
3759 If \fIhost\fP is a valid hostname or Internet address, and \fIport\fP
3760 is an integer port number or service name, \fBbash\fP attempts to open
3761 the corresponding UDP socket.
3765 A failure to open or create a file causes the redirection to fail.
3767 Redirections using file descriptors greater than 9 should be used with
3768 care, as they may conflict with file descriptors the shell uses
3770 .SS Redirecting Input
3772 Redirection of input causes the file whose name results from
3775 to be opened for reading on file descriptor
3777 or the standard input (file descriptor 0) if
3781 The general format for redirecting input is:
3784 [\fIn\fP]\fB<\fP\fIword\fP
3786 .SS Redirecting Output
3788 Redirection of output causes the file whose name results from
3791 to be opened for writing on file descriptor
3793 or the standard output (file descriptor 1) if
3795 is not specified. If the file does not exist it is created;
3796 if it does exist it is truncated to zero size.
3798 The general format for redirecting output is:
3801 [\fIn\fP]\fB>\fP\fIword\fP
3804 If the redirection operator is
3810 builtin has been enabled, the redirection will fail if the file
3811 whose name results from the expansion of \fIword\fP exists and is
3813 If the redirection operator is
3815 or the redirection operator is
3821 builtin command is not enabled, the redirection is attempted even
3822 if the file named by \fIword\fP exists.
3823 .SS Appending Redirected Output
3825 Redirection of output in this fashion
3826 causes the file whose name results from
3829 to be opened for appending on file descriptor
3831 or the standard output (file descriptor 1) if
3833 is not specified. If the file does not exist it is created.
3835 The general format for appending output is:
3838 [\fIn\fP]\fB>>\fP\fIword\fP
3841 .SS Redirecting Standard Output and Standard Error
3843 This construct allows both the
3844 standard output (file descriptor 1) and
3845 the standard error output (file descriptor 2)
3846 to be redirected to the file whose name is the
3850 There are two formats for redirecting standard output and
3861 Of the two forms, the first is preferred.
3862 This is semantically equivalent to
3865 \fB>\fP\fIword\fP 2\fB>&\fP1
3868 When using the second form, \fIword\fP may not expand to a number or
3869 \fB\-\fP. If it does, other redirection operators apply
3870 (see \fBDuplicating File Descriptors\fP below) for compatibility
3872 .SS Appending Standard Output and Standard Error
3874 This construct allows both the
3875 standard output (file descriptor 1) and
3876 the standard error output (file descriptor 2)
3877 to be appended to the file whose name is the
3881 The format for appending standard output and standard error is:
3887 This is semantically equivalent to
3890 \fB>>\fP\fIword\fP 2\fB>&\fP1
3893 (see \fBDuplicating File Descriptors\fP below).
3896 This type of redirection instructs the shell to read input from the
3897 current source until a line containing only
3899 (with no trailing blanks)
3901 the lines read up to that point are then used as the standard
3902 input (or file descriptor \fIn\fP if \fIn\fP is specified) for a command.
3904 The format of here-documents is:
3908 [\fIn\fP]\fB<<\fP[\fB\-\fP]\fIword\fP
3914 No parameter and variable expansion, command substitution,
3915 arithmetic expansion, or pathname expansion is performed on
3921 is the result of quote removal on
3923 and the lines in the here-document are not expanded.
3924 If \fIword\fP is unquoted,
3925 all lines of the here-document are subjected to
3926 parameter expansion, command substitution, and arithmetic expansion,
3927 the character sequence
3931 must be used to quote the characters
3937 If the redirection operator is
3939 then all leading tab characters are stripped from input lines and the
3943 here-documents within shell scripts to be indented in a
3946 A variant of here documents, the format is:
3950 [\fIn\fP]\fB<<<\fP\fIword\fP
3954 The \fIword\fP undergoes
3955 brace expansion, tilde expansion, parameter and variable expansion,
3956 command substitution, arithmetic expansion, and quote removal.
3957 Pathname expansion and word splitting are not performed.
3958 The result is supplied as a single string, with a newline appended,
3959 to the command on its
3960 standard input (or file descriptor \fIn\fP if \fIn\fP is specified).
3961 .SS "Duplicating File Descriptors"
3963 The redirection operator
3966 [\fIn\fP]\fB<&\fP\fIword\fP
3969 is used to duplicate input file descriptors.
3972 expands to one or more digits, the file descriptor denoted by
3974 is made to be a copy of that file descriptor.
3977 do not specify a file descriptor open for input, a redirection error occurs.
3986 is not specified, the standard input (file descriptor 0) is used.
3991 [\fIn\fP]\fB>&\fP\fIword\fP
3994 is used similarly to duplicate output file descriptors. If
3996 is not specified, the standard output (file descriptor 1) is used.
3999 do not specify a file descriptor open for output, a redirection error occurs.
4007 As a special case, if \fIn\fP is omitted, and \fIword\fP does not
4008 expand to one or more digits or \fB\-\fP, the standard output and standard
4009 error are redirected as described previously.
4010 .SS "Moving File Descriptors"
4012 The redirection operator
4015 [\fIn\fP]\fB<&\fP\fIdigit\fP\fB\-\fP
4018 moves the file descriptor \fIdigit\fP to file descriptor
4020 or the standard input (file descriptor 0) if \fIn\fP is not specified.
4021 \fIdigit\fP is closed after being duplicated to \fIn\fP.
4023 Similarly, the redirection operator
4026 [\fIn\fP]\fB>&\fP\fIdigit\fP\fB\-\fP
4029 moves the file descriptor \fIdigit\fP to file descriptor
4031 or the standard output (file descriptor 1) if \fIn\fP is not specified.
4032 .SS "Opening File Descriptors for Reading and Writing"
4034 The redirection operator
4037 [\fIn\fP]\fB<>\fP\fIword\fP
4040 causes the file whose name is the expansion of
4042 to be opened for both reading and writing on file descriptor
4044 or on file descriptor 0 if
4046 is not specified. If the file does not exist, it is created.
4048 \fIAliases\fP allow a string to be substituted for a word when it is used
4049 as the first word of a simple command.
4050 The shell maintains a list of aliases that may be set and unset with the
4054 builtin commands (see
4056 .B SHELL BUILTIN COMMANDS
4058 The first word of each simple command, if unquoted,
4059 is checked to see if it has an
4060 alias. If so, that word is replaced by the text of the alias.
4061 The characters \fB/\fP, \fB$\fP, \fB\`\fP, and \fB=\fP and
4062 any of the shell \fImetacharacters\fP or quoting characters
4063 listed above may not appear in an alias name.
4064 The replacement text may contain any valid shell input,
4065 including shell metacharacters.
4066 The first word of the replacement text is tested
4067 for aliases, but a word that is identical to an alias being expanded
4068 is not expanded a second time.
4069 This means that one may alias
4075 does not try to recursively expand the replacement text.
4076 If the last character of the alias value is a
4078 then the next command
4079 word following the alias is also checked for alias expansion.
4081 Aliases are created and listed with the
4083 command, and removed with the
4087 There is no mechanism for using arguments in the replacement text.
4088 If arguments are needed, a shell function should be used (see
4093 Aliases are not expanded when the shell is not interactive, unless
4096 shell option is set using
4098 (see the description of
4102 \fBSHELL BUILTIN COMMANDS\fP
4105 The rules concerning the definition and use of aliases are
4108 always reads at least one complete line
4109 of input before executing any
4110 of the commands on that line. Aliases are expanded when a
4111 command is read, not when it is executed. Therefore, an
4112 alias definition appearing on the same line as another
4113 command does not take effect until the next line of input is read.
4114 The commands following the alias definition
4115 on that line are not affected by the new alias.
4116 This behavior is also an issue when functions are executed.
4117 Aliases are expanded when a function definition is read,
4118 not when the function is executed, because a function definition
4119 is itself a command. As a consequence, aliases
4120 defined in a function are not available until after that
4121 function is executed. To be safe, always put
4122 alias definitions on a separate line, and do not use
4124 in compound commands.
4126 For almost every purpose, aliases are superseded by
4129 A shell function, defined as described above under
4131 .BR "SHELL GRAMMAR" ,
4132 stores a series of commands for later execution.
4133 When the name of a shell function is used as a simple command name,
4134 the list of commands associated with that function name is executed.
4135 Functions are executed in the context of the
4136 current shell; no new process is created to interpret
4137 them (contrast this with the execution of a shell script).
4138 When a function is executed, the arguments to the
4139 function become the positional parameters
4140 during its execution.
4141 The special parameter
4143 is updated to reflect the change. Special parameter \fB0\fP
4145 The first element of the
4148 variable is set to the name of the function while the function
4151 All other aspects of the shell execution
4152 environment are identical between a function and its caller
4153 with these exceptions: the
4158 traps (see the description of the
4162 .B SHELL BUILTIN COMMANDS
4163 below) are not inherited unless the function has been given the
4164 \fBtrace\fP attribute (see the description of the
4167 builtin below) or the
4168 \fB\-o functrace\fP shell option has been enabled with
4169 the \fBset\fP builtin
4170 (in which case all functions inherit the \fBDEBUG\fP and \fBRETURN\fP traps),
4174 trap is not inherited unless the \fB\-o errtrace\fP shell option has
4177 Variables local to the function may be declared with the
4179 builtin command. Ordinarily, variables and their values
4180 are shared between the function and its caller.
4182 The \fBFUNCNEST\fP variable, if set to a numeric value greater
4183 than 0, defines a maximum function nesting level. Function
4184 invocations that exceed the limit cause the entire command to
4187 If the builtin command
4189 is executed in a function, the function completes and
4190 execution resumes with the next command after the function
4192 Any command associated with the \fBRETURN\fP trap is executed
4193 before execution resumes.
4194 When a function completes, the values of the
4195 positional parameters and the special parameter
4197 are restored to the values they had prior to the function's
4200 Function names and definitions may be listed with the
4206 builtin commands. The
4212 will list the function names only
4213 (and optionally the source file and line number, if the \fBextdebug\fP
4214 shell option is enabled).
4215 Functions may be exported so that subshells
4216 automatically have them defined with the
4221 A function definition may be deleted using the \fB\-f\fP option to
4225 Note that shell functions and variables with the same name may result
4226 in multiple identically-named entries in the environment passed to the
4228 Care should be taken in cases where this may cause a problem.
4230 Functions may be recursive.
4231 The \fBFUNCNEST\fP variable may be used to limit the depth of the
4232 function call stack and restrict the number of function invocations.
4233 By default, no limit is imposed on the number of recursive calls.
4234 .SH "ARITHMETIC EVALUATION"
4235 The shell allows arithmetic expressions to be evaluated, under
4236 certain circumstances (see the \fBlet\fP and \fBdeclare\fP builtin
4237 commands, the \fB((\fP compound command, and \fBArithmetic Expansion\fP).
4238 Evaluation is done in fixed-width integers with no check for overflow,
4239 though division by 0 is trapped and flagged as an error.
4240 The operators and their precedence, associativity, and values
4241 are the same as in the C language.
4242 The following list of operators is grouped into levels of
4243 equal-precedence operators.
4244 The levels are listed in order of decreasing precedence.
4248 .B \fIid\fP++ \fIid\fP\-\-
4249 variable post-increment and post-decrement
4251 .B ++\fIid\fP \-\-\fIid\fP
4252 variable pre-increment and pre-decrement
4255 unary minus and plus
4258 logical and bitwise negation
4264 multiplication, division, remainder
4267 addition, subtraction
4270 left and right bitwise shifts
4276 equality and inequality
4282 bitwise exclusive OR
4293 .B \fIexpr\fP?\fIexpr\fP:\fIexpr\fP
4294 conditional operator
4296 .B = *= /= %= += \-= <<= >>= &= ^= |=
4299 .B \fIexpr1\fP , \fIexpr2\fP
4303 Shell variables are allowed as operands; parameter expansion is
4304 performed before the expression is evaluated.
4305 Within an expression, shell variables may also be referenced by name
4306 without using the parameter expansion syntax.
4307 A shell variable that is null or unset evaluates to 0 when referenced
4308 by name without using the parameter expansion syntax.
4309 The value of a variable is evaluated as an arithmetic expression
4310 when it is referenced, or when a variable which has been given the
4311 \fIinteger\fP attribute using \fBdeclare -i\fP is assigned a value.
4312 A null value evaluates to 0.
4313 A shell variable need not have its \fIinteger\fP attribute
4314 turned on to be used in an expression.
4316 Constants with a leading 0 are interpreted as octal numbers.
4317 A leading 0x or 0X denotes hexadecimal.
4318 Otherwise, numbers take the form [\fIbase#\fP]n, where the optional \fIbase\fP
4319 is a decimal number between 2 and 64 representing the arithmetic
4320 base, and \fIn\fP is a number in that base.
4321 If \fIbase#\fP is omitted, then base 10 is used.
4322 When specifying \fIn\fP,
4323 the digits greater than 9 are represented by the lowercase letters,
4324 the uppercase letters, @, and _, in that order.
4325 If \fIbase\fP is less than or equal to 36, lowercase and uppercase
4326 letters may be used interchangeably to represent numbers between 10
4329 Operators are evaluated in order of precedence. Sub-expressions in
4330 parentheses are evaluated first and may override the precedence
4332 .SH "CONDITIONAL EXPRESSIONS"
4333 Conditional expressions are used by the \fB[[\fP compound command and
4334 the \fBtest\fP and \fB[\fP builtin commands to test file attributes
4335 and perform string and arithmetic comparisons.
4336 Expressions are formed from the following unary or binary primaries.
4337 \fBBash\fP handles several filenames specially when they are used in
4339 If the operating system on which \fBbash\fP is running provides these
4340 special files, bash will use them; otherwise it will emulate them
4341 internally with this behavior:
4342 If any \fIfile\fP argument to one of the primaries is of the form
4343 \fI/dev/fd/n\fP, then file descriptor \fIn\fP is checked.
4344 If the \fIfile\fP argument to one of the primaries is one of
4345 \fI/dev/stdin\fP, \fI/dev/stdout\fP, or \fI/dev/stderr\fP, file
4346 descriptor 0, 1, or 2, respectively, is checked.
4348 Unless otherwise specified, primaries that operate on files follow symbolic
4349 links and operate on the target of the link, rather than the link itself.
4352 When used with \fB[[\fP, the \fB<\fP and \fB>\fP operators sort
4353 lexicographically using the current locale.
4354 The \fBtest\fP command sorts using ASCII ordering.
4359 True if \fIfile\fP exists.
4362 True if \fIfile\fP exists and is a block special file.
4365 True if \fIfile\fP exists and is a character special file.
4368 True if \fIfile\fP exists and is a directory.
4371 True if \fIfile\fP exists.
4374 True if \fIfile\fP exists and is a regular file.
4377 True if \fIfile\fP exists and is set-group-id.
4380 True if \fIfile\fP exists and is a symbolic link.
4383 True if \fIfile\fP exists and its ``sticky'' bit is set.
4386 True if \fIfile\fP exists and is a named pipe (FIFO).
4389 True if \fIfile\fP exists and is readable.
4392 True if \fIfile\fP exists and has a size greater than zero.
4395 True if file descriptor
4397 is open and refers to a terminal.
4400 True if \fIfile\fP exists and its set-user-id bit is set.
4403 True if \fIfile\fP exists and is writable.
4406 True if \fIfile\fP exists and is executable.
4409 True if \fIfile\fP exists and is owned by the effective group id.
4412 True if \fIfile\fP exists and is a symbolic link.
4415 True if \fIfile\fP exists and has been modified since it was last read.
4418 True if \fIfile\fP exists and is owned by the effective user id.
4421 True if \fIfile\fP exists and is a socket.
4423 \fIfile1\fP \fB\-ef\fP \fIfile2\fP
4424 True if \fIfile1\fP and \fIfile2\fP refer to the same device and
4427 \fIfile1\fP \-\fBnt\fP \fIfile2\fP
4428 True if \fIfile1\fP is newer (according to modification date) than \fIfile2\fP,
4429 or if \fIfile1\fP exists and \fPfile2\fP does not.
4431 \fIfile1\fP \-\fBot\fP \fIfile2\fP
4432 True if \fIfile1\fP is older than \fIfile2\fP, or if \fIfile2\fP exists
4433 and \fIfile1\fP does not.
4435 .B \-o \fIoptname\fP
4436 True if the shell option
4439 See the list of options under the description of the
4445 .B \-v \fIvarname\fP
4446 True if the shell variable
4448 is set (has been assigned a value).
4450 .B \-R \fIvarname\fP
4451 True if the shell variable
4453 is set and is a name reference.
4456 True if the length of \fIstring\fP is zero.
4463 True if the length of
4467 \fIstring1\fP \fB==\fP \fIstring2\fP
4470 \fIstring1\fP \fB=\fP \fIstring2\fP
4472 True if the strings are equal. \fB=\fP should be used
4473 with the \fBtest\fP command for POSIX conformance.
4474 When used with the \fB[[\fP command, this performs pattern matching as
4475 described above (\fBCompound Commands\fP).
4477 \fIstring1\fP \fB!=\fP \fIstring2\fP
4478 True if the strings are not equal.
4480 \fIstring1\fP \fB<\fP \fIstring2\fP
4481 True if \fIstring1\fP sorts before \fIstring2\fP lexicographically.
4483 \fIstring1\fP \fB>\fP \fIstring2\fP
4484 True if \fIstring1\fP sorts after \fIstring2\fP lexicographically.
4486 .I \fIarg1\fP \fBOP\fP \fIarg2\fP
4497 These arithmetic binary operators return true if \fIarg1\fP
4498 is equal to, not equal to, less than, less than or equal to,
4499 greater than, or greater than or equal to \fIarg2\fP, respectively.
4503 may be positive or negative integers.
4505 .SH "SIMPLE COMMAND EXPANSION"
4506 When a simple command is executed, the shell performs the following
4507 expansions, assignments, and redirections, from left to right.
4509 The words that the parser has marked as variable assignments (those
4510 preceding the command name) and redirections are saved for later
4513 The words that are not variable assignments or redirections are
4514 expanded. If any words remain after expansion, the first word
4515 is taken to be the name of the command and the remaining words are
4518 Redirections are performed as described above under
4522 The text after the \fB=\fP in each variable assignment undergoes tilde
4523 expansion, parameter expansion, command substitution, arithmetic expansion,
4524 and quote removal before being assigned to the variable.
4526 If no command name results, the variable assignments affect the current
4527 shell environment. Otherwise, the variables are added to the environment
4528 of the executed command and do not affect the current shell environment.
4529 If any of the assignments attempts to assign a value to a readonly variable,
4530 an error occurs, and the command exits with a non-zero status.
4532 If no command name results, redirections are performed, but do not
4533 affect the current shell environment. A redirection error causes the
4534 command to exit with a non-zero status.
4536 If there is a command name left after expansion, execution proceeds as
4537 described below. Otherwise, the command exits. If one of the expansions
4538 contained a command substitution, the exit status of the command is
4539 the exit status of the last command substitution performed. If there
4540 were no command substitutions, the command exits with a status of zero.
4541 .SH "COMMAND EXECUTION"
4542 After a command has been split into words, if it results in a
4543 simple command and an optional list of arguments, the following
4546 If the command name contains no slashes, the shell attempts to
4547 locate it. If there exists a shell function by that name, that
4548 function is invoked as described above in
4551 If the name does not match a function, the shell searches for
4552 it in the list of shell builtins. If a match is found, that
4555 If the name is neither a shell function nor a builtin,
4556 and contains no slashes,
4558 searches each element of the
4561 for a directory containing an executable file by that name.
4563 uses a hash table to remember the full pathnames of executable
4568 .B "SHELL BUILTIN COMMANDS"
4570 A full search of the directories in
4573 is performed only if the command is not found in the hash table.
4574 If the search is unsuccessful, the shell searches for a defined shell
4575 function named \fBcommand_not_found_handle\fP.
4576 If that function exists, it is invoked with the original command and
4577 the original command's arguments as its arguments, and the function's
4578 exit status becomes the exit status of the shell.
4579 If that function is not defined, the shell prints an error
4580 message and returns an exit status of 127.
4582 If the search is successful, or if the command name contains
4583 one or more slashes, the shell executes the named program in a
4584 separate execution environment.
4585 Argument 0 is set to the name given, and the remaining arguments
4586 to the command are set to the arguments given, if any.
4588 If this execution fails because the file is not in executable
4589 format, and the file is not a directory, it is assumed to be
4590 a \fIshell script\fP, a file
4591 containing shell commands. A subshell is spawned to execute
4592 it. This subshell reinitializes itself, so
4593 that the effect is as if a new shell had been invoked
4594 to handle the script, with the exception that the locations of
4595 commands remembered by the parent (see
4599 \fBSHELL BUILTIN COMMANDS\fP)
4600 are retained by the child.
4602 If the program is a file beginning with
4604 the remainder of the first line specifies an interpreter
4605 for the program. The shell executes the
4606 specified interpreter on operating systems that do not
4607 handle this executable format themselves. The arguments to the
4608 interpreter consist of a single optional argument following the
4609 interpreter name on the first line of the program, followed
4610 by the name of the program, followed by the command
4612 .SH COMMAND EXECUTION ENVIRONMENT
4613 The shell has an \fIexecution environment\fP, which consists of the
4616 open files inherited by the shell at invocation, as modified by
4617 redirections supplied to the \fBexec\fP builtin
4619 the current working directory as set by \fBcd\fP, \fBpushd\fP, or
4620 \fBpopd\fP, or inherited by the shell at invocation
4622 the file creation mode mask as set by \fBumask\fP or inherited from
4625 current traps set by \fBtrap\fP
4627 shell parameters that are set by variable assignment or with \fBset\fP
4628 or inherited from the shell's parent in the environment
4630 shell functions defined during execution or inherited from the shell's
4631 parent in the environment
4633 options enabled at invocation (either by default or with command-line
4634 arguments) or by \fBset\fP
4636 options enabled by \fBshopt\fP
4638 shell aliases defined with \fBalias\fP
4640 various process IDs, including those of background jobs, the value
4641 of \fB$$\fP, and the value of
4645 When a simple command other than a builtin or shell function
4646 is to be executed, it
4647 is invoked in a separate execution environment that consists of
4648 the following. Unless otherwise noted, the values are inherited
4652 the shell's open files, plus any modifications and additions specified
4653 by redirections to the command
4655 the current working directory
4657 the file creation mode mask
4659 shell variables and functions marked for export, along with variables
4660 exported for the command, passed in the environment
4662 traps caught by the shell are reset to the values inherited from the
4663 shell's parent, and traps ignored by the shell are ignored
4665 A command invoked in this separate environment cannot affect the
4666 shell's execution environment.
4668 Command substitution, commands grouped with parentheses,
4669 and asynchronous commands are invoked in a
4670 subshell environment that is a duplicate of the shell environment,
4671 except that traps caught by the shell are reset to the values
4672 that the shell inherited from its parent at invocation. Builtin
4673 commands that are invoked as part of a pipeline are also executed in a
4674 subshell environment. Changes made to the subshell environment
4675 cannot affect the shell's execution environment.
4677 Subshells spawned to execute command substitutions inherit the value of
4678 the \fB\-e\fP option from the parent shell. When not in \fIposix\fP mode,
4679 \fBbash\fP clears the \fB\-e\fP option in such subshells.
4681 If a command is followed by a \fB&\fP and job control is not active, the
4682 default standard input for the command is the empty file \fI/dev/null\fP.
4683 Otherwise, the invoked command inherits the file descriptors of the calling
4684 shell as modified by redirections.
4686 When a program is invoked it is given an array of strings
4690 \fIname\fP\-\fIvalue\fP pairs, of the form
4691 .IR "name\fR=\fPvalue" .
4693 The shell provides several ways to manipulate the environment.
4694 On invocation, the shell scans its own environment and
4695 creates a parameter for each name found, automatically marking
4698 to child processes. Executed commands inherit the environment.
4703 commands allow parameters and functions to be added to and
4704 deleted from the environment. If the value of a parameter
4705 in the environment is modified, the new value becomes part
4706 of the environment, replacing the old. The environment
4707 inherited by any executed command consists of the shell's
4708 initial environment, whose values may be modified in the shell,
4709 less any pairs removed by the
4711 command, plus any additions via the
4717 The environment for any
4719 or function may be augmented temporarily by prefixing it with
4720 parameter assignments, as described above in
4723 These assignment statements affect only the environment seen
4728 option is set (see the
4730 builtin command below), then
4732 parameter assignments are placed in the environment for a command,
4733 not just those that precede the command name.
4737 invokes an external command, the variable
4739 is set to the full filename of the command and passed to that
4740 command in its environment.
4743 The exit status of an executed command is the value returned by the
4744 \fIwaitpid\fP system call or equivalent function. Exit statuses
4745 fall between 0 and 255, though, as explained below, the shell may
4746 use values above 125 specially. Exit statuses from shell builtins and
4747 compound commands are also limited to this range. Under certain
4748 circumstances, the shell will use special values to indicate specific
4751 For the shell's purposes, a command which exits with a
4752 zero exit status has succeeded. An exit status of zero
4753 indicates success. A non-zero exit status indicates failure.
4754 When a command terminates on a fatal signal \fIN\fP, \fBbash\fP uses
4755 the value of 128+\fIN\fP as the exit status.
4757 If a command is not found, the child process created to
4758 execute it returns a status of 127. If a command is found
4759 but is not executable, the return status is 126.
4761 If a command fails because of an error during expansion or redirection,
4762 the exit status is greater than zero.
4764 Shell builtin commands return a status of 0 (\fItrue\fP) if
4765 successful, and non-zero (\fIfalse\fP) if an error occurs
4767 All builtins return an exit status of 2 to indicate incorrect usage,
4768 generally invalid options or missing arguments.
4770 \fBBash\fP itself returns the exit status of the last command
4771 executed, unless a syntax error occurs, in which case it exits
4772 with a non-zero value. See also the \fBexit\fP builtin
4775 When \fBbash\fP is interactive, in the absence of any traps, it ignores
4778 (so that \fBkill 0\fP does not kill an interactive shell),
4782 is caught and handled (so that the \fBwait\fP builtin is interruptible).
4783 In all cases, \fBbash\fP ignores
4786 If job control is in effect,
4797 Non-builtin commands run by \fBbash\fP have signal handlers
4798 set to the values inherited by the shell from its parent.
4799 When job control is not in effect, asynchronous commands
4806 in addition to these inherited handlers.
4807 Commands run as a result of command substitution ignore the
4808 keyboard-generated job control signals
4817 The shell exits by default upon receipt of a
4820 Before exiting, an interactive shell resends the
4823 to all jobs, running or stopped.
4824 Stopped jobs are sent
4827 to ensure that they receive the
4830 To prevent the shell from
4831 sending the signal to a particular job, it should be removed from the
4836 .B "SHELL BUILTIN COMMANDS"
4846 shell option has been set with
4852 to all jobs when an interactive login shell exits.
4854 If \fBbash\fP is waiting for a command to complete and receives a signal
4855 for which a trap has been set, the trap will not be executed until
4856 the command completes.
4857 When \fBbash\fP is waiting for an asynchronous command via the \fBwait\fP
4858 builtin, the reception of a signal for which a trap has been set will
4859 cause the \fBwait\fP builtin to return immediately with an exit status
4860 greater than 128, immediately after which the trap is executed.
4863 refers to the ability to selectively stop (\fIsuspend\fP)
4864 the execution of processes and continue (\fIresume\fP)
4865 their execution at a later point. A user typically employs
4866 this facility via an interactive interface supplied jointly
4867 by the operating system kernel's terminal driver and
4870 The shell associates a
4872 with each pipeline. It keeps a table of currently executing
4873 jobs, which may be listed with the
4877 starts a job asynchronously (in the
4879 it prints a line that looks like:
4885 indicating that this job is job number 1 and that the process ID
4886 of the last process in the pipeline associated with this job is 25647.
4887 All of the processes in a single pipeline are members of the same job.
4891 abstraction as the basis for job control.
4893 To facilitate the implementation of the user interface to job
4894 control, the operating system maintains the notion of a \fIcurrent terminal
4895 process group ID\fP. Members of this process group (processes whose
4896 process group ID is equal to the current terminal process group ID)
4897 receive keyboard-generated signals such as
4900 These processes are said to be in the
4903 processes are those whose process group ID differs from the terminal's;
4904 such processes are immune to keyboard-generated signals.
4905 Only foreground processes are allowed to read from or, if the
4906 user so specifies with \f(CWstty tostop\fP, write to the
4908 Background processes which attempt to read from (write to when
4909 \f(CWstty tostop\fP is in effect) the
4912 .B SIGTTIN (SIGTTOU)
4913 signal by the kernel's terminal driver,
4914 which, unless caught, suspends the process.
4916 If the operating system on which
4921 contains facilities to use it.
4924 character (typically
4926 Control-Z) while a process is running
4927 causes that process to be stopped and returns control to
4930 .I "delayed suspend"
4931 character (typically
4933 Control-Y) causes the process to be stopped when it
4934 attempts to read input from the terminal, and control to
4937 The user may then manipulate the state of this job, using the
4939 command to continue it in the background, the
4941 command to continue it in the foreground, or
4944 command to kill it. A \fB^Z\fP takes effect immediately,
4945 and has the additional side effect of causing pending output
4946 and typeahead to be discarded.
4948 There are a number of ways to refer to a job in the shell.
4951 introduces a job specification (\fIjobspec\fP). Job number
4953 may be referred to as
4955 A job may also be referred to using a prefix of the name used to
4956 start it, or using a substring that appears in its command line.
4961 job. If a prefix matches more than one job,
4963 reports an error. Using
4965 on the other hand, refers to any job containing the string
4967 in its command line. If the substring matches more than one job,
4969 reports an error. The symbols
4973 refer to the shell's notion of the
4975 which is the last job stopped while it was in
4976 the foreground or started in the background.
4979 may be referenced using
4981 If there is only a single job, \fB%+\fP and \fB%\-\fP can both be used
4982 to refer to that job.
4983 In output pertaining to jobs (e.g., the output of the
4985 command), the current job is always flagged with a
4987 and the previous job with a
4989 A single % (with no accompanying job specification) also refers to the
4992 Simply naming a job can be used to bring it into the
4997 bringing job 1 from the background into the foreground.
5000 resumes job 1 in the background, equivalent to
5003 The shell learns immediately whenever a job changes state.
5006 waits until it is about to print a prompt before reporting
5007 changes in a job's status so as to not interrupt
5008 any other output. If the
5015 reports such changes immediately.
5019 is executed for each child that exits.
5021 If an attempt to exit
5023 is made while jobs are stopped (or, if the \fBcheckjobs\fP shell option has
5024 been enabled using the \fBshopt\fP builtin, running), the shell prints a
5025 warning message, and, if the \fBcheckjobs\fP option is enabled, lists the
5026 jobs and their statuses.
5029 command may then be used to inspect their status.
5030 If a second attempt to exit is made without an intervening command,
5031 the shell does not print another warning, and any stopped
5032 jobs are terminated.
5034 When executing interactively,
5036 displays the primary prompt
5039 when it is ready to read a command, and the secondary prompt
5042 when it needs more input to complete a command.
5046 after it reads a command but before executing it.
5048 allows these prompt strings to be customized by inserting a number of
5049 backslash-escaped special characters that are decoded as follows:
5054 an ASCII bell character (07)
5057 the date in "Weekday Month Date" format (e.g., "Tue May 26")
5059 .B \eD{\fIformat\fP}
5060 the \fIformat\fP is passed to \fIstrftime\fP(3) and the result is inserted
5061 into the prompt string; an empty \fIformat\fP results in a locale-specific
5062 time representation. The braces are required
5065 an ASCII escape character (033)
5068 the hostname up to the first `.'
5074 the number of jobs currently managed by the shell
5077 the basename of the shell's terminal device name
5086 the name of the shell, the basename of
5088 (the portion following the final slash)
5091 the current time in 24-hour HH:MM:SS format
5094 the current time in 12-hour HH:MM:SS format
5097 the current time in 12-hour am/pm format
5100 the current time in 24-hour HH:MM format
5103 the username of the current user
5106 the version of \fBbash\fP (e.g., 2.00)
5109 the release of \fBbash\fP, version + patch level (e.g., 2.00.0)
5112 the current working directory, with
5115 abbreviated with a tilde
5116 (uses the value of the
5122 the basename of the current working directory, with
5125 abbreviated with a tilde
5128 the history number of this command
5131 the command number of this command
5134 if the effective UID is 0, a
5140 the character corresponding to the octal number \fInnn\fP
5146 begin a sequence of non-printing characters, which could be used to
5147 embed a terminal control sequence into the prompt
5150 end a sequence of non-printing characters
5154 The command number and the history number are usually different:
5155 the history number of a command is its position in the history
5156 list, which may include commands restored from the history file
5160 below), while the command number is the position in the sequence
5161 of commands executed during the current shell session.
5162 After the string is decoded, it is expanded via
5163 parameter expansion, command substitution, arithmetic
5164 expansion, and quote removal, subject to the value of the
5166 shell option (see the description of the
5170 .B "SHELL BUILTIN COMMANDS"
5173 This is the library that handles reading input when using an interactive
5176 option is given at shell invocation.
5177 Line editing is also used when using the \fB\-e\fP option to the
5179 By default, the line editing commands are similar to those of Emacs.
5180 A vi-style line editing interface is also available.
5181 Line editing can be enabled at any time using the
5189 .B SHELL BUILTIN COMMANDS
5191 To turn off line editing after the shell is running, use the
5198 .SS "Readline Notation"
5200 In this section, the Emacs-style notation is used to denote
5201 keystrokes. Control keys are denoted by C\-\fIkey\fR, e.g., C\-n
5202 means Control\-N. Similarly,
5204 keys are denoted by M\-\fIkey\fR, so M\-x means Meta\-X. (On keyboards
5207 key, M\-\fIx\fP means ESC \fIx\fP, i.e., press the Escape key
5210 key. This makes ESC the \fImeta prefix\fP.
5211 The combination M\-C\-\fIx\fP means ESC\-Control\-\fIx\fP,
5212 or press the Escape key
5213 then hold the Control key while pressing the
5217 Readline commands may be given numeric
5219 which normally act as a repeat count.
5220 Sometimes, however, it is the sign of the argument that is significant.
5221 Passing a negative argument to a command that acts in the forward
5222 direction (e.g., \fBkill\-line\fP) causes that command to act in a
5224 Commands whose behavior with arguments deviates from this are noted
5227 When a command is described as \fIkilling\fP text, the text
5228 deleted is saved for possible future retrieval
5229 (\fIyanking\fP). The killed text is saved in a
5230 \fIkill ring\fP. Consecutive kills cause the text to be
5231 accumulated into one unit, which can be yanked all at once.
5232 Commands which do not kill text separate the chunks of text
5234 .SS "Readline Initialization"
5236 Readline is customized by putting commands in an initialization
5237 file (the \fIinputrc\fP file).
5238 The name of this file is taken from the value of the
5241 variable. If that variable is unset, the default is
5243 When a program which uses the readline library starts up, the
5244 initialization file is read, and the key bindings and variables
5246 There are only a few basic constructs allowed in the
5247 readline initialization file.
5248 Blank lines are ignored.
5249 Lines beginning with a \fB#\fP are comments.
5250 Lines beginning with a \fB$\fP indicate conditional constructs.
5251 Other lines denote key bindings and variable settings.
5253 The default key-bindings may be changed with an
5256 Other programs that use this library may add their own commands
5259 For example, placing
5262 M\-Control\-u: universal\-argument
5266 C\-Meta\-u: universal\-argument
5270 would make M\-C\-u execute the readline command
5271 .IR universal\-argument .
5273 The following symbolic character names are recognized:
5286 In addition to command names, readline allows keys to be bound
5287 to a string that is inserted when the key is pressed (a \fImacro\fP).
5288 .SS "Readline Key Bindings"
5290 The syntax for controlling key bindings in the
5292 file is simple. All that is required is the name of the
5293 command or the text of a macro and a key sequence to which
5294 it should be bound. The name may be specified in one of two ways:
5295 as a symbolic key name, possibly with \fIMeta\-\fP or \fIControl\-\fP
5296 prefixes, or as a key sequence.
5298 When using the form \fBkeyname\fP:\^\fIfunction\-name\fP or \fImacro\fP,
5300 is the name of a key spelled out in English. For example:
5303 Control-u: universal\-argument
5305 Meta-Rubout: backward-kill-word
5307 Control-o: "> output"
5310 In the above example,
5312 is bound to the function
5313 .BR universal\-argument ,
5315 is bound to the function
5316 .BR backward\-kill\-word ,
5319 is bound to run the macro
5320 expressed on the right hand side (that is, to insert the text
5321 .if t \f(CW> output\fP
5325 In the second form, \fB"keyseq"\fP:\^\fIfunction\-name\fP or \fImacro\fP,
5329 above in that strings denoting
5330 an entire key sequence may be specified by placing the sequence
5331 within double quotes. Some GNU Emacs style key escapes can be
5332 used, as in the following example, but the symbolic character names
5336 "\eC\-u": universal\-argument
5338 "\eC\-x\eC\-r": re\-read\-init\-file
5340 "\ee[11~": "Function Key 1"
5345 is again bound to the function
5346 .BR universal\-argument .
5348 is bound to the function
5349 .BR re\-read\-init\-file ,
5352 is bound to insert the text
5353 .if t \f(CWFunction Key 1\fP.
5354 .if n ``Function Key 1''.
5356 The full set of GNU Emacs style escape sequences is
5380 In addition to the GNU Emacs style escape sequences, a second
5381 set of backslash escapes is available:
5410 the eight-bit character whose value is the octal value \fInnn\fP
5411 (one to three digits)
5414 the eight-bit character whose value is the hexadecimal value \fIHH\fP
5415 (one or two hex digits)
5419 When entering the text of a macro, single or double quotes must
5420 be used to indicate a macro definition.
5421 Unquoted text is assumed to be a function name.
5422 In the macro body, the backslash escapes described above are expanded.
5423 Backslash will quote any other character in the macro text,
5424 including " and \(aq.
5427 allows the current readline key bindings to be displayed or modified
5430 builtin command. The editing mode may be switched during interactive
5435 builtin command (see
5437 .B SHELL BUILTIN COMMANDS
5439 .SS "Readline Variables"
5441 Readline has variables that can be used to further customize its
5442 behavior. A variable may be set in the
5444 file with a statement of the form
5447 \fBset\fP \fIvariable\-name\fP \fIvalue\fP
5450 Except where noted, readline variables can take the values
5454 (without regard to case).
5455 Unrecognized variable names are ignored.
5456 When a variable value is read, empty or null values, "on" (case-insensitive),
5457 and "1" are equivalent to \fBOn\fP. All other values are equivalent to
5459 The variables and their default values are:
5463 .B bell\-style (audible)
5464 Controls what happens when readline wants to ring the terminal bell.
5465 If set to \fBnone\fP, readline never rings the bell. If set to
5466 \fBvisible\fP, readline uses a visible bell if one is available.
5467 If set to \fBaudible\fP, readline attempts to ring the terminal's bell.
5469 .B bind\-tty\-special\-chars (On)
5470 If set to \fBOn\fP, readline attempts to bind the control characters
5471 treated specially by the kernel's terminal driver to their readline
5474 .B blink\-matching\-paren (Off)
5475 If set to \fBOn\fP, readline attempts to briefly move the cursor to an
5476 opening parenthesis when a closing parenthesis is inserted.
5478 .B colored\-completion\-prefix (Off)
5479 If set to \fBOn\fP, when listing completions, readline displays the
5480 common prefix of the set of possible completions using a different color.
5481 The color definitions are taken from the value of the \fBLS_COLORS\fP
5482 environment variable.
5484 .B colored\-stats (Off)
5485 If set to \fBOn\fP, readline displays possible completions using different
5486 colors to indicate their file type.
5487 The color definitions are taken from the value of the \fBLS_COLORS\fP
5488 environment variable.
5490 .B comment\-begin (``#'')
5491 The string that is inserted when the readline
5493 command is executed.
5494 This command is bound to
5496 in emacs mode and to
5500 .B completion\-display\-width (-1)
5501 The number of screen columns used to display possible matches
5502 when performing completion.
5503 The value is ignored if it is less than 0 or greater than the terminal
5505 A value of 0 will cause matches to be displayed one per line.
5506 The default value is -1.
5508 .B completion\-ignore\-case (Off)
5509 If set to \fBOn\fP, readline performs filename matching and completion
5510 in a case\-insensitive fashion.
5512 .B completion\-map\-case (Off)
5513 If set to \fBOn\fP, and \fBcompletion\-ignore\-case\fP is enabled, readline
5514 treats hyphens (\fI\-\fP) and underscores (\fI_\fP) as equivalent when
5515 performing case\-insensitive filename matching and completion.
5517 .B completion\-prefix\-display\-length (0)
5518 The length in characters of the common prefix of a list of possible
5519 completions that is displayed without modification. When set to a
5520 value greater than zero, common prefixes longer than this value are
5521 replaced with an ellipsis when displaying possible completions.
5523 .B completion\-query\-items (100)
5524 This determines when the user is queried about viewing
5525 the number of possible completions
5526 generated by the \fBpossible\-completions\fP command.
5527 It may be set to any integer value greater than or equal to
5528 zero. If the number of possible completions is greater than
5529 or equal to the value of this variable, the user is asked whether
5530 or not he wishes to view them; otherwise they are simply listed
5533 .B convert\-meta (On)
5534 If set to \fBOn\fP, readline will convert characters with the
5535 eighth bit set to an ASCII key sequence
5536 by stripping the eighth bit and prefixing an
5537 escape character (in effect, using escape as the \fImeta prefix\fP).
5538 The default is \fIOn\fP, but readline will set it to \fIOff\fP if the
5539 locale contains eight-bit characters.
5541 .B disable\-completion (Off)
5542 If set to \fBOn\fP, readline will inhibit word completion. Completion
5543 characters will be inserted into the line as if they had been
5544 mapped to \fBself-insert\fP.
5546 .B echo\-control\-characters (On)
5547 When set to \fBOn\fP, on operating systems that indicate they support it,
5548 readline echoes a character corresponding to a signal generated from the
5551 .B editing\-mode (emacs)
5552 Controls whether readline begins with a set of key bindings similar
5553 to \fIEmacs\fP or \fIvi\fP.
5555 can be set to either
5560 .B enable\-bracketed\-paste (Off)
5561 When set to \fBOn\fP, readline will configure the terminal in a way
5562 that will enable it to insert each paste into the editing buffer as a
5563 single string of characters, instead of treating each character as if
5564 it had been read from the keyboard. This can prevent pasted characters
5565 from being interpreted as editing commands.
5567 .B enable\-keypad (Off)
5568 When set to \fBOn\fP, readline will try to enable the application
5569 keypad when it is called. Some systems need this to enable the
5572 .B enable\-meta\-key (On)
5573 When set to \fBOn\fP, readline will try to enable any meta modifier
5574 key the terminal claims to support when it is called. On many terminals,
5575 the meta key is used to send eight-bit characters.
5577 .B expand\-tilde (Off)
5578 If set to \fBOn\fP, tilde expansion is performed when readline
5579 attempts word completion.
5581 .B history\-preserve\-point (Off)
5582 If set to \fBOn\fP, the history code attempts to place point at the
5583 same location on each history line retrieved with \fBprevious-history\fP
5584 or \fBnext-history\fP.
5586 .B history\-size (unset)
5587 Set the maximum number of history entries saved in the history list.
5588 If set to zero, any existing history entries are deleted and no new entries
5590 If set to a value less than zero, the number of history entries is not
5592 By default, the number of history entries is set to the value of the
5593 \fBHISTSIZE\fP shell variable.
5594 If an attempt is made to set \fIhistory\-size\fP to a non-numeric value,
5595 the maximum number of history entries will be set to 500.
5597 .B horizontal\-scroll\-mode (Off)
5598 When set to \fBOn\fP, makes readline use a single line for display,
5599 scrolling the input horizontally on a single screen line when it
5600 becomes longer than the screen width rather than wrapping to a new line.
5602 .B input\-meta (Off)
5603 If set to \fBOn\fP, readline will enable eight-bit input (that is,
5604 it will not strip the eighth bit from the characters it reads),
5605 regardless of what the terminal claims it can support. The name
5607 is a synonym for this variable.
5608 The default is \fIOff\fP, but readline will set it to \fIOn\fP if the
5609 locale contains eight-bit characters.
5611 .B isearch\-terminators (``C\-[C\-J'')
5612 The string of characters that should terminate an incremental
5613 search without subsequently executing the character as a command.
5614 If this variable has not been given a value, the characters
5615 \fIESC\fP and \fIC\-J\fP will terminate an incremental search.
5618 Set the current readline keymap. The set of valid keymap names is
5619 \fIemacs, emacs\-standard, emacs\-meta, emacs\-ctlx, vi,
5622 \fIvi\fP is equivalent to \fIvi\-command\fP; \fIemacs\fP is
5623 equivalent to \fIemacs\-standard\fP. The default value is
5627 also affects the default keymap.
5629 .B emacs\-mode\-string (@)
5630 This string is displayed immediately before the last line of the primary
5631 prompt when emacs editing mode is active. The value is expanded like a
5632 key binding, so the standard set of meta- and control prefixes and
5633 backslash escape sequences is available.
5634 Use the \e1 and \e2 escapes to begin and end sequences of
5635 non-printing characters, which can be used to embed a terminal control
5636 sequence into the mode string.
5638 .B keyseq\-timeout (500)
5639 Specifies the duration \fIreadline\fP will wait for a character when reading an
5640 ambiguous key sequence (one that can form a complete key sequence using
5641 the input read so far, or can take additional input to complete a longer
5643 If no input is received within the timeout, \fIreadline\fP will use the shorter
5644 but complete key sequence.
5645 The value is specified in milliseconds, so a value of 1000 means that
5646 \fIreadline\fP will wait one second for additional input.
5647 If this variable is set to a value less than or equal to zero, or to a
5648 non-numeric value, \fIreadline\fP will wait until another key is pressed to
5649 decide which key sequence to complete.
5651 .B mark\-directories (On)
5652 If set to \fBOn\fP, completed directory names have a slash
5655 .B mark\-modified\-lines (Off)
5656 If set to \fBOn\fP, history lines that have been modified are displayed
5657 with a preceding asterisk (\fB*\fP).
5659 .B mark\-symlinked\-directories (Off)
5660 If set to \fBOn\fP, completed names which are symbolic links to directories
5661 have a slash appended (subject to the value of
5662 \fBmark\-directories\fP).
5664 .B match\-hidden\-files (On)
5665 This variable, when set to \fBOn\fP, causes readline to match files whose
5666 names begin with a `.' (hidden files) when performing filename
5668 If set to \fBOff\fP, the leading `.' must be
5669 supplied by the user in the filename to be completed.
5671 .B menu\-complete\-display\-prefix (Off)
5672 If set to \fBOn\fP, menu completion displays the common prefix of the
5673 list of possible completions (which may be empty) before cycling through
5676 .B output\-meta (Off)
5677 If set to \fBOn\fP, readline will display characters with the
5678 eighth bit set directly rather than as a meta-prefixed escape
5680 The default is \fIOff\fP, but readline will set it to \fIOn\fP if the
5681 locale contains eight-bit characters.
5683 .B page\-completions (On)
5684 If set to \fBOn\fP, readline uses an internal \fImore\fP-like pager
5685 to display a screenful of possible completions at a time.
5687 .B print\-completions\-horizontally (Off)
5688 If set to \fBOn\fP, readline will display completions with matches
5689 sorted horizontally in alphabetical order, rather than down the screen.
5691 .B revert\-all\-at\-newline (Off)
5692 If set to \fBOn\fP, readline will undo all changes to history lines
5693 before returning when \fBaccept\-line\fP is executed. By default,
5694 history lines may be modified and retain individual undo lists across
5695 calls to \fBreadline\fP.
5697 .B show\-all\-if\-ambiguous (Off)
5698 This alters the default behavior of the completion functions. If
5701 words which have more than one possible completion cause the
5702 matches to be listed immediately instead of ringing the bell.
5704 .B show\-all\-if\-unmodified (Off)
5705 This alters the default behavior of the completion functions in
5706 a fashion similar to \fBshow\-all\-if\-ambiguous\fP.
5709 words which have more than one possible completion without any
5710 possible partial completion (the possible completions don't share
5711 a common prefix) cause the matches to be listed immediately instead
5712 of ringing the bell.
5714 .B show\-mode\-in\-prompt (Off)
5715 If set to \fBOn\fP, add a character to the beginning of the prompt
5716 indicating the editing mode: emacs (@), vi command (:) or vi
5719 .B skip\-completed\-text (Off)
5720 If set to \fBOn\fP, this alters the default completion behavior when
5721 inserting a single match into the line. It's only active when
5722 performing completion in the middle of a word. If enabled, readline
5723 does not insert characters from the completion that match characters
5724 after point in the word being completed, so portions of the word
5725 following the cursor are not duplicated.
5727 .B vi\-cmd\-mode\-string ((cmd))
5728 This string is displayed immediately before the last line of the primary
5729 prompt when vi editing mode is active and in command mode.
5730 The value is expanded like a
5731 key binding, so the standard set of meta- and control prefixes and
5732 backslash escape sequences is available.
5733 Use the \e1 and \e2 escapes to begin and end sequences of
5734 non-printing characters, which can be used to embed a terminal control
5735 sequence into the mode string.
5737 .B vi\-ins\-mode\-string ((ins))
5738 This string is displayed immediately before the last line of the primary
5739 prompt when vi editing mode is active and in insertion mode.
5740 The value is expanded like a
5741 key binding, so the standard set of meta- and control prefixes and
5742 backslash escape sequences is available.
5743 Use the \e1 and \e2 escapes to begin and end sequences of
5744 non-printing characters, which can be used to embed a terminal control
5745 sequence into the mode string.
5747 .B visible\-stats (Off)
5748 If set to \fBOn\fP, a character denoting a file's type as reported
5749 by \fIstat\fP(2) is appended to the filename when listing possible
5752 .SS "Readline Conditional Constructs"
5754 Readline implements a facility similar in spirit to the conditional
5755 compilation features of the C preprocessor which allows key
5756 bindings and variable settings to be performed as the result
5757 of tests. There are four parser directives used.
5761 construct allows bindings to be made based on the
5762 editing mode, the terminal being used, or the application using
5763 readline. The text of the test extends to the end of the line;
5764 no characters are required to isolate it.
5767 The \fBmode=\fP form of the \fB$if\fP directive is used to test
5768 whether readline is in emacs or vi mode.
5769 This may be used in conjunction
5770 with the \fBset keymap\fP command, for instance, to set bindings in
5771 the \fIemacs\-standard\fP and \fIemacs\-ctlx\fP keymaps only if
5772 readline is starting out in emacs mode.
5774 The \fBterm=\fP form may be used to include terminal-specific
5775 key bindings, perhaps to bind the key sequences output by the
5776 terminal's function keys. The word on the right side of the
5778 is tested against both the full name of the terminal and the portion
5779 of the terminal name before the first \fB\-\fP. This allows
5786 .IP \fBapplication\fP
5787 The \fBapplication\fP construct is used to include
5788 application-specific settings. Each program using the readline
5789 library sets the \fIapplication name\fP, and an initialization
5790 file can test for a particular value.
5791 This could be used to bind key sequences to functions useful for
5792 a specific program. For instance, the following command adds a
5793 key sequence that quotes the current or previous word in \fBbash\fP:
5798 # Quote the current or previous word
5799 "\eC\-xq": "\eeb\e"\eef\e""
5805 This command, as seen in the previous example, terminates an
5808 Commands in this branch of the \fB$if\fP directive are executed if
5811 This directive takes a single filename as an argument and reads commands
5812 and bindings from that file. For example, the following directive
5813 would read \fI/etc/inputrc\fP:
5817 \fB$include\fP \^ \fI/etc/inputrc\fP
5822 Readline provides commands for searching through the command history
5826 below) for lines containing a specified string.
5827 There are two search modes:
5830 .IR non-incremental .
5832 Incremental searches begin before the user has finished typing the
5834 As each character of the search string is typed, readline displays
5835 the next entry from the history matching the string typed so far.
5836 An incremental search requires only as many characters as needed to
5837 find the desired history entry.
5838 The characters present in the value of the \fBisearch-terminators\fP
5839 variable are used to terminate an incremental search.
5840 If that variable has not been assigned a value the Escape and
5841 Control-J characters will terminate an incremental search.
5842 Control-G will abort an incremental search and restore the original
5844 When the search is terminated, the history entry containing the
5845 search string becomes the current line.
5847 To find other matching entries in the history list, type Control-S or
5848 Control-R as appropriate.
5849 This will search backward or forward in the history for the next
5850 entry matching the search string typed so far.
5851 Any other key sequence bound to a readline command will terminate
5852 the search and execute that command.
5853 For instance, a \fInewline\fP will terminate the search and accept
5854 the line, thereby executing the command from the history list.
5856 Readline remembers the last incremental search string. If two
5857 Control-Rs are typed without any intervening characters defining a
5858 new search string, any remembered search string is used.
5860 Non-incremental searches read the entire search string before starting
5861 to search for matching history lines. The search string may be
5862 typed by the user or be part of the contents of the current line.
5863 .SS "Readline Command Names"
5865 The following is a list of the names of the commands and the default
5866 key sequences to which they are bound.
5867 Command names without an accompanying key sequence are unbound by default.
5868 In the following descriptions, \fIpoint\fP refers to the current cursor
5869 position, and \fImark\fP refers to a cursor position saved by the
5870 \fBset\-mark\fP command.
5871 The text between the point and mark is referred to as the \fIregion\fP.
5872 .SS Commands for Moving
5876 .B beginning\-of\-line (C\-a)
5877 Move to the start of the current line.
5879 .B end\-of\-line (C\-e)
5880 Move to the end of the line.
5882 .B forward\-char (C\-f)
5883 Move forward a character.
5885 .B backward\-char (C\-b)
5886 Move back a character.
5888 .B forward\-word (M\-f)
5889 Move forward to the end of the next word. Words are composed of
5890 alphanumeric characters (letters and digits).
5892 .B backward\-word (M\-b)
5893 Move back to the start of the current or previous word.
5894 Words are composed of alphanumeric characters (letters and digits).
5896 .B shell\-forward\-word
5897 Move forward to the end of the next word.
5898 Words are delimited by non-quoted shell metacharacters.
5900 .B shell\-backward\-word
5901 Move back to the start of the current or previous word.
5902 Words are delimited by non-quoted shell metacharacters.
5904 .B clear\-screen (C\-l)
5905 Clear the screen leaving the current line at the top of the screen.
5906 With an argument, refresh the current line without clearing the
5909 .B redraw\-current\-line
5910 Refresh the current line.
5912 .SS Commands for Manipulating the History
5916 .B accept\-line (Newline, Return)
5917 Accept the line regardless of where the cursor is. If this line is
5918 non-empty, add it to the history list according to the state of the
5921 variable. If the line is a modified history
5922 line, then restore the history line to its original state.
5924 .B previous\-history (C\-p)
5925 Fetch the previous command from the history list, moving back in
5928 .B next\-history (C\-n)
5929 Fetch the next command from the history list, moving forward in the
5932 .B beginning\-of\-history (M\-<)
5933 Move to the first line in the history.
5935 .B end\-of\-history (M\->)
5936 Move to the end of the input history, i.e., the line currently being
5939 .B reverse\-search\-history (C\-r)
5940 Search backward starting at the current line and moving `up' through
5941 the history as necessary. This is an incremental search.
5943 .B forward\-search\-history (C\-s)
5944 Search forward starting at the current line and moving `down' through
5945 the history as necessary. This is an incremental search.
5947 .B non\-incremental\-reverse\-search\-history (M\-p)
5948 Search backward through the history starting at the current line
5949 using a non-incremental search for a string supplied by the user.
5951 .B non\-incremental\-forward\-search\-history (M\-n)
5952 Search forward through the history using a non-incremental search for
5953 a string supplied by the user.
5955 .B history\-search\-forward
5956 Search forward through the history for the string of characters
5957 between the start of the current line and the point.
5958 This is a non-incremental search.
5960 .B history\-search\-backward
5961 Search backward through the history for the string of characters
5962 between the start of the current line and the point.
5963 This is a non-incremental search.
5965 .B yank\-nth\-arg (M\-C\-y)
5966 Insert the first argument to the previous command (usually
5967 the second word on the previous line) at point.
5970 insert the \fIn\fPth word from the previous command (the words
5971 in the previous command begin with word 0). A negative argument
5972 inserts the \fIn\fPth word from the end of the previous command.
5973 Once the argument \fIn\fP is computed, the argument is extracted
5974 as if the "!\fIn\fP" history expansion had been specified.
5977 yank\-last\-arg (M\-.\^, M\-_\^)
5978 Insert the last argument to the previous command (the last word of
5979 the previous history entry).
5980 With a numeric argument, behave exactly like \fByank\-nth\-arg\fP.
5981 Successive calls to \fByank\-last\-arg\fP move back through the history
5982 list, inserting the last word (or the word specified by the argument to
5983 the first call) of each line in turn.
5984 Any numeric argument supplied to these successive calls determines
5985 the direction to move through the history. A negative argument switches
5986 the direction through the history (back or forward).
5987 The history expansion facilities are used to extract the last word,
5988 as if the "!$" history expansion had been specified.
5990 .B shell\-expand\-line (M\-C\-e)
5991 Expand the line as the shell does. This
5992 performs alias and history expansion as well as all of the shell
5993 word expansions. See
5995 .B HISTORY EXPANSION
5996 below for a description of history expansion.
5998 .B history\-expand\-line (M\-^)
5999 Perform history expansion on the current line.
6002 .B HISTORY EXPANSION
6003 below for a description of history expansion.
6006 Perform history expansion on the current line and insert a space.
6009 .B HISTORY EXPANSION
6010 below for a description of history expansion.
6012 .B alias\-expand\-line
6013 Perform alias expansion on the current line.
6017 above for a description of alias expansion.
6019 .B history\-and\-alias\-expand\-line
6020 Perform history and alias expansion on the current line.
6022 .B insert\-last\-argument (M\-.\^, M\-_\^)
6023 A synonym for \fByank\-last\-arg\fP.
6025 .B operate\-and\-get\-next (C\-o)
6026 Accept the current line for execution and fetch the next line
6027 relative to the current line from the history for editing. Any
6028 argument is ignored.
6030 .B edit\-and\-execute\-command (C\-xC\-e)
6031 Invoke an editor on the current command line, and execute the result as shell
6033 \fBBash\fP attempts to invoke
6038 and \fIemacs\fP as the editor, in that order.
6040 .SS Commands for Changing Text
6044 .B \fIend\-of\-file\fP (usually C\-d)
6045 The character indicating end-of-file as set, for example, by
6048 If this character is read when there are no characters
6049 on the line, and point is at the beginning of the line, Readline
6050 interprets it as the end of input and returns
6054 .B delete\-char (C\-d)
6055 Delete the character at point.
6056 If this function is bound to the
6057 same character as the tty \fBEOF\fP character, as \fBC\-d\fP
6058 commonly is, see above for the effects.
6060 .B backward\-delete\-char (Rubout)
6061 Delete the character behind the cursor. When given a numeric argument,
6062 save the deleted text on the kill ring.
6064 .B forward\-backward\-delete\-char
6065 Delete the character under the cursor, unless the cursor is at the
6066 end of the line, in which case the character behind the cursor is
6069 .B quoted\-insert (C\-q, C\-v)
6070 Add the next character typed to the line verbatim. This is
6071 how to insert characters like \fBC\-q\fP, for example.
6073 .B tab\-insert (C\-v TAB)
6074 Insert a tab character.
6076 .B self\-insert (a,\ b,\ A,\ 1,\ !,\ ...)
6077 Insert the character typed.
6079 .B transpose\-chars (C\-t)
6080 Drag the character before point forward over the character at point,
6081 moving point forward as well.
6082 If point is at the end of the line, then this transposes
6083 the two characters before point.
6084 Negative arguments have no effect.
6086 .B transpose\-words (M\-t)
6087 Drag the word before point past the word after point,
6088 moving point over that word as well.
6089 If point is at the end of the line, this transposes
6090 the last two words on the line.
6092 .B upcase\-word (M\-u)
6093 Uppercase the current (or following) word. With a negative argument,
6094 uppercase the previous word, but do not move point.
6096 .B downcase\-word (M\-l)
6097 Lowercase the current (or following) word. With a negative argument,
6098 lowercase the previous word, but do not move point.
6100 .B capitalize\-word (M\-c)
6101 Capitalize the current (or following) word. With a negative argument,
6102 capitalize the previous word, but do not move point.
6105 Toggle overwrite mode. With an explicit positive numeric argument,
6106 switches to overwrite mode. With an explicit non-positive numeric
6107 argument, switches to insert mode. This command affects only
6108 \fBemacs\fP mode; \fBvi\fP mode does overwrite differently.
6109 Each call to \fIreadline()\fP starts in insert mode.
6110 In overwrite mode, characters bound to \fBself\-insert\fP replace
6111 the text at point rather than pushing the text to the right.
6112 Characters bound to \fBbackward\-delete\-char\fP replace the character
6113 before point with a space. By default, this command is unbound.
6115 .SS Killing and Yanking
6119 .B kill\-line (C\-k)
6120 Kill the text from point to the end of the line.
6122 .B backward\-kill\-line (C\-x Rubout)
6123 Kill backward to the beginning of the line.
6125 .B unix\-line\-discard (C\-u)
6126 Kill backward from point to the beginning of the line.
6127 The killed text is saved on the kill-ring.
6128 .\" There is no real difference between this and backward-kill-line
6130 .B kill\-whole\-line
6131 Kill all characters on the current line, no matter where point is.
6133 .B kill\-word (M\-d)
6134 Kill from point to the end of the current word, or if between
6135 words, to the end of the next word.
6136 Word boundaries are the same as those used by \fBforward\-word\fP.
6138 .B backward\-kill\-word (M\-Rubout)
6139 Kill the word behind point.
6140 Word boundaries are the same as those used by \fBbackward\-word\fP.
6142 .B shell\-kill\-word
6143 Kill from point to the end of the current word, or if between
6144 words, to the end of the next word.
6145 Word boundaries are the same as those used by \fBshell\-forward\-word\fP.
6147 .B shell\-backward\-kill\-word
6148 Kill the word behind point.
6149 Word boundaries are the same as those used by \fBshell\-backward\-word\fP.
6151 .B unix\-word\-rubout (C\-w)
6152 Kill the word behind point, using white space as a word boundary.
6153 The killed text is saved on the kill-ring.
6155 .B unix\-filename\-rubout
6156 Kill the word behind point, using white space and the slash character
6157 as the word boundaries.
6158 The killed text is saved on the kill-ring.
6160 .B delete\-horizontal\-space (M\-\e)
6161 Delete all spaces and tabs around point.
6164 Kill the text in the current region.
6166 .B copy\-region\-as\-kill
6167 Copy the text in the region to the kill buffer.
6169 .B copy\-backward\-word
6170 Copy the word before point to the kill buffer.
6171 The word boundaries are the same as \fBbackward\-word\fP.
6173 .B copy\-forward\-word
6174 Copy the word following point to the kill buffer.
6175 The word boundaries are the same as \fBforward\-word\fP.
6178 Yank the top of the kill ring into the buffer at point.
6181 Rotate the kill ring, and yank the new top. Only works following
6186 .SS Numeric Arguments
6190 .B digit\-argument (M\-0, M\-1, ..., M\-\-)
6191 Add this digit to the argument already accumulating, or start a new
6192 argument. M\-\- starts a negative argument.
6194 .B universal\-argument
6195 This is another way to specify an argument.
6196 If this command is followed by one or more digits, optionally with a
6197 leading minus sign, those digits define the argument.
6198 If the command is followed by digits, executing
6199 .B universal\-argument
6200 again ends the numeric argument, but is otherwise ignored.
6201 As a special case, if this command is immediately followed by a
6202 character that is neither a digit nor minus sign, the argument count
6203 for the next command is multiplied by four.
6204 The argument count is initially one, so executing this function the
6205 first time makes the argument count four, a second time makes the
6206 argument count sixteen, and so on.
6213 Attempt to perform completion on the text before point.
6215 attempts completion treating the text as a variable (if the
6216 text begins with \fB$\fP), username (if the text begins with
6217 \fB~\fP), hostname (if the text begins with \fB@\fP), or
6218 command (including aliases and functions) in turn. If none
6219 of these produces a match, filename completion is attempted.
6221 .B possible\-completions (M\-?)
6222 List the possible completions of the text before point.
6224 .B insert\-completions (M\-*)
6225 Insert all completions of the text before point
6226 that would have been generated by
6227 \fBpossible\-completions\fP.
6230 Similar to \fBcomplete\fP, but replaces the word to be completed
6231 with a single match from the list of possible completions.
6232 Repeated execution of \fBmenu\-complete\fP steps through the list
6233 of possible completions, inserting each match in turn.
6234 At the end of the list of completions, the bell is rung
6235 (subject to the setting of \fBbell\-style\fP)
6236 and the original text is restored.
6237 An argument of \fIn\fP moves \fIn\fP positions forward in the list
6238 of matches; a negative argument may be used to move backward
6240 This command is intended to be bound to \fBTAB\fP, but is unbound
6243 .B menu\-complete\-backward
6244 Identical to \fBmenu\-complete\fP, but moves backward through the list
6245 of possible completions, as if \fBmenu\-complete\fP had been given a
6246 negative argument. This command is unbound by default.
6248 .B delete\-char\-or\-list
6249 Deletes the character under the cursor if not at the beginning or
6250 end of the line (like \fBdelete\-char\fP).
6251 If at the end of the line, behaves identically to
6252 \fBpossible\-completions\fP.
6253 This command is unbound by default.
6255 .B complete\-filename (M\-/)
6256 Attempt filename completion on the text before point.
6258 .B possible\-filename\-completions (C\-x /)
6259 List the possible completions of the text before point,
6260 treating it as a filename.
6262 .B complete\-username (M\-~)
6263 Attempt completion on the text before point, treating
6266 .B possible\-username\-completions (C\-x ~)
6267 List the possible completions of the text before point,
6268 treating it as a username.
6270 .B complete\-variable (M\-$)
6271 Attempt completion on the text before point, treating
6272 it as a shell variable.
6274 .B possible\-variable\-completions (C\-x $)
6275 List the possible completions of the text before point,
6276 treating it as a shell variable.
6278 .B complete\-hostname (M\-@)
6279 Attempt completion on the text before point, treating
6282 .B possible\-hostname\-completions (C\-x @)
6283 List the possible completions of the text before point,
6284 treating it as a hostname.
6286 .B complete\-command (M\-!)
6287 Attempt completion on the text before point, treating
6288 it as a command name. Command completion attempts to
6289 match the text against aliases, reserved words, shell
6290 functions, shell builtins, and finally executable filenames,
6293 .B possible\-command\-completions (C\-x !)
6294 List the possible completions of the text before point,
6295 treating it as a command name.
6297 .B dynamic\-complete\-history (M\-TAB)
6298 Attempt completion on the text before point, comparing
6299 the text against lines from the history list for possible
6303 Attempt menu completion on the text before point, comparing
6304 the text against lines from the history list for possible
6307 .B complete\-into\-braces (M\-{)
6308 Perform filename completion and insert the list of possible completions
6309 enclosed within braces so the list is available to the shell (see
6317 .B start\-kbd\-macro (C\-x (\^)
6318 Begin saving the characters typed into the current keyboard macro.
6320 .B end\-kbd\-macro (C\-x )\^)
6321 Stop saving the characters typed into the current keyboard macro
6322 and store the definition.
6324 .B call\-last\-kbd\-macro (C\-x e)
6325 Re-execute the last keyboard macro defined, by making the characters
6326 in the macro appear as if typed at the keyboard.
6328 .B print\-last\-kbd\-macro ()
6329 Print the last keyboard macro defined in a format suitable for the
6336 .B re\-read\-init\-file (C\-x C\-r)
6337 Read in the contents of the \fIinputrc\fP file, and incorporate
6338 any bindings or variable assignments found there.
6341 Abort the current editing command and
6342 ring the terminal's bell (subject to the setting of
6345 .B do\-uppercase\-version (M\-a, M\-b, M\-\fIx\fP, ...)
6346 If the metafied character \fIx\fP is lowercase, run the command
6347 that is bound to the corresponding uppercase character.
6349 .B prefix\-meta (ESC)
6350 Metafy the next character typed.
6357 .B undo (C\-_, C\-x C\-u)
6358 Incremental undo, separately remembered for each line.
6360 .B revert\-line (M\-r)
6361 Undo all changes made to this line. This is like executing the
6363 command enough times to return the line to its initial state.
6365 .B tilde\-expand (M\-&)
6366 Perform tilde expansion on the current word.
6368 .B set\-mark (C\-@, M\-<space>)
6369 Set the mark to the point. If a
6370 numeric argument is supplied, the mark is set to that position.
6372 .B exchange\-point\-and\-mark (C\-x C\-x)
6373 Swap the point with the mark. The current cursor position is set to
6374 the saved position, and the old cursor position is saved as the mark.
6376 .B character\-search (C\-])
6377 A character is read and point is moved to the next occurrence of that
6378 character. A negative count searches for previous occurrences.
6380 .B character\-search\-backward (M\-C\-])
6381 A character is read and point is moved to the previous occurrence of that
6382 character. A negative count searches for subsequent occurrences.
6384 .B skip\-csi\-sequence
6385 Read enough characters to consume a multi-key sequence such as those
6386 defined for keys like Home and End. Such sequences begin with a
6387 Control Sequence Indicator (CSI), usually ESC\-[. If this sequence is
6388 bound to "\e[", keys producing such sequences will have no effect
6389 unless explicitly bound to a readline command, instead of inserting
6390 stray characters into the editing buffer. This is unbound by default,
6391 but usually bound to ESC\-[.
6393 .B insert\-comment (M\-#)
6394 Without a numeric argument, the value of the readline
6396 variable is inserted at the beginning of the current line.
6397 If a numeric argument is supplied, this command acts as a toggle: if
6398 the characters at the beginning of the line do not match the value
6399 of \fBcomment\-begin\fP, the value is inserted, otherwise
6400 the characters in \fBcomment\-begin\fP are deleted from the beginning of
6402 In either case, the line is accepted as if a newline had been typed.
6403 The default value of
6404 \fBcomment\-begin\fP causes this command to make the current line
6406 If a numeric argument causes the comment character to be removed, the line
6407 will be executed by the shell.
6409 .B glob\-complete\-word (M\-g)
6410 The word before point is treated as a pattern for pathname expansion,
6411 with an asterisk implicitly appended. This pattern is used to
6412 generate a list of matching filenames for possible completions.
6414 .B glob\-expand\-word (C\-x *)
6415 The word before point is treated as a pattern for pathname expansion,
6416 and the list of matching filenames is inserted, replacing the word.
6417 If a numeric argument is supplied, an asterisk is appended before
6420 .B glob\-list\-expansions (C\-x g)
6421 The list of expansions that would have been generated by
6422 .B glob\-expand\-word
6423 is displayed, and the line is redrawn.
6424 If a numeric argument is supplied, an asterisk is appended before
6428 Print all of the functions and their key bindings to the
6429 readline output stream. If a numeric argument is supplied,
6430 the output is formatted in such a way that it can be made part
6431 of an \fIinputrc\fP file.
6434 Print all of the settable readline variables and their values to the
6435 readline output stream. If a numeric argument is supplied,
6436 the output is formatted in such a way that it can be made part
6437 of an \fIinputrc\fP file.
6440 Print all of the readline key sequences bound to macros and the
6441 strings they output. If a numeric argument is supplied,
6442 the output is formatted in such a way that it can be made part
6443 of an \fIinputrc\fP file.
6445 .B display\-shell\-version (C\-x C\-v)
6446 Display version information about the current instance of
6449 .SS Programmable Completion
6451 When word completion is attempted for an argument to a command for
6452 which a completion specification (a \fIcompspec\fP) has been defined
6453 using the \fBcomplete\fP builtin (see
6455 .B "SHELL BUILTIN COMMANDS"
6456 below), the programmable completion facilities are invoked.
6458 First, the command name is identified.
6459 If the command word is the empty string (completion attempted at the
6460 beginning of an empty line), any compspec defined with
6461 the \fB\-E\fP option to \fBcomplete\fP is used.
6462 If a compspec has been defined for that command, the
6463 compspec is used to generate the list of possible completions for the word.
6464 If the command word is a full pathname, a compspec for the full
6465 pathname is searched for first.
6466 If no compspec is found for the full pathname, an attempt is made to
6467 find a compspec for the portion following the final slash.
6468 If those searches do not result in a compspec, any compspec defined with
6469 the \fB\-D\fP option to \fBcomplete\fP is used as the default.
6471 Once a compspec has been found, it is used to generate the list of
6473 If a compspec is not found, the default \fBbash\fP completion as
6474 described above under \fBCompleting\fP is performed.
6476 First, the actions specified by the compspec are used.
6477 Only matches which are prefixed by the word being completed are
6483 option is used for filename or directory name completion, the shell
6487 is used to filter the matches.
6489 Any completions specified by a pathname expansion pattern to the
6490 \fB\-G\fP option are generated next.
6491 The words generated by the pattern need not match the word
6496 shell variable is not used to filter the matches, but the
6501 Next, the string specified as the argument to the \fB\-W\fP option
6503 The string is first split using the characters in the
6506 special variable as delimiters.
6507 Shell quoting is honored.
6508 Each word is then expanded using
6509 brace expansion, tilde expansion, parameter and variable expansion,
6510 command substitution, and arithmetic expansion,
6511 as described above under
6514 The results are split using the rules described above under
6515 \fBWord Splitting\fP.
6516 The results of the expansion are prefix-matched against the word being
6517 completed, and the matching words become the possible completions.
6519 After these matches have been generated, any shell function or command
6520 specified with the \fB\-F\fP and \fB\-C\fP options is invoked.
6521 When the command or function is invoked, the
6531 variables are assigned values as described above under
6532 \fBShell Variables\fP.
6533 If a shell function is being invoked, the
6539 variables are also set.
6540 When the function or command is invoked,
6541 the first argument (\fB$1\fP) is the name of the command whose arguments are
6543 the second argument (\fB$2\fP) is the word being completed,
6544 and the third argument (\fB$3\fP) is the word preceding the word being
6545 completed on the current command line.
6546 No filtering of the generated completions against the word being completed
6547 is performed; the function or command has complete freedom in generating
6550 Any function specified with \fB\-F\fP is invoked first.
6551 The function may use any of the shell facilities, including the
6552 \fBcompgen\fP builtin described below, to generate the matches.
6553 It must put the possible completions in the
6556 array variable, one per array element.
6558 Next, any command specified with the \fB\-C\fP option is invoked
6559 in an environment equivalent to command substitution.
6560 It should print a list of completions, one per line, to the
6562 Backslash may be used to escape a newline, if necessary.
6564 After all of the possible completions are generated, any filter
6565 specified with the \fB\-X\fP option is applied to the list.
6566 The filter is a pattern as used for pathname expansion; a \fB&\fP
6567 in the pattern is replaced with the text of the word being completed.
6568 A literal \fB&\fP may be escaped with a backslash; the backslash
6569 is removed before attempting a match.
6570 Any completion that matches the pattern will be removed from the list.
6571 A leading \fB!\fP negates the pattern; in this case any completion
6572 not matching the pattern will be removed.
6575 shell option is enabled, the match is performed without regard to the case
6576 of alphabetic characters.
6578 Finally, any prefix and suffix specified with the \fB\-P\fP and \fB\-S\fP
6579 options are added to each member of the completion list, and the result is
6580 returned to the readline completion code as the list of possible
6583 If the previously-applied actions do not generate any matches, and the
6584 \fB\-o dirnames\fP option was supplied to \fBcomplete\fP when the
6585 compspec was defined, directory name completion is attempted.
6587 If the \fB\-o plusdirs\fP option was supplied to \fBcomplete\fP when the
6588 compspec was defined, directory name completion is attempted and any
6589 matches are added to the results of the other actions.
6591 By default, if a compspec is found, whatever it generates is returned
6592 to the completion code as the full set of possible completions.
6593 The default \fBbash\fP completions are not attempted, and the readline
6594 default of filename completion is disabled.
6595 If the \fB\-o bashdefault\fP option was supplied to \fBcomplete\fP when
6596 the compspec was defined, the \fBbash\fP default completions are attempted
6597 if the compspec generates no matches.
6598 If the \fB\-o default\fP option was supplied to \fBcomplete\fP when the
6599 compspec was defined, readline's default completion will be performed
6600 if the compspec (and, if attempted, the default \fBbash\fP completions)
6601 generate no matches.
6603 When a compspec indicates that directory name completion is desired,
6604 the programmable completion functions force readline to append a slash
6605 to completed names which are symbolic links to directories, subject to
6606 the value of the \fBmark\-directories\fP readline variable, regardless
6607 of the setting of the \fBmark-symlinked\-directories\fP readline variable.
6609 There is some support for dynamically modifying completions. This is
6610 most useful when used in combination with a default completion specified
6611 with \fBcomplete -D\fP.
6612 It's possible for shell functions executed as completion
6613 handlers to indicate that completion should be retried by returning an
6614 exit status of 124. If a shell function returns 124, and changes
6615 the compspec associated with the command on which completion is being
6616 attempted (supplied as the first argument when the function is executed),
6617 programmable completion restarts from the beginning, with an
6618 attempt to find a new compspec for that command. This allows a set of
6619 completions to be built dynamically as completion is attempted, rather than
6620 being loaded all at once.
6622 For instance, assuming that there is a library of compspecs, each kept in a
6623 file corresponding to the name of the command, the following default
6624 completion function would load completions dynamically:
6626 \f(CW_completion_loader()
6630 . "/etc/bash_completion.d/$1.sh" >/dev/null 2>&1 && return 124
6634 complete -D -F _completion_loader -o bashdefault -o default
6642 builtin is enabled, the shell provides access to the
6643 \fIcommand history\fP,
6644 the list of commands previously typed.
6648 variable is used as the
6649 number of commands to save in a history list.
6650 The text of the last
6653 commands (default 500) is saved. The shell
6654 stores each command in the history list prior to parameter and
6655 variable expansion (see
6658 above) but after history expansion is performed, subject to the
6659 values of the shell variables
6666 On startup, the history is initialized from the file named by
6670 (default \fI~/.bash_history\fP).
6671 The file named by the value of
6674 is truncated, if necessary, to contain no more than
6675 the number of lines specified by the value of
6678 If \fBHISTFILESIZE\fP is unset, or set to null, a non-numeric value,
6679 or a numeric value less than zero, the history file is not truncated.
6680 When the history file is read,
6681 lines beginning with the history comment character followed immediately
6682 by a digit are interpreted as timestamps for the preceding history line.
6683 These timestamps are optionally displayed depending on the value of the
6687 When a shell with history enabled exits, the last
6690 lines are copied from the history list to
6695 shell option is enabled
6696 (see the description of
6700 .B "SHELL BUILTIN COMMANDS"
6701 below), the lines are appended to the history file,
6702 otherwise the history file is overwritten.
6706 is unset, or if the history file is unwritable, the history is
6711 variable is set, time stamps are written to the history file, marked
6712 with the history comment character, so
6713 they may be preserved across shell sessions.
6714 This uses the history comment character to distinguish timestamps from
6715 other history lines.
6716 After saving the history, the history file is truncated
6717 to contain no more than
6723 is unset, or set to null, a non-numeric value,
6724 or a numeric value less than zero, the history file is not truncated.
6730 .B SHELL BUILTIN COMMANDS
6731 below) may be used to list or edit and re-execute a portion of
6735 builtin may be used to display or modify the history list and
6736 manipulate the history file.
6737 When using command-line editing, search commands
6738 are available in each editing mode that provide access to the
6741 The shell allows control over which commands are saved on the history
6748 variables may be set to cause the shell to save only a subset of the
6752 shell option, if enabled, causes the shell to attempt to save each
6753 line of a multi-line command in the same history entry, adding
6754 semicolons where necessary to preserve syntactic correctness.
6757 shell option causes the shell to save the command with embedded newlines
6758 instead of semicolons. See the description of the
6762 .B "SHELL BUILTIN COMMANDS"
6763 for information on setting and unsetting shell options.
6764 .SH "HISTORY EXPANSION"
6766 The shell supports a history expansion feature that
6767 is similar to the history expansion in
6769 This section describes what syntax features are available. This
6770 feature is enabled by default for interactive shells, and can be
6775 builtin command (see
6777 .B SHELL BUILTIN COMMANDS
6778 below). Non-interactive shells do not perform history expansion
6781 History expansions introduce words from the history list into
6782 the input stream, making it easy to repeat commands, insert the
6783 arguments to a previous command into the current input line, or
6784 fix errors in previous commands quickly.
6786 History expansion is performed immediately after a complete line
6787 is read, before the shell breaks it into words.
6788 It takes place in two parts.
6789 The first is to determine which line from the history list
6790 to use during substitution.
6791 The second is to select portions of that line for inclusion into
6793 The line selected from the history is the \fIevent\fP,
6794 and the portions of that line that are acted upon are \fIwords\fP.
6795 Various \fImodifiers\fP are available to manipulate the selected words.
6796 The line is broken into words in the same fashion as when reading input,
6797 so that several \fImetacharacter\fP-separated words surrounded by
6798 quotes are considered one word.
6799 History expansions are introduced by the appearance of the
6800 history expansion character, which is \^\fB!\fP\^ by default.
6801 Only backslash (\^\fB\e\fP\^) and single quotes can quote
6802 the history expansion character, but the history expansion character is
6803 also treated as quoted if it immediately precedes the closing double quote
6804 in a double-quoted string.
6806 Several characters inhibit history expansion if found immediately
6807 following the history expansion character, even if it is unquoted:
6808 space, tab, newline, carriage return, and \fB=\fP.
6809 If the \fBextglob\fP shell option is enabled, \fB(\fP will also
6812 Several shell options settable with the
6814 builtin may be used to tailor the behavior of history expansion.
6817 shell option is enabled (see the description of the
6821 is being used, history substitutions are not immediately passed to
6823 Instead, the expanded line is reloaded into the
6825 editing buffer for further modification.
6828 is being used, and the
6830 shell option is enabled, a failed history substitution will be reloaded
6833 editing buffer for correction.
6838 builtin command may be used to see what a history expansion will
6844 builtin may be used to add commands to the end of the history list
6845 without actually executing them, so that they are available for
6848 The shell allows control of the various characters used by the
6849 history expansion mechanism (see the description of
6852 .BR "Shell Variables" ).
6854 the history comment character to mark history timestamps when
6855 writing the history file.
6856 .SS Event Designators
6858 An event designator is a reference to a command line entry in the
6860 Unless the reference is absolute, events are relative to the current
6861 position in the history list.
6866 Start a history substitution, except when followed by a
6868 newline, carriage return, =
6869 or ( (when the \fBextglob\fP shell option is enabled using
6870 the \fBshopt\fP builtin).
6873 Refer to command line
6877 Refer to the current command minus
6881 Refer to the previous command. This is a synonym for `!\-1'.
6884 Refer to the most recent command preceding the current position in the
6885 history list starting with
6888 .B !?\fIstring\fR\fB[?]\fR
6889 Refer to the most recent command preceding the current position in the
6890 history list containing
6892 The trailing \fB?\fP may be omitted if
6894 is followed immediately by a newline.
6896 .B \d\s+2^\s-2\u\fIstring1\fP\d\s+2^\s-2\u\fIstring2\fP\d\s+2^\s-2\u
6897 Quick substitution. Repeat the previous command, replacing
6902 ``!!:s/\fIstring1\fP/\fIstring2\fP/''
6903 (see \fBModifiers\fP below).
6906 The entire command line typed so far.
6908 .SS Word Designators
6910 Word designators are used to select desired words from the event.
6913 separates the event specification from the word designator.
6914 It may be omitted if the word designator begins with a
6921 Words are numbered from the beginning of the line,
6922 with the first word being denoted by 0 (zero).
6923 Words are inserted into the current line separated by single spaces.
6928 The zeroth word. For the shell, this is the command
6935 The first argument. That is, word 1.
6938 The last word. This is usually the last argument, but will expand to the
6939 zeroth word if there is only one word in the line.
6942 The word matched by the most recent `?\fIstring\fR?' search.
6945 A range of words; `\-\fIy\fR' abbreviates `0\-\fIy\fR'.
6948 All of the words but the zeroth. This is a synonym
6949 for `\fI1\-$\fP'. It is not an error to use
6951 if there is just one
6952 word in the event; the empty string is returned in that case.
6955 Abbreviates \fIx\-$\fP.
6958 Abbreviates \fIx\-$\fP like \fBx*\fP, but omits the last word.
6961 If a word designator is supplied without an event specification, the
6962 previous command is used as the event.
6965 After the optional word designator, there may appear a sequence of
6966 one or more of the following modifiers, each preceded by a `:'.
6972 Remove a trailing filename component, leaving only the head.
6975 Remove all leading filename components, leaving the tail.
6978 Remove a trailing suffix of the form \fI.xxx\fP, leaving the
6982 Remove all but the trailing suffix.
6985 Print the new command but do not execute it.
6988 Quote the substituted words, escaping further substitutions.
6991 Quote the substituted words as with
6993 but break into words at
6997 .B s/\fIold\fP/\fInew\fP/
7000 for the first occurrence of
7002 in the event line. Any delimiter can be used in place of /. The
7003 final delimiter is optional if it is the last character of the
7004 event line. The delimiter may be quoted in
7008 with a single backslash. If & appears in
7012 A single backslash will quote the &. If
7014 is null, it is set to the last
7016 substituted, or, if no previous history substitutions took place,
7020 .B !?\fIstring\fR\fB[?]\fR
7024 Repeat the previous substitution.
7027 Cause changes to be applied over the entire event line. This is
7028 used in conjunction with `\fB:s\fP' (e.g., `\fB:gs/\fIold\fP/\fInew\fP/\fR')
7029 or `\fB:&\fP'. If used with
7030 `\fB:s\fP', any delimiter can be used
7031 in place of /, and the final delimiter is optional
7032 if it is the last character of the event line.
7033 An \fBa\fP may be used as a synonym for \fBg\fP.
7036 Apply the following `\fBs\fP' modifier once to each word in the event line.
7038 .SH "SHELL BUILTIN COMMANDS"
7039 .\" start of bash_builtins
7042 Unless otherwise noted, each builtin command documented in this
7043 section as accepting options preceded by
7047 to signify the end of the options.
7048 The \fB:\fP, \fBtrue\fP, \fBfalse\fP, and \fBtest\fP builtins
7049 do not accept options and do not treat \fB\-\-\fP specially.
7050 The \fBexit\fP, \fBlogout\fP, \fBreturn\fP,
7051 \fBbreak\fP, \fBcontinue\fP, \fBlet\fP,
7052 and \fBshift\fP builtins accept and process arguments beginning with
7053 \fB\-\fP without requiring \fB\-\-\fP.
7054 Other builtins that accept arguments but are not specified as accepting
7055 options interpret arguments beginning with \fB\-\fP as invalid options and
7056 require \fB\-\-\fP to prevent this interpretation.
7060 \fB:\fP [\fIarguments\fP]
7062 No effect; the command does nothing beyond expanding
7064 and performing any specified
7066 The return status is zero.
7068 \fB .\| \fP \fIfilename\fP [\fIarguments\fP]
7071 \fBsource\fP \fIfilename\fP [\fIarguments\fP]
7073 Read and execute commands from
7076 shell environment and return the exit status of the last command
7081 does not contain a slash, filenames in
7084 are used to find the directory containing
7086 The file searched for in
7089 need not be executable.
7090 When \fBbash\fP is not in \fIposix mode\fP, the current directory is
7091 searched if no file is found in
7098 builtin command is turned off, the
7102 If any \fIarguments\fP are supplied, they become the positional
7103 parameters when \fIfilename\fP is executed. Otherwise the positional
7104 parameters are unchanged.
7105 If the \fB\-T\fP option is enabled, \fBsource\fP inherits any trap on
7106 \fBDEBUG\fP; if it is not, any \fBDEBUG\fP trap string is saved and
7107 restored around the call to \fBsource\fP, and \fBsource\fP unsets the
7108 \fBDEBUG\fP trap while it executes.
7109 If \fB\-T\fP is not set, and the sourced file changes
7110 the \fBDEBUG\fP trap, the new value is retained when \fBsource\fP completes.
7111 The return status is the status of the last command exited within
7112 the script (0 if no commands are executed), and false if
7114 is not found or cannot be read.
7116 \fBalias\fP [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP] ...]
7117 \fBAlias\fP with no arguments or with the
7119 option prints the list of aliases in the form
7120 \fBalias\fP \fIname\fP=\fIvalue\fP on standard output.
7121 When arguments are supplied, an alias is defined for
7122 each \fIname\fP whose \fIvalue\fP is given.
7123 A trailing space in \fIvalue\fP causes the next word to be
7124 checked for alias substitution when the alias is expanded.
7125 For each \fIname\fP in the argument list for which no \fIvalue\fP
7126 is supplied, the name and value of the alias is printed.
7127 \fBAlias\fP returns true unless a \fIname\fP is given for which
7128 no alias has been defined.
7130 \fBbg\fP [\fIjobspec\fP ...]
7131 Resume each suspended job \fIjobspec\fP in the background, as if it
7132 had been started with
7136 is not present, the shell's notion of the \fIcurrent job\fP is used.
7139 returns 0 unless run when job control is disabled or, when run with
7140 job control enabled, any specified \fIjobspec\fP was not found
7141 or was started without job control.
7143 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] [\fB\-lpsvPSVX\fP]
7146 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] [\fB\-q\fP \fIfunction\fP] [\fB\-u\fP \fIfunction\fP] [\fB\-r\fP \fIkeyseq\fP]
7148 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fB\-f\fP \fIfilename\fP
7150 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fB\-x\fP \fIkeyseq\fP:\fIshell\-command\fP
7152 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fIkeyseq\fP:\fIfunction\-name\fP
7154 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fIkeyseq\fP:\fIreadline\-command\fP
7158 key and function bindings, bind a key sequence to a
7160 function or macro, or set a
7163 Each non-option argument is a command as it would appear in
7165 but each binding or command must be passed as a separate argument;
7166 e.g., '"\eC\-x\eC\-r": re\-read\-init\-file'.
7167 Options, if supplied, have the following meanings:
7174 as the keymap to be affected by the subsequent bindings.
7178 \fIemacs, emacs\-standard, emacs\-meta, emacs\-ctlx, vi,
7179 vi\-move, vi\-command\fP, and
7181 \fIvi\fP is equivalent to \fIvi\-command\fP (\fIvi\-move\fP is also
7182 a synonym); \fIemacs\fP is
7183 equivalent to \fIemacs\-standard\fP.
7186 List the names of all \fBreadline\fP functions.
7189 Display \fBreadline\fP function names and bindings in such a way
7190 that they can be re-read.
7193 List current \fBreadline\fP function names and bindings.
7196 Display \fBreadline\fP key sequences bound to macros and the strings
7197 they output in such a way that they can be re-read.
7200 Display \fBreadline\fP key sequences bound to macros and the strings
7204 Display \fBreadline\fP variable names and values in such a way that they
7208 List current \fBreadline\fP variable names and values.
7210 .B \-f \fIfilename\fP
7211 Read key bindings from \fIfilename\fP.
7213 .B \-q \fIfunction\fP
7214 Query about which keys invoke the named \fIfunction\fP.
7216 .B \-u \fIfunction\fP
7217 Unbind all keys bound to the named \fIfunction\fP.
7220 Remove any current binding for \fIkeyseq\fP.
7222 .B \-x \fIkeyseq\fP:\fIshell\-command\fP
7223 Cause \fIshell\-command\fP to be executed whenever \fIkeyseq\fP is
7225 When \fIshell\-command\fP is executed, the shell sets the
7228 variable to the contents of the \fBreadline\fP line buffer and the
7231 variable to the current location of the insertion point.
7232 If the executed command changes the value of
7237 .BR READLINE_POINT ,
7238 those new values will be reflected in the editing state.
7241 List all key sequences bound to shell commands and the associated commands
7242 in a format that can be reused as input.
7245 The return value is 0 unless an unrecognized option is given or an
7249 \fBbreak\fP [\fIn\fP]
7256 loop. If \fIn\fP is specified, break \fIn\fP levels.
7260 is greater than the number of enclosing loops, all enclosing loops
7262 The return value is 0 unless \fIn\fP is not greater than or equal to 1.
7264 \fBbuiltin\fP \fIshell\-builtin\fP [\fIarguments\fP]
7265 Execute the specified shell builtin, passing it
7267 and return its exit status.
7268 This is useful when defining a
7269 function whose name is the same as a shell builtin,
7270 retaining the functionality of the builtin within the function.
7271 The \fBcd\fP builtin is commonly redefined this way.
7272 The return status is false if
7274 is not a shell builtin command.
7276 \fBcaller\fP [\fIexpr\fP]
7277 Returns the context of any active subroutine call (a shell function or
7278 a script executed with the \fB.\fP or \fBsource\fP builtins).
7279 Without \fIexpr\fP, \fBcaller\fP displays the line number and source
7280 filename of the current subroutine call.
7281 If a non-negative integer is supplied as \fIexpr\fP, \fBcaller\fP
7282 displays the line number, subroutine name, and source file corresponding
7283 to that position in the current execution call stack. This extra
7284 information may be used, for example, to print a stack trace. The
7285 current frame is frame 0.
7286 The return value is 0 unless the shell is not executing a subroutine
7287 call or \fIexpr\fP does not correspond to a valid position in the
7290 \fBcd\fP [\fB\-L\fP|[\fB\-P\fP [\fB\-e\fP]] [\-@]] [\fIdir\fP]
7291 Change the current directory to \fIdir\fP.
7292 if \fIdir\fP is not supplied, the value of the
7295 shell variable is the default.
7296 Any additional arguments following \fIdir\fP are ignored.
7300 defines the search path for the directory containing
7302 each directory name in
7305 is searched for \fIdir\fP.
7306 Alternative directory names in
7309 are separated by a colon (:). A null directory name in
7312 is the same as the current directory, i.e., ``\fB.\fP''. If
7314 begins with a slash (/),
7320 option causes \fBcd\fP to use the physical directory structure
7321 by resolving symbolic links while traversing \fIdir\fP and
7322 before processing instances of \fI..\fP in \fIdir\fP (see also the
7326 builtin command); the
7328 option forces symbolic links to be followed by resolving the link
7329 after processing instances of \fI..\fP in \fIdir\fP.
7330 If \fI..\fP appears in \fIdir\fP, it is processed by removing the
7331 immediately previous pathname component from \fIdir\fP, back to a slash
7332 or the beginning of \fIdir\fP.
7335 option is supplied with
7337 and the current working directory cannot be successfully determined
7338 after a successful directory change, \fBcd\fP will return an unsuccessful
7340 On systems that support it, the \fB\-@\fP option presents the extended
7341 attributes associated with a file as a directory.
7347 before the directory change is attempted.
7348 If a non-empty directory name from
7352 \fB\-\fP is the first argument, and the directory change is
7353 successful, the absolute pathname of the new working directory is
7354 written to the standard output.
7355 The return value is true if the directory was successfully changed;
7358 \fBcommand\fP [\fB\-pVv\fP] \fIcommand\fP [\fIarg\fP ...]
7363 suppressing the normal shell function lookup.
7364 Only builtin commands or commands found in the
7367 are executed. If the
7369 option is given, the search for
7371 is performed using a default value for
7374 that is guaranteed to find all of the standard utilities.
7379 option is supplied, a description of
7383 option causes a single word indicating the command or filename
7386 to be displayed; the
7388 option produces a more verbose description.
7393 option is supplied, the exit status is 0 if
7395 was found, and 1 if not. If neither option is supplied and
7396 an error occurred or
7398 cannot be found, the exit status is 127. Otherwise, the exit status of the
7400 builtin is the exit status of
7403 \fBcompgen\fP [\fIoption\fP] [\fIword\fP]
7404 Generate possible completion matches for \fIword\fP according to
7405 the \fIoption\fPs, which may be any option accepted by the
7407 builtin with the exception of \fB\-p\fP and \fB\-r\fP, and write
7408 the matches to the standard output.
7409 When using the \fB\-F\fP or \fB\-C\fP options, the various shell variables
7410 set by the programmable completion facilities, while available, will not
7413 The matches will be generated in the same way as if the programmable
7414 completion code had generated them directly from a completion specification
7415 with the same flags.
7416 If \fIword\fP is specified, only those completions matching \fIword\fP
7419 The return value is true unless an invalid option is supplied, or no
7420 matches were generated.
7422 \fBcomplete\fP [\fB\-abcdefgjksuv\fP] [\fB\-o\fP \fIcomp-option\fP] [\fB\-DE\fP] [\fB\-A\fP \fIaction\fP] [\fB\-G\fP \fIglobpat\fP] [\fB\-W\fP \fIwordlist\fP] [\fB\-F\fP \fIfunction\fP] [\fB\-C\fP \fIcommand\fP]
7424 [\fB\-X\fP \fIfilterpat\fP] [\fB\-P\fP \fIprefix\fP] [\fB\-S\fP \fIsuffix\fP] \fIname\fP [\fIname ...\fP]
7427 \fBcomplete\fP \fB\-pr\fP [\fB\-DE\fP] [\fIname\fP ...]
7429 Specify how arguments to each \fIname\fP should be completed.
7430 If the \fB\-p\fP option is supplied, or if no options are supplied,
7431 existing completion specifications are printed in a way that allows
7432 them to be reused as input.
7433 The \fB\-r\fP option removes a completion specification for
7434 each \fIname\fP, or, if no \fIname\fPs are supplied, all
7435 completion specifications.
7436 The \fB\-D\fP option indicates that the remaining options and actions should
7437 apply to the ``default'' command completion; that is, completion attempted
7438 on a command for which no completion has previously been defined.
7439 The \fB\-E\fP option indicates that the remaining options and actions should
7440 apply to ``empty'' command completion; that is, completion attempted on a
7443 The process of applying these completion specifications when word completion
7444 is attempted is described above under \fBProgrammable Completion\fP.
7446 Other options, if specified, have the following meanings.
7447 The arguments to the \fB\-G\fP, \fB\-W\fP, and \fB\-X\fP options
7448 (and, if necessary, the \fB\-P\fP and \fB\-S\fP options)
7449 should be quoted to protect them from expansion before the
7455 \fB\-o\fP \fIcomp-option\fP
7456 The \fIcomp-option\fP controls several aspects of the compspec's behavior
7457 beyond the simple generation of completions.
7458 \fIcomp-option\fP may be one of:
7462 Perform the rest of the default \fBbash\fP completions if the compspec
7463 generates no matches.
7466 Use readline's default filename completion if the compspec generates
7470 Perform directory name completion if the compspec generates no matches.
7473 Tell readline that the compspec generates filenames, so it can perform any
7474 filename\-specific processing (like adding a slash to directory names,
7475 quoting special characters, or suppressing trailing spaces).
7476 Intended to be used with shell functions.
7479 Tell readline not to quote the completed words if they are filenames
7480 (quoting filenames is the default).
7483 Tell readline not to sort the list of possible completions alphabetically.
7486 Tell readline not to append a space (the default) to words completed at
7487 the end of the line.
7490 After any matches defined by the compspec are generated,
7491 directory name completion is attempted and any
7492 matches are added to the results of the other actions.
7495 \fB\-A\fP \fIaction\fP
7496 The \fIaction\fP may be one of the following to generate a list of possible
7501 Alias names. May also be specified as \fB\-a\fP.
7504 Array variable names.
7507 \fBReadline\fP key binding names.
7510 Names of shell builtin commands. May also be specified as \fB\-b\fP.
7513 Command names. May also be specified as \fB\-c\fP.
7516 Directory names. May also be specified as \fB\-d\fP.
7519 Names of disabled shell builtins.
7522 Names of enabled shell builtins.
7525 Names of exported shell variables. May also be specified as \fB\-e\fP.
7528 File names. May also be specified as \fB\-f\fP.
7531 Names of shell functions.
7534 Group names. May also be specified as \fB\-g\fP.
7537 Help topics as accepted by the \fBhelp\fP builtin.
7540 Hostnames, as taken from the file specified by the
7546 Job names, if job control is active. May also be specified as \fB\-j\fP.
7549 Shell reserved words. May also be specified as \fB\-k\fP.
7552 Names of running jobs, if job control is active.
7555 Service names. May also be specified as \fB\-s\fP.
7558 Valid arguments for the \fB\-o\fP option to the \fBset\fP builtin.
7561 Shell option names as accepted by the \fBshopt\fP builtin.
7567 Names of stopped jobs, if job control is active.
7570 User names. May also be specified as \fB\-u\fP.
7573 Names of all shell variables. May also be specified as \fB\-v\fP.
7576 \fB\-C\fP \fIcommand\fP
7577 \fIcommand\fP is executed in a subshell environment, and its output is
7578 used as the possible completions.
7580 \fB\-F\fP \fIfunction\fP
7581 The shell function \fIfunction\fP is executed in the current shell
7583 When the function is executed,
7584 the first argument (\fB$1\fP) is the name of the command whose arguments are
7586 the second argument (\fB$2\fP) is the word being completed,
7587 and the third argument (\fB$3\fP) is the word preceding the word being
7588 completed on the current command line.
7589 When it finishes, the possible completions are retrieved from the value
7595 \fB\-G\fP \fIglobpat\fP
7596 The pathname expansion pattern \fIglobpat\fP is expanded to generate
7597 the possible completions.
7599 \fB\-P\fP \fIprefix\fP
7600 \fIprefix\fP is added at the beginning of each possible completion
7601 after all other options have been applied.
7603 \fB\-S\fP \fIsuffix\fP
7604 \fIsuffix\fP is appended to each possible completion
7605 after all other options have been applied.
7607 \fB\-W\fP \fIwordlist\fP
7608 The \fIwordlist\fP is split using the characters in the
7611 special variable as delimiters, and each resultant word is expanded.
7612 The possible completions are the members of the resultant list which
7613 match the word being completed.
7615 \fB\-X\fP \fIfilterpat\fP
7616 \fIfilterpat\fP is a pattern as used for pathname expansion.
7617 It is applied to the list of possible completions generated by the
7618 preceding options and arguments, and each completion matching
7619 \fIfilterpat\fP is removed from the list.
7620 A leading \fB!\fP in \fIfilterpat\fP negates the pattern; in this
7621 case, any completion not matching \fIfilterpat\fP is removed.
7624 The return value is true unless an invalid option is supplied, an option
7625 other than \fB\-p\fP or \fB\-r\fP is supplied without a \fIname\fP
7626 argument, an attempt is made to remove a completion specification for
7627 a \fIname\fP for which no specification exists, or
7628 an error occurs adding a completion specification.
7631 \fBcompopt\fP [\fB\-o\fP \fIoption\fP] [\fB\-DE\fP] [\fB+o\fP \fIoption\fP] [\fIname\fP]
7632 Modify completion options for each \fIname\fP according to the
7633 \fIoption\fPs, or for the
7634 currently-executing completion if no \fIname\fPs are supplied.
7635 If no \fIoption\fPs are given, display the completion options for each
7636 \fIname\fP or the current completion.
7637 The possible values of \fIoption\fP are those valid for the \fBcomplete\fP
7638 builtin described above.
7639 The \fB\-D\fP option indicates that the remaining options should
7640 apply to the ``default'' command completion; that is, completion attempted
7641 on a command for which no completion has previously been defined.
7642 The \fB\-E\fP option indicates that the remaining options should
7643 apply to ``empty'' command completion; that is, completion attempted on a
7646 The return value is true unless an invalid option is supplied, an attempt
7647 is made to modify the options for a \fIname\fP for which no completion
7648 specification exists, or an output error occurs.
7650 \fBcontinue\fP [\fIn\fP]
7651 Resume the next iteration of the enclosing
7660 is specified, resume at the \fIn\fPth enclosing loop.
7664 is greater than the number of enclosing loops, the last enclosing loop
7665 (the ``top-level'' loop) is resumed.
7666 The return value is 0 unless \fIn\fP is not greater than or equal to 1.
7668 \fBdeclare\fP [\fB\-aAfFgilnrtux\fP] [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP] ...]
7671 \fBtypeset\fP [\fB\-aAfFgilnrtux\fP] [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP] ...]
7673 Declare variables and/or give them attributes.
7674 If no \fIname\fPs are given then display the values of variables.
7677 option will display the attributes and values of each
7681 is used with \fIname\fP arguments, additional options,
7682 other than \fB\-f\fP and \fB\-F\fP, are ignored.
7685 is supplied without \fIname\fP arguments, it will display the attributes
7686 and values of all variables having the attributes specified by the
7688 If no other options are supplied with \fB\-p\fP, \fBdeclare\fP will display
7689 the attributes and values of all shell variables. The \fB\-f\fP option
7690 will restrict the display to shell functions.
7693 option inhibits the display of function definitions; only the
7694 function name and attributes are printed.
7695 If the \fBextdebug\fP shell option is enabled using \fBshopt\fP,
7696 the source file name and line number where each \fIname\fP
7697 is defined are displayed as well. The
7703 option forces variables to be created or modified at the global scope,
7704 even when \fBdeclare\fP is executed in a shell function.
7705 It is ignored in all other cases.
7706 The following options can
7707 be used to restrict output to variables with the specified attribute or
7708 to give variables attributes:
7713 Each \fIname\fP is an indexed array variable (see
7718 Each \fIname\fP is an associative array variable (see
7723 Use function names only.
7726 The variable is treated as an integer; arithmetic evaluation (see
7728 .B "ARITHMETIC EVALUATION"
7729 above) is performed when the variable is assigned a value.
7732 When the variable is assigned a value, all upper-case characters are
7733 converted to lower-case.
7734 The upper-case attribute is disabled.
7737 Give each \fIname\fP the \fInameref\fP attribute, making
7738 it a name reference to another variable.
7739 That other variable is defined by the value of \fIname\fP.
7740 All references, assignments, and attribute modifications
7741 to \fIname\fP, except those using or changing the
7742 \fB\-n\fP attribute itself, are performed on the variable referenced by
7744 The nameref attribute cannot be applied to array variables.
7747 Make \fIname\fPs readonly. These names cannot then be assigned values
7748 by subsequent assignment statements or unset.
7751 Give each \fIname\fP the \fItrace\fP attribute.
7752 Traced functions inherit the \fBDEBUG\fP and \fBRETURN\fP traps from
7754 The trace attribute has no special meaning for variables.
7757 When the variable is assigned a value, all lower-case characters are
7758 converted to upper-case.
7759 The lower-case attribute is disabled.
7762 Mark \fIname\fPs for export to subsequent commands via the environment.
7765 Using `+' instead of `\-'
7766 turns off the attribute instead,
7767 with the exceptions that \fB+a\fP
7768 may not be used to destroy an array variable and \fB+r\fP will not
7769 remove the readonly attribute.
7770 When used in a function,
7775 \fIname\fP local, as with the
7778 unless the \fB\-g\fP option is supplied.
7779 If a variable name is followed by =\fIvalue\fP, the value of
7780 the variable is set to \fIvalue\fP.
7781 When using \fB\-a\fP or \fB\-A\fP and the compound assignment syntax to
7782 create array variables, additional attributes do not take effect until
7783 subsequent assignments.
7784 The return value is 0 unless an invalid option is encountered,
7785 an attempt is made to define a function using
7786 .if n ``\-f foo=bar'',
7787 .if t \f(CW\-f foo=bar\fP,
7788 an attempt is made to assign a value to a readonly variable,
7789 an attempt is made to assign a value to an array variable without
7790 using the compound assignment syntax (see
7792 above), one of the \fInames\fP is not a valid shell variable name,
7793 an attempt is made to turn off readonly status for a readonly variable,
7794 an attempt is made to turn off array status for an array variable,
7795 or an attempt is made to display a non-existent function with \fB\-f\fP.
7798 .B dirs [\fB\-clpv\fP] [+\fIn\fP] [\-\fIn\fP]
7799 Without options, displays the list of currently remembered directories.
7800 The default display is on a single line with directory names separated
7802 Directories are added to the list with the
7806 command removes entries from the list.
7807 The current directory is always the first directory in the stack.
7812 Clears the directory stack by deleting all of the entries.
7815 Produces a listing using full pathnames;
7816 the default listing format uses a tilde to denote the home directory.
7819 Print the directory stack with one entry per line.
7822 Print the directory stack with one entry per line,
7823 prefixing each entry with its index in the stack.
7826 Displays the \fIn\fPth entry counting from the left of the list
7829 when invoked without options, starting with zero.
7832 Displays the \fIn\fPth entry counting from the right of the list
7835 when invoked without options, starting with zero.
7838 The return value is 0 unless an
7839 invalid option is supplied or \fIn\fP indexes beyond the end
7840 of the directory stack.
7843 \fBdisown\fP [\fB\-ar\fP] [\fB\-h\fP] [\fIjobspec\fP ... | \fIpid\fP ... ]
7844 Without options, remove each
7846 from the table of active jobs.
7849 is not present, and neither the \fB\-a\fP nor the \fB\-r\fP option
7850 is supplied, the \fIcurrent job\fP is used.
7851 If the \fB\-h\fP option is given, each
7853 is not removed from the table, but is marked so that
7856 is not sent to the job if the shell receives a
7863 option means to remove or mark all jobs; the
7867 argument restricts operation to running jobs.
7868 The return value is 0 unless a
7870 does not specify a valid job.
7872 \fBecho\fP [\fB\-neE\fP] [\fIarg\fP ...]
7873 Output the \fIarg\fPs, separated by spaces, followed by a newline.
7874 The return status is 0 unless a write error occurs.
7875 If \fB\-n\fP is specified, the trailing newline is
7876 suppressed. If the \fB\-e\fP option is given, interpretation of
7877 the following backslash-escaped characters is enabled. The
7879 option disables the interpretation of these escape characters,
7880 even on systems where they are interpreted by default.
7881 The \fBxpg_echo\fP shell option may be used to
7882 dynamically determine whether or not \fBecho\fP expands these
7883 escape characters by default.
7885 does not interpret \fB\-\-\fP to mean the end of options.
7887 interprets the following escape sequences:
7898 suppress further output
7924 the eight-bit character whose value is the octal value \fInnn\fP
7925 (zero to three octal digits)
7928 the eight-bit character whose value is the hexadecimal value \fIHH\fP
7929 (one or two hex digits)
7932 the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value
7933 \fIHHHH\fP (one to four hex digits)
7935 .B \eU\fIHHHHHHHH\fP
7936 the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value
7937 \fIHHHHHHHH\fP (one to eight hex digits)
7941 \fBenable\fP [\fB\-a\fP] [\fB\-dnps\fP] [\fB\-f\fP \fIfilename\fP] [\fIname\fP ...]
7942 Enable and disable builtin shell commands.
7943 Disabling a builtin allows a disk command which has the same name
7944 as a shell builtin to be executed without specifying a full pathname,
7945 even though the shell normally searches for builtins before disk commands.
7946 If \fB\-n\fP is used, each \fIname\fP
7947 is disabled; otherwise,
7948 \fInames\fP are enabled. For example, to use the
7950 binary found via the
7953 instead of the shell builtin version, run
7954 .if t \f(CWenable -n test\fP.
7955 .if n ``enable -n test''.
7958 option means to load the new builtin command
7962 on systems that support dynamic loading. The
7964 option will delete a builtin previously loaded with
7966 If no \fIname\fP arguments are given, or if the
7968 option is supplied, a list of shell builtins is printed.
7969 With no other option arguments, the list consists of all enabled
7971 If \fB\-n\fP is supplied, only disabled builtins are printed.
7972 If \fB\-a\fP is supplied, the list printed includes all builtins, with an
7973 indication of whether or not each is enabled.
7974 If \fB\-s\fP is supplied, the output is restricted to the POSIX
7975 \fIspecial\fP builtins.
7976 The return value is 0 unless a
7978 is not a shell builtin or there is an error loading a new builtin
7979 from a shared object.
7981 \fBeval\fP [\fIarg\fP ...]
7982 The \fIarg\fPs are read and concatenated together into a single
7983 command. This command is then read and executed by the shell, and
7984 its exit status is returned as the value of
7988 or only null arguments,
7992 \fBexec\fP [\fB\-cl\fP] [\fB\-a\fP \fIname\fP] [\fIcommand\fP [\fIarguments\fP]]
7995 is specified, it replaces the shell.
7996 No new process is created. The
7998 become the arguments to \fIcommand\fP.
8002 the shell places a dash at the beginning of the zeroth argument passed to
8010 to be executed with an empty environment. If
8012 is supplied, the shell passes
8014 as the zeroth argument to the executed command.
8017 cannot be executed for some reason, a non-interactive shell exits,
8021 is enabled. In that case, it returns failure.
8022 An interactive shell returns failure if the file cannot be executed.
8025 is not specified, any redirections take effect in the current shell,
8026 and the return status is 0. If there is a redirection error, the
8029 \fBexit\fP [\fIn\fP]
8030 Cause the shell to exit
8031 with a status of \fIn\fP. If
8033 is omitted, the exit status
8034 is that of the last command executed.
8038 is executed before the shell terminates.
8040 \fBexport\fP [\fB\-fn\fP\^] [\fIname\fP[=\fIword\fP]] ...
8047 are marked for automatic export to the environment of
8048 subsequently executed commands. If the
8050 option is given, the
8055 are given, or if the
8057 option is supplied, a list
8058 of names of all exported variables is printed.
8061 option causes the export property to be removed from each
8063 If a variable name is followed by =\fIword\fP, the value of
8064 the variable is set to \fIword\fP.
8066 returns an exit status of 0 unless an invalid option is
8068 one of the \fInames\fP is not a valid shell variable name, or
8072 that is not a function.
8074 \fBfc\fP [\fB\-e\fP \fIename\fP] [\fB\-lnr\fP] [\fIfirst\fP] [\fIlast\fP]
8077 \fBfc\fP \fB\-s\fP [\fIpat\fP=\fIrep\fP] [\fIcmd\fP]
8079 The first form selects a range of commands from
8083 from the history list and displays or edits and re-executes them.
8087 may be specified as a string (to locate the last command beginning
8088 with that string) or as a number (an index into the history list,
8089 where a negative number is used as an offset from the current
8092 is not specified it is set to
8093 the current command for listing (so that
8094 .if n ``fc \-l \-10''
8095 .if t \f(CWfc \-l \-10\fP
8096 prints the last 10 commands) and to
8101 is not specified it is set to the previous
8102 command for editing and \-16 for listing.
8107 the command numbers when listing. The
8109 option reverses the order of
8110 the commands. If the
8113 the commands are listed on
8114 standard output. Otherwise, the editor given by
8117 on a file containing those commands. If
8123 variable is used, and
8130 is not set. If neither variable is set,
8132 is used. When editing is complete, the edited commands are
8133 echoed and executed.
8135 In the second form, \fIcommand\fP is re-executed after each instance
8136 of \fIpat\fP is replaced by \fIrep\fP.
8137 \fICommand\fP is intepreted the same as \fIfirst\fP above.
8138 A useful alias to use with this is
8139 .if n ``r="fc -s"'',
8140 .if t \f(CWr='fc \-s'\fP,
8144 runs the last command beginning with
8150 re-executes the last command.
8152 If the first form is used, the return value is 0 unless an invalid
8153 option is encountered or
8157 specify history lines out of range.
8160 option is supplied, the return value is the value of the last
8161 command executed or failure if an error occurs with the temporary
8162 file of commands. If the second form is used, the return status
8163 is that of the command re-executed, unless
8165 does not specify a valid history line, in which case
8169 \fBfg\fP [\fIjobspec\fP]
8172 in the foreground, and make it the current job.
8175 is not present, the shell's notion of the \fIcurrent job\fP is used.
8176 The return value is that of the command placed into the foreground,
8177 or failure if run when job control is disabled or, when run with
8178 job control enabled, if
8180 does not specify a valid job or
8182 specifies a job that was started without job control.
8184 \fBgetopts\fP \fIoptstring\fP \fIname\fP [\fIargs\fP]
8186 is used by shell procedures to parse positional parameters.
8188 contains the option characters to be recognized; if a character
8189 is followed by a colon, the option is expected to have an
8190 argument, which should be separated from it by white space.
8191 The colon and question mark characters may not be used as
8193 Each time it is invoked,
8195 places the next option in the shell variable
8199 if it does not exist,
8200 and the index of the next argument to be processed into the
8206 is initialized to 1 each time the shell or a shell script
8207 is invoked. When an option requires an argument,
8209 places that argument into the variable
8212 The shell does not reset
8215 automatically; it must be manually reset between multiple
8218 within the same shell invocation if a new set of parameters
8221 When the end of options is encountered, \fBgetopts\fP exits with a
8222 return value greater than zero.
8225 is set to the index of the first non-option argument,
8226 and \fIname\fP is set to ?.
8229 normally parses the positional parameters, but if more arguments are
8233 parses those instead.
8236 can report errors in two ways. If the first character of
8240 error reporting is used. In normal operation, diagnostic messages
8241 are printed when invalid options or missing option arguments are
8246 is set to 0, no error messages will be displayed, even if the first
8251 If an invalid option is seen,
8256 prints an error message and unsets
8262 the option character found is placed in
8265 and no diagnostic message is printed.
8267 If a required argument is not found, and
8270 a question mark (\^\fB?\fP\^) is placed in
8274 is unset, and a diagnostic message is printed.
8277 is silent, then a colon (\^\fB:\fP\^) is placed in
8282 is set to the option character found.
8285 returns true if an option, specified or unspecified, is found.
8286 It returns false if the end of options is encountered or an
8289 \fBhash\fP [\fB\-lr\fP] [\fB\-p\fP \fIfilename\fP] [\fB\-dt\fP] [\fIname\fP]
8290 Each time \fBhash\fP is invoked,
8291 the full pathname of the command
8293 is determined by searching
8296 and remembered. Any previously-remembered pathname is discarded.
8299 option is supplied, no path search is performed, and
8301 is used as the full filename of the command.
8304 option causes the shell to forget all
8305 remembered locations.
8308 option causes the shell to forget the remembered location of each \fIname\fP.
8311 option is supplied, the full pathname to which each \fIname\fP corresponds
8312 is printed. If multiple \fIname\fP arguments are supplied with \fB\-t\fP,
8313 the \fIname\fP is printed before the hashed full pathname.
8316 option causes output to be displayed in a format that may be reused as input.
8317 If no arguments are given, or if only \fB\-l\fP is supplied,
8318 information about remembered commands is printed.
8319 The return status is true unless a
8321 is not found or an invalid option is supplied.
8323 \fBhelp\fP [\fB\-dms\fP] [\fIpattern\fP]
8324 Display helpful information about builtin commands. If
8328 gives detailed help on all commands matching
8330 otherwise help for all the builtins and shell control structures
8336 Display a short description of each \fIpattern\fP
8339 Display the description of each \fIpattern\fP in a manpage-like format
8342 Display only a short usage synopsis for each \fIpattern\fP
8345 The return status is 0 unless no command matches
8349 \fBhistory [\fIn\fP]
8352 \fBhistory\fP \fB\-c\fP
8354 \fBhistory \-d\fP \fIoffset\fP
8356 \fBhistory\fP \fB\-anrw\fP [\fIfilename\fP]
8358 \fBhistory\fP \fB\-p\fP \fIarg\fP [\fIarg ...\fP]
8360 \fBhistory\fP \fB\-s\fP \fIarg\fP [\fIarg ...\fP]
8362 With no options, display the command
8363 history list with line numbers. Lines listed
8366 have been modified. An argument of
8371 If the shell variable
8374 is set and not null,
8375 it is used as a format string for \fIstrftime\fP(3) to display
8376 the time stamp associated with each displayed history entry.
8377 No intervening blank is printed between the formatted time stamp
8378 and the history line.
8379 If \fIfilename\fP is supplied, it is used as the
8380 name of the history file; if not, the value of
8383 is used. Options, if supplied, have the following meanings:
8388 Clear the history list by deleting all the entries.
8390 \fB\-d\fP \fIoffset\fP
8391 Delete the history entry at position \fIoffset\fP.
8394 Append the ``new'' history lines to the history file.
8395 These are history lines entered since the beginning of the current
8396 \fBbash\fP session, but not already appended to the history file.
8399 Read the history lines not already read from the history
8400 file into the current history list. These are lines
8401 appended to the history file since the beginning of the
8402 current \fBbash\fP session.
8405 Read the contents of the history file
8406 and append them to the current history list.
8409 Write the current history list to the history file, overwriting the
8410 history file's contents.
8413 Perform history substitution on the following \fIargs\fP and display
8414 the result on the standard output.
8415 Does not store the results in the history list.
8416 Each \fIarg\fP must be quoted to disable normal history expansion.
8421 in the history list as a single entry. The last command in the
8422 history list is removed before the
8430 variable is set, the time stamp information
8431 associated with each history entry is written to the history file,
8432 marked with the history comment character.
8433 When the history file is read, lines beginning with the history
8434 comment character followed immediately by a digit are interpreted
8435 as timestamps for the following history entry.
8436 The return value is 0 unless an invalid option is encountered, an
8437 error occurs while reading or writing the history file, an invalid
8438 \fIoffset\fP is supplied as an argument to \fB\-d\fP, or the
8439 history expansion supplied as an argument to \fB\-p\fP fails.
8442 \fBjobs\fP [\fB\-lnprs\fP] [ \fIjobspec\fP ... ]
8445 \fBjobs\fP \fB\-x\fP \fIcommand\fP [ \fIargs\fP ... ]
8447 The first form lists the active jobs. The options have the following
8454 in addition to the normal information.
8457 Display information only about jobs that have changed status since
8458 the user was last notified of their status.
8461 List only the process ID of the job's process group
8465 Display only running jobs.
8468 Display only stopped jobs.
8473 is given, output is restricted to information about that job.
8474 The return status is 0 unless an invalid option is encountered
8489 with the corresponding process group ID, and executes
8493 returning its exit status.
8496 \fBkill\fP [\fB\-s\fP \fIsigspec\fP | \fB\-n\fP \fIsignum\fP | \fB\-\fP\fIsigspec\fP] [\fIpid\fP | \fIjobspec\fP] ...
8499 \fBkill\fP \fB\-l\fP|\fB\-L\fP [\fIsigspec\fP | \fIexit_status\fP]
8501 Send the signal named by
8505 to the processes named by
8510 is either a case-insensitive signal name such as
8513 (with or without the
8516 prefix) or a signal number;
8521 is not present, then
8527 lists the signal names.
8528 If any arguments are supplied when
8530 is given, the names of the signals corresponding to the arguments are
8531 listed, and the return status is 0.
8532 The \fIexit_status\fP argument to
8534 is a number specifying either a signal number or the exit status of
8535 a process terminated by a signal.
8538 option is equivalent to \fB\-l\fP.
8540 returns true if at least one signal was successfully sent, or false
8541 if an error occurs or an invalid option is encountered.
8543 \fBlet\fP \fIarg\fP [\fIarg\fP ...]
8546 is an arithmetic expression to be evaluated (see
8548 .B "ARITHMETIC EVALUATION"
8554 returns 1; 0 is returned otherwise.
8556 \fBlocal\fP [\fIoption\fP] [\fIname\fP[=\fIvalue\fP] ... | \- ]
8557 For each argument, a local variable named
8559 is created, and assigned
8561 The \fIoption\fP can be any of the options accepted by \fBdeclare\fP.
8564 is used within a function, it causes the variable
8566 to have a visible scope restricted to that function and its children.
8567 If \fIname\fP is \-, the set of shell options is made local to the function
8568 in which \fBlocal\fP is invoked: shell options changed using the
8569 \fBset\fP builtin inside the function are restored to their original values
8570 when the function returns.
8573 writes a list of local variables to the standard output. It is
8576 when not within a function. The return status is 0 unless
8578 is used outside a function, an invalid
8581 \fIname\fP is a readonly variable.
8586 \fBmapfile\fP [\fB\-d\fP \fIdelim\fP] [\fB\-n\fP \fIcount\fP] [\fB\-O\fP \fIorigin\fP] [\fB\-s\fP \fIcount\fP] [\fB\-t\fP] [\fB\-u\fP \fIfd\fP] [\fB\-C\fP \fIcallback\fP] [\fB\-c\fP \fIquantum\fP] [\fIarray\fP]
8589 \fBreadarray\fP [\fB\-d\fP \fIdelim\fP] [\fB\-n\fP \fIcount\fP] [\fB\-O\fP \fIorigin\fP] [\fB\-s\fP \fIcount\fP] [\fB\-t\fP] [\fB\-u\fP \fIfd\fP] [\fB\-C\fP \fIcallback\fP] [\fB\-c\fP \fIquantum\fP] [\fIarray\fP]
8591 Read lines from the standard input into the indexed array variable
8593 or from file descriptor
8601 is the default \fIarray\fP.
8602 Options, if supplied, have the following meanings:
8607 The first character of \fIdelim\fP is used to terminate each input line,
8608 rather than newline.
8613 lines. If \fIcount\fP is 0, all lines are copied.
8620 The default index is 0.
8623 Discard the first \fIcount\fP lines read.
8626 Remove a trailing \fIdelim\fP (default newline) from each line read.
8629 Read lines from file descriptor \fIfd\fP instead of the standard input.
8634 each time \fIquantum\fP lines are read. The \fB\-c\fP option specifies
8638 Specify the number of lines read between each call to
8644 is specified without
8646 the default quantum is 5000.
8647 When \fIcallback\fP is evaluated, it is supplied the index of the next
8648 array element to be assigned and the line to be assigned to that element
8649 as additional arguments.
8650 \fIcallback\fP is evaluated after the line is read but before the
8651 array element is assigned.
8653 If not supplied with an explicit origin, \fBmapfile\fP will clear \fIarray\fP
8654 before assigning to it.
8656 \fBmapfile\fP returns successfully unless an invalid option or option
8657 argument is supplied, \fIarray\fP is invalid or unassignable, or if
8658 \fIarray\fP is not an indexed array.
8661 \fBpopd\fP [\-\fBn\fP] [+\fIn\fP] [\-\fIn\fP]
8662 Removes entries from the directory stack. With no arguments,
8663 removes the top directory from the stack, and performs a
8665 to the new top directory.
8666 Arguments, if supplied, have the following meanings:
8671 Suppresses the normal change of directory when removing directories
8672 from the stack, so that only the stack is manipulated.
8675 Removes the \fIn\fPth entry counting from the left of the list
8678 starting with zero. For example:
8680 .if t \f(CWpopd +0\fP
8681 removes the first directory,
8683 .if t \f(CWpopd +1\fP
8687 Removes the \fIn\fPth entry counting from the right of the list
8690 starting with zero. For example:
8692 .if t \f(CWpopd -0\fP
8693 removes the last directory,
8695 .if t \f(CWpopd -1\fP
8701 command is successful, a
8703 is performed as well, and the return status is 0.
8705 returns false if an invalid option is encountered, the directory stack
8706 is empty, a non-existent directory stack entry is specified, or the
8707 directory change fails.
8710 \fBprintf\fP [\fB\-v\fP \fIvar\fP] \fIformat\fP [\fIarguments\fP]
8711 Write the formatted \fIarguments\fP to the standard output under the
8712 control of the \fIformat\fP.
8713 The \fB\-v\fP option causes the output to be assigned to the variable
8714 \fIvar\fP rather than being printed to the standard output.
8716 The \fIformat\fP is a character string which contains three types of objects:
8717 plain characters, which are simply copied to standard output, character
8718 escape sequences, which are converted and copied to the standard output, and
8719 format specifications, each of which causes printing of the next successive
8721 In addition to the standard \fIprintf\fP(1) format specifications,
8722 \fBprintf\fP interprets the following extensions:
8728 \fBprintf\fP to expand backslash escape sequences in the corresponding
8730 in the same way as \fBecho \-e\fP.
8733 causes \fBprintf\fP to output the corresponding
8734 \fIargument\fP in a format that can be reused as shell input.
8736 .B %(\fIdatefmt\fP)T
8737 causes \fBprintf\fP to output the date-time string resulting from using
8738 \fIdatefmt\fP as a format string for \fIstrftime\fP(3).
8739 The corresponding \fIargument\fP is an integer representing the number of
8740 seconds since the epoch.
8741 Two special argument values may be used: -1 represents the current
8742 time, and -2 represents the time the shell was invoked.
8743 If no argument is specified, conversion behaves as if -1 had been given.
8744 This is an exception to the usual \fBprintf\fP behavior.
8747 Arguments to non-string format specifiers are treated as C constants,
8748 except that a leading plus or minus sign is allowed, and if the leading
8749 character is a single or double quote, the value is the ASCII value of
8750 the following character.
8752 The \fIformat\fP is reused as necessary to consume all of the \fIarguments\fP.
8753 If the \fIformat\fP requires more \fIarguments\fP than are supplied, the
8754 extra format specifications behave as if a zero value or null string, as
8755 appropriate, had been supplied.
8756 The return value is zero on success, non-zero on failure.
8759 \fBpushd\fP [\fB\-n\fP] [+\fIn\fP] [\-\fIn\fP]
8762 \fBpushd\fP [\fB\-n\fP] [\fIdir\fP]
8764 Adds a directory to the top of the directory stack, or rotates
8765 the stack, making the new top of the stack the current working
8766 directory. With no arguments, \fBpushd\fP exchanges the top two directories
8767 and returns 0, unless the directory stack is empty.
8768 Arguments, if supplied, have the following meanings:
8773 Suppresses the normal change of directory when rotating or
8774 adding directories to the stack, so that only the stack is manipulated.
8777 Rotates the stack so that the \fIn\fPth directory
8778 (counting from the left of the list shown by
8784 Rotates the stack so that the \fIn\fPth directory
8785 (counting from the right of the list shown by
8787 starting with zero) is at the top.
8792 to the directory stack at the top, making it the
8793 new current working directory as if it had been supplied as the argument
8794 to the \fBcd\fP builtin.
8799 command is successful, a
8801 is performed as well.
8802 If the first form is used,
8804 returns 0 unless the cd to
8806 fails. With the second form,
8808 returns 0 unless the directory stack is empty,
8809 a non-existent directory stack element is specified,
8810 or the directory change to the specified new current directory
8814 \fBpwd\fP [\fB\-LP\fP]
8815 Print the absolute pathname of the current working directory.
8816 The pathname printed contains no symbolic links if the
8818 option is supplied or the
8822 builtin command is enabled.
8825 option is used, the pathname printed may contain symbolic links.
8826 The return status is 0 unless an error occurs while
8827 reading the name of the current directory or an
8828 invalid option is supplied.
8830 \fBread\fP [\fB\-ers\fP] [\fB\-a\fP \fIaname\fP] [\fB\-d\fP \fIdelim\fP] [\fB\-i\fP \fItext\fP] [\fB\-n\fP \fInchars\fP] [\fB\-N\fP \fInchars\fP] [\fB\-p\fP \fIprompt\fP] [\fB\-t\fP \fItimeout\fP] [\fB\-u\fP \fIfd\fP] [\fIname\fP ...]
8831 One line is read from the standard input, or from the file descriptor
8832 \fIfd\fP supplied as an argument to the \fB\-u\fP option,
8833 split into words as described above under \fBWord Splitting\fP,
8835 is assigned to the first
8837 the second word to the second
8840 If there are more words than names, the remaining words and their
8841 intervening delimiters are assigned to the last
8843 If there are fewer words read from the input stream than names,
8844 the remaining names are assigned empty values.
8848 are used to split the line into words using the same rules the shell
8849 uses for expansion (described above under \fBWord Splitting\fP).
8850 The backslash character (\fB\e\fP) may be used to remove any special
8851 meaning for the next character read and for line continuation.
8852 Options, if supplied, have the following meanings:
8857 The words are assigned to sequential indices
8858 of the array variable
8862 is unset before any new values are assigned.
8863 Other \fIname\fP arguments are ignored.
8866 The first character of \fIdelim\fP is used to terminate the input line,
8867 rather than newline.
8870 If the standard input
8871 is coming from a terminal,
8876 above) is used to obtain the line.
8877 Readline uses the current (or default, if line editing was not previously
8878 active) editing settings.
8883 is being used to read the line, \fItext\fP is placed into the editing
8884 buffer before editing begins.
8887 \fBread\fP returns after reading \fInchars\fP characters rather than
8888 waiting for a complete line of input, but honors a delimiter if fewer
8889 than \fInchars\fP characters are read before the delimiter.
8892 \fBread\fP returns after reading exactly \fInchars\fP characters rather
8893 than waiting for a complete line of input, unless EOF is encountered or
8894 \fBread\fP times out.
8895 Delimiter characters encountered in the input are
8896 not treated specially and do not cause \fBread\fP to return until
8897 \fInchars\fP characters are read.
8898 The result is not split on the characters in \fBIFS\fP; the intent is
8899 that the variable is assigned exactly the characters read
8900 (with the exception of backslash; see the \fB\-r\fP option below).
8903 Display \fIprompt\fP on standard error, without a
8904 trailing newline, before attempting to read any input. The prompt
8905 is displayed only if input is coming from a terminal.
8908 Backslash does not act as an escape character.
8909 The backslash is considered to be part of the line.
8910 In particular, a backslash-newline pair may not be used as a line
8914 Silent mode. If input is coming from a terminal, characters are
8917 .B \-t \fItimeout\fP
8918 Cause \fBread\fP to time out and return failure if a complete line of
8919 input (or a specified number of characters)
8920 is not read within \fItimeout\fP seconds.
8921 \fItimeout\fP may be a decimal number with a fractional portion following
8923 This option is only effective if \fBread\fP is reading input from a
8924 terminal, pipe, or other special file; it has no effect when reading
8926 If \fBread\fP times out, \fBread\fP saves any partial input read into
8927 the specified variable \fIname\fP.
8928 If \fItimeout\fP is 0, \fBread\fP returns immediately, without trying to
8929 read any data. The exit status is 0 if input is available on
8930 the specified file descriptor, non-zero otherwise.
8931 The exit status is greater than 128 if the timeout is exceeded.
8934 Read input from file descriptor \fIfd\fP.
8939 are supplied, the line read is assigned to the variable
8942 The exit status is zero, unless end-of-file is encountered, \fBread\fP
8943 times out (in which case the status is greater than 128),
8944 a variable assignment error (such as assigning to a readonly variable) occurs,
8945 or an invalid file descriptor is supplied as the argument to \fB\-u\fP.
8948 \fBreadonly\fP [\fB\-aAf\fP] [\fB\-p\fP] [\fIname\fP[=\fIword\fP] ...]
8951 \fInames\fP are marked readonly; the values of these
8953 may not be changed by subsequent assignment.
8956 option is supplied, the functions corresponding to the
8961 option restricts the variables to indexed arrays; the
8963 option restricts the variables to associative arrays.
8964 If both options are supplied,
8969 arguments are given, or if the
8971 option is supplied, a list of all readonly names is printed.
8972 The other options may be used to restrict the output to a subset of
8973 the set of readonly names.
8976 option causes output to be displayed in a format that
8977 may be reused as input.
8978 If a variable name is followed by =\fIword\fP, the value of
8979 the variable is set to \fIword\fP.
8980 The return status is 0 unless an invalid option is encountered,
8983 is not a valid shell variable name, or
8987 that is not a function.
8989 \fBreturn\fP [\fIn\fP]
8990 Causes a function to stop executing and return the value specified by
8995 is omitted, the return status is that of the last command
8996 executed in the function body.
8997 If \fBreturn\fP is executed by a trap handler, the last command used to
8998 determine the status is the last command executed before the trap handler.
8999 if \fBreturn\fP is executed during a \fBDEBUG\fP trap, the last command
9000 used to determine the status is the last command executed by the trap
9001 handler before \fBreturn\fP was invoked.
9004 is used outside a function,
9005 but during execution of a script by the
9007 (\fBsource\fP) command, it causes the shell to stop executing
9008 that script and return either
9010 or the exit status of the last command executed within the
9011 script as the exit status of the script.
9012 If \fIn\fP is supplied, the return value is its least significant
9014 The return status is non-zero if
9016 is supplied a non-numeric argument, or
9018 function and not during execution of a script by \fB.\fP\^ or \fBsource\fP.
9019 Any command associated with the \fBRETURN\fP trap is executed
9020 before execution resumes after the function or script.
9022 \fBset\fP [\fB\-\-abefhkmnptuvxBCEHPT\fP] [\fB\-o\fP \fIoption\-name\fP] [\fIarg\fP ...]
9025 \fBset\fP [\fB+abefhkmnptuvxBCEHPT\fP] [\fB+o\fP \fIoption\-name\fP] [\fIarg\fP ...]
9027 Without options, the name and value of each shell variable are displayed
9028 in a format that can be reused as input
9029 for setting or resetting the currently-set variables.
9030 Read-only variables cannot be reset.
9031 In \fIposix\fP mode, only shell variables are listed.
9032 The output is sorted according to the current locale.
9033 When options are specified, they set or unset shell attributes.
9034 Any arguments remaining after option processing are treated
9035 as values for the positional parameters and are assigned, in order, to
9040 Options, if specified, have the following meanings:
9045 Each variable or function that is created or modified is given the
9046 export attribute and marked for export to the environment of
9047 subsequent commands.
9050 Report the status of terminated background jobs
9051 immediately, rather than before the next primary prompt. This is
9052 effective only when job control is enabled.
9055 Exit immediately if a
9056 \fIpipeline\fP (which may consist of a single \fIsimple command\fP),
9058 or a \fIcompound command\fP
9062 above), exits with a non-zero status.
9063 The shell does not exit if the
9064 command that fails is part of the command list immediately following a
9069 part of the test following the
9073 reserved words, part of any command executed in a
9077 list except the command following the final \fB&&\fP or \fB||\fP,
9078 any command in a pipeline but the last,
9079 or if the command's return value is
9082 If a compound command other than a subshell
9083 returns a non-zero status because a command failed
9084 while \fB\-e\fP was being ignored, the shell does not exit.
9085 A trap on \fBERR\fP, if set, is executed before the shell exits.
9086 This option applies to the shell environment and each subshell environment
9089 .B "COMMAND EXECUTION ENVIRONMENT"
9090 above), and may cause
9091 subshells to exit before executing all the commands in the subshell.
9094 If a compound command or shell function executes in a context
9095 where \fB\-e\fP is being ignored,
9096 none of the commands executed within the compound command or function body
9097 will be affected by the \fB\-e\fP setting, even if \fB\-e\fP is set
9098 and a command returns a failure status.
9099 If a compound command or shell function sets \fB\-e\fP while executing in
9100 a context where \fB\-e\fP is ignored, that setting will not have any
9101 effect until the compound command or the command containing the function
9105 Disable pathname expansion.
9108 Remember the location of commands as they are looked up for execution.
9109 This is enabled by default.
9112 All arguments in the form of assignment statements
9113 are placed in the environment for a command, not just
9114 those that precede the command name.
9117 Monitor mode. Job control is enabled. This option is on
9118 by default for interactive shells on systems that support
9123 All processes run in a separate process group.
9124 When a background job completes, the shell prints a line
9125 containing its exit status.
9128 Read commands but do not execute them.
9129 This may be used to check a shell script for syntax errors.
9130 This is ignored by interactive shells.
9132 .B \-o \fIoption\-name\fP
9133 The \fIoption\-name\fP can be one of the following:
9145 Use an emacs-style command line editing interface. This is enabled
9146 by default when the shell is interactive, unless the shell is started
9150 This also affects the editing interface used for \fBread \-e\fP.
9173 Enable command history, as described above under
9176 This option is on by default in interactive shells.
9179 The effect is as if the shell command
9180 .if t \f(CWIGNOREEOF=10\fP
9181 .if n ``IGNOREEOF=10''
9227 If set, the return value of a pipeline is the value of the last
9228 (rightmost) command to exit with a non-zero status, or zero if all
9229 commands in the pipeline exit successfully.
9230 This option is disabled by default.
9233 Change the behavior of
9235 where the default operation differs
9236 from the POSIX standard to match the standard (\fIposix mode\fP).
9240 below for a reference to a document that details how posix mode affects
9252 Use a vi-style command line editing interface.
9253 This also affects the editing interface used for \fBread \-e\fP.
9262 is supplied with no \fIoption\-name\fP, the values of the current options are
9266 is supplied with no \fIoption\-name\fP, a series of
9268 commands to recreate the current option settings is displayed on
9269 the standard output.
9275 mode. In this mode, the
9281 files are not processed, shell functions are not inherited from the
9282 environment, and the
9292 variables, if they appear in the environment, are ignored.
9293 If the shell is started with the effective user (group) id not equal to the
9294 real user (group) id, and the \fB\-p\fP option is not supplied, these actions
9295 are taken and the effective user id is set to the real user id.
9296 If the \fB\-p\fP option is supplied at startup, the effective user id is
9298 Turning this option off causes the effective user
9299 and group ids to be set to the real user and group ids.
9302 Exit after reading and executing one command.
9305 Treat unset variables and parameters other than the special
9306 parameters "@" and "*" as an error when performing
9307 parameter expansion. If expansion is attempted on an
9308 unset variable or parameter, the shell prints an error message, and,
9309 if not interactive, exits with a non-zero status.
9312 Print shell input lines as they are read.
9315 After expanding each \fIsimple command\fP,
9316 \fBfor\fP command, \fBcase\fP command, \fBselect\fP command, or
9317 arithmetic \fBfor\fP command, display the expanded value of
9320 followed by the command and its expanded arguments
9321 or associated word list.
9324 The shell performs brace expansion (see
9326 above). This is on by default.
9331 does not overwrite an existing file with the
9336 redirection operators. This may be overridden when
9337 creating output files by using the redirection operator
9343 If set, any trap on \fBERR\fP is inherited by shell functions, command
9344 substitutions, and commands executed in a subshell environment.
9345 The \fBERR\fP trap is normally not inherited in such cases.
9350 style history substitution. This option is on by
9351 default when the shell is interactive.
9354 If set, the shell does not resolve symbolic links when executing
9357 that change the current working directory. It uses the
9358 physical directory structure instead. By default,
9360 follows the logical chain of directories when performing commands
9361 which change the current directory.
9364 If set, any traps on \fBDEBUG\fP and \fBRETURN\fP are inherited by shell
9365 functions, command substitutions, and commands executed in a
9366 subshell environment.
9367 The \fBDEBUG\fP and \fBRETURN\fP traps are normally not inherited
9371 If no arguments follow this option, then the positional parameters are
9372 unset. Otherwise, the positional parameters are set to the
9373 \fIarg\fPs, even if some of them begin with a
9377 Signal the end of options, cause all remaining \fIarg\fPs to be
9378 assigned to the positional parameters. The
9382 options are turned off.
9383 If there are no \fIarg\fPs,
9384 the positional parameters remain unchanged.
9387 The options are off by default unless otherwise noted.
9388 Using + rather than \- causes these options to be turned off.
9389 The options can also be specified as arguments to an invocation of
9391 The current set of options may be found in
9393 The return status is always true unless an invalid option is encountered.
9396 \fBshift\fP [\fIn\fP]
9397 The positional parameters from \fIn\fP+1 ... are renamed to
9400 Parameters represented by the numbers \fB$#\fP
9401 down to \fB$#\fP\-\fIn\fP+1 are unset.
9403 must be a non-negative number less than or equal to \fB$#\fP.
9406 is 0, no parameters are changed.
9409 is not given, it is assumed to be 1.
9412 is greater than \fB$#\fP, the positional parameters are not changed.
9413 The return status is greater than zero if
9417 or less than zero; otherwise 0.
9419 \fBshopt\fP [\fB\-pqsu\fP] [\fB\-o\fP] [\fIoptname\fP ...]
9420 Toggle the values of settings controlling optional shell behavior.
9421 The settings can be either those listed below, or, if the
9423 option is used, those available with the
9425 option to the \fBset\fP builtin command.
9426 With no options, or with the
9428 option, a list of all settable options is displayed, with
9429 an indication of whether or not each is set.
9430 The \fB\-p\fP option causes output to be displayed in a form that
9431 may be reused as input.
9432 Other options have the following meanings:
9437 Enable (set) each \fIoptname\fP.
9440 Disable (unset) each \fIoptname\fP.
9443 Suppresses normal output (quiet mode); the return status indicates
9444 whether the \fIoptname\fP is set or unset.
9445 If multiple \fIoptname\fP arguments are given with
9447 the return status is zero if all \fIoptnames\fP are enabled; non-zero
9451 Restricts the values of \fIoptname\fP to be those defined for the
9462 is used with no \fIoptname\fP arguments,
9464 shows only those options which are set or unset, respectively.
9465 Unless otherwise noted, the \fBshopt\fP options are disabled (unset)
9468 The return status when listing options is zero if all \fIoptnames\fP
9469 are enabled, non-zero otherwise. When setting or unsetting options,
9470 the return status is zero unless an \fIoptname\fP is not a valid shell
9473 The list of \fBshopt\fP options is:
9479 If set, a command name that is the name of a directory is executed as if
9480 it were the argument to the \fBcd\fP command.
9481 This option is only used by interactive shells.
9484 If set, an argument to the
9486 builtin command that
9487 is not a directory is assumed to be the name of a variable whose
9488 value is the directory to change to.
9491 If set, minor errors in the spelling of a directory component in a
9493 command will be corrected.
9494 The errors checked for are transposed characters,
9495 a missing character, and one character too many.
9496 If a correction is found, the corrected filename is printed,
9497 and the command proceeds.
9498 This option is only used by interactive shells.
9501 If set, \fBbash\fP checks that a command found in the hash
9502 table exists before trying to execute it. If a hashed command no
9503 longer exists, a normal path search is performed.
9506 If set, \fBbash\fP lists the status of any stopped and running jobs before
9507 exiting an interactive shell. If any jobs are running, this causes
9508 the exit to be deferred until a second exit is attempted without an
9509 intervening command (see
9512 above). The shell always
9513 postpones exiting if any jobs are stopped.
9516 If set, \fBbash\fP checks the window size after each command
9517 and, if necessary, updates the values of
9527 attempts to save all lines of a multiple-line
9528 command in the same history entry. This allows
9529 easy re-editing of multi-line commands.
9534 changes its behavior to that of version 3.1 with respect to quoted
9535 arguments to the \fB[[\fP conditional command's \fB=~\fP operator
9536 and locale-specific string comparison when using the \fB[[\fP
9537 conditional command's \fB<\fP and \fB>\fP operators.
9538 Bash versions prior to bash-4.1 use ASCII collation and
9540 bash-4.1 and later use the current locale's collation sequence and
9546 changes its behavior to that of version 3.2 with respect to
9547 locale-specific string comparison when using the \fB[[\fP
9548 conditional command's \fB<\fP and \fB>\fP operators (see previous item)
9549 and the effect of interrupting a command list.
9550 Bash versions 3.2 and earlier continue with the next command in the list
9551 after one terminates due to an interrupt.
9556 changes its behavior to that of version 4.0 with respect to locale-specific
9557 string comparison when using the \fB[[\fP
9558 conditional command's \fB<\fP and \fB>\fP operators (see description of
9560 and the effect of interrupting a command list.
9561 Bash versions 4.0 and later interrupt the list as if the shell received the
9562 interrupt; previous versions continue with the next command in the list.
9567 when in \fIposix\fP mode, treats a single quote in a double-quoted
9568 parameter expansion as a special character. The single quotes must match
9569 (an even number) and the characters between the single quotes are considered
9570 quoted. This is the behavior of posix mode through version 4.1.
9571 The default bash behavior remains as in previous versions.
9576 does not process the replacement string in the pattern substitution word
9577 expansion using quote removal.
9582 does not print a warning message if an attempt is made to use a quoted compound
9583 array assignment as an argument to \fBdeclare\fP,
9584 makes word expansion errors
9585 non-fatal errors that cause the current command to fail (the default behavior is
9586 to make them fatal errors that cause the shell to exit),
9587 and does not reset the
9588 loop state when a shell function is executed (this allows \fBbreak\fP or
9589 \fBcontinue\fP in a shell function to affect loops in the caller's context).
9591 .B complete_fullquote
9594 quotes all shell metacharacters in filenames and directory names when
9595 performing completion.
9598 removes metacharacters such as the dollar sign from the set of
9599 characters that will be quoted in completed filenames
9600 when these metacharacters appear in shell variable references in words to be
9602 This means that dollar signs in variable names that expand to directories
9604 however, any dollar signs appearing in filenames will not be quoted, either.
9605 This is active only when bash is using backslashes to quote completed
9607 This variable is set by default, which is the default bash behavior in
9608 versions through 4.2.
9613 replaces directory names with the results of word expansion when performing
9614 filename completion. This changes the contents of the readline editing
9618 attempts to preserve what the user typed.
9623 attempts spelling correction on directory names during word completion
9624 if the directory name initially supplied does not exist.
9629 includes filenames beginning with a `.' in the results of pathname
9633 If set, a non-interactive shell will not exit if
9634 it cannot execute the file specified as an argument to the
9636 builtin command. An interactive shell does not exit if
9641 If set, aliases are expanded as described above under
9644 This option is enabled by default for interactive shells.
9647 If set at shell invocation, arrange to execute the debugger profile
9648 before the shell starts, identical to the \fB\-\-debugger\fP option.
9649 If set after invocation, behavior intended for use by debuggers is enabled:
9653 The \fB\-F\fP option to the \fBdeclare\fP builtin displays the source
9654 file name and line number corresponding to each function name supplied
9658 If the command run by the \fBDEBUG\fP trap returns a non-zero value, the
9659 next command is skipped and not executed.
9662 If the command run by the \fBDEBUG\fP trap returns a value of 2, and the
9663 shell is executing in a subroutine (a shell function or a shell script
9664 executed by the \fB.\fP or \fBsource\fP builtins), the shell simulates
9665 a call to \fBreturn\fP.
9673 are updated as described in their descriptions above.
9676 Function tracing is enabled: command substitution, shell functions, and
9677 subshells invoked with \fB(\fP \fIcommand\fP \fB)\fP inherit the
9678 \fBDEBUG\fP and \fBRETURN\fP traps.
9681 Error tracing is enabled: command substitution, shell functions, and
9682 subshells invoked with \fB(\fP \fIcommand\fP \fB)\fP inherit the
9687 If set, the extended pattern matching features described above under
9688 \fBPathname Expansion\fP are enabled.
9691 If set, \fB$\fP\(aq\fIstring\fP\(aq and \fB$\fP"\fIstring\fP" quoting is
9692 performed within \fB${\fP\fIparameter\fP\fB}\fP expansions
9693 enclosed in double quotes. This option is enabled by default.
9696 If set, patterns which fail to match filenames during pathname expansion
9697 result in an expansion error.
9700 If set, the suffixes specified by the
9704 cause words to be ignored when performing word completion even if
9705 the ignored words are the only possible completions.
9708 \fBSHELL VARIABLES\fP
9709 above for a description of
9712 This option is enabled by default.
9715 If set, range expressions used in pattern matching bracket expressions (see
9718 above) behave as if in the traditional C locale when performing
9719 comparisons. That is, the current locale's collating sequence
9720 is not taken into account, so
9722 will not collate between
9726 and upper-case and lower-case ASCII characters will collate together.
9729 If set, the pattern \fB**\fP used in a pathname expansion context will
9730 match all files and zero or more directories and subdirectories.
9731 If the pattern is followed by a \fB/\fP, only directories and
9732 subdirectories match.
9735 If set, shell error messages are written in the standard GNU error
9739 If set, the history list is appended to the file named by the value
9743 variable when the shell exits, rather than overwriting the file.
9748 is being used, a user is given the opportunity to re-edit a
9749 failed history substitution.
9754 is being used, the results of history substitution are not immediately
9755 passed to the shell parser. Instead, the resulting line is loaded into
9756 the \fBreadline\fP editing buffer, allowing further modification.
9761 is being used, \fBbash\fP will attempt to perform hostname completion when a
9762 word containing a \fB@\fP is being completed (see
9768 This is enabled by default.
9771 If set, \fBbash\fP will send
9774 to all jobs when an interactive login shell exits.
9777 If set, command substitution inherits the value of the \fBerrexit\fP option,
9778 instead of unsetting it in the subshell environment.
9779 This option is enabled when \fIposix mode\fP is enabled.
9781 .B interactive_comments
9782 If set, allow a word beginning with
9784 to cause that word and all remaining characters on that
9785 line to be ignored in an interactive shell (see
9788 above). This option is enabled by default.
9791 If set, and job control is not active, the shell runs the last command of
9792 a pipeline not executed in the background in the current shell environment.
9797 option is enabled, multi-line commands are saved to the history with
9798 embedded newlines rather than using semicolon separators where possible.
9801 The shell sets this option if it is started as a login shell (see
9805 The value may not be changed.
9808 If set, and a file that \fBbash\fP is checking for mail has been
9809 accessed since the last time it was checked, the message ``The mail in
9810 \fImailfile\fP has been read'' is displayed.
9812 .B no_empty_cmd_completion
9817 will not attempt to search the
9820 for possible completions when
9821 completion is attempted on an empty line.
9826 matches filenames in a case\-insensitive fashion when performing pathname
9828 .B Pathname Expansion
9834 matches patterns in a case\-insensitive fashion when performing matching
9835 while executing \fBcase\fP or \fB[[\fP conditional commands,
9836 when performing pattern substitution word expansions,
9837 or when filtering possible completions as part of programmable completion.
9842 allows patterns which match no
9844 .B Pathname Expansion
9846 to expand to a null string, rather than themselves.
9849 If set, the programmable completion facilities (see
9850 \fBProgrammable Completion\fP above) are enabled.
9851 This option is enabled by default.
9854 If set, prompt strings undergo
9855 parameter expansion, command substitution, arithmetic
9856 expansion, and quote removal after being expanded as described in
9859 above. This option is enabled by default.
9862 The shell sets this option if it is started in restricted mode (see
9864 .B "RESTRICTED SHELL"
9866 The value may not be changed.
9867 This is not reset when the startup files are executed, allowing
9868 the startup files to discover whether or not a shell is restricted.
9873 builtin prints an error message when the shift count exceeds the
9874 number of positional parameters.
9878 \fBsource\fP (\fB.\fP) builtin uses the value of
9881 to find the directory containing the file supplied as an argument.
9882 This option is enabled by default.
9885 If set, the \fBecho\fP builtin expands backslash-escape sequences
9890 \fBsuspend\fP [\fB\-f\fP]
9891 Suspend the execution of this shell until it receives a
9894 signal. A login shell cannot be suspended; the
9896 option can be used to override this and force the suspension.
9897 The return status is 0 unless the shell is a login shell and
9899 is not supplied, or if job control is not enabled.
9901 \fBtest\fP \fIexpr\fP
9904 \fB[\fP \fIexpr\fP \fB]\fP
9905 Return a status of 0 (true) or 1 (false) depending on
9906 the evaluation of the conditional expression
9908 Each operator and operand must be a separate argument.
9909 Expressions are composed of the primaries described above under
9911 .BR "CONDITIONAL EXPRESSIONS" .
9912 \fBtest\fP does not accept any options, nor does it accept and ignore
9913 an argument of \fB\-\-\fP as signifying the end of options.
9916 Expressions may be combined using the following operators, listed
9917 in decreasing order of precedence.
9918 The evaluation depends on the number of arguments; see below.
9919 Operator precedence is used when there are five or more arguments.
9929 Returns the value of \fIexpr\fP.
9930 This may be used to override the normal precedence of operators.
9932 \fIexpr1\fP \-\fBa\fP \fIexpr2\fP
9939 \fIexpr1\fP \-\fBo\fP \fIexpr2\fP
9947 \fBtest\fP and \fB[\fP evaluate conditional
9948 expressions using a set of rules based on the number of arguments.
9954 The expression is false.
9957 The expression is true if and only if the argument is not null.
9960 If the first argument is \fB!\fP, the expression is true if and
9961 only if the second argument is null.
9962 If the first argument is one of the unary conditional operators listed above
9965 .BR "CONDITIONAL EXPRESSIONS" ,
9966 the expression is true if the unary test is true.
9967 If the first argument is not a valid unary conditional operator, the expression
9971 The following conditions are applied in the order listed.
9972 If the second argument is one of the binary conditional operators listed above
9975 .BR "CONDITIONAL EXPRESSIONS" ,
9976 the result of the expression is the result of the binary test using
9977 the first and third arguments as operands.
9978 The \fB\-a\fP and \fB\-o\fP operators are considered binary operators
9979 when there are three arguments.
9980 If the first argument is \fB!\fP, the value is the negation of
9981 the two-argument test using the second and third arguments.
9982 If the first argument is exactly \fB(\fP and the third argument is
9983 exactly \fB)\fP, the result is the one-argument test of the second
9985 Otherwise, the expression is false.
9988 If the first argument is \fB!\fP, the result is the negation of
9989 the three-argument expression composed of the remaining arguments.
9990 Otherwise, the expression is parsed and evaluated according to
9991 precedence using the rules listed above.
9994 The expression is parsed and evaluated according to precedence
9995 using the rules listed above.
9999 When used with \fBtest\fP or \fB[\fP, the \fB<\fP and \fB>\fP operators
10000 sort lexicographically using ASCII ordering.
10005 Print the accumulated user and system times for the shell and
10006 for processes run from the shell. The return status is 0.
10008 \fBtrap\fP [\fB\-lp\fP] [[\fIarg\fP] \fIsigspec\fP ...]
10011 is to be read and executed when the shell receives
10016 is absent (and there is a single \fIsigspec\fP) or
10018 each specified signal is
10019 reset to its original disposition (the value it had
10020 upon entrance to the shell).
10023 is the null string the signal specified by each
10025 is ignored by the shell and by the commands it invokes.
10030 has been supplied, then the trap commands associated with each
10033 If no arguments are supplied or if only
10037 prints the list of commands associated with each signal.
10040 option causes the shell to print a list of signal names and
10041 their corresponding numbers.
10045 a signal name defined in <\fIsignal.h\fP>, or a signal number.
10046 Signal names are case insensitive and the
10049 prefix is optional.
10059 is executed on exit from the shell.
10067 is executed before every \fIsimple command\fP, \fIfor\fP command,
10068 \fIcase\fP command, \fIselect\fP command, every arithmetic \fIfor\fP
10069 command, and before the first command executes in a shell function (see
10073 Refer to the description of the \fBextdebug\fP option to the
10074 \fBshopt\fP builtin for details of its effect on the \fBDEBUG\fP trap.
10082 is executed each time a shell function or a script executed with
10083 the \fB.\fP or \fBsource\fP builtins finishes executing.
10093 is executed whenever
10094 a pipeline (which may consist of a single simple
10095 command), a list, or a compound command returns a
10096 non\-zero exit status,
10097 subject to the following conditions.
10101 trap is not executed if the failed
10102 command is part of the command list immediately following a
10107 part of the test in an
10109 statement, part of a command executed in a
10113 list except the command following the final \fB&&\fP or \fB||\fP,
10114 any command in a pipeline but the last,
10115 or if the command's return value is
10116 being inverted using
10118 These are the same conditions obeyed by the \fBerrexit\fP (\fB\-e\fP) option.
10121 Signals ignored upon entry to the shell cannot be trapped or reset.
10122 Trapped signals that are not being ignored are reset to their original
10123 values in a subshell or subshell environment when one is created.
10124 The return status is false if any
10126 is invalid; otherwise
10130 \fBtype\fP [\fB\-aftpP\fP] \fIname\fP [\fIname\fP ...]
10134 would be interpreted if used as a command name.
10139 prints a string which is one of
10148 is an alias, shell reserved word, function, builtin, or disk file,
10152 is not found, then nothing is printed, and an exit status of false
10158 either returns the name of the disk file
10159 that would be executed if
10161 were specified as a command name,
10163 .if t \f(CWtype -t name\fP
10164 .if n ``type -t name''
10172 search for each \fIname\fP, even if
10173 .if t \f(CWtype -t name\fP
10174 .if n ``type -t name''
10177 If a command is hashed,
10181 print the hashed value, which is not necessarily the file that appears
10189 prints all of the places that contain
10190 an executable named
10192 This includes aliases and functions,
10195 option is not also used.
10196 The table of hashed commands is not consulted
10201 option suppresses shell function lookup, as with the \fBcommand\fP builtin.
10203 returns true if all of the arguments are found, false if
10206 \fBulimit\fP [\fB\-HSabcdefiklmnpqrstuvxPT\fP [\fIlimit\fP]]
10207 Provides control over the resources available to the shell and to
10208 processes started by it, on systems that allow such control.
10209 The \fB\-H\fP and \fB\-S\fP options specify that the hard or soft limit is
10210 set for the given resource.
10211 A hard limit cannot be increased by a non-root user once it is set;
10212 a soft limit may be increased up to the value of the hard limit.
10213 If neither \fB\-H\fP nor \fB\-S\fP is specified, both the soft and hard
10217 can be a number in the unit specified for the resource
10218 or one of the special values
10223 which stand for the current hard limit, the current soft limit, and
10224 no limit, respectively.
10227 is omitted, the current value of the soft limit of the resource is
10228 printed, unless the \fB\-H\fP option is given. When more than one
10229 resource is specified, the limit name and unit are printed before the value.
10230 Other options are interpreted as follows:
10235 All current limits are reported
10238 The maximum socket buffer size
10241 The maximum size of core files created
10244 The maximum size of a process's data segment
10247 The maximum scheduling priority ("nice")
10250 The maximum size of files written by the shell and its children
10253 The maximum number of pending signals
10256 The maximum number of kqueues that may be allocated
10259 The maximum size that may be locked into memory
10262 The maximum resident set size (many systems do not honor this limit)
10265 The maximum number of open file descriptors (most systems do not
10266 allow this value to be set)
10269 The pipe size in 512-byte blocks (this may not be set)
10272 The maximum number of bytes in POSIX message queues
10275 The maximum real-time scheduling priority
10278 The maximum stack size
10281 The maximum amount of cpu time in seconds
10284 The maximum number of processes available to a single user
10287 The maximum amount of virtual memory available to the shell and, on
10288 some systems, to its children
10291 The maximum number of file locks
10294 The maximum number of pseudoterminals
10297 The maximum number of threads
10304 option is not used,
10305 \fIlimit\fP is the new value of the specified resource.
10306 If no option is given, then
10308 is assumed. Values are in 1024-byte increments, except for
10310 which is in seconds;
10312 which is in units of 512-byte blocks;
10320 which are unscaled values;
10321 and, when in Posix mode,
10325 which are in 512-byte increments.
10326 The return status is 0 unless an invalid option or argument is supplied,
10327 or an error occurs while setting a new limit.
10330 \fBumask\fP [\fB\-p\fP] [\fB\-S\fP] [\fImode\fP]
10331 The user file-creation mask is set to
10335 begins with a digit, it
10336 is interpreted as an octal number; otherwise
10337 it is interpreted as a symbolic mode mask similar
10338 to that accepted by
10342 is omitted, the current value of the mask is printed.
10345 option causes the mask to be printed in symbolic form; the
10346 default output is an octal number.
10349 option is supplied, and
10351 is omitted, the output is in a form that may be reused as input.
10352 The return status is 0 if the mode was successfully changed or if
10353 no \fImode\fP argument was supplied, and false otherwise.
10355 \fBunalias\fP [\-\fBa\fP] [\fIname\fP ...]
10356 Remove each \fIname\fP from the list of defined aliases. If
10358 is supplied, all alias definitions are removed. The return
10359 value is true unless a supplied
10361 is not a defined alias.
10363 \fBunset\fP [\-\fBfv\fP] [\-\fBn\fP] [\fIname\fP ...]
10366 remove the corresponding variable or function.
10369 option is given, each
10371 refers to a shell variable, and that variable is removed.
10372 Read-only variables may not be unset.
10377 refers to a shell function, and the function definition
10381 option is supplied, and \fIname\fP is a variable with the \fInameref\fP
10382 attribute, \fIname\fP will be unset rather than the variable it
10384 \fB\-n\fP has no effect if the \fB\-f\fP option is supplied.
10385 If no options are supplied, each \fIname\fP refers to a variable; if
10386 there is no variable by that name, any function with that name is
10388 Each unset variable or function is removed from the environment
10389 passed to subsequent commands.
10392 .BR COMP_WORDBREAKS ,
10408 are unset, they lose their special properties, even if they are
10409 subsequently reset. The exit status is true unless a
10413 \fBwait\fP [\fB\-n\fP] [\fIn ...\fP]
10414 Wait for each specified child process and return its termination status.
10418 ID or a job specification; if a job spec is given, all processes
10419 in that job's pipeline are waited for. If
10421 is not given, all currently active child processes
10422 are waited for, and the return status is zero.
10423 If the \fB\-n\fP option is supplied, \fBwait\fP waits for any job to
10424 terminate and returns its exit status.
10427 specifies a non-existent process or job, the return status is
10428 127. Otherwise, the return status is the exit status of the last
10429 process or job waited for.
10432 .SH "RESTRICTED SHELL"
10438 is started with the name
10442 option is supplied at invocation,
10443 the shell becomes restricted.
10444 A restricted shell is used to
10445 set up an environment more controlled than the standard shell.
10446 It behaves identically to
10448 with the exception that the following are disallowed or not performed:
10450 changing directories with \fBcd\fP
10452 setting or unsetting the values of
10463 specifying command names containing
10466 specifying a filename containing a
10468 as an argument to the
10472 specifying a filename containing a slash as an argument to the
10478 importing function definitions from the shell environment at startup
10480 parsing the value of
10483 from the shell environment at startup
10485 redirecting output using the >, >|, <>, >&, &>, and >> redirection operators
10489 builtin command to replace the shell with another command
10491 adding or deleting builtin commands with the
10499 using the \fBenable\fP builtin command to enable disabled shell builtins
10507 turning off restricted mode with
10508 \fBset +r\fP or \fBset +o restricted\fP.
10510 These restrictions are enforced after any startup files are read.
10512 .ie \n(zY=1 When a command that is found to be a shell script is executed,
10513 .el \{ When a command that is found to be a shell script is executed
10516 .B "COMMAND EXECUTION"
10520 turns off any restrictions in the shell spawned to execute the
10527 \fIBash Reference Manual\fP, Brian Fox and Chet Ramey
10529 \fIThe Gnu Readline Library\fP, Brian Fox and Chet Ramey
10531 \fIThe Gnu History Library\fP, Brian Fox and Chet Ramey
10533 \fIPortable Operating System Interface (POSIX) Part 2: Shell and Utilities\fP, IEEE --
10534 http://pubs.opengroup.org/onlinepubs/9699919799/
10536 http://tiswww.case.edu/~chet/bash/POSIX -- a description of posix mode
10538 \fIsh\fP(1), \fIksh\fP(1), \fIcsh\fP(1)
10540 \fIemacs\fP(1), \fIvi\fP(1)
10548 The \fBbash\fP executable
10551 The systemwide initialization file, executed for login shells
10553 .FN ~/.bash_profile
10554 The personal initialization file, executed for login shells
10557 The individual per-interactive-shell startup file
10560 The individual login shell cleanup file, executed when a login shell exits
10563 Individual \fIreadline\fP initialization file
10566 Brian Fox, Free Software Foundation
10570 Chet Ramey, Case Western Reserve University
10572 chet.ramey@case.edu
10574 If you find a bug in
10576 you should report it. But first, you should
10577 make sure that it really is a bug, and that it appears in the latest
10580 The latest version is always available from
10581 \fIftp://ftp.gnu.org/pub/gnu/bash/\fP.
10583 Once you have determined that a bug actually exists, use the
10585 command to submit a bug report.
10586 If you have a fix, you are encouraged to mail that as well!
10587 Suggestions and `philosophical' bug reports may be mailed
10588 to \fIbug-bash@gnu.org\fP or posted to the Usenet
10592 ALL bug reports should include:
10596 The version number of \fBbash\fR
10598 The hardware and operating system
10600 The compiler used to compile
10602 A description of the bug behaviour
10604 A short script or `recipe' which exercises the bug
10608 inserts the first three items automatically into the template
10609 it provides for filing a bug report.
10611 Comments and bug reports concerning
10612 this manual page should be directed to
10613 .IR chet.ramey@case.edu .
10616 It's too big and too slow.
10618 There are some subtle differences between
10620 and traditional versions of
10622 mostly because of the
10627 Aliases are confusing in some uses.
10629 Shell builtin commands and functions are not stoppable/restartable.
10631 Compound commands and command sequences of the form `a ; b ; c'
10632 are not handled gracefully when process suspension is attempted.
10633 When a process is stopped, the shell immediately executes the next
10634 command in the sequence.
10635 It suffices to place the sequence of commands between
10636 parentheses to force it into a subshell, which may be stopped as
10639 Array variables may not (yet) be exported.
10641 There may be only one active coprocess at a time.
projects / thirdparty / bash.git / blob