2 .\" MAN PAGE COMMENTS to
5 .\" Case Western Reserve University
8 .\" Last Change: Sat Feb 7 20:50:40 EST 2009
10 .\" bash_builtins, strip all but Built-Ins section
13 .TH BASH 1 "2009 February 7" "GNU Bash-4.0"
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
53 .if n Bash is Copyright (C) 1989-2009 by the Free Software Foundation, Inc.
54 .if t Bash is Copyright \(co 1989-2009 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 In addition to the single-character shell options documented in the
71 description of the \fBset\fR builtin command, \fBbash\fR
72 interprets the following options when it is invoked:
79 option is present, then commands are read from
81 If there are arguments after the
83 they are assigned to the positional parameters, starting with
89 option is present, the shell is
95 act as if it had been invoked as a login shell (see
103 option is present, the shell becomes
107 .B "RESTRICTED SHELL"
113 option is present, or if no arguments remain after option
114 processing, then commands are read from the standard input.
115 This option allows the positional parameters to be set
116 when invoking an interactive shell.
119 A list of all double-quoted strings preceded by \fB$\fP
120 is printed on the standard output.
121 These are the strings that
122 are subject to language translation when the current locale
123 is not \fBC\fP or \fBPOSIX\fP.
124 This implies the \fB\-n\fP option; no commands will be executed.
126 .B [\-+]O [\fIshopt_option\fP]
127 \fIshopt_option\fP is one of the shell options accepted by the
128 \fBshopt\fP builtin (see
130 .B SHELL BUILTIN COMMANDS
132 If \fIshopt_option\fP is present, \fB\-O\fP sets the value of that option;
134 If \fIshopt_option\fP is not supplied, the names and values of the shell
135 options accepted by \fBshopt\fP are printed on the standard output.
136 If the invocation option is \fB+O\fP, the output is displayed in a format
137 that may be reused as input.
142 signals the end of options and disables further option processing.
143 Any arguments after the
145 are treated as filenames and arguments. An argument of
147 is equivalent to \fB\-\-\fP.
151 also interprets a number of multi-character options.
152 These options must appear on the command line before the
153 single-character options to be recognized.
158 Arrange for the debugger profile to be executed before the shell
160 Turns on extended debugging mode (see the description of the
165 and shell function tracing (see the description of the
166 \fB\-o functrace\fP option to the
170 .B \-\-dump\-po\-strings
171 Equivalent to \fB\-D\fP, but the output is in the GNU \fIgettext\fP
172 \fBpo\fP (portable object) file format.
175 Equivalent to \fB\-D\fP.
178 Display a usage message on standard output and exit successfully.
180 \fB\-\-init\-file\fP \fIfile\fP
183 \fB\-\-rcfile\fP \fIfile\fP
185 Execute commands from
187 instead of the standard personal initialization file
189 if the shell is interactive (see
195 Equivalent to \fB\-l\fP.
200 library to read command lines when the shell is interactive.
203 Do not read either the system-wide startup file
205 or any of the personal initialization files
206 .IR ~/.bash_profile ,
212 reads these files when it is invoked as a login shell (see
218 Do not read and execute the personal initialization file
220 if the shell is interactive.
221 This option is on by default if the shell is invoked as
225 Change the behavior of \fBbash\fP where the default operation differs
226 from the POSIX standard to match the standard (\fIposix mode\fP).
229 The shell becomes restricted (see
231 .B "RESTRICTED SHELL"
235 Equivalent to \fB\-v\fP.
238 Show version information for this instance of
240 on the standard output and exit successfully.
243 If arguments remain after option processing, and neither the
247 option has been supplied, the first argument is assumed to
248 be the name of a file containing shell commands.
251 is invoked in this fashion,
253 is set to the name of the file, and the positional parameters
254 are set to the remaining arguments.
256 reads and executes commands from this file, then exits.
257 \fBBash\fP's exit status is the exit status of the last command
258 executed in the script.
259 If no commands are executed, the exit status is 0.
260 An attempt is first made to open the file in the current directory, and,
261 if no file is found, then the shell searches the directories in
266 A \fIlogin shell\fP is one whose first character of argument zero is a
268 or one started with the
272 An \fIinteractive\fP shell is one started without non-option arguments
276 whose standard input and error are
277 both connected to terminals (as determined by
279 or one started with the
291 allowing a shell script or a startup file to test this state.
293 The following paragraphs describe how
295 executes its startup files.
296 If any of the files exist but cannot be read,
299 Tildes are expanded in file names as described below under
308 is invoked as an interactive login shell, or as a non-interactive shell
309 with the \fB\-\-login\fP option, it first reads and
310 executes commands from the file \fI/etc/profile\fP, if that
312 After reading that file, it looks for \fI~/.bash_profile\fP,
313 \fI~/.bash_login\fP, and \fI~/.profile\fP, in that order, and reads
314 and executes commands from the first one that exists and is readable.
317 option may be used when the shell is started to inhibit this behavior.
319 When a login shell exits,
321 reads and executes commands from the file \fI~/.bash_logout\fP, if it
324 When an interactive shell that is not a login shell is started,
326 reads and executes commands from \fI~/.bashrc\fP, if that file exists.
327 This may be inhibited by using the
330 The \fB\-\-rcfile\fP \fIfile\fP option will force
332 to read and execute commands from \fIfile\fP instead of \fI~/.bashrc\fP.
336 is started non-interactively, to run a shell script, for example, it
337 looks for the variable
340 in the environment, expands its value if it appears there, and uses the
341 expanded value as the name of a file to read and execute.
343 behaves as if the following command were executed:
346 .if t \f(CWif [ \-n "$BASH_ENV" ]; then . "$BASH_ENV"; fi\fP
347 .if n if [ \-n "$BASH_ENV" ]; then . "$BASH_ENV"; fi
353 variable is not used to search for the file name.
357 is invoked with the name
359 it tries to mimic the startup behavior of historical versions of
361 as closely as possible,
362 while conforming to the POSIX standard as well.
363 When invoked as an interactive login shell, or a non-interactive
364 shell with the \fB\-\-login\fP option, it first attempts to
365 read and execute commands from
372 option may be used to inhibit this behavior.
373 When invoked as an interactive shell with the name
376 looks for the variable
379 expands its value if it is defined, and uses the
380 expanded value as the name of a file to read and execute.
381 Since a shell invoked as
383 does not attempt to read and execute commands from any other startup
386 option has no effect.
387 A non-interactive shell invoked with the name
389 does not attempt to read any other startup files.
395 mode after the startup files are read.
403 command line option, it follows the POSIX standard for startup files.
404 In this mode, interactive shells expand the
407 variable and commands are read and executed from the file
408 whose name is the expanded value.
409 No other startup files are read.
412 attempts to determine when it is being run with its standard input
413 connected to a a network connection, as if by the remote shell
414 daemon, usually \fIrshd\fP, or the secure shell daemon \fIsshd\fP.
417 determines it is being run in this fashion, it reads and executes
418 commands from \fI~/.bashrc\fP, if that file exists and is readable.
419 It will not do this if invoked as \fBsh\fP.
422 option may be used to inhibit this behavior, and the
424 option may be used to force another file to be read, but
425 \fIrshd\fP does not generally invoke the shell with those options
426 or allow them to be specified.
428 If the shell is started with the effective user (group) id not equal to the
429 real user (group) id, and the \fB\-p\fP option is not supplied, no startup
430 files are read, shell functions are not inherited from the environment, the
433 variable, if it appears in the environment, is ignored,
434 and the effective user id is set to the real user id.
435 If the \fB\-p\fP option is supplied at invocation, the startup behavior is
436 the same, but the effective user id is not reset.
439 The following definitions are used throughout the rest of this
447 A sequence of characters considered as a single unit by the shell.
454 consisting only of alphanumeric characters and underscores, and
455 beginning with an alphabetic character or an underscore. Also
460 A character that, when unquoted, separates words. One of the following:
464 .if t \fB| & ; ( ) < > space tab\fP
465 .if n \fB| & ; ( ) < > space tab\fP
470 A \fItoken\fP that performs a control function. It is one of the following
474 .if t \fB\(bv\(bv & && ; ;; ( ) | |& <newline>\fP
475 .if n \fB|| & && ; ;; ( ) | |& <newline>\fP
479 \fIReserved words\fP are words that have a special meaning to the shell.
480 The following words are recognized as reserved when unquoted and either
481 the first word of a simple command (see
484 below) or the third word of a
492 .if n ! case do done elif else esac fi for function if in select then until while { } time [[ ]]
493 .if t ! case do done elif else esac fi for function if in select then until while { } time [[ ]]
498 A \fIsimple command\fP is a sequence of optional variable assignments
499 followed by \fBblank\fP-separated words and redirections, and
500 terminated by a \fIcontrol operator\fP. The first word
501 specifies the command to be executed, and is passed as argument zero.
502 The remaining words are passed as arguments to the invoked command.
504 The return value of a \fIsimple command\fP is its exit status, or
505 128+\fIn\^\fP if the command is terminated by signal
509 A \fIpipeline\fP is a sequence of one or more commands separated by
510 one of the control operators
513 The format for a pipeline is:
516 [\fBtime\fP [\fB\-p\fP]] [ ! ] \fIcommand\fP [ [\fB|\fP\(bv\fB|&\fP] \fIcommand2\fP ... ]
519 The standard output of
521 is connected via a pipe to the standard input of
523 This connection is performed before any redirections specified by the
528 If \fB|&\fP is used, the standard error of \fIcommand\fP is connected to
529 \fIcommand2\fP's standard input through the pipe; it is shorthand for
531 This implicit redirection of the standard error is performed after any
532 redirections specified by the command.
534 The return status of a pipeline is the exit status of the last
535 command, unless the \fBpipefail\fP option is enabled.
536 If \fBpipefail\fP is enabled, the pipeline's return status is the
537 value of the last (rightmost) command to exit with a non-zero status,
538 or zero if all commands exit successfully.
541 precedes a pipeline, the exit status of that pipeline is the logical
542 negation of the exit status as described above.
543 The shell waits for all commands in the pipeline to
544 terminate before returning a value.
548 reserved word precedes a pipeline, the elapsed as well as user and
549 system time consumed by its execution are reported when the pipeline
551 The \fB\-p\fP option changes the output format to that specified by POSIX.
555 variable may be set to a format string that specifies how the timing
556 information should be displayed; see the description of
563 Each command in a pipeline is executed as a separate process (i.e., in a
567 A \fIlist\fP is a sequence of one or more pipelines separated by one
574 and optionally terminated by one of
580 Of these list operators,
584 have equal precedence, followed by
588 which have equal precedence.
590 A sequence of one or more newlines may appear in a \fIlist\fP instead
591 of a semicolon to delimit commands.
593 If a command is terminated by the control operator
595 the shell executes the command in the \fIbackground\fP
596 in a subshell. The shell does not wait for the command to
597 finish, and the return status is 0. Commands separated by a
599 are executed sequentially; the shell waits for each
600 command to terminate in turn. The return status is the
601 exit status of the last command executed.
603 AND and OR lists are sequences of one of more pipelines separated by the
604 \fB&&\fP and \fB\(bv\(bv\fP control operators, respectively.
605 AND and OR lists are executed with left associativity.
606 An AND list has the form
609 \fIcommand1\fP \fB&&\fP \fIcommand2\fP
613 is executed if, and only if,
615 returns an exit status of zero.
617 An OR list has the form
620 \fIcommand1\fP \fB\(bv\(bv\fP \fIcommand2\fP
625 is executed if and only if
627 returns a non-zero exit status.
629 AND and OR lists is the exit status of the last command
630 executed in the list.
631 .SS Compound Commands
633 A \fIcompound command\fP is one of the following:
636 \fIlist\fP is executed in a subshell environment (see
638 \fBCOMMAND EXECUTION ENVIRONMENT\fP
640 Variable assignments and builtin
641 commands that affect the shell's environment do not remain in effect
642 after the command completes. The return status is the exit status of
646 \fIlist\fP is simply executed in the current shell environment.
647 \fIlist\fP must be terminated with a newline or semicolon.
648 This is known as a \fIgroup command\fP.
649 The return status is the exit status of
651 Note that unlike the metacharacters \fB(\fP and \fB)\fP, \fB{\fP and
652 \fB}\fP are \fIreserved words\fP and must occur where a reserved
653 word is permitted to be recognized. Since they do not cause a word
654 break, they must be separated from \fIlist\fP by whitespace or another
658 The \fIexpression\fP is evaluated according to the rules described
661 .BR "ARITHMETIC EVALUATION" .
662 If the value of the expression is non-zero, the return status is 0;
663 otherwise the return status is 1. This is exactly equivalent to
664 \fBlet "\fIexpression\fP"\fR.
666 \fB[[\fP \fIexpression\fP \fB]]\fP
667 Return a status of 0 or 1 depending on the evaluation of
668 the conditional expression \fIexpression\fP.
669 Expressions are composed of the primaries described below under
671 .BR "CONDITIONAL EXPRESSIONS" .
672 Word splitting and pathname expansion are not performed on the words
673 between the \fB[[\fP and \fB]]\fP; tilde expansion, parameter and
674 variable expansion, arithmetic expansion, command substitution, process
675 substitution, and quote removal are performed.
676 Conditional operators such as \fB\-f\fP must be unquoted to be recognized
680 When the \fB==\fP and \fB!=\fP operators are used, the string to the
681 right of the operator is considered a pattern and matched according
682 to the rules described below under \fBPattern Matching\fP.
685 is enabled, the match is performed without regard to the case
686 of alphabetic characters.
687 The return value is 0 if the string matches (\fB==\fP) or does not match
688 (\fB!=\fP) the pattern, and 1 otherwise.
689 Any part of the pattern may be quoted to force it to be matched as a
693 An additional binary operator, \fB=~\fP, is available, with the same
694 precedence as \fB==\fP and \fB!=\fP.
695 When it is used, the string to the right of the operator is considered
696 an extended regular expression and matched accordingly (as in \fIregex\fP(3)).
697 The return value is 0 if the string matches
698 the pattern, and 1 otherwise.
699 If the regular expression is syntactically incorrect, the conditional
700 expression's return value is 2.
703 is enabled, the match is performed without regard to the case
704 of alphabetic characters.
705 Any part of the pattern may be quoted to force it to be matched as a
707 Substrings matched by parenthesized subexpressions within the regular
708 expression are saved in the array variable \fBBASH_REMATCH\fP.
709 The element of \fBBASH_REMATCH\fP with index 0 is the portion of the string
710 matching the entire regular expression.
711 The element of \fBBASH_REMATCH\fP with index \fIn\fP is the portion of the
712 string matching the \fIn\fPth parenthesized subexpression.
715 Expressions may be combined using the following operators, listed
716 in decreasing order of precedence:
722 .B ( \fIexpression\fP )
723 Returns the value of \fIexpression\fP.
724 This may be used to override the normal precedence of operators.
726 .B ! \fIexpression\fP
731 \fIexpression1\fP \fB&&\fP \fIexpression2\fP
738 .if t \fIexpression1\fP \fB\(bv\(bv\fP \fIexpression2\fP
739 .if n \fIexpression1\fP \fB||\fP \fIexpression2\fP
750 operators do not evaluate \fIexpression2\fP if the value of
751 \fIexpression1\fP is sufficient to determine the return value of
752 the entire conditional expression.
755 \fBfor\fP \fIname\fP [ \fBin\fP \fIword\fP ] ; \fBdo\fP \fIlist\fP ; \fBdone\fP
756 The list of words following \fBin\fP is expanded, generating a list
758 The variable \fIname\fP is set to each element of this list
759 in turn, and \fIlist\fP is executed each time.
760 If the \fBin\fP \fIword\fP is omitted, the \fBfor\fP command executes
761 \fIlist\fP once for each positional parameter that is set (see
765 The return status is the exit status of the last command that executes.
766 If the expansion of the items following \fBin\fP results in an empty
767 list, no commands are executed, and the return status is 0.
769 \fBfor\fP (( \fIexpr1\fP ; \fIexpr2\fP ; \fIexpr3\fP )) ; \fBdo\fP \fIlist\fP ; \fBdone\fP
770 First, the arithmetic expression \fIexpr1\fP is evaluated according
771 to the rules described below under
773 .BR "ARITHMETIC EVALUATION" .
774 The arithmetic expression \fIexpr2\fP is then evaluated repeatedly
775 until it evaluates to zero.
776 Each time \fIexpr2\fP evaluates to a non-zero value, \fIlist\fP is
777 executed and the arithmetic expression \fIexpr3\fP is evaluated.
778 If any expression is omitted, it behaves as if it evaluates to 1.
779 The return value is the exit status of the last command in \fIlist\fP
780 that is executed, or false if any of the expressions is invalid.
782 \fBselect\fP \fIname\fP [ \fBin\fP \fIword\fP ] ; \fBdo\fP \fIlist\fP ; \fBdone\fP
783 The list of words following \fBin\fP is expanded, generating a list
784 of items. The set of expanded words is printed on the standard
785 error, each preceded by a number. If the \fBin\fP
786 \fIword\fP is omitted, the positional parameters are printed (see
791 prompt is then displayed and a line read from the standard input.
792 If the line consists of a number corresponding to one of
793 the displayed words, then the value of
795 is set to that word. If the line is empty, the words and prompt
796 are displayed again. If EOF is read, the command completes. Any
797 other value read causes
799 to be set to null. The line read is saved in the variable
803 is executed after each selection until a
808 is the exit status of the last command executed in
810 or zero if no commands were executed.
812 \fBcase\fP \fIword\fP \fBin\fP [ [(] \fIpattern\fP [ \fB|\fP \fIpattern\fP ] \
813 ... ) \fIlist\fP ;; ] ... \fBesac\fP
814 A \fBcase\fP command first expands \fIword\fP, and tries to match
815 it against each \fIpattern\fP in turn, using the same matching rules
816 as for pathname expansion (see
817 .B Pathname Expansion
819 The \fIword\fP is expanded using tilde
820 expansion, parameter and variable expansion, arithmetic substitution,
821 command substitution, process substitution and quote removal.
822 Each \fIpattern\fP examined is expanded using tilde
823 expansion, parameter and variable expansion, arithmetic substitution,
824 command substitution, and process substitution.
827 is enabled, the match is performed without regard to the case
828 of alphabetic characters.
829 When a match is found, the corresponding \fIlist\fP is executed.
830 If the \fB;;\fP operator is used, no subsequent matches are attempted after
831 the first pattern match.
832 Using \fB;&\fP in place of \fB;;\fP causes execution to continue with
833 the \fIlist\fP associated with the next set of patterns.
834 Using \fB;;&\fP in place of \fB;;\fP causes the shell to test the next
835 pattern list in the statement, if any, and execute any associated \fIlist\fP
836 on a successful match.
837 The exit status is zero if no
838 pattern matches. Otherwise, it is the exit status of the
839 last command executed in \fIlist\fP.
841 \fBif\fP \fIlist\fP; \fBthen\fP \fIlist;\fP \
842 [ \fBelif\fP \fIlist\fP; \fBthen\fP \fIlist\fP; ] ... \
843 [ \fBelse\fP \fIlist\fP; ] \fBfi\fP
847 is executed. If its exit status is zero, the
848 \fBthen\fP \fIlist\fP is executed. Otherwise, each \fBelif\fP
849 \fIlist\fP is executed in turn, and if its exit status is zero,
850 the corresponding \fBthen\fP \fIlist\fP is executed and the
851 command completes. Otherwise, the \fBelse\fP \fIlist\fP is
852 executed, if present. The exit status is the exit status of the
853 last command executed, or zero if no condition tested true.
855 \fBwhile\fP \fIlist\fP; \fBdo\fP \fIlist\fP; \fBdone\fP
858 \fBuntil\fP \fIlist\fP; \fBdo\fP \fIlist\fP; \fBdone\fP
860 The \fBwhile\fP command continuously executes the \fBdo\fP
861 \fIlist\fP as long as the last command in \fIlist\fP returns
862 an exit status of zero. The \fBuntil\fP command is identical
863 to the \fBwhile\fP command, except that the test is negated;
867 is executed as long as the last command in
869 returns a non-zero exit status.
870 The exit status of the \fBwhile\fP and \fBuntil\fP commands
872 of the last \fBdo\fP \fIlist\fP command executed, or zero if
876 A \fIcoprocess\fP is a shell command preceded by the \fBcoproc\fP reserved
878 A coprocess is executed asynchronously in a subshell, as if the command
879 had been terminated with the \fB&\fP control operator, with a two-way pipe
880 established between the executing shell and the coprocess.
882 The format for a coprocess is:
885 \fBcoproc\fP [\fINAME\fP] \fIcommand\fP [\fIredirections\fP]
888 This creates a coprocess named \fINAME\fP.
889 If \fINAME\fP is not supplied, the default name is \fICOPROC\fP.
890 \fINAME\fP must not be supplied if \fIcommand\fP is a \fIsimple
891 command\fP (see above); otherwise, it is interpreted as the first word
892 of the simple command.
893 When the coproc is executed, the shell creates an array variable (see
895 below) named \fINAME\fP in the context of the executing shell.
896 The standard output of
898 is connected via a pipe to a file descriptor in the executing shell,
899 and that file descriptor is assigned to \fINAME\fP[0].
900 The standard input of
902 is connected via a pipe to a file descriptor in the executing shell,
903 and that file descriptor is assigned to \fINAME\fP[1].
904 This pipe is established before any redirections specified by the
909 The file descriptors can be utilized as arguments to shell commands
910 and redirections using standard word expansions.
911 The process id of the shell spawned to execute the coprocess is
912 available as the value of the variable \fINAME\fP_PID.
914 builtin command may be used to wait for the coprocess to terminate.
916 The return status of a coprocess is the exit status of \fIcommand\fP.
917 .SS Shell Function Definitions
919 A shell function is an object that is called like a simple command and
920 executes a compound command with a new set of positional parameters.
921 Shell functions are declared as follows:
923 [ \fBfunction\fP ] \fIname\fP () \fIcompound\-command\fP [\fIredirection\fP]
924 This defines a function named \fIname\fP.
925 The reserved word \fBfunction\fP is optional.
926 If the \fBfunction\fP reserved word is supplied, the parentheses are optional.
927 The \fIbody\fP of the function is the compound command
929 (see \fBCompound Commands\fP above).
930 That command is usually a \fIlist\fP of commands between { and }, but
931 may be any command listed under \fBCompound Commands\fP above.
932 \fIcompound\-command\fP is executed whenever \fIname\fP is specified as the
933 name of a simple command.
934 Any redirections (see
937 below) specified when a function is defined are performed
938 when the function is executed.
939 The exit status of a function definition is zero unless a syntax error
940 occurs or a readonly function with the same name already exists.
941 When executed, the exit status of a function is the exit status of the
942 last command executed in the body. (See
947 In a non-interactive shell, or an interactive shell in which the
948 .B interactive_comments
951 builtin is enabled (see
953 .B "SHELL BUILTIN COMMANDS"
954 below), a word beginning with
956 causes that word and all remaining characters on that line to
957 be ignored. An interactive shell without the
958 .B interactive_comments
959 option enabled does not allow comments. The
960 .B interactive_comments
961 option is on by default in interactive shells.
963 \fIQuoting\fP is used to remove the special meaning of certain
964 characters or words to the shell. Quoting can be used to
965 disable special treatment for special characters, to prevent
966 reserved words from being recognized as such, and to prevent
969 Each of the \fImetacharacters\fP listed above under
972 has special meaning to the shell and must be quoted if it is to
975 When the command history expansion facilities are being used
980 \fIhistory expansion\fP character, usually \fB!\fP, must be quoted
981 to prevent history expansion.
983 There are three quoting mechanisms: the
984 .IR "escape character" ,
985 single quotes, and double quotes.
987 A non-quoted backslash (\fB\e\fP) is the
988 .IR "escape character" .
989 It preserves the literal value of the next character that follows,
990 with the exception of <newline>. If a \fB\e\fP<newline> pair
991 appears, and the backslash is not itself quoted, the \fB\e\fP<newline>
992 is treated as a line continuation (that is, it is removed from the
993 input stream and effectively ignored).
995 Enclosing characters in single quotes preserves the literal value
996 of each character within the quotes. A single quote may not occur
997 between single quotes, even when preceded by a backslash.
999 Enclosing characters in double quotes preserves the literal value
1000 of all characters within the quotes, with the exception of
1004 and, when history expansion is enabled,
1010 retain their special meaning within double quotes. The backslash
1011 retains its special meaning only when followed by one of the following
1019 A double quote may be quoted within double quotes by preceding it with
1021 If enabled, history expansion will be performed unless an
1023 appearing in double quotes is escaped using a backslash.
1024 The backslash preceding the
1028 The special parameters
1032 have special meaning when in double
1038 Words of the form \fB$\fP\(aq\fIstring\fP\(aq are treated specially. The
1039 word expands to \fIstring\fP, with backslash-escaped characters replaced
1040 as specified by the ANSI C standard. Backslash escape sequences, if
1041 present, are decoded as follows:
1076 the eight-bit character whose value is the octal value \fInnn\fP
1077 (one to three digits)
1080 the eight-bit character whose value is the hexadecimal value \fIHH\fP
1081 (one or two hex digits)
1084 a control-\fIx\fP character
1088 The expanded result is single-quoted, as if the dollar sign had
1091 A double-quoted string preceded by a dollar sign (\fB$\fP) will cause
1092 the string to be translated according to the current locale.
1093 If the current locale is \fBC\fP or \fBPOSIX\fP, the dollar sign
1095 If the string is translated and replaced, the replacement is
1100 is an entity that stores values.
1103 a number, or one of the special characters listed below under
1104 .BR "Special Parameters" .
1107 is a parameter denoted by a
1109 A variable has a \fIvalue\fP and zero or more \fIattributes\fP.
1110 Attributes are assigned using the
1112 builtin command (see
1116 .BR "SHELL BUILTIN COMMANDS" ).
1118 A parameter is set if it has been assigned a value. The null string is
1119 a valid value. Once a variable is set, it may be unset only by using
1122 builtin command (see
1124 .B SHELL BUILTIN COMMANDS
1129 may be assigned to by a statement of the form
1132 \fIname\fP=[\fIvalue\fP]
1137 is not given, the variable is assigned the null string. All
1139 undergo tilde expansion, parameter and variable expansion,
1140 command substitution, arithmetic expansion, and quote
1144 below). If the variable has its
1148 is evaluated as an arithmetic expression even if the $((...)) expansion is
1150 .B "Arithmetic Expansion"
1152 Word splitting is not performed, with the exception
1153 of \fB"$@"\fP as explained below under
1154 .BR "Special Parameters" .
1155 Pathname expansion is not performed.
1156 Assignment statements may also appear as arguments to the
1166 In the context where an assignment statement is assigning a value
1167 to a shell variable or array index, the += operator can be used to
1168 append to or add to the variable's previous value.
1169 When += is applied to a variable for which the integer attribute has been
1170 set, \fIvalue\fP is evaluated as an arithmetic expression and added to the
1171 variable's current value, which is also evaluated.
1172 When += is applied to an array variable using compound assignment (see
1175 variable's value is not unset (as it is when using =), and new values are
1176 appended to the array beginning at one greater than the array's maximum index
1177 (for indexed arrays) or added as additional key\-value pairs in an
1179 When applied to a string-valued variable, \fIvalue\fP is expanded and
1180 appended to the variable's value.
1181 .SS Positional Parameters
1184 .I positional parameter
1185 is a parameter denoted by one or more
1186 digits, other than the single digit 0. Positional parameters are
1187 assigned from the shell's arguments when it is invoked,
1188 and may be reassigned using the
1190 builtin command. Positional parameters may not be assigned to
1191 with assignment statements. The positional parameters are
1192 temporarily replaced when a shell function is executed (see
1197 When a positional parameter consisting of more than a single
1198 digit is expanded, it must be enclosed in braces (see
1202 .SS Special Parameters
1204 The shell treats several parameters specially. These parameters may
1205 only be referenced; assignment to them is not allowed.
1209 Expands to the positional parameters, starting from one. When the
1210 expansion occurs within double quotes, it expands to a single word
1211 with the value of each parameter separated by the first character
1215 special variable. That is, "\fB$*\fP" is equivalent
1216 to "\fB$1\fP\fIc\fP\fB$2\fP\fIc\fP\fB...\fP", where
1218 is the first character of the value of the
1224 is unset, the parameters are separated by spaces.
1228 is null, the parameters are joined without intervening separators.
1231 Expands to the positional parameters, starting from one. When the
1232 expansion occurs within double quotes, each parameter expands to a
1233 separate word. That is, "\fB$@\fP" is equivalent to
1234 "\fB$1\fP" "\fB$2\fP" ...
1235 If the double-quoted expansion occurs within a word, the expansion of
1236 the first parameter is joined with the beginning part of the original
1237 word, and the expansion of the last parameter is joined with the last
1238 part of the original word.
1239 When there are no positional parameters, "\fB$@\fP" and
1241 expand to nothing (i.e., they are removed).
1244 Expands to the number of positional parameters in decimal.
1247 Expands to the exit status of the most recently executed foreground
1251 Expands to the current option flags as specified upon invocation,
1254 builtin command, or those set by the shell itself
1260 Expands to the process ID of the shell. In a () subshell, it
1261 expands to the process ID of the current shell, not the
1265 Expands to the process ID of the most recently executed background
1266 (asynchronous) command.
1269 Expands to the name of the shell or shell script. This is set at
1270 shell initialization. If
1272 is invoked with a file of commands,
1274 is set to the name of that file. If
1280 is set to the first argument after the string to be
1281 executed, if one is present. Otherwise, it is set
1282 to the file name used to invoke
1284 as given by argument zero.
1287 At shell startup, set to the absolute pathname used to invoke the
1288 shell or shell script being executed as passed in the environment
1290 Subsequently, expands to the last argument to the previous command,
1292 Also set to the full pathname used to invoke each command executed
1293 and placed in the environment exported to that command.
1294 When checking mail, this parameter holds the name of the mail file
1295 currently being checked.
1299 The following variables are set by the shell:
1304 Expands to the full file name used to invoke this instance of
1308 Expands to the process id of the current \fBbash\fP process.
1309 This differs from \fB$$\fP under certain circumstances, such as subshells
1310 that do not require \fBbash\fP to be re-initialized.
1313 An associative array variable whose members correspond to the internal
1314 list of aliases as maintained by the \fBalias\fP builtin
1315 Elements added to this array appear in the alias list; unsetting array
1316 elements cause aliases to be removed from the alias list.
1319 An array variable whose values are the number of parameters in each
1320 frame of the current \fBbash\fP execution call stack.
1322 parameters to the current subroutine (shell function or script executed
1323 with \fB.\fP or \fBsource\fP) is at the top of the stack.
1324 When a subroutine is executed, the number of parameters passed is pushed onto
1326 The shell sets \fBBASH_ARGC\fP only when in extended debugging mode
1327 (see the description of the
1334 An array variable containing all of the parameters in the current \fBbash\fP
1335 execution call stack. The final parameter of the last subroutine call
1336 is at the top of the stack; the first parameter of the initial call is
1337 at the bottom. When a subroutine is executed, the parameters supplied
1338 are pushed onto \fBBASH_ARGV\fP.
1339 The shell sets \fBBASH_ARGV\fP only when in extended debugging mode
1340 (see the description of the
1347 An associative array variable whose members correspond to the internal
1348 hash table of commands as maintained by the \fBhash\fP builtin.
1349 Elements added to this array appear in the hash table; unsetting array
1350 elements cause commands to be removed from the hash table.
1353 The command currently being executed or about to be executed, unless the
1354 shell is executing a command as the result of a trap,
1355 in which case it is the command executing at the time of the trap.
1357 .B BASH_EXECUTION_STRING
1358 The command argument to the \fB\-c\fP invocation option.
1361 An array variable whose members are the line numbers in source files
1362 corresponding to each member of \fBFUNCNAME\fP.
1363 \fB${BASH_LINENO[\fP\fI$i\fP\fB]}\fP is the line number in the source
1364 file where \fB${FUNCNAME[\fP\fI$i\fP\fB]}\fP was called
1365 (or \fB${BASH_LINENO[\fP\fI$i-1\fP\fB]}\fP if referenced within another
1367 The corresponding source file name is \fB${BASH_SOURCE[\fP\fI$i\fP\fB]}\fP.
1368 Use \fBLINENO\fP to obtain the current line number.
1371 An array variable whose members are assigned by the \fB=~\fP binary
1372 operator to the \fB[[\fP conditional command.
1373 The element with index 0 is the portion of the string
1374 matching the entire regular expression.
1375 The element with index \fIn\fP is the portion of the
1376 string matching the \fIn\fPth parenthesized subexpression.
1377 This variable is read-only.
1380 An array variable whose members are the source filenames corresponding
1381 to the elements in the \fBFUNCNAME\fP array variable.
1384 Incremented by one each time a subshell or subshell environment is spawned.
1385 The initial value is 0.
1388 A readonly array variable whose members hold version information for
1391 The values assigned to the array members are as follows:
1396 .B BASH_VERSINFO[\fR0\fP]
1397 The major version number (the \fIrelease\fP).
1399 .B BASH_VERSINFO[\fR1\fP]
1400 The minor version number (the \fIversion\fP).
1402 .B BASH_VERSINFO[\fR2\fP]
1405 .B BASH_VERSINFO[\fR3\fP]
1408 .B BASH_VERSINFO[\fR4\fP]
1409 The release status (e.g., \fIbeta1\fP).
1411 .B BASH_VERSINFO[\fR5\fP]
1412 The value of \fBMACHTYPE\fP.
1417 Expands to a string describing the version of this instance of
1421 An index into \fB${COMP_WORDS}\fP of the word containing the current
1423 This variable is available only in shell functions invoked by the
1424 programmable completion facilities (see \fBProgrammable Completion\fP
1428 The key (or final key of a key sequence) used to invoke the current
1429 completion function.
1432 The current command line.
1433 This variable is available only in shell functions and external
1434 commands invoked by the
1435 programmable completion facilities (see \fBProgrammable Completion\fP
1439 The index of the current cursor position relative to the beginning of
1440 the current command.
1441 If the current cursor position is at the end of the current command,
1442 the value of this variable is equal to \fB${#COMP_LINE}\fP.
1443 This variable is available only in shell functions and external
1444 commands invoked by the
1445 programmable completion facilities (see \fBProgrammable Completion\fP
1449 Set to an integer value corresponding to the type of completion attempted
1450 that caused a completion function to be called:
1451 \fITAB\fP, for normal completion,
1452 \fI?\fP, for listing completions after successive tabs,
1453 \fI!\fP, for listing alternatives on partial word completion,
1454 \fI@\fP, to list completions if the word is not unmodified,
1456 \fI%\fP, for menu completion.
1457 This variable is available only in shell functions and external
1458 commands invoked by the
1459 programmable completion facilities (see \fBProgrammable Completion\fP
1463 The set of characters that the \fBreadline\fP library treats as word
1464 separators when performing word completion.
1468 is unset, it loses its special properties, even if it is
1472 An array variable (see \fBArrays\fP below) consisting of the individual
1473 words in the current command line.
1474 The line is split into words as \fBreadline\fP would split it, using
1475 \fBCOMP_WORDBREAKS\fP as described above.
1476 This variable is available only in shell functions invoked by the
1477 programmable completion facilities (see \fBProgrammable Completion\fP
1481 An array variable (see
1483 below) containing the current contents of the directory stack.
1484 Directories appear in the stack in the order they are displayed by the
1487 Assigning to members of this array variable may be used to modify
1488 directories already in the stack, but the
1492 builtins must be used to add and remove directories.
1493 Assignment to this variable will not change the current directory.
1497 is unset, it loses its special properties, even if it is
1501 Expands to the effective user ID of the current user, initialized at
1502 shell startup. This variable is readonly.
1505 An array variable containing the names of all shell functions
1506 currently in the execution call stack.
1507 The element with index 0 is the name of any currently-executing
1509 The bottom-most element is
1510 .if t \f(CW"main"\fP.
1512 This variable exists only when a shell function is executing.
1516 have no effect and return an error status.
1520 is unset, it loses its special properties, even if it is
1524 An array variable containing the list of groups of which the current
1529 have no effect and return an error status.
1533 is unset, it loses its special properties, even if it is
1537 The history number, or index in the history list, of the current
1542 is unset, it loses its special properties, even if it is
1546 Automatically set to the name of the current host.
1549 Automatically set to a string that uniquely
1550 describes the type of machine on which
1553 The default is system-dependent.
1556 Each time this parameter is referenced, the shell substitutes
1557 a decimal number representing the current sequential line number
1558 (starting with 1) within a script or function. When not in a
1559 script or function, the value substituted is not guaranteed to
1564 is unset, it loses its special properties, even if it is
1568 Automatically set to a string that fully describes the system
1571 is executing, in the standard GNU \fIcpu-company-system\fP format.
1572 The default is system-dependent.
1575 The previous working directory as set by the
1580 The value of the last option argument processed by the
1582 builtin command (see
1584 .B SHELL BUILTIN COMMANDS
1588 The index of the next argument to be processed by the
1590 builtin command (see
1592 .B SHELL BUILTIN COMMANDS
1596 Automatically set to a string that
1597 describes the operating system on which
1600 The default is system-dependent.
1603 An array variable (see
1605 below) containing a list of exit status values from the processes
1606 in the most-recently-executed foreground pipeline (which may
1607 contain only a single command).
1610 The process ID of the shell's parent. This variable is readonly.
1613 The current working directory as set by the
1618 Each time this parameter is referenced, a random integer between
1620 generated. The sequence of random numbers may be initialized by assigning
1627 is unset, it loses its special properties, even if it is
1631 Set to the line of input read by the
1633 builtin command when no arguments are supplied.
1636 Each time this parameter is
1637 referenced, the number of seconds since shell invocation is returned. If a
1638 value is assigned to
1641 the value returned upon subsequent
1643 the number of seconds since the assignment plus the value assigned.
1647 is unset, it loses its special properties, even if it is
1651 A colon-separated list of enabled shell options. Each word in
1652 the list is a valid argument for the
1656 builtin command (see
1658 .B "SHELL BUILTIN COMMANDS"
1659 below). The options appearing in
1662 are those reported as
1665 If this variable is in the environment when
1667 starts up, each shell option in the list will be enabled before
1668 reading any startup files.
1669 This variable is read-only.
1672 Incremented by one each time an instance of
1677 Expands to the user ID of the current user, initialized at shell startup.
1678 This variable is readonly.
1681 The following variables are used by the shell. In some cases,
1683 assigns a default value to a variable; these cases are noted
1689 If this parameter is set when \fBbash\fP is executing a shell script,
1690 its value is interpreted as a filename containing commands to
1691 initialize the shell, as in
1696 is subjected to parameter expansion, command substitution, and arithmetic
1697 expansion before being interpreted as a file name.
1700 is not used to search for the resultant file name.
1703 The search path for the
1706 This is a colon-separated list of directories in which the shell looks
1707 for destination directories specified by the
1711 .if t \f(CW".:~:/usr"\fP.
1715 Used by the \fBselect\fP builtin command to determine the terminal width
1716 when printing selection lists. Automatically set upon receipt of a SIGWINCH.
1719 An array variable from which \fBbash\fP reads the possible completions
1720 generated by a shell function invoked by the programmable completion
1721 facility (see \fBProgrammable Completion\fP below).
1724 If \fBbash\fP finds this variable in the environment when the shell starts
1728 it assumes that the shell is running in an emacs shell buffer and disables
1732 The default editor for the
1737 A colon-separated list of suffixes to ignore when performing
1738 filename completion (see
1742 A filename whose suffix matches one of the entries in
1745 is excluded from the list of matched filenames.
1747 .if t \f(CW".o:~"\fP.
1751 A colon-separated list of patterns defining the set of filenames to
1752 be ignored by pathname expansion.
1753 If a filename matched by a pathname expansion pattern also matches one
1757 it is removed from the list of matches.
1760 A colon-separated list of values controlling how commands are saved on
1762 If the list of values includes
1764 lines which begin with a
1766 character are not saved in the history list.
1769 causes lines matching the previous history entry to not be saved.
1772 is shorthand for \fIignorespace\fP and \fIignoredups\fP.
1775 causes all previous lines matching the current line to be removed from
1776 the history list before that line is saved.
1777 Any value not in the above list is ignored.
1778 If \fBHISTCONTROL\fP is unset, or does not include a valid value,
1779 all lines read by the shell parser are saved on the history list,
1780 subject to the value of
1782 The second and subsequent lines of a multi-line compound command are
1783 not tested, and are added to the history regardless of the value of
1787 The name of the file in which command history is saved (see
1790 below). The default value is \fI~/.bash_history\fP. If unset, the
1791 command history is not saved when an interactive shell exits.
1794 The maximum number of lines contained in the history file. When this
1795 variable is assigned a value, the history file is truncated, if
1796 necessary, by removing the oldest entries,
1797 to contain no more than that number of lines. The default
1798 value is 500. The history file is also truncated to this size after
1799 writing it when an interactive shell exits.
1802 A colon-separated list of patterns used to decide which command lines
1803 should be saved on the history list. Each pattern is anchored at the
1804 beginning of the line and must match the complete line (no implicit
1805 `\fB*\fP' is appended). Each pattern is tested against the line
1806 after the checks specified by
1809 In addition to the normal shell pattern matching characters, `\fB&\fP'
1810 matches the previous history line. `\fB&\fP' may be escaped using a
1811 backslash; the backslash is removed before attempting a match.
1812 The second and subsequent lines of a multi-line compound command are
1813 not tested, and are added to the history regardless of the value of
1817 The number of commands to remember in the command history (see
1820 below). The default value is 500.
1823 If this variable is set and not null, its value is used as a format string
1824 for \fIstrftime\fP(3) to print the time stamp associated with each history
1825 entry displayed by the \fBhistory\fP builtin.
1826 If this variable is set, time stamps are written to the history file so
1827 they may be preserved across shell sessions.
1828 This uses the history comment character to distinguish timestamps from
1829 other history lines.
1832 The home directory of the current user; the default argument for the
1833 \fBcd\fP builtin command.
1834 The value of this variable is also used when performing tilde expansion.
1837 Contains the name of a file in the same format as
1839 that should be read when the shell needs to complete a
1841 The list of possible hostname completions may be changed while the
1843 the next time hostname completion is attempted after the
1846 adds the contents of the new file to the existing list.
1850 is set, but has no value, \fBbash\fP attempts to read
1852 to obtain the list of possible hostname completions.
1856 is unset, the hostname list is cleared.
1860 .I Internal Field Separator
1862 for word splitting after expansion and to
1863 split lines into words with the
1865 builtin command. The default value is
1866 ``<space><tab><newline>''.
1870 action of an interactive shell on receipt of an
1873 character as the sole input. If set, the value is the number of
1877 characters which must be
1878 typed as the first characters on an input line before
1880 exits. If the variable exists but does not have a numeric value, or
1881 has no value, the default value is 10. If it does not exist,
1884 signifies the end of input to the shell.
1887 The filename for the
1889 startup file, overriding the default of
1897 Used to determine the locale category for any category not specifically
1898 selected with a variable starting with \fBLC_\fP.
1901 This variable overrides the value of \fBLANG\fP and any other
1902 \fBLC_\fP variable specifying a locale category.
1905 This variable determines the collation order used when sorting the
1906 results of pathname expansion, and determines the behavior of range
1907 expressions, equivalence classes, and collating sequences within
1908 pathname expansion and pattern matching.
1911 This variable determines the interpretation of characters and the
1912 behavior of character classes within pathname expansion and pattern
1916 This variable determines the locale used to translate double-quoted
1917 strings preceded by a \fB$\fP.
1920 This variable determines the locale category used for number formatting.
1923 Used by the \fBselect\fP builtin command to determine the column length
1924 for printing selection lists. Automatically set upon receipt of a SIGWINCH.
1927 If this parameter is set to a file name and the
1930 variable is not set,
1932 informs the user of the arrival of mail in the specified file.
1938 checks for mail. The default is 60 seconds. When it is time to check
1939 for mail, the shell does so before displaying the primary prompt.
1940 If this variable is unset, or set to a value that is not a number
1941 greater than or equal to zero, the shell disables mail checking.
1944 A colon-separated list of file names to be checked for mail.
1945 The message to be printed when mail arrives in a particular file
1946 may be specified by separating the file name from the message with a `?'.
1947 When used in the text of the message, \fB$_\fP expands to the name of
1948 the current mailfile.
1952 \fBMAILPATH\fP=\(aq/var/mail/bfox?"You have mail":~/shell\-mail?"$_ has mail!"\(aq
1955 supplies a default value for this variable, but the location of the user
1956 mail files that it uses is system dependent (e.g., /var/mail/\fB$USER\fP).
1960 If set to the value 1,
1962 displays error messages generated by the
1964 builtin command (see
1966 .B SHELL BUILTIN COMMANDS
1970 is initialized to 1 each time the shell is invoked or a shell
1974 The search path for commands. It
1975 is a colon-separated list of directories in which
1976 the shell looks for commands (see
1978 .B COMMAND EXECUTION
1980 A zero-length (null) directory name in the value of \fBPATH\fP indicates the
1982 A null directory name may appear as two adjacent colons, or as an initial
1984 The default path is system-dependent,
1985 and is set by the administrator who installs
1988 .if t \f(CW/usr/gnu/bin:/usr/local/bin:/usr/ucb:/bin:/usr/bin\fP.
1989 .if n ``/usr/gnu/bin:/usr/local/bin:/usr/ucb:/bin:/usr/bin''.
1992 If this variable is in the environment when \fBbash\fP starts, the shell
1993 enters \fIposix mode\fP before reading the startup files, as if the
1995 invocation option had been supplied. If it is set while the shell is
1996 running, \fBbash\fP enables \fIposix mode\fP, as if the command
1997 .if t \f(CWset -o posix\fP
1998 .if n \fIset -o posix\fP
2002 If set, the value is executed as a command prior to issuing each primary
2006 If set to a number greater than zero, the value is used as the number of
2007 trailing directory components to retain when expanding the \fB\ew\fB and
2008 \fB\eW\fP prompt string escapes (see
2011 below). Characters removed are replaced with an ellipsis.
2014 The value of this parameter is expanded (see
2017 below) and used as the primary prompt string. The default value is
2018 ``\fB\es\-\ev\e$ \fP''.
2021 The value of this parameter is expanded as with
2023 and used as the secondary prompt string. The default is
2027 The value of this parameter is used as the prompt for the
2035 The value of this parameter is expanded as with
2037 and the value is printed before each command
2039 displays during an execution trace. The first character of
2042 is replicated multiple times, as necessary, to indicate multiple
2043 levels of indirection. The default is ``\fB+ \fP''.
2046 The full pathname to the shell is kept in this environment variable.
2047 If it is not set when the shell starts,
2049 assigns to it the full pathname of the current user's login shell.
2052 The value of this parameter is used as a format string specifying
2053 how the timing information for pipelines prefixed with the
2055 reserved word should be displayed.
2056 The \fB%\fP character introduces an escape sequence that is
2057 expanded to a time value or other information.
2058 The escape sequences and their meanings are as follows; the
2059 braces denote optional portions.
2068 The elapsed time in seconds.
2071 The number of CPU seconds spent in user mode.
2074 The number of CPU seconds spent in system mode.
2077 The CPU percentage, computed as (%U + %S) / %R.
2081 The optional \fIp\fP is a digit specifying the \fIprecision\fP,
2082 the number of fractional digits after a decimal point.
2083 A value of 0 causes no decimal point or fraction to be output.
2084 At most three places after the decimal point may be specified;
2085 values of \fIp\fP greater than 3 are changed to 3.
2086 If \fIp\fP is not specified, the value 3 is used.
2088 The optional \fBl\fP specifies a longer format, including
2089 minutes, of the form \fIMM\fPm\fISS\fP.\fIFF\fPs.
2090 The value of \fIp\fP determines whether or not the fraction is
2093 If this variable is not set, \fBbash\fP acts as if it had the
2094 value \fB$\(aq\enreal\et%3lR\enuser\et%3lU\ensys\t%3lS\(aq\fP.
2095 If the value is null, no timing information is displayed.
2096 A trailing newline is added when the format string is displayed.
2099 If set to a value greater than zero, \fBTMOUT\fP is treated as the
2100 default timeout for the \fBread\fP builtin.
2101 The \fBselect\fP command terminates if input does not arrive
2102 after \fBTMOUT\fP seconds when input is coming from a terminal.
2103 In an interactive shell, the value is interpreted as the
2104 number of seconds to wait for input after issuing the primary prompt.
2106 terminates after waiting for that number of seconds if input does
2110 If set, \fBBash\fP uses its value as the name of a directory in which
2111 \fBBash\fP creates temporary files for the shell's use.
2114 This variable controls how the shell interacts with the user and
2115 job control. If this variable is set, single word simple
2116 commands without redirections are treated as candidates for resumption
2117 of an existing stopped job. There is no ambiguity allowed; if there is
2118 more than one job beginning with the string typed, the job most recently
2119 accessed is selected. The
2121 of a stopped job, in this context, is the command line used to
2125 the string supplied must match the name of a stopped job exactly;
2128 the string supplied needs to match a substring of the name of a
2131 value provides functionality analogous to the
2136 below). If set to any other value, the supplied string must
2137 be a prefix of a stopped job's name; this provides functionality
2138 analogous to the \fB%\fP\fIstring\fP job identifier.
2141 The two or three characters which control history expansion
2142 and tokenization (see
2144 .B HISTORY EXPANSION
2145 below). The first character is the \fIhistory expansion\fP character,
2146 the character which signals the start of a history
2147 expansion, normally `\fB!\fP'.
2148 The second character is the \fIquick substitution\fP
2149 character, which is used as shorthand for re-running the previous
2150 command entered, substituting one string for another in the command.
2151 The default is `\fB^\fP'.
2152 The optional third character is the character
2153 which indicates that the remainder of the line is a comment when found
2154 as the first character of a word, normally `\fB#\fP'. The history
2155 comment character causes history substitution to be skipped for the
2156 remaining words on the line. It does not necessarily cause the shell
2157 parser to treat the rest of the line as a comment.
2161 provides one-dimensional indexed and associative array variables.
2162 Any variable may be used as an indexed array; the
2164 builtin will explicitly declare an array.
2166 limit on the size of an array, nor any requirement that members
2167 be indexed or assigned contiguously.
2168 Indexed arrays are referenced using integers (including arithmetic
2169 expressions) and are zero-based; associative arrays are referenced
2170 using arbitrary strings.
2172 An indexed array is created automatically if any variable is assigned to
2173 using the syntax \fIname\fP[\fIsubscript\fP]=\fIvalue\fP. The
2175 is treated as an arithmetic expression that must evaluate to a number
2176 greater than or equal to zero. To explicitly declare an indexed array,
2178 .B declare \-a \fIname\fP
2181 .B SHELL BUILTIN COMMANDS
2183 .B declare \-a \fIname\fP[\fIsubscript\fP]
2184 is also accepted; the \fIsubscript\fP is ignored.
2186 Associative arrays are created using
2187 .BR "declare \-A \fIname\fP" .
2190 specified for an array variable using the
2194 builtins. Each attribute applies to all members of an array.
2196 Arrays are assigned to using compound assignments of the form
2197 \fIname\fP=\fB(\fPvalue\fI1\fP ... value\fIn\fP\fB)\fP, where each
2198 \fIvalue\fP is of the form [\fIsubscript\fP]=\fIstring\fP.
2199 Indexed array assignments do not require the bracket and subscript.
2200 When assigning to indexed arrays, if the optional brackets and subscript
2201 are supplied, that index is assigned to;
2202 otherwise the index of the element assigned is the last index assigned
2203 to by the statement plus one. Indexing starts at zero.
2205 When assigning to an associative array, the subscript is required.
2207 This syntax is also accepted by the
2209 builtin. Individual array elements may be assigned to using the
2210 \fIname\fP[\fIsubscript\fP]=\fIvalue\fP syntax introduced above.
2212 Any element of an array may be referenced using
2213 ${\fIname\fP[\fIsubscript\fP]}. The braces are required to avoid
2214 conflicts with pathname expansion. If
2215 \fIsubscript\fP is \fB@\fP or \fB*\fP, the word expands to
2216 all members of \fIname\fP. These subscripts differ only when the
2217 word appears within double quotes. If the word is double-quoted,
2218 ${\fIname\fP[*]} expands to a single
2219 word with the value of each array member separated by the first
2223 special variable, and ${\fIname\fP[@]} expands each element of
2224 \fIname\fP to a separate word. When there are no array members,
2225 ${\fIname\fP[@]} expands to nothing.
2226 If the double-quoted expansion occurs within a word, the expansion of
2227 the first parameter is joined with the beginning part of the original
2228 word, and the expansion of the last parameter is joined with the last
2229 part of the original word.
2230 This is analogous to the expansion
2231 of the special parameters \fB*\fP and \fB@\fP (see
2232 .B Special Parameters
2233 above). ${#\fIname\fP[\fIsubscript\fP]} expands to the length of
2234 ${\fIname\fP[\fIsubscript\fP]}. If \fIsubscript\fP is \fB*\fP or
2235 \fB@\fP, the expansion is the number of elements in the array.
2236 Referencing an array variable without a subscript is equivalent to
2237 referencing the array with a subscript of 0.
2241 builtin is used to destroy arrays. \fBunset\fP \fIname\fP[\fIsubscript\fP]
2242 destroys the array element at index \fIsubscript\fP.
2243 Care must be taken to avoid unwanted side effects caused by filename
2245 \fBunset\fP \fIname\fP, where \fIname\fP is an array, or
2246 \fBunset\fP \fIname\fP[\fIsubscript\fP], where
2247 \fIsubscript\fP is \fB*\fP or \fB@\fP, removes the entire array.
2254 builtins each accept a
2256 option to specify an indexed array and a
2258 option to specify an associative array.
2263 option to assign a list of words read from the standard input
2268 builtins display array values in a way that allows them to be
2269 reused as assignments.
2271 Expansion is performed on the command line after it has been split into
2272 words. There are seven kinds of expansion performed:
2273 .IR "brace expansion" ,
2274 .IR "tilde expansion" ,
2275 .IR "parameter and variable expansion" ,
2276 .IR "command substitution" ,
2277 .IR "arithmetic expansion" ,
2278 .IR "word splitting" ,
2280 .IR "pathname expansion" .
2282 The order of expansions is: brace expansion, tilde expansion,
2283 parameter, variable and arithmetic expansion and
2284 command substitution
2285 (done in a left-to-right fashion), word splitting, and pathname
2288 On systems that can support it, there is an additional expansion
2289 available: \fIprocess substitution\fP.
2291 Only brace expansion, word splitting, and pathname expansion
2292 can change the number of words of the expansion; other expansions
2293 expand a single word to a single word.
2294 The only exceptions to this are the expansions of
2295 "\fB$@\fP" and "\fB${\fP\fIname\fP\fB[@]}\fP"
2296 as explained above (see
2301 .I "Brace expansion"
2302 is a mechanism by which arbitrary strings
2303 may be generated. This mechanism is similar to
2304 \fIpathname expansion\fP, but the filenames generated
2305 need not exist. Patterns to be brace expanded take
2306 the form of an optional
2308 followed by either a series of comma-separated strings or
2309 a sequence expression between a pair of braces, followed by
2312 The preamble is prefixed to each string contained
2313 within the braces, and the postscript is then appended
2314 to each resulting string, expanding left to right.
2316 Brace expansions may be nested. The results of each expanded
2317 string are not sorted; left to right order is preserved.
2318 For example, a\fB{\fPd,c,b\fB}\fPe expands into `ade ace abe'.
2320 A sequence expression takes the form
2321 \fB{\fP\fIx\fP\fB..\fP\fIy\fP\fB[..\fP\fIincr\fP\fB]}\fP,
2322 where \fIx\fP and \fIy\fP are either integers or single characters,
2323 and \fIincr\fP, an optional increment, is an integer.
2324 When integers are supplied, the expression expands to each number between
2325 \fIx\fP and \fIy\fP, inclusive.
2326 Supplied integers may be prefixed with \fI0\fP to force each term to have the
2327 same width. When either \fIx\fP or \fPy\fP begins with a zero, the shell
2328 attempts to force all generated terms to contain the same number of digits,
2329 zero-padding where necessary.
2330 When characters are supplied, the expression expands to each character
2331 lexicographically between \fIx\fP and \fIy\fP, inclusive. Note that
2332 both \fIx\fP and \fIy\fP must be of the same type.
2333 When the increment is supplied, it is used as the difference between
2334 each term. The default increment is 1 or -1 as appropriate.
2336 Brace expansion is performed before any other expansions,
2337 and any characters special to other expansions are preserved
2338 in the result. It is strictly textual.
2340 does not apply any syntactic interpretation to the context of the
2341 expansion or the text between the braces.
2343 A correctly-formed brace expansion must contain unquoted opening
2344 and closing braces, and at least one unquoted comma or a valid
2345 sequence expression.
2346 Any incorrectly formed brace expansion is left unchanged.
2347 A \fB{\fP or \fB,\fP may be quoted with a backslash to prevent its
2348 being considered part of a brace expression.
2349 To avoid conflicts with parameter expansion, the string \fB${\fP
2350 is not considered eligible for brace expansion.
2352 This construct is typically used as shorthand when the common
2353 prefix of the strings to be generated is longer than in the
2357 mkdir /usr/local/src/bash/{old,new,dist,bugs}
2361 chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}
2364 Brace expansion introduces a slight incompatibility with
2365 historical versions of
2368 does not treat opening or closing braces specially when they
2369 appear as part of a word, and preserves them in the output.
2371 removes braces from words as a consequence of brace
2372 expansion. For example, a word entered to
2375 appears identically in the output. The same word is
2380 If strict compatibility with
2386 option or disable brace expansion with the
2392 .B SHELL BUILTIN COMMANDS
2396 If a word begins with an unquoted tilde character (`\fB~\fP'), all of
2397 the characters preceding the first unquoted slash (or all characters,
2398 if there is no unquoted slash) are considered a \fItilde-prefix\fP.
2399 If none of the characters in the tilde-prefix are quoted, the
2400 characters in the tilde-prefix following the tilde are treated as a
2401 possible \fIlogin name\fP.
2402 If this login name is the null string, the tilde is replaced with the
2403 value of the shell parameter
2409 is unset, the home directory of the user executing the shell is
2410 substituted instead.
2411 Otherwise, the tilde-prefix is replaced with the home directory
2412 associated with the specified login name.
2414 If the tilde-prefix is a `~+', the value of the shell variable
2417 replaces the tilde-prefix.
2418 If the tilde-prefix is a `~\-', the value of the shell variable
2421 if it is set, is substituted.
2422 If the characters following the tilde in the tilde-prefix consist
2423 of a number \fIN\fP, optionally prefixed
2424 by a `+' or a `\-', the tilde-prefix is replaced with the corresponding
2425 element from the directory stack, as it would be displayed by the
2427 builtin invoked with the tilde-prefix as an argument.
2428 If the characters following the tilde in the tilde-prefix consist of a
2429 number without a leading `+' or `\-', `+' is assumed.
2431 If the login name is invalid, or the tilde expansion fails, the word
2434 Each variable assignment is checked for unquoted tilde-prefixes immediately
2439 In these cases, tilde expansion is also performed.
2440 Consequently, one may use file names with tildes in assignments to
2448 and the shell assigns the expanded value.
2449 .SS Parameter Expansion
2451 The `\fB$\fP' character introduces parameter expansion,
2452 command substitution, or arithmetic expansion. The parameter name
2453 or symbol to be expanded may be enclosed in braces, which
2454 are optional but serve to protect the variable to be expanded from
2455 characters immediately following it which could be
2456 interpreted as part of the name.
2458 When braces are used, the matching ending brace is the first `\fB}\fP'
2459 not escaped by a backslash or within a quoted string, and not within an
2460 embedded arithmetic expansion, command substitution, or parameter
2466 The value of \fIparameter\fP is substituted. The braces are required
2469 is a positional parameter with more than one digit,
2472 is followed by a character which is not to be
2473 interpreted as part of its name.
2476 If the first character of \fIparameter\fP is an exclamation point,
2477 a level of variable indirection is introduced.
2478 \fBBash\fP uses the value of the variable formed from the rest of
2479 \fIparameter\fP as the name of the variable; this variable is then
2480 expanded and that value is used in the rest of the substitution, rather
2481 than the value of \fIparameter\fP itself.
2482 This is known as \fIindirect expansion\fP.
2483 The exceptions to this are the expansions of ${!\fIprefix\fP*} and
2484 ${\fB!\fP\fIname\fP[\fI@\fP]} described below.
2485 The exclamation point must immediately follow the left brace in order to
2486 introduce indirection.
2488 In each of the cases below, \fIword\fP is subject to tilde expansion,
2489 parameter expansion, command substitution, and arithmetic expansion.
2491 When not performing substring expansion, using the forms documented below,
2492 \fBbash\fP tests for a parameter that is unset or null. Omitting the colon
2493 results in a test only for a parameter that is unset.
2497 ${\fIparameter\fP\fB:\-\fP\fIword\fP}
2498 \fBUse Default Values\fP. If
2500 is unset or null, the expansion of
2502 is substituted. Otherwise, the value of
2506 ${\fIparameter\fP\fB:=\fP\fIword\fP}
2507 \fBAssign Default Values\fP.
2510 is unset or null, the expansion of
2516 is then substituted. Positional parameters and special parameters may
2517 not be assigned to in this way.
2519 ${\fIparameter\fP\fB:?\fP\fIword\fP}
2520 \fBDisplay Error if Null or Unset\fP.
2523 is null or unset, the expansion of \fIword\fP (or a message to that effect
2526 is not present) is written to the standard error and the shell, if it
2527 is not interactive, exits. Otherwise, the value of \fIparameter\fP is
2530 ${\fIparameter\fP\fB:+\fP\fIword\fP}
2531 \fBUse Alternate Value\fP.
2534 is null or unset, nothing is substituted, otherwise the expansion of
2538 ${\fIparameter\fP\fB:\fP\fIoffset\fP}
2541 ${\fIparameter\fP\fB:\fP\fIoffset\fP\fB:\fP\fIlength\fP}
2543 \fBSubstring Expansion.\fP
2544 Expands to up to \fIlength\fP characters of \fIparameter\fP
2545 starting at the character specified by \fIoffset\fP.
2546 If \fIlength\fP is omitted, expands to the substring of
2547 \fIparameter\fP starting at the character specified by \fIoffset\fP.
2548 \fIlength\fP and \fIoffset\fP are arithmetic expressions (see
2551 ARITHMETIC EVALUATION
2553 \fIlength\fP must evaluate to a number greater than or equal to zero.
2554 If \fIoffset\fP evaluates to a number less than zero, the value
2555 is used as an offset from the end of the value of \fIparameter\fP.
2556 If \fIparameter\fP is \fB@\fP, the result is \fIlength\fP positional
2557 parameters beginning at \fIoffset\fP.
2558 If \fIparameter\fP is an indexed array name subscripted by @ or *,
2559 the result is the \fIlength\fP
2560 members of the array beginning with ${\fIparameter\fP[\fIoffset\fP]}.
2561 A negative \fIoffset\fP is taken relative to one greater than the maximum
2562 index of the specified array.
2563 Substring expansion applied to an associative array produces undefined
2565 Note that a negative offset must be separated from the colon by at least
2566 one space to avoid being confused with the :- expansion.
2567 Substring indexing is zero-based unless the positional parameters
2568 are used, in which case the indexing starts at 1 by default.
2569 If \fIoffset\fP is 0, and the positional parameters are used, \fB$0\fP is
2570 prefixed to the list.
2572 ${\fB!\fP\fIprefix\fP\fB*\fP}
2575 ${\fB!\fP\fIprefix\fP\fB@\fP}
2577 \fBNames matching prefix.\fP
2578 Expands to the names of variables whose names begin with \fIprefix\fP,
2579 separated by the first character of the
2583 When \fI@\fP is used and the expansion appears within double quotes, each
2584 variable name expands to a separate word.
2586 ${\fB!\fP\fIname\fP[\fI@\fP]}
2589 ${\fB!\fP\fIname\fP[\fI*\fP]}
2591 \fBList of array keys.\fP
2592 If \fIname\fP is an array variable, expands to the list of array indices
2593 (keys) assigned in \fIname\fP.
2594 If \fIname\fP is not an array, expands to 0 if \fIname\fP is set and null
2596 When \fI@\fP is used and the expansion appears within double quotes, each
2597 key expands to a separate word.
2599 ${\fB#\fP\fIparameter\fP}
2600 \fBParameter length.\fP
2601 The length in characters of the value of \fIparameter\fP is substituted.
2608 the value substituted is the number of positional parameters.
2611 is an array name subscripted by
2615 the value substituted is the number of elements in the array.
2617 ${\fIparameter\fP\fB#\fP\fIword\fP}
2620 ${\fIparameter\fP\fB##\fP\fIword\fP}
2622 \fBRemove matching prefix pattern.\fP
2625 is expanded to produce a pattern just as in pathname
2626 expansion. If the pattern matches the beginning of
2629 then the result of the expansion is the expanded value of
2631 with the shortest matching pattern (the ``\fB#\fP'' case) or the
2632 longest matching pattern (the ``\fB##\fP'' case) deleted.
2639 the pattern removal operation is applied to each positional
2640 parameter in turn, and the expansion is the resultant list.
2643 is an array variable subscripted with
2647 the pattern removal operation is applied to each member of the
2648 array in turn, and the expansion is the resultant list.
2650 ${\fIparameter\fP\fB%\fP\fIword\fP}
2653 ${\fIparameter\fP\fB%%\fP\fIword\fP}
2655 \fBRemove matching suffix pattern.\fP
2656 The \fIword\fP is expanded to produce a pattern just as in
2658 If the pattern matches a trailing portion of the expanded value of
2660 then the result of the expansion is the expanded value of
2662 with the shortest matching pattern (the ``\fB%\fP'' case) or the
2663 longest matching pattern (the ``\fB%%\fP'' case) deleted.
2670 the pattern removal operation is applied to each positional
2671 parameter in turn, and the expansion is the resultant list.
2674 is an array variable subscripted with
2678 the pattern removal operation is applied to each member of the
2679 array in turn, and the expansion is the resultant list.
2681 ${\fIparameter\fP\fB/\fP\fIpattern\fP\fB/\fP\fIstring\fP}
2682 \fBPattern substitution.\fP
2683 The \fIpattern\fP is expanded to produce a pattern just as in
2685 \fIParameter\fP is expanded and the longest match of \fIpattern\fP
2686 against its value is replaced with \fIstring\fP.
2687 If \fIpattern\fP begins with \fB/\fP, all matches of \fIpattern\fP are
2688 replaced with \fIstring\fP. Normally only the first match is replaced.
2689 If \fIpattern\fP begins with \fB#\fP, it must match at the beginning
2690 of the expanded value of \fIparameter\fP.
2691 If \fIpattern\fP begins with \fB%\fP, it must match at the end
2692 of the expanded value of \fIparameter\fP.
2693 If \fIstring\fP is null, matches of \fIpattern\fP are deleted
2694 and the \fB/\fP following \fIpattern\fP may be omitted.
2701 the substitution operation is applied to each positional
2702 parameter in turn, and the expansion is the resultant list.
2705 is an array variable subscripted with
2709 the substitution operation is applied to each member of the
2710 array in turn, and the expansion is the resultant list.
2712 ${\fIparameter\fP\fB^\fP\fIpattern\fP}
2715 ${\fIparameter\fP\fB^^\fP\fIpattern\fP}
2717 ${\fIparameter\fP\fB,\fP\fIpattern\fP}
2719 ${\fIparameter\fP\fB,,\fP\fIpattern\fP}
2721 \fBCase modification.\fP
2722 This expansion modifies the case of alphabetic characters in \fIparameter\fP.
2723 The \fIpattern\fP is expanded to produce a pattern just as in
2725 The \fB^\fP operator converts lowercase letters matching \fIpattern\fP
2726 to uppercase; the \fB,\fP operator converts matching uppercase letters
2728 The \fB^^\fP and \fB,,\fP expansions convert each matched character in the
2729 expanded value; the \fB^\fP and \fB,\fP expansions match and convert only
2730 the first character in the expanded value..
2731 If \fIpattern\fP is omitted, it is treated like a \fB?\fP, which matches
2739 the case modification operation is applied to each positional
2740 parameter in turn, and the expansion is the resultant list.
2743 is an array variable subscripted with
2747 the case modification operation is applied to each member of the
2748 array in turn, and the expansion is the resultant list.
2749 .SS Command Substitution
2751 \fICommand substitution\fP allows the output of a command to replace
2752 the command name. There are two forms:
2756 \fB$(\fP\fIcommand\fP\|\fB)\fP
2760 \fB\`\fP\fIcommand\fP\fB\`\fP
2764 performs the expansion by executing \fIcommand\fP and
2765 replacing the command substitution with the standard output of the
2766 command, with any trailing newlines deleted.
2767 Embedded newlines are not deleted, but they may be removed during
2769 The command substitution \fB$(cat \fIfile\fP)\fR can be replaced by
2770 the equivalent but faster \fB$(< \fIfile\fP)\fR.
2772 When the old-style backquote form of substitution is used,
2773 backslash retains its literal meaning except when followed by
2778 The first backquote not preceded by a backslash terminates the
2779 command substitution.
2780 When using the $(\^\fIcommand\fP\|) form, all characters between the
2781 parentheses make up the command; none are treated specially.
2783 Command substitutions may be nested. To nest when using the backquoted form,
2784 escape the inner backquotes with backslashes.
2786 If the substitution appears within double quotes, word splitting and
2787 pathname expansion are not performed on the results.
2788 .SS Arithmetic Expansion
2790 Arithmetic expansion allows the evaluation of an arithmetic expression
2791 and the substitution of the result. The format for arithmetic expansion is:
2794 \fB$((\fP\fIexpression\fP\fB))\fP
2799 is treated as if it were within double quotes, but a double quote
2800 inside the parentheses is not treated specially.
2801 All tokens in the expression undergo parameter expansion, string
2802 expansion, command substitution, and quote removal.
2803 Arithmetic expansions may be nested.
2805 The evaluation is performed according to the rules listed below under
2807 .BR "ARITHMETIC EVALUATION" .
2812 prints a message indicating failure and no substitution occurs.
2813 .SS Process Substitution
2815 \fIProcess substitution\fP is supported on systems that support named
2816 pipes (\fIFIFOs\fP) or the \fB/dev/fd\fP method of naming open files.
2817 It takes the form of
2818 \fB<(\fP\fIlist\^\fP\fB)\fP
2820 \fB>(\fP\fIlist\^\fP\fB)\fP.
2821 The process \fIlist\fP is run with its input or output connected to a
2822 \fIFIFO\fP or some file in \fB/dev/fd\fP. The name of this file is
2823 passed as an argument to the current command as the result of the
2824 expansion. If the \fB>(\fP\fIlist\^\fP\fB)\fP form is used, writing to
2825 the file will provide input for \fIlist\fP. If the
2826 \fB<(\fP\fIlist\^\fP\fB)\fP form is used, the file passed as an
2827 argument should be read to obtain the output of \fIlist\fP.
2829 When available, process substitution is performed
2830 simultaneously with parameter and variable expansion,
2831 command substitution,
2832 and arithmetic expansion.
2835 The shell scans the results of
2836 parameter expansion,
2837 command substitution,
2839 arithmetic expansion
2840 that did not occur within double quotes for
2841 .IR "word splitting" .
2843 The shell treats each character of
2846 as a delimiter, and splits the results of the other
2847 expansions into words on these characters. If
2852 .BR <space><tab><newline> ,
2859 at the beginning and end of the results of the previous
2860 expansions are ignored, and
2864 characters not at the beginning or end serves to delimit words.
2868 has a value other than the default, then sequences of
2869 the whitespace characters
2873 are ignored at the beginning and end of the
2874 word, as long as the whitespace character is in the
2881 whitespace character).
2888 whitespace, along with any adjacent
2891 whitespace characters, delimits a field.
2895 whitespace characters is also treated as a delimiter.
2899 is null, no word splitting occurs.
2901 Explicit null arguments (\^\f3"\^"\fP or \^\f3\(aq\^\(aq\fP\^) are retained.
2902 Unquoted implicit null arguments, resulting from the expansion of
2903 parameters that have no values, are removed.
2904 If a parameter with no value is expanded within double quotes, a
2905 null argument results and is retained.
2907 Note that if no expansion occurs, no splitting
2909 .SS Pathname Expansion
2911 After word splitting,
2914 option has been set,
2916 scans each word for the characters
2921 If one of these characters appears, then the word is
2924 and replaced with an alphabetically sorted list of
2925 file names matching the pattern.
2926 If no matching file names are found,
2927 and the shell option
2929 is not enabled, the word is left unchanged.
2932 option is set, and no matches are found,
2933 the word is removed.
2936 shell option is set, and no matches are found, an error message
2937 is printed and the command is not executed.
2940 is enabled, the match is performed without regard to the case
2941 of alphabetic characters.
2942 When a pattern is used for pathname expansion,
2945 at the start of a name or immediately following a slash
2946 must be matched explicitly, unless the shell option
2949 When matching a pathname, the slash character must always be
2953 character is not treated specially.
2954 See the description of
2958 .B SHELL BUILTIN COMMANDS
2959 for a description of the
2970 shell variable may be used to restrict the set of file names matching a
2975 is set, each matching file name that also matches one of the patterns in
2978 is removed from the list of matches.
2983 are always ignored when
2986 is set and not null. However, setting
2989 to a non-null value has the effect of enabling the
2991 shell option, so all other file names beginning with a
2994 To get the old behavior of ignoring file names beginning with a
2998 one of the patterns in
3003 option is disabled when
3008 \fBPattern Matching\fP
3010 Any character that appears in a pattern, other than the special pattern
3011 characters described below, matches itself. The NUL character may not
3012 occur in a pattern. A backslash escapes the following character; the
3013 escaping backslash is discarded when matching.
3014 The special pattern characters must be quoted if
3015 they are to be matched literally.
3017 The special pattern characters have the following meanings:
3022 Matches any string, including the null string.
3023 When the \fBglobstar\fP shell option is enabled, and \fB*\fP is used in
3024 a filename expansion context, two adjacent \fB*\fPs used as a single
3025 pattern will match all files and zero or more directories and
3027 If followed by a \fB/\fP, two adjacent \fB*\fPs will match only directories
3031 Matches any single character.
3034 Matches any one of the enclosed characters. A pair of characters
3035 separated by a hyphen denotes a
3036 \fIrange expression\fP;
3037 any character that sorts between those two characters, inclusive,
3038 using the current locale's collating sequence and character set,
3039 is matched. If the first character following the
3045 then any character not enclosed is matched.
3046 The sorting order of characters in range expressions is determined by
3047 the current locale and the value of the \fBLC_COLLATE\fP shell variable,
3051 may be matched by including it as the first or last character
3055 may be matched by including it as the first character
3064 \fIcharacter classes\fP can be specified using the syntax
3065 \fB[:\fP\fIclass\fP\fB:]\fP, where \fIclass\fP is one of the
3066 following classes defined in the POSIX standard:
3070 .if n alnum alpha ascii blank cntrl digit graph lower print punct space upper word xdigit
3071 .if t alnum alpha ascii blank cntrl digit graph lower print punct space upper word xdigit
3073 A character class matches any character belonging to that class.
3074 The \fBword\fP character class matches letters, digits, and the character _.
3082 an \fIequivalence class\fP can be specified using the syntax
3083 \fB[=\fP\fIc\fP\fB=]\fP, which matches all characters with the
3084 same collation weight (as defined by the current locale) as
3085 the character \fIc\fP.
3093 the syntax \fB[.\fP\fIsymbol\fP\fB.]\fP matches the collating symbol
3098 If the \fBextglob\fP shell option is enabled using the \fBshopt\fP
3099 builtin, several extended pattern matching operators are recognized.
3100 In the following description, a \fIpattern-list\fP is a list of one
3101 or more patterns separated by a \fB|\fP.
3102 Composite patterns may be formed using one or more of the following
3108 \fB?(\fP\^\fIpattern-list\^\fP\fB)\fP
3109 Matches zero or one occurrence of the given patterns
3111 \fB*(\fP\^\fIpattern-list\^\fP\fB)\fP
3112 Matches zero or more occurrences of the given patterns
3114 \fB+(\fP\^\fIpattern-list\^\fP\fB)\fP
3115 Matches one or more occurrences of the given patterns
3117 \fB@(\fP\^\fIpattern-list\^\fP\fB)\fP
3118 Matches one of the given patterns
3120 \fB!(\fP\^\fIpattern-list\^\fP\fB)\fP
3121 Matches anything except one of the given patterns
3126 After the preceding expansions, all unquoted occurrences of the
3130 and \^\f3"\fP\^ that did not result from one of the above
3131 expansions are removed.
3133 Before a command is executed, its input and output
3136 using a special notation interpreted by the shell.
3137 Redirection may also be used to open and close files for the
3138 current shell execution environment. The following redirection
3139 operators may precede or appear anywhere within a
3143 Redirections are processed in the order they appear, from
3146 In the following descriptions, if the file descriptor number is
3147 omitted, and the first character of the redirection operator is
3149 the redirection refers to the standard input (file descriptor
3150 0). If the first character of the redirection operator is
3152 the redirection refers to the standard output (file descriptor
3155 The word following the redirection operator in the following
3156 descriptions, unless otherwise noted, is subjected to brace expansion,
3157 tilde expansion, parameter expansion, command substitution, arithmetic
3158 expansion, quote removal, pathname expansion, and word splitting.
3159 If it expands to more than one word,
3163 Note that the order of redirections is significant. For example,
3167 ls \fB>\fP dirlist 2\fB>&\fP1
3170 directs both standard output and standard error to the file
3175 ls 2\fB>&\fP1 \fB>\fP dirlist
3178 directs only the standard output to file
3180 because the standard error was duplicated from the standard output
3181 before the standard output was redirected to
3184 \fBBash\fP handles several filenames specially when they are used in
3185 redirections, as described in the following table:
3191 If \fIfd\fP is a valid integer, file descriptor \fIfd\fP is duplicated.
3194 File descriptor 0 is duplicated.
3197 File descriptor 1 is duplicated.
3200 File descriptor 2 is duplicated.
3202 .B /dev/tcp/\fIhost\fP/\fIport\fP
3203 If \fIhost\fP is a valid hostname or Internet address, and \fIport\fP
3204 is an integer port number or service name, \fBbash\fP attempts to open
3205 a TCP connection to the corresponding socket.
3207 .B /dev/udp/\fIhost\fP/\fIport\fP
3208 If \fIhost\fP is a valid hostname or Internet address, and \fIport\fP
3209 is an integer port number or service name, \fBbash\fP attempts to open
3210 a UDP connection to the corresponding socket.
3214 A failure to open or create a file causes the redirection to fail.
3216 Redirections using file descriptors greater than 9 should be used with
3217 care, as they may conflict with file descriptors the shell uses
3219 .SS Redirecting Input
3221 Redirection of input causes the file whose name results from
3224 to be opened for reading on file descriptor
3226 or the standard input (file descriptor 0) if
3230 The general format for redirecting input is:
3233 [\fIn\fP]\fB<\fP\fIword\fP
3235 .SS Redirecting Output
3237 Redirection of output causes the file whose name results from
3240 to be opened for writing on file descriptor
3242 or the standard output (file descriptor 1) if
3244 is not specified. If the file does not exist it is created;
3245 if it does exist it is truncated to zero size.
3247 The general format for redirecting output is:
3250 [\fIn\fP]\fB>\fP\fIword\fP
3253 If the redirection operator is
3259 builtin has been enabled, the redirection will fail if the file
3260 whose name results from the expansion of \fIword\fP exists and is
3262 If the redirection operator is
3264 or the redirection operator is
3270 builtin command is not enabled, the redirection is attempted even
3271 if the file named by \fIword\fP exists.
3272 .SS Appending Redirected Output
3274 Redirection of output in this fashion
3275 causes the file whose name results from
3278 to be opened for appending on file descriptor
3280 or the standard output (file descriptor 1) if
3282 is not specified. If the file does not exist it is created.
3284 The general format for appending output is:
3287 [\fIn\fP]\fB>>\fP\fIword\fP
3290 .SS Redirecting Standard Output and Standard Error
3292 This construct allows both the
3293 standard output (file descriptor 1) and
3294 the standard error output (file descriptor 2)
3295 to be redirected to the file whose name is the
3299 There are two formats for redirecting standard output and
3310 Of the two forms, the first is preferred.
3311 This is semantically equivalent to
3314 \fB>\fP\fIword\fP 2\fB>&\fP1
3317 .SS Appending Standard Output and Standard Error
3319 This construct allows both the
3320 standard output (file descriptor 1) and
3321 the standard error output (file descriptor 2)
3322 to be appended to the file whose name is the
3326 The format for appending standard output and standard error is:
3332 This is semantically equivalent to
3335 \fB>>\fP\fIword\fP 2\fB>&\fP1
3339 This type of redirection instructs the shell to read input from the
3340 current source until a line containing only
3342 (with no trailing blanks)
3344 the lines read up to that point are then used as the standard
3345 input for a command.
3347 The format of here-documents is:
3351 \fB<<\fP[\fB\-\fP]\fIword\fP
3357 No parameter expansion, command substitution, arithmetic expansion,
3358 or pathname expansion is performed on
3360 If any characters in
3364 is the result of quote removal on
3366 and the lines in the here-document are not expanded.
3367 If \fIword\fP is unquoted,
3368 all lines of the here-document are subjected to parameter expansion,
3369 command substitution, and arithmetic expansion. In the latter
3370 case, the character sequence
3374 must be used to quote the characters
3380 If the redirection operator is
3382 then all leading tab characters are stripped from input lines and the
3386 here-documents within shell scripts to be indented in a
3389 A variant of here documents, the format is:
3397 The \fIword\fP is expanded and supplied to the command on its standard
3399 .SS "Duplicating File Descriptors"
3401 The redirection operator
3404 [\fIn\fP]\fB<&\fP\fIword\fP
3407 is used to duplicate input file descriptors.
3410 expands to one or more digits, the file descriptor denoted by
3412 is made to be a copy of that file descriptor.
3415 do not specify a file descriptor open for input, a redirection error occurs.
3424 is not specified, the standard input (file descriptor 0) is used.
3429 [\fIn\fP]\fB>&\fP\fIword\fP
3432 is used similarly to duplicate output file descriptors. If
3434 is not specified, the standard output (file descriptor 1) is used.
3437 do not specify a file descriptor open for output, a redirection error occurs.
3438 As a special case, if \fIn\fP is omitted, and \fIword\fP does not
3439 expand to one or more digits, the standard output and standard
3440 error are redirected as described previously.
3441 .SS "Moving File Descriptors"
3443 The redirection operator
3446 [\fIn\fP]\fB<&\fP\fIdigit\fP\fB\-\fP
3449 moves the file descriptor \fIdigit\fP to file descriptor
3451 or the standard input (file descriptor 0) if \fIn\fP is not specified.
3452 \fIdigit\fP is closed after being duplicated to \fIn\fP.
3454 Similarly, the redirection operator
3457 [\fIn\fP]\fB>&\fP\fIdigit\fP\fB\-\fP
3460 moves the file descriptor \fIdigit\fP to file descriptor
3462 or the standard output (file descriptor 1) if \fIn\fP is not specified.
3463 .SS "Opening File Descriptors for Reading and Writing"
3465 The redirection operator
3468 [\fIn\fP]\fB<>\fP\fIword\fP
3471 causes the file whose name is the expansion of
3473 to be opened for both reading and writing on file descriptor
3475 or on file descriptor 0 if
3477 is not specified. If the file does not exist, it is created.
3479 \fIAliases\fP allow a string to be substituted for a word when it is used
3480 as the first word of a simple command.
3481 The shell maintains a list of aliases that may be set and unset with the
3485 builtin commands (see
3487 .B SHELL BUILTIN COMMANDS
3489 The first word of each simple command, if unquoted,
3490 is checked to see if it has an
3491 alias. If so, that word is replaced by the text of the alias.
3492 The characters \fB/\fP, \fB$\fP, \fB\`\fP, and \fB=\fP and
3493 any of the shell \fImetacharacters\fP or quoting characters
3494 listed above may not appear in an alias name.
3495 The replacement text may contain any valid shell input,
3496 including shell metacharacters.
3497 The first word of the replacement text is tested
3498 for aliases, but a word that is identical to an alias being expanded
3499 is not expanded a second time.
3500 This means that one may alias
3506 does not try to recursively expand the replacement text.
3507 If the last character of the alias value is a
3509 then the next command
3510 word following the alias is also checked for alias expansion.
3512 Aliases are created and listed with the
3514 command, and removed with the
3518 There is no mechanism for using arguments in the replacement text.
3519 If arguments are needed, a shell function should be used (see
3524 Aliases are not expanded when the shell is not interactive, unless
3527 shell option is set using
3529 (see the description of
3533 \fBSHELL BUILTIN COMMANDS\fP
3536 The rules concerning the definition and use of aliases are
3539 always reads at least one complete line
3540 of input before executing any
3541 of the commands on that line. Aliases are expanded when a
3542 command is read, not when it is executed. Therefore, an
3543 alias definition appearing on the same line as another
3544 command does not take effect until the next line of input is read.
3545 The commands following the alias definition
3546 on that line are not affected by the new alias.
3547 This behavior is also an issue when functions are executed.
3548 Aliases are expanded when a function definition is read,
3549 not when the function is executed, because a function definition
3550 is itself a compound command. As a consequence, aliases
3551 defined in a function are not available until after that
3552 function is executed. To be safe, always put
3553 alias definitions on a separate line, and do not use
3555 in compound commands.
3557 For almost every purpose, aliases are superseded by
3560 A shell function, defined as described above under
3562 .BR "SHELL GRAMMAR" ,
3563 stores a series of commands for later execution.
3564 When the name of a shell function is used as a simple command name,
3565 the list of commands associated with that function name is executed.
3566 Functions are executed in the context of the
3567 current shell; no new process is created to interpret
3568 them (contrast this with the execution of a shell script).
3569 When a function is executed, the arguments to the
3570 function become the positional parameters
3571 during its execution.
3572 The special parameter
3574 is updated to reflect the change. Special parameter 0
3576 The first element of the
3579 variable is set to the name of the function while the function
3581 All other aspects of the shell execution
3582 environment are identical between a function and its caller
3583 with the exception that the
3588 traps (see the description of the
3592 .B SHELL BUILTIN COMMANDS
3593 below) are not inherited unless the function has been given the
3594 \fBtrace\fP attribute (see the description of the
3597 builtin below) or the
3598 \fB\-o functrace\fP shell option has been enabled with
3599 the \fBset\fP builtin
3600 (in which case all functions inherit the \fBDEBUG\fP and \fBRETURN\fP traps).
3602 Variables local to the function may be declared with the
3604 builtin command. Ordinarily, variables and their values
3605 are shared between the function and its caller.
3607 If the builtin command
3609 is executed in a function, the function completes and
3610 execution resumes with the next command after the function
3612 Any command associated with the \fBRETURN\fP trap is executed
3613 before execution resumes.
3614 When a function completes, the values of the
3615 positional parameters and the special parameter
3617 are restored to the values they had prior to the function's
3620 Function names and definitions may be listed with the
3626 builtin commands. The
3632 will list the function names only
3633 (and optionally the source file and line number, if the \fBextdebug\fP
3634 shell option is enabled).
3635 Functions may be exported so that subshells
3636 automatically have them defined with the
3641 A function definition may be deleted using the \fB\-f\fP option to
3645 Note that shell functions and variables with the same name may result
3646 in multiple identically-named entries in the environment passed to the
3648 Care should be taken in cases where this may cause a problem.
3650 Functions may be recursive. No limit is imposed on the number
3652 .SH "ARITHMETIC EVALUATION"
3653 The shell allows arithmetic expressions to be evaluated, under
3654 certain circumstances (see the \fBlet\fP and \fBdeclare\fP builtin
3655 commands and \fBArithmetic Expansion\fP).
3656 Evaluation is done in fixed-width integers with no check for overflow,
3657 though division by 0 is trapped and flagged as an error.
3658 The operators and their precedence, associativity, and values
3659 are the same as in the C language.
3660 The following list of operators is grouped into levels of
3661 equal-precedence operators.
3662 The levels are listed in order of decreasing precedence.
3666 .B \fIid\fP++ \fIid\fP\-\-
3667 variable post-increment and post-decrement
3669 .B ++\fIid\fP \-\-\fIid\fP
3670 variable pre-increment and pre-decrement
3673 unary minus and plus
3676 logical and bitwise negation
3682 multiplication, division, remainder
3685 addition, subtraction
3688 left and right bitwise shifts
3694 equality and inequality
3700 bitwise exclusive OR
3711 .B \fIexpr\fP?\fIexpr\fP:\fIexpr\fP
3712 conditional operator
3714 .B = *= /= %= += \-= <<= >>= &= ^= |=
3717 .B \fIexpr1\fP , \fIexpr2\fP
3721 Shell variables are allowed as operands; parameter expansion is
3722 performed before the expression is evaluated.
3723 Within an expression, shell variables may also be referenced by name
3724 without using the parameter expansion syntax.
3725 A shell variable that is null or unset evaluates to 0 when referenced
3726 by name without using the parameter expansion syntax.
3727 The value of a variable is evaluated as an arithmetic expression
3728 when it is referenced, or when a variable which has been given the
3729 \fIinteger\fP attribute using \fBdeclare -i\fP is assigned a value.
3730 A null value evaluates to 0.
3731 A shell variable need not have its integer attribute
3732 turned on to be used in an expression.
3734 Constants with a leading 0 are interpreted as octal numbers.
3735 A leading 0x or 0X denotes hexadecimal.
3736 Otherwise, numbers take the form [\fIbase#\fP]n, where \fIbase\fP
3737 is a decimal number between 2 and 64 representing the arithmetic
3738 base, and \fIn\fP is a number in that base.
3739 If \fIbase#\fP is omitted, then base 10 is used.
3740 The digits greater than 9 are represented by the lowercase letters,
3741 the uppercase letters, @, and _, in that order.
3742 If \fIbase\fP is less than or equal to 36, lowercase and uppercase
3743 letters may be used interchangeably to represent numbers between 10
3746 Operators are evaluated in order of precedence. Sub-expressions in
3747 parentheses are evaluated first and may override the precedence
3749 .SH "CONDITIONAL EXPRESSIONS"
3750 Conditional expressions are used by the \fB[[\fP compound command and
3751 the \fBtest\fP and \fB[\fP builtin commands to test file attributes
3752 and perform string and arithmetic comparisons.
3753 Expressions are formed from the following unary or binary primaries.
3754 If any \fIfile\fP argument to one of the primaries is of the form
3755 \fI/dev/fd/n\fP, then file descriptor \fIn\fP is checked.
3756 If the \fIfile\fP argument to one of the primaries is one of
3757 \fI/dev/stdin\fP, \fI/dev/stdout\fP, or \fI/dev/stderr\fP, file
3758 descriptor 0, 1, or 2, respectively, is checked.
3760 Unless otherwise specified, primaries that operate on files follow symbolic
3761 links and operate on the target of the link, rather than the link itself.
3766 True if \fIfile\fP exists.
3769 True if \fIfile\fP exists and is a block special file.
3772 True if \fIfile\fP exists and is a character special file.
3775 True if \fIfile\fP exists and is a directory.
3778 True if \fIfile\fP exists.
3781 True if \fIfile\fP exists and is a regular file.
3784 True if \fIfile\fP exists and is set-group-id.
3787 True if \fIfile\fP exists and is a symbolic link.
3790 True if \fIfile\fP exists and its ``sticky'' bit is set.
3793 True if \fIfile\fP exists and is a named pipe (FIFO).
3796 True if \fIfile\fP exists and is readable.
3799 True if \fIfile\fP exists and has a size greater than zero.
3802 True if file descriptor
3804 is open and refers to a terminal.
3807 True if \fIfile\fP exists and its set-user-id bit is set.
3810 True if \fIfile\fP exists and is writable.
3813 True if \fIfile\fP exists and is executable.
3816 True if \fIfile\fP exists and is owned by the effective user id.
3819 True if \fIfile\fP exists and is owned by the effective group id.
3822 True if \fIfile\fP exists and is a symbolic link.
3825 True if \fIfile\fP exists and is a socket.
3828 True if \fIfile\fP exists and has been modified since it was last read.
3830 \fIfile1\fP \-\fBnt\fP \fIfile2\fP
3831 True if \fIfile1\fP is newer (according to modification date) than \fIfile2\fP,
3832 or if \fIfile1\fP exists and \fPfile2\fP does not.
3834 \fIfile1\fP \-\fBot\fP \fIfile2\fP
3835 True if \fIfile1\fP is older than \fIfile2\fP, or if \fIfile2\fP exists
3836 and \fIfile1\fP does not.
3838 \fIfile1\fP \fB\-ef\fP \fIfile2\fP
3839 True if \fIfile1\fP and \fIfile2\fP refer to the same device and
3842 .B \-o \fIoptname\fP
3843 True if shell option
3846 See the list of options under the description of the
3853 True if the length of \fIstring\fP is zero.
3860 True if the length of
3864 \fIstring1\fP \fB==\fP \fIstring2\fP
3865 True if the strings are equal. \fB=\fP may be used in place of
3866 \fB==\fP for strict POSIX compliance.
3868 \fIstring1\fP \fB!=\fP \fIstring2\fP
3869 True if the strings are not equal.
3871 \fIstring1\fP \fB<\fP \fIstring2\fP
3872 True if \fIstring1\fP sorts before \fIstring2\fP lexicographically
3873 in the current locale.
3875 \fIstring1\fP \fB>\fP \fIstring2\fP
3876 True if \fIstring1\fP sorts after \fIstring2\fP lexicographically
3877 in the current locale.
3879 .I \fIarg1\fP \fBOP\fP \fIarg2\fP
3890 These arithmetic binary operators return true if \fIarg1\fP
3891 is equal to, not equal to, less than, less than or equal to,
3892 greater than, or greater than or equal to \fIarg2\fP, respectively.
3896 may be positive or negative integers.
3898 .SH "SIMPLE COMMAND EXPANSION"
3899 When a simple command is executed, the shell performs the following
3900 expansions, assignments, and redirections, from left to right.
3902 The words that the parser has marked as variable assignments (those
3903 preceding the command name) and redirections are saved for later
3906 The words that are not variable assignments or redirections are
3907 expanded. If any words remain after expansion, the first word
3908 is taken to be the name of the command and the remaining words are
3911 Redirections are performed as described above under
3915 The text after the \fB=\fP in each variable assignment undergoes tilde
3916 expansion, parameter expansion, command substitution, arithmetic expansion,
3917 and quote removal before being assigned to the variable.
3919 If no command name results, the variable assignments affect the current
3920 shell environment. Otherwise, the variables are added to the environment
3921 of the executed command and do not affect the current shell environment.
3922 If any of the assignments attempts to assign a value to a readonly variable,
3923 an error occurs, and the command exits with a non-zero status.
3925 If no command name results, redirections are performed, but do not
3926 affect the current shell environment. A redirection error causes the
3927 command to exit with a non-zero status.
3929 If there is a command name left after expansion, execution proceeds as
3930 described below. Otherwise, the command exits. If one of the expansions
3931 contained a command substitution, the exit status of the command is
3932 the exit status of the last command substitution performed. If there
3933 were no command substitutions, the command exits with a status of zero.
3934 .SH "COMMAND EXECUTION"
3935 After a command has been split into words, if it results in a
3936 simple command and an optional list of arguments, the following
3939 If the command name contains no slashes, the shell attempts to
3940 locate it. If there exists a shell function by that name, that
3941 function is invoked as described above in
3944 If the name does not match a function, the shell searches for
3945 it in the list of shell builtins. If a match is found, that
3948 If the name is neither a shell function nor a builtin,
3949 and contains no slashes,
3951 searches each element of the
3954 for a directory containing an executable file by that name.
3956 uses a hash table to remember the full pathnames of executable
3961 .B "SHELL BUILTIN COMMANDS"
3963 A full search of the directories in
3966 is performed only if the command is not found in the hash table.
3967 If the search is unsuccessful, the shell searches for a defined shell
3968 function named \fBcommand_not_found_handle\fP.
3969 If that function exists, it is invoked with the original command and
3970 the original command's arguments as its arguments, and the function's
3971 exit status becomes the exit status of the shell.
3972 If that function is not defined, the shell prints an error
3973 message and returns an exit status of 127.
3975 If the search is successful, or if the command name contains
3976 one or more slashes, the shell executes the named program in a
3977 separate execution environment.
3978 Argument 0 is set to the name given, and the remaining arguments
3979 to the command are set to the arguments given, if any.
3981 If this execution fails because the file is not in executable
3982 format, and the file is not a directory, it is assumed to be
3983 a \fIshell script\fP, a file
3984 containing shell commands. A subshell is spawned to execute
3985 it. This subshell reinitializes itself, so
3986 that the effect is as if a new shell had been invoked
3987 to handle the script, with the exception that the locations of
3988 commands remembered by the parent (see
3992 \fBSHELL BUILTIN COMMANDS\fP)
3993 are retained by the child.
3995 If the program is a file beginning with
3997 the remainder of the first line specifies an interpreter
3998 for the program. The shell executes the
3999 specified interpreter on operating systems that do not
4000 handle this executable format themselves. The arguments to the
4001 interpreter consist of a single optional argument following the
4002 interpreter name on the first line of the program, followed
4003 by the name of the program, followed by the command
4005 .SH COMMAND EXECUTION ENVIRONMENT
4006 The shell has an \fIexecution environment\fP, which consists of the
4010 open files inherited by the shell at invocation, as modified by
4011 redirections supplied to the \fBexec\fP builtin
4013 the current working directory as set by \fBcd\fP, \fBpushd\fP, or
4014 \fBpopd\fP, or inherited by the shell at invocation
4016 the file creation mode mask as set by \fBumask\fP or inherited from
4019 current traps set by \fBtrap\fP
4021 shell parameters that are set by variable assignment or with \fBset\fP
4022 or inherited from the shell's parent in the environment
4024 shell functions defined during execution or inherited from the shell's
4025 parent in the environment
4027 options enabled at invocation (either by default or with command-line
4028 arguments) or by \fBset\fP
4030 options enabled by \fBshopt\fP
4032 shell aliases defined with \fBalias\fP
4034 various process IDs, including those of background jobs, the value
4035 of \fB$$\fP, and the value of \fB$PPID\fP
4037 When a simple command other than a builtin or shell function
4038 is to be executed, it
4039 is invoked in a separate execution environment that consists of
4040 the following. Unless otherwise noted, the values are inherited
4044 the shell's open files, plus any modifications and additions specified
4045 by redirections to the command
4047 the current working directory
4049 the file creation mode mask
4051 shell variables and functions marked for export, along with variables
4052 exported for the command, passed in the environment
4054 traps caught by the shell are reset to the values inherited from the
4055 shell's parent, and traps ignored by the shell are ignored
4057 A command invoked in this separate environment cannot affect the
4058 shell's execution environment.
4060 Command substitution, commands grouped with parentheses,
4061 and asynchronous commands are invoked in a
4062 subshell environment that is a duplicate of the shell environment,
4063 except that traps caught by the shell are reset to the values
4064 that the shell inherited from its parent at invocation. Builtin
4065 commands that are invoked as part of a pipeline are also executed in a
4066 subshell environment. Changes made to the subshell environment
4067 cannot affect the shell's execution environment.
4069 Subshells spawned to execute command substitutions inherit the value of
4070 the \fB\-e\fP option from the parent shell. When not in posix mode,
4071 Bash clears the \fB\-e\fP option in such subshells.
4073 If a command is followed by a \fB&\fP and job control is not active, the
4074 default standard input for the command is the empty file \fI/dev/null\fP.
4075 Otherwise, the invoked command inherits the file descriptors of the calling
4076 shell as modified by redirections.
4078 When a program is invoked it is given an array of strings
4082 \fIname\fP\-\fIvalue\fP pairs, of the form
4083 .IR "name\fR=\fPvalue" .
4085 The shell provides several ways to manipulate the environment.
4086 On invocation, the shell scans its own environment and
4087 creates a parameter for each name found, automatically marking
4090 to child processes. Executed commands inherit the environment.
4095 commands allow parameters and functions to be added to and
4096 deleted from the environment. If the value of a parameter
4097 in the environment is modified, the new value becomes part
4098 of the environment, replacing the old. The environment
4099 inherited by any executed command consists of the shell's
4100 initial environment, whose values may be modified in the shell,
4101 less any pairs removed by the
4103 command, plus any additions via the
4109 The environment for any
4111 or function may be augmented temporarily by prefixing it with
4112 parameter assignments, as described above in
4115 These assignment statements affect only the environment seen
4120 option is set (see the
4122 builtin command below), then
4124 parameter assignments are placed in the environment for a command,
4125 not just those that precede the command name.
4129 invokes an external command, the variable
4131 is set to the full file name of the command and passed to that
4132 command in its environment.
4135 The exit status of an executed command is the value returned by the
4136 \fIwaitpid\fP system call or equivalent function. Exit statuses
4137 fall between 0 and 255, though, as explained below, the shell may
4138 use values above 125 specially. Exit statuses from shell builtins and
4139 compound commands are also limited to this range. Under certain
4140 circumstances, the shell will use special values to indicate specific
4143 For the shell's purposes, a command which exits with a
4144 zero exit status has succeeded. An exit status of zero
4145 indicates success. A non-zero exit status indicates failure.
4146 When a command terminates on a fatal signal \fIN\fP, \fBbash\fP uses
4147 the value of 128+\fIN\fP as the exit status.
4149 If a command is not found, the child process created to
4150 execute it returns a status of 127. If a command is found
4151 but is not executable, the return status is 126.
4153 If a command fails because of an error during expansion or redirection,
4154 the exit status is greater than zero.
4156 Shell builtin commands return a status of 0 (\fItrue\fP) if
4157 successful, and non-zero (\fIfalse\fP) if an error occurs
4159 All builtins return an exit status of 2 to indicate incorrect usage.
4161 \fBBash\fP itself returns the exit status of the last command
4162 executed, unless a syntax error occurs, in which case it exits
4163 with a non-zero value. See also the \fBexit\fP builtin
4166 When \fBbash\fP is interactive, in the absence of any traps, it ignores
4169 (so that \fBkill 0\fP does not kill an interactive shell),
4173 is caught and handled (so that the \fBwait\fP builtin is interruptible).
4174 In all cases, \fBbash\fP ignores
4177 If job control is in effect,
4188 Non-builtin commands run by \fBbash\fP have signal handlers
4189 set to the values inherited by the shell from its parent.
4190 When job control is not in effect, asynchronous commands
4197 in addition to these inherited handlers.
4198 Commands run as a result of command substitution ignore the
4199 keyboard-generated job control signals
4208 The shell exits by default upon receipt of a
4211 Before exiting, an interactive shell resends the
4214 to all jobs, running or stopped.
4215 Stopped jobs are sent
4218 to ensure that they receive the
4221 To prevent the shell from
4222 sending the signal to a particular job, it should be removed from the
4227 .B "SHELL BUILTIN COMMANDS"
4237 shell option has been set with
4243 to all jobs when an interactive login shell exits.
4245 If \fBbash\fP is waiting for a command to complete and receives a signal
4246 for which a trap has been set, the trap will not be executed until
4247 the command completes.
4248 When \fBbash\fP is waiting for an asynchronous command via the \fBwait\fP
4249 builtin, the reception of a signal for which a trap has been set will
4250 cause the \fBwait\fP builtin to return immediately with an exit status
4251 greater than 128, immediately after which the trap is executed.
4254 refers to the ability to selectively stop (\fIsuspend\fP)
4255 the execution of processes and continue (\fIresume\fP)
4256 their execution at a later point. A user typically employs
4257 this facility via an interactive interface supplied jointly
4258 by the system's terminal driver and
4261 The shell associates a
4263 with each pipeline. It keeps a table of currently executing
4264 jobs, which may be listed with the
4268 starts a job asynchronously (in the
4270 it prints a line that looks like:
4276 indicating that this job is job number 1 and that the process ID
4277 of the last process in the pipeline associated with this job is 25647.
4278 All of the processes in a single pipeline are members of the same job.
4282 abstraction as the basis for job control.
4284 To facilitate the implementation of the user interface to job
4285 control, the operating system maintains the notion of a \fIcurrent terminal
4286 process group ID\fP. Members of this process group (processes whose
4287 process group ID is equal to the current terminal process group ID)
4288 receive keyboard-generated signals such as
4291 These processes are said to be in the
4294 processes are those whose process group ID differs from the terminal's;
4295 such processes are immune to keyboard-generated signals.
4296 Only foreground processes are allowed to read from or write to the
4297 terminal. Background processes which attempt to read from (write to) the
4300 .B SIGTTIN (SIGTTOU)
4301 signal by the terminal driver,
4302 which, unless caught, suspends the process.
4304 If the operating system on which
4309 contains facilities to use it.
4312 character (typically
4314 Control-Z) while a process is running
4315 causes that process to be stopped and returns control to
4318 .I "delayed suspend"
4319 character (typically
4321 Control-Y) causes the process to be stopped when it
4322 attempts to read input from the terminal, and control to
4325 The user may then manipulate the state of this job, using the
4327 command to continue it in the background, the
4329 command to continue it in the foreground, or
4332 command to kill it. A \fB^Z\fP takes effect immediately,
4333 and has the additional side effect of causing pending output
4334 and typeahead to be discarded.
4336 There are a number of ways to refer to a job in the shell.
4339 introduces a job specification (\fIjobspec\fP). Job number
4341 may be referred to as
4343 A job may also be referred to using a prefix of the name used to
4344 start it, or using a substring that appears in its command line.
4349 job. If a prefix matches more than one job,
4351 reports an error. Using
4353 on the other hand, refers to any job containing the string
4355 in its command line. If the substring matches more than one job,
4357 reports an error. The symbols
4361 refer to the shell's notion of the
4363 which is the last job stopped while it was in
4364 the foreground or started in the background.
4367 may be referenced using
4369 If there is only a single job, \fB%+\fP and \fB%\-\fP can both be used
4370 to refer to that job.
4371 In output pertaining to jobs (e.g., the output of the
4373 command), the current job is always flagged with a
4375 and the previous job with a
4377 A single % (with no accompanying job specification) also refers to the
4380 Simply naming a job can be used to bring it into the
4385 bringing job 1 from the background into the foreground.
4388 resumes job 1 in the background, equivalent to
4391 The shell learns immediately whenever a job changes state.
4394 waits until it is about to print a prompt before reporting
4395 changes in a job's status so as to not interrupt
4396 any other output. If the
4403 reports such changes immediately.
4407 is executed for each child that exits.
4409 If an attempt to exit
4411 is made while jobs are stopped (or, if the \fBcheckjobs\fP shell option has
4412 been enabled using the \fBshopt\fP builtin, running), the shell prints a
4413 warning message, and, if the \fBcheckjobs\fP option is enabled, lists the
4414 jobs and their statuses.
4417 command may then be used to inspect their status.
4418 If a second attempt to exit is made without an intervening command,
4419 the shell does not print another warning, and any stopped
4420 jobs are terminated.
4422 When executing interactively,
4424 displays the primary prompt
4427 when it is ready to read a command, and the secondary prompt
4430 when it needs more input to complete a command.
4432 allows these prompt strings to be customized by inserting a number of
4433 backslash-escaped special characters that are decoded as follows:
4438 an ASCII bell character (07)
4441 the date in "Weekday Month Date" format (e.g., "Tue May 26")
4443 .B \eD{\fIformat\fP}
4444 the \fIformat\fP is passed to \fIstrftime\fP(3) and the result is inserted
4445 into the prompt string; an empty \fIformat\fP results in a locale-specific
4446 time representation. The braces are required
4449 an ASCII escape character (033)
4452 the hostname up to the first `.'
4458 the number of jobs currently managed by the shell
4461 the basename of the shell's terminal device name
4470 the name of the shell, the basename of
4472 (the portion following the final slash)
4475 the current time in 24-hour HH:MM:SS format
4478 the current time in 12-hour HH:MM:SS format
4481 the current time in 12-hour am/pm format
4484 the current time in 24-hour HH:MM format
4487 the username of the current user
4490 the version of \fBbash\fP (e.g., 2.00)
4493 the release of \fBbash\fP, version + patch level (e.g., 2.00.0)
4496 the current working directory, with \fB$HOME\fP abbreviated with a tilde
4497 (uses the \fB$PROMPT_DIRTRIM\fP variable)
4500 the basename of the current working directory, with \fB$HOME\fP
4501 abbreviated with a tilde
4504 the history number of this command
4507 the command number of this command
4510 if the effective UID is 0, a
4516 the character corresponding to the octal number \fInnn\fP
4522 begin a sequence of non-printing characters, which could be used to
4523 embed a terminal control sequence into the prompt
4526 end a sequence of non-printing characters
4530 The command number and the history number are usually different:
4531 the history number of a command is its position in the history
4532 list, which may include commands restored from the history file
4536 below), while the command number is the position in the sequence
4537 of commands executed during the current shell session.
4538 After the string is decoded, it is expanded via
4539 parameter expansion, command substitution, arithmetic
4540 expansion, and quote removal, subject to the value of the
4542 shell option (see the description of the
4546 .B "SHELL BUILTIN COMMANDS"
4549 This is the library that handles reading input when using an interactive
4552 option is given at shell invocation.
4553 Line editing is also used when using the \fB\-e\fP option to the
4555 By default, the line editing commands are similar to those of emacs.
4556 A vi-style line editing interface is also available.
4557 Line editing can be enabled at any time using the
4565 .B SHELL BUILTIN COMMANDS
4567 To turn off line editing after the shell is running, use the
4574 .SS "Readline Notation"
4576 In this section, the emacs-style notation is used to denote
4577 keystrokes. Control keys are denoted by C\-\fIkey\fR, e.g., C\-n
4578 means Control\-N. Similarly,
4580 keys are denoted by M\-\fIkey\fR, so M\-x means Meta\-X. (On keyboards
4583 key, M\-\fIx\fP means ESC \fIx\fP, i.e., press the Escape key
4586 key. This makes ESC the \fImeta prefix\fP.
4587 The combination M\-C\-\fIx\fP means ESC\-Control\-\fIx\fP,
4588 or press the Escape key
4589 then hold the Control key while pressing the
4593 Readline commands may be given numeric
4595 which normally act as a repeat count.
4596 Sometimes, however, it is the sign of the argument that is significant.
4597 Passing a negative argument to a command that acts in the forward
4598 direction (e.g., \fBkill\-line\fP) causes that command to act in a
4600 Commands whose behavior with arguments deviates from this are noted
4603 When a command is described as \fIkilling\fP text, the text
4604 deleted is saved for possible future retrieval
4605 (\fIyanking\fP). The killed text is saved in a
4606 \fIkill ring\fP. Consecutive kills cause the text to be
4607 accumulated into one unit, which can be yanked all at once.
4608 Commands which do not kill text separate the chunks of text
4610 .SS "Readline Initialization"
4612 Readline is customized by putting commands in an initialization
4613 file (the \fIinputrc\fP file).
4614 The name of this file is taken from the value of the
4617 variable. If that variable is unset, the default is
4619 When a program which uses the readline library starts up, the
4620 initialization file is read, and the key bindings and variables
4622 There are only a few basic constructs allowed in the
4623 readline initialization file.
4624 Blank lines are ignored.
4625 Lines beginning with a \fB#\fP are comments.
4626 Lines beginning with a \fB$\fP indicate conditional constructs.
4627 Other lines denote key bindings and variable settings.
4629 The default key-bindings may be changed with an
4632 Other programs that use this library may add their own commands
4635 For example, placing
4638 M\-Control\-u: universal\-argument
4642 C\-Meta\-u: universal\-argument
4646 would make M\-C\-u execute the readline command
4647 .IR universal\-argument .
4649 The following symbolic character names are recognized:
4662 In addition to command names, readline allows keys to be bound
4663 to a string that is inserted when the key is pressed (a \fImacro\fP).
4664 .SS "Readline Key Bindings"
4666 The syntax for controlling key bindings in the
4668 file is simple. All that is required is the name of the
4669 command or the text of a macro and a key sequence to which
4670 it should be bound. The name may be specified in one of two ways:
4671 as a symbolic key name, possibly with \fIMeta\-\fP or \fIControl\-\fP
4672 prefixes, or as a key sequence.
4674 When using the form \fBkeyname\fP:\^\fIfunction\-name\fP or \fImacro\fP,
4676 is the name of a key spelled out in English. For example:
4679 Control-u: universal\-argument
4681 Meta-Rubout: backward-kill-word
4683 Control-o: "> output"
4686 In the above example,
4688 is bound to the function
4689 .BR universal\-argument ,
4691 is bound to the function
4692 .BR backward\-kill\-word ,
4695 is bound to run the macro
4696 expressed on the right hand side (that is, to insert the text
4697 .if t \f(CW> output\fP
4701 In the second form, \fB"keyseq"\fP:\^\fIfunction\-name\fP or \fImacro\fP,
4705 above in that strings denoting
4706 an entire key sequence may be specified by placing the sequence
4707 within double quotes. Some GNU Emacs style key escapes can be
4708 used, as in the following example, but the symbolic character names
4712 "\eC\-u": universal\-argument
4714 "\eC\-x\eC\-r": re\-read\-init\-file
4716 "\ee[11~": "Function Key 1"
4721 is again bound to the function
4722 .BR universal\-argument .
4724 is bound to the function
4725 .BR re\-read\-init\-file ,
4728 is bound to insert the text
4729 .if t \f(CWFunction Key 1\fP.
4730 .if n ``Function Key 1''.
4732 The full set of GNU Emacs style escape sequences is
4756 In addition to the GNU Emacs style escape sequences, a second
4757 set of backslash escapes is available:
4786 the eight-bit character whose value is the octal value \fInnn\fP
4787 (one to three digits)
4790 the eight-bit character whose value is the hexadecimal value \fIHH\fP
4791 (one or two hex digits)
4795 When entering the text of a macro, single or double quotes must
4796 be used to indicate a macro definition.
4797 Unquoted text is assumed to be a function name.
4798 In the macro body, the backslash escapes described above are expanded.
4799 Backslash will quote any other character in the macro text,
4800 including " and \(aq.
4803 allows the current readline key bindings to be displayed or modified
4806 builtin command. The editing mode may be switched during interactive
4811 builtin command (see
4813 .B SHELL BUILTIN COMMANDS
4815 .SS "Readline Variables"
4817 Readline has variables that can be used to further customize its
4818 behavior. A variable may be set in the
4820 file with a statement of the form
4823 \fBset\fP \fIvariable\-name\fP \fIvalue\fP
4826 Except where noted, readline variables can take the values
4830 (without regard to case).
4831 Unrecognized variable names are ignored.
4832 When a variable value is read, empty or null values, "on" (case-insensitive),
4833 and "1" are equivalent to \fBOn\fP. All other values are equivalent to
4835 The variables and their default values are:
4839 .B bell\-style (audible)
4840 Controls what happens when readline wants to ring the terminal bell.
4841 If set to \fBnone\fP, readline never rings the bell. If set to
4842 \fBvisible\fP, readline uses a visible bell if one is available.
4843 If set to \fBaudible\fP, readline attempts to ring the terminal's bell.
4845 .B bind\-tty\-special\-chars (On)
4846 If set to \fBOn\fP, readline attempts to bind the control characters
4847 treated specially by the kernel's terminal driver to their readline
4850 .B comment\-begin (``#'')
4851 The string that is inserted when the readline
4853 command is executed.
4854 This command is bound to
4856 in emacs mode and to
4860 .B completion\-ignore\-case (Off)
4861 If set to \fBOn\fP, readline performs filename matching and completion
4862 in a case\-insensitive fashion.
4864 .B completion\-prefix\-display\-length (0)
4865 The length in characters of the common prefix of a list of possible
4866 completions that is displayed without modification. When set to a
4867 value greater than zero, common prefixes longer than this value are
4868 replaced with an ellipsis when displaying possible completions.
4870 .B completion\-query\-items (100)
4871 This determines when the user is queried about viewing
4872 the number of possible completions
4873 generated by the \fBpossible\-completions\fP command.
4874 It may be set to any integer value greater than or equal to
4875 zero. If the number of possible completions is greater than
4876 or equal to the value of this variable, the user is asked whether
4877 or not he wishes to view them; otherwise they are simply listed
4880 .B convert\-meta (On)
4881 If set to \fBOn\fP, readline will convert characters with the
4882 eighth bit set to an ASCII key sequence
4883 by stripping the eighth bit and prefixing an
4884 escape character (in effect, using escape as the \fImeta prefix\fP).
4886 .B disable\-completion (Off)
4887 If set to \fBOn\fP, readline will inhibit word completion. Completion
4888 characters will be inserted into the line as if they had been
4889 mapped to \fBself-insert\fP.
4891 .B editing\-mode (emacs)
4892 Controls whether readline begins with a set of key bindings similar
4893 to \fIemacs\fP or \fIvi\fP.
4895 can be set to either
4900 .B enable\-keypad (Off)
4901 When set to \fBOn\fP, readline will try to enable the application
4902 keypad when it is called. Some systems need this to enable the
4905 .B expand\-tilde (Off)
4906 If set to \fBon\fP, tilde expansion is performed when readline
4907 attempts word completion.
4909 .B history\-preserve\-point (Off)
4910 If set to \fBon\fP, the history code attempts to place point at the
4911 same location on each history line retrieved with \fBprevious-history\fP
4912 or \fBnext-history\fP.
4914 .B history\-size (0)
4915 Set the maximum number of history entries saved in the history list. If
4916 set to zero, the number of entries in the history list is not limited.
4918 .B horizontal\-scroll\-mode (Off)
4919 When set to \fBOn\fP, makes readline use a single line for display,
4920 scrolling the input horizontally on a single screen line when it
4921 becomes longer than the screen width rather than wrapping to a new line.
4923 .B input\-meta (Off)
4924 If set to \fBOn\fP, readline will enable eight-bit input (that is,
4925 it will not strip the high bit from the characters it reads),
4926 regardless of what the terminal claims it can support. The name
4928 is a synonym for this variable.
4930 .B isearch\-terminators (``C\-[C\-J'')
4931 The string of characters that should terminate an incremental
4932 search without subsequently executing the character as a command.
4933 If this variable has not been given a value, the characters
4934 \fIESC\fP and \fIC\-J\fP will terminate an incremental search.
4937 Set the current readline keymap. The set of valid keymap names is
4938 \fIemacs, emacs\-standard, emacs\-meta, emacs\-ctlx, vi,
4941 \fIvi\fP is equivalent to \fIvi\-command\fP; \fIemacs\fP is
4942 equivalent to \fIemacs\-standard\fP. The default value is
4946 also affects the default keymap.
4948 .B mark\-directories (On)
4949 If set to \fBOn\fP, completed directory names have a slash
4952 .B mark\-modified\-lines (Off)
4953 If set to \fBOn\fP, history lines that have been modified are displayed
4954 with a preceding asterisk (\fB*\fP).
4956 .B mark\-symlinked\-directories (Off)
4957 If set to \fBOn\fP, completed names which are symbolic links to directories
4958 have a slash appended (subject to the value of
4959 \fBmark\-directories\fP).
4961 .B match\-hidden\-files (On)
4962 This variable, when set to \fBOn\fP, causes readline to match files whose
4963 names begin with a `.' (hidden files) when performing filename
4964 completion, unless the leading `.' is
4965 supplied by the user in the filename to be completed.
4967 .B output\-meta (Off)
4968 If set to \fBOn\fP, readline will display characters with the
4969 eighth bit set directly rather than as a meta-prefixed escape
4972 .B page\-completions (On)
4973 If set to \fBOn\fP, readline uses an internal \fImore\fP-like pager
4974 to display a screenful of possible completions at a time.
4976 .B print\-completions\-horizontally (Off)
4977 If set to \fBOn\fP, readline will display completions with matches
4978 sorted horizontally in alphabetical order, rather than down the screen.
4980 .B revert\-all\-at\-newline (Off)
4981 If set to \fBon\fP, readline will undo all changes to history lines
4982 before returning when \fBaccept\-line\fP is executed. By default,
4983 history lines may be modified and retain individual undo lists across
4984 calls to \fBreadline\fP.
4986 .B show\-all\-if\-ambiguous (Off)
4987 This alters the default behavior of the completion functions. If
4990 words which have more than one possible completion cause the
4991 matches to be listed immediately instead of ringing the bell.
4993 .B show\-all\-if\-unmodified (Off)
4994 This alters the default behavior of the completion functions in
4995 a fashion similar to \fBshow\-all\-if\-ambiguous\fP.
4998 words which have more than one possible completion without any
4999 possible partial completion (the possible completions don't share
5000 a common prefix) cause the matches to be listed immediately instead
5001 of ringing the bell.
5003 .B visible\-stats (Off)
5004 If set to \fBOn\fP, a character denoting a file's type as reported
5005 by \fIstat\fP(2) is appended to the filename when listing possible
5008 .SS "Readline Conditional Constructs"
5010 Readline implements a facility similar in spirit to the conditional
5011 compilation features of the C preprocessor which allows key
5012 bindings and variable settings to be performed as the result
5013 of tests. There are four parser directives used.
5017 construct allows bindings to be made based on the
5018 editing mode, the terminal being used, or the application using
5019 readline. The text of the test extends to the end of the line;
5020 no characters are required to isolate it.
5023 The \fBmode=\fP form of the \fB$if\fP directive is used to test
5024 whether readline is in emacs or vi mode.
5025 This may be used in conjunction
5026 with the \fBset keymap\fP command, for instance, to set bindings in
5027 the \fIemacs\-standard\fP and \fIemacs\-ctlx\fP keymaps only if
5028 readline is starting out in emacs mode.
5030 The \fBterm=\fP form may be used to include terminal-specific
5031 key bindings, perhaps to bind the key sequences output by the
5032 terminal's function keys. The word on the right side of the
5034 is tested against the both full name of the terminal and the portion
5035 of the terminal name before the first \fB\-\fP. This allows
5042 .IP \fBapplication\fP
5043 The \fBapplication\fP construct is used to include
5044 application-specific settings. Each program using the readline
5045 library sets the \fIapplication name\fP, and an initialization
5046 file can test for a particular value.
5047 This could be used to bind key sequences to functions useful for
5048 a specific program. For instance, the following command adds a
5049 key sequence that quotes the current or previous word in Bash:
5054 # Quote the current or previous word
5055 "\eC\-xq": "\eeb\e"\eef\e""
5061 This command, as seen in the previous example, terminates an
5064 Commands in this branch of the \fB$if\fP directive are executed if
5067 This directive takes a single filename as an argument and reads commands
5068 and bindings from that file. For example, the following directive
5069 would read \fI/etc/inputrc\fP:
5073 \fB$include\fP \^ \fI/etc/inputrc\fP
5078 Readline provides commands for searching through the command history
5082 below) for lines containing a specified string.
5083 There are two search modes:
5086 .IR non-incremental .
5088 Incremental searches begin before the user has finished typing the
5090 As each character of the search string is typed, readline displays
5091 the next entry from the history matching the string typed so far.
5092 An incremental search requires only as many characters as needed to
5093 find the desired history entry.
5094 The characters present in the value of the \fBisearch-terminators\fP
5095 variable are used to terminate an incremental search.
5096 If that variable has not been assigned a value the Escape and
5097 Control-J characters will terminate an incremental search.
5098 Control-G will abort an incremental search and restore the original
5100 When the search is terminated, the history entry containing the
5101 search string becomes the current line.
5103 To find other matching entries in the history list, type Control-S or
5104 Control-R as appropriate.
5105 This will search backward or forward in the history for the next
5106 entry matching the search string typed so far.
5107 Any other key sequence bound to a readline command will terminate
5108 the search and execute that command.
5109 For instance, a \fInewline\fP will terminate the search and accept
5110 the line, thereby executing the command from the history list.
5112 Readline remembers the last incremental search string. If two
5113 Control-Rs are typed without any intervening characters defining a
5114 new search string, any remembered search string is used.
5116 Non-incremental searches read the entire search string before starting
5117 to search for matching history lines. The search string may be
5118 typed by the user or be part of the contents of the current line.
5119 .SS "Readline Command Names"
5121 The following is a list of the names of the commands and the default
5122 key sequences to which they are bound.
5123 Command names without an accompanying key sequence are unbound by default.
5124 In the following descriptions, \fIpoint\fP refers to the current cursor
5125 position, and \fImark\fP refers to a cursor position saved by the
5126 \fBset\-mark\fP command.
5127 The text between the point and mark is referred to as the \fIregion\fP.
5128 .SS Commands for Moving
5132 .B beginning\-of\-line (C\-a)
5133 Move to the start of the current line.
5135 .B end\-of\-line (C\-e)
5136 Move to the end of the line.
5138 .B forward\-char (C\-f)
5139 Move forward a character.
5141 .B backward\-char (C\-b)
5142 Move back a character.
5144 .B forward\-word (M\-f)
5145 Move forward to the end of the next word. Words are composed of
5146 alphanumeric characters (letters and digits).
5148 .B backward\-word (M\-b)
5149 Move back to the start of the current or previous word.
5150 Words are composed of alphanumeric characters (letters and digits).
5152 .B shell\-forward\-word
5153 Move forward to the end of the next word.
5154 Words are delimited by non-quoted shell metacharacters.
5156 .B shell\-backward\-word
5157 Move back to the start of the current or previous word.
5158 Words are delimited by non-quoted shell metacharacters.
5160 .B clear\-screen (C\-l)
5161 Clear the screen leaving the current line at the top of the screen.
5162 With an argument, refresh the current line without clearing the
5165 .B redraw\-current\-line
5166 Refresh the current line.
5168 .SS Commands for Manipulating the History
5172 .B accept\-line (Newline, Return)
5173 Accept the line regardless of where the cursor is. If this line is
5174 non-empty, add it to the history list according to the state of the
5177 variable. If the line is a modified history
5178 line, then restore the history line to its original state.
5180 .B previous\-history (C\-p)
5181 Fetch the previous command from the history list, moving back in
5184 .B next\-history (C\-n)
5185 Fetch the next command from the history list, moving forward in the
5188 .B beginning\-of\-history (M\-<)
5189 Move to the first line in the history.
5191 .B end\-of\-history (M\->)
5192 Move to the end of the input history, i.e., the line currently being
5195 .B reverse\-search\-history (C\-r)
5196 Search backward starting at the current line and moving `up' through
5197 the history as necessary. This is an incremental search.
5199 .B forward\-search\-history (C\-s)
5200 Search forward starting at the current line and moving `down' through
5201 the history as necessary. This is an incremental search.
5203 .B non\-incremental\-reverse\-search\-history (M\-p)
5204 Search backward through the history starting at the current line
5205 using a non-incremental search for a string supplied by the user.
5207 .B non\-incremental\-forward\-search\-history (M\-n)
5208 Search forward through the history using a non-incremental search for
5209 a string supplied by the user.
5211 .B history\-search\-forward
5212 Search forward through the history for the string of characters
5213 between the start of the current line and the point.
5214 This is a non-incremental search.
5216 .B history\-search\-backward
5217 Search backward through the history for the string of characters
5218 between the start of the current line and the point.
5219 This is a non-incremental search.
5221 .B yank\-nth\-arg (M\-C\-y)
5222 Insert the first argument to the previous command (usually
5223 the second word on the previous line) at point.
5226 insert the \fIn\fPth word from the previous command (the words
5227 in the previous command begin with word 0). A negative argument
5228 inserts the \fIn\fPth word from the end of the previous command.
5229 Once the argument \fIn\fP is computed, the argument is extracted
5230 as if the "!\fIn\fP" history expansion had been specified.
5233 yank\-last\-arg (M\-.\^, M\-_\^)
5234 Insert the last argument to the previous command (the last word of
5235 the previous history entry). With an argument,
5236 behave exactly like \fByank\-nth\-arg\fP.
5237 Successive calls to \fByank\-last\-arg\fP move back through the history
5238 list, inserting the last argument of each line in turn.
5239 The history expansion facilities are used to extract the last argument,
5240 as if the "!$" history expansion had been specified.
5242 .B shell\-expand\-line (M\-C\-e)
5243 Expand the line as the shell does. This
5244 performs alias and history expansion as well as all of the shell
5245 word expansions. See
5247 .B HISTORY EXPANSION
5248 below for a description of history expansion.
5250 .B history\-expand\-line (M\-^)
5251 Perform history expansion on the current line.
5254 .B HISTORY EXPANSION
5255 below for a description of history expansion.
5258 Perform history expansion on the current line and insert a space.
5261 .B HISTORY EXPANSION
5262 below for a description of history expansion.
5264 .B alias\-expand\-line
5265 Perform alias expansion on the current line.
5269 above for a description of alias expansion.
5271 .B history\-and\-alias\-expand\-line
5272 Perform history and alias expansion on the current line.
5274 .B insert\-last\-argument (M\-.\^, M\-_\^)
5275 A synonym for \fByank\-last\-arg\fP.
5277 .B operate\-and\-get\-next (C\-o)
5278 Accept the current line for execution and fetch the next line
5279 relative to the current line from the history for editing. Any
5280 argument is ignored.
5282 .B edit\-and\-execute\-command (C\-xC\-e)
5283 Invoke an editor on the current command line, and execute the result as shell
5285 \fBBash\fP attempts to invoke
5290 and \fIemacs\fP as the editor, in that order.
5292 .SS Commands for Changing Text
5296 .B delete\-char (C\-d)
5297 Delete the character at point. If point is at the
5298 beginning of the line, there are no characters in the line, and
5299 the last character typed was not bound to \fBdelete\-char\fP,
5304 .B backward\-delete\-char (Rubout)
5305 Delete the character behind the cursor. When given a numeric argument,
5306 save the deleted text on the kill ring.
5308 .B forward\-backward\-delete\-char
5309 Delete the character under the cursor, unless the cursor is at the
5310 end of the line, in which case the character behind the cursor is
5313 .B quoted\-insert (C\-q, C\-v)
5314 Add the next character typed to the line verbatim. This is
5315 how to insert characters like \fBC\-q\fP, for example.
5317 .B tab\-insert (C\-v TAB)
5318 Insert a tab character.
5320 .B self\-insert (a,\ b,\ A,\ 1,\ !,\ ...)
5321 Insert the character typed.
5323 .B transpose\-chars (C\-t)
5324 Drag the character before point forward over the character at point,
5325 moving point forward as well.
5326 If point is at the end of the line, then this transposes
5327 the two characters before point.
5328 Negative arguments have no effect.
5330 .B transpose\-words (M\-t)
5331 Drag the word before point past the word after point,
5332 moving point over that word as well.
5333 If point is at the end of the line, this transposes
5334 the last two words on the line.
5336 .B upcase\-word (M\-u)
5337 Uppercase the current (or following) word. With a negative argument,
5338 uppercase the previous word, but do not move point.
5340 .B downcase\-word (M\-l)
5341 Lowercase the current (or following) word. With a negative argument,
5342 lowercase the previous word, but do not move point.
5344 .B capitalize\-word (M\-c)
5345 Capitalize the current (or following) word. With a negative argument,
5346 capitalize the previous word, but do not move point.
5349 Toggle overwrite mode. With an explicit positive numeric argument,
5350 switches to overwrite mode. With an explicit non-positive numeric
5351 argument, switches to insert mode. This command affects only
5352 \fBemacs\fP mode; \fBvi\fP mode does overwrite differently.
5353 Each call to \fIreadline()\fP starts in insert mode.
5354 In overwrite mode, characters bound to \fBself\-insert\fP replace
5355 the text at point rather than pushing the text to the right.
5356 Characters bound to \fBbackward\-delete\-char\fP replace the character
5357 before point with a space. By default, this command is unbound.
5359 .SS Killing and Yanking
5363 .B kill\-line (C\-k)
5364 Kill the text from point to the end of the line.
5366 .B backward\-kill\-line (C\-x Rubout)
5367 Kill backward to the beginning of the line.
5369 .B unix\-line\-discard (C\-u)
5370 Kill backward from point to the beginning of the line.
5371 The killed text is saved on the kill-ring.
5372 .\" There is no real difference between this and backward-kill-line
5374 .B kill\-whole\-line
5375 Kill all characters on the current line, no matter where point is.
5377 .B kill\-word (M\-d)
5378 Kill from point to the end of the current word, or if between
5379 words, to the end of the next word.
5380 Word boundaries are the same as those used by \fBforward\-word\fP.
5382 .B backward\-kill\-word (M\-Rubout)
5383 Kill the word behind point.
5384 Word boundaries are the same as those used by \fBbackward\-word\fP.
5386 .B shell\-kill\-word (M\-d)
5387 Kill from point to the end of the current word, or if between
5388 words, to the end of the next word.
5389 Word boundaries are the same as those used by \fBshell\-forward\-word\fP.
5391 .B shell\-backward\-kill\-word (M\-Rubout)
5392 Kill the word behind point.
5393 Word boundaries are the same as those used by \fBshell\-backward\-word\fP.
5395 .B unix\-word\-rubout (C\-w)
5396 Kill the word behind point, using white space as a word boundary.
5397 The killed text is saved on the kill-ring.
5399 .B unix\-filename\-rubout
5400 Kill the word behind point, using white space and the slash character
5401 as the word boundaries.
5402 The killed text is saved on the kill-ring.
5404 .B delete\-horizontal\-space (M\-\e)
5405 Delete all spaces and tabs around point.
5408 Kill the text in the current region.
5410 .B copy\-region\-as\-kill
5411 Copy the text in the region to the kill buffer.
5413 .B copy\-backward\-word
5414 Copy the word before point to the kill buffer.
5415 The word boundaries are the same as \fBbackward\-word\fP.
5417 .B copy\-forward\-word
5418 Copy the word following point to the kill buffer.
5419 The word boundaries are the same as \fBforward\-word\fP.
5422 Yank the top of the kill ring into the buffer at point.
5425 Rotate the kill ring, and yank the new top. Only works following
5430 .SS Numeric Arguments
5434 .B digit\-argument (M\-0, M\-1, ..., M\-\-)
5435 Add this digit to the argument already accumulating, or start a new
5436 argument. M\-\- starts a negative argument.
5438 .B universal\-argument
5439 This is another way to specify an argument.
5440 If this command is followed by one or more digits, optionally with a
5441 leading minus sign, those digits define the argument.
5442 If the command is followed by digits, executing
5443 .B universal\-argument
5444 again ends the numeric argument, but is otherwise ignored.
5445 As a special case, if this command is immediately followed by a
5446 character that is neither a digit or minus sign, the argument count
5447 for the next command is multiplied by four.
5448 The argument count is initially one, so executing this function the
5449 first time makes the argument count four, a second time makes the
5450 argument count sixteen, and so on.
5457 Attempt to perform completion on the text before point.
5459 attempts completion treating the text as a variable (if the
5460 text begins with \fB$\fP), username (if the text begins with
5461 \fB~\fP), hostname (if the text begins with \fB@\fP), or
5462 command (including aliases and functions) in turn. If none
5463 of these produces a match, filename completion is attempted.
5465 .B possible\-completions (M\-?)
5466 List the possible completions of the text before point.
5468 .B insert\-completions (M\-*)
5469 Insert all completions of the text before point
5470 that would have been generated by
5471 \fBpossible\-completions\fP.
5474 Similar to \fBcomplete\fP, but replaces the word to be completed
5475 with a single match from the list of possible completions.
5476 Repeated execution of \fBmenu\-complete\fP steps through the list
5477 of possible completions, inserting each match in turn.
5478 At the end of the list of completions, the bell is rung
5479 (subject to the setting of \fBbell\-style\fP)
5480 and the original text is restored.
5481 An argument of \fIn\fP moves \fIn\fP positions forward in the list
5482 of matches; a negative argument may be used to move backward
5484 This command is intended to be bound to \fBTAB\fP, but is unbound
5487 .B delete\-char\-or\-list
5488 Deletes the character under the cursor if not at the beginning or
5489 end of the line (like \fBdelete\-char\fP).
5490 If at the end of the line, behaves identically to
5491 \fBpossible\-completions\fP.
5492 This command is unbound by default.
5494 .B complete\-filename (M\-/)
5495 Attempt filename completion on the text before point.
5497 .B possible\-filename\-completions (C\-x /)
5498 List the possible completions of the text before point,
5499 treating it as a filename.
5501 .B complete\-username (M\-~)
5502 Attempt completion on the text before point, treating
5505 .B possible\-username\-completions (C\-x ~)
5506 List the possible completions of the text before point,
5507 treating it as a username.
5509 .B complete\-variable (M\-$)
5510 Attempt completion on the text before point, treating
5511 it as a shell variable.
5513 .B possible\-variable\-completions (C\-x $)
5514 List the possible completions of the text before point,
5515 treating it as a shell variable.
5517 .B complete\-hostname (M\-@)
5518 Attempt completion on the text before point, treating
5521 .B possible\-hostname\-completions (C\-x @)
5522 List the possible completions of the text before point,
5523 treating it as a hostname.
5525 .B complete\-command (M\-!)
5526 Attempt completion on the text before point, treating
5527 it as a command name. Command completion attempts to
5528 match the text against aliases, reserved words, shell
5529 functions, shell builtins, and finally executable filenames,
5532 .B possible\-command\-completions (C\-x !)
5533 List the possible completions of the text before point,
5534 treating it as a command name.
5536 .B dynamic\-complete\-history (M\-TAB)
5537 Attempt completion on the text before point, comparing
5538 the text against lines from the history list for possible
5542 Attempt menu completion on the text before point, comparing
5543 the text against lines from the history list for possible
5546 .B complete\-into\-braces (M\-{)
5547 Perform filename completion and insert the list of possible completions
5548 enclosed within braces so the list is available to the shell (see
5556 .B start\-kbd\-macro (C\-x (\^)
5557 Begin saving the characters typed into the current keyboard macro.
5559 .B end\-kbd\-macro (C\-x )\^)
5560 Stop saving the characters typed into the current keyboard macro
5561 and store the definition.
5563 .B call\-last\-kbd\-macro (C\-x e)
5564 Re-execute the last keyboard macro defined, by making the characters
5565 in the macro appear as if typed at the keyboard.
5571 .B re\-read\-init\-file (C\-x C\-r)
5572 Read in the contents of the \fIinputrc\fP file, and incorporate
5573 any bindings or variable assignments found there.
5576 Abort the current editing command and
5577 ring the terminal's bell (subject to the setting of
5580 .B do\-uppercase\-version (M\-a, M\-b, M\-\fIx\fP, ...)
5581 If the metafied character \fIx\fP is lowercase, run the command
5582 that is bound to the corresponding uppercase character.
5584 .B prefix\-meta (ESC)
5585 Metafy the next character typed.
5592 .B undo (C\-_, C\-x C\-u)
5593 Incremental undo, separately remembered for each line.
5595 .B revert\-line (M\-r)
5596 Undo all changes made to this line. This is like executing the
5598 command enough times to return the line to its initial state.
5600 .B tilde\-expand (M\-&)
5601 Perform tilde expansion on the current word.
5603 .B set\-mark (C\-@, M\-<space>)
5604 Set the mark to the point. If a
5605 numeric argument is supplied, the mark is set to that position.
5607 .B exchange\-point\-and\-mark (C\-x C\-x)
5608 Swap the point with the mark. The current cursor position is set to
5609 the saved position, and the old cursor position is saved as the mark.
5611 .B character\-search (C\-])
5612 A character is read and point is moved to the next occurrence of that
5613 character. A negative count searches for previous occurrences.
5615 .B character\-search\-backward (M\-C\-])
5616 A character is read and point is moved to the previous occurrence of that
5617 character. A negative count searches for subsequent occurrences.
5619 .B insert\-comment (M\-#)
5620 Without a numeric argument, the value of the readline
5622 variable is inserted at the beginning of the current line.
5623 If a numeric argument is supplied, this command acts as a toggle: if
5624 the characters at the beginning of the line do not match the value
5625 of \fBcomment\-begin\fP, the value is inserted, otherwise
5626 the characters in \fBcomment\-begin\fP are deleted from the beginning of
5628 In either case, the line is accepted as if a newline had been typed.
5629 The default value of
5630 \fBcomment\-begin\fP causes this command to make the current line
5632 If a numeric argument causes the comment character to be removed, the line
5633 will be executed by the shell.
5635 .B glob\-complete\-word (M\-g)
5636 The word before point is treated as a pattern for pathname expansion,
5637 with an asterisk implicitly appended. This pattern is used to
5638 generate a list of matching file names for possible completions.
5640 .B glob\-expand\-word (C\-x *)
5641 The word before point is treated as a pattern for pathname expansion,
5642 and the list of matching file names is inserted, replacing the word.
5643 If a numeric argument is supplied, an asterisk is appended before
5646 .B glob\-list\-expansions (C\-x g)
5647 The list of expansions that would have been generated by
5648 .B glob\-expand\-word
5649 is displayed, and the line is redrawn.
5650 If a numeric argument is supplied, an asterisk is appended before
5654 Print all of the functions and their key bindings to the
5655 readline output stream. If a numeric argument is supplied,
5656 the output is formatted in such a way that it can be made part
5657 of an \fIinputrc\fP file.
5660 Print all of the settable readline variables and their values to the
5661 readline output stream. If a numeric argument is supplied,
5662 the output is formatted in such a way that it can be made part
5663 of an \fIinputrc\fP file.
5666 Print all of the readline key sequences bound to macros and the
5667 strings they output. If a numeric argument is supplied,
5668 the output is formatted in such a way that it can be made part
5669 of an \fIinputrc\fP file.
5671 .B display\-shell\-version (C\-x C\-v)
5672 Display version information about the current instance of
5675 .SS Programmable Completion
5677 When word completion is attempted for an argument to a command for
5678 which a completion specification (a \fIcompspec\fP) has been defined
5679 using the \fBcomplete\fP builtin (see
5681 .B "SHELL BUILTIN COMMANDS"
5682 below), the programmable completion facilities are invoked.
5684 First, the command name is identified.
5685 If a compspec has been defined for that command, the
5686 compspec is used to generate the list of possible completions for the word.
5687 If the command word is a full pathname, a compspec for the full
5688 pathname is searched for first.
5689 If no compspec is found for the full pathname, an attempt is made to
5690 find a compspec for the portion following the final slash.
5692 Once a compspec has been found, it is used to generate the list of
5694 If a compspec is not found, the default \fBbash\fP completion as
5695 described above under \fBCompleting\fP is performed.
5697 First, the actions specified by the compspec are used.
5698 Only matches which are prefixed by the word being completed are
5704 option is used for filename or directory name completion, the shell
5708 is used to filter the matches.
5710 Any completions specified by a filename expansion pattern to the
5711 \fB\-G\fP option are generated next.
5712 The words generated by the pattern need not match the word
5717 shell variable is not used to filter the matches, but the
5722 Next, the string specified as the argument to the \fB\-W\fP option
5724 The string is first split using the characters in the
5727 special variable as delimiters.
5728 Shell quoting is honored.
5729 Each word is then expanded using
5730 brace expansion, tilde expansion, parameter and variable expansion,
5731 command substitution, and arithmetic expansion,
5732 as described above under
5735 The results are split using the rules described above under
5736 \fBWord Splitting\fP.
5737 The results of the expansion are prefix-matched against the word being
5738 completed, and the matching words become the possible completions.
5740 After these matches have been generated, any shell function or command
5741 specified with the \fB\-F\fP and \fB\-C\fP options is invoked.
5742 When the command or function is invoked, the
5752 variables are assigned values as described above under
5753 \fBShell Variables\fP.
5754 If a shell function is being invoked, the
5760 variables are also set.
5761 When the function or command is invoked, the first argument is the
5762 name of the command whose arguments are being completed, the
5763 second argument is the word being completed, and the third argument
5764 is the word preceding the word being completed on the current command line.
5765 No filtering of the generated completions against the word being completed
5766 is performed; the function or command has complete freedom in generating
5769 Any function specified with \fB\-F\fP is invoked first.
5770 The function may use any of the shell facilities, including the
5771 \fBcompgen\fP builtin described below, to generate the matches.
5772 It must put the possible completions in the
5777 Next, any command specified with the \fB\-C\fP option is invoked
5778 in an environment equivalent to command substitution.
5779 It should print a list of completions, one per line, to the
5781 Backslash may be used to escape a newline, if necessary.
5783 After all of the possible completions are generated, any filter
5784 specified with the \fB\-X\fP option is applied to the list.
5785 The filter is a pattern as used for pathname expansion; a \fB&\fP
5786 in the pattern is replaced with the text of the word being completed.
5787 A literal \fB&\fP may be escaped with a backslash; the backslash
5788 is removed before attempting a match.
5789 Any completion that matches the pattern will be removed from the list.
5790 A leading \fB!\fP negates the pattern; in this case any completion
5791 not matching the pattern will be removed.
5793 Finally, any prefix and suffix specified with the \fB\-P\fP and \fB\-S\fP
5794 options are added to each member of the completion list, and the result is
5795 returned to the readline completion code as the list of possible
5798 If the previously-applied actions do not generate any matches, and the
5799 \fB\-o dirnames\fP option was supplied to \fBcomplete\fP when the
5800 compspec was defined, directory name completion is attempted.
5802 If the \fB\-o plusdirs\fP option was supplied to \fBcomplete\fP when the
5803 compspec was defined, directory name completion is attempted and any
5804 matches are added to the results of the other actions.
5806 By default, if a compspec is found, whatever it generates is returned
5807 to the completion code as the full set of possible completions.
5808 The default \fBbash\fP completions are not attempted, and the readline
5809 default of filename completion is disabled.
5810 If the \fB\-o bashdefault\fP option was supplied to \fBcomplete\fP when
5811 the compspec was defined, the \fBbash\fP default completions are attempted
5812 if the compspec generates no matches.
5813 If the \fB\-o default\fP option was supplied to \fBcomplete\fP when the
5814 compspec was defined, readline's default completion will be performed
5815 if the compspec (and, if attempted, the default \fBbash\fP completions)
5816 generate no matches.
5818 When a compspec indicates that directory name completion is desired,
5819 the programmable completion functions force readline to append a slash
5820 to completed names which are symbolic links to directories, subject to
5821 the value of the \fBmark\-directories\fP readline variable, regardless
5822 of the setting of the \fBmark-symlinked\-directories\fP readline variable.
5828 builtin is enabled, the shell provides access to the
5829 \fIcommand history\fP,
5830 the list of commands previously typed.
5831 The value of the \fBHISTSIZE\fP variable is used as the
5832 number of commands to save in a history list.
5833 The text of the last
5836 commands (default 500) is saved. The shell
5837 stores each command in the history list prior to parameter and
5838 variable expansion (see
5841 above) but after history expansion is performed, subject to the
5842 values of the shell variables
5849 On startup, the history is initialized from the file named by
5853 (default \fI~/.bash_history\fP).
5854 The file named by the value of
5857 is truncated, if necessary, to contain no more than
5858 the number of lines specified by the value of
5861 When the history file is read,
5862 lines beginning with the history comment character followed immediately
5863 by a digit are interpreted as timestamps for the preceding history line.
5864 These timestamps are optionally displayed depending on the value of the
5868 When an interactive shell exits, the last
5871 lines are copied from the history list to
5876 shell option is enabled
5877 (see the description of
5881 .B "SHELL BUILTIN COMMANDS"
5882 below), the lines are appended to the history file,
5883 otherwise the history file is overwritten.
5887 is unset, or if the history file is unwritable, the history is
5892 variable is set, time stamps are written to the history file, marked
5893 with the history comment character, so
5894 they may be preserved across shell sessions.
5895 This uses the history comment character to distinguish timestamps from
5896 other history lines.
5897 After saving the history, the history file is truncated
5898 to contain no more than
5904 is not set, no truncation is performed.
5910 .B SHELL BUILTIN COMMANDS
5911 below) may be used to list or edit and re-execute a portion of
5915 builtin may be used to display or modify the history list and
5916 manipulate the history file.
5917 When using command-line editing, search commands
5918 are available in each editing mode that provide access to the
5921 The shell allows control over which commands are saved on the history
5928 variables may be set to cause the shell to save only a subset of the
5932 shell option, if enabled, causes the shell to attempt to save each
5933 line of a multi-line command in the same history entry, adding
5934 semicolons where necessary to preserve syntactic correctness.
5937 shell option causes the shell to save the command with embedded newlines
5938 instead of semicolons. See the description of the
5942 .B "SHELL BUILTIN COMMANDS"
5943 for information on setting and unsetting shell options.
5944 .SH "HISTORY EXPANSION"
5946 The shell supports a history expansion feature that
5947 is similar to the history expansion in
5949 This section describes what syntax features are available. This
5950 feature is enabled by default for interactive shells, and can be
5955 builtin command (see
5957 .B SHELL BUILTIN COMMANDS
5958 below). Non-interactive shells do not perform history expansion
5961 History expansions introduce words from the history list into
5962 the input stream, making it easy to repeat commands, insert the
5963 arguments to a previous command into the current input line, or
5964 fix errors in previous commands quickly.
5966 History expansion is performed immediately after a complete line
5967 is read, before the shell breaks it into words.
5968 It takes place in two parts.
5969 The first is to determine which line from the history list
5970 to use during substitution.
5971 The second is to select portions of that line for inclusion into
5973 The line selected from the history is the \fIevent\fP,
5974 and the portions of that line that are acted upon are \fIwords\fP.
5975 Various \fImodifiers\fP are available to manipulate the selected words.
5976 The line is broken into words in the same fashion as when reading input,
5977 so that several \fImetacharacter\fP-separated words surrounded by
5978 quotes are considered one word.
5979 History expansions are introduced by the appearance of the
5980 history expansion character, which is \^\fB!\fP\^ by default.
5981 Only backslash (\^\fB\e\fP\^) and single quotes can quote
5982 the history expansion character.
5984 Several characters inhibit history expansion if found immediately
5985 following the history expansion character, even if it is unquoted:
5986 space, tab, newline, carriage return, and \fB=\fP.
5987 If the \fBextglob\fP shell option is enabled, \fB(\fP will also
5990 Several shell options settable with the
5992 builtin may be used to tailor the behavior of history expansion.
5995 shell option is enabled (see the description of the
5999 is being used, history substitutions are not immediately passed to
6001 Instead, the expanded line is reloaded into the
6003 editing buffer for further modification.
6006 is being used, and the
6008 shell option is enabled, a failed history substitution will be reloaded
6011 editing buffer for correction.
6016 builtin command may be used to see what a history expansion will
6022 builtin may be used to add commands to the end of the history list
6023 without actually executing them, so that they are available for
6026 The shell allows control of the various characters used by the
6027 history expansion mechanism (see the description of
6030 .BR "Shell Variables" ).
6032 the history comment character to mark history timestamps when
6033 writing the history file.
6034 .SS Event Designators
6036 An event designator is a reference to a command line entry in the
6042 Start a history substitution, except when followed by a
6044 newline, carriage return, =
6045 or ( (when the \fBextglob\fP shell option is enabled using
6046 the \fBshopt\fP builtin).
6049 Refer to command line
6053 Refer to the current command line minus
6057 Refer to the previous command. This is a synonym for `!\-1'.
6060 Refer to the most recent command starting with
6063 .B !?\fIstring\fR\fB[?]\fR
6064 Refer to the most recent command containing
6066 The trailing \fB?\fP may be omitted if
6068 is followed immediately by a newline.
6070 .B \d\s+2^\s-2\u\fIstring1\fP\d\s+2^\s-2\u\fIstring2\fP\d\s+2^\s-2\u
6071 Quick substitution. Repeat the last command, replacing
6076 ``!!:s/\fIstring1\fP/\fIstring2\fP/''
6077 (see \fBModifiers\fP below).
6080 The entire command line typed so far.
6082 .SS Word Designators
6084 Word designators are used to select desired words from the event.
6087 separates the event specification from the word designator.
6088 It may be omitted if the word designator begins with a
6095 Words are numbered from the beginning of the line,
6096 with the first word being denoted by 0 (zero).
6097 Words are inserted into the current line separated by single spaces.
6102 The zeroth word. For the shell, this is the command
6109 The first argument. That is, word 1.
6115 The word matched by the most recent `?\fIstring\fR?' search.
6118 A range of words; `\-\fIy\fR' abbreviates `0\-\fIy\fR'.
6121 All of the words but the zeroth. This is a synonym
6122 for `\fI1\-$\fP'. It is not an error to use
6124 if there is just one
6125 word in the event; the empty string is returned in that case.
6128 Abbreviates \fIx\-$\fP.
6131 Abbreviates \fIx\-$\fP like \fBx*\fP, but omits the last word.
6134 If a word designator is supplied without an event specification, the
6135 previous command is used as the event.
6138 After the optional word designator, there may appear a sequence of
6139 one or more of the following modifiers, each preceded by a `:'.
6145 Remove a trailing file name component, leaving only the head.
6148 Remove all leading file name components, leaving the tail.
6151 Remove a trailing suffix of the form \fI.xxx\fP, leaving the
6155 Remove all but the trailing suffix.
6158 Print the new command but do not execute it.
6161 Quote the substituted words, escaping further substitutions.
6164 Quote the substituted words as with
6166 but break into words at
6170 .B s/\fIold\fP/\fInew\fP/
6173 for the first occurrence of
6175 in the event line. Any delimiter can be used in place of /. The
6176 final delimiter is optional if it is the last character of the
6177 event line. The delimiter may be quoted in
6181 with a single backslash. If & appears in
6185 A single backslash will quote the &. If
6187 is null, it is set to the last
6189 substituted, or, if no previous history substitutions took place,
6193 .B !?\fIstring\fR\fB[?]\fR
6197 Repeat the previous substitution.
6200 Cause changes to be applied over the entire event line. This is
6201 used in conjunction with `\fB:s\fP' (e.g., `\fB:gs/\fIold\fP/\fInew\fP/\fR')
6202 or `\fB:&\fP'. If used with
6203 `\fB:s\fP', any delimiter can be used
6204 in place of /, and the final delimiter is optional
6205 if it is the last character of the event line.
6206 An \fBa\fP may be used as a synonym for \fBg\fP.
6209 Apply the following `\fBs\fP' modifier once to each word in the event line.
6211 .SH "SHELL BUILTIN COMMANDS"
6212 .\" start of bash_builtins
6215 Unless otherwise noted, each builtin command documented in this
6216 section as accepting options preceded by
6220 to signify the end of the options.
6221 For example, the \fB:\fP, \fBtrue\fP, \fBfalse\fP, and \fBtest\fP builtins
6222 do not accept options.
6226 \fB:\fP [\fIarguments\fP]
6228 No effect; the command does nothing beyond expanding
6230 and performing any specified
6231 redirections. A zero exit code is returned.
6233 \fB .\| \fP \fIfilename\fP [\fIarguments\fP]
6236 \fBsource\fP \fIfilename\fP [\fIarguments\fP]
6238 Read and execute commands from
6241 shell environment and return the exit status of the last command
6246 does not contain a slash, file names in
6249 are used to find the directory containing
6251 The file searched for in
6254 need not be executable.
6255 When \fBbash\fP is not in \fIposix mode\fP, the current directory is
6256 searched if no file is found in
6263 builtin command is turned off, the
6267 If any \fIarguments\fP are supplied, they become the positional
6268 parameters when \fIfilename\fP is executed. Otherwise the positional
6269 parameters are unchanged.
6270 The return status is the status of the last command exited within
6271 the script (0 if no commands are executed), and false if
6273 is not found or cannot be read.
6275 \fBalias\fP [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP] ...]
6276 \fBAlias\fP with no arguments or with the
6278 option prints the list of aliases in the form
6279 \fBalias\fP \fIname\fP=\fIvalue\fP on standard output.
6280 When arguments are supplied, an alias is defined for
6281 each \fIname\fP whose \fIvalue\fP is given.
6282 A trailing space in \fIvalue\fP causes the next word to be
6283 checked for alias substitution when the alias is expanded.
6284 For each \fIname\fP in the argument list for which no \fIvalue\fP
6285 is supplied, the name and value of the alias is printed.
6286 \fBAlias\fP returns true unless a \fIname\fP is given for which
6287 no alias has been defined.
6289 \fBbg\fP [\fIjobspec\fP ...]
6290 Resume each suspended job \fIjobspec\fP in the background, as if it
6291 had been started with
6295 is not present, the shell's notion of the \fIcurrent job\fP is used.
6298 returns 0 unless run when job control is disabled or, when run with
6299 job control enabled, any specified \fIjobspec\fP was not found
6300 or was started without job control.
6302 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] [\fB\-lpsvPSV\fP]
6305 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] [\fB\-q\fP \fIfunction\fP] [\fB\-u\fP \fIfunction\fP] [\fB\-r\fP \fIkeyseq\fP]
6307 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fB\-f\fP \fIfilename\fP
6309 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fB\-x\fP \fIkeyseq\fP:\fIshell\-command\fP
6311 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fIkeyseq\fP:\fIfunction\-name\fP
6313 \fBbind\fP \fIreadline\-command\fP
6317 key and function bindings, bind a key sequence to a
6319 function or macro, or set a
6322 Each non-option argument is a command as it would appear in
6324 but each binding or command must be passed as a separate argument;
6325 e.g., '"\eC\-x\eC\-r": re\-read\-init\-file'.
6326 Options, if supplied, have the following meanings:
6333 as the keymap to be affected by the subsequent bindings.
6337 \fIemacs, emacs\-standard, emacs\-meta, emacs\-ctlx, vi,
6338 vi\-move, vi\-command\fP, and
6340 \fIvi\fP is equivalent to \fIvi\-command\fP; \fIemacs\fP is
6341 equivalent to \fIemacs\-standard\fP.
6344 List the names of all \fBreadline\fP functions.
6347 Display \fBreadline\fP function names and bindings in such a way
6348 that they can be re-read.
6351 List current \fBreadline\fP function names and bindings.
6354 Display \fBreadline\fP key sequences bound to macros and the strings
6355 they output in such a way that they can be re-read.
6358 Display \fBreadline\fP key sequences bound to macros and the strings
6362 Display \fBreadline\fP variable names and values in such a way that they
6366 List current \fBreadline\fP variable names and values.
6368 .B \-f \fIfilename\fP
6369 Read key bindings from \fIfilename\fP.
6371 .B \-q \fIfunction\fP
6372 Query about which keys invoke the named \fIfunction\fP.
6374 .B \-u \fIfunction\fP
6375 Unbind all keys bound to the named \fIfunction\fP.
6378 Remove any current binding for \fIkeyseq\fP.
6380 .B \-x \fIkeyseq\fP:\fIshell\-command\fP
6381 Cause \fIshell\-command\fP to be executed whenever \fIkeyseq\fP is
6383 When \fIshell\-command\fP is executed, the shell sets the
6385 variable to the contents of the \fBreadline\fP line buffer and the
6387 variable to the current location of the insertion point.
6388 If the executed command changes the value of
6391 .BR READLINE_POINT ,
6392 those new values will be reflected in the editing state.
6395 The return value is 0 unless an unrecognized option is given or an
6399 \fBbreak\fP [\fIn\fP]
6406 loop. If \fIn\fP is specified, break \fIn\fP levels.
6410 is greater than the number of enclosing loops, all enclosing loops
6412 The return value is 0 unless \fIn\fP is not greater than or equal to 1.
6414 \fBbuiltin\fP \fIshell\-builtin\fP [\fIarguments\fP]
6415 Execute the specified shell builtin, passing it
6417 and return its exit status.
6418 This is useful when defining a
6419 function whose name is the same as a shell builtin,
6420 retaining the functionality of the builtin within the function.
6421 The \fBcd\fP builtin is commonly redefined this way.
6422 The return status is false if
6424 is not a shell builtin command.
6426 \fBcaller\fP [\fIexpr\fP]
6427 Returns the context of any active subroutine call (a shell function or
6428 a script executed with the \fB.\fP or \fBsource\fP builtins.
6429 Without \fIexpr\fP, \fBcaller\fP displays the line number and source
6430 filename of the current subroutine call.
6431 If a non-negative integer is supplied as \fIexpr\fP, \fBcaller\fP
6432 displays the line number, subroutine name, and source file corresponding
6433 to that position in the current execution call stack. This extra
6434 information may be used, for example, to print a stack trace. The
6435 current frame is frame 0.
6436 The return value is 0 unless the shell is not executing a subroutine
6437 call or \fIexpr\fP does not correspond to a valid position in the
6440 \fBcd\fP [\fB\-L|-P\fP] [\fIdir\fP]
6441 Change the current directory to \fIdir\fP. The variable
6450 defines the search path for the directory containing
6452 Alternative directory names in
6455 are separated by a colon (:). A null directory name in
6458 is the same as the current directory, i.e., ``\fB.\fP''. If
6460 begins with a slash (/),
6466 option says to use the physical directory structure instead of
6467 following symbolic links (see also the
6471 builtin command); the
6473 option forces symbolic links to be followed. An argument of
6478 If a non-empty directory name from \fBCDPATH\fP is used, or if
6479 \fB\-\fP is the first argument, and the directory change is
6480 successful, the absolute pathname of the new working directory is
6481 written to the standard output.
6482 The return value is true if the directory was successfully changed;
6485 \fBcommand\fP [\fB\-pVv\fP] \fIcommand\fP [\fIarg\fP ...]
6490 suppressing the normal shell function lookup. Only builtin
6491 commands or commands found in the
6494 are executed. If the
6496 option is given, the search for
6498 is performed using a default value for
6500 that is guaranteed to find all of the standard utilities.
6505 option is supplied, a description of
6509 option causes a single word indicating the command or file name
6512 to be displayed; the
6514 option produces a more verbose description.
6519 option is supplied, the exit status is 0 if
6521 was found, and 1 if not. If neither option is supplied and
6522 an error occurred or
6524 cannot be found, the exit status is 127. Otherwise, the exit status of the
6526 builtin is the exit status of
6529 \fBcompgen\fP [\fIoption\fP] [\fIword\fP]
6530 Generate possible completion matches for \fIword\fP according to
6531 the \fIoption\fPs, which may be any option accepted by the
6533 builtin with the exception of \fB\-p\fP and \fB\-r\fP, and write
6534 the matches to the standard output.
6535 When using the \fB\-F\fP or \fB\-C\fP options, the various shell variables
6536 set by the programmable completion facilities, while available, will not
6539 The matches will be generated in the same way as if the programmable
6540 completion code had generated them directly from a completion specification
6541 with the same flags.
6542 If \fIword\fP is specified, only those completions matching \fIword\fP
6545 The return value is true unless an invalid option is supplied, or no
6546 matches were generated.
6548 \fBcomplete\fP [\fB\-abcdefgjksuv\fP] [\fB\-o\fP \fIcomp-option\fP] [\fB\-E\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]
6550 [\fB\-X\fP \fIfilterpat\fP] [\fB\-P\fP \fIprefix\fP] [\fB\-S\fP \fIsuffix\fP] \fIname\fP [\fIname ...\fP]
6553 \fBcomplete\fP \fB\-pr\fP [\fB\-E\fP] [\fIname\fP ...]
6555 Specify how arguments to each \fIname\fP should be completed.
6556 If the \fB\-p\fP option is supplied, or if no options are supplied,
6557 existing completion specifications are printed in a way that allows
6558 them to be reused as input.
6559 The \fB\-r\fP option removes a completion specification for
6560 each \fIname\fP, or, if no \fIname\fPs are supplied, all
6561 completion specifications.
6562 The \fB\-E\fP option indicates that the remaining options and actions should
6563 apply to ``empty'' command completion; that is, completion attempted on a
6566 The process of applying these completion specifications when word completion
6567 is attempted is described above under \fBProgrammable Completion\fP.
6569 Other options, if specified, have the following meanings.
6570 The arguments to the \fB\-G\fP, \fB\-W\fP, and \fB\-X\fP options
6571 (and, if necessary, the \fB\-P\fP and \fB\-S\fP options)
6572 should be quoted to protect them from expansion before the
6578 \fB\-o\fP \fIcomp-option\fP
6579 The \fIcomp-option\fP controls several aspects of the compspec's behavior
6580 beyond the simple generation of completions.
6581 \fIcomp-option\fP may be one of:
6585 Perform the rest of the default \fBbash\fP completions if the compspec
6586 generates no matches.
6589 Use readline's default filename completion if the compspec generates
6593 Perform directory name completion if the compspec generates no matches.
6596 Tell readline that the compspec generates filenames, so it can perform any
6597 filename\-specific processing (like adding a slash to directory names,
6598 quoting special characters, or suppressing trailing spaces).
6599 Intended to be used with shell functions.
6602 Tell readline not to append a space (the default) to words completed at
6603 the end of the line.
6606 After any matches defined by the compspec are generated,
6607 directory name completion is attempted and any
6608 matches are added to the results of the other actions.
6611 \fB\-A\fP \fIaction\fP
6612 The \fIaction\fP may be one of the following to generate a list of possible
6617 Alias names. May also be specified as \fB\-a\fP.
6620 Array variable names.
6623 \fBReadline\fP key binding names.
6626 Names of shell builtin commands. May also be specified as \fB\-b\fP.
6629 Command names. May also be specified as \fB\-c\fP.
6632 Directory names. May also be specified as \fB\-d\fP.
6635 Names of disabled shell builtins.
6638 Names of enabled shell builtins.
6641 Names of exported shell variables. May also be specified as \fB\-e\fP.
6644 File names. May also be specified as \fB\-f\fP.
6647 Names of shell functions.
6650 Group names. May also be specified as \fB\-g\fP.
6653 Help topics as accepted by the \fBhelp\fP builtin.
6656 Hostnames, as taken from the file specified by the
6662 Job names, if job control is active. May also be specified as \fB\-j\fP.
6665 Shell reserved words. May also be specified as \fB\-k\fP.
6668 Names of running jobs, if job control is active.
6671 Service names. May also be specified as \fB\-s\fP.
6674 Valid arguments for the \fB\-o\fP option to the \fBset\fP builtin.
6677 Shell option names as accepted by the \fBshopt\fP builtin.
6683 Names of stopped jobs, if job control is active.
6686 User names. May also be specified as \fB\-u\fP.
6689 Names of all shell variables. May also be specified as \fB\-v\fP.
6692 \fB\-G\fP \fIglobpat\fP
6693 The filename expansion pattern \fIglobpat\fP is expanded to generate
6694 the possible completions.
6696 \fB\-W\fP \fIwordlist\fP
6697 The \fIwordlist\fP is split using the characters in the
6700 special variable as delimiters, and each resultant word is expanded.
6701 The possible completions are the members of the resultant list which
6702 match the word being completed.
6704 \fB\-C\fP \fIcommand\fP
6705 \fIcommand\fP is executed in a subshell environment, and its output is
6706 used as the possible completions.
6708 \fB\-F\fP \fIfunction\fP
6709 The shell function \fIfunction\fP is executed in the current shell
6711 When it finishes, the possible completions are retrieved from the value
6717 \fB\-X\fP \fIfilterpat\fP
6718 \fIfilterpat\fP is a pattern as used for filename expansion.
6719 It is applied to the list of possible completions generated by the
6720 preceding options and arguments, and each completion matching
6721 \fIfilterpat\fP is removed from the list.
6722 A leading \fB!\fP in \fIfilterpat\fP negates the pattern; in this
6723 case, any completion not matching \fIfilterpat\fP is removed.
6725 \fB\-P\fP \fIprefix\fP
6726 \fIprefix\fP is added at the beginning of each possible completion
6727 after all other options have been applied.
6729 \fB\-S\fP \fIsuffix\fP
6730 \fIsuffix\fP is appended to each possible completion
6731 after all other options have been applied.
6734 The return value is true unless an invalid option is supplied, an option
6735 other than \fB\-p\fP or \fB\-r\fP is supplied without a \fIname\fP
6736 argument, an attempt is made to remove a completion specification for
6737 a \fIname\fP for which no specification exists, or
6738 an error occurs adding a completion specification.
6741 \fBcompopt\fP [\fB\-o\fP \fIoption\fP] [\fB+o\fP \fIoption\fP] [\fIname\fP]
6742 Modify completion options for each \fIname\fP according to the
6743 \fIoption\fPs, or for the
6744 currently-execution completion if no \fIname\fPs are supplied.
6745 If no \fIoption\fPs are given, display the completion options for each
6746 \fIname\fP or the current completion.
6747 The possible values of \fIoption\fP are those valid for the \fBcomplete\fP
6748 builtin described above.
6750 The return value is true unless an invalid option is supplied, an attempt
6751 is made to modify the options for a \fIname\fP for which no completion
6752 specification exists, or an output error occurs.
6754 \fBcontinue\fP [\fIn\fP]
6755 Resume the next iteration of the enclosing
6764 is specified, resume at the \fIn\fPth enclosing loop.
6768 is greater than the number of enclosing loops, the last enclosing loop
6769 (the ``top-level'' loop) is resumed.
6770 The return value is 0 unless \fIn\fP is not greater than or equal to 1.
6772 \fBdeclare\fP [\fB\-aAfFilrtux\fP] [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP] ...]
6775 \fBtypeset\fP [\fB\-aAfFilrtux\fP] [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP] ...]
6777 Declare variables and/or give them attributes.
6778 If no \fIname\fPs are given then display the values of variables.
6781 option will display the attributes and values of each
6785 is used with \fIname\fP arguments, additional options are ignored.
6788 is supplied without \fIname\fP arguments, it will display the attributes
6789 and values of all variables having the attributes specified by the
6791 If no other options are supplied with \fB\-p\fP, \fBdeclare\fP will display
6792 the attributes and values of all shell variables. The \fB\-f\fP option
6793 will restrict the display to shell functions.
6796 option inhibits the display of function definitions; only the
6797 function name and attributes are printed.
6798 If the \fBextdebug\fP shell option is enabled using \fBshopt\fP,
6799 the source file name and line number where the function is defined
6800 are displayed as well. The
6804 The following options can
6805 be used to restrict output to variables with the specified attribute or
6806 to give variables attributes:
6811 Each \fIname\fP is an indexed array variable (see
6816 Each \fIname\fP is an associative array variable (see
6821 Use function names only.
6824 The variable is treated as an integer; arithmetic evaluation (see
6826 .B "ARITHMETIC EVALUATION" ") "
6827 is performed when the variable is assigned a value.
6830 When the variable is assigned a value, all upper-case characters are
6831 converted to lower-case.
6832 The upper-case attribute is disabled.
6835 Make \fIname\fPs readonly. These names cannot then be assigned values
6836 by subsequent assignment statements or unset.
6839 Give each \fIname\fP the \fItrace\fP attribute.
6840 Traced functions inherit the \fBDEBUG\fP and \fBRETURN\fP traps from
6842 The trace attribute has no special meaning for variables.
6845 When the variable is assigned a value, all lower-case characters are
6846 converted to upper-case.
6847 The lower-case attribute is disabled.
6850 Mark \fIname\fPs for export to subsequent commands via the environment.
6853 Using `+' instead of `\-'
6854 turns off the attribute instead,
6855 with the exceptions that \fB+a\fP
6856 may not be used to destroy an array variable and \fB+r\fB will not
6857 remove the readonly attribute.
6858 When used in a function,
6860 \fIname\fP local, as with the
6863 If a variable name is followed by =\fIvalue\fP, the value of
6864 the variable is set to \fIvalue\fP.
6865 The return value is 0 unless an invalid option is encountered,
6866 an attempt is made to define a function using
6867 .if n ``\-f foo=bar'',
6868 .if t \f(CW\-f foo=bar\fP,
6869 an attempt is made to assign a value to a readonly variable,
6870 an attempt is made to assign a value to an array variable without
6871 using the compound assignment syntax (see
6873 above), one of the \fInames\fP is not a valid shell variable name,
6874 an attempt is made to turn off readonly status for a readonly variable,
6875 an attempt is made to turn off array status for an array variable,
6876 or an attempt is made to display a non-existent function with \fB\-f\fP.
6879 .B dirs [+\fIn\fP] [\-\fIn\fP] [\fB\-cplv\fP]
6880 Without options, displays the list of currently remembered directories.
6881 The default display is on a single line with directory names separated
6883 Directories are added to the list with the
6887 command removes entries from the list.
6892 Displays the \fIn\fPth entry counting from the left of the list
6895 when invoked without options, starting with zero.
6898 Displays the \fIn\fPth entry counting from the right of the list
6901 when invoked without options, starting with zero.
6904 Clears the directory stack by deleting all of the entries.
6907 Produces a longer listing; the default listing format uses a
6908 tilde to denote the home directory.
6911 Print the directory stack with one entry per line.
6914 Print the directory stack with one entry per line,
6915 prefixing each entry with its index in the stack.
6918 The return value is 0 unless an
6919 invalid option is supplied or \fIn\fP indexes beyond the end
6920 of the directory stack.
6923 \fBdisown\fP [\fB\-ar\fP] [\fB\-h\fP] [\fIjobspec\fP ...]
6924 Without options, each
6926 is removed from the table of active jobs.
6929 is not present, and neither \fB\-a\fB nor \fB\-r\fP is supplied,
6930 the shell's notion of the \fIcurrent job\fP is used.
6931 If the \fB\-h\fP option is given, each
6933 is not removed from the table, but is marked so that
6936 is not sent to the job if the shell receives a
6941 is present, and neither the
6945 option is supplied, the \fIcurrent job\fP is used.
6950 option means to remove or mark all jobs; the
6954 argument restricts operation to running jobs.
6955 The return value is 0 unless a
6957 does not specify a valid job.
6959 \fBecho\fP [\fB\-neE\fP] [\fIarg\fP ...]
6960 Output the \fIarg\fPs, separated by spaces, followed by a newline.
6961 The return status is always 0.
6962 If \fB\-n\fP is specified, the trailing newline is
6963 suppressed. If the \fB\-e\fP option is given, interpretation of
6964 the following backslash-escaped characters is enabled. The
6966 option disables the interpretation of these escape characters,
6967 even on systems where they are interpreted by default.
6968 The \fBxpg_echo\fP shell option may be used to
6969 dynamically determine whether or not \fBecho\fP expands these
6970 escape characters by default.
6972 does not interpret \fB\-\-\fP to mean the end of options.
6974 interprets the following escape sequences:
6985 suppress further output
7009 the eight-bit character whose value is the octal value \fInnn\fP
7010 (zero to three octal digits)
7013 the eight-bit character whose value is the hexadecimal value \fIHH\fP
7014 (one or two hex digits)
7018 \fBenable\fP [\fB\-a\fP] [\fB\-dnps\fP] [\fB\-f\fP \fIfilename\fP] [\fIname\fP ...]
7019 Enable and disable builtin shell commands.
7020 Disabling a builtin allows a disk command which has the same name
7021 as a shell builtin to be executed without specifying a full pathname,
7022 even though the shell normally searches for builtins before disk commands.
7023 If \fB\-n\fP is used, each \fIname\fP
7024 is disabled; otherwise,
7025 \fInames\fP are enabled. For example, to use the
7027 binary found via the
7030 instead of the shell builtin version, run
7031 .if t \f(CWenable -n test\fP.
7032 .if n ``enable -n test''.
7035 option means to load the new builtin command
7039 on systems that support dynamic loading. The
7041 option will delete a builtin previously loaded with
7043 If no \fIname\fP arguments are given, or if the
7045 option is supplied, a list of shell builtins is printed.
7046 With no other option arguments, the list consists of all enabled
7048 If \fB\-n\fP is supplied, only disabled builtins are printed.
7049 If \fB\-a\fP is supplied, the list printed includes all builtins, with an
7050 indication of whether or not each is enabled.
7051 If \fB\-s\fP is supplied, the output is restricted to the POSIX
7052 \fIspecial\fP builtins.
7053 The return value is 0 unless a
7055 is not a shell builtin or there is an error loading a new builtin
7056 from a shared object.
7058 \fBeval\fP [\fIarg\fP ...]
7059 The \fIarg\fPs are read and concatenated together into a single
7060 command. This command is then read and executed by the shell, and
7061 its exit status is returned as the value of
7065 or only null arguments,
7069 \fBexec\fP [\fB\-cl\fP] [\fB\-a\fP \fIname\fP] [\fIcommand\fP [\fIarguments\fP]]
7072 is specified, it replaces the shell.
7073 No new process is created. The
7075 become the arguments to \fIcommand\fP.
7079 the shell places a dash at the beginning of the zeroth argument passed to
7087 to be executed with an empty environment. If
7089 is supplied, the shell passes
7091 as the zeroth argument to the executed command. If
7093 cannot be executed for some reason, a non-interactive shell exits,
7094 unless the shell option
7096 is enabled, in which case it returns failure.
7097 An interactive shell returns failure if the file cannot be executed.
7100 is not specified, any redirections take effect in the current shell,
7101 and the return status is 0. If there is a redirection error, the
7104 \fBexit\fP [\fIn\fP]
7105 Cause the shell to exit
7106 with a status of \fIn\fP. If
7108 is omitted, the exit status
7109 is that of the last command executed.
7113 is executed before the shell terminates.
7115 \fBexport\fP [\fB\-fn\fP\^] [\fIname\fP[=\fIword\fP]] ...
7122 are marked for automatic export to the environment of
7123 subsequently executed commands. If the
7131 are given, or if the
7133 option is supplied, a list
7134 of all names that are exported in this shell is printed.
7137 option causes the export property to be removed from each
7139 If a variable name is followed by =\fIword\fP, the value of
7140 the variable is set to \fIword\fP.
7142 returns an exit status of 0 unless an invalid option is
7144 one of the \fInames\fP is not a valid shell variable name, or
7148 that is not a function.
7150 \fBfc\fP [\fB\-e\fP \fIename\fP] [\fB\-lnr\fP] [\fIfirst\fP] [\fIlast\fP]
7153 \fBfc\fP \fB\-s\fP [\fIpat\fP=\fIrep\fP] [\fIcmd\fP]
7155 Fix Command. In the first form, a range of commands from
7159 is selected from the history list.
7163 may be specified as a string (to locate the last command beginning
7164 with that string) or as a number (an index into the history list,
7165 where a negative number is used as an offset from the current
7168 is not specified it is set to
7169 the current command for listing (so that
7170 .if n ``fc \-l \-10''
7171 .if t \f(CWfc \-l \-10\fP
7172 prints the last 10 commands) and to
7177 is not specified it is set to the previous
7178 command for editing and \-16 for listing.
7183 the command numbers when listing. The
7185 option reverses the order of
7186 the commands. If the
7189 the commands are listed on
7190 standard output. Otherwise, the editor given by
7193 on a file containing those commands. If
7199 variable is used, and
7206 is not set. If neither variable is set,
7208 is used. When editing is complete, the edited commands are
7209 echoed and executed.
7211 In the second form, \fIcommand\fP is re-executed after each instance
7212 of \fIpat\fP is replaced by \fIrep\fP.
7213 A useful alias to use with this is
7214 .if n ``r="fc -s"'',
7215 .if t \f(CWr='fc \-s'\fP,
7219 runs the last command beginning with
7225 re-executes the last command.
7227 If the first form is used, the return value is 0 unless an invalid
7228 option is encountered or
7232 specify history lines out of range.
7235 option is supplied, the return value is the value of the last
7236 command executed or failure if an error occurs with the temporary
7237 file of commands. If the second form is used, the return status
7238 is that of the command re-executed, unless
7240 does not specify a valid history line, in which case
7244 \fBfg\fP [\fIjobspec\fP]
7247 in the foreground, and make it the current job.
7250 is not present, the shell's notion of the \fIcurrent job\fP is used.
7251 The return value is that of the command placed into the foreground,
7252 or failure if run when job control is disabled or, when run with
7253 job control enabled, if
7255 does not specify a valid job or
7257 specifies a job that was started without job control.
7259 \fBgetopts\fP \fIoptstring\fP \fIname\fP [\fIargs\fP]
7261 is used by shell procedures to parse positional parameters.
7263 contains the option characters to be recognized; if a character
7264 is followed by a colon, the option is expected to have an
7265 argument, which should be separated from it by white space.
7266 The colon and question mark characters may not be used as
7268 Each time it is invoked,
7270 places the next option in the shell variable
7274 if it does not exist,
7275 and the index of the next argument to be processed into the
7281 is initialized to 1 each time the shell or a shell script
7282 is invoked. When an option requires an argument,
7284 places that argument into the variable
7287 The shell does not reset
7290 automatically; it must be manually reset between multiple
7293 within the same shell invocation if a new set of parameters
7296 When the end of options is encountered, \fBgetopts\fP exits with a
7297 return value greater than zero.
7298 \fBOPTIND\fP is set to the index of the first non-option argument,
7299 and \fBname\fP is set to ?.
7302 normally parses the positional parameters, but if more arguments are
7306 parses those instead.
7309 can report errors in two ways. If the first character of
7313 error reporting is used. In normal operation diagnostic messages
7314 are printed when invalid options or missing option arguments are
7319 is set to 0, no error messages will be displayed, even if the first
7324 If an invalid option is seen,
7329 prints an error message and unsets
7335 the option character found is placed in
7338 and no diagnostic message is printed.
7340 If a required argument is not found, and
7343 a question mark (\^\fB?\fP\^) is placed in
7347 is unset, and a diagnostic message is printed.
7350 is silent, then a colon (\^\fB:\fP\^) is placed in
7355 is set to the option character found.
7358 returns true if an option, specified or unspecified, is found.
7359 It returns false if the end of options is encountered or an
7362 \fBhash\fP [\fB\-lr\fP] [\fB\-p\fP \fIfilename\fP] [\fB\-dt\fP] [\fIname\fP]
7365 the full file name of the command is determined by searching
7371 option is supplied, no path search is performed, and
7373 is used as the full file name of the command.
7376 option causes the shell to forget all
7377 remembered locations.
7380 option causes the shell to forget the remembered location of each \fIname\fP.
7383 option is supplied, the full pathname to which each \fIname\fP corresponds
7384 is printed. If multiple \fIname\fP arguments are supplied with \fB\-t\fP,
7385 the \fIname\fP is printed before the hashed full pathname.
7388 option causes output to be displayed in a format that may be reused as input.
7389 If no arguments are given, or if only \fB\-l\fP is supplied,
7390 information about remembered commands is printed.
7391 The return status is true unless a
7393 is not found or an invalid option is supplied.
7395 \fBhelp\fP [\fB\-dms\fP] [\fIpattern\fP]
7396 Display helpful information about builtin commands. If
7400 gives detailed help on all commands matching
7402 otherwise help for all the builtins and shell control structures
7408 Display a short description of each \fIpattern\fP
7411 Display the description of each \fIpattern\fP in a manpage-like format
7414 Display only a short usage synopsis for each \fIpattern\fP
7417 The return status is 0 unless no command matches
7420 \fBhistory [\fIn\fP]
7423 \fBhistory\fP \fB\-c\fP
7425 \fBhistory \-d\fP \fIoffset\fP
7427 \fBhistory\fP \fB\-anrw\fP [\fIfilename\fP]
7429 \fBhistory\fP \fB\-p\fP \fIarg\fP [\fIarg ...\fP]
7431 \fBhistory\fP \fB\-s\fP \fIarg\fP [\fIarg ...\fP]
7433 With no options, display the command
7434 history list with line numbers. Lines listed
7437 have been modified. An argument of
7442 If the shell variable \fBHISTTIMEFORMAT\fP is set and not null,
7443 it is used as a format string for \fIstrftime\fP(3) to display
7444 the time stamp associated with each displayed history entry.
7445 No intervening blank is printed between the formatted time stamp
7446 and the history line.
7447 If \fIfilename\fP is supplied, it is used as the
7448 name of the history file; if not, the value of
7451 is used. Options, if supplied, have the following meanings:
7456 Clear the history list by deleting all the entries.
7458 \fB\-d\fP \fIoffset\fP
7459 Delete the history entry at position \fIoffset\fP.
7462 Append the ``new'' history lines (history lines entered since the
7463 beginning of the current \fBbash\fP session) to the history file.
7466 Read the history lines not already read from the history
7467 file into the current history list. These are lines
7468 appended to the history file since the beginning of the
7469 current \fBbash\fP session.
7472 Read the contents of the history file
7473 and use them as the current history.
7476 Write the current history to the history file, overwriting the
7477 history file's contents.
7480 Perform history substitution on the following \fIargs\fP and display
7481 the result on the standard output.
7482 Does not store the results in the history list.
7483 Each \fIarg\fP must be quoted to disable normal history expansion.
7488 in the history list as a single entry. The last command in the
7489 history list is removed before the
7494 If the \fBHISTTIMEFORMAT\fP is set, the time stamp information
7495 associated with each history entry is written to the history file,
7496 marked with the history comment character.
7497 When the history file is read, lines beginning with the history
7498 comment character followed immediately by a digit are interpreted
7499 as timestamps for the previous history line.
7500 The return value is 0 unless an invalid option is encountered, an
7501 error occurs while reading or writing the history file, an invalid
7502 \fIoffset\fP is supplied as an argument to \fB\-d\fP, or the
7503 history expansion supplied as an argument to \fB\-p\fP fails.
7506 \fBjobs\fP [\fB\-lnprs\fP] [ \fIjobspec\fP ... ]
7509 \fBjobs\fP \fB\-x\fP \fIcommand\fP [ \fIargs\fP ... ]
7511 The first form lists the active jobs. The options have the following
7518 in addition to the normal information.
7521 List only the process ID of the job's process group
7525 Display information only about jobs that have changed status since
7526 the user was last notified of their status.
7529 Restrict output to running jobs.
7532 Restrict output to stopped jobs.
7537 is given, output is restricted to information about that job.
7538 The return status is 0 unless an invalid option is encountered
7553 with the corresponding process group ID, and executes
7557 returning its exit status.
7560 \fBkill\fP [\fB\-s\fP \fIsigspec\fP | \fB\-n\fP \fIsignum\fP | \fB\-\fP\fIsigspec\fP] [\fIpid\fP | \fIjobspec\fP] ...
7563 \fBkill\fP \fB\-l\fP [\fIsigspec\fP | \fIexit_status\fP]
7565 Send the signal named by
7569 to the processes named by
7574 is either a case-insensitive signal name such as
7577 (with or without the
7580 prefix) or a signal number;
7585 is not present, then
7591 lists the signal names.
7592 If any arguments are supplied when
7594 is given, the names of the signals corresponding to the arguments are
7595 listed, and the return status is 0.
7596 The \fIexit_status\fP argument to
7598 is a number specifying either a signal number or the exit status of
7599 a process terminated by a signal.
7601 returns true if at least one signal was successfully sent, or false
7602 if an error occurs or an invalid option is encountered.
7604 \fBlet\fP \fIarg\fP [\fIarg\fP ...]
7607 is an arithmetic expression to be evaluated (see
7609 .BR "ARITHMETIC EVALUATION" ).
7614 returns 1; 0 is returned otherwise.
7616 \fBlocal\fP [\fIoption\fP] [\fIname\fP[=\fIvalue\fP] ...]
7617 For each argument, a local variable named
7619 is created, and assigned
7621 The \fIoption\fP can be any of the options accepted by \fBdeclare\fP.
7624 is used within a function, it causes the variable
7626 to have a visible scope restricted to that function and its children.
7629 writes a list of local variables to the standard output. It is
7632 when not within a function. The return status is 0 unless
7634 is used outside a function, an invalid
7637 \fIname\fP is a readonly variable.
7642 \fBmapfile\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]
7645 \fBreadarray\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]
7647 Read lines from the standard input into array variable
7649 or from file descriptor
7654 The variable \fBMAPFILE\fP is the default \fIarray\fP.
7655 Options, if supplied, have the following meanings:
7662 lines. If \fIcount\fP is 0, all lines are copied.
7669 The default index is 0.
7672 Discard the first \fIcount\fP lines read.
7675 Remove a trailing line from each line read.
7678 Read lines from file descriptor \fIfd\fP instead of the standard input.
7683 each time \fIquantum\fP lines are read. The \fB\-c\fP option specifies
7687 Specify the number of lines read between each call to
7693 is specified without
7695 the default quantum is 5000.
7696 When \fIcallback\fP is evaluated, it is supplied the index of the next
7697 array element to be assigned as an additional argument.
7698 \fIcallback\fP is evaluated after the line is read but before the
7699 array element is assigned.
7701 If not supplied with an explicit origin, \fBmapfile\fP will clear \fIarray\fP
7702 before assigning to it.
7704 \fBmapfile\fP returns successfully unless an invalid option or option
7705 argument is supplied, or \fIarray\fP is invalid or unassignable.
7708 \fBpopd\fP [\-\fBn\fP] [+\fIn\fP] [\-\fIn\fP]
7709 Removes entries from the directory stack. With no arguments,
7710 removes the top directory from the stack, and performs a
7712 to the new top directory.
7713 Arguments, if supplied, have the following meanings:
7718 Suppresses the normal change of directory when removing directories
7719 from the stack, so that only the stack is manipulated.
7722 Removes the \fIn\fPth entry counting from the left of the list
7725 starting with zero. For example:
7727 .if t \f(CWpopd +0\fP
7728 removes the first directory,
7730 .if t \f(CWpopd +1\fP
7734 Removes the \fIn\fPth entry counting from the right of the list
7737 starting with zero. For example:
7739 .if t \f(CWpopd -0\fP
7740 removes the last directory,
7742 .if t \f(CWpopd -1\fP
7748 command is successful, a
7750 is performed as well, and the return status is 0.
7752 returns false if an invalid option is encountered, the directory stack
7753 is empty, a non-existent directory stack entry is specified, or the
7754 directory change fails.
7757 \fBprintf\fP [\fB\-v\fP \fIvar\fP] \fIformat\fP [\fIarguments\fP]
7758 Write the formatted \fIarguments\fP to the standard output under the
7759 control of the \fIformat\fP.
7760 The \fIformat\fP is a character string which contains three types of objects:
7761 plain characters, which are simply copied to standard output, character
7762 escape sequences, which are converted and copied to the standard output, and
7763 format specifications, each of which causes printing of the next successive
7765 In addition to the standard \fIprintf\fP(1) formats, \fB%b\fP causes
7766 \fBprintf\fP to expand backslash escape sequences in the corresponding
7767 \fIargument\fP (except that \fB\ec\fP terminates output, backslashes in
7768 \fB\e\(aq\fP, \fB\e"\fP, and \fB\e?\fP are not removed, and octal escapes
7769 beginning with \fB\e0\fP may contain up to four digits),
7770 and \fB%q\fP causes \fBprintf\fP to output the corresponding
7771 \fIargument\fP in a format that can be reused as shell input.
7773 The \fB\-v\fP option causes the output to be assigned to the variable
7774 \fIvar\fP rather than being printed to the standard output.
7776 The \fIformat\fP is reused as necessary to consume all of the \fIarguments\fP.
7777 If the \fIformat\fP requires more \fIarguments\fP than are supplied, the
7778 extra format specifications behave as if a zero value or null string, as
7779 appropriate, had been supplied. The return value is zero on success,
7780 non-zero on failure.
7782 \fBpushd\fP [\fB\-n\fP] [+\fIn\fP] [\-\fIn\fP]
7785 \fBpushd\fP [\fB\-n\fP] [\fIdir\fP]
7787 Adds a directory to the top of the directory stack, or rotates
7788 the stack, making the new top of the stack the current working
7789 directory. With no arguments, exchanges the top two directories
7790 and returns 0, unless the directory stack is empty.
7791 Arguments, if supplied, have the following meanings:
7796 Suppresses the normal change of directory when adding directories
7797 to the stack, so that only the stack is manipulated.
7800 Rotates the stack so that the \fIn\fPth directory
7801 (counting from the left of the list shown by
7807 Rotates the stack so that the \fIn\fPth directory
7808 (counting from the right of the list shown by
7810 starting with zero) is at the top.
7815 to the directory stack at the top, making it the
7816 new current working directory.
7821 command is successful, a
7823 is performed as well.
7824 If the first form is used,
7826 returns 0 unless the cd to
7828 fails. With the second form,
7830 returns 0 unless the directory stack is empty,
7831 a non-existent directory stack element is specified,
7832 or the directory change to the specified new current directory
7836 \fBpwd\fP [\fB\-LP\fP]
7837 Print the absolute pathname of the current working directory.
7838 The pathname printed contains no symbolic links if the
7840 option is supplied or the
7844 builtin command is enabled.
7847 option is used, the pathname printed may contain symbolic links.
7848 The return status is 0 unless an error occurs while
7849 reading the name of the current directory or an
7850 invalid option is supplied.
7852 \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\-p\fP \fIprompt\fP] [\fB\-t\fP \fItimeout\fP] [\fB\-u\fP \fIfd\fP] [\fIname\fP ...]
7853 One line is read from the standard input, or from the file descriptor
7854 \fIfd\fP supplied as an argument to the \fB\-u\fP option, and the first word
7855 is assigned to the first
7857 the second word to the second
7859 and so on, with leftover words and their intervening separators assigned
7862 If there are fewer words read from the input stream than names,
7863 the remaining names are assigned empty values.
7867 are used to split the line into words.
7868 The backslash character (\fB\e\fP) may be used to remove any special
7869 meaning for the next character read and for line continuation.
7870 Options, if supplied, have the following meanings:
7875 The words are assigned to sequential indices
7876 of the array variable
7880 is unset before any new values are assigned.
7881 Other \fIname\fP arguments are ignored.
7884 The first character of \fIdelim\fP is used to terminate the input line,
7885 rather than newline.
7888 If the standard input
7889 is coming from a terminal,
7894 above) is used to obtain the line.
7895 Readline uses the current (or default, if line editing was not previously
7896 active) editing settings.
7901 is being used to read the line, \fItext\fP is placed into the editing
7902 buffer before editing begins.
7905 \fBread\fP returns after reading \fInchars\fP characters rather than
7906 waiting for a complete line of input.
7909 Display \fIprompt\fP on standard error, without a
7910 trailing newline, before attempting to read any input. The prompt
7911 is displayed only if input is coming from a terminal.
7914 Backslash does not act as an escape character.
7915 The backslash is considered to be part of the line.
7916 In particular, a backslash-newline pair may not be used as a line
7920 Silent mode. If input is coming from a terminal, characters are
7923 .B \-t \fItimeout\fP
7924 Cause \fBread\fP to time out and return failure if a complete line of
7925 input is not read within \fItimeout\fP seconds.
7926 \fItimeout\fP may be a decimal number with a fractional portion following
7928 This option is only effective if \fBread\fP is reading input from a
7929 terminal, pipe, or other special file; it has no effect when reading
7931 If \fItimeout\fP is 0, \fBread\fP returns success if input is available on
7932 the specified file descriptor, failure otherwise.
7933 The exit status is greater than 128 if the timeout is exceeded.
7936 Read input from file descriptor \fIfd\fP.
7941 are supplied, the line read is assigned to the variable
7944 The return code is zero, unless end-of-file is encountered, \fBread\fP
7945 times out (in which case the return code is greater than 128), or an
7946 invalid file descriptor is supplied as the argument to \fB\-u\fP.
7949 \fBreadonly\fP [\fB\-aApf\fP] [\fIname\fP[=\fIword\fP] ...]
7952 \fInames\fP are marked readonly; the values of these
7954 may not be changed by subsequent assignment.
7957 option is supplied, the functions corresponding to the
7962 option restricts the variables to indexed arrays; the
7964 option restricts the variables to associative arrays.
7967 arguments are given, or if the
7969 option is supplied, a list of all readonly names is printed.
7972 option causes output to be displayed in a format that
7973 may be reused as input.
7974 If a variable name is followed by =\fIword\fP, the value of
7975 the variable is set to \fIword\fP.
7976 The return status is 0 unless an invalid option is encountered,
7979 is not a valid shell variable name, or
7983 that is not a function.
7985 \fBreturn\fP [\fIn\fP]
7986 Causes a function to exit with the return value specified by
7990 is omitted, the return status is that of the last command
7991 executed in the function body. If used outside a function,
7992 but during execution of a script by the
7994 (\fBsource\fP) command, it causes the shell to stop executing
7995 that script and return either
7997 or the exit status of the last command executed within the
7998 script as the exit status of the script. If used outside a
7999 function and not during execution of a script by \fB.\fP\^,
8000 the return status is false.
8001 Any command associated with the \fBRETURN\fP trap is executed
8002 before execution resumes after the function or script.
8004 \fBset\fP [\fB\-\-abefhkmnptuvxBCEHPT\fP] [\fB\-o\fP \fIoption\fP] [\fIarg\fP ...]
8007 \fBset\fP [\fB+abefhkmnptuvxBCEHPT\fP] [\fB+o\fP \fIoption\fP] [\fIarg\fP ...]
8009 Without options, the name and value of each shell variable are displayed
8010 in a format that can be reused as input
8011 for setting or resetting the currently-set variables.
8012 Read-only variables cannot be reset.
8013 In \fIposix mode\fP, only shell variables are listed.
8014 The output is sorted according to the current locale.
8015 When options are specified, they set or unset shell attributes.
8016 Any arguments remaining after option processing are treated
8017 as values for the positional parameters and are assigned, in order, to
8022 Options, if specified, have the following meanings:
8027 Automatically mark variables and functions which are modified or
8028 created for export to the environment of subsequent commands.
8031 Report the status of terminated background jobs
8032 immediately, rather than before the next primary prompt. This is
8033 effective only when job control is enabled.
8036 Exit immediately if a \fIpipeline\fP (which may consist of a single
8037 \fIsimple command\fP), a \fIsubshell\fP command enclosed in parentheses,
8038 or one of the commands executed as part of a command list enclosed
8042 above) exits with a non-zero status.
8043 The shell does not exit if the
8044 command that fails is part of the command list immediately following a
8049 part of the test following the
8053 reserved words, part of any command executed in a
8057 list except the command following the final \fB&&\fP or \fB\(bv\(bv\fP,
8058 any command in a pipeline but the last,
8059 or if the command's return value is
8062 A trap on \fBERR\fP, if set, is executed before the shell exits.
8063 This option applies to the shell environment and each subshell environment
8065 .B "COMMAND EXECUTION ENVIRONMENT"
8066 above), and may cause
8067 subshells to exit before executing all the commands in the subshell.
8070 Disable pathname expansion.
8073 Remember the location of commands as they are looked up for execution.
8074 This is enabled by default.
8077 All arguments in the form of assignment statements
8078 are placed in the environment for a command, not just
8079 those that precede the command name.
8082 Monitor mode. Job control is enabled. This option is on
8083 by default for interactive shells on systems that support
8087 above). Background processes run in a separate process
8088 group and a line containing their exit status is printed
8089 upon their completion.
8092 Read commands but do not execute them. This may be used to
8093 check a shell script for syntax errors. This is ignored by
8096 .B \-o \fIoption\-name\fP
8097 The \fIoption\-name\fP can be one of the following:
8109 Use an emacs-style command line editing interface. This is enabled
8110 by default when the shell is interactive, unless the shell is started
8114 This also affects the editing interface used for \fBread \-e\fP.
8137 Enable command history, as described above under
8140 This option is on by default in interactive shells.
8143 The effect is as if the shell command
8144 .if t \f(CWIGNOREEOF=10\fP
8145 .if n ``IGNOREEOF=10''
8191 If set, the return value of a pipeline is the value of the last
8192 (rightmost) command to exit with a non-zero status, or zero if all
8193 commands in the pipeline exit successfully.
8194 This option is disabled by default.
8197 Change the behavior of
8199 where the default operation differs
8200 from the POSIX standard to match the standard (\fIposix mode\fP).
8211 Use a vi-style command line editing interface.
8212 This also affects the editing interface used for \fBread \-e\fP.
8221 is supplied with no \fIoption\-name\fP, the values of the current options are
8225 is supplied with no \fIoption\-name\fP, a series of
8227 commands to recreate the current option settings is displayed on
8228 the standard output.
8234 mode. In this mode, the
8240 files are not processed, shell functions are not inherited from the
8241 environment, and the
8247 variables, if they appear in the environment, are ignored.
8248 If the shell is started with the effective user (group) id not equal to the
8249 real user (group) id, and the \fB\-p\fP option is not supplied, these actions
8250 are taken and the effective user id is set to the real user id.
8251 If the \fB\-p\fP option is supplied at startup, the effective user id is
8253 Turning this option off causes the effective user
8254 and group ids to be set to the real user and group ids.
8257 Exit after reading and executing one command.
8260 Treat unset variables and parameters other than the special
8261 parameters "@" and "*" as an error when performing
8262 parameter expansion. If expansion is attempted on an
8263 unset variable or parameter, the shell prints an error message, and,
8264 if not interactive, exits with a non-zero status.
8267 Print shell input lines as they are read.
8270 After expanding each \fIsimple command\fP,
8271 \fBfor\fP command, \fBcase\fP command, \fBselect\fP command, or
8272 arithmetic \fBfor\fP command, display the expanded value of
8275 followed by the command and its expanded arguments
8276 or associated word list.
8279 The shell performs brace expansion (see
8281 above). This is on by default.
8286 does not overwrite an existing file with the
8291 redirection operators. This may be overridden when
8292 creating output files by using the redirection operator
8298 If set, any trap on \fBERR\fP is inherited by shell functions, command
8299 substitutions, and commands executed in a subshell environment.
8300 The \fBERR\fP trap is normally not inherited in such cases.
8305 style history substitution. This option is on by
8306 default when the shell is interactive.
8309 If set, the shell does not follow symbolic links when executing
8312 that change the current working directory. It uses the
8313 physical directory structure instead. By default,
8315 follows the logical chain of directories when performing commands
8316 which change the current directory.
8319 If set, any traps on \fBDEBUG\fP and \fBRETURN\fP are inherited by shell
8320 functions, command substitutions, and commands executed in a
8321 subshell environment.
8322 The \fBDEBUG\fP and \fBRETURN\fP traps are normally not inherited
8326 If no arguments follow this option, then the positional parameters are
8327 unset. Otherwise, the positional parameters are set to the
8328 \fIarg\fPs, even if some of them begin with a
8332 Signal the end of options, cause all remaining \fIarg\fPs to be
8333 assigned to the positional parameters. The
8337 options are turned off.
8338 If there are no \fIarg\fPs,
8339 the positional parameters remain unchanged.
8342 The options are off by default unless otherwise noted.
8343 Using + rather than \- causes these options to be turned off.
8344 The options can also be specified as arguments to an invocation of
8346 The current set of options may be found in
8348 The return status is always true unless an invalid option is encountered.
8351 \fBshift\fP [\fIn\fP]
8352 The positional parameters from \fIn\fP+1 ... are renamed to
8355 Parameters represented by the numbers \fB$#\fP
8356 down to \fB$#\fP\-\fIn\fP+1 are unset.
8358 must be a non-negative number less than or equal to \fB$#\fP.
8361 is 0, no parameters are changed.
8364 is not given, it is assumed to be 1.
8367 is greater than \fB$#\fP, the positional parameters are not changed.
8368 The return status is greater than zero if
8372 or less than zero; otherwise 0.
8374 \fBshopt\fP [\fB\-pqsu\fP] [\fB\-o\fP] [\fIoptname\fP ...]
8375 Toggle the values of variables controlling optional shell behavior.
8376 With no options, or with the
8378 option, a list of all settable options is displayed, with
8379 an indication of whether or not each is set.
8380 The \fB\-p\fP option causes output to be displayed in a form that
8381 may be reused as input.
8382 Other options have the following meanings:
8387 Enable (set) each \fIoptname\fP.
8390 Disable (unset) each \fIoptname\fP.
8393 Suppresses normal output (quiet mode); the return status indicates
8394 whether the \fIoptname\fP is set or unset.
8395 If multiple \fIoptname\fP arguments are given with
8397 the return status is zero if all \fIoptnames\fP are enabled; non-zero
8401 Restricts the values of \fIoptname\fP to be those defined for the
8412 is used with no \fIoptname\fP arguments, the display is limited to
8413 those options which are set or unset, respectively.
8414 Unless otherwise noted, the \fBshopt\fP options are disabled (unset)
8417 The return status when listing options is zero if all \fIoptnames\fP
8418 are enabled, non-zero otherwise. When setting or unsetting options,
8419 the return status is zero unless an \fIoptname\fP is not a valid shell
8422 The list of \fBshopt\fP options is:
8428 If set, a command name that is the name of a directory is executed as if
8429 it were the argument to the \fBcd\fP command.
8430 This option is only used by interactive shells.
8433 If set, an argument to the
8435 builtin command that
8436 is not a directory is assumed to be the name of a variable whose
8437 value is the directory to change to.
8440 If set, minor errors in the spelling of a directory component in a
8442 command will be corrected.
8443 The errors checked for are transposed characters,
8444 a missing character, and one character too many.
8445 If a correction is found, the corrected file name is printed,
8446 and the command proceeds.
8447 This option is only used by interactive shells.
8450 If set, \fBbash\fP checks that a command found in the hash
8451 table exists before trying to execute it. If a hashed command no
8452 longer exists, a normal path search is performed.
8455 If set, \fBbash\fP lists the status of any stopped and running jobs before
8456 exiting an interactive shell. If any jobs are running, this causes
8457 the exit to be deferred until a second exit is attempted without an
8458 intervening command (see \fBJOB CONTROL\fP above). The shell always
8459 postpones exiting if any jobs are stopped.
8462 If set, \fBbash\fP checks the window size after each command
8463 and, if necessary, updates the values of
8473 attempts to save all lines of a multiple-line
8474 command in the same history entry. This allows
8475 easy re-editing of multi-line commands.
8480 changes its behavior to that of version 3.1 with respect to quoted
8481 arguments to the conditional command's =~ operator.
8486 attempts spelling correction on directory names during word completion
8487 if the directory name initially supplied does not exist.
8492 includes filenames beginning with a `.' in the results of pathname
8496 If set, a non-interactive shell will not exit if
8497 it cannot execute the file specified as an argument to the
8499 builtin command. An interactive shell does not exit if
8504 If set, aliases are expanded as described above under
8507 This option is enabled by default for interactive shells.
8510 If set, behavior intended for use by debuggers is enabled:
8514 The \fB\-F\fP option to the \fBdeclare\fP builtin displays the source
8515 file name and line number corresponding to each function name supplied
8519 If the command run by the \fBDEBUG\fP trap returns a non-zero value, the
8520 next command is skipped and not executed.
8523 If the command run by the \fBDEBUG\fP trap returns a value of 2, and the
8524 shell is executing in a subroutine (a shell function or a shell script
8525 executed by the \fB.\fP or \fBsource\fP builtins), a call to
8526 \fBreturn\fP is simulated.
8529 \fBBASH_ARGC\fP and \fBBASH_ARGV\fP are updated as described in their
8533 Function tracing is enabled: command substitution, shell functions, and
8534 subshells invoked with \fB(\fP \fIcommand\fP \fB)\fP inherit the
8535 \fBDEBUG\fP and \fBRETURN\fP traps.
8538 Error tracing is enabled: command substitution, shell functions, and
8539 subshells invoked with \fB(\fP \fIcommand\fP \fB)\fP inherit the
8544 If set, the extended pattern matching features described above under
8545 \fBPathname Expansion\fP are enabled.
8548 If set, \fB$\fP\(aq\fIstring\fP\(aq and \fB$\fP"\fIstring\fP" quoting is
8549 performed within \fB${\fP\fIparameter\fP\fB}\fP expansions
8550 enclosed in double quotes. This option is enabled by default.
8553 If set, patterns which fail to match filenames during pathname expansion
8554 result in an expansion error.
8557 If set, the suffixes specified by the \fBFIGNORE\fP shell variable
8558 cause words to be ignored when performing word completion even if
8559 the ignored words are the only possible completions.
8562 \fBSHELL VARIABLES\fP
8563 above for a description of \fBFIGNORE\fP.
8564 This option is enabled by default.
8567 If set, the pattern \fB**\fP used in a filename expansion context will
8568 match a files and zero or more directories and subdirectories.
8569 If the pattern is followed by a \fB/\fP, only directories and
8570 subdirectories match.
8573 If set, shell error messages are written in the standard GNU error
8577 If set, the history list is appended to the file named by the value
8580 variable when the shell exits, rather than overwriting the file.
8585 is being used, a user is given the opportunity to re-edit a
8586 failed history substitution.
8591 is being used, the results of history substitution are not immediately
8592 passed to the shell parser. Instead, the resulting line is loaded into
8593 the \fBreadline\fP editing buffer, allowing further modification.
8598 is being used, \fBbash\fP will attempt to perform hostname completion when a
8599 word containing a \fB@\fP is being completed (see
8605 This is enabled by default.
8608 If set, \fBbash\fP will send
8611 to all jobs when an interactive login shell exits.
8613 .B interactive_comments
8614 If set, allow a word beginning with
8616 to cause that word and all remaining characters on that
8617 line to be ignored in an interactive shell (see
8620 above). This option is enabled by default.
8625 option is enabled, multi-line commands are saved to the history with
8626 embedded newlines rather than using semicolon separators where possible.
8629 The shell sets this option if it is started as a login shell (see
8633 The value may not be changed.
8636 If set, and a file that \fBbash\fP is checking for mail has been
8637 accessed since the last time it was checked, the message ``The mail in
8638 \fImailfile\fP has been read'' is displayed.
8640 .B no_empty_cmd_completion
8645 will not attempt to search the \fBPATH\fP for possible completions when
8646 completion is attempted on an empty line.
8651 matches filenames in a case\-insensitive fashion when performing pathname
8653 .B Pathname Expansion
8659 matches patterns in a case\-insensitive fashion when performing matching
8660 while executing \fBcase\fP or \fB[[\fP conditional commands.
8665 allows patterns which match no
8667 .B Pathname Expansion
8669 to expand to a null string, rather than themselves.
8672 If set, the programmable completion facilities (see
8673 \fBProgrammable Completion\fP above) are enabled.
8674 This option is enabled by default.
8677 If set, prompt strings undergo
8678 parameter expansion, command substitution, arithmetic
8679 expansion, and quote removal after being expanded as described in
8682 above. This option is enabled by default.
8685 The shell sets this option if it is started in restricted mode (see
8687 .B "RESTRICTED SHELL"
8689 The value may not be changed.
8690 This is not reset when the startup files are executed, allowing
8691 the startup files to discover whether or not a shell is restricted.
8696 builtin prints an error message when the shift count exceeds the
8697 number of positional parameters.
8701 \fBsource\fP (\fB.\fP) builtin uses the value of
8704 to find the directory containing the file supplied as an argument.
8705 This option is enabled by default.
8708 If set, the \fBecho\fP builtin expands backslash-escape sequences
8712 \fBsuspend\fP [\fB\-f\fP]
8713 Suspend the execution of this shell until it receives a
8716 signal. A login shell cannot be suspended; the
8718 option can be used to override this and force the suspension.
8719 The return status is 0 unless the shell is a login shell and
8721 is not supplied, or if job control is not enabled.
8723 \fBtest\fP \fIexpr\fP
8726 \fB[\fP \fIexpr\fP \fB]\fP
8727 Return a status of 0 or 1 depending on
8728 the evaluation of the conditional expression
8730 Each operator and operand must be a separate argument.
8731 Expressions are composed of the primaries described above under
8733 .BR "CONDITIONAL EXPRESSIONS" .
8734 \fBtest\fP does not accept any options, nor does it accept and ignore
8735 an argument of \fB\-\-\fP as signifying the end of options.
8738 Expressions may be combined using the following operators, listed
8739 in decreasing order of precedence.
8740 The evaluation depends on the number of arguments; see below.
8750 Returns the value of \fIexpr\fP.
8751 This may be used to override the normal precedence of operators.
8753 \fIexpr1\fP \-\fBa\fP \fIexpr2\fP
8760 \fIexpr1\fP \-\fBo\fP \fIexpr2\fP
8768 \fBtest\fP and \fB[\fP evaluate conditional
8769 expressions using a set of rules based on the number of arguments.
8775 The expression is false.
8778 The expression is true if and only if the argument is not null.
8781 If the first argument is \fB!\fP, the expression is true if and
8782 only if the second argument is null.
8783 If the first argument is one of the unary conditional operators listed above
8786 .BR "CONDITIONAL EXPRESSIONS" ,
8787 the expression is true if the unary test is true.
8788 If the first argument is not a valid unary conditional operator, the expression
8792 If the second argument is one of the binary conditional operators listed above
8795 .BR "CONDITIONAL EXPRESSIONS" ,
8796 the result of the expression is the result of the binary test using
8797 the first and third arguments as operands.
8798 The \fB\-a\fP and \fB\-o\fP operators are considered binary operators
8799 when there are three arguments.
8800 If the first argument is \fB!\fP, the value is the negation of
8801 the two-argument test using the second and third arguments.
8802 If the first argument is exactly \fB(\fP and the third argument is
8803 exactly \fB)\fP, the result is the one-argument test of the second
8805 Otherwise, the expression is false.
8808 If the first argument is \fB!\fP, the result is the negation of
8809 the three-argument expression composed of the remaining arguments.
8810 Otherwise, the expression is parsed and evaluated according to
8811 precedence using the rules listed above.
8814 The expression is parsed and evaluated according to precedence
8815 using the rules listed above.
8820 Print the accumulated user and system times for the shell and
8821 for processes run from the shell. The return status is 0.
8823 \fBtrap\fP [\fB\-lp\fP] [[\fIarg\fP] \fIsigspec\fP ...]
8826 is to be read and executed when the shell receives
8831 is absent (and there is a single \fIsigspec\fP) or
8833 each specified signal is
8834 reset to its original disposition (the value it had
8835 upon entrance to the shell).
8838 is the null string the signal specified by each
8840 is ignored by the shell and by the commands it invokes.
8845 has been supplied, then the trap commands associated with each
8848 If no arguments are supplied or if only
8852 prints the list of commands associated with each signal.
8855 option causes the shell to print a list of signal names and
8856 their corresponding numbers.
8860 a signal name defined in <\fIsignal.h\fP>, or a signal number.
8861 Signal names are case insensitive and the SIG prefix is optional.
8869 is executed on exit from the shell.
8877 is executed before every \fIsimple command\fP, \fIfor\fP command,
8878 \fIcase\fP command, \fIselect\fP command, every arithmetic \fIfor\fP
8879 command, and before the first command executes in a shell function (see
8883 Refer to the description of the \fBextdebug\fP option to the
8884 \fBshopt\fP builtin for details of its effect on the \fBDEBUG\fP trap.
8892 is executed whenever a simple command has a non\-zero exit status,
8893 subject to the following conditions.
8897 trap is not executed if the failed
8898 command is part of the command list immediately following a
8903 part of the test in an
8905 statement, part of a command executed in a
8909 list, or if the command's return value is
8912 These are the same conditions obeyed by the \fBerrexit\fP option.
8920 is executed each time a shell function or a script executed with the
8921 \fB.\fP or \fBsource\fP builtins finishes executing.
8922 Signals ignored upon entry to the shell cannot be trapped or reset.
8923 Trapped signals that are not being ignored are reset to their original
8924 values in a child process when it is created.
8925 The return status is false if any
8927 is invalid; otherwise
8931 \fBtype\fP [\fB\-aftpP\fP] \fIname\fP [\fIname\fP ...]
8935 would be interpreted if used as a command name.
8940 prints a string which is one of
8949 is an alias, shell reserved word, function, builtin, or disk file,
8953 is not found, then nothing is printed, and an exit status of false
8959 either returns the name of the disk file
8960 that would be executed if
8962 were specified as a command name,
8964 .if t \f(CWtype -t name\fP
8965 .if n ``type -t name''
8973 search for each \fIname\fP, even if
8974 .if t \f(CWtype -t name\fP
8975 .if n ``type -t name''
8978 If a command is hashed,
8982 print the hashed value, not necessarily the file that appears
8990 prints all of the places that contain
8993 This includes aliases and functions,
8996 option is not also used.
8997 The table of hashed commands is not consulted
9002 option suppresses shell function lookup, as with the \fBcommand\fP builtin.
9004 returns true if all of the arguments are found, false if
9007 \fBulimit\fP [\fB\-HSTabcdefilmnpqrstuvx\fP [\fIlimit\fP]]
9008 Provides control over the resources available to the shell and to
9009 processes started by it, on systems that allow such control.
9010 The \fB\-H\fP and \fB\-S\fP options specify that the hard or soft limit is
9011 set for the given resource.
9012 A hard limit cannot be increased by a non-root user once it is set;
9013 a soft limit may be increased up to the value of the hard limit.
9014 If neither \fB\-H\fP nor \fB\-S\fP is specified, both the soft and hard
9018 can be a number in the unit specified for the resource
9019 or one of the special values
9024 which stand for the current hard limit, the current soft limit, and
9025 no limit, respectively.
9028 is omitted, the current value of the soft limit of the resource is
9029 printed, unless the \fB\-H\fP option is given. When more than one
9030 resource is specified, the limit name and unit are printed before the value.
9031 Other options are interpreted as follows:
9036 All current limits are reported
9039 The maximum socket buffer size
9042 The maximum size of core files created
9045 The maximum size of a process's data segment
9048 The maximum scheduling priority ("nice")
9051 The maximum size of files written by the shell and its children
9054 The maximum number of pending signals
9057 The maximum size that may be locked into memory
9060 The maximum resident set size (many systems do not honor this limit)
9063 The maximum number of open file descriptors (most systems do not
9064 allow this value to be set)
9067 The pipe size in 512-byte blocks (this may not be set)
9070 The maximum number of bytes in POSIX message queues
9073 The maximum real-time scheduling priority
9076 The maximum stack size
9079 The maximum amount of cpu time in seconds
9082 The maximum number of processes available to a single user
9085 The maximum amount of virtual memory available to the shell
9088 The maximum number of file locks
9091 The maximum number of threads
9096 is given, it is the new value of the specified resource (the
9098 option is display only).
9099 If no option is given, then
9101 is assumed. Values are in 1024-byte increments, except for
9103 which is in seconds,
9105 which is in units of 512-byte blocks,
9112 which are unscaled values.
9113 The return status is 0 unless an invalid option or argument is supplied,
9114 or an error occurs while setting a new limit.
9117 \fBumask\fP [\fB\-p\fP] [\fB\-S\fP] [\fImode\fP]
9118 The user file-creation mask is set to
9122 begins with a digit, it
9123 is interpreted as an octal number; otherwise
9124 it is interpreted as a symbolic mode mask similar
9129 is omitted, the current value of the mask is printed.
9132 option causes the mask to be printed in symbolic form; the
9133 default output is an octal number.
9136 option is supplied, and
9138 is omitted, the output is in a form that may be reused as input.
9139 The return status is 0 if the mode was successfully changed or if
9140 no \fImode\fP argument was supplied, and false otherwise.
9142 \fBunalias\fP [\-\fBa\fP] [\fIname\fP ...]
9143 Remove each \fIname\fP from the list of defined aliases. If
9145 is supplied, all alias definitions are removed. The return
9146 value is true unless a supplied
9148 is not a defined alias.
9150 \fBunset\fP [\-\fBfv\fP] [\fIname\fP ...]
9153 remove the corresponding variable or function.
9154 If no options are supplied, or the
9156 option is given, each
9158 refers to a shell variable.
9159 Read-only variables may not be unset.
9164 refers to a shell function, and the function definition
9166 Each unset variable or function is removed from the environment
9167 passed to subsequent commands.
9184 are unset, they lose their special properties, even if they are
9185 subsequently reset. The exit status is true unless a
9189 \fBwait\fP [\fIn ...\fP]
9190 Wait for each specified process and return its termination status.
9194 ID or a job specification; if a job spec is given, all processes
9195 in that job's pipeline are waited for. If
9197 is not given, all currently active child processes
9198 are waited for, and the return status is zero. If
9200 specifies a non-existent process or job, the return status is
9201 127. Otherwise, the return status is the exit status of the last
9202 process or job waited for.
9205 .SH "RESTRICTED SHELL"
9211 is started with the name
9215 option is supplied at invocation,
9216 the shell becomes restricted.
9217 A restricted shell is used to
9218 set up an environment more controlled than the standard shell.
9219 It behaves identically to
9221 with the exception that the following are disallowed or not performed:
9223 changing directories with \fBcd\fP
9225 setting or unsetting the values of
9232 specifying command names containing
9235 specifying a file name containing a
9237 as an argument to the
9241 Specifying a filename containing a slash as an argument to the
9247 importing function definitions from the shell environment at startup
9249 parsing the value of \fBSHELLOPTS\fP from the shell environment at startup
9251 redirecting output using the >, >|, <>, >&, &>, and >> redirection operators
9255 builtin command to replace the shell with another command
9257 adding or deleting builtin commands with the
9265 Using the \fBenable\fP builtin command to enable disabled shell builtins
9273 turning off restricted mode with
9274 \fBset +r\fP or \fBset +o restricted\fP.
9276 These restrictions are enforced after any startup files are read.
9278 .ie \n(zY=1 When a command that is found to be a shell script is executed,
9279 .el \{ When a command that is found to be a shell script is executed
9282 .B "COMMAND EXECUTION"
9286 turns off any restrictions in the shell spawned to execute the
9293 \fIBash Reference Manual\fP, Brian Fox and Chet Ramey
9295 \fIThe Gnu Readline Library\fP, Brian Fox and Chet Ramey
9297 \fIThe Gnu History Library\fP, Brian Fox and Chet Ramey
9299 \fIPortable Operating System Interface (POSIX) Part 2: Shell and Utilities\fP, IEEE
9301 \fIsh\fP(1), \fIksh\fP(1), \fIcsh\fP(1)
9303 \fIemacs\fP(1), \fIvi\fP(1)
9311 The \fBbash\fP executable
9314 The systemwide initialization file, executed for login shells
9317 The personal initialization file, executed for login shells
9320 The individual per-interactive-shell startup file
9323 The individual login shell cleanup file, executed when a login shell exits
9326 Individual \fIreadline\fP initialization file
9329 Brian Fox, Free Software Foundation
9333 Chet Ramey, Case Western Reserve University
9337 If you find a bug in
9339 you should report it. But first, you should
9340 make sure that it really is a bug, and that it appears in the latest
9343 The latest version is always available from
9344 \fIftp://ftp.gnu.org/pub/bash/\fP.
9346 Once you have determined that a bug actually exists, use the
9348 command to submit a bug report.
9349 If you have a fix, you are encouraged to mail that as well!
9350 Suggestions and `philosophical' bug reports may be mailed
9351 to \fIbug-bash@gnu.org\fP or posted to the Usenet
9355 ALL bug reports should include:
9359 The version number of \fBbash\fR
9361 The hardware and operating system
9363 The compiler used to compile
9365 A description of the bug behaviour
9367 A short script or `recipe' which exercises the bug
9371 inserts the first three items automatically into the template
9372 it provides for filing a bug report.
9374 Comments and bug reports concerning
9375 this manual page should be directed to
9376 .IR chet@po.cwru.edu .
9379 It's too big and too slow.
9381 There are some subtle differences between
9383 and traditional versions of
9385 mostly because of the
9390 Aliases are confusing in some uses.
9392 Shell builtin commands and functions are not stoppable/restartable.
9394 Compound commands and command sequences of the form `a ; b ; c'
9395 are not handled gracefully when process suspension is attempted.
9396 When a process is stopped, the shell immediately executes the next
9397 command in the sequence.
9398 It suffices to place the sequence of commands between
9399 parentheses to force it into a subshell, which may be stopped as
9402 Array variables may not (yet) be exported.
9404 There may be only one active coprocess at a time.
projects / platform / upstream / bash.git / blob