2 .\" MAN PAGE COMMENTS to
5 .\" Information Network Services
6 .\" Case Western Reserve University
9 .\" Last Change: Fri Jul 15 23:15:01 EDT 2005
11 .\" bash_builtins, strip all but Built-Ins section
14 .TH BASH 1 "2005 Jul 15" "GNU Bash-3.1-devel"
16 .\" There's some problem with having a `@'
17 .\" in a tagged paragraph with the BSD man macros.
18 .\" It has to do with `@' appearing in the }1 macro.
19 .\" This is a problem on 4.3 BSD and Ultrix, but Sun
20 .\" appears to have fixed it.
21 .\" If you're seeing the characters
22 .\" `@u-3p' appearing before the lines reading
23 .\" `possible-hostname-completions
24 .\" and `complete-hostname' down in READLINE,
25 .\" then uncomment this redefinition.
30 .if !"\\$1"" .nr )I \\$1n
33 .in \\n()Ru+\\n(INu+\\n()Iu
35 .ie !\\n()Iu+\\n()Ru-\w
\a\\*(]X
\au-3p \{\\*(]X
37 .el \\*(]X\h
\a|\\n()Iu+\\n()Ru
\a\c
41 .\" File Name macro. This used to be `.PN', for Path Name,
42 .\" but Sun doesn't seem to like that very much.
48 bash \- GNU Bourne-Again SHell
54 .if n Bash is Copyright (C) 1989-2005 by the Free Software Foundation, Inc.
55 .if t Bash is Copyright \(co 1989-2005 by the Free Software Foundation, Inc.
58 is an \fBsh\fR-compatible command language interpreter that
59 executes commands read from the standard input or from a file.
61 also incorporates useful features from the \fIKorn\fP and \fIC\fP
62 shells (\fBksh\fP and \fBcsh\fP).
65 is intended to be a conformant implementation of the IEEE
66 POSIX Shell and Tools specification (IEEE Working Group 1003\.2).
68 In addition to the single-character shell options documented in the
69 description of the \fBset\fR builtin command, \fBbash\fR
70 interprets the following options when it is invoked:
77 option is present, then commands are read from
79 If there are arguments after the
81 they are assigned to the positional parameters, starting with
87 option is present, the shell is
93 act as if it had been invoked as a login shell (see
101 option is present, the shell becomes
105 .B "RESTRICTED SHELL"
111 option is present, or if no arguments remain after option
112 processing, then commands are read from the standard input.
113 This option allows the positional parameters to be set
114 when invoking an interactive shell.
117 A list of all double-quoted strings preceded by \fB$\fP
118 is printed on the standard output.
119 These are the strings that
120 are subject to language translation when the current locale
121 is not \fBC\fP or \fBPOSIX\fP.
122 This implies the \fB\-n\fP option; no commands will be executed.
124 .B [\-+]O [\fIshopt_option\fP]
125 \fIshopt_option\fP is one of the shell options accepted by the
126 \fBshopt\fP builtin (see
128 .B SHELL BUILTIN COMMANDS
130 If \fIshopt_option\fP is present, \fB\-O\fP sets the value of that option;
132 If \fIshopt_option\fP is not supplied, the names and values of the shell
133 options accepted by \fBshopt\fP are printed on the standard output.
134 If the invocation option is \fB+O\fP, the output is displayed in a format
135 that may be reused as input.
140 signals the end of options and disables further option processing.
141 Any arguments after the
143 are treated as filenames and arguments. An argument of
145 is equivalent to \fB\-\-\fP.
149 also interprets a number of multi-character options.
150 These options must appear on the command line before the
151 single-character options to be recognized.
156 Arrange for the debugger profile to be executed before the shell
158 Turns on extended debugging mode (see the description of the
163 and shell function tracing (see the description of the
164 \fB\-o functrace\fP option to the
168 .B \-\-dump\-po\-strings
169 Equivalent to \fB\-D\fP, but the output is in the GNU \fIgettext\fP
170 \fBpo\fP (portable object) file format.
173 Equivalent to \fB\-D\fP.
176 Display a usage message on standard output and exit successfully.
178 \fB\-\-init\-file\fP \fIfile\fP
181 \fB\-\-rcfile\fP \fIfile\fP
183 Execute commands from
185 instead of the standard personal initialization file
187 if the shell is interactive (see
193 Equivalent to \fB\-l\fP.
198 library to read command lines when the shell is interactive.
201 Do not read either the system-wide startup file
203 or any of the personal initialization files
204 .IR ~/.bash_profile ,
210 reads these files when it is invoked as a login shell (see
216 Do not read and execute the personal initialization file
218 if the shell is interactive.
219 This option is on by default if the shell is invoked as
223 Change the behavior of \fBbash\fP where the default operation differs
224 from the POSIX 1003.2 standard to match the standard (\fIposix mode\fP).
227 The shell becomes restricted (see
229 .B "RESTRICTED SHELL"
233 Equivalent to \fB\-v\fP.
236 Show version information for this instance of
238 on the standard output and exit successfully.
241 If arguments remain after option processing, and neither the
245 option has been supplied, the first argument is assumed to
246 be the name of a file containing shell commands.
249 is invoked in this fashion,
251 is set to the name of the file, and the positional parameters
252 are set to the remaining arguments.
254 reads and executes commands from this file, then exits.
255 \fBBash\fP's exit status is the exit status of the last command
256 executed in the script.
257 If no commands are executed, the exit status is 0.
258 An attempt is first made to open the file in the current directory, and,
259 if no file is found, then the shell searches the directories in
264 A \fIlogin shell\fP is one whose first character of argument zero is a
266 or one started with the
270 An \fIinteractive\fP shell is one started without non-option arguments
274 whose standard input and error are
275 both connected to terminals (as determined by
277 or one started with the
289 allowing a shell script or a startup file to test this state.
291 The following paragraphs describe how
293 executes its startup files.
294 If any of the files exist but cannot be read,
297 Tildes are expanded in file names as described below under
306 is invoked as an interactive login shell, or as a non-interactive shell
307 with the \fB\-\-login\fP option, it first reads and
308 executes commands from the file \fI/etc/profile\fP, if that
310 After reading that file, it looks for \fI~/.bash_profile\fP,
311 \fI~/.bash_login\fP, and \fI~/.profile\fP, in that order, and reads
312 and executes commands from the first one that exists and is readable.
315 option may be used when the shell is started to inhibit this behavior.
317 When a login shell exits,
319 reads and executes commands from the file \fI~/.bash_logout\fP, if it
322 When an interactive shell that is not a login shell is started,
324 reads and executes commands from \fI~/.bashrc\fP, if that file exists.
325 This may be inhibited by using the
328 The \fB\-\-rcfile\fP \fIfile\fP option will force
330 to read and execute commands from \fIfile\fP instead of \fI~/.bashrc\fP.
334 is started non-interactively, to run a shell script, for example, it
335 looks for the variable
338 in the environment, expands its value if it appears there, and uses the
339 expanded value as the name of a file to read and execute.
341 behaves as if the following command were executed:
344 .if t \f(CWif [ \-n "$BASH_ENV" ]; then . "$BASH_ENV"; fi\fP
345 .if n if [ \-n "$BASH_ENV" ]; then . "$BASH_ENV"; fi
351 variable is not used to search for the file name.
355 is invoked with the name
357 it tries to mimic the startup behavior of historical versions of
359 as closely as possible,
360 while conforming to the POSIX standard as well.
361 When invoked as an interactive login shell, or a non-interactive
362 shell with the \fB\-\-login\fP option, it first attempts to
363 read and execute commands from
370 option may be used to inhibit this behavior.
371 When invoked as an interactive shell with the name
374 looks for the variable
377 expands its value if it is defined, and uses the
378 expanded value as the name of a file to read and execute.
379 Since a shell invoked as
381 does not attempt to read and execute commands from any other startup
384 option has no effect.
385 A non-interactive shell invoked with the name
387 does not attempt to read any other startup files.
393 mode after the startup files are read.
401 command line option, it follows the POSIX standard for startup files.
402 In this mode, interactive shells expand the
405 variable and commands are read and executed from the file
406 whose name is the expanded value.
407 No other startup files are read.
410 attempts to determine when it is being run by the remote shell
411 daemon, usually \fIrshd\fP.
414 determines it is being run by \fIrshd\fP, it reads and executes
415 commands from \fI~/.bashrc\fP, if that file exists and is readable.
416 It will not do this if invoked as \fBsh\fP.
419 option may be used to inhibit this behavior, and the
421 option may be used to force another file to be read, but
422 \fIrshd\fP does not generally invoke the shell with those options
423 or allow them to be specified.
425 If the shell is started with the effective user (group) id not equal to the
426 real user (group) id, and the \fB\-p\fP option is not supplied, no startup
427 files are read, shell functions are not inherited from the environment, the
430 variable, if it appears in the environment, is ignored,
431 and the effective user id is set to the real user id.
432 If the \fB\-p\fP option is supplied at invocation, the startup behavior is
433 the same, but the effective user id is not reset.
436 The following definitions are used throughout the rest of this
444 A sequence of characters considered as a single unit by the shell.
451 consisting only of alphanumeric characters and underscores, and
452 beginning with an alphabetic character or an underscore. Also
457 A character that, when unquoted, separates words. One of the following:
461 .if t \fB| & ; ( ) < > space tab\fP
462 .if n \fB| & ; ( ) < > space tab\fP
467 A \fItoken\fP that performs a control function. It is one of the following
471 .if t \fB\(bv\(bv & && ; ;; ( ) | <newline>\fP
472 .if n \fB|| & && ; ;; ( ) | <newline>\fP
476 \fIReserved words\fP are words that have a special meaning to the shell.
477 The following words are recognized as reserved when unquoted and either
478 the first word of a simple command (see
481 below) or the third word of a
489 .if n ! case do done elif else esac fi for function if in select then until while { } time [[ ]]
490 .if t ! case do done elif else esac fi for function if in select then until while { } time [[ ]]
495 A \fIsimple command\fP is a sequence of optional variable assignments
496 followed by \fBblank\fP-separated words and redirections, and
497 terminated by a \fIcontrol operator\fP. The first word
498 specifies the command to be executed, and is passed as argument zero.
499 The remaining words are passed as arguments to the invoked command.
501 The return value of a \fIsimple command\fP is its exit status, or
502 128+\fIn\^\fP if the command is terminated by signal
506 A \fIpipeline\fP is a sequence of one or more commands separated by
509 The format for a pipeline is:
512 [\fBtime\fP [\fB\-p\fP]] [ ! ] \fIcommand\fP [ \fB|\fP \fIcommand2\fP ... ]
515 The standard output of
517 is connected via a pipe to the standard input of
519 This connection is performed before any redirections specified by the
525 The return status of a pipeline is the exit status of the last
526 command, unless the \fBpipefail\fP option is enabled.
527 If \fBpipefail\fP is enabled, the pipeline's return status is the
528 value of the last (rightmost) command to exit with a non-zero status,
529 or zero if all commands exit successfully.
532 precedes a pipeline, the exit status of that pipeline is the logical
533 negation of the exit status as described above.
534 The shell waits for all commands in the pipeline to
535 terminate before returning a value.
539 reserved word precedes a pipeline, the elapsed as well as user and
540 system time consumed by its execution are reported when the pipeline
542 The \fB\-p\fP option changes the output format to that specified by POSIX.
546 variable may be set to a format string that specifies how the timing
547 information should be displayed; see the description of
554 Each command in a pipeline is executed as a separate process (i.e., in a
558 A \fIlist\fP is a sequence of one or more pipelines separated by one
565 and optionally terminated by one of
571 Of these list operators,
575 have equal precedence, followed by
579 which have equal precedence.
581 A sequence of one or more newlines may appear in a \fIlist\fP instead
582 of a semicolon to delimit commands.
584 If a command is terminated by the control operator
586 the shell executes the command in the \fIbackground\fP
587 in a subshell. The shell does not wait for the command to
588 finish, and the return status is 0. Commands separated by a
590 are executed sequentially; the shell waits for each
591 command to terminate in turn. The return status is the
592 exit status of the last command executed.
594 The control operators
598 denote AND lists and OR lists, respectively.
599 An AND list has the form
602 \fIcommand1\fP \fB&&\fP \fIcommand2\fP
606 is executed if, and only if,
608 returns an exit status of zero.
610 An OR list has the form
613 \fIcommand1\fP \fB\(bv\(bv\fP \fIcommand2\fP
618 is executed if and only if
620 returns a non-zero exit status. The return status of
621 AND and OR lists is the exit status of the last command
622 executed in the list.
623 .SS Compound Commands
625 A \fIcompound command\fP is one of the following:
628 \fIlist\fP is executed in a subshell environment (see
630 \fBCOMMAND EXECUTION ENVIRONMENT\fP
632 Variable assignments and builtin
633 commands that affect the shell's environment do not remain in effect
634 after the command completes. The return status is the exit status of
638 \fIlist\fP is simply executed in the current shell environment.
639 \fIlist\fP must be terminated with a newline or semicolon.
640 This is known as a \fIgroup command\fP.
641 The return status is the exit status of
643 Note that unlike the metacharacters \fB(\fP and \fB)\fP, \fB{\fP and
644 \fB}\fP are \fIreserved words\fP and must occur where a reserved
645 word is permitted to be recognized. Since they do not cause a word
646 break, they must be separated from \fIlist\fP by whitespace.
649 The \fIexpression\fP is evaluated according to the rules described
652 .BR "ARITHMETIC EVALUATION" .
653 If the value of the expression is non-zero, the return status is 0;
654 otherwise the return status is 1. This is exactly equivalent to
655 \fBlet "\fIexpression\fP"\fR.
657 \fB[[\fP \fIexpression\fP \fB]]\fP
658 Return a status of 0 or 1 depending on the evaluation of
659 the conditional expression \fIexpression\fP.
660 Expressions are composed of the primaries described below under
662 .BR "CONDITIONAL EXPRESSIONS" .
663 Word splitting and pathname expansion are not performed on the words
664 between the \fB[[\fP and \fB]]\fP; tilde expansion, parameter and
665 variable expansion, arithmetic expansion, command substitution, process
666 substitution, and quote removal are performed.
667 Conditional operators such as \fB\-f\fP must be unquoted to be recognized
671 When the \fB==\fP and \fB!=\fP operators are used, the string to the
672 right of the operator is considered a pattern and matched according
673 to the rules described below under \fBPattern Matching\fP.
676 is enabled, the match is performed without regard to the case
677 of alphabetic characters.
678 The return value is 0 if the string matches or does not match
679 the pattern, respectively, and 1 otherwise.
680 Any part of the pattern may be quoted to force it to be matched as a
684 An additional binary operator, \fB=~\fP, is available, with the same
685 precedence as \fB==\fP and \fB!=\fP.
686 When it is used, the string to the right of the operator is considered
687 an extended regular expression and matched accordingly (as in \fIregex\fP(3)).
688 The return value is 0 if the string matches
689 the pattern, and 1 otherwise.
690 If the regular expression is syntactically incorrect, the conditional
691 expression's return value is 2.
694 is enabled, the match is performed without regard to the case
695 of alphabetic characters.
696 Substrings matched by parenthesized subexpressions within the regular
697 expression are saved in the array variable \fBBASH_REMATCH\fP.
698 The element of \fBBASH_REMATCH\fP with index 0 is the portion of the string
699 matching the entire regular expression.
700 The element of \fBBASH_REMATCH\fP with index \fIn\fP is the portion of the
701 string matching the \fIn\fPth parenthesized subexpression.
704 Expressions may be combined using the following operators, listed
705 in decreasing order of precedence:
711 .B ( \fIexpression\fP )
712 Returns the value of \fIexpression\fP.
713 This may be used to override the normal precedence of operators.
715 .B ! \fIexpression\fP
720 \fIexpression1\fP \fB&&\fP \fIexpression2\fP
727 .if t \fIexpression1\fP \fB\(bv\(bv\fP \fIexpression2\fP
728 .if n \fIexpression1\fP \fB||\fP \fIexpression2\fP
739 operators do not evaluate \fIexpression2\fP if the value of
740 \fIexpression1\fP is sufficient to determine the return value of
741 the entire conditional expression.
744 \fBfor\fP \fIname\fP [ \fBin\fP \fIword\fP ] ; \fBdo\fP \fIlist\fP ; \fBdone\fP
745 The list of words following \fBin\fP is expanded, generating a list
747 The variable \fIname\fP is set to each element of this list
748 in turn, and \fIlist\fP is executed each time.
749 If the \fBin\fP \fIword\fP is omitted, the \fBfor\fP command executes
750 \fIlist\fP once for each positional parameter that is set (see
754 The return status is the exit status of the last command that executes.
755 If the expansion of the items following \fBin\fP results in an empty
756 list, no commands are executed, and the return status is 0.
758 \fBfor\fP (( \fIexpr1\fP ; \fIexpr2\fP ; \fIexpr3\fP )) ; \fBdo\fP \fIlist\fP ; \fBdone\fP
759 First, the arithmetic expression \fIexpr1\fP is evaluated according
760 to the rules described below under
762 .BR "ARITHMETIC EVALUATION" .
763 The arithmetic expression \fIexpr2\fP is then evaluated repeatedly
764 until it evaluates to zero.
765 Each time \fIexpr2\fP evaluates to a non-zero value, \fIlist\fP is
766 executed and the arithmetic expression \fIexpr3\fP is evaluated.
767 If any expression is omitted, it behaves as if it evaluates to 1.
768 The return value is the exit status of the last command in \fIlist\fP
769 that is executed, or false if any of the expressions is invalid.
771 \fBselect\fP \fIname\fP [ \fBin\fP \fIword\fP ] ; \fBdo\fP \fIlist\fP ; \fBdone\fP
772 The list of words following \fBin\fP is expanded, generating a list
773 of items. The set of expanded words is printed on the standard
774 error, each preceded by a number. If the \fBin\fP
775 \fIword\fP is omitted, the positional parameters are printed (see
780 prompt is then displayed and a line read from the standard input.
781 If the line consists of a number corresponding to one of
782 the displayed words, then the value of
784 is set to that word. If the line is empty, the words and prompt
785 are displayed again. If EOF is read, the command completes. Any
786 other value read causes
788 to be set to null. The line read is saved in the variable
792 is executed after each selection until a
797 is the exit status of the last command executed in
799 or zero if no commands were executed.
801 \fBcase\fP \fIword\fP \fBin\fP [ [(] \fIpattern\fP [ \fB|\fP \fIpattern\fP ] \
802 ... ) \fIlist\fP ;; ] ... \fBesac\fP
803 A \fBcase\fP command first expands \fIword\fP, and tries to match
804 it against each \fIpattern\fP in turn, using the same matching rules
805 as for pathname expansion (see
806 .B Pathname Expansion
810 is enabled, the match is performed without regard to the case
811 of alphabetic characters.
812 When a match is found, the
813 corresponding \fIlist\fP is executed. After the first match, no
814 subsequent matches are attempted. The exit status is zero if no
815 pattern matches. Otherwise, it is the exit status of the
816 last command executed in \fIlist\fP.
818 \fBif\fP \fIlist\fP; \fBthen\fP \fIlist;\fP \
819 [ \fBelif\fP \fIlist\fP; \fBthen\fP \fIlist\fP; ] ... \
820 [ \fBelse\fP \fIlist\fP; ] \fBfi\fP
824 is executed. If its exit status is zero, the
825 \fBthen\fP \fIlist\fP is executed. Otherwise, each \fBelif\fP
826 \fIlist\fP is executed in turn, and if its exit status is zero,
827 the corresponding \fBthen\fP \fIlist\fP is executed and the
828 command completes. Otherwise, the \fBelse\fP \fIlist\fP is
829 executed, if present. The exit status is the exit status of the
830 last command executed, or zero if no condition tested true.
832 \fBwhile\fP \fIlist\fP; \fBdo\fP \fIlist\fP; \fBdone\fP
835 \fBuntil\fP \fIlist\fP; \fBdo\fP \fIlist\fP; \fBdone\fP
837 The \fBwhile\fP command continuously executes the \fBdo\fP
838 \fIlist\fP as long as the last command in \fIlist\fP returns
839 an exit status of zero. The \fBuntil\fP command is identical
840 to the \fBwhile\fP command, except that the test is negated;
844 is executed as long as the last command in
846 returns a non-zero exit status.
847 The exit status of the \fBwhile\fP and \fBuntil\fP commands
849 of the last \fBdo\fP \fIlist\fP command executed, or zero if
851 .SS Shell Function Definitions
853 A shell function is an object that is called like a simple command and
854 executes a compound command with a new set of positional parameters.
855 Shell functions are declared as follows:
857 [ \fBfunction\fP ] \fIname\fP () \fIcompound\-command\fP [\fIredirection\fP]
858 This defines a function named \fIname\fP.
859 The reserved word \fBfunction\fP is optional.
860 If the \fBfunction\fP reserved word is supplied, the parentheses are optional.
861 The \fIbody\fP of the function is the compound command
863 (see \fBCompound Commands\fP above).
864 That command is usually a \fIlist\fP of commands between { and }, but
865 may be any command listed under \fBCompound Commands\fP above.
866 \fIcompound\-command\fP is executed whenever \fIname\fP is specified as the
867 name of a simple command.
868 Any redirections (see
871 below) specified when a function is defined are performed
872 when the function is executed.
873 The exit status of a function definition is zero unless a syntax error
874 occurs or a readonly function with the same name already exists.
875 When executed, the exit status of a function is the exit status of the
876 last command executed in the body. (See
881 In a non-interactive shell, or an interactive shell in which the
882 .B interactive_comments
885 builtin is enabled (see
887 .B "SHELL BUILTIN COMMANDS"
888 below), a word beginning with
890 causes that word and all remaining characters on that line to
891 be ignored. An interactive shell without the
892 .B interactive_comments
893 option enabled does not allow comments. The
894 .B interactive_comments
895 option is on by default in interactive shells.
897 \fIQuoting\fP is used to remove the special meaning of certain
898 characters or words to the shell. Quoting can be used to
899 disable special treatment for special characters, to prevent
900 reserved words from being recognized as such, and to prevent
903 Each of the \fImetacharacters\fP listed above under
906 has special meaning to the shell and must be quoted if it is to
909 When the command history expansion facilities are being used
914 \fIhistory expansion\fP character, usually \fB!\fP, must be quoted
915 to prevent history expansion.
917 There are three quoting mechanisms: the
918 .IR "escape character" ,
919 single quotes, and double quotes.
921 A non-quoted backslash (\fB\e\fP) is the
922 .IR "escape character" .
923 It preserves the literal value of the next character that follows,
924 with the exception of <newline>. If a \fB\e\fP<newline> pair
925 appears, and the backslash is not itself quoted, the \fB\e\fP<newline>
926 is treated as a line continuation (that is, it is removed from the
927 input stream and effectively ignored).
929 Enclosing characters in single quotes preserves the literal value
930 of each character within the quotes. A single quote may not occur
931 between single quotes, even when preceded by a backslash.
933 Enclosing characters in double quotes preserves the literal value
934 of all characters within the quotes, with the exception of
938 and, when history expansion is enabled,
944 retain their special meaning within double quotes. The backslash
945 retains its special meaning only when followed by one of the following
953 A double quote may be quoted within double quotes by preceding it with
955 If enabled, history expansion will be performed unless an
957 appearing in double quotes is escaped using a backslash.
958 The backslash preceding the
962 The special parameters
966 have special meaning when in double
972 Words of the form \fB$\fP'\fIstring\fP' are treated specially. The
973 word expands to \fIstring\fP, with backslash-escaped characters replaced
974 as specified by the ANSI C standard. Backslash escape sequences, if
975 present, are decoded as follows:
1010 the eight-bit character whose value is the octal value \fInnn\fP
1011 (one to three digits)
1014 the eight-bit character whose value is the hexadecimal value \fIHH\fP
1015 (one or two hex digits)
1018 a control-\fIx\fP character
1022 The expanded result is single-quoted, as if the dollar sign had
1025 A double-quoted string preceded by a dollar sign (\fB$\fP) will cause
1026 the string to be translated according to the current locale.
1027 If the current locale is \fBC\fP or \fBPOSIX\fP, the dollar sign
1029 If the string is translated and replaced, the replacement is
1034 is an entity that stores values.
1037 a number, or one of the special characters listed below under
1038 .BR "Special Parameters" .
1041 is a parameter denoted by a
1043 A variable has a \fIvalue\fP and zero or more \fIattributes\fP.
1044 Attributes are assigned using the
1046 builtin command (see
1050 .BR "SHELL BUILTIN COMMANDS" ).
1052 A parameter is set if it has been assigned a value. The null string is
1053 a valid value. Once a variable is set, it may be unset only by using
1056 builtin command (see
1058 .B SHELL BUILTIN COMMANDS
1063 may be assigned to by a statement of the form
1066 \fIname\fP=[\fIvalue\fP]
1071 is not given, the variable is assigned the null string. All
1073 undergo tilde expansion, parameter and variable expansion,
1074 command substitution, arithmetic expansion, and quote
1078 below). If the variable has its
1082 is evaluated as an arithmetic expression even if the $((...)) expansion is
1084 .B "Arithmetic Expansion"
1086 Word splitting is not performed, with the exception
1087 of \fB"$@"\fP as explained below under
1088 .BR "Special Parameters" .
1089 Pathname expansion is not performed.
1090 Assignment statements may also appear as arguments to the
1100 In the context where an assignment statement is assigning a value
1101 to a shell variable or array index, the += operator can be used to
1102 append to or add to the variable's previous value.
1103 When += is applied to a variable for which the integer attribute has been
1104 set, \fIvalue\fP is evaluated as an arithmetic expression and added to the
1105 variable's current value, which is also evaluated.
1106 When += is applied to an array variable using compound assignment (see
1109 variable's value is not unset (as it is when using =), and new values are
1110 appended to the array beginning at one greater than the array's maximum index.
1111 When applied to a string-valued variable, \fIvalue\fP is expanded and
1112 appended to the variable's value.
1113 .SS Positional Parameters
1116 .I positional parameter
1117 is a parameter denoted by one or more
1118 digits, other than the single digit 0. Positional parameters are
1119 assigned from the shell's arguments when it is invoked,
1120 and may be reassigned using the
1122 builtin command. Positional parameters may not be assigned to
1123 with assignment statements. The positional parameters are
1124 temporarily replaced when a shell function is executed (see
1129 When a positional parameter consisting of more than a single
1130 digit is expanded, it must be enclosed in braces (see
1134 .SS Special Parameters
1136 The shell treats several parameters specially. These parameters may
1137 only be referenced; assignment to them is not allowed.
1141 Expands to the positional parameters, starting from one. When the
1142 expansion occurs within double quotes, it expands to a single word
1143 with the value of each parameter separated by the first character
1147 special variable. That is, "\fB$*\fP" is equivalent
1148 to "\fB$1\fP\fIc\fP\fB$2\fP\fIc\fP\fB...\fP", where
1150 is the first character of the value of the
1156 is unset, the parameters are separated by spaces.
1160 is null, the parameters are joined without intervening separators.
1163 Expands to the positional parameters, starting from one. When the
1164 expansion occurs within double quotes, each parameter expands to a
1165 separate word. That is, "\fB$@\fP" is equivalent to
1166 "\fB$1\fP" "\fB$2\fP" ...
1167 If the double-quoted expansion occurs within a word, the expansion of
1168 the first parameter is joined with the beginning part of the original
1169 word, and the expansion of the last parameter is joined with the last
1170 part of the original word.
1171 When there are no positional parameters, "\fB$@\fP" and
1173 expand to nothing (i.e., they are removed).
1176 Expands to the number of positional parameters in decimal.
1179 Expands to the status of the most recently executed foreground
1183 Expands to the current option flags as specified upon invocation,
1186 builtin command, or those set by the shell itself
1192 Expands to the process ID of the shell. In a () subshell, it
1193 expands to the process ID of the current shell, not the
1197 Expands to the process ID of the most recently executed background
1198 (asynchronous) command.
1201 Expands to the name of the shell or shell script. This is set at
1202 shell initialization. If
1204 is invoked with a file of commands,
1206 is set to the name of that file. If
1212 is set to the first argument after the string to be
1213 executed, if one is present. Otherwise, it is set
1214 to the file name used to invoke
1216 as given by argument zero.
1219 At shell startup, set to the absolute pathname used to invoke the
1220 shell or shell script being executed as passed in the environment
1222 Subsequently, expands to the last argument to the previous command,
1224 Also set to the full pathname used to invoke each command executed
1225 and placed in the environment exported to that command.
1226 When checking mail, this parameter holds the name of the mail file
1227 currently being checked.
1231 The following variables are set by the shell:
1236 Expands to the full file name used to invoke this instance of
1240 An array variable whose values are the number of parameters in each
1241 frame of the current bash execution call stack.
1243 parameters to the current subroutine (shell function or script executed
1244 with \fB.\fP or \fBsource\fP) is at the top of the stack.
1245 When a subroutine is executed, the number of parameters passed is pushed onto
1247 The shell sets \fBBASH_ARGC\fP only when in extended debugging mode
1248 (see the description of the
1255 An array variable containing all of the parameters in the current bash
1256 execution call stack. The final parameter of the last subroutine call
1257 is at the top of the stack; the first parameter of the initial call is
1258 at the bottom. When a subroutine is executed, the parameters supplied
1259 are pushed onto \fBBASH_ARGV\fP.
1260 The shell sets \fBBASH_ARGV\fP only when in extended debugging mode
1261 (see the description of the
1268 The command currently being executed or about to be executed, unless the
1269 shell is executing a command as the result of a trap,
1270 in which case it is the command executing at the time of the trap.
1272 .B BASH_EXECUTION_STRING
1273 The command argument to the \fB\-c\fP invocation option.
1276 An array variable whose members are the line numbers in source files
1277 corresponding to each member of \fBFUNCNAME\fP.
1278 \fB${BASH_LINENO[\fP\fI$i\fP\fB]}\fP is the line number in the source
1279 file where \fB${FUNCNAME[\fP\fI$ifP\fB]}\fP was called.
1280 The corresponding source file name is \fB${BASH_SOURCE[\fP\fI$i\fP\fB]}\fB.
1281 Use \fBLINENO\fP to obtain the current line number.
1284 An array variable whose members are assigned by the \fB=~\fP binary
1285 operator to the \fB[[\fP conditional command.
1286 The element with index 0 is the portion of the string
1287 matching the entire regular expression.
1288 The element with index \fIn\fP is the portion of the
1289 string matching the \fIn\fPth parenthesized subexpression.
1290 This variable is read-only.
1293 An array variable whose members are the source filenames corresponding
1294 to the elements in the \fBFUNCNAME\fP array variable.
1297 Incremented by one each time a subshell or subshell environment is spawned.
1298 The initial value is 0.
1301 A readonly array variable whose members hold version information for
1304 The values assigned to the array members are as follows:
1309 .B BASH_VERSINFO[\fR0\fP]
1310 The major version number (the \fIrelease\fP).
1312 .B BASH_VERSINFO[\fR1\fP]
1313 The minor version number (the \fIversion\fP).
1315 .B BASH_VERSINFO[\fR2\fP]
1318 .B BASH_VERSINFO[\fR3\fP]
1321 .B BASH_VERSINFO[\fR4\fP]
1322 The release status (e.g., \fIbeta1\fP).
1324 .B BASH_VERSINFO[\fR5\fP]
1325 The value of \fBMACHTYPE\fP.
1330 Expands to a string describing the version of this instance of
1334 An index into \fB${COMP_WORDS}\fP of the word containing the current
1336 This variable is available only in shell functions invoked by the
1337 programmable completion facilities (see \fBProgrammable Completion\fP
1341 The current command line.
1342 This variable is available only in shell functions and external
1343 commands invoked by the
1344 programmable completion facilities (see \fBProgrammable Completion\fP
1348 The index of the current cursor position relative to the beginning of
1349 the current command.
1350 If the current cursor position is at the end of the current command,
1351 the value of this variable is equal to \fB${#COMP_LINE}\fP.
1352 This variable is available only in shell functions and external
1353 commands invoked by the
1354 programmable completion facilities (see \fBProgrammable Completion\fP
1358 The set of characters that the Readline library treats as word
1359 separators when performing word completion.
1363 is unset, it loses its special properties, even if it is
1367 An array variable (see \fBArrays\fP below) consisting of the individual
1368 words in the current command line.
1369 This variable is available only in shell functions invoked by the
1370 programmable completion facilities (see \fBProgrammable Completion\fP
1374 An array variable (see
1376 below) containing the current contents of the directory stack.
1377 Directories appear in the stack in the order they are displayed by the
1380 Assigning to members of this array variable may be used to modify
1381 directories already in the stack, but the
1385 builtins must be used to add and remove directories.
1386 Assignment to this variable will not change the current directory.
1390 is unset, it loses its special properties, even if it is
1394 Expands to the effective user ID of the current user, initialized at
1395 shell startup. This variable is readonly.
1398 An array variable containing the names of all shell functions
1399 currently in the execution call stack.
1400 The element with index 0 is the name of any currently-executing
1402 The bottom-most element is "main".
1403 This variable exists only when a shell function is executing.
1407 have no effect and return an error status.
1411 is unset, it loses its special properties, even if it is
1415 An array variable containing the list of groups of which the current
1420 have no effect and return an error status.
1424 is unset, it loses its special properties, even if it is
1428 The history number, or index in the history list, of the current
1433 is unset, it loses its special properties, even if it is
1437 Automatically set to the name of the current host.
1440 Automatically set to a string that uniquely
1441 describes the type of machine on which
1444 The default is system-dependent.
1447 Each time this parameter is referenced, the shell substitutes
1448 a decimal number representing the current sequential line number
1449 (starting with 1) within a script or function. When not in a
1450 script or function, the value substituted is not guaranteed to
1455 is unset, it loses its special properties, even if it is
1459 Automatically set to a string that fully describes the system
1462 is executing, in the standard GNU \fIcpu-company-system\fP format.
1463 The default is system-dependent.
1466 The previous working directory as set by the
1471 The value of the last option argument processed by the
1473 builtin command (see
1475 .B SHELL BUILTIN COMMANDS
1479 The index of the next argument to be processed by the
1481 builtin command (see
1483 .B SHELL BUILTIN COMMANDS
1487 Automatically set to a string that
1488 describes the operating system on which
1491 The default is system-dependent.
1494 An array variable (see
1496 below) containing a list of exit status values from the processes
1497 in the most-recently-executed foreground pipeline (which may
1498 contain only a single command).
1501 The process ID of the shell's parent. This variable is readonly.
1504 The current working directory as set by the
1509 Each time this parameter is referenced, a random integer between
1511 generated. The sequence of random numbers may be initialized by assigning
1518 is unset, it loses its special properties, even if it is
1522 Set to the line of input read by the
1524 builtin command when no arguments are supplied.
1527 Each time this parameter is
1528 referenced, the number of seconds since shell invocation is returned. If a
1529 value is assigned to
1532 the value returned upon subsequent
1534 the number of seconds since the assignment plus the value assigned.
1538 is unset, it loses its special properties, even if it is
1542 A colon-separated list of enabled shell options. Each word in
1543 the list is a valid argument for the
1547 builtin command (see
1549 .B "SHELL BUILTIN COMMANDS"
1550 below). The options appearing in
1553 are those reported as
1556 If this variable is in the environment when
1558 starts up, each shell option in the list will be enabled before
1559 reading any startup files.
1560 This variable is read-only.
1563 Incremented by one each time an instance of
1568 Expands to the user ID of the current user, initialized at shell startup.
1569 This variable is readonly.
1572 The following variables are used by the shell. In some cases,
1574 assigns a default value to a variable; these cases are noted
1580 If this parameter is set when \fBbash\fP is executing a shell script,
1581 its value is interpreted as a filename containing commands to
1582 initialize the shell, as in
1587 is subjected to parameter expansion, command substitution, and arithmetic
1588 expansion before being interpreted as a file name.
1591 is not used to search for the resultant file name.
1594 The search path for the
1597 This is a colon-separated list of directories in which the shell looks
1598 for destination directories specified by the
1602 .if t \f(CW".:~:/usr"\fP.
1606 Used by the \fBselect\fP builtin command to determine the terminal width
1607 when printing selection lists. Automatically set upon receipt of a SIGWINCH.
1610 An array variable from which \fBbash\fP reads the possible completions
1611 generated by a shell function invoked by the programmable completion
1612 facility (see \fBProgrammable Completion\fP below).
1615 If \fBbash\fP finds this variable in the environment when the shell starts
1619 it assumes that the shell is running in an emacs shell buffer and disables
1623 The default editor for the
1628 A colon-separated list of suffixes to ignore when performing
1629 filename completion (see
1633 A filename whose suffix matches one of the entries in
1636 is excluded from the list of matched filenames.
1638 .if t \f(CW".o:~"\fP.
1642 A colon-separated list of patterns defining the set of filenames to
1643 be ignored by pathname expansion.
1644 If a filename matched by a pathname expansion pattern also matches one
1648 it is removed from the list of matches.
1651 A colon-separated list of values controlling how commands are saved on
1653 If the list of values includes
1655 lines which begin with a
1657 character are not saved in the history list.
1660 causes lines matching the previous history entry to not be saved.
1663 is shorthand for \fIignorespace\fP and \fIignoredups\fP.
1666 causes all previous lines matching the current line to be removed from
1667 the history list before that line is saved.
1668 Any value not in the above list is ignored.
1669 If \fBHISTCONTROL\fP is unset, or does not include a valid value,
1670 all lines read by the shell parser are saved on the history list,
1671 subject to the value of
1673 The second and subsequent lines of a multi-line compound command are
1674 not tested, and are added to the history regardless of the value of
1678 The name of the file in which command history is saved (see
1681 below). The default value is \fI~/.bash_history\fP. If unset, the
1682 command history is not saved when an interactive shell exits.
1685 The maximum number of lines contained in the history file. When this
1686 variable is assigned a value, the history file is truncated, if
1687 necessary, to contain no more than that number of lines. The default
1688 value is 500. The history file is also truncated to this size after
1689 writing it when an interactive shell exits.
1692 A colon-separated list of patterns used to decide which command lines
1693 should be saved on the history list. Each pattern is anchored at the
1694 beginning of the line and must match the complete line (no implicit
1695 `\fB*\fP' is appended). Each pattern is tested against the line
1696 after the checks specified by
1699 In addition to the normal shell pattern matching characters, `\fB&\fP'
1700 matches the previous history line. `\fB&\fP' may be escaped using a
1701 backslash; the backslash is removed before attempting a match.
1702 The second and subsequent lines of a multi-line compound command are
1703 not tested, and are added to the history regardless of the value of
1707 The number of commands to remember in the command history (see
1710 below). The default value is 500.
1713 If this variable is set and not null, its value is used as a format string
1714 for \fIstrftime\fP(3) to print the time stamp associated with each history
1715 entry displayed by the \fBhistory\fP builtin.
1716 If this variable is set, time stamps are written to the history file so
1717 they may be preserved across shell sessions.
1720 The home directory of the current user; the default argument for the
1721 \fBcd\fP builtin command.
1722 The value of this variable is also used when performing tilde expansion.
1725 Contains the name of a file in the same format as
1727 that should be read when the shell needs to complete a
1729 The list of possible hostname completions may be changed while the
1731 the next time hostname completion is attempted after the
1734 adds the contents of the new file to the existing list.
1738 is set, but has no value, \fBbash\fP attempts to read
1740 to obtain the list of possible hostname completions.
1744 is unset, the hostname list is cleared.
1748 .I Internal Field Separator
1750 for word splitting after expansion and to
1751 split lines into words with the
1753 builtin command. The default value is
1754 ``<space><tab><newline>''.
1758 action of an interactive shell on receipt of an
1761 character as the sole input. If set, the value is the number of
1765 characters which must be
1766 typed as the first characters on an input line before
1768 exits. If the variable exists but does not have a numeric value, or
1769 has no value, the default value is 10. If it does not exist,
1772 signifies the end of input to the shell.
1775 The filename for the
1777 startup file, overriding the default of
1785 Used to determine the locale category for any category not specifically
1786 selected with a variable starting with \fBLC_\fP.
1789 This variable overrides the value of \fBLANG\fP and any other
1790 \fBLC_\fP variable specifying a locale category.
1793 This variable determines the collation order used when sorting the
1794 results of pathname expansion, and determines the behavior of range
1795 expressions, equivalence classes, and collating sequences within
1796 pathname expansion and pattern matching.
1799 This variable determines the interpretation of characters and the
1800 behavior of character classes within pathname expansion and pattern
1804 This variable determines the locale used to translate double-quoted
1805 strings preceded by a \fB$\fP.
1808 This variable determines the locale category used for number formatting.
1811 Used by the \fBselect\fP builtin command to determine the column length
1812 for printing selection lists. Automatically set upon receipt of a SIGWINCH.
1815 If this parameter is set to a file name and the
1818 variable is not set,
1820 informs the user of the arrival of mail in the specified file.
1826 checks for mail. The default is 60 seconds. When it is time to check
1827 for mail, the shell does so before displaying the primary prompt.
1828 If this variable is unset, or set to a value that is not a number
1829 greater than or equal to zero, the shell disables mail checking.
1832 A colon-separated list of file names to be checked for mail.
1833 The message to be printed when mail arrives in a particular file
1834 may be specified by separating the file name from the message with a `?'.
1835 When used in the text of the message, \fB$_\fP expands to the name of
1836 the current mailfile.
1840 \fBMAILPATH\fP='/var/mail/bfox?"You have mail":~/shell\-mail?"$_ has mail!"'
1843 supplies a default value for this variable, but the location of the user
1844 mail files that it uses is system dependent (e.g., /var/mail/\fB$USER\fP).
1848 If set to the value 1,
1850 displays error messages generated by the
1852 builtin command (see
1854 .B SHELL BUILTIN COMMANDS
1858 is initialized to 1 each time the shell is invoked or a shell
1862 The search path for commands. It
1863 is a colon-separated list of directories in which
1864 the shell looks for commands (see
1866 .B COMMAND EXECUTION
1868 A zero-length (null) directory name in the value of \fBPATH\fP indicates the
1870 A null directory name may appear as two adjacent colons, or as an initial
1872 The default path is system-dependent,
1873 and is set by the administrator who installs
1876 .if t \f(CW/usr/gnu/bin:/usr/local/bin:/usr/ucb:/bin:/usr/bin\fP.
1877 .if n ``/usr/gnu/bin:/usr/local/bin:/usr/ucb:/bin:/usr/bin''.
1880 If this variable is in the environment when \fBbash\fP starts, the shell
1881 enters \fIposix mode\fP before reading the startup files, as if the
1883 invocation option had been supplied. If it is set while the shell is
1884 running, \fBbash\fP enables \fIposix mode\fP, as if the command
1885 .if t \f(CWset -o posix\fP
1886 .if n \fIset -o posix\fP
1890 If set, the value is executed as a command prior to issuing each primary
1894 The value of this parameter is expanded (see
1897 below) and used as the primary prompt string. The default value is
1898 ``\fB\es\-\ev\e$ \fP''.
1901 The value of this parameter is expanded as with
1903 and used as the secondary prompt string. The default is
1907 The value of this parameter is used as the prompt for the
1915 The value of this parameter is expanded as with
1917 and the value is printed before each command
1919 displays during an execution trace. The first character of
1922 is replicated multiple times, as necessary, to indicate multiple
1923 levels of indirection. The default is ``\fB+ \fP''.
1926 The full pathname to the shell is kept in this environment variable.
1927 If it is not set when the shell starts,
1929 assigns to it the full pathname of the current user's login shell.
1932 The value of this parameter is used as a format string specifying
1933 how the timing information for pipelines prefixed with the
1935 reserved word should be displayed.
1936 The \fB%\fP character introduces an escape sequence that is
1937 expanded to a time value or other information.
1938 The escape sequences and their meanings are as follows; the
1939 braces denote optional portions.
1948 The elapsed time in seconds.
1951 The number of CPU seconds spent in user mode.
1954 The number of CPU seconds spent in system mode.
1957 The CPU percentage, computed as (%U + %S) / %R.
1961 The optional \fIp\fP is a digit specifying the \fIprecision\fP,
1962 the number of fractional digits after a decimal point.
1963 A value of 0 causes no decimal point or fraction to be output.
1964 At most three places after the decimal point may be specified;
1965 values of \fIp\fP greater than 3 are changed to 3.
1966 If \fIp\fP is not specified, the value 3 is used.
1968 The optional \fBl\fP specifies a longer format, including
1969 minutes, of the form \fIMM\fPm\fISS\fP.\fIFF\fPs.
1970 The value of \fIp\fP determines whether or not the fraction is
1973 If this variable is not set, \fBbash\fP acts as if it had the
1974 value \fB$'\enreal\et%3lR\enuser\et%3lU\ensys\t%3lS'\fP.
1975 If the value is null, no timing information is displayed.
1976 A trailing newline is added when the format string is displayed.
1979 If set to a value greater than zero, \fBTMOUT\fP is treated as the
1980 default timeout for the \fBread\fP builtin.
1981 The \fBselect\fP command terminates if input does not arrive
1982 after \fBTMOUT\fP seconds when input is coming from a terminal.
1983 In an interactive shell, the value is interpreted as the
1984 number of seconds to wait for input after issuing the primary prompt.
1986 terminates after waiting for that number of seconds if input does
1990 If set, \fBBash\fP uses its value as the name of a directory in which
1991 \fBBash\fP creates temporary files for the shell's use.
1994 This variable controls how the shell interacts with the user and
1995 job control. If this variable is set, single word simple
1996 commands without redirections are treated as candidates for resumption
1997 of an existing stopped job. There is no ambiguity allowed; if there is
1998 more than one job beginning with the string typed, the job most recently
1999 accessed is selected. The
2001 of a stopped job, in this context, is the command line used to
2005 the string supplied must match the name of a stopped job exactly;
2008 the string supplied needs to match a substring of the name of a
2011 value provides functionality analogous to the
2016 below). If set to any other value, the supplied string must
2017 be a prefix of a stopped job's name; this provides functionality
2018 analogous to the \fB%\fP\fIstring\fP job identifier.
2021 The two or three characters which control history expansion
2022 and tokenization (see
2024 .B HISTORY EXPANSION
2025 below). The first character is the \fIhistory expansion\fP character,
2026 the character which signals the start of a history
2027 expansion, normally `\fB!\fP'.
2028 The second character is the \fIquick substitution\fP
2029 character, which is used as shorthand for re-running the previous
2030 command entered, substituting one string for another in the command.
2031 The default is `\fB^\fP'.
2032 The optional third character is the character
2033 which indicates that the remainder of the line is a comment when found
2034 as the first character of a word, normally `\fB#\fP'. The history
2035 comment character causes history substitution to be skipped for the
2036 remaining words on the line. It does not necessarily cause the shell
2037 parser to treat the rest of the line as a comment.
2041 provides one-dimensional array variables. Any variable may be used as
2044 builtin will explicitly declare an array. There is no maximum
2045 limit on the size of an array, nor any requirement that members
2046 be indexed or assigned contiguously. Arrays are indexed using
2047 integers and are zero-based.
2049 An array is created automatically if any variable is assigned to using
2050 the syntax \fIname\fP[\fIsubscript\fP]=\fIvalue\fP. The
2052 is treated as an arithmetic expression that must evaluate to a number
2053 greater than or equal to zero. To explicitly declare an array, use
2054 .B declare \-a \fIname\fP
2057 .B SHELL BUILTIN COMMANDS
2059 .B declare \-a \fIname\fP[\fIsubscript\fP]
2060 is also accepted; the \fIsubscript\fP is ignored. Attributes may be
2061 specified for an array variable using the
2065 builtins. Each attribute applies to all members of an array.
2067 Arrays are assigned to using compound assignments of the form
2068 \fIname\fP=\fB(\fPvalue\fI1\fP ... value\fIn\fP\fB)\fP, where each
2069 \fIvalue\fP is of the form [\fIsubscript\fP]=\fIstring\fP. Only
2070 \fIstring\fP is required. If
2071 the optional brackets and subscript are supplied, that index is assigned to;
2072 otherwise the index of the element assigned is the last index assigned
2073 to by the statement plus one. Indexing starts at zero.
2074 This syntax is also accepted by the
2076 builtin. Individual array elements may be assigned to using the
2077 \fIname\fP[\fIsubscript\fP]=\fIvalue\fP syntax introduced above.
2079 Any element of an array may be referenced using
2080 ${\fIname\fP[\fIsubscript\fP]}. The braces are required to avoid
2081 conflicts with pathname expansion. If
2082 \fIsubscript\fP is \fB@\fP or \fB*\fP, the word expands to
2083 all members of \fIname\fP. These subscripts differ only when the
2084 word appears within double quotes. If the word is double-quoted,
2085 ${\fIname\fP[*]} expands to a single
2086 word with the value of each array member separated by the first
2090 special variable, and ${\fIname\fP[@]} expands each element of
2091 \fIname\fP to a separate word. When there are no array members,
2092 ${\fIname\fP[@]} expands to nothing.
2093 If the double-quoted expansion occurs within a word, the expansion of
2094 the first parameter is joined with the beginning part of the original
2095 word, and the expansion of the last parameter is joined with the last
2096 part of the original word.
2097 This is analogous to the expansion
2098 of the special parameters \fB*\fP and \fB@\fP (see
2099 .B Special Parameters
2100 above). ${#\fIname\fP[\fIsubscript\fP]} expands to the length of
2101 ${\fIname\fP[\fIsubscript\fP]}. If \fIsubscript\fP is \fB*\fP or
2102 \fB@\fP, the expansion is the number of elements in the array.
2103 Referencing an array variable without a subscript is equivalent to
2104 referencing element zero.
2108 builtin is used to destroy arrays. \fBunset\fP \fIname\fP[\fIsubscript\fP]
2109 destroys the array element at index \fIsubscript\fP.
2110 Care must be taken to avoid unwanted side effects caused by filename
2112 \fBunset\fP \fIname\fP, where \fIname\fP is an array, or
2113 \fBunset\fP \fIname\fP[\fIsubscript\fP], where
2114 \fIsubscript\fP is \fB*\fP or \fB@\fP, removes the entire array.
2121 builtins each accept a
2123 option to specify an array. The
2127 option to assign a list of words read from the standard input
2132 builtins display array values in a way that allows them to be
2133 reused as assignments.
2135 Expansion is performed on the command line after it has been split into
2136 words. There are seven kinds of expansion performed:
2137 .IR "brace expansion" ,
2138 .IR "tilde expansion" ,
2139 .IR "parameter and variable expansion" ,
2140 .IR "command substitution" ,
2141 .IR "arithmetic expansion" ,
2142 .IR "word splitting" ,
2144 .IR "pathname expansion" .
2146 The order of expansions is: brace expansion, tilde expansion,
2147 parameter, variable and arithmetic expansion and
2148 command substitution
2149 (done in a left-to-right fashion), word splitting, and pathname
2152 On systems that can support it, there is an additional expansion
2153 available: \fIprocess substitution\fP.
2155 Only brace expansion, word splitting, and pathname expansion
2156 can change the number of words of the expansion; other expansions
2157 expand a single word to a single word.
2158 The only exceptions to this are the expansions of
2159 "\fB$@\fP" and "\fB${\fP\fIname\fP\fB[@]}\fP"
2160 as explained above (see
2165 .I "Brace expansion"
2166 is a mechanism by which arbitrary strings
2167 may be generated. This mechanism is similar to
2168 \fIpathname expansion\fP, but the filenames generated
2169 need not exist. Patterns to be brace expanded take
2170 the form of an optional
2172 followed by either a series of comma-separated strings or
2173 a sequence expression between a pair of braces, followed by
2176 The preamble is prefixed to each string contained
2177 within the braces, and the postscript is then appended
2178 to each resulting string, expanding left to right.
2180 Brace expansions may be nested. The results of each expanded
2181 string are not sorted; left to right order is preserved.
2182 For example, a\fB{\fPd,c,b\fB}\fPe expands into `ade ace abe'.
2184 A sequence expression takes the form \fB{\fP\fIx\fP\fB..\fP\fIy\fP\fB}\fP,
2185 where \fIx\fP and \fIy\fP are either integers or single characters.
2186 When integers are supplied, the expression expands to each number between
2187 \fIx\fP and \fIy\fP, inclusive.
2188 When characters are supplied, the expression expands to each character
2189 lexicographically between \fIx\fP and \fIy\fP, inclusive. Note that
2190 both \fIx\fP and \fIy\fP must be of the same type.
2192 Brace expansion is performed before any other expansions,
2193 and any characters special to other expansions are preserved
2194 in the result. It is strictly textual.
2196 does not apply any syntactic interpretation to the context of the
2197 expansion or the text between the braces.
2199 A correctly-formed brace expansion must contain unquoted opening
2200 and closing braces, and at least one unquoted comma or a valid
2201 sequence expression.
2202 Any incorrectly formed brace expansion is left unchanged.
2203 A \fB{\fP or \fB,\fP may be quoted with a backslash to prevent its
2204 being considered part of a brace expression.
2205 To avoid conflicts with parameter expansion, the string \fB${\fP
2206 is not considered eligible for brace expansion.
2208 This construct is typically used as shorthand when the common
2209 prefix of the strings to be generated is longer than in the
2213 mkdir /usr/local/src/bash/{old,new,dist,bugs}
2217 chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}
2220 Brace expansion introduces a slight incompatibility with
2221 historical versions of
2224 does not treat opening or closing braces specially when they
2225 appear as part of a word, and preserves them in the output.
2227 removes braces from words as a consequence of brace
2228 expansion. For example, a word entered to
2231 appears identically in the output. The same word is
2236 If strict compatibility with
2242 option or disable brace expansion with the
2248 .B SHELL BUILTIN COMMANDS
2252 If a word begins with an unquoted tilde character (`\fB~\fP'), all of
2253 the characters preceding the first unquoted slash (or all characters,
2254 if there is no unquoted slash) are considered a \fItilde-prefix\fP.
2255 If none of the characters in the tilde-prefix are quoted, the
2256 characters in the tilde-prefix following the tilde are treated as a
2257 possible \fIlogin name\fP.
2258 If this login name is the null string, the tilde is replaced with the
2259 value of the shell parameter
2265 is unset, the home directory of the user executing the shell is
2266 substituted instead.
2267 Otherwise, the tilde-prefix is replaced with the home directory
2268 associated with the specified login name.
2270 If the tilde-prefix is a `~+', the value of the shell variable
2273 replaces the tilde-prefix.
2274 If the tilde-prefix is a `~\-', the value of the shell variable
2277 if it is set, is substituted.
2278 If the characters following the tilde in the tilde-prefix consist
2279 of a number \fIN\fP, optionally prefixed
2280 by a `+' or a `\-', the tilde-prefix is replaced with the corresponding
2281 element from the directory stack, as it would be displayed by the
2283 builtin invoked with the tilde-prefix as an argument.
2284 If the characters following the tilde in the tilde-prefix consist of a
2285 number without a leading `+' or `\-', `+' is assumed.
2287 If the login name is invalid, or the tilde expansion fails, the word
2290 Each variable assignment is checked for unquoted tilde-prefixes immediately
2295 In these cases, tilde expansion is also performed.
2296 Consequently, one may use file names with tildes in assignments to
2304 and the shell assigns the expanded value.
2305 .SS Parameter Expansion
2307 The `\fB$\fP' character introduces parameter expansion,
2308 command substitution, or arithmetic expansion. The parameter name
2309 or symbol to be expanded may be enclosed in braces, which
2310 are optional but serve to protect the variable to be expanded from
2311 characters immediately following it which could be
2312 interpreted as part of the name.
2314 When braces are used, the matching ending brace is the first `\fB}\fP'
2315 not escaped by a backslash or within a quoted string, and not within an
2316 embedded arithmetic expansion, command substitution, or parameter
2322 The value of \fIparameter\fP is substituted. The braces are required
2325 is a positional parameter with more than one digit,
2328 is followed by a character which is not to be
2329 interpreted as part of its name.
2332 If the first character of \fIparameter\fP is an exclamation point,
2333 a level of variable indirection is introduced.
2334 \fBBash\fP uses the value of the variable formed from the rest of
2335 \fIparameter\fP as the name of the variable; this variable is then
2336 expanded and that value is used in the rest of the substitution, rather
2337 than the value of \fIparameter\fP itself.
2338 This is known as \fIindirect expansion\fP.
2339 The exceptions to this are the expansions of ${!\fIprefix\fP*} and
2340 ${\fB!\fP\fIname\fP[\fI@\fP]} described below.
2341 The exclamation point must immediately follow the left brace in order to
2342 introduce indirection.
2344 In each of the cases below, \fIword\fP is subject to tilde expansion,
2345 parameter expansion, command substitution, and arithmetic expansion.
2346 When not performing substring expansion, \fBbash\fP tests for a parameter
2347 that is unset or null; omitting the colon results in a test only for a
2348 parameter that is unset.
2352 ${\fIparameter\fP\fB:\-\fP\fIword\fP}
2353 \fBUse Default Values\fP. If
2355 is unset or null, the expansion of
2357 is substituted. Otherwise, the value of
2361 ${\fIparameter\fP\fB:=\fP\fIword\fP}
2362 \fBAssign Default Values\fP.
2365 is unset or null, the expansion of
2371 is then substituted. Positional parameters and special parameters may
2372 not be assigned to in this way.
2374 ${\fIparameter\fP\fB:?\fP\fIword\fP}
2375 \fBDisplay Error if Null or Unset\fP.
2378 is null or unset, the expansion of \fIword\fP (or a message to that effect
2381 is not present) is written to the standard error and the shell, if it
2382 is not interactive, exits. Otherwise, the value of \fIparameter\fP is
2385 ${\fIparameter\fP\fB:+\fP\fIword\fP}
2386 \fBUse Alternate Value\fP.
2389 is null or unset, nothing is substituted, otherwise the expansion of
2393 ${\fIparameter\fP\fB:\fP\fIoffset\fP}
2396 ${\fIparameter\fP\fB:\fP\fIoffset\fP\fB:\fP\fIlength\fP}
2398 \fBSubstring Expansion.\fP
2399 Expands to up to \fIlength\fP characters of \fIparameter\fP
2400 starting at the character specified by \fIoffset\fP.
2401 If \fIlength\fP is omitted, expands to the substring of
2402 \fIparameter\fP starting at the character specified by \fIoffset\fP.
2403 \fIlength\fP and \fIoffset\fP are arithmetic expressions (see
2406 ARITHMETIC EVALUATION
2408 \fIlength\fP must evaluate to a number greater than or equal to zero.
2409 If \fIoffset\fP evaluates to a number less than zero, the value
2410 is used as an offset from the end of the value of \fIparameter\fP.
2411 If \fIparameter\fP is \fB@\fP, the result is \fIlength\fP positional
2412 parameters beginning at \fIoffset\fP.
2413 If \fIparameter\fP is an array name indexed by @ or *,
2414 the result is the \fIlength\fP
2415 members of the array beginning with ${\fIparameter\fP[\fIoffset\fP]}.
2416 A negative \fIoffset\fP is taken relative to one greater than the maximum
2417 index of the specified array.
2418 Note that a negative offset must be separated from the colon by at least
2419 one space to avoid being confused with the :- expansion.
2420 Substring indexing is zero-based unless the positional parameters
2421 are used, in which case the indexing starts at 1.
2423 ${\fB!\fP\fIprefix\fP\fB*\fP}
2426 ${\fB!\fP\fIprefix\fP\fB@\fP}
2428 Expands to the names of variables whose names begin with \fIprefix\fP,
2429 separated by the first character of the
2434 ${\fB!\fP\fIname\fP[\fI@\fP]}
2437 ${\fB!\fP\fIname\fP[\fI*\fP]}
2439 If \fIname\fP is an array variable, expands to the list of array indices
2440 (keys) assigned in \fIname\fP.
2441 If \fIname\fP is not an array, expands to 0 if \fIname\fP is set and null
2443 When \fI@\fP is used and the expansion appears within double quotes, each
2444 key expands to a separate word.
2446 ${\fB#\fP\fIparameter\fP}
2447 The length in characters of the value of \fIparameter\fP is substituted.
2454 the value substituted is the number of positional parameters.
2457 is an array name subscripted by
2461 the value substituted is the number of elements in the array.
2463 ${\fIparameter\fP\fB#\fP\fIword\fP}
2466 ${\fIparameter\fP\fB##\fP\fIword\fP}
2470 is expanded to produce a pattern just as in pathname
2471 expansion. If the pattern matches the beginning of
2474 then the result of the expansion is the expanded value of
2476 with the shortest matching pattern (the ``\fB#\fP'' case) or the
2477 longest matching pattern (the ``\fB##\fP'' case) deleted.
2484 the pattern removal operation is applied to each positional
2485 parameter in turn, and the expansion is the resultant list.
2488 is an array variable subscripted with
2492 the pattern removal operation is applied to each member of the
2493 array in turn, and the expansion is the resultant list.
2495 ${\fIparameter\fP\fB%\fP\fIword\fP}
2498 ${\fIparameter\fP\fB%%\fP\fIword\fP}
2500 The \fIword\fP is expanded to produce a pattern just as in
2502 If the pattern matches a trailing portion of the expanded value of
2504 then the result of the expansion is the expanded value of
2506 with the shortest matching pattern (the ``\fB%\fP'' case) or the
2507 longest matching pattern (the ``\fB%%\fP'' case) deleted.
2514 the pattern removal operation is applied to each positional
2515 parameter in turn, and the expansion is the resultant list.
2518 is an array variable subscripted with
2522 the pattern removal operation is applied to each member of the
2523 array in turn, and the expansion is the resultant list.
2525 ${\fIparameter\fP\fB/\fP\fIpattern\fP\fB/\fP\fIstring\fP}
2528 ${\fIparameter\fP\fB//\fP\fIpattern\fP\fB/\fP\fIstring\fP}
2530 The \fIpattern\fP is expanded to produce a pattern just as in
2532 \fIParameter\fP is expanded and the longest match of \fIpattern\fP
2533 against its value is replaced with \fIstring\fP.
2534 In the first form, only the first match is replaced.
2535 The second form causes all matches of \fIpattern\fP to be
2536 replaced with \fIstring\fP.
2537 If \fIpattern\fP begins with \fB#\fP, it must match at the beginning
2538 of the expanded value of \fIparameter\fP.
2539 If \fIpattern\fP begins with \fB%\fP, it must match at the end
2540 of the expanded value of \fIparameter\fP.
2541 If \fIstring\fP is null, matches of \fIpattern\fP are deleted
2542 and the \fB/\fP following \fIpattern\fP may be omitted.
2549 the substitution operation is applied to each positional
2550 parameter in turn, and the expansion is the resultant list.
2553 is an array variable subscripted with
2557 the substitution operation is applied to each member of the
2558 array in turn, and the expansion is the resultant list.
2559 .SS Command Substitution
2561 \fICommand substitution\fP allows the output of a command to replace
2562 the command name. There are two forms:
2566 \fB$(\fP\fIcommand\fP\|\fB)\fP
2570 \fB`\fP\fIcommand\fP\fB`\fP
2574 performs the expansion by executing \fIcommand\fP and
2575 replacing the command substitution with the standard output of the
2576 command, with any trailing newlines deleted.
2577 Embedded newlines are not deleted, but they may be removed during
2579 The command substitution \fB$(cat \fIfile\fP)\fR can be replaced by
2580 the equivalent but faster \fB$(< \fIfile\fP)\fR.
2582 When the old-style backquote form of substitution is used,
2583 backslash retains its literal meaning except when followed by
2588 The first backquote not preceded by a backslash terminates the
2589 command substitution.
2590 When using the $(\^\fIcommand\fP\|) form, all characters between the
2591 parentheses make up the command; none are treated specially.
2593 Command substitutions may be nested. To nest when using the backquoted form,
2594 escape the inner backquotes with backslashes.
2596 If the substitution appears within double quotes, word splitting and
2597 pathname expansion are not performed on the results.
2598 .SS Arithmetic Expansion
2600 Arithmetic expansion allows the evaluation of an arithmetic expression
2601 and the substitution of the result. The format for arithmetic expansion is:
2604 \fB$((\fP\fIexpression\fP\fB))\fP
2609 is treated as if it were within double quotes, but a double quote
2610 inside the parentheses is not treated specially.
2611 All tokens in the expression undergo parameter expansion, string
2612 expansion, command substitution, and quote removal.
2613 Arithmetic expansions may be nested.
2615 The evaluation is performed according to the rules listed below under
2617 .BR "ARITHMETIC EVALUATION" .
2622 prints a message indicating failure and no substitution occurs.
2623 .SS Process Substitution
2625 \fIProcess substitution\fP is supported on systems that support named
2626 pipes (\fIFIFOs\fP) or the \fB/dev/fd\fP method of naming open files.
2627 It takes the form of
2628 \fB<(\fP\fIlist\^\fP\fB)\fP
2630 \fB>(\fP\fIlist\^\fP\fB)\fP.
2631 The process \fIlist\fP is run with its input or output connected to a
2632 \fIFIFO\fP or some file in \fB/dev/fd\fP. The name of this file is
2633 passed as an argument to the current command as the result of the
2634 expansion. If the \fB>(\fP\fIlist\^\fP\fB)\fP form is used, writing to
2635 the file will provide input for \fIlist\fP. If the
2636 \fB<(\fP\fIlist\^\fP\fB)\fP form is used, the file passed as an
2637 argument should be read to obtain the output of \fIlist\fP.
2639 When available, process substitution is performed
2640 simultaneously with parameter and variable expansion,
2641 command substitution,
2642 and arithmetic expansion.
2645 The shell scans the results of
2646 parameter expansion,
2647 command substitution,
2649 arithmetic expansion
2650 that did not occur within double quotes for
2651 .IR "word splitting" .
2653 The shell treats each character of
2656 as a delimiter, and splits the results of the other
2657 expansions into words on these characters. If
2662 .BR <space><tab><newline> ,
2667 characters serves to delimit words. If
2670 has a value other than the default, then sequences of
2671 the whitespace characters
2675 are ignored at the beginning and end of the
2676 word, as long as the whitespace character is in the
2683 whitespace character).
2690 whitespace, along with any adjacent
2693 whitespace characters, delimits a field.
2697 whitespace characters is also treated as a delimiter.
2701 is null, no word splitting occurs.
2703 Explicit null arguments (\^\f3"\^"\fP or \^\f3'\^'\fP\^) are retained.
2704 Unquoted implicit null arguments, resulting from the expansion of
2705 parameters that have no values, are removed.
2706 If a parameter with no value is expanded within double quotes, a
2707 null argument results and is retained.
2709 Note that if no expansion occurs, no splitting
2711 .SS Pathname Expansion
2713 After word splitting,
2716 option has been set,
2718 scans each word for the characters
2723 If one of these characters appears, then the word is
2726 and replaced with an alphabetically sorted list of
2727 file names matching the pattern.
2728 If no matching file names are found,
2729 and the shell option
2731 is disabled, the word is left unchanged.
2734 option is set, and no matches are found,
2735 the word is removed.
2738 shell option is set, and no matches are found, an error message
2739 is printed and the command is not executed.
2742 is enabled, the match is performed without regard to the case
2743 of alphabetic characters.
2744 When a pattern is used for pathname expansion,
2747 at the start of a name or immediately following a slash
2748 must be matched explicitly, unless the shell option
2751 When matching a pathname, the slash character must always be
2755 character is not treated specially.
2756 See the description of
2760 .B SHELL BUILTIN COMMANDS
2761 for a description of the
2772 shell variable may be used to restrict the set of file names matching a
2777 is set, each matching file name that also matches one of the patterns in
2780 is removed from the list of matches.
2785 are always ignored when
2788 is set and not null. However, setting
2791 to a non-null value has the effect of enabling the
2793 shell option, so all other file names beginning with a
2796 To get the old behavior of ignoring file names beginning with a
2800 one of the patterns in
2805 option is disabled when
2810 \fBPattern Matching\fP
2812 Any character that appears in a pattern, other than the special pattern
2813 characters described below, matches itself. The NUL character may not
2814 occur in a pattern. A backslash escapes the following character; the
2815 escaping backslash is discarded when matching.
2816 The special pattern characters must be quoted if
2817 they are to be matched literally.
2819 The special pattern characters have the following meanings:
2824 Matches any string, including the null string.
2827 Matches any single character.
2830 Matches any one of the enclosed characters. A pair of characters
2831 separated by a hyphen denotes a
2832 \fIrange expression\fP;
2833 any character that sorts between those two characters, inclusive,
2834 using the current locale's collating sequence and character set,
2835 is matched. If the first character following the
2841 then any character not enclosed is matched.
2842 The sorting order of characters in range expressions is determined by
2843 the current locale and the value of the \fBLC_COLLATE\fP shell variable,
2847 may be matched by including it as the first or last character
2851 may be matched by including it as the first character
2860 \fIcharacter classes\fP can be specified using the syntax
2861 \fB[:\fP\fIclass\fP\fB:]\fP, where \fIclass\fP is one of the
2862 following classes defined in the POSIX.2 standard:
2866 .if n alnum alpha ascii blank cntrl digit graph lower print punct space upper word xdigit
2867 .if t alnum alpha ascii blank cntrl digit graph lower print punct space upper word xdigit
2869 A character class matches any character belonging to that class.
2870 The \fBword\fP character class matches letters, digits, and the character _.
2878 an \fIequivalence class\fP can be specified using the syntax
2879 \fB[=\fP\fIc\fP\fB=]\fP, which matches all characters with the
2880 same collation weight (as defined by the current locale) as
2881 the character \fIc\fP.
2889 the syntax \fB[.\fP\fIsymbol\fP\fB.]\fP matches the collating symbol
2894 If the \fBextglob\fP shell option is enabled using the \fBshopt\fP
2895 builtin, several extended pattern matching operators are recognized.
2896 In the following description, a \fIpattern-list\fP is a list of one
2897 or more patterns separated by a \fB|\fP.
2898 Composite patterns may be formed using one or more of the following
2904 \fB?(\fP\^\fIpattern-list\^\fP\fB)\fP
2905 Matches zero or one occurrence of the given patterns
2907 \fB*(\fP\^\fIpattern-list\^\fP\fB)\fP
2908 Matches zero or more occurrences of the given patterns
2910 \fB+(\fP\^\fIpattern-list\^\fP\fB)\fP
2911 Matches one or more occurrences of the given patterns
2913 \fB@(\fP\^\fIpattern-list\^\fP\fB)\fP
2914 Matches one of the given patterns
2916 \fB!(\fP\^\fIpattern-list\^\fP\fB)\fP
2917 Matches anything except one of the given patterns
2922 After the preceding expansions, all unquoted occurrences of the
2926 and \^\f3"\fP\^ that did not result from one of the above
2927 expansions are removed.
2929 Before a command is executed, its input and output
2932 using a special notation interpreted by the shell.
2933 Redirection may also be used to open and close files for the
2934 current shell execution environment. The following redirection
2935 operators may precede or appear anywhere within a
2939 Redirections are processed in the order they appear, from
2942 In the following descriptions, if the file descriptor number is
2943 omitted, and the first character of the redirection operator is
2945 the redirection refers to the standard input (file descriptor
2946 0). If the first character of the redirection operator is
2948 the redirection refers to the standard output (file descriptor
2951 The word following the redirection operator in the following
2952 descriptions, unless otherwise noted, is subjected to brace expansion,
2953 tilde expansion, parameter expansion, command substitution, arithmetic
2954 expansion, quote removal, pathname expansion, and word splitting.
2955 If it expands to more than one word,
2959 Note that the order of redirections is significant. For example,
2963 ls \fB>\fP dirlist 2\fB>&\fP1
2966 directs both standard output and standard error to the file
2971 ls 2\fB>&\fP1 \fB>\fP dirlist
2974 directs only the standard output to file
2976 because the standard error was duplicated as standard output
2977 before the standard output was redirected to
2980 \fBBash\fP handles several filenames specially when they are used in
2981 redirections, as described in the following table:
2987 If \fIfd\fP is a valid integer, file descriptor \fIfd\fP is duplicated.
2990 File descriptor 0 is duplicated.
2993 File descriptor 1 is duplicated.
2996 File descriptor 2 is duplicated.
2998 .B /dev/tcp/\fIhost\fP/\fIport\fP
2999 If \fIhost\fP is a valid hostname or Internet address, and \fIport\fP
3000 is an integer port number or service name, \fBbash\fP attempts to open
3001 a TCP connection to the corresponding socket.
3003 .B /dev/udp/\fIhost\fP/\fIport\fP
3004 If \fIhost\fP is a valid hostname or Internet address, and \fIport\fP
3005 is an integer port number or service name, \fBbash\fP attempts to open
3006 a UDP connection to the corresponding socket.
3010 A failure to open or create a file causes the redirection to fail.
3012 Redirections using file descriptors greater than 9 should be used with
3013 care, as they may conflict with file descriptors the shell uses
3015 .SS Redirecting Input
3017 Redirection of input causes the file whose name results from
3020 to be opened for reading on file descriptor
3022 or the standard input (file descriptor 0) if
3026 The general format for redirecting input is:
3029 [\fIn\fP]\fB<\fP\fIword\fP
3031 .SS Redirecting Output
3033 Redirection of output causes the file whose name results from
3036 to be opened for writing on file descriptor
3038 or the standard output (file descriptor 1) if
3040 is not specified. If the file does not exist it is created;
3041 if it does exist it is truncated to zero size.
3043 The general format for redirecting output is:
3046 [\fIn\fP]\fB>\fP\fIword\fP
3049 If the redirection operator is
3055 builtin has been enabled, the redirection will fail if the file
3056 whose name results from the expansion of \fIword\fP exists and is
3058 If the redirection operator is
3060 or the redirection operator is
3066 builtin command is not enabled, the redirection is attempted even
3067 if the file named by \fIword\fP exists.
3068 .SS Appending Redirected Output
3070 Redirection of output in this fashion
3071 causes the file whose name results from
3074 to be opened for appending on file descriptor
3076 or the standard output (file descriptor 1) if
3078 is not specified. If the file does not exist it is created.
3080 The general format for appending output is:
3083 [\fIn\fP]\fB>>\fP\fIword\fP
3086 .SS Redirecting Standard Output and Standard Error
3090 standard output (file descriptor 1) and
3091 the standard error output (file descriptor 2)
3092 to be redirected to the file whose name is the
3095 with this construct.
3097 There are two formats for redirecting standard output and
3108 Of the two forms, the first is preferred.
3109 This is semantically equivalent to
3112 \fB>\fP\fIword\fP 2\fB>&\fP1
3116 This type of redirection instructs the shell to read input from the
3117 current source until a line containing only
3119 (with no trailing blanks)
3121 the lines read up to that point are then used as the standard
3122 input for a command.
3124 The format of here-documents is:
3128 \fB<<\fP[\fB\-\fP]\fIword\fP
3134 No parameter expansion, command substitution, arithmetic expansion,
3135 or pathname expansion is performed on
3137 If any characters in
3141 is the result of quote removal on
3143 and the lines in the here-document are not expanded.
3144 If \fIword\fP is unquoted,
3145 all lines of the here-document are subjected to parameter expansion,
3146 command substitution, and arithmetic expansion. In the latter
3147 case, the character sequence
3151 must be used to quote the characters
3157 If the redirection operator is
3159 then all leading tab characters are stripped from input lines and the
3163 here-documents within shell scripts to be indented in a
3166 A variant of here documents, the format is:
3174 The \fIword\fP is expanded and supplied to the command on its standard
3176 .SS "Duplicating File Descriptors"
3178 The redirection operator
3181 [\fIn\fP]\fB<&\fP\fIword\fP
3184 is used to duplicate input file descriptors.
3187 expands to one or more digits, the file descriptor denoted by
3189 is made to be a copy of that file descriptor.
3192 do not specify a file descriptor open for input, a redirection error occurs.
3201 is not specified, the standard input (file descriptor 0) is used.
3206 [\fIn\fP]\fB>&\fP\fIword\fP
3209 is used similarly to duplicate output file descriptors. If
3211 is not specified, the standard output (file descriptor 1) is used.
3214 do not specify a file descriptor open for output, a redirection error occurs.
3215 As a special case, if \fIn\fP is omitted, and \fIword\fP does not
3216 expand to one or more digits, the standard output and standard
3217 error are redirected as described previously.
3218 .SS "Moving File Descriptors"
3220 The redirection operator
3223 [\fIn\fP]\fB<&\fP\fIdigit\fP\fB\-\fP
3226 moves the file descriptor \fIdigit\fP to file descriptor
3228 or the standard input (file descriptor 0) if \fIn\fP is not specified.
3229 \fIdigit\fP is closed after being duplicated to \fIn\fP.
3231 Similarly, the redirection operator
3234 [\fIn\fP]\fB>&\fP\fIdigit\fP\fB\-\fP
3237 moves the file descriptor \fIdigit\fP to file descriptor
3239 or the standard output (file descriptor 1) if \fIn\fP is not specified.
3240 .SS "Opening File Descriptors for Reading and Writing"
3242 The redirection operator
3245 [\fIn\fP]\fB<>\fP\fIword\fP
3248 causes the file whose name is the expansion of
3250 to be opened for both reading and writing on file descriptor
3252 or on file descriptor 0 if
3254 is not specified. If the file does not exist, it is created.
3256 \fIAliases\fP allow a string to be substituted for a word when it is used
3257 as the first word of a simple command.
3258 The shell maintains a list of aliases that may be set and unset with the
3262 builtin commands (see
3264 .B SHELL BUILTIN COMMANDS
3266 The first word of each simple command, if unquoted,
3267 is checked to see if it has an
3268 alias. If so, that word is replaced by the text of the alias.
3269 The characters \fB/\fP, \fB$\fP, \fB`\fP, and \fB=\fP and
3270 any of the shell \fImetacharacters\fP or quoting characters
3271 listed above may not appear in an alias name.
3272 The replacement text may contain any valid shell input,
3273 including shell metacharacters.
3274 The first word of the replacement text is tested
3275 for aliases, but a word that is identical to an alias being expanded
3276 is not expanded a second time.
3277 This means that one may alias
3283 does not try to recursively expand the replacement text.
3284 If the last character of the alias value is a
3286 then the next command
3287 word following the alias is also checked for alias expansion.
3289 Aliases are created and listed with the
3291 command, and removed with the
3295 There is no mechanism for using arguments in the replacement text.
3296 If arguments are needed, a shell function should be used (see
3301 Aliases are not expanded when the shell is not interactive, unless
3304 shell option is set using
3306 (see the description of
3310 \fBSHELL BUILTIN COMMANDS\fP
3313 The rules concerning the definition and use of aliases are
3316 always reads at least one complete line
3317 of input before executing any
3318 of the commands on that line. Aliases are expanded when a
3319 command is read, not when it is executed. Therefore, an
3320 alias definition appearing on the same line as another
3321 command does not take effect until the next line of input is read.
3322 The commands following the alias definition
3323 on that line are not affected by the new alias.
3324 This behavior is also an issue when functions are executed.
3325 Aliases are expanded when a function definition is read,
3326 not when the function is executed, because a function definition
3327 is itself a compound command. As a consequence, aliases
3328 defined in a function are not available until after that
3329 function is executed. To be safe, always put
3330 alias definitions on a separate line, and do not use
3332 in compound commands.
3334 For almost every purpose, aliases are superseded by
3337 A shell function, defined as described above under
3339 .BR "SHELL GRAMMAR" ,
3340 stores a series of commands for later execution.
3341 When the name of a shell function is used as a simple command name,
3342 the list of commands associated with that function name is executed.
3343 Functions are executed in the context of the
3344 current shell; no new process is created to interpret
3345 them (contrast this with the execution of a shell script).
3346 When a function is executed, the arguments to the
3347 function become the positional parameters
3348 during its execution.
3349 The special parameter
3351 is updated to reflect the change. Special parameter 0
3353 The first element of the
3356 variable is set to the name of the function while the function
3358 All other aspects of the shell execution
3359 environment are identical between a function and its caller
3360 with the exception that the
3365 traps (see the description of the
3369 .B SHELL BUILTIN COMMANDS
3370 below) are not inherited unless the function has been given the
3371 \fBtrace\fP attribute (see the description of the
3374 builtin below) or the
3375 \fB\-o functrace\fP shell option has been enabled with
3376 the \fBset\fP builtin
3377 (in which case all functions inherit the \fBDEBUG\fP and \fBRETURN\fP traps).
3379 Variables local to the function may be declared with the
3381 builtin command. Ordinarily, variables and their values
3382 are shared between the function and its caller.
3384 If the builtin command
3386 is executed in a function, the function completes and
3387 execution resumes with the next command after the function
3389 Any command associated with the \fBRETURN\fP trap is executed
3390 before execution resumes.
3391 When a function completes, the values of the
3392 positional parameters and the special parameter
3394 are restored to the values they had prior to the function's
3397 Function names and definitions may be listed with the
3403 builtin commands. The
3409 will list the function names only
3410 (and optionally the source file and line number, if the \fBextdebug\fP
3411 shell option is enabled).
3412 Functions may be exported so that subshells
3413 automatically have them defined with the
3418 Note that shell functions and variables with the same name may result
3419 in multiple identically-named entries in the environment passed to the
3421 Care should be taken in cases where this may cause a problem.
3423 Functions may be recursive. No limit is imposed on the number
3425 .SH "ARITHMETIC EVALUATION"
3426 The shell allows arithmetic expressions to be evaluated, under
3427 certain circumstances (see the \fBlet\fP and \fBdeclare\fP builtin
3428 commands and \fBArithmetic Expansion\fP).
3429 Evaluation is done in fixed-width integers with no check for overflow,
3430 though division by 0 is trapped and flagged as an error.
3431 The operators and their precedence, associativity, and values
3432 are the same as in the C language.
3433 The following list of operators is grouped into levels of
3434 equal-precedence operators.
3435 The levels are listed in order of decreasing precedence.
3439 .B \fIid\fP++ \fIid\fP\-\-
3440 variable post-increment and post-decrement
3442 .B ++\fIid\fP \-\-\fIid\fP
3443 variable pre-increment and pre-decrement
3446 unary minus and plus
3449 logical and bitwise negation
3455 multiplication, division, remainder
3458 addition, subtraction
3461 left and right bitwise shifts
3467 equality and inequality
3473 bitwise exclusive OR
3484 .B \fIexpr\fP?\fIexpr\fP:\fIexpr\fP
3485 conditional operator
3487 .B = *= /= %= += \-= <<= >>= &= ^= |=
3490 .B \fIexpr1\fP , \fIexpr2\fP
3494 Shell variables are allowed as operands; parameter expansion is
3495 performed before the expression is evaluated.
3496 Within an expression, shell variables may also be referenced by name
3497 without using the parameter expansion syntax.
3498 A shell variable that is null or unset evaluates to 0 when referenced
3499 by name without using the parameter expansion syntax.
3500 The value of a variable is evaluated as an arithmetic expression
3501 when it is referenced, or when a variable which has been given the
3502 \fIinteger\fP attribute using \fBdeclare -i\fP is assigned a value.
3503 A null value evaluates to 0.
3504 A shell variable need not have its integer attribute
3505 turned on to be used in an expression.
3507 Constants with a leading 0 are interpreted as octal numbers.
3508 A leading 0x or 0X denotes hexadecimal.
3509 Otherwise, numbers take the form [\fIbase#\fP]n, where \fIbase\fP
3510 is a decimal number between 2 and 64 representing the arithmetic
3511 base, and \fIn\fP is a number in that base.
3512 If \fIbase#\fP is omitted, then base 10 is used.
3513 The digits greater than 9 are represented by the lowercase letters,
3514 the uppercase letters, @, and _, in that order.
3515 If \fIbase\fP is less than or equal to 36, lowercase and uppercase
3516 letters may be used interchangeably to represent numbers between 10
3519 Operators are evaluated in order of precedence. Sub-expressions in
3520 parentheses are evaluated first and may override the precedence
3522 .SH "CONDITIONAL EXPRESSIONS"
3523 Conditional expressions are used by the \fB[[\fP compound command and
3524 the \fBtest\fP and \fB[\fP builtin commands to test file attributes
3525 and perform string and arithmetic comparisons.
3526 Expressions are formed from the following unary or binary primaries.
3527 If any \fIfile\fP argument to one of the primaries is of the form
3528 \fI/dev/fd/n\fP, then file descriptor \fIn\fP is checked.
3529 If the \fIfile\fP argument to one of the primaries is one of
3530 \fI/dev/stdin\fP, \fI/dev/stdout\fP, or \fI/dev/stderr\fP, file
3531 descriptor 0, 1, or 2, respectively, is checked.
3533 Unless otherwise specified, primaries that operate on files follow symbolic
3534 links and operate on the target of the link, rather than the link itself.
3539 True if \fIfile\fP exists.
3542 True if \fIfile\fP exists and is a block special file.
3545 True if \fIfile\fP exists and is a character special file.
3548 True if \fIfile\fP exists and is a directory.
3551 True if \fIfile\fP exists.
3554 True if \fIfile\fP exists and is a regular file.
3557 True if \fIfile\fP exists and is set-group-id.
3560 True if \fIfile\fP exists and is a symbolic link.
3563 True if \fIfile\fP exists and its ``sticky'' bit is set.
3566 True if \fIfile\fP exists and is a named pipe (FIFO).
3569 True if \fIfile\fP exists and is readable.
3572 True if \fIfile\fP exists and has a size greater than zero.
3575 True if file descriptor
3577 is open and refers to a terminal.
3580 True if \fIfile\fP exists and its set-user-id bit is set.
3583 True if \fIfile\fP exists and is writable.
3586 True if \fIfile\fP exists and is executable.
3589 True if \fIfile\fP exists and is owned by the effective user id.
3592 True if \fIfile\fP exists and is owned by the effective group id.
3595 True if \fIfile\fP exists and is a symbolic link.
3598 True if \fIfile\fP exists and is a socket.
3601 True if \fIfile\fP exists and has been modified since it was last read.
3603 \fIfile1\fP \-\fBnt\fP \fIfile2\fP
3604 True if \fIfile1\fP is newer (according to modification date) than \fIfile2\fP,
3605 or if \fIfile1\fP exists and \fPfile2\fP does not.
3607 \fIfile1\fP \-\fBot\fP \fIfile2\fP
3608 True if \fIfile1\fP is older than \fIfile2\fP, or if \fIfile2\fP exists
3609 and \fIfile1\fP does not.
3611 \fIfile1\fP \fB\-ef\fP \fIfile2\fP
3612 True if \fIfile1\fP and \fIfile2\fP refer to the same device and
3615 .B \-o \fIoptname\fP
3616 True if shell option
3619 See the list of options under the description of the
3626 True if the length of \fIstring\fP is zero.
3633 True if the length of
3637 \fIstring1\fP \fB==\fP \fIstring2\fP
3638 True if the strings are equal. \fB=\fP may be used in place of
3639 \fB==\fP for strict POSIX compliance.
3641 \fIstring1\fP \fB!=\fP \fIstring2\fP
3642 True if the strings are not equal.
3644 \fIstring1\fP \fB<\fP \fIstring2\fP
3645 True if \fIstring1\fP sorts before \fIstring2\fP lexicographically
3646 in the current locale.
3648 \fIstring1\fP \fB>\fP \fIstring2\fP
3649 True if \fIstring1\fP sorts after \fIstring2\fP lexicographically
3650 in the current locale.
3652 .I \fIarg1\fP \fBOP\fP \fIarg2\fP
3663 These arithmetic binary operators return true if \fIarg1\fP
3664 is equal to, not equal to, less than, less than or equal to,
3665 greater than, or greater than or equal to \fIarg2\fP, respectively.
3669 may be positive or negative integers.
3671 .SH "SIMPLE COMMAND EXPANSION"
3672 When a simple command is executed, the shell performs the following
3673 expansions, assignments, and redirections, from left to right.
3675 The words that the parser has marked as variable assignments (those
3676 preceding the command name) and redirections are saved for later
3679 The words that are not variable assignments or redirections are
3680 expanded. If any words remain after expansion, the first word
3681 is taken to be the name of the command and the remaining words are
3684 Redirections are performed as described above under
3688 The text after the \fB=\fP in each variable assignment undergoes tilde
3689 expansion, parameter expansion, command substitution, arithmetic expansion,
3690 and quote removal before being assigned to the variable.
3692 If no command name results, the variable assignments affect the current
3693 shell environment. Otherwise, the variables are added to the environment
3694 of the executed command and do not affect the current shell environment.
3695 If any of the assignments attempts to assign a value to a readonly variable,
3696 an error occurs, and the command exits with a non-zero status.
3698 If no command name results, redirections are performed, but do not
3699 affect the current shell environment. A redirection error causes the
3700 command to exit with a non-zero status.
3702 If there is a command name left after expansion, execution proceeds as
3703 described below. Otherwise, the command exits. If one of the expansions
3704 contained a command substitution, the exit status of the command is
3705 the exit status of the last command substitution performed. If there
3706 were no command substitutions, the command exits with a status of zero.
3707 .SH "COMMAND EXECUTION"
3708 After a command has been split into words, if it results in a
3709 simple command and an optional list of arguments, the following
3712 If the command name contains no slashes, the shell attempts to
3713 locate it. If there exists a shell function by that name, that
3714 function is invoked as described above in
3717 If the name does not match a function, the shell searches for
3718 it in the list of shell builtins. If a match is found, that
3721 If the name is neither a shell function nor a builtin,
3722 and contains no slashes,
3724 searches each element of the
3727 for a directory containing an executable file by that name.
3729 uses a hash table to remember the full pathnames of executable
3734 .B "SHELL BUILTIN COMMANDS"
3736 A full search of the directories in
3739 is performed only if the command is not found in the hash table.
3740 If the search is unsuccessful, the shell prints an error
3741 message and returns an exit status of 127.
3743 If the search is successful, or if the command name contains
3744 one or more slashes, the shell executes the named program in a
3745 separate execution environment.
3746 Argument 0 is set to the name given, and the remaining arguments
3747 to the command are set to the arguments given, if any.
3749 If this execution fails because the file is not in executable
3750 format, and the file is not a directory, it is assumed to be
3751 a \fIshell script\fP, a file
3752 containing shell commands. A subshell is spawned to execute
3753 it. This subshell reinitializes itself, so
3754 that the effect is as if a new shell had been invoked
3755 to handle the script, with the exception that the locations of
3756 commands remembered by the parent (see
3760 \fBSHELL BUILTIN COMMANDS\fP)
3761 are retained by the child.
3763 If the program is a file beginning with
3765 the remainder of the first line specifies an interpreter
3766 for the program. The shell executes the
3767 specified interpreter on operating systems that do not
3768 handle this executable format themselves. The arguments to the
3769 interpreter consist of a single optional argument following the
3770 interpreter name on the first line of the program, followed
3771 by the name of the program, followed by the command
3773 .SH COMMAND EXECUTION ENVIRONMENT
3774 The shell has an \fIexecution environment\fP, which consists of the
3778 open files inherited by the shell at invocation, as modified by
3779 redirections supplied to the \fBexec\fP builtin
3781 the current working directory as set by \fBcd\fP, \fBpushd\fP, or
3782 \fBpopd\fP, or inherited by the shell at invocation
3784 the file creation mode mask as set by \fBumask\fP or inherited from
3787 current traps set by \fBtrap\fP
3789 shell parameters that are set by variable assignment or with \fBset\fP
3790 or inherited from the shell's parent in the environment
3792 shell functions defined during execution or inherited from the shell's
3793 parent in the environment
3795 options enabled at invocation (either by default or with command-line
3796 arguments) or by \fBset\fP
3798 options enabled by \fBshopt\fP
3800 shell aliases defined with \fBalias\fP
3802 various process IDs, including those of background jobs, the value
3803 of \fB$$\fP, and the value of \fB$PPID\fP
3805 When a simple command other than a builtin or shell function
3806 is to be executed, it
3807 is invoked in a separate execution environment that consists of
3808 the following. Unless otherwise noted, the values are inherited
3812 the shell's open files, plus any modifications and additions specified
3813 by redirections to the command
3815 the current working directory
3817 the file creation mode mask
3819 shell variables and functions marked for export, along with variables
3820 exported for the command, passed in the environment
3822 traps caught by the shell are reset to the values inherited from the
3823 shell's parent, and traps ignored by the shell are ignored
3825 A command invoked in this separate environment cannot affect the
3826 shell's execution environment.
3828 Command substitution, commands grouped with parentheses,
3829 and asynchronous commands are invoked in a
3830 subshell environment that is a duplicate of the shell environment,
3831 except that traps caught by the shell are reset to the values
3832 that the shell inherited from its parent at invocation. Builtin
3833 commands that are invoked as part of a pipeline are also executed in a
3834 subshell environment. Changes made to the subshell environment
3835 cannot affect the shell's execution environment.
3837 If a command is followed by a \fB&\fP and job control is not active, the
3838 default standard input for the command is the empty file \fI/dev/null\fP.
3839 Otherwise, the invoked command inherits the file descriptors of the calling
3840 shell as modified by redirections.
3842 When a program is invoked it is given an array of strings
3846 \fIname\fP\-\fIvalue\fP pairs, of the form
3847 .IR "name\fR=\fPvalue" .
3849 The shell provides several ways to manipulate the environment.
3850 On invocation, the shell scans its own environment and
3851 creates a parameter for each name found, automatically marking
3854 to child processes. Executed commands inherit the environment.
3859 commands allow parameters and functions to be added to and
3860 deleted from the environment. If the value of a parameter
3861 in the environment is modified, the new value becomes part
3862 of the environment, replacing the old. The environment
3863 inherited by any executed command consists of the shell's
3864 initial environment, whose values may be modified in the shell,
3865 less any pairs removed by the
3867 command, plus any additions via the
3873 The environment for any
3875 or function may be augmented temporarily by prefixing it with
3876 parameter assignments, as described above in
3879 These assignment statements affect only the environment seen
3884 option is set (see the
3886 builtin command below), then
3888 parameter assignments are placed in the environment for a command,
3889 not just those that precede the command name.
3893 invokes an external command, the variable
3895 is set to the full file name of the command and passed to that
3896 command in its environment.
3898 For the shell's purposes, a command which exits with a
3899 zero exit status has succeeded. An exit status of zero
3900 indicates success. A non-zero exit status indicates failure.
3901 When a command terminates on a fatal signal \fIN\fP, \fBbash\fP uses
3902 the value of 128+\fIN\fP as the exit status.
3904 If a command is not found, the child process created to
3905 execute it returns a status of 127. If a command is found
3906 but is not executable, the return status is 126.
3908 If a command fails because of an error during expansion or redirection,
3909 the exit status is greater than zero.
3911 Shell builtin commands return a status of 0 (\fItrue\fP) if
3912 successful, and non-zero (\fIfalse\fP) if an error occurs
3914 All builtins return an exit status of 2 to indicate incorrect usage.
3916 \fBBash\fP itself returns the exit status of the last command
3917 executed, unless a syntax error occurs, in which case it exits
3918 with a non-zero value. See also the \fBexit\fP builtin
3921 When \fBbash\fP is interactive, in the absence of any traps, it ignores
3924 (so that \fBkill 0\fP does not kill an interactive shell),
3928 is caught and handled (so that the \fBwait\fP builtin is interruptible).
3929 In all cases, \fBbash\fP ignores
3932 If job control is in effect,
3943 Non-builtin commands run by \fBbash\fP have signal handlers
3944 set to the values inherited by the shell from its parent.
3945 When job control is not in effect, asynchronous commands
3952 in addition to these inherited handlers.
3953 Commands run as a result of command substitution ignore the
3954 keyboard-generated job control signals
3963 The shell exits by default upon receipt of a
3966 Before exiting, an interactive shell resends the
3969 to all jobs, running or stopped.
3970 Stopped jobs are sent
3973 to ensure that they receive the
3976 To prevent the shell from
3977 sending the signal to a particular job, it should be removed from the
3982 .B "SHELL BUILTIN COMMANDS"
3992 shell option has been set with
3998 to all jobs when an interactive login shell exits.
4000 If \fBbash\fP is waiting for a command to complete and receives a signal
4001 for which a trap has been set, the trap will not be executed until
4002 the command completes.
4003 When \fBbash\fP is waiting for an asynchronous command via the \fBwait\fP
4004 builtin, the reception of a signal for which a trap has been set will
4005 cause the \fBwait\fP builtin to return immediately with an exit status
4006 greater than 128, immediately after which the trap is executed.
4009 refers to the ability to selectively stop (\fIsuspend\fP)
4010 the execution of processes and continue (\fIresume\fP)
4011 their execution at a later point. A user typically employs
4012 this facility via an interactive interface supplied jointly
4013 by the system's terminal driver and
4016 The shell associates a
4018 with each pipeline. It keeps a table of currently executing
4019 jobs, which may be listed with the
4023 starts a job asynchronously (in the
4025 it prints a line that looks like:
4031 indicating that this job is job number 1 and that the process ID
4032 of the last process in the pipeline associated with this job is 25647.
4033 All of the processes in a single pipeline are members of the same job.
4037 abstraction as the basis for job control.
4039 To facilitate the implementation of the user interface to job
4040 control, the operating system maintains the notion of a \fIcurrent terminal
4041 process group ID\fP. Members of this process group (processes whose
4042 process group ID is equal to the current terminal process group ID)
4043 receive keyboard-generated signals such as
4046 These processes are said to be in the
4049 processes are those whose process group ID differs from the terminal's;
4050 such processes are immune to keyboard-generated signals.
4051 Only foreground processes are allowed to read from or write to the
4052 terminal. Background processes which attempt to read from (write to) the
4055 .B SIGTTIN (SIGTTOU)
4056 signal by the terminal driver,
4057 which, unless caught, suspends the process.
4059 If the operating system on which
4064 contains facilities to use it.
4067 character (typically
4069 Control-Z) while a process is running
4070 causes that process to be stopped and returns control to
4073 .I "delayed suspend"
4074 character (typically
4076 Control-Y) causes the process to be stopped when it
4077 attempts to read input from the terminal, and control to
4080 The user may then manipulate the state of this job, using the
4082 command to continue it in the background, the
4084 command to continue it in the foreground, or
4087 command to kill it. A \fB^Z\fP takes effect immediately,
4088 and has the additional side effect of causing pending output
4089 and typeahead to be discarded.
4091 There are a number of ways to refer to a job in the shell.
4094 introduces a job name. Job number
4096 may be referred to as
4098 A job may also be referred to using a prefix of the name used to
4099 start it, or using a substring that appears in its command line.
4104 job. If a prefix matches more than one job,
4106 reports an error. Using
4108 on the other hand, refers to any job containing the string
4110 in its command line. If the substring matches more than one job,
4112 reports an error. The symbols
4116 refer to the shell's notion of the
4118 which is the last job stopped while it was in
4119 the foreground or started in the background.
4122 may be referenced using
4124 In output pertaining to jobs (e.g., the output of the
4126 command), the current job is always flagged with a
4128 and the previous job with a
4130 A single % (with no accompanying job specification) also refers to the
4133 Simply naming a job can be used to bring it into the
4138 bringing job 1 from the background into the foreground.
4141 resumes job 1 in the background, equivalent to
4144 The shell learns immediately whenever a job changes state.
4147 waits until it is about to print a prompt before reporting
4148 changes in a job's status so as to not interrupt
4149 any other output. If the
4156 reports such changes immediately.
4160 is executed for each child that exits.
4162 If an attempt to exit
4164 is made while jobs are stopped, the shell prints a warning message. The
4166 command may then be used to inspect their status.
4167 If a second attempt to exit is made without an intervening command,
4168 the shell does not print another warning, and the stopped
4169 jobs are terminated.
4171 When executing interactively,
4173 displays the primary prompt
4176 when it is ready to read a command, and the secondary prompt
4179 when it needs more input to complete a command.
4181 allows these prompt strings to be customized by inserting a number of
4182 backslash-escaped special characters that are decoded as follows:
4187 an ASCII bell character (07)
4190 the date in "Weekday Month Date" format (e.g., "Tue May 26")
4192 .B \eD{\fIformat\fP}
4193 the \fIformat\fP is passed to \fIstrftime\fP(3) and the result is inserted
4194 into the prompt string; an empty \fIformat\fP results in a locale-specific
4195 time representation. The braces are required
4198 an ASCII escape character (033)
4201 the hostname up to the first `.'
4207 the number of jobs currently managed by the shell
4210 the basename of the shell's terminal device name
4219 the name of the shell, the basename of
4221 (the portion following the final slash)
4224 the current time in 24-hour HH:MM:SS format
4227 the current time in 12-hour HH:MM:SS format
4230 the current time in 12-hour am/pm format
4233 the current time in 24-hour HH:MM format
4236 the username of the current user
4239 the version of \fBbash\fP (e.g., 2.00)
4242 the release of \fBbash\fP, version + patch level (e.g., 2.00.0)
4245 the current working directory, with \fB$HOME\fP abbreviated with a tilde
4248 the basename of the current working directory, with \fB$HOME\fP
4249 abbreviated with a tilde
4252 the history number of this command
4255 the command number of this command
4258 if the effective UID is 0, a
4264 the character corresponding to the octal number \fInnn\fP
4270 begin a sequence of non-printing characters, which could be used to
4271 embed a terminal control sequence into the prompt
4274 end a sequence of non-printing characters
4278 The command number and the history number are usually different:
4279 the history number of a command is its position in the history
4280 list, which may include commands restored from the history file
4284 below), while the command number is the position in the sequence
4285 of commands executed during the current shell session.
4286 After the string is decoded, it is expanded via
4287 parameter expansion, command substitution, arithmetic
4288 expansion, and quote removal, subject to the value of the
4290 shell option (see the description of the
4294 .B "SHELL BUILTIN COMMANDS"
4297 This is the library that handles reading input when using an interactive
4300 option is given at shell invocation.
4301 By default, the line editing commands are similar to those of emacs.
4302 A vi-style line editing interface is also available.
4303 To turn off line editing after the shell is running, use the
4311 .B SHELL BUILTIN COMMANDS
4313 .SS "Readline Notation"
4315 In this section, the emacs-style notation is used to denote
4316 keystrokes. Control keys are denoted by C\-\fIkey\fR, e.g., C\-n
4317 means Control\-N. Similarly,
4319 keys are denoted by M\-\fIkey\fR, so M\-x means Meta\-X. (On keyboards
4322 key, M\-\fIx\fP means ESC \fIx\fP, i.e., press the Escape key
4325 key. This makes ESC the \fImeta prefix\fP.
4326 The combination M\-C\-\fIx\fP means ESC\-Control\-\fIx\fP,
4327 or press the Escape key
4328 then hold the Control key while pressing the
4332 Readline commands may be given numeric
4334 which normally act as a repeat count.
4335 Sometimes, however, it is the sign of the argument that is significant.
4336 Passing a negative argument to a command that acts in the forward
4337 direction (e.g., \fBkill\-line\fP) causes that command to act in a
4339 Commands whose behavior with arguments deviates from this are noted
4342 When a command is described as \fIkilling\fP text, the text
4343 deleted is saved for possible future retrieval
4344 (\fIyanking\fP). The killed text is saved in a
4345 \fIkill ring\fP. Consecutive kills cause the text to be
4346 accumulated into one unit, which can be yanked all at once.
4347 Commands which do not kill text separate the chunks of text
4349 .SS "Readline Initialization"
4351 Readline is customized by putting commands in an initialization
4352 file (the \fIinputrc\fP file).
4353 The name of this file is taken from the value of the
4356 variable. If that variable is unset, the default is
4358 When a program which uses the readline library starts up, the
4359 initialization file is read, and the key bindings and variables
4361 There are only a few basic constructs allowed in the
4362 readline initialization file.
4363 Blank lines are ignored.
4364 Lines beginning with a \fB#\fP are comments.
4365 Lines beginning with a \fB$\fP indicate conditional constructs.
4366 Other lines denote key bindings and variable settings.
4368 The default key-bindings may be changed with an
4371 Other programs that use this library may add their own commands
4374 For example, placing
4377 M\-Control\-u: universal\-argument
4381 C\-Meta\-u: universal\-argument
4385 would make M\-C\-u execute the readline command
4386 .IR universal\-argument .
4388 The following symbolic character names are recognized:
4401 In addition to command names, readline allows keys to be bound
4402 to a string that is inserted when the key is pressed (a \fImacro\fP).
4403 .SS "Readline Key Bindings"
4405 The syntax for controlling key bindings in the
4407 file is simple. All that is required is the name of the
4408 command or the text of a macro and a key sequence to which
4409 it should be bound. The name may be specified in one of two ways:
4410 as a symbolic key name, possibly with \fIMeta\-\fP or \fIControl\-\fP
4411 prefixes, or as a key sequence.
4413 When using the form \fBkeyname\fP:\^\fIfunction\-name\fP or \fImacro\fP,
4415 is the name of a key spelled out in English. For example:
4418 Control-u: universal\-argument
4420 Meta-Rubout: backward-kill-word
4422 Control-o: "> output"
4425 In the above example,
4427 is bound to the function
4428 .BR universal\-argument ,
4430 is bound to the function
4431 .BR backward\-kill\-word ,
4434 is bound to run the macro
4435 expressed on the right hand side (that is, to insert the text
4436 .if t \f(CW> output\fP
4440 In the second form, \fB"keyseq"\fP:\^\fIfunction\-name\fP or \fImacro\fP,
4444 above in that strings denoting
4445 an entire key sequence may be specified by placing the sequence
4446 within double quotes. Some GNU Emacs style key escapes can be
4447 used, as in the following example, but the symbolic character names
4451 "\eC\-u": universal\-argument
4453 "\eC\-x\eC\-r": re\-read\-init\-file
4455 "\ee[11~": "Function Key 1"
4460 is again bound to the function
4461 .BR universal\-argument .
4463 is bound to the function
4464 .BR re\-read\-init\-file ,
4467 is bound to insert the text
4468 .if t \f(CWFunction Key 1\fP.
4469 .if n ``Function Key 1''.
4471 The full set of GNU Emacs style escape sequences is
4495 In addition to the GNU Emacs style escape sequences, a second
4496 set of backslash escapes is available:
4525 the eight-bit character whose value is the octal value \fInnn\fP
4526 (one to three digits)
4529 the eight-bit character whose value is the hexadecimal value \fIHH\fP
4530 (one or two hex digits)
4534 When entering the text of a macro, single or double quotes must
4535 be used to indicate a macro definition.
4536 Unquoted text is assumed to be a function name.
4537 In the macro body, the backslash escapes described above are expanded.
4538 Backslash will quote any other character in the macro text,
4542 allows the current readline key bindings to be displayed or modified
4545 builtin command. The editing mode may be switched during interactive
4550 builtin command (see
4552 .B SHELL BUILTIN COMMANDS
4554 .SS "Readline Variables"
4556 Readline has variables that can be used to further customize its
4557 behavior. A variable may be set in the
4559 file with a statement of the form
4562 \fBset\fP \fIvariable\-name\fP \fIvalue\fP
4565 Except where noted, readline variables can take the values
4569 The variables and their default values are:
4573 .B bell\-style (audible)
4574 Controls what happens when readline wants to ring the terminal bell.
4575 If set to \fBnone\fP, readline never rings the bell. If set to
4576 \fBvisible\fP, readline uses a visible bell if one is available.
4577 If set to \fBaudible\fP, readline attempts to ring the terminal's bell.
4579 .B bind\-tty\-special\-chars (On)
4580 If set to \fBOn\fP, readline attempts to bind the control characters
4581 treated specially by the kernel's terminal driver to their readline
4584 .B comment\-begin (``#'')
4585 The string that is inserted when the readline
4587 command is executed.
4588 This command is bound to
4590 in emacs mode and to
4594 .B completion\-ignore\-case (Off)
4595 If set to \fBOn\fP, readline performs filename matching and completion
4596 in a case\-insensitive fashion.
4598 .B completion\-query\-items (100)
4599 This determines when the user is queried about viewing
4600 the number of possible completions
4601 generated by the \fBpossible\-completions\fP command.
4602 It may be set to any integer value greater than or equal to
4603 zero. If the number of possible completions is greater than
4604 or equal to the value of this variable, the user is asked whether
4605 or not he wishes to view them; otherwise they are simply listed
4608 .B convert\-meta (On)
4609 If set to \fBOn\fP, readline will convert characters with the
4610 eighth bit set to an ASCII key sequence
4611 by stripping the eighth bit and prefixing an
4612 escape character (in effect, using escape as the \fImeta prefix\fP).
4614 .B disable\-completion (Off)
4615 If set to \fBOn\fP, readline will inhibit word completion. Completion
4616 characters will be inserted into the line as if they had been
4617 mapped to \fBself-insert\fP.
4619 .B editing\-mode (emacs)
4620 Controls whether readline begins with a set of key bindings similar
4621 to \fIemacs\fP or \fIvi\fP.
4623 can be set to either
4628 .B enable\-keypad (Off)
4629 When set to \fBOn\fP, readline will try to enable the application
4630 keypad when it is called. Some systems need this to enable the
4633 .B expand\-tilde (Off)
4634 If set to \fBon\fP, tilde expansion is performed when readline
4635 attempts word completion.
4637 .B history-preserve-point
4638 If set to \fBon\fP, the history code attempts to place point at the
4639 same location on each history line retrieved with \fBprevious-history\fP
4640 or \fBnext-history\fP.
4642 .B horizontal\-scroll\-mode (Off)
4643 When set to \fBOn\fP, makes readline use a single line for display,
4644 scrolling the input horizontally on a single screen line when it
4645 becomes longer than the screen width rather than wrapping to a new line.
4647 .B input\-meta (Off)
4648 If set to \fBOn\fP, readline will enable eight-bit input (that is,
4649 it will not strip the high bit from the characters it reads),
4650 regardless of what the terminal claims it can support. The name
4652 is a synonym for this variable.
4654 .B isearch\-terminators (``C\-[C\-J'')
4655 The string of characters that should terminate an incremental
4656 search without subsequently executing the character as a command.
4657 If this variable has not been given a value, the characters
4658 \fIESC\fP and \fIC\-J\fP will terminate an incremental search.
4661 Set the current readline keymap. The set of valid keymap names is
4662 \fIemacs, emacs\-standard, emacs\-meta, emacs\-ctlx, vi,
4665 \fIvi\fP is equivalent to \fIvi\-command\fP; \fIemacs\fP is
4666 equivalent to \fIemacs\-standard\fP. The default value is
4670 also affects the default keymap.
4672 .B mark\-directories (On)
4673 If set to \fBOn\fP, completed directory names have a slash
4676 .B mark\-modified\-lines (Off)
4677 If set to \fBOn\fP, history lines that have been modified are displayed
4678 with a preceding asterisk (\fB*\fP).
4680 .B mark\-symlinked\-directories (Off)
4681 If set to \fBOn\fP, completed names which are symbolic links to directories
4682 have a slash appended (subject to the value of
4683 \fBmark\-directories\fP).
4685 .B match\-hidden\-files (On)
4686 This variable, when set to \fBOn\fP, causes readline to match files whose
4687 names begin with a `.' (hidden files) when performing filename
4688 completion, unless the leading `.' is
4689 supplied by the user in the filename to be completed.
4691 .B output\-meta (Off)
4692 If set to \fBOn\fP, readline will display characters with the
4693 eighth bit set directly rather than as a meta-prefixed escape
4696 .B page\-completions (On)
4697 If set to \fBOn\fP, readline uses an internal \fImore\fP-like pager
4698 to display a screenful of possible completions at a time.
4700 .B print\-completions\-horizontally (Off)
4701 If set to \fBOn\fP, readline will display completions with matches
4702 sorted horizontally in alphabetical order, rather than down the screen.
4704 .B show\-all\-if\-ambiguous (Off)
4705 This alters the default behavior of the completion functions. If
4708 words which have more than one possible completion cause the
4709 matches to be listed immediately instead of ringing the bell.
4711 .B show\-all\-if\-unmodified (Off)
4712 This alters the default behavior of the completion functions in
4713 a fashion similar to \fBshow\-all\-if\-ambiguous\fP.
4716 words which have more than one possible completion without any
4717 possible partial completion (the possible completions don't share
4718 a common prefix) cause the matches to be listed immediately instead
4719 of ringing the bell.
4721 .B visible\-stats (Off)
4722 If set to \fBOn\fP, a character denoting a file's type as reported
4723 by \fIstat\fP(2) is appended to the filename when listing possible
4726 .SS "Readline Conditional Constructs"
4728 Readline implements a facility similar in spirit to the conditional
4729 compilation features of the C preprocessor which allows key
4730 bindings and variable settings to be performed as the result
4731 of tests. There are four parser directives used.
4735 construct allows bindings to be made based on the
4736 editing mode, the terminal being used, or the application using
4737 readline. The text of the test extends to the end of the line;
4738 no characters are required to isolate it.
4741 The \fBmode=\fP form of the \fB$if\fP directive is used to test
4742 whether readline is in emacs or vi mode.
4743 This may be used in conjunction
4744 with the \fBset keymap\fP command, for instance, to set bindings in
4745 the \fIemacs\-standard\fP and \fIemacs\-ctlx\fP keymaps only if
4746 readline is starting out in emacs mode.
4748 The \fBterm=\fP form may be used to include terminal-specific
4749 key bindings, perhaps to bind the key sequences output by the
4750 terminal's function keys. The word on the right side of the
4752 is tested against the both full name of the terminal and the portion
4753 of the terminal name before the first \fB\-\fP. This allows
4760 .IP \fBapplication\fP
4761 The \fBapplication\fP construct is used to include
4762 application-specific settings. Each program using the readline
4763 library sets the \fIapplication name\fP, and an initialization
4764 file can test for a particular value.
4765 This could be used to bind key sequences to functions useful for
4766 a specific program. For instance, the following command adds a
4767 key sequence that quotes the current or previous word in Bash:
4772 # Quote the current or previous word
4773 "\eC\-xq": "\eeb\e"\eef\e""
4779 This command, as seen in the previous example, terminates an
4782 Commands in this branch of the \fB$if\fP directive are executed if
4785 This directive takes a single filename as an argument and reads commands
4786 and bindings from that file. For example, the following directive
4787 would read \fI/etc/inputrc\fP:
4791 \fB$include\fP \^ \fI/etc/inputrc\fP
4796 Readline provides commands for searching through the command history
4800 below) for lines containing a specified string.
4801 There are two search modes:
4804 .IR non-incremental .
4806 Incremental searches begin before the user has finished typing the
4808 As each character of the search string is typed, readline displays
4809 the next entry from the history matching the string typed so far.
4810 An incremental search requires only as many characters as needed to
4811 find the desired history entry.
4812 The characters present in the value of the \fBisearch-terminators\fP
4813 variable are used to terminate an incremental search.
4814 If that variable has not been assigned a value the Escape and
4815 Control-J characters will terminate an incremental search.
4816 Control-G will abort an incremental search and restore the original
4818 When the search is terminated, the history entry containing the
4819 search string becomes the current line.
4821 To find other matching entries in the history list, type Control-S or
4822 Control-R as appropriate.
4823 This will search backward or forward in the history for the next
4824 entry matching the search string typed so far.
4825 Any other key sequence bound to a readline command will terminate
4826 the search and execute that command.
4827 For instance, a \fInewline\fP will terminate the search and accept
4828 the line, thereby executing the command from the history list.
4830 Readline remembers the last incremental search string. If two
4831 Control-Rs are typed without any intervening characters defining a
4832 new search string, any remembered search string is used.
4834 Non-incremental searches read the entire search string before starting
4835 to search for matching history lines. The search string may be
4836 typed by the user or be part of the contents of the current line.
4837 .SS "Readline Command Names"
4839 The following is a list of the names of the commands and the default
4840 key sequences to which they are bound.
4841 Command names without an accompanying key sequence are unbound by default.
4842 In the following descriptions, \fIpoint\fP refers to the current cursor
4843 position, and \fImark\fP refers to a cursor position saved by the
4844 \fBset\-mark\fP command.
4845 The text between the point and mark is referred to as the \fIregion\fP.
4846 .SS Commands for Moving
4850 .B beginning\-of\-line (C\-a)
4851 Move to the start of the current line.
4853 .B end\-of\-line (C\-e)
4854 Move to the end of the line.
4856 .B forward\-char (C\-f)
4857 Move forward a character.
4859 .B backward\-char (C\-b)
4860 Move back a character.
4862 .B forward\-word (M\-f)
4863 Move forward to the end of the next word. Words are composed of
4864 alphanumeric characters (letters and digits).
4866 .B backward\-word (M\-b)
4867 Move back to the start of the current or previous word. Words are
4868 composed of alphanumeric characters (letters and digits).
4870 .B clear\-screen (C\-l)
4871 Clear the screen leaving the current line at the top of the screen.
4872 With an argument, refresh the current line without clearing the
4875 .B redraw\-current\-line
4876 Refresh the current line.
4878 .SS Commands for Manipulating the History
4882 .B accept\-line (Newline, Return)
4883 Accept the line regardless of where the cursor is. If this line is
4884 non-empty, add it to the history list according to the state of the
4887 variable. If the line is a modified history
4888 line, then restore the history line to its original state.
4890 .B previous\-history (C\-p)
4891 Fetch the previous command from the history list, moving back in
4894 .B next\-history (C\-n)
4895 Fetch the next command from the history list, moving forward in the
4898 .B beginning\-of\-history (M\-<)
4899 Move to the first line in the history.
4901 .B end\-of\-history (M\->)
4902 Move to the end of the input history, i.e., the line currently being
4905 .B reverse\-search\-history (C\-r)
4906 Search backward starting at the current line and moving `up' through
4907 the history as necessary. This is an incremental search.
4909 .B forward\-search\-history (C\-s)
4910 Search forward starting at the current line and moving `down' through
4911 the history as necessary. This is an incremental search.
4913 .B non\-incremental\-reverse\-search\-history (M\-p)
4914 Search backward through the history starting at the current line
4915 using a non-incremental search for a string supplied by the user.
4917 .B non\-incremental\-forward\-search\-history (M\-n)
4918 Search forward through the history using a non-incremental search for
4919 a string supplied by the user.
4921 .B history\-search\-forward
4922 Search forward through the history for the string of characters
4923 between the start of the current line and the point.
4924 This is a non-incremental search.
4926 .B history\-search\-backward
4927 Search backward through the history for the string of characters
4928 between the start of the current line and the point.
4929 This is a non-incremental search.
4931 .B yank\-nth\-arg (M\-C\-y)
4932 Insert the first argument to the previous command (usually
4933 the second word on the previous line) at point.
4936 insert the \fIn\fPth word from the previous command (the words
4937 in the previous command begin with word 0). A negative argument
4938 inserts the \fIn\fPth word from the end of the previous command.
4939 Once the argument \fIn\fP is computed, the argument is extracted
4940 as if the "!\fIn\fP" history expansion had been specified.
4943 yank\-last\-arg (M\-.\^, M\-_\^)
4944 Insert the last argument to the previous command (the last word of
4945 the previous history entry). With an argument,
4946 behave exactly like \fByank\-nth\-arg\fP.
4947 Successive calls to \fByank\-last\-arg\fP move back through the history
4948 list, inserting the last argument of each line in turn.
4949 The history expansion facilities are used to extract the last argument,
4950 as if the "!$" history expansion had been specified.
4952 .B shell\-expand\-line (M\-C\-e)
4953 Expand the line as the shell does. This
4954 performs alias and history expansion as well as all of the shell
4955 word expansions. See
4957 .B HISTORY EXPANSION
4958 below for a description of history expansion.
4960 .B history\-expand\-line (M\-^)
4961 Perform history expansion on the current line.
4964 .B HISTORY EXPANSION
4965 below for a description of history expansion.
4968 Perform history expansion on the current line and insert a space.
4971 .B HISTORY EXPANSION
4972 below for a description of history expansion.
4974 .B alias\-expand\-line
4975 Perform alias expansion on the current line.
4979 above for a description of alias expansion.
4981 .B history\-and\-alias\-expand\-line
4982 Perform history and alias expansion on the current line.
4984 .B insert\-last\-argument (M\-.\^, M\-_\^)
4985 A synonym for \fByank\-last\-arg\fP.
4987 .B operate\-and\-get\-next (C\-o)
4988 Accept the current line for execution and fetch the next line
4989 relative to the current line from the history for editing. Any
4990 argument is ignored.
4992 .B edit\-and\-execute\-command (C\-xC\-e)
4993 Invoke an editor on the current command line, and execute the result as shell
4995 \fBBash\fP attempts to invoke
5000 and \fIemacs\fP as the editor, in that order.
5002 .SS Commands for Changing Text
5006 .B delete\-char (C\-d)
5007 Delete the character at point. If point is at the
5008 beginning of the line, there are no characters in the line, and
5009 the last character typed was not bound to \fBdelete\-char\fP,
5014 .B backward\-delete\-char (Rubout)
5015 Delete the character behind the cursor. When given a numeric argument,
5016 save the deleted text on the kill ring.
5018 .B forward\-backward\-delete\-char
5019 Delete the character under the cursor, unless the cursor is at the
5020 end of the line, in which case the character behind the cursor is
5023 .B quoted\-insert (C\-q, C\-v)
5024 Add the next character typed to the line verbatim. This is
5025 how to insert characters like \fBC\-q\fP, for example.
5027 .B tab\-insert (C\-v TAB)
5028 Insert a tab character.
5030 .B self\-insert (a,\ b,\ A,\ 1,\ !,\ ...)
5031 Insert the character typed.
5033 .B transpose\-chars (C\-t)
5034 Drag the character before point forward over the character at point,
5035 moving point forward as well.
5036 If point is at the end of the line, then this transposes
5037 the two characters before point.
5038 Negative arguments have no effect.
5040 .B transpose\-words (M\-t)
5041 Drag the word before point past the word after point,
5042 moving point over that word as well.
5043 If point is at the end of the line, this transposes
5044 the last two words on the line.
5046 .B upcase\-word (M\-u)
5047 Uppercase the current (or following) word. With a negative argument,
5048 uppercase the previous word, but do not move point.
5050 .B downcase\-word (M\-l)
5051 Lowercase the current (or following) word. With a negative argument,
5052 lowercase the previous word, but do not move point.
5054 .B capitalize\-word (M\-c)
5055 Capitalize the current (or following) word. With a negative argument,
5056 capitalize the previous word, but do not move point.
5059 Toggle overwrite mode. With an explicit positive numeric argument,
5060 switches to overwrite mode. With an explicit non-positive numeric
5061 argument, switches to insert mode. This command affects only
5062 \fBemacs\fP mode; \fBvi\fP mode does overwrite differently.
5063 Each call to \fIreadline()\fP starts in insert mode.
5064 In overwrite mode, characters bound to \fBself\-insert\fP replace
5065 the text at point rather than pushing the text to the right.
5066 Characters bound to \fBbackward\-delete\-char\fP replace the character
5067 before point with a space. By default, this command is unbound.
5069 .SS Killing and Yanking
5073 .B kill\-line (C\-k)
5074 Kill the text from point to the end of the line.
5076 .B backward\-kill\-line (C\-x Rubout)
5077 Kill backward to the beginning of the line.
5079 .B unix\-line\-discard (C\-u)
5080 Kill backward from point to the beginning of the line.
5081 The killed text is saved on the kill-ring.
5082 .\" There is no real difference between this and backward-kill-line
5084 .B kill\-whole\-line
5085 Kill all characters on the current line, no matter where point is.
5087 .B kill\-word (M\-d)
5088 Kill from point to the end of the current word, or if between
5089 words, to the end of the next word.
5090 Word boundaries are the same as those used by \fBforward\-word\fP.
5092 .B backward\-kill\-word (M\-Rubout)
5093 Kill the word behind point.
5094 Word boundaries are the same as those used by \fBbackward\-word\fP.
5096 .B unix\-word\-rubout (C\-w)
5097 Kill the word behind point, using white space as a word boundary.
5098 The killed text is saved on the kill-ring.
5100 .B unix\-filename\-rubout
5101 Kill the word behind point, using white space and the slash character
5102 as the word boundaries.
5103 The killed text is saved on the kill-ring.
5105 .B delete\-horizontal\-space (M\-\e)
5106 Delete all spaces and tabs around point.
5109 Kill the text in the current region.
5111 .B copy\-region\-as\-kill
5112 Copy the text in the region to the kill buffer.
5114 .B copy\-backward\-word
5115 Copy the word before point to the kill buffer.
5116 The word boundaries are the same as \fBbackward\-word\fP.
5118 .B copy\-forward\-word
5119 Copy the word following point to the kill buffer.
5120 The word boundaries are the same as \fBforward\-word\fP.
5123 Yank the top of the kill ring into the buffer at point.
5126 Rotate the kill ring, and yank the new top. Only works following
5131 .SS Numeric Arguments
5135 .B digit\-argument (M\-0, M\-1, ..., M\-\-)
5136 Add this digit to the argument already accumulating, or start a new
5137 argument. M\-\- starts a negative argument.
5139 .B universal\-argument
5140 This is another way to specify an argument.
5141 If this command is followed by one or more digits, optionally with a
5142 leading minus sign, those digits define the argument.
5143 If the command is followed by digits, executing
5144 .B universal\-argument
5145 again ends the numeric argument, but is otherwise ignored.
5146 As a special case, if this command is immediately followed by a
5147 character that is neither a digit or minus sign, the argument count
5148 for the next command is multiplied by four.
5149 The argument count is initially one, so executing this function the
5150 first time makes the argument count four, a second time makes the
5151 argument count sixteen, and so on.
5158 Attempt to perform completion on the text before point.
5160 attempts completion treating the text as a variable (if the
5161 text begins with \fB$\fP), username (if the text begins with
5162 \fB~\fP), hostname (if the text begins with \fB@\fP), or
5163 command (including aliases and functions) in turn. If none
5164 of these produces a match, filename completion is attempted.
5166 .B possible\-completions (M\-?)
5167 List the possible completions of the text before point.
5169 .B insert\-completions (M\-*)
5170 Insert all completions of the text before point
5171 that would have been generated by
5172 \fBpossible\-completions\fP.
5175 Similar to \fBcomplete\fP, but replaces the word to be completed
5176 with a single match from the list of possible completions.
5177 Repeated execution of \fBmenu\-complete\fP steps through the list
5178 of possible completions, inserting each match in turn.
5179 At the end of the list of completions, the bell is rung
5180 (subject to the setting of \fBbell\-style\fP)
5181 and the original text is restored.
5182 An argument of \fIn\fP moves \fIn\fP positions forward in the list
5183 of matches; a negative argument may be used to move backward
5185 This command is intended to be bound to \fBTAB\fP, but is unbound
5188 .B delete\-char\-or\-list
5189 Deletes the character under the cursor if not at the beginning or
5190 end of the line (like \fBdelete\-char\fP).
5191 If at the end of the line, behaves identically to
5192 \fBpossible\-completions\fP.
5193 This command is unbound by default.
5195 .B complete\-filename (M\-/)
5196 Attempt filename completion on the text before point.
5198 .B possible\-filename\-completions (C\-x /)
5199 List the possible completions of the text before point,
5200 treating it as a filename.
5202 .B complete\-username (M\-~)
5203 Attempt completion on the text before point, treating
5206 .B possible\-username\-completions (C\-x ~)
5207 List the possible completions of the text before point,
5208 treating it as a username.
5210 .B complete\-variable (M\-$)
5211 Attempt completion on the text before point, treating
5212 it as a shell variable.
5214 .B possible\-variable\-completions (C\-x $)
5215 List the possible completions of the text before point,
5216 treating it as a shell variable.
5218 .B complete\-hostname (M\-@)
5219 Attempt completion on the text before point, treating
5222 .B possible\-hostname\-completions (C\-x @)
5223 List the possible completions of the text before point,
5224 treating it as a hostname.
5226 .B complete\-command (M\-!)
5227 Attempt completion on the text before point, treating
5228 it as a command name. Command completion attempts to
5229 match the text against aliases, reserved words, shell
5230 functions, shell builtins, and finally executable filenames,
5233 .B possible\-command\-completions (C\-x !)
5234 List the possible completions of the text before point,
5235 treating it as a command name.
5237 .B dynamic\-complete\-history (M\-TAB)
5238 Attempt completion on the text before point, comparing
5239 the text against lines from the history list for possible
5242 .B complete\-into\-braces (M\-{)
5243 Perform filename completion and insert the list of possible completions
5244 enclosed within braces so the list is available to the shell (see
5252 .B start\-kbd\-macro (C\-x (\^)
5253 Begin saving the characters typed into the current keyboard macro.
5255 .B end\-kbd\-macro (C\-x )\^)
5256 Stop saving the characters typed into the current keyboard macro
5257 and store the definition.
5259 .B call\-last\-kbd\-macro (C\-x e)
5260 Re-execute the last keyboard macro defined, by making the characters
5261 in the macro appear as if typed at the keyboard.
5267 .B re\-read\-init\-file (C\-x C\-r)
5268 Read in the contents of the \fIinputrc\fP file, and incorporate
5269 any bindings or variable assignments found there.
5272 Abort the current editing command and
5273 ring the terminal's bell (subject to the setting of
5276 .B do\-uppercase\-version (M\-a, M\-b, M\-\fIx\fP, ...)
5277 If the metafied character \fIx\fP is lowercase, run the command
5278 that is bound to the corresponding uppercase character.
5280 .B prefix\-meta (ESC)
5281 Metafy the next character typed.
5288 .B undo (C\-_, C\-x C\-u)
5289 Incremental undo, separately remembered for each line.
5291 .B revert\-line (M\-r)
5292 Undo all changes made to this line. This is like executing the
5294 command enough times to return the line to its initial state.
5296 .B tilde\-expand (M\-&)
5297 Perform tilde expansion on the current word.
5299 .B set\-mark (C\-@, M\-<space>)
5300 Set the mark to the point. If a
5301 numeric argument is supplied, the mark is set to that position.
5303 .B exchange\-point\-and\-mark (C\-x C\-x)
5304 Swap the point with the mark. The current cursor position is set to
5305 the saved position, and the old cursor position is saved as the mark.
5307 .B character\-search (C\-])
5308 A character is read and point is moved to the next occurrence of that
5309 character. A negative count searches for previous occurrences.
5311 .B character\-search\-backward (M\-C\-])
5312 A character is read and point is moved to the previous occurrence of that
5313 character. A negative count searches for subsequent occurrences.
5315 .B insert\-comment (M\-#)
5316 Without a numeric argument, the value of the readline
5318 variable is inserted at the beginning of the current line.
5319 If a numeric argument is supplied, this command acts as a toggle: if
5320 the characters at the beginning of the line do not match the value
5321 of \fBcomment\-begin\fP, the value is inserted, otherwise
5322 the characters in \fBcomment-begin\fP are deleted from the beginning of
5324 In either case, the line is accepted as if a newline had been typed.
5325 The default value of
5326 \fBcomment\-begin\fP causes this command to make the current line
5328 If a numeric argument causes the comment character to be removed, the line
5329 will be executed by the shell.
5331 .B glob\-complete\-word (M\-g)
5332 The word before point is treated as a pattern for pathname expansion,
5333 with an asterisk implicitly appended. This pattern is used to
5334 generate a list of matching file names for possible completions.
5336 .B glob\-expand\-word (C\-x *)
5337 The word before point is treated as a pattern for pathname expansion,
5338 and the list of matching file names is inserted, replacing the word.
5339 If a numeric argument is supplied, an asterisk is appended before
5342 .B glob\-list\-expansions (C\-x g)
5343 The list of expansions that would have been generated by
5344 .B glob\-expand\-word
5345 is displayed, and the line is redrawn.
5346 If a numeric argument is supplied, an asterisk is appended before
5350 Print all of the functions and their key bindings to the
5351 readline output stream. If a numeric argument is supplied,
5352 the output is formatted in such a way that it can be made part
5353 of an \fIinputrc\fP file.
5356 Print all of the settable readline variables and their values to the
5357 readline output stream. If a numeric argument is supplied,
5358 the output is formatted in such a way that it can be made part
5359 of an \fIinputrc\fP file.
5362 Print all of the readline key sequences bound to macros and the
5363 strings they output. If a numeric argument is supplied,
5364 the output is formatted in such a way that it can be made part
5365 of an \fIinputrc\fP file.
5367 .B display\-shell\-version (C\-x C\-v)
5368 Display version information about the current instance of
5371 .SS Programmable Completion
5373 When word completion is attempted for an argument to a command for
5374 which a completion specification (a \fIcompspec\fP) has been defined
5375 using the \fBcomplete\fP builtin (see
5377 .B "SHELL BUILTIN COMMANDS"
5378 below), the programmable completion facilities are invoked.
5380 First, the command name is identified.
5381 If a compspec has been defined for that command, the
5382 compspec is used to generate the list of possible completions for the word.
5383 If the command word is a full pathname, a compspec for the full
5384 pathname is searched for first.
5385 If no compspec is found for the full pathname, an attempt is made to
5386 find a compspec for the portion following the final slash.
5388 Once a compspec has been found, it is used to generate the list of
5390 If a compspec is not found, the default \fBbash\fP completion as
5391 described above under \fBCompleting\fP is performed.
5393 First, the actions specified by the compspec are used.
5394 Only matches which are prefixed by the word being completed are
5400 option is used for filename or directory name completion, the shell
5404 is used to filter the matches.
5406 Any completions specified by a filename expansion pattern to the
5407 \fB\-G\fP option are generated next.
5408 The words generated by the pattern need not match the word
5413 shell variable is not used to filter the matches, but the
5418 Next, the string specified as the argument to the \fB\-W\fP option
5420 The string is first split using the characters in the
5423 special variable as delimiters.
5424 Shell quoting is honored.
5425 Each word is then expanded using
5426 brace expansion, tilde expansion, parameter and variable expansion,
5427 command substitution, and arithmetic expansion,
5428 as described above under
5431 The results are split using the rules described above under
5432 \fBWord Splitting\fP.
5433 The results of the expansion are prefix-matched against the word being
5434 completed, and the matching words become the possible completions.
5436 After these matches have been generated, any shell function or command
5437 specified with the \fB\-F\fP and \fB\-C\fP options is invoked.
5438 When the command or function is invoked, the
5444 variables are assigned values as described above under
5445 \fBShell Variables\fP.
5446 If a shell function is being invoked, the
5452 variables are also set.
5453 When the function or command is invoked, the first argument is the
5454 name of the command whose arguments are being completed, the
5455 second argument is the word being completed, and the third argument
5456 is the word preceding the word being completed on the current command line.
5457 No filtering of the generated completions against the word being completed
5458 is performed; the function or command has complete freedom in generating
5461 Any function specified with \fB\-F\fP is invoked first.
5462 The function may use any of the shell facilities, including the
5463 \fBcompgen\fP builtin described below, to generate the matches.
5464 It must put the possible completions in the
5469 Next, any command specified with the \fB\-C\fP option is invoked
5470 in an environment equivalent to command substitution.
5471 It should print a list of completions, one per line, to the
5473 Backslash may be used to escape a newline, if necessary.
5475 After all of the possible completions are generated, any filter
5476 specified with the \fB\-X\fP option is applied to the list.
5477 The filter is a pattern as used for pathname expansion; a \fB&\fP
5478 in the pattern is replaced with the text of the word being completed.
5479 A literal \fB&\fP may be escaped with a backslash; the backslash
5480 is removed before attempting a match.
5481 Any completion that matches the pattern will be removed from the list.
5482 A leading \fB!\fP negates the pattern; in this case any completion
5483 not matching the pattern will be removed.
5485 Finally, any prefix and suffix specified with the \fB\-P\fP and \fB\-S\fP
5486 options are added to each member of the completion list, and the result is
5487 returned to the readline completion code as the list of possible
5490 If the previously-applied actions do not generate any matches, and the
5491 \fB\-o dirnames\fP option was supplied to \fBcomplete\fP when the
5492 compspec was defined, directory name completion is attempted.
5494 If the \fB\-o plusdirs\fP option was supplied to \fBcomplete\fP when the
5495 compspec was defined, directory name completion is attempted and any
5496 matches are added to the results of the other actions.
5498 By default, if a compspec is found, whatever it generates is returned
5499 to the completion code as the full set of possible completions.
5500 The default \fBbash\fP completions are not attempted, and the readline
5501 default of filename completion is disabled.
5502 If the \fB\-o bashdefault\fP option was supplied to \fBcomplete\fP when
5503 the compspec was defined, the \fBbash\fP default completions are attempted
5504 if the compspec generates no matches.
5505 If the \fB\-o default\fP option was supplied to \fBcomplete\fP when the
5506 compspec was defined, readline's default completion will be performed
5507 if the compspec (and, if attempted, the default \fBbash\fP completions)
5508 generate no matches.
5510 When a compspec indicates that directory name completion is desired,
5511 the programmable completion functions force readline to append a slash
5512 to completed names which are symbolic links to directories, subject to
5513 the value of the \fBmark\-directories\fP readline variable, regardless
5514 of the setting of the \fBmark-symlinked\-directories\fP readline variable.
5520 builtin is enabled, the shell provides access to the
5521 \fIcommand history\fP,
5522 the list of commands previously typed.
5523 The value of the \fBHISTSIZE\fP variable is used as the
5524 number of commands to save in a history list.
5525 The text of the last
5528 commands (default 500) is saved. The shell
5529 stores each command in the history list prior to parameter and
5530 variable expansion (see
5533 above) but after history expansion is performed, subject to the
5534 values of the shell variables
5541 On startup, the history is initialized from the file named by
5545 (default \fI~/.bash_history\fP).
5546 The file named by the value of
5549 is truncated, if necessary, to contain no more than
5550 the number of lines specified by the value of
5553 When an interactive shell exits, the last
5556 lines are copied from the history list to
5561 shell option is enabled
5562 (see the description of
5566 .B "SHELL BUILTIN COMMANDS"
5567 below), the lines are appended to the history file,
5568 otherwise the history file is overwritten.
5572 is unset, or if the history file is unwritable, the history is
5573 not saved. After saving the history, the history file is truncated
5574 to contain no more than
5580 is not set, no truncation is performed.
5586 .B SHELL BUILTIN COMMANDS
5587 below) may be used to list or edit and re-execute a portion of
5591 builtin may be used to display or modify the history list and
5592 manipulate the history file.
5593 When using command-line editing, search commands
5594 are available in each editing mode that provide access to the
5597 The shell allows control over which commands are saved on the history
5604 variables may be set to cause the shell to save only a subset of the
5608 shell option, if enabled, causes the shell to attempt to save each
5609 line of a multi-line command in the same history entry, adding
5610 semicolons where necessary to preserve syntactic correctness.
5613 shell option causes the shell to save the command with embedded newlines
5614 instead of semicolons. See the description of the
5618 .B "SHELL BUILTIN COMMANDS"
5619 for information on setting and unsetting shell options.
5620 .SH "HISTORY EXPANSION"
5622 The shell supports a history expansion feature that
5623 is similar to the history expansion in
5625 This section describes what syntax features are available. This
5626 feature is enabled by default for interactive shells, and can be
5631 builtin command (see
5633 .B SHELL BUILTIN COMMANDS
5634 below). Non-interactive shells do not perform history expansion
5637 History expansions introduce words from the history list into
5638 the input stream, making it easy to repeat commands, insert the
5639 arguments to a previous command into the current input line, or
5640 fix errors in previous commands quickly.
5642 History expansion is performed immediately after a complete line
5643 is read, before the shell breaks it into words.
5644 It takes place in two parts.
5645 The first is to determine which line from the history list
5646 to use during substitution.
5647 The second is to select portions of that line for inclusion into
5649 The line selected from the history is the \fIevent\fP,
5650 and the portions of that line that are acted upon are \fIwords\fP.
5651 Various \fImodifiers\fP are available to manipulate the selected words.
5652 The line is broken into words in the same fashion as when reading input,
5653 so that several \fImetacharacter\fP-separated words surrounded by
5654 quotes are considered one word.
5655 History expansions are introduced by the appearance of the
5656 history expansion character, which is \^\fB!\fP\^ by default.
5657 Only backslash (\^\fB\e\fP\^) and single quotes can quote
5658 the history expansion character.
5660 Several characters inhibit history expansion if found immediately
5661 following the history expansion character, even if it is unquoted:
5662 space, tab, newline, carriage return, and \fB=\fP.
5663 If the \fBextglob\fP shell option is enabled, \fB(\fP will also
5666 Several shell options settable with the
5668 builtin may be used to tailor the behavior of history expansion.
5671 shell option is enabled (see the description of the
5675 is being used, history substitutions are not immediately passed to
5677 Instead, the expanded line is reloaded into the
5679 editing buffer for further modification.
5682 is being used, and the
5684 shell option is enabled, a failed history substitution will be reloaded
5687 editing buffer for correction.
5692 builtin command may be used to see what a history expansion will
5698 builtin may be used to add commands to the end of the history list
5699 without actually executing them, so that they are available for
5702 The shell allows control of the various characters used by the
5703 history expansion mechanism (see the description of
5706 .BR "Shell Variables" ).
5707 .SS Event Designators
5709 An event designator is a reference to a command line entry in the
5715 Start a history substitution, except when followed by a
5717 newline, carriage return, =
5718 or ( (when the \fBextglob\fP shell option is enabled using
5719 the \fBshopt\fP builtin).
5722 Refer to command line
5726 Refer to the current command line minus
5730 Refer to the previous command. This is a synonym for `!\-1'.
5733 Refer to the most recent command starting with
5736 .B !?\fIstring\fR\fB[?]\fR
5737 Refer to the most recent command containing
5739 The trailing \fB?\fP may be omitted if
5741 is followed immediately by a newline.
5743 .B \d\s+2^\s-2\u\fIstring1\fP\d\s+2^\s-2\u\fIstring2\fP\d\s+2^\s-2\u
5744 Quick substitution. Repeat the last command, replacing
5749 ``!!:s/\fIstring1\fP/\fIstring2\fP/''
5750 (see \fBModifiers\fP below).
5753 The entire command line typed so far.
5755 .SS Word Designators
5757 Word designators are used to select desired words from the event.
5760 separates the event specification from the word designator.
5761 It may be omitted if the word designator begins with a
5768 Words are numbered from the beginning of the line,
5769 with the first word being denoted by 0 (zero).
5770 Words are inserted into the current line separated by single spaces.
5775 The zeroth word. For the shell, this is the command
5782 The first argument. That is, word 1.
5788 The word matched by the most recent `?\fIstring\fR?' search.
5791 A range of words; `\-\fIy\fR' abbreviates `0\-\fIy\fR'.
5794 All of the words but the zeroth. This is a synonym
5795 for `\fI1\-$\fP'. It is not an error to use
5797 if there is just one
5798 word in the event; the empty string is returned in that case.
5801 Abbreviates \fIx\-$\fP.
5804 Abbreviates \fIx\-$\fP like \fBx*\fP, but omits the last word.
5807 If a word designator is supplied without an event specification, the
5808 previous command is used as the event.
5811 After the optional word designator, there may appear a sequence of
5812 one or more of the following modifiers, each preceded by a `:'.
5818 Remove a trailing file name component, leaving only the head.
5821 Remove all leading file name components, leaving the tail.
5824 Remove a trailing suffix of the form \fI.xxx\fP, leaving the
5828 Remove all but the trailing suffix.
5831 Print the new command but do not execute it.
5834 Quote the substituted words, escaping further substitutions.
5837 Quote the substituted words as with
5839 but break into words at
5843 .B s/\fIold\fP/\fInew\fP/
5846 for the first occurrence of
5848 in the event line. Any delimiter can be used in place of /. The
5849 final delimiter is optional if it is the last character of the
5850 event line. The delimiter may be quoted in
5854 with a single backslash. If & appears in
5858 A single backslash will quote the &. If
5860 is null, it is set to the last
5862 substituted, or, if no previous history substitutions took place,
5866 .B !?\fIstring\fR\fB[?]\fR
5870 Repeat the previous substitution.
5873 Cause changes to be applied over the entire event line. This is
5874 used in conjunction with `\fB:s\fP' (e.g., `\fB:gs/\fIold\fP/\fInew\fP/\fR')
5875 or `\fB:&\fP'. If used with
5876 `\fB:s\fP', any delimiter can be used
5877 in place of /, and the final delimiter is optional
5878 if it is the last character of the event line.
5879 An \fBa\fP may be used as a synonym for \fBg\fP.
5882 Apply the following `\fBs\fP' modifier once to each word in the event line.
5884 .SH "SHELL BUILTIN COMMANDS"
5885 .\" start of bash_builtins
5888 Unless otherwise noted, each builtin command documented in this
5889 section as accepting options preceded by
5893 to signify the end of the options.
5894 For example, the \fB:\fP, \fBtrue\fP, \fBfalse\fP, and \fBtest\fP builtins
5895 do not accept options.
5899 \fB:\fP [\fIarguments\fP]
5901 No effect; the command does nothing beyond expanding
5903 and performing any specified
5904 redirections. A zero exit code is returned.
5906 \fB .\| \fP \fIfilename\fP [\fIarguments\fP]
5909 \fBsource\fP \fIfilename\fP [\fIarguments\fP]
5911 Read and execute commands from
5914 shell environment and return the exit status of the last command
5919 does not contain a slash, file names in
5922 are used to find the directory containing
5924 The file searched for in
5927 need not be executable.
5928 When \fBbash\fP is not in \fIposix mode\fP, the current directory is
5929 searched if no file is found in
5936 builtin command is turned off, the
5940 If any \fIarguments\fP are supplied, they become the positional
5941 parameters when \fIfilename\fP is executed. Otherwise the positional
5942 parameters are unchanged.
5943 The return status is the status of the last command exited within
5944 the script (0 if no commands are executed), and false if
5946 is not found or cannot be read.
5948 \fBalias\fP [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP] ...]
5949 \fBAlias\fP with no arguments or with the
5951 option prints the list of aliases in the form
5952 \fBalias\fP \fIname\fP=\fIvalue\fP on standard output.
5953 When arguments are supplied, an alias is defined for
5954 each \fIname\fP whose \fIvalue\fP is given.
5955 A trailing space in \fIvalue\fP causes the next word to be
5956 checked for alias substitution when the alias is expanded.
5957 For each \fIname\fP in the argument list for which no \fIvalue\fP
5958 is supplied, the name and value of the alias is printed.
5959 \fBAlias\fP returns true unless a \fIname\fP is given for which
5960 no alias has been defined.
5962 \fBbg\fP [\fIjobspec\fP ...]
5963 Resume each suspended job \fIjobspec\fP in the background, as if it
5964 had been started with
5966 If \fIjobspec\fP is not present, the shell's notion of the
5967 \fIcurrent job\fP is used.
5970 returns 0 unless run when job control is disabled or, when run with
5971 job control enabled, if the last \fIjobspec\fP was not found or was
5972 started without job control.
5974 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] [\fB\-lpsvPSV\fP]
5977 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] [\fB\-q\fP \fIfunction\fP] [\fB\-u\fP \fIfunction\fP] [\fB\-r\fP \fIkeyseq\fP]
5979 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fB\-f\fP \fIfilename\fP
5981 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fB\-x\fP \fIkeyseq\fP:\fIshell\-command\fP
5983 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fIkeyseq\fP:\fIfunction\-name\fP
5985 \fBbind\fP \fIreadline\-command\fP
5989 key and function bindings, bind a key sequence to a
5991 function or macro, or set a
5994 Each non-option argument is a command as it would appear in
5996 but each binding or command must be passed as a separate argument;
5997 e.g., '"\eC\-x\eC\-r": re\-read\-init\-file'.
5998 Options, if supplied, have the following meanings:
6005 as the keymap to be affected by the subsequent bindings.
6009 \fIemacs, emacs\-standard, emacs\-meta, emacs\-ctlx, vi,
6010 vi\-move, vi\-command\fP, and
6012 \fIvi\fP is equivalent to \fIvi\-command\fP; \fIemacs\fP is
6013 equivalent to \fIemacs\-standard\fP.
6016 List the names of all \fBreadline\fP functions.
6019 Display \fBreadline\fP function names and bindings in such a way
6020 that they can be re-read.
6023 List current \fBreadline\fP function names and bindings.
6026 Display \fBreadline\fP variable names and values in such a way that they
6030 List current \fBreadline\fP variable names and values.
6033 Display \fBreadline\fP key sequences bound to macros and the strings
6034 they output in such a way that they can be re-read.
6037 Display \fBreadline\fP key sequences bound to macros and the strings
6040 .B \-f \fIfilename\fP
6041 Read key bindings from \fIfilename\fP.
6043 .B \-q \fIfunction\fP
6044 Query about which keys invoke the named \fIfunction\fP.
6046 .B \-u \fIfunction\fP
6047 Unbind all keys bound to the named \fIfunction\fP.
6050 Remove any current binding for \fIkeyseq\fP.
6052 .B \-x \fIkeyseq\fP:\fIshell\-command\fP
6053 Cause \fIshell\-command\fP to be executed whenever \fIkeyseq\fP is
6057 The return value is 0 unless an unrecognized option is given or an
6061 \fBbreak\fP [\fIn\fP]
6068 loop. If \fIn\fP is specified, break \fIn\fP levels.
6072 is greater than the number of enclosing loops, all enclosing loops
6073 are exited. The return value is 0 unless the shell is not executing
6078 \fBbuiltin\fP \fIshell\-builtin\fP [\fIarguments\fP]
6079 Execute the specified shell builtin, passing it
6081 and return its exit status.
6082 This is useful when defining a
6083 function whose name is the same as a shell builtin,
6084 retaining the functionality of the builtin within the function.
6085 The \fBcd\fP builtin is commonly redefined this way.
6086 The return status is false if
6088 is not a shell builtin command.
6090 \fBcd\fP [\fB\-L|-P\fP] [\fIdir\fP]
6091 Change the current directory to \fIdir\fP. The variable
6100 defines the search path for the directory containing
6102 Alternative directory names in
6105 are separated by a colon (:). A null directory name in
6108 is the same as the current directory, i.e., ``\fB.\fP''. If
6110 begins with a slash (/),
6116 option says to use the physical directory structure instead of
6117 following symbolic links (see also the
6121 builtin command); the
6123 option forces symbolic links to be followed. An argument of
6128 If a non-empty directory name from \fBCDPATH\fP is used, or if
6129 \fB\-\fP is the first argument, and the directory change is
6130 successful, the absolute pathname of the new working directory is
6131 written to the standard output.
6132 The return value is true if the directory was successfully changed;
6135 \fBcaller\fP [\fIexpr\fP]
6136 Returns the context of any active subroutine call (a shell function or
6137 a script executed with the \fB.\fP or \fBsource\fP builtins.
6138 Without \fIexpr\fP, \fBcaller\fP displays the line number and source
6139 filename of the current subroutine call.
6140 If a non-negative integer is supplied as \fIexpr\fP, \fBcaller\fP
6141 displays the line number, subroutine name, and source file corresponding
6142 to that position in the current execution call stack. This extra
6143 information may be used, for example, to print a stack trace. The
6144 current frame is frame 0.
6145 The return value is 0 unless the shell is not executing a subroutine
6146 call or \fIexpr\fP does not correspond to a valid position in the
6149 \fBcommand\fP [\fB\-pVv\fP] \fIcommand\fP [\fIarg\fP ...]
6154 suppressing the normal shell function lookup. Only builtin
6155 commands or commands found in the
6158 are executed. If the
6160 option is given, the search for
6162 is performed using a default value for
6164 that is guaranteed to find all of the standard utilities.
6169 option is supplied, a description of
6173 option causes a single word indicating the command or file name
6176 to be displayed; the
6178 option produces a more verbose description.
6183 option is supplied, the exit status is 0 if
6185 was found, and 1 if not. If neither option is supplied and
6186 an error occurred or
6188 cannot be found, the exit status is 127. Otherwise, the exit status of the
6190 builtin is the exit status of
6193 \fBcompgen\fP [\fIoption\fP] [\fIword\fP]
6194 Generate possible completion matches for \fIword\fP according to
6195 the \fIoption\fPs, which may be any option accepted by the
6197 builtin with the exception of \fB\-p\fP and \fB\-r\fP, and write
6198 the matches to the standard output.
6199 When using the \fB\-F\fP or \fB\-C\fP options, the various shell variables
6200 set by the programmable completion facilities, while available, will not
6203 The matches will be generated in the same way as if the programmable
6204 completion code had generated them directly from a completion specification
6205 with the same flags.
6206 If \fIword\fP is specified, only those completions matching \fIword\fP
6209 The return value is true unless an invalid option is supplied, or no
6210 matches were generated.
6212 \fBcomplete\fP [\fB\-abcdefgjksuv\fP] [\fB\-o\fP \fIcomp-option\fP] [\fB\-A\fP \fIaction\fP] [\fB\-G\fP \fIglobpat\fP] [\fB\-W\fP \fIwordlist\fP] [\fB\-P\fP \fIprefix\fP] [\fB\-S\fP \fIsuffix\fP]
6214 [\fB\-X\fP \fIfilterpat\fP] [\fB\-F\fP \fIfunction\fP] [\fB\-C\fP \fIcommand\fP] \fIname\fP [\fIname ...\fP]
6217 \fBcomplete\fP \fB\-pr\fP [\fIname\fP ...]
6219 Specify how arguments to each \fIname\fP should be completed.
6220 If the \fB\-p\fP option is supplied, or if no options are supplied,
6221 existing completion specifications are printed in a way that allows
6222 them to be reused as input.
6223 The \fB\-r\fP option removes a completion specification for
6224 each \fIname\fP, or, if no \fIname\fPs are supplied, all
6225 completion specifications.
6227 The process of applying these completion specifications when word completion
6228 is attempted is described above under \fBProgrammable Completion\fP.
6230 Other options, if specified, have the following meanings.
6231 The arguments to the \fB\-G\fP, \fB\-W\fP, and \fB\-X\fP options
6232 (and, if necessary, the \fB\-P\fP and \fB\-S\fP options)
6233 should be quoted to protect them from expansion before the
6239 \fB\-o\fP \fIcomp-option\fP
6240 The \fIcomp-option\fP controls several aspects of the compspec's behavior
6241 beyond the simple generation of completions.
6242 \fIcomp-option\fP may be one of:
6246 Perform the rest of the default \fBbash\fP completions if the compspec
6247 generates no matches.
6250 Use readline's default filename completion if the compspec generates
6254 Perform directory name completion if the compspec generates no matches.
6257 Tell readline that the compspec generates filenames, so it can perform any
6258 filename\-specific processing (like adding a slash to directory names or
6259 suppressing trailing spaces). Intended to be used with shell functions.
6262 Tell readline not to append a space (the default) to words completed at
6263 the end of the line.
6266 After any matches defined by the compspec are generated,
6267 directory name completion is attempted and any
6268 matches are added to the results of the other actions.
6271 \fB\-A\fP \fIaction\fP
6272 The \fIaction\fP may be one of the following to generate a list of possible
6277 Alias names. May also be specified as \fB\-a\fP.
6280 Array variable names.
6283 \fBReadline\fP key binding names.
6286 Names of shell builtin commands. May also be specified as \fB\-b\fP.
6289 Command names. May also be specified as \fB\-c\fP.
6292 Directory names. May also be specified as \fB\-d\fP.
6295 Names of disabled shell builtins.
6298 Names of enabled shell builtins.
6301 Names of exported shell variables. May also be specified as \fB\-e\fP.
6304 File names. May also be specified as \fB\-f\fP.
6307 Names of shell functions.
6310 Group names. May also be specified as \fB\-g\fP.
6313 Help topics as accepted by the \fBhelp\fP builtin.
6316 Hostnames, as taken from the file specified by the
6322 Job names, if job control is active. May also be specified as \fB\-j\fP.
6325 Shell reserved words. May also be specified as \fB\-k\fP.
6328 Names of running jobs, if job control is active.
6331 Service names. May also be specified as \fB\-s\fP.
6334 Valid arguments for the \fB\-o\fP option to the \fBset\fP builtin.
6337 Shell option names as accepted by the \fBshopt\fP builtin.
6343 Names of stopped jobs, if job control is active.
6346 User names. May also be specified as \fB\-u\fP.
6349 Names of all shell variables. May also be specified as \fB\-v\fP.
6352 \fB\-G\fP \fIglobpat\fP
6353 The filename expansion pattern \fIglobpat\fP is expanded to generate
6354 the possible completions.
6356 \fB\-W\fP \fIwordlist\fP
6357 The \fIwordlist\fP is split using the characters in the
6360 special variable as delimiters, and each resultant word is expanded.
6361 The possible completions are the members of the resultant list which
6362 match the word being completed.
6364 \fB\-C\fP \fIcommand\fP
6365 \fIcommand\fP is executed in a subshell environment, and its output is
6366 used as the possible completions.
6368 \fB\-F\fP \fIfunction\fP
6369 The shell function \fIfunction\fP is executed in the current shell
6371 When it finishes, the possible completions are retrieved from the value
6377 \fB\-X\fP \fIfilterpat\fP
6378 \fIfilterpat\fP is a pattern as used for filename expansion.
6379 It is applied to the list of possible completions generated by the
6380 preceding options and arguments, and each completion matching
6381 \fIfilterpat\fP is removed from the list.
6382 A leading \fB!\fP in \fIfilterpat\fP negates the pattern; in this
6383 case, any completion not matching \fIfilterpat\fP is removed.
6385 \fB\-P\fP \fIprefix\fP
6386 \fIprefix\fP is added at the beginning of each possible completion
6387 after all other options have been applied.
6389 \fB\-S\fP \fIsuffix\fP
6390 \fIsuffix\fP is appended to each possible completion
6391 after all other options have been applied.
6394 The return value is true unless an invalid option is supplied, an option
6395 other than \fB\-p\fP or \fB\-r\fP is supplied without a \fIname\fP
6396 argument, an attempt is made to remove a completion specification for
6397 a \fIname\fP for which no specification exists, or
6398 an error occurs adding a completion specification.
6401 \fBcontinue\fP [\fIn\fP]
6402 Resume the next iteration of the enclosing
6411 is specified, resume at the \fIn\fPth enclosing loop.
6415 is greater than the number of enclosing loops, the last enclosing loop
6416 (the ``top-level'' loop) is resumed. The return value is 0 unless the
6417 shell is not executing a loop when
6421 \fBdeclare\fP [\fB\-afFirtx\fP] [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP] ...]
6424 \fBtypeset\fP [\fB\-afFirtx\fP] [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP] ...]
6426 Declare variables and/or give them attributes.
6427 If no \fIname\fPs are given then display the values of variables.
6430 option will display the attributes and values of each
6434 is used, additional options are ignored.
6437 option inhibits the display of function definitions; only the
6438 function name and attributes are printed.
6439 If the \fBextdebug\fP shell option is enabled using \fBshopt\fP,
6440 the source file name and line number where the function is defined
6441 are displayed as well. The
6445 The following options can
6446 be used to restrict output to variables with the specified attribute or
6447 to give variables attributes:
6452 Each \fIname\fP is an array variable (see
6457 Use function names only.
6460 The variable is treated as an integer; arithmetic evaluation (see
6462 .B "ARITHMETIC EVALUATION" ") "
6463 is performed when the variable is assigned a value.
6466 Make \fIname\fPs readonly. These names cannot then be assigned values
6467 by subsequent assignment statements or unset.
6470 Give each \fIname\fP the \fItrace\fP attribute.
6471 Traced functions inherit the \fBDEBUG\fP and \fBRETURN\fP traps from
6473 The trace attribute has no special meaning for variables.
6476 Mark \fIname\fPs for export to subsequent commands via the environment.
6479 Using `+' instead of `\-'
6480 turns off the attribute instead, with the exception that \fB+a\fP
6481 may not be used to destroy an array variable. When used in a function,
6483 \fIname\fP local, as with the
6486 If a variable name is followed by =\fIvalue\fP, the value of
6487 the variable is set to \fIvalue\fP.
6488 The return value is 0 unless an invalid option is encountered,
6489 an attempt is made to define a function using
6490 .if n ``\-f foo=bar'',
6491 .if t \f(CW\-f foo=bar\fP,
6492 an attempt is made to assign a value to a readonly variable,
6493 an attempt is made to assign a value to an array variable without
6494 using the compound assignment syntax (see
6496 above), one of the \fInames\fP is not a valid shell variable name,
6497 an attempt is made to turn off readonly status for a readonly variable,
6498 an attempt is made to turn off array status for an array variable,
6499 or an attempt is made to display a non-existent function with \fB\-f\fP.
6502 .B dirs [\fB\-clpv\fP] [+\fIn\fP] [\-\fIn\fP]
6503 Without options, displays the list of currently remembered directories.
6504 The default display is on a single line with directory names separated
6506 Directories are added to the list with the
6510 command removes entries from the list.
6515 Displays the \fIn\fPth entry counting from the left of the list
6518 when invoked without options, starting with zero.
6521 Displays the \fIn\fPth entry counting from the right of the list
6524 when invoked without options, starting with zero.
6527 Clears the directory stack by deleting all of the entries.
6530 Produces a longer listing; the default listing format uses a
6531 tilde to denote the home directory.
6534 Print the directory stack with one entry per line.
6537 Print the directory stack with one entry per line,
6538 prefixing each entry with its index in the stack.
6541 The return value is 0 unless an
6542 invalid option is supplied or \fIn\fP indexes beyond the end
6543 of the directory stack.
6546 \fBdisown\fP [\fB\-ar\fP] [\fB\-h\fP] [\fIjobspec\fP ...]
6547 Without options, each
6549 is removed from the table of active jobs.
6550 If the \fB\-h\fP option is given, each
6552 is not removed from the table, but is marked so that
6555 is not sent to the job if the shell receives a
6560 is present, and neither the
6564 option is supplied, the \fIcurrent job\fP is used.
6569 option means to remove or mark all jobs; the
6573 argument restricts operation to running jobs.
6574 The return value is 0 unless a
6576 does not specify a valid job.
6578 \fBecho\fP [\fB\-neE\fP] [\fIarg\fP ...]
6579 Output the \fIarg\fPs, separated by spaces, followed by a newline.
6580 The return status is always 0.
6581 If \fB\-n\fP is specified, the trailing newline is
6582 suppressed. If the \fB\-e\fP option is given, interpretation of
6583 the following backslash-escaped characters is enabled. The
6585 option disables the interpretation of these escape characters,
6586 even on systems where they are interpreted by default.
6587 The \fBxpg_echo\fP shell option may be used to
6588 dynamically determine whether or not \fBecho\fP expands these
6589 escape characters by default.
6591 does not interpret \fB\-\-\fP to mean the end of options.
6593 interprets the following escape sequences:
6604 suppress trailing newline
6628 the eight-bit character whose value is the octal value \fInnn\fP
6629 (zero to three octal digits)
6632 the eight-bit character whose value is the octal value \fInnn\fP
6633 (one to three octal digits)
6636 the eight-bit character whose value is the hexadecimal value \fIHH\fP
6637 (one or two hex digits)
6641 \fBenable\fP [\fB\-adnps\fP] [\fB\-f\fP \fIfilename\fP] [\fIname\fP ...]
6642 Enable and disable builtin shell commands.
6643 Disabling a builtin allows a disk command which has the same name
6644 as a shell builtin to be executed without specifying a full pathname,
6645 even though the shell normally searches for builtins before disk commands.
6646 If \fB\-n\fP is used, each \fIname\fP
6647 is disabled; otherwise,
6648 \fInames\fP are enabled. For example, to use the
6650 binary found via the
6653 instead of the shell builtin version, run
6654 .if t \f(CWenable -n test\fP.
6655 .if n ``enable -n test''.
6658 option means to load the new builtin command
6662 on systems that support dynamic loading. The
6664 option will delete a builtin previously loaded with
6666 If no \fIname\fP arguments are given, or if the
6668 option is supplied, a list of shell builtins is printed.
6669 With no other option arguments, the list consists of all enabled
6671 If \fB\-n\fP is supplied, only disabled builtins are printed.
6672 If \fB\-a\fP is supplied, the list printed includes all builtins, with an
6673 indication of whether or not each is enabled.
6674 If \fB\-s\fP is supplied, the output is restricted to the POSIX
6675 \fIspecial\fP builtins.
6676 The return value is 0 unless a
6678 is not a shell builtin or there is an error loading a new builtin
6679 from a shared object.
6681 \fBeval\fP [\fIarg\fP ...]
6682 The \fIarg\fPs are read and concatenated together into a single
6683 command. This command is then read and executed by the shell, and
6684 its exit status is returned as the value of
6688 or only null arguments,
6692 \fBexec\fP [\fB\-cl\fP] [\fB\-a\fP \fIname\fP] [\fIcommand\fP [\fIarguments\fP]]
6695 is specified, it replaces the shell.
6696 No new process is created. The
6698 become the arguments to \fIcommand\fP.
6702 the shell places a dash at the beginning of the zeroth arg passed to
6710 to be executed with an empty environment. If
6712 is supplied, the shell passes
6714 as the zeroth argument to the executed command. If
6716 cannot be executed for some reason, a non-interactive shell exits,
6717 unless the shell option
6719 is enabled, in which case it returns failure.
6720 An interactive shell returns failure if the file cannot be executed.
6723 is not specified, any redirections take effect in the current shell,
6724 and the return status is 0. If there is a redirection error, the
6727 \fBexit\fP [\fIn\fP]
6728 Cause the shell to exit
6729 with a status of \fIn\fP. If
6731 is omitted, the exit status
6732 is that of the last command executed.
6736 is executed before the shell terminates.
6738 \fBexport\fP [\fB\-fn\fP\^] [\fIname\fP[=\fIword\fP]] ...
6745 are marked for automatic export to the environment of
6746 subsequently executed commands. If the
6754 are given, or if the
6756 option is supplied, a list
6757 of all names that are exported in this shell is printed.
6760 option causes the export property to be removed from each
6762 If a variable name is followed by =\fIword\fP, the value of
6763 the variable is set to \fIword\fP.
6765 returns an exit status of 0 unless an invalid option is
6767 one of the \fInames\fP is not a valid shell variable name, or
6771 that is not a function.
6773 \fBfc\fP [\fB\-e\fP \fIename\fP] [\fB\-nlr\fP] [\fIfirst\fP] [\fIlast\fP]
6776 \fBfc\fP \fB\-s\fP [\fIpat\fP=\fIrep\fP] [\fIcmd\fP]
6778 Fix Command. In the first form, a range of commands from
6782 is selected from the history list.
6786 may be specified as a string (to locate the last command beginning
6787 with that string) or as a number (an index into the history list,
6788 where a negative number is used as an offset from the current
6791 is not specified it is set to
6792 the current command for listing (so that
6793 .if n ``fc \-l \-10''
6794 .if t \f(CWfc \-l \-10\fP
6795 prints the last 10 commands) and to
6800 is not specified it is set to the previous
6801 command for editing and \-16 for listing.
6806 the command numbers when listing. The
6808 option reverses the order of
6809 the commands. If the
6812 the commands are listed on
6813 standard output. Otherwise, the editor given by
6816 on a file containing those commands. If
6822 variable is used, and
6829 is not set. If neither variable is set,
6831 is used. When editing is complete, the edited commands are
6832 echoed and executed.
6834 In the second form, \fIcommand\fP is re-executed after each instance
6835 of \fIpat\fP is replaced by \fIrep\fP.
6836 A useful alias to use with this is
6837 .if n ``r="fc -s"'',
6838 .if t \f(CWr='fc \-s'\fP,
6842 runs the last command beginning with
6848 re-executes the last command.
6850 If the first form is used, the return value is 0 unless an invalid
6851 option is encountered or
6855 specify history lines out of range.
6858 option is supplied, the return value is the value of the last
6859 command executed or failure if an error occurs with the temporary
6860 file of commands. If the second form is used, the return status
6861 is that of the command re-executed, unless
6863 does not specify a valid history line, in which case
6867 \fBfg\fP [\fIjobspec\fP]
6870 in the foreground, and make it the current job.
6873 is not present, the shell's notion of the \fIcurrent job\fP is used.
6874 The return value is that of the command placed into the foreground,
6875 or failure if run when job control is disabled or, when run with
6876 job control enabled, if
6878 does not specify a valid job or
6880 specifies a job that was started without job control.
6882 \fBgetopts\fP \fIoptstring\fP \fIname\fP [\fIargs\fP]
6884 is used by shell procedures to parse positional parameters.
6886 contains the option characters to be recognized; if a character
6887 is followed by a colon, the option is expected to have an
6888 argument, which should be separated from it by white space.
6889 The colon and question mark characters may not be used as
6891 Each time it is invoked,
6893 places the next option in the shell variable
6897 if it does not exist,
6898 and the index of the next argument to be processed into the
6904 is initialized to 1 each time the shell or a shell script
6905 is invoked. When an option requires an argument,
6907 places that argument into the variable
6910 The shell does not reset
6913 automatically; it must be manually reset between multiple
6916 within the same shell invocation if a new set of parameters
6919 When the end of options is encountered, \fBgetopts\fP exits with a
6920 return value greater than zero.
6921 \fBOPTIND\fP is set to the index of the first non-option argument,
6922 and \fBname\fP is set to ?.
6925 normally parses the positional parameters, but if more arguments are
6929 parses those instead.
6932 can report errors in two ways. If the first character of
6936 error reporting is used. In normal operation diagnostic messages
6937 are printed when invalid options or missing option arguments are
6942 is set to 0, no error messages will be displayed, even if the first
6947 If an invalid option is seen,
6952 prints an error message and unsets
6958 the option character found is placed in
6961 and no diagnostic message is printed.
6963 If a required argument is not found, and
6966 a question mark (\^\fB?\fP\^) is placed in
6970 is unset, and a diagnostic message is printed.
6973 is silent, then a colon (\^\fB:\fP\^) is placed in
6978 is set to the option character found.
6981 returns true if an option, specified or unspecified, is found.
6982 It returns false if the end of options is encountered or an
6985 \fBhash\fP [\fB\-lr\fP] [\fB\-p\fP \fIfilename\fP] [\fB\-dt\fP] [\fIname\fP]
6988 the full file name of the command is determined by searching
6994 option is supplied, no path search is performed, and
6996 is used as the full file name of the command.
6999 option causes the shell to forget all
7000 remembered locations.
7003 option causes the shell to forget the remembered location of each \fIname\fP.
7006 option is supplied, the full pathname to which each \fIname\fP corresponds
7007 is printed. If multiple \fIname\fP arguments are supplied with \fB\-t\fP,
7008 the \fIname\fP is printed before the hashed full pathname.
7011 option causes output to be displayed in a format that may be reused as input.
7012 If no arguments are given, or if only \fB\-l\fP is supplied,
7013 information about remembered commands is printed.
7014 The return status is true unless a
7016 is not found or an invalid option is supplied.
7018 \fBhelp\fP [\fB\-s\fP] [\fIpattern\fP]
7019 Display helpful information about builtin commands. If
7023 gives detailed help on all commands matching
7025 otherwise help for all the builtins and shell control structures
7027 The \fB\-s\fP option restricts the information displayed to a short
7029 The return status is 0 unless no command matches
7032 \fBhistory [\fIn\fP]
7035 \fBhistory\fP \fB\-c\fP
7037 \fBhistory \-d\fP \fIoffset\fP
7039 \fBhistory\fP \fB\-anrw\fP [\fIfilename\fP]
7041 \fBhistory\fP \fB\-p\fP \fIarg\fP [\fIarg ...\fP]
7043 \fBhistory\fP \fB\-s\fP \fIarg\fP [\fIarg ...\fP]
7045 With no options, display the command
7046 history list with line numbers. Lines listed
7049 have been modified. An argument of
7054 If the shell variable \fBHISTTIMEFORMAT\fP is set and not null,
7055 it is used as a format string for \fIstrftime\fP(3) to display
7056 the time stamp associated with each displayed history entry.
7057 No intervening blank is printed between the formatted time stamp
7058 and the history line.
7059 If \fIfilename\fP is supplied, it is used as the
7060 name of the history file; if not, the value of
7063 is used. Options, if supplied, have the following meanings:
7068 Clear the history list by deleting all the entries.
7070 \fB\-d\fP \fIoffset\fP
7071 Delete the history entry at position \fIoffset\fP.
7074 Append the ``new'' history lines (history lines entered since the
7075 beginning of the current \fBbash\fP session) to the history file.
7078 Read the history lines not already read from the history
7079 file into the current history list. These are lines
7080 appended to the history file since the beginning of the
7081 current \fBbash\fP session.
7084 Read the contents of the history file
7085 and use them as the current history.
7088 Write the current history to the history file, overwriting the
7089 history file's contents.
7092 Perform history substitution on the following \fIargs\fP and display
7093 the result on the standard output.
7094 Does not store the results in the history list.
7095 Each \fIarg\fP must be quoted to disable normal history expansion.
7100 in the history list as a single entry. The last command in the
7101 history list is removed before the
7106 If the \fBHISTTIMEFORMAT\fP is set, the time stamp information
7107 associated with each history entry is written to the history file.
7108 The return value is 0 unless an invalid option is encountered, an
7109 error occurs while reading or writing the history file, an invalid
7110 \fIoffset\fP is supplied as an argument to \fB\-d\fP, or the
7111 history expansion supplied as an argument to \fB\-p\fP fails.
7114 \fBjobs\fP [\fB\-lnprs\fP] [ \fIjobspec\fP ... ]
7117 \fBjobs\fP \fB\-x\fP \fIcommand\fP [ \fIargs\fP ... ]
7119 The first form lists the active jobs. The options have the following
7126 in addition to the normal information.
7129 List only the process ID of the job's process group
7133 Display information only about jobs that have changed status since
7134 the user was last notified of their status.
7137 Restrict output to running jobs.
7140 Restrict output to stopped jobs.
7145 is given, output is restricted to information about that job.
7146 The return status is 0 unless an invalid option is encountered
7161 with the corresponding process group ID, and executes
7165 returning its exit status.
7168 \fBkill\fP [\fB\-s\fP \fIsigspec\fP | \fB\-n\fP \fIsignum\fP | \fB\-\fP\fIsigspec\fP] [\fIpid\fP | \fIjobspec\fP] ...
7171 \fBkill\fP \fB\-l\fP [\fIsigspec\fP | \fIexit_status\fP]
7173 Send the signal named by
7177 to the processes named by
7182 is either a case-insensitive signal name such as
7185 (with or without the
7188 prefix) or a signal number;
7193 is not present, then
7199 lists the signal names.
7200 If any arguments are supplied when
7202 is given, the names of the signals corresponding to the arguments are
7203 listed, and the return status is 0.
7204 The \fIexit_status\fP argument to
7206 is a number specifying either a signal number or the exit status of
7207 a process terminated by a signal.
7209 returns true if at least one signal was successfully sent, or false
7210 if an error occurs or an invalid option is encountered.
7212 \fBlet\fP \fIarg\fP [\fIarg\fP ...]
7215 is an arithmetic expression to be evaluated (see
7217 .BR "ARITHMETIC EVALUATION" ).
7222 returns 1; 0 is returned otherwise.
7224 \fBlocal\fP [\fIoption\fP] [\fIname\fP[=\fIvalue\fP] ...]
7225 For each argument, a local variable named
7227 is created, and assigned
7229 The \fIoption\fP can be any of the options accepted by \fBdeclare\fP.
7232 is used within a function, it causes the variable
7234 to have a visible scope restricted to that function and its children.
7237 writes a list of local variables to the standard output. It is
7240 when not within a function. The return status is 0 unless
7242 is used outside a function, an invalid
7245 \fIname\fP is a readonly variable.
7250 \fBpopd\fP [\-\fBn\fP] [+\fIn\fP] [\-\fIn\fP]
7251 Removes entries from the directory stack. With no arguments,
7252 removes the top directory from the stack, and performs a
7254 to the new top directory.
7255 Arguments, if supplied, have the following meanings:
7260 Removes the \fIn\fPth entry counting from the left of the list
7263 starting with zero. For example:
7265 .if t \f(CWpopd +0\fP
7266 removes the first directory,
7268 .if t \f(CWpopd +1\fP
7272 Removes the \fIn\fPth entry counting from the right of the list
7275 starting with zero. For example:
7277 .if t \f(CWpopd -0\fP
7278 removes the last directory,
7280 .if t \f(CWpopd -1\fP
7284 Suppresses the normal change of directory when removing directories
7285 from the stack, so that only the stack is manipulated.
7290 command is successful, a
7292 is performed as well, and the return status is 0.
7294 returns false if an invalid option is encountered, the directory stack
7295 is empty, a non-existent directory stack entry is specified, or the
7296 directory change fails.
7299 \fBprintf\fP [\fB\-v\fP \fIvar\fP] \fIformat\fP [\fIarguments\fP]
7300 Write the formatted \fIarguments\fP to the standard output under the
7301 control of the \fIformat\fP.
7302 The \fIformat\fP is a character string which contains three types of objects:
7303 plain characters, which are simply copied to standard output, character
7304 escape sequences, which are converted and copied to the standard output, and
7305 format specifications, each of which causes printing of the next successive
7307 In addition to the standard \fIprintf\fP(1) formats, \fB%b\fP causes
7308 \fBprintf\fP to expand backslash escape sequences in the corresponding
7309 \fIargument\fP (except that \fB\ec\fP terminates output, backslashes in
7310 \fB\e'\fP, \fB\e"\fP, and \fB\e?\fP are not removed, and octal escapes
7311 beginning with \fB\e0\fP may contain up to four digits),
7312 and \fB%q\fP causes \fBprintf\fP to output the corresponding
7313 \fIargument\fP in a format that can be reused as shell input.
7315 The \fB\-v\fP option causes the output to be assigned to the variable
7316 \fIvar\fP rather than being printed to the standard output.
7318 The \fIformat\fP is reused as necessary to consume all of the \fIarguments\fP.
7319 If the \fIformat\fP requires more \fIarguments\fP than are supplied, the
7320 extra format specifications behave as if a zero value or null string, as
7321 appropriate, had been supplied. The return value is zero on success,
7322 non-zero on failure.
7324 \fBpushd\fP [\fB\-n\fP] [\fIdir\fP]
7327 \fBpushd\fP [\fB\-n\fP] [+\fIn\fP] [\-\fIn\fP]
7329 Adds a directory to the top of the directory stack, or rotates
7330 the stack, making the new top of the stack the current working
7331 directory. With no arguments, exchanges the top two directories
7332 and returns 0, unless the directory stack is empty.
7333 Arguments, if supplied, have the following meanings:
7338 Rotates the stack so that the \fIn\fPth directory
7339 (counting from the left of the list shown by
7345 Rotates the stack so that the \fIn\fPth directory
7346 (counting from the right of the list shown by
7348 starting with zero) is at the top.
7351 Suppresses the normal change of directory when adding directories
7352 to the stack, so that only the stack is manipulated.
7357 to the directory stack at the top, making it the
7358 new current working directory.
7363 command is successful, a
7365 is performed as well.
7366 If the first form is used,
7368 returns 0 unless the cd to
7370 fails. With the second form,
7372 returns 0 unless the directory stack is empty,
7373 a non-existent directory stack element is specified,
7374 or the directory change to the specified new current directory
7378 \fBpwd\fP [\fB\-LP\fP]
7379 Print the absolute pathname of the current working directory.
7380 The pathname printed contains no symbolic links if the
7382 option is supplied or the
7386 builtin command is enabled.
7389 option is used, the pathname printed may contain symbolic links.
7390 The return status is 0 unless an error occurs while
7391 reading the name of the current directory or an
7392 invalid option is supplied.
7394 \fBread\fP [\fB\-ers\fP] [\fB\-u\fP \fIfd\fP] [\fB\-t\fP \fItimeout\fP] [\fB\-a\fP \fIaname\fP] [\fB\-p\fP \fIprompt\fP] [\fB\-n\fP \fInchars\fP] [\fB\-d\fP \fIdelim\fP] [\fIname\fP ...]
7395 One line is read from the standard input, or from the file descriptor
7396 \fIfd\fP supplied as an argument to the \fB\-u\fP option, and the first word
7397 is assigned to the first
7399 the second word to the second
7401 and so on, with leftover words and their intervening separators assigned
7404 If there are fewer words read from the input stream than names,
7405 the remaining names are assigned empty values.
7409 are used to split the line into words.
7410 The backslash character (\fB\e\fP) may be used to remove any special
7411 meaning for the next character read and for line continuation.
7412 Options, if supplied, have the following meanings:
7417 The words are assigned to sequential indices
7418 of the array variable
7422 is unset before any new values are assigned.
7423 Other \fIname\fP arguments are ignored.
7426 The first character of \fIdelim\fP is used to terminate the input line,
7427 rather than newline.
7430 If the standard input
7431 is coming from a terminal,
7436 above) is used to obtain the line.
7439 \fBread\fP returns after reading \fInchars\fP characters rather than
7440 waiting for a complete line of input.
7443 Display \fIprompt\fP on standard error, without a
7444 trailing newline, before attempting to read any input. The prompt
7445 is displayed only if input is coming from a terminal.
7448 Backslash does not act as an escape character.
7449 The backslash is considered to be part of the line.
7450 In particular, a backslash-newline pair may not be used as a line
7454 Silent mode. If input is coming from a terminal, characters are
7457 .B \-t \fItimeout\fP
7458 Cause \fBread\fP to time out and return failure if a complete line of
7459 input is not read within \fItimeout\fP seconds.
7460 This option has no effect if \fBread\fP is not reading input from the
7464 Read input from file descriptor \fIfd\fP.
7469 are supplied, the line read is assigned to the variable
7472 The return code is zero, unless end-of-file is encountered, \fBread\fP
7473 times out, or an invalid file descriptor is supplied as the argument to
7477 \fBreadonly\fP [\fB\-apf\fP] [\fIname\fP[=\fIword\fP] ...]
7480 \fInames\fP are marked readonly; the values of these
7482 may not be changed by subsequent assignment.
7485 option is supplied, the functions corresponding to the
7490 option restricts the variables to arrays.
7493 arguments are given, or if the
7495 option is supplied, a list of all readonly names is printed.
7498 option causes output to be displayed in a format that
7499 may be reused as input.
7500 If a variable name is followed by =\fIword\fP, the value of
7501 the variable is set to \fIword\fP.
7502 The return status is 0 unless an invalid option is encountered,
7505 is not a valid shell variable name, or
7509 that is not a function.
7511 \fBreturn\fP [\fIn\fP]
7512 Causes a function to exit with the return value specified by
7516 is omitted, the return status is that of the last command
7517 executed in the function body. If used outside a function,
7518 but during execution of a script by the
7520 (\fBsource\fP) command, it causes the shell to stop executing
7521 that script and return either
7523 or the exit status of the last command executed within the
7524 script as the exit status of the script. If used outside a
7525 function and not during execution of a script by \fB.\fP\^,
7526 the return status is false.
7527 Any command associated with the \fBRETURN\fP trap is executed
7528 before execution resumes after the function or script.
7530 \fBset\fP [\fB\-\-abefhkmnptuvxBCHP\fP] [\fB\-o\fP \fIoption\fP] [\fIarg\fP ...]
7531 Without options, the name and value of each shell variable are displayed
7532 in a format that can be reused as input
7533 for setting or resetting the currently-set variables.
7534 Read-only variables cannot be reset.
7535 In \fIposix mode\fP, only shell variables are listed.
7536 The output is sorted according to the current locale.
7537 When options are specified, they set or unset shell attributes.
7538 Any arguments remaining after the options are processed are treated
7539 as values for the positional parameters and are assigned, in order, to
7544 Options, if specified, have the following meanings:
7549 Automatically mark variables and functions which are modified or
7550 created for export to the environment of subsequent commands.
7553 Report the status of terminated background jobs
7554 immediately, rather than before the next primary prompt. This is
7555 effective only when job control is enabled.
7558 Exit immediately if a \fIsimple command\fP (see
7561 above) exits with a non-zero status.
7562 The shell does not exit if the
7563 command that fails is part of the command list immediately following a
7568 part of the test in an
7570 statement, part of a
7574 list, or if the command's return value is
7577 A trap on \fBERR\fP, if set, is executed before the shell exits.
7580 Disable pathname expansion.
7583 Remember the location of commands as they are looked up for execution.
7584 This is enabled by default.
7587 All arguments in the form of assignment statements
7588 are placed in the environment for a command, not just
7589 those that precede the command name.
7592 Monitor mode. Job control is enabled. This option is on
7593 by default for interactive shells on systems that support
7597 above). Background processes run in a separate process
7598 group and a line containing their exit status is printed
7599 upon their completion.
7602 Read commands but do not execute them. This may be used to
7603 check a shell script for syntax errors. This is ignored by
7606 .B \-o \fIoption\-name\fP
7607 The \fIoption\-name\fP can be one of the following:
7619 Use an emacs-style command line editing interface. This is enabled
7620 by default when the shell is interactive, unless the shell is started
7646 Enable command history, as described above under
7649 This option is on by default in interactive shells.
7652 The effect is as if the shell command
7653 .if t \f(CWIGNOREEOF=10\fP
7654 .if n ``IGNOREEOF=10''
7699 If set, the return value of a pipeline is the value of the last
7700 (rightmost) command to exit with a non-zero status, or zero if all
7701 commands in the pipeline exit successfully.
7702 This option is disabled by default.
7705 Change the behavior of
7707 where the default operation differs
7708 from the POSIX 1003.2 standard to match the standard (\fIposix mode\fP).
7719 Use a vi-style command line editing interface.
7728 is supplied with no \fIoption\-name\fP, the values of the current options are
7732 is supplied with no \fIoption\-name\fP, a series of
7734 commands to recreate the current option settings is displayed on
7735 the standard output.
7741 mode. In this mode, the
7747 files are not processed, shell functions are not inherited from the
7748 environment, and the
7751 variable, if it appears in the environment, is ignored.
7752 If the shell is started with the effective user (group) id not equal to the
7753 real user (group) id, and the \fB\-p\fP option is not supplied, these actions
7754 are taken and the effective user id is set to the real user id.
7755 If the \fB\-p\fP option is supplied at startup, the effective user id is
7757 Turning this option off causes the effective user
7758 and group ids to be set to the real user and group ids.
7761 Exit after reading and executing one command.
7764 Treat unset variables as an error when performing
7765 parameter expansion. If expansion is attempted on an
7766 unset variable, the shell prints an error message, and,
7767 if not interactive, exits with a non-zero status.
7770 Print shell input lines as they are read.
7773 After expanding each \fIsimple command\fP,
7774 \fBfor\fP command, \fBcase\fP command, \fBselect\fP command, or
7775 arithmetic \fBfor\fP command, display the expanded value of
7778 followed by the command and its expanded arguments
7779 or associated word list.
7782 The shell performs brace expansion (see
7784 above). This is on by default.
7789 does not overwrite an existing file with the
7794 redirection operators. This may be overridden when
7795 creating output files by using the redirection operator
7801 If set, any trap on \fBERR\fP is inherited by shell functions, command
7802 substitutions, and commands executed in a subshell environment.
7803 The \fBERR\fP trap is normally not inherited in such cases.
7808 style history substitution. This option is on by
7809 default when the shell is interactive.
7812 If set, the shell does not follow symbolic links when executing
7815 that change the current working directory. It uses the
7816 physical directory structure instead. By default,
7818 follows the logical chain of directories when performing commands
7819 which change the current directory.
7822 If set, any traps on \fBDEBUG\fP and \fBRETURN\fP are inherited by shell
7823 functions, command substitutions, and commands executed in a
7824 subshell environment.
7825 The \fBDEBUG\fP and \fBRETURN\fP traps are normally not inherited
7829 If no arguments follow this option, then the positional parameters are
7830 unset. Otherwise, the positional parameters are set to the
7831 \fIarg\fPs, even if some of them begin with a
7835 Signal the end of options, cause all remaining \fIarg\fPs to be
7836 assigned to the positional parameters. The
7840 options are turned off.
7841 If there are no \fIarg\fPs,
7842 the positional parameters remain unchanged.
7845 The options are off by default unless otherwise noted.
7846 Using + rather than \- causes these options to be turned off.
7847 The options can also be specified as arguments to an invocation of
7849 The current set of options may be found in
7851 The return status is always true unless an invalid option is encountered.
7854 \fBshift\fP [\fIn\fP]
7855 The positional parameters from \fIn\fP+1 ... are renamed to
7858 Parameters represented by the numbers \fB$#\fP
7859 down to \fB$#\fP\-\fIn\fP+1 are unset.
7861 must be a non-negative number less than or equal to \fB$#\fP.
7864 is 0, no parameters are changed.
7867 is not given, it is assumed to be 1.
7870 is greater than \fB$#\fP, the positional parameters are not changed.
7871 The return status is greater than zero if
7875 or less than zero; otherwise 0.
7877 \fBshopt\fP [\fB\-pqsu\fP] [\fB\-o\fP] [\fIoptname\fP ...]
7878 Toggle the values of variables controlling optional shell behavior.
7879 With no options, or with the
7881 option, a list of all settable options is displayed, with
7882 an indication of whether or not each is set.
7883 The \fB\-p\fP option causes output to be displayed in a form that
7884 may be reused as input.
7885 Other options have the following meanings:
7890 Enable (set) each \fIoptname\fP.
7893 Disable (unset) each \fIoptname\fP.
7896 Suppresses normal output (quiet mode); the return status indicates
7897 whether the \fIoptname\fP is set or unset.
7898 If multiple \fIoptname\fP arguments are given with
7900 the return status is zero if all \fIoptnames\fP are enabled; non-zero
7904 Restricts the values of \fIoptname\fP to be those defined for the
7915 is used with no \fIoptname\fP arguments, the display is limited to
7916 those options which are set or unset, respectively.
7917 Unless otherwise noted, the \fBshopt\fP options are disabled (unset)
7920 The return status when listing options is zero if all \fIoptnames\fP
7921 are enabled, non-zero otherwise. When setting or unsetting options,
7922 the return status is zero unless an \fIoptname\fP is not a valid shell
7925 The list of \fBshopt\fP options is:
7931 If set, an argument to the
7933 builtin command that
7934 is not a directory is assumed to be the name of a variable whose
7935 value is the directory to change to.
7938 If set, minor errors in the spelling of a directory component in a
7940 command will be corrected.
7941 The errors checked for are transposed characters,
7942 a missing character, and one character too many.
7943 If a correction is found, the corrected file name is printed,
7944 and the command proceeds.
7945 This option is only used by interactive shells.
7948 If set, \fBbash\fP checks that a command found in the hash
7949 table exists before trying to execute it. If a hashed command no
7950 longer exists, a normal path search is performed.
7953 If set, \fBbash\fP checks the window size after each command
7954 and, if necessary, updates the values of
7964 attempts to save all lines of a multiple-line
7965 command in the same history entry. This allows
7966 easy re-editing of multi-line commands.
7971 includes filenames beginning with a `.' in the results of pathname
7975 If set, a non-interactive shell will not exit if
7976 it cannot execute the file specified as an argument to the
7978 builtin command. An interactive shell does not exit if
7983 If set, aliases are expanded as described above under
7986 This option is enabled by default for interactive shells.
7989 If set, behavior intended for use by debuggers is enabled:
7993 The \fB\-F\fP option to the \fBdeclare\fP builtin displays the source
7994 file name and line number corresponding to each function name supplied
7998 If the command run by the \fBDEBUG\fP trap returns a non-zero value, the
7999 next command is skipped and not executed.
8002 If the command run by the \fBDEBUG\fP trap returns a value of 2, and the
8003 shell is executing in a subroutine (a shell function or a shell script
8004 executed by the \fB.\fP or \fBsource\fP builtins), a call to
8005 \fBreturn\fP is simulated.
8008 \fBBASH_ARGC\fP and \fBBASH_ARGV\fP are updated as described in their
8012 Function tracing is enabled: command substitution, shell functions, and
8013 subshells invoked with \fB(\fP \fIcommand\fP \fB)\fP inherit the
8014 \fBDEBUG\fP and \fBRETURN\fP traps.
8017 Error tracing is enabled: command substitution, shell functions, and
8018 subshells invoked with \fB(\fP \fIcommand\fP \fB)\fP inherit the
8023 If set, the extended pattern matching features described above under
8024 \fBPathname Expansion\fP are enabled.
8027 If set, \fB$\fP'\fIstring\fP' and \fB$\fP"\fIstring\fP" quoting is
8028 performed within \fB${\fP\fIparameter\fP\fB}\fP expansions
8029 enclosed in double quotes. This option is enabled by default.
8032 If set, patterns which fail to match filenames during pathname expansion
8033 result in an expansion error.
8036 If set, the suffixes specified by the \fBFIGNORE\fP shell variable
8037 cause words to be ignored when performing word completion even if
8038 the ignored words are the only possible completions.
8041 \fBSHELL VARIABLES\fP
8042 above for a description of \fBFIGNORE\fP.
8043 This option is enabled by default.
8046 If set, shell error messages are written in the standard GNU error
8050 If set, the history list is appended to the file named by the value
8053 variable when the shell exits, rather than overwriting the file.
8058 is being used, a user is given the opportunity to re-edit a
8059 failed history substitution.
8064 is being used, the results of history substitution are not immediately
8065 passed to the shell parser. Instead, the resulting line is loaded into
8066 the \fBreadline\fP editing buffer, allowing further modification.
8071 is being used, \fBbash\fP will attempt to perform hostname completion when a
8072 word containing a \fB@\fP is being completed (see
8078 This is enabled by default.
8081 If set, \fBbash\fP will send
8084 to all jobs when an interactive login shell exits.
8086 .B interactive_comments
8087 If set, allow a word beginning with
8089 to cause that word and all remaining characters on that
8090 line to be ignored in an interactive shell (see
8093 above). This option is enabled by default.
8098 option is enabled, multi-line commands are saved to the history with
8099 embedded newlines rather than using semicolon separators where possible.
8102 The shell sets this option if it is started as a login shell (see
8106 The value may not be changed.
8109 If set, and a file that \fBbash\fP is checking for mail has been
8110 accessed since the last time it was checked, the message ``The mail in
8111 \fImailfile\fP has been read'' is displayed.
8113 .B no_empty_cmd_completion
8118 will not attempt to search the \fBPATH\fP for possible completions when
8119 completion is attempted on an empty line.
8124 matches filenames in a case\-insensitive fashion when performing pathname
8126 .B Pathname Expansion
8132 matches patterns in a case\-insensitive fashion when performing matching
8133 while executing \fBcase\fP or \fB[[\fP conditional commands.
8138 allows patterns which match no
8140 .B Pathname Expansion
8142 to expand to a null string, rather than themselves.
8145 If set, the programmable completion facilities (see
8146 \fBProgrammable Completion\fP above) are enabled.
8147 This option is enabled by default.
8150 If set, prompt strings undergo
8151 parameter expansion, command substitution, arithmetic
8152 expansion, and quote removal after being expanded as described in
8155 above. This option is enabled by default.
8158 The shell sets this option if it is started in restricted mode (see
8160 .B "RESTRICTED SHELL"
8162 The value may not be changed.
8163 This is not reset when the startup files are executed, allowing
8164 the startup files to discover whether or not a shell is restricted.
8169 builtin prints an error message when the shift count exceeds the
8170 number of positional parameters.
8174 \fBsource\fP (\fB.\fP) builtin uses the value of
8177 to find the directory containing the file supplied as an argument.
8178 This option is enabled by default.
8181 If set, the \fBecho\fP builtin expands backslash-escape sequences
8185 \fBsuspend\fP [\fB\-f\fP]
8186 Suspend the execution of this shell until it receives a
8191 option says not to complain if this is
8192 a login shell; just suspend anyway. The return status is 0 unless
8193 the shell is a login shell and
8195 is not supplied, or if job control is not enabled.
8197 \fBtest\fP \fIexpr\fP
8200 \fB[\fP \fIexpr\fP \fB]\fP
8201 Return a status of 0 or 1 depending on
8202 the evaluation of the conditional expression
8204 Each operator and operand must be a separate argument.
8205 Expressions are composed of the primaries described above under
8207 .BR "CONDITIONAL EXPRESSIONS" .
8208 \fBtest\fP does not accept any options, nor does it accept and ignore
8209 an argument of \fB\-\-\fP as signifying the end of options.
8212 Expressions may be combined using the following operators, listed
8213 in decreasing order of precedence.
8223 Returns the value of \fIexpr\fP.
8224 This may be used to override the normal precedence of operators.
8226 \fIexpr1\fP \-\fBa\fP \fIexpr2\fP
8233 \fIexpr1\fP \-\fBo\fP \fIexpr2\fP
8241 \fBtest\fP and \fB[\fP evaluate conditional
8242 expressions using a set of rules based on the number of arguments.
8248 The expression is false.
8251 The expression is true if and only if the argument is not null.
8254 If the first argument is \fB!\fP, the expression is true if and
8255 only if the second argument is null.
8256 If the first argument is one of the unary conditional operators listed above
8259 .BR "CONDITIONAL EXPRESSIONS" ,
8260 the expression is true if the unary test is true.
8261 If the first argument is not a valid unary conditional operator, the expression
8265 If the second argument is one of the binary conditional operators listed above
8268 .BR "CONDITIONAL EXPRESSIONS" ,
8269 the result of the expression is the result of the binary test using
8270 the first and third arguments as operands.
8271 If the first argument is \fB!\fP, the value is the negation of
8272 the two-argument test using the second and third arguments.
8273 If the first argument is exactly \fB(\fP and the third argument is
8274 exactly \fB)\fP, the result is the one-argument test of the second
8276 Otherwise, the expression is false.
8277 The \fB\-a\fP and \fB\-o\fP operators are considered binary operators
8281 If the first argument is \fB!\fP, the result is the negation of
8282 the three-argument expression composed of the remaining arguments.
8283 Otherwise, the expression is parsed and evaluated according to
8284 precedence using the rules listed above.
8287 The expression is parsed and evaluated according to precedence
8288 using the rules listed above.
8293 Print the accumulated user and system times for the shell and
8294 for processes run from the shell. The return status is 0.
8296 \fBtrap\fP [\fB\-lp\fP] [[\fIarg\fP] \fIsigspec\fP ...]
8299 is to be read and executed when the shell receives
8304 is absent (and there is a single \fIsigspec\fP) or
8306 each specified signal is
8307 reset to its original disposition (the value it had
8308 upon entrance to the shell).
8311 is the null string the signal specified by each
8313 is ignored by the shell and by the commands it invokes.
8318 has been supplied, then the trap commands associated with each
8321 If no arguments are supplied or if only
8325 prints the list of commands associated with each signal.
8328 option causes the shell to print a list of signal names and
8329 their corresponding numbers.
8333 a signal name defined in <\fIsignal.h\fP>, or a signal number.
8334 Signal names are case insensitive and the SIG prefix is optional.
8342 is executed on exit from the shell.
8350 is executed before every \fIsimple command\fP, \fIfor\fP command,
8351 \fIcase\fP command, \fIselect\fP command, every arithmetic \fIfor\fP
8352 command, and before the first command executes in a shell function (see
8356 Refer to the description of the \fBextdebug\fP option to the
8357 \fBshopt\fP builtin for details of its effect on the \fBDEBUG\fP trap.
8365 is executed whenever a simple command has a non\-zero exit status,
8366 subject to the following conditions.
8370 trap is not executed if the failed
8371 command is part of the command list immediately following a
8376 part of the test in an
8378 statement, part of a
8382 list, or if the command's return value is
8385 These are the same conditions obeyed by the \fBerrexit\fP option.
8393 is executed each time a shell function or a script executed with the
8394 \fB.\fP or \fBsource\fP builtins finishes executing.
8395 Signals ignored upon entry to the shell cannot be trapped or reset.
8396 Trapped signals are reset to their original values in a child
8397 process when it is created.
8398 The return status is false if any
8400 is invalid; otherwise
8404 \fBtype\fP [\fB\-aftpP\fP] \fIname\fP [\fIname\fP ...]
8408 would be interpreted if used as a command name.
8413 prints a string which is one of
8422 is an alias, shell reserved word, function, builtin, or disk file,
8426 is not found, then nothing is printed, and an exit status of false
8432 either returns the name of the disk file
8433 that would be executed if
8435 were specified as a command name,
8437 .if t \f(CWtype -t name\fP
8438 .if n ``type -t name''
8446 search for each \fIname\fP, even if
8447 .if t \f(CWtype -t name\fP
8448 .if n ``type -t name''
8451 If a command is hashed,
8455 print the hashed value, not necessarily the file that appears
8463 prints all of the places that contain
8466 This includes aliases and functions,
8469 option is not also used.
8470 The table of hashed commands is not consulted
8475 option suppresses shell function lookup, as with the \fBcommand\fP builtin.
8477 returns true if any of the arguments are found, false if
8480 \fBulimit\fP [\fB\-SHacdflmnpstuv\fP [\fIlimit\fP]]
8481 Provides control over the resources available to the shell and to
8482 processes started by it, on systems that allow such control.
8483 The \fB\-H\fP and \fB\-S\fP options specify that the hard or soft limit is
8484 set for the given resource. A hard limit cannot be increased once it
8485 is set; a soft limit may be increased up to the value of the hard limit.
8486 If neither \fB\-H\fP nor \fB\-S\fP is specified, both the soft and hard
8490 can be a number in the unit specified for the resource
8491 or one of the special values
8496 which stand for the current hard limit, the current soft limit, and
8497 no limit, respectively.
8500 is omitted, the current value of the soft limit of the resource is
8501 printed, unless the \fB\-H\fP option is given. When more than one
8502 resource is specified, the limit name and unit are printed before the value.
8503 Other options are interpreted as follows:
8508 All current limits are reported
8511 The maximum size of core files created
8514 The maximum size of a process's data segment
8517 The maximum size of files created by the shell
8520 The maximum size that may be locked into memory
8523 The maximum resident set size
8526 The maximum number of open file descriptors (most systems do not
8527 allow this value to be set)
8530 The pipe size in 512-byte blocks (this may not be set)
8533 The maximum stack size
8536 The maximum amount of cpu time in seconds
8539 The maximum number of processes available to a single user
8542 The maximum amount of virtual memory available to the shell
8547 is given, it is the new value of the specified resource (the
8549 option is display only).
8550 If no option is given, then
8552 is assumed. Values are in 1024-byte increments, except for
8554 which is in seconds,
8556 which is in units of 512-byte blocks,
8561 which are unscaled values.
8562 The return status is 0 unless an invalid option or argument is supplied,
8563 or an error occurs while setting a new limit.
8566 \fBumask\fP [\fB\-p\fP] [\fB\-S\fP] [\fImode\fP]
8567 The user file-creation mask is set to
8571 begins with a digit, it
8572 is interpreted as an octal number; otherwise
8573 it is interpreted as a symbolic mode mask similar
8578 is omitted, the current value of the mask is printed.
8581 option causes the mask to be printed in symbolic form; the
8582 default output is an octal number.
8585 option is supplied, and
8587 is omitted, the output is in a form that may be reused as input.
8588 The return status is 0 if the mode was successfully changed or if
8589 no \fImode\fP argument was supplied, and false otherwise.
8591 \fBunalias\fP [\-\fBa\fP] [\fIname\fP ...]
8592 Remove each \fIname\fP from the list of defined aliases. If
8594 is supplied, all alias definitions are removed. The return
8595 value is true unless a supplied
8597 is not a defined alias.
8599 \fBunset\fP [\-\fBfv\fP] [\fIname\fP ...]
8602 remove the corresponding variable or function.
8603 If no options are supplied, or the
8605 option is given, each
8607 refers to a shell variable.
8608 Read-only variables may not be unset.
8613 refers to a shell function, and the function definition
8615 Each unset variable or function is removed from the environment
8616 passed to subsequent commands.
8633 are unset, they lose their special properties, even if they are
8634 subsequently reset. The exit status is true unless a
8638 \fBwait\fP [\fIn ...\fP]
8639 Wait for each specified process and return its termination status.
8643 ID or a job specification; if a job spec is given, all processes
8644 in that job's pipeline are waited for. If
8646 is not given, all currently active child processes
8647 are waited for, and the return status is zero. If
8649 specifies a non-existent process or job, the return status is
8650 127. Otherwise, the return status is the exit status of the last
8651 process or job waited for.
8654 .SH "RESTRICTED SHELL"
8660 is started with the name
8664 option is supplied at invocation,
8665 the shell becomes restricted.
8666 A restricted shell is used to
8667 set up an environment more controlled than the standard shell.
8668 It behaves identically to
8670 with the exception that the following are disallowed or not performed:
8672 changing directories with \fBcd\fP
8674 setting or unsetting the values of
8681 specifying command names containing
8684 specifying a file name containing a
8686 as an argument to the
8690 Specifying a filename containing a slash as an argument to the
8696 importing function definitions from the shell environment at startup
8698 parsing the value of \fBSHELLOPTS\fP from the shell environment at startup
8700 redirecting output using the >, >|, <>, >&, &>, and >> redirection operators
8704 builtin command to replace the shell with another command
8706 adding or deleting builtin commands with the
8714 Using the \fBenable\fP builtin command to enable disabled shell builtins
8722 turning off restricted mode with
8723 \fBset +r\fP or \fBset +o restricted\fP.
8725 These restrictions are enforced after any startup files are read.
8727 .ie \n(zY=1 When a command that is found to be a shell script is executed,
8728 .el \{ When a command that is found to be a shell script is executed
8731 .B "COMMAND EXECUTION"
8735 turns off any restrictions in the shell spawned to execute the
8742 \fIBash Reference Manual\fP, Brian Fox and Chet Ramey
8744 \fIThe Gnu Readline Library\fP, Brian Fox and Chet Ramey
8746 \fIThe Gnu History Library\fP, Brian Fox and Chet Ramey
8748 \fIPortable Operating System Interface (POSIX) Part 2: Shell and Utilities\fP, IEEE
8750 \fIsh\fP(1), \fIksh\fP(1), \fIcsh\fP(1)
8752 \fIemacs\fP(1), \fIvi\fP(1)
8760 The \fBbash\fP executable
8763 The systemwide initialization file, executed for login shells
8766 The personal initialization file, executed for login shells
8769 The individual per-interactive-shell startup file
8772 The individual login shell cleanup file, executed when a login shell exits
8775 Individual \fIreadline\fP initialization file
8778 Brian Fox, Free Software Foundation
8782 Chet Ramey, Case Western Reserve University
8786 If you find a bug in
8788 you should report it. But first, you should
8789 make sure that it really is a bug, and that it appears in the latest
8792 The latest version is always available from
8793 \fIftp://ftp.gnu.org/pub/bash/\fP.
8795 Once you have determined that a bug actually exists, use the
8797 command to submit a bug report.
8798 If you have a fix, you are encouraged to mail that as well!
8799 Suggestions and `philosophical' bug reports may be mailed
8800 to \fIbug-bash@gnu.org\fP or posted to the Usenet
8804 ALL bug reports should include:
8808 The version number of \fBbash\fR
8810 The hardware and operating system
8812 The compiler used to compile
8814 A description of the bug behaviour
8816 A short script or `recipe' which exercises the bug
8820 inserts the first three items automatically into the template
8821 it provides for filing a bug report.
8823 Comments and bug reports concerning
8824 this manual page should be directed to
8825 .IR chet@po.CWRU.Edu .
8828 It's too big and too slow.
8830 There are some subtle differences between
8832 and traditional versions of
8834 mostly because of the
8839 Aliases are confusing in some uses.
8841 Shell builtin commands and functions are not stoppable/restartable.
8843 Compound commands and command sequences of the form `a ; b ; c'
8844 are not handled gracefully when process suspension is attempted.
8845 When a process is stopped, the shell immediately executes the next
8846 command in the sequence.
8847 It suffices to place the sequence of commands between
8848 parentheses to force it into a subshell, which may be stopped as
8851 Commands inside of \fB$(\fP...\fB)\fP command substitution are not
8852 parsed until substitution is attempted. This will delay error
8853 reporting until some time after the command is entered. For example,
8854 unmatched parentheses, even inside shell comments, will result in
8855 error messages while the construct is being read.
8857 Array variables may not (yet) be exported.
projects / thirdparty / bash.git / blob