2 .\" MAN PAGE COMMENTS to
5 .\" Information Network Services
6 .\" Case Western Reserve University
9 .\" Last Change: Thu Sep 28 10:25:59 EDT 2006
11 .\" bash_builtins, strip all but Built-Ins section
14 .TH BASH 1 "2006 September 28" "GNU Bash-3.2"
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
66 Shell and Utilities portion of the IEEE POSIX specification
67 (IEEE Standard 1003.1).
69 can be configured to be POSIX-conformant by default.
71 In addition to the single-character shell options documented in the
72 description of the \fBset\fR builtin command, \fBbash\fR
73 interprets the following options when it is invoked:
80 option is present, then commands are read from
82 If there are arguments after the
84 they are assigned to the positional parameters, starting with
90 option is present, the shell is
96 act as if it had been invoked as a login shell (see
104 option is present, the shell becomes
108 .B "RESTRICTED SHELL"
114 option is present, or if no arguments remain after option
115 processing, then commands are read from the standard input.
116 This option allows the positional parameters to be set
117 when invoking an interactive shell.
120 A list of all double-quoted strings preceded by \fB$\fP
121 is printed on the standard output.
122 These are the strings that
123 are subject to language translation when the current locale
124 is not \fBC\fP or \fBPOSIX\fP.
125 This implies the \fB\-n\fP option; no commands will be executed.
127 .B [\-+]O [\fIshopt_option\fP]
128 \fIshopt_option\fP is one of the shell options accepted by the
129 \fBshopt\fP builtin (see
131 .B SHELL BUILTIN COMMANDS
133 If \fIshopt_option\fP is present, \fB\-O\fP sets the value of that option;
135 If \fIshopt_option\fP is not supplied, the names and values of the shell
136 options accepted by \fBshopt\fP are printed on the standard output.
137 If the invocation option is \fB+O\fP, the output is displayed in a format
138 that may be reused as input.
143 signals the end of options and disables further option processing.
144 Any arguments after the
146 are treated as filenames and arguments. An argument of
148 is equivalent to \fB\-\-\fP.
152 also interprets a number of multi-character options.
153 These options must appear on the command line before the
154 single-character options to be recognized.
159 Arrange for the debugger profile to be executed before the shell
161 Turns on extended debugging mode (see the description of the
166 and shell function tracing (see the description of the
167 \fB\-o functrace\fP option to the
171 .B \-\-dump\-po\-strings
172 Equivalent to \fB\-D\fP, but the output is in the GNU \fIgettext\fP
173 \fBpo\fP (portable object) file format.
176 Equivalent to \fB\-D\fP.
179 Display a usage message on standard output and exit successfully.
181 \fB\-\-init\-file\fP \fIfile\fP
184 \fB\-\-rcfile\fP \fIfile\fP
186 Execute commands from
188 instead of the standard personal initialization file
190 if the shell is interactive (see
196 Equivalent to \fB\-l\fP.
201 library to read command lines when the shell is interactive.
204 Do not read either the system-wide startup file
206 or any of the personal initialization files
207 .IR ~/.bash_profile ,
213 reads these files when it is invoked as a login shell (see
219 Do not read and execute the personal initialization file
221 if the shell is interactive.
222 This option is on by default if the shell is invoked as
226 Change the behavior of \fBbash\fP where the default operation differs
227 from the POSIX standard to match the standard (\fIposix mode\fP).
230 The shell becomes restricted (see
232 .B "RESTRICTED SHELL"
236 Equivalent to \fB\-v\fP.
239 Show version information for this instance of
241 on the standard output and exit successfully.
244 If arguments remain after option processing, and neither the
248 option has been supplied, the first argument is assumed to
249 be the name of a file containing shell commands.
252 is invoked in this fashion,
254 is set to the name of the file, and the positional parameters
255 are set to the remaining arguments.
257 reads and executes commands from this file, then exits.
258 \fBBash\fP's exit status is the exit status of the last command
259 executed in the script.
260 If no commands are executed, the exit status is 0.
261 An attempt is first made to open the file in the current directory, and,
262 if no file is found, then the shell searches the directories in
267 A \fIlogin shell\fP is one whose first character of argument zero is a
269 or one started with the
273 An \fIinteractive\fP shell is one started without non-option arguments
277 whose standard input and error are
278 both connected to terminals (as determined by
280 or one started with the
292 allowing a shell script or a startup file to test this state.
294 The following paragraphs describe how
296 executes its startup files.
297 If any of the files exist but cannot be read,
300 Tildes are expanded in file names as described below under
309 is invoked as an interactive login shell, or as a non-interactive shell
310 with the \fB\-\-login\fP option, it first reads and
311 executes commands from the file \fI/etc/profile\fP, if that
313 After reading that file, it looks for \fI~/.bash_profile\fP,
314 \fI~/.bash_login\fP, and \fI~/.profile\fP, in that order, and reads
315 and executes commands from the first one that exists and is readable.
318 option may be used when the shell is started to inhibit this behavior.
320 When a login shell exits,
322 reads and executes commands from the file \fI~/.bash_logout\fP, if it
325 When an interactive shell that is not a login shell is started,
327 reads and executes commands from \fI~/.bashrc\fP, if that file exists.
328 This may be inhibited by using the
331 The \fB\-\-rcfile\fP \fIfile\fP option will force
333 to read and execute commands from \fIfile\fP instead of \fI~/.bashrc\fP.
337 is started non-interactively, to run a shell script, for example, it
338 looks for the variable
341 in the environment, expands its value if it appears there, and uses the
342 expanded value as the name of a file to read and execute.
344 behaves as if the following command were executed:
347 .if t \f(CWif [ \-n "$BASH_ENV" ]; then . "$BASH_ENV"; fi\fP
348 .if n if [ \-n "$BASH_ENV" ]; then . "$BASH_ENV"; fi
354 variable is not used to search for the file name.
358 is invoked with the name
360 it tries to mimic the startup behavior of historical versions of
362 as closely as possible,
363 while conforming to the POSIX standard as well.
364 When invoked as an interactive login shell, or a non-interactive
365 shell with the \fB\-\-login\fP option, it first attempts to
366 read and execute commands from
373 option may be used to inhibit this behavior.
374 When invoked as an interactive shell with the name
377 looks for the variable
380 expands its value if it is defined, and uses the
381 expanded value as the name of a file to read and execute.
382 Since a shell invoked as
384 does not attempt to read and execute commands from any other startup
387 option has no effect.
388 A non-interactive shell invoked with the name
390 does not attempt to read any other startup files.
396 mode after the startup files are read.
404 command line option, it follows the POSIX standard for startup files.
405 In this mode, interactive shells expand the
408 variable and commands are read and executed from the file
409 whose name is the expanded value.
410 No other startup files are read.
413 attempts to determine when it is being run by the remote shell
414 daemon, usually \fIrshd\fP.
417 determines it is being run by \fIrshd\fP, it reads and executes
418 commands from \fI~/.bashrc\fP, if that file exists and is readable.
419 It will not do this if invoked as \fBsh\fP.
422 option may be used to inhibit this behavior, and the
424 option may be used to force another file to be read, but
425 \fIrshd\fP does not generally invoke the shell with those options
426 or allow them to be specified.
428 If the shell is started with the effective user (group) id not equal to the
429 real user (group) id, and the \fB\-p\fP option is not supplied, no startup
430 files are read, shell functions are not inherited from the environment, the
433 variable, if it appears in the environment, is ignored,
434 and the effective user id is set to the real user id.
435 If the \fB\-p\fP option is supplied at invocation, the startup behavior is
436 the same, but the effective user id is not reset.
439 The following definitions are used throughout the rest of this
447 A sequence of characters considered as a single unit by the shell.
454 consisting only of alphanumeric characters and underscores, and
455 beginning with an alphabetic character or an underscore. Also
460 A character that, when unquoted, separates words. One of the following:
464 .if t \fB| & ; ( ) < > space tab\fP
465 .if n \fB| & ; ( ) < > space tab\fP
470 A \fItoken\fP that performs a control function. It is one of the following
474 .if t \fB\(bv\(bv & && ; ;; ( ) | <newline>\fP
475 .if n \fB|| & && ; ;; ( ) | <newline>\fP
479 \fIReserved words\fP are words that have a special meaning to the shell.
480 The following words are recognized as reserved when unquoted and either
481 the first word of a simple command (see
484 below) or the third word of a
492 .if n ! case do done elif else esac fi for function if in select then until while { } time [[ ]]
493 .if t ! case do done elif else esac fi for function if in select then until while { } time [[ ]]
498 A \fIsimple command\fP is a sequence of optional variable assignments
499 followed by \fBblank\fP-separated words and redirections, and
500 terminated by a \fIcontrol operator\fP. The first word
501 specifies the command to be executed, and is passed as argument zero.
502 The remaining words are passed as arguments to the invoked command.
504 The return value of a \fIsimple command\fP is its exit status, or
505 128+\fIn\^\fP if the command is terminated by signal
509 A \fIpipeline\fP is a sequence of one or more commands separated by
512 The format for a pipeline is:
515 [\fBtime\fP [\fB\-p\fP]] [ ! ] \fIcommand\fP [ \fB|\fP \fIcommand2\fP ... ]
518 The standard output of
520 is connected via a pipe to the standard input of
522 This connection is performed before any redirections specified by the
528 The return status of a pipeline is the exit status of the last
529 command, unless the \fBpipefail\fP option is enabled.
530 If \fBpipefail\fP is enabled, the pipeline's return status is the
531 value of the last (rightmost) command to exit with a non-zero status,
532 or zero if all commands exit successfully.
535 precedes a pipeline, the exit status of that pipeline is the logical
536 negation of the exit status as described above.
537 The shell waits for all commands in the pipeline to
538 terminate before returning a value.
542 reserved word precedes a pipeline, the elapsed as well as user and
543 system time consumed by its execution are reported when the pipeline
545 The \fB\-p\fP option changes the output format to that specified by POSIX.
549 variable may be set to a format string that specifies how the timing
550 information should be displayed; see the description of
557 Each command in a pipeline is executed as a separate process (i.e., in a
561 A \fIlist\fP is a sequence of one or more pipelines separated by one
568 and optionally terminated by one of
574 Of these list operators,
578 have equal precedence, followed by
582 which have equal precedence.
584 A sequence of one or more newlines may appear in a \fIlist\fP instead
585 of a semicolon to delimit commands.
587 If a command is terminated by the control operator
589 the shell executes the command in the \fIbackground\fP
590 in a subshell. The shell does not wait for the command to
591 finish, and the return status is 0. Commands separated by a
593 are executed sequentially; the shell waits for each
594 command to terminate in turn. The return status is the
595 exit status of the last command executed.
597 The control operators
601 denote AND lists and OR lists, respectively.
602 An AND list has the form
605 \fIcommand1\fP \fB&&\fP \fIcommand2\fP
609 is executed if, and only if,
611 returns an exit status of zero.
613 An OR list has the form
616 \fIcommand1\fP \fB\(bv\(bv\fP \fIcommand2\fP
621 is executed if and only if
623 returns a non-zero exit status. The return status of
624 AND and OR lists is the exit status of the last command
625 executed in the list.
626 .SS Compound Commands
628 A \fIcompound command\fP is one of the following:
631 \fIlist\fP is executed in a subshell environment (see
633 \fBCOMMAND EXECUTION ENVIRONMENT\fP
635 Variable assignments and builtin
636 commands that affect the shell's environment do not remain in effect
637 after the command completes. The return status is the exit status of
641 \fIlist\fP is simply executed in the current shell environment.
642 \fIlist\fP must be terminated with a newline or semicolon.
643 This is known as a \fIgroup command\fP.
644 The return status is the exit status of
646 Note that unlike the metacharacters \fB(\fP and \fB)\fP, \fB{\fP and
647 \fB}\fP are \fIreserved words\fP and must occur where a reserved
648 word is permitted to be recognized. Since they do not cause a word
649 break, they must be separated from \fIlist\fP by whitespace.
652 The \fIexpression\fP is evaluated according to the rules described
655 .BR "ARITHMETIC EVALUATION" .
656 If the value of the expression is non-zero, the return status is 0;
657 otherwise the return status is 1. This is exactly equivalent to
658 \fBlet "\fIexpression\fP"\fR.
660 \fB[[\fP \fIexpression\fP \fB]]\fP
661 Return a status of 0 or 1 depending on the evaluation of
662 the conditional expression \fIexpression\fP.
663 Expressions are composed of the primaries described below under
665 .BR "CONDITIONAL EXPRESSIONS" .
666 Word splitting and pathname expansion are not performed on the words
667 between the \fB[[\fP and \fB]]\fP; tilde expansion, parameter and
668 variable expansion, arithmetic expansion, command substitution, process
669 substitution, and quote removal are performed.
670 Conditional operators such as \fB\-f\fP must be unquoted to be recognized
674 When the \fB==\fP and \fB!=\fP operators are used, the string to the
675 right of the operator is considered a pattern and matched according
676 to the rules described below under \fBPattern Matching\fP.
679 is enabled, the match is performed without regard to the case
680 of alphabetic characters.
681 The return value is 0 if the string matches (\fB==\fP) or does not match
682 (\fB!=\fP) the pattern, and 1 otherwise.
683 Any part of the pattern may be quoted to force it to be matched as a
687 An additional binary operator, \fB=~\fP, is available, with the same
688 precedence as \fB==\fP and \fB!=\fP.
689 When it is used, the string to the right of the operator is considered
690 an extended regular expression and matched accordingly (as in \fIregex\fP(3)).
691 The return value is 0 if the string matches
692 the pattern, and 1 otherwise.
693 If the regular expression is syntactically incorrect, the conditional
694 expression's return value is 2.
697 is enabled, the match is performed without regard to the case
698 of alphabetic characters.
699 Substrings matched by parenthesized subexpressions within the regular
700 expression are saved in the array variable \fBBASH_REMATCH\fP.
701 The element of \fBBASH_REMATCH\fP with index 0 is the portion of the string
702 matching the entire regular expression.
703 The element of \fBBASH_REMATCH\fP with index \fIn\fP is the portion of the
704 string matching the \fIn\fPth parenthesized subexpression.
707 Expressions may be combined using the following operators, listed
708 in decreasing order of precedence:
714 .B ( \fIexpression\fP )
715 Returns the value of \fIexpression\fP.
716 This may be used to override the normal precedence of operators.
718 .B ! \fIexpression\fP
723 \fIexpression1\fP \fB&&\fP \fIexpression2\fP
730 .if t \fIexpression1\fP \fB\(bv\(bv\fP \fIexpression2\fP
731 .if n \fIexpression1\fP \fB||\fP \fIexpression2\fP
742 operators do not evaluate \fIexpression2\fP if the value of
743 \fIexpression1\fP is sufficient to determine the return value of
744 the entire conditional expression.
747 \fBfor\fP \fIname\fP [ \fBin\fP \fIword\fP ] ; \fBdo\fP \fIlist\fP ; \fBdone\fP
748 The list of words following \fBin\fP is expanded, generating a list
750 The variable \fIname\fP is set to each element of this list
751 in turn, and \fIlist\fP is executed each time.
752 If the \fBin\fP \fIword\fP is omitted, the \fBfor\fP command executes
753 \fIlist\fP once for each positional parameter that is set (see
757 The return status is the exit status of the last command that executes.
758 If the expansion of the items following \fBin\fP results in an empty
759 list, no commands are executed, and the return status is 0.
761 \fBfor\fP (( \fIexpr1\fP ; \fIexpr2\fP ; \fIexpr3\fP )) ; \fBdo\fP \fIlist\fP ; \fBdone\fP
762 First, the arithmetic expression \fIexpr1\fP is evaluated according
763 to the rules described below under
765 .BR "ARITHMETIC EVALUATION" .
766 The arithmetic expression \fIexpr2\fP is then evaluated repeatedly
767 until it evaluates to zero.
768 Each time \fIexpr2\fP evaluates to a non-zero value, \fIlist\fP is
769 executed and the arithmetic expression \fIexpr3\fP is evaluated.
770 If any expression is omitted, it behaves as if it evaluates to 1.
771 The return value is the exit status of the last command in \fIlist\fP
772 that is executed, or false if any of the expressions is invalid.
774 \fBselect\fP \fIname\fP [ \fBin\fP \fIword\fP ] ; \fBdo\fP \fIlist\fP ; \fBdone\fP
775 The list of words following \fBin\fP is expanded, generating a list
776 of items. The set of expanded words is printed on the standard
777 error, each preceded by a number. If the \fBin\fP
778 \fIword\fP is omitted, the positional parameters are printed (see
783 prompt is then displayed and a line read from the standard input.
784 If the line consists of a number corresponding to one of
785 the displayed words, then the value of
787 is set to that word. If the line is empty, the words and prompt
788 are displayed again. If EOF is read, the command completes. Any
789 other value read causes
791 to be set to null. The line read is saved in the variable
795 is executed after each selection until a
800 is the exit status of the last command executed in
802 or zero if no commands were executed.
804 \fBcase\fP \fIword\fP \fBin\fP [ [(] \fIpattern\fP [ \fB|\fP \fIpattern\fP ] \
805 ... ) \fIlist\fP ;; ] ... \fBesac\fP
806 A \fBcase\fP command first expands \fIword\fP, and tries to match
807 it against each \fIpattern\fP in turn, using the same matching rules
808 as for pathname expansion (see
809 .B Pathname Expansion
811 The \fIword\fP is expanded using tilde
812 expansion, parameter and variable expansion, arithmetic substitution,
813 command substitution, process substitution and quote removal.
814 Each \fIpattern\fP examined is expanded using tilde
815 expansion, parameter and variable expansion, arithmetic substitution,
816 command substitution, and process substitution.
819 is enabled, the match is performed without regard to the case
820 of alphabetic characters.
821 When a match is found, the
822 corresponding \fIlist\fP is executed. After the first match, no
823 subsequent matches are attempted. The exit status is zero if no
824 pattern matches. Otherwise, it is the exit status of the
825 last command executed in \fIlist\fP.
827 \fBif\fP \fIlist\fP; \fBthen\fP \fIlist;\fP \
828 [ \fBelif\fP \fIlist\fP; \fBthen\fP \fIlist\fP; ] ... \
829 [ \fBelse\fP \fIlist\fP; ] \fBfi\fP
833 is executed. If its exit status is zero, the
834 \fBthen\fP \fIlist\fP is executed. Otherwise, each \fBelif\fP
835 \fIlist\fP is executed in turn, and if its exit status is zero,
836 the corresponding \fBthen\fP \fIlist\fP is executed and the
837 command completes. Otherwise, the \fBelse\fP \fIlist\fP is
838 executed, if present. The exit status is the exit status of the
839 last command executed, or zero if no condition tested true.
841 \fBwhile\fP \fIlist\fP; \fBdo\fP \fIlist\fP; \fBdone\fP
844 \fBuntil\fP \fIlist\fP; \fBdo\fP \fIlist\fP; \fBdone\fP
846 The \fBwhile\fP command continuously executes the \fBdo\fP
847 \fIlist\fP as long as the last command in \fIlist\fP returns
848 an exit status of zero. The \fBuntil\fP command is identical
849 to the \fBwhile\fP command, except that the test is negated;
853 is executed as long as the last command in
855 returns a non-zero exit status.
856 The exit status of the \fBwhile\fP and \fBuntil\fP commands
858 of the last \fBdo\fP \fIlist\fP command executed, or zero if
860 .SS Shell Function Definitions
862 A shell function is an object that is called like a simple command and
863 executes a compound command with a new set of positional parameters.
864 Shell functions are declared as follows:
866 [ \fBfunction\fP ] \fIname\fP () \fIcompound\-command\fP [\fIredirection\fP]
867 This defines a function named \fIname\fP.
868 The reserved word \fBfunction\fP is optional.
869 If the \fBfunction\fP reserved word is supplied, the parentheses are optional.
870 The \fIbody\fP of the function is the compound command
872 (see \fBCompound Commands\fP above).
873 That command is usually a \fIlist\fP of commands between { and }, but
874 may be any command listed under \fBCompound Commands\fP above.
875 \fIcompound\-command\fP is executed whenever \fIname\fP is specified as the
876 name of a simple command.
877 Any redirections (see
880 below) specified when a function is defined are performed
881 when the function is executed.
882 The exit status of a function definition is zero unless a syntax error
883 occurs or a readonly function with the same name already exists.
884 When executed, the exit status of a function is the exit status of the
885 last command executed in the body. (See
890 In a non-interactive shell, or an interactive shell in which the
891 .B interactive_comments
894 builtin is enabled (see
896 .B "SHELL BUILTIN COMMANDS"
897 below), a word beginning with
899 causes that word and all remaining characters on that line to
900 be ignored. An interactive shell without the
901 .B interactive_comments
902 option enabled does not allow comments. The
903 .B interactive_comments
904 option is on by default in interactive shells.
906 \fIQuoting\fP is used to remove the special meaning of certain
907 characters or words to the shell. Quoting can be used to
908 disable special treatment for special characters, to prevent
909 reserved words from being recognized as such, and to prevent
912 Each of the \fImetacharacters\fP listed above under
915 has special meaning to the shell and must be quoted if it is to
918 When the command history expansion facilities are being used
923 \fIhistory expansion\fP character, usually \fB!\fP, must be quoted
924 to prevent history expansion.
926 There are three quoting mechanisms: the
927 .IR "escape character" ,
928 single quotes, and double quotes.
930 A non-quoted backslash (\fB\e\fP) is the
931 .IR "escape character" .
932 It preserves the literal value of the next character that follows,
933 with the exception of <newline>. If a \fB\e\fP<newline> pair
934 appears, and the backslash is not itself quoted, the \fB\e\fP<newline>
935 is treated as a line continuation (that is, it is removed from the
936 input stream and effectively ignored).
938 Enclosing characters in single quotes preserves the literal value
939 of each character within the quotes. A single quote may not occur
940 between single quotes, even when preceded by a backslash.
942 Enclosing characters in double quotes preserves the literal value
943 of all characters within the quotes, with the exception of
947 and, when history expansion is enabled,
953 retain their special meaning within double quotes. The backslash
954 retains its special meaning only when followed by one of the following
962 A double quote may be quoted within double quotes by preceding it with
964 If enabled, history expansion will be performed unless an
966 appearing in double quotes is escaped using a backslash.
967 The backslash preceding the
971 The special parameters
975 have special meaning when in double
981 Words of the form \fB$\fP\(aq\fIstring\fP\(aq are treated specially. The
982 word expands to \fIstring\fP, with backslash-escaped characters replaced
983 as specified by the ANSI C standard. Backslash escape sequences, if
984 present, are decoded as follows:
1019 the eight-bit character whose value is the octal value \fInnn\fP
1020 (one to three digits)
1023 the eight-bit character whose value is the hexadecimal value \fIHH\fP
1024 (one or two hex digits)
1027 a control-\fIx\fP character
1031 The expanded result is single-quoted, as if the dollar sign had
1034 A double-quoted string preceded by a dollar sign (\fB$\fP) will cause
1035 the string to be translated according to the current locale.
1036 If the current locale is \fBC\fP or \fBPOSIX\fP, the dollar sign
1038 If the string is translated and replaced, the replacement is
1043 is an entity that stores values.
1046 a number, or one of the special characters listed below under
1047 .BR "Special Parameters" .
1050 is a parameter denoted by a
1052 A variable has a \fIvalue\fP and zero or more \fIattributes\fP.
1053 Attributes are assigned using the
1055 builtin command (see
1059 .BR "SHELL BUILTIN COMMANDS" ).
1061 A parameter is set if it has been assigned a value. The null string is
1062 a valid value. Once a variable is set, it may be unset only by using
1065 builtin command (see
1067 .B SHELL BUILTIN COMMANDS
1072 may be assigned to by a statement of the form
1075 \fIname\fP=[\fIvalue\fP]
1080 is not given, the variable is assigned the null string. All
1082 undergo tilde expansion, parameter and variable expansion,
1083 command substitution, arithmetic expansion, and quote
1087 below). If the variable has its
1091 is evaluated as an arithmetic expression even if the $((...)) expansion is
1093 .B "Arithmetic Expansion"
1095 Word splitting is not performed, with the exception
1096 of \fB"$@"\fP as explained below under
1097 .BR "Special Parameters" .
1098 Pathname expansion is not performed.
1099 Assignment statements may also appear as arguments to the
1109 In the context where an assignment statement is assigning a value
1110 to a shell variable or array index, the += operator can be used to
1111 append to or add to the variable's previous value.
1112 When += is applied to a variable for which the integer attribute has been
1113 set, \fIvalue\fP is evaluated as an arithmetic expression and added to the
1114 variable's current value, which is also evaluated.
1115 When += is applied to an array variable using compound assignment (see
1118 variable's value is not unset (as it is when using =), and new values are
1119 appended to the array beginning at one greater than the array's maximum index.
1120 When applied to a string-valued variable, \fIvalue\fP is expanded and
1121 appended to the variable's value.
1122 .SS Positional Parameters
1125 .I positional parameter
1126 is a parameter denoted by one or more
1127 digits, other than the single digit 0. Positional parameters are
1128 assigned from the shell's arguments when it is invoked,
1129 and may be reassigned using the
1131 builtin command. Positional parameters may not be assigned to
1132 with assignment statements. The positional parameters are
1133 temporarily replaced when a shell function is executed (see
1138 When a positional parameter consisting of more than a single
1139 digit is expanded, it must be enclosed in braces (see
1143 .SS Special Parameters
1145 The shell treats several parameters specially. These parameters may
1146 only be referenced; assignment to them is not allowed.
1150 Expands to the positional parameters, starting from one. When the
1151 expansion occurs within double quotes, it expands to a single word
1152 with the value of each parameter separated by the first character
1156 special variable. That is, "\fB$*\fP" is equivalent
1157 to "\fB$1\fP\fIc\fP\fB$2\fP\fIc\fP\fB...\fP", where
1159 is the first character of the value of the
1165 is unset, the parameters are separated by spaces.
1169 is null, the parameters are joined without intervening separators.
1172 Expands to the positional parameters, starting from one. When the
1173 expansion occurs within double quotes, each parameter expands to a
1174 separate word. That is, "\fB$@\fP" is equivalent to
1175 "\fB$1\fP" "\fB$2\fP" ...
1176 If the double-quoted expansion occurs within a word, the expansion of
1177 the first parameter is joined with the beginning part of the original
1178 word, and the expansion of the last parameter is joined with the last
1179 part of the original word.
1180 When there are no positional parameters, "\fB$@\fP" and
1182 expand to nothing (i.e., they are removed).
1185 Expands to the number of positional parameters in decimal.
1188 Expands to the status of the most recently executed foreground
1192 Expands to the current option flags as specified upon invocation,
1195 builtin command, or those set by the shell itself
1201 Expands to the process ID of the shell. In a () subshell, it
1202 expands to the process ID of the current shell, not the
1206 Expands to the process ID of the most recently executed background
1207 (asynchronous) command.
1210 Expands to the name of the shell or shell script. This is set at
1211 shell initialization. If
1213 is invoked with a file of commands,
1215 is set to the name of that file. If
1221 is set to the first argument after the string to be
1222 executed, if one is present. Otherwise, it is set
1223 to the file name used to invoke
1225 as given by argument zero.
1228 At shell startup, set to the absolute pathname used to invoke the
1229 shell or shell script being executed as passed in the environment
1231 Subsequently, expands to the last argument to the previous command,
1233 Also set to the full pathname used to invoke each command executed
1234 and placed in the environment exported to that command.
1235 When checking mail, this parameter holds the name of the mail file
1236 currently being checked.
1240 The following variables are set by the shell:
1245 Expands to the full file name used to invoke this instance of
1249 An array variable whose values are the number of parameters in each
1250 frame of the current bash execution call stack.
1252 parameters to the current subroutine (shell function or script executed
1253 with \fB.\fP or \fBsource\fP) is at the top of the stack.
1254 When a subroutine is executed, the number of parameters passed is pushed onto
1256 The shell sets \fBBASH_ARGC\fP only when in extended debugging mode
1257 (see the description of the
1264 An array variable containing all of the parameters in the current bash
1265 execution call stack. The final parameter of the last subroutine call
1266 is at the top of the stack; the first parameter of the initial call is
1267 at the bottom. When a subroutine is executed, the parameters supplied
1268 are pushed onto \fBBASH_ARGV\fP.
1269 The shell sets \fBBASH_ARGV\fP only when in extended debugging mode
1270 (see the description of the
1277 The command currently being executed or about to be executed, unless the
1278 shell is executing a command as the result of a trap,
1279 in which case it is the command executing at the time of the trap.
1281 .B BASH_EXECUTION_STRING
1282 The command argument to the \fB\-c\fP invocation option.
1285 An array variable whose members are the line numbers in source files
1286 corresponding to each member of \fBFUNCNAME\fP.
1287 \fB${BASH_LINENO[\fP\fI$i\fP\fB]}\fP is the line number in the source
1288 file where \fB${FUNCNAME[\fP\fI$ifP\fB]}\fP was called.
1289 The corresponding source file name is \fB${BASH_SOURCE[\fP\fI$i\fP\fB]}\fB.
1290 Use \fBLINENO\fP to obtain the current line number.
1293 An array variable whose members are assigned by the \fB=~\fP binary
1294 operator to the \fB[[\fP conditional command.
1295 The element with index 0 is the portion of the string
1296 matching the entire regular expression.
1297 The element with index \fIn\fP is the portion of the
1298 string matching the \fIn\fPth parenthesized subexpression.
1299 This variable is read-only.
1302 An array variable whose members are the source filenames corresponding
1303 to the elements in the \fBFUNCNAME\fP array variable.
1306 Incremented by one each time a subshell or subshell environment is spawned.
1307 The initial value is 0.
1310 A readonly array variable whose members hold version information for
1313 The values assigned to the array members are as follows:
1318 .B BASH_VERSINFO[\fR0\fP]
1319 The major version number (the \fIrelease\fP).
1321 .B BASH_VERSINFO[\fR1\fP]
1322 The minor version number (the \fIversion\fP).
1324 .B BASH_VERSINFO[\fR2\fP]
1327 .B BASH_VERSINFO[\fR3\fP]
1330 .B BASH_VERSINFO[\fR4\fP]
1331 The release status (e.g., \fIbeta1\fP).
1333 .B BASH_VERSINFO[\fR5\fP]
1334 The value of \fBMACHTYPE\fP.
1339 Expands to a string describing the version of this instance of
1343 An index into \fB${COMP_WORDS}\fP of the word containing the current
1345 This variable is available only in shell functions invoked by the
1346 programmable completion facilities (see \fBProgrammable Completion\fP
1350 The current command line.
1351 This variable is available only in shell functions and external
1352 commands invoked by the
1353 programmable completion facilities (see \fBProgrammable Completion\fP
1357 The index of the current cursor position relative to the beginning of
1358 the current command.
1359 If the current cursor position is at the end of the current command,
1360 the value of this variable is equal to \fB${#COMP_LINE}\fP.
1361 This variable is available only in shell functions and external
1362 commands invoked by the
1363 programmable completion facilities (see \fBProgrammable Completion\fP
1367 The set of characters that the Readline library treats as word
1368 separators when performing word completion.
1372 is unset, it loses its special properties, even if it is
1376 An array variable (see \fBArrays\fP below) consisting of the individual
1377 words in the current command line.
1378 The words are split on shell metacharacters as the shell parser would
1380 This variable is available only in shell functions invoked by the
1381 programmable completion facilities (see \fBProgrammable Completion\fP
1385 An array variable (see
1387 below) containing the current contents of the directory stack.
1388 Directories appear in the stack in the order they are displayed by the
1391 Assigning to members of this array variable may be used to modify
1392 directories already in the stack, but the
1396 builtins must be used to add and remove directories.
1397 Assignment to this variable will not change the current directory.
1401 is unset, it loses its special properties, even if it is
1405 Expands to the effective user ID of the current user, initialized at
1406 shell startup. This variable is readonly.
1409 An array variable containing the names of all shell functions
1410 currently in the execution call stack.
1411 The element with index 0 is the name of any currently-executing
1413 The bottom-most element is "main".
1414 This variable exists only when a shell function is executing.
1418 have no effect and return an error status.
1422 is unset, it loses its special properties, even if it is
1426 An array variable containing the list of groups of which the current
1431 have no effect and return an error status.
1435 is unset, it loses its special properties, even if it is
1439 The history number, or index in the history list, of the current
1444 is unset, it loses its special properties, even if it is
1448 Automatically set to the name of the current host.
1451 Automatically set to a string that uniquely
1452 describes the type of machine on which
1455 The default is system-dependent.
1458 Each time this parameter is referenced, the shell substitutes
1459 a decimal number representing the current sequential line number
1460 (starting with 1) within a script or function. When not in a
1461 script or function, the value substituted is not guaranteed to
1466 is unset, it loses its special properties, even if it is
1470 Automatically set to a string that fully describes the system
1473 is executing, in the standard GNU \fIcpu-company-system\fP format.
1474 The default is system-dependent.
1477 The previous working directory as set by the
1482 The value of the last option argument processed by the
1484 builtin command (see
1486 .B SHELL BUILTIN COMMANDS
1490 The index of the next argument to be processed by the
1492 builtin command (see
1494 .B SHELL BUILTIN COMMANDS
1498 Automatically set to a string that
1499 describes the operating system on which
1502 The default is system-dependent.
1505 An array variable (see
1507 below) containing a list of exit status values from the processes
1508 in the most-recently-executed foreground pipeline (which may
1509 contain only a single command).
1512 The process ID of the shell's parent. This variable is readonly.
1515 The current working directory as set by the
1520 Each time this parameter is referenced, a random integer between
1522 generated. The sequence of random numbers may be initialized by assigning
1529 is unset, it loses its special properties, even if it is
1533 Set to the line of input read by the
1535 builtin command when no arguments are supplied.
1538 Each time this parameter is
1539 referenced, the number of seconds since shell invocation is returned. If a
1540 value is assigned to
1543 the value returned upon subsequent
1545 the number of seconds since the assignment plus the value assigned.
1549 is unset, it loses its special properties, even if it is
1553 A colon-separated list of enabled shell options. Each word in
1554 the list is a valid argument for the
1558 builtin command (see
1560 .B "SHELL BUILTIN COMMANDS"
1561 below). The options appearing in
1564 are those reported as
1567 If this variable is in the environment when
1569 starts up, each shell option in the list will be enabled before
1570 reading any startup files.
1571 This variable is read-only.
1574 Incremented by one each time an instance of
1579 Expands to the user ID of the current user, initialized at shell startup.
1580 This variable is readonly.
1583 The following variables are used by the shell. In some cases,
1585 assigns a default value to a variable; these cases are noted
1591 If this parameter is set when \fBbash\fP is executing a shell script,
1592 its value is interpreted as a filename containing commands to
1593 initialize the shell, as in
1598 is subjected to parameter expansion, command substitution, and arithmetic
1599 expansion before being interpreted as a file name.
1602 is not used to search for the resultant file name.
1605 The search path for the
1608 This is a colon-separated list of directories in which the shell looks
1609 for destination directories specified by the
1613 .if t \f(CW".:~:/usr"\fP.
1617 Used by the \fBselect\fP builtin command to determine the terminal width
1618 when printing selection lists. Automatically set upon receipt of a SIGWINCH.
1621 An array variable from which \fBbash\fP reads the possible completions
1622 generated by a shell function invoked by the programmable completion
1623 facility (see \fBProgrammable Completion\fP below).
1626 If \fBbash\fP finds this variable in the environment when the shell starts
1630 it assumes that the shell is running in an emacs shell buffer and disables
1634 The default editor for the
1639 A colon-separated list of suffixes to ignore when performing
1640 filename completion (see
1644 A filename whose suffix matches one of the entries in
1647 is excluded from the list of matched filenames.
1649 .if t \f(CW".o:~"\fP.
1653 A colon-separated list of patterns defining the set of filenames to
1654 be ignored by pathname expansion.
1655 If a filename matched by a pathname expansion pattern also matches one
1659 it is removed from the list of matches.
1662 A colon-separated list of values controlling how commands are saved on
1664 If the list of values includes
1666 lines which begin with a
1668 character are not saved in the history list.
1671 causes lines matching the previous history entry to not be saved.
1674 is shorthand for \fIignorespace\fP and \fIignoredups\fP.
1677 causes all previous lines matching the current line to be removed from
1678 the history list before that line is saved.
1679 Any value not in the above list is ignored.
1680 If \fBHISTCONTROL\fP is unset, or does not include a valid value,
1681 all lines read by the shell parser are saved on the history list,
1682 subject to the value of
1684 The second and subsequent lines of a multi-line compound command are
1685 not tested, and are added to the history regardless of the value of
1689 The name of the file in which command history is saved (see
1692 below). The default value is \fI~/.bash_history\fP. If unset, the
1693 command history is not saved when an interactive shell exits.
1696 The maximum number of lines contained in the history file. When this
1697 variable is assigned a value, the history file is truncated, if
1698 necessary, by removing the oldest entries,
1699 to contain no more than that number of lines. The default
1700 value is 500. The history file is also truncated to this size after
1701 writing it when an interactive shell exits.
1704 A colon-separated list of patterns used to decide which command lines
1705 should be saved on the history list. Each pattern is anchored at the
1706 beginning of the line and must match the complete line (no implicit
1707 `\fB*\fP' is appended). Each pattern is tested against the line
1708 after the checks specified by
1711 In addition to the normal shell pattern matching characters, `\fB&\fP'
1712 matches the previous history line. `\fB&\fP' may be escaped using a
1713 backslash; the backslash is removed before attempting a match.
1714 The second and subsequent lines of a multi-line compound command are
1715 not tested, and are added to the history regardless of the value of
1719 The number of commands to remember in the command history (see
1722 below). The default value is 500.
1725 If this variable is set and not null, its value is used as a format string
1726 for \fIstrftime\fP(3) to print the time stamp associated with each history
1727 entry displayed by the \fBhistory\fP builtin.
1728 If this variable is set, time stamps are written to the history file so
1729 they may be preserved across shell sessions.
1732 The home directory of the current user; the default argument for the
1733 \fBcd\fP builtin command.
1734 The value of this variable is also used when performing tilde expansion.
1737 Contains the name of a file in the same format as
1739 that should be read when the shell needs to complete a
1741 The list of possible hostname completions may be changed while the
1743 the next time hostname completion is attempted after the
1746 adds the contents of the new file to the existing list.
1750 is set, but has no value, \fBbash\fP attempts to read
1752 to obtain the list of possible hostname completions.
1756 is unset, the hostname list is cleared.
1760 .I Internal Field Separator
1762 for word splitting after expansion and to
1763 split lines into words with the
1765 builtin command. The default value is
1766 ``<space><tab><newline>''.
1770 action of an interactive shell on receipt of an
1773 character as the sole input. If set, the value is the number of
1777 characters which must be
1778 typed as the first characters on an input line before
1780 exits. If the variable exists but does not have a numeric value, or
1781 has no value, the default value is 10. If it does not exist,
1784 signifies the end of input to the shell.
1787 The filename for the
1789 startup file, overriding the default of
1797 Used to determine the locale category for any category not specifically
1798 selected with a variable starting with \fBLC_\fP.
1801 This variable overrides the value of \fBLANG\fP and any other
1802 \fBLC_\fP variable specifying a locale category.
1805 This variable determines the collation order used when sorting the
1806 results of pathname expansion, and determines the behavior of range
1807 expressions, equivalence classes, and collating sequences within
1808 pathname expansion and pattern matching.
1811 This variable determines the interpretation of characters and the
1812 behavior of character classes within pathname expansion and pattern
1816 This variable determines the locale used to translate double-quoted
1817 strings preceded by a \fB$\fP.
1820 This variable determines the locale category used for number formatting.
1823 Used by the \fBselect\fP builtin command to determine the column length
1824 for printing selection lists. Automatically set upon receipt of a SIGWINCH.
1827 If this parameter is set to a file name and the
1830 variable is not set,
1832 informs the user of the arrival of mail in the specified file.
1838 checks for mail. The default is 60 seconds. When it is time to check
1839 for mail, the shell does so before displaying the primary prompt.
1840 If this variable is unset, or set to a value that is not a number
1841 greater than or equal to zero, the shell disables mail checking.
1844 A colon-separated list of file names to be checked for mail.
1845 The message to be printed when mail arrives in a particular file
1846 may be specified by separating the file name from the message with a `?'.
1847 When used in the text of the message, \fB$_\fP expands to the name of
1848 the current mailfile.
1852 \fBMAILPATH\fP=\(aq/var/mail/bfox?"You have mail":~/shell\-mail?"$_ has mail!"\(aq
1855 supplies a default value for this variable, but the location of the user
1856 mail files that it uses is system dependent (e.g., /var/mail/\fB$USER\fP).
1860 If set to the value 1,
1862 displays error messages generated by the
1864 builtin command (see
1866 .B SHELL BUILTIN COMMANDS
1870 is initialized to 1 each time the shell is invoked or a shell
1874 The search path for commands. It
1875 is a colon-separated list of directories in which
1876 the shell looks for commands (see
1878 .B COMMAND EXECUTION
1880 A zero-length (null) directory name in the value of \fBPATH\fP indicates the
1882 A null directory name may appear as two adjacent colons, or as an initial
1884 The default path is system-dependent,
1885 and is set by the administrator who installs
1888 .if t \f(CW/usr/gnu/bin:/usr/local/bin:/usr/ucb:/bin:/usr/bin\fP.
1889 .if n ``/usr/gnu/bin:/usr/local/bin:/usr/ucb:/bin:/usr/bin''.
1892 If this variable is in the environment when \fBbash\fP starts, the shell
1893 enters \fIposix mode\fP before reading the startup files, as if the
1895 invocation option had been supplied. If it is set while the shell is
1896 running, \fBbash\fP enables \fIposix mode\fP, as if the command
1897 .if t \f(CWset -o posix\fP
1898 .if n \fIset -o posix\fP
1902 If set, the value is executed as a command prior to issuing each primary
1906 The value of this parameter is expanded (see
1909 below) and used as the primary prompt string. The default value is
1910 ``\fB\es\-\ev\e$ \fP''.
1913 The value of this parameter is expanded as with
1915 and used as the secondary prompt string. The default is
1919 The value of this parameter is used as the prompt for the
1927 The value of this parameter is expanded as with
1929 and the value is printed before each command
1931 displays during an execution trace. The first character of
1934 is replicated multiple times, as necessary, to indicate multiple
1935 levels of indirection. The default is ``\fB+ \fP''.
1938 The full pathname to the shell is kept in this environment variable.
1939 If it is not set when the shell starts,
1941 assigns to it the full pathname of the current user's login shell.
1944 The value of this parameter is used as a format string specifying
1945 how the timing information for pipelines prefixed with the
1947 reserved word should be displayed.
1948 The \fB%\fP character introduces an escape sequence that is
1949 expanded to a time value or other information.
1950 The escape sequences and their meanings are as follows; the
1951 braces denote optional portions.
1960 The elapsed time in seconds.
1963 The number of CPU seconds spent in user mode.
1966 The number of CPU seconds spent in system mode.
1969 The CPU percentage, computed as (%U + %S) / %R.
1973 The optional \fIp\fP is a digit specifying the \fIprecision\fP,
1974 the number of fractional digits after a decimal point.
1975 A value of 0 causes no decimal point or fraction to be output.
1976 At most three places after the decimal point may be specified;
1977 values of \fIp\fP greater than 3 are changed to 3.
1978 If \fIp\fP is not specified, the value 3 is used.
1980 The optional \fBl\fP specifies a longer format, including
1981 minutes, of the form \fIMM\fPm\fISS\fP.\fIFF\fPs.
1982 The value of \fIp\fP determines whether or not the fraction is
1985 If this variable is not set, \fBbash\fP acts as if it had the
1986 value \fB$\(aq\enreal\et%3lR\enuser\et%3lU\ensys\t%3lS\(aq\fP.
1987 If the value is null, no timing information is displayed.
1988 A trailing newline is added when the format string is displayed.
1991 If set to a value greater than zero, \fBTMOUT\fP is treated as the
1992 default timeout for the \fBread\fP builtin.
1993 The \fBselect\fP command terminates if input does not arrive
1994 after \fBTMOUT\fP seconds when input is coming from a terminal.
1995 In an interactive shell, the value is interpreted as the
1996 number of seconds to wait for input after issuing the primary prompt.
1998 terminates after waiting for that number of seconds if input does
2002 If set, \fBBash\fP uses its value as the name of a directory in which
2003 \fBBash\fP creates temporary files for the shell's use.
2006 This variable controls how the shell interacts with the user and
2007 job control. If this variable is set, single word simple
2008 commands without redirections are treated as candidates for resumption
2009 of an existing stopped job. There is no ambiguity allowed; if there is
2010 more than one job beginning with the string typed, the job most recently
2011 accessed is selected. The
2013 of a stopped job, in this context, is the command line used to
2017 the string supplied must match the name of a stopped job exactly;
2020 the string supplied needs to match a substring of the name of a
2023 value provides functionality analogous to the
2028 below). If set to any other value, the supplied string must
2029 be a prefix of a stopped job's name; this provides functionality
2030 analogous to the \fB%\fP\fIstring\fP job identifier.
2033 The two or three characters which control history expansion
2034 and tokenization (see
2036 .B HISTORY EXPANSION
2037 below). The first character is the \fIhistory expansion\fP character,
2038 the character which signals the start of a history
2039 expansion, normally `\fB!\fP'.
2040 The second character is the \fIquick substitution\fP
2041 character, which is used as shorthand for re-running the previous
2042 command entered, substituting one string for another in the command.
2043 The default is `\fB^\fP'.
2044 The optional third character is the character
2045 which indicates that the remainder of the line is a comment when found
2046 as the first character of a word, normally `\fB#\fP'. The history
2047 comment character causes history substitution to be skipped for the
2048 remaining words on the line. It does not necessarily cause the shell
2049 parser to treat the rest of the line as a comment.
2053 provides one-dimensional array variables. Any variable may be used as
2056 builtin will explicitly declare an array. There is no maximum
2057 limit on the size of an array, nor any requirement that members
2058 be indexed or assigned contiguously. Arrays are indexed using
2059 integers and are zero-based.
2061 An array is created automatically if any variable is assigned to using
2062 the syntax \fIname\fP[\fIsubscript\fP]=\fIvalue\fP. The
2064 is treated as an arithmetic expression that must evaluate to a number
2065 greater than or equal to zero. To explicitly declare an array, use
2066 .B declare \-a \fIname\fP
2069 .B SHELL BUILTIN COMMANDS
2071 .B declare \-a \fIname\fP[\fIsubscript\fP]
2072 is also accepted; the \fIsubscript\fP is ignored. Attributes may be
2073 specified for an array variable using the
2077 builtins. Each attribute applies to all members of an array.
2079 Arrays are assigned to using compound assignments of the form
2080 \fIname\fP=\fB(\fPvalue\fI1\fP ... value\fIn\fP\fB)\fP, where each
2081 \fIvalue\fP is of the form [\fIsubscript\fP]=\fIstring\fP. Only
2082 \fIstring\fP is required. If
2083 the optional brackets and subscript are supplied, that index is assigned to;
2084 otherwise the index of the element assigned is the last index assigned
2085 to by the statement plus one. Indexing starts at zero.
2086 This syntax is also accepted by the
2088 builtin. Individual array elements may be assigned to using the
2089 \fIname\fP[\fIsubscript\fP]=\fIvalue\fP syntax introduced above.
2091 Any element of an array may be referenced using
2092 ${\fIname\fP[\fIsubscript\fP]}. The braces are required to avoid
2093 conflicts with pathname expansion. If
2094 \fIsubscript\fP is \fB@\fP or \fB*\fP, the word expands to
2095 all members of \fIname\fP. These subscripts differ only when the
2096 word appears within double quotes. If the word is double-quoted,
2097 ${\fIname\fP[*]} expands to a single
2098 word with the value of each array member separated by the first
2102 special variable, and ${\fIname\fP[@]} expands each element of
2103 \fIname\fP to a separate word. When there are no array members,
2104 ${\fIname\fP[@]} expands to nothing.
2105 If the double-quoted expansion occurs within a word, the expansion of
2106 the first parameter is joined with the beginning part of the original
2107 word, and the expansion of the last parameter is joined with the last
2108 part of the original word.
2109 This is analogous to the expansion
2110 of the special parameters \fB*\fP and \fB@\fP (see
2111 .B Special Parameters
2112 above). ${#\fIname\fP[\fIsubscript\fP]} expands to the length of
2113 ${\fIname\fP[\fIsubscript\fP]}. If \fIsubscript\fP is \fB*\fP or
2114 \fB@\fP, the expansion is the number of elements in the array.
2115 Referencing an array variable without a subscript is equivalent to
2116 referencing element zero.
2120 builtin is used to destroy arrays. \fBunset\fP \fIname\fP[\fIsubscript\fP]
2121 destroys the array element at index \fIsubscript\fP.
2122 Care must be taken to avoid unwanted side effects caused by filename
2124 \fBunset\fP \fIname\fP, where \fIname\fP is an array, or
2125 \fBunset\fP \fIname\fP[\fIsubscript\fP], where
2126 \fIsubscript\fP is \fB*\fP or \fB@\fP, removes the entire array.
2133 builtins each accept a
2135 option to specify an array. The
2139 option to assign a list of words read from the standard input
2144 builtins display array values in a way that allows them to be
2145 reused as assignments.
2147 Expansion is performed on the command line after it has been split into
2148 words. There are seven kinds of expansion performed:
2149 .IR "brace expansion" ,
2150 .IR "tilde expansion" ,
2151 .IR "parameter and variable expansion" ,
2152 .IR "command substitution" ,
2153 .IR "arithmetic expansion" ,
2154 .IR "word splitting" ,
2156 .IR "pathname expansion" .
2158 The order of expansions is: brace expansion, tilde expansion,
2159 parameter, variable and arithmetic expansion and
2160 command substitution
2161 (done in a left-to-right fashion), word splitting, and pathname
2164 On systems that can support it, there is an additional expansion
2165 available: \fIprocess substitution\fP.
2167 Only brace expansion, word splitting, and pathname expansion
2168 can change the number of words of the expansion; other expansions
2169 expand a single word to a single word.
2170 The only exceptions to this are the expansions of
2171 "\fB$@\fP" and "\fB${\fP\fIname\fP\fB[@]}\fP"
2172 as explained above (see
2177 .I "Brace expansion"
2178 is a mechanism by which arbitrary strings
2179 may be generated. This mechanism is similar to
2180 \fIpathname expansion\fP, but the filenames generated
2181 need not exist. Patterns to be brace expanded take
2182 the form of an optional
2184 followed by either a series of comma-separated strings or
2185 a sequence expression between a pair of braces, followed by
2188 The preamble is prefixed to each string contained
2189 within the braces, and the postscript is then appended
2190 to each resulting string, expanding left to right.
2192 Brace expansions may be nested. The results of each expanded
2193 string are not sorted; left to right order is preserved.
2194 For example, a\fB{\fPd,c,b\fB}\fPe expands into `ade ace abe'.
2196 A sequence expression takes the form \fB{\fP\fIx\fP\fB..\fP\fIy\fP\fB}\fP,
2197 where \fIx\fP and \fIy\fP are either integers or single characters.
2198 When integers are supplied, the expression expands to each number between
2199 \fIx\fP and \fIy\fP, inclusive.
2200 When characters are supplied, the expression expands to each character
2201 lexicographically between \fIx\fP and \fIy\fP, inclusive. Note that
2202 both \fIx\fP and \fIy\fP must be of the same type.
2204 Brace expansion is performed before any other expansions,
2205 and any characters special to other expansions are preserved
2206 in the result. It is strictly textual.
2208 does not apply any syntactic interpretation to the context of the
2209 expansion or the text between the braces.
2211 A correctly-formed brace expansion must contain unquoted opening
2212 and closing braces, and at least one unquoted comma or a valid
2213 sequence expression.
2214 Any incorrectly formed brace expansion is left unchanged.
2215 A \fB{\fP or \fB,\fP may be quoted with a backslash to prevent its
2216 being considered part of a brace expression.
2217 To avoid conflicts with parameter expansion, the string \fB${\fP
2218 is not considered eligible for brace expansion.
2220 This construct is typically used as shorthand when the common
2221 prefix of the strings to be generated is longer than in the
2225 mkdir /usr/local/src/bash/{old,new,dist,bugs}
2229 chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}
2232 Brace expansion introduces a slight incompatibility with
2233 historical versions of
2236 does not treat opening or closing braces specially when they
2237 appear as part of a word, and preserves them in the output.
2239 removes braces from words as a consequence of brace
2240 expansion. For example, a word entered to
2243 appears identically in the output. The same word is
2248 If strict compatibility with
2254 option or disable brace expansion with the
2260 .B SHELL BUILTIN COMMANDS
2264 If a word begins with an unquoted tilde character (`\fB~\fP'), all of
2265 the characters preceding the first unquoted slash (or all characters,
2266 if there is no unquoted slash) are considered a \fItilde-prefix\fP.
2267 If none of the characters in the tilde-prefix are quoted, the
2268 characters in the tilde-prefix following the tilde are treated as a
2269 possible \fIlogin name\fP.
2270 If this login name is the null string, the tilde is replaced with the
2271 value of the shell parameter
2277 is unset, the home directory of the user executing the shell is
2278 substituted instead.
2279 Otherwise, the tilde-prefix is replaced with the home directory
2280 associated with the specified login name.
2282 If the tilde-prefix is a `~+', the value of the shell variable
2285 replaces the tilde-prefix.
2286 If the tilde-prefix is a `~\-', the value of the shell variable
2289 if it is set, is substituted.
2290 If the characters following the tilde in the tilde-prefix consist
2291 of a number \fIN\fP, optionally prefixed
2292 by a `+' or a `\-', the tilde-prefix is replaced with the corresponding
2293 element from the directory stack, as it would be displayed by the
2295 builtin invoked with the tilde-prefix as an argument.
2296 If the characters following the tilde in the tilde-prefix consist of a
2297 number without a leading `+' or `\-', `+' is assumed.
2299 If the login name is invalid, or the tilde expansion fails, the word
2302 Each variable assignment is checked for unquoted tilde-prefixes immediately
2307 In these cases, tilde expansion is also performed.
2308 Consequently, one may use file names with tildes in assignments to
2316 and the shell assigns the expanded value.
2317 .SS Parameter Expansion
2319 The `\fB$\fP' character introduces parameter expansion,
2320 command substitution, or arithmetic expansion. The parameter name
2321 or symbol to be expanded may be enclosed in braces, which
2322 are optional but serve to protect the variable to be expanded from
2323 characters immediately following it which could be
2324 interpreted as part of the name.
2326 When braces are used, the matching ending brace is the first `\fB}\fP'
2327 not escaped by a backslash or within a quoted string, and not within an
2328 embedded arithmetic expansion, command substitution, or parameter
2334 The value of \fIparameter\fP is substituted. The braces are required
2337 is a positional parameter with more than one digit,
2340 is followed by a character which is not to be
2341 interpreted as part of its name.
2344 If the first character of \fIparameter\fP is an exclamation point,
2345 a level of variable indirection is introduced.
2346 \fBBash\fP uses the value of the variable formed from the rest of
2347 \fIparameter\fP as the name of the variable; this variable is then
2348 expanded and that value is used in the rest of the substitution, rather
2349 than the value of \fIparameter\fP itself.
2350 This is known as \fIindirect expansion\fP.
2351 The exceptions to this are the expansions of ${!\fIprefix\fP*} and
2352 ${\fB!\fP\fIname\fP[\fI@\fP]} described below.
2353 The exclamation point must immediately follow the left brace in order to
2354 introduce indirection.
2356 In each of the cases below, \fIword\fP is subject to tilde expansion,
2357 parameter expansion, command substitution, and arithmetic expansion.
2358 When not performing substring expansion, \fBbash\fP tests for a parameter
2359 that is unset or null; omitting the colon results in a test only for a
2360 parameter that is unset.
2364 ${\fIparameter\fP\fB:\-\fP\fIword\fP}
2365 \fBUse Default Values\fP. If
2367 is unset or null, the expansion of
2369 is substituted. Otherwise, the value of
2373 ${\fIparameter\fP\fB:=\fP\fIword\fP}
2374 \fBAssign Default Values\fP.
2377 is unset or null, the expansion of
2383 is then substituted. Positional parameters and special parameters may
2384 not be assigned to in this way.
2386 ${\fIparameter\fP\fB:?\fP\fIword\fP}
2387 \fBDisplay Error if Null or Unset\fP.
2390 is null or unset, the expansion of \fIword\fP (or a message to that effect
2393 is not present) is written to the standard error and the shell, if it
2394 is not interactive, exits. Otherwise, the value of \fIparameter\fP is
2397 ${\fIparameter\fP\fB:+\fP\fIword\fP}
2398 \fBUse Alternate Value\fP.
2401 is null or unset, nothing is substituted, otherwise the expansion of
2405 ${\fIparameter\fP\fB:\fP\fIoffset\fP}
2408 ${\fIparameter\fP\fB:\fP\fIoffset\fP\fB:\fP\fIlength\fP}
2410 \fBSubstring Expansion.\fP
2411 Expands to up to \fIlength\fP characters of \fIparameter\fP
2412 starting at the character specified by \fIoffset\fP.
2413 If \fIlength\fP is omitted, expands to the substring of
2414 \fIparameter\fP starting at the character specified by \fIoffset\fP.
2415 \fIlength\fP and \fIoffset\fP are arithmetic expressions (see
2418 ARITHMETIC EVALUATION
2420 \fIlength\fP must evaluate to a number greater than or equal to zero.
2421 If \fIoffset\fP evaluates to a number less than zero, the value
2422 is used as an offset from the end of the value of \fIparameter\fP.
2423 If \fIparameter\fP is \fB@\fP, the result is \fIlength\fP positional
2424 parameters beginning at \fIoffset\fP.
2425 If \fIparameter\fP is an array name indexed by @ or *,
2426 the result is the \fIlength\fP
2427 members of the array beginning with ${\fIparameter\fP[\fIoffset\fP]}.
2428 A negative \fIoffset\fP is taken relative to one greater than the maximum
2429 index of the specified array.
2430 Note that a negative offset must be separated from the colon by at least
2431 one space to avoid being confused with the :- expansion.
2432 Substring indexing is zero-based unless the positional parameters
2433 are used, in which case the indexing starts at 1.
2435 ${\fB!\fP\fIprefix\fP\fB*\fP}
2438 ${\fB!\fP\fIprefix\fP\fB@\fP}
2440 Expands to the names of variables whose names begin with \fIprefix\fP,
2441 separated by the first character of the
2446 ${\fB!\fP\fIname\fP[\fI@\fP]}
2449 ${\fB!\fP\fIname\fP[\fI*\fP]}
2451 If \fIname\fP is an array variable, expands to the list of array indices
2452 (keys) assigned in \fIname\fP.
2453 If \fIname\fP is not an array, expands to 0 if \fIname\fP is set and null
2455 When \fI@\fP is used and the expansion appears within double quotes, each
2456 key expands to a separate word.
2458 ${\fB#\fP\fIparameter\fP}
2459 The length in characters of the value of \fIparameter\fP is substituted.
2466 the value substituted is the number of positional parameters.
2469 is an array name subscripted by
2473 the value substituted is the number of elements in the array.
2475 ${\fIparameter\fP\fB#\fP\fIword\fP}
2478 ${\fIparameter\fP\fB##\fP\fIword\fP}
2482 is expanded to produce a pattern just as in pathname
2483 expansion. If the pattern matches the beginning of
2486 then the result of the expansion is the expanded value of
2488 with the shortest matching pattern (the ``\fB#\fP'' case) or the
2489 longest matching pattern (the ``\fB##\fP'' case) deleted.
2496 the pattern removal operation is applied to each positional
2497 parameter in turn, and the expansion is the resultant list.
2500 is an array variable subscripted with
2504 the pattern removal operation is applied to each member of the
2505 array in turn, and the expansion is the resultant list.
2507 ${\fIparameter\fP\fB%\fP\fIword\fP}
2510 ${\fIparameter\fP\fB%%\fP\fIword\fP}
2512 The \fIword\fP is expanded to produce a pattern just as in
2514 If the pattern matches a trailing portion of the expanded value of
2516 then the result of the expansion is the expanded value of
2518 with the shortest matching pattern (the ``\fB%\fP'' case) or the
2519 longest matching pattern (the ``\fB%%\fP'' case) deleted.
2526 the pattern removal operation is applied to each positional
2527 parameter in turn, and the expansion is the resultant list.
2530 is an array variable subscripted with
2534 the pattern removal operation is applied to each member of the
2535 array in turn, and the expansion is the resultant list.
2537 ${\fIparameter\fP\fB/\fP\fIpattern\fP\fB/\fP\fIstring\fP}
2538 The \fIpattern\fP is expanded to produce a pattern just as in
2540 \fIParameter\fP is expanded and the longest match of \fIpattern\fP
2541 against its value is replaced with \fIstring\fP.
2542 If \Ipattern\fP begins with \fB/\fP, all matches of \fIpattern\fP are
2543 replaced with \fIstring\fP. Normally only the first match is replaced.
2544 If \fIpattern\fP begins with \fB#\fP, it must match at the beginning
2545 of the expanded value of \fIparameter\fP.
2546 If \fIpattern\fP begins with \fB%\fP, it must match at the end
2547 of the expanded value of \fIparameter\fP.
2548 If \fIstring\fP is null, matches of \fIpattern\fP are deleted
2549 and the \fB/\fP following \fIpattern\fP may be omitted.
2556 the substitution operation is applied to each positional
2557 parameter in turn, and the expansion is the resultant list.
2560 is an array variable subscripted with
2564 the substitution operation is applied to each member of the
2565 array in turn, and the expansion is the resultant list.
2566 .SS Command Substitution
2568 \fICommand substitution\fP allows the output of a command to replace
2569 the command name. There are two forms:
2573 \fB$(\fP\fIcommand\fP\|\fB)\fP
2577 \fB`\fP\fIcommand\fP\fB`\fP
2581 performs the expansion by executing \fIcommand\fP and
2582 replacing the command substitution with the standard output of the
2583 command, with any trailing newlines deleted.
2584 Embedded newlines are not deleted, but they may be removed during
2586 The command substitution \fB$(cat \fIfile\fP)\fR can be replaced by
2587 the equivalent but faster \fB$(< \fIfile\fP)\fR.
2589 When the old-style backquote form of substitution is used,
2590 backslash retains its literal meaning except when followed by
2595 The first backquote not preceded by a backslash terminates the
2596 command substitution.
2597 When using the $(\^\fIcommand\fP\|) form, all characters between the
2598 parentheses make up the command; none are treated specially.
2600 Command substitutions may be nested. To nest when using the backquoted form,
2601 escape the inner backquotes with backslashes.
2603 If the substitution appears within double quotes, word splitting and
2604 pathname expansion are not performed on the results.
2605 .SS Arithmetic Expansion
2607 Arithmetic expansion allows the evaluation of an arithmetic expression
2608 and the substitution of the result. The format for arithmetic expansion is:
2611 \fB$((\fP\fIexpression\fP\fB))\fP
2616 is treated as if it were within double quotes, but a double quote
2617 inside the parentheses is not treated specially.
2618 All tokens in the expression undergo parameter expansion, string
2619 expansion, command substitution, and quote removal.
2620 Arithmetic expansions may be nested.
2622 The evaluation is performed according to the rules listed below under
2624 .BR "ARITHMETIC EVALUATION" .
2629 prints a message indicating failure and no substitution occurs.
2630 .SS Process Substitution
2632 \fIProcess substitution\fP is supported on systems that support named
2633 pipes (\fIFIFOs\fP) or the \fB/dev/fd\fP method of naming open files.
2634 It takes the form of
2635 \fB<(\fP\fIlist\^\fP\fB)\fP
2637 \fB>(\fP\fIlist\^\fP\fB)\fP.
2638 The process \fIlist\fP is run with its input or output connected to a
2639 \fIFIFO\fP or some file in \fB/dev/fd\fP. The name of this file is
2640 passed as an argument to the current command as the result of the
2641 expansion. If the \fB>(\fP\fIlist\^\fP\fB)\fP form is used, writing to
2642 the file will provide input for \fIlist\fP. If the
2643 \fB<(\fP\fIlist\^\fP\fB)\fP form is used, the file passed as an
2644 argument should be read to obtain the output of \fIlist\fP.
2646 When available, process substitution is performed
2647 simultaneously with parameter and variable expansion,
2648 command substitution,
2649 and arithmetic expansion.
2652 The shell scans the results of
2653 parameter expansion,
2654 command substitution,
2656 arithmetic expansion
2657 that did not occur within double quotes for
2658 .IR "word splitting" .
2660 The shell treats each character of
2663 as a delimiter, and splits the results of the other
2664 expansions into words on these characters. If
2669 .BR <space><tab><newline> ,
2674 characters serves to delimit words. If
2677 has a value other than the default, then sequences of
2678 the whitespace characters
2682 are ignored at the beginning and end of the
2683 word, as long as the whitespace character is in the
2690 whitespace character).
2697 whitespace, along with any adjacent
2700 whitespace characters, delimits a field.
2704 whitespace characters is also treated as a delimiter.
2708 is null, no word splitting occurs.
2710 Explicit null arguments (\^\f3"\^"\fP or \^\f3\(aq\^\(aq\fP\^) are retained.
2711 Unquoted implicit null arguments, resulting from the expansion of
2712 parameters that have no values, are removed.
2713 If a parameter with no value is expanded within double quotes, a
2714 null argument results and is retained.
2716 Note that if no expansion occurs, no splitting
2718 .SS Pathname Expansion
2720 After word splitting,
2723 option has been set,
2725 scans each word for the characters
2730 If one of these characters appears, then the word is
2733 and replaced with an alphabetically sorted list of
2734 file names matching the pattern.
2735 If no matching file names are found,
2736 and the shell option
2738 is disabled, the word is left unchanged.
2741 option is set, and no matches are found,
2742 the word is removed.
2745 shell option is set, and no matches are found, an error message
2746 is printed and the command is not executed.
2749 is enabled, the match is performed without regard to the case
2750 of alphabetic characters.
2751 When a pattern is used for pathname expansion,
2754 at the start of a name or immediately following a slash
2755 must be matched explicitly, unless the shell option
2758 When matching a pathname, the slash character must always be
2762 character is not treated specially.
2763 See the description of
2767 .B SHELL BUILTIN COMMANDS
2768 for a description of the
2779 shell variable may be used to restrict the set of file names matching a
2784 is set, each matching file name that also matches one of the patterns in
2787 is removed from the list of matches.
2792 are always ignored when
2795 is set and not null. However, setting
2798 to a non-null value has the effect of enabling the
2800 shell option, so all other file names beginning with a
2803 To get the old behavior of ignoring file names beginning with a
2807 one of the patterns in
2812 option is disabled when
2817 \fBPattern Matching\fP
2819 Any character that appears in a pattern, other than the special pattern
2820 characters described below, matches itself. The NUL character may not
2821 occur in a pattern. A backslash escapes the following character; the
2822 escaping backslash is discarded when matching.
2823 The special pattern characters must be quoted if
2824 they are to be matched literally.
2826 The special pattern characters have the following meanings:
2831 Matches any string, including the null string.
2834 Matches any single character.
2837 Matches any one of the enclosed characters. A pair of characters
2838 separated by a hyphen denotes a
2839 \fIrange expression\fP;
2840 any character that sorts between those two characters, inclusive,
2841 using the current locale's collating sequence and character set,
2842 is matched. If the first character following the
2848 then any character not enclosed is matched.
2849 The sorting order of characters in range expressions is determined by
2850 the current locale and the value of the \fBLC_COLLATE\fP shell variable,
2854 may be matched by including it as the first or last character
2858 may be matched by including it as the first character
2867 \fIcharacter classes\fP can be specified using the syntax
2868 \fB[:\fP\fIclass\fP\fB:]\fP, where \fIclass\fP is one of the
2869 following classes defined in the POSIX standard:
2873 .if n alnum alpha ascii blank cntrl digit graph lower print punct space upper word xdigit
2874 .if t alnum alpha ascii blank cntrl digit graph lower print punct space upper word xdigit
2876 A character class matches any character belonging to that class.
2877 The \fBword\fP character class matches letters, digits, and the character _.
2885 an \fIequivalence class\fP can be specified using the syntax
2886 \fB[=\fP\fIc\fP\fB=]\fP, which matches all characters with the
2887 same collation weight (as defined by the current locale) as
2888 the character \fIc\fP.
2896 the syntax \fB[.\fP\fIsymbol\fP\fB.]\fP matches the collating symbol
2901 If the \fBextglob\fP shell option is enabled using the \fBshopt\fP
2902 builtin, several extended pattern matching operators are recognized.
2903 In the following description, a \fIpattern-list\fP is a list of one
2904 or more patterns separated by a \fB|\fP.
2905 Composite patterns may be formed using one or more of the following
2911 \fB?(\fP\^\fIpattern-list\^\fP\fB)\fP
2912 Matches zero or one occurrence of the given patterns
2914 \fB*(\fP\^\fIpattern-list\^\fP\fB)\fP
2915 Matches zero or more occurrences of the given patterns
2917 \fB+(\fP\^\fIpattern-list\^\fP\fB)\fP
2918 Matches one or more occurrences of the given patterns
2920 \fB@(\fP\^\fIpattern-list\^\fP\fB)\fP
2921 Matches one of the given patterns
2923 \fB!(\fP\^\fIpattern-list\^\fP\fB)\fP
2924 Matches anything except one of the given patterns
2929 After the preceding expansions, all unquoted occurrences of the
2933 and \^\f3"\fP\^ that did not result from one of the above
2934 expansions are removed.
2936 Before a command is executed, its input and output
2939 using a special notation interpreted by the shell.
2940 Redirection may also be used to open and close files for the
2941 current shell execution environment. The following redirection
2942 operators may precede or appear anywhere within a
2946 Redirections are processed in the order they appear, from
2949 In the following descriptions, if the file descriptor number is
2950 omitted, and the first character of the redirection operator is
2952 the redirection refers to the standard input (file descriptor
2953 0). If the first character of the redirection operator is
2955 the redirection refers to the standard output (file descriptor
2958 The word following the redirection operator in the following
2959 descriptions, unless otherwise noted, is subjected to brace expansion,
2960 tilde expansion, parameter expansion, command substitution, arithmetic
2961 expansion, quote removal, pathname expansion, and word splitting.
2962 If it expands to more than one word,
2966 Note that the order of redirections is significant. For example,
2970 ls \fB>\fP dirlist 2\fB>&\fP1
2973 directs both standard output and standard error to the file
2978 ls 2\fB>&\fP1 \fB>\fP dirlist
2981 directs only the standard output to file
2983 because the standard error was duplicated as standard output
2984 before the standard output was redirected to
2987 \fBBash\fP handles several filenames specially when they are used in
2988 redirections, as described in the following table:
2994 If \fIfd\fP is a valid integer, file descriptor \fIfd\fP is duplicated.
2997 File descriptor 0 is duplicated.
3000 File descriptor 1 is duplicated.
3003 File descriptor 2 is duplicated.
3005 .B /dev/tcp/\fIhost\fP/\fIport\fP
3006 If \fIhost\fP is a valid hostname or Internet address, and \fIport\fP
3007 is an integer port number or service name, \fBbash\fP attempts to open
3008 a TCP connection to the corresponding socket.
3010 .B /dev/udp/\fIhost\fP/\fIport\fP
3011 If \fIhost\fP is a valid hostname or Internet address, and \fIport\fP
3012 is an integer port number or service name, \fBbash\fP attempts to open
3013 a UDP connection to the corresponding socket.
3017 A failure to open or create a file causes the redirection to fail.
3019 Redirections using file descriptors greater than 9 should be used with
3020 care, as they may conflict with file descriptors the shell uses
3022 .SS Redirecting Input
3024 Redirection of input causes the file whose name results from
3027 to be opened for reading on file descriptor
3029 or the standard input (file descriptor 0) if
3033 The general format for redirecting input is:
3036 [\fIn\fP]\fB<\fP\fIword\fP
3038 .SS Redirecting Output
3040 Redirection of output causes the file whose name results from
3043 to be opened for writing on file descriptor
3045 or the standard output (file descriptor 1) if
3047 is not specified. If the file does not exist it is created;
3048 if it does exist it is truncated to zero size.
3050 The general format for redirecting output is:
3053 [\fIn\fP]\fB>\fP\fIword\fP
3056 If the redirection operator is
3062 builtin has been enabled, the redirection will fail if the file
3063 whose name results from the expansion of \fIword\fP exists and is
3065 If the redirection operator is
3067 or the redirection operator is
3073 builtin command is not enabled, the redirection is attempted even
3074 if the file named by \fIword\fP exists.
3075 .SS Appending Redirected Output
3077 Redirection of output in this fashion
3078 causes the file whose name results from
3081 to be opened for appending on file descriptor
3083 or the standard output (file descriptor 1) if
3085 is not specified. If the file does not exist it is created.
3087 The general format for appending output is:
3090 [\fIn\fP]\fB>>\fP\fIword\fP
3093 .SS Redirecting Standard Output and Standard Error
3097 standard output (file descriptor 1) and
3098 the standard error output (file descriptor 2)
3099 to be redirected to the file whose name is the
3102 with this construct.
3104 There are two formats for redirecting standard output and
3115 Of the two forms, the first is preferred.
3116 This is semantically equivalent to
3119 \fB>\fP\fIword\fP 2\fB>&\fP1
3123 This type of redirection instructs the shell to read input from the
3124 current source until a line containing only
3126 (with no trailing blanks)
3128 the lines read up to that point are then used as the standard
3129 input for a command.
3131 The format of here-documents is:
3135 \fB<<\fP[\fB\-\fP]\fIword\fP
3141 No parameter expansion, command substitution, arithmetic expansion,
3142 or pathname expansion is performed on
3144 If any characters in
3148 is the result of quote removal on
3150 and the lines in the here-document are not expanded.
3151 If \fIword\fP is unquoted,
3152 all lines of the here-document are subjected to parameter expansion,
3153 command substitution, and arithmetic expansion. In the latter
3154 case, the character sequence
3158 must be used to quote the characters
3164 If the redirection operator is
3166 then all leading tab characters are stripped from input lines and the
3170 here-documents within shell scripts to be indented in a
3173 A variant of here documents, the format is:
3181 The \fIword\fP is expanded and supplied to the command on its standard
3183 .SS "Duplicating File Descriptors"
3185 The redirection operator
3188 [\fIn\fP]\fB<&\fP\fIword\fP
3191 is used to duplicate input file descriptors.
3194 expands to one or more digits, the file descriptor denoted by
3196 is made to be a copy of that file descriptor.
3199 do not specify a file descriptor open for input, a redirection error occurs.
3208 is not specified, the standard input (file descriptor 0) is used.
3213 [\fIn\fP]\fB>&\fP\fIword\fP
3216 is used similarly to duplicate output file descriptors. If
3218 is not specified, the standard output (file descriptor 1) is used.
3221 do not specify a file descriptor open for output, a redirection error occurs.
3222 As a special case, if \fIn\fP is omitted, and \fIword\fP does not
3223 expand to one or more digits, the standard output and standard
3224 error are redirected as described previously.
3225 .SS "Moving File Descriptors"
3227 The redirection operator
3230 [\fIn\fP]\fB<&\fP\fIdigit\fP\fB\-\fP
3233 moves the file descriptor \fIdigit\fP to file descriptor
3235 or the standard input (file descriptor 0) if \fIn\fP is not specified.
3236 \fIdigit\fP is closed after being duplicated to \fIn\fP.
3238 Similarly, the redirection operator
3241 [\fIn\fP]\fB>&\fP\fIdigit\fP\fB\-\fP
3244 moves the file descriptor \fIdigit\fP to file descriptor
3246 or the standard output (file descriptor 1) if \fIn\fP is not specified.
3247 .SS "Opening File Descriptors for Reading and Writing"
3249 The redirection operator
3252 [\fIn\fP]\fB<>\fP\fIword\fP
3255 causes the file whose name is the expansion of
3257 to be opened for both reading and writing on file descriptor
3259 or on file descriptor 0 if
3261 is not specified. If the file does not exist, it is created.
3263 \fIAliases\fP allow a string to be substituted for a word when it is used
3264 as the first word of a simple command.
3265 The shell maintains a list of aliases that may be set and unset with the
3269 builtin commands (see
3271 .B SHELL BUILTIN COMMANDS
3273 The first word of each simple command, if unquoted,
3274 is checked to see if it has an
3275 alias. If so, that word is replaced by the text of the alias.
3276 The characters \fB/\fP, \fB$\fP, \fB`\fP, and \fB=\fP and
3277 any of the shell \fImetacharacters\fP or quoting characters
3278 listed above may not appear in an alias name.
3279 The replacement text may contain any valid shell input,
3280 including shell metacharacters.
3281 The first word of the replacement text is tested
3282 for aliases, but a word that is identical to an alias being expanded
3283 is not expanded a second time.
3284 This means that one may alias
3290 does not try to recursively expand the replacement text.
3291 If the last character of the alias value is a
3293 then the next command
3294 word following the alias is also checked for alias expansion.
3296 Aliases are created and listed with the
3298 command, and removed with the
3302 There is no mechanism for using arguments in the replacement text.
3303 If arguments are needed, a shell function should be used (see
3308 Aliases are not expanded when the shell is not interactive, unless
3311 shell option is set using
3313 (see the description of
3317 \fBSHELL BUILTIN COMMANDS\fP
3320 The rules concerning the definition and use of aliases are
3323 always reads at least one complete line
3324 of input before executing any
3325 of the commands on that line. Aliases are expanded when a
3326 command is read, not when it is executed. Therefore, an
3327 alias definition appearing on the same line as another
3328 command does not take effect until the next line of input is read.
3329 The commands following the alias definition
3330 on that line are not affected by the new alias.
3331 This behavior is also an issue when functions are executed.
3332 Aliases are expanded when a function definition is read,
3333 not when the function is executed, because a function definition
3334 is itself a compound command. As a consequence, aliases
3335 defined in a function are not available until after that
3336 function is executed. To be safe, always put
3337 alias definitions on a separate line, and do not use
3339 in compound commands.
3341 For almost every purpose, aliases are superseded by
3344 A shell function, defined as described above under
3346 .BR "SHELL GRAMMAR" ,
3347 stores a series of commands for later execution.
3348 When the name of a shell function is used as a simple command name,
3349 the list of commands associated with that function name is executed.
3350 Functions are executed in the context of the
3351 current shell; no new process is created to interpret
3352 them (contrast this with the execution of a shell script).
3353 When a function is executed, the arguments to the
3354 function become the positional parameters
3355 during its execution.
3356 The special parameter
3358 is updated to reflect the change. Special parameter 0
3360 The first element of the
3363 variable is set to the name of the function while the function
3365 All other aspects of the shell execution
3366 environment are identical between a function and its caller
3367 with the exception that the
3372 traps (see the description of the
3376 .B SHELL BUILTIN COMMANDS
3377 below) are not inherited unless the function has been given the
3378 \fBtrace\fP attribute (see the description of the
3381 builtin below) or the
3382 \fB\-o functrace\fP shell option has been enabled with
3383 the \fBset\fP builtin
3384 (in which case all functions inherit the \fBDEBUG\fP and \fBRETURN\fP traps).
3386 Variables local to the function may be declared with the
3388 builtin command. Ordinarily, variables and their values
3389 are shared between the function and its caller.
3391 If the builtin command
3393 is executed in a function, the function completes and
3394 execution resumes with the next command after the function
3396 Any command associated with the \fBRETURN\fP trap is executed
3397 before execution resumes.
3398 When a function completes, the values of the
3399 positional parameters and the special parameter
3401 are restored to the values they had prior to the function's
3404 Function names and definitions may be listed with the
3410 builtin commands. The
3416 will list the function names only
3417 (and optionally the source file and line number, if the \fBextdebug\fP
3418 shell option is enabled).
3419 Functions may be exported so that subshells
3420 automatically have them defined with the
3425 A function definition may be deleted using the \fB\-f\fP option to
3429 Note that shell functions and variables with the same name may result
3430 in multiple identically-named entries in the environment passed to the
3432 Care should be taken in cases where this may cause a problem.
3434 Functions may be recursive. No limit is imposed on the number
3436 .SH "ARITHMETIC EVALUATION"
3437 The shell allows arithmetic expressions to be evaluated, under
3438 certain circumstances (see the \fBlet\fP and \fBdeclare\fP builtin
3439 commands and \fBArithmetic Expansion\fP).
3440 Evaluation is done in fixed-width integers with no check for overflow,
3441 though division by 0 is trapped and flagged as an error.
3442 The operators and their precedence, associativity, and values
3443 are the same as in the C language.
3444 The following list of operators is grouped into levels of
3445 equal-precedence operators.
3446 The levels are listed in order of decreasing precedence.
3450 .B \fIid\fP++ \fIid\fP\-\-
3451 variable post-increment and post-decrement
3453 .B ++\fIid\fP \-\-\fIid\fP
3454 variable pre-increment and pre-decrement
3457 unary minus and plus
3460 logical and bitwise negation
3466 multiplication, division, remainder
3469 addition, subtraction
3472 left and right bitwise shifts
3478 equality and inequality
3484 bitwise exclusive OR
3495 .B \fIexpr\fP?\fIexpr\fP:\fIexpr\fP
3496 conditional operator
3498 .B = *= /= %= += \-= <<= >>= &= ^= |=
3501 .B \fIexpr1\fP , \fIexpr2\fP
3505 Shell variables are allowed as operands; parameter expansion is
3506 performed before the expression is evaluated.
3507 Within an expression, shell variables may also be referenced by name
3508 without using the parameter expansion syntax.
3509 A shell variable that is null or unset evaluates to 0 when referenced
3510 by name without using the parameter expansion syntax.
3511 The value of a variable is evaluated as an arithmetic expression
3512 when it is referenced, or when a variable which has been given the
3513 \fIinteger\fP attribute using \fBdeclare -i\fP is assigned a value.
3514 A null value evaluates to 0.
3515 A shell variable need not have its integer attribute
3516 turned on to be used in an expression.
3518 Constants with a leading 0 are interpreted as octal numbers.
3519 A leading 0x or 0X denotes hexadecimal.
3520 Otherwise, numbers take the form [\fIbase#\fP]n, where \fIbase\fP
3521 is a decimal number between 2 and 64 representing the arithmetic
3522 base, and \fIn\fP is a number in that base.
3523 If \fIbase#\fP is omitted, then base 10 is used.
3524 The digits greater than 9 are represented by the lowercase letters,
3525 the uppercase letters, @, and _, in that order.
3526 If \fIbase\fP is less than or equal to 36, lowercase and uppercase
3527 letters may be used interchangeably to represent numbers between 10
3530 Operators are evaluated in order of precedence. Sub-expressions in
3531 parentheses are evaluated first and may override the precedence
3533 .SH "CONDITIONAL EXPRESSIONS"
3534 Conditional expressions are used by the \fB[[\fP compound command and
3535 the \fBtest\fP and \fB[\fP builtin commands to test file attributes
3536 and perform string and arithmetic comparisons.
3537 Expressions are formed from the following unary or binary primaries.
3538 If any \fIfile\fP argument to one of the primaries is of the form
3539 \fI/dev/fd/n\fP, then file descriptor \fIn\fP is checked.
3540 If the \fIfile\fP argument to one of the primaries is one of
3541 \fI/dev/stdin\fP, \fI/dev/stdout\fP, or \fI/dev/stderr\fP, file
3542 descriptor 0, 1, or 2, respectively, is checked.
3544 Unless otherwise specified, primaries that operate on files follow symbolic
3545 links and operate on the target of the link, rather than the link itself.
3550 True if \fIfile\fP exists.
3553 True if \fIfile\fP exists and is a block special file.
3556 True if \fIfile\fP exists and is a character special file.
3559 True if \fIfile\fP exists and is a directory.
3562 True if \fIfile\fP exists.
3565 True if \fIfile\fP exists and is a regular file.
3568 True if \fIfile\fP exists and is set-group-id.
3571 True if \fIfile\fP exists and is a symbolic link.
3574 True if \fIfile\fP exists and its ``sticky'' bit is set.
3577 True if \fIfile\fP exists and is a named pipe (FIFO).
3580 True if \fIfile\fP exists and is readable.
3583 True if \fIfile\fP exists and has a size greater than zero.
3586 True if file descriptor
3588 is open and refers to a terminal.
3591 True if \fIfile\fP exists and its set-user-id bit is set.
3594 True if \fIfile\fP exists and is writable.
3597 True if \fIfile\fP exists and is executable.
3600 True if \fIfile\fP exists and is owned by the effective user id.
3603 True if \fIfile\fP exists and is owned by the effective group id.
3606 True if \fIfile\fP exists and is a symbolic link.
3609 True if \fIfile\fP exists and is a socket.
3612 True if \fIfile\fP exists and has been modified since it was last read.
3614 \fIfile1\fP \-\fBnt\fP \fIfile2\fP
3615 True if \fIfile1\fP is newer (according to modification date) than \fIfile2\fP,
3616 or if \fIfile1\fP exists and \fPfile2\fP does not.
3618 \fIfile1\fP \-\fBot\fP \fIfile2\fP
3619 True if \fIfile1\fP is older than \fIfile2\fP, or if \fIfile2\fP exists
3620 and \fIfile1\fP does not.
3622 \fIfile1\fP \fB\-ef\fP \fIfile2\fP
3623 True if \fIfile1\fP and \fIfile2\fP refer to the same device and
3626 .B \-o \fIoptname\fP
3627 True if shell option
3630 See the list of options under the description of the
3637 True if the length of \fIstring\fP is zero.
3644 True if the length of
3648 \fIstring1\fP \fB==\fP \fIstring2\fP
3649 True if the strings are equal. \fB=\fP may be used in place of
3650 \fB==\fP for strict POSIX compliance.
3652 \fIstring1\fP \fB!=\fP \fIstring2\fP
3653 True if the strings are not equal.
3655 \fIstring1\fP \fB<\fP \fIstring2\fP
3656 True if \fIstring1\fP sorts before \fIstring2\fP lexicographically
3657 in the current locale.
3659 \fIstring1\fP \fB>\fP \fIstring2\fP
3660 True if \fIstring1\fP sorts after \fIstring2\fP lexicographically
3661 in the current locale.
3663 .I \fIarg1\fP \fBOP\fP \fIarg2\fP
3674 These arithmetic binary operators return true if \fIarg1\fP
3675 is equal to, not equal to, less than, less than or equal to,
3676 greater than, or greater than or equal to \fIarg2\fP, respectively.
3680 may be positive or negative integers.
3682 .SH "SIMPLE COMMAND EXPANSION"
3683 When a simple command is executed, the shell performs the following
3684 expansions, assignments, and redirections, from left to right.
3686 The words that the parser has marked as variable assignments (those
3687 preceding the command name) and redirections are saved for later
3690 The words that are not variable assignments or redirections are
3691 expanded. If any words remain after expansion, the first word
3692 is taken to be the name of the command and the remaining words are
3695 Redirections are performed as described above under
3699 The text after the \fB=\fP in each variable assignment undergoes tilde
3700 expansion, parameter expansion, command substitution, arithmetic expansion,
3701 and quote removal before being assigned to the variable.
3703 If no command name results, the variable assignments affect the current
3704 shell environment. Otherwise, the variables are added to the environment
3705 of the executed command and do not affect the current shell environment.
3706 If any of the assignments attempts to assign a value to a readonly variable,
3707 an error occurs, and the command exits with a non-zero status.
3709 If no command name results, redirections are performed, but do not
3710 affect the current shell environment. A redirection error causes the
3711 command to exit with a non-zero status.
3713 If there is a command name left after expansion, execution proceeds as
3714 described below. Otherwise, the command exits. If one of the expansions
3715 contained a command substitution, the exit status of the command is
3716 the exit status of the last command substitution performed. If there
3717 were no command substitutions, the command exits with a status of zero.
3718 .SH "COMMAND EXECUTION"
3719 After a command has been split into words, if it results in a
3720 simple command and an optional list of arguments, the following
3723 If the command name contains no slashes, the shell attempts to
3724 locate it. If there exists a shell function by that name, that
3725 function is invoked as described above in
3728 If the name does not match a function, the shell searches for
3729 it in the list of shell builtins. If a match is found, that
3732 If the name is neither a shell function nor a builtin,
3733 and contains no slashes,
3735 searches each element of the
3738 for a directory containing an executable file by that name.
3740 uses a hash table to remember the full pathnames of executable
3745 .B "SHELL BUILTIN COMMANDS"
3747 A full search of the directories in
3750 is performed only if the command is not found in the hash table.
3751 If the search is unsuccessful, the shell prints an error
3752 message and returns an exit status of 127.
3754 If the search is successful, or if the command name contains
3755 one or more slashes, the shell executes the named program in a
3756 separate execution environment.
3757 Argument 0 is set to the name given, and the remaining arguments
3758 to the command are set to the arguments given, if any.
3760 If this execution fails because the file is not in executable
3761 format, and the file is not a directory, it is assumed to be
3762 a \fIshell script\fP, a file
3763 containing shell commands. A subshell is spawned to execute
3764 it. This subshell reinitializes itself, so
3765 that the effect is as if a new shell had been invoked
3766 to handle the script, with the exception that the locations of
3767 commands remembered by the parent (see
3771 \fBSHELL BUILTIN COMMANDS\fP)
3772 are retained by the child.
3774 If the program is a file beginning with
3776 the remainder of the first line specifies an interpreter
3777 for the program. The shell executes the
3778 specified interpreter on operating systems that do not
3779 handle this executable format themselves. The arguments to the
3780 interpreter consist of a single optional argument following the
3781 interpreter name on the first line of the program, followed
3782 by the name of the program, followed by the command
3784 .SH COMMAND EXECUTION ENVIRONMENT
3785 The shell has an \fIexecution environment\fP, which consists of the
3789 open files inherited by the shell at invocation, as modified by
3790 redirections supplied to the \fBexec\fP builtin
3792 the current working directory as set by \fBcd\fP, \fBpushd\fP, or
3793 \fBpopd\fP, or inherited by the shell at invocation
3795 the file creation mode mask as set by \fBumask\fP or inherited from
3798 current traps set by \fBtrap\fP
3800 shell parameters that are set by variable assignment or with \fBset\fP
3801 or inherited from the shell's parent in the environment
3803 shell functions defined during execution or inherited from the shell's
3804 parent in the environment
3806 options enabled at invocation (either by default or with command-line
3807 arguments) or by \fBset\fP
3809 options enabled by \fBshopt\fP
3811 shell aliases defined with \fBalias\fP
3813 various process IDs, including those of background jobs, the value
3814 of \fB$$\fP, and the value of \fB$PPID\fP
3816 When a simple command other than a builtin or shell function
3817 is to be executed, it
3818 is invoked in a separate execution environment that consists of
3819 the following. Unless otherwise noted, the values are inherited
3823 the shell's open files, plus any modifications and additions specified
3824 by redirections to the command
3826 the current working directory
3828 the file creation mode mask
3830 shell variables and functions marked for export, along with variables
3831 exported for the command, passed in the environment
3833 traps caught by the shell are reset to the values inherited from the
3834 shell's parent, and traps ignored by the shell are ignored
3836 A command invoked in this separate environment cannot affect the
3837 shell's execution environment.
3839 Command substitution, commands grouped with parentheses,
3840 and asynchronous commands are invoked in a
3841 subshell environment that is a duplicate of the shell environment,
3842 except that traps caught by the shell are reset to the values
3843 that the shell inherited from its parent at invocation. Builtin
3844 commands that are invoked as part of a pipeline are also executed in a
3845 subshell environment. Changes made to the subshell environment
3846 cannot affect the shell's execution environment.
3848 If a command is followed by a \fB&\fP and job control is not active, the
3849 default standard input for the command is the empty file \fI/dev/null\fP.
3850 Otherwise, the invoked command inherits the file descriptors of the calling
3851 shell as modified by redirections.
3853 When a program is invoked it is given an array of strings
3857 \fIname\fP\-\fIvalue\fP pairs, of the form
3858 .IR "name\fR=\fPvalue" .
3860 The shell provides several ways to manipulate the environment.
3861 On invocation, the shell scans its own environment and
3862 creates a parameter for each name found, automatically marking
3865 to child processes. Executed commands inherit the environment.
3870 commands allow parameters and functions to be added to and
3871 deleted from the environment. If the value of a parameter
3872 in the environment is modified, the new value becomes part
3873 of the environment, replacing the old. The environment
3874 inherited by any executed command consists of the shell's
3875 initial environment, whose values may be modified in the shell,
3876 less any pairs removed by the
3878 command, plus any additions via the
3884 The environment for any
3886 or function may be augmented temporarily by prefixing it with
3887 parameter assignments, as described above in
3890 These assignment statements affect only the environment seen
3895 option is set (see the
3897 builtin command below), then
3899 parameter assignments are placed in the environment for a command,
3900 not just those that precede the command name.
3904 invokes an external command, the variable
3906 is set to the full file name of the command and passed to that
3907 command in its environment.
3909 For the shell's purposes, a command which exits with a
3910 zero exit status has succeeded. An exit status of zero
3911 indicates success. A non-zero exit status indicates failure.
3912 When a command terminates on a fatal signal \fIN\fP, \fBbash\fP uses
3913 the value of 128+\fIN\fP as the exit status.
3915 If a command is not found, the child process created to
3916 execute it returns a status of 127. If a command is found
3917 but is not executable, the return status is 126.
3919 If a command fails because of an error during expansion or redirection,
3920 the exit status is greater than zero.
3922 Shell builtin commands return a status of 0 (\fItrue\fP) if
3923 successful, and non-zero (\fIfalse\fP) if an error occurs
3925 All builtins return an exit status of 2 to indicate incorrect usage.
3927 \fBBash\fP itself returns the exit status of the last command
3928 executed, unless a syntax error occurs, in which case it exits
3929 with a non-zero value. See also the \fBexit\fP builtin
3932 When \fBbash\fP is interactive, in the absence of any traps, it ignores
3935 (so that \fBkill 0\fP does not kill an interactive shell),
3939 is caught and handled (so that the \fBwait\fP builtin is interruptible).
3940 In all cases, \fBbash\fP ignores
3943 If job control is in effect,
3954 Non-builtin commands run by \fBbash\fP have signal handlers
3955 set to the values inherited by the shell from its parent.
3956 When job control is not in effect, asynchronous commands
3963 in addition to these inherited handlers.
3964 Commands run as a result of command substitution ignore the
3965 keyboard-generated job control signals
3974 The shell exits by default upon receipt of a
3977 Before exiting, an interactive shell resends the
3980 to all jobs, running or stopped.
3981 Stopped jobs are sent
3984 to ensure that they receive the
3987 To prevent the shell from
3988 sending the signal to a particular job, it should be removed from the
3993 .B "SHELL BUILTIN COMMANDS"
4003 shell option has been set with
4009 to all jobs when an interactive login shell exits.
4011 If \fBbash\fP is waiting for a command to complete and receives a signal
4012 for which a trap has been set, the trap will not be executed until
4013 the command completes.
4014 When \fBbash\fP is waiting for an asynchronous command via the \fBwait\fP
4015 builtin, the reception of a signal for which a trap has been set will
4016 cause the \fBwait\fP builtin to return immediately with an exit status
4017 greater than 128, immediately after which the trap is executed.
4020 refers to the ability to selectively stop (\fIsuspend\fP)
4021 the execution of processes and continue (\fIresume\fP)
4022 their execution at a later point. A user typically employs
4023 this facility via an interactive interface supplied jointly
4024 by the system's terminal driver and
4027 The shell associates a
4029 with each pipeline. It keeps a table of currently executing
4030 jobs, which may be listed with the
4034 starts a job asynchronously (in the
4036 it prints a line that looks like:
4042 indicating that this job is job number 1 and that the process ID
4043 of the last process in the pipeline associated with this job is 25647.
4044 All of the processes in a single pipeline are members of the same job.
4048 abstraction as the basis for job control.
4050 To facilitate the implementation of the user interface to job
4051 control, the operating system maintains the notion of a \fIcurrent terminal
4052 process group ID\fP. Members of this process group (processes whose
4053 process group ID is equal to the current terminal process group ID)
4054 receive keyboard-generated signals such as
4057 These processes are said to be in the
4060 processes are those whose process group ID differs from the terminal's;
4061 such processes are immune to keyboard-generated signals.
4062 Only foreground processes are allowed to read from or write to the
4063 terminal. Background processes which attempt to read from (write to) the
4066 .B SIGTTIN (SIGTTOU)
4067 signal by the terminal driver,
4068 which, unless caught, suspends the process.
4070 If the operating system on which
4075 contains facilities to use it.
4078 character (typically
4080 Control-Z) while a process is running
4081 causes that process to be stopped and returns control to
4084 .I "delayed suspend"
4085 character (typically
4087 Control-Y) causes the process to be stopped when it
4088 attempts to read input from the terminal, and control to
4091 The user may then manipulate the state of this job, using the
4093 command to continue it in the background, the
4095 command to continue it in the foreground, or
4098 command to kill it. A \fB^Z\fP takes effect immediately,
4099 and has the additional side effect of causing pending output
4100 and typeahead to be discarded.
4102 There are a number of ways to refer to a job in the shell.
4105 introduces a job name. Job number
4107 may be referred to as
4109 A job may also be referred to using a prefix of the name used to
4110 start it, or using a substring that appears in its command line.
4115 job. If a prefix matches more than one job,
4117 reports an error. Using
4119 on the other hand, refers to any job containing the string
4121 in its command line. If the substring matches more than one job,
4123 reports an error. The symbols
4127 refer to the shell's notion of the
4129 which is the last job stopped while it was in
4130 the foreground or started in the background.
4133 may be referenced using
4135 In output pertaining to jobs (e.g., the output of the
4137 command), the current job is always flagged with a
4139 and the previous job with a
4141 A single % (with no accompanying job specification) also refers to the
4144 Simply naming a job can be used to bring it into the
4149 bringing job 1 from the background into the foreground.
4152 resumes job 1 in the background, equivalent to
4155 The shell learns immediately whenever a job changes state.
4158 waits until it is about to print a prompt before reporting
4159 changes in a job's status so as to not interrupt
4160 any other output. If the
4167 reports such changes immediately.
4171 is executed for each child that exits.
4173 If an attempt to exit
4175 is made while jobs are stopped, the shell prints a warning message. The
4177 command may then be used to inspect their status.
4178 If a second attempt to exit is made without an intervening command,
4179 the shell does not print another warning, and the stopped
4180 jobs are terminated.
4182 When executing interactively,
4184 displays the primary prompt
4187 when it is ready to read a command, and the secondary prompt
4190 when it needs more input to complete a command.
4192 allows these prompt strings to be customized by inserting a number of
4193 backslash-escaped special characters that are decoded as follows:
4198 an ASCII bell character (07)
4201 the date in "Weekday Month Date" format (e.g., "Tue May 26")
4203 .B \eD{\fIformat\fP}
4204 the \fIformat\fP is passed to \fIstrftime\fP(3) and the result is inserted
4205 into the prompt string; an empty \fIformat\fP results in a locale-specific
4206 time representation. The braces are required
4209 an ASCII escape character (033)
4212 the hostname up to the first `.'
4218 the number of jobs currently managed by the shell
4221 the basename of the shell's terminal device name
4230 the name of the shell, the basename of
4232 (the portion following the final slash)
4235 the current time in 24-hour HH:MM:SS format
4238 the current time in 12-hour HH:MM:SS format
4241 the current time in 12-hour am/pm format
4244 the current time in 24-hour HH:MM format
4247 the username of the current user
4250 the version of \fBbash\fP (e.g., 2.00)
4253 the release of \fBbash\fP, version + patch level (e.g., 2.00.0)
4256 the current working directory, with \fB$HOME\fP abbreviated with a tilde
4259 the basename of the current working directory, with \fB$HOME\fP
4260 abbreviated with a tilde
4263 the history number of this command
4266 the command number of this command
4269 if the effective UID is 0, a
4275 the character corresponding to the octal number \fInnn\fP
4281 begin a sequence of non-printing characters, which could be used to
4282 embed a terminal control sequence into the prompt
4285 end a sequence of non-printing characters
4289 The command number and the history number are usually different:
4290 the history number of a command is its position in the history
4291 list, which may include commands restored from the history file
4295 below), while the command number is the position in the sequence
4296 of commands executed during the current shell session.
4297 After the string is decoded, it is expanded via
4298 parameter expansion, command substitution, arithmetic
4299 expansion, and quote removal, subject to the value of the
4301 shell option (see the description of the
4305 .B "SHELL BUILTIN COMMANDS"
4308 This is the library that handles reading input when using an interactive
4311 option is given at shell invocation.
4312 By default, the line editing commands are similar to those of emacs.
4313 A vi-style line editing interface is also available.
4314 To turn off line editing after the shell is running, use the
4322 .B SHELL BUILTIN COMMANDS
4324 .SS "Readline Notation"
4326 In this section, the emacs-style notation is used to denote
4327 keystrokes. Control keys are denoted by C\-\fIkey\fR, e.g., C\-n
4328 means Control\-N. Similarly,
4330 keys are denoted by M\-\fIkey\fR, so M\-x means Meta\-X. (On keyboards
4333 key, M\-\fIx\fP means ESC \fIx\fP, i.e., press the Escape key
4336 key. This makes ESC the \fImeta prefix\fP.
4337 The combination M\-C\-\fIx\fP means ESC\-Control\-\fIx\fP,
4338 or press the Escape key
4339 then hold the Control key while pressing the
4343 Readline commands may be given numeric
4345 which normally act as a repeat count.
4346 Sometimes, however, it is the sign of the argument that is significant.
4347 Passing a negative argument to a command that acts in the forward
4348 direction (e.g., \fBkill\-line\fP) causes that command to act in a
4350 Commands whose behavior with arguments deviates from this are noted
4353 When a command is described as \fIkilling\fP text, the text
4354 deleted is saved for possible future retrieval
4355 (\fIyanking\fP). The killed text is saved in a
4356 \fIkill ring\fP. Consecutive kills cause the text to be
4357 accumulated into one unit, which can be yanked all at once.
4358 Commands which do not kill text separate the chunks of text
4360 .SS "Readline Initialization"
4362 Readline is customized by putting commands in an initialization
4363 file (the \fIinputrc\fP file).
4364 The name of this file is taken from the value of the
4367 variable. If that variable is unset, the default is
4369 When a program which uses the readline library starts up, the
4370 initialization file is read, and the key bindings and variables
4372 There are only a few basic constructs allowed in the
4373 readline initialization file.
4374 Blank lines are ignored.
4375 Lines beginning with a \fB#\fP are comments.
4376 Lines beginning with a \fB$\fP indicate conditional constructs.
4377 Other lines denote key bindings and variable settings.
4379 The default key-bindings may be changed with an
4382 Other programs that use this library may add their own commands
4385 For example, placing
4388 M\-Control\-u: universal\-argument
4392 C\-Meta\-u: universal\-argument
4396 would make M\-C\-u execute the readline command
4397 .IR universal\-argument .
4399 The following symbolic character names are recognized:
4412 In addition to command names, readline allows keys to be bound
4413 to a string that is inserted when the key is pressed (a \fImacro\fP).
4414 .SS "Readline Key Bindings"
4416 The syntax for controlling key bindings in the
4418 file is simple. All that is required is the name of the
4419 command or the text of a macro and a key sequence to which
4420 it should be bound. The name may be specified in one of two ways:
4421 as a symbolic key name, possibly with \fIMeta\-\fP or \fIControl\-\fP
4422 prefixes, or as a key sequence.
4424 When using the form \fBkeyname\fP:\^\fIfunction\-name\fP or \fImacro\fP,
4426 is the name of a key spelled out in English. For example:
4429 Control-u: universal\-argument
4431 Meta-Rubout: backward-kill-word
4433 Control-o: "> output"
4436 In the above example,
4438 is bound to the function
4439 .BR universal\-argument ,
4441 is bound to the function
4442 .BR backward\-kill\-word ,
4445 is bound to run the macro
4446 expressed on the right hand side (that is, to insert the text
4447 .if t \f(CW> output\fP
4451 In the second form, \fB"keyseq"\fP:\^\fIfunction\-name\fP or \fImacro\fP,
4455 above in that strings denoting
4456 an entire key sequence may be specified by placing the sequence
4457 within double quotes. Some GNU Emacs style key escapes can be
4458 used, as in the following example, but the symbolic character names
4462 "\eC\-u": universal\-argument
4464 "\eC\-x\eC\-r": re\-read\-init\-file
4466 "\ee[11~": "Function Key 1"
4471 is again bound to the function
4472 .BR universal\-argument .
4474 is bound to the function
4475 .BR re\-read\-init\-file ,
4478 is bound to insert the text
4479 .if t \f(CWFunction Key 1\fP.
4480 .if n ``Function Key 1''.
4482 The full set of GNU Emacs style escape sequences is
4506 In addition to the GNU Emacs style escape sequences, a second
4507 set of backslash escapes is available:
4536 the eight-bit character whose value is the octal value \fInnn\fP
4537 (one to three digits)
4540 the eight-bit character whose value is the hexadecimal value \fIHH\fP
4541 (one or two hex digits)
4545 When entering the text of a macro, single or double quotes must
4546 be used to indicate a macro definition.
4547 Unquoted text is assumed to be a function name.
4548 In the macro body, the backslash escapes described above are expanded.
4549 Backslash will quote any other character in the macro text,
4550 including " and \(aq.
4553 allows the current readline key bindings to be displayed or modified
4556 builtin command. The editing mode may be switched during interactive
4561 builtin command (see
4563 .B SHELL BUILTIN COMMANDS
4565 .SS "Readline Variables"
4567 Readline has variables that can be used to further customize its
4568 behavior. A variable may be set in the
4570 file with a statement of the form
4573 \fBset\fP \fIvariable\-name\fP \fIvalue\fP
4576 Except where noted, readline variables can take the values
4580 (without regard to case).
4581 Unrecognized variable names are ignored.
4582 When a variable value is read, empty or null values, "on" (case-insensitive),
4583 and "1" are equivalent to \fBOn\fP. All other values are equivalent to
4585 The variables and their default values are:
4589 .B bell\-style (audible)
4590 Controls what happens when readline wants to ring the terminal bell.
4591 If set to \fBnone\fP, readline never rings the bell. If set to
4592 \fBvisible\fP, readline uses a visible bell if one is available.
4593 If set to \fBaudible\fP, readline attempts to ring the terminal's bell.
4595 .B bind\-tty\-special\-chars (On)
4596 If set to \fBOn\fP, readline attempts to bind the control characters
4597 treated specially by the kernel's terminal driver to their readline
4600 .B comment\-begin (``#'')
4601 The string that is inserted when the readline
4603 command is executed.
4604 This command is bound to
4606 in emacs mode and to
4610 .B completion\-ignore\-case (Off)
4611 If set to \fBOn\fP, readline performs filename matching and completion
4612 in a case\-insensitive fashion.
4614 .B completion\-query\-items (100)
4615 This determines when the user is queried about viewing
4616 the number of possible completions
4617 generated by the \fBpossible\-completions\fP command.
4618 It may be set to any integer value greater than or equal to
4619 zero. If the number of possible completions is greater than
4620 or equal to the value of this variable, the user is asked whether
4621 or not he wishes to view them; otherwise they are simply listed
4624 .B convert\-meta (On)
4625 If set to \fBOn\fP, readline will convert characters with the
4626 eighth bit set to an ASCII key sequence
4627 by stripping the eighth bit and prefixing an
4628 escape character (in effect, using escape as the \fImeta prefix\fP).
4630 .B disable\-completion (Off)
4631 If set to \fBOn\fP, readline will inhibit word completion. Completion
4632 characters will be inserted into the line as if they had been
4633 mapped to \fBself-insert\fP.
4635 .B editing\-mode (emacs)
4636 Controls whether readline begins with a set of key bindings similar
4637 to \fIemacs\fP or \fIvi\fP.
4639 can be set to either
4644 .B enable\-keypad (Off)
4645 When set to \fBOn\fP, readline will try to enable the application
4646 keypad when it is called. Some systems need this to enable the
4649 .B expand\-tilde (Off)
4650 If set to \fBon\fP, tilde expansion is performed when readline
4651 attempts word completion.
4653 .B history\-preserve\-point (Off)
4654 If set to \fBon\fP, the history code attempts to place point at the
4655 same location on each history line retrieved with \fBprevious-history\fP
4656 or \fBnext-history\fP.
4658 .B horizontal\-scroll\-mode (Off)
4659 When set to \fBOn\fP, makes readline use a single line for display,
4660 scrolling the input horizontally on a single screen line when it
4661 becomes longer than the screen width rather than wrapping to a new line.
4663 .B input\-meta (Off)
4664 If set to \fBOn\fP, readline will enable eight-bit input (that is,
4665 it will not strip the high bit from the characters it reads),
4666 regardless of what the terminal claims it can support. The name
4668 is a synonym for this variable.
4670 .B isearch\-terminators (``C\-[C\-J'')
4671 The string of characters that should terminate an incremental
4672 search without subsequently executing the character as a command.
4673 If this variable has not been given a value, the characters
4674 \fIESC\fP and \fIC\-J\fP will terminate an incremental search.
4677 Set the current readline keymap. The set of valid keymap names is
4678 \fIemacs, emacs\-standard, emacs\-meta, emacs\-ctlx, vi,
4681 \fIvi\fP is equivalent to \fIvi\-command\fP; \fIemacs\fP is
4682 equivalent to \fIemacs\-standard\fP. The default value is
4686 also affects the default keymap.
4688 .B mark\-directories (On)
4689 If set to \fBOn\fP, completed directory names have a slash
4692 .B mark\-modified\-lines (Off)
4693 If set to \fBOn\fP, history lines that have been modified are displayed
4694 with a preceding asterisk (\fB*\fP).
4696 .B mark\-symlinked\-directories (Off)
4697 If set to \fBOn\fP, completed names which are symbolic links to directories
4698 have a slash appended (subject to the value of
4699 \fBmark\-directories\fP).
4701 .B match\-hidden\-files (On)
4702 This variable, when set to \fBOn\fP, causes readline to match files whose
4703 names begin with a `.' (hidden files) when performing filename
4704 completion, unless the leading `.' is
4705 supplied by the user in the filename to be completed.
4707 .B output\-meta (Off)
4708 If set to \fBOn\fP, readline will display characters with the
4709 eighth bit set directly rather than as a meta-prefixed escape
4712 .B page\-completions (On)
4713 If set to \fBOn\fP, readline uses an internal \fImore\fP-like pager
4714 to display a screenful of possible completions at a time.
4716 .B print\-completions\-horizontally (Off)
4717 If set to \fBOn\fP, readline will display completions with matches
4718 sorted horizontally in alphabetical order, rather than down the screen.
4720 .B show\-all\-if\-ambiguous (Off)
4721 This alters the default behavior of the completion functions. If
4724 words which have more than one possible completion cause the
4725 matches to be listed immediately instead of ringing the bell.
4727 .B show\-all\-if\-unmodified (Off)
4728 This alters the default behavior of the completion functions in
4729 a fashion similar to \fBshow\-all\-if\-ambiguous\fP.
4732 words which have more than one possible completion without any
4733 possible partial completion (the possible completions don't share
4734 a common prefix) cause the matches to be listed immediately instead
4735 of ringing the bell.
4737 .B visible\-stats (Off)
4738 If set to \fBOn\fP, a character denoting a file's type as reported
4739 by \fIstat\fP(2) is appended to the filename when listing possible
4742 .SS "Readline Conditional Constructs"
4744 Readline implements a facility similar in spirit to the conditional
4745 compilation features of the C preprocessor which allows key
4746 bindings and variable settings to be performed as the result
4747 of tests. There are four parser directives used.
4751 construct allows bindings to be made based on the
4752 editing mode, the terminal being used, or the application using
4753 readline. The text of the test extends to the end of the line;
4754 no characters are required to isolate it.
4757 The \fBmode=\fP form of the \fB$if\fP directive is used to test
4758 whether readline is in emacs or vi mode.
4759 This may be used in conjunction
4760 with the \fBset keymap\fP command, for instance, to set bindings in
4761 the \fIemacs\-standard\fP and \fIemacs\-ctlx\fP keymaps only if
4762 readline is starting out in emacs mode.
4764 The \fBterm=\fP form may be used to include terminal-specific
4765 key bindings, perhaps to bind the key sequences output by the
4766 terminal's function keys. The word on the right side of the
4768 is tested against the both full name of the terminal and the portion
4769 of the terminal name before the first \fB\-\fP. This allows
4776 .IP \fBapplication\fP
4777 The \fBapplication\fP construct is used to include
4778 application-specific settings. Each program using the readline
4779 library sets the \fIapplication name\fP, and an initialization
4780 file can test for a particular value.
4781 This could be used to bind key sequences to functions useful for
4782 a specific program. For instance, the following command adds a
4783 key sequence that quotes the current or previous word in Bash:
4788 # Quote the current or previous word
4789 "\eC\-xq": "\eeb\e"\eef\e""
4795 This command, as seen in the previous example, terminates an
4798 Commands in this branch of the \fB$if\fP directive are executed if
4801 This directive takes a single filename as an argument and reads commands
4802 and bindings from that file. For example, the following directive
4803 would read \fI/etc/inputrc\fP:
4807 \fB$include\fP \^ \fI/etc/inputrc\fP
4812 Readline provides commands for searching through the command history
4816 below) for lines containing a specified string.
4817 There are two search modes:
4820 .IR non-incremental .
4822 Incremental searches begin before the user has finished typing the
4824 As each character of the search string is typed, readline displays
4825 the next entry from the history matching the string typed so far.
4826 An incremental search requires only as many characters as needed to
4827 find the desired history entry.
4828 The characters present in the value of the \fBisearch-terminators\fP
4829 variable are used to terminate an incremental search.
4830 If that variable has not been assigned a value the Escape and
4831 Control-J characters will terminate an incremental search.
4832 Control-G will abort an incremental search and restore the original
4834 When the search is terminated, the history entry containing the
4835 search string becomes the current line.
4837 To find other matching entries in the history list, type Control-S or
4838 Control-R as appropriate.
4839 This will search backward or forward in the history for the next
4840 entry matching the search string typed so far.
4841 Any other key sequence bound to a readline command will terminate
4842 the search and execute that command.
4843 For instance, a \fInewline\fP will terminate the search and accept
4844 the line, thereby executing the command from the history list.
4846 Readline remembers the last incremental search string. If two
4847 Control-Rs are typed without any intervening characters defining a
4848 new search string, any remembered search string is used.
4850 Non-incremental searches read the entire search string before starting
4851 to search for matching history lines. The search string may be
4852 typed by the user or be part of the contents of the current line.
4853 .SS "Readline Command Names"
4855 The following is a list of the names of the commands and the default
4856 key sequences to which they are bound.
4857 Command names without an accompanying key sequence are unbound by default.
4858 In the following descriptions, \fIpoint\fP refers to the current cursor
4859 position, and \fImark\fP refers to a cursor position saved by the
4860 \fBset\-mark\fP command.
4861 The text between the point and mark is referred to as the \fIregion\fP.
4862 .SS Commands for Moving
4866 .B beginning\-of\-line (C\-a)
4867 Move to the start of the current line.
4869 .B end\-of\-line (C\-e)
4870 Move to the end of the line.
4872 .B forward\-char (C\-f)
4873 Move forward a character.
4875 .B backward\-char (C\-b)
4876 Move back a character.
4878 .B forward\-word (M\-f)
4879 Move forward to the end of the next word. Words are composed of
4880 alphanumeric characters (letters and digits).
4882 .B backward\-word (M\-b)
4883 Move back to the start of the current or previous word. Words are
4884 composed of alphanumeric characters (letters and digits).
4886 .B clear\-screen (C\-l)
4887 Clear the screen leaving the current line at the top of the screen.
4888 With an argument, refresh the current line without clearing the
4891 .B redraw\-current\-line
4892 Refresh the current line.
4894 .SS Commands for Manipulating the History
4898 .B accept\-line (Newline, Return)
4899 Accept the line regardless of where the cursor is. If this line is
4900 non-empty, add it to the history list according to the state of the
4903 variable. If the line is a modified history
4904 line, then restore the history line to its original state.
4906 .B previous\-history (C\-p)
4907 Fetch the previous command from the history list, moving back in
4910 .B next\-history (C\-n)
4911 Fetch the next command from the history list, moving forward in the
4914 .B beginning\-of\-history (M\-<)
4915 Move to the first line in the history.
4917 .B end\-of\-history (M\->)
4918 Move to the end of the input history, i.e., the line currently being
4921 .B reverse\-search\-history (C\-r)
4922 Search backward starting at the current line and moving `up' through
4923 the history as necessary. This is an incremental search.
4925 .B forward\-search\-history (C\-s)
4926 Search forward starting at the current line and moving `down' through
4927 the history as necessary. This is an incremental search.
4929 .B non\-incremental\-reverse\-search\-history (M\-p)
4930 Search backward through the history starting at the current line
4931 using a non-incremental search for a string supplied by the user.
4933 .B non\-incremental\-forward\-search\-history (M\-n)
4934 Search forward through the history using a non-incremental search for
4935 a string supplied by the user.
4937 .B history\-search\-forward
4938 Search forward through the history for the string of characters
4939 between the start of the current line and the point.
4940 This is a non-incremental search.
4942 .B history\-search\-backward
4943 Search backward through the history for the string of characters
4944 between the start of the current line and the point.
4945 This is a non-incremental search.
4947 .B yank\-nth\-arg (M\-C\-y)
4948 Insert the first argument to the previous command (usually
4949 the second word on the previous line) at point.
4952 insert the \fIn\fPth word from the previous command (the words
4953 in the previous command begin with word 0). A negative argument
4954 inserts the \fIn\fPth word from the end of the previous command.
4955 Once the argument \fIn\fP is computed, the argument is extracted
4956 as if the "!\fIn\fP" history expansion had been specified.
4959 yank\-last\-arg (M\-.\^, M\-_\^)
4960 Insert the last argument to the previous command (the last word of
4961 the previous history entry). With an argument,
4962 behave exactly like \fByank\-nth\-arg\fP.
4963 Successive calls to \fByank\-last\-arg\fP move back through the history
4964 list, inserting the last argument of each line in turn.
4965 The history expansion facilities are used to extract the last argument,
4966 as if the "!$" history expansion had been specified.
4968 .B shell\-expand\-line (M\-C\-e)
4969 Expand the line as the shell does. This
4970 performs alias and history expansion as well as all of the shell
4971 word expansions. See
4973 .B HISTORY EXPANSION
4974 below for a description of history expansion.
4976 .B history\-expand\-line (M\-^)
4977 Perform history expansion on the current line.
4980 .B HISTORY EXPANSION
4981 below for a description of history expansion.
4984 Perform history expansion on the current line and insert a space.
4987 .B HISTORY EXPANSION
4988 below for a description of history expansion.
4990 .B alias\-expand\-line
4991 Perform alias expansion on the current line.
4995 above for a description of alias expansion.
4997 .B history\-and\-alias\-expand\-line
4998 Perform history and alias expansion on the current line.
5000 .B insert\-last\-argument (M\-.\^, M\-_\^)
5001 A synonym for \fByank\-last\-arg\fP.
5003 .B operate\-and\-get\-next (C\-o)
5004 Accept the current line for execution and fetch the next line
5005 relative to the current line from the history for editing. Any
5006 argument is ignored.
5008 .B edit\-and\-execute\-command (C\-xC\-e)
5009 Invoke an editor on the current command line, and execute the result as shell
5011 \fBBash\fP attempts to invoke
5016 and \fIemacs\fP as the editor, in that order.
5018 .SS Commands for Changing Text
5022 .B delete\-char (C\-d)
5023 Delete the character at point. If point is at the
5024 beginning of the line, there are no characters in the line, and
5025 the last character typed was not bound to \fBdelete\-char\fP,
5030 .B backward\-delete\-char (Rubout)
5031 Delete the character behind the cursor. When given a numeric argument,
5032 save the deleted text on the kill ring.
5034 .B forward\-backward\-delete\-char
5035 Delete the character under the cursor, unless the cursor is at the
5036 end of the line, in which case the character behind the cursor is
5039 .B quoted\-insert (C\-q, C\-v)
5040 Add the next character typed to the line verbatim. This is
5041 how to insert characters like \fBC\-q\fP, for example.
5043 .B tab\-insert (C\-v TAB)
5044 Insert a tab character.
5046 .B self\-insert (a,\ b,\ A,\ 1,\ !,\ ...)
5047 Insert the character typed.
5049 .B transpose\-chars (C\-t)
5050 Drag the character before point forward over the character at point,
5051 moving point forward as well.
5052 If point is at the end of the line, then this transposes
5053 the two characters before point.
5054 Negative arguments have no effect.
5056 .B transpose\-words (M\-t)
5057 Drag the word before point past the word after point,
5058 moving point over that word as well.
5059 If point is at the end of the line, this transposes
5060 the last two words on the line.
5062 .B upcase\-word (M\-u)
5063 Uppercase the current (or following) word. With a negative argument,
5064 uppercase the previous word, but do not move point.
5066 .B downcase\-word (M\-l)
5067 Lowercase the current (or following) word. With a negative argument,
5068 lowercase the previous word, but do not move point.
5070 .B capitalize\-word (M\-c)
5071 Capitalize the current (or following) word. With a negative argument,
5072 capitalize the previous word, but do not move point.
5075 Toggle overwrite mode. With an explicit positive numeric argument,
5076 switches to overwrite mode. With an explicit non-positive numeric
5077 argument, switches to insert mode. This command affects only
5078 \fBemacs\fP mode; \fBvi\fP mode does overwrite differently.
5079 Each call to \fIreadline()\fP starts in insert mode.
5080 In overwrite mode, characters bound to \fBself\-insert\fP replace
5081 the text at point rather than pushing the text to the right.
5082 Characters bound to \fBbackward\-delete\-char\fP replace the character
5083 before point with a space. By default, this command is unbound.
5085 .SS Killing and Yanking
5089 .B kill\-line (C\-k)
5090 Kill the text from point to the end of the line.
5092 .B backward\-kill\-line (C\-x Rubout)
5093 Kill backward to the beginning of the line.
5095 .B unix\-line\-discard (C\-u)
5096 Kill backward from point to the beginning of the line.
5097 The killed text is saved on the kill-ring.
5098 .\" There is no real difference between this and backward-kill-line
5100 .B kill\-whole\-line
5101 Kill all characters on the current line, no matter where point is.
5103 .B kill\-word (M\-d)
5104 Kill from point to the end of the current word, or if between
5105 words, to the end of the next word.
5106 Word boundaries are the same as those used by \fBforward\-word\fP.
5108 .B backward\-kill\-word (M\-Rubout)
5109 Kill the word behind point.
5110 Word boundaries are the same as those used by \fBbackward\-word\fP.
5112 .B unix\-word\-rubout (C\-w)
5113 Kill the word behind point, using white space as a word boundary.
5114 The killed text is saved on the kill-ring.
5116 .B unix\-filename\-rubout
5117 Kill the word behind point, using white space and the slash character
5118 as the word boundaries.
5119 The killed text is saved on the kill-ring.
5121 .B delete\-horizontal\-space (M\-\e)
5122 Delete all spaces and tabs around point.
5125 Kill the text in the current region.
5127 .B copy\-region\-as\-kill
5128 Copy the text in the region to the kill buffer.
5130 .B copy\-backward\-word
5131 Copy the word before point to the kill buffer.
5132 The word boundaries are the same as \fBbackward\-word\fP.
5134 .B copy\-forward\-word
5135 Copy the word following point to the kill buffer.
5136 The word boundaries are the same as \fBforward\-word\fP.
5139 Yank the top of the kill ring into the buffer at point.
5142 Rotate the kill ring, and yank the new top. Only works following
5147 .SS Numeric Arguments
5151 .B digit\-argument (M\-0, M\-1, ..., M\-\-)
5152 Add this digit to the argument already accumulating, or start a new
5153 argument. M\-\- starts a negative argument.
5155 .B universal\-argument
5156 This is another way to specify an argument.
5157 If this command is followed by one or more digits, optionally with a
5158 leading minus sign, those digits define the argument.
5159 If the command is followed by digits, executing
5160 .B universal\-argument
5161 again ends the numeric argument, but is otherwise ignored.
5162 As a special case, if this command is immediately followed by a
5163 character that is neither a digit or minus sign, the argument count
5164 for the next command is multiplied by four.
5165 The argument count is initially one, so executing this function the
5166 first time makes the argument count four, a second time makes the
5167 argument count sixteen, and so on.
5174 Attempt to perform completion on the text before point.
5176 attempts completion treating the text as a variable (if the
5177 text begins with \fB$\fP), username (if the text begins with
5178 \fB~\fP), hostname (if the text begins with \fB@\fP), or
5179 command (including aliases and functions) in turn. If none
5180 of these produces a match, filename completion is attempted.
5182 .B possible\-completions (M\-?)
5183 List the possible completions of the text before point.
5185 .B insert\-completions (M\-*)
5186 Insert all completions of the text before point
5187 that would have been generated by
5188 \fBpossible\-completions\fP.
5191 Similar to \fBcomplete\fP, but replaces the word to be completed
5192 with a single match from the list of possible completions.
5193 Repeated execution of \fBmenu\-complete\fP steps through the list
5194 of possible completions, inserting each match in turn.
5195 At the end of the list of completions, the bell is rung
5196 (subject to the setting of \fBbell\-style\fP)
5197 and the original text is restored.
5198 An argument of \fIn\fP moves \fIn\fP positions forward in the list
5199 of matches; a negative argument may be used to move backward
5201 This command is intended to be bound to \fBTAB\fP, but is unbound
5204 .B delete\-char\-or\-list
5205 Deletes the character under the cursor if not at the beginning or
5206 end of the line (like \fBdelete\-char\fP).
5207 If at the end of the line, behaves identically to
5208 \fBpossible\-completions\fP.
5209 This command is unbound by default.
5211 .B complete\-filename (M\-/)
5212 Attempt filename completion on the text before point.
5214 .B possible\-filename\-completions (C\-x /)
5215 List the possible completions of the text before point,
5216 treating it as a filename.
5218 .B complete\-username (M\-~)
5219 Attempt completion on the text before point, treating
5222 .B possible\-username\-completions (C\-x ~)
5223 List the possible completions of the text before point,
5224 treating it as a username.
5226 .B complete\-variable (M\-$)
5227 Attempt completion on the text before point, treating
5228 it as a shell variable.
5230 .B possible\-variable\-completions (C\-x $)
5231 List the possible completions of the text before point,
5232 treating it as a shell variable.
5234 .B complete\-hostname (M\-@)
5235 Attempt completion on the text before point, treating
5238 .B possible\-hostname\-completions (C\-x @)
5239 List the possible completions of the text before point,
5240 treating it as a hostname.
5242 .B complete\-command (M\-!)
5243 Attempt completion on the text before point, treating
5244 it as a command name. Command completion attempts to
5245 match the text against aliases, reserved words, shell
5246 functions, shell builtins, and finally executable filenames,
5249 .B possible\-command\-completions (C\-x !)
5250 List the possible completions of the text before point,
5251 treating it as a command name.
5253 .B dynamic\-complete\-history (M\-TAB)
5254 Attempt completion on the text before point, comparing
5255 the text against lines from the history list for possible
5258 .B complete\-into\-braces (M\-{)
5259 Perform filename completion and insert the list of possible completions
5260 enclosed within braces so the list is available to the shell (see
5268 .B start\-kbd\-macro (C\-x (\^)
5269 Begin saving the characters typed into the current keyboard macro.
5271 .B end\-kbd\-macro (C\-x )\^)
5272 Stop saving the characters typed into the current keyboard macro
5273 and store the definition.
5275 .B call\-last\-kbd\-macro (C\-x e)
5276 Re-execute the last keyboard macro defined, by making the characters
5277 in the macro appear as if typed at the keyboard.
5283 .B re\-read\-init\-file (C\-x C\-r)
5284 Read in the contents of the \fIinputrc\fP file, and incorporate
5285 any bindings or variable assignments found there.
5288 Abort the current editing command and
5289 ring the terminal's bell (subject to the setting of
5292 .B do\-uppercase\-version (M\-a, M\-b, M\-\fIx\fP, ...)
5293 If the metafied character \fIx\fP is lowercase, run the command
5294 that is bound to the corresponding uppercase character.
5296 .B prefix\-meta (ESC)
5297 Metafy the next character typed.
5304 .B undo (C\-_, C\-x C\-u)
5305 Incremental undo, separately remembered for each line.
5307 .B revert\-line (M\-r)
5308 Undo all changes made to this line. This is like executing the
5310 command enough times to return the line to its initial state.
5312 .B tilde\-expand (M\-&)
5313 Perform tilde expansion on the current word.
5315 .B set\-mark (C\-@, M\-<space>)
5316 Set the mark to the point. If a
5317 numeric argument is supplied, the mark is set to that position.
5319 .B exchange\-point\-and\-mark (C\-x C\-x)
5320 Swap the point with the mark. The current cursor position is set to
5321 the saved position, and the old cursor position is saved as the mark.
5323 .B character\-search (C\-])
5324 A character is read and point is moved to the next occurrence of that
5325 character. A negative count searches for previous occurrences.
5327 .B character\-search\-backward (M\-C\-])
5328 A character is read and point is moved to the previous occurrence of that
5329 character. A negative count searches for subsequent occurrences.
5331 .B insert\-comment (M\-#)
5332 Without a numeric argument, the value of the readline
5334 variable is inserted at the beginning of the current line.
5335 If a numeric argument is supplied, this command acts as a toggle: if
5336 the characters at the beginning of the line do not match the value
5337 of \fBcomment\-begin\fP, the value is inserted, otherwise
5338 the characters in \fBcomment-begin\fP are deleted from the beginning of
5340 In either case, the line is accepted as if a newline had been typed.
5341 The default value of
5342 \fBcomment\-begin\fP causes this command to make the current line
5344 If a numeric argument causes the comment character to be removed, the line
5345 will be executed by the shell.
5347 .B glob\-complete\-word (M\-g)
5348 The word before point is treated as a pattern for pathname expansion,
5349 with an asterisk implicitly appended. This pattern is used to
5350 generate a list of matching file names for possible completions.
5352 .B glob\-expand\-word (C\-x *)
5353 The word before point is treated as a pattern for pathname expansion,
5354 and the list of matching file names is inserted, replacing the word.
5355 If a numeric argument is supplied, an asterisk is appended before
5358 .B glob\-list\-expansions (C\-x g)
5359 The list of expansions that would have been generated by
5360 .B glob\-expand\-word
5361 is displayed, and the line is redrawn.
5362 If a numeric argument is supplied, an asterisk is appended before
5366 Print all of the functions and their key bindings to the
5367 readline output stream. If a numeric argument is supplied,
5368 the output is formatted in such a way that it can be made part
5369 of an \fIinputrc\fP file.
5372 Print all of the settable readline variables and their values to the
5373 readline output stream. If a numeric argument is supplied,
5374 the output is formatted in such a way that it can be made part
5375 of an \fIinputrc\fP file.
5378 Print all of the readline key sequences bound to macros and the
5379 strings they output. If a numeric argument is supplied,
5380 the output is formatted in such a way that it can be made part
5381 of an \fIinputrc\fP file.
5383 .B display\-shell\-version (C\-x C\-v)
5384 Display version information about the current instance of
5387 .SS Programmable Completion
5389 When word completion is attempted for an argument to a command for
5390 which a completion specification (a \fIcompspec\fP) has been defined
5391 using the \fBcomplete\fP builtin (see
5393 .B "SHELL BUILTIN COMMANDS"
5394 below), the programmable completion facilities are invoked.
5396 First, the command name is identified.
5397 If a compspec has been defined for that command, the
5398 compspec is used to generate the list of possible completions for the word.
5399 If the command word is a full pathname, a compspec for the full
5400 pathname is searched for first.
5401 If no compspec is found for the full pathname, an attempt is made to
5402 find a compspec for the portion following the final slash.
5404 Once a compspec has been found, it is used to generate the list of
5406 If a compspec is not found, the default \fBbash\fP completion as
5407 described above under \fBCompleting\fP is performed.
5409 First, the actions specified by the compspec are used.
5410 Only matches which are prefixed by the word being completed are
5416 option is used for filename or directory name completion, the shell
5420 is used to filter the matches.
5422 Any completions specified by a filename expansion pattern to the
5423 \fB\-G\fP option are generated next.
5424 The words generated by the pattern need not match the word
5429 shell variable is not used to filter the matches, but the
5434 Next, the string specified as the argument to the \fB\-W\fP option
5436 The string is first split using the characters in the
5439 special variable as delimiters.
5440 Shell quoting is honored.
5441 Each word is then expanded using
5442 brace expansion, tilde expansion, parameter and variable expansion,
5443 command substitution, and arithmetic expansion,
5444 as described above under
5447 The results are split using the rules described above under
5448 \fBWord Splitting\fP.
5449 The results of the expansion are prefix-matched against the word being
5450 completed, and the matching words become the possible completions.
5452 After these matches have been generated, any shell function or command
5453 specified with the \fB\-F\fP and \fB\-C\fP options is invoked.
5454 When the command or function is invoked, the
5460 variables are assigned values as described above under
5461 \fBShell Variables\fP.
5462 If a shell function is being invoked, the
5468 variables are also set.
5469 When the function or command is invoked, the first argument is the
5470 name of the command whose arguments are being completed, the
5471 second argument is the word being completed, and the third argument
5472 is the word preceding the word being completed on the current command line.
5473 No filtering of the generated completions against the word being completed
5474 is performed; the function or command has complete freedom in generating
5477 Any function specified with \fB\-F\fP is invoked first.
5478 The function may use any of the shell facilities, including the
5479 \fBcompgen\fP builtin described below, to generate the matches.
5480 It must put the possible completions in the
5485 Next, any command specified with the \fB\-C\fP option is invoked
5486 in an environment equivalent to command substitution.
5487 It should print a list of completions, one per line, to the
5489 Backslash may be used to escape a newline, if necessary.
5491 After all of the possible completions are generated, any filter
5492 specified with the \fB\-X\fP option is applied to the list.
5493 The filter is a pattern as used for pathname expansion; a \fB&\fP
5494 in the pattern is replaced with the text of the word being completed.
5495 A literal \fB&\fP may be escaped with a backslash; the backslash
5496 is removed before attempting a match.
5497 Any completion that matches the pattern will be removed from the list.
5498 A leading \fB!\fP negates the pattern; in this case any completion
5499 not matching the pattern will be removed.
5501 Finally, any prefix and suffix specified with the \fB\-P\fP and \fB\-S\fP
5502 options are added to each member of the completion list, and the result is
5503 returned to the readline completion code as the list of possible
5506 If the previously-applied actions do not generate any matches, and the
5507 \fB\-o dirnames\fP option was supplied to \fBcomplete\fP when the
5508 compspec was defined, directory name completion is attempted.
5510 If the \fB\-o plusdirs\fP option was supplied to \fBcomplete\fP when the
5511 compspec was defined, directory name completion is attempted and any
5512 matches are added to the results of the other actions.
5514 By default, if a compspec is found, whatever it generates is returned
5515 to the completion code as the full set of possible completions.
5516 The default \fBbash\fP completions are not attempted, and the readline
5517 default of filename completion is disabled.
5518 If the \fB\-o bashdefault\fP option was supplied to \fBcomplete\fP when
5519 the compspec was defined, the \fBbash\fP default completions are attempted
5520 if the compspec generates no matches.
5521 If the \fB\-o default\fP option was supplied to \fBcomplete\fP when the
5522 compspec was defined, readline's default completion will be performed
5523 if the compspec (and, if attempted, the default \fBbash\fP completions)
5524 generate no matches.
5526 When a compspec indicates that directory name completion is desired,
5527 the programmable completion functions force readline to append a slash
5528 to completed names which are symbolic links to directories, subject to
5529 the value of the \fBmark\-directories\fP readline variable, regardless
5530 of the setting of the \fBmark-symlinked\-directories\fP readline variable.
5536 builtin is enabled, the shell provides access to the
5537 \fIcommand history\fP,
5538 the list of commands previously typed.
5539 The value of the \fBHISTSIZE\fP variable is used as the
5540 number of commands to save in a history list.
5541 The text of the last
5544 commands (default 500) is saved. The shell
5545 stores each command in the history list prior to parameter and
5546 variable expansion (see
5549 above) but after history expansion is performed, subject to the
5550 values of the shell variables
5557 On startup, the history is initialized from the file named by
5561 (default \fI~/.bash_history\fP).
5562 The file named by the value of
5565 is truncated, if necessary, to contain no more than
5566 the number of lines specified by the value of
5569 When an interactive shell exits, the last
5572 lines are copied from the history list to
5577 shell option is enabled
5578 (see the description of
5582 .B "SHELL BUILTIN COMMANDS"
5583 below), the lines are appended to the history file,
5584 otherwise the history file is overwritten.
5588 is unset, or if the history file is unwritable, the history is
5589 not saved. After saving the history, the history file is truncated
5590 to contain no more than
5596 is not set, no truncation is performed.
5602 .B SHELL BUILTIN COMMANDS
5603 below) may be used to list or edit and re-execute a portion of
5607 builtin may be used to display or modify the history list and
5608 manipulate the history file.
5609 When using command-line editing, search commands
5610 are available in each editing mode that provide access to the
5613 The shell allows control over which commands are saved on the history
5620 variables may be set to cause the shell to save only a subset of the
5624 shell option, if enabled, causes the shell to attempt to save each
5625 line of a multi-line command in the same history entry, adding
5626 semicolons where necessary to preserve syntactic correctness.
5629 shell option causes the shell to save the command with embedded newlines
5630 instead of semicolons. See the description of the
5634 .B "SHELL BUILTIN COMMANDS"
5635 for information on setting and unsetting shell options.
5636 .SH "HISTORY EXPANSION"
5638 The shell supports a history expansion feature that
5639 is similar to the history expansion in
5641 This section describes what syntax features are available. This
5642 feature is enabled by default for interactive shells, and can be
5647 builtin command (see
5649 .B SHELL BUILTIN COMMANDS
5650 below). Non-interactive shells do not perform history expansion
5653 History expansions introduce words from the history list into
5654 the input stream, making it easy to repeat commands, insert the
5655 arguments to a previous command into the current input line, or
5656 fix errors in previous commands quickly.
5658 History expansion is performed immediately after a complete line
5659 is read, before the shell breaks it into words.
5660 It takes place in two parts.
5661 The first is to determine which line from the history list
5662 to use during substitution.
5663 The second is to select portions of that line for inclusion into
5665 The line selected from the history is the \fIevent\fP,
5666 and the portions of that line that are acted upon are \fIwords\fP.
5667 Various \fImodifiers\fP are available to manipulate the selected words.
5668 The line is broken into words in the same fashion as when reading input,
5669 so that several \fImetacharacter\fP-separated words surrounded by
5670 quotes are considered one word.
5671 History expansions are introduced by the appearance of the
5672 history expansion character, which is \^\fB!\fP\^ by default.
5673 Only backslash (\^\fB\e\fP\^) and single quotes can quote
5674 the history expansion character.
5676 Several characters inhibit history expansion if found immediately
5677 following the history expansion character, even if it is unquoted:
5678 space, tab, newline, carriage return, and \fB=\fP.
5679 If the \fBextglob\fP shell option is enabled, \fB(\fP will also
5682 Several shell options settable with the
5684 builtin may be used to tailor the behavior of history expansion.
5687 shell option is enabled (see the description of the
5691 is being used, history substitutions are not immediately passed to
5693 Instead, the expanded line is reloaded into the
5695 editing buffer for further modification.
5698 is being used, and the
5700 shell option is enabled, a failed history substitution will be reloaded
5703 editing buffer for correction.
5708 builtin command may be used to see what a history expansion will
5714 builtin may be used to add commands to the end of the history list
5715 without actually executing them, so that they are available for
5718 The shell allows control of the various characters used by the
5719 history expansion mechanism (see the description of
5722 .BR "Shell Variables" ).
5723 .SS Event Designators
5725 An event designator is a reference to a command line entry in the
5731 Start a history substitution, except when followed by a
5733 newline, carriage return, =
5734 or ( (when the \fBextglob\fP shell option is enabled using
5735 the \fBshopt\fP builtin).
5738 Refer to command line
5742 Refer to the current command line minus
5746 Refer to the previous command. This is a synonym for `!\-1'.
5749 Refer to the most recent command starting with
5752 .B !?\fIstring\fR\fB[?]\fR
5753 Refer to the most recent command containing
5755 The trailing \fB?\fP may be omitted if
5757 is followed immediately by a newline.
5759 .B \d\s+2^\s-2\u\fIstring1\fP\d\s+2^\s-2\u\fIstring2\fP\d\s+2^\s-2\u
5760 Quick substitution. Repeat the last command, replacing
5765 ``!!:s/\fIstring1\fP/\fIstring2\fP/''
5766 (see \fBModifiers\fP below).
5769 The entire command line typed so far.
5771 .SS Word Designators
5773 Word designators are used to select desired words from the event.
5776 separates the event specification from the word designator.
5777 It may be omitted if the word designator begins with a
5784 Words are numbered from the beginning of the line,
5785 with the first word being denoted by 0 (zero).
5786 Words are inserted into the current line separated by single spaces.
5791 The zeroth word. For the shell, this is the command
5798 The first argument. That is, word 1.
5804 The word matched by the most recent `?\fIstring\fR?' search.
5807 A range of words; `\-\fIy\fR' abbreviates `0\-\fIy\fR'.
5810 All of the words but the zeroth. This is a synonym
5811 for `\fI1\-$\fP'. It is not an error to use
5813 if there is just one
5814 word in the event; the empty string is returned in that case.
5817 Abbreviates \fIx\-$\fP.
5820 Abbreviates \fIx\-$\fP like \fBx*\fP, but omits the last word.
5823 If a word designator is supplied without an event specification, the
5824 previous command is used as the event.
5827 After the optional word designator, there may appear a sequence of
5828 one or more of the following modifiers, each preceded by a `:'.
5834 Remove a trailing file name component, leaving only the head.
5837 Remove all leading file name components, leaving the tail.
5840 Remove a trailing suffix of the form \fI.xxx\fP, leaving the
5844 Remove all but the trailing suffix.
5847 Print the new command but do not execute it.
5850 Quote the substituted words, escaping further substitutions.
5853 Quote the substituted words as with
5855 but break into words at
5859 .B s/\fIold\fP/\fInew\fP/
5862 for the first occurrence of
5864 in the event line. Any delimiter can be used in place of /. The
5865 final delimiter is optional if it is the last character of the
5866 event line. The delimiter may be quoted in
5870 with a single backslash. If & appears in
5874 A single backslash will quote the &. If
5876 is null, it is set to the last
5878 substituted, or, if no previous history substitutions took place,
5882 .B !?\fIstring\fR\fB[?]\fR
5886 Repeat the previous substitution.
5889 Cause changes to be applied over the entire event line. This is
5890 used in conjunction with `\fB:s\fP' (e.g., `\fB:gs/\fIold\fP/\fInew\fP/\fR')
5891 or `\fB:&\fP'. If used with
5892 `\fB:s\fP', any delimiter can be used
5893 in place of /, and the final delimiter is optional
5894 if it is the last character of the event line.
5895 An \fBa\fP may be used as a synonym for \fBg\fP.
5898 Apply the following `\fBs\fP' modifier once to each word in the event line.
5900 .SH "SHELL BUILTIN COMMANDS"
5901 .\" start of bash_builtins
5904 Unless otherwise noted, each builtin command documented in this
5905 section as accepting options preceded by
5909 to signify the end of the options.
5910 For example, the \fB:\fP, \fBtrue\fP, \fBfalse\fP, and \fBtest\fP builtins
5911 do not accept options.
5915 \fB:\fP [\fIarguments\fP]
5917 No effect; the command does nothing beyond expanding
5919 and performing any specified
5920 redirections. A zero exit code is returned.
5922 \fB .\| \fP \fIfilename\fP [\fIarguments\fP]
5925 \fBsource\fP \fIfilename\fP [\fIarguments\fP]
5927 Read and execute commands from
5930 shell environment and return the exit status of the last command
5935 does not contain a slash, file names in
5938 are used to find the directory containing
5940 The file searched for in
5943 need not be executable.
5944 When \fBbash\fP is not in \fIposix mode\fP, the current directory is
5945 searched if no file is found in
5952 builtin command is turned off, the
5956 If any \fIarguments\fP are supplied, they become the positional
5957 parameters when \fIfilename\fP is executed. Otherwise the positional
5958 parameters are unchanged.
5959 The return status is the status of the last command exited within
5960 the script (0 if no commands are executed), and false if
5962 is not found or cannot be read.
5964 \fBalias\fP [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP] ...]
5965 \fBAlias\fP with no arguments or with the
5967 option prints the list of aliases in the form
5968 \fBalias\fP \fIname\fP=\fIvalue\fP on standard output.
5969 When arguments are supplied, an alias is defined for
5970 each \fIname\fP whose \fIvalue\fP is given.
5971 A trailing space in \fIvalue\fP causes the next word to be
5972 checked for alias substitution when the alias is expanded.
5973 For each \fIname\fP in the argument list for which no \fIvalue\fP
5974 is supplied, the name and value of the alias is printed.
5975 \fBAlias\fP returns true unless a \fIname\fP is given for which
5976 no alias has been defined.
5978 \fBbg\fP [\fIjobspec\fP ...]
5979 Resume each suspended job \fIjobspec\fP in the background, as if it
5980 had been started with
5982 If \fIjobspec\fP is not present, the shell's notion of the
5983 \fIcurrent job\fP is used.
5986 returns 0 unless run when job control is disabled or, when run with
5987 job control enabled, any specified \fIjobspec\fP was not found
5988 or was started without job control.
5990 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] [\fB\-lpsvPSV\fP]
5993 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] [\fB\-q\fP \fIfunction\fP] [\fB\-u\fP \fIfunction\fP] [\fB\-r\fP \fIkeyseq\fP]
5995 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fB\-f\fP \fIfilename\fP
5997 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fB\-x\fP \fIkeyseq\fP:\fIshell\-command\fP
5999 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fIkeyseq\fP:\fIfunction\-name\fP
6001 \fBbind\fP \fIreadline\-command\fP
6005 key and function bindings, bind a key sequence to a
6007 function or macro, or set a
6010 Each non-option argument is a command as it would appear in
6012 but each binding or command must be passed as a separate argument;
6013 e.g., '"\eC\-x\eC\-r": re\-read\-init\-file'.
6014 Options, if supplied, have the following meanings:
6021 as the keymap to be affected by the subsequent bindings.
6025 \fIemacs, emacs\-standard, emacs\-meta, emacs\-ctlx, vi,
6026 vi\-move, vi\-command\fP, and
6028 \fIvi\fP is equivalent to \fIvi\-command\fP; \fIemacs\fP is
6029 equivalent to \fIemacs\-standard\fP.
6032 List the names of all \fBreadline\fP functions.
6035 Display \fBreadline\fP function names and bindings in such a way
6036 that they can be re-read.
6039 List current \fBreadline\fP function names and bindings.
6042 Display \fBreadline\fP variable names and values in such a way that they
6046 List current \fBreadline\fP variable names and values.
6049 Display \fBreadline\fP key sequences bound to macros and the strings
6050 they output in such a way that they can be re-read.
6053 Display \fBreadline\fP key sequences bound to macros and the strings
6056 .B \-f \fIfilename\fP
6057 Read key bindings from \fIfilename\fP.
6059 .B \-q \fIfunction\fP
6060 Query about which keys invoke the named \fIfunction\fP.
6062 .B \-u \fIfunction\fP
6063 Unbind all keys bound to the named \fIfunction\fP.
6066 Remove any current binding for \fIkeyseq\fP.
6068 .B \-x \fIkeyseq\fP:\fIshell\-command\fP
6069 Cause \fIshell\-command\fP to be executed whenever \fIkeyseq\fP is
6073 The return value is 0 unless an unrecognized option is given or an
6077 \fBbreak\fP [\fIn\fP]
6084 loop. If \fIn\fP is specified, break \fIn\fP levels.
6088 is greater than the number of enclosing loops, all enclosing loops
6089 are exited. The return value is 0 unless the shell is not executing
6094 \fBbuiltin\fP \fIshell\-builtin\fP [\fIarguments\fP]
6095 Execute the specified shell builtin, passing it
6097 and return its exit status.
6098 This is useful when defining a
6099 function whose name is the same as a shell builtin,
6100 retaining the functionality of the builtin within the function.
6101 The \fBcd\fP builtin is commonly redefined this way.
6102 The return status is false if
6104 is not a shell builtin command.
6106 \fBcd\fP [\fB\-L|-P\fP] [\fIdir\fP]
6107 Change the current directory to \fIdir\fP. The variable
6116 defines the search path for the directory containing
6118 Alternative directory names in
6121 are separated by a colon (:). A null directory name in
6124 is the same as the current directory, i.e., ``\fB.\fP''. If
6126 begins with a slash (/),
6132 option says to use the physical directory structure instead of
6133 following symbolic links (see also the
6137 builtin command); the
6139 option forces symbolic links to be followed. An argument of
6144 If a non-empty directory name from \fBCDPATH\fP is used, or if
6145 \fB\-\fP is the first argument, and the directory change is
6146 successful, the absolute pathname of the new working directory is
6147 written to the standard output.
6148 The return value is true if the directory was successfully changed;
6151 \fBcaller\fP [\fIexpr\fP]
6152 Returns the context of any active subroutine call (a shell function or
6153 a script executed with the \fB.\fP or \fBsource\fP builtins.
6154 Without \fIexpr\fP, \fBcaller\fP displays the line number and source
6155 filename of the current subroutine call.
6156 If a non-negative integer is supplied as \fIexpr\fP, \fBcaller\fP
6157 displays the line number, subroutine name, and source file corresponding
6158 to that position in the current execution call stack. This extra
6159 information may be used, for example, to print a stack trace. The
6160 current frame is frame 0.
6161 The return value is 0 unless the shell is not executing a subroutine
6162 call or \fIexpr\fP does not correspond to a valid position in the
6165 \fBcommand\fP [\fB\-pVv\fP] \fIcommand\fP [\fIarg\fP ...]
6170 suppressing the normal shell function lookup. Only builtin
6171 commands or commands found in the
6174 are executed. If the
6176 option is given, the search for
6178 is performed using a default value for
6180 that is guaranteed to find all of the standard utilities.
6185 option is supplied, a description of
6189 option causes a single word indicating the command or file name
6192 to be displayed; the
6194 option produces a more verbose description.
6199 option is supplied, the exit status is 0 if
6201 was found, and 1 if not. If neither option is supplied and
6202 an error occurred or
6204 cannot be found, the exit status is 127. Otherwise, the exit status of the
6206 builtin is the exit status of
6209 \fBcompgen\fP [\fIoption\fP] [\fIword\fP]
6210 Generate possible completion matches for \fIword\fP according to
6211 the \fIoption\fPs, which may be any option accepted by the
6213 builtin with the exception of \fB\-p\fP and \fB\-r\fP, and write
6214 the matches to the standard output.
6215 When using the \fB\-F\fP or \fB\-C\fP options, the various shell variables
6216 set by the programmable completion facilities, while available, will not
6219 The matches will be generated in the same way as if the programmable
6220 completion code had generated them directly from a completion specification
6221 with the same flags.
6222 If \fIword\fP is specified, only those completions matching \fIword\fP
6225 The return value is true unless an invalid option is supplied, or no
6226 matches were generated.
6228 \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]
6230 [\fB\-X\fP \fIfilterpat\fP] [\fB\-F\fP \fIfunction\fP] [\fB\-C\fP \fIcommand\fP] \fIname\fP [\fIname ...\fP]
6233 \fBcomplete\fP \fB\-pr\fP [\fIname\fP ...]
6235 Specify how arguments to each \fIname\fP should be completed.
6236 If the \fB\-p\fP option is supplied, or if no options are supplied,
6237 existing completion specifications are printed in a way that allows
6238 them to be reused as input.
6239 The \fB\-r\fP option removes a completion specification for
6240 each \fIname\fP, or, if no \fIname\fPs are supplied, all
6241 completion specifications.
6243 The process of applying these completion specifications when word completion
6244 is attempted is described above under \fBProgrammable Completion\fP.
6246 Other options, if specified, have the following meanings.
6247 The arguments to the \fB\-G\fP, \fB\-W\fP, and \fB\-X\fP options
6248 (and, if necessary, the \fB\-P\fP and \fB\-S\fP options)
6249 should be quoted to protect them from expansion before the
6255 \fB\-o\fP \fIcomp-option\fP
6256 The \fIcomp-option\fP controls several aspects of the compspec's behavior
6257 beyond the simple generation of completions.
6258 \fIcomp-option\fP may be one of:
6262 Perform the rest of the default \fBbash\fP completions if the compspec
6263 generates no matches.
6266 Use readline's default filename completion if the compspec generates
6270 Perform directory name completion if the compspec generates no matches.
6273 Tell readline that the compspec generates filenames, so it can perform any
6274 filename\-specific processing (like adding a slash to directory names or
6275 suppressing trailing spaces). Intended to be used with shell functions.
6278 Tell readline not to append a space (the default) to words completed at
6279 the end of the line.
6282 After any matches defined by the compspec are generated,
6283 directory name completion is attempted and any
6284 matches are added to the results of the other actions.
6287 \fB\-A\fP \fIaction\fP
6288 The \fIaction\fP may be one of the following to generate a list of possible
6293 Alias names. May also be specified as \fB\-a\fP.
6296 Array variable names.
6299 \fBReadline\fP key binding names.
6302 Names of shell builtin commands. May also be specified as \fB\-b\fP.
6305 Command names. May also be specified as \fB\-c\fP.
6308 Directory names. May also be specified as \fB\-d\fP.
6311 Names of disabled shell builtins.
6314 Names of enabled shell builtins.
6317 Names of exported shell variables. May also be specified as \fB\-e\fP.
6320 File names. May also be specified as \fB\-f\fP.
6323 Names of shell functions.
6326 Group names. May also be specified as \fB\-g\fP.
6329 Help topics as accepted by the \fBhelp\fP builtin.
6332 Hostnames, as taken from the file specified by the
6338 Job names, if job control is active. May also be specified as \fB\-j\fP.
6341 Shell reserved words. May also be specified as \fB\-k\fP.
6344 Names of running jobs, if job control is active.
6347 Service names. May also be specified as \fB\-s\fP.
6350 Valid arguments for the \fB\-o\fP option to the \fBset\fP builtin.
6353 Shell option names as accepted by the \fBshopt\fP builtin.
6359 Names of stopped jobs, if job control is active.
6362 User names. May also be specified as \fB\-u\fP.
6365 Names of all shell variables. May also be specified as \fB\-v\fP.
6368 \fB\-G\fP \fIglobpat\fP
6369 The filename expansion pattern \fIglobpat\fP is expanded to generate
6370 the possible completions.
6372 \fB\-W\fP \fIwordlist\fP
6373 The \fIwordlist\fP is split using the characters in the
6376 special variable as delimiters, and each resultant word is expanded.
6377 The possible completions are the members of the resultant list which
6378 match the word being completed.
6380 \fB\-C\fP \fIcommand\fP
6381 \fIcommand\fP is executed in a subshell environment, and its output is
6382 used as the possible completions.
6384 \fB\-F\fP \fIfunction\fP
6385 The shell function \fIfunction\fP is executed in the current shell
6387 When it finishes, the possible completions are retrieved from the value
6393 \fB\-X\fP \fIfilterpat\fP
6394 \fIfilterpat\fP is a pattern as used for filename expansion.
6395 It is applied to the list of possible completions generated by the
6396 preceding options and arguments, and each completion matching
6397 \fIfilterpat\fP is removed from the list.
6398 A leading \fB!\fP in \fIfilterpat\fP negates the pattern; in this
6399 case, any completion not matching \fIfilterpat\fP is removed.
6401 \fB\-P\fP \fIprefix\fP
6402 \fIprefix\fP is added at the beginning of each possible completion
6403 after all other options have been applied.
6405 \fB\-S\fP \fIsuffix\fP
6406 \fIsuffix\fP is appended to each possible completion
6407 after all other options have been applied.
6410 The return value is true unless an invalid option is supplied, an option
6411 other than \fB\-p\fP or \fB\-r\fP is supplied without a \fIname\fP
6412 argument, an attempt is made to remove a completion specification for
6413 a \fIname\fP for which no specification exists, or
6414 an error occurs adding a completion specification.
6417 \fBcontinue\fP [\fIn\fP]
6418 Resume the next iteration of the enclosing
6427 is specified, resume at the \fIn\fPth enclosing loop.
6431 is greater than the number of enclosing loops, the last enclosing loop
6432 (the ``top-level'' loop) is resumed. The return value is 0 unless the
6433 shell is not executing a loop when
6437 \fBdeclare\fP [\fB\-afFirtx\fP] [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP] ...]
6440 \fBtypeset\fP [\fB\-afFirtx\fP] [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP] ...]
6442 Declare variables and/or give them attributes.
6443 If no \fIname\fPs are given then display the values of variables.
6446 option will display the attributes and values of each
6450 is used, additional options are ignored.
6453 option inhibits the display of function definitions; only the
6454 function name and attributes are printed.
6455 If the \fBextdebug\fP shell option is enabled using \fBshopt\fP,
6456 the source file name and line number where the function is defined
6457 are displayed as well. The
6461 The following options can
6462 be used to restrict output to variables with the specified attribute or
6463 to give variables attributes:
6468 Each \fIname\fP is an array variable (see
6473 Use function names only.
6476 The variable is treated as an integer; arithmetic evaluation (see
6478 .B "ARITHMETIC EVALUATION" ") "
6479 is performed when the variable is assigned a value.
6482 Make \fIname\fPs readonly. These names cannot then be assigned values
6483 by subsequent assignment statements or unset.
6486 Give each \fIname\fP the \fItrace\fP attribute.
6487 Traced functions inherit the \fBDEBUG\fP and \fBRETURN\fP traps from
6489 The trace attribute has no special meaning for variables.
6492 Mark \fIname\fPs for export to subsequent commands via the environment.
6495 Using `+' instead of `\-'
6496 turns off the attribute instead, with the exception that \fB+a\fP
6497 may not be used to destroy an array variable. When used in a function,
6499 \fIname\fP local, as with the
6502 If a variable name is followed by =\fIvalue\fP, the value of
6503 the variable is set to \fIvalue\fP.
6504 The return value is 0 unless an invalid option is encountered,
6505 an attempt is made to define a function using
6506 .if n ``\-f foo=bar'',
6507 .if t \f(CW\-f foo=bar\fP,
6508 an attempt is made to assign a value to a readonly variable,
6509 an attempt is made to assign a value to an array variable without
6510 using the compound assignment syntax (see
6512 above), one of the \fInames\fP is not a valid shell variable name,
6513 an attempt is made to turn off readonly status for a readonly variable,
6514 an attempt is made to turn off array status for an array variable,
6515 or an attempt is made to display a non-existent function with \fB\-f\fP.
6518 .B dirs [\fB\-clpv\fP] [+\fIn\fP] [\-\fIn\fP]
6519 Without options, displays the list of currently remembered directories.
6520 The default display is on a single line with directory names separated
6522 Directories are added to the list with the
6526 command removes entries from the list.
6531 Displays the \fIn\fPth entry counting from the left of the list
6534 when invoked without options, starting with zero.
6537 Displays the \fIn\fPth entry counting from the right of the list
6540 when invoked without options, starting with zero.
6543 Clears the directory stack by deleting all of the entries.
6546 Produces a longer listing; the default listing format uses a
6547 tilde to denote the home directory.
6550 Print the directory stack with one entry per line.
6553 Print the directory stack with one entry per line,
6554 prefixing each entry with its index in the stack.
6557 The return value is 0 unless an
6558 invalid option is supplied or \fIn\fP indexes beyond the end
6559 of the directory stack.
6562 \fBdisown\fP [\fB\-ar\fP] [\fB\-h\fP] [\fIjobspec\fP ...]
6563 Without options, each
6565 is removed from the table of active jobs.
6566 If the \fB\-h\fP option is given, each
6568 is not removed from the table, but is marked so that
6571 is not sent to the job if the shell receives a
6576 is present, and neither the
6580 option is supplied, the \fIcurrent job\fP is used.
6585 option means to remove or mark all jobs; the
6589 argument restricts operation to running jobs.
6590 The return value is 0 unless a
6592 does not specify a valid job.
6594 \fBecho\fP [\fB\-neE\fP] [\fIarg\fP ...]
6595 Output the \fIarg\fPs, separated by spaces, followed by a newline.
6596 The return status is always 0.
6597 If \fB\-n\fP is specified, the trailing newline is
6598 suppressed. If the \fB\-e\fP option is given, interpretation of
6599 the following backslash-escaped characters is enabled. The
6601 option disables the interpretation of these escape characters,
6602 even on systems where they are interpreted by default.
6603 The \fBxpg_echo\fP shell option may be used to
6604 dynamically determine whether or not \fBecho\fP expands these
6605 escape characters by default.
6607 does not interpret \fB\-\-\fP to mean the end of options.
6609 interprets the following escape sequences:
6620 suppress trailing newline
6644 the eight-bit character whose value is the octal value \fInnn\fP
6645 (zero to three octal digits)
6648 the eight-bit character whose value is the hexadecimal value \fIHH\fP
6649 (one or two hex digits)
6653 \fBenable\fP [\fB\-adnps\fP] [\fB\-f\fP \fIfilename\fP] [\fIname\fP ...]
6654 Enable and disable builtin shell commands.
6655 Disabling a builtin allows a disk command which has the same name
6656 as a shell builtin to be executed without specifying a full pathname,
6657 even though the shell normally searches for builtins before disk commands.
6658 If \fB\-n\fP is used, each \fIname\fP
6659 is disabled; otherwise,
6660 \fInames\fP are enabled. For example, to use the
6662 binary found via the
6665 instead of the shell builtin version, run
6666 .if t \f(CWenable -n test\fP.
6667 .if n ``enable -n test''.
6670 option means to load the new builtin command
6674 on systems that support dynamic loading. The
6676 option will delete a builtin previously loaded with
6678 If no \fIname\fP arguments are given, or if the
6680 option is supplied, a list of shell builtins is printed.
6681 With no other option arguments, the list consists of all enabled
6683 If \fB\-n\fP is supplied, only disabled builtins are printed.
6684 If \fB\-a\fP is supplied, the list printed includes all builtins, with an
6685 indication of whether or not each is enabled.
6686 If \fB\-s\fP is supplied, the output is restricted to the POSIX
6687 \fIspecial\fP builtins.
6688 The return value is 0 unless a
6690 is not a shell builtin or there is an error loading a new builtin
6691 from a shared object.
6693 \fBeval\fP [\fIarg\fP ...]
6694 The \fIarg\fPs are read and concatenated together into a single
6695 command. This command is then read and executed by the shell, and
6696 its exit status is returned as the value of
6700 or only null arguments,
6704 \fBexec\fP [\fB\-cl\fP] [\fB\-a\fP \fIname\fP] [\fIcommand\fP [\fIarguments\fP]]
6707 is specified, it replaces the shell.
6708 No new process is created. The
6710 become the arguments to \fIcommand\fP.
6714 the shell places a dash at the beginning of the zeroth arg passed to
6722 to be executed with an empty environment. If
6724 is supplied, the shell passes
6726 as the zeroth argument to the executed command. If
6728 cannot be executed for some reason, a non-interactive shell exits,
6729 unless the shell option
6731 is enabled, in which case it returns failure.
6732 An interactive shell returns failure if the file cannot be executed.
6735 is not specified, any redirections take effect in the current shell,
6736 and the return status is 0. If there is a redirection error, the
6739 \fBexit\fP [\fIn\fP]
6740 Cause the shell to exit
6741 with a status of \fIn\fP. If
6743 is omitted, the exit status
6744 is that of the last command executed.
6748 is executed before the shell terminates.
6750 \fBexport\fP [\fB\-fn\fP\^] [\fIname\fP[=\fIword\fP]] ...
6757 are marked for automatic export to the environment of
6758 subsequently executed commands. If the
6766 are given, or if the
6768 option is supplied, a list
6769 of all names that are exported in this shell is printed.
6772 option causes the export property to be removed from each
6774 If a variable name is followed by =\fIword\fP, the value of
6775 the variable is set to \fIword\fP.
6777 returns an exit status of 0 unless an invalid option is
6779 one of the \fInames\fP is not a valid shell variable name, or
6783 that is not a function.
6785 \fBfc\fP [\fB\-e\fP \fIename\fP] [\fB\-nlr\fP] [\fIfirst\fP] [\fIlast\fP]
6788 \fBfc\fP \fB\-s\fP [\fIpat\fP=\fIrep\fP] [\fIcmd\fP]
6790 Fix Command. In the first form, a range of commands from
6794 is selected from the history list.
6798 may be specified as a string (to locate the last command beginning
6799 with that string) or as a number (an index into the history list,
6800 where a negative number is used as an offset from the current
6803 is not specified it is set to
6804 the current command for listing (so that
6805 .if n ``fc \-l \-10''
6806 .if t \f(CWfc \-l \-10\fP
6807 prints the last 10 commands) and to
6812 is not specified it is set to the previous
6813 command for editing and \-16 for listing.
6818 the command numbers when listing. The
6820 option reverses the order of
6821 the commands. If the
6824 the commands are listed on
6825 standard output. Otherwise, the editor given by
6828 on a file containing those commands. If
6834 variable is used, and
6841 is not set. If neither variable is set,
6843 is used. When editing is complete, the edited commands are
6844 echoed and executed.
6846 In the second form, \fIcommand\fP is re-executed after each instance
6847 of \fIpat\fP is replaced by \fIrep\fP.
6848 A useful alias to use with this is
6849 .if n ``r="fc -s"'',
6850 .if t \f(CWr='fc \-s'\fP,
6854 runs the last command beginning with
6860 re-executes the last command.
6862 If the first form is used, the return value is 0 unless an invalid
6863 option is encountered or
6867 specify history lines out of range.
6870 option is supplied, the return value is the value of the last
6871 command executed or failure if an error occurs with the temporary
6872 file of commands. If the second form is used, the return status
6873 is that of the command re-executed, unless
6875 does not specify a valid history line, in which case
6879 \fBfg\fP [\fIjobspec\fP]
6882 in the foreground, and make it the current job.
6885 is not present, the shell's notion of the \fIcurrent job\fP is used.
6886 The return value is that of the command placed into the foreground,
6887 or failure if run when job control is disabled or, when run with
6888 job control enabled, if
6890 does not specify a valid job or
6892 specifies a job that was started without job control.
6894 \fBgetopts\fP \fIoptstring\fP \fIname\fP [\fIargs\fP]
6896 is used by shell procedures to parse positional parameters.
6898 contains the option characters to be recognized; if a character
6899 is followed by a colon, the option is expected to have an
6900 argument, which should be separated from it by white space.
6901 The colon and question mark characters may not be used as
6903 Each time it is invoked,
6905 places the next option in the shell variable
6909 if it does not exist,
6910 and the index of the next argument to be processed into the
6916 is initialized to 1 each time the shell or a shell script
6917 is invoked. When an option requires an argument,
6919 places that argument into the variable
6922 The shell does not reset
6925 automatically; it must be manually reset between multiple
6928 within the same shell invocation if a new set of parameters
6931 When the end of options is encountered, \fBgetopts\fP exits with a
6932 return value greater than zero.
6933 \fBOPTIND\fP is set to the index of the first non-option argument,
6934 and \fBname\fP is set to ?.
6937 normally parses the positional parameters, but if more arguments are
6941 parses those instead.
6944 can report errors in two ways. If the first character of
6948 error reporting is used. In normal operation diagnostic messages
6949 are printed when invalid options or missing option arguments are
6954 is set to 0, no error messages will be displayed, even if the first
6959 If an invalid option is seen,
6964 prints an error message and unsets
6970 the option character found is placed in
6973 and no diagnostic message is printed.
6975 If a required argument is not found, and
6978 a question mark (\^\fB?\fP\^) is placed in
6982 is unset, and a diagnostic message is printed.
6985 is silent, then a colon (\^\fB:\fP\^) is placed in
6990 is set to the option character found.
6993 returns true if an option, specified or unspecified, is found.
6994 It returns false if the end of options is encountered or an
6997 \fBhash\fP [\fB\-lr\fP] [\fB\-p\fP \fIfilename\fP] [\fB\-dt\fP] [\fIname\fP]
7000 the full file name of the command is determined by searching
7006 option is supplied, no path search is performed, and
7008 is used as the full file name of the command.
7011 option causes the shell to forget all
7012 remembered locations.
7015 option causes the shell to forget the remembered location of each \fIname\fP.
7018 option is supplied, the full pathname to which each \fIname\fP corresponds
7019 is printed. If multiple \fIname\fP arguments are supplied with \fB\-t\fP,
7020 the \fIname\fP is printed before the hashed full pathname.
7023 option causes output to be displayed in a format that may be reused as input.
7024 If no arguments are given, or if only \fB\-l\fP is supplied,
7025 information about remembered commands is printed.
7026 The return status is true unless a
7028 is not found or an invalid option is supplied.
7030 \fBhelp\fP [\fB\-s\fP] [\fIpattern\fP]
7031 Display helpful information about builtin commands. If
7035 gives detailed help on all commands matching
7037 otherwise help for all the builtins and shell control structures
7039 The \fB\-s\fP option restricts the information displayed to a short
7041 The return status is 0 unless no command matches
7044 \fBhistory [\fIn\fP]
7047 \fBhistory\fP \fB\-c\fP
7049 \fBhistory \-d\fP \fIoffset\fP
7051 \fBhistory\fP \fB\-anrw\fP [\fIfilename\fP]
7053 \fBhistory\fP \fB\-p\fP \fIarg\fP [\fIarg ...\fP]
7055 \fBhistory\fP \fB\-s\fP \fIarg\fP [\fIarg ...\fP]
7057 With no options, display the command
7058 history list with line numbers. Lines listed
7061 have been modified. An argument of
7066 If the shell variable \fBHISTTIMEFORMAT\fP is set and not null,
7067 it is used as a format string for \fIstrftime\fP(3) to display
7068 the time stamp associated with each displayed history entry.
7069 No intervening blank is printed between the formatted time stamp
7070 and the history line.
7071 If \fIfilename\fP is supplied, it is used as the
7072 name of the history file; if not, the value of
7075 is used. Options, if supplied, have the following meanings:
7080 Clear the history list by deleting all the entries.
7082 \fB\-d\fP \fIoffset\fP
7083 Delete the history entry at position \fIoffset\fP.
7086 Append the ``new'' history lines (history lines entered since the
7087 beginning of the current \fBbash\fP session) to the history file.
7090 Read the history lines not already read from the history
7091 file into the current history list. These are lines
7092 appended to the history file since the beginning of the
7093 current \fBbash\fP session.
7096 Read the contents of the history file
7097 and use them as the current history.
7100 Write the current history to the history file, overwriting the
7101 history file's contents.
7104 Perform history substitution on the following \fIargs\fP and display
7105 the result on the standard output.
7106 Does not store the results in the history list.
7107 Each \fIarg\fP must be quoted to disable normal history expansion.
7112 in the history list as a single entry. The last command in the
7113 history list is removed before the
7118 If the \fBHISTTIMEFORMAT\fP is set, the time stamp information
7119 associated with each history entry is written to the history file.
7120 The return value is 0 unless an invalid option is encountered, an
7121 error occurs while reading or writing the history file, an invalid
7122 \fIoffset\fP is supplied as an argument to \fB\-d\fP, or the
7123 history expansion supplied as an argument to \fB\-p\fP fails.
7126 \fBjobs\fP [\fB\-lnprs\fP] [ \fIjobspec\fP ... ]
7129 \fBjobs\fP \fB\-x\fP \fIcommand\fP [ \fIargs\fP ... ]
7131 The first form lists the active jobs. The options have the following
7138 in addition to the normal information.
7141 List only the process ID of the job's process group
7145 Display information only about jobs that have changed status since
7146 the user was last notified of their status.
7149 Restrict output to running jobs.
7152 Restrict output to stopped jobs.
7157 is given, output is restricted to information about that job.
7158 The return status is 0 unless an invalid option is encountered
7173 with the corresponding process group ID, and executes
7177 returning its exit status.
7180 \fBkill\fP [\fB\-s\fP \fIsigspec\fP | \fB\-n\fP \fIsignum\fP | \fB\-\fP\fIsigspec\fP] [\fIpid\fP | \fIjobspec\fP] ...
7183 \fBkill\fP \fB\-l\fP [\fIsigspec\fP | \fIexit_status\fP]
7185 Send the signal named by
7189 to the processes named by
7194 is either a case-insensitive signal name such as
7197 (with or without the
7200 prefix) or a signal number;
7205 is not present, then
7211 lists the signal names.
7212 If any arguments are supplied when
7214 is given, the names of the signals corresponding to the arguments are
7215 listed, and the return status is 0.
7216 The \fIexit_status\fP argument to
7218 is a number specifying either a signal number or the exit status of
7219 a process terminated by a signal.
7221 returns true if at least one signal was successfully sent, or false
7222 if an error occurs or an invalid option is encountered.
7224 \fBlet\fP \fIarg\fP [\fIarg\fP ...]
7227 is an arithmetic expression to be evaluated (see
7229 .BR "ARITHMETIC EVALUATION" ).
7234 returns 1; 0 is returned otherwise.
7236 \fBlocal\fP [\fIoption\fP] [\fIname\fP[=\fIvalue\fP] ...]
7237 For each argument, a local variable named
7239 is created, and assigned
7241 The \fIoption\fP can be any of the options accepted by \fBdeclare\fP.
7244 is used within a function, it causes the variable
7246 to have a visible scope restricted to that function and its children.
7249 writes a list of local variables to the standard output. It is
7252 when not within a function. The return status is 0 unless
7254 is used outside a function, an invalid
7257 \fIname\fP is a readonly variable.
7262 \fBpopd\fP [\-\fBn\fP] [+\fIn\fP] [\-\fIn\fP]
7263 Removes entries from the directory stack. With no arguments,
7264 removes the top directory from the stack, and performs a
7266 to the new top directory.
7267 Arguments, if supplied, have the following meanings:
7272 Removes the \fIn\fPth entry counting from the left of the list
7275 starting with zero. For example:
7277 .if t \f(CWpopd +0\fP
7278 removes the first directory,
7280 .if t \f(CWpopd +1\fP
7284 Removes the \fIn\fPth entry counting from the right of the list
7287 starting with zero. For example:
7289 .if t \f(CWpopd -0\fP
7290 removes the last directory,
7292 .if t \f(CWpopd -1\fP
7296 Suppresses the normal change of directory when removing directories
7297 from the stack, so that only the stack is manipulated.
7302 command is successful, a
7304 is performed as well, and the return status is 0.
7306 returns false if an invalid option is encountered, the directory stack
7307 is empty, a non-existent directory stack entry is specified, or the
7308 directory change fails.
7311 \fBprintf\fP [\fB\-v\fP \fIvar\fP] \fIformat\fP [\fIarguments\fP]
7312 Write the formatted \fIarguments\fP to the standard output under the
7313 control of the \fIformat\fP.
7314 The \fIformat\fP is a character string which contains three types of objects:
7315 plain characters, which are simply copied to standard output, character
7316 escape sequences, which are converted and copied to the standard output, and
7317 format specifications, each of which causes printing of the next successive
7319 In addition to the standard \fIprintf\fP(1) formats, \fB%b\fP causes
7320 \fBprintf\fP to expand backslash escape sequences in the corresponding
7321 \fIargument\fP (except that \fB\ec\fP terminates output, backslashes in
7322 \fB\e\(aq\fP, \fB\e"\fP, and \fB\e?\fP are not removed, and octal escapes
7323 beginning with \fB\e0\fP may contain up to four digits),
7324 and \fB%q\fP causes \fBprintf\fP to output the corresponding
7325 \fIargument\fP in a format that can be reused as shell input.
7327 The \fB\-v\fP option causes the output to be assigned to the variable
7328 \fIvar\fP rather than being printed to the standard output.
7330 The \fIformat\fP is reused as necessary to consume all of the \fIarguments\fP.
7331 If the \fIformat\fP requires more \fIarguments\fP than are supplied, the
7332 extra format specifications behave as if a zero value or null string, as
7333 appropriate, had been supplied. The return value is zero on success,
7334 non-zero on failure.
7336 \fBpushd\fP [\fB\-n\fP] [\fIdir\fP]
7339 \fBpushd\fP [\fB\-n\fP] [+\fIn\fP] [\-\fIn\fP]
7341 Adds a directory to the top of the directory stack, or rotates
7342 the stack, making the new top of the stack the current working
7343 directory. With no arguments, exchanges the top two directories
7344 and returns 0, unless the directory stack is empty.
7345 Arguments, if supplied, have the following meanings:
7350 Rotates the stack so that the \fIn\fPth directory
7351 (counting from the left of the list shown by
7357 Rotates the stack so that the \fIn\fPth directory
7358 (counting from the right of the list shown by
7360 starting with zero) is at the top.
7363 Suppresses the normal change of directory when adding directories
7364 to the stack, so that only the stack is manipulated.
7369 to the directory stack at the top, making it the
7370 new current working directory.
7375 command is successful, a
7377 is performed as well.
7378 If the first form is used,
7380 returns 0 unless the cd to
7382 fails. With the second form,
7384 returns 0 unless the directory stack is empty,
7385 a non-existent directory stack element is specified,
7386 or the directory change to the specified new current directory
7390 \fBpwd\fP [\fB\-LP\fP]
7391 Print the absolute pathname of the current working directory.
7392 The pathname printed contains no symbolic links if the
7394 option is supplied or the
7398 builtin command is enabled.
7401 option is used, the pathname printed may contain symbolic links.
7402 The return status is 0 unless an error occurs while
7403 reading the name of the current directory or an
7404 invalid option is supplied.
7406 \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 ...]
7407 One line is read from the standard input, or from the file descriptor
7408 \fIfd\fP supplied as an argument to the \fB\-u\fP option, and the first word
7409 is assigned to the first
7411 the second word to the second
7413 and so on, with leftover words and their intervening separators assigned
7416 If there are fewer words read from the input stream than names,
7417 the remaining names are assigned empty values.
7421 are used to split the line into words.
7422 The backslash character (\fB\e\fP) may be used to remove any special
7423 meaning for the next character read and for line continuation.
7424 Options, if supplied, have the following meanings:
7429 The words are assigned to sequential indices
7430 of the array variable
7434 is unset before any new values are assigned.
7435 Other \fIname\fP arguments are ignored.
7438 The first character of \fIdelim\fP is used to terminate the input line,
7439 rather than newline.
7442 If the standard input
7443 is coming from a terminal,
7448 above) is used to obtain the line.
7451 \fBread\fP returns after reading \fInchars\fP characters rather than
7452 waiting for a complete line of input.
7455 Display \fIprompt\fP on standard error, without a
7456 trailing newline, before attempting to read any input. The prompt
7457 is displayed only if input is coming from a terminal.
7460 Backslash does not act as an escape character.
7461 The backslash is considered to be part of the line.
7462 In particular, a backslash-newline pair may not be used as a line
7466 Silent mode. If input is coming from a terminal, characters are
7469 .B \-t \fItimeout\fP
7470 Cause \fBread\fP to time out and return failure if a complete line of
7471 input is not read within \fItimeout\fP seconds.
7472 This option has no effect if \fBread\fP is not reading input from the
7476 Read input from file descriptor \fIfd\fP.
7481 are supplied, the line read is assigned to the variable
7484 The return code is zero, unless end-of-file is encountered, \fBread\fP
7485 times out, or an invalid file descriptor is supplied as the argument to
7489 \fBreadonly\fP [\fB\-apf\fP] [\fIname\fP[=\fIword\fP] ...]
7492 \fInames\fP are marked readonly; the values of these
7494 may not be changed by subsequent assignment.
7497 option is supplied, the functions corresponding to the
7502 option restricts the variables to arrays.
7505 arguments are given, or if the
7507 option is supplied, a list of all readonly names is printed.
7510 option causes output to be displayed in a format that
7511 may be reused as input.
7512 If a variable name is followed by =\fIword\fP, the value of
7513 the variable is set to \fIword\fP.
7514 The return status is 0 unless an invalid option is encountered,
7517 is not a valid shell variable name, or
7521 that is not a function.
7523 \fBreturn\fP [\fIn\fP]
7524 Causes a function to exit with the return value specified by
7528 is omitted, the return status is that of the last command
7529 executed in the function body. If used outside a function,
7530 but during execution of a script by the
7532 (\fBsource\fP) command, it causes the shell to stop executing
7533 that script and return either
7535 or the exit status of the last command executed within the
7536 script as the exit status of the script. If used outside a
7537 function and not during execution of a script by \fB.\fP\^,
7538 the return status is false.
7539 Any command associated with the \fBRETURN\fP trap is executed
7540 before execution resumes after the function or script.
7542 \fBset\fP [\fB\-\-abefhkmnptuvxBCHP\fP] [\fB\-o\fP \fIoption\fP] [\fIarg\fP ...]
7543 Without options, the name and value of each shell variable are displayed
7544 in a format that can be reused as input
7545 for setting or resetting the currently-set variables.
7546 Read-only variables cannot be reset.
7547 In \fIposix mode\fP, only shell variables are listed.
7548 The output is sorted according to the current locale.
7549 When options are specified, they set or unset shell attributes.
7550 Any arguments remaining after the options are processed are treated
7551 as values for the positional parameters and are assigned, in order, to
7556 Options, if specified, have the following meanings:
7561 Automatically mark variables and functions which are modified or
7562 created for export to the environment of subsequent commands.
7565 Report the status of terminated background jobs
7566 immediately, rather than before the next primary prompt. This is
7567 effective only when job control is enabled.
7570 Exit immediately if a \fIsimple command\fP (see
7573 above) exits with a non-zero status.
7574 The shell does not exit if the
7575 command that fails is part of the command list immediately following a
7580 part of the test in an
7582 statement, part of a
7586 list, or if the command's return value is
7589 A trap on \fBERR\fP, if set, is executed before the shell exits.
7592 Disable pathname expansion.
7595 Remember the location of commands as they are looked up for execution.
7596 This is enabled by default.
7599 All arguments in the form of assignment statements
7600 are placed in the environment for a command, not just
7601 those that precede the command name.
7604 Monitor mode. Job control is enabled. This option is on
7605 by default for interactive shells on systems that support
7609 above). Background processes run in a separate process
7610 group and a line containing their exit status is printed
7611 upon their completion.
7614 Read commands but do not execute them. This may be used to
7615 check a shell script for syntax errors. This is ignored by
7618 .B \-o \fIoption\-name\fP
7619 The \fIoption\-name\fP can be one of the following:
7631 Use an emacs-style command line editing interface. This is enabled
7632 by default when the shell is interactive, unless the shell is started
7658 Enable command history, as described above under
7661 This option is on by default in interactive shells.
7664 The effect is as if the shell command
7665 .if t \f(CWIGNOREEOF=10\fP
7666 .if n ``IGNOREEOF=10''
7711 If set, the return value of a pipeline is the value of the last
7712 (rightmost) command to exit with a non-zero status, or zero if all
7713 commands in the pipeline exit successfully.
7714 This option is disabled by default.
7717 Change the behavior of
7719 where the default operation differs
7720 from the POSIX standard to match the standard (\fIposix mode\fP).
7731 Use a vi-style command line editing interface.
7740 is supplied with no \fIoption\-name\fP, the values of the current options are
7744 is supplied with no \fIoption\-name\fP, a series of
7746 commands to recreate the current option settings is displayed on
7747 the standard output.
7753 mode. In this mode, the
7759 files are not processed, shell functions are not inherited from the
7760 environment, and the
7763 variable, if it appears in the environment, is ignored.
7764 If the shell is started with the effective user (group) id not equal to the
7765 real user (group) id, and the \fB\-p\fP option is not supplied, these actions
7766 are taken and the effective user id is set to the real user id.
7767 If the \fB\-p\fP option is supplied at startup, the effective user id is
7769 Turning this option off causes the effective user
7770 and group ids to be set to the real user and group ids.
7773 Exit after reading and executing one command.
7776 Treat unset variables as an error when performing
7777 parameter expansion. If expansion is attempted on an
7778 unset variable, the shell prints an error message, and,
7779 if not interactive, exits with a non-zero status.
7782 Print shell input lines as they are read.
7785 After expanding each \fIsimple command\fP,
7786 \fBfor\fP command, \fBcase\fP command, \fBselect\fP command, or
7787 arithmetic \fBfor\fP command, display the expanded value of
7790 followed by the command and its expanded arguments
7791 or associated word list.
7794 The shell performs brace expansion (see
7796 above). This is on by default.
7801 does not overwrite an existing file with the
7806 redirection operators. This may be overridden when
7807 creating output files by using the redirection operator
7813 If set, any trap on \fBERR\fP is inherited by shell functions, command
7814 substitutions, and commands executed in a subshell environment.
7815 The \fBERR\fP trap is normally not inherited in such cases.
7820 style history substitution. This option is on by
7821 default when the shell is interactive.
7824 If set, the shell does not follow symbolic links when executing
7827 that change the current working directory. It uses the
7828 physical directory structure instead. By default,
7830 follows the logical chain of directories when performing commands
7831 which change the current directory.
7834 If set, any traps on \fBDEBUG\fP and \fBRETURN\fP are inherited by shell
7835 functions, command substitutions, and commands executed in a
7836 subshell environment.
7837 The \fBDEBUG\fP and \fBRETURN\fP traps are normally not inherited
7841 If no arguments follow this option, then the positional parameters are
7842 unset. Otherwise, the positional parameters are set to the
7843 \fIarg\fPs, even if some of them begin with a
7847 Signal the end of options, cause all remaining \fIarg\fPs to be
7848 assigned to the positional parameters. The
7852 options are turned off.
7853 If there are no \fIarg\fPs,
7854 the positional parameters remain unchanged.
7857 The options are off by default unless otherwise noted.
7858 Using + rather than \- causes these options to be turned off.
7859 The options can also be specified as arguments to an invocation of
7861 The current set of options may be found in
7863 The return status is always true unless an invalid option is encountered.
7866 \fBshift\fP [\fIn\fP]
7867 The positional parameters from \fIn\fP+1 ... are renamed to
7870 Parameters represented by the numbers \fB$#\fP
7871 down to \fB$#\fP\-\fIn\fP+1 are unset.
7873 must be a non-negative number less than or equal to \fB$#\fP.
7876 is 0, no parameters are changed.
7879 is not given, it is assumed to be 1.
7882 is greater than \fB$#\fP, the positional parameters are not changed.
7883 The return status is greater than zero if
7887 or less than zero; otherwise 0.
7889 \fBshopt\fP [\fB\-pqsu\fP] [\fB\-o\fP] [\fIoptname\fP ...]
7890 Toggle the values of variables controlling optional shell behavior.
7891 With no options, or with the
7893 option, a list of all settable options is displayed, with
7894 an indication of whether or not each is set.
7895 The \fB\-p\fP option causes output to be displayed in a form that
7896 may be reused as input.
7897 Other options have the following meanings:
7902 Enable (set) each \fIoptname\fP.
7905 Disable (unset) each \fIoptname\fP.
7908 Suppresses normal output (quiet mode); the return status indicates
7909 whether the \fIoptname\fP is set or unset.
7910 If multiple \fIoptname\fP arguments are given with
7912 the return status is zero if all \fIoptnames\fP are enabled; non-zero
7916 Restricts the values of \fIoptname\fP to be those defined for the
7927 is used with no \fIoptname\fP arguments, the display is limited to
7928 those options which are set or unset, respectively.
7929 Unless otherwise noted, the \fBshopt\fP options are disabled (unset)
7932 The return status when listing options is zero if all \fIoptnames\fP
7933 are enabled, non-zero otherwise. When setting or unsetting options,
7934 the return status is zero unless an \fIoptname\fP is not a valid shell
7937 The list of \fBshopt\fP options is:
7943 If set, an argument to the
7945 builtin command that
7946 is not a directory is assumed to be the name of a variable whose
7947 value is the directory to change to.
7950 If set, minor errors in the spelling of a directory component in a
7952 command will be corrected.
7953 The errors checked for are transposed characters,
7954 a missing character, and one character too many.
7955 If a correction is found, the corrected file name is printed,
7956 and the command proceeds.
7957 This option is only used by interactive shells.
7960 If set, \fBbash\fP checks that a command found in the hash
7961 table exists before trying to execute it. If a hashed command no
7962 longer exists, a normal path search is performed.
7965 If set, \fBbash\fP checks the window size after each command
7966 and, if necessary, updates the values of
7976 attempts to save all lines of a multiple-line
7977 command in the same history entry. This allows
7978 easy re-editing of multi-line commands.
7983 includes filenames beginning with a `.' in the results of pathname
7987 If set, a non-interactive shell will not exit if
7988 it cannot execute the file specified as an argument to the
7990 builtin command. An interactive shell does not exit if
7995 If set, aliases are expanded as described above under
7998 This option is enabled by default for interactive shells.
8001 If set, behavior intended for use by debuggers is enabled:
8005 The \fB\-F\fP option to the \fBdeclare\fP builtin displays the source
8006 file name and line number corresponding to each function name supplied
8010 If the command run by the \fBDEBUG\fP trap returns a non-zero value, the
8011 next command is skipped and not executed.
8014 If the command run by the \fBDEBUG\fP trap returns a value of 2, and the
8015 shell is executing in a subroutine (a shell function or a shell script
8016 executed by the \fB.\fP or \fBsource\fP builtins), a call to
8017 \fBreturn\fP is simulated.
8020 \fBBASH_ARGC\fP and \fBBASH_ARGV\fP are updated as described in their
8024 Function tracing is enabled: command substitution, shell functions, and
8025 subshells invoked with \fB(\fP \fIcommand\fP \fB)\fP inherit the
8026 \fBDEBUG\fP and \fBRETURN\fP traps.
8029 Error tracing is enabled: command substitution, shell functions, and
8030 subshells invoked with \fB(\fP \fIcommand\fP \fB)\fP inherit the
8035 If set, the extended pattern matching features described above under
8036 \fBPathname Expansion\fP are enabled.
8039 If set, \fB$\fP\(aq\fIstring\fP\(aq and \fB$\fP"\fIstring\fP" quoting is
8040 performed within \fB${\fP\fIparameter\fP\fB}\fP expansions
8041 enclosed in double quotes. This option is enabled by default.
8044 If set, patterns which fail to match filenames during pathname expansion
8045 result in an expansion error.
8048 If set, the suffixes specified by the \fBFIGNORE\fP shell variable
8049 cause words to be ignored when performing word completion even if
8050 the ignored words are the only possible completions.
8053 \fBSHELL VARIABLES\fP
8054 above for a description of \fBFIGNORE\fP.
8055 This option is enabled by default.
8058 If set, shell error messages are written in the standard GNU error
8062 If set, the history list is appended to the file named by the value
8065 variable when the shell exits, rather than overwriting the file.
8070 is being used, a user is given the opportunity to re-edit a
8071 failed history substitution.
8076 is being used, the results of history substitution are not immediately
8077 passed to the shell parser. Instead, the resulting line is loaded into
8078 the \fBreadline\fP editing buffer, allowing further modification.
8083 is being used, \fBbash\fP will attempt to perform hostname completion when a
8084 word containing a \fB@\fP is being completed (see
8090 This is enabled by default.
8093 If set, \fBbash\fP will send
8096 to all jobs when an interactive login shell exits.
8098 .B interactive_comments
8099 If set, allow a word beginning with
8101 to cause that word and all remaining characters on that
8102 line to be ignored in an interactive shell (see
8105 above). This option is enabled by default.
8110 option is enabled, multi-line commands are saved to the history with
8111 embedded newlines rather than using semicolon separators where possible.
8114 The shell sets this option if it is started as a login shell (see
8118 The value may not be changed.
8121 If set, and a file that \fBbash\fP is checking for mail has been
8122 accessed since the last time it was checked, the message ``The mail in
8123 \fImailfile\fP has been read'' is displayed.
8125 .B no_empty_cmd_completion
8130 will not attempt to search the \fBPATH\fP for possible completions when
8131 completion is attempted on an empty line.
8136 matches filenames in a case\-insensitive fashion when performing pathname
8138 .B Pathname Expansion
8144 matches patterns in a case\-insensitive fashion when performing matching
8145 while executing \fBcase\fP or \fB[[\fP conditional commands.
8150 allows patterns which match no
8152 .B Pathname Expansion
8154 to expand to a null string, rather than themselves.
8157 If set, the programmable completion facilities (see
8158 \fBProgrammable Completion\fP above) are enabled.
8159 This option is enabled by default.
8162 If set, prompt strings undergo
8163 parameter expansion, command substitution, arithmetic
8164 expansion, and quote removal after being expanded as described in
8167 above. This option is enabled by default.
8170 The shell sets this option if it is started in restricted mode (see
8172 .B "RESTRICTED SHELL"
8174 The value may not be changed.
8175 This is not reset when the startup files are executed, allowing
8176 the startup files to discover whether or not a shell is restricted.
8181 builtin prints an error message when the shift count exceeds the
8182 number of positional parameters.
8186 \fBsource\fP (\fB.\fP) builtin uses the value of
8189 to find the directory containing the file supplied as an argument.
8190 This option is enabled by default.
8193 If set, the \fBecho\fP builtin expands backslash-escape sequences
8197 \fBsuspend\fP [\fB\-f\fP]
8198 Suspend the execution of this shell until it receives a
8203 option says not to complain if this is
8204 a login shell; just suspend anyway. The return status is 0 unless
8205 the shell is a login shell and
8207 is not supplied, or if job control is not enabled.
8209 \fBtest\fP \fIexpr\fP
8212 \fB[\fP \fIexpr\fP \fB]\fP
8213 Return a status of 0 or 1 depending on
8214 the evaluation of the conditional expression
8216 Each operator and operand must be a separate argument.
8217 Expressions are composed of the primaries described above under
8219 .BR "CONDITIONAL EXPRESSIONS" .
8220 \fBtest\fP does not accept any options, nor does it accept and ignore
8221 an argument of \fB\-\-\fP as signifying the end of options.
8224 Expressions may be combined using the following operators, listed
8225 in decreasing order of precedence.
8235 Returns the value of \fIexpr\fP.
8236 This may be used to override the normal precedence of operators.
8238 \fIexpr1\fP \-\fBa\fP \fIexpr2\fP
8245 \fIexpr1\fP \-\fBo\fP \fIexpr2\fP
8253 \fBtest\fP and \fB[\fP evaluate conditional
8254 expressions using a set of rules based on the number of arguments.
8260 The expression is false.
8263 The expression is true if and only if the argument is not null.
8266 If the first argument is \fB!\fP, the expression is true if and
8267 only if the second argument is null.
8268 If the first argument is one of the unary conditional operators listed above
8271 .BR "CONDITIONAL EXPRESSIONS" ,
8272 the expression is true if the unary test is true.
8273 If the first argument is not a valid unary conditional operator, the expression
8277 If the second argument is one of the binary conditional operators listed above
8280 .BR "CONDITIONAL EXPRESSIONS" ,
8281 the result of the expression is the result of the binary test using
8282 the first and third arguments as operands.
8283 If the first argument is \fB!\fP, the value is the negation of
8284 the two-argument test using the second and third arguments.
8285 If the first argument is exactly \fB(\fP and the third argument is
8286 exactly \fB)\fP, the result is the one-argument test of the second
8288 Otherwise, the expression is false.
8289 The \fB\-a\fP and \fB\-o\fP operators are considered binary operators
8293 If the first argument is \fB!\fP, the result is the negation of
8294 the three-argument expression composed of the remaining arguments.
8295 Otherwise, the expression is parsed and evaluated according to
8296 precedence using the rules listed above.
8299 The expression is parsed and evaluated according to precedence
8300 using the rules listed above.
8305 Print the accumulated user and system times for the shell and
8306 for processes run from the shell. The return status is 0.
8308 \fBtrap\fP [\fB\-lp\fP] [[\fIarg\fP] \fIsigspec\fP ...]
8311 is to be read and executed when the shell receives
8316 is absent (and there is a single \fIsigspec\fP) or
8318 each specified signal is
8319 reset to its original disposition (the value it had
8320 upon entrance to the shell).
8323 is the null string the signal specified by each
8325 is ignored by the shell and by the commands it invokes.
8330 has been supplied, then the trap commands associated with each
8333 If no arguments are supplied or if only
8337 prints the list of commands associated with each signal.
8340 option causes the shell to print a list of signal names and
8341 their corresponding numbers.
8345 a signal name defined in <\fIsignal.h\fP>, or a signal number.
8346 Signal names are case insensitive and the SIG prefix is optional.
8354 is executed on exit from the shell.
8362 is executed before every \fIsimple command\fP, \fIfor\fP command,
8363 \fIcase\fP command, \fIselect\fP command, every arithmetic \fIfor\fP
8364 command, and before the first command executes in a shell function (see
8368 Refer to the description of the \fBextdebug\fP option to the
8369 \fBshopt\fP builtin for details of its effect on the \fBDEBUG\fP trap.
8377 is executed whenever a simple command has a non\-zero exit status,
8378 subject to the following conditions.
8382 trap is not executed if the failed
8383 command is part of the command list immediately following a
8388 part of the test in an
8390 statement, part of a
8394 list, or if the command's return value is
8397 These are the same conditions obeyed by the \fBerrexit\fP option.
8405 is executed each time a shell function or a script executed with the
8406 \fB.\fP or \fBsource\fP builtins finishes executing.
8407 Signals ignored upon entry to the shell cannot be trapped or reset.
8408 Trapped signals that are not being ignored are reset to their original
8409 values in a child process when it is created.
8410 The return status is false if any
8412 is invalid; otherwise
8416 \fBtype\fP [\fB\-aftpP\fP] \fIname\fP [\fIname\fP ...]
8420 would be interpreted if used as a command name.
8425 prints a string which is one of
8434 is an alias, shell reserved word, function, builtin, or disk file,
8438 is not found, then nothing is printed, and an exit status of false
8444 either returns the name of the disk file
8445 that would be executed if
8447 were specified as a command name,
8449 .if t \f(CWtype -t name\fP
8450 .if n ``type -t name''
8458 search for each \fIname\fP, even if
8459 .if t \f(CWtype -t name\fP
8460 .if n ``type -t name''
8463 If a command is hashed,
8467 print the hashed value, not necessarily the file that appears
8475 prints all of the places that contain
8478 This includes aliases and functions,
8481 option is not also used.
8482 The table of hashed commands is not consulted
8487 option suppresses shell function lookup, as with the \fBcommand\fP builtin.
8489 returns true if any of the arguments are found, false if
8492 \fBulimit\fP [\fB\-SHacdefilmnpqrstuvx\fP [\fIlimit\fP]]
8493 Provides control over the resources available to the shell and to
8494 processes started by it, on systems that allow such control.
8495 The \fB\-H\fP and \fB\-S\fP options specify that the hard or soft limit is
8496 set for the given resource. A hard limit cannot be increased once it
8497 is set; a soft limit may be increased up to the value of the hard limit.
8498 If neither \fB\-H\fP nor \fB\-S\fP is specified, both the soft and hard
8502 can be a number in the unit specified for the resource
8503 or one of the special values
8508 which stand for the current hard limit, the current soft limit, and
8509 no limit, respectively.
8512 is omitted, the current value of the soft limit of the resource is
8513 printed, unless the \fB\-H\fP option is given. When more than one
8514 resource is specified, the limit name and unit are printed before the value.
8515 Other options are interpreted as follows:
8520 All current limits are reported
8523 The maximum size of core files created
8526 The maximum size of a process's data segment
8529 The maximum scheduling priority ("nice")
8532 The maximum size of files written by the shell and its children
8535 The maximum number of pending signals
8538 The maximum size that may be locked into memory
8541 The maximum resident set size
8544 The maximum number of open file descriptors (most systems do not
8545 allow this value to be set)
8548 The pipe size in 512-byte blocks (this may not be set)
8551 The maximum number of bytes in POSIX message queues
8554 The maximum real-time scheduling priority
8557 The maximum stack size
8560 The maximum amount of cpu time in seconds
8563 The maximum number of processes available to a single user
8566 The maximum amount of virtual memory available to the shell
8569 The maximum number of file locks
8574 is given, it is the new value of the specified resource (the
8576 option is display only).
8577 If no option is given, then
8579 is assumed. Values are in 1024-byte increments, except for
8581 which is in seconds,
8583 which is in units of 512-byte blocks,
8588 which are unscaled values.
8589 The return status is 0 unless an invalid option or argument is supplied,
8590 or an error occurs while setting a new limit.
8593 \fBumask\fP [\fB\-p\fP] [\fB\-S\fP] [\fImode\fP]
8594 The user file-creation mask is set to
8598 begins with a digit, it
8599 is interpreted as an octal number; otherwise
8600 it is interpreted as a symbolic mode mask similar
8605 is omitted, the current value of the mask is printed.
8608 option causes the mask to be printed in symbolic form; the
8609 default output is an octal number.
8612 option is supplied, and
8614 is omitted, the output is in a form that may be reused as input.
8615 The return status is 0 if the mode was successfully changed or if
8616 no \fImode\fP argument was supplied, and false otherwise.
8618 \fBunalias\fP [\-\fBa\fP] [\fIname\fP ...]
8619 Remove each \fIname\fP from the list of defined aliases. If
8621 is supplied, all alias definitions are removed. The return
8622 value is true unless a supplied
8624 is not a defined alias.
8626 \fBunset\fP [\-\fBfv\fP] [\fIname\fP ...]
8629 remove the corresponding variable or function.
8630 If no options are supplied, or the
8632 option is given, each
8634 refers to a shell variable.
8635 Read-only variables may not be unset.
8640 refers to a shell function, and the function definition
8642 Each unset variable or function is removed from the environment
8643 passed to subsequent commands.
8660 are unset, they lose their special properties, even if they are
8661 subsequently reset. The exit status is true unless a
8665 \fBwait\fP [\fIn ...\fP]
8666 Wait for each specified process and return its termination status.
8670 ID or a job specification; if a job spec is given, all processes
8671 in that job's pipeline are waited for. If
8673 is not given, all currently active child processes
8674 are waited for, and the return status is zero. If
8676 specifies a non-existent process or job, the return status is
8677 127. Otherwise, the return status is the exit status of the last
8678 process or job waited for.
8681 .SH "RESTRICTED SHELL"
8687 is started with the name
8691 option is supplied at invocation,
8692 the shell becomes restricted.
8693 A restricted shell is used to
8694 set up an environment more controlled than the standard shell.
8695 It behaves identically to
8697 with the exception that the following are disallowed or not performed:
8699 changing directories with \fBcd\fP
8701 setting or unsetting the values of
8708 specifying command names containing
8711 specifying a file name containing a
8713 as an argument to the
8717 Specifying a filename containing a slash as an argument to the
8723 importing function definitions from the shell environment at startup
8725 parsing the value of \fBSHELLOPTS\fP from the shell environment at startup
8727 redirecting output using the >, >|, <>, >&, &>, and >> redirection operators
8731 builtin command to replace the shell with another command
8733 adding or deleting builtin commands with the
8741 Using the \fBenable\fP builtin command to enable disabled shell builtins
8749 turning off restricted mode with
8750 \fBset +r\fP or \fBset +o restricted\fP.
8752 These restrictions are enforced after any startup files are read.
8754 .ie \n(zY=1 When a command that is found to be a shell script is executed,
8755 .el \{ When a command that is found to be a shell script is executed
8758 .B "COMMAND EXECUTION"
8762 turns off any restrictions in the shell spawned to execute the
8769 \fIBash Reference Manual\fP, Brian Fox and Chet Ramey
8771 \fIThe Gnu Readline Library\fP, Brian Fox and Chet Ramey
8773 \fIThe Gnu History Library\fP, Brian Fox and Chet Ramey
8775 \fIPortable Operating System Interface (POSIX) Part 2: Shell and Utilities\fP, IEEE
8777 \fIsh\fP(1), \fIksh\fP(1), \fIcsh\fP(1)
8779 \fIemacs\fP(1), \fIvi\fP(1)
8787 The \fBbash\fP executable
8790 The systemwide initialization file, executed for login shells
8793 The personal initialization file, executed for login shells
8796 The individual per-interactive-shell startup file
8799 The individual login shell cleanup file, executed when a login shell exits
8802 Individual \fIreadline\fP initialization file
8805 Brian Fox, Free Software Foundation
8809 Chet Ramey, Case Western Reserve University
8813 If you find a bug in
8815 you should report it. But first, you should
8816 make sure that it really is a bug, and that it appears in the latest
8819 The latest version is always available from
8820 \fIftp://ftp.gnu.org/pub/bash/\fP.
8822 Once you have determined that a bug actually exists, use the
8824 command to submit a bug report.
8825 If you have a fix, you are encouraged to mail that as well!
8826 Suggestions and `philosophical' bug reports may be mailed
8827 to \fIbug-bash@gnu.org\fP or posted to the Usenet
8831 ALL bug reports should include:
8835 The version number of \fBbash\fR
8837 The hardware and operating system
8839 The compiler used to compile
8841 A description of the bug behaviour
8843 A short script or `recipe' which exercises the bug
8847 inserts the first three items automatically into the template
8848 it provides for filing a bug report.
8850 Comments and bug reports concerning
8851 this manual page should be directed to
8852 .IR chet@po.cwru.edu .
8855 It's too big and too slow.
8857 There are some subtle differences between
8859 and traditional versions of
8861 mostly because of the
8866 Aliases are confusing in some uses.
8868 Shell builtin commands and functions are not stoppable/restartable.
8870 Compound commands and command sequences of the form `a ; b ; c'
8871 are not handled gracefully when process suspension is attempted.
8872 When a process is stopped, the shell immediately executes the next
8873 command in the sequence.
8874 It suffices to place the sequence of commands between
8875 parentheses to force it into a subshell, which may be stopped as
8878 Commands inside of \fB$(\fP...\fB)\fP command substitution are not
8879 parsed until substitution is attempted. This will delay error
8880 reporting until some time after the command is entered. For example,
8881 unmatched parentheses, even inside shell comments, will result in
8882 error messages while the construct is being read.
8884 Array variables may not (yet) be exported.
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