1 This is bashref.info, produced by makeinfo version 4.0 from
2 /usr/homes/chet/src/bash/src/doc/bashref.texi.
4 INFO-DIR-SECTION Utilities
6 * Bash: (bash). The GNU Bourne-Again SHell.
9 This text is a brief description of the features that are present in
12 This is Edition 2.5a, last updated 13 November 2001,
13 of `The GNU Bash Reference Manual',
14 for `Bash', Version 2.05a.
16 Copyright (C) 1991-2001 Free Software Foundation, Inc.
18 Permission is granted to make and distribute verbatim copies of
19 this manual provided the copyright notice and this permission notice
20 are preserved on all copies.
22 Permission is granted to copy and distribute modified versions of this
23 manual under the conditions for verbatim copying, provided that the entire
24 resulting derived work is distributed under the terms of a permission
25 notice identical to this one.
27 Permission is granted to copy and distribute translations of this manual
28 into another language, under the above conditions for modified versions,
29 except that this permission notice may be stated in a translation approved
30 by the Free Software Foundation.
33 File: bashref.info, Node: Top, Next: Introduction, Prev: (dir), Up: (dir)
38 This text is a brief description of the features that are present in
41 This is Edition 2.5a, last updated 13 November 2001, of `The GNU
42 Bash Reference Manual', for `Bash', Version 2.05a.
44 Copyright (C) 1991, 1993, 1996 Free Software Foundation, Inc.
46 Bash contains features that appear in other popular shells, and some
47 features that only appear in Bash. Some of the shells that Bash has
48 borrowed concepts from are the Bourne Shell (`sh'), the Korn Shell
49 (`ksh'), and the C-shell (`csh' and its successor, `tcsh'). The
50 following menu breaks the features up into categories based upon which
51 one of these other shells inspired the feature.
53 This manual is meant as a brief introduction to features found in
54 Bash. The Bash manual page should be used as the definitive reference
59 * Introduction:: An introduction to the shell.
61 * Definitions:: Some definitions used in the rest of this
64 * Basic Shell Features:: The shell "building blocks".
66 * Shell Builtin Commands:: Commands that are a part of the shell.
68 * Shell Variables:: Variables used or set by Bash.
70 * Bash Features:: Features found only in Bash.
72 * Job Control:: A chapter describing what job control is
73 and how Bash allows you to use it.
75 * Using History Interactively:: Chapter dealing with history expansion
78 * Command Line Editing:: Chapter describing the command line
81 * Installing Bash:: How to build and install Bash on your system.
83 * Reporting Bugs:: How to report bugs in Bash.
85 * Major Differences From The Bourne Shell:: A terse list of the differences
86 between Bash and historical
89 * Builtin Index:: Index of Bash builtin commands.
91 * Reserved Word Index:: Index of Bash reserved words.
93 * Variable Index:: Quick reference helps you find the
96 * Function Index:: Index of bindable Readline functions.
98 * Concept Index:: General index for concepts described in
102 File: bashref.info, Node: Introduction, Next: Definitions, Prev: Top, Up: Top
109 * What is Bash?:: A short description of Bash.
111 * What is a shell?:: A brief introduction to shells.
114 File: bashref.info, Node: What is Bash?, Next: What is a shell?, Up: Introduction
119 Bash is the shell, or command language interpreter, for the GNU
120 operating system. The name is an acronym for the `Bourne-Again SHell',
121 a pun on Stephen Bourne, the author of the direct ancestor of the
122 current Unix shell `/bin/sh', which appeared in the Seventh Edition
123 Bell Labs Research version of Unix.
125 Bash is largely compatible with `sh' and incorporates useful
126 features from the Korn shell `ksh' and the C shell `csh'. It is
127 intended to be a conformant implementation of the IEEE POSIX Shell and
128 Tools specification (IEEE Working Group 1003.2). It offers functional
129 improvements over `sh' for both interactive and programming use.
131 While the GNU operating system provides other shells, including a
132 version of `csh', Bash is the default shell. Like other GNU software,
133 Bash is quite portable. It currently runs on nearly every version of
134 Unix and a few other operating systems - independently-supported ports
135 exist for MS-DOS, OS/2, Windows 95/98, and Windows NT.
138 File: bashref.info, Node: What is a shell?, Prev: What is Bash?, Up: Introduction
143 At its base, a shell is simply a macro processor that executes
144 commands. A Unix shell is both a command interpreter, which provides
145 the user interface to the rich set of GNU utilities, and a programming
146 language, allowing these utilitites to be combined. Files containing
147 commands can be created, and become commands themselves. These new
148 commands have the same status as system commands in directories such as
149 `/bin', allowing users or groups to establish custom environments.
151 A shell allows execution of GNU commands, both synchronously and
152 asynchronously. The shell waits for synchronous commands to complete
153 before accepting more input; asynchronous commands continue to execute
154 in parallel with the shell while it reads and executes additional
155 commands. The "redirection" constructs permit fine-grained control of
156 the input and output of those commands. Moreover, the shell allows
157 control over the contents of commands' environments. Shells may be
158 used interactively or non-interactively: they accept input typed from
159 the keyboard or from a file.
161 Shells also provide a small set of built-in commands ("builtins")
162 implementing functionality impossible or inconvenient to obtain via
163 separate utilities. For example, `cd', `break', `continue', and
164 `exec') cannot be implemented outside of the shell because they
165 directly manipulate the shell itself. The `history', `getopts',
166 `kill', or `pwd' builtins, among others, could be implemented in
167 separate utilities, but they are more convenient to use as builtin
168 commands. All of the shell builtins are described in subsequent
171 While executing commands is essential, most of the power (and
172 complexity) of shells is due to their embedded programming languages.
173 Like any high-level language, the shell provides variables, flow
174 control constructs, quoting, and functions.
176 Shells offer features geared specifically for interactive use rather
177 than to augment the programming language. These interactive features
178 include job control, command line editing, history and aliases. Each
179 of these features is described in this manual.
182 File: bashref.info, Node: Definitions, Next: Basic Shell Features, Prev: Introduction, Up: Top
187 These definitions are used throughout the remainder of this manual.
190 A family of open system standards based on Unix. Bash is
191 concerned with POSIX 1003.2, the Shell and Tools Standard.
194 A space or tab character.
197 A command that is implemented internally by the shell itself,
198 rather than by an executable program somewhere in the file system.
201 A `word' that performs a control function. It is a `newline' or
202 one of the following: `||', `&&', `&', `;', `;;', `|', `(', or `)'.
205 The value returned by a command to its caller. The value is
206 restricted to eight bits, so the maximum value is 255.
209 A unit of text that is the result of one of the shell expansions.
210 After expansion, when executing a command, the resulting fields
211 are used as the command name and arguments.
214 A string of characters used to identify a file.
217 A set of processes comprising a pipeline, and any processes
218 descended from it, that are all in the same process group.
221 A mechanism by which users can selectively stop (suspend) and
222 restart (resume) execution of processes.
225 A character that, when unquoted, separates words. A metacharacter
226 is a `blank' or one of the following characters: `|', `&', `;',
227 `(', `)', `<', or `>'.
230 A `word' consisting solely of letters, numbers, and underscores,
231 and beginning with a letter or underscore. `Name's are used as
232 shell variable and function names. Also referred to as an
236 A `control operator' or a `redirection operator'. *Note
237 Redirections::, for a list of redirection operators.
240 A collection of related processes each having the same process
244 A unique identifer that represents a `process group' during its
248 A `word' that has a special meaning to the shell. Most reserved
249 words introduce shell flow control constructs, such as `for' and
253 A synonym for `exit status'.
256 A mechanism by which a process may be notified by the kernel of an
257 event occurring in the system.
260 A shell builtin command that has been classified as special by the
261 POSIX 1003.2 standard.
264 A sequence of characters considered a single unit by the shell.
265 It is either a `word' or an `operator'.
268 A `token' that is not an `operator'.
271 File: bashref.info, Node: Basic Shell Features, Next: Shell Builtin Commands, Prev: Definitions, Up: Top
276 Bash is an acronym for `Bourne-Again SHell'. The Bourne shell is
277 the traditional Unix shell originally written by Stephen Bourne. All
278 of the Bourne shell builtin commands are available in Bash, and the
279 rules for evaluation and quoting are taken from the POSIX 1003.2
280 specification for the `standard' Unix shell.
282 This chapter briefly summarizes the shell's `building blocks':
283 commands, control structures, shell functions, shell parameters, shell
284 expansions, redirections, which are a way to direct input and output
285 from and to named files, and how the shell executes commands.
289 * Shell Syntax:: What your input means to the shell.
290 * Shell Commands:: The types of commands you can use.
291 * Shell Functions:: Grouping commands by name.
292 * Shell Parameters:: Special shell variables.
293 * Shell Expansions:: How Bash expands variables and the various
294 expansions available.
295 * Redirections:: A way to control where input and output go.
296 * Executing Commands:: What happens when you run a command.
297 * Shell Scripts:: Executing files of shell commands.
300 File: bashref.info, Node: Shell Syntax, Next: Shell Commands, Up: Basic Shell Features
307 * Shell Operation:: The basic operation of the shell.
309 * Quoting:: How to remove the special meaning from characters.
311 * Comments:: How to specify comments.
313 When the shell reads input, it proceeds through a sequence of
314 operations. If the input indicates the beginning of a comment, the
315 shell ignores the comment symbol (`#'), and the rest of that line.
317 Otherwise, roughly speaking, the shell reads its input and divides
318 the input into words and operators, employing the quoting rules to
319 select which meanings to assign various words and characters.
321 The shell then parses these tokens into commands and other
322 constructs, removes the special meaning of certain words or characters,
323 expands others, redirects input and output as needed, executes the
324 specified command, waits for the command's exit status, and makes that
325 exit status available for further inspection or processing.
328 File: bashref.info, Node: Shell Operation, Next: Quoting, Up: Shell Syntax
333 The following is a brief description of the shell's operation when it
334 reads and executes a command. Basically, the shell does the following:
336 1. Reads its input from a file (*note Shell Scripts::), from a string
337 supplied as an argument to the `-c' invocation option (*note
338 Invoking Bash::), or from the user's terminal.
340 2. Breaks the input into words and operators, obeying the quoting
341 rules described in *Note Quoting::. These tokens are separated by
342 `metacharacters'. Alias expansion is performed by this step
345 3. Parses the tokens into simple and compound commands (*note Shell
348 4. Performs the various shell expansions (*note Shell Expansions::),
349 breaking the expanded tokens into lists of filenames (*note
350 Filename Expansion::) and commands and arguments.
352 5. Performs any necessary redirections (*note Redirections::) and
353 removes the redirection operators and their operands from the
356 6. Executes the command (*note Executing Commands::).
358 7. Optionally waits for the command to complete and collects its exit
359 status (*note Exit Status::).
363 File: bashref.info, Node: Quoting, Next: Comments, Prev: Shell Operation, Up: Shell Syntax
370 * Escape Character:: How to remove the special meaning from a single
372 * Single Quotes:: How to inhibit all interpretation of a sequence
374 * Double Quotes:: How to suppress most of the interpretation of a
375 sequence of characters.
376 * ANSI-C Quoting:: How to expand ANSI-C sequences in quoted strings.
378 * Locale Translation:: How to translate strings into different languages.
380 Quoting is used to remove the special meaning of certain characters
381 or words to the shell. Quoting can be used to disable special
382 treatment for special characters, to prevent reserved words from being
383 recognized as such, and to prevent parameter expansion.
385 Each of the shell metacharacters (*note Definitions::) has special
386 meaning to the shell and must be quoted if it is to represent itself.
387 When the command history expansion facilities are being used, the
388 HISTORY EXPANSION character, usually `!', must be quoted to prevent
389 history expansion. *Note Bash History Facilities::, for more details
390 concerning history expansion. There are three quoting mechanisms: the
391 ESCAPE CHARACTER, single quotes, and double quotes.
394 File: bashref.info, Node: Escape Character, Next: Single Quotes, Up: Quoting
399 A non-quoted backslash `\' is the Bash escape character. It
400 preserves the literal value of the next character that follows, with
401 the exception of `newline'. If a `\newline' pair appears, and the
402 backslash itself is not quoted, the `\newline' is treated as a line
403 continuation (that is, it is removed from the input stream and
404 effectively ignored).
407 File: bashref.info, Node: Single Quotes, Next: Double Quotes, Prev: Escape Character, Up: Quoting
412 Enclosing characters in single quotes (`'') preserves the literal
413 value of each character within the quotes. A single quote may not occur
414 between single quotes, even when preceded by a backslash.
417 File: bashref.info, Node: Double Quotes, Next: ANSI-C Quoting, Prev: Single Quotes, Up: Quoting
422 Enclosing characters in double quotes (`"') preserves the literal
423 value of all characters within the quotes, with the exception of `$',
424 ``', and `\'. The characters `$' and ``' retain their special meaning
425 within double quotes (*note Shell Expansions::). The backslash retains
426 its special meaning only when followed by one of the following
427 characters: `$', ``', `"', `\', or `newline'. Within double quotes,
428 backslashes that are followed by one of these characters are removed.
429 Backslashes preceding characters without a special meaning are left
430 unmodified. A double quote may be quoted within double quotes by
431 preceding it with a backslash.
433 The special parameters `*' and `@' have special meaning when in
434 double quotes (*note Shell Parameter Expansion::).
437 File: bashref.info, Node: ANSI-C Quoting, Next: Locale Translation, Prev: Double Quotes, Up: Quoting
442 Words of the form `$'STRING'' are treated specially. The word
443 expands to STRING, with backslash-escaped characters replaced as
444 specified by the ANSI C standard. Backslash escape sequences, if
445 present, are decoded as follows:
454 an escape character (not ANSI C)
478 the eight-bit character whose value is the octal value NNN (one to
482 the eight-bit character whose value is the hexadecimal value HH
483 (one or two hex digits)
485 The expanded result is single-quoted, as if the dollar sign had not
489 File: bashref.info, Node: Locale Translation, Prev: ANSI-C Quoting, Up: Quoting
491 Locale-Specific Translation
492 ...........................
494 A double-quoted string preceded by a dollar sign (`$') will cause
495 the string to be translated according to the current locale. If the
496 current locale is `C' or `POSIX', the dollar sign is ignored. If the
497 string is translated and replaced, the replacement is double-quoted.
499 Some systems use the message catalog selected by the `LC_MESSAGES'
500 shell variable. Others create the name of the message catalog from the
501 value of the `TEXTDOMAIN' shell variable, possibly adding a suffix of
502 `.mo'. If you use the `TEXTDOMAIN' variable, you may need to set the
503 `TEXTDOMAINDIR' variable to the location of the message catalog files.
504 Still others use both variables in this fashion:
505 `TEXTDOMAINDIR'/`LC_MESSAGES'/LC_MESSAGES/`TEXTDOMAIN'.mo.
508 File: bashref.info, Node: Comments, Prev: Quoting, Up: Shell Syntax
513 In a non-interactive shell, or an interactive shell in which the
514 `interactive_comments' option to the `shopt' builtin is enabled (*note
515 Bash Builtins::), a word beginning with `#' causes that word and all
516 remaining characters on that line to be ignored. An interactive shell
517 without the `interactive_comments' option enabled does not allow
518 comments. The `interactive_comments' option is on by default in
519 interactive shells. *Note Interactive Shells::, for a description of
520 what makes a shell interactive.
523 File: bashref.info, Node: Shell Commands, Next: Shell Functions, Prev: Shell Syntax, Up: Basic Shell Features
528 A simple shell command such as `echo a b c' consists of the command
529 itself followed by arguments, separated by spaces.
531 More complex shell commands are composed of simple commands arranged
532 together in a variety of ways: in a pipeline in which the output of one
533 command becomes the input of a second, in a loop or conditional
534 construct, or in some other grouping.
538 * Simple Commands:: The most common type of command.
539 * Pipelines:: Connecting the input and output of several
541 * Lists:: How to execute commands sequentially.
542 * Looping Constructs:: Shell commands for iterative action.
543 * Conditional Constructs:: Shell commands for conditional execution.
544 * Command Grouping:: Ways to group commands.
547 File: bashref.info, Node: Simple Commands, Next: Pipelines, Up: Shell Commands
552 A simple command is the kind of command encountered most often.
553 It's just a sequence of words separated by `blank's, terminated by one
554 of the shell's control operators (*note Definitions::). The first word
555 generally specifies a command to be executed, with the rest of the
556 words being that command's arguments.
558 The return status (*note Exit Status::) of a simple command is its
559 exit status as provided by the POSIX 1003.1 `waitpid' function, or
560 128+N if the command was terminated by signal N.
563 File: bashref.info, Node: Pipelines, Next: Lists, Prev: Simple Commands, Up: Shell Commands
568 A `pipeline' is a sequence of simple commands separated by `|'.
570 The format for a pipeline is
571 [`time' [`-p']] [`!'] COMMAND1 [`|' COMMAND2 ...]
573 The output of each command in the pipeline is connected via a pipe to
574 the input of the next command. That is, each command reads the
575 previous command's output.
577 The reserved word `time' causes timing statistics to be printed for
578 the pipeline once it finishes. The statistics currently consist of
579 elapsed (wall-clock) time and user and system time consumed by the
580 command's execution. The `-p' option changes the output format to that
581 specified by POSIX. The `TIMEFORMAT' variable may be set to a format
582 string that specifies how the timing information should be displayed.
583 *Note Bash Variables::, for a description of the available formats.
584 The use of `time' as a reserved word permits the timing of shell
585 builtins, shell functions, and pipelines. An external `time' command
586 cannot time these easily.
588 If the pipeline is not executed asynchronously (*note Lists::), the
589 shell waits for all commands in the pipeline to complete.
591 Each command in a pipeline is executed in its own subshell (*note
592 Command Execution Environment::). The exit status of a pipeline is the
593 exit status of the last command in the pipeline. If the reserved word
594 `!' precedes the pipeline, the exit status is the logical negation of
595 the exit status of the last command.
598 File: bashref.info, Node: Lists, Next: Looping Constructs, Prev: Pipelines, Up: Shell Commands
603 A `list' is a sequence of one or more pipelines separated by one of
604 the operators `;', `&', `&&', or `||', and optionally terminated by one
605 of `;', `&', or a `newline'.
607 Of these list operators, `&&' and `||' have equal precedence,
608 followed by `;' and `&', which have equal precedence.
610 If a command is terminated by the control operator `&', the shell
611 executes the command asynchronously in a subshell. This is known as
612 executing the command in the BACKGROUND. The shell does not wait for
613 the command to finish, and the return status is 0 (true). When job
614 control is not active (*note Job Control::), the standard input for
615 asynchronous commands, in the absence of any explicit redirections, is
616 redirected from `/dev/null'.
618 Commands separated by a `;' are executed sequentially; the shell
619 waits for each command to terminate in turn. The return status is the
620 exit status of the last command executed.
622 The control operators `&&' and `||' denote AND lists and OR lists,
623 respectively. An AND list has the form
626 COMMAND2 is executed if, and only if, COMMAND1 returns an exit status
629 An OR list has the form
632 COMMAND2 is executed if, and only if, COMMAND1 returns a non-zero exit
635 The return status of AND and OR lists is the exit status of the last
636 command executed in the list.
639 File: bashref.info, Node: Looping Constructs, Next: Conditional Constructs, Prev: Lists, Up: Shell Commands
644 Bash supports the following looping constructs.
646 Note that wherever a `;' appears in the description of a command's
647 syntax, it may be replaced with one or more newlines.
650 The syntax of the `until' command is:
651 until TEST-COMMANDS; do CONSEQUENT-COMMANDS; done
652 Execute CONSEQUENT-COMMANDS as long as TEST-COMMANDS has an exit
653 status which is not zero. The return status is the exit status of
654 the last command executed in CONSEQUENT-COMMANDS, or zero if none
658 The syntax of the `while' command is:
659 while TEST-COMMANDS; do CONSEQUENT-COMMANDS; done
661 Execute CONSEQUENT-COMMANDS as long as TEST-COMMANDS has an exit
662 status of zero. The return status is the exit status of the last
663 command executed in CONSEQUENT-COMMANDS, or zero if none was
667 The syntax of the `for' command is:
669 for NAME [in WORDS ...]; do COMMANDS; done
670 Expand WORDS, and execute COMMANDS once for each member in the
671 resultant list, with NAME bound to the current member. If `in
672 WORDS' is not present, the `for' command executes the COMMANDS
673 once for each positional parameter that is set, as if `in "$@"'
674 had been specified (*note Special Parameters::). The return
675 status is the exit status of the last command that executes. If
676 there are no items in the expansion of WORDS, no commands are
677 executed, and the return status is zero.
679 An alternate form of the `for' command is also supported:
681 for (( EXPR1 ; EXPR2 ; EXPR3 )) ; do COMMANDS ; done
682 First, the arithmetic expression EXPR1 is evaluated according to
683 the rules described below (*note Shell Arithmetic::). The
684 arithmetic expression EXPR2 is then evaluated repeatedly until it
685 evaluates to zero. Each time EXPR2 evaluates to a non-zero value,
686 COMMANDS are executed and the arithmetic expression EXPR3 is
687 evaluated. If any expression is omitted, it behaves as if it
688 evaluates to 1. The return value is the exit status of the last
689 command in LIST that is executed, or false if any of the
690 expressions is invalid.
692 The `break' and `continue' builtins (*note Bourne Shell Builtins::)
693 may be used to control loop execution.
696 File: bashref.info, Node: Conditional Constructs, Next: Command Grouping, Prev: Looping Constructs, Up: Shell Commands
698 Conditional Constructs
699 ----------------------
702 The syntax of the `if' command is:
704 if TEST-COMMANDS; then
706 [elif MORE-TEST-COMMANDS; then
708 [else ALTERNATE-CONSEQUENTS;]
711 The TEST-COMMANDS list is executed, and if its return status is
712 zero, the CONSEQUENT-COMMANDS list is executed. If TEST-COMMANDS
713 returns a non-zero status, each `elif' list is executed in turn,
714 and if its exit status is zero, the corresponding MORE-CONSEQUENTS
715 is executed and the command completes. If `else
716 ALTERNATE-CONSEQUENTS' is present, and the final command in the
717 final `if' or `elif' clause has a non-zero exit status, then
718 ALTERNATE-CONSEQUENTS is executed. The return status is the exit
719 status of the last command executed, or zero if no condition
723 The syntax of the `case' command is:
725 `case WORD in [ [(] PATTERN [| PATTERN]...) COMMAND-LIST ;;]... esac'
727 `case' will selectively execute the COMMAND-LIST corresponding to
728 the first PATTERN that matches WORD. The `|' is used to separate
729 multiple patterns, and the `)' operator terminates a pattern list.
730 A list of patterns and an associated command-list is known as a
731 CLAUSE. Each clause must be terminated with `;;'. The WORD
732 undergoes tilde expansion, parameter expansion, command
733 substitution, arithmetic expansion, and quote removal before
734 matching is attempted. Each PATTERN undergoes tilde expansion,
735 parameter expansion, command substitution, and arithmetic
738 There may be an arbitrary number of `case' clauses, each terminated
739 by a `;;'. The first pattern that matches determines the
740 command-list that is executed.
742 Here is an example using `case' in a script that could be used to
743 describe one interesting feature of an animal:
745 echo -n "Enter the name of an animal: "
747 echo -n "The $ANIMAL has "
749 horse | dog | cat) echo -n "four";;
750 man | kangaroo ) echo -n "two";;
751 *) echo -n "an unknown number of";;
755 The return status is zero if no PATTERN is matched. Otherwise, the
756 return status is the exit status of the COMMAND-LIST executed.
759 The `select' construct allows the easy generation of menus. It
760 has almost the same syntax as the `for' command:
762 select NAME [in WORDS ...]; do COMMANDS; done
764 The list of words following `in' is expanded, generating a list of
765 items. The set of expanded words is printed on the standard error
766 output stream, each preceded by a number. If the `in WORDS' is
767 omitted, the positional parameters are printed, as if `in "$@"'
768 had been specifed. The `PS3' prompt is then displayed and a line
769 is read from the standard input. If the line consists of a number
770 corresponding to one of the displayed words, then the value of
771 NAME is set to that word. If the line is empty, the words and
772 prompt are displayed again. If `EOF' is read, the `select'
773 command completes. Any other value read causes NAME to be set to
774 null. The line read is saved in the variable `REPLY'.
776 The COMMANDS are executed after each selection until a `break'
777 command is executed, at which point the `select' command completes.
779 Here is an example that allows the user to pick a filename from the
780 current directory, and displays the name and index of the file
785 echo you picked $fname \($REPLY\)
792 The arithmetic EXPRESSION is evaluated according to the rules
793 described below (*note Shell Arithmetic::). If the value of the
794 expression is non-zero, the return status is 0; otherwise the
795 return status is 1. This is exactly equivalent to
798 *Note Bash Builtins::, for a full description of the `let' builtin.
803 Return a status of 0 or 1 depending on the evaluation of the
804 conditional expression EXPRESSION. Expressions are composed of
805 the primaries described below in *Note Bash Conditional
806 Expressions::. Word splitting and filename expansion are not
807 performed on the words between the `[[' and `]]'; tilde expansion,
808 parameter and variable expansion, arithmetic expansion, command
809 substitution, process substitution, and quote removal are
812 When the `==' and `!=' operators are used, the string to the right
813 of the operator is considered a pattern and matched according to
814 the rules described below in *Note Pattern Matching::. The return
815 value is 0 if the string matches or does not match the pattern,
816 respectively, and 1 otherwise. Any part of the pattern may be
817 quoted to force it to be matched as a string.
819 Expressions may be combined using the following operators, listed
820 in decreasing order of precedence:
823 Returns the value of EXPRESSION. This may be used to
824 override the normal precedence of operators.
827 True if EXPRESSION is false.
829 `EXPRESSION1 && EXPRESSION2'
830 True if both EXPRESSION1 and EXPRESSION2 are true.
832 `EXPRESSION1 || EXPRESSION2'
833 True if either EXPRESSION1 or EXPRESSION2 is true.
835 The `&&' and `||' commands do not execute EXPRESSION2 if the value
836 of EXPRESSION1 is sufficient to determine the return value of the
837 entire conditional expression.
840 File: bashref.info, Node: Command Grouping, Prev: Conditional Constructs, Up: Shell Commands
845 Bash provides two ways to group a list of commands to be executed as
846 a unit. When commands are grouped, redirections may be applied to the
847 entire command list. For example, the output of all the commands in
848 the list may be redirected to a single stream.
853 Placing a list of commands between parentheses causes a subshell
854 to be created, and each of the commands in LIST to be executed in
855 that subshell. Since the LIST is executed in a subshell, variable
856 assignments do not remain in effect after the subshell completes.
861 Placing a list of commands between curly braces causes the list to
862 be executed in the current shell context. No subshell is created.
863 The semicolon (or newline) following LIST is required.
865 In addition to the creation of a subshell, there is a subtle
866 difference between these two constructs due to historical reasons. The
867 braces are `reserved words', so they must be separated from the LIST by
868 `blank's. The parentheses are `operators', and are recognized as
869 separate tokens by the shell even if they are not separated from the
872 The exit status of both of these constructs is the exit status of
876 File: bashref.info, Node: Shell Functions, Next: Shell Parameters, Prev: Shell Commands, Up: Basic Shell Features
881 Shell functions are a way to group commands for later execution
882 using a single name for the group. They are executed just like a
883 "regular" command. When the name of a shell function is used as a
884 simple command name, the list of commands associated with that function
885 name is executed. Shell functions are executed in the current shell
886 context; no new process is created to interpret them.
888 Functions are declared using this syntax:
889 [ `function' ] NAME () { COMMAND-LIST; }
891 This defines a shell function named NAME. The reserved word
892 `function' is optional. If the `function' reserved word is supplied,
893 the parentheses are optional. The BODY of the function is the
894 COMMAND-LIST between { and }. This list is executed whenever NAME is
895 specified as the name of a command. The exit status of a function is
896 the exit status of the last command executed in the body.
898 Note that for historical reasons, the curly braces that surround the
899 body of the function must be separated from the body by `blank's or
900 newlines. This is because the braces are reserved words and are only
901 recognized as such when they are separated by whitespace. Also, the
902 COMMAND-LIST must be terminated with a semicolon or a newline.
904 When a function is executed, the arguments to the function become
905 the positional parameters during its execution (*note Positional
906 Parameters::). The special parameter `#' that expands to the number of
907 positional parameters is updated to reflect the change. Positional
908 parameter `0' is unchanged. The `FUNCNAME' variable is set to the name
909 of the function while the function is executing.
911 If the builtin command `return' is executed in a function, the
912 function completes and execution resumes with the next command after
913 the function call. When a function completes, the values of the
914 positional parameters and the special parameter `#' are restored to the
915 values they had prior to the function's execution. If a numeric
916 argument is given to `return', that is the function's return status;
917 otherwise the function's return status is the exit status of the last
918 command executed before the `return'.
920 Variables local to the function may be declared with the `local'
921 builtin. These variables are visible only to the function and the
924 Functions may be recursive. No limit is placed on the number of
928 File: bashref.info, Node: Shell Parameters, Next: Shell Expansions, Prev: Shell Functions, Up: Basic Shell Features
935 * Positional Parameters:: The shell's command-line arguments.
936 * Special Parameters:: Parameters with special meanings.
938 A PARAMETER is an entity that stores values. It can be a `name', a
939 number, or one of the special characters listed below. For the shell's
940 purposes, a VARIABLE is a parameter denoted by a `name'. A variable
941 has a VALUE and zero or more ATTRIBUTES. Attributes are assigned using
942 the `declare' builtin command (see the description of the `declare'
943 builtin in *Note Bash Builtins::).
945 A parameter is set if it has been assigned a value. The null string
946 is a valid value. Once a variable is set, it may be unset only by using
947 the `unset' builtin command.
949 A variable may be assigned to by a statement of the form
952 If VALUE is not given, the variable is assigned the null string. All
953 VALUEs undergo tilde expansion, parameter and variable expansion,
954 command substitution, arithmetic expansion, and quote removal (detailed
955 below). If the variable has its `integer' attribute set, then VALUE is
956 subject to arithmetic expansion even if the `$((...))' expansion is not
957 used (*note Arithmetic Expansion::). Word splitting is not performed,
958 with the exception of `"$@"' as explained below. Filename expansion is
959 not performed. Assignment statements may also appear as arguments to
960 the `declare', `typeset', `export', `readonly', and `local' builtin
964 File: bashref.info, Node: Positional Parameters, Next: Special Parameters, Up: Shell Parameters
966 Positional Parameters
967 ---------------------
969 A POSITIONAL PARAMETER is a parameter denoted by one or more digits,
970 other than the single digit `0'. Positional parameters are assigned
971 from the shell's arguments when it is invoked, and may be reassigned
972 using the `set' builtin command. Positional parameter `N' may be
973 referenced as `${N}', or as `$N' when `N' consists of a single digit.
974 Positional parameters may not be assigned to with assignment statements.
975 The `set' and `shift' builtins are used to set and unset them (*note
976 Shell Builtin Commands::). The positional parameters are temporarily
977 replaced when a shell function is executed (*note Shell Functions::).
979 When a positional parameter consisting of more than a single digit
980 is expanded, it must be enclosed in braces.
983 File: bashref.info, Node: Special Parameters, Prev: Positional Parameters, Up: Shell Parameters
988 The shell treats several parameters specially. These parameters may
989 only be referenced; assignment to them is not allowed.
992 Expands to the positional parameters, starting from one. When the
993 expansion occurs within double quotes, it expands to a single word
994 with the value of each parameter separated by the first character
995 of the `IFS' special variable. That is, `"$*"' is equivalent to
996 `"$1C$2C..."', where C is the first character of the value of the
997 `IFS' variable. If `IFS' is unset, the parameters are separated
998 by spaces. If `IFS' is null, the parameters are joined without
999 intervening separators.
1002 Expands to the positional parameters, starting from one. When the
1003 expansion occurs within double quotes, each parameter expands to a
1004 separate word. That is, `"$@"' is equivalent to `"$1" "$2" ...'.
1005 When there are no positional parameters, `"$@"' and `$@' expand to
1006 nothing (i.e., they are removed).
1009 Expands to the number of positional parameters in decimal.
1012 Expands to the exit status of the most recently executed foreground
1016 (A hyphen.) Expands to the current option flags as specified upon
1017 invocation, by the `set' builtin command, or those set by the
1018 shell itself (such as the `-i' option).
1021 Expands to the process ID of the shell. In a `()' subshell, it
1022 expands to the process ID of the invoking shell, not the subshell.
1025 Expands to the process ID of the most recently executed background
1026 (asynchronous) command.
1029 Expands to the name of the shell or shell script. This is set at
1030 shell initialization. If Bash is invoked with a file of commands
1031 (*note Shell Scripts::), `$0' is set to the name of that file. If
1032 Bash is started with the `-c' option (*note Invoking Bash::), then
1033 `$0' is set to the first argument after the string to be executed,
1034 if one is present. Otherwise, it is set to the filename used to
1035 invoke Bash, as given by argument zero.
1038 (An underscore.) At shell startup, set to the absolute filename
1039 of the shell or shell script being executed as passed in the
1040 argument list. Subsequently, expands to the last argument to the
1041 previous command, after expansion. Also set to the full pathname
1042 of each command executed and placed in the environment exported to
1043 that command. When checking mail, this parameter holds the name
1047 File: bashref.info, Node: Shell Expansions, Next: Redirections, Prev: Shell Parameters, Up: Basic Shell Features
1052 Expansion is performed on the command line after it has been split
1053 into `token's. There are seven kinds of expansion performed:
1058 * parameter and variable expansion
1060 * command substitution
1062 * arithmetic expansion
1066 * filename expansion
1070 * Brace Expansion:: Expansion of expressions within braces.
1071 * Tilde Expansion:: Expansion of the ~ character.
1072 * Shell Parameter Expansion:: How Bash expands variables to their values.
1073 * Command Substitution:: Using the output of a command as an argument.
1074 * Arithmetic Expansion:: How to use arithmetic in shell expansions.
1075 * Process Substitution:: A way to write and read to and from a
1077 * Word Splitting:: How the results of expansion are split into separate
1079 * Filename Expansion:: A shorthand for specifying filenames matching patterns.
1080 * Quote Removal:: How and when quote characters are removed from
1083 The order of expansions is: brace expansion, tilde expansion,
1084 parameter, variable, and arithmetic expansion and command substitution
1085 (done in a left-to-right fashion), word splitting, and filename
1088 On systems that can support it, there is an additional expansion
1089 available: PROCESS SUBSTITUTION. This is performed at the same time as
1090 parameter, variable, and arithmetic expansion and command substitution.
1092 Only brace expansion, word splitting, and filename expansion can
1093 change the number of words of the expansion; other expansions expand a
1094 single word to a single word. The only exceptions to this are the
1095 expansions of `"$@"' (*note Special Parameters::) and `"${NAME[@]}"'
1098 After all expansions, `quote removal' (*note Quote Removal::) is
1102 File: bashref.info, Node: Brace Expansion, Next: Tilde Expansion, Up: Shell Expansions
1107 Brace expansion is a mechanism by which arbitrary strings may be
1108 generated. This mechanism is similar to FILENAME EXPANSION (*note
1109 Filename Expansion::), but the file names generated need not exist.
1110 Patterns to be brace expanded take the form of an optional PREAMBLE,
1111 followed by a series of comma-separated strings between a pair of
1112 braces, followed by an optional POSTSCRIPT. The preamble is prefixed
1113 to each string contained within the braces, and the postscript is then
1114 appended to each resulting string, expanding left to right.
1116 Brace expansions may be nested. The results of each expanded string
1117 are not sorted; left to right order is preserved. For example,
1118 bash$ echo a{d,c,b}e
1121 Brace expansion is performed before any other expansions, and any
1122 characters special to other expansions are preserved in the result. It
1123 is strictly textual. Bash does not apply any syntactic interpretation
1124 to the context of the expansion or the text between the braces. To
1125 avoid conflicts with parameter expansion, the string `${' is not
1126 considered eligible for brace expansion.
1128 A correctly-formed brace expansion must contain unquoted opening and
1129 closing braces, and at least one unquoted comma. Any incorrectly
1130 formed brace expansion is left unchanged.
1132 This construct is typically used as shorthand when the common prefix
1133 of the strings to be generated is longer than in the above example:
1134 mkdir /usr/local/src/bash/{old,new,dist,bugs}
1136 chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}
1139 File: bashref.info, Node: Tilde Expansion, Next: Shell Parameter Expansion, Prev: Brace Expansion, Up: Shell Expansions
1144 If a word begins with an unquoted tilde character (`~'), all of the
1145 characters up to the first unquoted slash (or all characters, if there
1146 is no unquoted slash) are considered a TILDE-PREFIX. If none of the
1147 characters in the tilde-prefix are quoted, the characters in the
1148 tilde-prefix following the tilde are treated as a possible LOGIN NAME.
1149 If this login name is the null string, the tilde is replaced with the
1150 value of the `HOME' shell variable. If `HOME' is unset, the home
1151 directory of the user executing the shell is substituted instead.
1152 Otherwise, the tilde-prefix is replaced with the home directory
1153 associated with the specified login name.
1155 If the tilde-prefix is `~+', the value of the shell variable `PWD'
1156 replaces the tilde-prefix. If the tilde-prefix is `~-', the value of
1157 the shell variable `OLDPWD', if it is set, is substituted.
1159 If the characters following the tilde in the tilde-prefix consist of
1160 a number N, optionally prefixed by a `+' or a `-', the tilde-prefix is
1161 replaced with the corresponding element from the directory stack, as it
1162 would be displayed by the `dirs' builtin invoked with the characters
1163 following tilde in the tilde-prefix as an argument (*note The Directory
1164 Stack::). If the tilde-prefix, sans the tilde, consists of a number
1165 without a leading `+' or `-', `+' is assumed.
1167 If the login name is invalid, or the tilde expansion fails, the word
1170 Each variable assignment is checked for unquoted tilde-prefixes
1171 immediately following a `:' or `='. In these cases, tilde expansion is
1172 also performed. Consequently, one may use file names with tildes in
1173 assignments to `PATH', `MAILPATH', and `CDPATH', and the shell assigns
1176 The following table shows how Bash treats unquoted tilde-prefixes:
1179 The value of `$HOME'
1185 The subdirectory `foo' of the home directory of the user `fred'
1191 `${OLDPWD-'~-'}/foo'
1194 The string that would be displayed by `dirs +N'
1197 The string that would be displayed by `dirs +N'
1200 The string that would be displayed by `dirs -N'
1203 File: bashref.info, Node: Shell Parameter Expansion, Next: Command Substitution, Prev: Tilde Expansion, Up: Shell Expansions
1205 Shell Parameter Expansion
1206 -------------------------
1208 The `$' character introduces parameter expansion, command
1209 substitution, or arithmetic expansion. The parameter name or symbol to
1210 be expanded may be enclosed in braces, which are optional but serve to
1211 protect the variable to be expanded from characters immediately
1212 following it which could be interpreted as part of the name.
1214 When braces are used, the matching ending brace is the first `}' not
1215 escaped by a backslash or within a quoted string, and not within an
1216 embedded arithmetic expansion, command substitution, or parameter
1219 The basic form of parameter expansion is ${PARAMETER}. The value of
1220 PARAMETER is substituted. The braces are required when PARAMETER is a
1221 positional parameter with more than one digit, or when PARAMETER is
1222 followed by a character that is not to be interpreted as part of its
1225 If the first character of PARAMETER is an exclamation point, a level
1226 of variable indirection is introduced. Bash uses the value of the
1227 variable formed from the rest of PARAMETER as the name of the variable;
1228 this variable is then expanded and that value is used in the rest of
1229 the substitution, rather than the value of PARAMETER itself. This is
1230 known as `indirect expansion'. The exception to this is the expansion
1231 of ${!PREFIX*} described below.
1233 In each of the cases below, WORD is subject to tilde expansion,
1234 parameter expansion, command substitution, and arithmetic expansion.
1236 When not performing substring expansion, Bash tests for a parameter
1237 that is unset or null; omitting the colon results in a test only for a
1238 parameter that is unset. Put another way, if the colon is included,
1239 the operator tests for both existence and that the value is not null;
1240 if the colon is omitted, the operator tests only for existence.
1242 `${PARAMETER:-WORD}'
1243 If PARAMETER is unset or null, the expansion of WORD is
1244 substituted. Otherwise, the value of PARAMETER is substituted.
1246 `${PARAMETER:=WORD}'
1247 If PARAMETER is unset or null, the expansion of WORD is assigned
1248 to PARAMETER. The value of PARAMETER is then substituted.
1249 Positional parameters and special parameters may not be assigned
1252 `${PARAMETER:?WORD}'
1253 If PARAMETER is null or unset, the expansion of WORD (or a message
1254 to that effect if WORD is not present) is written to the standard
1255 error and the shell, if it is not interactive, exits. Otherwise,
1256 the value of PARAMETER is substituted.
1258 `${PARAMETER:+WORD}'
1259 If PARAMETER is null or unset, nothing is substituted, otherwise
1260 the expansion of WORD is substituted.
1262 `${PARAMETER:OFFSET}'
1263 `${PARAMETER:OFFSET:LENGTH}'
1264 Expands to up to LENGTH characters of PARAMETER starting at the
1265 character specified by OFFSET. If LENGTH is omitted, expands to
1266 the substring of PARAMETER starting at the character specified by
1267 OFFSET. LENGTH and OFFSET are arithmetic expressions (*note Shell
1268 Arithmetic::). This is referred to as Substring Expansion.
1270 LENGTH must evaluate to a number greater than or equal to zero.
1271 If OFFSET evaluates to a number less than zero, the value is used
1272 as an offset from the end of the value of PARAMETER. If PARAMETER
1273 is `@', the result is LENGTH positional parameters beginning at
1274 OFFSET. If PARAMETER is an array name indexed by `@' or `*', the
1275 result is the LENGTH members of the array beginning with
1276 `${PARAMETER[OFFSET]}'. Substring indexing is zero-based unless
1277 the positional parameters are used, in which case the indexing
1281 Expands to the names of variables whose names begin with PREFIX,
1282 separated by the first character of the `IFS' special variable.
1285 The length in characters of the expanded value of PARAMETER is
1286 substituted. If PARAMETER is `*' or `@', the value substituted is
1287 the number of positional parameters. If PARAMETER is an array
1288 name subscripted by `*' or `@', the value substituted is the
1289 number of elements in the array.
1292 `${PARAMETER##WORD}'
1293 The WORD is expanded to produce a pattern just as in filename
1294 expansion (*note Filename Expansion::). If the pattern matches
1295 the beginning of the expanded value of PARAMETER, then the result
1296 of the expansion is the expanded value of PARAMETER with the
1297 shortest matching pattern (the `#' case) or the longest matching
1298 pattern (the `##' case) deleted. If PARAMETER is `@' or `*', the
1299 pattern removal operation is applied to each positional parameter
1300 in turn, and the expansion is the resultant list. If PARAMETER is
1301 an array variable subscripted with `@' or `*', the pattern removal
1302 operation is applied to each member of the array in turn, and the
1303 expansion is the resultant list.
1306 `${PARAMETER%%WORD}'
1307 The WORD is expanded to produce a pattern just as in filename
1308 expansion. If the pattern matches a trailing portion of the
1309 expanded value of PARAMETER, then the result of the expansion is
1310 the value of PARAMETER with the shortest matching pattern (the `%'
1311 case) or the longest matching pattern (the `%%' case) deleted. If
1312 PARAMETER is `@' or `*', the pattern removal operation is applied
1313 to each positional parameter in turn, and the expansion is the
1314 resultant list. If PARAMETER is an array variable subscripted
1315 with `@' or `*', the pattern removal operation is applied to each
1316 member of the array in turn, and the expansion is the resultant
1319 `${PARAMETER/PATTERN/STRING}'
1320 `${PARAMETER//PATTERN/STRING}'
1321 The PATTERN is expanded to produce a pattern just as in filename
1322 expansion. PARAMETER is expanded and the longest match of PATTERN
1323 against its value is replaced with STRING. In the first form,
1324 only the first match is replaced. The second form causes all
1325 matches of PATTERN to be replaced with STRING. If PATTERN begins
1326 with `#', it must match at the beginning of the expanded value of
1327 PARAMETER. If PATTERN begins with `%', it must match at the end
1328 of the expanded value of PARAMETER. If STRING is null, matches of
1329 PATTERN are deleted and the `/' following PATTERN may be omitted.
1330 If PARAMETER is `@' or `*', the substitution operation is applied
1331 to each positional parameter in turn, and the expansion is the
1332 resultant list. If PARAMETER is an array variable subscripted
1333 with `@' or `*', the substitution operation is applied to each
1334 member of the array in turn, and the expansion is the resultant
1338 File: bashref.info, Node: Command Substitution, Next: Arithmetic Expansion, Prev: Shell Parameter Expansion, Up: Shell Expansions
1340 Command Substitution
1341 --------------------
1343 Command substitution allows the output of a command to replace the
1344 command itself. Command substitution occurs when a command is enclosed
1351 Bash performs the expansion by executing COMMAND and replacing the
1352 command substitution with the standard output of the command, with any
1353 trailing newlines deleted. Embedded newlines are not deleted, but they
1354 may be removed during word splitting. The command substitution `$(cat
1355 FILE)' can be replaced by the equivalent but faster `$(< FILE)'.
1357 When the old-style backquote form of substitution is used, backslash
1358 retains its literal meaning except when followed by `$', ``', or `\'.
1359 The first backquote not preceded by a backslash terminates the command
1360 substitution. When using the `$(COMMAND)' form, all characters between
1361 the parentheses make up the command; none are treated specially.
1363 Command substitutions may be nested. To nest when using the
1364 backquoted form, escape the inner backquotes with backslashes.
1366 If the substitution appears within double quotes, word splitting and
1367 filename expansion are not performed on the results.
1370 File: bashref.info, Node: Arithmetic Expansion, Next: Process Substitution, Prev: Command Substitution, Up: Shell Expansions
1372 Arithmetic Expansion
1373 --------------------
1375 Arithmetic expansion allows the evaluation of an arithmetic
1376 expression and the substitution of the result. The format for
1377 arithmetic expansion is:
1381 The expression is treated as if it were within double quotes, but a
1382 double quote inside the parentheses is not treated specially. All
1383 tokens in the expression undergo parameter expansion, command
1384 substitution, and quote removal. Arithmetic substitutions may be
1387 The evaluation is performed according to the rules listed below
1388 (*note Shell Arithmetic::). If the expression is invalid, Bash prints
1389 a message indicating failure to the standard error and no substitution
1393 File: bashref.info, Node: Process Substitution, Next: Word Splitting, Prev: Arithmetic Expansion, Up: Shell Expansions
1395 Process Substitution
1396 --------------------
1398 Process substitution is supported on systems that support named
1399 pipes (FIFOs) or the `/dev/fd' method of naming open files. It takes
1406 The process LIST is run with its input or output connected to a FIFO or
1407 some file in `/dev/fd'. The name of this file is passed as an argument
1408 to the current command as the result of the expansion. If the
1409 `>(LIST)' form is used, writing to the file will provide input for
1410 LIST. If the `<(LIST)' form is used, the file passed as an argument
1411 should be read to obtain the output of LIST. Note that no space may
1412 appear between the `<' or `>' and the left parenthesis, otherwise the
1413 construct would be interpreted as a redirection.
1415 When available, process substitution is performed simultaneously with
1416 parameter and variable expansion, command substitution, and arithmetic
1420 File: bashref.info, Node: Word Splitting, Next: Filename Expansion, Prev: Process Substitution, Up: Shell Expansions
1425 The shell scans the results of parameter expansion, command
1426 substitution, and arithmetic expansion that did not occur within double
1427 quotes for word splitting.
1429 The shell treats each character of `$IFS' as a delimiter, and splits
1430 the results of the other expansions into words on these characters. If
1431 `IFS' is unset, or its value is exactly `<space><tab><newline>', the
1432 default, then any sequence of `IFS' characters serves to delimit words.
1433 If `IFS' has a value other than the default, then sequences of the
1434 whitespace characters `space' and `tab' are ignored at the beginning
1435 and end of the word, as long as the whitespace character is in the
1436 value of `IFS' (an `IFS' whitespace character). Any character in `IFS'
1437 that is not `IFS' whitespace, along with any adjacent `IFS' whitespace
1438 characters, delimits a field. A sequence of `IFS' whitespace
1439 characters is also treated as a delimiter. If the value of `IFS' is
1440 null, no word splitting occurs.
1442 Explicit null arguments (`""' or `''') are retained. Unquoted
1443 implicit null arguments, resulting from the expansion of parameters
1444 that have no values, are removed. If a parameter with no value is
1445 expanded within double quotes, a null argument results and is retained.
1447 Note that if no expansion occurs, no splitting is performed.
1450 File: bashref.info, Node: Filename Expansion, Next: Quote Removal, Prev: Word Splitting, Up: Shell Expansions
1457 * Pattern Matching:: How the shell matches patterns.
1459 After word splitting, unless the `-f' option has been set (*note The
1460 Set Builtin::), Bash scans each word for the characters `*', `?', and
1461 `['. If one of these characters appears, then the word is regarded as
1462 a PATTERN, and replaced with an alphabetically sorted list of file
1463 names matching the pattern. If no matching file names are found, and
1464 the shell option `nullglob' is disabled, the word is left unchanged.
1465 If the `nullglob' option is set, and no matches are found, the word is
1466 removed. If the shell option `nocaseglob' is enabled, the match is
1467 performed without regard to the case of alphabetic characters.
1469 When a pattern is used for filename generation, the character `.' at
1470 the start of a filename or immediately following a slash must be
1471 matched explicitly, unless the shell option `dotglob' is set. When
1472 matching a file name, the slash character must always be matched
1473 explicitly. In other cases, the `.' character is not treated specially.
1475 See the description of `shopt' in *Note Bash Builtins::, for a
1476 description of the `nocaseglob', `nullglob', and `dotglob' options.
1478 The `GLOBIGNORE' shell variable may be used to restrict the set of
1479 filenames matching a pattern. If `GLOBIGNORE' is set, each matching
1480 filename that also matches one of the patterns in `GLOBIGNORE' is
1481 removed from the list of matches. The filenames `.' and `..' are
1482 always ignored, even when `GLOBIGNORE' is set. However, setting
1483 `GLOBIGNORE' has the effect of enabling the `dotglob' shell option, so
1484 all other filenames beginning with a `.' will match. To get the old
1485 behavior of ignoring filenames beginning with a `.', make `.*' one of
1486 the patterns in `GLOBIGNORE'. The `dotglob' option is disabled when
1487 `GLOBIGNORE' is unset.
1490 File: bashref.info, Node: Pattern Matching, Up: Filename Expansion
1495 Any character that appears in a pattern, other than the special
1496 pattern characters described below, matches itself. The NUL character
1497 may not occur in a pattern. The special pattern characters must be
1498 quoted if they are to be matched literally.
1500 The special pattern characters have the following meanings:
1502 Matches any string, including the null string.
1505 Matches any single character.
1508 Matches any one of the enclosed characters. A pair of characters
1509 separated by a hyphen denotes a RANGE EXPRESSION; any character
1510 that sorts between those two characters, inclusive, using the
1511 current locale's collating sequence and character set, is matched.
1512 If the first character following the `[' is a `!' or a `^' then
1513 any character not enclosed is matched. A `-' may be matched by
1514 including it as the first or last character in the set. A `]' may
1515 be matched by including it as the first character in the set. The
1516 sorting order of characters in range expressions is determined by
1517 the current locale and the value of the `LC_COLLATE' shell
1520 For example, in the default C locale, `[a-dx-z]' is equivalent to
1521 `[abcdxyz]'. Many locales sort characters in dictionary order,
1522 and in these locales `[a-dx-z]' is typically not equivalent to
1523 `[abcdxyz]'; it might be equivalent to `[aBbCcDdxXyYz]', for
1524 example. To obtain the traditional interpretation of ranges in
1525 bracket expressions, you can force the use of the C locale by
1526 setting the `LC_COLLATE' or `LC_ALL' environment variable to the
1529 Within `[' and `]', CHARACTER CLASSES can be specified using the
1530 syntax `[:'CLASS`:]', where CLASS is one of the following classes
1531 defined in the POSIX 1003.2 standard:
1532 alnum alpha ascii blank cntrl digit graph lower
1533 print punct space upper xdigit
1535 A character class matches any character belonging to that class.
1537 Within `[' and `]', an EQUIVALENCE CLASS can be specified using
1538 the syntax `[='C`=]', which matches all characters with the same
1539 collation weight (as defined by the current locale) as the
1542 Within `[' and `]', the syntax `[.'SYMBOL`.]' matches the
1543 collating symbol SYMBOL.
1545 If the `extglob' shell option is enabled using the `shopt' builtin,
1546 several extended pattern matching operators are recognized. In the
1547 following description, a PATTERN-LIST is a list of one or more patterns
1548 separated by a `|'. Composite patterns may be formed using one or more
1549 of the following sub-patterns:
1552 Matches zero or one occurrence of the given patterns.
1555 Matches zero or more occurrences of the given patterns.
1558 Matches one or more occurrences of the given patterns.
1561 Matches exactly one of the given patterns.
1564 Matches anything except one of the given patterns.
1567 File: bashref.info, Node: Quote Removal, Prev: Filename Expansion, Up: Shell Expansions
1572 After the preceding expansions, all unquoted occurrences of the
1573 characters `\', `'', and `"' that did not result from one of the above
1574 expansions are removed.
1577 File: bashref.info, Node: Redirections, Next: Executing Commands, Prev: Shell Expansions, Up: Basic Shell Features
1582 Before a command is executed, its input and output may be REDIRECTED
1583 using a special notation interpreted by the shell. Redirection may
1584 also be used to open and close files for the current shell execution
1585 environment. The following redirection operators may precede or appear
1586 anywhere within a simple command or may follow a command. Redirections
1587 are processed in the order they appear, from left to right.
1589 In the following descriptions, if the file descriptor number is
1590 omitted, and the first character of the redirection operator is `<',
1591 the redirection refers to the standard input (file descriptor 0). If
1592 the first character of the redirection operator is `>', the redirection
1593 refers to the standard output (file descriptor 1).
1595 The word following the redirection operator in the following
1596 descriptions, unless otherwise noted, is subjected to brace expansion,
1597 tilde expansion, parameter expansion, command substitution, arithmetic
1598 expansion, quote removal, filename expansion, and word splitting. If
1599 it expands to more than one word, Bash reports an error.
1601 Note that the order of redirections is significant. For example,
1605 directs both standard output (file descriptor 1) and standard error
1606 (file descriptor 2) to the file DIRLIST, while the command
1609 directs only the standard output to file DIRLIST, because the standard
1610 error was duplicated as standard output before the standard output was
1611 redirected to DIRLIST.
1613 Bash handles several filenames specially when they are used in
1614 redirections, as described in the following table:
1617 If FD is a valid integer, file descriptor FD is duplicated.
1620 File descriptor 0 is duplicated.
1623 File descriptor 1 is duplicated.
1626 File descriptor 2 is duplicated.
1628 `/dev/tcp/HOST/PORT'
1629 If HOST is a valid hostname or Internet address, and PORT is an
1630 integer port number or service name, Bash attempts to open a TCP
1631 connection to the corresponding socket.
1633 `/dev/udp/HOST/PORT'
1634 If HOST is a valid hostname or Internet address, and PORT is an
1635 integer port number or service name, Bash attempts to open a UDP
1636 connection to the corresponding socket.
1638 A failure to open or create a file causes the redirection to fail.
1643 Redirection of input causes the file whose name results from the
1644 expansion of WORD to be opened for reading on file descriptor `n', or
1645 the standard input (file descriptor 0) if `n' is not specified.
1647 The general format for redirecting input is:
1653 Redirection of output causes the file whose name results from the
1654 expansion of WORD to be opened for writing on file descriptor `n', or
1655 the standard output (file descriptor 1) if `n' is not specified. If
1656 the file does not exist it is created; if it does exist it is truncated
1659 The general format for redirecting output is:
1662 If the redirection operator is `>', and the `noclobber' option to
1663 the `set' builtin has been enabled, the redirection will fail if the
1664 file whose name results from the expansion of WORD exists and is a
1665 regular file. If the redirection operator is `>|', or the redirection
1666 operator is `>' and the `noclobber' option is not enabled, the
1667 redirection is attempted even if the file named by WORD exists.
1669 Appending Redirected Output
1670 ---------------------------
1672 Redirection of output in this fashion causes the file whose name
1673 results from the expansion of WORD to be opened for appending on file
1674 descriptor `n', or the standard output (file descriptor 1) if `n' is
1675 not specified. If the file does not exist it is created.
1677 The general format for appending output is:
1680 Redirecting Standard Output and Standard Error
1681 ----------------------------------------------
1683 Bash allows both the standard output (file descriptor 1) and the
1684 standard error output (file descriptor 2) to be redirected to the file
1685 whose name is the expansion of WORD with this construct.
1687 There are two formats for redirecting standard output and standard
1694 Of the two forms, the first is preferred. This is semantically
1701 This type of redirection instructs the shell to read input from the
1702 current source until a line containing only WORD (with no trailing
1703 blanks) is seen. All of the lines read up to that point are then used
1704 as the standard input for a command.
1706 The format of here-documents is as follows:
1711 No parameter expansion, command substitution, arithmetic expansion,
1712 or filename expansion is performed on WORD. If any characters in WORD
1713 are quoted, the DELIMITER is the result of quote removal on WORD, and
1714 the lines in the here-document are not expanded. If WORD is unquoted,
1715 all lines of the here-document are subjected to parameter expansion,
1716 command substitution, and arithmetic expansion. In the latter case,
1717 the character sequence `\newline' is ignored, and `\' must be used to
1718 quote the characters `\', `$', and ``'.
1720 If the redirection operator is `<<-', then all leading tab
1721 characters are stripped from input lines and the line containing
1722 DELIMITER. This allows here-documents within shell scripts to be
1723 indented in a natural fashion.
1725 Duplicating File Descriptors
1726 ----------------------------
1728 The redirection operator
1731 is used to duplicate input file descriptors. If WORD expands to one or
1732 more digits, the file descriptor denoted by `n' is made to be a copy of
1733 that file descriptor. If the digits in WORD do not specify a file
1734 descriptor open for input, a redirection error occurs. If WORD
1735 evaluates to `-', file descriptor `n' is closed. If `n' is not
1736 specified, the standard input (file descriptor 0) is used.
1741 is used similarly to duplicate output file descriptors. If `n' is not
1742 specified, the standard output (file descriptor 1) is used. If the
1743 digits in WORD do not specify a file descriptor open for output, a
1744 redirection error occurs. As a special case, if `n' is omitted, and
1745 WORD does not expand to one or more digits, the standard output and
1746 standard error are redirected as described previously.
1748 Opening File Descriptors for Reading and Writing
1749 ------------------------------------------------
1751 The redirection operator
1754 causes the file whose name is the expansion of WORD to be opened for
1755 both reading and writing on file descriptor `n', or on file descriptor
1756 0 if `n' is not specified. If the file does not exist, it is created.
1759 File: bashref.info, Node: Executing Commands, Next: Shell Scripts, Prev: Redirections, Up: Basic Shell Features
1766 * Simple Command Expansion:: How Bash expands simple commands before
1769 * Command Search and Execution:: How Bash finds commands and runs them.
1771 * Command Execution Environment:: The environment in which Bash
1772 executes commands that are not
1775 * Environment:: The environment given to a command.
1777 * Exit Status:: The status returned by commands and how Bash
1780 * Signals:: What happens when Bash or a command it runs
1784 File: bashref.info, Node: Simple Command Expansion, Next: Command Search and Execution, Up: Executing Commands
1786 Simple Command Expansion
1787 ------------------------
1789 When a simple command is executed, the shell performs the following
1790 expansions, assignments, and redirections, from left to right.
1792 1. The words that the parser has marked as variable assignments (those
1793 preceding the command name) and redirections are saved for later
1796 2. The words that are not variable assignments or redirections are
1797 expanded (*note Shell Expansions::). If any words remain after
1798 expansion, the first word is taken to be the name of the command
1799 and the remaining words are the arguments.
1801 3. Redirections are performed as described above (*note
1804 4. The text after the `=' in each variable assignment undergoes tilde
1805 expansion, parameter expansion, command substitution, arithmetic
1806 expansion, and quote removal before being assigned to the variable.
1808 If no command name results, the variable assignments affect the
1809 current shell environment. Otherwise, the variables are added to the
1810 environment of the executed command and do not affect the current shell
1811 environment. If any of the assignments attempts to assign a value to a
1812 readonly variable, an error occurs, and the command exits with a
1815 If no command name results, redirections are performed, but do not
1816 affect the current shell environment. A redirection error causes the
1817 command to exit with a non-zero status.
1819 If there is a command name left after expansion, execution proceeds
1820 as described below. Otherwise, the command exits. If one of the
1821 expansions contained a command substitution, the exit status of the
1822 command is the exit status of the last command substitution performed.
1823 If there were no command substitutions, the command exits with a status
1827 File: bashref.info, Node: Command Search and Execution, Next: Command Execution Environment, Prev: Simple Command Expansion, Up: Executing Commands
1829 Command Search and Execution
1830 ----------------------------
1832 After a command has been split into words, if it results in a simple
1833 command and an optional list of arguments, the following actions are
1836 1. If the command name contains no slashes, the shell attempts to
1837 locate it. If there exists a shell function by that name, that
1838 function is invoked as described in *Note Shell Functions::.
1840 2. If the name does not match a function, the shell searches for it
1841 in the list of shell builtins. If a match is found, that builtin
1844 3. If the name is neither a shell function nor a builtin, and
1845 contains no slashes, Bash searches each element of `$PATH' for a
1846 directory containing an executable file by that name. Bash uses a
1847 hash table to remember the full pathnames of executable files to
1848 avoid multiple `PATH' searches (see the description of `hash' in
1849 *Note Bourne Shell Builtins::). A full search of the directories
1850 in `$PATH' is performed only if the command is not found in the
1851 hash table. If the search is unsuccessful, the shell prints an
1852 error message and returns an exit status of 127.
1854 4. If the search is successful, or if the command name contains one
1855 or more slashes, the shell executes the named program in a
1856 separate execution environment. Argument 0 is set to the name
1857 given, and the remaining arguments to the command are set to the
1858 arguments supplied, if any.
1860 5. If this execution fails because the file is not in executable
1861 format, and the file is not a directory, it is assumed to be a
1862 SHELL SCRIPT and the shell executes it as described in *Note Shell
1865 6. If the command was not begun asynchronously, the shell waits for
1866 the command to complete and collects its exit status.
1870 File: bashref.info, Node: Command Execution Environment, Next: Environment, Prev: Command Search and Execution, Up: Executing Commands
1872 Command Execution Environment
1873 -----------------------------
1875 The shell has an EXECUTION ENVIRONMENT, which consists of the
1878 * open files inherited by the shell at invocation, as modified by
1879 redirections supplied to the `exec' builtin
1881 * the current working directory as set by `cd', `pushd', or `popd',
1882 or inherited by the shell at invocation
1884 * the file creation mode mask as set by `umask' or inherited from
1887 * current traps set by `trap'
1889 * shell parameters that are set by variable assignment or with `set'
1890 or inherited from the shell's parent in the environment
1892 * shell functions defined during execution or inherited from the
1893 shell's parent in the environment
1895 * options enabled at invocation (either by default or with
1896 command-line arguments) or by `set'
1898 * options enabled by `shopt'
1900 * shell aliases defined with `alias' (*note Aliases::)
1902 * various process IDs, including those of background jobs (*note
1903 Lists::), the value of `$$', and the value of `$PPID'
1906 When a simple command other than a builtin or shell function is to
1907 be executed, it is invoked in a separate execution environment that
1908 consists of the following. Unless otherwise noted, the values are
1909 inherited from the shell.
1911 * the shell's open files, plus any modifications and additions
1912 specified by redirections to the command
1914 * the current working directory
1916 * the file creation mode mask
1918 * shell variables marked for export, along with variables exported
1919 for the command, passed in the environment (*note Environment::)
1921 * traps caught by the shell are reset to the values inherited from
1922 the shell's parent, and traps ignored by the shell are ignored
1925 A command invoked in this separate environment cannot affect the
1926 shell's execution environment.
1928 Command substitution and asynchronous commands are invoked in a
1929 subshell environment that is a duplicate of the shell environment,
1930 except that traps caught by the shell are reset to the values that the
1931 shell inherited from its parent at invocation. Builtin commands that
1932 are invoked as part of a pipeline are also executed in a subshell
1933 environment. Changes made to the subshell environment cannot affect
1934 the shell's execution environment.
1936 If a command is followed by a `&' and job control is not active, the
1937 default standard input for the command is the empty file `/dev/null'.
1938 Otherwise, the invoked command inherits the file descriptors of the
1939 calling shell as modified by redirections.
1942 File: bashref.info, Node: Environment, Next: Exit Status, Prev: Command Execution Environment, Up: Executing Commands
1947 When a program is invoked it is given an array of strings called the
1948 ENVIRONMENT. This is a list of name-value pairs, of the form
1951 Bash provides several ways to manipulate the environment. On
1952 invocation, the shell scans its own environment and creates a parameter
1953 for each name found, automatically marking it for EXPORT to child
1954 processes. Executed commands inherit the environment. The `export'
1955 and `declare -x' commands allow parameters and functions to be added to
1956 and deleted from the environment. If the value of a parameter in the
1957 environment is modified, the new value becomes part of the environment,
1958 replacing the old. The environment inherited by any executed command
1959 consists of the shell's initial environment, whose values may be
1960 modified in the shell, less any pairs removed by the `unset' and
1961 `export -n' commands, plus any additions via the `export' and `declare
1964 The environment for any simple command or function may be augmented
1965 temporarily by prefixing it with parameter assignments, as described in
1966 *Note Shell Parameters::. These assignment statements affect only the
1967 environment seen by that command.
1969 If the `-k' option is set (*note The Set Builtin::), then all
1970 parameter assignments are placed in the environment for a command, not
1971 just those that precede the command name.
1973 When Bash invokes an external command, the variable `$_' is set to
1974 the full path name of the command and passed to that command in its
1978 File: bashref.info, Node: Exit Status, Next: Signals, Prev: Environment, Up: Executing Commands
1983 For the shell's purposes, a command which exits with a zero exit
1984 status has succeeded. A non-zero exit status indicates failure. This
1985 seemingly counter-intuitive scheme is used so there is one well-defined
1986 way to indicate success and a variety of ways to indicate various
1987 failure modes. When a command terminates on a fatal signal whose
1988 number is N, Bash uses the value 128+N as the exit status.
1990 If a command is not found, the child process created to execute it
1991 returns a status of 127. If a command is found but is not executable,
1992 the return status is 126.
1994 If a command fails because of an error during expansion or
1995 redirection, the exit status is greater than zero.
1997 The exit status is used by the Bash conditional commands (*note
1998 Conditional Constructs::) and some of the list constructs (*note
2001 All of the Bash builtins return an exit status of zero if they
2002 succeed and a non-zero status on failure, so they may be used by the
2003 conditional and list constructs. All builtins return an exit status of
2004 2 to indicate incorrect usage.
2007 File: bashref.info, Node: Signals, Prev: Exit Status, Up: Executing Commands
2012 When Bash is interactive, in the absence of any traps, it ignores
2013 `SIGTERM' (so that `kill 0' does not kill an interactive shell), and
2014 `SIGINT' is caught and handled (so that the `wait' builtin is
2015 interruptible). When Bash receives a `SIGINT', it breaks out of any
2016 executing loops. In all cases, Bash ignores `SIGQUIT'. If job control
2017 is in effect (*note Job Control::), Bash ignores `SIGTTIN', `SIGTTOU',
2020 Commands started by Bash have signal handlers set to the values
2021 inherited by the shell from its parent. When job control is not in
2022 effect, asynchronous commands ignore `SIGINT' and `SIGQUIT' as well.
2023 Commands run as a result of command substitution ignore the
2024 keyboard-generated job control signals `SIGTTIN', `SIGTTOU', and
2027 The shell exits by default upon receipt of a `SIGHUP'. Before
2028 exiting, an interactive shell resends the `SIGHUP' to all jobs, running
2029 or stopped. Stopped jobs are sent `SIGCONT' to ensure that they receive
2030 the `SIGHUP'. To prevent the shell from sending the `SIGHUP' signal to
2031 a particular job, it should be removed from the jobs table with the
2032 `disown' builtin (*note Job Control Builtins::) or marked to not
2033 receive `SIGHUP' using `disown -h'.
2035 If the `huponexit' shell option has been set with `shopt' (*note
2036 Bash Builtins::), Bash sends a `SIGHUP' to all jobs when an interactive
2039 When Bash receives a signal for which a trap has been set while
2040 waiting for a command to complete, the trap will not be executed until
2041 the command completes. When Bash is waiting for an asynchronous
2042 command via the `wait' builtin, the reception of a signal for which a
2043 trap has been set will cause the `wait' builtin to return immediately
2044 with an exit status greater than 128, immediately after which the trap
2048 File: bashref.info, Node: Shell Scripts, Prev: Executing Commands, Up: Basic Shell Features
2053 A shell script is a text file containing shell commands. When such
2054 a file is used as the first non-option argument when invoking Bash, and
2055 neither the `-c' nor `-s' option is supplied (*note Invoking Bash::),
2056 Bash reads and executes commands from the file, then exits. This mode
2057 of operation creates a non-interactive shell. The shell first searches
2058 for the file in the current directory, and looks in the directories in
2059 `$PATH' if not found there.
2061 When Bash runs a shell script, it sets the special parameter `0' to
2062 the name of the file, rather than the name of the shell, and the
2063 positional parameters are set to the remaining arguments, if any are
2064 given. If no additional arguments are supplied, the positional
2065 parameters are unset.
2067 A shell script may be made executable by using the `chmod' command
2068 to turn on the execute bit. When Bash finds such a file while
2069 searching the `$PATH' for a command, it spawns a subshell to execute
2070 it. In other words, executing
2073 is equivalent to executing
2074 bash filename ARGUMENTS
2076 if `filename' is an executable shell script. This subshell
2077 reinitializes itself, so that the effect is as if a new shell had been
2078 invoked to interpret the script, with the exception that the locations
2079 of commands remembered by the parent (see the description of `hash' in
2080 *Note Bourne Shell Builtins::) are retained by the child.
2082 Most versions of Unix make this a part of the operating system's
2083 command execution mechanism. If the first line of a script begins with
2084 the two characters `#!', the remainder of the line specifies an
2085 interpreter for the program. Thus, you can specify Bash, `awk', Perl,
2086 or some other interpreter and write the rest of the script file in that
2089 The arguments to the interpreter consist of a single optional
2090 argument following the interpreter name on the first line of the script
2091 file, followed by the name of the script file, followed by the rest of
2092 the arguments. Bash will perform this action on operating systems that
2093 do not handle it themselves. Note that some older versions of Unix
2094 limit the interpreter name and argument to a maximum of 32 characters.
2096 Bash scripts often begin with `#! /bin/bash' (assuming that Bash has
2097 been installed in `/bin'), since this ensures that Bash will be used to
2098 interpret the script, even if it is executed under another shell.
2101 File: bashref.info, Node: Shell Builtin Commands, Next: Shell Variables, Prev: Basic Shell Features, Up: Top
2103 Shell Builtin Commands
2104 **********************
2108 * Bourne Shell Builtins:: Builtin commands inherited from the Bourne
2110 * Bash Builtins:: Table of builtins specific to Bash.
2111 * The Set Builtin:: This builtin is so overloaded it
2112 deserves its own section.
2113 * Special Builtins:: Builtin commands classified specially by
2116 Builtin commands are contained within the shell itself. When the
2117 name of a builtin command is used as the first word of a simple command
2118 (*note Simple Commands::), the shell executes the command directly,
2119 without invoking another program. Builtin commands are necessary to
2120 implement functionality impossible or inconvenient to obtain with
2123 This section briefly the builtins which Bash inherits from the
2124 Bourne Shell, as well as the builtin commands which are unique to or
2125 have been extended in Bash.
2127 Several builtin commands are described in other chapters: builtin
2128 commands which provide the Bash interface to the job control facilities
2129 (*note Job Control Builtins::), the directory stack (*note Directory
2130 Stack Builtins::), the command history (*note Bash History Builtins::),
2131 and the programmable completion facilities (*note Programmable
2132 Completion Builtins::).
2134 Many of the builtins have been extended by POSIX or Bash.
2137 File: bashref.info, Node: Bourne Shell Builtins, Next: Bash Builtins, Up: Shell Builtin Commands
2139 Bourne Shell Builtins
2140 =====================
2142 The following shell builtin commands are inherited from the Bourne
2143 Shell. These commands are implemented as specified by the POSIX 1003.2
2148 Do nothing beyond expanding ARGUMENTS and performing redirections.
2149 The return status is zero.
2152 . FILENAME [ARGUMENTS]
2153 Read and execute commands from the FILENAME argument in the
2154 current shell context. If FILENAME does not contain a slash, the
2155 `PATH' variable is used to find FILENAME. When Bash is not in
2156 POSIX mode, the current directory is searched if FILENAME is not
2157 found in `$PATH'. If any ARGUMENTS are supplied, they become the
2158 positional parameters when FILENAME is executed. Otherwise the
2159 positional parameters are unchanged. The return status is the
2160 exit status of the last command executed, or zero if no commands
2161 are executed. If FILENAME is not found, or cannot be read, the
2162 return status is non-zero. This builtin is equivalent to `source'.
2166 Exit from a `for', `while', `until', or `select' loop. If N is
2167 supplied, the Nth enclosing loop is exited. N must be greater
2168 than or equal to 1. The return status is zero unless N is not
2169 greater than or equal to 1.
2172 cd [-LP] [DIRECTORY]
2173 Change the current working directory to DIRECTORY. If DIRECTORY
2174 is not given, the value of the `HOME' shell variable is used. If
2175 the shell variable `CDPATH' exists, it is used as a search path.
2176 If DIRECTORY begins with a slash, `CDPATH' is not used. The `-P'
2177 option means to not follow symbolic links; symbolic links are
2178 followed by default or with the `-L' option. If DIRECTORY is `-',
2179 it is equivalent to `$OLDPWD'. The return status is zero if the
2180 directory is successfully changed, non-zero otherwise.
2184 Resume the next iteration of an enclosing `for', `while', `until',
2185 or `select' loop. If N is supplied, the execution of the Nth
2186 enclosing loop is resumed. N must be greater than or equal to 1.
2187 The return status is zero unless N is not greater than or equal to
2192 The arguments are concatenated together into a single command,
2193 which is then read and executed, and its exit status returned as
2194 the exit status of `eval'. If there are no arguments or only
2195 empty arguments, the return status is zero.
2198 exec [-cl] [-a NAME] [COMMAND [ARGUMENTS]]
2199 If COMMAND is supplied, it replaces the shell without creating a
2200 new process. If the `-l' option is supplied, the shell places a
2201 dash at the beginning of the zeroth arg passed to COMMAND. This
2202 is what the `login' program does. The `-c' option causes COMMAND
2203 to be executed with an empty environment. If `-a' is supplied,
2204 the shell passes NAME as the zeroth argument to COMMAND. If no
2205 COMMAND is specified, redirections may be used to affect the
2206 current shell environment. If there are no redirection errors, the
2207 return status is zero; otherwise the return status is non-zero.
2211 Exit the shell, returning a status of N to the shell's parent. If
2212 N is omitted, the exit status is that of the last command executed.
2213 Any trap on `EXIT' is executed before the shell terminates.
2216 export [-fn] [-p] [NAME[=VALUE]]
2217 Mark each NAME to be passed to child processes in the environment.
2218 If the `-f' option is supplied, the NAMEs refer to shell
2219 functions; otherwise the names refer to shell variables. The `-n'
2220 option means to no longer mark each NAME for export. If no NAMES
2221 are supplied, or if the `-p' option is given, a list of exported
2222 names is displayed. The `-p' option displays output in a form
2223 that may be reused as input. The return status is zero unless an
2224 invalid option is supplied, one of the names is not a valid shell
2225 variable name, or `-f' is supplied with a name that is not a shell
2229 getopts OPTSTRING NAME [ARGS]
2230 `getopts' is used by shell scripts to parse positional parameters.
2231 OPTSTRING contains the option characters to be recognized; if a
2232 character is followed by a colon, the option is expected to have an
2233 argument, which should be separated from it by white space. The
2234 colon (`:') and question mark (`?') may not be used as option
2235 characters. Each time it is invoked, `getopts' places the next
2236 option in the shell variable NAME, initializing NAME if it does
2237 not exist, and the index of the next argument to be processed into
2238 the variable `OPTIND'. `OPTIND' is initialized to 1 each time the
2239 shell or a shell script is invoked. When an option requires an
2240 argument, `getopts' places that argument into the variable
2241 `OPTARG'. The shell does not reset `OPTIND' automatically; it
2242 must be manually reset between multiple calls to `getopts' within
2243 the same shell invocation if a new set of parameters is to be used.
2245 When the end of options is encountered, `getopts' exits with a
2246 return value greater than zero. `OPTIND' is set to the index of
2247 the first non-option argument, and `name' is set to `?'.
2249 `getopts' normally parses the positional parameters, but if more
2250 arguments are given in ARGS, `getopts' parses those instead.
2252 `getopts' can report errors in two ways. If the first character of
2253 OPTSTRING is a colon, SILENT error reporting is used. In normal
2254 operation diagnostic messages are printed when invalid options or
2255 missing option arguments are encountered. If the variable `OPTERR'
2256 is set to 0, no error messages will be displayed, even if the first
2257 character of `optstring' is not a colon.
2259 If an invalid option is seen, `getopts' places `?' into NAME and,
2260 if not silent, prints an error message and unsets `OPTARG'. If
2261 `getopts' is silent, the option character found is placed in
2262 `OPTARG' and no diagnostic message is printed.
2264 If a required argument is not found, and `getopts' is not silent,
2265 a question mark (`?') is placed in NAME, `OPTARG' is unset, and a
2266 diagnostic message is printed. If `getopts' is silent, then a
2267 colon (`:') is placed in NAME and `OPTARG' is set to the option
2271 hash [-r] [-p FILENAME] [-t] [NAME]
2272 Remember the full pathnames of commands specified as NAME
2273 arguments, so they need not be searched for on subsequent
2274 invocations. The commands are found by searching through the
2275 directories listed in `$PATH'. The `-p' option inhibits the path
2276 search, and FILENAME is used as the location of NAME. The `-r'
2277 option causes the shell to forget all remembered locations. If
2278 the `-t' option is supplied, the full pathname to which each NAME
2279 corresponds is printed. If multiple NAME arguments are supplied
2280 with `-t' the NAME is printed before the hashed full pathname. If
2281 no arguments are given, information about remembered commands is
2282 printed. The return status is zero unless a NAME is not found or
2283 an invalid option is supplied.
2287 Print the absolute pathname of the current working directory. If
2288 the `-P' option is supplied, the pathname printed will not contain
2289 symbolic links. If the `-L' option is supplied, the pathname
2290 printed may contain symbolic links. The return status is zero
2291 unless an error is encountered while determining the name of the
2292 current directory or an invalid option is supplied.
2295 readonly [-apf] [NAME] ...
2296 Mark each NAME as readonly. The values of these names may not be
2297 changed by subsequent assignment. If the `-f' option is supplied,
2298 each NAME refers to a shell function. The `-a' option means each
2299 NAME refers to an array variable. If no NAME arguments are given,
2300 or if the `-p' option is supplied, a list of all readonly names is
2301 printed. The `-p' option causes output to be displayed in a
2302 format that may be reused as input. The return status is zero
2303 unless an invalid option is supplied, one of the NAME arguments is
2304 not a valid shell variable or function name, or the `-f' option is
2305 supplied with a name that is not a shell function.
2309 Cause a shell function to exit with the return value N. If N is
2310 not supplied, the return value is the exit status of the last
2311 command executed in the function. This may also be used to
2312 terminate execution of a script being executed with the `.' (or
2313 `source') builtin, returning either N or the exit status of the
2314 last command executed within the script as the exit status of the
2315 script. The return status is non-zero if `return' is used outside
2316 a function and not during the execution of a script by `.' or
2321 Shift the positional parameters to the left by N. The positional
2322 parameters from N+1 ... `$#' are renamed to `$1' ... `$#'-N+1.
2323 Parameters represented by the numbers `$#' to N+1 are unset. N
2324 must be a non-negative number less than or equal to `$#'. If N is
2325 zero or greater than `$#', the positional parameters are not
2326 changed. If N is not supplied, it is assumed to be 1. The return
2327 status is zero unless N is greater than `$#' or less than zero,
2332 Evaluate a conditional expression EXPR. Each operator and operand
2333 must be a separate argument. Expressions are composed of the
2334 primaries described below in *Note Bash Conditional Expressions::.
2336 When the `[' form is used, the last argument to the command must
2339 Expressions may be combined using the following operators, listed
2340 in decreasing order of precedence.
2343 True if EXPR is false.
2346 Returns the value of EXPR. This may be used to override the
2347 normal precedence of operators.
2350 True if both EXPR1 and EXPR2 are true.
2353 True if either EXPR1 or EXPR2 is true.
2355 The `test' and `[' builtins evaluate conditional expressions using
2356 a set of rules based on the number of arguments.
2359 The expression is false.
2362 The expression is true if and only if the argument is not
2366 If the first argument is `!', the expression is true if and
2367 only if the second argument is null. If the first argument
2368 is one of the unary conditional operators (*note Bash
2369 Conditional Expressions::), the expression is true if the
2370 unary test is true. If the first argument is not a valid
2371 unary operator, the expression is false.
2374 If the second argument is one of the binary conditional
2375 operators (*note Bash Conditional Expressions::), the result
2376 of the expression is the result of the binary test using the
2377 first and third arguments as operands. If the first argument
2378 is `!', the value is the negation of the two-argument test
2379 using the second and third arguments. If the first argument
2380 is exactly `(' and the third argument is exactly `)', the
2381 result is the one-argument test of the second argument.
2382 Otherwise, the expression is false. The `-a' and `-o'
2383 operators are considered binary operators in this case.
2386 If the first argument is `!', the result is the negation of
2387 the three-argument expression composed of the remaining
2388 arguments. Otherwise, the expression is parsed and evaluated
2389 according to precedence using the rules listed above.
2392 The expression is parsed and evaluated according to precedence
2393 using the rules listed above.
2397 Print out the user and system times used by the shell and its
2398 children. The return status is zero.
2401 trap [-lp] [ARG] [SIGSPEC ...]
2402 The commands in ARG are to be read and executed when the shell
2403 receives signal SIGSPEC. If ARG is absent or equal to `-', all
2404 specified signals are reset to the values they had when the shell
2405 was started. If ARG is the null string, then the signal specified
2406 by each SIGSPEC is ignored by the shell and commands it invokes.
2407 If ARG is not present and `-p' has been supplied, the shell
2408 displays the trap commands associated with each SIGSPEC. If no
2409 arguments are supplied, or only `-p' is given, `trap' prints the
2410 list of commands associated with each signal number in a form that
2411 may be reused as shell input. Each SIGSPEC is either a signal
2412 name such as `SIGINT' (with or without the `SIG' prefix) or a
2413 signal number. If a SIGSPEC is `0' or `EXIT', ARG is executed
2414 when the shell exits. If a SIGSPEC is `DEBUG', the command ARG is
2415 executed after every simple command. If a SIGSPEC is `ERR', the
2416 command ARG is executed whenever a simple command has a non-zero
2417 exit status. The `ERR' trap is not executed if the failed command
2418 is part of an `until' or `while' loop, part of an `if' statement,
2419 part of a `&&' or `||' list, or if the command's return status is
2420 being inverted using `!'. The `-l' option causes the shell to
2421 print a list of signal names and their corresponding numbers.
2423 Signals ignored upon entry to the shell cannot be trapped or reset.
2424 Trapped signals are reset to their original values in a child
2425 process when it is created.
2427 The return status is zero unless a SIGSPEC does not specify a
2431 umask [-p] [-S] [MODE]
2432 Set the shell process's file creation mask to MODE. If MODE
2433 begins with a digit, it is interpreted as an octal number; if not,
2434 it is interpreted as a symbolic mode mask similar to that accepted
2435 by the `chmod' command. If MODE is omitted, the current value of
2436 the mask is printed. If the `-S' option is supplied without a
2437 MODE argument, the mask is printed in a symbolic format. If the
2438 `-p' option is supplied, and MODE is omitted, the output is in a
2439 form that may be reused as input. The return status is zero if
2440 the mode is successfully changed or if no MODE argument is
2441 supplied, and non-zero otherwise.
2443 Note that when the mode is interpreted as an octal number, each
2444 number of the umask is subtracted from `7'. Thus, a umask of `022'
2445 results in permissions of `755'.
2449 Each variable or function NAME is removed. If no options are
2450 supplied, or the `-v' option is given, each NAME refers to a shell
2451 variable. If the `-f' option is given, the NAMEs refer to shell
2452 functions, and the function definition is removed. Readonly
2453 variables and functions may not be unset. The return status is
2454 zero unless a NAME does not exist or is readonly.
2457 File: bashref.info, Node: Bash Builtins, Next: The Set Builtin, Prev: Bourne Shell Builtins, Up: Shell Builtin Commands
2459 Bash Builtin Commands
2460 =====================
2462 This section describes builtin commands which are unique to or have
2463 been extended in Bash. Some of these commands are specified in the
2464 POSIX 1003.2 standard.
2467 alias [`-p'] [NAME[=VALUE] ...]
2469 Without arguments or with the `-p' option, `alias' prints the list
2470 of aliases on the standard output in a form that allows them to be
2471 reused as input. If arguments are supplied, an alias is defined
2472 for each NAME whose VALUE is given. If no VALUE is given, the name
2473 and value of the alias is printed. Aliases are described in *Note
2477 bind [-m KEYMAP] [-lpsvPSV]
2478 bind [-m KEYMAP] [-q FUNCTION] [-u FUNCTION] [-r KEYSEQ]
2479 bind [-m KEYMAP] -f FILENAME
2480 bind [-m KEYMAP] -x KEYSEQ:SHELL-COMMAND
2481 bind [-m KEYMAP] KEYSEQ:FUNCTION-NAME
2483 Display current Readline (*note Command Line Editing::) key and
2484 function bindings, or bind a key sequence to a Readline function
2485 or macro. The binding syntax accepted is identical to that of a
2486 Readline initialization file (*note Readline Init File::), but
2487 each binding must be passed as a separate argument: e.g.,
2488 `"\C-x\C-r":re-read-init-file'. Options, if supplied, have the
2492 Use KEYMAP as the keymap to be affected by the subsequent
2493 bindings. Acceptable KEYMAP names are `emacs',
2494 `emacs-standard', `emacs-meta', `emacs-ctlx', `vi', `vi-move',
2495 `vi-command', and `vi-insert'. `vi' is equivalent to
2496 `vi-command'; `emacs' is equivalent to `emacs-standard'.
2499 List the names of all Readline functions.
2502 Display Readline function names and bindings in such a way
2503 that they can be used as input or in a Readline
2504 initialization file.
2507 List current Readline function names and bindings.
2510 Display Readline variable names and values in such a way that
2511 they can be used as input or in a Readline initialization
2515 List current Readline variable names and values.
2518 Display Readline key sequences bound to macros and the
2519 strings they output in such a way that they can be used as
2520 input or in a Readline initialization file.
2523 Display Readline key sequences bound to macros and the
2524 strings they output.
2527 Read key bindings from FILENAME.
2530 Query about which keys invoke the named FUNCTION.
2533 Unbind all keys bound to the named FUNCTION.
2536 Remove any current binding for KEYSEQ.
2538 `-x KEYSEQ:SHELL-COMMAND'
2539 Cause SHELL-COMMAND to be executed whenever KEYSEQ is entered.
2541 The return status is zero unless an invalid option is supplied or
2545 builtin [SHELL-BUILTIN [ARGS]]
2546 Run a shell builtin, passing it ARGS, and return its exit status.
2547 This is useful when defining a shell function with the same name
2548 as a shell builtin, retaining the functionality of the builtin
2549 within the function. The return status is non-zero if
2550 SHELL-BUILTIN is not a shell builtin command.
2553 command [-pVv] COMMAND [ARGUMENTS ...]
2554 Runs COMMAND with ARGUMENTS ignoring any shell function named
2555 COMMAND. Only shell builtin commands or commands found by
2556 searching the `PATH' are executed. If there is a shell function
2557 named `ls', running `command ls' within the function will execute
2558 the external command `ls' instead of calling the function
2559 recursively. The `-p' option means to use a default value for
2560 `PATH' that is guaranteed to find all of the standard utilities.
2561 The return status in this case is 127 if COMMAND cannot be found
2562 or an error occurred, and the exit status of COMMAND otherwise.
2564 If either the `-V' or `-v' option is supplied, a description of
2565 COMMAND is printed. The `-v' option causes a single word
2566 indicating the command or file name used to invoke COMMAND to be
2567 displayed; the `-V' option produces a more verbose description.
2568 In this case, the return status is zero if COMMAND is found, and
2572 declare [-afFrxi] [-p] [NAME[=VALUE]]
2574 Declare variables and give them attributes. If no NAMEs are
2575 given, then display the values of variables instead.
2577 The `-p' option will display the attributes and values of each
2578 NAME. When `-p' is used, additional options are ignored. The
2579 `-F' option inhibits the display of function definitions; only the
2580 function name and attributes are printed. `-F' implies `-f'. The
2581 following options can be used to restrict output to variables with
2582 the specified attributes or to give variables attributes:
2585 Each NAME is an array variable (*note Arrays::).
2588 Use function names only.
2591 The variable is to be treated as an integer; arithmetic
2592 evaluation (*note Shell Arithmetic::) is performed when the
2593 variable is assigned a value.
2596 Make NAMEs readonly. These names cannot then be assigned
2597 values by subsequent assignment statements or unset.
2600 Mark each NAME for export to subsequent commands via the
2603 Using `+' instead of `-' turns off the attribute instead. When
2604 used in a function, `declare' makes each NAME local, as with the
2607 The return status is zero unless an invalid option is encountered,
2608 an attempt is made to define a function using `-f foo=bar', an
2609 attempt is made to assign a value to a readonly variable, an
2610 attempt is made to assign a value to an array variable without
2611 using the compound assignment syntax (*note Arrays::), one of the
2612 NAMES is not a valid shell variable name, an attempt is made to
2613 turn off readonly status for a readonly variable, an attempt is
2614 made to turn off array status for an array variable, or an attempt
2615 is made to display a non-existent function with `-f'.
2618 echo [-neE] [ARG ...]
2619 Output the ARGs, separated by spaces, terminated with a newline.
2620 The return status is always 0. If `-n' is specified, the trailing
2621 newline is suppressed. If the `-e' option is given,
2622 interpretation of the following backslash-escaped characters is
2623 enabled. The `-E' option disables the interpretation of these
2624 escape characters, even on systems where they are interpreted by
2625 default. The `xpg_echo' shell option may be used to dynamically
2626 determine whether or not `echo' expands these escape characters by
2627 default. `echo' interprets the following escape sequences:
2635 suppress trailing newline
2659 the eight-bit character whose value is the octal value NNN
2660 (one to three digits)
2663 the eight-bit character whose value is the hexadecimal value
2664 HH (one or two hex digits)
2667 enable [-n] [-p] [-f FILENAME] [-ads] [NAME ...]
2668 Enable and disable builtin shell commands. Disabling a builtin
2669 allows a disk command which has the same name as a shell builtin
2670 to be executed without specifying a full pathname, even though the
2671 shell normally searches for builtins before disk commands. If
2672 `-n' is used, the NAMEs become disabled. Otherwise NAMEs are
2673 enabled. For example, to use the `test' binary found via `$PATH'
2674 instead of the shell builtin version, type `enable -n test'.
2676 If the `-p' option is supplied, or no NAME arguments appear, a
2677 list of shell builtins is printed. With no other arguments, the
2678 list consists of all enabled shell builtins. The `-a' option
2679 means to list each builtin with an indication of whether or not it
2682 The `-f' option means to load the new builtin command NAME from
2683 shared object FILENAME, on systems that support dynamic loading.
2684 The `-d' option will delete a builtin loaded with `-f'.
2686 If there are no options, a list of the shell builtins is displayed.
2687 The `-s' option restricts `enable' to the POSIX special builtins.
2688 If `-s' is used with `-f', the new builtin becomes a special
2689 builtin (*note Special Builtins::).
2691 The return status is zero unless a NAME is not a shell builtin or
2692 there is an error loading a new builtin from a shared object.
2696 Display helpful information about builtin commands. If PATTERN is
2697 specified, `help' gives detailed help on all commands matching
2698 PATTERN, otherwise a list of the builtins is printed. The `-s'
2699 option restricts the information displayed to a short usage
2700 synopsis. The return status is zero unless no command matches
2704 let EXPRESSION [EXPRESSION]
2705 The `let' builtin allows arithmetic to be performed on shell
2706 variables. Each EXPRESSION is evaluated according to the rules
2707 given below in *Note Shell Arithmetic::. If the last EXPRESSION
2708 evaluates to 0, `let' returns 1; otherwise 0 is returned.
2711 local [OPTION] NAME[=VALUE]
2712 For each argument, a local variable named NAME is created, and
2713 assigned VALUE. The OPTION can be any of the options accepted by
2714 `declare'. `local' can only be used within a function; it makes
2715 the variable NAME have a visible scope restricted to that function
2716 and its children. The return status is zero unless `local' is
2717 used outside a function, an invalid NAME is supplied, or NAME is a
2722 Exit a login shell, returning a status of N to the shell's parent.
2725 `printf' FORMAT [ARGUMENTS]
2726 Write the formatted ARGUMENTS to the standard output under the
2727 control of the FORMAT. The FORMAT is a character string which
2728 contains three types of objects: plain characters, which are
2729 simply copied to standard output, character escape sequences,
2730 which are converted and copied to the standard output, and format
2731 specifications, each of which causes printing of the next
2732 successive ARGUMENT. In addition to the standard `printf(1)'
2733 formats, `%b' causes `printf' to expand backslash escape sequences
2734 in the corresponding ARGUMENT, and `%q' causes `printf' to output
2735 the corresponding ARGUMENT in a format that can be reused as shell
2738 The FORMAT is reused as necessary to consume all of the ARGUMENTS.
2739 If the FORMAT requires more ARGUMENTS than are supplied, the extra
2740 format specifications behave as if a zero value or null string, as
2741 appropriate, had been supplied. The return value is zero on
2742 success, non-zero on failure.
2745 read [-ers] [-a ANAME] [-p PROMPT] [-t TIMEOUT] [-n NCHARS] [-d DELIM] [NAME ...]
2746 One line is read from the standard input, and the first word is
2747 assigned to the first NAME, the second word to the second NAME,
2748 and so on, with leftover words and their intervening separators
2749 assigned to the last NAME. If there are fewer words read from the
2750 standard input than names, the remaining names are assigned empty
2751 values. The characters in the value of the `IFS' variable are
2752 used to split the line into words. The backslash character `\'
2753 may be used to remove any special meaning for the next character
2754 read and for line continuation. If no names are supplied, the
2755 line read is assigned to the variable `REPLY'. The return code is
2756 zero, unless end-of-file is encountered or `read' times out.
2757 Options, if supplied, have the following meanings:
2760 The words are assigned to sequential indices of the array
2761 variable ANAME, starting at 0. All elements are removed from
2762 ANAME before the assignment. Other NAME arguments are
2766 The first character of DELIM is used to terminate the input
2767 line, rather than newline.
2770 Readline (*note Command Line Editing::) is used to obtain the
2774 `read' returns after reading NCHARS characters rather than
2775 waiting for a complete line of input.
2778 Display PROMPT, without a trailing newline, before attempting
2779 to read any input. The prompt is displayed only if input is
2780 coming from a terminal.
2783 If this option is given, backslash does not act as an escape
2784 character. The backslash is considered to be part of the
2785 line. In particular, a backslash-newline pair may not be
2786 used as a line continuation.
2789 Silent mode. If input is coming from a terminal, characters
2793 Cause `read' to time out and return failure if a complete
2794 line of input is not read within TIMEOUT seconds. This
2795 option has no effect if `read' is not reading input from the
2799 shopt [-pqsu] [-o] [OPTNAME ...]
2800 Toggle the values of variables controlling optional shell behavior.
2801 With no options, or with the `-p' option, a list of all settable
2802 options is displayed, with an indication of whether or not each is
2803 set. The `-p' option causes output to be displayed in a form that
2804 may be reused as input. Other options have the following meanings:
2807 Enable (set) each OPTNAME.
2810 Disable (unset) each OPTNAME.
2813 Suppresses normal output; the return status indicates whether
2814 the OPTNAME is set or unset. If multiple OPTNAME arguments
2815 are given with `-q', the return status is zero if all
2816 OPTNAMES are enabled; non-zero otherwise.
2819 Restricts the values of OPTNAME to be those defined for the
2820 `-o' option to the `set' builtin (*note The Set Builtin::).
2822 If either `-s' or `-u' is used with no OPTNAME arguments, the
2823 display is limited to those options which are set or unset,
2826 Unless otherwise noted, the `shopt' options are disabled (off) by
2829 The return status when listing options is zero if all OPTNAMES are
2830 enabled, non-zero otherwise. When setting or unsetting options,
2831 the return status is zero unless an OPTNAME is not a valid shell
2834 The list of `shopt' options is:
2836 If this is set, an argument to the `cd' builtin command that
2837 is not a directory is assumed to be the name of a variable
2838 whose value is the directory to change to.
2841 If set, minor errors in the spelling of a directory component
2842 in a `cd' command will be corrected. The errors checked for
2843 are transposed characters, a missing character, and a
2844 character too many. If a correction is found, the corrected
2845 path is printed, and the command proceeds. This option is
2846 only used by interactive shells.
2849 If this is set, Bash checks that a command found in the hash
2850 table exists before trying to execute it. If a hashed
2851 command no longer exists, a normal path search is performed.
2854 If set, Bash checks the window size after each command and,
2855 if necessary, updates the values of `LINES' and `COLUMNS'.
2858 If set, Bash attempts to save all lines of a multiple-line
2859 command in the same history entry. This allows easy
2860 re-editing of multi-line commands.
2863 If set, Bash includes filenames beginning with a `.' in the
2864 results of filename expansion.
2867 If this is set, a non-interactive shell will not exit if it
2868 cannot execute the file specified as an argument to the `exec'
2869 builtin command. An interactive shell does not exit if `exec'
2873 If set, aliases are expanded as described below under Aliases,
2874 *Note Aliases::. This option is enabled by default for
2878 If set, the extended pattern matching features described above
2879 (*note Pattern Matching::) are enabled.
2882 If set, the history list is appended to the file named by the
2883 value of the `HISTFILE' variable when the shell exits, rather
2884 than overwriting the file.
2887 If set, and Readline is being used, a user is given the
2888 opportunity to re-edit a failed history substitution.
2891 If set, and Readline is being used, the results of history
2892 substitution are not immediately passed to the shell parser.
2893 Instead, the resulting line is loaded into the Readline
2894 editing buffer, allowing further modification.
2897 If set, and Readline is being used, Bash will attempt to
2898 perform hostname completion when a word containing a `@' is
2899 being completed (*note Commands For Completion::). This
2900 option is enabled by default.
2903 If set, Bash will send `SIGHUP' to all jobs when an
2904 interactive login shell exits (*note Signals::).
2906 `interactive_comments'
2907 Allow a word beginning with `#' to cause that word and all
2908 remaining characters on that line to be ignored in an
2909 interactive shell. This option is enabled by default.
2912 If enabled, and the `cmdhist' option is enabled, multi-line
2913 commands are saved to the history with embedded newlines
2914 rather than using semicolon separators where possible.
2917 The shell sets this option if it is started as a login shell
2918 (*note Invoking Bash::). The value may not be changed.
2921 If set, and a file that Bash is checking for mail has been
2922 accessed since the last time it was checked, the message
2923 `"The mail in MAILFILE has been read"' is displayed.
2925 `no_empty_cmd_completion'
2926 If set, and Readline is being used, Bash will not attempt to
2927 search the `PATH' for possible completions when completion is
2928 attempted on an empty line.
2931 If set, Bash matches filenames in a case-insensitive fashion
2932 when performing filename expansion.
2935 If set, Bash allows filename patterns which match no files to
2936 expand to a null string, rather than themselves.
2939 If set, the programmable completion facilities (*note
2940 Programmable Completion::) are enabled. This option is
2944 If set, prompt strings undergo variable and parameter
2945 expansion after being expanded (*note Printing a Prompt::).
2946 This option is enabled by default.
2949 The shell sets this option if it is started in restricted mode
2950 (*note The Restricted Shell::). The value may not be changed.
2951 This is not reset when the startup files are executed,
2952 allowing the startup files to discover whether or not a shell
2956 If this is set, the `shift' builtin prints an error message
2957 when the shift count exceeds the number of positional
2961 If set, the `source' builtin uses the value of `PATH' to find
2962 the directory containing the file supplied as an argument.
2963 This option is enabled by default.
2966 If set, the `echo' builtin expands backslash-escape sequences
2969 The return status when listing options is zero if all OPTNAMES are
2970 enabled, non-zero otherwise. When setting or unsetting options,
2971 the return status is zero unless an OPTNAME is not a valid shell
2976 A synonym for `.' (*note Bourne Shell Builtins::).
2979 type [-atp] [NAME ...]
2980 For each NAME, indicate how it would be interpreted if used as a
2983 If the `-t' option is used, `type' prints a single word which is
2984 one of `alias', `function', `builtin', `file' or `keyword', if
2985 NAME is an alias, shell function, shell builtin, disk file, or
2986 shell reserved word, respectively. If the NAME is not found, then
2987 nothing is printed, and `type' returns a failure status.
2989 If the `-p' option is used, `type' either returns the name of the
2990 disk file that would be executed, or nothing if `-t' would not
2993 If the `-a' option is used, `type' returns all of the places that
2994 contain an executable named FILE. This includes aliases and
2995 functions, if and only if the `-p' option is not also used.
2997 The return status is zero if any of the NAMES are found, non-zero
3001 typeset [-afFrxi] [-p] [NAME[=VALUE]]
3002 The `typeset' command is supplied for compatibility with the Korn
3003 shell; however, it has been deprecated in favor of the `declare'
3007 ulimit [-acdflmnpstuvSH] [LIMIT]
3008 `ulimit' provides control over the resources available to processes
3009 started by the shell, on systems that allow such control. If an
3010 option is given, it is interpreted as follows:
3012 Change and report the soft limit associated with a resource.
3015 Change and report the hard limit associated with a resource.
3018 All current limits are reported.
3021 The maximum size of core files created.
3024 The maximum size of a process's data segment.
3027 The maximum size of files created by the shell.
3030 The maximum size that may be locked into memory.
3033 The maximum resident set size.
3036 The maximum number of open file descriptors.
3039 The pipe buffer size.
3042 The maximum stack size.
3045 The maximum amount of cpu time in seconds.
3048 The maximum number of processes available to a single user.
3051 The maximum amount of virtual memory available to the process.
3053 If LIMIT is given, it is the new value of the specified resource;
3054 the special LIMIT values `hard', `soft', and `unlimited' stand for
3055 the current hard limit, the current soft limit, and no limit,
3056 respectively. Otherwise, the current value of the soft limit for
3057 the specified resource is printed, unless the `-H' option is
3058 supplied. When setting new limits, if neither `-H' nor `-S' is
3059 supplied, both the hard and soft limits are set. If no option is
3060 given, then `-f' is assumed. Values are in 1024-byte increments,
3061 except for `-t', which is in seconds, `-p', which is in units of
3062 512-byte blocks, and `-n' and `-u', which are unscaled values.
3064 The return status is zero unless an invalid option or argument is
3065 supplied, or an error occurs while setting a new limit.
3068 unalias [-a] [NAME ... ]
3070 Remove each NAME from the list of aliases. If `-a' is supplied,
3071 all aliases are removed. Aliases are described in *Note Aliases::.
3074 File: bashref.info, Node: The Set Builtin, Next: Special Builtins, Prev: Bash Builtins, Up: Shell Builtin Commands
3079 This builtin is so complicated that it deserves its own section.
3082 set [--abefhkmnptuvxBCHP] [-o OPTION] [ARGUMENT ...]
3084 If no options or arguments are supplied, `set' displays the names
3085 and values of all shell variables and functions, sorted according
3086 to the current locale, in a format that may be reused as input.
3088 When options are supplied, they set or unset shell attributes.
3089 Options, if specified, have the following meanings:
3092 Mark variables and function which are modified or created for
3093 export to the environment of subsequent commands.
3096 Cause the status of terminated background jobs to be reported
3097 immediately, rather than before printing the next primary
3101 Exit immediately if a simple command (*note Simple
3102 Commands::) exits with a non-zero status, unless the command
3103 that fails is part of an `until' or `while' loop, part of an
3104 `if' statement, part of a `&&' or `||' list, or if the
3105 command's return status is being inverted using `!'. A trap
3106 on `ERR', if set, is executed before the shell exits.
3109 Disable file name generation (globbing).
3112 Locate and remember (hash) commands as they are looked up for
3113 execution. This option is enabled by default.
3116 All arguments in the form of assignment statements are placed
3117 in the environment for a command, not just those that precede
3121 Job control is enabled (*note Job Control::).
3124 Read commands but do not execute them; this may be used to
3125 check a script for syntax errors. This option is ignored by
3129 Set the option corresponding to OPTION-NAME:
3138 Use an `emacs'-style line editing interface (*note
3139 Command Line Editing::).
3151 Enable command history, as described in *Note Bash
3152 History Facilities::. This option is on by default in
3156 An interactive shell will not exit upon reading EOF.
3189 Change the behavior of Bash where the default operation
3190 differs from the POSIX 1003.2 standard to match the
3191 standard (*note Bash POSIX Mode::). This is intended to
3192 make Bash behave as a strict superset of that standard.
3201 Use a `vi'-style line editing interface.
3207 Turn on privileged mode. In this mode, the `$BASH_ENV' and
3208 `$ENV' files are not processed, shell functions are not
3209 inherited from the environment, and the `SHELLOPTS' variable,
3210 if it appears in the environment, is ignored. If the shell
3211 is started with the effective user (group) id not equal to the
3212 real user (group) id, and the `-p' option is not supplied,
3213 these actions are taken and the effective user id is set to
3214 the real user id. If the `-p' option is supplied at startup,
3215 the effective user id is not reset. Turning this option off
3216 causes the effective user and group ids to be set to the real
3220 Exit after reading and executing one command.
3223 Treat unset variables as an error when performing parameter
3224 expansion. An error message will be written to the standard
3225 error, and a non-interactive shell will exit.
3228 Print shell input lines as they are read.
3231 Print a trace of simple commands and their arguments after
3232 they are expanded and before they are executed.
3235 The shell will perform brace expansion (*note Brace
3236 Expansion::). This option is on by default.
3239 Prevent output redirection using `>', `>&', and `<>' from
3240 overwriting existing files.
3243 Enable `!' style history substitution (*note History
3244 Interaction::). This option is on by default for interactive
3248 If set, do not follow symbolic links when performing commands
3249 such as `cd' which change the current directory. The
3250 physical directory is used instead. By default, Bash follows
3251 the logical chain of directories when performing commands
3252 which change the current directory.
3254 For example, if `/usr/sys' is a symbolic link to
3255 `/usr/local/sys' then:
3256 $ cd /usr/sys; echo $PWD
3261 If `set -P' is on, then:
3262 $ cd /usr/sys; echo $PWD
3268 If no arguments follow this option, then the positional
3269 parameters are unset. Otherwise, the positional parameters
3270 are set to the ARGUMENTS, even if some of them begin with a
3274 Signal the end of options, cause all remaining ARGUMENTS to
3275 be assigned to the positional parameters. The `-x' and `-v'
3276 options are turned off. If there are no arguments, the
3277 positional parameters remain unchanged.
3279 Using `+' rather than `-' causes these options to be turned off.
3280 The options can also be used upon invocation of the shell. The
3281 current set of options may be found in `$-'.
3283 The remaining N ARGUMENTS are positional parameters and are
3284 assigned, in order, to `$1', `$2', ... `$N'. The special
3285 parameter `#' is set to N.
3287 The return status is always zero unless an invalid option is
3291 File: bashref.info, Node: Special Builtins, Prev: The Set Builtin, Up: Shell Builtin Commands
3296 For historical reasons, the POSIX 1003.2 standard has classified
3297 several builtin commands as _special_. When Bash is executing in POSIX
3298 mode, the special builtins differ from other builtin commands in three
3301 1. Special builtins are found before shell functions during command
3304 2. If a special builtin returns an error status, a non-interactive
3307 3. Assignment statements preceding the command stay in effect in the
3308 shell environment after the command completes.
3310 When Bash is not executing in POSIX mode, these builtins behave no
3311 differently than the rest of the Bash builtin commands. The Bash POSIX
3312 mode is described in *Note Bash POSIX Mode::.
3314 These are the POSIX special builtins:
3315 break : . continue eval exec exit export readonly return set
3319 File: bashref.info, Node: Shell Variables, Next: Bash Features, Prev: Shell Builtin Commands, Up: Top
3326 * Bourne Shell Variables:: Variables which Bash uses in the same way
3327 as the Bourne Shell.
3328 * Bash Variables:: List of variables that exist in Bash.
3330 This chapter describes the shell variables that Bash uses. Bash
3331 automatically assigns default values to a number of variables.
3334 File: bashref.info, Node: Bourne Shell Variables, Next: Bash Variables, Up: Shell Variables
3336 Bourne Shell Variables
3337 ======================
3339 Bash uses certain shell variables in the same way as the Bourne
3340 shell. In some cases, Bash assigns a default value to the variable.
3343 A colon-separated list of directories used as a search path for
3344 the `cd' builtin command.
3347 The current user's home directory; the default for the `cd' builtin
3348 command. The value of this variable is also used by tilde
3349 expansion (*note Tilde Expansion::).
3352 A list of characters that separate fields; used when the shell
3353 splits words as part of expansion.
3356 If this parameter is set to a filename and the `MAILPATH' variable
3357 is not set, Bash informs the user of the arrival of mail in the
3361 A colon-separated list of filenames which the shell periodically
3362 checks for new mail. Each list entry can specify the message that
3363 is printed when new mail arrives in the mail file by separating
3364 the file name from the message with a `?'. When used in the text
3365 of the message, `$_' expands to the name of the current mail file.
3368 The value of the last option argument processed by the `getopts'
3372 The index of the last option argument processed by the `getopts'
3376 A colon-separated list of directories in which the shell looks for
3380 The primary prompt string. The default value is `\s-\v\$ '.
3381 *Note Printing a Prompt::, for the complete list of escape
3382 sequences that are expanded before `PS1' is displayed.
3385 The secondary prompt string. The default value is `> '.
3388 File: bashref.info, Node: Bash Variables, Prev: Bourne Shell Variables, Up: Shell Variables
3393 These variables are set or used by Bash, but other shells do not
3394 normally treat them specially.
3396 A few variables used by Bash are described in different chapters:
3397 variables for controlling the job control facilities (*note Job Control
3401 The full pathname used to execute the current instance of Bash.
3404 If this variable is set when Bash is invoked to execute a shell
3405 script, its value is expanded and used as the name of a startup
3406 file to read before executing the script. *Note Bash Startup
3410 The version number of the current instance of Bash.
3413 A readonly array variable (*note Arrays::) whose members hold
3414 version information for this instance of Bash. The values
3415 assigned to the array members are as follows:
3418 The major version number (the RELEASE).
3421 The minor version number (the VERSION).
3430 The release status (e.g., BETA1).
3433 The value of `MACHTYPE'.
3436 Used by the `select' builtin command to determine the terminal
3437 width when printing selection lists. Automatically set upon
3438 receipt of a `SIGWINCH'.
3441 An index into `${COMP_WORDS}' of the word containing the current
3442 cursor position. This variable is available only in shell
3443 functions invoked by the programmable completion facilities (*note
3444 Programmable Completion::).
3447 The current command line. This variable is available only in
3448 shell functions and external commands invoked by the programmable
3449 completion facilities (*note Programmable Completion::).
3452 The index of the current cursor position relative to the beginning
3453 of the current command. If the current cursor position is at the
3454 end of the current command, the value of this variable is equal to
3455 `${#COMP_LINE}'. This variable is available only in shell
3456 functions and external commands invoked by the programmable
3457 completion facilities (*note Programmable Completion::).
3460 An array variable consisting of the individual words in the
3461 current command line. This variable is available only in shell
3462 functions invoked by the programmable completion facilities (*note
3463 Programmable Completion::).
3466 An array variable from which Bash reads the possible completions
3467 generated by a shell function invoked by the programmable
3468 completion facility (*note Programmable Completion::).
3471 An array variable containing the current contents of the directory
3472 stack. Directories appear in the stack in the order they are
3473 displayed by the `dirs' builtin. Assigning to members of this
3474 array variable may be used to modify directories already in the
3475 stack, but the `pushd' and `popd' builtins must be used to add and
3476 remove directories. Assignment to this variable will not change
3477 the current directory. If `DIRSTACK' is unset, it loses its
3478 special properties, even if it is subsequently reset.
3481 The numeric effective user id of the current user. This variable
3485 The editor used as a default by the `-e' option to the `fc'
3489 A colon-separated list of suffixes to ignore when performing
3490 filename completion. A file name whose suffix matches one of the
3491 entries in `FIGNORE' is excluded from the list of matched file
3492 names. A sample value is `.o:~'
3495 The name of any currently-executing shell function. This variable
3496 exists only when a shell function is executing. Assignments to
3497 `FUNCNAME' have no effect and return an error status. If
3498 `FUNCNAME' is unset, it loses its special properties, even if it
3499 is subsequently reset.
3502 A colon-separated list of patterns defining the set of filenames to
3503 be ignored by filename expansion. If a filename matched by a
3504 filename expansion pattern also matches one of the patterns in
3505 `GLOBIGNORE', it is removed from the list of matches.
3508 An array variable containing the list of groups of which the
3509 current user is a member. Assignments to `GROUPS' have no effect
3510 and return an error status. If `GROUPS' is unset, it loses its
3511 special properties, even if it is subsequently reset.
3514 Up to three characters which control history expansion, quick
3515 substitution, and tokenization (*note History Interaction::). The
3516 first character is the HISTORY EXPANSION character, that is, the
3517 character which signifies the start of a history expansion,
3518 normally `!'. The second character is the character which
3519 signifies `quick substitution' when seen as the first character on
3520 a line, normally `^'. The optional third character is the
3521 character which indicates that the remainder of the line is a
3522 comment when found as the first character of a word, usually `#'.
3523 The history comment character causes history substitution to be
3524 skipped for the remaining words on the line. It does not
3525 necessarily cause the shell parser to treat the rest of the line
3529 The history number, or index in the history list, of the current
3530 command. If `HISTCMD' is unset, it loses its special properties,
3531 even if it is subsequently reset.
3534 A value of `ignorespace' means to not enter lines which begin with
3535 a space or tab into the history list. A value of `ignoredups'
3536 means to not enter lines which match the last entered line. A
3537 value of `ignoreboth' combines the two options. Unset, or set to
3538 any other value than those above, means to save all lines on the
3539 history list. The second and subsequent lines of a multi-line
3540 compound command are not tested, and are added to the history
3541 regardless of the value of `HISTCONTROL'.
3544 The name of the file to which the command history is saved. The
3545 default value is `~/.bash_history'.
3548 The maximum number of lines contained in the history file. When
3549 this variable is assigned a value, the history file is truncated,
3550 if necessary, to contain no more than that number of lines. The
3551 history file is also truncated to this size after writing it when
3552 an interactive shell exits. The default value is 500.
3555 A colon-separated list of patterns used to decide which command
3556 lines should be saved on the history list. Each pattern is
3557 anchored at the beginning of the line and must match the complete
3558 line (no implicit `*' is appended). Each pattern is tested
3559 against the line after the checks specified by `HISTCONTROL' are
3560 applied. In addition to the normal shell pattern matching
3561 characters, `&' matches the previous history line. `&' may be
3562 escaped using a backslash; the backslash is removed before
3563 attempting a match. The second and subsequent lines of a
3564 multi-line compound command are not tested, and are added to the
3565 history regardless of the value of `HISTIGNORE'.
3567 `HISTIGNORE' subsumes the function of `HISTCONTROL'. A pattern of
3568 `&' is identical to `ignoredups', and a pattern of `[ ]*' is
3569 identical to `ignorespace'. Combining these two patterns,
3570 separating them with a colon, provides the functionality of
3574 The maximum number of commands to remember on the history list.
3575 The default value is 500.
3578 Contains the name of a file in the same format as `/etc/hosts' that
3579 should be read when the shell needs to complete a hostname. The
3580 list of possible hostname completions may be changed while the
3581 shell is running; the next time hostname completion is attempted
3582 after the value is changed, Bash adds the contents of the new file
3583 to the existing list. If `HOSTFILE' is set, but has no value,
3584 Bash attempts to read `/etc/hosts' to obtain the list of possible
3585 hostname completions. When `HOSTFILE' is unset, the hostname list
3589 The name of the current host.
3592 A string describing the machine Bash is running on.
3595 Controls the action of the shell on receipt of an `EOF' character
3596 as the sole input. If set, the value denotes the number of
3597 consecutive `EOF' characters that can be read as the first
3598 character on an input line before the shell will exit. If the
3599 variable exists but does not have a numeric value (or has no
3600 value) then the default is 10. If the variable does not exist,
3601 then `EOF' signifies the end of input to the shell. This is only
3602 in effect for interactive shells.
3605 The name of the Readline initialization file, overriding the
3606 default of `~/.inputrc'.
3609 Used to determine the locale category for any category not
3610 specifically selected with a variable starting with `LC_'.
3613 This variable overrides the value of `LANG' and any other `LC_'
3614 variable specifying a locale category.
3617 This variable determines the collation order used when sorting the
3618 results of filename expansion, and determines the behavior of
3619 range expressions, equivalence classes, and collating sequences
3620 within filename expansion and pattern matching (*note Filename
3624 This variable determines the interpretation of characters and the
3625 behavior of character classes within filename expansion and pattern
3626 matching (*note Filename Expansion::).
3629 This variable determines the locale used to translate double-quoted
3630 strings preceded by a `$' (*note Locale Translation::).
3633 This variable determines the locale category used for number
3637 The line number in the script or shell function currently
3641 Used by the `select' builtin command to determine the column length
3642 for printing selection lists. Automatically set upon receipt of a
3646 A string that fully describes the system type on which Bash is
3647 executing, in the standard GNU CPU-COMPANY-SYSTEM format.
3650 How often (in seconds) that the shell should check for mail in the
3651 files specified in the `MAILPATH' or `MAIL' variables. The
3652 default is 60 seconds. When it is time to check for mail, the
3653 shell does so before displaying the primary prompt. If this
3654 variable is unset, or set to a value that is not a number greater
3655 than or equal to zero, the shell disables mail checking.
3658 The previous working directory as set by the `cd' builtin.
3661 If set to the value 1, Bash displays error messages generated by
3662 the `getopts' builtin command.
3665 A string describing the operating system Bash is running on.
3668 An array variable (*note Arrays::) containing a list of exit
3669 status values from the processes in the most-recently-executed
3670 foreground pipeline (which may contain only a single command).
3673 If this variable is in the environment when `bash' starts, the
3674 shell enters POSIX mode (*note Bash POSIX Mode::) before reading
3675 the startup files, as if the `--posix' invocation option had been
3676 supplied. If it is set while the shell is running, `bash' enables
3677 POSIX mode, as if the command
3683 The process ID of the shell's parent process. This variable is
3687 If set, the value is interpreted as a command to execute before
3688 the printing of each primary prompt (`$PS1').
3691 The value of this variable is used as the prompt for the `select'
3692 command. If this variable is not set, the `select' command
3696 The value is the prompt printed before the command line is echoed
3697 when the `-x' option is set (*note The Set Builtin::). The first
3698 character of `PS4' is replicated multiple times, as necessary, to
3699 indicate multiple levels of indirection. The default is `+ '.
3702 The current working directory as set by the `cd' builtin.
3705 Each time this parameter is referenced, a random integer between 0
3706 and 32767 is generated. Assigning a value to this variable seeds
3707 the random number generator.
3710 The default variable for the `read' builtin.
3713 This variable expands to the number of seconds since the shell was
3714 started. Assignment to this variable resets the count to the
3715 value assigned, and the expanded value becomes the value assigned
3716 plus the number of seconds since the assignment.
3719 A colon-separated list of enabled shell options. Each word in the
3720 list is a valid argument for the `-o' option to the `set' builtin
3721 command (*note The Set Builtin::). The options appearing in
3722 `SHELLOPTS' are those reported as `on' by `set -o'. If this
3723 variable is in the environment when Bash starts up, each shell
3724 option in the list will be enabled before reading any startup
3725 files. This variable is readonly.
3728 Incremented by one each time a new instance of Bash is started.
3729 This is intended to be a count of how deeply your Bash shells are
3733 The value of this parameter is used as a format string specifying
3734 how the timing information for pipelines prefixed with the `time'
3735 reserved word should be displayed. The `%' character introduces an
3736 escape sequence that is expanded to a time value or other
3737 information. The escape sequences and their meanings are as
3738 follows; the braces denote optional portions.
3744 The elapsed time in seconds.
3747 The number of CPU seconds spent in user mode.
3750 The number of CPU seconds spent in system mode.
3753 The CPU percentage, computed as (%U + %S) / %R.
3755 The optional P is a digit specifying the precision, the number of
3756 fractional digits after a decimal point. A value of 0 causes no
3757 decimal point or fraction to be output. At most three places
3758 after the decimal point may be specified; values of P greater than
3759 3 are changed to 3. If P is not specified, the value 3 is used.
3761 The optional `l' specifies a longer format, including minutes, of
3762 the form MMmSS.FFs. The value of P determines whether or not the
3763 fraction is included.
3765 If this variable is not set, Bash acts as if it had the value
3766 `$'\nreal\t%3lR\nuser\t%3lU\nsys\t%3lS''
3767 If the value is null, no timing information is displayed. A
3768 trailing newline is added when the format string is displayed.
3771 If set to a value greater than zero, the value is interpreted as
3772 the number of seconds to wait for input after issuing the primary
3773 prompt when the shell is interactive. Bash terminates after that
3774 number of seconds if input does not arrive.
3777 The numeric real user id of the current user. This variable is
3781 File: bashref.info, Node: Bash Features, Next: Job Control, Prev: Shell Variables, Up: Top
3786 This section describes features unique to Bash.
3790 * Invoking Bash:: Command line options that you can give
3792 * Bash Startup Files:: When and how Bash executes scripts.
3793 * Interactive Shells:: What an interactive shell is.
3794 * Bash Conditional Expressions:: Primitives used in composing expressions for
3796 * Shell Arithmetic:: Arithmetic on shell variables.
3797 * Aliases:: Substituting one command for another.
3798 * Arrays:: Array Variables.
3799 * The Directory Stack:: History of visited directories.
3800 * Printing a Prompt:: Controlling the PS1 string.
3801 * The Restricted Shell:: A more controlled mode of shell execution.
3802 * Bash POSIX Mode:: Making Bash behave more closely to what
3803 the POSIX standard specifies.
3806 File: bashref.info, Node: Invoking Bash, Next: Bash Startup Files, Up: Bash Features
3811 bash [long-opt] [-ir] [-abefhkmnptuvxdBCDHP] [-o OPTION] [-O SHOPT_OPTION] [ARGUMENT ...]
3812 bash [long-opt] [-abefhkmnptuvxdBCDHP] [-o OPTION] [-O SHOPT_OPTION] -c STRING [ARGUMENT ...]
3813 bash [long-opt] -s [-abefhkmnptuvxdBCDHP] [-o OPTION] [-O SHOPT_OPTION] [ARGUMENT ...]
3815 In addition to the single-character shell command-line options
3816 (*note The Set Builtin::), there are several multi-character options
3817 that you can use. These options must appear on the command line before
3818 the single-character options in order for them to be recognized.
3821 A list of all double-quoted strings preceded by `$' is printed on
3822 the standard ouput in the GNU `gettext' PO (portable object) file
3823 format. Equivalent to `-D' except for the output format.
3829 Display a usage message on standard output and exit sucessfully.
3831 `--init-file FILENAME'
3833 Execute commands from FILENAME (instead of `~/.bashrc') in an
3837 Make this shell act as if it had been directly invoked by login.
3838 When the shell is interactive, this is equivalent to starting a
3839 login shell with `exec -l bash'. When the shell is not
3840 interactive, the login shell startup files will be executed.
3841 `exec bash --login' will replace the current shell with a Bash
3842 login shell. *Note Bash Startup Files::, for a description of the
3843 special behavior of a login shell.
3846 Do not use the GNU Readline library (*note Command Line Editing::)
3847 to read command lines when the shell is interactive.
3850 Don't load the system-wide startup file `/etc/profile' or any of
3851 the personal initialization files `~/.bash_profile',
3852 `~/.bash_login', or `~/.profile' when Bash is invoked as a login
3856 Don't read the `~/.bashrc' initialization file in an interactive
3857 shell. This is on by default if the shell is invoked as `sh'.
3860 Change the behavior of Bash where the default operation differs
3861 from the POSIX 1003.2 standard to match the standard. This is
3862 intended to make Bash behave as a strict superset of that
3863 standard. *Note Bash POSIX Mode::, for a description of the Bash
3867 Make the shell a restricted shell (*note The Restricted Shell::).
3870 Equivalent to `-v'. Print shell input lines as they're read.
3873 Show version information for this instance of Bash on the standard
3874 output and exit successfully.
3876 There are several single-character options that may be supplied at
3877 invocation which are not available with the `set' builtin.
3880 Read and execute commands from STRING after processing the
3881 options, then exit. Any remaining arguments are assigned to the
3882 positional parameters, starting with `$0'.
3885 Force the shell to run interactively. Interactive shells are
3886 described in *Note Interactive Shells::.
3889 Make the shell a restricted shell (*note The Restricted Shell::).
3892 If this option is present, or if no arguments remain after option
3893 processing, then commands are read from the standard input. This
3894 option allows the positional parameters to be set when invoking an
3898 A list of all double-quoted strings preceded by `$' is printed on
3899 the standard ouput. These are the strings that are subject to
3900 language translation when the current locale is not `C' or `POSIX'
3901 (*note Locale Translation::). This implies the `-n' option; no
3902 commands will be executed.
3904 `[-+]O [SHOPT_OPTION]'
3905 SHOPT_OPTION is one of the shell options accepted by the `shopt'
3906 builtin (*note Shell Builtin Commands::). If SHOPT_OPTION is
3907 present, `-O' sets the value of that option; `+O' unsets it. If
3908 SHOPT_OPTION is not supplied, the names and values of the shell
3909 options accepted by `shopt' are printed on the standard output.
3910 If the invocation option is `+O', the output is displayed in a
3911 format that may be reused as input.
3914 A `--' signals the end of options and disables further option
3915 processing. Any arguments after the `--' are treated as filenames
3918 A _login_ shell is one whose first character of argument zero is
3919 `-', or one invoked with the `--login' option.
3921 An _interactive_ shell is one started without non-option arguments,
3922 unless `-s' is specified, without specifying the `-c' option, and whose
3923 input and output are both connected to terminals (as determined by
3924 `isatty(3)'), or one started with the `-i' option. *Note Interactive
3925 Shells::, for more information.
3927 If arguments remain after option processing, and neither the `-c'
3928 nor the `-s' option has been supplied, the first argument is assumed to
3929 be the name of a file containing shell commands (*note Shell Scripts::).
3930 When Bash is invoked in this fashion, `$0' is set to the name of the
3931 file, and the positional parameters are set to the remaining arguments.
3932 Bash reads and executes commands from this file, then exits. Bash's
3933 exit status is the exit status of the last command executed in the
3934 script. If no commands are executed, the exit status is 0.
3937 File: bashref.info, Node: Bash Startup Files, Next: Interactive Shells, Prev: Invoking Bash, Up: Bash Features
3942 This section describs how Bash executes its startup files. If any
3943 of the files exist but cannot be read, Bash reports an error. Tildes
3944 are expanded in file names as described above under Tilde Expansion
3945 (*note Tilde Expansion::).
3947 Interactive shells are described in *Note Interactive Shells::.
3949 Invoked as an interactive login shell, or with `--login'
3950 ........................................................
3952 When Bash is invoked as an interactive login shell, or as a
3953 non-interactive shell with the `--login' option, it first reads and
3954 executes commands from the file `/etc/profile', if that file exists.
3955 After reading that file, it looks for `~/.bash_profile',
3956 `~/.bash_login', and `~/.profile', in that order, and reads and
3957 executes commands from the first one that exists and is readable. The
3958 `--noprofile' option may be used when the shell is started to inhibit
3961 When a login shell exits, Bash reads and executes commands from the
3962 file `~/.bash_logout', if it exists.
3964 Invoked as an interactive non-login shell
3965 .........................................
3967 When an interactive shell that is not a login shell is started, Bash
3968 reads and executes commands from `~/.bashrc', if that file exists.
3969 This may be inhibited by using the `--norc' option. The `--rcfile
3970 FILE' option will force Bash to read and execute commands from FILE
3971 instead of `~/.bashrc'.
3973 So, typically, your `~/.bash_profile' contains the line
3974 `if [ -f ~/.bashrc ]; then . ~/.bashrc; fi'
3976 after (or before) any login-specific initializations.
3978 Invoked non-interactively
3979 .........................
3981 When Bash is started non-interactively, to run a shell script, for
3982 example, it looks for the variable `BASH_ENV' in the environment,
3983 expands its value if it appears there, and uses the expanded value as
3984 the name of a file to read and execute. Bash behaves as if the
3985 following command were executed:
3986 `if [ -n "$BASH_ENV" ]; then . "$BASH_ENV"; fi'
3988 but the value of the `PATH' variable is not used to search for the file
3991 As noted above, if a non-interactive shell is invoked with the
3992 `--login' option, Bash attempts to read and execute commands from the
3993 login shell startup files.
3995 Invoked with name `sh'
3996 ......................
3998 If Bash is invoked with the name `sh', it tries to mimic the startup
3999 behavior of historical versions of `sh' as closely as possible, while
4000 conforming to the POSIX standard as well.
4002 When invoked as an interactive login shell, or as a non-interactive
4003 shell with the `--login' option, it first attempts to read and execute
4004 commands from `/etc/profile' and `~/.profile', in that order. The
4005 `--noprofile' option may be used to inhibit this behavior. When
4006 invoked as an interactive shell with the name `sh', Bash looks for the
4007 variable `ENV', expands its value if it is defined, and uses the
4008 expanded value as the name of a file to read and execute. Since a
4009 shell invoked as `sh' does not attempt to read and execute commands
4010 from any other startup files, the `--rcfile' option has no effect. A
4011 non-interactive shell invoked with the name `sh' does not attempt to
4012 read any other startup files.
4014 When invoked as `sh', Bash enters POSIX mode after the startup files
4017 Invoked in POSIX mode
4018 .....................
4020 When Bash is started in POSIX mode, as with the `--posix' command
4021 line option, it follows the POSIX standard for startup files. In this
4022 mode, interactive shells expand the `ENV' variable and commands are
4023 read and executed from the file whose name is the expanded value. No
4024 other startup files are read.
4026 Invoked by remote shell daemon
4027 ..............................
4029 Bash attempts to determine when it is being run by the remote shell
4030 daemon, usually `rshd'. If Bash determines it is being run by rshd, it
4031 reads and executes commands from `~/.bashrc', if that file exists and
4032 is readable. It will not do this if invoked as `sh'. The `--norc'
4033 option may be used to inhibit this behavior, and the `--rcfile' option
4034 may be used to force another file to be read, but `rshd' does not
4035 generally invoke the shell with those options or allow them to be
4038 Invoked with unequal effective and real UID/GIDs
4039 ................................................
4041 If Bash is started with the effective user (group) id not equal to
4042 the real user (group) id, and the `-p' option is not supplied, no
4043 startup files are read, shell functions are not inherited from the
4044 environment, the `SHELLOPTS' variable, if it appears in the
4045 environment, is ignored, and the effective user id is set to the real
4046 user id. If the `-p' option is supplied at invocation, the startup
4047 behavior is the same, but the effective user id is not reset.
4050 File: bashref.info, Node: Interactive Shells, Next: Bash Conditional Expressions, Prev: Bash Startup Files, Up: Bash Features
4057 * What is an Interactive Shell?:: What determines whether a shell is Interactive.
4058 * Is this Shell Interactive?:: How to tell if a shell is interactive.
4059 * Interactive Shell Behavior:: What changes in a interactive shell?
4062 File: bashref.info, Node: What is an Interactive Shell?, Next: Is this Shell Interactive?, Up: Interactive Shells
4064 What is an Interactive Shell?
4065 -----------------------------
4067 An interactive shell is one started without non-option arguments,
4068 unless `-s' is specified, without specifiying the `-c' option, and
4069 whose input and output are both connected to terminals (as determined
4070 by `isatty(3)'), or one started with the `-i' option.
4072 An interactive shell generally reads from and writes to a user's
4075 The `-s' invocation option may be used to set the positional
4076 parameters when an interactive shell is started.
4079 File: bashref.info, Node: Is this Shell Interactive?, Next: Interactive Shell Behavior, Prev: What is an Interactive Shell?, Up: Interactive Shells
4081 Is this Shell Interactive?
4082 --------------------------
4084 To determine within a startup script whether or not Bash is running
4085 interactively, test the value of the `-' special parameter. It
4086 contains `i' when the shell is interactive. For example:
4089 *i*) echo This shell is interactive ;;
4090 *) echo This shell is not interactive ;;
4093 Alternatively, startup scripts may examine the variable `PS1'; it is
4094 unset in non-interactive shells, and set in interactive shells. Thus:
4096 if [ -z "$PS1" ]; then
4097 echo This shell is not interactive
4099 echo This shell is interactive
4103 File: bashref.info, Node: Interactive Shell Behavior, Prev: Is this Shell Interactive?, Up: Interactive Shells
4105 Interactive Shell Behavior
4106 --------------------------
4108 When the shell is running interactively, it changes its behavior in
4111 1. Startup files are read and executed as described in *Note Bash
4114 2. Job Control (*note Job Control::) is enabled by default. When job
4115 control is in effect, Bash ignores the keyboard-generated job
4116 control signals `SIGTTIN', `SIGTTOU', and `SIGTSTP'.
4118 3. Bash expands and displays `PS1' before reading the first line of a
4119 command, and expands and displays `PS2' before reading the second
4120 and subsequent lines of a multi-line command.
4122 4. Bash executes the value of the `PROMPT_COMMAND' variable as a
4123 command before printing the primary prompt, `$PS1' (*note Bash
4126 5. Readline (*note Command Line Editing::) is used to read commands
4127 from the user's terminal.
4129 6. Bash inspects the value of the `ignoreeof' option to `set -o'
4130 instead of exiting immediately when it receives an `EOF' on its
4131 standard input when reading a command (*note The Set Builtin::).
4133 7. Command history (*note Bash History Facilities::) and history
4134 expansion (*note History Interaction::) are enabled by default.
4135 Bash will save the command history to the file named by `$HISTFILE'
4136 when an interactive shell exits.
4138 8. Alias expansion (*note Aliases::) is performed by default.
4140 9. In the absence of any traps, Bash ignores `SIGTERM' (*note
4143 10. In the absence of any traps, `SIGINT' is caught and handled
4144 ((*note Signals::). `SIGINT' will interrupt some shell builtins.
4146 11. An interactive login shell sends a `SIGHUP' to all jobs on exit if
4147 the `hupoxexit' shell option has been enabled (*note Signals::).
4149 12. The `-n' invocation option is ignored, and `set -n' has no effect
4150 (*note The Set Builtin::).
4152 13. Bash will check for mail periodically, depending on the values of
4153 the `MAIL', `MAILPATH', and `MAILCHECK' shell variables (*note
4156 14. Expansion errors due to references to unbound shell variables after
4157 `set -u' has been enabled will not cause the shell to exit (*note
4160 15. The shell will not exit on expansion errors caused by VAR being
4161 unset or null in `${VAR:?WORD}' expansions (*note Shell Parameter
4164 16. Redirection errors encountered by shell builtins will not cause the
4167 17. When running in POSIX mode, a special builtin returning an error
4168 status will not cause the shell to exit (*note Bash POSIX Mode::).
4170 18. A failed `exec' will not cause the shell to exit (*note Bourne
4173 19. Parser syntax errors will not cause the shell to exit.
4175 20. Simple spelling correction for directory arguments to the `cd'
4176 builtin is enabled by default (see the description of the `cdspell'
4177 option to the `shopt' builtin in *Note Bash Builtins::).
4179 21. The shell will check the value of the `TMOUT' variable and exit if
4180 a command is not read within the specified number of seconds after
4181 printing `$PS1' (*note Bash Variables::).
4185 File: bashref.info, Node: Bash Conditional Expressions, Next: Shell Arithmetic, Prev: Interactive Shells, Up: Bash Features
4187 Bash Conditional Expressions
4188 ============================
4190 Conditional expressions are used by the `[[' compound command and
4191 the `test' and `[' builtin commands.
4193 Expressions may be unary or binary. Unary expressions are often
4194 used to examine the status of a file. There are string operators and
4195 numeric comparison operators as well. If the FILE argument to one of
4196 the primaries is of the form `/dev/fd/N', then file descriptor N is
4197 checked. If the FILE argument to one of the primaries is one of
4198 `/dev/stdin', `/dev/stdout', or `/dev/stderr', file descriptor 0, 1, or
4199 2, respectively, is checked.
4202 True if FILE exists.
4205 True if FILE exists and is a block special file.
4208 True if FILE exists and is a character special file.
4211 True if FILE exists and is a directory.
4214 True if FILE exists.
4217 True if FILE exists and is a regular file.
4220 True if FILE exists and its set-group-id bit is set.
4223 True if FILE exists and is a symbolic link.
4226 True if FILE exists and its "sticky" bit is set.
4229 True if FILE exists and is a named pipe (FIFO).
4232 True if FILE exists and is readable.
4235 True if FILE exists and has a size greater than zero.
4238 True if file descriptor FD is open and refers to a terminal.
4241 True if FILE exists and its set-user-id bit is set.
4244 True if FILE exists and is writable.
4247 True if FILE exists and is executable.
4250 True if FILE exists and is owned by the effective user id.
4253 True if FILE exists and is owned by the effective group id.
4256 True if FILE exists and is a symbolic link.
4259 True if FILE exists and is a socket.
4262 True if FILE exists and has been modified since it was last read.
4265 True if FILE1 is newer (according to modification date) than FILE2.
4268 True if FILE1 is older than FILE2.
4271 True if FILE1 and FILE2 have the same device and inode numbers.
4274 True if shell option OPTNAME is enabled. The list of options
4275 appears in the description of the `-o' option to the `set' builtin
4276 (*note The Set Builtin::).
4279 True if the length of STRING is zero.
4283 True if the length of STRING is non-zero.
4285 `STRING1 == STRING2'
4286 True if the strings are equal. `=' may be used in place of `=='.
4288 `STRING1 != STRING2'
4289 True if the strings are not equal.
4292 True if STRING1 sorts before STRING2 lexicographically in the
4296 True if STRING1 sorts after STRING2 lexicographically in the
4300 `OP' is one of `-eq', `-ne', `-lt', `-le', `-gt', or `-ge'. These
4301 arithmetic binary operators return true if ARG1 is equal to, not
4302 equal to, less than, less than or equal to, greater than, or
4303 greater than or equal to ARG2, respectively. ARG1 and ARG2 may be
4304 positive or negative integers.
4307 File: bashref.info, Node: Shell Arithmetic, Next: Aliases, Prev: Bash Conditional Expressions, Up: Bash Features
4312 The shell allows arithmetic expressions to be evaluated, as one of
4313 the shell expansions or by the `let' builtin.
4315 Evaluation is done in long integers with no check for overflow,
4316 though division by 0 is trapped and flagged as an error. The operators
4317 and their precedence and associativity are the same as in the C
4318 language. The following list of operators is grouped into levels of
4319 equal-precedence operators. The levels are listed in order of
4320 decreasing precedence.
4323 variable post-increment and post-decrement
4326 variable pre-increment and pre-decrement
4329 unary minus and plus
4332 logical and bitwise negation
4338 multiplication, division, remainder
4341 addition, subtraction
4344 left and right bitwise shifts
4350 equality and inequality
4356 bitwise exclusive OR
4367 `expr ? expr : expr'
4368 conditional evaluation
4370 `= *= /= %= += -= <<= >>= &= ^= |='
4376 Shell variables are allowed as operands; parameter expansion is
4377 performed before the expression is evaluated. Within an expression,
4378 shell variables may also be referenced by name without using the
4379 parameter expansion syntax. The value of a variable is evaluated as an
4380 arithmetic expression when it is referenced. A shell variable need not
4381 have its integer attribute turned on to be used in an expression.
4383 Constants with a leading 0 are interpreted as octal numbers. A
4384 leading `0x' or `0X' denotes hexadecimal. Otherwise, numbers take the
4385 form [BASE`#']N, where BASE is a decimal number between 2 and 64
4386 representing the arithmetic base, and N is a number in that base. If
4387 BASE`#' is omitted, then base 10 is used. The digits greater than 9
4388 are represented by the lowercase letters, the uppercase letters, `@',
4389 and `_', in that order. If BASE is less than or equal to 36, lowercase
4390 and uppercase letters may be used interchangably to represent numbers
4393 Operators are evaluated in order of precedence. Sub-expressions in
4394 parentheses are evaluated first and may override the precedence rules
4398 File: bashref.info, Node: Aliases, Next: Arrays, Prev: Shell Arithmetic, Up: Bash Features
4403 ALIASES allow a string to be substituted for a word when it is used
4404 as the first word of a simple command. The shell maintains a list of
4405 aliases that may be set and unset with the `alias' and `unalias'
4408 The first word of each simple command, if unquoted, is checked to see
4409 if it has an alias. If so, that word is replaced by the text of the
4410 alias. The alias name and the replacement text may contain any valid
4411 shell input, including shell metacharacters, with the exception that
4412 the alias name may not contain `='. The first word of the replacement
4413 text is tested for aliases, but a word that is identical to an alias
4414 being expanded is not expanded a second time. This means that one may
4415 alias `ls' to `"ls -F"', for instance, and Bash does not try to
4416 recursively expand the replacement text. If the last character of the
4417 alias value is a space or tab character, then the next command word
4418 following the alias is also checked for alias expansion.
4420 Aliases are created and listed with the `alias' command, and removed
4421 with the `unalias' command.
4423 There is no mechanism for using arguments in the replacement text,
4424 as in `csh'. If arguments are needed, a shell function should be used
4425 (*note Shell Functions::).
4427 Aliases are not expanded when the shell is not interactive, unless
4428 the `expand_aliases' shell option is set using `shopt' (*note Bash
4431 The rules concerning the definition and use of aliases are somewhat
4432 confusing. Bash always reads at least one complete line of input
4433 before executing any of the commands on that line. Aliases are
4434 expanded when a command is read, not when it is executed. Therefore, an
4435 alias definition appearing on the same line as another command does not
4436 take effect until the next line of input is read. The commands
4437 following the alias definition on that line are not affected by the new
4438 alias. This behavior is also an issue when functions are executed.
4439 Aliases are expanded when a function definition is read, not when the
4440 function is executed, because a function definition is itself a
4441 compound command. As a consequence, aliases defined in a function are
4442 not available until after that function is executed. To be safe,
4443 always put alias definitions on a separate line, and do not use `alias'
4444 in compound commands.
4446 For almost every purpose, shell functions are preferred over aliases.
4449 File: bashref.info, Node: Arrays, Next: The Directory Stack, Prev: Aliases, Up: Bash Features
4454 Bash provides one-dimensional array variables. Any variable may be
4455 used as an array; the `declare' builtin will explicitly declare an
4456 array. There is no maximum limit on the size of an array, nor any
4457 requirement that members be indexed or assigned contiguously. Arrays
4460 An array is created automatically if any variable is assigned to
4462 name[SUBSCRIPT]=VALUE
4464 The SUBSCRIPT is treated as an arithmetic expression that must evaluate
4465 to a number greater than or equal to zero. To explicitly declare an
4470 declare -a NAME[SUBSCRIPT]
4472 is also accepted; the SUBSCRIPT is ignored. Attributes may be
4473 specified for an array variable using the `declare' and `readonly'
4474 builtins. Each attribute applies to all members of an array.
4476 Arrays are assigned to using compound assignments of the form
4477 name=(value1 ... valueN)
4479 where each VALUE is of the form `[[SUBSCRIPT]=]'STRING. If the
4480 optional subscript is supplied, that index is assigned to; otherwise
4481 the index of the element assigned is the last index assigned to by the
4482 statement plus one. Indexing starts at zero. This syntax is also
4483 accepted by the `declare' builtin. Individual array elements may be
4484 assigned to using the `name['SUBSCRIPT`]='VALUE syntax introduced above.
4486 Any element of an array may be referenced using
4487 `${name['SUBSCRIPT`]}'. The braces are required to avoid conflicts
4488 with the shell's filename expansion operators. If the SUBSCRIPT is `@'
4489 or `*', the word expands to all members of the array NAME. These
4490 subscripts differ only when the word appears within double quotes. If
4491 the word is double-quoted, `${name[*]}' expands to a single word with
4492 the value of each array member separated by the first character of the
4493 `IFS' variable, and `${name[@]}' expands each element of NAME to a
4494 separate word. When there are no array members, `${name[@]}' expands
4495 to nothing. This is analogous to the expansion of the special
4496 parameters `@' and `*'. `${#name['SUBSCRIPT`]}' expands to the length
4497 of `${name['SUBSCRIPT`]}'. If SUBSCRIPT is `@' or `*', the expansion
4498 is the number of elements in the array. Referencing an array variable
4499 without a subscript is equivalent to referencing element zero.
4501 The `unset' builtin is used to destroy arrays. `unset'
4502 NAME[SUBSCRIPT] destroys the array element at index SUBSCRIPT. `unset'
4503 NAME, where NAME is an array, removes the entire array. A subscript of
4504 `*' or `@' also removes the entire array.
4506 The `declare', `local', and `readonly' builtins each accept a `-a'
4507 option to specify an array. The `read' builtin accepts a `-a' option
4508 to assign a list of words read from the standard input to an array, and
4509 can read values from the standard input into individual array elements.
4510 The `set' and `declare' builtins display array values in a way that
4511 allows them to be reused as input.
4514 File: bashref.info, Node: The Directory Stack, Next: Printing a Prompt, Prev: Arrays, Up: Bash Features
4521 * Directory Stack Builtins:: Bash builtin commands to manipulate
4522 the directory stack.
4524 The directory stack is a list of recently-visited directories. The
4525 `pushd' builtin adds directories to the stack as it changes the current
4526 directory, and the `popd' builtin removes specified directories from
4527 the stack and changes the current directory to the directory removed.
4528 The `dirs' builtin displays the contents of the directory stack.
4530 The contents of the directory stack are also visible as the value of
4531 the `DIRSTACK' shell variable.
4534 File: bashref.info, Node: Directory Stack Builtins, Up: The Directory Stack
4536 Directory Stack Builtins
4537 ------------------------
4540 dirs [+N | -N] [-clpv]
4541 Display the list of currently remembered directories. Directories
4542 are added to the list with the `pushd' command; the `popd' command
4543 removes directories from the list.
4545 Displays the Nth directory (counting from the left of the
4546 list printed by `dirs' when invoked without options), starting
4550 Displays the Nth directory (counting from the right of the
4551 list printed by `dirs' when invoked without options), starting
4555 Clears the directory stack by deleting all of the elements.
4558 Produces a longer listing; the default listing format uses a
4559 tilde to denote the home directory.
4562 Causes `dirs' to print the directory stack with one entry per
4566 Causes `dirs' to print the directory stack with one entry per
4567 line, prefixing each entry with its index in the stack.
4572 Remove the top entry from the directory stack, and `cd' to the new
4573 top directory. When no arguments are given, `popd' removes the
4574 top directory from the stack and performs a `cd' to the new top
4575 directory. The elements are numbered from 0 starting at the first
4576 directory listed with `dirs'; i.e., `popd' is equivalent to `popd
4579 Removes the Nth directory (counting from the left of the list
4580 printed by `dirs'), starting with zero.
4583 Removes the Nth directory (counting from the right of the
4584 list printed by `dirs'), starting with zero.
4587 Suppresses the normal change of directory when removing
4588 directories from the stack, so that only the stack is
4592 pushd [DIR | +N | -N] [-n]
4594 Save the current directory on the top of the directory stack and
4595 then `cd' to DIR. With no arguments, `pushd' exchanges the top
4599 Brings the Nth directory (counting from the left of the list
4600 printed by `dirs', starting with zero) to the top of the list
4601 by rotating the stack.
4604 Brings the Nth directory (counting from the right of the list
4605 printed by `dirs', starting with zero) to the top of the list
4606 by rotating the stack.
4609 Suppresses the normal change of directory when adding
4610 directories to the stack, so that only the stack is
4614 Makes the current working directory be the top of the stack,
4615 and then executes the equivalent of ``cd' DIR'. `cd's to DIR.
4618 File: bashref.info, Node: Printing a Prompt, Next: The Restricted Shell, Prev: The Directory Stack, Up: Bash Features
4620 Controlling the Prompt
4621 ======================
4623 The value of the variable `PROMPT_COMMAND' is examined just before
4624 Bash prints each primary prompt. If `PROMPT_COMMAND' is set and has a
4625 non-null value, then the value is executed just as if it had been typed
4626 on the command line.
4628 In addition, the following table describes the special characters
4629 which can appear in the prompt variables:
4635 The date, in "Weekday Month Date" format (e.g., "Tue May 26").
4638 An escape character.
4641 The hostname, up to the first `.'.
4647 The number of jobs currently managed by the shell.
4650 The basename of the shell's terminal device name.
4659 The name of the shell, the basename of `$0' (the portion following
4663 The time, in 24-hour HH:MM:SS format.
4666 The time, in 12-hour HH:MM:SS format.
4669 The time, in 12-hour am/pm format.
4672 The time, in 24-hour HH:MM format.
4675 The username of the current user.
4678 The version of Bash (e.g., 2.00)
4681 The release of Bash, version + patchlevel (e.g., 2.00.0)
4684 The current working directory.
4687 The basename of `$PWD'.
4690 The history number of this command.
4693 The command number of this command.
4696 If the effective uid is 0, `#', otherwise `$'.
4699 The character whose ASCII code is the octal value NNN.
4705 Begin a sequence of non-printing characters. This could be used to
4706 embed a terminal control sequence into the prompt.
4709 End a sequence of non-printing characters.
4711 The command number and the history number are usually different: the
4712 history number of a command is its position in the history list, which
4713 may include commands restored from the history file (*note Bash History
4714 Facilities::), while the command number is the position in the sequence
4715 of commands executed during the current shell session.
4717 After the string is decoded, it is expanded via parameter expansion,
4718 command substitution, arithmetic expansion, and quote removal, subject
4719 to the value of the `promptvars' shell option (*note Bash Builtins::).
4722 File: bashref.info, Node: The Restricted Shell, Next: Bash POSIX Mode, Prev: Printing a Prompt, Up: Bash Features
4724 The Restricted Shell
4725 ====================
4727 If Bash is started with the name `rbash', or the `--restricted'
4728 option is supplied at invocation, the shell becomes restricted. A
4729 restricted shell is used to set up an environment more controlled than
4730 the standard shell. A restricted shell behaves identically to `bash'
4731 with the exception that the following are disallowed:
4732 * Changing directories with the `cd' builtin.
4734 * Setting or unsetting the values of the `SHELL', `PATH', `ENV', or
4735 `BASH_ENV' variables.
4737 * Specifying command names containing slashes.
4739 * Specifying a filename containing a slash as an argument to the `.'
4742 * Specifying a filename containing a slash as an argument to the `-p'
4743 option to the `hash' builtin command.
4745 * Importing function definitions from the shell environment at
4748 * Parsing the value of `SHELLOPTS' from the shell environment at
4751 * Redirecting output using the `>', `>|', `<>', `>&', `&>', and `>>'
4752 redirection operators.
4754 * Using the `exec' builtin to replace the shell with another command.
4756 * Adding or deleting builtin commands with the `-f' and `-d' options
4757 to the `enable' builtin.
4759 * Specifying the `-p' option to the `command' builtin.
4761 * Turning off restricted mode with `set +r' or `set +o restricted'.
4764 File: bashref.info, Node: Bash POSIX Mode, Prev: The Restricted Shell, Up: Bash Features
4769 Starting Bash with the `--posix' command-line option or executing
4770 `set -o posix' while Bash is running will cause Bash to conform more
4771 closely to the POSIX 1003.2 standard by changing the behavior to match
4772 that specified by POSIX in areas where the Bash default differs.
4774 The following list is what's changed when `POSIX mode' is in effect:
4776 1. When a command in the hash table no longer exists, Bash will
4777 re-search `$PATH' to find the new location. This is also
4778 available with `shopt -s checkhash'.
4780 2. The message printed by the job control code and builtins when a job
4781 exits with a non-zero status is `Done(status)'.
4783 3. The message printed by the job control code and builtins when a job
4784 is stopped is `Stopped(SIGNAME)', where SIGNAME is, for example,
4787 4. Reserved words may not be aliased.
4789 5. The POSIX 1003.2 `PS1' and `PS2' expansions of `!' to the history
4790 number and `!!' to `!' are enabled, and parameter expansion is
4791 performed on the values of `PS1' and `PS2' regardless of the
4792 setting of the `promptvars' option.
4794 6. Interactive comments are enabled by default. (Bash has them on by
4797 7. The POSIX 1003.2 startup files are executed (`$ENV') rather than
4798 the normal Bash files.
4800 8. Tilde expansion is only performed on assignments preceding a
4801 command name, rather than on all assignment statements on the line.
4803 9. The default history file is `~/.sh_history' (this is the default
4804 value of `$HISTFILE').
4806 10. The output of `kill -l' prints all the signal names on a single
4807 line, separated by spaces.
4809 11. Non-interactive shells exit if FILENAME in `.' FILENAME is not
4812 12. Non-interactive shells exit if a syntax error in an arithmetic
4813 expansion results in an invalid expression.
4815 13. Redirection operators do not perform filename expansion on the word
4816 in the redirection unless the shell is interactive.
4818 14. Redirection operators do not perform word splitting on the word in
4821 15. Function names must be valid shell `name's. That is, they may not
4822 contain characters other than letters, digits, and underscores, and
4823 may not start with a digit. Declaring a function with an invalid
4824 name causes a fatal syntax error in non-interactive shells.
4826 16. POSIX 1003.2 `special' builtins are found before shell functions
4827 during command lookup.
4829 17. If a POSIX 1003.2 special builtin returns an error status, a
4830 non-interactive shell exits. The fatal errors are those listed in
4831 the POSIX.2 standard, and include things like passing incorrect
4832 options, redirection errors, variable assignment errors for
4833 assignments preceding the command name, and so on.
4835 18. If the `cd' builtin finds a directory to change to using
4836 `$CDPATH', the value it assigns to the `PWD' variable does not
4837 contain any symbolic links, as if `cd -P' had been executed.
4839 19. If `CDPATH' is set, the `cd' builtin will not implicitly append
4840 the current directory to it. This means that `cd' will fail if no
4841 valid directory name can be constructed from any of the entries in
4842 `$CDPATH', even if the a directory with the same name as the name
4843 given as an argument to `cd' exists in the current directory.
4845 20. A non-interactive shell exits with an error status if a variable
4846 assignment error occurs when no command name follows the assignment
4847 statements. A variable assignment error occurs, for example, when
4848 trying to assign a value to a readonly variable.
4850 21. A non-interactive shell exits with an error status if the iteration
4851 variable in a `for' statement or the selection variable in a
4852 `select' statement is a readonly variable.
4854 22. Process substitution is not available.
4856 23. Assignment statements preceding POSIX 1003.2 special builtins
4857 persist in the shell environment after the builtin completes.
4859 24. Assignment statements preceding shell function calls persist in the
4860 shell environment after the function returns, as if a POSIX
4861 special builtin command had been executed.
4863 25. The `export' and `readonly' builtin commands display their output
4864 in the format required by POSIX 1003.2.
4866 26. The `trap' builtin displays signal names without the leading `SIG'.
4868 27. The `.' and `source' builtins do not search the current directory
4869 for the filename argument if it is not found by searching `PATH'.
4871 28. Subshells spawned to execute command substitutions inherit the
4872 value of the `-e' option from the parent shell. When not in POSIX
4873 mode, Bash clears the `-e' option in such subshells.
4875 29. Alias expansion is always enabled, even in non-interactive shells.
4877 30. When the `set' builtin is invoked without options, it does not
4878 display shell function names and definitions.
4880 31. When the `set' builtin is invoked without options, it displays
4881 variable values without quotes, unless they contain shell
4882 metacharacters, even if the result contains nonprinting characters.
4884 There is other POSIX 1003.2 behavior that Bash does not implement.
4887 1. Assignment statements affect the execution environment of all
4888 builtins, not just special ones.
4890 2. When a subshell is created to execute a shell script with execute
4891 permission, but without a leading `#!', Bash sets `$0' to the full
4892 pathname of the script as found by searching `$PATH', rather than
4893 the command as typed by the user.
4895 3. When using `.' to source a shell script found in `$PATH', bash
4896 checks execute permission bits rather than read permission bits,
4897 just as if it were searching for a command.
4901 File: bashref.info, Node: Job Control, Next: Using History Interactively, Prev: Bash Features, Up: Top
4906 This chapter discusses what job control is, how it works, and how
4907 Bash allows you to access its facilities.
4911 * Job Control Basics:: How job control works.
4912 * Job Control Builtins:: Bash builtin commands used to interact
4914 * Job Control Variables:: Variables Bash uses to customize job
4918 File: bashref.info, Node: Job Control Basics, Next: Job Control Builtins, Up: Job Control
4923 Job control refers to the ability to selectively stop (suspend) the
4924 execution of processes and continue (resume) their execution at a later
4925 point. A user typically employs this facility via an interactive
4926 interface supplied jointly by the system's terminal driver and Bash.
4928 The shell associates a JOB with each pipeline. It keeps a table of
4929 currently executing jobs, which may be listed with the `jobs' command.
4930 When Bash starts a job asynchronously, it prints a line that looks like:
4933 indicating that this job is job number 1 and that the process ID of the
4934 last process in the pipeline associated with this job is 25647. All of
4935 the processes in a single pipeline are members of the same job. Bash
4936 uses the JOB abstraction as the basis for job control.
4938 To facilitate the implementation of the user interface to job
4939 control, the operating system maintains the notion of a current terminal
4940 process group ID. Members of this process group (processes whose
4941 process group ID is equal to the current terminal process group ID)
4942 receive keyboard-generated signals such as `SIGINT'. These processes
4943 are said to be in the foreground. Background processes are those whose
4944 process group ID differs from the terminal's; such processes are immune
4945 to keyboard-generated signals. Only foreground processes are allowed
4946 to read from or write to the terminal. Background processes which
4947 attempt to read from (write to) the terminal are sent a `SIGTTIN'
4948 (`SIGTTOU') signal by the terminal driver, which, unless caught,
4949 suspends the process.
4951 If the operating system on which Bash is running supports job
4952 control, Bash contains facilities to use it. Typing the SUSPEND
4953 character (typically `^Z', Control-Z) while a process is running causes
4954 that process to be stopped and returns control to Bash. Typing the
4955 DELAYED SUSPEND character (typically `^Y', Control-Y) causes the
4956 process to be stopped when it attempts to read input from the terminal,
4957 and control to be returned to Bash. The user then manipulates the
4958 state of this job, using the `bg' command to continue it in the
4959 background, the `fg' command to continue it in the foreground, or the
4960 `kill' command to kill it. A `^Z' takes effect immediately, and has
4961 the additional side effect of causing pending output and typeahead to
4964 There are a number of ways to refer to a job in the shell. The
4965 character `%' introduces a job name.
4967 Job number `n' may be referred to as `%n'. The symbols `%%' and
4968 `%+' refer to the shell's notion of the current job, which is the last
4969 job stopped while it was in the foreground or started in the
4970 background. The previous job may be referenced using `%-'. In output
4971 pertaining to jobs (e.g., the output of the `jobs' command), the
4972 current job is always flagged with a `+', and the previous job with a
4975 A job may also be referred to using a prefix of the name used to
4976 start it, or using a substring that appears in its command line. For
4977 example, `%ce' refers to a stopped `ce' job. Using `%?ce', on the other
4978 hand, refers to any job containing the string `ce' in its command line.
4979 If the prefix or substring matches more than one job, Bash reports an
4982 Simply naming a job can be used to bring it into the foreground:
4983 `%1' is a synonym for `fg %1', bringing job 1 from the background into
4984 the foreground. Similarly, `%1 &' resumes job 1 in the background,
4985 equivalent to `bg %1'
4987 The shell learns immediately whenever a job changes state.
4988 Normally, Bash waits until it is about to print a prompt before
4989 reporting changes in a job's status so as to not interrupt any other
4990 output. If the `-b' option to the `set' builtin is enabled, Bash
4991 reports such changes immediately (*note The Set Builtin::). Any trap
4992 on `SIGCHLD' is executed for each child process that exits.
4994 If an attempt to exit Bash is while jobs are stopped, the shell
4995 prints a message warning that there are stopped jobs. The `jobs'
4996 command may then be used to inspect their status. If a second attempt
4997 to exit is made without an intervening command, Bash does not print
4998 another warning, and the stopped jobs are terminated.
5001 File: bashref.info, Node: Job Control Builtins, Next: Job Control Variables, Prev: Job Control Basics, Up: Job Control
5003 Job Control Builtins
5004 ====================
5008 Resume the suspended job JOBSPEC in the background, as if it had
5009 been started with `&'. If JOBSPEC is not supplied, the current
5010 job is used. The return status is zero unless it is run when job
5011 control is not enabled, or, when run with job control enabled, if
5012 JOBSPEC was not found or JOBSPEC specifies a job that was started
5013 without job control.
5017 Resume the job JOBSPEC in the foreground and make it the current
5018 job. If JOBSPEC is not supplied, the current job is used. The
5019 return status is that of the command placed into the foreground,
5020 or non-zero if run when job control is disabled or, when run with
5021 job control enabled, JOBSPEC does not specify a valid job or
5022 JOBSPEC specifies a job that was started without job control.
5025 jobs [-lnprs] [JOBSPEC]
5026 jobs -x COMMAND [ARGUMENTS]
5028 The first form lists the active jobs. The options have the
5032 List process IDs in addition to the normal information.
5035 Display information only about jobs that have changed status
5036 since the user was last notified of their status.
5039 List only the process ID of the job's process group leader.
5042 Restrict output to running jobs.
5045 Restrict output to stopped jobs.
5047 If JOBSPEC is given, output is restricted to information about
5048 that job. If JOBSPEC is not supplied, the status of all jobs is
5051 If the `-x' option is supplied, `jobs' replaces any JOBSPEC found
5052 in COMMAND or ARGUMENTS with the corresponding process group ID,
5053 and executes COMMAND, passing it ARGUMENTs, returning its exit
5057 kill [-s SIGSPEC] [-n SIGNUM] [-SIGSPEC] JOBSPEC or PID
5058 kill -l [EXIT_STATUS]
5059 Send a signal specified by SIGSPEC or SIGNUM to the process named
5060 by job specification JOBSPEC or process ID PID. SIGSPEC is either
5061 a signal name such as `SIGINT' (with or without the `SIG' prefix)
5062 or a signal number; SIGNUM is a signal number. If SIGSPEC and
5063 SIGNUM are not present, `SIGTERM' is used. The `-l' option lists
5064 the signal names. If any arguments are supplied when `-l' is
5065 given, the names of the signals corresponding to the arguments are
5066 listed, and the return status is zero. EXIT_STATUS is a number
5067 specifying a signal number or the exit status of a process
5068 terminated by a signal. The return status is zero if at least one
5069 signal was successfully sent, or non-zero if an error occurs or an
5070 invalid option is encountered.
5073 wait [JOBSPEC or PID]
5074 Wait until the child process specified by process ID PID or job
5075 specification JOBSPEC exits and return the exit status of the last
5076 command waited for. If a job spec is given, all processes in the
5077 job are waited for. If no arguments are given, all currently
5078 active child processes are waited for, and the return status is
5079 zero. If neither JOBSPEC nor PID specifies an active child process
5080 of the shell, the return status is 127.
5083 disown [-ar] [-h] [JOBSPEC ...]
5084 Without options, each JOBSPEC is removed from the table of active
5085 jobs. If the `-h' option is given, the job is not removed from
5086 the table, but is marked so that `SIGHUP' is not sent to the job
5087 if the shell receives a `SIGHUP'. If JOBSPEC is not present, and
5088 neither the `-a' nor `-r' option is supplied, the current job is
5089 used. If no JOBSPEC is supplied, the `-a' option means to remove
5090 or mark all jobs; the `-r' option without a JOBSPEC argument
5091 restricts operation to running jobs.
5095 Suspend the execution of this shell until it receives a `SIGCONT'
5096 signal. The `-f' option means to suspend even if the shell is a
5099 When job control is not active, the `kill' and `wait' builtins do
5100 not accept JOBSPEC arguments. They must be supplied process IDs.
5103 File: bashref.info, Node: Job Control Variables, Prev: Job Control Builtins, Up: Job Control
5105 Job Control Variables
5106 =====================
5109 This variable controls how the shell interacts with the user and
5110 job control. If this variable exists then single word simple
5111 commands without redirections are treated as candidates for
5112 resumption of an existing job. There is no ambiguity allowed; if
5113 there is more than one job beginning with the string typed, then
5114 the most recently accessed job will be selected. The name of a
5115 stopped job, in this context, is the command line used to start
5116 it. If this variable is set to the value `exact', the string
5117 supplied must match the name of a stopped job exactly; if set to
5118 `substring', the string supplied needs to match a substring of the
5119 name of a stopped job. The `substring' value provides
5120 functionality analogous to the `%?' job ID (*note Job Control
5121 Basics::). If set to any other value, the supplied string must be
5122 a prefix of a stopped job's name; this provides functionality
5123 analogous to the `%' job ID.
5126 File: bashref.info, Node: Command Line Editing, Next: Installing Bash, Prev: Using History Interactively, Up: Top
5128 Command Line Editing
5129 ********************
5131 This chapter describes the basic features of the GNU command line
5132 editing interface. Command line editing is provided by the Readline
5133 library, which is used by several different programs, including Bash.
5137 * Introduction and Notation:: Notation used in this text.
5138 * Readline Interaction:: The minimum set of commands for editing a line.
5139 * Readline Init File:: Customizing Readline from a user's view.
5140 * Bindable Readline Commands:: A description of most of the Readline commands
5141 available for binding
5142 * Readline vi Mode:: A short description of how to make Readline
5143 behave like the vi editor.
5145 * Programmable Completion:: How to specify the possible completions for
5147 * Programmable Completion Builtins:: Builtin commands to specify how to
5148 complete arguments for a particular command.
5151 File: bashref.info, Node: Introduction and Notation, Next: Readline Interaction, Up: Command Line Editing
5153 Introduction to Line Editing
5154 ============================
5156 The following paragraphs describe the notation used to represent
5159 The text `C-k' is read as `Control-K' and describes the character
5160 produced when the <k> key is pressed while the Control key is depressed.
5162 The text `M-k' is read as `Meta-K' and describes the character
5163 produced when the Meta key (if you have one) is depressed, and the <k>
5164 key is pressed. The Meta key is labeled <ALT> on many keyboards. On
5165 keyboards with two keys labeled <ALT> (usually to either side of the
5166 space bar), the <ALT> on the left side is generally set to work as a
5167 Meta key. The <ALT> key on the right may also be configured to work as
5168 a Meta key or may be configured as some other modifier, such as a
5169 Compose key for typing accented characters.
5171 If you do not have a Meta or <ALT> key, or another key working as a
5172 Meta key, the identical keystroke can be generated by typing <ESC>
5173 _first_, and then typing <k>. Either process is known as "metafying"
5176 The text `M-C-k' is read as `Meta-Control-k' and describes the
5177 character produced by "metafying" `C-k'.
5179 In addition, several keys have their own names. Specifically,
5180 <DEL>, <ESC>, <LFD>, <SPC>, <RET>, and <TAB> all stand for themselves
5181 when seen in this text, or in an init file (*note Readline Init File::).
5182 If your keyboard lacks a <LFD> key, typing <C-j> will produce the
5183 desired character. The <RET> key may be labeled <Return> or <Enter> on
5187 File: bashref.info, Node: Readline Interaction, Next: Readline Init File, Prev: Introduction and Notation, Up: Command Line Editing
5189 Readline Interaction
5190 ====================
5192 Often during an interactive session you type in a long line of text,
5193 only to notice that the first word on the line is misspelled. The
5194 Readline library gives you a set of commands for manipulating the text
5195 as you type it in, allowing you to just fix your typo, and not forcing
5196 you to retype the majority of the line. Using these editing commands,
5197 you move the cursor to the place that needs correction, and delete or
5198 insert the text of the corrections. Then, when you are satisfied with
5199 the line, you simply press <RET>. You do not have to be at the end of
5200 the line to press <RET>; the entire line is accepted regardless of the
5201 location of the cursor within the line.
5205 * Readline Bare Essentials:: The least you need to know about Readline.
5206 * Readline Movement Commands:: Moving about the input line.
5207 * Readline Killing Commands:: How to delete text, and how to get it back!
5208 * Readline Arguments:: Giving numeric arguments to commands.
5209 * Searching:: Searching through previous lines.
5212 File: bashref.info, Node: Readline Bare Essentials, Next: Readline Movement Commands, Up: Readline Interaction
5214 Readline Bare Essentials
5215 ------------------------
5217 In order to enter characters into the line, simply type them. The
5218 typed character appears where the cursor was, and then the cursor moves
5219 one space to the right. If you mistype a character, you can use your
5220 erase character to back up and delete the mistyped character.
5222 Sometimes you may mistype a character, and not notice the error
5223 until you have typed several other characters. In that case, you can
5224 type `C-b' to move the cursor to the left, and then correct your
5225 mistake. Afterwards, you can move the cursor to the right with `C-f'.
5227 When you add text in the middle of a line, you will notice that
5228 characters to the right of the cursor are `pushed over' to make room
5229 for the text that you have inserted. Likewise, when you delete text
5230 behind the cursor, characters to the right of the cursor are `pulled
5231 back' to fill in the blank space created by the removal of the text. A
5232 list of the bare essentials for editing the text of an input line
5236 Move back one character.
5239 Move forward one character.
5241 <DEL> or <Backspace>
5242 Delete the character to the left of the cursor.
5245 Delete the character underneath the cursor.
5248 Insert the character into the line at the cursor.
5251 Undo the last editing command. You can undo all the way back to an
5254 (Depending on your configuration, the <Backspace> key be set to delete
5255 the character to the left of the cursor and the <DEL> key set to delete
5256 the character underneath the cursor, like `C-d', rather than the
5257 character to the left of the cursor.)
5260 File: bashref.info, Node: Readline Movement Commands, Next: Readline Killing Commands, Prev: Readline Bare Essentials, Up: Readline Interaction
5262 Readline Movement Commands
5263 --------------------------
5265 The above table describes the most basic keystrokes that you need in
5266 order to do editing of the input line. For your convenience, many
5267 other commands have been added in addition to `C-b', `C-f', `C-d', and
5268 <DEL>. Here are some commands for moving more rapidly about the line.
5271 Move to the start of the line.
5274 Move to the end of the line.
5277 Move forward a word, where a word is composed of letters and
5281 Move backward a word.
5284 Clear the screen, reprinting the current line at the top.
5286 Notice how `C-f' moves forward a character, while `M-f' moves
5287 forward a word. It is a loose convention that control keystrokes
5288 operate on characters while meta keystrokes operate on words.
5291 File: bashref.info, Node: Readline Killing Commands, Next: Readline Arguments, Prev: Readline Movement Commands, Up: Readline Interaction
5293 Readline Killing Commands
5294 -------------------------
5296 "Killing" text means to delete the text from the line, but to save
5297 it away for later use, usually by "yanking" (re-inserting) it back into
5298 the line. (`Cut' and `paste' are more recent jargon for `kill' and
5301 If the description for a command says that it `kills' text, then you
5302 can be sure that you can get the text back in a different (or the same)
5305 When you use a kill command, the text is saved in a "kill-ring".
5306 Any number of consecutive kills save all of the killed text together, so
5307 that when you yank it back, you get it all. The kill ring is not line
5308 specific; the text that you killed on a previously typed line is
5309 available to be yanked back later, when you are typing another line.
5311 Here is the list of commands for killing text.
5314 Kill the text from the current cursor position to the end of the
5318 Kill from the cursor to the end of the current word, or, if between
5319 words, to the end of the next word. Word boundaries are the same
5320 as those used by `M-f'.
5323 Kill from the cursor the start of the current word, or, if between
5324 words, to the start of the previous word. Word boundaries are the
5325 same as those used by `M-b'.
5328 Kill from the cursor to the previous whitespace. This is
5329 different than `M-<DEL>' because the word boundaries differ.
5331 Here is how to "yank" the text back into the line. Yanking means to
5332 copy the most-recently-killed text from the kill buffer.
5335 Yank the most recently killed text back into the buffer at the
5339 Rotate the kill-ring, and yank the new top. You can only do this
5340 if the prior command is `C-y' or `M-y'.
5343 File: bashref.info, Node: Readline Arguments, Next: Searching, Prev: Readline Killing Commands, Up: Readline Interaction
5348 You can pass numeric arguments to Readline commands. Sometimes the
5349 argument acts as a repeat count, other times it is the sign of the
5350 argument that is significant. If you pass a negative argument to a
5351 command which normally acts in a forward direction, that command will
5352 act in a backward direction. For example, to kill text back to the
5353 start of the line, you might type `M-- C-k'.
5355 The general way to pass numeric arguments to a command is to type
5356 meta digits before the command. If the first `digit' typed is a minus
5357 sign (`-'), then the sign of the argument will be negative. Once you
5358 have typed one meta digit to get the argument started, you can type the
5359 remainder of the digits, and then the command. For example, to give
5360 the `C-d' command an argument of 10, you could type `M-1 0 C-d', which
5361 will delete the next ten characters on the input line.
5364 File: bashref.info, Node: Searching, Prev: Readline Arguments, Up: Readline Interaction
5366 Searching for Commands in the History
5367 -------------------------------------
5369 Readline provides commands for searching through the command history
5370 (*note Bash History Facilities::) for lines containing a specified
5371 string. There are two search modes: "incremental" and
5374 Incremental searches begin before the user has finished typing the
5375 search string. As each character of the search string is typed,
5376 Readline displays the next entry from the history matching the string
5377 typed so far. An incremental search requires only as many characters
5378 as needed to find the desired history entry. To search backward in the
5379 history for a particular string, type `C-r'. Typing `C-s' searches
5380 forward through the history. The characters present in the value of
5381 the `isearch-terminators' variable are used to terminate an incremental
5382 search. If that variable has not been assigned a value, the <ESC> and
5383 `C-J' characters will terminate an incremental search. `C-g' will
5384 abort an incremental search and restore the original line. When the
5385 search is terminated, the history entry containing the search string
5386 becomes the current line.
5388 To find other matching entries in the history list, type `C-r' or
5389 `C-s' as appropriate. This will search backward or forward in the
5390 history for the next entry matching the search string typed so far.
5391 Any other key sequence bound to a Readline command will terminate the
5392 search and execute that command. For instance, a <RET> will terminate
5393 the search and accept the line, thereby executing the command from the
5394 history list. A movement command will terminate the search, make the
5395 last line found the current line, and begin editing.
5397 Readline remembers the last incremental search string. If two
5398 `C-r's are typed without any intervening characters defining a new
5399 search string, any remembered search string is used.
5401 Non-incremental searches read the entire search string before
5402 starting to search for matching history lines. The search string may be
5403 typed by the user or be part of the contents of the current line.
5406 File: bashref.info, Node: Readline Init File, Next: Bindable Readline Commands, Prev: Readline Interaction, Up: Command Line Editing
5411 Although the Readline library comes with a set of Emacs-like
5412 keybindings installed by default, it is possible to use a different set
5413 of keybindings. Any user can customize programs that use Readline by
5414 putting commands in an "inputrc" file, conventionally in his home
5415 directory. The name of this file is taken from the value of the shell
5416 variable `INPUTRC'. If that variable is unset, the default is
5419 When a program which uses the Readline library starts up, the init
5420 file is read, and the key bindings are set.
5422 In addition, the `C-x C-r' command re-reads this init file, thus
5423 incorporating any changes that you might have made to it.
5427 * Readline Init File Syntax:: Syntax for the commands in the inputrc file.
5429 * Conditional Init Constructs:: Conditional key bindings in the inputrc file.
5431 * Sample Init File:: An example inputrc file.
5434 File: bashref.info, Node: Readline Init File Syntax, Next: Conditional Init Constructs, Up: Readline Init File
5436 Readline Init File Syntax
5437 -------------------------
5439 There are only a few basic constructs allowed in the Readline init
5440 file. Blank lines are ignored. Lines beginning with a `#' are
5441 comments. Lines beginning with a `$' indicate conditional constructs
5442 (*note Conditional Init Constructs::). Other lines denote variable
5443 settings and key bindings.
5446 You can modify the run-time behavior of Readline by altering the
5447 values of variables in Readline using the `set' command within the
5448 init file. The syntax is simple:
5452 Here, for example, is how to change from the default Emacs-like
5453 key binding to use `vi' line editing commands:
5457 Variable names and values, where appropriate, are recognized
5458 without regard to case.
5460 The `bind -V' command lists the current Readline variable names
5461 and values. *Note Bash Builtins::.
5463 A great deal of run-time behavior is changeable with the following
5467 Controls what happens when Readline wants to ring the
5468 terminal bell. If set to `none', Readline never rings the
5469 bell. If set to `visible', Readline uses a visible bell if
5470 one is available. If set to `audible' (the default),
5471 Readline attempts to ring the terminal's bell.
5474 The string to insert at the beginning of the line when the
5475 `insert-comment' command is executed. The default value is
5478 `completion-ignore-case'
5479 If set to `on', Readline performs filename matching and
5480 completion in a case-insensitive fashion. The default value
5483 `completion-query-items'
5484 The number of possible completions that determines when the
5485 user is asked whether he wants to see the list of
5486 possibilities. If the number of possible completions is
5487 greater than this value, Readline will ask the user whether
5488 or not he wishes to view them; otherwise, they are simply
5489 listed. This variable must be set to an integer value
5490 greater than or equal to 0. The default limit is `100'.
5493 If set to `on', Readline will convert characters with the
5494 eighth bit set to an ASCII key sequence by stripping the
5495 eighth bit and prefixing an <ESC> character, converting them
5496 to a meta-prefixed key sequence. The default value is `on'.
5498 `disable-completion'
5499 If set to `On', Readline will inhibit word completion.
5500 Completion characters will be inserted into the line as if
5501 they had been mapped to `self-insert'. The default is `off'.
5504 The `editing-mode' variable controls which default set of key
5505 bindings is used. By default, Readline starts up in Emacs
5506 editing mode, where the keystrokes are most similar to Emacs.
5507 This variable can be set to either `emacs' or `vi'.
5510 When set to `on', Readline will try to enable the application
5511 keypad when it is called. Some systems need this to enable
5512 the arrow keys. The default is `off'.
5515 If set to `on', tilde expansion is performed when Readline
5516 attempts word completion. The default is `off'.
5518 If set to `on', the history code attempts to place point at
5519 the same location on each history line retrived with
5520 `previous-history' or `next-history'.
5522 `horizontal-scroll-mode'
5523 This variable can be set to either `on' or `off'. Setting it
5524 to `on' means that the text of the lines being edited will
5525 scroll horizontally on a single screen line when they are
5526 longer than the width of the screen, instead of wrapping onto
5527 a new screen line. By default, this variable is set to `off'.
5530 If set to `on', Readline will enable eight-bit input (it will
5531 not clear the eighth bit in the characters it reads),
5532 regardless of what the terminal claims it can support. The
5533 default value is `off'. The name `meta-flag' is a synonym
5536 `isearch-terminators'
5537 The string of characters that should terminate an incremental
5538 search without subsequently executing the character as a
5539 command (*note Searching::). If this variable has not been
5540 given a value, the characters <ESC> and `C-J' will terminate
5541 an incremental search.
5544 Sets Readline's idea of the current keymap for key binding
5545 commands. Acceptable `keymap' names are `emacs',
5546 `emacs-standard', `emacs-meta', `emacs-ctlx', `vi', `vi-move',
5547 `vi-command', and `vi-insert'. `vi' is equivalent to
5548 `vi-command'; `emacs' is equivalent to `emacs-standard'. The
5549 default value is `emacs'. The value of the `editing-mode'
5550 variable also affects the default keymap.
5553 If set to `on', completed directory names have a slash
5554 appended. The default is `on'.
5556 `mark-modified-lines'
5557 This variable, when set to `on', causes Readline to display an
5558 asterisk (`*') at the start of history lines which have been
5559 modified. This variable is `off' by default.
5561 `match-hidden-files'
5562 This variable, when set to `on', causes Readline to match
5563 files whose names begin with a `.' (hidden files) when
5564 performing filename completion, unless the leading `.' is
5565 supplied by the user in the filename to be completed. This
5566 variable is `on' by default.
5569 If set to `on', Readline will display characters with the
5570 eighth bit set directly rather than as a meta-prefixed escape
5571 sequence. The default is `off'.
5573 `print-completions-horizontally'
5574 If set to `on', Readline will display completions with matches
5575 sorted horizontally in alphabetical order, rather than down
5576 the screen. The default is `off'.
5578 `show-all-if-ambiguous'
5579 This alters the default behavior of the completion functions.
5580 If set to `on', words which have more than one possible
5581 completion cause the matches to be listed immediately instead
5582 of ringing the bell. The default value is `off'.
5585 If set to `on', a character denoting a file's type is
5586 appended to the filename when listing possible completions.
5587 The default is `off'.
5590 The syntax for controlling key bindings in the init file is
5591 simple. First you need to find the name of the command that you
5592 want to change. The following sections contain tables of the
5593 command name, the default keybinding, if any, and a short
5594 description of what the command does.
5596 Once you know the name of the command, simply place on a line in
5597 the init file the name of the key you wish to bind the command to,
5598 a colon, and then the name of the command. The name of the key
5599 can be expressed in different ways, depending on what you find most
5602 In addition to command names, readline allows keys to be bound to
5603 a string that is inserted when the key is pressed (a MACRO).
5605 The `bind -p' command displays Readline function names and
5606 bindings in a format that can put directly into an initialization
5607 file. *Note Bash Builtins::.
5609 KEYNAME: FUNCTION-NAME or MACRO
5610 KEYNAME is the name of a key spelled out in English. For
5612 Control-u: universal-argument
5613 Meta-Rubout: backward-kill-word
5614 Control-o: "> output"
5616 In the above example, `C-u' is bound to the function
5617 `universal-argument', `M-DEL' is bound to the function
5618 `backward-kill-word', and `C-o' is bound to run the macro
5619 expressed on the right hand side (that is, to insert the text
5620 `> output' into the line).
5622 A number of symbolic character names are recognized while
5623 processing this key binding syntax: DEL, ESC, ESCAPE, LFD,
5624 NEWLINE, RET, RETURN, RUBOUT, SPACE, SPC, and TAB.
5626 "KEYSEQ": FUNCTION-NAME or MACRO
5627 KEYSEQ differs from KEYNAME above in that strings denoting an
5628 entire key sequence can be specified, by placing the key
5629 sequence in double quotes. Some GNU Emacs style key escapes
5630 can be used, as in the following example, but the special
5631 character names are not recognized.
5633 "\C-u": universal-argument
5634 "\C-x\C-r": re-read-init-file
5635 "\e[11~": "Function Key 1"
5637 In the above example, `C-u' is again bound to the function
5638 `universal-argument' (just as it was in the first example),
5639 `C-x C-r' is bound to the function `re-read-init-file', and
5640 `<ESC> <[> <1> <1> <~>' is bound to insert the text `Function
5643 The following GNU Emacs style escape sequences are available when
5644 specifying key sequences:
5659 <">, a double quotation mark
5662 <'>, a single quote or apostrophe
5664 In addition to the GNU Emacs style escape sequences, a second set
5665 of backslash escapes is available:
5692 the eight-bit character whose value is the octal value NNN
5693 (one to three digits)
5696 the eight-bit character whose value is the hexadecimal value
5697 HH (one or two hex digits)
5699 When entering the text of a macro, single or double quotes must be
5700 used to indicate a macro definition. Unquoted text is assumed to
5701 be a function name. In the macro body, the backslash escapes
5702 described above are expanded. Backslash will quote any other
5703 character in the macro text, including `"' and `''. For example,
5704 the following binding will make `C-x \' insert a single `\' into
5709 File: bashref.info, Node: Conditional Init Constructs, Next: Sample Init File, Prev: Readline Init File Syntax, Up: Readline Init File
5711 Conditional Init Constructs
5712 ---------------------------
5714 Readline implements a facility similar in spirit to the conditional
5715 compilation features of the C preprocessor which allows key bindings
5716 and variable settings to be performed as the result of tests. There
5717 are four parser directives used.
5720 The `$if' construct allows bindings to be made based on the
5721 editing mode, the terminal being used, or the application using
5722 Readline. The text of the test extends to the end of the line; no
5723 characters are required to isolate it.
5726 The `mode=' form of the `$if' directive is used to test
5727 whether Readline is in `emacs' or `vi' mode. This may be
5728 used in conjunction with the `set keymap' command, for
5729 instance, to set bindings in the `emacs-standard' and
5730 `emacs-ctlx' keymaps only if Readline is starting out in
5734 The `term=' form may be used to include terminal-specific key
5735 bindings, perhaps to bind the key sequences output by the
5736 terminal's function keys. The word on the right side of the
5737 `=' is tested against both the full name of the terminal and
5738 the portion of the terminal name before the first `-'. This
5739 allows `sun' to match both `sun' and `sun-cmd', for instance.
5742 The APPLICATION construct is used to include
5743 application-specific settings. Each program using the
5744 Readline library sets the APPLICATION NAME, and you can test
5745 for a particular value. This could be used to bind key
5746 sequences to functions useful for a specific program. For
5747 instance, the following command adds a key sequence that
5748 quotes the current or previous word in Bash:
5750 # Quote the current or previous word
5751 "\C-xq": "\eb\"\ef\""
5755 This command, as seen in the previous example, terminates an `$if'
5759 Commands in this branch of the `$if' directive are executed if the
5763 This directive takes a single filename as an argument and reads
5764 commands and bindings from that file. For example, the following
5765 directive reads from `/etc/inputrc':
5766 $include /etc/inputrc
5769 File: bashref.info, Node: Sample Init File, Prev: Conditional Init Constructs, Up: Readline Init File
5774 Here is an example of an INPUTRC file. This illustrates key
5775 binding, variable assignment, and conditional syntax.
5778 # This file controls the behaviour of line input editing for
5779 # programs that use the Gnu Readline library. Existing programs
5780 # include FTP, Bash, and Gdb.
5782 # You can re-read the inputrc file with C-x C-r.
5783 # Lines beginning with '#' are comments.
5785 # First, include any systemwide bindings and variable assignments from
5787 $include /etc/Inputrc
5790 # Set various bindings for emacs mode.
5792 set editing-mode emacs
5796 Meta-Control-h: backward-kill-word Text after the function name is ignored
5799 # Arrow keys in keypad mode
5801 #"\M-OD": backward-char
5802 #"\M-OC": forward-char
5803 #"\M-OA": previous-history
5804 #"\M-OB": next-history
5806 # Arrow keys in ANSI mode
5808 "\M-[D": backward-char
5809 "\M-[C": forward-char
5810 "\M-[A": previous-history
5811 "\M-[B": next-history
5813 # Arrow keys in 8 bit keypad mode
5815 #"\M-\C-OD": backward-char
5816 #"\M-\C-OC": forward-char
5817 #"\M-\C-OA": previous-history
5818 #"\M-\C-OB": next-history
5820 # Arrow keys in 8 bit ANSI mode
5822 #"\M-\C-[D": backward-char
5823 #"\M-\C-[C": forward-char
5824 #"\M-\C-[A": previous-history
5825 #"\M-\C-[B": next-history
5831 # An old-style binding. This happens to be the default.
5834 # Macros that are convenient for shell interaction
5837 "\C-xp": "PATH=${PATH}\e\C-e\C-a\ef\C-f"
5838 # prepare to type a quoted word -- insert open and close double quotes
5839 # and move to just after the open quote
5840 "\C-x\"": "\"\"\C-b"
5841 # insert a backslash (testing backslash escapes in sequences and macros)
5843 # Quote the current or previous word
5844 "\C-xq": "\eb\"\ef\""
5845 # Add a binding to refresh the line, which is unbound
5846 "\C-xr": redraw-current-line
5847 # Edit variable on current line.
5848 "\M-\C-v": "\C-a\C-k$\C-y\M-\C-e\C-a\C-y="
5851 # use a visible bell if one is available
5852 set bell-style visible
5854 # don't strip characters to 7 bits when reading
5857 # allow iso-latin1 characters to be inserted rather than converted to
5858 # prefix-meta sequences
5859 set convert-meta off
5861 # display characters with the eighth bit set directly rather than
5862 # as meta-prefixed characters
5865 # if there are more than 150 possible completions for a word, ask the
5866 # user if he wants to see all of them
5867 set completion-query-items 150
5873 "\M-.": yank-last-arg
5877 File: bashref.info, Node: Bindable Readline Commands, Next: Readline vi Mode, Prev: Readline Init File, Up: Command Line Editing
5879 Bindable Readline Commands
5880 ==========================
5884 * Commands For Moving:: Moving about the line.
5885 * Commands For History:: Getting at previous lines.
5886 * Commands For Text:: Commands for changing text.
5887 * Commands For Killing:: Commands for killing and yanking.
5888 * Numeric Arguments:: Specifying numeric arguments, repeat counts.
5889 * Commands For Completion:: Getting Readline to do the typing for you.
5890 * Keyboard Macros:: Saving and re-executing typed characters
5891 * Miscellaneous Commands:: Other miscellaneous commands.
5893 This section describes Readline commands that may be bound to key
5894 sequences. You can list your key bindings by executing `bind -P' or,
5895 for a more terse format, suitable for an INPUTRC file, `bind -p'.
5896 (*Note Bash Builtins::.) Command names without an accompanying key
5897 sequence are unbound by default.
5899 In the following descriptions, "point" refers to the current cursor
5900 position, and "mark" refers to a cursor position saved by the
5901 `set-mark' command. The text between the point and mark is referred to
5905 File: bashref.info, Node: Commands For Moving, Next: Commands For History, Up: Bindable Readline Commands
5910 `beginning-of-line (C-a)'
5911 Move to the start of the current line.
5914 Move to the end of the line.
5916 `forward-char (C-f)'
5917 Move forward a character.
5919 `backward-char (C-b)'
5920 Move back a character.
5922 `forward-word (M-f)'
5923 Move forward to the end of the next word. Words are composed of
5926 `backward-word (M-b)'
5927 Move back to the start of the current or previous word. Words are
5928 composed of letters and digits.
5930 `clear-screen (C-l)'
5931 Clear the screen and redraw the current line, leaving the current
5932 line at the top of the screen.
5934 `redraw-current-line ()'
5935 Refresh the current line. By default, this is unbound.
5938 File: bashref.info, Node: Commands For History, Next: Commands For Text, Prev: Commands For Moving, Up: Bindable Readline Commands
5940 Commands For Manipulating The History
5941 -------------------------------------
5943 `accept-line (Newline or Return)'
5944 Accept the line regardless of where the cursor is. If this line is
5945 non-empty, add it to the history list according to the setting of
5946 the `HISTCONTROL' and `HISTIGNORE' variables. If this line is a
5947 modified history line, then restore the history line to its
5950 `previous-history (C-p)'
5951 Move `back' through the history list, fetching the previous
5954 `next-history (C-n)'
5955 Move `forward' through the history list, fetching the next command.
5957 `beginning-of-history (M-<)'
5958 Move to the first line in the history.
5960 `end-of-history (M->)'
5961 Move to the end of the input history, i.e., the line currently
5964 `reverse-search-history (C-r)'
5965 Search backward starting at the current line and moving `up'
5966 through the history as necessary. This is an incremental search.
5968 `forward-search-history (C-s)'
5969 Search forward starting at the current line and moving `down'
5970 through the the history as necessary. This is an incremental
5973 `non-incremental-reverse-search-history (M-p)'
5974 Search backward starting at the current line and moving `up'
5975 through the history as necessary using a non-incremental search
5976 for a string supplied by the user.
5978 `non-incremental-forward-search-history (M-n)'
5979 Search forward starting at the current line and moving `down'
5980 through the the history as necessary using a non-incremental search
5981 for a string supplied by the user.
5983 `history-search-forward ()'
5984 Search forward through the history for the string of characters
5985 between the start of the current line and the point. This is a
5986 non-incremental search. By default, this command is unbound.
5988 `history-search-backward ()'
5989 Search backward through the history for the string of characters
5990 between the start of the current line and the point. This is a
5991 non-incremental search. By default, this command is unbound.
5993 `yank-nth-arg (M-C-y)'
5994 Insert the first argument to the previous command (usually the
5995 second word on the previous line) at point. With an argument N,
5996 insert the Nth word from the previous command (the words in the
5997 previous command begin with word 0). A negative argument inserts
5998 the Nth word from the end of the previous command.
6000 `yank-last-arg (M-. or M-_)'
6001 Insert last argument to the previous command (the last word of the
6002 previous history entry). With an argument, behave exactly like
6003 `yank-nth-arg'. Successive calls to `yank-last-arg' move back
6004 through the history list, inserting the last argument of each line
6008 File: bashref.info, Node: Commands For Text, Next: Commands For Killing, Prev: Commands For History, Up: Bindable Readline Commands
6010 Commands For Changing Text
6011 --------------------------
6014 Delete the character at point. If point is at the beginning of
6015 the line, there are no characters in the line, and the last
6016 character typed was not bound to `delete-char', then return EOF.
6018 `backward-delete-char (Rubout)'
6019 Delete the character behind the cursor. A numeric argument means
6020 to kill the characters instead of deleting them.
6022 `forward-backward-delete-char ()'
6023 Delete the character under the cursor, unless the cursor is at the
6024 end of the line, in which case the character behind the cursor is
6025 deleted. By default, this is not bound to a key.
6027 `quoted-insert (C-q or C-v)'
6028 Add the next character typed to the line verbatim. This is how to
6029 insert key sequences like `C-q', for example.
6031 `self-insert (a, b, A, 1, !, ...)'
6034 `transpose-chars (C-t)'
6035 Drag the character before the cursor forward over the character at
6036 the cursor, moving the cursor forward as well. If the insertion
6037 point is at the end of the line, then this transposes the last two
6038 characters of the line. Negative arguments have no effect.
6040 `transpose-words (M-t)'
6041 Drag the word before point past the word after point, moving point
6042 past that word as well. If the insertion point is at the end of
6043 the line, this transposes the last two words on the line.
6046 Uppercase the current (or following) word. With a negative
6047 argument, uppercase the previous word, but do not move the cursor.
6049 `downcase-word (M-l)'
6050 Lowercase the current (or following) word. With a negative
6051 argument, lowercase the previous word, but do not move the cursor.
6053 `capitalize-word (M-c)'
6054 Capitalize the current (or following) word. With a negative
6055 argument, capitalize the previous word, but do not move the cursor.
6058 File: bashref.info, Node: Commands For Killing, Next: Numeric Arguments, Prev: Commands For Text, Up: Bindable Readline Commands
6064 Kill the text from point to the end of the line.
6066 `backward-kill-line (C-x Rubout)'
6067 Kill backward to the beginning of the line.
6069 `unix-line-discard (C-u)'
6070 Kill backward from the cursor to the beginning of the current line.
6072 `kill-whole-line ()'
6073 Kill all characters on the current line, no matter where point is.
6074 By default, this is unbound.
6077 Kill from point to the end of the current word, or if between
6078 words, to the end of the next word. Word boundaries are the same
6081 `backward-kill-word (M-<DEL>)'
6082 Kill the word behind point. Word boundaries are the same as
6085 `unix-word-rubout (C-w)'
6086 Kill the word behind point, using white space as a word boundary.
6087 The killed text is saved on the kill-ring.
6089 `delete-horizontal-space ()'
6090 Delete all spaces and tabs around point. By default, this is
6094 Kill the text in the current region. By default, this command is
6097 `copy-region-as-kill ()'
6098 Copy the text in the region to the kill buffer, so it can be yanked
6099 right away. By default, this command is unbound.
6101 `copy-backward-word ()'
6102 Copy the word before point to the kill buffer. The word
6103 boundaries are the same as `backward-word'. By default, this
6106 `copy-forward-word ()'
6107 Copy the word following point to the kill buffer. The word
6108 boundaries are the same as `forward-word'. By default, this
6112 Yank the top of the kill ring into the buffer at point.
6115 Rotate the kill-ring, and yank the new top. You can only do this
6116 if the prior command is `yank' or `yank-pop'.
6119 File: bashref.info, Node: Numeric Arguments, Next: Commands For Completion, Prev: Commands For Killing, Up: Bindable Readline Commands
6121 Specifying Numeric Arguments
6122 ----------------------------
6124 `digit-argument (M-0, M-1, ... M--)'
6125 Add this digit to the argument already accumulating, or start a new
6126 argument. `M--' starts a negative argument.
6128 `universal-argument ()'
6129 This is another way to specify an argument. If this command is
6130 followed by one or more digits, optionally with a leading minus
6131 sign, those digits define the argument. If the command is
6132 followed by digits, executing `universal-argument' again ends the
6133 numeric argument, but is otherwise ignored. As a special case, if
6134 this command is immediately followed by a character that is
6135 neither a digit or minus sign, the argument count for the next
6136 command is multiplied by four. The argument count is initially
6137 one, so executing this function the first time makes the argument
6138 count four, a second time makes the argument count sixteen, and so
6139 on. By default, this is not bound to a key.
6142 File: bashref.info, Node: Commands For Completion, Next: Keyboard Macros, Prev: Numeric Arguments, Up: Bindable Readline Commands
6144 Letting Readline Type For You
6145 -----------------------------
6148 Attempt to perform completion on the text before point. The
6149 actual completion performed is application-specific. Bash
6150 attempts completion treating the text as a variable (if the text
6151 begins with `$'), username (if the text begins with `~'), hostname
6152 (if the text begins with `@'), or command (including aliases and
6153 functions) in turn. If none of these produces a match, filename
6154 completion is attempted.
6156 `possible-completions (M-?)'
6157 List the possible completions of the text before point.
6159 `insert-completions (M-*)'
6160 Insert all completions of the text before point that would have
6161 been generated by `possible-completions'.
6164 Similar to `complete', but replaces the word to be completed with
6165 a single match from the list of possible completions. Repeated
6166 execution of `menu-complete' steps through the list of possible
6167 completions, inserting each match in turn. At the end of the list
6168 of completions, the bell is rung (subject to the setting of
6169 `bell-style') and the original text is restored. An argument of N
6170 moves N positions forward in the list of matches; a negative
6171 argument may be used to move backward through the list. This
6172 command is intended to be bound to <TAB>, but is unbound by
6175 `delete-char-or-list ()'
6176 Deletes the character under the cursor if not at the beginning or
6177 end of the line (like `delete-char'). If at the end of the line,
6178 behaves identically to `possible-completions'. This command is
6181 `complete-filename (M-/)'
6182 Attempt filename completion on the text before point.
6184 `possible-filename-completions (C-x /)'
6185 List the possible completions of the text before point, treating
6188 `complete-username (M-~)'
6189 Attempt completion on the text before point, treating it as a
6192 `possible-username-completions (C-x ~)'
6193 List the possible completions of the text before point, treating
6196 `complete-variable (M-$)'
6197 Attempt completion on the text before point, treating it as a
6200 `possible-variable-completions (C-x $)'
6201 List the possible completions of the text before point, treating
6202 it as a shell variable.
6204 `complete-hostname (M-@)'
6205 Attempt completion on the text before point, treating it as a
6208 `possible-hostname-completions (C-x @)'
6209 List the possible completions of the text before point, treating
6212 `complete-command (M-!)'
6213 Attempt completion on the text before point, treating it as a
6214 command name. Command completion attempts to match the text
6215 against aliases, reserved words, shell functions, shell builtins,
6216 and finally executable filenames, in that order.
6218 `possible-command-completions (C-x !)'
6219 List the possible completions of the text before point, treating
6220 it as a command name.
6222 `dynamic-complete-history (M-<TAB>)'
6223 Attempt completion on the text before point, comparing the text
6224 against lines from the history list for possible completion
6227 `complete-into-braces (M-{)'
6228 Perform filename completion and insert the list of possible
6229 completions enclosed within braces so the list is available to the
6230 shell (*note Brace Expansion::).
6233 File: bashref.info, Node: Keyboard Macros, Next: Miscellaneous Commands, Prev: Commands For Completion, Up: Bindable Readline Commands
6238 `start-kbd-macro (C-x ()'
6239 Begin saving the characters typed into the current keyboard macro.
6241 `end-kbd-macro (C-x ))'
6242 Stop saving the characters typed into the current keyboard macro
6243 and save the definition.
6245 `call-last-kbd-macro (C-x e)'
6246 Re-execute the last keyboard macro defined, by making the
6247 characters in the macro appear as if typed at the keyboard.
6250 File: bashref.info, Node: Miscellaneous Commands, Prev: Keyboard Macros, Up: Bindable Readline Commands
6252 Some Miscellaneous Commands
6253 ---------------------------
6255 `re-read-init-file (C-x C-r)'
6256 Read in the contents of the INPUTRC file, and incorporate any
6257 bindings or variable assignments found there.
6260 Abort the current editing command and ring the terminal's bell
6261 (subject to the setting of `bell-style').
6263 `do-uppercase-version (M-a, M-b, M-X, ...)'
6264 If the metafied character X is lowercase, run the command that is
6265 bound to the corresponding uppercase character.
6267 `prefix-meta (<ESC>)'
6268 Metafy the next character typed. This is for keyboards without a
6269 meta key. Typing `<ESC> f' is equivalent to typing `M-f'.
6271 `undo (C-_ or C-x C-u)'
6272 Incremental undo, separately remembered for each line.
6275 Undo all changes made to this line. This is like executing the
6276 `undo' command enough times to get back to the beginning.
6278 `tilde-expand (M-&)'
6279 Perform tilde expansion on the current word.
6282 Set the mark to the point. If a numeric argument is supplied, the
6283 mark is set to that position.
6285 `exchange-point-and-mark (C-x C-x)'
6286 Swap the point with the mark. The current cursor position is set
6287 to the saved position, and the old cursor position is saved as the
6290 `character-search (C-])'
6291 A character is read and point is moved to the next occurrence of
6292 that character. A negative count searches for previous
6295 `character-search-backward (M-C-])'
6296 A character is read and point is moved to the previous occurrence
6297 of that character. A negative count searches for subsequent
6300 `insert-comment (M-#)'
6301 The value of the `comment-begin' variable is inserted at the
6302 beginning of the current line, and the line is accepted as if a
6303 newline had been typed. The default value of `comment-begin'
6304 causes this command to make the current line a shell comment.
6307 Print all of the functions and their key bindings to the Readline
6308 output stream. If a numeric argument is supplied, the output is
6309 formatted in such a way that it can be made part of an INPUTRC
6310 file. This command is unbound by default.
6313 Print all of the settable variables and their values to the
6314 Readline output stream. If a numeric argument is supplied, the
6315 output is formatted in such a way that it can be made part of an
6316 INPUTRC file. This command is unbound by default.
6319 Print all of the Readline key sequences bound to macros and the
6320 strings they output. If a numeric argument is supplied, the
6321 output is formatted in such a way that it can be made part of an
6322 INPUTRC file. This command is unbound by default.
6324 `glob-expand-word (C-x *)'
6325 The word before point is treated as a pattern for pathname
6326 expansion, and the list of matching file names is inserted,
6329 `glob-list-expansions (C-x g)'
6330 The list of expansions that would have been generated by
6331 `glob-expand-word' is displayed, and the line is redrawn.
6333 `display-shell-version (C-x C-v)'
6334 Display version information about the current instance of Bash.
6336 `shell-expand-line (M-C-e)'
6337 Expand the line as the shell does. This performs alias and
6338 history expansion as well as all of the shell word expansions
6339 (*note Shell Expansions::).
6341 `history-expand-line (M-^)'
6342 Perform history expansion on the current line.
6345 Perform history expansion on the current line and insert a space
6346 (*note History Interaction::).
6348 `alias-expand-line ()'
6349 Perform alias expansion on the current line (*note Aliases::).
6351 `history-and-alias-expand-line ()'
6352 Perform history and alias expansion on the current line.
6354 `insert-last-argument (M-. or M-_)'
6355 A synonym for `yank-last-arg'.
6357 `operate-and-get-next (C-o)'
6358 Accept the current line for execution and fetch the next line
6359 relative to the current line from the history for editing. Any
6360 argument is ignored.
6362 `emacs-editing-mode (C-e)'
6363 When in `vi' editing mode, this causes a switch back to `emacs'
6364 editing mode, as if the command `set -o emacs' had been executed.
6367 File: bashref.info, Node: Readline vi Mode, Next: Programmable Completion, Prev: Bindable Readline Commands, Up: Command Line Editing
6372 While the Readline library does not have a full set of `vi' editing
6373 functions, it does contain enough to allow simple editing of the line.
6374 The Readline `vi' mode behaves as specified in the POSIX 1003.2
6377 In order to switch interactively between `emacs' and `vi' editing
6378 modes, use the `set -o emacs' and `set -o vi' commands (*note The Set
6379 Builtin::). The Readline default is `emacs' mode.
6381 When you enter a line in `vi' mode, you are already placed in
6382 `insertion' mode, as if you had typed an `i'. Pressing <ESC> switches
6383 you into `command' mode, where you can edit the text of the line with
6384 the standard `vi' movement keys, move to previous history lines with
6385 `k' and subsequent lines with `j', and so forth.
6388 File: bashref.info, Node: Programmable Completion, Next: Programmable Completion Builtins, Prev: Readline vi Mode, Up: Command Line Editing
6390 Programmable Completion
6391 =======================
6393 When word completion is attempted for an argument to a command for
6394 which a completion specification (a COMPSPEC) has been defined using
6395 the `complete' builtin (*note Programmable Completion Builtins::), the
6396 programmable completion facilities are invoked.
6398 First, the command name is identified. If a compspec has been
6399 defined for that command, the compspec is used to generate the list of
6400 possible completions for the word. If the command word is a full
6401 pathname, a compspec for the full pathname is searched for first. If
6402 no compspec is found for the full pathname, an attempt is made to find
6403 a compspec for the portion following the final slash.
6405 Once a compspec has been found, it is used to generate the list of
6406 matching words. If a compspec is not found, the default Bash completion
6407 described above (*note Commands For Completion::) is performed.
6409 First, the actions specified by the compspec are used. Only matches
6410 which are prefixed by the word being completed are returned. When the
6411 `-f' or `-d' option is used for filename or directory name completion,
6412 the shell variable `FIGNORE' is used to filter the matches. *Note Bash
6413 Variables::, for a description of `FIGNORE'.
6415 Any completions specified by a filename expansion pattern to the
6416 `-G' option are generated next. The words generated by the pattern
6417 need not match the word being completed. The `GLOBIGNORE' shell
6418 variable is not used to filter the matches, but the `FIGNORE' shell
6421 Next, the string specified as the argument to the `-W' option is
6422 considered. The string is first split using the characters in the `IFS'
6423 special variable as delimiters. Shell quoting is honored. Each word
6424 is then expanded using brace expansion, tilde expansion, parameter and
6425 variable expansion, command substitution, arithmetic expansion, and
6426 pathname expansion, as described above (*note Shell Expansions::). The
6427 results are split using the rules described above (*note Word
6428 Splitting::). The results of the expansion are prefix-matched against
6429 the word being completed, and the matching words become the possible
6432 After these matches have been generated, any shell function or
6433 command specified with the `-F' and `-C' options is invoked. When the
6434 command or function is invoked, the `COMP_LINE' and `COMP_POINT'
6435 variables are assigned values as described above (*note Bash
6436 Variables::). If a shell function is being invoked, the `COMP_WORDS'
6437 and `COMP_CWORD' variables are also set. When the function or command
6438 is invoked, the first argument is the name of the command whose
6439 arguments are being completed, the second argument is the word being
6440 completed, and the third argument is the word preceding the word being
6441 completed on the current command line. No filtering of the generated
6442 completions against the word being completed is performed; the function
6443 or command has complete freedom in generating the matches.
6445 Any function specified with `-F' is invoked first. The function may
6446 use any of the shell facilities, including the `compgen' builtin
6447 described below (*note Programmable Completion Builtins::), to generate
6448 the matches. It must put the possible completions in the `COMPREPLY'
6451 Next, any command specified with the `-C' option is invoked in an
6452 environment equivalent to command substitution. It should print a list
6453 of completions, one per line, to the standard output. Backslash may be
6454 used to escape a newline, if necessary.
6456 After all of the possible completions are generated, any filter
6457 specified with the `-X' option is applied to the list. The filter is a
6458 pattern as used for pathname expansion; a `&' in the pattern is
6459 replaced with the text of the word being completed. A literal `&' may
6460 be escaped with a backslash; the backslash is removed before attempting
6461 a match. Any completion that matches the pattern will be removed from
6462 the list. A leading `!' negates the pattern; in this case any
6463 completion not matching the pattern will be removed.
6465 Finally, any prefix and suffix specified with the `-P' and `-S'
6466 options are added to each member of the completion list, and the result
6467 is returned to the Readline completion code as the list of possible
6470 If the previously-applied actions do not generate any matches, and
6471 the `-o dirnames' option was supplied to `complete' when the compspec
6472 was defined, directory name completion is attempted.
6474 By default, if a compspec is found, whatever it generates is
6475 returned to the completion code as the full set of possible completions.
6476 The default Bash completions are not attempted, and the Readline default
6477 of filename completion is disabled. If the `-o default' option was
6478 supplied to `complete' when the compspec was defined, Readline's
6479 default completion will be performed if the compspec generates no
6483 File: bashref.info, Node: Programmable Completion Builtins, Prev: Programmable Completion, Up: Command Line Editing
6485 Programmable Completion Builtins
6486 ================================
6488 Two builtin commands are available to manipulate the programmable
6489 completion facilities.
6492 `compgen [OPTION] [WORD]'
6494 Generate possible completion matches for WORD according to the
6495 OPTIONs, which may be any option accepted by the `complete'
6496 builtin with the exception of `-p' and `-r', and write the matches
6497 to the standard output. When using the `-F' or `-C' options, the
6498 various shell variables set by the programmable completion
6499 facilities, while available, will not have useful values.
6501 The matches will be generated in the same way as if the
6502 programmable completion code had generated them directly from a
6503 completion specification with the same flags. If WORD is
6504 specified, only those completions matching WORD will be displayed.
6506 The return value is true unless an invalid option is supplied, or
6507 no matches were generated.
6510 `complete [-abcdefgjkvu] [-o COMP-OPTION] [-A ACTION] [-G GLOBPAT] [-W WORDLIST]
6511 [-P PREFIX] [-S SUFFIX] [-X FILTERPAT] [-F FUNCTION]
6512 [-C COMMAND] NAME [NAME ...]'
6513 `complete -pr [NAME ...]'
6515 Specify how arguments to each NAME should be completed. If the
6516 `-p' option is supplied, or if no options are supplied, existing
6517 completion specifications are printed in a way that allows them to
6518 be reused as input. The `-r' option removes a completion
6519 specification for each NAME, or, if no NAMEs are supplied, all
6520 completion specifications.
6522 The process of applying these completion specifications when word
6523 completion is attempted is described above (*note Programmable
6526 Other options, if specified, have the following meanings. The
6527 arguments to the `-G', `-W', and `-X' options (and, if necessary,
6528 the `-P' and `-S' options) should be quoted to protect them from
6529 expansion before the `complete' builtin is invoked.
6532 The COMP-OPTION controls several aspects of the compspec's
6533 behavior beyond the simple generation of completions.
6534 COMP-OPTION may be one of:
6537 Use readline's default completion if the compspec
6538 generates no matches.
6541 Perform directory name completion if the compspec
6542 generates no matches.
6545 Tell Readline that the compspec generates filenames, so
6546 it can perform any filename\-specific processing (like
6547 adding a slash to directory names or suppressing
6548 trailing spaces). This option is intended to be used
6549 with shell functions specified with `-F'.
6552 The ACTION may be one of the following to generate a list of
6553 possible completions:
6556 Alias names. May also be specified as `-a'.
6559 Array variable names.
6562 Readline key binding names (*note Bindable Readline
6566 Names of shell builtin commands. May also be specified
6570 Command names. May also be specified as `-c'.
6573 Directory names. May also be specified as `-d'.
6576 Names of disabled shell builtins.
6579 Names of enabled shell builtins.
6582 Names of exported shell variables. May also be
6586 File names. May also be specified as `-f'.
6589 Names of shell functions.
6592 Group names. May also be specified as `-g'.
6595 Help topics as accepted by the `help' builtin (*note
6599 Hostnames, as taken from the file specified by the
6600 `HOSTFILE' shell variable (*note Bash Variables::).
6603 Job names, if job control is active. May also be
6607 Shell reserved words. May also be specified as `-k'.
6610 Names of running jobs, if job control is active.
6613 Valid arguments for the `-o' option to the `set' builtin
6614 (*note The Set Builtin::).
6617 Shell option names as accepted by the `shopt' builtin
6618 (*note Bash Builtins::).
6624 Names of stopped jobs, if job control is active.
6627 User names. May also be specified as `-u'.
6630 Names of all shell variables. May also be specified as
6634 The filename expansion pattern GLOBPAT is expanded to generate
6635 the possible completions.
6638 The WORDLIST is split using the characters in the `IFS'
6639 special variable as delimiters, and each resultant word is
6640 expanded. The possible completions are the members of the
6641 resultant list which match the word being completed.
6644 COMMAND is executed in a subshell environment, and its output
6645 is used as the possible completions.
6648 The shell function FUNCTION is executed in the current shell
6649 environment. When it finishes, the possible completions are
6650 retrieved from the value of the `COMPREPLY' array variable.
6653 FILTERPAT is a pattern as used for filename expansion. It is
6654 applied to the list of possible completions generated by the
6655 preceding options and arguments, and each completion matching
6656 FILTERPAT is removed from the list. A leading `!' in
6657 FILTERPAT negates the pattern; in this case, any completion
6658 not matching FILTERPAT is removed.
6661 PREFIX is added at the beginning of each possible completion
6662 after all other options have been applied.
6665 SUFFIX is appended to each possible completion after all
6666 other options have been applied.
6668 The return value is true unless an invalid option is supplied, an
6669 option other than `-p' or `-r' is supplied without a NAME
6670 argument, an attempt is made to remove a completion specification
6671 for a NAME for which no specification exists, or an error occurs
6672 adding a completion specification.
6675 File: bashref.info, Node: Using History Interactively, Next: Command Line Editing, Prev: Job Control, Up: Top
6677 Using History Interactively
6678 ***************************
6680 This chapter describes how to use the GNU History Library
6681 interactively, from a user's standpoint. It should be considered a
6682 user's guide. For information on using the GNU History Library in
6683 other programs, see the GNU Readline Library Manual.
6687 * Bash History Facilities:: How Bash lets you manipulate your command
6689 * Bash History Builtins:: The Bash builtin commands that manipulate
6690 the command history.
6691 * History Interaction:: What it feels like using History as a user.
6694 File: bashref.info, Node: Bash History Facilities, Next: Bash History Builtins, Up: Using History Interactively
6696 Bash History Facilities
6697 =======================
6699 When the `-o history' option to the `set' builtin is enabled (*note
6700 The Set Builtin::), the shell provides access to the "command history",
6701 the list of commands previously typed. The value of the `HISTSIZE'
6702 shell variable is used as the number of commands to save in a history
6703 list. The text of the last `$HISTSIZE' commands (default 500) is saved.
6704 The shell stores each command in the history list prior to parameter
6705 and variable expansion but after history expansion is performed,
6706 subject to the values of the shell variables `HISTIGNORE' and
6709 When the shell starts up, the history is initialized from the file
6710 named by the `HISTFILE' variable (default `~/.bash_history'). The file
6711 named by the value of `HISTFILE' is truncated, if necessary, to contain
6712 no more than the number of lines specified by the value of the
6713 `HISTFILESIZE' variable. When an interactive shell exits, the last
6714 `$HISTSIZE' lines are copied from the history list to the file named by
6715 `$HISTFILE'. If the `histappend' shell option is set (*note Bash
6716 Builtins::), the lines are appended to the history file, otherwise the
6717 history file is overwritten. If `HISTFILE' is unset, or if the history
6718 file is unwritable, the history is not saved. After saving the
6719 history, the history file is truncated to contain no more than
6720 `$HISTFILESIZE' lines. If `HISTFILESIZE' is not set, no truncation is
6723 The builtin command `fc' may be used to list or edit and re-execute
6724 a portion of the history list. The `history' builtin may be used to
6725 display or modify the history list and manipulate the history file.
6726 When using command-line editing, search commands are available in each
6727 editing mode that provide access to the history list (*note Commands
6730 The shell allows control over which commands are saved on the history
6731 list. The `HISTCONTROL' and `HISTIGNORE' variables may be set to cause
6732 the shell to save only a subset of the commands entered. The `cmdhist'
6733 shell option, if enabled, causes the shell to attempt to save each line
6734 of a multi-line command in the same history entry, adding semicolons
6735 where necessary to preserve syntactic correctness. The `lithist' shell
6736 option causes the shell to save the command with embedded newlines
6737 instead of semicolons. The `shopt' builtin is used to set these
6738 options. *Note Bash Builtins::, for a description of `shopt'.
6741 File: bashref.info, Node: Bash History Builtins, Next: History Interaction, Prev: Bash History Facilities, Up: Using History Interactively
6743 Bash History Builtins
6744 =====================
6746 Bash provides two builtin commands which manipulate the history list
6750 `fc [-e ENAME] [-nlr] [FIRST] [LAST]'
6751 `fc -s [PAT=REP] [COMMAND]'
6753 Fix Command. In the first form, a range of commands from FIRST to
6754 LAST is selected from the history list. Both FIRST and LAST may
6755 be specified as a string (to locate the most recent command
6756 beginning with that string) or as a number (an index into the
6757 history list, where a negative number is used as an offset from the
6758 current command number). If LAST is not specified it is set to
6759 FIRST. If FIRST is not specified it is set to the previous
6760 command for editing and -16 for listing. If the `-l' flag is
6761 given, the commands are listed on standard output. The `-n' flag
6762 suppresses the command numbers when listing. The `-r' flag
6763 reverses the order of the listing. Otherwise, the editor given by
6764 ENAME is invoked on a file containing those commands. If ENAME is
6765 not given, the value of the following variable expansion is used:
6766 `${FCEDIT:-${EDITOR:-vi}}'. This says to use the value of the
6767 `FCEDIT' variable if set, or the value of the `EDITOR' variable if
6768 that is set, or `vi' if neither is set. When editing is complete,
6769 the edited commands are echoed and executed.
6771 In the second form, COMMAND is re-executed after each instance of
6772 PAT in the selected command is replaced by REP.
6774 A useful alias to use with the `fc' command is `r='fc -s'', so
6775 that typing `r cc' runs the last command beginning with `cc' and
6776 typing `r' re-executes the last command (*note Aliases::).
6782 history [-anrw] [FILENAME]
6785 With no options, display the history list with line numbers.
6786 Lines prefixed with a `*' have been modified. An argument of N
6787 lists only the last N lines. Options, if supplied, have the
6791 Clear the history list. This may be combined with the other
6792 options to replace the history list completely.
6795 Delete the history entry at position OFFSET. OFFSET should
6796 be specified as it appears when the history is displayed.
6799 Append the new history lines (history lines entered since the
6800 beginning of the current Bash session) to the history file.
6803 Append the history lines not already read from the history
6804 file to the current history list. These are lines appended
6805 to the history file since the beginning of the current Bash
6809 Read the current history file and append its contents to the
6813 Write out the current history to the history file.
6816 Perform history substitution on the ARGs and display the
6817 result on the standard output, without storing the results in
6821 The ARGs are added to the end of the history list as a single
6824 When any of the `-w', `-r', `-a', or `-n' options is used, if
6825 FILENAME is given, then it is used as the history file. If not,
6826 then the value of the `HISTFILE' variable is used.
6829 File: bashref.info, Node: History Interaction, Prev: Bash History Builtins, Up: Using History Interactively
6834 The History library provides a history expansion feature that is
6835 similar to the history expansion provided by `csh'. This section
6836 describes the syntax used to manipulate the history information.
6838 History expansions introduce words from the history list into the
6839 input stream, making it easy to repeat commands, insert the arguments
6840 to a previous command into the current input line, or fix errors in
6841 previous commands quickly.
6843 History expansion takes place in two parts. The first is to
6844 determine which line from the history list should be used during
6845 substitution. The second is to select portions of that line for
6846 inclusion into the current one. The line selected from the history is
6847 called the "event", and the portions of that line that are acted upon
6848 are called "words". Various "modifiers" are available to manipulate
6849 the selected words. The line is broken into words in the same fashion
6850 that Bash does, so that several words surrounded by quotes are
6851 considered one word. History expansions are introduced by the
6852 appearance of the history expansion character, which is `!' by default.
6853 Only `\' and `'' may be used to escape the history expansion character.
6855 Several shell options settable with the `shopt' builtin (*note Bash
6856 Builtins::) may be used to tailor the behavior of history expansion.
6857 If the `histverify' shell option is enabled, and Readline is being
6858 used, history substitutions are not immediately passed to the shell
6859 parser. Instead, the expanded line is reloaded into the Readline
6860 editing buffer for further modification. If Readline is being used,
6861 and the `histreedit' shell option is enabled, a failed history
6862 expansion will be reloaded into the Readline editing buffer for
6863 correction. The `-p' option to the `history' builtin command may be
6864 used to see what a history expansion will do before using it. The `-s'
6865 option to the `history' builtin may be used to add commands to the end
6866 of the history list without actually executing them, so that they are
6867 available for subsequent recall. This is most useful in conjunction
6870 The shell allows control of the various characters used by the
6871 history expansion mechanism with the `histchars' variable.
6875 * Event Designators:: How to specify which history line to use.
6876 * Word Designators:: Specifying which words are of interest.
6877 * Modifiers:: Modifying the results of substitution.
6880 File: bashref.info, Node: Event Designators, Next: Word Designators, Up: History Interaction
6885 An event designator is a reference to a command line entry in the
6889 Start a history substitution, except when followed by a space, tab,
6890 the end of the line, `=' or `('.
6893 Refer to command line N.
6896 Refer to the command N lines back.
6899 Refer to the previous command. This is a synonym for `!-1'.
6902 Refer to the most recent command starting with STRING.
6905 Refer to the most recent command containing STRING. The trailing
6906 `?' may be omitted if the STRING is followed immediately by a
6910 Quick Substitution. Repeat the last command, replacing STRING1
6911 with STRING2. Equivalent to `!!:s/STRING1/STRING2/'.
6914 The entire command line typed so far.
6917 File: bashref.info, Node: Word Designators, Next: Modifiers, Prev: Event Designators, Up: History Interaction
6922 Word designators are used to select desired words from the event. A
6923 `:' separates the event specification from the word designator. It may
6924 be omitted if the word designator begins with a `^', `$', `*', `-', or
6925 `%'. Words are numbered from the beginning of the line, with the first
6926 word being denoted by 0 (zero). Words are inserted into the current
6927 line separated by single spaces.
6932 designates the preceding command. When you type this, the
6933 preceding command is repeated in toto.
6936 designates the last argument of the preceding command. This may be
6940 designates the second argument of the most recent command starting
6941 with the letters `fi'.
6943 Here are the word designators:
6946 The `0'th word. For many applications, this is the command word.
6952 The first argument; that is, word 1.
6958 The word matched by the most recent `?STRING?' search.
6961 A range of words; `-Y' abbreviates `0-Y'.
6964 All of the words, except the `0'th. This is a synonym for `1-$'.
6965 It is not an error to use `*' if there is just one word in the
6966 event; the empty string is returned in that case.
6972 Abbreviates `X-$' like `X*', but omits the last word.
6974 If a word designator is supplied without an event specification, the
6975 previous command is used as the event.
6978 File: bashref.info, Node: Modifiers, Prev: Word Designators, Up: History Interaction
6983 After the optional word designator, you can add a sequence of one or
6984 more of the following modifiers, each preceded by a `:'.
6987 Remove a trailing pathname component, leaving only the head.
6990 Remove all leading pathname components, leaving the tail.
6993 Remove a trailing suffix of the form `.SUFFIX', leaving the
6997 Remove all but the trailing suffix.
7000 Print the new command but do not execute it.
7003 Quote the substituted words, escaping further substitutions.
7006 Quote the substituted words as with `q', but break into words at
7007 spaces, tabs, and newlines.
7010 Substitute NEW for the first occurrence of OLD in the event line.
7011 Any delimiter may be used in place of `/'. The delimiter may be
7012 quoted in OLD and NEW with a single backslash. If `&' appears in
7013 NEW, it is replaced by OLD. A single backslash will quote the
7014 `&'. The final delimiter is optional if it is the last character
7018 Repeat the previous substitution.
7021 Cause changes to be applied over the entire event line. Used in
7022 conjunction with `s', as in `gs/OLD/NEW/', or with `&'.
7025 File: bashref.info, Node: Installing Bash, Next: Reporting Bugs, Prev: Command Line Editing, Up: Top
7030 This chapter provides basic instructions for installing Bash on the
7031 various supported platforms. The distribution supports the GNU
7032 operating systems, nearly every version of Unix, and several non-Unix
7033 systems such as BeOS and Interix. Other independent ports exist for
7034 MS-DOS, OS/2, Windows 95/98, and Windows NT.
7038 * Basic Installation:: Installation instructions.
7040 * Compilers and Options:: How to set special options for various
7043 * Compiling For Multiple Architectures:: How to compile Bash for more
7044 than one kind of system from
7045 the same source tree.
7047 * Installation Names:: How to set the various paths used by the installation.
7049 * Specifying the System Type:: How to configure Bash for a particular system.
7051 * Sharing Defaults:: How to share default configuration values among GNU
7054 * Operation Controls:: Options recognized by the configuration program.
7056 * Optional Features:: How to enable and disable optional features when
7060 File: bashref.info, Node: Basic Installation, Next: Compilers and Options, Up: Installing Bash
7065 These are installation instructions for Bash.
7067 The simplest way to compile Bash is:
7069 1. `cd' to the directory containing the source code and type
7070 `./configure' to configure Bash for your system. If you're using
7071 `csh' on an old version of System V, you might need to type `sh
7072 ./configure' instead to prevent `csh' from trying to execute
7075 Running `configure' takes some time. While running, it prints
7076 messages telling which features it is checking for.
7078 2. Type `make' to compile Bash and build the `bashbug' bug reporting
7081 3. Optionally, type `make tests' to run the Bash test suite.
7083 4. Type `make install' to install `bash' and `bashbug'. This will
7084 also install the manual pages and Info file.
7087 The `configure' shell script attempts to guess correct values for
7088 various system-dependent variables used during compilation. It uses
7089 those values to create a `Makefile' in each directory of the package
7090 (the top directory, the `builtins', `doc', and `support' directories,
7091 each directory under `lib', and several others). It also creates a
7092 `config.h' file containing system-dependent definitions. Finally, it
7093 creates a shell script named `config.status' that you can run in the
7094 future to recreate the current configuration, a file `config.cache'
7095 that saves the results of its tests to speed up reconfiguring, and a
7096 file `config.log' containing compiler output (useful mainly for
7097 debugging `configure'). If at some point `config.cache' contains
7098 results you don't want to keep, you may remove or edit it.
7100 To find out more about the options and arguments that the
7101 `configure' script understands, type
7103 bash-2.04$ ./configure --help
7105 at the Bash prompt in your Bash source directory.
7107 If you need to do unusual things to compile Bash, please try to
7108 figure out how `configure' could check whether or not to do them, and
7109 mail diffs or instructions to <bash-maintainers@gnu.org> so they can be
7110 considered for the next release.
7112 The file `configure.in' is used to create `configure' by a program
7113 called Autoconf. You only need `configure.in' if you want to change it
7114 or regenerate `configure' using a newer version of Autoconf. If you do
7115 this, make sure you are using Autoconf version 2.50 or newer.
7117 You can remove the program binaries and object files from the source
7118 code directory by typing `make clean'. To also remove the files that
7119 `configure' created (so you can compile Bash for a different kind of
7120 computer), type `make distclean'.
7123 File: bashref.info, Node: Compilers and Options, Next: Compiling For Multiple Architectures, Prev: Basic Installation, Up: Installing Bash
7125 Compilers and Options
7126 =====================
7128 Some systems require unusual options for compilation or linking that
7129 the `configure' script does not know about. You can give `configure'
7130 initial values for variables by setting them in the environment. Using
7131 a Bourne-compatible shell, you can do that on the command line like
7134 CC=c89 CFLAGS=-O2 LIBS=-lposix ./configure
7136 On systems that have the `env' program, you can do it like this:
7138 env CPPFLAGS=-I/usr/local/include LDFLAGS=-s ./configure
7140 The configuration process uses GCC to build Bash if it is available.
7143 File: bashref.info, Node: Compiling For Multiple Architectures, Next: Installation Names, Prev: Compilers and Options, Up: Installing Bash
7145 Compiling For Multiple Architectures
7146 ====================================
7148 You can compile Bash for more than one kind of computer at the same
7149 time, by placing the object files for each architecture in their own
7150 directory. To do this, you must use a version of `make' that supports
7151 the `VPATH' variable, such as GNU `make'. `cd' to the directory where
7152 you want the object files and executables to go and run the `configure'
7153 script from the source directory. You may need to supply the
7154 `--srcdir=PATH' argument to tell `configure' where the source files
7155 are. `configure' automatically checks for the source code in the
7156 directory that `configure' is in and in `..'.
7158 If you have to use a `make' that does not supports the `VPATH'
7159 variable, you can compile Bash for one architecture at a time in the
7160 source code directory. After you have installed Bash for one
7161 architecture, use `make distclean' before reconfiguring for another
7164 Alternatively, if your system supports symbolic links, you can use
7165 the `support/mkclone' script to create a build tree which has symbolic
7166 links back to each file in the source directory. Here's an example
7167 that creates a build directory in the current directory from a source
7168 directory `/usr/gnu/src/bash-2.0':
7170 bash /usr/gnu/src/bash-2.0/support/mkclone -s /usr/gnu/src/bash-2.0 .
7172 The `mkclone' script requires Bash, so you must have already built Bash
7173 for at least one architecture before you can create build directories
7174 for other architectures.
7177 File: bashref.info, Node: Installation Names, Next: Specifying the System Type, Prev: Compiling For Multiple Architectures, Up: Installing Bash
7182 By default, `make install' will install into `/usr/local/bin',
7183 `/usr/local/man', etc. You can specify an installation prefix other
7184 than `/usr/local' by giving `configure' the option `--prefix=PATH', or
7185 by specifying a value for the `DESTDIR' `make' variable when running
7188 You can specify separate installation prefixes for
7189 architecture-specific files and architecture-independent files. If you
7190 give `configure' the option `--exec-prefix=PATH', `make install' will
7191 use PATH as the prefix for installing programs and libraries.
7192 Documentation and other data files will still use the regular prefix.
7195 File: bashref.info, Node: Specifying the System Type, Next: Sharing Defaults, Prev: Installation Names, Up: Installing Bash
7197 Specifying the System Type
7198 ==========================
7200 There may be some features `configure' can not figure out
7201 automatically, but need to determine by the type of host Bash will run
7202 on. Usually `configure' can figure that out, but if it prints a
7203 message saying it can not guess the host type, give it the
7204 `--host=TYPE' option. `TYPE' can either be a short name for the system
7205 type, such as `sun4', or a canonical name with three fields:
7206 `CPU-COMPANY-SYSTEM' (e.g., `i386-unknown-freebsd4.2').
7208 See the file `support/config.sub' for the possible values of each
7212 File: bashref.info, Node: Sharing Defaults, Next: Operation Controls, Prev: Specifying the System Type, Up: Installing Bash
7217 If you want to set default values for `configure' scripts to share,
7218 you can create a site shell script called `config.site' that gives
7219 default values for variables like `CC', `cache_file', and `prefix'.
7220 `configure' looks for `PREFIX/share/config.site' if it exists, then
7221 `PREFIX/etc/config.site' if it exists. Or, you can set the
7222 `CONFIG_SITE' environment variable to the location of the site script.
7223 A warning: the Bash `configure' looks for a site script, but not all
7224 `configure' scripts do.
7227 File: bashref.info, Node: Operation Controls, Next: Optional Features, Prev: Sharing Defaults, Up: Installing Bash
7232 `configure' recognizes the following options to control how it
7236 Use and save the results of the tests in FILE instead of
7237 `./config.cache'. Set FILE to `/dev/null' to disable caching, for
7238 debugging `configure'.
7241 Print a summary of the options to `configure', and exit.
7246 Do not print messages saying which checks are being made.
7249 Look for the Bash source code in directory DIR. Usually
7250 `configure' can determine that directory automatically.
7253 Print the version of Autoconf used to generate the `configure'
7256 `configure' also accepts some other, not widely used, boilerplate
7257 options. `configure --help' prints the complete list.
7260 File: bashref.info, Node: Optional Features, Prev: Operation Controls, Up: Installing Bash
7265 The Bash `configure' has a number of `--enable-FEATURE' options,
7266 where FEATURE indicates an optional part of Bash. There are also
7267 several `--with-PACKAGE' options, where PACKAGE is something like
7268 `bash-malloc' or `purify'. To turn off the default use of a package,
7269 use `--without-PACKAGE'. To configure Bash without a feature that is
7270 enabled by default, use `--disable-FEATURE'.
7272 Here is a complete list of the `--enable-' and `--with-' options
7273 that the Bash `configure' recognizes.
7276 Define if you are using the Andrew File System from Transarc.
7278 `--with-bash-malloc'
7279 Use the Bash version of `malloc' in `lib/malloc/malloc.c'. This
7280 is not the same `malloc' that appears in GNU libc, but an older
7281 version derived from the 4.2 BSD `malloc'. This `malloc' is very
7282 fast, but wastes some space on each allocation. This option is
7283 enabled by default. The `NOTES' file contains a list of systems
7284 for which this should be turned off, and `configure' disables this
7285 option automatically for a number of systems.
7288 Use the curses library instead of the termcap library. This should
7289 be supplied if your system has an inadequate or incomplete termcap
7293 A synonym for `--with-bash-malloc'.
7295 `--with-installed-readline[=PREFIX]'
7296 Define this to make Bash link with a locally-installed version of
7297 Readline rather than the version in `lib/readline'. This works
7298 only with Readline 4.2 and later versions. If PREFIX is `yes' or
7299 not supplied, `configure' uses the values of the make variables
7300 `includedir' and `libdir', which are subdirectories of `prefix' by
7301 default, to find the installed version of Readline if it is not in
7302 the standard system include and library directories. If PREFIX is
7303 `no', Bash links with the version in `lib/readline'. If PREFIX is
7304 set to any other value, `configure' treats it as a directory
7305 pathname and looks for the installed version of Readline in
7306 subdirectories of that directory (include files in
7307 PREFIX/`include' and the library in PREFIX/`lib').
7310 Define this to use the Purify memory allocation checker from
7313 `--enable-minimal-config'
7314 This produces a shell with minimal features, close to the
7315 historical Bourne shell.
7317 There are several `--enable-' options that alter how Bash is
7318 compiled and linked, rather than changing run-time features.
7320 `--enable-largefile'
7321 Enable support for large files
7322 (http://www.sas.com/standards/large_file/x_open.20Mar96.html) if
7323 the operating system requires special compiler options to build
7324 programs which can access large files.
7326 `--enable-profiling'
7327 This builds a Bash binary that produces profiling information to be
7328 processed by `gprof' each time it is executed.
7330 `--enable-static-link'
7331 This causes Bash to be linked statically, if `gcc' is being used.
7332 This could be used to build a version to use as root's shell.
7334 The `minimal-config' option can be used to disable all of the
7335 following options, but it is processed first, so individual options may
7336 be enabled using `enable-FEATURE'.
7338 All of the following options except for `disabled-builtins' and
7339 `xpg-echo-default' are enabled by default, unless the operating system
7340 does not provide the necessary support.
7343 Allow alias expansion and include the `alias' and `unalias'
7344 builtins (*note Aliases::).
7346 `--enable-arith-for-command'
7347 Include support for the alternate form of the `for' command that
7348 behaves like the C language `for' statement (*note Looping
7351 `--enable-array-variables'
7352 Include support for one-dimensional array shell variables (*note
7355 `--enable-bang-history'
7356 Include support for `csh'-like history substitution (*note History
7359 `--enable-brace-expansion'
7360 Include `csh'-like brace expansion ( `b{a,b}c' ==> `bac bbc' ).
7361 See *Note Brace Expansion::, for a complete description.
7363 `--enable-command-timing'
7364 Include support for recognizing `time' as a reserved word and for
7365 displaying timing statistics for the pipeline following `time'
7366 (*note Pipelines::). This allows pipelines as well as shell
7367 builtins and functions to be timed.
7369 `--enable-cond-command'
7370 Include support for the `[[' conditional command (*note
7371 Conditional Constructs::).
7373 `--enable-directory-stack'
7374 Include support for a `csh'-like directory stack and the `pushd',
7375 `popd', and `dirs' builtins (*note The Directory Stack::).
7377 `--enable-disabled-builtins'
7378 Allow builtin commands to be invoked via `builtin xxx' even after
7379 `xxx' has been disabled using `enable -n xxx'. See *Note Bash
7380 Builtins::, for details of the `builtin' and `enable' builtin
7383 `--enable-dparen-arithmetic'
7384 Include support for the `((...))' command (*note Conditional
7387 `--enable-extended-glob'
7388 Include support for the extended pattern matching features
7389 described above under *Note Pattern Matching::.
7391 `--enable-help-builtin'
7392 Include the `help' builtin, which displays help on shell builtins
7393 and variables (*note Bash Builtins::).
7396 Include command history and the `fc' and `history' builtin
7397 commands (*note Bash History Facilities::).
7399 `--enable-job-control'
7400 This enables the job control features (*note Job Control::), if
7401 the operating system supports them.
7403 `--enable-net-redirections'
7404 This enables the special handling of filenames of the form
7405 `/dev/tcp/HOST/PORT' and `/dev/udp/HOST/PORT' when used in
7406 redirections (*note Redirections::).
7408 `--enable-process-substitution'
7409 This enables process substitution (*note Process Substitution::) if
7410 the operating system provides the necessary support.
7412 `--enable-prompt-string-decoding'
7413 Turn on the interpretation of a number of backslash-escaped
7414 characters in the `$PS1', `$PS2', `$PS3', and `$PS4' prompt
7415 strings. See *Note Printing a Prompt::, for a complete list of
7416 prompt string escape sequences.
7419 Enable the programmable completion facilities (*note Programmable
7420 Completion::). If Readline is not enabled, this option has no
7424 Include support for command-line editing and history with the Bash
7425 version of the Readline library (*note Command Line Editing::).
7427 `--enable-restricted'
7428 Include support for a "restricted shell". If this is enabled,
7429 Bash, when called as `rbash', enters a restricted mode. See *Note
7430 The Restricted Shell::, for a description of restricted mode.
7433 Include the `select' builtin, which allows the generation of simple
7434 menus (*note Conditional Constructs::).
7436 `--enable-usg-echo-default'
7437 A synonym for `--enable-xpg-echo-default'.
7439 `--enable-xpg-echo-default'
7440 Make the `echo' builtin expand backslash-escaped characters by
7441 default, without requiring the `-e' option. This sets the default
7442 value of the `xpg_echo' shell option to `on', which makes the Bash
7443 `echo' behave more like the version specified in the Single Unix
7444 Specification, version 2. *Note Bash Builtins::, for a
7445 description of the escape sequences that `echo' recognizes.
7447 The file `config-top.h' contains C Preprocessor `#define' statements
7448 for options which are not settable from `configure'. Some of these are
7449 not meant to be changed; beware of the consequences if you do. Read
7450 the comments associated with each definition for more information about
7454 File: bashref.info, Node: Reporting Bugs, Next: Major Differences From The Bourne Shell, Prev: Installing Bash, Up: Top
7459 Please report all bugs you find in Bash. But first, you should make
7460 sure that it really is a bug, and that it appears in the latest version
7461 of Bash that you have.
7463 Once you have determined that a bug actually exists, use the
7464 `bashbug' command to submit a bug report. If you have a fix, you are
7465 encouraged to mail that as well! Suggestions and `philosophical' bug
7466 reports may be mailed to <bug-bash@gnu.org> or posted to the Usenet
7467 newsgroup `gnu.bash.bug'.
7469 All bug reports should include:
7470 * The version number of Bash.
7472 * The hardware and operating system.
7474 * The compiler used to compile Bash.
7476 * A description of the bug behaviour.
7478 * A short script or `recipe' which exercises the bug and may be used
7481 `bashbug' inserts the first three items automatically into the template
7482 it provides for filing a bug report.
7484 Please send all reports concerning this manual to <chet@po.CWRU.Edu>.
7487 File: bashref.info, Node: Major Differences From The Bourne Shell, Next: Builtin Index, Prev: Reporting Bugs, Up: Top
7489 Major Differences From The Bourne Shell
7490 ***************************************
7492 Bash implements essentially the same grammar, parameter and variable
7493 expansion, redirection, and quoting as the Bourne Shell. Bash uses the
7494 POSIX 1003.2 standard as the specification of how these features are to
7495 be implemented. There are some differences between the traditional
7496 Bourne shell and Bash; this section quickly details the differences of
7497 significance. A number of these differences are explained in greater
7498 depth in previous sections. This section uses the version of `sh'
7499 included in SVR4.2 as the baseline reference.
7501 * Bash is POSIX-conformant, even where the POSIX specification
7502 differs from traditional `sh' behavior (*note Bash POSIX Mode::).
7504 * Bash has multi-character invocation options (*note Invoking
7507 * Bash has command-line editing (*note Command Line Editing::) and
7510 * Bash provides a programmable word completion mechanism (*note
7511 Programmable Completion::), and two builtin commands, `complete'
7512 and `compgen', to manipulate it.
7514 * Bash has command history (*note Bash History Facilities::) and the
7515 `history' and `fc' builtins to manipulate it.
7517 * Bash implements `csh'-like history expansion (*note History
7520 * Bash has one-dimensional array variables (*note Arrays::), and the
7521 appropriate variable expansions and assignment syntax to use them.
7522 Several of the Bash builtins take options to act on arrays. Bash
7523 provides a number of built-in array variables.
7525 * The `$'...'' quoting syntax, which expands ANSI-C
7526 backslash-escaped characters in the text between the single quotes,
7527 is supported (*note ANSI-C Quoting::).
7529 * Bash supports the `$"..."' quoting syntax to do locale-specific
7530 translation of the characters between the double quotes. The
7531 `-D', `--dump-strings', and `--dump-po-strings' invocation options
7532 list the translatable strings found in a script (*note Locale
7535 * Bash implements the `!' keyword to negate the return value of a
7536 pipeline (*note Pipelines::). Very useful when an `if' statement
7537 needs to act only if a test fails.
7539 * Bash has the `time' reserved word and command timing (*note
7540 Pipelines::). The display of the timing statistics may be
7541 controlled with the `TIMEFORMAT' variable.
7543 * Bash implements the `for (( EXPR1 ; EXPR2 ; EXPR3 ))' arithmetic
7544 for command, similar to the C language (*note Looping
7547 * Bash includes the `select' compound command, which allows the
7548 generation of simple menus (*note Conditional Constructs::).
7550 * Bash includes the `[[' compound command, which makes conditional
7551 testing part of the shell grammar (*note Conditional Constructs::).
7553 * Bash includes brace expansion (*note Brace Expansion::) and tilde
7554 expansion (*note Tilde Expansion::).
7556 * Bash implements command aliases and the `alias' and `unalias'
7557 builtins (*note Aliases::).
7559 * Bash provides shell arithmetic, the `((' compound command (*note
7560 Conditional Constructs::), and arithmetic expansion (*note Shell
7563 * Variables present in the shell's initial environment are
7564 automatically exported to child processes. The Bourne shell does
7565 not normally do this unless the variables are explicitly marked
7566 using the `export' command.
7568 * Bash includes the POSIX pattern removal `%', `#', `%%' and `##'
7569 expansions to remove leading or trailing substrings from variable
7570 values (*note Shell Parameter Expansion::).
7572 * The expansion `${#xx}', which returns the length of `${xx}', is
7573 supported (*note Shell Parameter Expansion::).
7575 * The expansion `${var:'OFFSET`[:'LENGTH`]}', which expands to the
7576 substring of `var''s value of length LENGTH, beginning at OFFSET,
7577 is present (*note Shell Parameter Expansion::).
7579 * The expansion `${var/[/]'PATTERN`[/'REPLACEMENT`]}', which matches
7580 PATTERN and replaces it with REPLACEMENT in the value of `var', is
7581 available (*note Shell Parameter Expansion::).
7583 * The expansion `${!PREFIX}*' expansion, which expands to the names
7584 of all shell variables whose names begin with PREFIX, is available
7585 (*note Shell Parameter Expansion::).
7587 * Bash has INDIRECT variable expansion using `${!word}' (*note Shell
7588 Parameter Expansion::).
7590 * Bash can expand positional parameters beyond `$9' using `${NUM}'.
7592 * The POSIX `$()' form of command substitution is implemented (*note
7593 Command Substitution::), and preferred to the Bourne shell's ```'
7594 (which is also implemented for backwards compatibility).
7596 * Bash has process substitution (*note Process Substitution::).
7598 * Bash automatically assigns variables that provide information
7599 about the current user (`UID', `EUID', and `GROUPS'), the current
7600 host (`HOSTTYPE', `OSTYPE', `MACHTYPE', and `HOSTNAME'), and the
7601 instance of Bash that is running (`BASH', `BASH_VERSION', and
7602 `BASH_VERSINFO'). *Note Bash Variables::, for details.
7604 * The `IFS' variable is used to split only the results of expansion,
7605 not all words (*note Word Splitting::). This closes a
7606 longstanding shell security hole.
7608 * Bash implements the full set of POSIX 1003.2 filename expansion
7609 operators, including CHARACTER CLASSES, EQUIVALENCE CLASSES, and
7610 COLLATING SYMBOLS (*note Filename Expansion::).
7612 * Bash implements extended pattern matching features when the
7613 `extglob' shell option is enabled (*note Pattern Matching::).
7615 * It is possible to have a variable and a function with the same
7616 name; `sh' does not separate the two name spaces.
7618 * Bash functions are permitted to have local variables using the
7619 `local' builtin, and thus useful recursive functions may be written
7620 (*note Bash Builtins::).
7622 * Variable assignments preceding commands affect only that command,
7623 even builtins and functions (*note Environment::). In `sh', all
7624 variable assignments preceding commands are global unless the
7625 command is executed from the file system.
7627 * Bash performs filename expansion on filenames specified as operands
7628 to input and output redirection operators (*note Redirections::).
7630 * Bash contains the `<>' redirection operator, allowing a file to be
7631 opened for both reading and writing, and the `&>' redirection
7632 operator, for directing standard output and standard error to the
7633 same file (*note Redirections::).
7635 * Bash treats a number of filenames specially when they are used in
7636 redirection operators (*note Redirections::).
7638 * Bash can open network connections to arbitrary machines and
7639 services with the redirection operators (*note Redirections::).
7641 * The `noclobber' option is available to avoid overwriting existing
7642 files with output redirection (*note The Set Builtin::). The `>|'
7643 redirection operator may be used to override `noclobber'.
7645 * The Bash `cd' and `pwd' builtins (*note Bourne Shell Builtins::)
7646 each take `-L' and `-P' options to switch between logical and
7649 * Bash allows a function to override a builtin with the same name,
7650 and provides access to that builtin's functionality within the
7651 function via the `builtin' and `command' builtins (*note Bash
7654 * The `command' builtin allows selective disabling of functions when
7655 command lookup is performed (*note Bash Builtins::).
7657 * Individual builtins may be enabled or disabled using the `enable'
7658 builtin (*note Bash Builtins::).
7660 * The Bash `exec' builtin takes additional options that allow users
7661 to control the contents of the environment passed to the executed
7662 command, and what the zeroth argument to the command is to be
7663 (*note Bourne Shell Builtins::).
7665 * Shell functions may be exported to children via the environment
7666 using `export -f' (*note Shell Functions::).
7668 * The Bash `export', `readonly', and `declare' builtins can take a
7669 `-f' option to act on shell functions, a `-p' option to display
7670 variables with various attributes set in a format that can be used
7671 as shell input, a `-n' option to remove various variable
7672 attributes, and `name=value' arguments to set variable attributes
7673 and values simultaneously.
7675 * The Bash `hash' builtin allows a name to be associated with an
7676 arbitrary filename, even when that filename cannot be found by
7677 searching the `$PATH', using `hash -p' (*note Bourne Shell
7680 * Bash includes a `help' builtin for quick reference to shell
7681 facilities (*note Bash Builtins::).
7683 * The `printf' builtin is available to display formatted output
7684 (*note Bash Builtins::).
7686 * The Bash `read' builtin (*note Bash Builtins::) will read a line
7687 ending in `\' with the `-r' option, and will use the `REPLY'
7688 variable as a default if no non-option arguments are supplied.
7689 The Bash `read' builtin also accepts a prompt string with the `-p'
7690 option and will use Readline to obtain the line when given the
7691 `-e' option. The `read' builtin also has additional options to
7692 control input: the `-s' option will turn off echoing of input
7693 characters as they are read, the `-t' option will allow `read' to
7694 time out if input does not arrive within a specified number of
7695 seconds, the `-n' option will allow reading only a specified
7696 number of characters rather than a full line, and the `-d' option
7697 will read until a particular character rather than newline.
7699 * The `return' builtin may be used to abort execution of scripts
7700 executed with the `.' or `source' builtins (*note Bourne Shell
7703 * Bash includes the `shopt' builtin, for finer control of shell
7704 optional capabilities (*note Bash Builtins::), and allows these
7705 options to be set and unset at shell invocation (*note Invoking
7708 * Bash has much more optional behavior controllable with the `set'
7709 builtin (*note The Set Builtin::).
7711 * The `test' builtin (*note Bourne Shell Builtins::) is slightly
7712 different, as it implements the POSIX algorithm, which specifies
7713 the behavior based on the number of arguments.
7715 * The `trap' builtin (*note Bourne Shell Builtins::) allows a
7716 `DEBUG' pseudo-signal specification, similar to `EXIT'. Commands
7717 specified with a `DEBUG' trap are executed after every simple
7718 command. The `DEBUG' trap is not inherited by shell functions.
7720 The `trap' builtin (*note Bourne Shell Builtins::) allows an `ERR'
7721 pseudo-signal specification, similar to `EXIT' and `DEBUG'.
7722 Commands specified with an `ERR' trap are executed after a simple
7723 command fails, with a few exceptions. The `ERR' trap is not
7724 inherited by shell functions.
7726 * The Bash `type' builtin is more extensive and gives more
7727 information about the names it finds (*note Bash Builtins::).
7729 * The Bash `umask' builtin permits a `-p' option to cause the output
7730 to be displayed in the form of a `umask' command that may be
7731 reused as input (*note Bourne Shell Builtins::).
7733 * Bash implements a `csh'-like directory stack, and provides the
7734 `pushd', `popd', and `dirs' builtins to manipulate it (*note The
7735 Directory Stack::). Bash also makes the directory stack visible
7736 as the value of the `DIRSTACK' shell variable.
7738 * Bash interprets special backslash-escaped characters in the prompt
7739 strings when interactive (*note Printing a Prompt::).
7741 * The Bash restricted mode is more useful (*note The Restricted
7742 Shell::); the SVR4.2 shell restricted mode is too limited.
7744 * The `disown' builtin can remove a job from the internal shell job
7745 table (*note Job Control Builtins::) or suppress the sending of
7746 `SIGHUP' to a job when the shell exits as the result of a `SIGHUP'.
7748 * The SVR4.2 shell has two privilege-related builtins (`mldmode' and
7749 `priv') not present in Bash.
7751 * Bash does not have the `stop' or `newgrp' builtins.
7753 * Bash does not use the `SHACCT' variable or perform shell
7756 * The SVR4.2 `sh' uses a `TIMEOUT' variable like Bash uses `TMOUT'.
7759 More features unique to Bash may be found in *Note Bash Features::.
7761 Implementation Differences From The SVR4.2 Shell
7762 ================================================
7764 Since Bash is a completely new implementation, it does not suffer
7765 from many of the limitations of the SVR4.2 shell. For instance:
7767 * Bash does not fork a subshell when redirecting into or out of a
7768 shell control structure such as an `if' or `while' statement.
7770 * Bash does not allow unbalanced quotes. The SVR4.2 shell will
7771 silently insert a needed closing quote at `EOF' under certain
7772 circumstances. This can be the cause of some hard-to-find errors.
7774 * The SVR4.2 shell uses a baroque memory management scheme based on
7775 trapping `SIGSEGV'. If the shell is started from a process with
7776 `SIGSEGV' blocked (e.g., by using the `system()' C library
7777 function call), it misbehaves badly.
7779 * In a questionable attempt at security, the SVR4.2 shell, when
7780 invoked without the `-p' option, will alter its real and effective
7781 UID and GID if they are less than some magic threshold value,
7782 commonly 100. This can lead to unexpected results.
7784 * The SVR4.2 shell does not allow users to trap `SIGSEGV',
7785 `SIGALRM', or `SIGCHLD'.
7787 * The SVR4.2 shell does not allow the `IFS', `MAILCHECK', `PATH',
7788 `PS1', or `PS2' variables to be unset.
7790 * The SVR4.2 shell treats `^' as the undocumented equivalent of `|'.
7792 * Bash allows multiple option arguments when it is invoked (`-x -v');
7793 the SVR4.2 shell allows only one option argument (`-xv'). In
7794 fact, some versions of the shell dump core if the second argument
7797 * The SVR4.2 shell exits a script if any builtin fails; Bash exits a
7798 script only if one of the POSIX 1003.2 special builtins fails, and
7799 only for certain failures, as enumerated in the POSIX 1003.2
7802 * The SVR4.2 shell behaves differently when invoked as `jsh' (it
7803 turns on job control).
7806 File: bashref.info, Node: Builtin Index, Next: Reserved Word Index, Prev: Major Differences From The Bourne Shell, Up: Top
7808 Index of Shell Builtin Commands
7809 *******************************
7813 * .: Bourne Shell Builtins.
7814 * :: Bourne Shell Builtins.
7815 * [: Bourne Shell Builtins.
7816 * alias: Bash Builtins.
7817 * bg: Job Control Builtins.
7818 * bind: Bash Builtins.
7819 * break: Bourne Shell Builtins.
7820 * builtin: Bash Builtins.
7821 * cd: Bourne Shell Builtins.
7822 * command: Bash Builtins.
7823 * compgen: Programmable Completion Builtins.
7824 * complete: Programmable Completion Builtins.
7825 * continue: Bourne Shell Builtins.
7826 * declare: Bash Builtins.
7827 * dirs: Directory Stack Builtins.
7828 * disown: Job Control Builtins.
7829 * echo: Bash Builtins.
7830 * enable: Bash Builtins.
7831 * eval: Bourne Shell Builtins.
7832 * exec: Bourne Shell Builtins.
7833 * exit: Bourne Shell Builtins.
7834 * export: Bourne Shell Builtins.
7835 * fc: Bash History Builtins.
7836 * fg: Job Control Builtins.
7837 * getopts: Bourne Shell Builtins.
7838 * hash: Bourne Shell Builtins.
7839 * help: Bash Builtins.
7840 * history: Bash History Builtins.
7841 * jobs: Job Control Builtins.
7842 * kill: Job Control Builtins.
7843 * let: Bash Builtins.
7844 * local: Bash Builtins.
7845 * logout: Bash Builtins.
7846 * popd: Directory Stack Builtins.
7847 * printf: Bash Builtins.
7848 * pushd: Directory Stack Builtins.
7849 * pwd: Bourne Shell Builtins.
7850 * read: Bash Builtins.
7851 * readonly: Bourne Shell Builtins.
7852 * return: Bourne Shell Builtins.
7853 * set: The Set Builtin.
7854 * shift: Bourne Shell Builtins.
7855 * shopt: Bash Builtins.
7856 * source: Bash Builtins.
7857 * suspend: Job Control Builtins.
7858 * test: Bourne Shell Builtins.
7859 * times: Bourne Shell Builtins.
7860 * trap: Bourne Shell Builtins.
7861 * type: Bash Builtins.
7862 * typeset: Bash Builtins.
7863 * ulimit: Bash Builtins.
7864 * umask: Bourne Shell Builtins.
7865 * unalias: Bash Builtins.
7866 * unset: Bourne Shell Builtins.
7867 * wait: Job Control Builtins.
7870 File: bashref.info, Node: Reserved Word Index, Next: Variable Index, Prev: Builtin Index, Up: Top
7872 Index of Shell Reserved Words
7873 *****************************
7878 * [[: Conditional Constructs.
7879 * ]]: Conditional Constructs.
7880 * case: Conditional Constructs.
7881 * do: Looping Constructs.
7882 * done: Looping Constructs.
7883 * elif: Conditional Constructs.
7884 * else: Conditional Constructs.
7885 * esac: Conditional Constructs.
7886 * fi: Conditional Constructs.
7887 * for: Looping Constructs.
7888 * function: Shell Functions.
7889 * if: Conditional Constructs.
7890 * in: Conditional Constructs.
7891 * select: Conditional Constructs.
7892 * then: Conditional Constructs.
7894 * until: Looping Constructs.
7895 * while: Looping Constructs.
7896 * {: Command Grouping.
7897 * }: Command Grouping.
7900 File: bashref.info, Node: Variable Index, Next: Function Index, Prev: Reserved Word Index, Up: Top
7902 Parameter and Variable Index
7903 ****************************
7907 * !: Special Parameters.
7908 * #: Special Parameters.
7909 * $: Special Parameters.
7910 * *: Special Parameters.
7911 * -: Special Parameters.
7912 * 0: Special Parameters.
7913 * ?: Special Parameters.
7914 * @: Special Parameters.
7915 * _: Special Parameters.
7916 * auto_resume: Job Control Variables.
7917 * BASH: Bash Variables.
7918 * BASH_ENV: Bash Variables.
7919 * BASH_VERSINFO: Bash Variables.
7920 * BASH_VERSION: Bash Variables.
7921 * bell-style: Readline Init File Syntax.
7922 * CDPATH: Bourne Shell Variables.
7923 * COLUMNS: Bash Variables.
7924 * comment-begin: Readline Init File Syntax.
7925 * COMP_CWORD: Bash Variables.
7926 * COMP_LINE: Bash Variables.
7927 * COMP_POINT: Bash Variables.
7928 * COMP_WORDS: Bash Variables.
7929 * completion-query-items: Readline Init File Syntax.
7930 * COMPREPLY: Bash Variables.
7931 * convert-meta: Readline Init File Syntax.
7932 * DIRSTACK: Bash Variables.
7933 * disable-completion: Readline Init File Syntax.
7934 * editing-mode: Readline Init File Syntax.
7935 * enable-keypad: Readline Init File Syntax.
7936 * EUID: Bash Variables.
7937 * expand-tilde: Readline Init File Syntax.
7938 * FCEDIT: Bash Variables.
7939 * FIGNORE: Bash Variables.
7940 * FUNCNAME: Bash Variables.
7941 * GLOBIGNORE: Bash Variables.
7942 * GROUPS: Bash Variables.
7943 * histchars: Bash Variables.
7944 * HISTCMD: Bash Variables.
7945 * HISTCONTROL: Bash Variables.
7946 * HISTFILE: Bash Variables.
7947 * HISTFILESIZE: Bash Variables.
7948 * HISTIGNORE: Bash Variables.
7949 * history-preserve-point: Readline Init File Syntax.
7950 * HISTSIZE: Bash Variables.
7951 * HOME: Bourne Shell Variables.
7952 * horizontal-scroll-mode: Readline Init File Syntax.
7953 * HOSTFILE: Bash Variables.
7954 * HOSTNAME: Bash Variables.
7955 * HOSTTYPE: Bash Variables.
7956 * IFS: Bourne Shell Variables.
7957 * IGNOREEOF: Bash Variables.
7958 * input-meta: Readline Init File Syntax.
7959 * INPUTRC: Bash Variables.
7960 * isearch-terminators: Readline Init File Syntax.
7961 * keymap: Readline Init File Syntax.
7962 * LANG: Bash Variables.
7963 * LC_ALL: Bash Variables.
7964 * LC_COLLATE: Bash Variables.
7965 * LC_CTYPE: Bash Variables.
7966 * LC_MESSAGES <1>: Bash Variables.
7967 * LC_MESSAGES: Locale Translation.
7968 * LC_NUMERIC: Bash Variables.
7969 * LINENO: Bash Variables.
7970 * LINES: Bash Variables.
7971 * MACHTYPE: Bash Variables.
7972 * MAIL: Bourne Shell Variables.
7973 * MAILCHECK: Bash Variables.
7974 * MAILPATH: Bourne Shell Variables.
7975 * mark-modified-lines: Readline Init File Syntax.
7976 * match-hidden-files: Readline Init File Syntax.
7977 * meta-flag: Readline Init File Syntax.
7978 * OLDPWD: Bash Variables.
7979 * OPTARG: Bourne Shell Variables.
7980 * OPTERR: Bash Variables.
7981 * OPTIND: Bourne Shell Variables.
7982 * OSTYPE: Bash Variables.
7983 * output-meta: Readline Init File Syntax.
7984 * PATH: Bourne Shell Variables.
7985 * PIPESTATUS: Bash Variables.
7986 * POSIXLY_CORRECT: Bash Variables.
7987 * PPID: Bash Variables.
7988 * PROMPT_COMMAND: Bash Variables.
7989 * PS1: Bourne Shell Variables.
7990 * PS2: Bourne Shell Variables.
7991 * PS3: Bash Variables.
7992 * PS4: Bash Variables.
7993 * PWD: Bash Variables.
7994 * RANDOM: Bash Variables.
7995 * REPLY: Bash Variables.
7996 * SECONDS: Bash Variables.
7997 * SHELLOPTS: Bash Variables.
7998 * SHLVL: Bash Variables.
7999 * show-all-if-ambiguous: Readline Init File Syntax.
8000 * TEXTDOMAIN: Locale Translation.
8001 * TEXTDOMAINDIR: Locale Translation.
8002 * TIMEFORMAT: Bash Variables.
8003 * TMOUT: Bash Variables.
8004 * UID: Bash Variables.
8005 * visible-stats: Readline Init File Syntax.
8008 File: bashref.info, Node: Function Index, Next: Concept Index, Prev: Variable Index, Up: Top
8015 * abort (C-g): Miscellaneous Commands.
8016 * accept-line (Newline or Return): Commands For History.
8017 * backward-char (C-b): Commands For Moving.
8018 * backward-delete-char (Rubout): Commands For Text.
8019 * backward-kill-line (C-x Rubout): Commands For Killing.
8020 * backward-kill-word (M-<DEL>): Commands For Killing.
8021 * backward-word (M-b): Commands For Moving.
8022 * beginning-of-history (M-<): Commands For History.
8023 * beginning-of-line (C-a): Commands For Moving.
8024 * call-last-kbd-macro (C-x e): Keyboard Macros.
8025 * capitalize-word (M-c): Commands For Text.
8026 * character-search (C-]): Miscellaneous Commands.
8027 * character-search-backward (M-C-]): Miscellaneous Commands.
8028 * clear-screen (C-l): Commands For Moving.
8029 * complete (<TAB>): Commands For Completion.
8030 * copy-backward-word (): Commands For Killing.
8031 * copy-forward-word (): Commands For Killing.
8032 * copy-region-as-kill (): Commands For Killing.
8033 * delete-char (C-d): Commands For Text.
8034 * delete-char-or-list (): Commands For Completion.
8035 * delete-horizontal-space (): Commands For Killing.
8036 * digit-argument (M-0, M-1, ... M--): Numeric Arguments.
8037 * do-uppercase-version (M-a, M-b, M-X, ...): Miscellaneous Commands.
8038 * downcase-word (M-l): Commands For Text.
8039 * dump-functions (): Miscellaneous Commands.
8040 * dump-macros (): Miscellaneous Commands.
8041 * dump-variables (): Miscellaneous Commands.
8042 * end-kbd-macro (C-x )): Keyboard Macros.
8043 * end-of-history (M->): Commands For History.
8044 * end-of-line (C-e): Commands For Moving.
8045 * exchange-point-and-mark (C-x C-x): Miscellaneous Commands.
8046 * forward-backward-delete-char (): Commands For Text.
8047 * forward-char (C-f): Commands For Moving.
8048 * forward-search-history (C-s): Commands For History.
8049 * forward-word (M-f): Commands For Moving.
8050 * history-search-backward (): Commands For History.
8051 * history-search-forward (): Commands For History.
8052 * insert-comment (M-#): Miscellaneous Commands.
8053 * insert-completions (M-*): Commands For Completion.
8054 * kill-line (C-k): Commands For Killing.
8055 * kill-region (): Commands For Killing.
8056 * kill-whole-line (): Commands For Killing.
8057 * kill-word (M-d): Commands For Killing.
8058 * menu-complete (): Commands For Completion.
8059 * next-history (C-n): Commands For History.
8060 * non-incremental-forward-search-history (M-n): Commands For History.
8061 * non-incremental-reverse-search-history (M-p): Commands For History.
8062 * possible-completions (M-?): Commands For Completion.
8063 * prefix-meta (<ESC>): Miscellaneous Commands.
8064 * previous-history (C-p): Commands For History.
8065 * quoted-insert (C-q or C-v): Commands For Text.
8066 * re-read-init-file (C-x C-r): Miscellaneous Commands.
8067 * redraw-current-line (): Commands For Moving.
8068 * reverse-search-history (C-r): Commands For History.
8069 * revert-line (M-r): Miscellaneous Commands.
8070 * self-insert (a, b, A, 1, !, ...): Commands For Text.
8071 * set-mark (C-@): Miscellaneous Commands.
8072 * start-kbd-macro (C-x (): Keyboard Macros.
8073 * transpose-chars (C-t): Commands For Text.
8074 * transpose-words (M-t): Commands For Text.
8075 * undo (C-_ or C-x C-u): Miscellaneous Commands.
8076 * universal-argument (): Numeric Arguments.
8077 * unix-line-discard (C-u): Commands For Killing.
8078 * unix-word-rubout (C-w): Commands For Killing.
8079 * upcase-word (M-u): Commands For Text.
8080 * yank (C-y): Commands For Killing.
8081 * yank-last-arg (M-. or M-_): Commands For History.
8082 * yank-nth-arg (M-C-y): Commands For History.
8083 * yank-pop (M-y): Commands For Killing.
8086 File: bashref.info, Node: Concept Index, Prev: Function Index, Up: Top
8093 * alias expansion: Aliases.
8094 * arithmetic evaluation: Shell Arithmetic.
8095 * arithmetic expansion: Arithmetic Expansion.
8096 * arithmetic, shell: Shell Arithmetic.
8098 * background: Job Control Basics.
8099 * Bash configuration: Basic Installation.
8100 * Bash installation: Basic Installation.
8101 * Bourne shell: Basic Shell Features.
8102 * brace expansion: Brace Expansion.
8103 * builtin: Definitions.
8104 * command editing: Readline Bare Essentials.
8105 * command execution: Command Search and Execution.
8106 * command expansion: Simple Command Expansion.
8107 * command history: Bash History Facilities.
8108 * command search: Command Search and Execution.
8109 * command substitution: Command Substitution.
8110 * command timing: Pipelines.
8111 * commands, conditional: Conditional Constructs.
8112 * commands, grouping: Command Grouping.
8113 * commands, lists: Lists.
8114 * commands, looping: Looping Constructs.
8115 * commands, pipelines: Pipelines.
8116 * commands, shell: Shell Commands.
8117 * commands, simple: Simple Commands.
8118 * comments, shell: Comments.
8119 * completion builtins: Programmable Completion Builtins.
8120 * configuration: Basic Installation.
8121 * control operator: Definitions.
8122 * directory stack: The Directory Stack.
8123 * editing command lines: Readline Bare Essentials.
8124 * environment: Environment.
8125 * evaluation, arithmetic: Shell Arithmetic.
8126 * event designators: Event Designators.
8127 * execution environment: Command Execution Environment.
8128 * exit status <1>: Exit Status.
8129 * exit status: Definitions.
8130 * expansion: Shell Expansions.
8131 * expansion, arithmetic: Arithmetic Expansion.
8132 * expansion, brace: Brace Expansion.
8133 * expansion, filename: Filename Expansion.
8134 * expansion, parameter: Shell Parameter Expansion.
8135 * expansion, pathname: Filename Expansion.
8136 * expansion, tilde: Tilde Expansion.
8137 * expressions, arithmetic: Shell Arithmetic.
8138 * expressions, conditional: Bash Conditional Expressions.
8139 * field: Definitions.
8140 * filename: Definitions.
8141 * filename expansion: Filename Expansion.
8142 * foreground: Job Control Basics.
8143 * functions, shell: Shell Functions.
8144 * history builtins: Bash History Builtins.
8145 * history events: Event Designators.
8146 * history expansion: History Interaction.
8147 * history list: Bash History Facilities.
8148 * History, how to use: Programmable Completion Builtins.
8149 * identifier: Definitions.
8150 * initialization file, readline: Readline Init File.
8151 * installation: Basic Installation.
8152 * interaction, readline: Readline Interaction.
8153 * interactive shell <1>: Invoking Bash.
8154 * interactive shell: Interactive Shells.
8155 * internationalization: Locale Translation.
8157 * job control <1>: Job Control Basics.
8158 * job control: Definitions.
8159 * kill ring: Readline Killing Commands.
8160 * killing text: Readline Killing Commands.
8161 * localization: Locale Translation.
8162 * login shell: Invoking Bash.
8163 * matching, pattern: Pattern Matching.
8164 * metacharacter: Definitions.
8165 * name: Definitions.
8166 * native languages: Locale Translation.
8167 * notation, readline: Readline Bare Essentials.
8168 * operator, shell: Definitions.
8169 * parameter expansion: Shell Parameter Expansion.
8170 * parameters: Shell Parameters.
8171 * parameters, positional: Positional Parameters.
8172 * parameters, special: Special Parameters.
8173 * pathname expansion: Filename Expansion.
8174 * pattern matching: Pattern Matching.
8175 * pipeline: Pipelines.
8176 * POSIX: Definitions.
8177 * POSIX Mode: Bash POSIX Mode.
8178 * process group: Definitions.
8179 * process group ID: Definitions.
8180 * process substitution: Process Substitution.
8181 * programmable completion: Programmable Completion.
8182 * prompting: Printing a Prompt.
8184 * quoting, ANSI: ANSI-C Quoting.
8185 * Readline, how to use: Job Control Variables.
8186 * redirection: Redirections.
8187 * reserved word: Definitions.
8188 * restricted shell: The Restricted Shell.
8189 * return status: Definitions.
8190 * shell arithmetic: Shell Arithmetic.
8191 * shell function: Shell Functions.
8192 * shell script: Shell Scripts.
8193 * shell variable: Shell Parameters.
8194 * shell, interactive: Interactive Shells.
8195 * signal: Definitions.
8196 * signal handling: Signals.
8197 * special builtin <1>: Special Builtins.
8198 * special builtin: Definitions.
8199 * startup files: Bash Startup Files.
8200 * suspending jobs: Job Control Basics.
8201 * tilde expansion: Tilde Expansion.
8202 * token: Definitions.
8203 * translation, native languages: Locale Translation.
8204 * variable, shell: Shell Parameters.
8205 * variables, readline: Readline Init File Syntax.
8206 * word: Definitions.
8207 * word splitting: Word Splitting.
8208 * yanking text: Readline Killing Commands.
8214 Node: Introduction
\7f3300
8215 Node: What is Bash?
\7f3525
8216 Node: What is a shell?
\7f4626
8217 Node: Definitions
\7f6860
8218 Node: Basic Shell Features
\7f9600
8219 Node: Shell Syntax
\7f10824
8220 Node: Shell Operation
\7f11848
8221 Node: Quoting
\7f13133
8222 Node: Escape Character
\7f14392
8223 Node: Single Quotes
\7f14864
8224 Node: Double Quotes
\7f15199
8225 Node: ANSI-C Quoting
\7f16100
8226 Node: Locale Translation
\7f17009
8227 Node: Comments
\7f17892
8228 Node: Shell Commands
\7f18497
8229 Node: Simple Commands
\7f19378
8230 Node: Pipelines
\7f19999
8232 Node: Looping Constructs
\7f23048
8233 Node: Conditional Constructs
\7f25492
8234 Node: Command Grouping
\7f31416
8235 Node: Shell Functions
\7f32793
8236 Node: Shell Parameters
\7f35329
8237 Node: Positional Parameters
\7f36903
8238 Node: Special Parameters
\7f37794
8239 Node: Shell Expansions
\7f40452
8240 Node: Brace Expansion
\7f42372
8241 Node: Tilde Expansion
\7f44041
8242 Node: Shell Parameter Expansion
\7f46372
8243 Node: Command Substitution
\7f53172
8244 Node: Arithmetic Expansion
\7f54494
8245 Node: Process Substitution
\7f55338
8246 Node: Word Splitting
\7f56375
8247 Node: Filename Expansion
\7f57827
8248 Node: Pattern Matching
\7f59785
8249 Node: Quote Removal
\7f62916
8250 Node: Redirections
\7f63202
8251 Node: Executing Commands
\7f70105
8252 Node: Simple Command Expansion
\7f70772
8253 Node: Command Search and Execution
\7f72693
8254 Node: Command Execution Environment
\7f74690
8255 Node: Environment
\7f77397
8256 Node: Exit Status
\7f79048
8257 Node: Signals
\7f80243
8258 Node: Shell Scripts
\7f82154
8259 Node: Shell Builtin Commands
\7f84665
8260 Node: Bourne Shell Builtins
\7f86095
8261 Node: Bash Builtins
\7f101581
8262 Node: The Set Builtin
\7f125866
8263 Node: Special Builtins
\7f132847
8264 Node: Shell Variables
\7f133819
8265 Node: Bourne Shell Variables
\7f134255
8266 Node: Bash Variables
\7f136034
8267 Node: Bash Features
\7f151763
8268 Node: Invoking Bash
\7f152645
8269 Node: Bash Startup Files
\7f158078
8270 Node: Interactive Shells
\7f162948
8271 Node: What is an Interactive Shell?
\7f163350
8272 Node: Is this Shell Interactive?
\7f163985
8273 Node: Interactive Shell Behavior
\7f164791
8274 Node: Bash Conditional Expressions
\7f168058
8275 Node: Shell Arithmetic
\7f171352
8276 Node: Aliases
\7f173783
8277 Node: Arrays
\7f176286
8278 Node: The Directory Stack
\7f179306
8279 Node: Directory Stack Builtins
\7f180012
8280 Node: Printing a Prompt
\7f182890
8281 Node: The Restricted Shell
\7f185306
8282 Node: Bash POSIX Mode
\7f186784
8283 Node: Job Control
\7f192616
8284 Node: Job Control Basics
\7f193082
8285 Node: Job Control Builtins
\7f197362
8286 Node: Job Control Variables
\7f201657
8287 Node: Command Line Editing
\7f202806
8288 Node: Introduction and Notation
\7f203804
8289 Node: Readline Interaction
\7f205421
8290 Node: Readline Bare Essentials
\7f206607
8291 Node: Readline Movement Commands
\7f208387
8292 Node: Readline Killing Commands
\7f209343
8293 Node: Readline Arguments
\7f211251
8294 Node: Searching
\7f212286
8295 Node: Readline Init File
\7f214463
8296 Node: Readline Init File Syntax
\7f215517
8297 Node: Conditional Init Constructs
\7f226248
8298 Node: Sample Init File
\7f228772
8299 Node: Bindable Readline Commands
\7f231941
8300 Node: Commands For Moving
\7f233140
8301 Node: Commands For History
\7f233988
8302 Node: Commands For Text
\7f236876
8303 Node: Commands For Killing
\7f238913
8304 Node: Numeric Arguments
\7f240863
8305 Node: Commands For Completion
\7f241990
8306 Node: Keyboard Macros
\7f245570
8307 Node: Miscellaneous Commands
\7f246128
8308 Node: Readline vi Mode
\7f250490
8309 Node: Programmable Completion
\7f251399
8310 Node: Programmable Completion Builtins
\7f256447
8311 Node: Using History Interactively
\7f263433
8312 Node: Bash History Facilities
\7f264112
8313 Node: Bash History Builtins
\7f266672
8314 Node: History Interaction
\7f270238
8315 Node: Event Designators
\7f272789
8316 Node: Word Designators
\7f273716
8317 Node: Modifiers
\7f275345
8318 Node: Installing Bash
\7f276662
8319 Node: Basic Installation
\7f277804
8320 Node: Compilers and Options
\7f280489
8321 Node: Compiling For Multiple Architectures
\7f281223
8322 Node: Installation Names
\7f282880
8323 Node: Specifying the System Type
\7f283691
8324 Node: Sharing Defaults
\7f284400
8325 Node: Operation Controls
\7f285065
8326 Node: Optional Features
\7f286016
8327 Node: Reporting Bugs
\7f293871
8328 Node: Major Differences From The Bourne Shell
\7f294968
8329 Node: Builtin Index
\7f309390
8330 Node: Reserved Word Index
\7f312981
8331 Node: Variable Index
\7f314457
8332 Node: Function Index
\7f320619
8333 Node: Concept Index
\7f325109
projects / platform / upstream / bash.git / blob