1 This is Info file bashref.info, produced by Makeinfo-1.64 from the
2 input file ./bashref.texi.
4 This text is a brief description of the features that are present in
7 This is Edition 2.0, last updated 25 November 1996,
8 of `The GNU Bash Reference Manual',
9 for `Bash', Version 2.0.
11 Copyright (C) 1991, 1993, 1996 Free Software Foundation, Inc.
13 Permission is granted to make and distribute verbatim copies of
14 this manual provided the copyright notice and this permission notice
15 are preserved on all copies.
17 Permission is granted to copy and distribute modified versions of this
18 manual under the conditions for verbatim copying, provided that the entire
19 resulting derived work is distributed under the terms of a permission
20 notice identical to this one.
22 Permission is granted to copy and distribute translations of this manual
23 into another language, under the above conditions for modified versions,
24 except that this permission notice may be stated in a translation approved
28 File: bashref.info, Node: Top, Next: Introduction, Prev: (dir), Up: (dir)
33 This text is a brief description of the features that are present in
36 This is Edition 2.0, last updated 25 November 1996, of `The GNU Bash
37 Reference Manual', for `Bash', Version 2.0.
39 Copyright (C) 1991, 1993, 1996 Free Software Foundation, Inc.
41 Bash contains features that appear in other popular shells, and some
42 features that only appear in Bash. Some of the shells that Bash has
43 borrowed concepts from are the Bourne Shell (`sh'), the Korn Shell
44 (`ksh'), and the C-shell (`csh' and its successor, `tcsh'). The
45 following menu breaks the features up into categories based upon which
46 one of these other shells inspired the feature.
48 This manual is meant as a brief introduction to features found in
49 Bash. The Bash manual page should be used as the definitive reference
54 * Introduction:: An introduction to the shell.
56 * Definitions:: Some definitions used in the rest of this
59 * Basic Shell Features:: The shell "building blocks".
61 * Bourne Shell Features:: Features similar to those found in the
64 * Csh Features:: Features originally found in the
67 * Korn Shell Features:: Features originally found in the Korn
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 * Builtin Index:: Index of Bash builtin commands.
87 * Reserved Word Index:: Index of Bash reserved words.
89 * Variable Index:: Quick reference helps you find the
92 * Function Index:: Index of bindable Readline functions.
94 * Concept Index:: General index for concepts described in
98 File: bashref.info, Node: Introduction, Next: Definitions, Prev: Top, Up: Top
105 * What is Bash?:: A short description of Bash.
107 * What is a shell?:: A brief introduction to shells.
110 File: bashref.info, Node: What is Bash?, Next: What is a shell?, Up: Introduction
115 Bash is the shell, or command language interpreter, that will appear
116 in the GNU operating system. The name is an acronym for the
117 `Bourne-Again SHell', a pun on Steve Bourne, the author of the direct
118 ancestor of the current Unix shell `/bin/sh', which appeared in the
119 Seventh Edition Bell Labs Research version of Unix.
121 Bash is an `sh'-compatible shell that incorporates useful features
122 from the Korn shell `ksh' and the C shell `csh'. It is ultimately
123 intended to be a conformant implementation of the IEEE POSIX Shell and
124 Tools specification (IEEE Working Group 1003.2). It offers functional
125 improvements over `sh' for both interactive and programming use.
127 While the GNU operating system will include a version of `csh', Bash
128 will be the default shell. Like other GNU software, Bash is quite
129 portable. It currently runs on nearly every version of Unix and a few
130 other operating systems - independently-supported ports exist for OS/2
134 File: bashref.info, Node: What is a shell?, Prev: What is Bash?, Up: Introduction
139 At its base, a shell is simply a macro processor that executes
140 commands. A Unix shell is both a command interpreter, which provides
141 the user interface to the rich set of Unix utilities, and a programming
142 language, allowing these utilitites to be combined. The shell reads
143 commands either from a terminal or a file. Files containing commands
144 can be created, and become commands themselves. These new commands
145 have the same status as system commands in directories like `/bin',
146 allowing users or groups to establish custom environments.
148 A shell allows execution of Unix commands, both synchronously and
149 asynchronously. The "redirection" constructs permit fine-grained
150 control of the input and output of those commands, and the shell allows
151 control over the contents of their environment. Unix shells also
152 provide a small set of built-in commands ("builtins") implementing
153 functionality impossible (e.g., `cd', `break', `continue', and `exec'),
154 or inconvenient (`history', `getopts', `kill', or `pwd', for example)
155 to obtain via separate utilities. Shells may be used interactively or
156 non-interactively: they accept input typed from the keyboard or from a
157 file. All of the shell builtins are described in subsequent sections.
159 While executing commands is essential, most of the power (and
160 complexity) of shells is due to their embedded programming languages.
161 Like any high-level language, the shell provides variables, flow
162 control constructs, quoting, and functions.
164 Shells have begun offering features geared specifically for
165 interactive use rather than to augment the programming language. These
166 interactive features include job control, command line editing, history
167 and aliases. Each of these features is described in this manual.
170 File: bashref.info, Node: Definitions, Next: Basic Shell Features, Prev: Introduction, Up: Top
175 These definitions are used throughout the remainder of this manual.
178 A family of open system standards based on Unix. Bash is
179 concerned with POSIX 1003.2, the Shell and Tools Standard.
182 A space or tab character.
185 A command that is implemented internally by the shell itself,
186 rather than by an executable program somewhere in the file system.
189 A `word' that performs a control function. It is a `newline' or
190 one of the following: `||', `&&', `&', `;', `;;', `|', `(', or `)'.
193 The value returned by a command to its caller.
196 A unit of text that is the result of one of the shell expansions.
197 After expansion, when executing a command, the resulting fields
198 are used as the command name and arguments.
201 A string of characters used to identify a file.
204 A set of processes comprising a pipeline, and any processes
205 descended from it, that are all in the same process group.
208 A mechanism by which users can selectively start and stop execution
212 A character that, when unquoted, separates words. A metacharacter
213 is a `blank' or one of the following characters: `|', `&', `;',
214 `(', `)', `<', or `>'.
217 A `word' consisting solely of letters, numbers, and underscores,
218 and beginning with a letter or underscore. `Name's are used as
219 shell variable and function names. Also referred to as an
223 A `control operator' or a `redirection operator'. *Note
224 Redirections::, for a list of redirection operators.
227 A collection of related processes each having the same process
231 A unique identifer that represents a `process group' during its
235 A `word' that has a special meaning to the shell. Most reserved
236 words introduce shell flow control constructs, such as `for' and
240 A synonym for `exit status'.
243 A mechanism by which a process may be notified by the kernal of an
244 event occurring in the system.
247 A shell builtin command that has been classified as special by the
251 A sequence of characters considered a single unit by the shell.
252 It is either a `word' or an `operator'.
255 A `token' that is not an `operator'.
258 File: bashref.info, Node: Basic Shell Features, Next: Bourne Shell Features, Prev: Definitions, Up: Top
263 Bash is an acronym for `Bourne-Again SHell'. The Bourne shell is
264 the traditional Unix shell originally written by Stephen Bourne. All
265 of the Bourne shell builtin commands are available in Bash, and the
266 rules for evaluation and quoting are taken from the POSIX 1003.2
267 specification for the `standard' Unix shell.
269 This chapter briefly summarizes the shell's "building blocks":
270 commands, control structures, shell functions, shell parameters, shell
271 expansions, redirections, which are a way to direct input and output
272 from and to named files, and how the shell executes commands.
276 * Shell Syntax:: What your input means to the shell.
277 * Simple Commands:: The most common type of command.
278 * Pipelines:: Connecting the input and output of several
280 * Lists:: How to execute commands sequentially.
281 * Looping Constructs:: Shell commands for iterative action.
282 * Conditional Constructs:: Shell commands for conditional execution.
283 * Command Grouping:: Ways to group commands.
284 * Shell Functions:: Grouping commands by name.
285 * Shell Parameters:: Special shell variables.
286 * Shell Expansions:: How Bash expands variables and the various
287 expansions available.
288 * Redirections:: A way to control where input and output go.
289 * Executing Commands:: What happens when you run a command.
290 * Shell Scripts:: Executing files of shell commands.
293 File: bashref.info, Node: Shell Syntax, Next: Simple Commands, Up: Basic Shell Features
300 * Shell Operation:: The basic operation of the shell.
302 * Quoting:: How to remove the special meaning from characters.
304 * Comments:: How to specify comments.
307 File: bashref.info, Node: Shell Operation, Next: Quoting, Up: Shell Syntax
312 The following is a brief description of the shell's operation when it
313 reads and executes a command. Basically, the shell does the following:
315 1. Reads its input from a file (*note Shell Scripts::.), from a string
316 supplied as an argument to the `-c' invocation option (*note
317 Invoking Bash::.), or from the user's terminal.
319 2. Breaks the input into words and operators, obeying the quoting
320 rules described in *Note Quoting::. Tokens are separated by
321 `metacharacters'. Alias expansion is performed by this step
324 3. Parses the tokens into simple and compound commands.
326 4. Performs the various shell expansions (*note Shell Expansions::.),
327 breaking the expanded tokens into lists of filenames (*note
328 Filename Expansion::.) and commands and arguments.
330 5. Performs any necessary redirections (*note Redirections::.) and
331 removes the redirection operators and their operands from the
334 6. Executes the command (*note Executing Commands::.).
336 7. Optionally waits for the command to complete and collects its exit
341 File: bashref.info, Node: Quoting, Next: Comments, Prev: Shell Operation, Up: Shell Syntax
348 * Escape Character:: How to remove the special meaning from a single
350 * Single Quotes:: How to inhibit all interpretation of a sequence
352 * Double Quotes:: How to suppress most of the interpretation of a
353 sequence of characters.
354 * ANSI-C Quoting:: How to expand ANSI-C sequences in quoted strings.
356 * Locale Translation:: How to translate strings into different languages.
358 Quoting is used to remove the special meaning of certain characters
359 or words to the shell. Quoting can be used to disable special
360 treatment for special characters, to prevent reserved words from being
361 recognized as such, and to prevent parameter expansion.
363 Each of the shell `metacharacters' (*note Definitions::.) has
364 special meaning to the shell and must be quoted if they are to
365 represent themselves. There are three quoting mechanisms: the ESCAPE
366 CHARACTER, single quotes, and double quotes.
369 File: bashref.info, Node: Escape Character, Next: Single Quotes, Up: Quoting
374 A non-quoted backslash `\' is the Bash escape character. It
375 preserves the literal value of the next character that follows, with
376 the exception of `newline'. If a `\newline' pair appears, and the
377 backslash is not quoted, the `\newline' is treated as a line
378 continuation (that is, it is effectively ignored).
381 File: bashref.info, Node: Single Quotes, Next: Double Quotes, Prev: Escape Character, Up: Quoting
386 Enclosing characters in single quotes preserves the literal value of
387 each character within the quotes. A single quote may not occur between
388 single quotes, even when preceded by a backslash.
391 File: bashref.info, Node: Double Quotes, Next: ANSI-C Quoting, Prev: Single Quotes, Up: Quoting
396 Enclosing characters in double quotes preserves the literal value of
397 all characters within the quotes, with the exception of `$', ``', and
398 `\'. The characters `$' and ``' retain their special meaning within
399 double quotes. The backslash retains its special meaning only when
400 followed by one of the following characters: `$', ``', `"', `\', or
401 `newline'. A double quote may be quoted within double quotes by
402 preceding it with a backslash.
404 The special parameters `*' and `@' have special meaning when in
405 double quotes (*note Shell Parameter Expansion::.).
408 File: bashref.info, Node: ANSI-C Quoting, Next: Locale Translation, Prev: Double Quotes, Up: Quoting
413 Words of the form `$'STRING'' are treated specially. The word
414 expands to STRING, with backslash-escaped characters replaced as
415 specifed by the ANSI C standard. Backslash escape sequences, if
416 present, are decoded as follows:
425 an escape character (not ANSI C)
446 the character whose `ASCII' code is NNN in octal
448 The result is single-quoted, as if the dollar sign had not been present.
451 File: bashref.info, Node: Locale Translation, Prev: ANSI-C Quoting, Up: Quoting
453 Locale-Specific Translation
454 ...........................
456 A double-quoted string preceded by a dollar sign (`$') will cause
457 the string to be translated according to the current locale. If the
458 current locale is `C' or `POSIX', the dollar sign is ignored. If the
459 string is translated and replaced, the replacement is double-quoted.
462 File: bashref.info, Node: Comments, Prev: Quoting, Up: Shell Syntax
467 In a non-interactive shell, or an interactive shell in which the
468 `interactive_comments' option to the `shopt' builtin is enabled (*note
469 Bash Builtins::.), a word beginning with `#' causes that word and all
470 remaining characters on that line to be ignored. An interactive shell
471 without the `interactive_comments' option enabled does not allow
472 comments. The `interactive_comments' option is on by default in
476 File: bashref.info, Node: Simple Commands, Next: Pipelines, Prev: Shell Syntax, Up: Basic Shell Features
481 A simple command is the kind of command you'll encounter most often.
482 It's just a sequence of words separated by `blank's, terminated by one
483 of the shell control operators (*note Definitions::.). The first word
484 generally specifies a command to be executed.
486 The return status (*note Exit Status::.) of a simple command is its
487 exit status as provided by the POSIX.1 `waitpid' function, or 128+N if
488 the command was terminated by signal N.
491 File: bashref.info, Node: Pipelines, Next: Lists, Prev: Simple Commands, Up: Basic Shell Features
496 A `pipeline' is a sequence of simple commands separated by `|'.
498 The format for a pipeline is
499 [`time' [`-p']] [`!'] COMMAND1 [`|' COMMAND2 ...]
501 The output of each command in the pipeline is connected to the input of
502 the next command. That is, each command reads the previous command's
505 The reserved word `time' causes timing statistics to be printed for
506 the pipeline once it finishes. The `-p' option changes the output
507 format to that specified by POSIX. The `TIMEFORMAT' variable may be
508 set to a format string that specifies how the timing information should
509 be displayed. *Note Bash Variables::, for a description of the
512 Each command in a pipeline is executed in its own subshell. The exit
513 status of a pipeline is the exit status of the last command in the
514 pipeline. If the reserved word `!' precedes the pipeline, the exit
515 status is the logical NOT of the exit status of the last command.
518 File: bashref.info, Node: Lists, Next: Looping Constructs, Prev: Pipelines, Up: Basic Shell Features
523 A `list' is a sequence of one or more pipelines separated by one of
524 the operators `;', `&', `&&', or `||', and optionally terminated by one
525 of `;', `&', or a `newline'.
527 Of these list operators, `&&' and `||' have equal precedence,
528 followed by `;' and `&', which have equal precedence.
530 If a command is terminated by the control operator `&', the shell
531 executes the command in the BACKGROUND in a subshell. The shell does
532 not wait for the command to finish, and the return status is 0 (true).
533 Commands separated by a `;' are executed sequentially; the shell waits
534 for each command to terminate in turn. The return status is the exit
535 status of the last command executed.
537 The control operators `&&' and `||' denote AND lists and OR lists,
538 respectively. An AND list has the form
541 COMMAND2 is executed if, and only if, COMMAND returns an exit status of
544 An OR list has the form
547 COMMAND2 is executed if and only if COMMAND returns a non-zero exit
550 The return status of AND and OR lists is the exit status of the last
551 command executed in the list.
554 File: bashref.info, Node: Looping Constructs, Next: Conditional Constructs, Prev: Lists, Up: Basic Shell Features
559 Note that wherever you see a `;' in the description of a command's
560 syntax, it may be replaced indiscriminately with one or more newlines.
562 Bash supports the following looping constructs.
565 The syntax of the `until' command is:
566 until TEST-COMMANDS; do CONSEQUENT-COMMANDS; done
567 Execute CONSEQUENT-COMMANDS as long as the final command in
568 TEST-COMMANDS has an exit status which is not zero.
571 The syntax of the `while' command is:
572 while TEST-COMMANDS; do CONSEQUENT-COMMANDS; done
574 Execute CONSEQUENT-COMMANDS as long as the final command in
575 TEST-COMMANDS has an exit status of zero.
578 The syntax of the `for' command is:
580 for NAME [in WORDS ...]; do COMMANDS; done
581 Execute COMMANDS for each member in WORDS, with NAME bound to the
582 current member. If `in WORDS' is not present, `in "$@"' is
585 The `break' and `continue' builtins (*note Bourne Shell Builtins::.)
586 may be used to control loop execution.
589 File: bashref.info, Node: Conditional Constructs, Next: Command Grouping, Prev: Looping Constructs, Up: Basic Shell Features
591 Conditional Constructs
592 ======================
595 The syntax of the `if' command is:
597 if TEST-COMMANDS; then
599 [elif MORE-TEST-COMMANDS; then
601 [else ALTERNATE-CONSEQUENTS;]
604 Execute CONSEQUENT-COMMANDS only if the final command in
605 TEST-COMMANDS has an exit status of zero. Otherwise, each `elif'
606 list is executed in turn, and if its exit status is zero, the
607 corresponding MORE-CONSEQUENTS is executed and the command
608 completes. If `else ALTERNATE-CONSEQUENTS' is present, and the
609 final command in the final `if' or `elif' clause has a non-zero
610 exit status, then execute ALTERNATE-CONSEQUENTS.
613 The syntax of the `case' command is:
615 `case WORD in [PATTERN [| PATTERN]...) COMMANDS ;;]... esac'
617 Selectively execute COMMANDS based upon WORD matching PATTERN.
618 The `|' is used to separate multiple patterns.
620 Here is an example using `case' in a script that could be used to
621 describe one interesting feature of an animal:
623 echo -n "Enter the name of an animal: "
625 echo -n "The $ANIMAL has "
627 horse | dog | cat) echo -n "four";;
628 man | kangaroo ) echo -n "two";;
629 *) echo -n "an unknown number of";;
636 The EXPRESSION is evaluated according to the rules described below
637 ((*note Arithmetic Evaluation::.). If the value of the expression
638 is non-zero, the return status is 0; otherwise the return status
639 is 1. This is exactly equivalent to
642 The `select' construct, which allows users to choose from a list of
643 items presented as a menu, is also available. *Note Korn Shell
644 Constructs::, for a full description of `select'.
647 File: bashref.info, Node: Command Grouping, Next: Shell Functions, Prev: Conditional Constructs, Up: Basic Shell Features
652 Bash provides two ways to group a list of commands to be executed as
653 a unit. When commands are grouped, redirections may be applied to the
654 entire command list. For example, the output of all the commands in
655 the list may be redirected to a single stream.
660 Placing a list of commands between parentheses causes a subshell
661 to be created, and each of the commands to be executed in that
662 subshell. Since the LIST is executed in a subshell, variable
663 assignments do not remain in effect after the subshell completes.
668 Placing a list of commands between curly braces causes the list to
669 be executed in the current shell context. No subshell is created.
670 The semicolon following LIST is required.
672 In addition to the creation of a subshell, there is a subtle
673 difference between these two constructs due to historical reasons. The
674 braces are `reserved words', so they must be separated from the LIST by
675 `blank's. The parentheses are `operators', and are recognized as
676 separate tokens by the shell even if they are not separated from `list'
679 The exit status of both of these constructs is the exit status of
683 File: bashref.info, Node: Shell Functions, Next: Shell Parameters, Prev: Command Grouping, Up: Basic Shell Features
688 Shell functions are a way to group commands for later execution
689 using a single name for the group. They are executed just like a
690 "regular" command. Shell functions are executed in the current shell
691 context; no new process is created to interpret them.
693 Functions are declared using this syntax:
694 [ `function' ] NAME () { COMMAND-LIST; }
696 This defines a shell function named NAME. The reserved word
697 `function' is optional. The BODY of the function is the COMMAND-LIST
698 between { and }. This list is executed whenever NAME is specified as
699 the name of a command. The exit status of a function is the exit
700 status of the last command executed in the body.
702 When a function is executed, the arguments to the function become
703 the positional parameters during its execution (*note Positional
704 Parameters::.). The special parameter `#' that gives the number of
705 positional parameters is updated to reflect the change. Positional
706 parameter `0' is unchanged.
708 If the builtin command `return' is executed in a function, the
709 function completes and execution resumes with the next command after
710 the function call. When a function completes, the values of the
711 positional parameters and the special parameter `#' are restored to the
712 values they had prior to function execution. If a numeric argument is
713 given to `return', that is the function return status.
715 Variables local to the function may be declared with the `local'
716 builtin. These variables are visible only to the function and the
719 Functions may be recursive. No limit is placed on the number of
723 File: bashref.info, Node: Shell Parameters, Next: Shell Expansions, Prev: Shell Functions, Up: Basic Shell Features
730 * Positional Parameters:: The shell's command-line arguments.
731 * Special Parameters:: Parameters with special meanings.
733 A PARAMETER is an entity that stores values. It can be a `name', a
734 number, or one of the special characters listed below. For the shell's
735 purposes, a VARIABLE is a parameter denoted by a `name'.
737 A parameter is set if it has been assigned a value. The null string
738 is a valid value. Once a variable is set, it may be unset only by using
739 the `unset' builtin command.
741 A variable may be assigned to by a statement of the form
744 If VALUE is not given, the variable is assigned the null string. All
745 VALUEs undergo tilde expansion, parameter and variable expansion,
746 command substitution, arithmetic expansion, and quote removal (detailed
747 below). If the variable has its `-i' attribute set (see the
748 description of the `declare' builtin in *Note Bash Builtins::), then
749 VALUE is subject to arithmetic expansion even if the `$((...))' syntax
750 does not appear (*note Arithmetic Expansion::.). Word splitting is not
751 performed, with the exception of `"$@"' as explained below. Filename
752 expansion is not performed.
755 File: bashref.info, Node: Positional Parameters, Next: Special Parameters, Up: Shell Parameters
757 Positional Parameters
758 ---------------------
760 A POSITIONAL PARAMETER is a parameter denoted by one or more digits,
761 other than the single digit `0'. Positional parameters are assigned
762 from the shell's arguments when it is invoked, and may be reassigned
763 using the `set' builtin command. Positional parameters may not be
764 assigned to with assignment statements. The positional parameters are
765 temporarily replaced when a shell function is executed (*note Shell
768 When a positional parameter consisting of more than a single digit
769 is expanded, it must be enclosed in braces.
772 File: bashref.info, Node: Special Parameters, Prev: Positional Parameters, Up: Shell Parameters
777 The shell treats several parameters specially. These parameters may
778 only be referenced; assignment to them is not allowed.
781 Expands to the positional parameters, starting from one. When the
782 expansion occurs within double quotes, it expands to a single word
783 with the value of each parameter separated by the first character
784 of the `IFS' special variable. That is, `"$*"' is equivalent to
785 `"$1C$2C..."', where C is the first character of the value of the
786 `IFS' variable. If `IFS' is null or unset, the parameters are
790 Expands to the positional parameters, starting from one. When the
791 expansion occurs within double quotes, each parameter expands as a
792 separate word. That is, `"$@"' is equivalent to `"$1" "$2" ...'.
793 When there are no positional parameters, `"$@"' and `$@' expand to
794 nothing (i.e., they are removed).
797 Expands to the number of positional parameters in decimal.
800 Expands to the exit status of the most recently executed foreground
804 Expands to the current option flags as specified upon invocation,
805 by the `set' builtin command, or those set by the shell itself
806 (such as the `-i' option).
809 Expands to the process ID of the shell. In a `()' subshell, it
810 expands to the process ID of the current shell, not the subshell.
813 Expands to the process ID of the most recently executed background
814 (asynchronous) command.
817 Expands to the name of the shell or shell script. This is set at
818 shell initialization. If Bash is invoked with a file of commands,
819 `$0' is set to the name of that file. If Bash is started with the
820 `-c' option, then `$0' is set to the first argument after the
821 string to be executed, if one is present. Otherwise, it is set to
822 the filename used to invoke Bash, as given by argument zero.
825 At shell startup, set to the absolute filename of the shell or
826 shell script being executed as passed in the argument list.
827 Subsequently, expands to the last argument to the previous command,
828 after expansion. Also set to the full filename of each command
829 executed and placed in the environment exported to that command.
830 When checking mail, this parameter holds the name of the mail file.
833 File: bashref.info, Node: Shell Expansions, Next: Redirections, Prev: Shell Parameters, Up: Basic Shell Features
838 Expansion is performed on the command line after it has been split
839 into `token's. There are seven kinds of expansion performed:
844 * parameter and variable expansion
846 * command substitution
848 * arithmetic expansion
856 * Shell Parameter Expansion:: How Bash expands variables to their values.
857 * Command Substitution:: Using the output of a command as an argument.
858 * Process Substitution:: A way to write and read to and from a
860 * Word Splitting:: How the results of expansion are split into separate
862 * Filename Expansion:: A shorthand for specifying filenames matching patterns.
863 * Quote Removal:: How and when quote characters are removed from
866 Brace expansion, tilde expansion, and arithmetic expansion are
867 described in other sections. For brace expansion, see *Note Brace
868 Expansion::; for tilde expansion, see *Note Tilde Expansion::; and for
869 arithmetic expansion, see *Note Arithmetic Expansion::.
871 The order of expansions is: brace expansion, tilde expansion,
872 parameter, variable, and arithmetic expansion and command substitution
873 (done in a left-to-right fashion), word splitting, and filename
876 On systems that can support it, there is an additional expansion
877 available: PROCESS SUBSTITUTION. This is performed at the same time as
878 parameter, variable, and arithemtic expansion and command substitution.
880 Only brace expansion, word splitting, and filename expansion can
881 change the number of words of the expansion; other expansions expand a
882 single word to a single word. The only exceptions to this are the
883 expansions of `"$@"' (*note Special Parameters::.) and `"${[@]}"'
886 After all expansions, `quote removal' (*note Quote Removal::.) is
890 File: bashref.info, Node: Shell Parameter Expansion, Next: Command Substitution, Up: Shell Expansions
892 Shell Parameter Expansion
893 -------------------------
895 The `$' character introduces parameter expansion, command
896 substitution, or arithmetic expansion. The parameter name or symbol to
897 be expanded may be enclosed in braces, which are optional but serve to
898 protect the variable to be expanded from characters immediately
899 following it which could be interpreted as part of the name.
901 The basic form of parameter expansion is ${PARAMETER}. The value of
902 PARAMETER is substituted. The braces are required when PARAMETER is a
903 positional parameter with more than one digit, or when PARAMETER is
904 followed by a character that is not to be interpreted as part of its
907 If the first character of PARAMETER is an exclamation point, a level
908 of variable indirection is introduced. Bash uses the value of the
909 variable formed from the rest of PARAMETER as the name of the variable;
910 this variable is then expanded and that value used in the rest of the
911 substitution, rather than the value of PARAMETER itself. This is known
912 as `indirect expansion'.
914 In each of the cases below, WORD is subject to tilde expansion,
915 parameter expansion, command substitution, and arithmetic expansion.
916 When not performing substring expansion, Bash tests for a parameter
917 that is unset or null; omitting the colon results in a test only for a
918 parameter that is unset.
921 If PARAMETER is unset or null, the expansion of WORD is
922 substituted. Otherwise, the value of PARAMETER is substituted.
925 If PARAMETER is unset or null, the expansion of WORD is assigned
926 to PARAMETER. The value of PARAMETER is then substituted.
927 Positional parameters and special parameters may not be assigned
931 If PARAMETER is null or unset, the expansion of WORD (or a message
932 to that effect if WORD is not present) is written to the standard
933 error and the shell, if it is not interactive, exits. Otherwise,
934 the value of PARAMETER is substituted.
937 If PARAMETER is null or unset, nothing is substituted, otherwise
938 the expansion of WORD is substituted.
940 `${PARAMETER:OFFSET}'
941 `${PARAMETER:OFFSET:LENGTH}'
942 Expands to up to LENGTH characters of PARAMETER, starting at
943 OFFSET. If LENGTH is omitted, expands to the substring of
944 PARAMETER, starting at the character specified by OFFSET. LENGTH
945 and OFFSET are arithmetic expressions (*note Arithmetic
946 Evaluation::.). This is referred to as Substring Expansion.
948 LENGTH must evaluate to a number greater than or equal to zero.
949 If OFFSET evaluates to a number less than zero, the value is used
950 as an offset from the end of the value of PARAMETER. If PARAMETER
951 is `@', the result is LENGTH positional parameters beginning at
952 OFFSET. If PARAMETER is an array name indexed by `@' or `*', the
953 result is the LENGTH members of the array beginning with
954 ${PARAMETER[OFFSET]}. Substring indexing is zero-based unless the
955 positional parameters are used, in which case the indexing starts
959 The length in characters of the value of PARAMETER is substituted.
960 If PARAMETER is `*' or `@', the length substituted is the number
961 of positional parameters. If PARAMETER is an array name
962 subscripted by `*' or `@', the length substituted is the number of
963 elements in the array.
967 The WORD is expanded to produce a pattern just as in filename
968 expansion (*note Filename Expansion::.). If the pattern matches
969 the beginning of the value of PARAMETER, then the expansion is the
970 value of PARAMETER with the shortest matching pattern (the `#'
971 case) or the longest matching pattern (the `##' case) deleted. If
972 PARAMETER is `@' or `*', the pattern removal operation is applied
973 to each positional parameter in turn, and the expansion is the
974 resultant list. If PARAMETER is an array variable subscripted with
975 `@' or `*', the pattern removal operation is applied to each
976 member of the array in turn, and the expansion is the resultant
981 The WORD is expanded to produce a pattern just as in filename
982 expansion. If the pattern matches a trailing portion of the value
983 of PARAMETER, then the expansion is the value of PARAMETER with
984 the shortest matching pattern (the `%' case) or the longest
985 matching pattern (the `%%' case) deleted. If PARAMETER is `@' or
986 `*', the pattern removal operation is applied to each positional
987 parameter in turn, and the expansion is the resultant list. If
988 PARAMETER is an array variable subscripted with `@' or `*', the
989 pattern removal operation is applied to each member of the array
990 in turn, and the expansion is the resultant list.
992 `${PARAMETER/PATTERN/STRING}'
993 `${PARAMETER//PATTERN/STRING}'
994 The PATTERN is expanded to produce a pattern just as in filename
995 expansion. PARAMETER is expanded and the longest match of PATTERN
996 against its value is replaced with STRING. In the first form,
997 only the first match is replaced. The second form causes all
998 matches of PATTERN to be replaced with STRING. If PATTERN begins
999 with `#', it must match at the beginning of STRING. If PATTERN
1000 begins with `%', it must match at the end of STRING. If STRING is
1001 null, matches of PATTERN are deleted and the `/' following PATTERN
1002 may be omitted. If PARAMETER is `@' or `*', the substitution
1003 operation is applied to each positional parameter in turn, and the
1004 expansion is the resultant list. If PARAMETER is an array
1005 variable subscripted with `@' or `*', the substitution operation
1006 is applied to each member of the array in turn, and the expansion
1007 is the resultant list.
1010 File: bashref.info, Node: Command Substitution, Next: Process Substitution, Prev: Shell Parameter Expansion, Up: Shell Expansions
1012 Command Substitution
1013 --------------------
1015 Command substitution allows the output of a command to replace the
1016 command name. There are two forms:
1022 Bash performs the expansion by executing COMMAND and replacing the
1023 command substitution with the standard output of the command, with any
1024 trailing newlines deleted.
1026 When the old-style backquote form of substitution is used, backslash
1027 retains its literal meaning except when followed by `$', ``', or `\'.
1028 When using the `$(COMMAND)' form, all characters between the
1029 parentheses make up the command; none are treated specially.
1031 Command substitutions may be nested. To nest when using the old
1032 form, escape the inner backquotes with backslashes.
1034 If the substitution appears within double quotes, word splitting and
1035 filename expansion are not performed on the results.
1038 File: bashref.info, Node: Process Substitution, Next: Word Splitting, Prev: Command Substitution, Up: Shell Expansions
1040 Process Substitution
1041 --------------------
1043 Process substitution is supported on systems that support named
1044 pipes (FIFOs) or the `/dev/fd' method of naming open files. It takes
1051 The process LIST is run with its input or output connected to a FIFO or
1052 some file in `/dev/fd'. The name of this file is passed as an argument
1053 to the current command as the result of the expansion. If the
1054 `>(LIST)' form is used, writing to the file will provide input for
1055 LIST. If the `<(LIST)' form is used, the file passed as an argument
1056 should be read to obtain the output of LIST.
1058 On systems that support it, process substitution is performed
1059 simultaneously with parameter and variable expansion, command
1060 substitution, and arithmetic expansion.
1063 File: bashref.info, Node: Word Splitting, Next: Filename Expansion, Prev: Process Substitution, Up: Shell Expansions
1068 The shell scans the results of parameter expansion, command
1069 substitution, and arithmetic expansion that did not occur within double
1070 quotes for word splitting.
1072 The shell treats each character of `$IFS' as a delimiter, and splits
1073 the results of the other expansions into words on these characters. If
1074 `IFS' is unset, or its value is exactly `<space><tab><newline>', the
1075 default, then any sequence of `IFS' characters serves to delimit words.
1076 If `IFS' has a value other than the default, then sequences of the
1077 whitespace characters `space' and `tab' are ignored at the beginning
1078 and end of the word, as long as the whitespace character is in the
1079 value of `IFS' (an `IFS' whitespace character). Any character in `IFS'
1080 that is not `IFS' whitespace, along with any adjacent `IFS' whitespace
1081 characters, delimits a field. A sequence of `IFS' whitespace
1082 characters is also treated as a delimiter. If the value of `IFS' is
1083 null, no word splitting occurs.
1085 Explicit null arguments (`""' or `''') are retained. Unquoted
1086 implicit null arguments, resulting from the expansion of PARAMETERs
1087 that have no values, are removed. If a parameter with no value is
1088 expanded within double quotes, a null argument results and is retained.
1090 Note that if no expansion occurs, no splitting is performed.
1093 File: bashref.info, Node: Filename Expansion, Next: Quote Removal, Prev: Word Splitting, Up: Shell Expansions
1098 After word splitting, unless the `-f' option has been set (*note The
1099 Set Builtin::.), Bash scans each word for the characters `*', `?', and
1100 `['. If one of these characters appears, then the word is regarded as
1101 a PATTERN, and replaced with an alphabetically sorted list of file
1102 names matching the pattern. If no matching file names are found, and
1103 the shell option `nullglob' is disabled, the word is left unchanged. If
1104 the option is set, and no matches are found, the word is removed. When
1105 a pattern is used for filename generation, the character `.' at the
1106 start of a filename or immediately following a slash must be matched
1107 explicitly, unless the shell option `dotglob' is set. The slash
1108 character must always be matched explicitly. In other cases, the `.'
1109 character is not treated specially. See the description of `shopt' in
1110 *Note Bash Builtins::, for a description of the `nullglob' and
1113 The `GLOBIGNORE' shell variable may be used to restrict the set of
1114 filenames matching a PATTERN. If `GLOBIGNORE' is set, each matching
1115 filename that also matches one of the patterns in `GLOBIGNORE' is
1116 removed from the list of matches. The filenames `.' and `..' are
1117 always ignored, even when `GLOBIGNORE'. is set. However, setting
1118 `GLOBIGNORE' has the effect of enabling the `dotglob' shell option, so
1119 all other filenames beginning with a `.' will match. To get the old
1120 behavior of ignoring filenames beginning with a `.', make `.*' one of
1121 the patterns in `GLOBIGNORE'. The `dotglob' option is disabled when
1122 `GLOBIGNORE' is unset.
1124 The special pattern characters have the following meanings:
1126 Matches any string, including the null string.
1129 Matches any single character.
1132 Matches any one of the enclosed characters. A pair of characters
1133 separated by a minus sign denotes a RANGE; any character lexically
1134 between those two characters, inclusive, is matched. If the first
1135 character following the `[' is a `!' or a `^' then any character
1136 not enclosed is matched. A `-' may be matched by including it as
1137 the first or last character in the set. A `]' may be matched by
1138 including it as the first character in the set.
1141 File: bashref.info, Node: Quote Removal, Prev: Filename Expansion, Up: Shell Expansions
1146 After the preceding expansions, all unquoted occurrences of the
1147 characters `\', `'', and `"' that did not result from one of the above
1148 expansions are removed.
1151 File: bashref.info, Node: Redirections, Next: Executing Commands, Prev: Shell Expansions, Up: Basic Shell Features
1156 Before a command is executed, its input and output may be REDIRECTED
1157 using a special notation interpreted by the shell. Redirection may
1158 also be used to open and close files for the current shell execution
1159 environment. The following redirection operators may precede or appear
1160 anywhere within a simple command or may follow a command. Redirections
1161 are processed in the order they appear, from left to right.
1163 In the following descriptions, if the file descriptor number is
1164 omitted, and the first character of the redirection operator is `<',
1165 the redirection refers to the standard input (file descriptor 0). If
1166 the first character of the redirection operator is `>', the redirection
1167 refers to the standard output (file descriptor 1).
1169 The word that follows the redirection operator in the following
1170 descriptions is subjected to brace expansion, tilde expansion,
1171 parameter expansion, command substitution, arithmetic expansion, quote
1172 removal, and filename expansion. If it expands to more than one word,
1173 Bash reports an error.
1175 Note that the order of redirections is significant. For example,
1179 directs both standard output and standard error to the file DIRLIST,
1183 directs only the standard output to file DIRLIST, because the standard
1184 error was duplicated as standard output before the standard output was
1185 redirected to DIRLIST.
1190 Redirection of input causes the file whose name results from the
1191 expansion of WORD to be opened for reading on file descriptor `n', or
1192 the standard input (file descriptor 0) if `n' is not specified.
1194 The general format for redirecting input is:
1200 Redirection of output causes the file whose name results from the
1201 expansion of WORD to be opened for writing on file descriptor `n', or
1202 the standard output (file descriptor 1) if `n' is not specified. If
1203 the file does not exist it is created; if it does exist it is truncated
1206 The general format for redirecting output is:
1209 If the redirection operator is `>', and the `-C' option to the `set'
1210 builtin has been enabled, the redirection will fail if the filename
1211 whose name results from the expansion of WORD exists. If the
1212 redirection operator is `>|', then the value of the `-C' option to the
1213 `set' builtin command is not tested, and the redirection is attempted
1214 even if the file named by WORD exists.
1216 Appending Redirected Output
1217 ---------------------------
1219 Redirection of output in this fashion causes the file whose name
1220 results from the expansion of WORD to be opened for appending on file
1221 descriptor `n', or the standard output (file descriptor 1) if `n' is
1222 not specified. If the file does not exist it is created.
1224 The general format for appending output is:
1227 Redirecting Standard Output and Standard Error
1228 ----------------------------------------------
1230 Bash allows both the standard output (file descriptor 1) and the
1231 standard error output (file descriptor 2) to be redirected to the file
1232 whose name is the expansion of WORD with this construct.
1234 There are two formats for redirecting standard output and standard
1241 Of the two forms, the first is preferred. This is semantically
1248 This type of redirection instructs the shell to read input from the
1249 current source until a line containing only WORD (with no trailing
1250 blanks) is seen. All of the lines read up to that point are then used
1251 as the standard input for a command.
1253 The format of here-documents is as follows:
1258 No parameter expansion, command substitution, filename expansion, or
1259 arithmetic expansion is performed on WORD. If any characters in WORD
1260 are quoted, the DELIMITER is the result of quote removal on WORD, and
1261 the lines in the here-document are not expanded. Otherwise, all lines
1262 of the here-document are subjected to parameter expansion, command
1263 substitution, and arithmetic expansion. In the latter case, the pair
1264 `\newline' is ignored, and `\' must be used to quote the characters
1267 If the redirection operator is `<<-', then all leading tab
1268 characters are stripped from input lines and the line containing
1269 DELIMITER. This allows here-documents within shell scripts to be
1270 indented in a natural fashion.
1272 Duplicating File Descriptors
1273 ----------------------------
1275 The redirection operator
1278 is used to duplicate input file descriptors. If WORD expands to one or
1279 more digits, the file descriptor denoted by `n' is made to be a copy of
1280 that file descriptor. If WORD evaluates to `-', file descriptor `n' is
1281 closed. If `n' is not specified, the standard input (file descriptor
1287 is used similarly to duplicate output file descriptors. If `n' is not
1288 specified, the standard output (file descriptor 1) is used. As a
1289 special case, if `n' is omitted, and WORD does not expand to one or
1290 more digits, the standard output and standard error are redirected as
1291 described previously.
1293 Opening File Descriptors for Reading and Writing
1294 ------------------------------------------------
1296 The redirection operator
1299 causes the file whose name is the expansion of WORD to be opened for
1300 both reading and writing on file descriptor `n', or on file descriptor
1301 0 if `n' is not specified. If the file does not exist, it is created.
1304 File: bashref.info, Node: Executing Commands, Next: Shell Scripts, Prev: Redirections, Up: Basic Shell Features
1311 * Command Search and Execution:: How Bash finds commands and runs them.
1313 * Environment:: The environment given to a command.
1315 * Exit Status:: The status returned by commands and how Bash
1318 * Signals:: What happens when Bash or a command it runs
1322 File: bashref.info, Node: Command Search and Execution, Next: Environment, Up: Executing Commands
1324 Command Search and Execution
1325 ----------------------------
1327 After a command has been split into words, if it results in a simple
1328 command and an optional list of arguments, the following actions are
1331 1. If the command name contains no slashes, the shell attempts to
1332 locate it. If there exists a shell function by that name, that
1333 function is invoked as described above in *Note Shell Functions::.
1335 2. If the name does not match a function, the shell searches for it
1336 in the list of shell builtins. If a match is found, that builtin
1339 3. If the name is neither a shell function nor a builtin, and
1340 contains no slashes, Bash searches each element of `$PATH' for a
1341 directory containing an executable file by that name. Bash uses a
1342 hash table to remember the full filenames of executable files (see
1343 the description of `hash' in *Note Bourne Shell Builtins::) to
1344 avoid multiple `PATH' searches. A full search of the directories
1345 in `$PATH' is performed only if the command is not found in the
1346 hash table. If the search is unsuccessful, the shell prints an
1347 error message and returns a nonzero exit status.
1349 4. If the search is successful, or if the command name contains one
1350 or more slashes, the shell executes the named program. Argument 0
1351 is set to the name given, and the remaining arguments to the
1352 command are set to the arguments supplied, if any.
1354 5. If this execution fails because the file is not in executable
1355 format, and the file is not a directory, it is assumed to be SHELL
1356 SCRIPT (*note Shell Scripts::.).
1359 File: bashref.info, Node: Environment, Next: Exit Status, Prev: Command Search and Execution, Up: Executing Commands
1364 When a program is invoked it is given an array of strings called the
1365 ENVIRONMENT. This is a list of name-value pairs, of the form
1368 Bash allows you to manipulate the environment in several ways. On
1369 invocation, the shell scans its own environment and creates a parameter
1370 for each name found, automatically marking it for EXPORT to child
1371 processes. Executed commands inherit the environment. The `export'
1372 and `declare -x' commands allow parameters and functions to be added to
1373 and deleted from the environment. If the value of a parameter in the
1374 environment is modified, the new value becomes part of the environment,
1375 replacing the old. The environment inherited by any executed command
1376 consists of the shell's initial environment, whose values may be
1377 modified in the shell, less any pairs removed by the `unset' command,
1378 plus any additions via the `export' and `declare -x' commands.
1380 The environment for any simple command or function may be augmented
1381 temporarily by prefixing it with parameter assignments, as described in
1382 *Note Shell Parameters::. These assignment statements affect only the
1383 environment seen by that command.
1385 If the `-k' flag is set (*note The Set Builtin::., then all
1386 parameter assignments are placed in the environment for a command, not
1387 just those that precede the command name.
1389 When Bash invokes an external command, the variable `$_' is set to
1390 the full path name of the command and passed to that command in its
1394 File: bashref.info, Node: Exit Status, Next: Signals, Prev: Environment, Up: Executing Commands
1399 For the purposes of the shell, a command which exits with a zero
1400 exit status has succeeded. A non-zero exit status indicates failure.
1401 This seemingly counter-intuitive scheme is used so there is one
1402 well-defined way to indicate success and a variety of ways to indicate
1403 various failure modes. When a command terminates on a fatal signal
1404 whose number is N, Bash uses the value 128+N as the exit status.
1406 If a command is not found, the child process created to execute it
1407 returns a status of 127. If a command is found but is not executable,
1408 the return status is 126.
1410 The exit status is used by the Bash conditional commands (*note
1411 Conditional Constructs::.) and some of the list constructs (*note
1414 All of the Bash builtins return an exit status of zero if they
1415 succeed and a non-zero status on failure, so they may be used by the
1416 conditional and list constructs.
1419 File: bashref.info, Node: Signals, Prev: Exit Status, Up: Executing Commands
1424 When Bash is interactive, it ignores `SIGTERM' (so that `kill 0'
1425 does not kill an interactive shell), and `SIGINT' is caught and handled
1426 (so that the `wait' builtin is interruptible). When Bash receives a
1427 `SIGINT', it breaks out of any executing loops. In all cases, Bash
1428 ignores `SIGQUIT'. If job control is in effect (*note Job Control::.),
1429 Bash ignores `SIGTTIN', `SIGTTOU', and `SIGTSTP'.
1431 Synchronous jobs started by Bash have signals set to the values
1432 inherited by the shell from its parent. When job control is not in
1433 effect, background jobs (commands terminated with `&') ignore `SIGINT'
1434 and `SIGQUIT'. Commands run as a result of command substitution ignore
1435 the keyboard-generated job control signals `SIGTTIN', `SIGTTOU', and
1438 The shell exits by default upon receipt of a `SIGHUP'. Before
1439 exiting, it resends the `SIGHUP' to all jobs, running or stopped. To
1440 prevent the shell from sending the `SIGHUP' signal to a particular job,
1441 remove it from the jobs table with the `disown' builtin (*note Job
1442 Control Builtins::.) or use `disown -h' to mark it to not receive
1446 File: bashref.info, Node: Shell Scripts, Prev: Executing Commands, Up: Basic Shell Features
1451 A shell script is a text file containing shell commands. When such
1452 a file is used as the first non-option argument when invoking Bash, and
1453 neither the `-c' nor `-s' option is supplied (*note Invoking Bash::.),
1454 Bash reads and executes commands from the file, then exits. This mode
1455 of operation creates a non-interactive shell. When Bash runs a shell
1456 script, it sets the special parameter `0' to the name of the file,
1457 rather than the name of the shell, and the positional parameters are
1458 set to the remaining arguments, if any are given. If no additional
1459 arguments are supplied, the positional parameters are unset.
1461 A shell script may be made executable by using the `chmod' command
1462 to turn on the execute bit. When Bash finds such a file while
1463 searching the `$PATH' for a command, it spawns a subshell to execute
1464 it. In other words, executing
1467 is equivalent to executing
1468 bash filename ARGUMENTS
1470 if `filename' is an executable shell script. This subshell
1471 reinitializes itself, so that the effect is as if a new shell had been
1472 invoked to interpret the script.
1474 Most versions of Unix make this a part of the kernel's command
1475 execution mechanism. If the first line of a script begins with the two
1476 characters `#!', the remainder of the line specifies an interpreter for
1477 the program. The arguments to the interpreter consist of a single
1478 optional argument following the interpreter name on the first line of
1479 the script file, followed by the name of the script file, followed by
1480 the rest of the arguments. Bash will perform this action on operating
1481 systems that do not handle it themselves. Note that some older
1482 versions of Unix limit the interpreter name and argument to a maximum
1486 File: bashref.info, Node: Bourne Shell Features, Next: Csh Features, Prev: Basic Shell Features, Up: Top
1488 Bourne Shell Style Features
1489 ***************************
1493 * Bourne Shell Builtins:: Builtin commands inherited from the Bourne
1495 * Bourne Shell Variables:: Variables which Bash uses in the same way
1496 as the Bourne Shell.
1497 * Other Bourne Shell Features:: Addtional aspects of Bash which behave in
1498 the same way as the Bourne Shell.
1500 This section briefly summarizes things which Bash inherits from the
1501 Bourne Shell: builtins, variables, and other features. It also lists
1502 the significant differences between Bash and the Bourne Shell.
1505 File: bashref.info, Node: Bourne Shell Builtins, Next: Bourne Shell Variables, Up: Bourne Shell Features
1507 Bourne Shell Builtins
1508 =====================
1510 The following shell builtin commands are inherited from the Bourne
1511 Shell. These commands are implemented as specified by the POSIX 1003.2
1516 Do nothing beyond expanding ARGUMENTS and performing redirections.
1520 Read and execute commands from the FILENAME argument in the
1521 current shell context.
1525 Exit from a `for', `while', `until', or `select' loop. If N is
1526 supplied, the Nth enclosing loop is exited.
1529 cd [-LP] [DIRECTORY]
1530 Change the current working directory to DIRECTORY. If DIRECTORY
1531 is not given, the value of the `HOME' shell variable is used. If
1532 the shell variable `CDPATH' exists, it is used as a search path.
1533 If DIRECTORY begins with a slash, `CDPATH' is not used. The `-P'
1534 option means to not follow symbolic links; symlinks are followed
1535 by default or with the `-L' option.
1539 Resume the next iteration of an enclosing `for', `while', `until',
1540 or `select' loop. If N is supplied, the execution of the Nth
1541 enclosing loop is resumed.
1545 The arguments are concatenated together into a single command,
1546 which is then read and executed.
1549 exec [-cl] [-a NAME] [COMMAND] [ARGUMENTS]
1550 If COMMAND is supplied, it replaces the shell. If the `-l' option
1551 is supplied, the shell places a dash in the zeroth arg passed to
1552 COMMAND. This is what the `login' program does. The `-c' option
1553 causes COMMAND to be executed with an empty environment. If `-a'
1554 is supplied, the shell passes NAME as the zeroth argument to
1555 COMMAND. If no COMMAND is specified, redirections may be used to
1556 affect the current shell environment.
1560 Exit the shell, returning a status of N to the shell's parent.
1563 export [-fn] [-p] [NAME[=VALUE]]
1564 Mark each NAME to be passed to child processes in the environment.
1565 If the `-f' option is supplied, the NAMEs refer to shell
1566 functions. The `-n' option means to no longer mark each NAME for
1567 export. If no NAMES are supplied, or if the `-p' option is given,
1568 a list of exported names is displayed.
1571 getopts OPTSTRING NAME [ARGS]
1572 `getopts' is used by shell scripts to parse positional parameters.
1573 OPTSTRING contains the option letters to be recognized; if a letter
1574 is followed by a colon, the option is expected to have an
1575 argument, which should be separated from it by white space. Each
1576 time it is invoked, `getopts' places the next option in the shell
1577 variable NAME, initializing NAME if it does not exist, and the
1578 index of the next argument to be processed into the variable
1579 `OPTIND'. `OPTIND' is initialized to 1 each time the shell or a
1580 shell script is invoked. When an option requires an argument,
1581 `getopts' places that argument into the variable `OPTARG'. The
1582 shell does not reset `OPTIND' automatically; it must be manually
1583 reset between multiple calls to `getopts' within the same shell
1584 invocation if a new set of parameters is to be used.
1586 `getopts' can report errors in two ways. If the first character of
1587 OPTSTRING is a colon, SILENT error reporting is used. In normal
1588 operation diagnostic messages are printed when illegal options or
1589 missing option arguments are encountered. If the variable `OPTERR'
1590 is set to 0, no error message will be displayed, even if the first
1591 character of `optstring' is not a colon.
1593 If an illegal option is seen, `getopts' places `?' into NAME and,
1594 if not silent, prints an error message and unsets `OPTARG'. If
1595 `getopts' is silent, the option character found is placed in
1596 `OPTARG' and no diagnostic message is printed.
1598 If a required argument is not found, and `getopts' is not silent,
1599 a question mark (`?') is placed in NAME, `OPTARG' is unset, and a
1600 diagnostic message is printed. If `getopts' is silent, then a
1601 colon (`:') is placed in NAME and `OPTARG' is set to the option
1604 `getopts' normally parses the positional parameters, but if more
1605 arguments are given in ARGS, `getopts' parses those instead.
1608 hash [-r] [-p FILENAME] [NAME]
1609 Remember the full filenames of commands specified as arguments, so
1610 they need not be searched for on subsequent invocations. The
1611 commands are found by searching through the directories listed in
1612 `$PATH'. The `-p' option inhibits the path search, and FILENAME
1613 is used as the location of NAME. The `-r' option causes the shell
1614 to forget all remembered locations. If no arguments are given,
1615 information about remembered commands is printed.
1619 Print the current working directory. If the `-P' option is
1620 supplied, the path printed will not contain symbolic links. If
1621 the `-L' option is supplied, the path printed may contain symbolic
1625 readonly [-apf] [NAME] ...
1626 Mark each NAME as unchangable. The values of these names may not
1627 be changed by subsequent assignment. If the `-f' option is
1628 supplied, each NAME refers to a shell function. The `-a' option
1629 means each NAME refers to an array variable. If no NAME arguments
1630 are given, or if the `-p' option is supplied, a list of all
1631 readonly names is printed.
1635 Cause a shell function to exit with value N. This may also be used
1636 to terminate execution of a script being executed with the `.'
1641 Shift positional parameters to the left by N. The positional
1642 parameters from N+1 ... are renamed to `$1' ... . Parameters
1643 represented by the numbers `$#' to N+1 are unset. N must be a
1644 non-negative number less than or equal to `$#'.
1648 Evaluate a conditional expression (*note Bash Conditional
1653 Print out the user and system times used by the shell and its
1657 trap [-lp] [ARG] [SIGSPEC]
1658 The commands in ARG are to be read and executed when the shell
1659 receives signal SIGSPEC. If ARG is absent or equal to `-', all
1660 specified signals are reset to the values they had when the shell
1661 was started. If ARG is the null string, then SIGSPEC is ignored by
1662 the shell and commands it invokes. If ARG is `-p', the shell
1663 displays the trap commands associated with each SIGSPEC. If no
1664 arguments are supplied, or only `-p' is given, `trap' prints the
1665 list of commands associated with each signal number. SIGSPEC is
1666 either a signal name such as `SIGINT' or a signal number. If
1667 SIGSPEC is `0' or `EXIT', ARG is executed when the shell exits.
1668 If SIGSPEC is `DEBUG', the command ARG is executed after every
1669 simple command. The `-l' option causes the shell to print a list
1670 of signal names and their corresponding numbers.
1672 Signals ignored upon entry to the shell cannot be trapped or reset.
1673 Trapped signals are reset to their original values in a child
1674 process when it is created.
1678 Set the shell process's file creation mask to MODE. If MODE
1679 begins with a digit, it is interpreted as an octal number; if not,
1680 it is interpreted as a symbolic mode mask similar to that accepted
1681 by the `chmod' command. If MODE is omitted, the current value of
1682 the mask is printed. If the `-S' option is supplied without a
1683 MODE argument, the mask is printed in a symbolic format.
1687 Each variable or function NAME is removed. If no options are
1688 supplied, or the `-v' option is given, each NAME refers to a shell
1689 variable. If the `-f' option is given, the NAMEs refer to shell
1690 functions, and the function definition is removed. Read-only
1691 variables and functions may not be unset.
1694 File: bashref.info, Node: Bourne Shell Variables, Next: Other Bourne Shell Features, Prev: Bourne Shell Builtins, Up: Bourne Shell Features
1696 Bourne Shell Variables
1697 ======================
1699 Bash uses certain shell variables in the same way as the Bourne
1700 shell. In some cases, Bash assigns a default value to the variable.
1703 A list of characters that separate fields; used when the shell
1704 splits words as part of expansion.
1707 A colon-separated list of directories in which the shell looks for
1711 The current user's home directory; the default for the `cd' builtin
1715 A colon-separated list of directories used as a search path for
1719 A colon-separated list of files which the shell periodically checks
1720 for new mail. You can also specify what message is printed by
1721 separating the file name from the message with a `?'. When used
1722 in the text of the message, `$_' stands for the name of the
1726 If this parameter is set to a filename and the `MAILPATH' variable
1727 is not set, Bash informs the user of the arrival of mail in the
1731 The primary prompt string. The default value is `\s-\v\$ '.
1734 The secondary prompt string. The default value is `> '.
1737 The index of the last option processed by the `getopts' builtin.
1740 The value of the last option argument processed by the `getopts'
1744 File: bashref.info, Node: Other Bourne Shell Features, Prev: Bourne Shell Variables, Up: Bourne Shell Features
1746 Other Bourne Shell Features
1747 ===========================
1751 * Major Differences From The Bourne Shell:: Major differences between
1752 Bash and the Bourne shell.
1754 Bash implements essentially the same grammar, parameter and variable
1755 expansion, redirection, and quoting as the Bourne Shell. Bash uses the
1756 POSIX 1003.2 standard as the specification of how these features are to
1757 be implemented. There are some differences between the traditional
1758 Bourne shell and the POSIX standard; this section quickly details the
1759 differences of significance. A number of these differences are
1760 explained in greater depth in subsequent sections.
1763 File: bashref.info, Node: Major Differences From The Bourne Shell, Up: Other Bourne Shell Features
1765 Major Differences From The SVR4.2 Bourne Shell
1766 ----------------------------------------------
1768 Bash is POSIX-conformant, even where the POSIX specification differs
1769 from traditional `sh' behavior.
1771 Bash has multi-character invocation options (*note Invoking Bash::.).
1773 Bash has command-line editing (*note Command Line Editing::.) and
1776 Bash has command history (*note Bash History Facilities::.) and the
1777 `history' and `fc' builtins to manipulate it.
1779 Bash implements `csh'-like history expansion (*note History
1782 Bash has one-dimensional array variables (*note Arrays::.), and the
1783 appropriate variable expansions and assignment syntax to use them.
1784 Some of the Bash builtins take options to act on arrays. Bash provides
1785 some built-in array variables.
1787 Bash implements the `!' keyword to negate the return value of a
1788 pipeline (*note Pipelines::.). Very useful when an `if' statement
1789 needs to act only if a test fails.
1791 Bash includes the `select' compound command, which allows the
1792 generation of simple menus (*note Korn Shell Constructs::.).
1794 Bash includes brace expansion (*note Brace Expansion::.) and tilde
1795 expansion (*note Tilde Expansion::.).
1797 Bash implements command aliases and the `alias' and `unalias'
1798 builtins (*note Aliases::.).
1800 Bash provides shell arithmetic and arithmetic expansion (*note Shell
1803 The POSIX and `ksh'-style `$()' form of command substitution is
1804 implemented (*note Command Substitution::.), and preferred to the
1805 Bourne shell's ```' (which is also implemented for backwards
1808 Variables present in the shell's initial environment are
1809 automatically exported to child processes. The Bourne shell does not
1810 normally do this unless the variables are explicitly marked using the
1813 Bash includes the POSIX and `ksh'-style pattern removal `%', `#',
1814 `%%' and `##' constructs to remove leading or trailing substrings from
1815 variable values (*note Shell Parameter Expansion::.).
1817 The expansion `${#xx}', which returns the length of `$xx', is
1818 supported (*note Shell Parameter Expansion::.).
1820 The `$'...'' quoting syntax, which expands ANSI-C backslash-escaped
1821 characters in the text between the single quotes, is supported (*note
1824 Bash supports the `$"..."' quoting syntax to do locale-specific
1825 translation of the characters between the double quotes. The `-D' and
1826 `--dump-strings' invocation options list the translatable strings found
1827 in a script (*note Locale Translation::.).
1829 The expansion `${var:'LENGTH`[:'OFFSET`]}', which expands to the
1830 substring of `var''s value of length LENGTH, optionally beginning at
1831 OFFSET, is present (*note Shell Parameter Expansion::.).
1833 The expansion `${var/[/]'PATTERN`[/'REPLACEMENT`]}', which matches
1834 PATTERN and replaces it with REPLACEMENT in the value of `var', is
1835 available (*note Shell Parameter Expansion::.).
1837 Bash has INDIRECT variable expansion using `${!word}' (*note Shell
1838 Parameter Expansion::.).
1840 Bash can expand positional parameters beyond `$9' using `${NUM}'.
1842 Bash has process substitution (*note Process Substitution::.).
1844 Bash automatically assigns variables that provide information about
1845 the current user (`UID' and `EUID'), the current host (`HOSTTYPE',
1846 `OSTYPE', `MACHTYPE', and `HOSTNAME'), and the instance of Bash that is
1847 running (`BASH', `BASH_VERSION', and `BASH_VERSINFO'. *Note Bash
1848 Variables::, for details.
1850 The `IFS' variable is used to split only the results of expansion,
1851 not all words (*note Word Splitting::.). This closes a longstanding
1852 shell security hole.
1854 It is possible to have a variable and a function with the same name;
1855 `sh' does not separate the two name spaces.
1857 Bash functions are permitted to have local variables using the
1858 `local' builtin, and thus useful recursive functions may be written.
1860 Variable assignments preceding commands affect only that command,
1861 even builtins and functions. In `sh', all variable assignments
1862 preceding commands are global unless the command is executed from the
1865 Bash performs filename expansion on filenames specified as operands
1866 to output redirection operators.
1868 Bash contains the `<>' redirection operator, allowing a file to be
1869 opened for both reading and writing, and the `&>' redirection operator,
1870 for directing standard output and standard error to the same file
1871 (*note Redirections::.).
1873 The `noclobber' option is available to avoid overwriting existing
1874 files with output redirection (*note The Set Builtin::.). The `>|'
1875 redirection operator may be used to override `noclobber'.
1877 Bash interprets special backslash-escaped characters in the prompt
1878 strings when interactive (*note Printing a Prompt::.).
1880 Bash allows you to write a function to override a builtin, and
1881 provides access to that builtin's functionality within the function via
1882 the `builtin' and `command' builtins (*note Bash Builtins::.).
1884 The `command' builtin allows selective disabling of functions when
1885 command lookup is performed (*note Bash Builtins::.).
1887 Individual builtins may be enabled or disabled using the `enable'
1888 builtin (*note Bash Builtins::.).
1890 The Bash `hash' builtin allows a name to be associated with an
1891 arbitrary filename, even when that filename cannot be found by
1892 searching the `$PATH', using `hash -p'.
1894 Shell functions may be exported to children via the environment
1895 (*note Shell Functions::.).
1897 Bash includes a `help' builtin for quick reference to shell
1898 facilities (*note Bash Builtins::.).
1900 The Bash `read' builtin (*note Bash Builtins::.) will read a line
1901 ending in `\' with the `-r' option, and will use the `REPLY' variable
1902 as a default if no arguments are supplied. The Bash `read' builtin
1903 also accepts a prompt string with the `-p' option and will use Readline
1904 to obtain the line when given the `-e' option.
1906 Bash includes the `shopt' builtin, for finer control of shell
1907 optional capabilities (*note Bash Builtins::.).
1909 Bash has much more optional behavior controllable with the `set'
1910 builtin (*note The Set Builtin::.).
1912 The `disown' builtin can remove a job from the internal shell job
1913 table (*note Job Control Builtins::.).
1915 The `return' builtin may be used to abort execution of scripts
1916 executed with the `.' or `source' builtins (*note Bourne Shell
1919 The `test' builtin (*note Bourne Shell Builtins::.) is slightly
1920 different, as it implements the POSIX 1003.2 algorithm, which specifies
1921 the behavior based on the number of arguments.
1923 The `trap' builtin (*note Bourne Shell Builtins::.) allows a `DEBUG'
1924 pseudo-signal specification, similar to `EXIT'. Commands specified
1925 with a `DEBUG' trap are executed after every simple command. The
1926 `DEBUG' trap is not inherited by shell functions.
1928 The Bash `export', `readonly', and `declare' builtins can take a
1929 `-f' option to act on shell functions, a `-p' option to display
1930 variables with various attributes set in a format that can be used as
1931 shell input, a `-n' option to remove various variable attributes, and
1932 `name=value' arguments to set variable attributes and values
1935 The Bash `cd' and `pwd' builtins each take `-L' and `-P' builtins to
1936 switch between logical and physical modes.
1938 The Bash `type' builtin is more extensive and gives more information
1939 about the names it finds.
1941 Bash implements a `csh'-like directory stack, and provides the
1942 `pushd', `popd', and `dirs' builtins to manipulate it. Bash also makes
1943 the directory stack visible as the value of the `DIRSTACK' shell
1946 The Bash restricted mode is more useful (*note The Restricted
1947 Shell::.); the SVR4.2 shell restricted mode is too limited.
1949 Bash has the `time' reserved word and command timing (*note
1950 Pipelines::.). The display of the timing statistics may be controlled
1951 with the `TIMEFORMAT' variable.
1953 The SVR4.2 shell has two privilege-related builtins (`mldmode' and
1954 `priv') not present in Bash.
1956 Bash does not have the `stop' or `newgrp' builtins.
1958 Bash does not use the `SHACCT' variable or perform shell accounting.
1960 The SVR4.2 `sh' uses a `TIMEOUT' variable like Bash uses `TMOUT'.
1962 More features unique to Bash may be found in *Note Bash Features::.
1964 Implementation Differences From The SVR4.2 Shell
1965 ------------------------------------------------
1967 Since Bash is a completely new implementation, it does not suffer
1968 from many of the limitations of the SVR4.2 shell. For instance:
1970 * Bash does not fork a subshell when redirecting into or out of a
1971 shell control structure such as an `if' or `while' statement.
1973 * Bash does not allow unbalanced quotes. The SVR4.2 shell will
1974 silently insert a needed closing quote at `EOF' under certain
1975 circumstances. This can be the cause of some hard-to-find errors.
1977 * The SVR4.2 shell uses a baroque memory management scheme based on
1978 trapping `SIGSEGV'. If the shell is started from a process with
1979 `SIGSEGV' blocked (e.g., by using the `system()' C library
1980 function call), the shell misbehaves badly.
1982 * In a questionable attempt at security, the SVR4.2 shell will alter
1983 its real and effective UID and GID if they are less than some
1984 threshold value, commonly 100. This can lead to unexpected
1987 * The SVR4.2 shell does not allow users to trap `SIGALRM' or
1990 * For some reason, the SVR4.2 shell does not allow the `MAILCHECK'
1991 variable to be unset.
1993 * The SVR4.2 shell treats `^' as the undocumented equivalent of `|'.
1995 * Bash allows multiple option arguments when it is invoked (`-x -v');
1996 the SVR4.2 shell allows only one option argument (`-xv'). In
1997 fact, some versions of the shell dump core if the second argument
2000 * The SVR4.2 shell exits a script if any builtin fails; Bash exits a
2001 script only if one of the POSIX.2 special builtins fails, and only
2002 for certain failures, as enumerated in the `POSIX.2' standard.
2004 * The SVR4.2 shell behaves differently when invoked as `jsh' (it
2005 turns on job control).
2008 File: bashref.info, Node: Csh Features, Next: Korn Shell Features, Prev: Bourne Shell Features, Up: Top
2010 C-Shell Style Features
2011 **********************
2013 The C-Shell ("`csh'") was created by Bill Joy at The University of
2014 California at Berkeley. It is generally considered to have better
2015 features for interactive use than the original Bourne shell. Some of
2016 the `csh' features present in Bash include job control, history
2017 expansion, `protected' redirection, and several variables to control
2018 the interactive behaviour of the shell (e.g., `IGNOREEOF').
2020 *Note Using History Interactively::, for details on history
2025 * Brace Expansion:: Expansion of expressions within braces.
2026 * Tilde Expansion:: Expansion of the ~ character.
2027 * C Shell Builtins:: Builtin commands adopted from the C Shell.
2028 * C Shell Variables:: Variables which Bash uses in essentially
2029 the same way as the C Shell.
2032 File: bashref.info, Node: Brace Expansion, Next: Tilde Expansion, Up: Csh Features
2037 Brace expansion is a mechanism by which arbitrary strings may be
2038 generated. This mechanism is similar to FILENAME EXPANSION (*note
2039 Filename Expansion::.), but the file names generated need not exist.
2040 Patterns to be brace expanded take the form of an optional PREAMBLE,
2041 followed by a series of comma-separated strings between a pair of
2042 braces, followed by an optional POSTAMBLE. The preamble is prepended
2043 to each string contained within the braces, and the postamble is then
2044 appended to each resulting string, expanding left to right.
2046 Brace expansions may be nested. The results of each expanded string
2047 are not sorted; left to right order is preserved. For example,
2048 bash$ echo a{d,c,b}e
2051 Brace expansion is performed before any other expansions, and any
2052 characters special to other expansions are preserved in the result. It
2053 is strictly textual. Bash does not apply any syntactic interpretation
2054 to the context of the expansion or the text between the braces.
2056 A correctly-formed brace expansion must contain unquoted opening and
2057 closing braces, and at least one unquoted comma. Any incorrectly
2058 formed brace expansion is left unchanged.
2060 This construct is typically used as shorthand when the common prefix
2061 of the strings to be generated is longer than in the above example:
2062 mkdir /usr/local/src/bash/{old,new,dist,bugs}
2064 chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}
2067 File: bashref.info, Node: Tilde Expansion, Next: C Shell Builtins, Prev: Brace Expansion, Up: Csh Features
2072 Bash has tilde (~) expansion, similar, but not identical, to that of
2073 `csh'. The following table shows what unquoted words beginning with a
2077 The current value of `$HOME'.
2083 The subdirectory `foo' of the home directory of the user `fred'.
2091 Bash will also tilde expand words following redirection operators
2092 and words following `=' in assignment statements.
2095 File: bashref.info, Node: C Shell Builtins, Next: C Shell Variables, Prev: Tilde Expansion, Up: Csh Features
2100 Bash has several builtin commands whose definition is very similar
2104 pushd [DIR | +N | -N] [-n]
2106 Save the current directory on a list and then `cd' to DIR. With no
2107 arguments, exchanges the top two directories.
2110 Brings the Nth directory (counting from the left of the list
2111 printed by `dirs') to the top of the list by rotating the
2115 Brings the Nth directory (counting from the right of the list
2116 printed by `dirs') to the top of the list by rotating the
2120 Suppresses the normal change of directory when adding
2121 directories to the stack, so that only the stack is
2125 Makes the current working directory be the top of the stack,
2126 and then `cd's to DIR. You can see the saved directory list
2127 with the `dirs' command.
2132 Pop the directory stack, and `cd' to the new top directory. When
2133 no arguments are given, `popd' removes the top directory from the
2134 stack and performs a `cd' to the new top directory. The elements
2135 are numbered from 0 starting at the first directory listed with
2136 `dirs'; i.e., `popd' is equivalent to `popd +0'.
2138 Removes the Nth directory (counting from the left of the list
2139 printed by `dirs'), starting with zero.
2142 Removes the Nth directory (counting from the right of the
2143 list printed by `dirs'), starting with zero.
2146 Suppresses the normal change of directory when removing
2147 directories from the stack, so that only the stack is
2151 dirs [+N | -N] [-clvp]
2152 Display the list of currently remembered directories. Directories
2153 find their way onto the list with the `pushd' command; you can get
2154 back up through the list with the `popd' command.
2156 Displays the Nth directory (counting from the left of the
2157 list printed by `dirs' when invoked without options), starting
2161 Displays the Nth directory (counting from the right of the
2162 list printed by `dirs' when invoked without options), starting
2166 Clears the directory stack by deleting all of the elements.
2169 Produces a longer listing; the default listing format uses a
2170 tilde to denote the home directory.
2173 Causes `dirs' to print the directory stack with one entry per
2177 Causes `dirs' to print the directory stack with one entry per
2178 line, prepending each entry with its index in the stack.
2182 history [-anrw] [FILENAME]
2185 Display the history list with line numbers. Lines prefixed with
2186 with a `*' have been modified. An argument of N says to list only
2187 the last N lines. Options, if supplied, have the following
2191 Write out the current history to the history file.
2194 Read the current history file and append its contents to the
2198 Append the new history lines (history lines entered since the
2199 beginning of the current Bash session) to the history file.
2202 Append the history lines not already read from the history
2203 file to the current history list. These are lines appended
2204 to the history file since the beginning of the current Bash
2208 Clear the history list. This may be combined with the other
2209 options to replace the history list completely.
2212 The ARGs are added to the end of the history list as a single
2216 Perform history substitution on the ARGs and display the
2217 result on the standard output, without storing the results in
2220 When the `-w', `-r', `-a', or `-n' option is used, if FILENAME is
2221 given, then it is used as the history file. If not, then the
2222 value of the `HISTFILE' variable is used.
2228 A synonym for `.' (*note Bourne Shell Builtins::.).
2231 File: bashref.info, Node: C Shell Variables, Prev: C Shell Builtins, Up: Csh Features
2237 If this variable is set, its value is used the number of
2238 consecutive `EOF's Bash will read before exiting. By default,
2239 Bash will exit upon reading a single `EOF'. If `IGNOREEOF' is not
2240 set to a numeric value, Bash acts as if its value were 10.
2243 File: bashref.info, Node: Korn Shell Features, Next: Bash Features, Prev: Csh Features, Up: Top
2245 Korn Shell Style Features
2246 *************************
2248 This section describes features primarily inspired by the Korn Shell
2249 (`ksh'). In some cases, the POSIX 1003.2 standard has adopted these
2250 commands and variables from the Korn Shell; Bash implements those
2251 features using the POSIX standard as a guide.
2255 * Korn Shell Constructs:: Shell grammar constructs adopted from the
2257 * Korn Shell Builtins:: Builtin commands adopted from the Korn Shell.
2258 * Korn Shell Variables:: Variables which Bash uses in essentially
2259 the same way as the Korn Shell.
2260 * Aliases:: Substituting one command for another.
2263 File: bashref.info, Node: Korn Shell Constructs, Next: Korn Shell Builtins, Up: Korn Shell Features
2265 Korn Shell Constructs
2266 =====================
2268 Bash includes the Korn Shell `select' construct. This construct
2269 allows the easy generation of menus. It has almost the same syntax as
2272 The syntax of the `select' command is:
2273 select NAME [in WORDS ...]; do COMMANDS; done
2275 The list of words following `in' is expanded, generating a list of
2276 items. The set of expanded words is printed on the standard error,
2277 each preceded by a number. If the `in WORDS' is omitted, the
2278 positional parameters are printed. The `PS3' prompt is then displayed
2279 and a line is read from the standard input. If the line consists of a
2280 number corresponding to one of the displayed words, then the value of
2281 NAME is set to that word. If the line is empty, the words and prompt
2282 are displayed again. If `EOF' is read, the `select' command completes.
2283 Any other value read causes NAME to be set to null. The line read is
2284 saved in the variable `REPLY'.
2286 The COMMANDS are executed after each selection until a `break' or
2287 `return' command is executed, at which point the `select' command
2290 Bash also has adopted command timing from the Korn shell. If the
2291 `time' reserved word precedes a pipeline or simple command, timing
2292 statistics for the pipeline are displayed when it completes. The
2293 statistics currently consist of elapsed (wall-clock) time and user and
2294 system time consumed by the command's execution.
2296 The use of `time' as a reserved word permits the timing of shell
2297 builtins, shell functions, and pipelines. An external `time' command
2298 cannot time these easily.
2301 File: bashref.info, Node: Korn Shell Builtins, Next: Korn Shell Variables, Prev: Korn Shell Constructs, Up: Korn Shell Features
2306 This section describes Bash builtin commands taken from `ksh'.
2309 `fc [-e ENAME] [-nlr] [FIRST] [LAST]'
2310 `fc -s [PAT=REP] [COMMAND]'
2312 Fix Command. In the first form, a range of commands from FIRST to
2313 LAST is selected from the history list. Both FIRST and LAST may
2314 be specified as a string (to locate the most recent command
2315 beginning with that string) or as a number (an index into the
2316 history list, where a negative number is used as an offset from the
2317 current command number). If LAST is not specified it is set to
2318 FIRST. If FIRST is not specified it is set to the previous
2319 command for editing and -16 for listing. If the `-l' flag is
2320 given, the commands are listed on standard output. The `-n' flag
2321 suppresses the command numbers when listing. The `-r' flag
2322 reverses the order of the listing. Otherwise, the editor given by
2323 ENAME is invoked on a file containing those commands. If ENAME is
2324 not given, the value of the following variable expansion is used:
2325 `${FCEDIT:-${EDITOR:-vi}}'. This says to use the value of the
2326 `FCEDIT' variable if set, or the value of the `EDITOR' variable if
2327 that is set, or `vi' if neither is set. When editing is complete,
2328 the edited commands are echoed and executed.
2330 In the second form, COMMAND is re-executed after each instance of
2331 PAT in the selected command is replaced by REP.
2333 A useful alias to use with the `fc' command is `r='fc -s'', so
2334 that typing `r cc' runs the last command beginning with `cc' and
2335 typing `r' re-executes the last command (*note Aliases::.).
2338 The `let' builtin allows arithmetic to be performed on shell
2339 variables. For details, refer to *Note Arithmetic Builtins::.
2342 The `typeset' command is supplied for compatibility with the Korn
2343 shell; however, it has been deprecated in favor of the `declare'
2344 command (*note Bash Builtins::.).
2347 File: bashref.info, Node: Korn Shell Variables, Next: Aliases, Prev: Korn Shell Builtins, Up: Korn Shell Features
2349 Korn Shell Variables
2350 ====================
2353 The default variable for the `read' builtin.
2356 Each time this parameter is referenced, a random integer between 0
2357 and 32767 is generated. Assigning a value to this variable seeds
2358 the random number generator.
2361 This variable expands to the number of seconds since the shell was
2362 started. Assignment to this variable resets the count to the
2363 value assigned, and the expanded value becomes the value assigned
2364 plus the number of seconds since the assignment.
2367 The value of this variable is used as the prompt for the `select'
2368 command. If this variable is not set, the `select' command
2372 This is the prompt printed before the command line is echoed when
2373 the `-x' option is set (*note The Set Builtin::.). The default is
2377 The current working directory as set by the `cd' builtin.
2380 The previous working directory as set by the `cd' builtin.
2383 If set to a value greater than zero, the value is interpreted as
2384 the number of seconds to wait for input after issuing the primary
2385 prompt. Bash terminates after that number of seconds if input does
2389 The line number in the script or shell function currently
2393 If this variable is set when Bash is invoked to execute a shell
2394 script, its value is expanded and used as the name of a startup
2395 file to read before executing the script. *Note Bash Startup
2399 The editor used as a default by the `fc' builtin command.
2402 File: bashref.info, Node: Aliases, Prev: Korn Shell Variables, Up: Korn Shell Features
2409 * Alias Builtins:: Builtins commands to maniuplate aliases.
2411 The shell maintains a list of ALIASES that may be set and unset with
2412 the `alias' and `unalias' builtin commands.
2414 The first word of each command, if unquoted, is checked to see if it
2415 has an alias. If so, that word is replaced by the text of the alias.
2416 The alias name and the replacement text may contain any valid shell
2417 input, including shell metacharacters, with the exception that the
2418 alias name may not contain =. The first word of the replacement text
2419 is tested for aliases, but a word that is identical to an alias being
2420 expanded is not expanded a second time. This means that one may alias
2421 `ls' to `"ls -F"', for instance, and Bash does not try to recursively
2422 expand the replacement text. If the last character of the alias value
2423 is a space or tab character, then the next command word following the
2424 alias is also checked for alias expansion.
2426 Aliases are created and listed with the `alias' command, and removed
2427 with the `unalias' command.
2429 There is no mechanism for using arguments in the replacement text,
2430 as in `csh'. If arguments are needed, a shell function should be used
2431 (*note Shell Functions::.).
2433 Aliases are not expanded when the shell is not interactive, unless
2434 the `expand_aliases' shell option is set using `shopt' (*note Bash
2437 The rules concerning the definition and use of aliases are somewhat
2438 confusing. Bash always reads at least one complete line of input
2439 before executing any of the commands on that line. Aliases are
2440 expanded when a command is read, not when it is executed. Therefore, an
2441 alias definition appearing on the same line as another command does not
2442 take effect until the next line of input is read. The commands
2443 following the alias definition on that line are not affected by the new
2444 alias. This behavior is also an issue when functions are executed.
2445 Aliases are expanded when the function definition is read, not when the
2446 function is executed, because a function definition is itself a
2447 compound command. As a consequence, aliases defined in a function are
2448 not available until after that function is executed. To be safe,
2449 always put alias definitions on a separate line, and do not use `alias'
2450 in compound commands.
2452 Note that for almost every purpose, aliases are superseded by shell
2456 File: bashref.info, Node: Alias Builtins, Up: Aliases
2462 alias [`-p'] [NAME[=VALUE] ...]
2464 Without arguments or with the `-p' option, `alias' prints the list
2465 of aliases on the standard output in a form that allows them to be
2466 reused as input. If arguments are supplied, an alias is defined
2467 for each NAME whose VALUE is given. If no VALUE is given, the name
2468 and value of the alias is printed.
2471 unalias [-a] [NAME ... ]
2473 Remove each NAME from the list of aliases. If `-a' is supplied,
2474 all aliases are removed.
2477 File: bashref.info, Node: Bash Features, Next: Job Control, Prev: Korn Shell Features, Up: Top
2482 This section describes features unique to Bash.
2486 * Invoking Bash:: Command line options that you can give
2488 * Bash Startup Files:: When and how Bash executes scripts.
2489 * Is This Shell Interactive?:: Determining the state of a running Bash.
2490 * Bash Builtins:: Table of builtins specific to Bash.
2491 * The Set Builtin:: This builtin is so overloaded it
2492 deserves its own section.
2493 * Bash Conditional Expressions:: Primitives used in composing expressions for
2495 * Bash Variables:: List of variables that exist in Bash.
2496 * Shell Arithmetic:: Arithmetic on shell variables.
2497 * Arrays:: Array Variables
2498 * Printing a Prompt:: Controlling the PS1 string.
2499 * The Restricted Shell:: A more controlled mode of shell execution.
2500 * Bash POSIX Mode:: Making Bash behave more closely to what
2501 the POSIX standard specifies.
2504 File: bashref.info, Node: Invoking Bash, Next: Bash Startup Files, Up: Bash Features
2509 bash [long-opt] [-ir] [-abefhkmnptuvxdBCDHP] [-o OPTION] [ARGUMENT ...]
2510 bash [long-opt] [-abefhkmnptuvxdBCDHP] [-o OPTION] -c STRING [ARGUMENT ...]
2511 bash [long-opt] -s [-abefhkmnptuvxdBCDHP] [-o OPTION] [ARGUMENT ...]
2513 In addition to the single-character shell command-line options
2514 (*note The Set Builtin::.), there are several multi-character options
2515 that you can use. These options must appear on the command line before
2516 the single-character options in order for them to be recognized.
2522 Display a usage message on standard output and exit sucessfully.
2525 Make this shell act as if it were directly invoked by login. This
2526 is equivalent to `exec -l bash' but can be issued from another
2527 shell, such as `csh'. If you wanted to replace your current login
2528 shell with a Bash login shell, you would say `exec bash --login'.
2531 Do not use the GNU Readline library (*note Command Line Editing::.)
2532 to read interactive command lines.
2535 Don't load the system-wide startup file `/etc/profile' or any of
2536 the personal initialization files `~/.bash_profile',
2537 `~/.bash_login', or `~/.profile' when Bash is invoked as a login
2541 Don't read the `~/.bashrc' initialization file in an interactive
2542 shell. This is on by default if the shell is invoked as `sh'.
2545 Change the behavior of Bash where the default operation differs
2546 from the POSIX 1003.2 standard to match the standard. This is
2547 intended to make Bash behave as a strict superset of that
2548 standard. *Note Bash POSIX Mode::, for a description of the Bash
2552 Execute commands from FILENAME (instead of `~/.bashrc') in an
2556 Make the shell a restricted shell (*note The Restricted Shell::.).
2562 Show version information for this instance of Bash on the standard
2563 output and exit successfully.
2565 There are several single-character options you can give which are
2566 not available with the `set' builtin.
2569 Read and execute commands from STRING after processing the
2570 options, then exit. Any remaining arguments are assigned to the
2571 positional parameters, starting with `$0'.
2574 Force the shell to run interactively.
2577 Make the shell restricted.
2580 If this flag is present, or if no arguments remain after option
2581 processing, then commands are read from the standard input. This
2582 option allows the positional parameters to be set when invoking an
2586 A list of all double-quoted strings preceded by `$' is printed on
2587 the standard ouput. These are the strings that are subject to
2588 language translation when the current locale is not `C' or `POSIX'
2589 (*note Locale Translation::.). This implies the `-n' option; no
2590 commands will be executed.
2592 An *interactive* shell is one whose input and output are both
2593 connected to terminals (as determined by `isatty()'), or one started
2594 with the `-i' option.
2596 If arguments remain after option processing, and neither the `-c'
2597 nor the `-s' option has been supplied, the first argument is assumed to
2598 be the name of a file containing shell commands (*note Shell
2599 Scripts::.). When Bash is invoked in this fashion, `$0' is set to the
2600 name of the file, and the positional parameters are set to the
2601 remaining arguments. Bash reads and executes commands from this file,
2602 then exits. Bash's exit status is the exit status of the last command
2603 executed in the script. If no commands are executed, the exit status
2607 File: bashref.info, Node: Bash Startup Files, Next: Is This Shell Interactive?, Prev: Invoking Bash, Up: Bash Features
2612 This section describs how bash executes its startup files. If any
2613 of the files exist but cannot be read, bash reports an error. Tildes
2614 are expanded in file names as described above under Tilde Expansion
2615 (*note Tilde Expansion::.).
2617 When Bash is invoked as a login shell, it first reads and executes
2618 commands from the file `/etc/profile', if that file exists. After
2619 reading that file, it looks for `~/.bash_profile', `~/.bash_login', and
2620 `~/.profile', in that order, and reads and executes commands from the
2621 first one that exists and is readable. The `--noprofile' option may be
2622 used when the shell is started to inhibit this behavior.
2624 When a login shell exits, Bash reads and executes commands from the
2625 file `~/.bash_logout', if it exists.
2627 When an interactive shell that is not a login shell is started, Bash
2628 reads and executes commands from `~/.bashrc', if that file exists.
2629 This may be inhibited by using the `--norc' option. The `--rcfile
2630 FILE' option will force Bash to read and execute commands from FILE
2631 instead of `~/.bashrc'.
2633 So, typically, your `~/.bash_profile' contains the line
2634 `if [ -f `~/.bashrc' ]; then . `~/.bashrc'; fi'
2636 after (or before) any login-specific initializations.
2638 When Bash is started non-interactively, to run a shell script, for
2639 example, it looks for the variable `BASH_ENV' in the environment,
2640 expands its value if it appears there, and uses the expanded value as
2641 the name of a file to read and execute. Bash behaves as if the
2642 following command were executed:
2643 `if [ -n "$BASH_ENV" ]; then . "$BASH_ENV"; fi'
2645 but the value of the `PATH' variable is not used to search for the file
2648 If Bash is invoked with the name `sh', it tries to mimic the startup
2649 behavior of historical versions of `sh' as closely as possible, while
2650 conforming to the POSIX standard as well.
2652 When invoked as a login shell, it first attempts to read and execute
2653 commands from `/etc/profile' and `~/.profile', in that order. The
2654 `--noprofile' option may be used to inhibit this behavior. When
2655 invoked as an interactive shell with the name `sh', `bash' looks for
2656 the variable `ENV', expands its value if it is defined, and uses the
2657 expanded value as the name of a file to read and execute. Since a
2658 shell invoked as `sh' does not attempt to read and execute commands
2659 from any other startup files, the `--rcfile' option has no effect. A
2660 non-interactive shell invoked with the name `sh' does not attempt to
2661 read any startup files.
2663 When invoked as `sh', Bash enters POSIX mode after the startup files
2666 When Bash is started in POSIX mode, as with the `--posix' command
2667 line option, it follows the POSIX standard for startup files. In this
2668 mode, the `ENV' variable is expanded and commands are read and executed
2669 from the file whose name is the expanded value. No other startup files
2670 are read. This is done by both interactive and non-interactive shells.
2672 Bash attempts to determine when it is being run by the remote shell
2673 daemon, usually `rshd'. If Bash determines it is being run by rshd, it
2674 reads and executes commands from `~/.bashrc', if that file exists and
2675 is readable. It will not do this if invoked as `sh'. The `--norc'
2676 option may be used to inhibit this behavior, and the `--rcfile' option
2677 may be used to force another file to be read, but rshd does not
2678 generally invoke the shell with those options or allow them to be
2682 File: bashref.info, Node: Is This Shell Interactive?, Next: Bash Builtins, Prev: Bash Startup Files, Up: Bash Features
2684 Is This Shell Interactive?
2685 ==========================
2687 As defined in *Note Invoking Bash::, an interactive shell is one
2688 whose input and output are both connected to terminals (as determined
2689 by `isatty(3)'), or one started with the `-i' option.
2691 You may wish to determine within a startup script whether Bash is
2692 running interactively or not. To do this, examine the variable `$PS1';
2693 it is unset in non-interactive shells, and set in interactive shells.
2696 if [ -z "$PS1" ]; then
2697 echo This shell is not interactive
2699 echo This shell is interactive
2703 File: bashref.info, Node: Bash Builtins, Next: The Set Builtin, Prev: Is This Shell Interactive?, Up: Bash Features
2705 Bash Builtin Commands
2706 =====================
2708 This section describes builtin commands which are unique to or have
2709 been extended in Bash.
2712 bind [-m KEYMAP] [-lpsvPSV] [-q NAME] [-r KEYSEQ]
2713 bind [-m KEYMAP] -f FILENAME
2714 bind [-m KEYMAP] KEYSEQ:FUNCTION-NAME
2716 Display current Readline (*note Command Line Editing::.) key and
2717 function bindings, or bind a key sequence to a Readline function
2718 or macro. The binding syntax accepted is identical to that of
2719 `.inputrc' (*note Readline Init File::.), but each binding must be
2720 passed as a separate argument: e.g.,
2721 `"\C-x\C-r":re-read-init-file'. Options, if supplied, have the
2725 Use KEYMAP as the keymap to be affected by the subsequent
2726 bindings. Acceptable KEYMAP names are `emacs',
2727 `emacs-standard', `emacs-meta', `emacs-ctlx', `vi',
2728 `vi-command', and `vi-insert'. `vi' is equivalent to
2729 `vi-command'; `emacs' is equivalent to `emacs-standard'.
2732 List the names of all Readline functions
2735 Display Readline function names and bindings in such a way
2736 that they can be re-read
2739 List current Readline function names and bindings
2742 Display Readline variable names and values in such a way that
2746 List current Readline variable names and values
2749 Display Readline key sequences bound to macros and the
2750 strings they output in such a way that they can be re-read
2753 Display Readline key sequences bound to macros and the
2757 Read key bindings from FILENAME
2760 Query about which keys invoke the named FUNCTION
2763 Remove any current binding for KEYSEQ
2766 builtin [SHELL-BUILTIN [ARGS]]
2767 Run a shell builtin. This is useful when you wish to rename a
2768 shell builtin to be a function, but need the functionality of the
2769 builtin within the function itself.
2772 command [-pVv] COMMAND [ARGS ...]
2773 Runs COMMAND with ARG ignoring shell functions. If you have a
2774 shell function called `ls', and you wish to call the command `ls',
2775 you can say `command ls'. The `-p' option means to use a default
2776 value for `$PATH' that is guaranteed to find all of the standard
2779 If either the `-V' or `-v' option is supplied, a description of
2780 COMMAND is printed. The `-v' option causes a single word
2781 indicating the command or file name used to invoke COMMAND to be
2782 printed; the `-V' option produces a more verbose description.
2785 declare [-afFrxi] [-p] [NAME[=VALUE]]
2787 Declare variables and give them attributes. If no NAMEs are
2788 given, then display the values of variables instead.
2790 The `-p' option will display the attributes and values of each
2791 NAME. When `-p' is used, additional options are ignored. The
2792 `-F' option inhibits the display of function definitions; only the
2793 function name and attributes are printed. `-F' implies `-f'. The
2794 following options can be used to restrict output to variables with
2795 the specified attributes or to give variables attributes:
2798 Each NAME is an array variable (*note Arrays::.).
2801 Use function names only.
2804 The variable is to be treated as an integer; arithmetic
2805 evaluation (*note Shell Arithmetic::.) is performed when the
2806 variable is assigned a value.
2809 Make NAMEs readonly. These names cannot then be assigned
2810 values by subsequent assignment statements.
2813 Mark each NAME for export to subsequent commands via the
2816 Using `+' instead of `-' turns off the attribute instead. When
2817 used in a function, `declare' makes each NAME local, as with the
2821 echo [-neE] [arg ...]
2822 Output the `arg's, separated by spaces, terminated with a newline.
2823 The return status is always 0. If `-n' is specified, the
2824 trailing newline is suppressed. If the `-e' option is given,
2825 interpretation of the following backslash-escaped characters is
2826 enabled. The `-E' option disables the interpretation of these
2827 escape characters, even on systems where they are interpreted by
2828 default. `echo' interprets the following escape sequences:
2836 suppress trailing newline
2860 the character whose ASCII code is `nnn' (octal)
2863 enable [-n] [-p] [-f FILENAME] [-ads] [NAME ...]
2864 Enable and disable builtin shell commands. This allows you to use
2865 a disk command which has the same name as a shell builtin. If
2866 `-n' is used, the NAMEs become disabled. Otherwise NAMEs are
2867 enabled. For example, to use the `test' binary found via `$PATH'
2868 instead of the shell builtin version, type `enable -n test'.
2870 If the `-p' option is supplied, or no NAME arguments appear, a
2871 list of shell builtins is printed. With no other arguments, the
2872 list consists of all enabled shell builtins. The `-a' option
2873 means to list each builtin with an indication of whether or not it
2876 The `-f' option means to load the new builtin command NAME from
2877 shared object FILENAME, on systems that support dynamic loading.
2878 The `-d' option will delete a builtin loaded with `-f'. If there
2879 are no options, a list of the shell builtins is displayed. The
2880 `-s' option restricts `enable' to the POSIX.2 special builtins.
2881 If `-s' is used with `-f', the new builtin becomes a special
2886 Display helpful information about builtin commands. If PATTERN is
2887 specified, `help' gives detailed help on all commands matching
2888 PATTERN, otherwise a list of the builtins is printed.
2892 For each argument, create a local variable called NAME, and give
2893 it VALUE. `local' can only be used within a function; it makes
2894 the variable NAME have a visible scope restricted to that function
2899 Exit a login shell, returning a status of N to the shell's parent.
2902 read [-a ANAME] [-p PROMPT] [-er] [NAME ...]
2903 One line is read from the standard input, and the first word is
2904 assigned to the first NAME, the second word to the second NAME,
2905 and so on, with leftover words assigned to the last NAME. Only
2906 the characters in the value of the `IFS' variable are recognized
2907 as word delimiters. If no names are supplied, the line read is
2908 assigned to the variable `REPLY'. The return code is zero, unless
2909 end-of-file is encountered. Options, if supplied, have the
2913 If this option is given, a backslash-newline pair is not
2914 ignored, and the backslash is considered to be part of the
2918 Display `prompt', without a trailing newline, before
2919 attempting to read any input. The prompt is displayed only
2920 if input is coming from a terminal.
2923 The words are assigned to sequential indices of the array
2924 variable ANAME, starting at 0.
2927 Readline (*note Command Line Editing::.) is used to obtain
2931 shopt [-pqsu] [-o] [OPTNAME ...]
2932 Toggle the values of variables controlling optional shell behavior.
2933 With no options, or with the `-p' option, a list of all settable
2934 options is displayed, with an indication of whether or not each is
2935 set. Other options have the following meanings:
2938 Enable (set) each OPTNAME
2941 Disable (unset) each OPTNAME.
2944 Suppresses normal output; the return status indicates whether
2945 the OPTNAME is set or unset. If multiple OPTNAME arguments
2946 are given with `-q', the return status is zero if all
2947 OPTNAMES are enabled; non-zero otherwise.
2950 Restricts the values of OPTNAME to be those defined for the
2951 `-o' option to the `set' builtin (*note The Set Builtin::.).
2953 If either of `-s' or `-u' is used with no OPTNAME arguments, the
2954 display is limited to those options which are set or unset,
2957 Unless otherwise noted, the `shopt' options are disabled (off) by
2960 The return status when listing options is zero if all OPTNAMES are
2961 enabled, non-zero otherwise. When setting or unsetting options,
2962 the return status is zero unless an OPTNAME is not a legal shell
2965 The list of `shopt' options is:
2967 If this is set, an argument to the `cd' builtin command that
2968 is not a directory is assumed to be the name of a variable
2969 whose value is the directory to change to.
2972 If set, minor errors in the spelling of a directory component
2973 in a `cd' command will be corrected. The errors checked for
2974 are transposed characters, a missing character, and a
2975 character too many. If a correction is found, the corrected
2976 path is printed, and the command proceeds. This option is
2977 enabled by default, but is only used by interactive shells.
2980 If this is set, Bash checks that a command found in the hash
2981 table exists before trying to execute it. If a hashed
2982 command no longer exists, a normal path search is performed.
2985 If set, Bash checks the window size after each command and,
2986 if necessary, updates the values of `LINES' and `COLUMNS'.
2989 If set, Bash attempts to save all lines of a multiple-line
2990 command in the same history entry. This allows easy
2991 re-editing of multi-line commands.
2994 If set, Bash includes filenames beginning with a `.' in the
2995 results of filename expansion.
2998 If this is set, a non-interactive shell will not exit if it
2999 cannot execute the file specified as an argument to the `exec'
3000 builtin command. An interactive shell does not exit if `exec'
3004 If set, the history list is appended to the file named by the
3005 value of the `HISTFILE' variable when the shell exits, rather
3006 than overwriting the file.
3009 If set, and Readline is being used, a user is given the
3010 opportunity to re-edit a failed history substitution.
3013 If set, and Readline is being used, the results of history
3014 substitution are not immediately passed to the shell parser.
3015 Instead, the resulting line is loaded into the Readline
3016 editing buffer, allowing further modification.
3019 If set, and Readline is being used, Bash will attempt to
3020 perform hostname completion when a word beginning with `@' is
3021 being completed (*note Commands For Completion::.).
3023 `interactive_comments'
3024 Allow a word beginning with `#' to cause that word and all
3025 remaining characters on that line to be ignored in an
3026 interactive shell. This option is enabled by default.
3029 If enabled, and the `cmdhist' option is enabled, multi-line
3030 commands are saved to the history with embedded newlines
3031 rather than using semicolon separators where possible.
3034 If set, and a file that Bash is checking for mail has been
3035 accessed since the last time it was checked, the message
3036 `"The mail in MAILFILE has been read"' is displayed.
3039 If set, Bash allows filename patterns which match no files to
3040 expand to a null string, rather than themselves.
3043 If set, prompt strings undergo variable and parameter
3044 expansion after being expanded (*note Printing a Prompt::.).
3045 This option is enabled by default.
3048 If this is set, the `shift' builtin prints an error message
3049 when the shift count exceeds the number of positional
3053 If set, the `source' builtin uses the value of `PATH' to find
3054 the directory containing the file supplied as an argument.
3055 This is enabled by default.
3058 type [-all] [-type | -path] [NAME ...]
3059 For each NAME, indicate how it would be interpreted if used as a
3062 If the `-type' flag is used, `type' returns a single word which is
3063 one of `alias', `function', `builtin', `file' or `keyword', if
3064 NAME is an alias, shell function, shell builtin, disk file, or
3065 shell reserved word, respectively. If the NAME is not found, then
3066 nothing is printed, and `type' returns a failure status.
3068 If the `-path' flag is used, `type' either returns the name of the
3069 disk file that would be executed, or nothing if `-type' would not
3072 If the `-all' flag is used, returns all of the places that contain
3073 an executable named FILE. This includes aliases and functions, if
3074 and only if the `-path' flag is not also used.
3076 `type' accepts `-a', `-t', and `-p' as equivalent to `-all',
3077 `-type', and `-path', respectively.
3080 ulimit [-acdflmnpstuvSH] [LIMIT]
3081 `ulimit' provides control over the resources available to processes
3082 started by the shell, on systems that allow such control. If an
3083 option is given, it is interpreted as follows:
3085 change and report the soft limit associated with a resource.
3088 change and report the hard limit associated with a resource.
3091 all current limits are reported.
3094 the maximum size of core files created.
3097 the maximum size of a process's data segment.
3100 the maximum size of files created by the shell.
3103 The maximum size that may be locked into memory.
3106 the maximum resident set size.
3109 the maximum number of open file descriptors.
3112 the pipe buffer size.
3115 the maximum stack size.
3118 the maximum amount of cpu time in seconds.
3121 the maximum number of processes available to a single user.
3124 the maximum amount of virtual memory available to the process.
3126 If LIMIT is given, it is the new value of the specified resource.
3127 Otherwise, the current value of the soft limit for the specified
3128 resource is printed, unless the `-H' option is supplied. When
3129 setting new limits, if neither `-H' nor `-S' is supplied, both the
3130 hard and soft limits are set. If no option is given, then `-f' is
3131 assumed. Values are in 1024-byte increments, except for `-t',
3132 which is in seconds, `-p', which is in units of 512-byte blocks,
3133 and `-n' and `-u', which are unscaled values.
3136 File: bashref.info, Node: The Set Builtin, Next: Bash Conditional Expressions, Prev: Bash Builtins, Up: Bash Features
3141 This builtin is so overloaded that it deserves its own section.
3144 set [-abefhkmnptuvxdBCHP] [-o OPTION] [ARGUMENT ...]
3147 Mark variables which are modified or created for export.
3150 Cause the status of terminated background jobs to be reported
3151 immediately, rather than before printing the next primary
3155 Exit immediately if a simple command exits with a non-zero
3159 Disable file name generation (globbing).
3162 Locate and remember (hash) commands as they are looked up for
3166 All arguments in the form of assignment statements are placed
3167 in the environment for a command, not just those that precede
3171 Job control is enabled (*note Job Control::.).
3174 Read commands but do not execute them.
3177 Set the flag corresponding to OPTION-NAME:
3186 use an `emacs'-style line editing interface (*note
3187 Command Line Editing::.).
3199 Enable command history, as described in *Note Bash
3200 History Facilities::. This option is on by default in
3204 the shell will not exit upon reading EOF.
3234 change the behavior of Bash where the default operation
3235 differs from the POSIX 1003.2 standard to match the
3236 standard. This is intended to make Bash behave as a
3237 strict superset of that standard.
3246 use a `vi'-style line editing interface.
3252 Turn on privileged mode. In this mode, the `$ENV' file is
3253 not processed, and shell functions are not inherited from the
3254 environment. This is enabled automatically on startup if the
3255 effective user (group) id is not equal to the real user
3256 (group) id. Turning this option off causes the effective user
3257 and group ids to be set to the real user and group ids.
3260 Exit after reading and executing one command.
3263 Treat unset variables as an error when substituting.
3266 Print shell input lines as they are read.
3269 Print commands and their arguments as they are executed.
3272 The shell will perform brace expansion (*note Brace
3273 Expansion::.). This option is on by default.
3276 Disallow output redirection to existing files.
3279 Enable `!' style history substitution (*note History
3280 Interaction::.). This flag is on by default for interactive
3284 If set, do not follow symbolic links when performing commands
3285 such as `cd' which change the current directory. The
3286 physical directory is used instead. By default, Bash follows
3287 the logical chain of directories when performing commands
3288 which change the current directory.
3290 For example, if `/usr/sys' is a link to `/usr/local/sys' then:
3291 $ cd /usr/sys; echo $PWD
3296 If `set -P' is on, then:
3297 $ cd /usr/sys; echo $PWD
3303 If no arguments follow this flag, then the positional
3304 parameters are unset. Otherwise, the positional parameters
3305 are set to the ARGUMENTS, even if some of them begin with a
3309 Signal the end of options, cause all remaining ARGUMENTS to
3310 be assigned to the positional parameters. The `-x' and `-v'
3311 options are turned off. If there are no arguments, the
3312 positional parameters remain unchanged.
3314 Using `+' rather than `-' causes these flags to be turned off.
3315 The flags can also be used upon invocation of the shell. The
3316 current set of flags may be found in `$-'.
3318 The remaining N ARGUMENTS are positional parameters and are
3319 assigned, in order, to `$1', `$2', ... `$N'. If no arguments are
3320 given, all shell variables are printed.
3323 File: bashref.info, Node: Bash Conditional Expressions, Next: Bash Variables, Prev: The Set Builtin, Up: Bash Features
3325 Bash Conditional Expressions
3326 ============================
3328 Conditional expressions are used by the `test' and `[' builtins.
3330 Expressions may be unary or binary. Unary expressions are often
3331 used to examine the status of a file. There are string operators and
3332 numeric comparison operators as well. Each operator and operand must
3333 be a separate argument. If FILE is of the form `/dev/fd/N', then file
3334 descriptor N is checked. Expressions are composed of the following
3338 True if FILE exists and is a block special file.
3341 True if FILE exists and is a character special file.
3344 True if FILE exists and is a directory.
3347 True if FILE exists.
3350 True if FILE exists and is a regular file.
3353 True if FILE exists and is set-group-id.
3356 True if FILE has its "sticky" bit set.
3359 True if FILE exists and is a symbolic link.
3362 True if FILE exists and is a named pipe.
3365 True if FILE exists and is readable.
3368 True if FILE exists and has a size greater than zero.
3371 True if FILE exists and is a socket.
3374 True if FD is opened on a terminal.
3377 True if FILE exists and its set-user-id bit is set.
3380 True if FILE exists and is writable.
3383 True if FILE exists and is executable.
3386 True if FILE exists and is owned by the effective user id.
3389 True if FILE exists and is owned by the effective group id.
3392 True if FILE1 is newer (according to modification date) than FILE2.
3395 True if FILE1 is older than FILE2.
3398 True if FILE1 and FILE2 have the same device and inode numbers.
3401 True if shell option OPTNAME is enabled. The list of options
3402 appears in the description of the `-o' option to the `set' builtin
3403 (*note The Set Builtin::.).
3406 True if the length of STRING is zero.
3410 True if the length of STRING is non-zero.
3413 True if the strings are equal. `==' may be used in place of `='.
3415 `STRING1 != STRING2'
3416 True if the strings are not equal.
3419 True if STRING1 sorts before STRING2 lexicographically.
3422 True if STRING1 sorts after STRING2 lexicographically.
3425 True if EXPR is false.
3428 True if both EXPR1 and EXPR2 are true.
3431 True if either EXPR1 and EXPR2 is true.
3434 `OP' is one of `-eq', `-ne', `-lt', `-le', `-gt', or `-ge'. These
3435 arithmetic binary operators return true if ARG1 is equal to, not
3436 equal to, less than, less than or equal to, greater than, or
3437 greater than or equal to ARG2, respectively. ARG1 and ARG2 may be
3438 positive or negative integers.
3440 The Bash `test' and `[' builtins evaluate conditional expressions
3441 using a set of rules based on the number of arguments. These are the
3445 The expression is false.
3448 The expression is true if and only if the argument is not null.
3451 If the first argument is `!', the expression is true if and only
3452 if the second argument is null. If the first argument is one of
3453 the listed unary operators, the expression is true if the unary
3454 test is true. If the first argument is not a legal unary
3455 operator, the expression is false.
3458 If the first argument is `!', the value is the negation of the
3459 two-argument test using the second and third arguments. If the
3460 second argument is one of the binary operators, the result of the
3461 expression is the result of the binary test using the first and
3462 third arguments as operands. If the first argument is exactly `('
3463 and the third argument is exactly `)', the result is the
3464 one-argument test of the second argument. Otherwise, the
3465 expression is false. The `-a' and `-o' operators are considered
3466 binary operators in this case.
3469 If the first argument is `!', the result is the negation of the
3470 three-argument expression composed of the remaining arguments.
3471 Otherwise, the expression is parsed and evaluated according to
3472 precedence. `-a' has a higher precedence than `-o'.
3475 The expression is parsed and evaluated according to precedence,
3476 with `-a' having a higher precedence than `-o'.
3479 File: bashref.info, Node: Bash Variables, Next: Shell Arithmetic, Prev: Bash Conditional Expressions, Up: Bash Features
3484 These variables are set or used by Bash, but other shells do not
3485 normally treat them specially.
3488 The value of this parameter is used as a format string specifying
3489 how the timing information for pipelines prefixed with the `time'
3490 reserved word should be displayed. The `%' character introduces an
3491 escape sequence that is expanded to a time value or other
3492 information. The escape sequences and their meanings are as
3493 follows; the braces denote optional portions.
3499 The elapsed time in seconds.
3502 The number of CPU seconds spent in user mode.
3505 The number of CPU seconds spent in system mode.
3508 The CPU percentage, computed as (%U + %S) / %R.
3510 The optional P is a digit specifying the precision, the number of
3511 fractional digits after a decimal point. A value of 0 causes no
3512 decimal point or fraction to be output. At most three places
3513 after the decimal point may be specified; values of P greater than
3514 3 are changed to 3. If P is not specified, the value 3 is used.
3516 The optional `l' specifies a longer format, including minutes, of
3517 the form MMmSS.FFs. The value of P determines whether or not the
3518 fraction is included.
3520 If this variable is not set, bash acts as if it had the value
3521 `$'\nreal\t%3lR\nuser\t%3lU\nsys\t%3lS''. If the value is null,
3522 no timing information is displayed. A trailing newline is added
3523 when the format string is displayed.
3526 Set to a value of `ignorespace', it means don't enter lines which
3527 begin with a space or tab into the history list. Set to a value
3528 of `ignoredups', it means don't enter lines which match the last
3529 entered line. A value of `ignoreboth' combines the two options.
3530 Unset, or set to any other value than those above, means to save
3531 all lines on the history list.
3534 A colon-separated list of patterns used to decide which command
3535 lines should be saved on the history list. Each pattern is
3536 anchored at the beginning of the line and must fully specify the
3537 line (no implicit `*' is appended). Each pattern is tested
3538 against the line after the checks specified by `HISTCONTROL' are
3539 applied. In addition to the normal shell pattern matching
3540 characters, `&' matches the previous history line. `&' may be
3541 escaped using a backslash. The backslash is removed before
3544 `HISTIGNORE' subsumes the function of `HISTCONTROL'. A pattern of
3545 `&' is identical to `ignoredups', and a pattern of `[ ]*' is
3546 identical to `ignorespace'. Combining these two patterns,
3547 separating them with a colon, provides the functionality of
3551 The name of the file to which the command history is saved. The
3552 default is `~/.bash_history'.
3555 If set, this is the maximum number of commands to remember in the
3559 The maximum number of lines contained in the history file. When
3560 this variable is assigned a value, the history file is truncated,
3561 if necessary, to contain no more than that number of lines. The
3562 default value is 500. The history file is also truncated to this
3563 size after writing it when an interactive shell exits.
3566 Up to three characters which control history expansion, quick
3567 substitution, and tokenization (*note History Interaction::.).
3568 The first character is the "history-expansion-char", that is, the
3569 character which signifies the start of a history expansion,
3570 normally `!'. The second character is the character which
3571 signifies `quick substitution' when seen as the first character on
3572 a line, normally `^'. The optional third character is the
3573 character which signifies the remainder of the line is a comment,
3574 when found as the first character of a word, usually `#'. The
3575 history comment character causes history substitution to be
3576 skipped for the remaining words on the line. It does not
3577 necessarily cause the shell parser to treat the rest of the line
3581 The history number, or index in the history list, of the current
3582 command. If `HISTCMD' is unset, it loses its special properties,
3583 even if it is subsequently reset.
3586 Contains the name of a file in the same format as `/etc/hosts' that
3587 should be read when the shell needs to complete a hostname. You
3588 can change the file interactively; the next time you attempt to
3589 complete a hostname, Bash will add the contents of the new file to
3590 the already existing database.
3593 How often (in seconds) that the shell should check for mail in the
3594 files specified in `MAILPATH'.
3597 If present, this contains a string which is a command to execute
3598 before the printing of each primary prompt (`$PS1').
3601 The numeric real user id of the current user.
3604 The numeric effective user id of the current user.
3607 The process id of the shell's parent process.
3610 The name of the current host.
3613 A string describing the machine Bash is running on.
3616 A string describing the operating system Bash is running on.
3619 A string that fully describes the system type on which Bash is
3620 executing, in the standard GNU CPU-COMPANY-SYSTEM format.
3623 A colon-separated list of enabled shell options. Each word in the
3624 list is a valid argument for the `-o' option to the `set' builtin
3625 command (*note The Set Builtin::.). The options appearing in
3626 `SHELLOPTS' are those reported as `on' by `set -o'. If this
3627 variable is in the environment when Bash starts up, each shell
3628 option in the list will be enabled before reading any startup
3629 files. This variable is readonly.
3632 A colon-separated list of suffixes to ignore when performing
3633 filename completion. A file name whose suffix matches one of the
3634 entries in `FIGNORE' is excluded from the list of matched file
3635 names. A sample value is `.o:~'
3638 A colon-separated list of patterns defining the set of filenames to
3639 be ignored by filename expansion. If a filename matched by a
3640 filename expansion pattern also matches one of the patterns in
3641 `GLOBIGNORE', it is removed from the list of matches.
3644 An array variable (*note Arrays::.) containing the current
3645 contents of the directory stack. Directories appear in the stack
3646 in the order they are displayed by the `dirs' builtin. Assigning
3647 to members of this array variable may be used to modify
3648 directories already in the stack, but the `pushd' and `popd'
3649 builtins must be used to add and remove directories. Assignment
3650 to this variable will not change the current directory. If
3651 `DIRSTACK' is unset, it loses its special properties, even if it
3652 is subsequently reset.
3655 An array variable (*note Arrays::.) containing a list of exit
3656 status values from the processes in the most-recently-executed
3657 foreground pipeline (which may contain only a single command).
3660 The name of the Readline startup file, overriding the default of
3664 The full filename used to execute the current instance of Bash.
3667 The version number of the current instance of Bash.
3670 An array variable whose members hold version information for this
3671 instance of Bash. The values assigned to the array members are as
3675 The major version number (the RELEASE).
3678 The minor version number (the VERSION).
3687 The release status (e.g., BETA1).
3690 The value of `MACHTYPE'.
3693 Incremented by one each time a new instance of Bash is started.
3694 This is intended to be an account of how deeply your Bash shells
3698 If set to the value 1, Bash displays error messages generated by
3699 the `getopts' builtin command.
3702 Used to determine the locale category for any category not
3703 specifically selected with a variable starting with `LC_'.
3706 This variable overrides the value of `LANG' and any other `LC_'
3707 variable specifying a locale category.
3710 This variable determines the locale used to translate double-quoted
3711 strings preceded by a `$'.
3714 Controls the action of the shell on receipt of an `EOF' character
3715 as the sole input. If set, then the value of it is the number of
3716 consecutive `EOF' characters that can be read as the first
3717 character on an input line before the shell will exit. If the
3718 variable exists but does not have a numeric value (or has no
3719 value) then the default is 10. If the variable does not exist,
3720 then `EOF' signifies the end of input to the shell. This is only
3721 in effect for interactive shells.
3724 File: bashref.info, Node: Shell Arithmetic, Next: Arrays, Prev: Bash Variables, Up: Bash Features
3731 * Arithmetic Evaluation:: How shell arithmetic works.
3732 * Arithmetic Expansion:: How to use arithmetic in shell expansions.
3733 * Arithmetic Builtins:: Builtin commands that use shell arithmetic.
3735 Bash includes several mechanisms to evaluate arithmetic expressions
3736 and display the result or use it as part of a command.
3739 File: bashref.info, Node: Arithmetic Evaluation, Next: Arithmetic Expansion, Up: Shell Arithmetic
3741 Arithmetic Evaluation
3742 ---------------------
3744 The shell allows arithmetic expressions to be evaluated, as one of
3745 the shell expansions or by the `let' builtin.
3747 Evaluation is done in long integers with no check for overflow,
3748 though division by 0 is trapped and flagged as an error. The following
3749 list of operators is grouped into levels of equal-precedence operators.
3750 The levels are listed in order of decreasing precedence.
3753 unary minus and plus
3756 logical and bitwise negation
3759 multiplication, division, remainder
3762 addition, subtraction
3765 left and right bitwise shifts
3771 equality and inequality
3777 bitwise exclusive OR
3788 `expr ? expr : expr'
3789 conditional evaluation
3791 `= *= /= %= += -= <<= >>= &= ^= |='
3794 Shell variables are allowed as operands; parameter expansion is
3795 performed before the expression is evaluated. The value of a parameter
3796 is coerced to a long integer within an expression. A shell variable
3797 need not have its integer attribute turned on to be used in an
3800 Constants with a leading 0 are interpreted as octal numbers. A
3801 leading `0x' or `0X' denotes hexadecimal. Otherwise, numbers take the
3802 form [BASE`#']N, where BASE is a decimal number between 2 and 64
3803 representing the arithmetic base, and N is a number in that base. If
3804 BASE is omitted, then base 10 is used. The digits greater than 9 are
3805 represented by the lowercase letters, the uppercase letters, `_', and
3806 `@', in that order. If BASE is less than or equal to 36, lowercase and
3807 uppercase letters may be used interchangably to represent numbers
3810 Operators are evaluated in order of precedence. Sub-expressions in
3811 parentheses are evaluated first and may override the precedence rules
3815 File: bashref.info, Node: Arithmetic Expansion, Next: Arithmetic Builtins, Prev: Arithmetic Evaluation, Up: Shell Arithmetic
3817 Arithmetic Expansion
3818 --------------------
3820 Arithmetic expansion allows the evaluation of an arithmetic
3821 expression and the substitution of the result. The format for
3822 arithmetic expansion is:
3826 The expression is treated as if it were within double quotes, but a
3827 double quote inside the braces or parentheses is not treated specially.
3828 All tokens in the expression undergo parameter expansion, command
3829 substitution, and quote removal. Arithmetic substitutions may be
3832 The evaluation is performed according to the rules listed above. If
3833 the expression is invalid, Bash prints a message indicating failure and
3834 no substitution occurs.
3837 File: bashref.info, Node: Arithmetic Builtins, Prev: Arithmetic Expansion, Up: Shell Arithmetic
3843 let EXPRESSION [EXPRESSION]
3844 The `let' builtin allows arithmetic to be performed on shell
3845 variables. Each EXPRESSION is evaluated according to the rules
3846 given previously (*note Arithmetic Evaluation::.). If the last
3847 EXPRESSION evaluates to 0, `let' returns 1; otherwise 0 is
3851 File: bashref.info, Node: Arrays, Next: Printing a Prompt, Prev: Shell Arithmetic, Up: Bash Features
3856 Bash provides one-dimensional array variables. Any variable may be
3857 used as an array; the `declare' builtin will explicitly declare an
3858 array. There is no maximum limit on the size of an array, nor any
3859 requirement that members be indexed or assigned contiguously. Arrays
3862 An array is created automatically if any variable is assigned to
3864 name[SUBSCRIPT]=VALUE
3866 The SUBSCRIPT is treated as an arithmetic expression that must evaluate
3867 to a number greater than or equal to zero. To explicitly declare an
3872 declare -a NAME[SUBSCRIPT]
3874 is also accepted; the SUBSCRIPT is ignored. Attributes may be
3875 specified for an array variable using the `declare' and `readonly'
3876 builtins. Each attribute applies to all members of an array.
3878 Arrays are assigned to using compound assignments of the form
3879 name=(value1 ... valueN)
3881 where each VALUE is of the form `[[SUBSCRIPT]=]'STRING. If the
3882 optional subscript is supplied, that index is assigned to; otherwise
3883 the index of the element assigned is the last index assigned to by the
3884 statement plus one. Indexing starts at zero. This syntax is also
3885 accepted by the `declare' builtin. Individual array elements may be
3886 assigned to using the `name['SUBSCRIPT`]='VALUE syntax introduced above.
3888 Any element of an array may be referenced using
3889 `${name['SUBSCRIPT`]}'. The braces are required to avoid conflicts
3890 with the shell's filename expansion operators. If the SUBSCRIPT is `@'
3891 or `*', the word expands to all members of the array NAME. These
3892 subscripts differ only when the word appears within double quotes. If
3893 the word is double-quoted, `${name[*]}' expands to a single word with
3894 the value of each array member separated by the first character of the
3895 `IFS' variable, and `${name[@]}' expands each element of NAME to a
3896 separate word. When there are no array members, `${name[@]}' expands
3897 to nothing. This is analogous to the expansion of the special
3898 parameters `@' and `*'. `${#name['SUBSCRIPT`]}' expands to the length
3899 of `${name['SUBSCRIPT`]}'. If SUBSCRIPT is `@' or `*', the expansion
3900 is the number of elements in the array. Referencing an array variable
3901 without a subscript is equivalent to referencing element zero.
3903 The `unset' builtin is used to destroy arrays. `unset'
3904 NAME[SUBSCRIPT] destroys the array element at index SUBSCRIPT. `unset'
3905 NAME, where NAME is an array, removes the entire array. A subscript of
3906 `*' or `@' also removes the entire array.
3908 The `declare', `local', and `readonly' builtins each accept a `-a'
3909 option to specify an array. The `read' builtin accepts a `-a' option
3910 to assign a list of words read from the standard input to an array, and
3911 can read values from the standard input into individual array elements.
3912 The `set' and `declare' builtins display array values in a way that
3913 allows them to be reused as input.
3916 File: bashref.info, Node: Printing a Prompt, Next: The Restricted Shell, Prev: Arrays, Up: Bash Features
3918 Controlling the Prompt
3919 ======================
3921 The value of the variable `PROMPT_COMMAND' is examined just before
3922 Bash prints each primary prompt. If it is set and non-null, then the
3923 value is executed just as if you had typed it on the command line.
3925 In addition, the following table describes the special characters
3926 which can appear in the prompt variables:
3932 the date, in "Weekday Month Date" format (e.g., "Tue May 26").
3935 an escape character.
3938 the hostname, up to the first `.'.
3947 the name of the shell, the basename of `$0' (the portion following
3951 the time, in 24-hour HH:MM:SS format.
3954 the time, in 12-hour HH:MM:SS format.
3957 the time, in 12-hour am/pm format.
3960 the version of Bash (e.g., 2.00)
3963 the release of Bash, version + patchlevel (e.g., 2.00.0)
3966 the current working directory.
3969 the basename of `$PWD'.
3975 the history number of this command.
3978 the command number of this command.
3981 if the effective uid is 0, `#', otherwise `$'.
3984 the character corresponding to the octal number `nnn'.
3990 begin a sequence of non-printing characters. This could be used to
3991 embed a terminal control sequence into the prompt.
3994 end a sequence of non-printing characters.
3997 File: bashref.info, Node: The Restricted Shell, Next: Bash POSIX Mode, Prev: Printing a Prompt, Up: Bash Features
3999 The Restricted Shell
4000 ====================
4002 If Bash is started with the name `rbash', or the `--restricted'
4003 option is supplied at invocation, the shell becomes restricted. A
4004 restricted shell is used to set up an environment more controlled than
4005 the standard shell. A restricted shell behaves identically to `bash'
4006 with the exception that the following are disallowed:
4007 * Changing directories with the `cd' builtin.
4009 * Setting or unsetting the values of the `SHELL' or `PATH' variables.
4011 * Specifying command names containing slashes.
4013 * Specifying a filename containing a slash as an argument to the `.'
4016 * Importing function definitions from the shell environment at
4019 * Redirecting output using the `>', `>|', `<>', `>&', `&>', and `>>'
4020 redirection operators.
4022 * Using the `exec' builtin to replace the shell with another command.
4024 * Adding or deleting builtin commands with the `-f' and `-d' options
4025 to the `enable' builtin.
4027 * Specifying the `-p' option to the `command' builtin.
4029 * Turning off restricted mode with `set +r'.
4032 File: bashref.info, Node: Bash POSIX Mode, Prev: The Restricted Shell, Up: Bash Features
4037 Starting Bash with the `--posix' command-line option or executing
4038 `set -o posix' while Bash is running will cause Bash to conform more
4039 closely to the POSIX.2 standard by changing the behavior to match that
4040 specified by POSIX.2 in areas where the Bash default differs.
4042 The following list is what's changed when `POSIX mode' is in effect:
4044 1. When a command in the hash table no longer exists, Bash will
4045 re-search `$PATH' to find the new location. This is also
4046 available with `shopt -s checkhash'.
4048 2. The `>&' redirection does not redirect stdout and stderr.
4050 3. The message printed by the job control code and builtins when a job
4051 exits with a non-zero status is `Done(status)'.
4053 4. Reserved words may not be aliased.
4055 5. The POSIX.2 `PS1' and `PS2' expansions of `!' to the history
4056 number and `!!' to `!' are enabled, and parameter expansion is
4057 performed on the value regardless of the setting of the
4058 `promptvars' option.
4060 6. Interactive comments are enabled by default. (Note that Bash has
4061 them on by default anyway.)
4063 7. The POSIX.2 startup files are executed (`$ENV') rather than the
4066 8. Tilde expansion is only performed on assignments preceding a
4067 command name, rather than on all assignment statements on the line.
4069 9. The default history file is `~/.sh_history' (this is the default
4070 value of `$HISTFILE').
4072 10. The output of `kill -l' prints all the signal names on a single
4073 line, separated by spaces.
4075 11. Non-interactive shells exit if FILENAME in `.' FILENAME is not
4078 12. Redirection operators do not perform filename expansion on the word
4079 in the redirection unless the shell is interactive.
4081 13. Function names must be valid shell `name's. That is, they may not
4082 contain characters other than letters, digits, and underscores, and
4083 may not start with a digit. Declaring a function with an illegal
4084 name causes a fatal syntax error in non-interactive shells.
4086 14. POSIX.2 `special' builtins are found before shell functions during
4089 15. If a POSIX.2 special builtin returns an error status, a
4090 non-interactive shell exits. The fatal errors are those listed in
4091 the POSIX.2 standard, and include things like passing incorrect
4092 options, redirection errors, variable assignment errors for
4093 assignments preceding the command name, and so on.
4095 16. If the `cd' builtin finds a directory to change to using
4096 `$CDPATH', the value it assigns to the `PWD' variable does not
4097 contain any symbolic links, as if `cd -P' had been executed.
4099 17. A non-interactive shell exits with an error status if a variable
4100 assignment error occurs when no command name follows the assignment
4101 statements. A variable assignment error occurs, for example, when
4102 trying to assign a value to a read-only variable.
4104 18. A non-interactive shell exits with an error status if the iteration
4105 variable in a `for' statement or the selection variable in a
4106 `select' statement is a read-only variable.
4108 19. Process substitution is not available.
4110 20. Assignment statements preceding POSIX.2 `special' builtins persist
4111 in the shell environment after the builtin completes.
4114 There is other POSIX.2 behavior that Bash does not implement.
4117 1. Assignment statements affect the execution environment of all
4118 builtins, not just special ones.
4121 File: bashref.info, Node: Job Control, Next: Using History Interactively, Prev: Bash Features, Up: Top
4126 This chapter disusses what job control is, how it works, and how
4127 Bash allows you to access its facilities.
4131 * Job Control Basics:: How job control works.
4132 * Job Control Builtins:: Bash builtin commands used to interact
4134 * Job Control Variables:: Variables Bash uses to customize job
4138 File: bashref.info, Node: Job Control Basics, Next: Job Control Builtins, Up: Job Control
4143 Job control refers to the ability to selectively stop (suspend) the
4144 execution of processes and continue (resume) their execution at a later
4145 point. A user typically employs this facility via an interactive
4146 interface supplied jointly by the system's terminal driver and Bash.
4148 The shell associates a JOB with each pipeline. It keeps a table of
4149 currently executing jobs, which may be listed with the `jobs' command.
4150 When Bash starts a job asynchronously (in the background), it prints a
4151 line that looks like:
4154 indicating that this job is job number 1 and that the process ID of the
4155 last process in the pipeline associated with this job is 25647. All of
4156 the processes in a single pipeline are members of the same job. Bash
4157 uses the JOB abstraction as the basis for job control.
4159 To facilitate the implementation of the user interface to job
4160 control, the system maintains the notion of a current terminal process
4161 group ID. Members of this process group (processes whose process group
4162 ID is equal to the current terminal process group ID) receive
4163 keyboard-generated signals such as `SIGINT'. These processes are said
4164 to be in the foreground. Background processes are those whose process
4165 group ID differs from the terminal's; such processes are immune to
4166 keyboard-generated signals. Only foreground processes are allowed to
4167 read from or write to the terminal. Background processes which attempt
4168 to read from (write to) the terminal are sent a `SIGTTIN' (`SIGTTOU')
4169 signal by the terminal driver, which, unless caught, suspends the
4172 If the operating system on which Bash is running supports job
4173 control, Bash allows you to use it. Typing the SUSPEND character
4174 (typically `^Z', Control-Z) while a process is running causes that
4175 process to be stopped and returns you to Bash. Typing the DELAYED
4176 SUSPEND character (typically `^Y', Control-Y) causes the process to be
4177 stopped when it attempts to read input from the terminal, and control to
4178 be returned to Bash. You may then manipulate the state of this job,
4179 using the `bg' command to continue it in the background, the `fg'
4180 command to continue it in the foreground, or the `kill' command to kill
4181 it. A `^Z' takes effect immediately, and has the additional side
4182 effect of causing pending output and typeahead to be discarded.
4184 There are a number of ways to refer to a job in the shell. The
4185 character `%' introduces a job name. Job number `n' may be referred to
4186 as `%n'. A job may also be referred to using a prefix of the name used
4187 to start it, or using a substring that appears in its command line.
4188 For example, `%ce' refers to a stopped `ce' job. Using `%?ce', on the
4189 other hand, refers to any job containing the string `ce' in its command
4190 line. If the prefix or substring matches more than one job, Bash
4191 reports an error. The symbols `%%' and `%+' refer to the shell's
4192 notion of the current job, which is the last job stopped while it was
4193 in the foreground. The previous job may be referenced using `%-'. In
4194 output pertaining to jobs (e.g., the output of the `jobs' command), the
4195 current job is always flagged with a `+', and the previous job with a
4198 Simply naming a job can be used to bring it into the foreground:
4199 `%1' is a synonym for `fg %1', bringing job 1 from the background into
4200 the foreground. Similarly, `%1 &' resumes job 1 in the background,
4201 equivalent to `bg %1'
4203 The shell learns immediately whenever a job changes state.
4204 Normally, Bash waits until it is about to print a prompt before
4205 reporting changes in a job's status so as to not interrupt any other
4206 output. If the the `-b' option to the `set' builtin is set, Bash
4207 reports such changes immediately (*note The Set Builtin::.).
4209 If you attempt to exit Bash while jobs are stopped, the shell prints
4210 a message warning you that you have stopped jobs. You may then use the
4211 `jobs' command to inspect their status. If you do this, or try to exit
4212 again immediately, you are not warned again, and the stopped jobs are
4216 File: bashref.info, Node: Job Control Builtins, Next: Job Control Variables, Prev: Job Control Basics, Up: Job Control
4218 Job Control Builtins
4219 ====================
4223 Place JOBSPEC into the background, as if it had been started with
4224 `&'. If JOBSPEC is not supplied, the current job is used.
4228 Bring JOBSPEC into the foreground and make it the current job. If
4229 JOBSPEC is not supplied, the current job is used.
4232 jobs [-lpnrs] [JOBSPEC]
4233 jobs -x COMMAND [JOBSPEC]
4235 The first form lists the active jobs. The options have the
4239 List process IDs in addition to the normal information
4242 Display information only about jobs that have changed status
4243 since you were last notified of their status.
4246 List only the process ID of the job's process group leader.
4249 Restrict output to running jobs.
4252 Restrict output to stopped jobs.
4254 If JOBSPEC is given, output is restricted to information about
4255 that job. If JOBSPEC is not supplied, the status of all jobs is
4258 If the `-x' option is supplied, `jobs' replaces any JOBSPEC found
4259 in COMMAND or ARGUMENTS with the corresponding process group ID,
4260 and executes COMMAND, passing it ARGUMENTs, returning its exit
4264 kill [-s SIGSPEC] [-n SIGNUM] [-SIGSPEC] JOBSPEC
4266 Send a signal specified by SIGSPEC or SIGNUM to the process named
4267 by JOBSPEC. SIGSPEC is either a signal name such as `SIGINT' or a
4268 signal number; SIGNUM is a signal number. If SIGSPEC and SIGNUM
4269 are not present, `SIGTERM' is used. The `-l' option lists the
4270 signal names, or the signal name corresponding to SIGSPEC.
4274 Wait until the child process specified by process ID PID or job
4275 specification JOBSPEC exits and report its exit status. If a job
4276 spec is given, all processes in the job are waited for. If no
4277 arguments are given, all currently active child processes are
4281 disown [-h] [JOBSPEC ...]
4282 Without options, each JOBSPEC is removed from the table of active
4283 jobs. If the `-h' option is given, the job is not removed from
4284 the table, but is marked so that `SIGHUP' is not sent to the job
4285 if the shell receives a `SIGHUP'. If JOBSPEC is not present, the
4286 current job is used.
4290 Suspend the execution of this shell until it receives a `SIGCONT'
4291 signal. The `-f' option means to suspend even if the shell is a
4294 When job control is not active, the `kill' and `wait' builtins do
4295 not accept JOBSPEC arguments. They must be supplied process IDs.
4298 File: bashref.info, Node: Job Control Variables, Prev: Job Control Builtins, Up: Job Control
4300 Job Control Variables
4301 =====================
4304 This variable controls how the shell interacts with the user and
4305 job control. If this variable exists then single word simple
4306 commands without redirects are treated as candidates for resumption
4307 of an existing job. There is no ambiguity allowed; if you have
4308 more than one job beginning with the string that you have typed,
4309 then the most recently accessed job will be selected. The name of
4310 a stopped job, in this context, is the command line used to start
4311 it. If this variable is set to the value `exact', the string
4312 supplied must match the name of a stopped job exactly; if set to
4313 `substring', the string supplied needs to match a substring of the
4314 name of a stopped job. The `substring' value provides
4315 functionality analogous to the `%?' job ID (*note Job Control
4316 Basics::.). If set to any other value, the supplied string must
4317 be a prefix of a stopped job's name; this provides functionality
4318 analogous to the `%' job ID.
4321 File: bashref.info, Node: Using History Interactively, Next: Command Line Editing, Prev: Job Control, Up: Top
4323 Using History Interactively
4324 ***************************
4326 This chapter describes how to use the GNU History Library
4327 interactively, from a user's standpoint. It should be considered a
4328 user's guide. For information on using the GNU History Library in your
4329 own programs, see the GNU Readline Library Manual.
4333 * Bash History Facilities:: How Bash lets you manipulate your command
4335 * History Interaction:: What it feels like using History as a user.
4338 File: bashref.info, Node: Bash History Facilities, Next: History Interaction, Up: Using History Interactively
4340 Bash History Facilities
4341 =======================
4343 When the `-o history' option to the `set' builtin is enabled (*note
4344 The Set Builtin::.), the shell provides access to the COMMAND HISTORY,
4345 the list of commands previously typed. The text of the last `HISTSIZE'
4346 commands (default 500) is saved in a history list. The shell stores
4347 each command in the history list prior to parameter and variable
4348 expansion but after history expansion is performed, subject to the
4349 values of the shell variables `HISTIGNORE' and `HISTCONTROL'. When the
4350 shell starts up, the history is initialized from the file named by the
4351 `HISTFILE' variable (default `~/.bash_history'). `HISTFILE' is
4352 truncated, if necessary, to contain no more than the number of lines
4353 specified by the value of the `HISTFILESIZE' variable. When an
4354 interactive shell exits, the last `HISTSIZE' lines are copied from the
4355 history list to `HISTFILE'. If the `histappend' shell option is set
4356 (*note Bash Builtins::.), the lines are appended to the history file,
4357 otherwise the history file is overwritten. If `HISTFILE' is unset, or
4358 if the history file is unwritable, the history is not saved. After
4359 saving the history, the history file is truncated to contain no more
4360 than `$HISTFILESIZE' lines. If `HISTFILESIZE' is not set, no
4361 truncation is performed.
4363 The builtin command `fc' (*note Korn Shell Builtins::.) may be used
4364 to list or edit and re-execute a portion of the history list. The
4365 `history' builtin (*note C Shell Builtins::.) can be used to display or
4366 modify the history list and manipulate the history file. When using
4367 the command-line editing, search commands are available in each editing
4368 mode that provide access to the history list.
4370 The shell allows control over which commands are saved on the history
4371 list. The `HISTCONTROL' and `HISTIGNORE' variables may be set to cause
4372 the shell to save only a subset of the commands entered. The `cmdhist'
4373 shell option, if enabled, causes the shell to attempt to save each line
4374 of a multi-line command in the same history entry, adding semicolons
4375 where necessary to preserve syntactic correctness. The `lithist' shell
4376 option causes the shell to save the command with embedded newlines
4377 instead of semicolons. *Note Bash Builtins:: for a description of
4381 File: bashref.info, Node: History Interaction, Prev: Bash History Facilities, Up: Using History Interactively
4383 Interactive History Expansion
4384 =============================
4386 The History library provides a history expansion feature that is
4387 similar to the history expansion provided by `csh'. This section
4388 describes the syntax used to manipulate the history information.
4390 History expansions introduce words from the history list into the
4391 input stream, making it easy to repeat commands, insert the arguments
4392 to a previous command into the current input line, or fix errors in
4393 previous commands quickly.
4395 History expansion takes place in two parts. The first is to
4396 determine which line from the previous history should be used during
4397 substitution. The second is to select portions of that line for
4398 inclusion into the current one. The line selected from the previous
4399 history is called the "event", and the portions of that line that are
4400 acted upon are called "words". Various "modifiers" are available to
4401 manipulate the selected words. The line is broken into words in the
4402 same fashion that Bash does, so that several English (or Unix) words
4403 surrounded by quotes are considered as one word. History expansions
4404 are introduced by the appearance of the history expansion character,
4405 which is `!' by default. Only `\' and `'' may be used to escape the
4406 history expansion character.
4408 Several shell options settable with the `shopt' builtin (*note Bash
4409 Builtins::.) may be used to tailor the behavior of history expansion.
4410 If the `histverify' shell option is enabled, and Readline is being
4411 used, history substitutions are not immediately passed to the shell
4412 parser. Instead, the expanded line is reloaded into the Readline
4413 editing buffer for further modification. If Readline is being used,
4414 and the `histreedit' shell option is enabled, a failed history
4415 expansion will be reloaded into the Readline editing buffer for
4416 correction. The `-p' option to the `history' builtin command may be
4417 used to see what a history expansion will do before using it. The `-s'
4418 option to the `history' builtin may be used to add commands to the end
4419 of the history list without actually executing them, so that they are
4420 available for subsequent recall.
4422 The shell allows control of the various characters used by the
4423 history expansion mechanism with the `histchars' variable.
4427 * Event Designators:: How to specify which history line to use.
4428 * Word Designators:: Specifying which words are of interest.
4429 * Modifiers:: Modifying the results of substitution.
4432 File: bashref.info, Node: Event Designators, Next: Word Designators, Up: History Interaction
4437 An event designator is a reference to a command line entry in the
4441 Start a history substitution, except when followed by a space, tab,
4442 the end of the line, = or (.
4445 Refer to command line N.
4448 Refer to the command N lines back.
4451 Refer to the previous command. This is a synonym for `!-1'.
4454 Refer to the most recent command starting with STRING.
4457 Refer to the most recent command containing STRING. The trailing
4458 `?' may be omitted if the STRING is followed immediately by a
4462 Quick Substitution. Repeat the last command, replacing STRING1
4463 with STRING2. Equivalent to `!!:s/STRING1/STRING2/'.
4466 The entire command line typed so far.
4469 File: bashref.info, Node: Word Designators, Next: Modifiers, Prev: Event Designators, Up: History Interaction
4474 Word designators are used to select desired words from the event. A
4475 `:' separates the event specification from the word designator. It can
4476 be omitted if the word designator begins with a `^', `$', `*', `-', or
4477 `%'. Words are numbered from the beginning of the line, with the first
4478 word being denoted by 0 (zero). Words are inserted into the current
4479 line separated by single spaces.
4482 The `0'th word. For many applications, this is the command word.
4488 The first argument; that is, word 1.
4494 The word matched by the most recent `?STRING?' search.
4497 A range of words; `-Y' abbreviates `0-Y'.
4500 All of the words, except the `0'th. This is a synonym for `1-$'.
4501 It is not an error to use `*' if there is just one word in the
4502 event; the empty string is returned in that case.
4508 Abbreviates `X-$' like `X*', but omits the last word.
4510 If a word designator is supplied without an event specification, the
4511 previous command is used as the event.
4514 File: bashref.info, Node: Modifiers, Prev: Word Designators, Up: History Interaction
4519 After the optional word designator, you can add a sequence of one or
4520 more of the following modifiers, each preceded by a `:'.
4523 Remove a trailing pathname component, leaving only the head.
4526 Remove all leading pathname components, leaving the tail.
4529 Remove a trailing suffix of the form `.SUFFIX', leaving the
4533 Remove all but the trailing suffix.
4536 Print the new command but do not execute it.
4539 Quote the substituted words, escaping further substitutions.
4542 Quote the substituted words as with `q', but break into words at
4543 spaces, tabs, and newlines.
4546 Substitute NEW for the first occurrence of OLD in the event line.
4547 Any delimiter may be used in place of `/'. The delimiter may be
4548 quoted in OLD and NEW with a single backslash. If `&' appears in
4549 NEW, it is replaced by OLD. A single backslash will quote the
4550 `&'. The final delimiter is optional if it is the last character
4554 Repeat the previous substitution.
4557 Cause changes to be applied over the entire event line. Used in
4558 conjunction with `s', as in `gs/OLD/NEW/', or with `&'.
4561 File: bashref.info, Node: Command Line Editing, Next: Installing Bash, Prev: Using History Interactively, Up: Top
4563 Command Line Editing
4564 ********************
4566 This chapter describes the basic features of the GNU command line
4571 * Introduction and Notation:: Notation used in this text.
4572 * Readline Interaction:: The minimum set of commands for editing a line.
4573 * Readline Init File:: Customizing Readline from a user's view.
4574 * Bindable Readline Commands:: A description of most of the Readline commands
4575 available for binding
4576 * Readline vi Mode:: A short description of how to make Readline
4577 behave like the vi editor.
4580 File: bashref.info, Node: Introduction and Notation, Next: Readline Interaction, Up: Command Line Editing
4582 Introduction to Line Editing
4583 ============================
4585 The following paragraphs describe the notation used to represent
4588 The text C-k is read as `Control-K' and describes the character
4589 produced when the k key is pressed while the Control key is depressed.
4591 The text M-k is read as `Meta-K' and describes the character
4592 produced when the meta key (if you have one) is depressed, and the k
4593 key is pressed. If you do not have a meta key, the identical keystroke
4594 can be generated by typing ESC first, and then typing k. Either
4595 process is known as "metafying" the k key.
4597 The text M-C-k is read as `Meta-Control-k' and describes the
4598 character produced by "metafying" C-k.
4600 In addition, several keys have their own names. Specifically, DEL,
4601 ESC, LFD, SPC, RET, and TAB all stand for themselves when seen in this
4602 text, or in an init file (*note Readline Init File::.).
4605 File: bashref.info, Node: Readline Interaction, Next: Readline Init File, Prev: Introduction and Notation, Up: Command Line Editing
4607 Readline Interaction
4608 ====================
4610 Often during an interactive session you type in a long line of text,
4611 only to notice that the first word on the line is misspelled. The
4612 Readline library gives you a set of commands for manipulating the text
4613 as you type it in, allowing you to just fix your typo, and not forcing
4614 you to retype the majority of the line. Using these editing commands,
4615 you move the cursor to the place that needs correction, and delete or
4616 insert the text of the corrections. Then, when you are satisfied with
4617 the line, you simply press RETURN. You do not have to be at the end of
4618 the line to press RETURN; the entire line is accepted regardless of the
4619 location of the cursor within the line.
4623 * Readline Bare Essentials:: The least you need to know about Readline.
4624 * Readline Movement Commands:: Moving about the input line.
4625 * Readline Killing Commands:: How to delete text, and how to get it back!
4626 * Readline Arguments:: Giving numeric arguments to commands.
4627 * Searching:: Searching through previous lines.
4630 File: bashref.info, Node: Readline Bare Essentials, Next: Readline Movement Commands, Up: Readline Interaction
4632 Readline Bare Essentials
4633 ------------------------
4635 In order to enter characters into the line, simply type them. The
4636 typed character appears where the cursor was, and then the cursor moves
4637 one space to the right. If you mistype a character, you can use your
4638 erase character to back up and delete the mistyped character.
4640 Sometimes you may miss typing a character that you wanted to type,
4641 and not notice your error until you have typed several other
4642 characters. In that case, you can type C-b to move the cursor to the
4643 left, and then correct your mistake. Afterwards, you can move the
4644 cursor to the right with C-f.
4646 When you add text in the middle of a line, you will notice that
4647 characters to the right of the cursor are `pushed over' to make room
4648 for the text that you have inserted. Likewise, when you delete text
4649 behind the cursor, characters to the right of the cursor are `pulled
4650 back' to fill in the blank space created by the removal of the text. A
4651 list of the basic bare essentials for editing the text of an input line
4655 Move back one character.
4658 Move forward one character.
4661 Delete the character to the left of the cursor.
4664 Delete the character underneath the cursor.
4667 Insert the character into the line at the cursor.
4670 Undo the last thing that you did. You can undo all the way back
4674 File: bashref.info, Node: Readline Movement Commands, Next: Readline Killing Commands, Prev: Readline Bare Essentials, Up: Readline Interaction
4676 Readline Movement Commands
4677 --------------------------
4679 The above table describes the most basic possible keystrokes that
4680 you need in order to do editing of the input line. For your
4681 convenience, many other commands have been added in addition to C-b,
4682 C-f, C-d, and DEL. Here are some commands for moving more rapidly
4686 Move to the start of the line.
4689 Move to the end of the line.
4692 Move forward a word.
4695 Move backward a word.
4698 Clear the screen, reprinting the current line at the top.
4700 Notice how C-f moves forward a character, while M-f moves forward a
4701 word. It is a loose convention that control keystrokes operate on
4702 characters while meta keystrokes operate on words.
4705 File: bashref.info, Node: Readline Killing Commands, Next: Readline Arguments, Prev: Readline Movement Commands, Up: Readline Interaction
4707 Readline Killing Commands
4708 -------------------------
4710 "Killing" text means to delete the text from the line, but to save
4711 it away for later use, usually by "yanking" (re-inserting) it back into
4712 the line. If the description for a command says that it `kills' text,
4713 then you can be sure that you can get the text back in a different (or
4714 the same) place later.
4716 When you use a kill command, the text is saved in a "kill-ring".
4717 Any number of consecutive kills save all of the killed text together, so
4718 that when you yank it back, you get it all. The kill ring is not line
4719 specific; the text that you killed on a previously typed line is
4720 available to be yanked back later, when you are typing another line.
4722 Here is the list of commands for killing text.
4725 Kill the text from the current cursor position to the end of the
4729 Kill from the cursor to the end of the current word, or if between
4730 words, to the end of the next word.
4733 Kill from the cursor the start of the previous word, or if between
4734 words, to the start of the previous word.
4737 Kill from the cursor to the previous whitespace. This is
4738 different than M-DEL because the word boundaries differ.
4740 And, here is how to "yank" the text back into the line. Yanking
4741 means to copy the most-recently-killed text from the kill buffer.
4744 Yank the most recently killed text back into the buffer at the
4748 Rotate the kill-ring, and yank the new top. You can only do this
4749 if the prior command is C-y or M-y.
4752 File: bashref.info, Node: Readline Arguments, Next: Searching, Prev: Readline Killing Commands, Up: Readline Interaction
4757 You can pass numeric arguments to Readline commands. Sometimes the
4758 argument acts as a repeat count, other times it is the sign of the
4759 argument that is significant. If you pass a negative argument to a
4760 command which normally acts in a forward direction, that command will
4761 act in a backward direction. For example, to kill text back to the
4762 start of the line, you might type `M-- C-k'.
4764 The general way to pass numeric arguments to a command is to type
4765 meta digits before the command. If the first `digit' you type is a
4766 minus sign (-), then the sign of the argument will be negative. Once
4767 you have typed one meta digit to get the argument started, you can type
4768 the remainder of the digits, and then the command. For example, to give
4769 the C-d command an argument of 10, you could type `M-1 0 C-d'.
4772 File: bashref.info, Node: Searching, Prev: Readline Arguments, Up: Readline Interaction
4774 Searching for Commands in the History
4775 -------------------------------------
4777 Readline provides commands for searching through the command history
4778 (*note Bash History Facilities::.) for lines containing a specified
4779 string. There are two search modes: INCREMENTAL and NON-INCREMENTAL.
4781 Incremental searches begin before the user has finished typing the
4782 search string. As each character of the search string is typed,
4783 readline displays the next entry from the history matching the string
4784 typed so far. An incremental search requires only as many characters
4785 as needed to find the desired history entry. The Escape character is
4786 used to terminate an incremental search. Control-J will also terminate
4787 the search. Control-G will abort an incremental search and restore the
4788 original line. When the search is terminated, the history entry
4789 containing the search string becomes the current line. To find other
4790 matching entries in the history list, type Control-S or Control-R as
4791 appropriate. This will search backward or forward in the history for
4792 the next entry matching the search string typed so far. Any other key
4793 sequence bound to a readline command will terminate the search and
4794 execute that command. For instance, a `newline' will terminate the
4795 search and accept the line, thereby executing the command from the
4798 Non-incremental searches read the entire search string before
4799 starting to search for matching history lines. The search string may be
4800 typed by the user or part of the contents of the current line.
4803 File: bashref.info, Node: Readline Init File, Next: Bindable Readline Commands, Prev: Readline Interaction, Up: Command Line Editing
4808 Although the Readline library comes with a set of `emacs'-like
4809 keybindings installed by default, it is possible that you would like to
4810 use a different set of keybindings. You can customize programs that
4811 use Readline by putting commands in an "inputrc" file in your home
4812 directory. The name of this file is taken from the value of the shell
4813 variable `INPUTRC'. If that variable is unset, the default is
4816 When a program which uses the Readline library starts up, the init
4817 file is read, and the key bindings are set.
4819 In addition, the `C-x C-r' command re-reads this init file, thus
4820 incorporating any changes that you might have made to it.
4824 * Readline Init File Syntax:: Syntax for the commands in the inputrc file.
4826 * Conditional Init Constructs:: Conditional key bindings in the inputrc file.
4828 * Sample Init File:: An example inputrc file.
4831 File: bashref.info, Node: Readline Init File Syntax, Next: Conditional Init Constructs, Up: Readline Init File
4833 Readline Init File Syntax
4834 -------------------------
4836 There are only a few basic constructs allowed in the Readline init
4837 file. Blank lines are ignored. Lines beginning with a `#' are
4838 comments. Lines beginning with a `$' indicate conditional constructs
4839 (*note Conditional Init Constructs::.). Other lines denote variable
4840 settings and key bindings.
4843 You can change the state of a few variables in Readline by using
4844 the `set' command within the init file. Here is how you would
4845 specify that you wish to use `vi' line editing commands:
4849 Right now, there are only a few variables which can be set; so
4850 few, in fact, that we just list them here:
4853 Controls what happens when Readline wants to ring the
4854 terminal bell. If set to `none', Readline never rings the
4855 bell. If set to `visible', Readline uses a visible bell if
4856 one is available. If set to `audible' (the default),
4857 Readline attempts to ring the terminal's bell.
4860 The string to insert at the beginning of the line when the
4861 `insert-comment' command is executed. The default value is
4864 `completion-query-items'
4865 The number of possible completions that determines when the
4866 user is asked whether he wants to see the list of
4867 possibilities. If the number of possible completions is
4868 greater than this value, Readline will ask the user whether
4869 or not he wishes to view them; otherwise, they are simply
4870 listed. The default limit is `100'.
4873 If set to `on', Readline will convert characters with the
4874 eigth bit set to an ASCII key sequence by stripping the eigth
4875 bit and prepending an ESC character, converting them to a
4876 meta-prefixed key sequence. The default value is `on'.
4878 `disable-completion'
4879 If set to `On', readline will inhibit word completion.
4880 Completion characters will be inserted into the line as if
4881 they had been mapped to `self-insert'. The default is `off'.
4884 The `editing-mode' variable controls which editing mode you
4885 are using. By default, Readline starts up in Emacs editing
4886 mode, where the keystrokes are most similar to Emacs. This
4887 variable can be set to either `emacs' or `vi'.
4890 When set to `on', readline will try to enable the application
4891 keypad when it is called. Some systems need this to enable
4892 the arrow keys. The default is `off'.
4895 If set to `on', tilde expansion is performed when Readline
4896 attempts word completion. The default is `off'.
4898 `horizontal-scroll-mode'
4899 This variable can be set to either `on' or `off'. Setting it
4900 to `on' means that the text of the lines that you edit will
4901 scroll horizontally on a single screen line when they are
4902 longer than the width of the screen, instead of wrapping onto
4903 a new screen line. By default, this variable is set to `off'.
4906 Sets Readline's idea of the current keymap for key binding
4907 commands. Acceptable `keymap' names are `emacs',
4908 `emacs-standard', `emacs-meta', `emacs-ctlx', `vi',
4909 `vi-command', and `vi-insert'. `vi' is equivalent to
4910 `vi-command'; `emacs' is equivalent to `emacs-standard'. The
4911 default value is `emacs'. The value of the `editing-mode'
4912 variable also affects the default keymap.
4915 If set to `on', completed directory names have a slash
4916 appended. The default is `on'.
4918 `mark-modified-lines'
4919 This variable, when set to `on', says to display an asterisk
4920 (`*') at the start of history lines which have been modified.
4921 This variable is `off' by default.
4924 If set to `on', Readline will enable eight-bit input (it will
4925 not strip the eighth bit from the characters it reads),
4926 regardless of what the terminal claims it can support. The
4927 default value is `off'. The name `meta-flag' is a synonym
4931 If set to `on', Readline will display characters with the
4932 eighth bit set directly rather than as a meta-prefixed escape
4933 sequence. The default is `off'.
4935 `show-all-if-ambiguous'
4936 This alters the default behavior of the completion functions.
4937 If set to `on', words which have more than one possible
4938 completion cause the matches to be listed immediately instead
4939 of ringing the bell. The default value is `off'.
4942 If set to `on', a character denoting a file's type is
4943 appended to the filename when listing possible completions.
4944 The default is `off'.
4947 The syntax for controlling key bindings in the init file is
4948 simple. First you have to know the name of the command that you
4949 want to change. The following pages contain tables of the command
4950 name, the default keybinding, and a short description of what the
4953 Once you know the name of the command, simply place the name of
4954 the key you wish to bind the command to, a colon, and then the
4955 name of the command on a line in the init file. The name of the
4956 key can be expressed in different ways, depending on which is most
4957 comfortable for you.
4959 KEYNAME: FUNCTION-NAME or MACRO
4960 KEYNAME is the name of a key spelled out in English. For
4962 Control-u: universal-argument
4963 Meta-Rubout: backward-kill-word
4964 Control-o: "> output"
4966 In the above example, `C-u' is bound to the function
4967 `universal-argument', and `C-o' is bound to run the macro
4968 expressed on the right hand side (that is, to insert the text
4969 `> output' into the line).
4971 "KEYSEQ": FUNCTION-NAME or MACRO
4972 KEYSEQ differs from KEYNAME above in that strings denoting an
4973 entire key sequence can be specified, by placing the key
4974 sequence in double quotes. Some GNU Emacs style key escapes
4975 can be used, as in the following example, but the special
4976 character names are not recognized.
4978 "\C-u": universal-argument
4979 "\C-x\C-r": re-read-init-file
4980 "\e[11~": "Function Key 1"
4982 In the above example, `C-u' is bound to the function
4983 `universal-argument' (just as it was in the first example),
4984 `C-x C-r' is bound to the function `re-read-init-file', and
4985 `ESC [ 1 1 ~' is bound to insert the text `Function Key 1'.
4986 The following escape sequences are available when specifying
5007 When entering the text of a macro, single or double quotes
5008 should be used to indicate a macro definition. Unquoted text
5009 is assumed to be a function name. Backslash will quote any
5010 character in the macro text, including `"' and `''. For
5011 example, the following binding will make `C-x \' insert a
5012 single `\' into the line:
5016 File: bashref.info, Node: Conditional Init Constructs, Next: Sample Init File, Prev: Readline Init File Syntax, Up: Readline Init File
5018 Conditional Init Constructs
5019 ---------------------------
5021 Readline implements a facility similar in spirit to the conditional
5022 compilation features of the C preprocessor which allows key bindings
5023 and variable settings to be performed as the result of tests. There
5024 are three parser directives used.
5027 The `$if' construct allows bindings to be made based on the
5028 editing mode, the terminal being used, or the application using
5029 Readline. The text of the test extends to the end of the line; no
5030 characters are required to isolate it.
5033 The `mode=' form of the `$if' directive is used to test
5034 whether Readline is in `emacs' or `vi' mode. This may be
5035 used in conjunction with the `set keymap' command, for
5036 instance, to set bindings in the `emacs-standard' and
5037 `emacs-ctlx' keymaps only if Readline is starting out in
5041 The `term=' form may be used to include terminal-specific key
5042 bindings, perhaps to bind the key sequences output by the
5043 terminal's function keys. The word on the right side of the
5044 `=' is tested against the full name of the terminal and the
5045 portion of the terminal name before the first `-'. This
5046 allows `sun' to match both `sun' and `sun-cmd', for instance.
5049 The APPLICATION construct is used to include
5050 application-specific settings. Each program using the
5051 Readline library sets the APPLICATION NAME, and you can test
5052 for it. This could be used to bind key sequences to
5053 functions useful for a specific program. For instance, the
5054 following command adds a key sequence that quotes the current
5055 or previous word in Bash:
5057 # Quote the current or previous word
5058 "\C-xq": "\eb\"\ef\""
5062 This command, as you saw in the previous example, terminates an
5066 Commands in this branch of the `$if' directive are executed if the
5070 File: bashref.info, Node: Sample Init File, Prev: Conditional Init Constructs, Up: Readline Init File
5075 Here is an example of an inputrc file. This illustrates key
5076 binding, variable assignment, and conditional syntax.
5079 # This file controls the behaviour of line input editing for
5080 # programs that use the Gnu Readline library. Existing programs
5081 # include FTP, Bash, and Gdb.
5083 # You can re-read the inputrc file with C-x C-r.
5084 # Lines beginning with '#' are comments.
5086 # Set various bindings for emacs mode.
5088 set editing-mode emacs
5092 Meta-Control-h: backward-kill-word Text after the function name is ignored
5095 # Arrow keys in keypad mode
5097 #"\M-OD" backward-char
5098 #"\M-OC" forward-char
5099 #"\M-OA" previous-history
5100 #"\M-OB" next-history
5102 # Arrow keys in ANSI mode
5104 "\M-[D" backward-char
5105 "\M-[C" forward-char
5106 "\M-[A" previous-history
5107 "\M-[B" next-history
5109 # Arrow keys in 8 bit keypad mode
5111 #"\M-\C-OD" backward-char
5112 #"\M-\C-OC" forward-char
5113 #"\M-\C-OA" previous-history
5114 #"\M-\C-OB" next-history
5116 # Arrow keys in 8 bit ANSI mode
5118 #"\M-\C-[D" backward-char
5119 #"\M-\C-[C" forward-char
5120 #"\M-\C-[A" previous-history
5121 #"\M-\C-[B" next-history
5127 # An old-style binding. This happens to be the default.
5130 # Macros that are convenient for shell interaction
5133 "\C-xp": "PATH=${PATH}\e\C-e\C-a\ef\C-f"
5134 # prepare to type a quoted word -- insert open and close double quotes
5135 # and move to just after the open quote
5136 "\C-x\"": "\"\"\C-b"
5137 # insert a backslash (testing backslash escapes in sequences and macros)
5139 # Quote the current or previous word
5140 "\C-xq": "\eb\"\ef\""
5141 # Add a binding to refresh the line, which is unbound
5142 "\C-xr": redraw-current-line
5143 # Edit variable on current line.
5144 "\M-\C-v": "\C-a\C-k$\C-y\M-\C-e\C-a\C-y="
5147 # use a visible bell if one is available
5148 set bell-style visible
5150 # don't strip characters to 7 bits when reading
5153 # allow iso-latin1 characters to be inserted rather than converted to
5154 # prefix-meta sequences
5155 set convert-meta off
5157 # display characters with the eighth bit set directly rather than
5158 # as meta-prefixed characters
5161 # if there are more than 150 possible completions for a word, ask the
5162 # user if he wants to see all of them
5163 set completion-query-items 150
5169 "\M-.": yank-last-arg
5173 File: bashref.info, Node: Bindable Readline Commands, Next: Readline vi Mode, Prev: Readline Init File, Up: Command Line Editing
5175 Bindable Readline Commands
5176 ==========================
5180 * Commands For Moving:: Moving about the line.
5181 * Commands For History:: Getting at previous lines.
5182 * Commands For Text:: Commands for changing text.
5183 * Commands For Killing:: Commands for killing and yanking.
5184 * Numeric Arguments:: Specifying numeric arguments, repeat counts.
5185 * Commands For Completion:: Getting Readline to do the typing for you.
5186 * Keyboard Macros:: Saving and re-executing typed characters
5187 * Miscellaneous Commands:: Other miscellaneous commands.
5189 This section describes Readline commands that may be bound to key
5193 File: bashref.info, Node: Commands For Moving, Next: Commands For History, Up: Bindable Readline Commands
5198 `beginning-of-line (C-a)'
5199 Move to the start of the current line.
5202 Move to the end of the line.
5204 `forward-char (C-f)'
5205 Move forward a character.
5207 `backward-char (C-b)'
5208 Move back a character.
5210 `forward-word (M-f)'
5211 Move forward to the end of the next word. Words are composed of
5214 `backward-word (M-b)'
5215 Move back to the start of this, or the previous, word. Words are
5216 composed of letters and digits.
5218 `clear-screen (C-l)'
5219 Clear the screen and redraw the current line, leaving the current
5220 line at the top of the screen.
5222 `redraw-current-line ()'
5223 Refresh the current line. By default, this is unbound.
5226 File: bashref.info, Node: Commands For History, Next: Commands For Text, Prev: Commands For Moving, Up: Bindable Readline Commands
5228 Commands For Manipulating The History
5229 -------------------------------------
5231 `accept-line (Newline, Return)'
5232 Accept the line regardless of where the cursor is. If this line is
5233 non-empty, add it to the history list according to the setting of
5234 the `HISTCONTROL' variable. If this line was a history line, then
5235 restore the history line to its original state.
5237 `previous-history (C-p)'
5238 Move `up' through the history list.
5240 `next-history (C-n)'
5241 Move `down' through the history list.
5243 `beginning-of-history (M-<)'
5244 Move to the first line in the history.
5246 `end-of-history (M->)'
5247 Move to the end of the input history, i.e., the line you are
5250 `reverse-search-history (C-r)'
5251 Search backward starting at the current line and moving `up'
5252 through the history as necessary. This is an incremental search.
5254 `forward-search-history (C-s)'
5255 Search forward starting at the current line and moving `down'
5256 through the the history as necessary. This is an incremental
5259 `non-incremental-reverse-search-history (M-p)'
5260 Search backward starting at the current line and moving `up'
5261 through the history as necessary using a non-incremental search
5262 for a string supplied by the user.
5264 `non-incremental-forward-search-history (M-n)'
5265 Search forward starting at the current line and moving `down'
5266 through the the history as necessary using a non-incremental search
5267 for a string supplied by the user.
5269 `history-search-forward ()'
5270 Search forward through the history for the string of characters
5271 between the start of the current line and the current cursor
5272 position (the `point'). This is a non-incremental search. By
5273 default, this command is unbound.
5275 `history-search-backward ()'
5276 Search backward through the history for the string of characters
5277 between the start of the current line and the point. This is a
5278 non-incremental search. By default, this command is unbound.
5280 `yank-nth-arg (M-C-y)'
5281 Insert the first argument to the previous command (usually the
5282 second word on the previous line). With an argument N, insert the
5283 Nth word from the previous command (the words in the previous
5284 command begin with word 0). A negative argument inserts the Nth
5285 word from the end of the previous command.
5287 `yank-last-arg (M-., M-_)'
5288 Insert last argument to the previous command (the last word of the
5289 previous history entry). With an argument, behave exactly like
5293 File: bashref.info, Node: Commands For Text, Next: Commands For Killing, Prev: Commands For History, Up: Bindable Readline Commands
5295 Commands For Changing Text
5296 --------------------------
5299 Delete the character under the cursor. If the cursor is at the
5300 beginning of the line, there are no characters in the line, and
5301 the last character typed was not `C-d', then return `EOF'.
5303 `backward-delete-char (Rubout)'
5304 Delete the character behind the cursor. A numeric arg says to kill
5305 the characters instead of deleting them.
5307 `quoted-insert (C-q, C-v)'
5308 Add the next character that you type to the line verbatim. This is
5309 how to insert key sequences like C-q, for example.
5311 `tab-insert (M-TAB)'
5312 Insert a tab character.
5314 `self-insert (a, b, A, 1, !, ...)'
5317 `transpose-chars (C-t)'
5318 Drag the character before the cursor forward over the character at
5319 the cursor, moving the cursor forward as well. If the insertion
5320 point is at the end of the line, then this transposes the last two
5321 characters of the line. Negative argumentss don't work.
5323 `transpose-words (M-t)'
5324 Drag the word behind the cursor past the word in front of the
5325 cursor moving the cursor over that word as well.
5328 Uppercase the current (or following) word. With a negative
5329 argument, do the previous word, but do not move the cursor.
5331 `downcase-word (M-l)'
5332 Lowercase the current (or following) word. With a negative
5333 argument, do the previous word, but do not move the cursor.
5335 `capitalize-word (M-c)'
5336 Capitalize the current (or following) word. With a negative
5337 argument, do the previous word, but do not move the cursor.
5340 File: bashref.info, Node: Commands For Killing, Next: Numeric Arguments, Prev: Commands For Text, Up: Bindable Readline Commands
5346 Kill the text from the current cursor position to the end of the
5349 `backward-kill-line (C-x Rubout)'
5350 Kill backward to the beginning of the line.
5352 `unix-line-discard (C-u)'
5353 Kill backward from the cursor to the beginning of the current line.
5354 Save the killed text on the kill-ring.
5356 `kill-whole-line ()'
5357 Kill all characters on the current line, no matter where the
5358 cursor is. By default, this is unbound.
5361 Kill from the cursor to the end of the current word, or if between
5362 words, to the end of the next word. Word boundaries are the same
5365 `backward-kill-word (M-DEL)'
5366 Kill the word behind the cursor. Word boundaries are the same as
5369 `unix-word-rubout (C-w)'
5370 Kill the word behind the cursor, using white space as a word
5371 boundary. The killed text is saved on the kill-ring.
5373 `delete-horizontal-space ()'
5374 Delete all spaces and tabs around point. By default, this is
5378 Kill the text between the point and the *mark* (saved cursor
5379 position. This text is referred to as the REGION. By default,
5380 this command is unbound.
5382 `copy-region-as-kill ()'
5383 Copy the text in the region to the kill buffer, so you can yank it
5384 right away. By default, this command is unbound.
5386 `copy-backward-word ()'
5387 Copy the word before point to the kill buffer. By default, this
5390 `copy-forward-word ()'
5391 Copy the word following point to the kill buffer. By default,
5392 this command is unbound.
5395 Yank the top of the kill ring into the buffer at the current
5399 Rotate the kill-ring, and yank the new top. You can only do this
5400 if the prior command is yank or yank-pop.
5403 File: bashref.info, Node: Numeric Arguments, Next: Commands For Completion, Prev: Commands For Killing, Up: Bindable Readline Commands
5405 Specifying Numeric Arguments
5406 ----------------------------
5408 `digit-argument (M-0, M-1, ... M--)'
5409 Add this digit to the argument already accumulating, or start a new
5410 argument. M- starts a negative argument.
5412 `universal-argument ()'
5413 Each time this is executed, the argument count is multiplied by
5414 four. The argument count is initially one, so executing this
5415 function the first time makes the argument count four. By
5416 default, this is not bound to a key.
5419 File: bashref.info, Node: Commands For Completion, Next: Keyboard Macros, Prev: Numeric Arguments, Up: Bindable Readline Commands
5421 Letting Readline Type For You
5422 -----------------------------
5425 Attempt to do completion on the text before the cursor. This is
5426 application-specific. Generally, if you are typing a filename
5427 argument, you can do filename completion; if you are typing a
5428 command, you can do command completion, if you are typing in a
5429 symbol to GDB, you can do symbol name completion, if you are
5430 typing in a variable to Bash, you can do variable name completion,
5431 and so on. Bash attempts completion treating the text as a
5432 variable (if the text begins with `$'), username (if the text
5433 begins with `~'), hostname (if the text begins with `@'), or
5434 command (including aliases and functions) in turn. If none of
5435 these produces a match, filename completion is attempted.
5437 `possible-completions (M-?)'
5438 List the possible completions of the text before the cursor.
5440 `insert-completions (M-*)'
5441 Insert all completions of the text before point that would have
5442 been generated by `possible-completions'.
5444 `complete-filename (M-/)'
5445 Attempt filename completion on the text before point.
5447 `possible-filename-completions (C-x /)'
5448 List the possible completions of the text before point, treating
5451 `complete-username (M-~)'
5452 Attempt completion on the text before point, treating it as a
5455 `possible-username-completions (C-x ~)'
5456 List the possible completions of the text before point, treating
5459 `complete-variable (M-$)'
5460 Attempt completion on the text before point, treating it as a
5463 `possible-variable-completions (C-x $)'
5464 List the possible completions of the text before point, treating
5465 it as a shell variable.
5467 `complete-hostname (M-@)'
5468 Attempt completion on the text before point, treating it as a
5471 `possible-hostname-completions (C-x @)'
5472 List the possible completions of the text before point, treating
5475 `complete-command (M-!)'
5476 Attempt completion on the text before point, treating it as a
5477 command name. Command completion attempts to match the text
5478 against aliases, reserved words, shell functions, builtins, and
5479 finally executable filenames, in that order.
5481 `possible-command-completions (C-x !)'
5482 List the possible completions of the text before point, treating
5483 it as a command name.
5485 `dynamic-complete-history (M-TAB)'
5486 Attempt completion on the text before point, comparing the text
5487 against lines from the history list for possible completion
5490 `complete-into-braces (M-{)'
5491 Perform filename completion and return the list of possible
5492 completions enclosed within braces so the list is available to the
5493 shell (*note Brace Expansion::.).
5496 File: bashref.info, Node: Keyboard Macros, Next: Miscellaneous Commands, Prev: Commands For Completion, Up: Bindable Readline Commands
5501 `start-kbd-macro (C-x ()'
5502 Begin saving the characters typed into the current keyboard macro.
5504 `end-kbd-macro (C-x ))'
5505 Stop saving the characters typed into the current keyboard macro
5506 and save the definition.
5508 `call-last-kbd-macro (C-x e)'
5509 Re-execute the last keyboard macro defined, by making the
5510 characters in the macro appear as if typed at the keyboard.
5513 File: bashref.info, Node: Miscellaneous Commands, Prev: Keyboard Macros, Up: Bindable Readline Commands
5515 Some Miscellaneous Commands
5516 ---------------------------
5518 `re-read-init-file (C-x C-r)'
5519 Read in the contents of the inputrc file, and incorporate any
5520 bindings or variable assignments found there.
5523 Abort the current editing command and ring the terminal's bell
5524 (subject to the setting of `bell-style').
5526 `do-uppercase-version (M-a, M-b, M-X, ...)'
5527 If the metafied character X is lowercase, run the command that is
5528 bound to the corresponding uppercase character.
5531 Make the next character that you type be metafied. This is for
5532 people without a meta key. Typing `ESC f' is equivalent to typing
5535 `undo (C-_, C-x C-u)'
5536 Incremental undo, separately remembered for each line.
5539 Undo all changes made to this line. This is like typing the `undo'
5540 command enough times to get back to the beginning.
5542 `tilde-expand (M-~)'
5543 Perform tilde expansion on the current word.
5546 Set the mark to the current point. If a numeric argument is
5547 supplied, the mark is set to that position.
5549 `exchange-point-and-mark (C-x C-x)'
5550 Swap the point with the mark. The current cursor position is set
5551 to the saved position, and the old cursor position is saved as the
5554 `character-search (C-])'
5555 A character is read and point is moved to the next occurrence of
5556 that character. A negative count searches for previous
5559 `character-search-backward (M-C-])'
5560 A character is read and point is moved to the previous occurrence
5561 of that character. A negative count searches for subsequent
5564 `insert-comment (M-#)'
5565 The value of the `comment-begin' variable is inserted at the
5566 beginning of the current line, and the line is accepted as if a
5567 newline had been typed. This makes the current line a shell
5571 Print all of the functions and their key bindings to the readline
5572 output stream. If a numeric argument is supplied, the output is
5573 formatted in such a way that it can be made part of an INPUTRC
5574 file. This command is unbound by default.
5577 Print all of the settable variables and their values to the
5578 readline output stream. If a numeric argument is supplied, the
5579 output is formatted in such a way that it can be made part of an
5580 INPUTRC file. This command is unbound by default.
5583 Print all of the readline key sequences bound to macros and the
5584 strings they ouput. If a numeric argument is supplied, the output
5585 is formatted in such a way that it can be made part of an INPUTRC
5586 file. This command is unbound by default.
5588 `glob-expand-word (C-x *)'
5589 The word before point is treated as a pattern for pathname
5590 expansion, and the list of matching file names is inserted,
5593 `glob-list-expansions (C-x g)'
5594 The list of expansions that would have been generated by
5595 `glob-expand-word' is inserted into the line, replacing the word
5598 `display-shell-version (C-x C-v)'
5599 Display version information about the current instance of Bash.
5601 `shell-expand-line (M-C-e)'
5602 Expand the line the way the shell does when it reads it. This
5603 performs alias and history expansion as well as all of the shell
5606 `history-expand-line (M-^)'
5607 Perform history expansion on the current line.
5609 `insert-last-argument (M-., M-_)'
5610 A synonym for `yank-last-arg'.
5612 `operate-and-get-next (C-o)'
5613 Accept the current line for execution and fetch the next line
5614 relative to the current line from the history for editing. Any
5615 argument is ignored.
5617 `emacs-editing-mode (C-e)'
5618 When in `vi' editing mode, this causes a switch back to `emacs'
5619 editing mode, as if the command `set -o emacs' had been executed.
5622 File: bashref.info, Node: Readline vi Mode, Prev: Bindable Readline Commands, Up: Command Line Editing
5627 While the Readline library does not have a full set of `vi' editing
5628 functions, it does contain enough to allow simple editing of the line.
5629 The Readline `vi' mode behaves as specified in the POSIX 1003.2
5632 In order to switch interactively between `emacs' and `vi' editing
5633 modes, use the `set -o emacs' and `set -o vi' commands (*note The Set
5634 Builtin::.). The Readline default is `emacs' mode.
5636 When you enter a line in `vi' mode, you are already placed in
5637 `insertion' mode, as if you had typed an `i'. Pressing ESC switches
5638 you into `command' mode, where you can edit the text of the line with
5639 the standard `vi' movement keys, move to previous history lines with
5640 `k' and subsequent lines with `j', and so forth.
5643 File: bashref.info, Node: Installing Bash, Next: Reporting Bugs, Prev: Command Line Editing, Up: Top
5648 This chapter provides basic instructions for installing Bash on the
5649 various supported platforms. The distribution supports nearly every
5650 version of Unix (and, someday, GNU). Other independent ports exist for
5651 OS/2, Windows 95, and Windows NT.
5655 * Basic Installation:: Generic installation instructions.
5657 * Compilers and Options:: How to set special options for various
5660 * Compiling For Multiple Architectures:: How to compile Bash for more
5661 than one kind of system from
5662 the same source tree.
5664 * Installation Names:: How to set the various paths used by the installation.
5666 * Specifying the System Type:: How to configure Bash for a particular system.
5668 * Sharing Defaults:: How to share default configuration values among GNU
5671 * Operation Controls:: Options recognized by the configuration program.
5673 * Optional Features:: How to enable and disable optional features when
5677 File: bashref.info, Node: Basic Installation, Next: Compilers and Options, Up: Installing Bash
5682 These are generic installation instructions for Bash.
5684 The `configure' shell script attempts to guess correct values for
5685 various system-dependent variables used during compilation. It uses
5686 those values to create a `Makefile' in each directory of the package
5687 (the top directory, the `builtins' and `doc' directories, and the each
5688 directory under `lib'). It also creates a `config.h' file containing
5689 system-dependent definitions. Finally, it creates a shell script named
5690 `config.status' that you can run in the future to recreate the current
5691 configuration, a file `config.cache' that saves the results of its
5692 tests to speed up reconfiguring, and a file `config.log' containing
5693 compiler output (useful mainly for debugging `configure'). If at some
5694 point `config.cache' contains results you don't want to keep, you may
5697 If you need to do unusual things to compile the package, please try
5698 to figure out how `configure' could check whether or not to do them,
5699 and mail diffs or instructions to `bash-maintainers@prep.ai.mit.edu' so
5700 they can be considered for the next release.
5702 The file `configure.in' is used to create `configure' by a program
5703 called Autoconf. You only need `configure.in' if you want to change it
5704 or regenerate `configure' using a newer version of Autoconf. If you do
5705 this, make sure you are using Autoconf version 2.9 or newer.
5707 The simplest way to compile Bash is:
5709 1. `cd' to the directory containing the source code and type
5710 `./configure' to configure Bash for your system. If you're using
5711 `csh' on an old version of System V, you might need to type `sh
5712 ./configure' instead to prevent `csh' from trying to execute
5715 Running `configure' takes awhile. While running, it prints some
5716 messages telling which features it is checking for.
5718 2. Type `make' to compile Bash and build the `bashbug' bug reporting
5721 3. Optionally, type `make tests' to run the Bash test suite.
5723 4. Type `make install' to install `bash' and `bashbug'. This will
5724 also install the manual pages and Info file.
5727 You can remove the program binaries and object files from the source
5728 code directory by typing `make clean'. To also remove the files that
5729 `configure' created (so you can compile Bash for a different kind of
5730 computer), type `make distclean'.
5733 File: bashref.info, Node: Compilers and Options, Next: Compiling For Multiple Architectures, Prev: Basic Installation, Up: Installing Bash
5735 Compilers and Options
5736 =====================
5738 Some systems require unusual options for compilation or linking that
5739 the `configure' script does not know about. You can give `configure'
5740 initial values for variables by setting them in the environment. Using
5741 a Bourne-compatible shell, you can do that on the command line like
5744 CC=c89 CFLAGS=-O2 LIBS=-lposix ./configure
5746 On systems that have the `env' program, you can do it like this:
5748 env CPPFLAGS=-I/usr/local/include LDFLAGS=-s ./configure
5750 The configuration process uses GCC to build Bash if it is available.
5753 File: bashref.info, Node: Compiling For Multiple Architectures, Next: Installation Names, Prev: Compilers and Options, Up: Installing Bash
5755 Compiling For Multiple Architectures
5756 ====================================
5758 You can compile Bash for more than one kind of computer at the same
5759 time, by placing the object files for each architecture in their own
5760 directory. To do this, you must use a version of `make' that supports
5761 the `VPATH' variable, such as GNU `make'. `cd' to the directory where
5762 you want the object files and executables to go and run the `configure'
5763 script from the source directory. You may need to supply the
5764 `--srcdir=PATH' argument to tell `configure' where the source files
5765 are. `configure' automatically checks for the source code in the
5766 directory that `configure' is in and in `..'.
5768 If you have to use a `make' that does not supports the `VPATH'
5769 variable, you can compile Bash for one architecture at a time in the
5770 source code directory. After you have installed Bash for one
5771 architecture, use `make distclean' before reconfiguring for another
5774 Alternatively, if your system supports symbolic links, you can use
5775 the `support/mkclone' script to create a build tree which has symbolic
5776 links back to each file in the source directory. Here's an example
5777 that creates a build directory in the current directory from a source
5778 directory `/usr/gnu/src/bash-2.0':
5780 bash /usr/gnu/src/bash-2.0/support/mkclone -s /usr/gnu/src/bash-2.0 .
5782 The `mkclone' script requires Bash, so you must have already built Bash
5783 for at least one architecture before you can create build directories
5784 for other architectures.
5787 File: bashref.info, Node: Installation Names, Next: Specifying the System Type, Prev: Compiling For Multiple Architectures, Up: Installing Bash
5792 By default, `make install' will install into `/usr/local/bin',
5793 `/usr/local/man', etc. You can specify an installation prefix other
5794 than `/usr/local' by giving `configure' the option `--prefix=PATH'.
5796 You can specify separate installation prefixes for
5797 architecture-specific files and architecture-independent files. If you
5798 give `configure' the option `--exec-prefix=PATH', the package will use
5799 `PATH' as the prefix for installing programs and libraries.
5800 Documentation and other data files will still use the regular prefix.
5803 File: bashref.info, Node: Specifying the System Type, Next: Sharing Defaults, Prev: Installation Names, Up: Installing Bash
5805 Specifying the System Type
5806 ==========================
5808 There may be some features `configure' can not figure out
5809 automatically, but needs to determine by the type of host the package
5810 will run on. Usually `configure' can figure that out, but if it prints
5811 a message saying it can not guess the host type, give it the
5812 `--host=TYPE' option. `TYPE' can either be a short name for the system
5813 type, such as `sun4', or a canonical name with three fields:
5814 `CPU-COMPANY-SYSTEM' (e.g., `sparc-sun-sunos4.1.2').
5816 See the file `support/config.sub' for the possible values of each field.
5819 File: bashref.info, Node: Sharing Defaults, Next: Operation Controls, Prev: Specifying the System Type, Up: Installing Bash
5824 If you want to set default values for `configure' scripts to share,
5825 you can create a site shell script called `config.site' that gives
5826 default values for variables like `CC', `cache_file', and `prefix'.
5827 `configure' looks for `PREFIX/share/config.site' if it exists, then
5828 `PREFIX/etc/config.site' if it exists. Or, you can set the
5829 `CONFIG_SITE' environment variable to the location of the site script.
5830 A warning: the Bash `configure' looks for a site script, but not all
5831 `configure' scripts do.
5834 File: bashref.info, Node: Operation Controls, Next: Optional Features, Prev: Sharing Defaults, Up: Installing Bash
5839 `configure' recognizes the following options to control how it
5843 Use and save the results of the tests in FILE instead of
5844 `./config.cache'. Set FILE to `/dev/null' to disable caching, for
5845 debugging `configure'.
5848 Print a summary of the options to `configure', and exit.
5853 Do not print messages saying which checks are being made.
5856 Look for the Bash source code in directory DIR. Usually
5857 `configure' can determine that directory automatically.
5860 Print the version of Autoconf used to generate the `configure'
5863 `configure' also accepts some other, not widely used, boilerplate
5867 File: bashref.info, Node: Optional Features, Prev: Operation Controls, Up: Installing Bash
5872 The Bash `configure' has a number of `--enable-FEATURE' options,
5873 where FEATURE indicates an optional part of the package. There are
5874 also several `--with-PACKAGE' options, where PACKAGE is something like
5875 `gnu-malloc' or `purify' (for the Purify memory allocation checker). To
5876 turn off the default use of a package, use `--without-PACKAGE'. To
5877 configure Bash without a feature that is enabled by default, use
5878 `--disable-FEATURE'.
5880 Here is a complete list of the `--enable-' and `--with-' options
5881 that the Bash `configure' recognizes.
5884 Use the GNU version of `malloc' in `lib/malloc/malloc.c'. This is
5885 not the same `malloc' that appears in GNU libc, but an older
5886 version derived from the 4.2 BSD `malloc'. This `malloc' is very
5887 fast, but wastes a lot of space. This option is enabled by
5888 default. The `NOTES' file contains a list of systems for which
5889 this should be turned off.
5891 `--with-glibc-malloc'
5892 Use the GNU libc version of `malloc' in `lib/malloc/gmalloc.c'.
5893 This is somewhat slower than the default `malloc', but wastes
5894 considerably less space.
5897 Define if you are using the Andrew File System from Transarc.
5900 Define this to use the Purify memory allocation checker from Pure
5903 `--enable-minimal-config'
5904 This produces a shell with minimal features, close to the
5905 historical Bourne shell.
5907 The `minimal-config' option can be used to disable all of the following
5908 options, but it is processed first, so individual options may be
5909 enabled using `enable-FEATURE'.
5911 All of the following options except for `disabled-builtins' and
5912 `usg-echo-default' are enabled by default, unless the operating system
5913 does not provide the necessary support.
5915 `--enable-job-control'
5916 This enables job control features, if the OS supports them.
5919 Allow alias expansion and include the `alias' and `unalias'
5923 Include support for command-line editing and history with the Bash
5924 version of the Readline library.
5927 Include command history and the `fc' and `history' builtin
5930 `--enable-bang-history'
5931 Include support for `csh'-like history substitution.
5933 `--enable-directory-stack'
5934 Include support for a `csh'-like directory stack and the `pushd',
5935 `popd', and `dirs' builtins.
5937 `--enable-restricted'
5938 Include support for a "restricted shell". If this is enabled,
5939 Bash, when called as `rbash', enters a restricted mode. See *Note
5940 The Restricted Shell::, for a description of restricted mode.
5942 `--enable-process-substitution'
5943 This enables process substitution (*note Process Substitution::.)
5944 if the OS provides the necessary support.
5946 `--enable-prompt-string-decoding'
5947 Turn on the interpretation of a number of backslash-escaped
5948 characters in the `$PS1', `$PS2', `$PS3', and `$PS4' prompt
5952 Include the `ksh' `select' builtin, which allows the generation of
5955 `--enable-help-builtin'
5956 Include the `help' builtin, which displays help on shell builtins
5959 `--enable-array-variables'
5960 Include support for one-dimensional array shell variables.
5962 `--enable-dparen-arithmetic'
5963 Include support for the `ksh' `((...))' command.
5965 `--enable-brace-expansion'
5966 Include `csh'-like brace expansion ( `b{a,b}c' ==> `bac bbc' ).
5968 `--enable-disabled-builtins'
5969 Allow builtin commands to be invoked via `builtin xxx' even after
5970 `xxx' has been disabled using `enable -n xxx'. See *Note Bash
5971 Builtins::, for details of the `builtin' and `enable' builtin
5974 `--enable-command-timing'
5975 Include support for recognizing `time' as a reserved word and for
5976 displaying timing statistics for the pipeline following `time'.
5977 This allows pipelines as well as shell builtins and functions to
5980 `--enable-usg-echo-default'
5981 Make the `echo' builtin expand backslash-escaped characters by
5982 default, without requiring the `-e' option. This makes the Bash
5983 `echo' behave more like the System V version.
5985 The file `config.h.top' contains C Preprocessor `#define' statements
5986 for options which are not settable from `configure'. Some of these are
5987 not meant to be changed; beware of the consequences if you do. Read
5988 the comments associated with each definition for more information about
5992 File: bashref.info, Node: Reporting Bugs, Next: Builtin Index, Prev: Installing Bash, Up: Top
5997 Please report all bugs you find in Bash. But first, you should make
5998 sure that it really is a bug, and that it appears in the latest version
5999 of Bash that you have.
6001 Once you have determined that a bug actually exists, use the
6002 `bashbug' command to submit a bug report. If you have a fix, you are
6003 welcome to mail that as well! Suggestions and `philosophical' bug
6004 reports may be mailed to `bug-bash@prep.ai.MIT.Edu' or posted to the
6005 Usenet newsgroup `gnu.bash.bug'.
6007 All bug reports should include:
6008 * The version number of Bash.
6010 * The hardware and operating system.
6012 * The compiler used to compile Bash.
6014 * A description of the bug behaviour.
6016 * A short script or `recipe' which exercises the bug and may be used
6019 `bashbug' inserts the first three items automatically into the template
6020 it provides for filing a bug report.
6022 Please send all reports concerning this manual to
6023 `chet@ins.CWRU.Edu'.
6026 File: bashref.info, Node: Builtin Index, Next: Reserved Word Index, Prev: Reporting Bugs, Up: Top
6028 Index of Shell Builtin Commands
6029 *******************************
6033 * .: Bourne Shell Builtins.
6034 * :: Bourne Shell Builtins.
6035 * [: Bourne Shell Builtins.
6036 * alias: Alias Builtins.
6037 * bg: Job Control Builtins.
6038 * bind: Bash Builtins.
6039 * break: Bourne Shell Builtins.
6040 * builtin: Bash Builtins.
6041 * cd: Bourne Shell Builtins.
6042 * command: Bash Builtins.
6043 * continue: Bourne Shell Builtins.
6044 * declare: Bash Builtins.
6045 * dirs: C Shell Builtins.
6046 * disown: Job Control Builtins.
6047 * echo: Bash Builtins.
6048 * enable: Bash Builtins.
6049 * eval: Bourne Shell Builtins.
6050 * exec: Bourne Shell Builtins.
6051 * exit: Bourne Shell Builtins.
6052 * export: Bourne Shell Builtins.
6053 * fc: Korn Shell Builtins.
6054 * fg: Job Control Builtins.
6055 * getopts: Bourne Shell Builtins.
6056 * hash: Bourne Shell Builtins.
6057 * help: Bash Builtins.
6058 * history: C Shell Builtins.
6059 * jobs: Job Control Builtins.
6060 * kill: Job Control Builtins.
6061 * let <1>: Arithmetic Builtins.
6062 * let: Korn Shell Builtins.
6063 * local: Bash Builtins.
6064 * logout <1>: Bash Builtins.
6065 * logout: C Shell Builtins.
6066 * popd: C Shell Builtins.
6067 * pushd: C Shell Builtins.
6068 * pwd: Bourne Shell Builtins.
6069 * read: Bash Builtins.
6070 * readonly: Bourne Shell Builtins.
6071 * return: Bourne Shell Builtins.
6072 * set: The Set Builtin.
6073 * shift: Bourne Shell Builtins.
6074 * shopt: Bash Builtins.
6075 * source: C Shell Builtins.
6076 * suspend: Job Control Builtins.
6077 * test: Bourne Shell Builtins.
6078 * times: Bourne Shell Builtins.
6079 * trap: Bourne Shell Builtins.
6080 * type: Bash Builtins.
6081 * typeset: Korn Shell Builtins.
6082 * ulimit: Bash Builtins.
6083 * umask: Bourne Shell Builtins.
6084 * unalias: Alias Builtins.
6085 * unset: Bourne Shell Builtins.
6086 * wait: Job Control Builtins.
6089 File: bashref.info, Node: Reserved Word Index, Next: Variable Index, Prev: Builtin Index, Up: Top
6091 Shell Reserved Words
6092 ********************
6097 * {: Command Grouping.
6098 * }: Command Grouping.
6099 * case: Conditional Constructs.
6100 * do: Looping Constructs.
6101 * done: Looping Constructs.
6102 * elif: Conditional Constructs.
6103 * else: Conditional Constructs.
6104 * esac: Conditional Constructs.
6105 * fi: Conditional Constructs.
6106 * for: Looping Constructs.
6107 * function: Shell Functions.
6108 * if: Conditional Constructs.
6109 * in: Conditional Constructs.
6110 * select: Korn Shell Constructs.
6111 * then: Conditional Constructs.
6113 * until: Looping Constructs.
6114 * while: Looping Constructs.
6117 File: bashref.info, Node: Variable Index, Next: Function Index, Prev: Reserved Word Index, Up: Top
6119 Parameter and Variable Index
6120 ****************************
6124 * !: Special Parameters.
6125 * #: Special Parameters.
6126 * $: Special Parameters.
6127 * *: Special Parameters.
6128 * -: Special Parameters.
6129 * 0: Special Parameters.
6130 * ?: Special Parameters.
6131 * @: Special Parameters.
6132 * _: Special Parameters.
6133 * auto_resume: Job Control Variables.
6134 * BASH: Bash Variables.
6135 * BASH_VERSINFO: Bash Variables.
6136 * BASH_VERSION: Bash Variables.
6137 * bell-style: Readline Init File Syntax.
6138 * CDPATH: Bourne Shell Variables.
6139 * comment-begin: Readline Init File Syntax.
6140 * completion-query-items: Readline Init File Syntax.
6141 * convert-meta: Readline Init File Syntax.
6142 * DIRSTACK: Bash Variables.
6143 * disable-completion: Readline Init File Syntax.
6144 * editing-mode: Readline Init File Syntax.
6145 * enable-keypad: Readline Init File Syntax.
6146 * ENV: Korn Shell Variables.
6147 * EUID: Bash Variables.
6148 * expand-tilde: Readline Init File Syntax.
6149 * FCEDIT: Korn Shell Variables.
6150 * FIGNORE: Bash Variables.
6151 * GLOBIGNORE: Bash Variables.
6152 * histchars: Bash Variables.
6153 * HISTCMD: Bash Variables.
6154 * HISTCONTROL: Bash Variables.
6155 * HISTFILE: Bash Variables.
6156 * HISTFILESIZE: Bash Variables.
6157 * HISTIGNORE: Bash Variables.
6158 * HISTSIZE: Bash Variables.
6159 * HOME: Bourne Shell Variables.
6160 * horizontal-scroll-mode: Readline Init File Syntax.
6161 * HOSTFILE: Bash Variables.
6162 * HOSTNAME: Bash Variables.
6163 * HOSTTYPE: Bash Variables.
6164 * IFS: Bourne Shell Variables.
6165 * IGNOREEOF <1>: Bash Variables.
6166 * IGNOREEOF: C Shell Variables.
6167 * input-meta: Readline Init File Syntax.
6168 * INPUTRC: Bash Variables.
6169 * keymap: Readline Init File Syntax.
6170 * LANG: Bash Variables.
6171 * LC_ALL: Bash Variables.
6172 * LC_MESSAGES: Bash Variables.
6173 * LINENO: Korn Shell Variables.
6174 * MACHTYPE: Bash Variables.
6175 * MAIL: Bourne Shell Variables.
6176 * MAILCHECK: Bash Variables.
6177 * MAILPATH: Bourne Shell Variables.
6178 * mark-modified-lines: Readline Init File Syntax.
6179 * meta-flag: Readline Init File Syntax.
6180 * OLDPWD: Korn Shell Variables.
6181 * OPTARG: Bourne Shell Variables.
6182 * OPTERR: Bash Variables.
6183 * OPTIND: Bourne Shell Variables.
6184 * OSTYPE: Bash Variables.
6185 * output-meta: Readline Init File Syntax.
6186 * PATH: Bourne Shell Variables.
6187 * PIPESTATUS: Bash Variables.
6188 * PPID: Bash Variables.
6189 * PROMPT_COMMAND: Bash Variables.
6190 * PS1: Bourne Shell Variables.
6191 * PS2: Bourne Shell Variables.
6192 * PS3: Korn Shell Variables.
6193 * PS4: Korn Shell Variables.
6194 * PWD: Korn Shell Variables.
6195 * RANDOM: Korn Shell Variables.
6196 * REPLY: Korn Shell Variables.
6197 * SECONDS: Korn Shell Variables.
6198 * SHELLOPTS: Bash Variables.
6199 * SHLVL: Bash Variables.
6200 * show-all-if-ambiguous: Readline Init File Syntax.
6201 * TIMEFORMAT: Bash Variables.
6202 * TMOUT: Korn Shell Variables.
6203 * UID: Bash Variables.
6204 * visible-stats: Readline Init File Syntax.
6207 File: bashref.info, Node: Function Index, Next: Concept Index, Prev: Variable Index, Up: Top
6214 * abort (C-g): Miscellaneous Commands.
6215 * accept-line (Newline, Return): Commands For History.
6216 * backward-char (C-b): Commands For Moving.
6217 * backward-delete-char (Rubout): Commands For Text.
6218 * backward-kill-line (C-x Rubout): Commands For Killing.
6219 * backward-kill-word (M-DEL): Commands For Killing.
6220 * backward-word (M-b): Commands For Moving.
6221 * beginning-of-history (M-<): Commands For History.
6222 * beginning-of-line (C-a): Commands For Moving.
6223 * call-last-kbd-macro (C-x e): Keyboard Macros.
6224 * capitalize-word (M-c): Commands For Text.
6225 * character-search (C-]): Miscellaneous Commands.
6226 * character-search-backward (M-C-]): Miscellaneous Commands.
6227 * clear-screen (C-l): Commands For Moving.
6228 * complete (TAB): Commands For Completion.
6229 * copy-backward-word (): Commands For Killing.
6230 * copy-forward-word (): Commands For Killing.
6231 * copy-region-as-kill (): Commands For Killing.
6232 * delete-char (C-d): Commands For Text.
6233 * delete-horizontal-space (): Commands For Killing.
6234 * digit-argument (M-0, M-1, ... M-): Numeric Arguments.
6235 * do-uppercase-version (M-a, M-b, M-X, ...): Miscellaneous Commands.
6236 * downcase-word (M-l): Commands For Text.
6237 * dump-functions (): Miscellaneous Commands.
6238 * dump-macros (): Miscellaneous Commands.
6239 * dump-variables (): Miscellaneous Commands.
6240 * end-kbd-macro (C-x )): Keyboard Macros.
6241 * end-of-history (M->): Commands For History.
6242 * end-of-line (C-e): Commands For Moving.
6243 * exchange-point-and-mark (C-x C-x): Miscellaneous Commands.
6244 * forward-char (C-f): Commands For Moving.
6245 * forward-search-history (C-s): Commands For History.
6246 * forward-word (M-f): Commands For Moving.
6247 * history-search-backward (): Commands For History.
6248 * history-search-forward (): Commands For History.
6249 * insert-comment (M-#): Miscellaneous Commands.
6250 * insert-completions (M-*): Commands For Completion.
6251 * kill-line (C-k): Commands For Killing.
6252 * kill-region (): Commands For Killing.
6253 * kill-whole-line (): Commands For Killing.
6254 * kill-word (M-d): Commands For Killing.
6255 * next-history (C-n): Commands For History.
6256 * non-incremental-forward-search-history (M-n): Commands For History.
6257 * non-incremental-reverse-search-history (M-p): Commands For History.
6258 * possible-completions (M-?): Commands For Completion.
6259 * prefix-meta (ESC): Miscellaneous Commands.
6260 * previous-history (C-p): Commands For History.
6261 * quoted-insert (C-q, C-v): Commands For Text.
6262 * re-read-init-file (C-x C-r): Miscellaneous Commands.
6263 * redraw-current-line (): Commands For Moving.
6264 * reverse-search-history (C-r): Commands For History.
6265 * revert-line (M-r): Miscellaneous Commands.
6266 * self-insert (a, b, A, 1, !, ...): Commands For Text.
6267 * set-mark (C-@): Miscellaneous Commands.
6268 * start-kbd-macro (C-x (): Keyboard Macros.
6269 * tab-insert (M-TAB): Commands For Text.
6270 * tilde-expand (M-~): Miscellaneous Commands.
6271 * transpose-chars (C-t): Commands For Text.
6272 * transpose-words (M-t): Commands For Text.
6273 * undo (C-_, C-x C-u): Miscellaneous Commands.
6274 * universal-argument (): Numeric Arguments.
6275 * unix-line-discard (C-u): Commands For Killing.
6276 * unix-word-rubout (C-w): Commands For Killing.
6277 * upcase-word (M-u): Commands For Text.
6278 * yank (C-y): Commands For Killing.
6279 * yank-last-arg (M-., M-_): Commands For History.
6280 * yank-nth-arg (M-C-y): Commands For History.
6281 * yank-pop (M-y): Commands For Killing.
6284 File: bashref.info, Node: Concept Index, Prev: Function Index, Up: Top
6291 * alias expansion: Aliases.
6292 * arithmetic evaluation: Arithmetic Evaluation.
6293 * arithmetic expansion: Arithmetic Expansion.
6294 * arithmetic, shell: Shell Arithmetic.
6296 * background: Job Control Basics.
6297 * Bash configuration: Basic Installation.
6298 * Bash installation: Basic Installation.
6299 * Bourne shell: Basic Shell Features.
6300 * brace expansion: Brace Expansion.
6301 * builtin: Definitions.
6302 * command editing: Readline Bare Essentials.
6303 * command execution: Command Search and Execution.
6304 * command history: Bash History Facilities.
6305 * command search: Command Search and Execution.
6306 * command substitution: Command Substitution.
6307 * command timing: Pipelines.
6308 * commands, conditional: Conditional Constructs.
6309 * commands, grouping: Command Grouping.
6310 * commands, lists: Lists.
6311 * commands, looping: Looping Constructs.
6312 * commands, pipelines: Pipelines.
6313 * commands, simple: Simple Commands.
6314 * comments, shell: Comments.
6315 * configuration: Basic Installation.
6316 * control operator: Definitions.
6317 * editing command lines: Readline Bare Essentials.
6318 * environment: Environment.
6319 * evaluation, arithmetic: Arithmetic Evaluation.
6320 * event designators: Event Designators.
6321 * exit status <1>: Definitions.
6322 * exit status: Exit Status.
6323 * expansion: Shell Expansions.
6324 * expansion, arithmetic: Arithmetic Expansion.
6325 * expansion, brace: Brace Expansion.
6326 * expansion, filename: Filename Expansion.
6327 * expansion, parameter: Shell Parameter Expansion.
6328 * expansion, pathname: Filename Expansion.
6329 * expansion, tilde: Tilde Expansion.
6330 * expressions, arithmetic: Arithmetic Evaluation.
6331 * expressions, conditional: Bash Conditional Expressions.
6332 * field: Definitions.
6333 * filename: Definitions.
6334 * filename expansion: Filename Expansion.
6335 * foreground: Job Control Basics.
6336 * functions, shell: Shell Functions.
6337 * history events: Event Designators.
6338 * history expansion: History Interaction.
6339 * history list: Bash History Facilities.
6340 * History, how to use: Job Control Variables.
6341 * identifier: Definitions.
6342 * initialization file, readline: Readline Init File.
6343 * installation: Basic Installation.
6344 * interaction, readline: Readline Interaction.
6345 * interactive shell <1>: Is This Shell Interactive?.
6346 * interactive shell: Invoking Bash.
6348 * job control <1>: Definitions.
6349 * job control: Job Control Basics.
6350 * kill ring: Readline Killing Commands.
6351 * killing text: Readline Killing Commands.
6352 * localization: Locale Translation.
6353 * metacharacter: Definitions.
6354 * name: Definitions.
6355 * notation, readline: Readline Bare Essentials.
6356 * operator, shell: Definitions.
6357 * parameter expansion: Shell Parameter Expansion.
6358 * parameters: Shell Parameters.
6359 * parameters, positional: Positional Parameters.
6360 * parameters, special: Special Parameters.
6361 * pathname expansion: Filename Expansion.
6362 * pipeline: Pipelines.
6363 * POSIX: Definitions.
6364 * POSIX Mode: Bash POSIX Mode.
6365 * process group: Definitions.
6366 * process group ID: Definitions.
6367 * process substitution: Process Substitution.
6368 * prompting: Printing a Prompt.
6370 * quoting, ANSI: ANSI-C Quoting.
6371 * Readline, how to use: Modifiers.
6372 * redirection: Redirections.
6373 * reserved word: Definitions.
6374 * restricted shell: The Restricted Shell.
6375 * return status: Definitions.
6376 * shell function: Shell Functions.
6377 * shell script: Shell Scripts.
6378 * shell variable: Shell Parameters.
6379 * signal: Definitions.
6380 * signal handling: Signals.
6381 * special builtin: Definitions.
6382 * startup files: Bash Startup Files.
6383 * suspending jobs: Job Control Basics.
6384 * tilde expansion: Tilde Expansion.
6385 * token: Definitions.
6386 * variable, shell: Shell Parameters.
6387 * word: Definitions.
6388 * word splitting: Word Splitting.
6389 * yanking text: Readline Killing Commands.
6395 Node: Introduction
\7f3117
6396 Node: What is Bash?
\7f3342
6397 Node: What is a shell?
\7f4426
6398 Node: Definitions
\7f6307
6399 Node: Basic Shell Features
\7f8947
6400 Node: Shell Syntax
\7f10468
6401 Node: Shell Operation
\7f10758
6402 Node: Quoting
\7f11992
6403 Node: Escape Character
\7f13027
6404 Node: Single Quotes
\7f13458
6405 Node: Double Quotes
\7f13787
6406 Node: ANSI-C Quoting
\7f14483
6407 Node: Locale Translation
\7f15215
6408 Node: Comments
\7f15636
6409 Node: Simple Commands
\7f16160
6410 Node: Pipelines
\7f16749
6412 Node: Looping Constructs
\7f19095
6413 Node: Conditional Constructs
\7f20272
6414 Node: Command Grouping
\7f22337
6415 Node: Shell Functions
\7f23721
6416 Node: Shell Parameters
\7f25489
6417 Node: Positional Parameters
\7f26812
6418 Node: Special Parameters
\7f27506
6419 Node: Shell Expansions
\7f29998
6420 Node: Shell Parameter Expansion
\7f31998
6421 Node: Command Substitution
\7f38003
6422 Node: Process Substitution
\7f39003
6423 Node: Word Splitting
\7f39909
6424 Node: Filename Expansion
\7f41361
6425 Node: Quote Removal
\7f43727
6426 Node: Redirections
\7f44013
6427 Node: Executing Commands
\7f49754
6428 Node: Command Search and Execution
\7f50209
6429 Node: Environment
\7f51943
6430 Node: Exit Status
\7f53579
6431 Node: Signals
\7f54596
6432 Node: Shell Scripts
\7f55807
6433 Node: Bourne Shell Features
\7f57676
6434 Node: Bourne Shell Builtins
\7f58346
6435 Node: Bourne Shell Variables
\7f66619
6436 Node: Other Bourne Shell Features
\7f68156
6437 Node: Major Differences From The Bourne Shell
\7f68913
6438 Node: Csh Features
\7f79111
6439 Node: Brace Expansion
\7f80029
6440 Node: Tilde Expansion
\7f81584
6441 Node: C Shell Builtins
\7f82216
6442 Node: C Shell Variables
\7f86732
6443 Node: Korn Shell Features
\7f87140
6444 Node: Korn Shell Constructs
\7f87868
6445 Node: Korn Shell Builtins
\7f89562
6446 Node: Korn Shell Variables
\7f91720
6447 Node: Aliases
\7f93505
6448 Node: Alias Builtins
\7f95969
6449 Node: Bash Features
\7f96585
6450 Node: Invoking Bash
\7f97576
6451 Node: Bash Startup Files
\7f101441
6452 Node: Is This Shell Interactive?
\7f105024
6453 Node: Bash Builtins
\7f105755
6454 Node: The Set Builtin
\7f121569
6455 Node: Bash Conditional Expressions
\7f126939
6456 Node: Bash Variables
\7f131590
6457 Node: Shell Arithmetic
\7f141103
6458 Node: Arithmetic Evaluation
\7f141571
6459 Node: Arithmetic Expansion
\7f143601
6460 Node: Arithmetic Builtins
\7f144405
6461 Node: Arrays
\7f144876
6462 Node: Printing a Prompt
\7f147903
6463 Node: The Restricted Shell
\7f149501
6464 Node: Bash POSIX Mode
\7f150731
6465 Node: Job Control
\7f154303
6466 Node: Job Control Basics
\7f154768
6467 Node: Job Control Builtins
\7f158911
6468 Node: Job Control Variables
\7f161794
6469 Node: Using History Interactively
\7f162955
6470 Node: Bash History Facilities
\7f163544
6471 Node: History Interaction
\7f165942
6472 Node: Event Designators
\7f168504
6473 Node: Word Designators
\7f169427
6474 Node: Modifiers
\7f170676
6475 Node: Command Line Editing
\7f171993
6476 Node: Introduction and Notation
\7f172653
6477 Node: Readline Interaction
\7f173661
6478 Node: Readline Bare Essentials
\7f174849
6479 Node: Readline Movement Commands
\7f176378
6480 Node: Readline Killing Commands
\7f177268
6481 Node: Readline Arguments
\7f178970
6482 Node: Searching
\7f179943
6483 Node: Readline Init File
\7f181579
6484 Node: Readline Init File Syntax
\7f182635
6485 Node: Conditional Init Constructs
\7f190424
6486 Node: Sample Init File
\7f192705
6487 Node: Bindable Readline Commands
\7f195722
6488 Node: Commands For Moving
\7f196472
6489 Node: Commands For History
\7f197319
6490 Node: Commands For Text
\7f199992
6491 Node: Commands For Killing
\7f201734
6492 Node: Numeric Arguments
\7f203760
6493 Node: Commands For Completion
\7f204386
6494 Node: Keyboard Macros
\7f207348
6495 Node: Miscellaneous Commands
\7f207906
6496 Node: Readline vi Mode
\7f211937
6497 Node: Installing Bash
\7f212813
6498 Node: Basic Installation
\7f213890
6499 Node: Compilers and Options
\7f216389
6500 Node: Compiling For Multiple Architectures
\7f217123
6501 Node: Installation Names
\7f218780
6502 Node: Specifying the System Type
\7f219502
6503 Node: Sharing Defaults
\7f220213
6504 Node: Operation Controls
\7f220878
6505 Node: Optional Features
\7f221783
6506 Node: Reporting Bugs
\7f226408
6507 Node: Builtin Index
\7f227485
6508 Node: Reserved Word Index
\7f230898
6509 Node: Variable Index
\7f232206
6510 Node: Function Index
\7f237285
6511 Node: Concept Index
\7f241643
projects / platform / upstream / bash.git / blob