NAME

SYNOPSIS

COPYRIGHT

DESCRIPTION

OPTIONS

-c string

If the -c option is present, then commands are read from string. If there are arguments after the string, they are assigned to the positional parameters, starting with $0.

-i

If the -i option is present, the shell is interactive.

-l

Make bash act as if it had been invoked as a login shell (see INVOCATION below).

-r

If the -r option is present, the shell becomes restricted (see RESTRICTED SHELL below).

-s

If the -s option is present, or if no arguments remain after option processing, then commands are read from the standard input. This option allows the positional parameters to be set when invoking an interactive shell.

-D

A list of all double-quoted strings preceded by $ is printed on the standard output. These are the strings that are subject to language translation when the current locale is not C or POSIX. This implies the -n option; no commands will be executed.

[-+]O [shopt_option]

shopt_option is one of the shell options accepted by the shopt builtin (see SHELL BUILTIN COMMANDS below). If shopt_option is present, -O sets the value of that option; +O unsets it. If shopt_option is not supplied, the names and values of the shell options accepted by shopt are printed on the standard output. If the invocation option is +O, the output is displayed in a format that may be reused as input.

--

A -- signals the end of options and disables further option processing. Any arguments after the -- are treated as filenames and arguments. An argument of - is equivalent to --.

--debugger

Arrange for the debugger profile to be executed before the shell starts. Turns on extended debugging mode (see the description of the extdebug option to the shopt builtin below).

--dump-po-strings

Equivalent to -D, but the output is in the GNU gettext po (portable object) file format.

--dump-strings

Equivalent to -D.

--help

Display a usage message on standard output and exit successfully.

--init-file file

--rcfile file

Execute commands from file instead of the standard personal initialization file ~/.bashrc if the shell is interactive (see INVOCATION below).

--login

Equivalent to -l.

--noediting

Do not use the GNU readline library to read command lines when the shell is interactive.

--noprofile

Do not read either the system-wide startup file /etc/profile or any of the personal initialization files ~/.bash_profile, ~/.bash_login, or ~/.profile. By default, bash reads these files when it is invoked as a login shell (see INVOCATION below).

--norc

Do not read and execute the personal initialization file ~/.bashrc if the shell is interactive. This option is on by default if the shell is invoked as sh.

--posix

Change the behavior of bash where the default operation differs from the POSIX standard to match the standard ( posix mode).

--restricted

The shell becomes restricted (see RESTRICTED SHELL below).

--rpm-requires

Produce the list of files that are required for the shell script to run. This implies '-n' and is subject to the same limitations as compile time error checking checking; Command substitutions, Conditional expressions and eval builtin are not parsed so some dependencies may be missed.

--verbose

Equivalent to -v.

--version

Show version information for this instance of bash on the standard output and exit successfully.

ARGUMENTS

INVOCATION

DEFINITIONS

blank

A space or tab.

word

A sequence of characters considered as a single unit by the shell. Also known as a token.

name

A word consisting only of alphanumeric characters and underscores, and beginning with an alphabetic character or an underscore. Also referred to as an identifier.

metacharacter

A character that, when unquoted, separates words. One of the following:

 

control operator

A token that performs a control function. It is one of the following symbols:

RESERVED WORDS

SHELL GRAMMAR

Simple Commands

Pipelines

Lists

Compound Commands

(list)

list is executed in a subshell environment (see COMMAND EXECUTION ENVIRONMENT below). Variable assignments and builtin commands that affect the shell's environment do not remain in effect after the command completes. The return status is the exit status of list.

{ list; }

list is simply executed in the current shell environment. list must be terminated with a newline or semicolon. This is known as a group command. The return status is the exit status of list. Note that unlike the metacharacters ( and ), { and } are reserved words and must occur where a reserved word is permitted to be recognized. Since they do not cause a word break, they must be separated from list by whitespace or another shell metacharacter.

((expression))

The expression is evaluated according to the rules described below under ARITHMETIC EVALUATION. If the value of the expression is non-zero, the return status is 0; otherwise the return status is 1. This is exactly equivalent to let "expression".

[[ expression ]]

Return a status of 0 or 1 depending on the evaluation of the conditional expression expression. Expressions are composed of the primaries described below under CONDITIONAL EXPRESSIONS. Word splitting and pathname expansion are not performed on the words between the [[ and ]]; tilde expansion, parameter and variable expansion, arithmetic expansion, command substitution, process substitution, and quote removal are performed. Conditional operators such as -f must be unquoted to be recognized as primaries.

When used with [[, the < and > operators sort lexicographically using the current locale.

When the == and != operators are used, the string to the right of the operator is considered a pattern and matched according to the rules described below under Pattern Matching. If the shell option nocasematch is enabled, the match is performed without regard to the case of alphabetic characters. The return value is 0 if the string matches ( ==) or does not match ( !=) the pattern, and 1 otherwise. Any part of the pattern may be quoted to force it to be matched as a string.

An additional binary operator, =~, is available, with the same precedence as == and !=. When it is used, the string to the right of the operator is considered an extended regular expression and matched accordingly (as in regex(3)). The return value is 0 if the string matches the pattern, and 1 otherwise. If the regular expression is syntactically incorrect, the conditional expression's return value is 2. If the shell option nocasematch is enabled, the match is performed without regard to the case of alphabetic characters. Any part of the pattern may be quoted to force it to be matched as a string. Substrings matched by parenthesized subexpressions within the regular expression are saved in the array variable BASH_REMATCH. The element of BASH_REMATCH with index 0 is the portion of the string matching the entire regular expression. The element of BASH_REMATCH with index n is the portion of the string matching the nth parenthesized subexpression.

Expressions may be combined using the following operators, listed in decreasing order of precedence:

for name [ [ in [ word ... ] ] ; ] do list ; done

The list of words following in is expanded, generating a list of items. The variable name is set to each element of this list in turn, and list is executed each time. If the in word is omitted, the for command executes list once for each positional parameter that is set (see PARAMETERS below). The return status is the exit status of the last command that executes. If the expansion of the items following in results in an empty list, no commands are executed, and the return status is 0.

for (( expr1 ; expr2 ; expr3 )) ; do list ; done

First, the arithmetic expression expr1 is evaluated according to the rules described below under ARITHMETIC EVALUATION. The arithmetic expression expr2 is then evaluated repeatedly until it evaluates to zero. Each time expr2 evaluates to a non-zero value, list is executed and the arithmetic expression expr3 is evaluated. If any expression is omitted, it behaves as if it evaluates to 1. The return value is the exit status of the last command in list that is executed, or false if any of the expressions is invalid.

select name [ in word ] ; do list ; done

The list of words following in is expanded, generating a list of items. The set of expanded words is printed on the standard error, each preceded by a number. If the in word is omitted, the positional parameters are printed (see PARAMETERS below). The PS3 prompt is then displayed and a line read from the standard input. If the line consists of a number corresponding to one of the displayed words, then the value of name is set to that word. If the line is empty, the words and prompt are displayed again. If EOF is read, the command completes. Any other value read causes name to be set to null. The line read is saved in the variable REPLY. The list is executed after each selection until a break command is executed. The exit status of select is the exit status of the last command executed in list, or zero if no commands were executed.

case word in [ [(] pattern [ | pattern ] ... ) list ;; ] ... esac

A case command first expands word, and tries to match it against each pattern in turn, using the same matching rules as for pathname expansion (see Pathname Expansion below). The word is expanded using tilde expansion, parameter and variable expansion, arithmetic substitution, command substitution, process substitution and quote removal. Each pattern examined is expanded using tilde expansion, parameter and variable expansion, arithmetic substitution, command substitution, and process substitution. If the shell option nocasematch is enabled, the match is performed without regard to the case of alphabetic characters. When a match is found, the corresponding list is executed. If the ;; operator is used, no subsequent matches are attempted after the first pattern match. Using ;& in place of ;; causes execution to continue with the list associated with the next set of patterns. Using ;;& in place of ;; causes the shell to test the next pattern list in the statement, if any, and execute any associated list on a successful match. The exit status is zero if no pattern matches. Otherwise, it is the exit status of the last command executed in list.

if list; then list; [ elif list; then list; ] ... [ else list; ] fi

The if list is executed. If its exit status is zero, the then list is executed. Otherwise, each elif list is executed in turn, and if its exit status is zero, the corresponding then list is executed and the command completes. Otherwise, the else list is executed, if present. The exit status is the exit status of the last command executed, or zero if no condition tested true.

while list-1; do list-2; done

until list-1; do list-2; done

The while command continuously executes the list list-2 as long as the last command in the list list-1 returns an exit status of zero. The until command is identical to the while command, except that the test is negated; list-2 is executed as long as the last command in list-1 returns a non-zero exit status. The exit status of the while and until commands is the exit status of the last command executed in list-2, or zero if none was executed.

Coprocesses

Shell Function Definitions

name () compound-command [redirection]

function name [()] compound-command [redirection]

This defines a function named name. The reserved word function is optional. If the function reserved word is supplied, the parentheses are optional. The body of the function is the compound command compound-command (see Compound Commands above). That command is usually a list of commands between { and }, but may be any command listed under Compound Commands above. compound-command is executed whenever name is specified as the name of a simple command. Any redirections (see REDIRECTION below) specified when a function is defined are performed when the function is executed. The exit status of a function definition is zero unless a syntax error occurs or a readonly function with the same name already exists. When executed, the exit status of a function is the exit status of the last command executed in the body. (See FUNCTIONS below.)

COMMENTS

QUOTING

PARAMETERS

Positional Parameters

Special Parameters

*

Expands to the positional parameters, starting from one. When the expansion occurs within double quotes, it expands to a single word with the value of each parameter separated by the first character of the IFS special variable. That is, " $*" is equivalent to " $1c$2c...", where c is the first character of the value of the IFS variable. If IFS is unset, the parameters are separated by spaces. If IFS is null, the parameters are joined without intervening separators.

@

Expands to the positional parameters, starting from one. When the expansion occurs within double quotes, each parameter expands to a separate word. That is, " $@" is equivalent to " $1" " $2" ... If the double-quoted expansion occurs within a word, the expansion of the first parameter is joined with the beginning part of the original word, and the expansion of the last parameter is joined with the last part of the original word. When there are no positional parameters, " $@" and $@ expand to nothing (i.e., they are removed).

#

Expands to the number of positional parameters in decimal.

?

Expands to the exit status of the most recently executed foreground pipeline.

-

Expands to the current option flags as specified upon invocation, by the set builtin command, or those set by the shell itself (such as the -i option).

$

Expands to the process ID of the shell. In a () subshell, it expands to the process ID of the current shell, not the subshell.

!

Expands to the process ID of the most recently executed background (asynchronous) command.

0

Expands to the name of the shell or shell script. This is set at shell initialization. If bash is invoked with a file of commands, $0 is set to the name of that file. If bash is started with the -c option, then $0 is set to the first argument after the string to be executed, if one is present. Otherwise, it is set to the file name used to invoke bash, as given by argument zero.

_

At shell startup, set to the absolute pathname used to invoke the shell or shell script being executed as passed in the environment or argument list. Subsequently, expands to the last argument to the previous command, after expansion. Also set to the full pathname used to invoke each command executed and placed in the environment exported to that command. When checking mail, this parameter holds the name of the mail file currently being checked.

Shell Variables

BASH

Expands to the full file name used to invoke this instance of bash.

BASHOPTS

A colon-separated list of enabled shell options. Each word in the list is a valid argument for the -s option to the shopt builtin command (see SHELL BUILTIN COMMANDS below). The options appearing in BASHOPTS are those reported as on by shopt. If this variable is in the environment when bash starts up, each shell option in the list will be enabled before reading any startup files. This variable is read-only.

BASHPID

Expands to the process ID of the current bash process. This differs from $$ under certain circumstances, such as subshells that do not require bash to be re-initialized.

BASH_ALIASES

An associative array variable whose members correspond to the internal list of aliases as maintained by the alias builtin. Elements added to this array appear in the alias list; unsetting array elements cause aliases to be removed from the alias list.

BASH_ARGC

An array variable whose values are the number of parameters in each frame of the current bash execution call stack. The number of parameters to the current subroutine (shell function or script executed with . or source) is at the top of the stack. When a subroutine is executed, the number of parameters passed is pushed onto BASH_ARGC. The shell sets BASH_ARGC only when in extended debugging mode (see the description of the extdebug option to the shopt builtin below)

BASH_ARGV

An array variable containing all of the parameters in the current bash execution call stack. The final parameter of the last subroutine call is at the top of the stack; the first parameter of the initial call is at the bottom. When a subroutine is executed, the parameters supplied are pushed onto BASH_ARGV. The shell sets BASH_ARGV only when in extended debugging mode (see the description of the extdebug option to the shopt builtin below)

BASH_CMDS

An associative array variable whose members correspond to the internal hash table of commands as maintained by the hash builtin. Elements added to this array appear in the hash table; unsetting array elements cause commands to be removed from the hash table.

BASH_COMMAND

The command currently being executed or about to be executed, unless the shell is executing a command as the result of a trap, in which case it is the command executing at the time of the trap.

BASH_EXECUTION_STRING

The command argument to the -c invocation option.

BASH_LINENO

An array variable whose members are the line numbers in source files where each corresponding member of FUNCNAME was invoked. ${BASH_LINENO[ $i]} is the line number in the source file ( ${BASH_SOURCE[$i+1]}) where ${FUNCNAME[$i]} was called (or ${BASH_LINENO[$i-1]} if referenced within another shell function). Use LINENO to obtain the current line number.

BASH_REMATCH

An array variable whose members are assigned by the =~ binary operator to the [[ conditional command. The element with index 0 is the portion of the string matching the entire regular expression. The element with index n is the portion of the string matching the nth parenthesized subexpression. This variable is read-only.

BASH_SOURCE

An array variable whose members are the source filenames where the corresponding shell function names in the FUNCNAME array variable are defined. The shell function ${FUNCNAME[$i]} is defined in the file ${BASH_SOURCE[$i]} and called from ${BASH_SOURCE[$i+1]}.

BASH_SUBSHELL

Incremented by one each time a subshell or subshell environment is spawned. The initial value is 0.

BASH_VERSINFO

A readonly array variable whose members hold version information for this instance of bash. The values assigned to the array members are as follows:

BASH_VERSION

Expands to a string describing the version of this instance of bash.

COMP_CWORD

An index into ${COMP_WORDS} of the word containing the current cursor position. This variable is available only in shell functions invoked by the programmable completion facilities (see Programmable Completion below).

COMP_KEY

The key (or final key of a key sequence) used to invoke the current completion function.

COMP_LINE

The current command line. This variable is available only in shell functions and external commands invoked by the programmable completion facilities (see Programmable Completion below).

COMP_POINT

The index of the current cursor position relative to the beginning of the current command. If the current cursor position is at the end of the current command, the value of this variable is equal to ${#COMP_LINE}. This variable is available only in shell functions and external commands invoked by the programmable completion facilities (see Programmable Completion below).

COMP_TYPE

Set to an integer value corresponding to the type of completion attempted that caused a completion function to be called: TAB, for normal completion, ?, for listing completions after successive tabs, !, for listing alternatives on partial word completion, @, to list completions if the word is not unmodified, or %, for menu completion. This variable is available only in shell functions and external commands invoked by the programmable completion facilities (see Programmable Completion below).

COMP_WORDBREAKS

The set of characters that the readline library treats as word separators when performing word completion. If COMP_WORDBREAKS is unset, it loses its special properties, even if it is subsequently reset.

COMP_WORDS

An array variable (see Arrays below) consisting of the individual words in the current command line. The line is split into words as readline would split it, using COMP_WORDBREAKS as described above. This variable is available only in shell functions invoked by the programmable completion facilities (see Programmable Completion below).

COPROC

An array variable (see Arrays below) created to hold the file descriptors for output from and input to an unnamed coprocess (see Coprocesses above).

DIRSTACK

An array variable (see Arrays below) containing the current contents of the directory stack. Directories appear in the stack in the order they are displayed by the dirs builtin. Assigning to members of this array variable may be used to modify directories already in the stack, but the pushd and popd builtins must be used to add and remove directories. Assignment to this variable will not change the current directory. If DIRSTACK is unset, it loses its special properties, even if it is subsequently reset.

EUID

Expands to the effective user ID of the current user, initialized at shell startup. This variable is readonly.

FUNCNAME

An array variable containing the names of all shell functions currently in the execution call stack. The element with index 0 is the name of any currently-executing shell function. The bottom-most element (the one with the highest index) is "main". This variable exists only when a shell function is executing. Assignments to FUNCNAME have no effect and return an error status. If FUNCNAME is unset, it loses its special properties, even if it is subsequently reset.

This variable can be used with BASH_LINENO and BASH_SOURCE. Each element of FUNCNAME has corresponding elements in BASH_LINENO and BASH_SOURCE to describe the call stack. For instance, ${FUNCNAME[$i]} was called from the file ${BASH_SOURCE[$i+1]} at line number ${BASH_LINENO[ $i]}. The caller builtin displays the current call stack using this information.

GROUPS

An array variable containing the list of groups of which the current user is a member. Assignments to GROUPS have no effect and return an error status. If GROUPS is unset, it loses its special properties, even if it is subsequently reset.

HISTCMD

The history number, or index in the history list, of the current command. If HISTCMD is unset, it loses its special properties, even if it is subsequently reset.

HOSTNAME

Automatically set to the name of the current host.

HOSTTYPE

Automatically set to a string that uniquely describes the type of machine on which bash is executing. The default is system-dependent.

LINENO

Each time this parameter is referenced, the shell substitutes a decimal number representing the current sequential line number (starting with 1) within a script or function. When not in a script or function, the value substituted is not guaranteed to be meaningful. If LINENO is unset, it loses its special properties, even if it is subsequently reset.

MACHTYPE

Automatically set to a string that fully describes the system type on which bash is executing, in the standard GNU cpu-company-system format. The default is system-dependent.

MAPFILE

An array variable (see Arrays below) created to hold the text read by the mapfile builtin when no variable name is supplied.

OLDPWD

The previous working directory as set by the cd command.

OPTARG

The value of the last option argument processed by the getopts builtin command (see SHELL BUILTIN COMMANDS below).

OPTIND

The index of the next argument to be processed by the getopts builtin command (see SHELL BUILTIN COMMANDS below).

OSTYPE

Automatically set to a string that describes the operating system on which bash is executing. The default is system-dependent.

PIPESTATUS

An array variable (see Arrays below) containing a list of exit status values from the processes in the most-recently-executed foreground pipeline (which may contain only a single command).

PPID

The process ID of the shell's parent. This variable is readonly.

PWD

The current working directory as set by the cd command.

RANDOM

Each time this parameter is referenced, a random integer between 0 and 32767 is generated. The sequence of random numbers may be initialized by assigning a value to RANDOM. If RANDOM is unset, it loses its special properties, even if it is subsequently reset.

READLINE_LINE

The contents of the readline line buffer, for use with "bind -x" (see SHELL BUILTIN COMMANDS below).

READLINE_POINT

The position of the insertion point in the readline line buffer, for use with "bind -x" (see SHELL BUILTIN COMMANDS below).

REPLY

Set to the line of input read by the read builtin command when no arguments are supplied.

SECONDS

Each time this parameter is referenced, the number of seconds since shell invocation is returned. If a value is assigned to SECONDS, the value returned upon subsequent references is the number of seconds since the assignment plus the value assigned. If SECONDS is unset, it loses its special properties, even if it is subsequently reset.

SHELLOPTS

A colon-separated list of enabled shell options. Each word in the list is a valid argument for the -o option to the set builtin command (see SHELL BUILTIN COMMANDS below). The options appearing in SHELLOPTS are those reported as on by set -o. If this variable is in the environment when bash starts up, each shell option in the list will be enabled before reading any startup files. This variable is read-only.

SHLVL

Incremented by one each time an instance of bash is started.

UID

Expands to the user ID of the current user, initialized at shell startup. This variable is readonly.

BASH_ENV

If this parameter is set when bash is executing a shell script, its value is interpreted as a filename containing commands to initialize the shell, as in ~/.bashrc. The value of BASH_ENV is subjected to parameter expansion, command substitution, and arithmetic expansion before being interpreted as a file name. PATH is not used to search for the resultant file name.

BASH_XTRACEFD

If set to an integer corresponding to a valid file descriptor, bash will write the trace output generated when set -x is enabled to that file descriptor. The file descriptor is closed when BASH_XTRACEFD is unset or assigned a new value. Unsetting BASH_XTRACEFD or assigning it the empty string causes the trace output to be sent to the standard error. Note that setting BASH_XTRACEFD to 2 (the standard error file descriptor) and then unsetting it will result in the standard error being closed.

CDPATH

The search path for the cd command. This is a colon-separated list of directories in which the shell looks for destination directories specified by the cd command. A sample value is ".:~:/usr".

COLUMNS

Used by the select compound command to determine the terminal width when printing selection lists. Automatically set upon receipt of a SIGWINCH.

COMPREPLY

An array variable from which bash reads the possible completions generated by a shell function invoked by the programmable completion facility (see Programmable Completion below).

EMACS

If bash finds this variable in the environment when the shell starts with value "t", it assumes that the shell is running in an Emacs shell buffer and disables line editing.

ENV

Similar to BASH_ENV; used when the shell is invoked in POSIX mode.

FCEDIT

The default editor for the fc builtin command.

FIGNORE

A colon-separated list of suffixes to ignore when performing filename completion (see READLINE below). A filename whose suffix matches one of the entries in FIGNORE is excluded from the list of matched filenames. A sample value is ".o:~".

FUNCNEST

If set to a numeric value greater than 0, defines a maximum function nesting level. Function invocations that exceed this nesting level will cause the current command to abort.

GLOBIGNORE

A colon-separated list of patterns defining the set of filenames to be ignored by pathname expansion. If a filename matched by a pathname expansion pattern also matches one of the patterns in GLOBIGNORE, it is removed from the list of matches.

HISTCONTROL

A colon-separated list of values controlling how commands are saved on the history list. If the list of values includes ignorespace, lines which begin with a space character are not saved in the history list. A value of ignoredups causes lines matching the previous history entry to not be saved. A value of ignoreboth is shorthand for ignorespace and ignoredups. A value of erasedups causes all previous lines matching the current line to be removed from the history list before that line is saved. Any value not in the above list is ignored. If HISTCONTROL is unset, or does not include a valid value, all lines read by the shell parser are saved on the history list, subject to the value of HISTIGNORE. The second and subsequent lines of a multi-line compound command are not tested, and are added to the history regardless of the value of HISTCONTROL.

HISTFILE

The name of the file in which command history is saved (see HISTORY below). The default value is ~/.bash_history. If unset, the command history is not saved when an interactive shell exits.

HISTFILESIZE

The maximum number of lines contained in the history file. When this variable is assigned a value, the history file is truncated, if necessary, by removing the oldest entries, to contain no more than that number of lines. The default value is 500. The history file is also truncated to this size after writing it when an interactive shell exits.

HISTIGNORE

A colon-separated list of patterns used to decide which command lines should be saved on the history list. Each pattern is anchored at the beginning of the line and must match the complete line (no implicit ` *' is appended). Each pattern is tested against the line after the checks specified by HISTCONTROL are applied. In addition to the normal shell pattern matching characters, ` &' matches the previous history line. ` &' may be escaped using a backslash; the backslash is removed before attempting a match. The second and subsequent lines of a multi-line compound command are not tested, and are added to the history regardless of the value of HISTIGNORE.

HISTSIZE

The number of commands to remember in the command history (see HISTORY below). The default value is 500.

HISTTIMEFORMAT

If this variable is set and not null, its value is used as a format string for strftime(3) to print the time stamp associated with each history entry displayed by the history builtin. If this variable is set, time stamps are written to the history file so they may be preserved across shell sessions. This uses the history comment character to distinguish timestamps from other history lines.

HOME

The home directory of the current user; the default argument for the cd builtin command. The value of this variable is also used when performing tilde expansion.

HOSTFILE

Contains the name of a file in the same format as /etc/hosts that should be read when the shell needs to complete a hostname. The list of possible hostname completions may be changed while the shell is running; the next time hostname completion is attempted after the value is changed, bash adds the contents of the new file to the existing list. If HOSTFILE is set, but has no value, or does not name a readable file, bash attempts to read /etc/hosts to obtain the list of possible hostname completions. When HOSTFILE is unset, the hostname list is cleared.

IFS

The Internal Field Separator that is used for word splitting after expansion and to split lines into words with the read builtin command. The default value is ``<space><tab><newline>''.

IGNOREEOF

Controls the action of an interactive shell on receipt of an EOF character as the sole input. If set, the value is the number of consecutive EOF characters which must be typed as the first characters on an input line before bash exits. If the variable exists but does not have a numeric value, or has no value, the default value is 10. If it does not exist, EOF signifies the end of input to the shell.

INPUTRC

The filename for the readline startup file, overriding the default of ~/.inputrc (see READLINE below).

LANG

Used to determine the locale category for any category not specifically selected with a variable starting with LC_.

LC_ALL

This variable overrides the value of LANG and any other LC_ variable specifying a locale category.

LC_COLLATE

This variable determines the collation order used when sorting the results of pathname expansion, and determines the behavior of range expressions, equivalence classes, and collating sequences within pathname expansion and pattern matching.

LC_CTYPE

This variable determines the interpretation of characters and the behavior of character classes within pathname expansion and pattern matching.

LC_MESSAGES

This variable determines the locale used to translate double-quoted strings preceded by a $.

LC_NUMERIC

This variable determines the locale category used for number formatting.

LINES

Used by the select compound command to determine the column length for printing selection lists. Automatically set upon receipt of a SIGWINCH.

MAIL

If this parameter is set to a file or directory name and the MAILPATH variable is not set, bash informs the user of the arrival of mail in the specified file or Maildir-format directory.

MAILCHECK

Specifies how often (in seconds) bash checks for mail. The default is 60 seconds. When it is time to check for mail, the shell does so before displaying the primary prompt. If this variable is unset, or set to a value that is not a number greater than or equal to zero, the shell disables mail checking.

MAILPATH

A colon-separated list of file names to be checked for mail. The message to be printed when mail arrives in a particular file may be specified by separating the file name from the message with a `?'. When used in the text of the message, $_ expands to the name of the current mailfile. Example:

OPTERR

If set to the value 1, bash displays error messages generated by the getopts builtin command (see SHELL BUILTIN COMMANDS below). OPTERR is initialized to 1 each time the shell is invoked or a shell script is executed.

PATH

The search path for commands. It is a colon-separated list of directories in which the shell looks for commands (see COMMAND EXECUTION below). A zero-length (null) directory name in the value of PATH indicates the current directory. A null directory name may appear as two adjacent colons, or as an initial or trailing colon. The default path is system-dependent, and is set by the administrator who installs bash. A common value is ``/usr/gnu/bin:/usr/local/bin:/usr/ucb:/bin:/usr/bin''.

POSIXLY_CORRECT

If this variable is in the environment when bash starts, the shell enters posix mode before reading the startup files, as if the --posix invocation option had been supplied. If it is set while the shell is running, bash enables posix mode, as if the command set -o posix had been executed.

PROMPT_COMMAND

If set, the value is executed as a command prior to issuing each primary prompt.

PROMPT_DIRTRIM

If set to a number greater than zero, the value is used as the number of trailing directory components to retain when expanding the \w and \W prompt string escapes (see PROMPTING below). Characters removed are replaced with an ellipsis.

PS1

The value of this parameter is expanded (see PROMPTING below) and used as the primary prompt string. The default value is `` \s-\v\$ ''.

PS2

The value of this parameter is expanded as with PS1 and used as the secondary prompt string. The default is `` > ''.

PS3

The value of this parameter is used as the prompt for the select command (see SHELL GRAMMAR above).

PS4

The value of this parameter is expanded as with PS1 and the value is printed before each command bash displays during an execution trace. The first character of PS4 is replicated multiple times, as necessary, to indicate multiple levels of indirection. The default is `` + ''.

SHELL

The full pathname to the shell is kept in this environment variable. If it is not set when the shell starts, bash assigns to it the full pathname of the current user's login shell.

TIMEFORMAT

The value of this parameter is used as a format string specifying how the timing information for pipelines prefixed with the time reserved word should be displayed. The % character introduces an escape sequence that is expanded to a time value or other information. The escape sequences and their meanings are as follows; the braces denote optional portions.

The optional p is a digit specifying the precision, the number of fractional digits after a decimal point. A value of 0 causes no decimal point or fraction to be output. At most three places after the decimal point may be specified; values of p greater than 3 are changed to 3. If p is not specified, the value 3 is used.

The optional l specifies a longer format, including minutes, of the form MMmSS.FFs. The value of p determines whether or not the fraction is included.

If this variable is not set, bash acts as if it had the value $'\nreal\t%3lR\nuser\t%3lU\nsys%3lS'. If the value is null, no timing information is displayed. A trailing newline is added when the format string is displayed.

TMOUT

If set to a value greater than zero, TMOUT is treated as the default timeout for the read builtin. The select command terminates if input does not arrive after TMOUT seconds when input is coming from a terminal. In an interactive shell, the value is interpreted as the number of seconds to wait for input after issuing the primary prompt. Bash terminates after waiting for that number of seconds if input does not arrive.

TMPDIR

If set, bash uses its value as the name of a directory in which bash creates temporary files for the shell's use.

auto_resume

This variable controls how the shell interacts with the user and job control. If this variable is set, single word simple commands without redirections are treated as candidates for resumption of an existing stopped job. There is no ambiguity allowed; if there is more than one job beginning with the string typed, the job most recently accessed is selected. The name of a stopped job, in this context, is the command line used to start it. If set to the value exact, the string supplied must match the name of a stopped job exactly; if set to substring, the string supplied needs to match a substring of the name of a stopped job. The substring value provides functionality analogous to the %? job identifier (see JOB CONTROL below). If set to any other value, the supplied string must be a prefix of a stopped job's name; this provides functionality analogous to the %string job identifier.

histchars

The two or three characters which control history expansion and tokenization (see HISTORY EXPANSION below). The first character is the history expansion character, the character which signals the start of a history expansion, normally ` !'. The second character is the quick substitution character, which is used as shorthand for re-running the previous command entered, substituting one string for another in the command. The default is ` ^'. The optional third character is the character which indicates that the remainder of the line is a comment when found as the first character of a word, normally ` #'. The history comment character causes history substitution to be skipped for the remaining words on the line. It does not necessarily cause the shell parser to treat the rest of the line as a comment.

Arrays

EXPANSION

Brace Expansion

Tilde Expansion

Parameter Expansion

${parameter}

The value of parameter is substituted. The braces are required when parameter is a positional parameter with more than one digit, or when parameter is followed by a character which is not to be interpreted as part of its name.

${parameter:-word}

Use Default Values. If parameter is unset or null, the expansion of word is substituted. Otherwise, the value of parameter is substituted.

${parameter:=word}

Assign Default Values. If parameter is unset or null, the expansion of word is assigned to parameter. The value of parameter is then substituted. Positional parameters and special parameters may not be assigned to in this way.

${parameter:?word}

Display Error if Null or Unset. If parameter is null or unset, the expansion of word (or a message to that effect if word is not present) is written to the standard error and the shell, if it is not interactive, exits. Otherwise, the value of parameter is substituted.

${parameter:+word}

Use Alternate Value. If parameter is null or unset, nothing is substituted, otherwise the expansion of word is substituted.

${parameter:offset}

${parameter:offset:length}

Substring Expansion. Expands to up to length characters of parameter starting at the character specified by offset. If length is omitted, expands to the substring of parameter starting at the character specified by offset. length and offset are arithmetic expressions (see ARITHMETIC EVALUATION below). If offset evaluates to a number less than zero, the value is used as an offset from the end of the value of parameter. If length evaluates to a number less than zero, and parameter is not @ and not an indexed or associative array, it is interpreted as an offset from the end of the value of parameter rather than a number of characters, and the expansion is the characters between the two offsets. If parameter is @, the result is length positional parameters beginning at offset. If parameter is an indexed array name subscripted by @ or *, the result is the length members of the array beginning with ${ parameter[offset]}. A negative offset is taken relative to one greater than the maximum index of the specified array. Substring expansion applied to an associative array produces undefined results. Note that a negative offset must be separated from the colon by at least one space to avoid being confused with the :- expansion. Substring indexing is zero-based unless the positional parameters are used, in which case the indexing starts at 1 by default. If offset is 0, and the positional parameters are used, $0 is prefixed to the list.

${!prefix*}

${!prefix@}

Names matching prefix. Expands to the names of variables whose names begin with prefix, separated by the first character of the IFS special variable. When @ is used and the expansion appears within double quotes, each variable name expands to a separate word.

${!name[@]}

${!name[*]}

List of array keys. If name is an array variable, expands to the list of array indices (keys) assigned in name. If name is not an array, expands to 0 if name is set and null otherwise. When @ is used and the expansion appears within double quotes, each key expands to a separate word.

${#parameter}

Parameter length. The length in characters of the value of parameter is substituted. If parameter is * or @, the value substituted is the number of positional parameters. If parameter is an array name subscripted by * or @, the value substituted is the number of elements in the array.

${parameter#word}

${parameter##word}

Remove matching prefix pattern. The word is expanded to produce a pattern just as in pathname expansion. If the pattern matches the beginning of the value of parameter, then the result of the expansion is the expanded value of parameter with the shortest matching pattern (the `` #'' case) or the longest matching pattern (the `` ##'' case) deleted. If parameter is @ or *, the pattern removal operation is applied to each positional parameter in turn, and the expansion is the resultant list. If parameter is an array variable subscripted with @ or *, the pattern removal operation is applied to each member of the array in turn, and the expansion is the resultant list.

${parameter%word}

${parameter%%word}

Remove matching suffix pattern. The word is expanded to produce a pattern just as in pathname expansion. If the pattern matches a trailing portion of the expanded value of parameter, then the result of the expansion is the expanded value of parameter with the shortest matching pattern (the `` %'' case) or the longest matching pattern (the `` %%'' case) deleted. If parameter is @ or *, the pattern removal operation is applied to each positional parameter in turn, and the expansion is the resultant list. If parameter is an array variable subscripted with @ or *, the pattern removal operation is applied to each member of the array in turn, and the expansion is the resultant list.

${parameter/pattern/string}

Pattern substitution. The pattern is expanded to produce a pattern just as in pathname expansion. Parameter is expanded and the longest match of pattern against its value is replaced with string. If pattern begins with /, all matches of pattern are replaced with string. Normally only the first match is replaced. If pattern begins with #, it must match at the beginning of the expanded value of parameter. If pattern begins with %, it must match at the end of the expanded value of parameter. If string is null, matches of pattern are deleted and the / following pattern may be omitted. If parameter is @ or *, the substitution operation is applied to each positional parameter in turn, and the expansion is the resultant list. If parameter is an array variable subscripted with @ or *, the substitution operation is applied to each member of the array in turn, and the expansion is the resultant list.

${parameter^pattern}

${parameter^^pattern}

${parameter,pattern}

${parameter,,pattern}

Case modification. This expansion modifies the case of alphabetic characters in parameter. The pattern is expanded to produce a pattern just as in pathname expansion. The ^ operator converts lowercase letters matching pattern to uppercase; the , operator converts matching uppercase letters to lowercase. The ^^ and ,, expansions convert each matched character in the expanded value; the ^ and , expansions match and convert only the first character in the expanded value. If pattern is omitted, it is treated like a ?, which matches every character. If parameter is @ or *, the case modification operation is applied to each positional parameter in turn, and the expansion is the resultant list. If parameter is an array variable subscripted with @ or *, the case modification operation is applied to each member of the array in turn, and the expansion is the resultant list.

Command Substitution

Arithmetic Expansion

Process Substitution

Word Splitting

Pathname Expansion

Quote Removal

REDIRECTION

Redirecting Input

Redirecting Output

Appending Redirected Output

Redirecting Standard Output and Standard Error

Appending Standard Output and Standard Error

Here Documents

<<[-]word
         here-document
delimiter

Here Strings

<<<word

Duplicating File Descriptors

Moving File Descriptors

Opening File Descriptors for Reading and Writing

ALIASES

FUNCTIONS

ARITHMETIC EVALUATION

id++ id--

variable post-increment and post-decrement

++id --id

variable pre-increment and pre-decrement

- +

unary minus and plus

! ~

logical and bitwise negation

**

exponentiation

* / %

multiplication, division, remainder

+ -

addition, subtraction

<< >>

left and right bitwise shifts

<= >= < >

comparison

== !=

equality and inequality

&

bitwise AND

^

bitwise exclusive OR

|

bitwise OR

&&

logical AND

||

logical OR

expr?expr:expr

conditional operator

= *= /= %= += -= <<= >>= &= ^= |=

assignment

expr1 , expr2

comma

CONDITIONAL EXPRESSIONS

-a file

True if file exists.

-b file

True if file exists and is a block special file.

-c file

True if file exists and is a character special file.

-d file

True if file exists and is a directory.

-e file

True if file exists.

-f file

True if file exists and is a regular file.

-g file

True if file exists and is set-group-id.

-h file

True if file exists and is a symbolic link.

-k file

True if file exists and its ``sticky'' bit is set.

-p file

True if file exists and is a named pipe (FIFO).

-r file

True if file exists and is readable.

-s file

True if file exists and has a size greater than zero.

-t fd

True if file descriptor fd is open and refers to a terminal.

-u file

True if file exists and its set-user-id bit is set.

-w file

True if file exists and is writable.

-x file

True if file exists and is executable.

-G file

True if file exists and is owned by the effective group id.

-L file

True if file exists and is a symbolic link.

-N file

True if file exists and has been modified since it was last read.

-O file

True if file exists and is owned by the effective user id.

-S file

True if file exists and is a socket.

file1 -ef file2

True if file1 and file2 refer to the same device and inode numbers.

file1 -nt file2

True if file1 is newer (according to modification date) than file2, or if file1 exists and file2 does not.

file1 -ot file2

True if file1 is older than file2, or if file2 exists and file1 does not.

-o optname

True if the shell option optname is enabled. See the list of options under the description of the -o option to the set builtin below.

-v varname

True if the shell variable varname is set (has been assigned a value).

-z string

True if the length of string is zero.

string

-n string

True if the length of string is non-zero.

string1 == string2

string1 = string2

True if the strings are equal. = should be used with the test command for POSIX conformance.

string1 != string2

True if the strings are not equal.

string1 < string2

True if string1 sorts before string2 lexicographically.

string1 > string2

True if string1 sorts after string2 lexicographically.

arg1 OP arg2

OP is one of -eq, -ne, -lt, -le, -gt, or -ge. These arithmetic binary operators return true if arg1 is equal to, not equal to, less than, less than or equal to, greater than, or greater than or equal to arg2, respectively. Arg1 and arg2 may be positive or negative integers.

SIMPLE COMMAND EXPANSION

1.

The words that the parser has marked as variable assignments (those preceding the command name) and redirections are saved for later processing.

2.

The words that are not variable assignments or redirections are expanded. If any words remain after expansion, the first word is taken to be the name of the command and the remaining words are the arguments.

3.

Redirections are performed as described above under REDIRECTION.

4.

The text after the = in each variable assignment undergoes tilde expansion, parameter expansion, command substitution, arithmetic expansion, and quote removal before being assigned to the variable.

COMMAND EXECUTION

COMMAND EXECUTION ENVIRONMENT

•

open files inherited by the shell at invocation, as modified by redirections supplied to the exec builtin

•

the current working directory as set by cd, pushd, or popd, or inherited by the shell at invocation

•

the file creation mode mask as set by umask or inherited from the shell's parent

•

current traps set by trap

•

shell parameters that are set by variable assignment or with set or inherited from the shell's parent in the environment

•

shell functions defined during execution or inherited from the shell's parent in the environment

•

options enabled at invocation (either by default or with command-line arguments) or by set

•

options enabled by shopt

•

shell aliases defined with alias

•

various process IDs, including those of background jobs, the value of $$, and the value of PPID

•

the shell's open files, plus any modifications and additions specified by redirections to the command

•

the current working directory

•

the file creation mode mask

•

shell variables and functions marked for export, along with variables exported for the command, passed in the environment

•

traps caught by the shell are reset to the values inherited from the shell's parent, and traps ignored by the shell are ignored

ENVIRONMENT

EXIT STATUS

SIGNALS

JOB CONTROL

PROMPTING

READLINE

Readline Notation

Readline Initialization

Readline Key Bindings

Readline Variables

bell-style (audible)

Controls what happens when readline wants to ring the terminal bell. If set to none, readline never rings the bell. If set to visible, readline uses a visible bell if one is available. If set to audible, readline attempts to ring the terminal's bell.

bind-tty-special-chars (On)

If set to On, readline attempts to bind the control characters treated specially by the kernel's terminal driver to their readline equivalents.

comment-begin (``#'')

The string that is inserted when the readline insert-comment command is executed. This command is bound to M-# in emacs mode and to # in vi command mode.

completion-ignore-case (Off)

If set to On, readline performs filename matching and completion in a case-insensitive fashion.

completion-prefix-display-length (0)

The length in characters of the common prefix of a list of possible completions that is displayed without modification. When set to a value greater than zero, common prefixes longer than this value are replaced with an ellipsis when displaying possible completions.

completion-query-items (100)

This determines when the user is queried about viewing the number of possible completions generated by the possible-completions command. It may be set to any integer value greater than or equal to zero. If the number of possible completions is greater than or equal to the value of this variable, the user is asked whether or not he wishes to view them; otherwise they are simply listed on the terminal.

convert-meta (On)

If set to On, readline will convert characters with the eighth bit set to an ASCII key sequence by stripping the eighth bit and prefixing an escape character (in effect, using escape as the meta prefix).

disable-completion (Off)

If set to On, readline will inhibit word completion. Completion characters will be inserted into the line as if they had been mapped to self-insert.

editing-mode (emacs)

Controls whether readline begins with a set of key bindings similar to Emacs or vi. editing-mode can be set to either emacs or vi.

echo-control-characters (On)

When set to On, on operating systems that indicate they support it, readline echoes a character corresponding to a signal generated from the keyboard.

enable-keypad (Off)

When set to On, readline will try to enable the application keypad when it is called. Some systems need this to enable the arrow keys.

enable-meta-key (On)

When set to On, readline will try to enable any meta modifier key the terminal claims to support when it is called. On many terminals, the meta key is used to send eight-bit characters.

expand-tilde (Off)

If set to On, tilde expansion is performed when readline attempts word completion.

history-preserve-point (Off)

If set to On, the history code attempts to place point at the same location on each history line retrieved with previous-history or next-history.

history-size (0)

Set the maximum number of history entries saved in the history list. If set to zero, the number of entries in the history list is not limited.

horizontal-scroll-mode (Off)

When set to On, makes readline use a single line for display, scrolling the input horizontally on a single screen line when it becomes longer than the screen width rather than wrapping to a new line.

input-meta (Off)

If set to On, readline will enable eight-bit input (that is, it will not strip the high bit from the characters it reads), regardless of what the terminal claims it can support. The name meta-flag is a synonym for this variable.

isearch-terminators (``C-[C-J'')

The string of characters that should terminate an incremental search without subsequently executing the character as a command. If this variable has not been given a value, the characters ESC and C-J will terminate an incremental search.

keymap (emacs)

Set the current readline keymap. The set of valid keymap names is emacs, emacs-standard, emacs-meta, emacs-ctlx, vi, vi-command, and vi-insert. vi is equivalent to vi-command; emacs is equivalent to emacs-standard. The default value is emacs; the value of editing-mode also affects the default keymap.

mark-directories (On)

If set to On, completed directory names have a slash appended.

mark-modified-lines (Off)

If set to On, history lines that have been modified are displayed with a preceding asterisk ( *).

mark-symlinked-directories (Off)

If set to On, completed names which are symbolic links to directories have a slash appended (subject to the value of mark-directories).

match-hidden-files (On)

This variable, when set to On, causes readline to match files whose names begin with a `.' (hidden files) when performing filename completion. If set to Off, the leading `.' must be supplied by the user in the filename to be completed.

menu-complete-display-prefix (Off)

If set to On, menu completion displays the common prefix of the list of possible completions (which may be empty) before cycling through the list.

output-meta (Off)

If set to On, readline will display characters with the eighth bit set directly rather than as a meta-prefixed escape sequence.

page-completions (On)

If set to On, readline uses an internal more-like pager to display a screenful of possible completions at a time.

print-completions-horizontally (Off)

If set to On, readline will display completions with matches sorted horizontally in alphabetical order, rather than down the screen.

revert-all-at-newline (Off)

If set to On, readline will undo all changes to history lines before returning when accept-line is executed. By default, history lines may be modified and retain individual undo lists across calls to readline.

show-all-if-ambiguous (Off)

This alters the default behavior of the completion functions. If set to On, words which have more than one possible completion cause the matches to be listed immediately instead of ringing the bell.

show-all-if-unmodified (Off)

This alters the default behavior of the completion functions in a fashion similar to show-all-if-ambiguous. If set to On, words which have more than one possible completion without any possible partial completion (the possible completions don't share a common prefix) cause the matches to be listed immediately instead of ringing the bell.

skip-completed-text (Off)

If set to On, this alters the default completion behavior when inserting a single match into the line. It's only active when performing completion in the middle of a word. If enabled, readline does not insert characters from the completion that match characters after point in the word being completed, so portions of the word following the cursor are not duplicated.

visible-stats (Off)

If set to On, a character denoting a file's type as reported by stat(2) is appended to the filename when listing possible completions.

Readline Conditional Constructs

$if

The $if construct allows bindings to be made based on the editing mode, the terminal being used, or the application using readline. The text of the test extends to the end of the line; no characters are required to isolate it.

$if Bash
# Quote the current or previous word
"\C-xq": "\eb\"\ef\""
$endif

$endif

This command, as seen in the previous example, terminates an $if command.

$else

Commands in this branch of the $if directive are executed if the test fails.

$include

This directive takes a single filename as an argument and reads commands and bindings from that file. For example, the following directive would read /etc/inputrc:

$include  /etc/inputrc

Searching

Readline Command Names

Commands for Moving

beginning-of-line (C-a)

Move to the start of the current line.

end-of-line (C-e)

Move to the end of the line.

forward-char (C-f)

Move forward a character.

backward-char (C-b)

Move back a character.

forward-word (M-f)

Move forward to the end of the next word. Words are composed of alphanumeric characters (letters and digits).

backward-word (M-b)

Move back to the start of the current or previous word. Words are composed of alphanumeric characters (letters and digits).

shell-forward-word

Move forward to the end of the next word. Words are delimited by non-quoted shell metacharacters.

shell-backward-word

Move back to the start of the current or previous word. Words are delimited by non-quoted shell metacharacters.

clear-screen (C-l)

Clear the screen leaving the current line at the top of the screen. With an argument, refresh the current line without clearing the screen.

redraw-current-line

Refresh the current line.

Commands for Manipulating the History

accept-line (Newline, Return)

Accept the line regardless of where the cursor is. If this line is non-empty, add it to the history list according to the state of the HISTCONTROL variable. If the line is a modified history line, then restore the history line to its original state.

previous-history (C-p)

Fetch the previous command from the history list, moving back in the list.

next-history (C-n)

Fetch the next command from the history list, moving forward in the list.

beginning-of-history (M-<)

Move to the first line in the history.

end-of-history (M->)

Move to the end of the input history, i.e., the line currently being entered.

reverse-search-history (C-r)

Search backward starting at the current line and moving `up' through the history as necessary. This is an incremental search.

forward-search-history (C-s)

Search forward starting at the current line and moving `down' through the history as necessary. This is an incremental search.

non-incremental-reverse-search-history (M-p)

Search backward through the history starting at the current line using a non-incremental search for a string supplied by the user.

non-incremental-forward-search-history (M-n)

Search forward through the history using a non-incremental search for a string supplied by the user.

history-search-forward

Search forward through the history for the string of characters between the start of the current line and the point. This is a non-incremental search.

history-search-backward

Search backward through the history for the string of characters between the start of the current line and the point. This is a non-incremental search.

yank-nth-arg (M-C-y)

Insert the first argument to the previous command (usually the second word on the previous line) at point. With an argument n, insert the nth word from the previous command (the words in the previous command begin with word 0). A negative argument inserts the nth word from the end of the previous command. Once the argument n is computed, the argument is extracted as if the "! n" history expansion had been specified.

yank-last-arg (M-., M-_)

Insert the last argument to the previous command (the last word of the previous history entry). With a numeric argument, behave exactly like yank-nth-arg. Successive calls to yank-last-arg move back through the history list, inserting the last word (or the word specified by the argument to the first call) of each line in turn. Any numeric argument supplied to these successive calls determines the direction to move through the history. A negative argument switches the direction through the history (back or forward). The history expansion facilities are used to extract the last argument, as if the "!$" history expansion had been specified.

shell-expand-line (M-C-e)

Expand the line as the shell does. This performs alias and history expansion as well as all of the shell word expansions. See HISTORY EXPANSION below for a description of history expansion.

history-expand-line (M-^)

Perform history expansion on the current line. See HISTORY EXPANSION below for a description of history expansion.

magic-space

Perform history expansion on the current line and insert a space. See HISTORY EXPANSION below for a description of history expansion.

alias-expand-line

Perform alias expansion on the current line. See ALIASES above for a description of alias expansion.

history-and-alias-expand-line

Perform history and alias expansion on the current line.

insert-last-argument (M-., M-_)

A synonym for yank-last-arg.

operate-and-get-next (C-o)

Accept the current line for execution and fetch the next line relative to the current line from the history for editing. Any argument is ignored.

edit-and-execute-command (C-xC-e)

Invoke an editor on the current command line, and execute the result as shell commands. Bash attempts to invoke $VISUAL, $EDITOR, and emacs as the editor, in that order.

Commands for Changing Text

delete-char (C-d)

Delete the character at point. If point is at the beginning of the line, there are no characters in the line, and the last character typed was not bound to delete-char, then return EOF.

backward-delete-char (Rubout)

Delete the character behind the cursor. When given a numeric argument, save the deleted text on the kill ring.

forward-backward-delete-char

Delete the character under the cursor, unless the cursor is at the end of the line, in which case the character behind the cursor is deleted.

quoted-insert (C-q, C-v)

Add the next character typed to the line verbatim. This is how to insert characters like C-q, for example.

tab-insert (C-v TAB)

Insert a tab character.

self-insert (a, b, A, 1, !, ...)

Insert the character typed.

transpose-chars (C-t)

Drag the character before point forward over the character at point, moving point forward as well. If point is at the end of the line, then this transposes the two characters before point. Negative arguments have no effect.

transpose-words (M-t)

Drag the word before point past the word after point, moving point over that word as well. If point is at the end of the line, this transposes the last two words on the line.

upcase-word (M-u)

Uppercase the current (or following) word. With a negative argument, uppercase the previous word, but do not move point.

downcase-word (M-l)

Lowercase the current (or following) word. With a negative argument, lowercase the previous word, but do not move point.

capitalize-word (M-c)

Capitalize the current (or following) word. With a negative argument, capitalize the previous word, but do not move point.

overwrite-mode

Toggle overwrite mode. With an explicit positive numeric argument, switches to overwrite mode. With an explicit non-positive numeric argument, switches to insert mode. This command affects only emacs mode; vi mode does overwrite differently. Each call to readline() starts in insert mode. In overwrite mode, characters bound to self-insert replace the text at point rather than pushing the text to the right. Characters bound to backward-delete-char replace the character before point with a space. By default, this command is unbound.

Killing and Yanking

kill-line (C-k)

Kill the text from point to the end of the line.

backward-kill-line (C-x Rubout)

Kill backward to the beginning of the line.

unix-line-discard (C-u)

Kill backward from point to the beginning of the line. The killed text is saved on the kill-ring.

kill-whole-line

Kill all characters on the current line, no matter where point is.

kill-word (M-d)

Kill from point to the end of the current word, or if between words, to the end of the next word. Word boundaries are the same as those used by forward-word.

backward-kill-word (M-Rubout)

Kill the word behind point. Word boundaries are the same as those used by backward-word.

shell-kill-word (M-d)

Kill from point to the end of the current word, or if between words, to the end of the next word. Word boundaries are the same as those used by shell-forward-word.

shell-backward-kill-word (M-Rubout)

Kill the word behind point. Word boundaries are the same as those used by shell-backward-word.

unix-word-rubout (C-w)

Kill the word behind point, using white space as a word boundary. The killed text is saved on the kill-ring.

unix-filename-rubout

Kill the word behind point, using white space and the slash character as the word boundaries. The killed text is saved on the kill-ring.

delete-horizontal-space (M-\)

Delete all spaces and tabs around point.

kill-region

Kill the text in the current region.

copy-region-as-kill

Copy the text in the region to the kill buffer.

copy-backward-word

Copy the word before point to the kill buffer. The word boundaries are the same as backward-word.

copy-forward-word

Copy the word following point to the kill buffer. The word boundaries are the same as forward-word.

yank (C-y)

Yank the top of the kill ring into the buffer at point.

yank-pop (M-y)

Rotate the kill ring, and yank the new top. Only works following yank or yank-pop.

Numeric Arguments

digit-argument (M-0, M-1, ..., M--)

Add this digit to the argument already accumulating, or start a new argument. M-- starts a negative argument.

universal-argument

This is another way to specify an argument. If this command is followed by one or more digits, optionally with a leading minus sign, those digits define the argument. If the command is followed by digits, executing universal-argument again ends the numeric argument, but is otherwise ignored. As a special case, if this command is immediately followed by a character that is neither a digit or minus sign, the argument count for the next command is multiplied by four. The argument count is initially one, so executing this function the first time makes the argument count four, a second time makes the argument count sixteen, and so on.

Completing

complete (TAB)

Attempt to perform completion on the text before point. Bash attempts completion treating the text as a variable (if the text begins with $), username (if the text begins with ~), hostname (if the text begins with @), or command (including aliases and functions) in turn. If none of these produces a match, filename completion is attempted.

possible-completions (M-?)

List the possible completions of the text before point.

insert-completions (M-*)

Insert all completions of the text before point that would have been generated by possible-completions.

menu-complete

Similar to complete, but replaces the word to be completed with a single match from the list of possible completions. Repeated execution of menu-complete steps through the list of possible completions, inserting each match in turn. At the end of the list of completions, the bell is rung (subject to the setting of bell-style) and the original text is restored. An argument of n moves n positions forward in the list of matches; a negative argument may be used to move backward through the list. This command is intended to be bound to TAB, but is unbound by default.

menu-complete-backward

Identical to menu-complete, but moves backward through the list of possible completions, as if menu-complete had been given a negative argument. This command is unbound by default.

delete-char-or-list

Deletes the character under the cursor if not at the beginning or end of the line (like delete-char). If at the end of the line, behaves identically to possible-completions. This command is unbound by default.

complete-filename (M-/)

Attempt filename completion on the text before point.

possible-filename-completions (C-x /)

List the possible completions of the text before point, treating it as a filename.

complete-username (M-~)

Attempt completion on the text before point, treating it as a username.

possible-username-completions (C-x ~)

List the possible completions of the text before point, treating it as a username.

complete-variable (M-$)

Attempt completion on the text before point, treating it as a shell variable.

possible-variable-completions (C-x $)

List the possible completions of the text before point, treating it as a shell variable.

complete-hostname (M-@)

Attempt completion on the text before point, treating it as a hostname.

possible-hostname-completions (C-x @)

List the possible completions of the text before point, treating it as a hostname.

complete-command (M-!)

Attempt completion on the text before point, treating it as a command name. Command completion attempts to match the text against aliases, reserved words, shell functions, shell builtins, and finally executable filenames, in that order.

possible-command-completions (C-x !)

List the possible completions of the text before point, treating it as a command name.

dynamic-complete-history (M-TAB)

Attempt completion on the text before point, comparing the text against lines from the history list for possible completion matches.

dabbrev-expand

Attempt menu completion on the text before point, comparing the text against lines from the history list for possible completion matches.

complete-into-braces (M-{)

Perform filename completion and insert the list of possible completions enclosed within braces so the list is available to the shell (see Brace Expansion above).

Keyboard Macros

start-kbd-macro (C-x ()

Begin saving the characters typed into the current keyboard macro.

end-kbd-macro (C-x ))

Stop saving the characters typed into the current keyboard macro and store the definition.

call-last-kbd-macro (C-x e)

Re-execute the last keyboard macro defined, by making the characters in the macro appear as if typed at the keyboard.

Miscellaneous

re-read-init-file (C-x C-r)

Read in the contents of the inputrc file, and incorporate any bindings or variable assignments found there.

abort (C-g)

Abort the current editing command and ring the terminal's bell (subject to the setting of bell-style).

do-uppercase-version (M-a, M-b, M-x, ...)

If the metafied character x is lowercase, run the command that is bound to the corresponding uppercase character.

prefix-meta (ESC)

Metafy the next character typed. ESC f is equivalent to Meta-f.

undo (C-_, C-x C-u)

Incremental undo, separately remembered for each line.

revert-line (M-r)

Undo all changes made to this line. This is like executing the undo command enough times to return the line to its initial state.

tilde-expand (M-&)

Perform tilde expansion on the current word.

set-mark (C-@, M-<space>)

Set the mark to the point. If a numeric argument is supplied, the mark is set to that position.

exchange-point-and-mark (C-x C-x)

Swap the point with the mark. The current cursor position is set to the saved position, and the old cursor position is saved as the mark.

character-search (C-])

A character is read and point is moved to the next occurrence of that character. A negative count searches for previous occurrences.

character-search-backward (M-C-])

A character is read and point is moved to the previous occurrence of that character. A negative count searches for subsequent occurrences.

skip-csi-sequence

Read enough characters to consume a multi-key sequence such as those defined for keys like Home and End. Such sequences begin with a Control Sequence Indicator (CSI), usually ESC-[. If this sequence is bound to "\[", keys producing such sequences will have no effect unless explicitly bound to a readline command, instead of inserting stray characters into the editing buffer. This is unbound by default, but usually bound to ESC-[.

insert-comment (M-#)

Without a numeric argument, the value of the readline comment-begin variable is inserted at the beginning of the current line. If a numeric argument is supplied, this command acts as a toggle: if the characters at the beginning of the line do not match the value of comment-begin, the value is inserted, otherwise the characters in comment-begin are deleted from the beginning of the line. In either case, the line is accepted as if a newline had been typed. The default value of comment-begin causes this command to make the current line a shell comment. If a numeric argument causes the comment character to be removed, the line will be executed by the shell.

glob-complete-word (M-g)

The word before point is treated as a pattern for pathname expansion, with an asterisk implicitly appended. This pattern is used to generate a list of matching file names for possible completions.

glob-expand-word (C-x *)

The word before point is treated as a pattern for pathname expansion, and the list of matching file names is inserted, replacing the word. If a numeric argument is supplied, an asterisk is appended before pathname expansion.

glob-list-expansions (C-x g)

The list of expansions that would have been generated by glob-expand-word is displayed, and the line is redrawn. If a numeric argument is supplied, an asterisk is appended before pathname expansion.

dump-functions

Print all of the functions and their key bindings to the readline output stream. If a numeric argument is supplied, the output is formatted in such a way that it can be made part of an inputrc file.

dump-variables

Print all of the settable readline variables and their values to the readline output stream. If a numeric argument is supplied, the output is formatted in such a way that it can be made part of an inputrc file.

dump-macros

Print all of the readline key sequences bound to macros and the strings they output. If a numeric argument is supplied, the output is formatted in such a way that it can be made part of an inputrc file.

display-shell-version (C-x C-v)

Display version information about the current instance of bash.

Programmable Completion

HISTORY

HISTORY EXPANSION

Event Designators

!

Start a history substitution, except when followed by a blank, newline, carriage return, = or ( (when the extglob shell option is enabled using the shopt builtin).

!n

Refer to command line n.

!-n

Refer to the current command minus n.

!!

Refer to the previous command. This is a synonym for `!-1'.

!string

Refer to the most recent command preceding the current position in the history list starting with string.

!?string[?]

Refer to the most recent command preceding the current postition in the history list containing string. The trailing ? may be omitted if string is followed immediately by a newline.

^string1^string2^

Quick substitution. Repeat the previous command, replacing string1 with string2. Equivalent to ``!!:s/ string1/string2/'' (see Modifiers below).

!#

The entire command line typed so far.

Word Designators

0 (zero)

The zeroth word. For the shell, this is the command word.

n

The nth word.

^

The first argument. That is, word 1.

$

The last argument.

%

The word matched by the most recent `?string?' search.

x-y

A range of words; `-y' abbreviates `0-y'.

*

All of the words but the zeroth. This is a synonym for ` 1-$'. It is not an error to use * if there is just one word in the event; the empty string is returned in that case.

x*

Abbreviates x-$.

x-

Abbreviates x-$ like x*, but omits the last word.

Modifiers

h

Remove a trailing file name component, leaving only the head.

t

Remove all leading file name components, leaving the tail.

r

Remove a trailing suffix of the form .xxx, leaving the basename.

e

Remove all but the trailing suffix.

p

Print the new command but do not execute it.

q

Quote the substituted words, escaping further substitutions.

x

Quote the substituted words as with q, but break into words at blanks and newlines.

s/old/new/

Substitute new for the first occurrence of old in the event line. Any delimiter can be used in place of /. The final delimiter is optional if it is the last character of the event line. The delimiter may be quoted in old and new with a single backslash. If & appears in new, it is replaced by old. A single backslash will quote the &. If old is null, it is set to the last old substituted, or, if no previous history substitutions took place, the last string in a !?string[?] search.

&

Repeat the previous substitution.

g

Cause changes to be applied over the entire event line. This is used in conjunction with ` :s' (e.g., `:gs/old/new /') or ` :&'. If used with ` :s', any delimiter can be used in place of /, and the final delimiter is optional if it is the last character of the event line. An a may be used as a synonym for g.

G

Apply the following `s' modifier once to each word in the event line.

SHELL BUILTIN COMMANDS

: [arguments]

No effect; the command does nothing beyond expanding arguments and performing any specified redirections. A zero exit code is returned.

. filename [arguments]

source filename [arguments]

Read and execute commands from filename in the current shell environment and return the exit status of the last command executed from filename. If filename does not contain a slash, file names in PATH are used to find the directory containing filename. The file searched for in PATH need not be executable. When bash is not in posix mode, the current directory is searched if no file is found in PATH. If the sourcepath option to the shopt builtin command is turned off, the PATH is not searched. If any arguments are supplied, they become the positional parameters when filename is executed. Otherwise the positional parameters are unchanged. The return status is the status of the last command exited within the script (0 if no commands are executed), and false if filename is not found or cannot be read.

alias [-p] [name[=value] ...]

Alias with no arguments or with the -p option prints the list of aliases in the form alias name=value on standard output. When arguments are supplied, an alias is defined for each name whose value is given. A trailing space in value causes the next word to be checked for alias substitution when the alias is expanded. For each name in the argument list for which no value is supplied, the name and value of the alias is printed. Alias returns true unless a name is given for which no alias has been defined.

bg [jobspec ...]

Resume each suspended job jobspec in the background, as if it had been started with &. If jobspec is not present, the shell's notion of the current job is used. bg jobspec returns 0 unless run when job control is disabled or, when run with job control enabled, any specified jobspec was not found or was started without job control.

bind [-m keymap] [-lpsvPSV]

bind [-m keymap] [-q function] [-u function] [-r keyseq]

bind [-m keymap] -f filename

bind [-m keymap] -x keyseq:shell-command

bind [-m keymap] keyseq:function-name

bind readline-command

Display current readline key and function bindings, bind a key sequence to a readline function or macro, or set a readline variable. Each non-option argument is a command as it would appear in .inputrc, but each binding or command must be passed as a separate argument; e.g., '"\C-x\C-r": re-read-init-file'. Options, if supplied, have the following meanings:

break [n]

Exit from within a for, while, until, or select loop. If n is specified, break n levels. n must be ≥ 1. If n is greater than the number of enclosing loops, all enclosing loops are exited. The return value is non-zero when n is ≤ 0; Otherwise, break returns 0 value.

builtin shell-builtin [arguments]

Execute the specified shell builtin, passing it arguments, and return its exit status. This is useful when defining a function whose name is the same as a shell builtin, retaining the functionality of the builtin within the function. The cd builtin is commonly redefined this way. The return status is false if shell-builtin is not a shell builtin command.

caller [expr]

Returns the context of any active subroutine call (a shell function or a script executed with the . or source builtins). Without expr, caller displays the line number and source filename of the current subroutine call. If a non-negative integer is supplied as expr, caller displays the line number, subroutine name, and source file corresponding to that position in the current execution call stack. This extra information may be used, for example, to print a stack trace. The current frame is frame 0. The return value is 0 unless the shell is not executing a subroutine call or expr does not correspond to a valid position in the call stack.

cd [-L|[-P [-e]]] [dir]

Change the current directory to dir. The variable HOME is the default dir. The variable CDPATH defines the search path for the directory containing dir. Alternative directory names in CDPATH are separated by a colon (:). A null directory name in CDPATH is the same as the current directory, i.e., `` .''. If dir begins with a slash (/), then CDPATH is not used. The -P option says to use the physical directory structure instead of following symbolic links (see also the -P option to the set builtin command); the -L option forces symbolic links to be followed. If the -e option is supplied with -P, and the current working directory cannot be successfully determined after a successful directory change, cd will return an unsuccessful status. An argument of - is equivalent to $OLDPWD. If a non-empty directory name from CDPATH is used, or if - is the first argument, and the directory change is successful, the absolute pathname of the new working directory is written to the standard output. The return value is true if the directory was successfully changed; false otherwise.

command [-pVv] command [arg ...]

Run command with args suppressing the normal shell function lookup. Only builtin commands or commands found in the PATH are executed. If the -p option is given, the search for command is performed using a default value for PATH that is guaranteed to find all of the standard utilities. If either the -V or -v option is supplied, a description of command is printed. The -v option causes a single word indicating the command or file name used to invoke command to be displayed; the -V option produces a more verbose description. If the -V or -v option is supplied, the exit status is 0 if command was found, and 1 if not. If neither option is supplied and an error occurred or command cannot be found, the exit status is 127. Otherwise, the exit status of the command builtin is the exit status of command.

compgen [option] [word]

Generate possible completion matches for word according to the options, which may be any option accepted by the complete builtin with the exception of -p and -r, and write the matches to the standard output. When using the -F or -C options, the various shell variables set by the programmable completion facilities, while available, will not have useful values.

The matches will be generated in the same way as if the programmable completion code had generated them directly from a completion specification with the same flags. If word is specified, only those completions matching word will be displayed.

The return value is true unless an invalid option is supplied, or no matches were generated.

complete [-abcdefgjksuv] [-o comp-option] [-DE] [ -A action] [-G globpat] [-W wordlist] [-F function] [-C command]

 

[ -X filterpat] [-P prefix] [-S suffix] name [name ...]

complete -pr [-DE] [name ...]

Specify how arguments to each name should be completed. If the -p option is supplied, or if no options are supplied, existing completion specifications are printed in a way that allows them to be reused as input. The -r option removes a completion specification for each name, or, if no names are supplied, all completion specifications. The -D option indicates that the remaining options and actions should apply to the ``default'' command completion; that is, completion attempted on a command for which no completion has previously been defined. The -E option indicates that the remaining options and actions should apply to ``empty'' command completion; that is, completion attempted on a blank line.

The process of applying these completion specifications when word completion is attempted is described above under Programmable Completion.

Other options, if specified, have the following meanings. The arguments to the -G, -W, and -X options (and, if necessary, the -P and -S options) should be quoted to protect them from expansion before the complete builtin is invoked.

compopt [-o option] [-DE] [+o option] [ name]

Modify completion options for each name according to the options, or for the currently-executing completion if no names are supplied. If no options are given, display the completion options for each name or the current completion. The possible values of option are those valid for the complete builtin described above. The -D option indicates that the remaining options should apply to the ``default'' command completion; that is, completion attempted on a command for which no completion has previously been defined. The -E option indicates that the remaining options should apply to ``empty'' command completion; that is, completion attempted on a blank line.

The return value is true unless an invalid option is supplied, an attempt is made to modify the options for a name for which no completion specification exists, or an output error occurs.

continue [n]

Resume the next iteration of the enclosing for, while, until, or select loop. If n is specified, resume at the nth enclosing loop. n must be ≥ 1. If n is greater than the number of enclosing loops, the last enclosing loop (the ``top-level'' loop) is resumed. When continue is executed inside of loop, the return value is non-zero when n is ≤ 0; Otherwise, continue returns 0 value. When continue is executed outside of loop, the return value is 0.

declare [-aAfFgilrtux] [-p] [name[=value] ...]

typeset [-aAfFgilrtux] [-p] [name[=value] ...]

Declare variables and/or give them attributes. If no names are given then display the values of variables. The -p option will display the attributes and values of each name. When -p is used with name arguments, additional options are ignored. When -p is supplied without name arguments, it will display the attributes and values of all variables having the attributes specified by the additional options. If no other options are supplied with -p, declare will display the attributes and values of all shell variables. The -f option will restrict the display to shell functions. The -F option inhibits the display of function definitions; only the function name and attributes are printed. If the extdebug shell option is enabled using shopt, the source file name and line number where the function is defined are displayed as well. The -F option implies -f. The -g option forces variables to be created or modified at the global scope, even when declare is executed in a shell function. It is ignored in all other cases. The following options can be used to restrict output to variables with the specified attribute or to give variables attributes:

dirs [+n] [-n] [-clpv]

Without options, displays the list of currently remembered directories. The default display is on a single line with directory names separated by spaces. Directories are added to the list with the pushd command; the popd command removes entries from the list.

disown [-ar] [-h] [jobspec ...]

Without options, each jobspec is removed from the table of active jobs. If jobspec is not present, and neither -a nor -r is supplied, the shell's notion of the current job is used. If the -h option is given, each jobspec is not removed from the table, but is marked so that SIGHUP is not sent to the job if the shell receives a SIGHUP. If no jobspec is present, and neither the -a nor the -r option is supplied, the current job is used. If no jobspec is supplied, the -a option means to remove or mark all jobs; the -r option without a jobspec argument restricts operation to running jobs. The return value is 0 unless a jobspec does not specify a valid job.

echo [-neE] [arg ...]

Output the args, separated by spaces, followed by a newline. The return status is always 0. If -n is specified, the trailing newline is suppressed. If the -e option is given, interpretation of the following backslash-escaped characters is enabled. The -E option disables the interpretation of these escape characters, even on systems where they are interpreted by default. The xpg_echo shell option may be used to dynamically determine whether or not echo expands these escape characters by default. echo does not interpret -- to mean the end of options. echo interprets the following escape sequences:

enable [-a] [-dnps] [-f filename] [name ...]

Enable and disable builtin shell commands. Disabling a builtin allows a disk command which has the same name as a shell builtin to be executed without specifying a full pathname, even though the shell normally searches for builtins before disk commands. If -n is used, each name is disabled; otherwise, names are enabled. For example, to use the test binary found via the PATH instead of the shell builtin version, run ``enable -n test''. The -f option means to load the new builtin command name from shared object filename, on systems that support dynamic loading. The -d option will delete a builtin previously loaded with -f. If no name arguments are given, or if the -p option is supplied, a list of shell builtins is printed. With no other option arguments, the list consists of all enabled shell builtins. If -n is supplied, only disabled builtins are printed. If -a is supplied, the list printed includes all builtins, with an indication of whether or not each is enabled. If -s is supplied, the output is restricted to the POSIX special builtins. The return value is 0 unless a name is not a shell builtin or there is an error loading a new builtin from a shared object.

eval [arg ...]

The args are read and concatenated together into a single command. This command is then read and executed by the shell, and its exit status is returned as the value of eval. If there are no args, or only null arguments, eval returns 0.

exec [-cl] [-a name] [command [arguments]]

If command is specified, it replaces the shell. No new process is created. The arguments become the arguments to command. If the -l option is supplied, the shell places a dash at the beginning of the zeroth argument passed to command. This is what login(1) does. The -c option causes command to be executed with an empty environment. If -a is supplied, the shell passes name as the zeroth argument to the executed command. If command cannot be executed for some reason, a non-interactive shell exits, unless the shell option execfail is enabled, in which case it returns failure. An interactive shell returns failure if the file cannot be executed. If command is not specified, any redirections take effect in the current shell, and the return status is 0. If there is a redirection error, the return status is 1.

exit [n]

Cause the shell to exit with a status of n. If n is omitted, the exit status is that of the last command executed. A trap on EXIT is executed before the shell terminates.

export [-fn] [name[=word]] ...

export -p

The supplied names are marked for automatic export to the environment of subsequently executed commands. If the -f option is given, the names refer to functions. If no names are given, or if the -p option is supplied, a list of all names that are exported in this shell is printed. The -n option causes the export property to be removed from each name. If a variable name is followed by = word, the value of the variable is set to word. export returns an exit status of 0 unless an invalid option is encountered, one of the names is not a valid shell variable name, or -f is supplied with a name that is not a function.

fc [-e ename] [-lnr] [first] [last]

fc -s [pat=rep] [cmd]

Fix Command. In the first form, a range of commands from first to last is selected from the history list. First and last may be specified as a string (to locate the last command beginning with that string) or as a number (an index into the history list, where a negative number is used as an offset from the current command number). If last is not specified it is set to the current command for listing (so that ``fc -l -10'' prints the last 10 commands) and to first otherwise. If first is not specified it is set to the previous command for editing and -16 for listing.

The -n option suppresses the command numbers when listing. The -r option reverses the order of the commands. If the -l option is given, the commands are listed on standard output. Otherwise, the editor given by ename is invoked on a file containing those commands. If ename is not given, the value of the FCEDIT variable is used, and the value of EDITOR if FCEDIT is not set. If neither variable is set, vi is used. When editing is complete, the edited commands are echoed and executed.

In the second form, command is re-executed after each instance of pat is replaced by rep. A useful alias to use with this is ``r="fc -s"'', so that typing ``r cc'' runs the last command beginning with ``cc'' and typing ``r'' re-executes the last command.

If the first form is used, the return value is 0 unless an invalid option is encountered or first or last specify history lines out of range. If the -e option is supplied, the return value is the value of the last command executed or failure if an error occurs with the temporary file of commands. If the second form is used, the return status is that of the command re-executed, unless cmd does not specify a valid history line, in which case fc returns failure.

fg [jobspec]

Resume jobspec in the foreground, and make it the current job. If jobspec is not present, the shell's notion of the current job is used. The return value is that of the command placed into the foreground, or failure if run when job control is disabled or, when run with job control enabled, if jobspec does not specify a valid job or jobspec specifies a job that was started without job control.

getopts optstring name [args]

getopts is used by shell procedures to parse positional parameters. optstring contains the option characters to be recognized; if a character is followed by a colon, the option is expected to have an argument, which should be separated from it by white space. The colon and question mark characters may not be used as option characters. Each time it is invoked, getopts places the next option in the shell variable name, initializing name if it does not exist, and the index of the next argument to be processed into the variable OPTIND. OPTIND is initialized to 1 each time the shell or a shell script is invoked. When an option requires an argument, getopts places that argument into the variable OPTARG. The shell does not reset OPTIND automatically; it must be manually reset between multiple calls to getopts within the same shell invocation if a new set of parameters is to be used.

When the end of options is encountered, getopts exits with a return value greater than zero. OPTIND is set to the index of the first non-option argument, and name is set to ?.

getopts normally parses the positional parameters, but if more arguments are given in args, getopts parses those instead.

getopts can report errors in two ways. If the first character of optstring is a colon, silent error reporting is used. In normal operation diagnostic messages are printed when invalid options or missing option arguments are encountered. If the variable OPTERR is set to 0, no error messages will be displayed, even if the first character of optstring is not a colon.

If an invalid option is seen, getopts places ? into name and, if not silent, prints an error message and unsets OPTARG. If getopts is silent, the option character found is placed in OPTARG and no diagnostic message is printed.

If a required argument is not found, and getopts is not silent, a question mark ( ?) is placed in name, OPTARG is unset, and a diagnostic message is printed. If getopts is silent, then a colon ( :) is placed in name and OPTARG is set to the option character found.

getopts returns true if an option, specified or unspecified, is found. It returns false if the end of options is encountered or an error occurs.

hash [-lr] [-p filename] [-dt] [name]

Each time hash is invoked, the full pathname of the command name is determined by searching the directories in $PATH and remembered. Any previously-remembered pathname is discarded. If the -p option is supplied, no path search is performed, and filename is used as the full file name of the command. The -r option causes the shell to forget all remembered locations. The -d option causes the shell to forget the remembered location of each name. If the -t option is supplied, the full pathname to which each name corresponds is printed. If multiple name arguments are supplied with -t, the name is printed before the hashed full pathname. The -l option causes output to be displayed in a format that may be reused as input. If no arguments are given, or if only -l is supplied, information about remembered commands is printed. The return status is true unless a name is not found or an invalid option is supplied.

help [-dms] [pattern]

Display helpful information about builtin commands. If pattern is specified, help gives detailed help on all commands matching pattern; otherwise help for all the builtins and shell control structures is printed.

history [n]

history -c

history -d offset

history -anrw [filename]

history -p arg [arg ...]

history -s arg [arg ...]

With no options, display the command history list with line numbers. Lines listed with a * have been modified. An argument of n lists only the last n lines. If the shell variable HISTTIMEFORMAT is set and not null, it is used as a format string for strftime(3) to display the time stamp associated with each displayed history entry. No intervening blank is printed between the formatted time stamp and the history line. If filename is supplied, it is used as the name of the history file; if not, the value of HISTFILE is used. Options, if supplied, have the following meanings:

jobs [-lnprs] [ jobspec ... ]

jobs -x command [ args ... ]

The first form lists the active jobs. The options have the following meanings:

kill [-s sigspec | -n signum | -sigspec] [pid | jobspec] ...

kill -l [sigspec | exit_status]

Send the signal named by sigspec or signum to the processes named by pid or jobspec. sigspec is either a case-insensitive signal name such as SIGKILL (with or without the SIG prefix) or a signal number; signum is a signal number. If sigspec is not present, then SIGTERM is assumed. An argument of -l lists the signal names. If any arguments are supplied when -l is given, the names of the signals corresponding to the arguments are listed, and the return status is 0. The exit_status argument to -l is a number specifying either a signal number or the exit status of a process terminated by a signal. kill returns true if at least one signal was successfully sent, or false if an error occurs or an invalid option is encountered.

let arg [arg ...]

Each arg is an arithmetic expression to be evaluated (see ARITHMETIC EVALUATION above). If the last arg evaluates to 0, let returns 1; 0 is returned otherwise.

local [option] [name[=value] ...]

For each argument, a local variable named name is created, and assigned value. The option can be any of the options accepted by declare. When local is used within a function, it causes the variable name to have a visible scope restricted to that function and its children. With no operands, local writes a list of local variables to the standard output. It is an error to use local when not within a function. The return status is 0 unless local is used outside a function, an invalid name is supplied, or name is a readonly variable.

logout

Exit a login shell.

mapfile [-n count] [-O origin] [-s count] [-t] [-u fd] [-C callback] [ -c quantum] [array]

readarray [-n count] [-O origin] [-s count] [-t] [-u fd] [-C callback] [ -c quantum] [array]

Read lines from the standard input into the indexed array variable array, or from file descriptor fd if the -u option is supplied. The variable MAPFILE is the default array. Options, if supplied, have the following meanings:

popd [-n] [+n] [-n]

Removes entries from the directory stack. With no arguments, removes the top directory from the stack, and performs a cd to the new top directory. Arguments, if supplied, have the following meanings:

printf [-v var] format [arguments]

Write the formatted arguments to the standard output under the control of the format. The -v option causes the output to be assigned to the variable var rather than being printed to the standard output.

The format is a character string which contains three types of objects: plain characters, which are simply copied to standard output, character escape sequences, which are converted and copied to the standard output, and format specifications, each of which causes printing of the next successive argument. In addition to the standard printf(1) format specifications, printf interprets the following extensions:

pushd [-n] [+n] [-n]

pushd [-n] [dir]

Adds a directory to the top of the directory stack, or rotates the stack, making the new top of the stack the current working directory. With no arguments, exchanges the top two directories and returns 0, unless the directory stack is empty. Arguments, if supplied, have the following meanings:

pwd [-LP]

Print the absolute pathname of the current working directory. The pathname printed contains no symbolic links if the -P option is supplied or the -o physical option to the set builtin command is enabled. If the -L option is used, the pathname printed may contain symbolic links. The return status is 0 unless an error occurs while reading the name of the current directory or an invalid option is supplied.

read [-ers] [-a aname] [-d delim] [ -i text] [-n nchars] [-N nchars] [-p prompt] [-t timeout] [-u fd] [name ...]

One line is read from the standard input, or from the file descriptor fd supplied as an argument to the -u option, and the first word is assigned to the first name, the second word to the second name, and so on, with leftover words and their intervening separators assigned to the last name. If there are fewer words read from the input stream than names, the remaining names are assigned empty values. The characters in IFS are used to split the line into words. The backslash character ( \) may be used to remove any special meaning for the next character read and for line continuation. Options, if supplied, have the following meanings:

readonly [-aAf] [-p] [name[=word] ...]

The given names are marked readonly; the values of these names may not be changed by subsequent assignment. If the -f option is supplied, the functions corresponding to the names are so marked. The -a option restricts the variables to indexed arrays; the -A option restricts the variables to associative arrays. If both options are supplied, -A takes precedence. If no name arguments are given, or if the -p option is supplied, a list of all readonly names is printed. The other options may be used to restrict the output to a subset of the set of readonly names. The -p option causes output to be displayed in a format that may be reused as input. If a variable name is followed by = word, the value of the variable is set to word. The return status is 0 unless an invalid option is encountered, one of the names is not a valid shell variable name, or -f is supplied with a name that is not a function.

return [n]

Causes a function to exit with the return value specified by n. If n is omitted, the return status is that of the last command executed in the function body. If used outside a function, but during execution of a script by the . ( source) command, it causes the shell to stop executing that script and return either n or the exit status of the last command executed within the script as the exit status of the script. If used outside a function and not during execution of a script by ., the return status is false. Any command associated with the RETURN trap is executed before execution resumes after the function or script.

set [--abefhkmnptuvxBCEHPT] [-o option-name] [arg ...]

set [+abefhkmnptuvxBCEHPT] [+o option-name] [arg ...]

Without options, the name and value of each shell variable are displayed in a format that can be reused as input for setting or resetting the currently-set variables. Read-only variables cannot be reset. In posix mode, only shell variables are listed. The output is sorted according to the current locale. When options are specified, they set or unset shell attributes. Any arguments remaining after option processing are treated as values for the positional parameters and are assigned, in order, to $1, $2, ... $n. Options, if specified, have the following meanings:

shift [n]

The positional parameters from n+1 ... are renamed to $1 .... Parameters represented by the numbers $# down to $#- n+1 are unset. n must be a non-negative number less than or equal to $#. If n is 0, no parameters are changed. If n is not given, it is assumed to be 1. If n is greater than $#, the positional parameters are not changed. The return status is greater than zero if n is greater than $# or less than zero; otherwise 0.

shopt [-pqsu] [-o] [optname ...]

Toggle the values of variables controlling optional shell behavior. With no options, or with the -p option, a list of all settable options is displayed, with an indication of whether or not each is set. The -p option causes output to be displayed in a form that may be reused as input. Other options have the following meanings:

suspend [-f]

Suspend the execution of this shell until it receives a SIGCONT signal. When the suspended shell is a background process, it can be restarted by the fg command. For more information, read the JOB CONTROL section. The suspend command can not suspend the login shell. However, when -f option is specified, suspend command can suspend even login shell. The return status is 0 unless the shell is a login shell and -f is not supplied, or if job control is not enabled.

test expr

[ expr ]

Return a status of 0 or 1 depending on the evaluation of the conditional expression expr. Each operator and operand must be a separate argument. Expressions are composed of the primaries described above under CONDITIONAL EXPRESSIONS. test does not accept any options, nor does it accept and ignore an argument of -- as signifying the end of options.

Expressions may be combined using the following operators, listed in decreasing order of precedence. The evaluation depends on the number of arguments; see below. Operator precedence is used when there are five or more arguments.

times

Print the accumulated user and system times for the shell and for processes run from the shell. The return status is 0.

trap [-lp] [[arg] sigspec ...]

The command arg is to be read and executed when the shell receives signal(s) sigspec. If arg is absent (and there is a single sigspec) or -, each specified signal is reset to its original disposition (the value it had upon entrance to the shell). If arg is the null string the signal specified by each sigspec is ignored by the shell and by the commands it invokes. If arg is not present and -p has been supplied, then the trap commands associated with each sigspec are displayed. If no arguments are supplied or if only -p is given, trap prints the list of commands associated with each signal. The -l option causes the shell to print a list of signal names and their corresponding numbers. Each sigspec is either a signal name defined in < signal.h>, or a signal number. Signal names are case insensitive and the SIG prefix is optional.

If a sigspec is EXIT (0) the command arg is executed on exit from the shell. If a sigspec is DEBUG, the command arg is executed before every simple command, for command, case command, select command, every arithmetic for command, and before the first command executes in a shell function (see SHELL GRAMMAR above). Refer to the description of the extdebug option to the shopt builtin for details of its effect on the DEBUG trap. If a sigspec is RETURN, the command arg is executed each time a shell function or a script executed with the . or source builtins finishes executing.

If a sigspec is ERR, the command arg is executed whenever a simple command has a non-zero exit status, subject to the following conditions. The ERR trap is not executed if the failed command is part of the command list immediately following a while or until keyword, part of the test in an if statement, part of a command executed in a && or || list, or if the command's return value is being inverted via !. These are the same conditions obeyed by the errexit option.

Signals ignored upon entry to the shell cannot be trapped, reset or listed. Trapped signals that are not being ignored are reset to their original values in a subshell or subshell environment when one is created. The return status is false if any sigspec is invalid; otherwise trap returns true.

type [-aftpP] name [name ...]

With no options, indicate how each name would be interpreted if used as a command name. If the -t option is used, type prints a string which is one of alias, keyword, function, builtin, or file if name is an alias, shell reserved word, function, builtin, or disk file, respectively. If the name is not found, then nothing is printed, and an exit status of false is returned. If the -p option is used, type either returns the name of the disk file that would be executed if name were specified as a command name, or nothing if ``type -t name'' would not return file. The -P option forces a PATH search for each name, even if ``type -t name'' would not return file. If a command is hashed, -p and -P print the hashed value, not necessarily the file that appears first in PATH. If the -a option is used, type prints all of the places that contain an executable named name. This includes aliases and functions, if and only if the -p option is not also used. The table of hashed commands is not consulted when using -a. The -f option suppresses shell function lookup, as with the command builtin. type returns true if all of the arguments are found, false if any are not found.

ulimit [-HSTabcdefilmnpqrstuvx [limit]]

Provides control over the resources available to the shell and to processes started by it, on systems that allow such control. The -H and -S options specify that the hard or soft limit is set for the given resource. A hard limit cannot be increased by a non-root user once it is set; a soft limit may be increased up to the value of the hard limit. If neither -H nor -S is specified, both the soft and hard limits are set. The value of limit can be a number in the unit specified for the resource or one of the special values hard, soft, or unlimited, which stand for the current hard limit, the current soft limit, and no limit, respectively. If limit is omitted, the current value of the soft limit of the resource is printed, unless the -H option is given. When more than one resource is specified, the limit name and unit are printed before the value. Other options are interpreted as follows:

umask [-p] [-S] [mode]

The user file-creation mask is set to mode. If mode begins with a digit, it is interpreted as an octal number; otherwise it is interpreted as a symbolic mode mask similar to that accepted by chmod(1). If mode is omitted, the current value of the mask is printed. The -S option causes the mask to be printed in symbolic form; the default output is an octal number. If the -p option is supplied, and mode is omitted, the output is in a form that may be reused as input. The return status is 0 if the mode was successfully changed or if no mode argument was supplied, and false otherwise.

unalias [-a] [name ...]

Remove each name from the list of defined aliases. If -a is supplied, all alias definitions are removed. The return value is true unless a supplied name is not a defined alias.

unset [-fv] [name ...]

For each name, remove the corresponding variable or function. If no options are supplied, or the -v option is given, each name refers to a shell variable. Read-only variables may not be unset. If -f is specified, each name refers to a shell function, and the function definition is removed. Each unset variable or function is removed from the environment passed to subsequent commands. If any of COMP_WORDBREAKS, RANDOM, SECONDS, LINENO, HISTCMD, FUNCNAME, GROUPS, or DIRSTACK are unset, they lose their special properties, even if they are subsequently reset. The exit status is true unless a name is readonly.

wait [n ...]

Wait for each specified process and return its termination status. Each n may be a process ID or a job specification; if a job spec is given, all processes in that job's pipeline are waited for. If n is not given, all currently active child processes are waited for, and the return status is zero. If n specifies a non-existent process or job, the return status is 127. Otherwise, the return status is the exit status of the last process or job waited for.

RESTRICTED SHELL

•

changing directories with cd

•

setting or unsetting the values of SHELL, PATH, ENV, or BASH_ENV

•

specifying command names containing /

•

specifying a file name containing a / as an argument to the . builtin command

•

specifying a filename containing a slash as an argument to the -p option to the hash builtin command

•

importing function definitions from the shell environment at startup

•

parsing the value of SHELLOPTS from the shell environment at startup

•

redirecting output using the >, >|, <>, >&, &>, and >> redirection operators

•

using the exec builtin command to replace the shell with another command

•

adding or deleting builtin commands with the -f and -d options to the enable builtin command

•

using the enable builtin command to enable disabled shell builtins

•

specifying the -p option to the command builtin command

•

turning off restricted mode with set +r or set +o restricted.

SEE ALSO

Bash Reference Manual, Brian Fox and Chet Ramey

The Gnu Readline Library, Brian Fox and Chet Ramey

The Gnu History Library, Brian Fox and Chet Ramey

Portable Operating System Interface (POSIX) Part 2: Shell and Utilities, IEEE

sh(1), ksh(1), csh(1)

emacs(1), vi(1)

readline(3)

FILES

/bin/bash

The bash executable

/etc/profile

The systemwide initialization file, executed for login shells

/etc/bash.bash_logout

The systemwide login shell cleanup file, executed when a login shell exits

~/.bash_profile

The personal initialization file, executed for login shells

~/.bashrc

The individual per-interactive-shell startup file

~/.bash_logout

The individual login shell cleanup file, executed when a login shell exits

~/.inputrc

Individual readline initialization file

AUTHORS

BUG REPORTS

The version number of bash

The hardware and operating system

The compiler used to compile

A description of the bug behaviour

A short script or `recipe' which exercises the bug

BUGS