Manual Pages for UNIX Darwin command on man sh

BASH(1) BASH(1)

NAME

bash - GNU Bourne-Again SHell

SYNOPSIS

bbaasshh [options] [file]

Bash is Copyright (C) 1989-2002 by the Free Software Foundation, Inc.

DESCRIPTION

BBaasshh is an sshh-compatible command language interpreter that executes

commands read from the standard input or from a file. BBaasshh also incor-

porates useful features from the Korn and C shells (kksshh and ccsshh).

BBaasshh is intended to be a conformant implementation of the IEEE POSIX

Shell and Tools specification (IEEE Working Group 1003.2). OOPPTTIIOONNSS

In addition to the single-character shell options documented in the

description of the sseett builtin command, bbaasshh interprets the following

options when it is invoked:

-cc string If the -cc 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 $$00.

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

-ll Make bbaasshh act as if it had been invoked as a login shell (see

IINNVVOOCCAATTIIOONN below).

-rr If the -rr option is present, the shell becomes restricted

(see RREESSTTRRIICCTTEEDD SSHHEELLLL below).

-ss If the -ss 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.

-DD A list of all double-quoted strings preceded by $$ is printed

on the standard ouput. These are the strings that are sub-

ject to language translation when the current locale is not CC

or PPOOSSIIXX. This implies the -nn option; no commands will be

executed.

[[-++]]OO [[shoptoption]]

shoptoption is one of the shell options accepted by the

sshhoopptt builtin (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below). If

shoptoption is present, -OO sets the value of that option; ++OO

unsets it. If shoptoption is not supplied, the names and

values of the shell options accepted by sshhoopptt are printed on

the standard output. If the invocation option is ++OO, 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 file-

names and arguments. An argument of - is equivalent to --.

BBaasshh also interprets a number of multi-character options. These

options must appear on the command line before the single-character

options to be recognized.

--dduummpp-ppoo-ssttrriinnggss

Equivalent to -DD, but the output is in the GNU gettext ppoo (por-

table object) file format.

--dduummpp-ssttrriinnggss

Equivalent to -DD.

--hheellpp Display a usage message on standard output and exit success-

fully.

--iinniitt-ffiillee file

--rrccffiillee file

Execute commands from file instead of the standard personal ini-

tialization file ~/.bashrc if the shell is interactive (see

IINNVVOOCCAATTIIOONN below).

--llooggiinn

Equivalent to -ll.

--nnooeeddiittiinngg

Do not use the GNU rreeaaddlliinnee library to read command lines when

the shell is interactive.

--nnoopprrooffiillee

Do not read either the system-wide startup file /etc/profile or

any of the personal initialization files ~/.bashprofile,

~/.bashlogin, or ~/.profile. By default, bbaasshh reads these

files when it is invoked as a login shell (see IINNVVOOCCAATTIIOONN

below).

--nnoorrcc 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 sshh.

--ppoossiixx

Change the behavior of bbaasshh where the default operation differs

from the POSIX 1003.2 standard to match the standard (posix mode).

--rreessttrriicctteedd

The shell becomes restricted (see RREESSTTRRIICCTTEEDD SSHHEELLLL below).

--vveerrbboossee

Equivalent to -vv.

--vveerrssiioonn

Show version information for this instance of bbaasshh on the stan-

dard output and exit successfully. AARRGGUUMMEENNTTSS

If arguments remain after option processing, and neither the -cc nor the

-ss option has been supplied, the first argument is assumed to be the

name of a file containing shell commands. If bbaasshh is invoked in this

fashion, $$00 is set to the name of the file, and the positional parame-

ters are set to the remaining arguments. BBaasshh reads and executes com-

mands from this file, then exits. BBaasshh's exit status is the exit sta-

tus of the last command executed in the script. If no commands are executed, the exit status is 0. An attempt is first made to open the

file in the current directory, and, if no file is found, then the shell

searches the directories in PPAATTHH for the script. IINNVVOOCCAATTIIOONN

A login shell is one whose first character of argument zero is a -, or

one started with the --llooggiinn option.

An interactive shell is one started without non-option arguments and

without the -cc option whose standard input and error are both connected

to terminals (as determined by isatty(3)), or one started with the -ii

option. PPSS11 is set and $$- includes ii if bbaasshh is interactive, allowing

a shell script or a startup file to test this state.

The following paragraphs describe how bbaasshh executes its startup files.

If any of the files exist but cannot be read, bbaasshh reports an error.

Tildes are expanded in file names as described below under TTiillddee EExxppaann-

ssiioonn in the EEXXPPAANNSSIIOONN section.

When bbaasshh is invoked as an interactive login shell, or as a non-inter-

active shell with the --llooggiinn option, it first reads and executes com-

mands from the file /etc/profile, if that file exists. After reading

that file, it looks for ~/.bashprofile, ~/.bashlogin, and ~/.profile,

in that order, and reads and executes commands from the first one that

exists and is readable. The --nnoopprrooffiillee option may be used when the

shell is started to inhibit this behavior.

When a login shell exits, bbaasshh reads and executes commands from the

file ~/.bashlogout, if it exists.

When an interactive shell that is not a login shell is started, bbaasshh

reads and executes commands from ~/.bashrc, if that file exists. This

may be inhibited by using the --nnoorrcc option. The --rrccffiillee file option

will force bbaasshh to read and execute commands from file instead of

~/.bashrc.

When bbaasshh is started non-interactively, to run a shell script, for

example, it looks for the variable BBAASSHHEENNVV in the environment, expands its value if it appears there, and uses the expanded value as the name

of a file to read and execute. BBaasshh behaves as if the following com-

mand were executed:

if [ -n "$BASHENV" ]; then . "$BASHENV"; fi

but the value of the PPAATTHH variable is not used to search for the file name.

If bbaasshh is invoked with the name sshh, it tries to mimic the startup

behavior of historical versions of sshh as closely as possible, while

conforming to the POSIX standard as well. When invoked as an interac-

tive login shell, or a non-interactive shell with the --llooggiinn option,

it first attempts to read and execute commands from /etc/profile and

~/.profile, in that order. The --nnoopprrooffiillee option may be used to

inhibit this behavior. When invoked as an interactive shell with the

name sshh, bbaasshh looks for the variable EENNVV, expands its value if it is

defined, and uses the expanded value as the name of a file to read and

execute. Since a shell invoked as sshh does not attempt to read and exe-

cute commands from any other startup files, the --rrccffiillee option has no

effect. A non-interactive shell invoked with the name sshh does not

attempt to read any other startup files. When invoked as sshh, bbaasshh

enters posix mode after the startup files are read.

When bbaasshh is started in posix mode, as with the --ppoossiixx command line

option, it follows the POSIX standard for startup files. In this mode,

interactive shells expand the EENNVV variable and commands are read and

executed from the file whose name is the expanded value. No other startup files are read.

BBaasshh attempts to determine when it is being run by the remote shell

daemon, usually rshd. If bbaasshh determines it is being run by rshd, it

reads and executes commands from ~/.bashrc, if that file exists and is

readable. It will not do this if invoked as sshh. The --nnoorrcc option may

be used to inhibit this behavior, and the --rrccffiillee option may be used

to force another file to be read, but rshd does not generally invoke

the shell with those options or allow them to be specified.

If the shell is started with the effective user (group) id not equal to

the real user (group) id, and the -pp option is not supplied, no startup

files are read, shell functions are not inherited from the environment,

the SSHHEELLLLOOPPTTSS variable, if it appears in the environment, is ignored,

and the effective user id is set to the real user id. If the -pp option

is supplied at invocation, the startup behavior is the same, but the effective user id is not reset. DDEEFFIINNIITTIIOONNSS

The following definitions are used throughout the rest of this docu-

ment. bbllaannkk A space or tab. wwoorrdd A sequence of characters considered as a single unit by the

shell. Also known as a ttookkeenn.

nnaammee A word consisting only of alphanumeric characters and under-

scores, and beginning with an alphabetic character or an under-

score. Also referred to as an iiddeennttiiffiieerr. mmeettaacchhaarraacctteerr A character that, when unquoted, separates words. One of the following: || && ;; (( )) << >> ssppaaccee ttaabb ccoonnttrrooll ooppeerraattoorr

A token that performs a control function. It is one of the fol-

lowing symbols: |||| && &&&& ;; ;;;; (( )) || <> RREESSEERRVVEEDD WWOORRDDSS

Reserved words are words that have a special meaning to the shell. The

following words are recognized as reserved when unquoted and either the first word of a simple command (see SSHHEELLLL GGRRAAMMMMAARR below) or the third word of a ccaassee or ffoorr command: !! ccaassee ddoo ddoonnee eelliiff eellssee eessaacc ffii ffoorr ffuunnccttiioonn iiff iinn sseelleecctt tthheenn uunnttiill wwhhiillee {{ }} ttiimmee [[[[ ]]]] SSHHEELLLL GGRRAAMMMMAARR SSiimmppllee CCoommmmaannddss

A simple command is a sequence of optional variable assignments fol-

lowed by bbllaannkk-separated words and redirections, and terminated by a

control operator. The first word specifies the command to be executed, and is passed as argument zero. The remaining words are passed as arguments to the invoked command. The return value of a simple command is its exit status, or 128+n if the command is terminated by signal n. PPiippeelliinneess

A pipeline is a sequence of one or more commands separated by the char-

acter ||. The format for a pipeline is:

[ttiimmee [-pp]] [ ! ] command [ || command2 ... ]

The standard output of command is connected via a pipe to the standard

input of command2. This connection is performed before any redirec-

tions specified by the command (see RREEDDIIRREECCTTIIOONN below). If the reserved word !! precedes a pipeline, the exit status of that pipeline is the logical NOT of the exit status of the last command. Otherwise, the status of the pipeline is the exit status of the last

command. The shell waits for all commands in the pipeline to terminate

before returning a value. If the ttiimmee reserved word precedes a pipeline, the elapsed as well as user and system time consumed by its execution are reported when the

pipeline terminates. The -pp option changes the output format to that

specified by POSIX. The TTIIMMEEFFOORRMMAATT variable may be set to a format

string that specifies how the timing information should be displayed;

see the description of TTIIMMEEFFOORRMMAATT under SShheellll VVaarriiaabblleess below. Each command in a pipeline is executed as a separate process (i.e., in

a subshell).

LLiissttss A list is a sequence of one or more pipelines separated by one of the operators ;;, &&, &&&&, or ||||, and optionally terminated by one of ;;, &&, or <>. Of these list operators, &&&& and |||| have equal precedence, followed by ;; and &&,, which have equal precedence. A sequence of one or more newlines may appear in a list instead of a semicolon to delimit commands.

If a command is terminated by the control operator &&, the shell exe-

cutes the command in the background in a subshell. The shell does not

wait for the command to finish, and the return status is 0. Commands

separated by a ;; are executed sequentially; the shell waits for each

command to terminate in turn. The return status is the exit status of the last command executed.

The control operators &&&& and |||| denote AND lists and OR lists, respec-

tively. An AND list has the form command1 &&&& command2 command2 is executed if, and only if, command1 returns an exit status of zero. An OR list has the form command1 |||| command2

command2 is executed if and only if command1 returns a non-zero exit

status. The return status of AND and OR lists is the exit status of the last command executed in the list. CCoommppoouunndd CCoommmmaannddss A compound command is one of the following:

(list) list is executed in a subshell. 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. ((expression)) The expression is evaluated according to the rules described

below under AARRIITTHHMMEETTIICC EEVVAALLUUAATTIIOONN. If the value of the expres-

sion is non-zero, the return status is 0; otherwise the return

status is 1. This is exactly equivalent to lleett ""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 CCOONNDDIITTIIOONNAALL EEXXPPRREESSSSIIOONNSS. 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. 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 PPaatttteerrnn MMaattcchhiinngg. The return value is 0 if the string matches or does not match the pattern, respectively, and 1 otherwise. Any part of the pattern may be quoted to force it to be matched as a string. Expressions may be combined using the following operators, listed in decreasing order of precedence: (( expression )) Returns the value of expression. This may be used to override the normal precedence of operators. !! expression True if expression is false. expression1 &&&& expression2 True if both expression1 and expression2 are true. expression1 |||| expression2 True if either expression1 or expression2 is true. The &&&& and |||| operators do not evaluate expression2 if the value of expression1 is sufficient to determine the return value of the entire conditional expression. ffoorr name [ iinn word ] ; ddoo list ; ddoonnee The list of words following iinn 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 iinn word is omit-

ted, the ffoorr command executes list once for each positional parameter that is set (see PPAARRAAMMEETTEERRSS below). The return status is the exit status of the last command that executes. If the expansion of the items following iinn results in an empty list, no commands are executed, and the return status is 0. ffoorr (( expr1 ; expr2 ; expr3 )) ; ddoo list ; ddoonnee First, the arithmetic expression expr1 is evaluated according to the rules described below under AARRIITTHHMMEETTIICC EEVVAALLUUAATTIIOONN. 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 expres-

sions is invalid. sseelleecctt name [ iinn word ] ; ddoo list ; ddoonnee The list of words following iinn 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 iinn word is omitted, the positional parameters are printed (see PPAARRAAMMEETTEERRSS below).

The PPSS33 prompt is then displayed and a line read from the stan-

dard 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 dis-

played 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 RREEPPLLYY. The list is executed after each selection until a bbrreeaakk command is executed. The exit status of sseelleecctt is the exit status of the last command executed in list, or zero if no commands were executed. ccaassee word iinn [ [(] pattern [ || pattern ] ... ) list ;; ] ... eessaacc A ccaassee command first expands word, and tries to match it against

each pattern in turn, using the same matching rules as for path-

name expansion (see PPaatthhnnaammee EExxppaannssiioonn below). When a match is found, the corresponding list is executed. After the first match, no subsequent matches are attempted. The exit status is zero if no pattern matches. Otherwise, it is the exit status of the last command executed in list. iiff list; tthheenn list; [ eelliiff list; tthheenn list; ] ... [ eellssee list; ] ffii The iiff list is executed. If its exit status is zero, the tthheenn list is executed. Otherwise, each eelliiff list is executed in turn, and if its exit status is zero, the corresponding tthheenn list is executed and the command completes. Otherwise, the eellssee

list is executed, if present. The exit status is the exit sta-

tus of the last command executed, or zero if no condition tested true. wwhhiillee list; ddoo list; ddoonnee uunnttiill list; ddoo list; ddoonnee The wwhhiillee command continuously executes the ddoo list as long as the last command in list returns an exit status of zero. The uunnttiill command is identical to the wwhhiillee command, except that the test is negated; the ddoo list is executed as long as the last

command in list returns a non-zero exit status. The exit status

of the wwhhiillee and uunnttiill commands is the exit status of the last ddoo list command executed, or zero if none was executed. [ ffuunnccttiioonn ] name () { list; } This defines a function named name. The body of the function is the list of commands between { and }. This list is executed whenever name is specified as the name of a simple command. The exit status of a function is the exit status of the last command executed in the body. (See FFUUNNCCTTIIOONNSS below.) CCOOMMMMEENNTTSS

In a non-interactive shell, or an interactive shell in which the iinntteerr-

aaccttiivveeccoommmmeennttss option to the sshhoopptt builtin is enabled (see SSHHEELLLL

BBUUIILLTTIINN CCOOMMMMAANNDDSS below), a word beginning with ## causes that word and

all remaining characters on that line to be ignored. An interactive

shell without the iinntteerraaccttiivveeccoommmmeennttss option enabled does not allow

comments. The iinntteerraaccttiivveeccoommmmeennttss option is on by default in interac-

tive shells.

QQUUOOTTIINNGG Quoting is used to remove the special meaning of certain characters or

words to the shell. Quoting can be used to disable special treatment

for special characters, to prevent reserved words from being recognized as such, and to prevent parameter expansion. Each of the metacharacters listed above under DDEEFFIINNIITTIIOONNSS has special

meaning to the shell and must be quoted if it is to represent itself.

When the command history expansion facilities are being used, the his-

tory expansion character, usually !!, must be quoted to prevent history expansion. There are three quoting mechanisms: the escape character, single quotes, and double quotes.

A non-quoted backslash (\\) is the escape character. It preserves the

literal value of the next character that follows, with the exception of

. If a \\ pair appears, and the backslash is not

itself quoted, the \\ is treated as a line continuation (that is, it is removed from the input stream and effectively ignored). Enclosing characters in single quotes preserves the literal value of each character within the quotes. A single quote may not occur between

single quotes, even when preceded by a backslash.

Enclosing characters in double quotes preserves the literal value of

all characters within the quotes, with the exception of $$, ``, and \\.

The characters $$ and `` retain their special meaning within double

quotes. The backslash retains its special meaning only when followed

by one of the following characters: $$, ``, "", \\, or <>. A double

quote may be quoted within double quotes by preceding it with a back-

slash.

The special parameters ** and @@ have special meaning when in double quotes (see PPAARRAAMMEETTEERRSS below).

Words of the form $$'string' are treated specially. The word expands to

string, with backslash-escaped characters replaced as specifed by the

ANSI C standard. Backslash escape sequences, if present, are decoded

as follows: \\aa alert (bell) \\bb backspace \\ee an escape character \\ff form feed \\nn new line \\rr carriage return \\tt horizontal tab \\vv vertical tab

\\\\ backslash

\\'' single quote

\\nnn the eight-bit character whose value is the octal value

nnn (one to three digits)

\\xxHH the eight-bit character whose value is the hexadecimal

value HH (one or two hex digits)

\\ccx a control-x character

The expanded result is single-quoted, as if the dollar sign had not

been present.

A double-quoted string preceded by a dollar sign ($$) will cause the

string to be translated according to the current locale. If the cur-

rent locale is CC or PPOOSSIIXX, the dollar sign is ignored. If the string

is translated and replaced, the replacement is double-quoted.

PPAARRAAMMEETTEERRSS

A parameter is an entity that stores values. It can be a name, a num-

ber, or one of the special characters listed below under SSppeecciiaall PPaarraamm-

eetteerrss. For the shell's purposes, a variable is a parameter denoted by

a name. A variable has a value and zero or more attributes. Attributes are assigned using the ddeeccllaarree builtin command (see ddeeccllaarree below in SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS). A parameter is set if it has been assigned a value. The null string is a valid value. Once a variable is set, it may be unset only by using the uunnsseett builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below). A variable may be assigned to by a statement of the form name=[value] If value is not given, the variable is assigned the null string. All

values undergo tilde expansion, parameter and variable expansion, com-

mand substitution, arithmetic expansion, and quote removal (see EEXXPPAANN-

SSIIOONN below). If the variable has its iinntteeggeerr attribute set, then value

is subject to arithmetic expansion even if the $((...)) expansion is

not used (see AArriitthhmmeettiicc EExxppaannssiioonn below). Word splitting is not per-

formed, with the exception of ""$$@@"" as explained below under SSppeecciiaall

PPaarraammeetteerrss. Pathname expansion is not performed. Assignment state-

ments may also appear as arguments to the ddeeccllaarree, ttyyppeesseett, eexxppoorrtt, rreeaaddoonnllyy, and llooccaall builtin commands. PPoossiittiioonnaall PPaarraammeetteerrss A positional parameter is a parameter denoted by one or more digits, other than the single digit 0. Positional parameters are assigned from

the shell's arguments when it is invoked, and may be reassigned using

the sseett builtin command. Positional parameters may not be assigned to with assignment statements. The positional parameters are temporarily

replaced when a shell function is executed (see FFUUNNCCTTIIOONNSS below).

When a positional parameter consisting of more than a single digit is expanded, it must be enclosed in braces (see EEXXPPAANNSSIIOONN below). SSppeecciiaall PPaarraammeetteerrss

The shell treats several parameters specially. These parameters may

only be referenced; assignment to them is not allowed. ** Expands to the positional parameters, starting from one. When

the expansion occurs within double quotes, it expands to a sin-

gle word with the value of each parameter separated by the first

character of the IIFFSS special variable. That is, "$$**" is equiva-

lent to "$$11c$$22c......", where c is the first character of the value

of the IIFFSS variable. If IIFFSS is unset, the parameters are sepa-

rated by spaces. If IIFFSS 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, "$$@@" is equivalent to "$$11"

"$$22" ... When there are no positional parameters, "$$@@" and $$@@

expand to nothing (i.e., they are removed).

## Expands to the number of positional parameters in decimal.

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

- Expands to the current option flags as specified upon invoca-

tion, by the sseett builtin command, or those set by the shell

itself (such as the -ii option).

$$ Expands to the process ID of the shell. In a () subshell, it

expands to the process ID of the current shell, not the sub-

shell.

!! Expands to the process ID of the most recently executed back-

ground (asynchronous) command.

00 Expands to the name of the shell or shell script. This is set

at shell initialization. If bbaasshh is invoked with a file of com-

mands, $$00 is set to the name of that file. If bbaasshh is started

with the -cc option, then $$00 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 bbaasshh, as given by argument

zero.

At shell startup, set to the absolute file name of the shell or

shell script being executed as passed in the argument list.

Subsequently, expands to the last argument to the previous com-

mand, after expansion. Also set to the full file name of 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. SShheellll VVaarriiaabblleess

The following variables are set by the shell:

BBAASSHH Expands to the full file name used to invoke this instance of

bbaasshh.

BBAASSHHVVEERRSSIINNFFOO A readonly array variable whose members hold version information

for this instance of bbaasshh. The values assigned to the array

members are as follows: BBAASSHHVVEERRSSIINNFFOO[[0]] The major version number (the release). BBAASSHHVVEERRSSIINNFFOO[[1]] The minor version number (the version). BBAASSHHVVEERRSSIINNFFOO[[2]] The patch level. BBAASSHHVVEERRSSIINNFFOO[[3]] The build version. BBAASSHHVVEERRSSIINNFFOO[[4]] The release status (e.g., beta1). BBAASSHHVVEERRSSIINNFFOO[[5]] The value of MMAACCHHTTYYPPEE. BBAASSHHVVEERRSSIIOONN Expands to a string describing the version of this instance of

bbaasshh.

CCOOMMPPCCWWOORRDD

An index into $${{CCOOMMPPWWOORRDDSS}} of the word containing the current

cursor position. This variable is available only in shell func-

tions invoked by the programmable completion facilities (see PPrrooggrraammmmaabbllee CCoommpplleettiioonn below). CCOOMMPPLLIINNEE The current command line. This variable is available only in

shell functions and external commands invoked by the pro-

grammable completion facilities (see PPrrooggrraammmmaabbllee CCoommpplleettiioonn below). CCOOMMPPPPOOIINNTT

The index of the current cursor position relative to the begin-

ning 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 $${{##CCOOMMPPLLIINNEE}}. This variable is available only in

shell functions and external commands invoked by the pro-

grammable completion facilities (see PPrrooggrraammmmaabbllee CCoommpplleettiioonn below). CCOOMMPPWWOORRDDSS

An array variable (see AArrrraayyss below) consisting of the individ-

ual words in the current command line. This variable is avail-

able only in shell functions invoked by the programmable comple-

tion facilities (see PPrrooggrraammmmaabbllee CCoommpplleettiioonn below). DDIIRRSSTTAACCKK

An array variable (see AArrrraayyss below) containing the current con-

tents of the directory stack. Directories appear in the stack in the order they are displayed by the ddiirrss builtin. Assigning

to members of this array variable may be used to modify directo-

ries already in the stack, but the ppuusshhdd and ppooppdd builtins must

be used to add and remove directories. Assignment to this vari-

able will not change the current directory. If DDIIRRSSTTAACCKK is

unset, it loses its special properties, even if it is subse-

quently reset.

EEUUIIDD Expands to the effective user ID of the current user, initial-

ized at shell startup. This variable is readonly.

FUNCNAME

The name of any currently-executing shell function. This vari-

able exists only when a shell function is executing. Assign-

et t FUNCNAME hv n efc ad eun n ro sau. f

FUNCNAME s ne, t oe is pca poete, vn f t

is subsequently reset. GGRROOUUPPSS An array variable containing the list of groups of which the current user is a member. Assignments to GGRROOUUPPSS have no effect and return an error status. If GGRROOUUPPSS is unset, it loses its special properties, even if it is subsequently reset. HHIISSTTCCMMDD The history number, or index in the history list, of the current command. If HHIISSTTCCMMDD is unset, it loses its special properties, even if it is subsequently reset.

HOSTNAME

Automatically set to the name of the current host. HHOOSSTTTTYYPPEE Automatically set to a string that uniquely describes the type

of machine on which bbaasshh is executing. The default is system-

dependent.

LLIINNEENNOO 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 LLIINNEENNOO is unset, it loses its special proper-

ties, even if it is subsequently reset. MMAACCHHTTYYPPEE Automatically set to a string that fully describes the system

type on which bbaasshh is executing, in the standard GNU cpu-com-

pany-system format. The default is system-dependent.

OOLLDDPPWWDD The previous working directory as set by the ccdd command. OOPPTTAARRGG The value of the last option argument processed by the ggeettooppttss builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below). OOPPTTIINNDD The index of the next argument to be processed by the ggeettooppttss builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).

OOSSTTYYPPEE Automatically set to a string that describes the operating sys-

tem on which bbaasshh is executing. The default is system-depen-

dent. PPIIPPEESSTTAATTUUSS An array variable (see AArrrraayyss 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).

PPPPIIDD The process ID of the shell's parent. This variable is read-

only. PPWWDD The current working directory as set by the ccdd command. RRAANNDDOOMM 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 RRAANNDDOOMM. If RRAANNDDOOMM is unset, it loses its special properties, even if it is subsequently reset. RREEPPLLYY Set to the line of input read by the rreeaadd builtin command when no arguments are supplied. SSEECCOONNDDSS Each time this parameter is referenced, the number of seconds

since shell invocation is returned. If a value is assigned to

SSEECCOONNDDSS, the value returned upon subsequent references is the number of seconds since the assignment plus the value assigned. If SSEECCOONNDDSS is unset, it loses its special properties, even if it is subsequently reset. SSHHEELLLLOOPPTTSS

A colon-separated list of enabled shell options. Each word in

the list is a valid argument for the -oo option to the sseett

builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below). The options

appearing in SSHHEELLLLOOPPTTSS are those reported as on by sseett -oo. If

this variable is in the environment when bbaasshh starts up, each

shell option in the list will be enabled before reading any

startup files. This variable is read-only.

SSHHLLVVLL Incremented by one each time an instance of bbaasshh is started.

UUIIDD Expands to the user ID of the current user, initialized at shell

startup. This variable is readonly.

The following variables are used by the shell. In some cases, bbaasshh

assigns a default value to a variable; these cases are noted below. BBAASSHHEENNVV

If this parameter is set when bbaasshh is executing a shell script,

its value is interpreted as a filename containing commands to

initialize the shell, as in ~/.bashrc. The value of BBAASSHHEENNVV is

subjected to parameter expansion, command substitution, and arithmetic expansion before being interpreted as a file name. PPAATTHH is not used to search for the resultant file name.

CCDDPPAATTHH The search path for the ccdd command. This is a colon-separated

list of directories in which the shell looks for destination

directories specified by the ccdd command. A sample value is ".:~:/usr". CCOOLLUUMMNNSS Used by the sseelleecctt builtin command to determine the terminal width when printing selection lists. Automatically set upon receipt of a SIGWINCH. CCOOMMPPRREEPPLLYY

An array variable from which bbaasshh reads the possible completions

generated by a shell function invoked by the programmable com-

pletion facility (see PPrrooggrraammmmaabbllee CCoommpplleettiioonn below). FFCCEEDDIITT The default editor for the ffcc builtin command. FFIIGGNNOORREE

A colon-separated list of suffixes to ignore when performing

filename completion (see RREEAADDLLIINNEE below). A filename whose suf-

fix matches one of the entries in FFIIGGNNOORREE is excluded from the list of matched filenames. A sample value is ".o:~". GGLLOOBBIIGGNNOORREE

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 GGLLOOBBIIGGNNOORREE, it is removed from the list of matches. HHIISSTTCCOONNTTRROOLL If set to a value of ignorespace, lines which begin with a ssppaaccee character are not entered on the history list. If set to a value of ignoredups, lines matching the last history line are not entered. A value of ignoreboth combines the two options. If unset, or if set to any other value than those above, all lines read by the parser are saved on the history list, subject

to the value of HHIISSTTIIGGNNOORREE. This variable's function is super-

seded by HHIISSTTIIGGNNOORREE. 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 HHIISSTTCCOONNTTRROOLL. HHIISSTTFFIILLEE

The name of the file in which command history is saved (see HHIISS-

TTOORRYY below). The default value is ~/.bashhistory. 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 trun-

cated, if necessary, 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.

HHIISSTTIIGGNNOORREE

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 com-

plete line (no implicit `**' is appended). Each pattern is

tested against the line after the checks specified by HHIISSTTCCOONN-

TTRROOLL 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 HHIISSTTIIGGNNOORREE. HHIISSTTSSIIZZEE The number of commands to remember in the command history (see HISTORY eo) Te eal vle s 0. HHOOMMEE The home directory of the current user; the default argument for the ccdd builtin command. The value of this variable is also used when performing tilde expansion. HHOOSSTTFFIILLEE 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, bbaasshh adds the contents of

the new file to the existing list. If HHOOSSTTFFIILLEE is set, but has

no value, bbaasshh attempts to read /etc/hosts to obtain the list of

possible hostname completions. When HHOOSSTTFFIILLEE is unset, the hostname list is cleared. IIFFSS The Internal Field Separator that is used for word splitting after expansion and to split lines into words with the rreeaadd

builtin command. The default value is `` line>''. IIGGNNOORREEEEOOFF

Controls the action of an interactive shell on receipt of an EEOOFF

character as the sole input. If set, the value is the number of consecutive EEOOFF characters which must be typed as the first

characters on an input line before bbaasshh 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, EEOOFF signifies the

end of input to the shell.

IINNPPUUTTRRCC The filename for the rreeaaddlliinnee startup file, overriding the default of ~/.inputrc (see RREEAADDLLIINNEE below). LLAANNGG Used to determine the locale category for any category not specifically selected with a variable starting with LLCC. LLCCAALLLL This variable overrides the value of LLAANNGG and any other LLCC variable specifying a locale category. LLCCCCOOLLLLAATTEE 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. LLCCCCTTYYPPEE This variable determines the interpretation of characters and the behavior of character classes within pathname expansion and pattern matching. LLCCMMEESSSSAAGGEESS

This variable determines the locale used to translate double-

quoted strings preceded by a $$.

LLCCNNUUMMEERRIICC This variable determines the locale category used for number formatting. LLIINNEESS Used by the sseelleecctt builtin command to determine the column length for printing selection lists. Automatically set upon receipt of a SIGWINCH.

MMAAIILL If this parameter is set to a file name and the MMAAIILLPPAATTHH vari-

able is not set, bbaasshh informs the user of the arrival of mail in

the specified file. MMAAIILLCCHHEECCKK

Specifies how often (in seconds) bbaasshh 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.

MMAAIILLPPAATTHH

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:

MMAAIILLPPAATTHH='/var/mail/bfox?"You have mail":~/shell-mail?"$ has

mail!"'

BBaasshh supplies a default value for this variable, but the loca-

tion of the user mail files that it uses is system dependent

(e.g., /var/mail/$$UUSSEERR).

OOPPTTEERRRR If set to the value 1, bbaasshh displays error messages generated by

the ggeettooppttss builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).

OOPPTTEERRRR is initialized to 1 each time the shell is invoked or a

shell script is executed.

PPAATTHH The search path for commands. It is a colon-separated list of

directories in which the shell looks for commands (see CCOOMMMMAANNDD

EEXXEECCUUTTIIOONN below). The default path is system-dependent, and is

set by the administrator who installs bbaasshh. A common value is

``/usr/gnu/bin:/usr/local/bin:/usr/ucb:/bin:/usr/bin:.''. PPOOSSIIXXLLYYCCOORRRREECCTT

If this variable is in the environment when bbaasshh starts, the

shell enters posix mode before reading the startup files, as if

the --ppoossiixx invocation option had been supplied. If it is set

while the shell is running, bbaasshh enables posix mode, as if the

command set -o posix had been executed.

PPRROOMMPPTTCCOOMMMMAANNDD If set, the value is executed as a command prior to issuing each primary prompt. PPSS11 The value of this parameter is expanded (see PPRROOMMPPTTIINNGG below) and used as the primary prompt string. The default value is

``\\ss-\\vv\\$$ ''.

PPSS22 The value of this parameter is expanded as with PPSS11 and used as the secondary prompt string. The default is ``>> ''. PPSS33 The value of this parameter is used as the prompt for the sseelleecctt command (see SSHHEELLLL GGRRAAMMMMAARR above). PPSS44 The value of this parameter is expanded as with PPSS11 and the

value is printed before each command bbaasshh displays during an

execution trace. The first character of PPSS44 is replicated mul-

tiple times, as necessary, to indicate multiple levels of indi-

rection. The default is ``++ ''. TTIIMMEEFFOORRMMAATT

The value of this parameter is used as a format string specify-

ing how the timing information for pipelines prefixed with the

ttiimmee reserved word should be displayed. The %% character intro-

duces 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.

%%%% A literal %%.

%%[[p]][[ll]]RR The elapsed time in seconds.

%%[[p]][[ll]]UU The number of CPU seconds spent in user mode.

%%[[p]][[ll]]SS The number of CPU seconds spent in system mode.

%%PP The CPU percentage, computed as (%U + %S) / %R.

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 ll 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, bbaasshh acts as if it had the value

$$''\\nnrreeaall\\tt%%33llRR\\nnuusseerr\\tt%%33llUU\\nnssyyss%%33llSS''. If the value is null, no

timing information is displayed. A trailing newline is added when the format string is displayed. TTMMOOUUTT If set to a value greater than zero, TTMMOOUUTT is treated as the

default timeout for the rreeaadd builtin. The sseelleecctt command termi-

nates if input does not arrive after TTMMOOUUTT 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. BBaasshh terminates after waiting for

that number of seconds if input does not arrive. aauuttoorreessuummee

This variable controls how the shell interacts with the user and

job control. If this variable is set, single word simple com-

mands without redirections are treated as candidates for resump-

tion 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 analo-

gous to the %%?? job identifier (see JJOOBB CCOONNTTRROOLL 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

%% job identifier.

hhiissttcchhaarrss The two or three characters which control history expansion and oeiain se HISTORY EXPANSION eo) Te is caatr 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, substi-

tuting one string for another in the command. The default is

`^^'. The optional third character is the character which indi-

cates that the remainder of the line is a comment when found as

the first character of a word, normally `##'. The history com-

ment 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.

AArrrraayyss

BBaasshh provides one-dimensional array variables. Any variable may be

used as an array; the ddeeccllaarree builtin will explicitly declare an array. There is no maximum limit on the size of an array, nor any requirement that members be indexed or assigned contiguously. Arrays are indexed

using integers and are zero-based.

An array is created automatically if any variable is assigned to using the syntax name[subscript]=value. The subscript is treated as an arithmetic expression that must evaluate to a number greater than or

equal to zero. To explicitly declare an array, use ddeeccllaarree -aa name

(see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below). ddeeccllaarree -aa name[[subscript]] is also

accepted; the subscript is ignored. Attributes may be specified for an array variable using the ddeeccllaarree and rreeaaddoonnllyy builtins. Each attribute applies to all members of an array. Arrays are assigned to using compound assignments of the form

name=((value1 ... valuen)), where each value is of the form [sub-

script]=string. Only string is required. If the optional brackets and subscript are supplied, that index is assigned to; otherwise the index of the element assigned is the last index assigned to by the statement plus one. Indexing starts at zero. This syntax is also accepted by the ddeeccllaarree builtin. Individual array elements may be assigned to using the name[subscript]=value syntax introduced above.

Any element of an array may be referenced using ${name[subscript]}.

The braces are required to avoid conflicts with pathname expansion. If subscript is @@ or **, the word expands to all members of name. These subscripts differ only when the word appears within double quotes. If

the word is double-quoted, ${name[*]} expands to a single word with the

value of each array member separated by the first character of the IIFFSS

special variable, and ${name[@]} expands each element of name to a sep-

arate word. When there are no array members, ${name[@]} expands to

nothing. This is analogous to the expansion of the special parameters

** and @@ (see SSppeecciiaall PPaarraammeetteerrss above). ${#name[subscript]} expands to

the length of ${name[subscript]}. If subscript is ** or @@, the expan-

sion is the number of elements in the array. Referencing an array variable without a subscript is equivalent to referencing element zero. The uunnsseett builtin is used to destroy arrays. uunnsseett name[subscript] destroys the array element at index subscript. uunnsseett name, where name is an array, or uunnsseett name[subscript], where subscript is ** or @@, removes the entire array.

The ddeeccllaarree, llooccaall, and rreeaaddoonnllyy builtins each accept a -aa option to

specify an array. The rreeaadd builtin accepts a -aa option to assign a

list of words read from the standard input to an array. The sseett and ddeeccllaarree builtins display array values in a way that allows them to be reused as assignments. EEXXPPAANNSSIIOONN Expansion is performed on the command line after it has been split into words. There are seven kinds of expansion performed: brace expansion,

tilde expansion, parameter and variable expansion, command substitu-

tion, arithmetic expansion, word splitting, and pathname expansion.

The order of expansions is: brace expansion, tilde expansion, parame-

ter, variable and arithmetic expansion and command substitution (done

in a left-to-right fashion), word splitting, and pathname expansion.

On systems that can support it, there is an additional expansion avail-

able: process substitution. Only brace expansion, word splitting, and pathname expansion can change the number of words of the expansion; other expansions expand a single word to a single word. The only exceptions to this are the expansions

of "$$@@" and "$${{name[[@@]]}}" as explained above (see PPAARRAAMMEETTEERRSS).

BBrraaccee EExxppaannssiioonn

Brace expansion is a mechanism by which arbitrary strings may be gener-

ated. This mechanism is similar to pathname expansion, but the file-

names generated need not exist. Patterns to be brace expanded take the

form of an optional preamble, followed by a series of comma-separated

strings between a pair of braces, followed by an optional postscript. The preamble is prefixed to each string contained within the braces, and the postscript is then appended to each resulting string, expanding left to right. Brace expansions may be nested. The results of each expanded string are not sorted; left to right order is preserved. For example, a{{d,c,b}}e expands into `ade ace abe'.

Brace expansion is performed before any other expansions, and any char-

acters special to other expansions are preserved in the result. It is

strictly textual. BBaasshh does not apply any syntactic interpretation to

the context of the expansion or the text between the braces.

A correctly-formed brace expansion must contain unquoted opening and

closing braces, and at least one unquoted comma. Any incorrectly formed brace expansion is left unchanged. A {{ or ,, may be quoted with

a backslash to prevent its being considered part of a brace expression.

To avoid conflicts with parameter expansion, the string $${{ is not con-

sidered eligible for brace expansion.

This construct is typically used as shorthand when the common prefix of

the strings to be generated is longer than in the above example:

mkdir /usr/local/src/bash/{old,new,dist,bugs}

or chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,howex}} Brace expansion introduces a slight incompatibility with historical

versions of sshh. sshh does not treat opening or closing braces specially

when they appear as part of a word, and preserves them in the output.

BBaasshh removes braces from words as a consequence of brace expansion.

For example, a word entered to sshh as file{1,2} appears identically in

the output. The same word is output as file1 file2 after expansion by

bbaasshh. If strict compatibility with sshh is desired, start bbaasshh with the

++BB option or disable brace expansion with the ++BB option to the sseett com-

mand (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below). TTiillddee EExxppaannssiioonn If a word begins with an unquoted tilde character (`~~'), all of the

characters preceding the first unquoted slash (or all characters, if

there is no unquoted slash) are considered a tilde-prefix. If none of

the characters in the tilde-prefix are quoted, the characters in the

tilde-prefix following the tilde are treated as a possible login name.

If this login name is the null string, the tilde is replaced with the

value of the shell parameter HHOOMMEE. If HHOOMMEE is unset, the home direc-

tory of the user executing the shell is substituted instead. Other-

wise, the tilde-prefix is replaced with the home directory associated

with the specified login name.

If the tilde-prefix is a `~+', the value of the shell variable PPWWDD

replaces the tilde-prefix. If the tilde-prefix is a `~-', the value of

the shell variable OOLLDDPPWWDD, if it is set, is substituted. If the char-

acters following the tilde in the tilde-prefix consist of a number N,

optionally prefixed by a `+' or a `-', the tilde-prefix is replaced

with the corresponding element from the directory stack, as it would be

displayed by the ddiirrss builtin invoked with the tilde-prefix as an argu-

ment. If the characters following the tilde in the tilde-prefix con-

sist of a number without a leading `+' or `-', `+' is assumed.

If the login name is invalid, or the tilde expansion fails, the word is unchanged.

Each variable assignment is checked for unquoted tilde-prefixes immedi-

ately following a :: or ==. In these cases, tilde expansion is also per-

formed. Consequently, one may use file names with tildes in assign-

ments to PPAATTHH, MMAAIILLPPAATTHH, and CCDDPPAATTHH, and the shell assigns the expanded

value. PPaarraammeetteerr EExxppaannssiioonn

The `$$' character introduces parameter expansion, command substitution,

or arithmetic expansion. The parameter name or symbol to be expanded may be enclosed in braces, which are optional but serve to protect the variable to be expanded from characters immediately following it which could be interpreted as part of the name. When braces are used, the matching ending brace is the first `}}' not

escaped by a backslash or within a quoted string, and not within an

embedded arithmetic expansion, command substitution, or paramter expan-

sion.

${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. If the first character of parameter is an exclamation point, a level of

variable indirection is introduced. BBaasshh uses the value of the vari-

able formed from the rest of parameter as the name of the variable; this variable is then expanded and that value is used in the rest of the substitution, rather than the value of parameter itself. This is known as indirect expansion. The exception to this is the expansion of

${!prefix*} described below.

In each of the cases below, word is subject to tilde expansion, parame-

ter expansion, command substitution, and arithmetic expansion. When

not performing substring expansion, bbaasshh tests for a parameter that is

unset or null; omitting the colon results in a test only for a parame-

ter that is unset.

${parameter::-word}

UUssee DDeeffaauulltt VVaalluueess. If parameter is unset or null, the expan-

sion of word is substituted. Otherwise, the value of parameter is substituted.

${parameter::==word}

AAssssiiggnn DDeeffaauulltt VVaalluueess. If parameter is unset or null, the

expansion of word is assigned to parameter. The value of param-

eter is then substituted. Positional parameters and special parameters may not be assigned to in this way.

${parameter::??word}

DDiissppllaayy EErrrroorr iiff NNuullll oorr UUnnsseett. 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}

UUssee AAlltteerrnnaattee VVaalluuee. If parameter is null or unset, nothing is substituted, otherwise the expansion of word is substituted.

${parameter::offset}

${parameter::offset::length}

SSuubbssttrriinngg EExxppaannssiioonn.. 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 start-

ing at the character specified by offset. length and offset are arithmetic expressions (see AARRIITTHHMMEETTIICC EEVVAALLUUAATTIIOONN below). length must evaluate to a number greater than or equal to zero. 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 parameter is @@, the result is length positional parameters beginning at offset. If parameter is an array name indexed by @ or *, the result is the length members of the array beginning

with ${parameter[offset]}. Substring indexing is zero-based

unless the positional parameters are used, in which case the indexing starts at 1.

${!!prefix**}

Expands to the names of variables whose names begin with prefix, separated by the first character of the IIFFSS special variable.

${##parameter}

The length in characters of the value of parameter is substi-

tuted. 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}

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}

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 pat-

tern (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}

${parameter////pattern//string}

The pattern is expanded to produce a pattern just as in pathname

expansion. Parameter is expanded and the longest match of pat-

tern against its value is replaced with string. In the first form, only the first match is replaced. The second form causes all matches of pattern to be replaced with string. 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 expan-

sion 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. CCoommmmaanndd SSuubbssttiittuuttiioonn

Command substitution allows the output of a command to replace the com-

mand name. There are two forms:

$$((command))

or ``command``

BBaasshh performs the expansion by executing command and replacing the com-

mand substitution with the standard output of the command, with any trailing newlines deleted. Embedded newlines are not deleted, but they

may be removed during word splitting. The command substitution $$((ccaatt

file)) can be replaced by the equivalent but faster $$((<< file)).

When the old-style backquote form of substitution is used, backslash

retains its literal meaning except when followed by $$, ``, or \\. The

first backquote not preceded by a backslash terminates the command sub-

stitution. When using the $(command) form, all characters between the

parentheses make up the command; none are treated specially. Command substitutions may be nested. To nest when using the backquoted

form, escape the inner backquotes with backslashes.

If the substitution appears within double quotes, word splitting and pathname expansion are not performed on the results. AArriitthhmmeettiicc EExxppaannssiioonn Arithmetic expansion allows the evaluation of an arithmetic expression

and the substitution of the result. The format for arithmetic expan-

sion is:

$$((((expression))))

The expression is treated as if it were within double quotes, but a double quote inside the parentheses is not treated specially. All tokens in the expression undergo parameter expansion, string expansion, command substitution, and quote removal. Arithmetic substitutions may be nested. The evaluation is performed according to the rules listed below under

AARRIITTHHMMEETTIICC EEVVAALLUUAATTIIOONN. If expression is invalid, bbaasshh prints a message

indicating failure and no substitution occurs. PPrroocceessss SSuubbssttiittuuttiioonn Process substitution is supported on systems that support named pipes (FIFOs) or the //ddeevv//ffdd method of naming open files. It takes the form

of <<((list)) or >>((list)). The process list is run with its input or out-

put connected to a FIFO or some file in //ddeevv//ffdd. The name of this file is passed as an argument to the current command as the result of the

expansion. If the >>((list)) form is used, writing to the file will pro-

vide input for list. If the <<((list)) form is used, the file passed as

an argument should be read to obtain the output of list.

When available, process substitution is performed simultaneously with parameter and variable expansion, command substitution, and arithmetic expansion. WWoorrdd SSpplliittttiinngg

The shell scans the results of parameter expansion, command substitu-

tion, and arithmetic expansion that did not occur within double quotes for word splitting.

The shell treats each character of IIFFSS as a delimiter, and splits the

results of the other expansions into words on these characters. If IIFFSS is unset, or its value is exactly <><><>, the default, then any sequence of IIFFSS characters serves to delimit words. If IIFFSS has a value other than the default, then sequences of the whitespace characters ssppaaccee and ttaabb are ignored at the beginning and end of the word, as long as the whitespace character is in the value of IIFFSS (an

IIFFSS whitespace character). Any character in IIFFSS that is not IIFFSS white-

space, along with any adjacent IIFFSS whitespace characters, delimits a field. A sequence of IIFFSS whitespace characters is also treated as a delimiter. If the value of IIFFSS is null, no word splitting occurs. Explicit null arguments ("""" or '''') are retained. Unquoted implicit null arguments, resulting from the expansion of parameters that have no values, are removed. If a parameter with no value is expanded within double quotes, a null argument results and is retained. Note that if no expansion occurs, no splitting is performed. PPaatthhnnaammee EExxppaannssiioonn

After word splitting, unless the -ff option has been set, bbaasshh scans

each word for the characters **, ??, and [[. If one of these characters appears, then the word is regarded as a pattern, and replaced with an alphabetically sorted list of file names matching the pattern. If no

matching file names are found, and the shell option nnuullllgglloobb is dis-

abled, the word is left unchanged. If the nnuullllgglloobb option is set, and

no matches are found, the word is removed. If the shell option nnooccaassee-

gglloobb is enabled, the match is performed without regard to the case of alphabetic characters. When a pattern is used for pathname expansion, the character ````..'''' at the start of a name or immediately following a

slash must be matched explicitly, unless the shell option ddoottgglloobb is

set. When matching a pathname, the slash character must always be

matched explicitly. In other cases, the ````..'''' character is not

treated specially. See the description of sshhoopptt below under SSHHEELLLL

BBUUIILLTTIINN CCOOMMMMAANNDDSS for a description of the nnooccaasseegglloobb, nnuullllgglloobb, and

ddoottgglloobb shell options.

The GGLLOOBBIIGGNNOORREE shell variable may be used to restrict the set of file

names matching a pattern. If GGLLOOBBIIGGNNOORREE is set, each matching file name that also matches one of the patterns in GGLLOOBBIIGGNNOORREE is removed from the list of matches. The file names ````..'''' and ````....'''' are always ignored, even when GGLLOOBBIIGGNNOORREE is set. However, setting GGLLOOBBIIGGNNOORREE has

the effect of enabling the ddoottgglloobb shell option, so all other file

names beginning with a ````..'''' will match. To get the old behavior of ignoring file names beginning with a ````..'''', make ````..**'''' one of the patterns in GGLLOOBBIIGGNNOORREE. The ddoottgglloobb option is disabled when GGLLOOBBIIGGNNOORREE is unset. PPaatttteerrnn MMaattcchhiinngg Any character that appears in a pattern, other than the special pattern characters described below, matches itself. The NUL character may not occur in a pattern. The special pattern characters must be quoted if they are to be matched literally. The special pattern characters have the following meanings: ** Matches any string, including the null string. ?? Matches any single character.

[[......]] Matches any one of the enclosed characters. A pair of charac-

ters separated by a hyphen denotes a range expression; any char-

acter that sorts between those two characters, inclusive, using the current locale's collating sequence and character set, is matched. If the first character following the [[ is a !! or a ^^ then any character not enclosed is matched. The sorting order of characters in range expressions is determined by the current

locale and the value of the LLCCCCOOLLLLAATTEE shell variable, if set.

A - may be matched by including it as the first or last charac-

ter in the set. A ]] may be matched by including it as the first character in the set. Within [[ and ]], character classes can be specified using the syntax [[::class::]], where class is one of the following classes defined in the POSIX.2 standard: aallnnuumm aallpphhaa aasscciiii bbllaannkk ccnnttrrll ddiiggiitt ggrraapphh lloowweerr pprriinntt ppuunncctt ssppaaccee uuppppeerr wwoorrdd xxddiiggiitt A character class matches any character belonging to that class.

The wwoorrdd character class matches letters, digits, and the char-

acter . Within [[ and ]], an equivalence class can be specified using the

syntax [[==c==]], which matches all characters with the same colla-

tion weight (as defined by the current locale) as the character c.

Within [[ and ]], the syntax [[..symbol..]] matches the collating sym-

bol symbol.

If the eexxttgglloobb shell option is enabled using the sshhoopptt builtin, several

extended pattern matching operators are recognized. In the following

description, a pattern-list is a list of one or more patterns separated

by a ||. Composite patterns may be formed using one or more of the fol-

lowing sub-patterns:

??((pattern-list))

Matches zero or one occurrence of the given patterns

**((pattern-list))

Matches zero or more occurrences of the given patterns

++((pattern-list))

Matches one or more occurrences of the given patterns

@@((pattern-list))

Matches exactly one of the given patterns

!!((pattern-list))

Matches anything except one of the given patterns QQuuoottee RReemmoovvaall

After the preceding expansions, all unquoted occurrences of the charac-

ters \\, '', and "" that did not result from one of the above expansions are removed. RREEDDIIRREECCTTIIOONN Before a command is executed, its input and output may be redirected

using a special notation interpreted by the shell. Redirection may

also be used to open and close files for the current shell execution

environment. The following redirection operators may precede or appear anywhere within a simple command or may follow a command. Redirections are processed in the order they appear, from left to right.

In the following descriptions, if the file descriptor number is omit-

ted, and the first character of the redirection operator is <<, the re-

direction refers to the standard input (file descriptor 0). If the first character of the redirection operator is >>, the redirection refers to the standard output (file descriptor 1).

The word following the redirection operator in the following descrip-

tions, unless otherwise noted, is subjected to brace expansion, tilde

expansion, parameter expansion, command substitution, arithmetic expan-

sion, quote removal, pathname expansion, and word splitting. If it

expands to more than one word, bbaasshh reports an error.

Note that the order of redirections is significant. For example, the command ls >> dirlist 2>>&&1 directs both standard output and standard error to the file dirlist, while the command ls 2>>&&1 >> dirlist directs only the standard output to file dirlist, because the standard error was duplicated as standard output before the standard output was redirected to dirlist.

BBaasshh handles several filenames specially when they are used in redirec-

tions, as described in the following table: //ddeevv//ffdd//fd

If fd is a valid integer, file descriptor fd is dupli-

cated. //ddeevv//ssttddiinn File descriptor 0 is duplicated. //ddeevv//ssttddoouutt File descriptor 1 is duplicated. //ddeevv//ssttddeerrrr File descriptor 2 is duplicated. //ddeevv//ttccpp//host//port If host is a valid hostname or Internet address, and port

is an integer port number or service name, bbaasshh attempts

to open a TCP connection to the corresponding socket. //ddeevv//uuddpp//host//port If host is a valid hostname or Internet address, and port

is an integer port number or service name, bbaasshh attempts

to open a UDP connection to the corresponding socket. A failure to open or create a file causes the redirection to fail. RReeddiirreeccttiinngg IInnppuutt

Redirection of input causes the file whose name results from the expan-

sion of word to be opened for reading on file descriptor n, or the standard input (file descriptor 0) if n is not specified. The general format for redirecting input is: [n]<>word If the redirection operator is >>, and the nnoocclloobbbbeerr option to the sseett builtin has been enabled, the redirection will fail if the file whose name results from the expansion of word exists and is a regular file. If the redirection operator is >>||, or the redirection operator is >> and

the nnoocclloobbbbeerr option to the sseett builtin command is not enabled, the re-

direction is attempted even if the file named by word exists. AAppppeennddiinngg RReeddiirreecctteedd OOuuttppuutt

Redirection of output in this fashion causes the file whose name

results from the expansion of word to be opened for appending on file descriptor n, or the standard output (file descriptor 1) if n is not specified. If the file does not exist it is created. The general format for appending output is: [n]>>>>word RReeddiirreeccttiinngg SSttaannddaarrdd OOuuttppuutt aanndd SSttaannddaarrdd EErrrroorr

BBaasshh allows both the standard output (file descriptor 1) and the stan-

dard error output (file descriptor 2) to be redirected to the file whose name is the expansion of word with this construct. There are two formats for redirecting standard output and standard error: &&>>word and >>&&word

Of the two forms, the first is preferred. This is semantically equiva-

lent to >>word 2>>&&1 HHeerree DDooccuummeennttss

This type of redirection instructs the shell to read input from the

current source until a line containing only word (with no trailing blanks) is seen. All of the lines read up to that point are then used as the standard input for a command.

The format of here-documents is:

<<<<[-]word

here-document

delimiter No parameter expansion, command substitution, arithmetic expansion, or pathname expansion is performed on word. If any characters in word are quoted, the delimiter is the result of quote removal on word, and the

lines in the here-document are not expanded. If word is unquoted, all

lines of the here-document are subjected to parameter expansion, com-

mand substitution, and arithmetic expansion. In the latter case, the character sequence \\<> is ignored, and \\ must be used to quote

the characters \\, $$, and ``.

If the redirection operator is <<<<-, then all leading tab characters are

stripped from input lines and the line containing delimiter. This

allows here-documents within shell scripts to be indented in a natural

fashion.

HHeerree SSttrriinnggss A variant of here documents, the format is: <<<<< descriptor open for input, a redirection error occurs. If word evalu-

ates to -, file descriptor n is closed. If n is not specified, the

standard input (file descriptor 0) is used. The operator [n]>>&&word is used similarly to duplicate output file descriptors. If n is not specified, the standard output (file descriptor 1) is used. If the

digits in word do not specify a file descriptor open for output, a re-

direction error occurs. As a special case, if n is omitted, and word does not expand to one or more digits, the standard output and standard error are redirected as described previously. MMoovviinngg FFiillee DDeessccrriippttoorrss The redirection operator

[n]<<&&digit-

moves the file descriptor digit to file descriptor n, or the standard input (file descriptor 0) if n is not specified. digit is closed after being duplicated to n. Similarly, the redirection operator

[n]>>&&digit-

moves the file descriptor digit to file descriptor n, or the standard output (file descriptor 1) if n is not specified. OOppeenniinngg FFiillee DDeessccrriippttoorrss ffoorr RReeaaddiinngg aanndd WWrriittiinngg The redirection operator [n]<<>>word causes the file whose name is the expansion of word to be opened for both reading and writing on file descriptor n, or on file descriptor 0 if n is not specified. If the file does not exist, it is created. AALLIIAASSEESS Aliases allow a string to be substituted for a word when it is used as

the first word of a simple command. The shell maintains a list of

aliases that may be set and unset with the aalliiaass and uunnaalliiaass builtin commands (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below). The first word of each command, if unquoted, is checked to see if it has an alias. If so, that word is replaced by the text of the alias. The alias name and the

replacement text may contain any valid shell input, including the

metacharacters listed above, with the exception that the alias name may not contain =. The first word of the replacement text is tested for aliases, but a word that is identical to an alias being expanded is not

expanded a second time. This means that one may alias llss to llss -FF, for

instance, and bbaasshh does not try to recursively expand the replacement

text. If the last character of the alias value is a blank, then the

next command word following the alias is also checked for alias expan-

sion. Aliases are created and listed with the aalliiaass command, and removed with the uunnaalliiaass command. There is no mechanism for using arguments in the replacement text. If

arguments are needed, a shell function should be used (see FFUUNNCCTTIIOONNSS

below).

Aliases are not expanded when the shell is not interactive, unless the

eexxppaannddaalliiaasseess shell option is set using sshhoopptt (see the description of

sshhoopptt under SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).

The rules concerning the definition and use of aliases are somewhat

confusing. BBaasshh always reads at least one complete line of input

before executing any of the commands on that line. Aliases are expanded when a command is read, not when it is executed. Therefore, an alias definition appearing on the same line as another command does not take effect until the next line of input is read. The commands following the alias definition on that line are not affected by the new alias. This behavior is also an issue when functions are executed. Aliases are expanded when a function definition is read, not when the

function is executed, because a function definition is itself a com-

pound command. As a consequence, aliases defined in a function are not available until after that function is executed. To be safe, always

put alias definitions on a separate line, and do not use aalliiaass in com-

pound commands.

For almost every purpose, aliases are superseded by shell functions.

FFUUNNCCTTIIOONNSS

A shell function, defined as described above under SSHHEELLLL GGRRAAMMMMAARR,

stores a series of commands for later execution. When the name of a

shell function is used as a simple command name, the list of commands

associated with that function name is executed. Functions are executed

in the context of the current shell; no new process is created to

interpret them (contrast this with the execution of a shell script).

When a function is executed, the arguments to the function become the

positional parameters during its execution. The special parameter ## is

updated to reflect the change. Positional parameter 0 is unchanged.

h FUNCNAME vral i st o h nm o te ucin hl te

function is executing. All other aspects of the shell execution envi-

ronment are identical between a function and its caller with the excep-

tion that the DDEEBBUUGG trap (see the description of the ttrraapp builtin under SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below) is not inherited unless the function has been given the ttrraaccee attribute (see the description of the ddeeccllaarree builtin below). Variables local to the function may be declared with the llooccaall builtin

command. Ordinarily, variables and their values are shared between the

function and its caller. If the builtin command rreettuurrnn is executed in a function, the function

completes and execution resumes with the next command after the func-

tion call. When a function completes, the values of the positional

parameters and the special parameter ## are restored to the values they

had prior to the function's execution.

Function names and definitions may be listed with the -ff option to the

ddeeccllaarree or ttyyppeesseett builtin commands. The -FF option to ddeeccllaarree or ttyyppee-

sseett will list the function names only. Functions may be exported so

that subshells automatically have them defined with the -ff option to

the eexxppoorrtt builtin. Functions may be recursive. No limit is imposed on the number of recursive calls. AARRIITTHHMMEETTIICC EEVVAALLUUAATTIIOONN

The shell allows arithmetic expressions to be evaluated, under certain

circumstances (see the lleett builtin command and AArriitthhmmeettiicc EExxppaannssiioonn).

Evaluation is done in fixed-width integers with no check for overflow,

though division by 0 is trapped and flagged as an error. The operators

and their precedence and associativity are the same as in the C lan-

guage. The following list of operators is grouped into levels of

equal-precedence operators. The levels are listed in order of decreas-

ing precedence.

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 evaluation

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

assignment expr1 ,, expr2 comma

Shell variables are allowed as operands; parameter expansion is per-

formed before the expression is evaluated. Within an expression, shell

variables may also be referenced by name without using the parameter

expansion syntax. The value of a variable is evaluated as an arith-

metic expression when it is referenced. A shell variable need not have

its integer attribute turned on to be used in an expression. Constants with a leading 0 are interpreted as octal numbers. A leading 0x or 0X denotes hexadecimal. Otherwise, numbers take the form

[base#]n, where base is a decimal number between 2 and 64 representing

the arithmetic base, and n is a number in that base. If base# is omit-

ted, then base 10 is used. The digits greater than 9 are represented by the lowercase letters, the uppercase letters, @, and , in that order. If base is less than or equal to 36, lowercase and uppercase letters may be used interchangably to represent numbers between 10 and 35.

Operators are evaluated in order of precedence. Sub-expressions in

parentheses are evaluated first and may override the precedence rules above. CCOONNDDIITTIIOONNAALL EEXXPPRREESSSSIIOONNSS Conditional expressions are used by the [[[[ compound command and the tteesstt and [[ builtin commands to test file attributes and perform string and arithmetic comparisons. Expressions are formed from the following

unary or binary primaries. If any file argument to one of the pri-

maries is of the form /dev/fd/n, then file descriptor n is checked. If the file argument to one of the primaries is one of /dev/stdin, /dev/stdout, or /dev/stderr, file descriptor 0, 1, or 2, respectively, is checked.

-aa file

True if file exists.

-bb file

True if file exists and is a block special file.

-cc file

True if file exists and is a character special file.

-dd file

True if file exists and is a directory.

-ee file

True if file exists.

-ff file

True if file exists and is a regular file.

-gg file

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

-hh file

True if file exists and is a symbolic link.

-kk file

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

-pp file

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

-rr file

True if file exists and is readable.

-ss file

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

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

-uu file

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

-ww file

True if file exists and is writable.

-xx file

True if file exists and is executable.

-OO file

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

-GG file

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

-LL file

True if file exists and is a symbolic link.

-SS file

True if file exists and is a socket.

-NN file

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

file1 -nntt file2

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

file1 -oott file2

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

file1 -eeff file2

True if file1 and file2 refer to the same device and inode num-

bers.

-oo optname

True if shell option optname is enabled. See the list of

options under the description of the -oo option to the sseett

builtin below.

-zz string

True if the length of string is zero.

-nn string

string True if the length of string is non-zero.

string1 ==== string2 True if the strings are equal. == may be used in place of ==== for strict POSIX compliance. string1 !!== string2 True if the strings are not equal. string1 << string2 True if string1 sorts before string2 lexicographically in the current locale. string1 >> string2 True if string1 sorts after string2 lexicographically in the current locale. arg1 OOPP arg2

OOPP is one of -eeqq, -nnee, -lltt, -llee, -ggtt, or -ggee. 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. SSIIMMPPLLEE CCOOMMMMAANNDD EEXXPPAANNSSIIOONN

When a simple command is executed, the shell performs the following

expansions, assignments, and redirections, from left to right. 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 RREEDDIIRREECCTTIIOONN. 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 vari-

able. If no command name results, the variable assignments affect the current

shell environment. Otherwise, the variables are added to the environ-

ment of the executed command and do not affect the current shell envi-

ronment. If any of the assignments attempts to assign a value to a

readonly variable, an error occurs, and the command exits with a non-

zero status. If no command name results, redirections are performed, but do not

affect the current shell environment. A redirection error causes the

command to exit with a non-zero status.

If there is a command name left after expansion, execution proceeds as

described below. Otherwise, the command exits. If one of the expan-

sions contained a command substitution, the exit status of the command is the exit status of the last command substitution performed. If there were no command substitutions, the command exits with a status of zero. CCOOMMMMAANNDD EEXXEECCUUTTIIOONN After a command has been split into words, if it results in a simple command and an optional list of arguments, the following actions are taken.

If the command name contains no slashes, the shell attempts to locate

it. If there exists a shell function by that name, that function is

invoked as described above in FFUUNNCCTTIIOONNSS. If the name does not match a

function, the shell searches for it in the list of shell builtins. If

a match is found, that builtin is invoked.

If the name is neither a shell function nor a builtin, and contains no

slashes, bbaasshh searches each element of the PPAATTHH for a directory con-

taining an executable file by that name. BBaasshh uses a hash table to

remember the full pathnames of executable files (see hhaasshh under SSHHEELLLL

BBUUIILLTTIINN CCOOMMMMAANNDDSS below). A full search of the directories in PPAATTHH is

performed only if the command is not found in the hash table. If the

search is unsuccessful, the shell prints an error message and returns

an exit status of 127. If the search is successful, or if the command name contains one or

more slashes, the shell executes the named program in a separate execu-

tion environment. Argument 0 is set to the name given, and the remain-

ing arguments to the command are set to the arguments given, if any. If this execution fails because the file is not in executable format,

and the file is not a directory, it is assumed to be a shell script, a

file containing shell commands. A subshell is spawned to execute it.

This subshell reinitializes itself, so that the effect is as if a new

shell had been invoked to handle the script, with the exception that

the locations of commands remembered by the parent (see hhaasshh below

under SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS) are retained by the child.

If the program is a file beginning with ##!!, the remainder of the first

line specifies an interpreter for the program. The shell executes the

specified interpreter on operating systems that do not handle this exe-

cutable format themselves. The arguments to the interpreter consist of a single optional argument following the interpreter name on the first line of the program, followed by the name of the program, followed by the command arguments, if any. COMMAND EXECUTION ENVIRONMENT

The shell has an execution environment, which consists of the follow-

ing:

+o open files inherited by the shell at invocation, as modified by

redirections supplied to the eexxeecc builtin

+o the current working directory as set by ccdd, ppuusshhdd, or ppooppdd, or

inherited by the shell at invocation

+o the file creation mode mask as set by uummaasskk or inherited from

the shell's parent

+o current traps set by ttrraapp

+o shell parameters that are set by variable assignment or with sseett

or inherited from the shell's parent in the environment

+o shell functions defined during execution or inherited from the

shell's parent in the environment

+o options enabled at invocation (either by default or with com-

mand-line arguments) or by sseett

+o options enabled by sshhoopptt

+o shell aliases defined with aalliiaass

+o various process IDs, including those of background jobs, the

value of $$$$, and the value of $$PPPPIIDD

When a simple command other than a builtin or shell function is to be

executed, it is invoked in a separate execution environment that con-

sists of the following. Unless otherwise noted, the values are inher-

ited from the shell.

+o the shell's open files, plus any modifications and additions

specified by redirections to the command +o the current working directory +o the file creation mode mask

+o shell variables marked for export, along with variables exported

for the command, passed in the environment

+o traps caught by the shell are reset to the values the inherited

from the shell's parent, and traps ignored by the shell are

ignored A command invoked in this separate environment cannot affect the

shell's execution environment.

Command substitution and asynchronous commands are invoked in a sub-

shell environment that is a duplicate of the shell environment, except

that traps caught by the shell are reset to the values that the shell

inherited from its parent at invocation. Builtin commands that are

invoked as part of a pipeline are also executed in a subshell environ-

ment. Changes made to the subshell environment cannot affect the

shell's execution environment.

If a command is followed by a && and job control is not active, the default standard input for the command is the empty file /dev/null. Otherwise, the invoked command inherits the file descriptors of the

calling shell as modified by redirections.

ENVIRONMENT When a program is invoked it is given an array of strings called the

environment. This is a list of name-value pairs, of the form

name=value.

The shell provides several ways to manipulate the environment. On

invocation, the shell scans its own environment and creates a parameter

for each name found, automatically marking it for export to child pro-

cesses. Executed commands inherit the environment. The eexxppoorrtt and

ddeeccllaarree -xx commands allow parameters and functions to be added to and

deleted from the environment. If the value of a parameter in the envi-

ronment is modified, the new value becomes part of the environment, replacing the old. The environment inherited by any executed command

consists of the shell's initial environment, whose values may be modi-

fied in the shell, less any pairs removed by the uunnsseett command, plus

any additions via the eexxppoorrtt and ddeeccllaarree -xx commands.

The environment for any simple command or function may be augmented temporarily by prefixing it with parameter assignments, as described

above in PPAARRAAMMEETTEERRSS. These assignment statements affect only the envi-

ronment seen by that command.

If the -kk option is set (see the sseett builtin command below), then all

parameter assignments are placed in the environment for a command, not just those that precede the command name.

When bbaasshh invokes an external command, the variable is set to the

full file name of the command and passed to that command in its envi-

ronment. EEXXIITT SSTTAATTUUSS

For the shell's purposes, a command which exits with a zero exit status

has succeeded. An exit status of zero indicates success. A non-zero

exit status indicates failure. When a command terminates on a fatal

signal N, bbaasshh uses the value of 128+N as the exit status.

If a command is not found, the child process created to execute it returns a status of 127. If a command is found but is not executable, the return status is 126. If a command fails because of an error during expansion or redirection, the exit status is greater than zero. Shell builtin commands return a status of 0 (true) if successful, and

non-zero (false) if an error occurs while they execute. All builtins

return an exit status of 2 to indicate incorrect usage.

BBaasshh itself returns the exit status of the last command executed,

unless a syntax error occurs, in which case it exits with a non-zero

value. See also the eexxiitt builtin command below. SSIIGGNNAALLSS

When bbaasshh is interactive, in the absence of any traps, it ignores

SSIIGGTTEERRMM (so that kkiillll 00 does not kill an interactive shell), and SSIIGGIINNTT

is caught and handled (so that the wwaaiitt builtin is interruptible). In

all cases, bbaasshh ignores SSIIGGQQUUIITT. If job control is in effect, bbaasshh

ignores SSIIGGTTTTIINN, SSIIGGTTTTOOUU, and SSIIGGTTSSTTPP.

Synchronous jobs started by bbaasshh have signal handlers set to the values

inherited by the shell from its parent. When job control is not in

effect, asynchronous commands ignore SSIIGGIINNTT and SSIIGGQQUUIITT as well. Com-

mands run as a result of command substitution ignore the keyboard-gen-

erated job control signals SSIIGGTTTTIINN, SSIIGGTTTTOOUU, and SSIIGGTTSSTTPP.

The shell exits by default upon receipt of a SSIIGGHHUUPP. Before exiting,

an interactive shell resends the SSIIGGHHUUPP to all jobs, running or

stopped. Stopped jobs are sent SSIIGGCCOONNTT to ensure that they receive the

SSIIGGHHUUPP. To prevent the shell from sending the signal to a particular

job, it should be removed from the jobs table with the ddiissoowwnn builtin

(see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below) or marked to not receive SSIIGGHHUUPP

using ddiissoowwnn -hh.

If the hhuuppoonneexxiitt shell option has been set with sshhoopptt, bbaasshh sends a

SSIIGGHHUUPP to all jobs when an interactive login shell exits.

When bbaasshh receives a signal for which a trap has been set while waiting

for a command to complete, the trap will not be executed until the com-

mand completes. When bbaasshh is waiting for an asynchronous command via

the wwaaiitt builtin, the reception of a signal for which a trap has been

set will cause the wwaaiitt builtin to return immediately with an exit sta-

tus greater than 128, immediately after which the trap is executed. JJOOBB CCOONNTTRROOLL Job control refers to the ability to selectively stop (suspend) the execution of processes and continue (resume) their execution at a later point. A user typically employs this facility via an interactive

interface supplied jointly by the system's terminal driver and bbaasshh.

The shell associates a job with each pipeline. It keeps a table of

currently executing jobs, which may be listed with the jjoobbss command.

When bbaasshh starts a job asynchronously (in the background), it prints a

line that looks like: [1] 25647 indicating that this job is job number 1 and that the process ID of the last process in the pipeline associated with this job is 25647. All of

the processes in a single pipeline are members of the same job. BBaasshh

uses the job abstraction as the basis for job control. To facilitate the implementation of the user interface to job control, the operating system maintains the notion of a current terminal process group ID. Members of this process group (processes whose process group

ID is equal to the current terminal process group ID) receive keyboard-

generated signals such as SSIIGGIINNTT. These processes are said to be in the foreground. Background processes are those whose process group ID

differs from the terminal's; such processes are immune to keyboard-gen-

erated signals. Only foreground processes are allowed to read from or write to the terminal. Background processes which attempt to read from

(write to) the terminal are sent a SSIIGGTTTTIINN ((SSIIGGTTTTOOUU)) signal by the ter-

minal driver, which, unless caught, suspends the process.

If the operating system on which bbaasshh is running supports job control,

bbaasshh contains facilities to use it. Typing the suspend character (typ-

ically ^^ZZ, Control-Z) while a process is running causes that process to

be stopped and returns control to bbaasshh. Typing the delayed suspend

character (typically ^^YY, Control-Y) causes the process to be stopped

when it attempts to read input from the terminal, and control to be

returned to bbaasshh. The user may then manipulate the state of this job,

using the bbgg command to continue it in the background, the ffgg command to continue it in the foreground, or the kkiillll command to kill it. A ^^ZZ takes effect immediately, and has the additional side effect of causing pending output and typeahead to be discarded.

There are a number of ways to refer to a job in the shell. The charac-

ter %% introduces a job name. Job number n may be referred to as %%nn. A

job may also be referred to using a prefix of the name used to start

it, or using a substring that appears in its command line. For exam-

ple, %%ccee refers to a stopped ccee job. If a prefix matches more than one

job, bbaasshh reports an error. Using %%??ccee, on the other hand, refers to

any job containing the string ccee in its command line. If the substring

matches more than one job, bbaasshh reports an error. The symbols %%%% and

%%++ refer to the shell's notion of the current job, which is the last

job stopped while it was in the foreground or started in the back-

ground. The previous job may be referenced using %%-. In output per-

taining to jobs (e.g., the output of the jjoobbss command), the current job

is always flagged with a ++, and the previous job with a -.

Simply naming a job can be used to bring it into the foreground: %%11 is

a synonym for ````ffgg %%11'''', bringing job 1 from the background into the

foreground. Similarly, ````%%11 &&'''' resumes job 1 in the background,

equivalent to ````bbgg %%11''''.

The shell learns immediately whenever a job changes state. Normally,

bbaasshh waits until it is about to print a prompt before reporting changes

in a job's status so as to not interrupt any other output. If the -bb

option to the sseett builtin command is enabled, bbaasshh reports such changes

immediately. Any trap on SSIIGGCCHHLLDD is executed for each child that exits.

If an attempt to exit bbaasshh is made while jobs are stopped, the shell

prints a warning message. The jjoobbss command may then be used to inspect

their status. If a second attempt to exit is made without an interven-

ing command, the shell does not print another warning, and the stopped

jobs are terminated. PPRROOMMPPTTIINNGG

When executing interactively, bbaasshh displays the primary prompt PPSS11 when

it is ready to read a command, and the secondary prompt PPSS22 when it

needs more input to complete a command. BBaasshh allows these prompt

strings to be customized by inserting a number of backslash-escaped

special characters that are decoded as follows: \\aa an ASCII bell character (07) \\dd the date in "Weekday Month Date" format (e.g., "Tue May 26") \\DD{{format}} the format is passed to strftime(3) and the result is inserted into the prompt string; an empty format results

in a locale-specific time representation. The braces are

required \\ee an ASCII escape character (033) \\hh the hostname up to the first `.' \\HH the hostname

\\jj the number of jobs currently managed by the shell

\\ll the basename of the shell's terminal device name

\\nn newline \\rr carriage return

\\ss the name of the shell, the basename of $$00 (the portion

following the final slash)

\\tt the current time in 24-hour HH:MM:SS format

\\TT the current time in 12-hour HH:MM:SS format

\\@@ the current time in 12-hour am/pm format

\\AA the current time in 24-hour HH:MM format

\\uu the username of the current user

\\vv the version of bbaasshh (e.g., 2.00)

\\VV the release of bbaasshh, version + patchelvel (e.g., 2.00.0)

\\ww the current working directory \\WW the basename of the current working directory \\!! the history number of this command

\\## the command number of this command

\\$$ if the effective UID is 0, a ##, otherwise a $$

\\nnn the character corresponding to the octal number nnn

\\\\ a backslash

\\[[ begin a sequence of non-printing characters, which could

be used to embed a terminal control sequence into the prompt

\\]] end a sequence of non-printing characters

The command number and the history number are usually different: the history number of a command is its position in the history list, which a icue omns etrd rm h hsoy ie se HISTORY below), while the command number is the position in the sequence of

commands executed during the current shell session. After the string

is decoded, it is expanded via parameter expansion, command substitu-

tion, arithmetic expansion, and quote removal, subject to the value of

the pprroommppttvvaarrss shell option (see the description of the sshhoopptt command

under SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below). RREEAADDLLIINNEE

This is the library that handles reading input when using an interac-

tive shell, unless the --nnooeeddiittiinngg option is given at shell invocation.

By default, the line editing commands are similar to those of emacs. A

vi-style line editing interface is also available. To turn off line

editing after the shell is running, use the ++oo eemmaaccss or ++oo vvii options

to the sseett builtin (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below). RReeaaddlliinnee NNoottaattiioonn

In this section, the emacs-style notation is used to denote keystrokes.

Control keys are denoted by C-key, e.g., C-n means Control-N. Simi-

larly, meta keys are denoted by M-key, so M-x means Meta-X. (On key-

boards without a meta key, M-x means ESC x, i.e., press the Escape key

then the x key. This makes ESC the meta prefix. The combination M-C-x

means ESC-Control-x, or press the Escape key then hold the Control key

while pressing the x key.) Readline commands may be given numeric arguments, which normally act as a repeat count. Sometimes, however, it is the sign of the argument that is significant. Passing a negative argument to a command that

acts in the forward direction (e.g., kkiillll-lliinnee) causes that command to

act in a backward direction. Commands whose behavior with arguments deviates from this are noted below. When a command is described as killing text, the text deleted is saved for possible future retrieval (yanking). The killed text is saved in a kill ring. Consecutive kills cause the text to be accumulated into one unit, which can be yanked all at once. Commands which do not kill text separate the chunks of text on the kill ring. RReeaaddlliinnee IInniittiiaalliizzaattiioonn Readline is customized by putting commands in an initialization file (the inputrc file). The name of this file is taken from the value of the IINNPPUUTTRRCC variable. If that variable is unset, the default is ~/.inputrc. When a program which uses the readline library starts up, the initialization file is read, and the key bindings and variables are set. There are only a few basic constructs allowed in the readline initialization file. Blank lines are ignored. Lines beginning with a

## are comments. Lines beginning with a $$ indicate conditional con-

structs. Other lines denote key bindings and variable settings.

The default key-bindings may be changed with an inputrc file. Other

programs that use this library may add their own commands and bindings. For example, placing

M-Control-u: universal-argument

C-Meta-u: universal-argument

into the inputrc would make M-C-u execute the readline command univer-

sal-argument.

The following symbolic character names are recognized: RUBOUT, DEL, ESC, LFD, NEWLINE, RET, RETURN, SPC, SPACE, and TAB. In addition to command names, readline allows keys to be bound to a string that is inserted when the key is pressed (a macro). RReeaaddlliinnee KKeeyy BBiinnddiinnggss The syntax for controlling key bindings in the inputrc file is simple. All that is required is the name of the command or the text of a macro

and a key sequence to which it should be bound. The name may be speci-

fied in one of two ways: as a symbolic key name, possibly with Meta- or

Control- prefixes, or as a key sequence.

When using the form kkeeyynnaammee:function-name or macro, keyname is the name

of a key spelled out in English. For example:

Control-u: universal-argument

Meta-Rubout: backward-kill-word

Control-o: "> output"

In the above example, C-u is bound to the function uunniivveerrssaall-aarrgguummeenntt,

M-DEL is bound to the function bbaacckkwwaarrdd-kkiillll-wwoorrdd, and C-o is bound to

run the macro expressed on the right hand side (that is, to insert the text ``> output'' into the line).

In the second form, ""kkeeyysseeqq"":function-name or macro, kkeeyysseeqq differs

from kkeeyynnaammee above in that strings denoting an entire key sequence may be specified by placing the sequence within double quotes. Some GNU Emacs style key escapes can be used, as in the following example, but the symbolic character names are not recognized.

"\C-u": universal-argument

"\C-x\C-r": re-read-init-file

"\e[11~": "Function Key 1"

In this example, C-u is again bound to the function uunniivveerrssaall-aarrgguummeenntt.

C-x C-r is bound to the function rree-rreeaadd-iinniitt-ffiillee, and ESC [ 1 1 ~ is

bound to insert the text ``Function Key 1''. The full set of GNU Emacs style escape sequences is

\\CC- control prefix

\\MM- meta prefix

\\ee an escape character

\\\\ backslash

\\"" literal " \\'' literal ' In addition to the GNU Emacs style escape sequences, a second set of

backslash escapes is available:

\\aa alert (bell) \\bb backspace \\dd delete \\ff form feed \\nn newline \\rr carriage return \\tt horizontal tab \\vv vertical tab

\\nnn the eight-bit character whose value is the octal value

nnn (one to three digits)

\\xxHH the eight-bit character whose value is the hexadecimal

value HH (one or two hex digits) When entering the text of a macro, single or double quotes must be used

to indicate a macro definition. Unquoted text is assumed to be a func-

tion name. In the macro body, the backslash escapes described above

are expanded. Backslash will quote any other character in the macro

text, including " and '.

BBaasshh allows the current readline key bindings to be displayed or modi-

fied with the bbiinndd builtin command. The editing mode may be switched

during interactive use by using the -oo option to the sseett builtin com-

mand (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below). RReeaaddlliinnee VVaarriiaabblleess

Readline has variables that can be used to further customize its behav-

ior. A variable may be set in the inputrc file with a statement of the form

sseett variable-name value

Except where noted, readline variables can take the values OOnn or OOffff. The variables and their default values are:

bbeellll-ssttyyllee ((aauuddiibbllee))

Controls what happens when readline wants to ring the terminal bell. If set to nnoonnee, readline never rings the bell. If set to vviissiibbllee, readline uses a visible bell if one is available. If set to aauuddiibbllee, readline attempts to ring the terminal's bell.

ccoommmmeenntt-bbeeggiinn ((````##''''))

The string that is inserted when the readline iinnsseerrtt-ccoommmmeenntt

command is executed. This command is bound to MM-## in emacs mode

and to ## in vi command mode.

ccoommpplleettiioonn-iiggnnoorree-ccaassee ((OOffff))

If set to OOnn, readline performs filename matching and completion

in a case-insensitive fashion.

ccoommpplleettiioonn-qquueerryy-iitteemmss ((110000))

This determines when the user is queried about viewing the num-

ber of possible completions generated by the ppoossssiibbllee-ccoommppllee-

ttiioonnss 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.

ccoonnvveerrtt-mmeettaa ((OOnn))

If set to OOnn, 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).

ddiissaabbllee-ccoommpplleettiioonn ((OOffff))

If set to OOnn, readline will inhibit word completion. Completion characters will be inserted into the line as if they had been

mapped to sseellff-iinnsseerrtt.

eeddiittiinngg-mmooddee ((eemmaaccss))

Controls whether readline begins with a set of key bindings sim-

ilar to emacs or vi. eeddiittiinngg-mmooddee can be set to either eemmaaccss or

vvii.

eennaabbllee-kkeeyyppaadd ((OOffff))

When set to OOnn, readline will try to enable the application key-

pad when it is called. Some systems need this to enable the arrow keys.

eexxppaanndd-ttiillddee ((OOffff))

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

hhiissttoorryy-pprreesseerrvvee-ppooiinntt

If set to oonn, the history code attempts to place point at the

same location on each history line retrived with pprreevviioouuss-hhiiss-

ttoorryy or nneexxtt-hhiissttoorryy.

hhoorriizzoonnttaall-ssccrroollll-mmooddee ((OOffff))

When set to OOnn, 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.

iinnppuutt-mmeettaa ((OOffff))

If set to OOnn, 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

mmeettaa-ffllaagg is a synonym for this variable.

iisseeaarrcchh-tteerrmmiinnaattoorrss ((````CC-[[CC-JJ''''))

The string of characters that should terminate an incremental

search without subsequently executing the character as a com-

mand. If this variable has not been given a value, the charac-

ters ESC and C-J will terminate an incremental search.

kkeeyymmaapp ((eemmaaccss)) Set the current readline keymap. The set of valid keymap names

is emacs, emacs-standard, emacs-meta, emacs-ctlx, vi, vi-com-

mand, and vi-insert. vi is equivalent to vi-command; emacs is

equivalent to emacs-standard. The default value is emacs; the

value of eeddiittiinngg-mmooddee also affects the default keymap.

mmaarrkk-ddiirreeccttoorriieess ((OOnn))

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

mmaarrkk-mmooddiiffiieedd-lliinneess ((OOffff))

If set to OOnn, history lines that have been modified are dis-

played with a preceding asterisk (**).

mmaarrkk-ssyymmlliinnkkeedd-ddiirreeccttoorriieess ((OOffff))

If set to OOnn, completed names which are symbolic links to direc-

tories have a slash appended (subject to the value of

mmaarrkk-ddiirreeccttoorriieess).

mmaattcchh-hhiiddddeenn-ffiilleess ((OOnn))

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

oouuttppuutt-mmeettaa ((OOffff))

If set to OOnn, readline will display characters with the eighth

bit set directly rather than as a meta-prefixed escape sequence.

ppaaggee-ccoommpplleettiioonnss ((OOnn))

If set to OOnn, readline uses an internal more-like pager to dis-

play a screenful of possible completions at a time.

pprriinntt-ccoommpplleettiioonnss-hhoorriizzoonnttaallllyy ((OOffff))

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

sshhooww-aallll-iiff-aammbbiigguuoouuss ((OOffff))

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

vviissiibbllee-ssttaattss ((OOffff))

If set to OOnn, a character denoting a file's type as reported by

stat(2) is appended to the filename when listing possible com-

pletions. RReeaaddlliinnee CCoonnddiittiioonnaall CCoonnssttrruuccttss Readline implements a facility similar in spirit to the conditional compilation features of the C preprocessor which allows key bindings and variable settings to be performed as the result of tests. There are four parser directives used.

$$iiff The $$iiff construct allows bindings to be made based on the edit-

ing 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.

mmooddee The mmooddee== form of the $$iiff directive is used to test

whether readline is in emacs or vi mode. This may be used in conjunction with the sseett kkeeyymmaapp command, for

instance, to set bindings in the emacs-standard and

emacs-ctlx keymaps only if readline is starting out in

emacs mode.

tteerrmm The tteerrmm== form may be used to include terminal-specific

key bindings, perhaps to bind the key sequences output by the terminal's function keys. The word on the right side

of the == is tested against the both full name of the ter-

minal and the portion of the terminal name before the

first -. This allows sun to match both sun and sun-cmd,

for instance. aapppplliiccaattiioonn

The aapppplliiccaattiioonn construct is used to include application-

specific settings. Each program using the readline library sets the application name, and an initialization file can test for a particular value. This could be used to bind key sequences to functions useful for a specific program. For instance, the following command adds a key sequence that quotes the current or previous word in

Bash:

$$iiff Bash

# Quote the current or previous word

"\C-xq": "\eb\"\ef\""

$$eennddiiff

$$eennddiiff This command, as seen in the previous example, terminates an $$iiff

command.

$$eellssee Commands in this branch of the $$iiff directive are executed if the

test fails.

$$iinncclluuddee

This directive takes a single filename as an argument and reads

commands and bindings from that file. For example, the follow-

ing directive would read /etc/inputrc:

$$iinncclluuddee /etc/inputrc

SSeeaarrcchhiinngg Readline provides commands for searching through the command history se HISTORY eo) o lns otiig seiid tig Tee r

two search modes: incremental and non-incremental.

Incremental searches begin before the user has finished typing the

search string. As each character of the search string is typed, read-

line displays the next entry from the history matching the string typed so far. An incremental search requires only as many characters as needed to find the desired history entry. The characters present in

the value of the iisseeaarrcchh-tteerrmmiinnaattoorrss variable are used to terminate an

incremental search. If that variable has not been assigned a value the

Escape and Control-J characters will terminate an incremental search.

Control-G will abort an incremental search and restore the original

line. When the search is terminated, the history entry containing the search string becomes the current line.

To find other matching entries in the history list, type Control-S or

Control-R as appropriate. This will search backward or forward in the

history for the next entry matching the search string typed so far. Any other key sequence bound to a readline command will terminate the

search and execute that command. For instance, a newline will termi-

nate the search and accept the line, thereby executing the command from the history list.

Readline remembers the last incremental search string. If two Control-

Rs are typed without any intervening characters defining a new search string, any remembered search string is used.

Non-incremental searches read the entire search string before starting

to search for matching history lines. The search string may be typed by the user or be part of the contents of the current line. RReeaaddlliinnee CCoommmmaanndd NNaammeess The following is a list of the names of the commands and the default

key sequences to which they are bound. Command names without an accom-

panying key sequence are unbound by default. In the following descrip-

tions, point refers to the current cursor position, and mark refers to

a cursor position saved by the sseett-mmaarrkk command. The text between the

point and mark is referred to as the region. CCoommmmaannddss ffoorr MMoovviinngg

bbeeggiinnnniinngg-ooff-lliinnee ((CC-aa))

Move to the start of the current line.

eenndd-ooff-lliinnee ((CC-ee))

Move to the end of the line.

ffoorrwwaarrdd-cchhaarr ((CC-ff))

Move forward a character.

bbaacckkwwaarrdd-cchhaarr ((CC-bb))

Move back a character.

ffoorrwwaarrdd-wwoorrdd ((MM-ff))

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

bbaacckkwwaarrdd-wwoorrdd ((MM-bb))

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

cclleeaarr-ssccrreeeenn ((CC-ll))

Clear the screen leaving the current line at the top of the

screen. With an argument, refresh the current line without

clearing the screen.

rreeddrraaww-ccuurrrreenntt-lliinnee

Refresh the current line.

CCoommmmaannddss ffoorr MMaanniippuullaattiinngg tthhee HHiissttoorryy

aacccceepptt-lliinnee ((NNeewwlliinnee,, RReettuurrnn))

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 HHIISSTTCCOONNTTRROOLL variable. If the line is a modified history line, then restore the history line to its original state.

pprreevviioouuss-hhiissttoorryy ((CC-pp))

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

nneexxtt-hhiissttoorryy ((CC-nn))

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

bbeeggiinnnniinngg-ooff-hhiissttoorryy ((MM-<<))

Move to the first line in the history.

eenndd-ooff-hhiissttoorryy ((MM->>))

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

rreevveerrssee-sseeaarrcchh-hhiissttoorryy ((CC-rr))

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

ffoorrwwaarrdd-sseeaarrcchh-hhiissttoorryy ((CC-ss))

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

nnoonn-iinnccrreemmeennttaall-rreevveerrssee-sseeaarrcchh-hhiissttoorryy ((MM-pp))

Search backward through the history starting at the current line

using a non-incremental search for a string supplied by the

user.

nnoonn-iinnccrreemmeennttaall-ffoorrwwaarrdd-sseeaarrcchh-hhiissttoorryy ((MM-nn))

Search forward through the history using a non-incremental

search for a string supplied by the user.

hhiissttoorryy-sseeaarrcchh-ffoorrwwaarrdd

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.

hhiissttoorryy-sseeaarrcchh-bbaacckkwwaarrdd

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.

yyaannkk-nntthh-aarrgg ((MM-CC-yy))

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.

yyaannkk-llaasstt-aarrgg ((MM-..,, MM-))

Insert the last argument to the previous command (the last word of the previous history entry). With an argument, behave

exactly like yyaannkk-nntthh-aarrgg. Successive calls to yyaannkk-llaasstt-aarrgg

move back through the history list, inserting the last argument of each line in turn.

sshheellll-eexxppaanndd-lliinnee ((MM-CC-ee))

Expand the line as the shell does. This performs alias and his-

tory expansion as well as all of the shell word expansions. See

HISTORY EXPANSION eo fr dsrpin f itr epnin

hhiissttoorryy-eexxppaanndd-lliinnee ((MM-^^))

efr hsoy xaso o te urn ln. e HISTORY EEXXPPAANNSSIIOONN below for a description of history expansion.

mmaaggiicc-ssppaaccee

Perform history expansion on the current line and insert a pc. e HISTORY EXPANSION blw o a ecito o hsoy expansion.

aalliiaass-eexxppaanndd-lliinnee

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

hhiissttoorryy-aanndd-aalliiaass-eexxppaanndd-lliinnee

Perform history and alias expansion on the current line.

iinnsseerrtt-llaasstt-aarrgguummeenntt ((MM-..,, MM-))

A synonym for yyaannkk-llaasstt-aarrgg.

ooppeerraattee-aanndd-ggeett-nneexxtt ((CC-oo))

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.

eeddiitt-aanndd-eexxeeccuuttee-ccoommmmaanndd ((CC-xxCC-ee))

Invoke an editor on the current command line, and execute the

result as shell commands. BBaasshh attempts to invoke $$FFCCEEDDIITT,

$$EEDDIITTOORR, and emacs as the editor, in that order.

CCoommmmaannddss ffoorr CChhaannggiinngg TTeexxtt

ddeelleettee-cchhaarr ((CC-dd))

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 ddeelleettee-cchhaarr, then return EEOOFF.

bbaacckkwwaarrdd-ddeelleettee-cchhaarr ((RRuubboouutt))

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

ffoorrwwaarrdd-bbaacckkwwaarrdd-ddeelleettee-cchhaarr

Delete the character under the cursor, unless the cursor is at

the end of the line, in which case the character behind the cur-

sor is deleted.

qquuootteedd-iinnsseerrtt ((CC-qq,, CC-vv))

Add the next character typed to the line verbatim. This is how

to insert characters like CC-qq, for example.

ttaabb-iinnsseerrtt ((CC-vv TTAABB))

Insert a tab character.

sseellff-iinnsseerrtt ((aa,, bb,, AA,, 11,, !!,, ......))

Insert the character typed.

ttrraannssppoossee-cchhaarrss ((CC-tt))

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.

ttrraannssppoossee-wwoorrddss ((MM-tt))

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.

uuppccaassee-wwoorrdd ((MM-uu))

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

ddoowwnnccaassee-wwoorrdd ((MM-ll))

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

ccaappiittaalliizzee-wwoorrdd ((MM-cc))

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

oovveerrwwrriittee-mmooddee

Toggle overwrite mode. With an explicit positive numeric argu-

ment, switches to overwrite mode. With an explicit non-positive

numeric argument, switches to insert mode. This command affects only eemmaaccss mode; vvii mode does overwrite differently. Each call

to readline() starts in insert mode. In overwrite mode, charac-

ters bound to sseellff-iinnsseerrtt replace the text at point rather than

pushing the text to the right. Characters bound to bbaacckk-

wwaarrdd-ddeelleettee-cchhaarr replace the character before point with a

space. By default, this command is unbound. KKiilllliinngg aanndd YYaannkkiinngg

kkiillll-lliinnee ((CC-kk))

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

bbaacckkwwaarrdd-kkiillll-lliinnee ((CC-xx RRuubboouutt))

Kill backward to the beginning of the line.

uunniixx-lliinnee-ddiissccaarrdd ((CC-uu))

Kill backward from point to the beginning of the line. The

killed text is saved on the kill-ring.

kkiillll-wwhhoollee-lliinnee

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

kkiillll-wwoorrdd ((MM-dd))

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 ffoorrwwaarrdd-wwoorrdd.

bbaacckkwwaarrdd-kkiillll-wwoorrdd ((MM-RRuubboouutt))

Kill the word behind point. Word boundaries are the same as

those used by bbaacckkwwaarrdd-wwoorrdd.

uunniixx-wwoorrdd-rruubboouutt ((CC-ww))

Kill the word behind point, using white space as a word bound-

ary. The killed text is saved on the kill-ring.

ddeelleettee-hhoorriizzoonnttaall-ssppaaccee ((MM-\\))

Delete all spaces and tabs around point.

kkiillll-rreeggiioonn

Kill the text in the current region.

ccooppyy-rreeggiioonn-aass-kkiillll

Copy the text in the region to the kill buffer.

ccooppyy-bbaacckkwwaarrdd-wwoorrdd

Copy the word before point to the kill buffer. The word bound-

aries are the same as bbaacckkwwaarrdd-wwoorrdd.

ccooppyy-ffoorrwwaarrdd-wwoorrdd

Copy the word following point to the kill buffer. The word

boundaries are the same as ffoorrwwaarrdd-wwoorrdd.

yyaannkk ((CC-yy))

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

yyaannkk-ppoopp ((MM-yy))

Rotate the kill ring, and yank the new top. Only works follow-

ing yyaannkk or yyaannkk-ppoopp.

NNuummeerriicc AArrgguummeennttss

ddiiggiitt-aarrgguummeenntt ((MM-00,, MM-11,, ......,, MM--))

Add this digit to the argument already accumulating, or start a

new argument. M- starts a negative argument.

uunniivveerrssaall-aarrgguummeenntt

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 fol-

lowed by digits, executing uunniivveerrssaall-aarrgguummeenntt 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 argu-

ment count four, a second time makes the argument count sixteen, and so on. CCoommpplleettiinngg ccoommpplleettee ((TTAABB))

Attempt to perform completion on the text before point. BBaasshh

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.

ppoossssiibbllee-ccoommpplleettiioonnss ((MM-??))

List the possible completions of the text before point.

iinnsseerrtt-ccoommpplleettiioonnss ((MM-**))

Insert all completions of the text before point that would have

been generated by ppoossssiibbllee-ccoommpplleettiioonnss.

mmeennuu-ccoommpplleettee

Similar to ccoommpplleettee, but replaces the word to be completed with a single match from the list of possible completions. Repeated

execution of mmeennuu-ccoommpplleettee 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

bbeellll-ssttyyllee) 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 TTAABB, but is unbound by default.

ddeelleettee-cchhaarr-oorr-lliisstt

Deletes the character under the cursor if not at the beginning

or end of the line (like ddeelleettee-cchhaarr). If at the end of the

line, behaves identically to ppoossssiibbllee-ccoommpplleettiioonnss. This command

is unbound by default.

ccoommpplleettee-ffiilleennaammee ((MM-//))

Attempt filename completion on the text before point.

ppoossssiibbllee-ffiilleennaammee-ccoommpplleettiioonnss ((CC-xx //))

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

ccoommpplleettee-uusseerrnnaammee ((MM-~~))

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

ppoossssiibbllee-uusseerrnnaammee-ccoommpplleettiioonnss ((CC-xx ~~))

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

ccoommpplleettee-vvaarriiaabbllee ((MM-$$))

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

shell variable.

ppoossssiibbllee-vvaarriiaabbllee-ccoommpplleettiioonnss ((CC-xx $$))

List the possible completions of the text before point, treating

it as a shell variable.

ccoommpplleettee-hhoossttnnaammee ((MM-@@))

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

ppoossssiibbllee-hhoossttnnaammee-ccoommpplleettiioonnss ((CC-xx @@))

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

ccoommpplleettee-ccoommmmaanndd ((MM-!!))

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.

ppoossssiibbllee-ccoommmmaanndd-ccoommpplleettiioonnss ((CC-xx !!))

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

ddyynnaammiicc-ccoommpplleettee-hhiissttoorryy ((MM-TTAABB))

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

ccoommpplleettee-iinnttoo-bbrraacceess ((MM-{{))

Perform filename completion and insert the list of possible com-

pletions enclosed within braces so the list is available to the

shell (see BBrraaccee EExxppaannssiioonn above).

KKeeyybbooaarrdd MMaaccrrooss

ssttaarrtt-kkbbdd-mmaaccrroo ((CC-xx (())

Begin saving the characters typed into the current keyboard macro.

eenndd-kkbbdd-mmaaccrroo ((CC-xx ))))

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

ccaallll-llaasstt-kkbbdd-mmaaccrroo ((CC-xx ee))

Re-execute the last keyboard macro defined, by making the char-

acters in the macro appear as if typed at the keyboard. MMiisscceellllaanneeoouuss

rree-rreeaadd-iinniitt-ffiillee ((CC-xx CC-rr))

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

aabboorrtt ((CC-gg))

Abort the current editing command and ring the terminal's bell

(subject to the setting of bbeellll-ssttyyllee).

ddoo-uuppppeerrccaassee-vveerrssiioonn ((MM-aa,, MM-bb,, MM-x,, ......))

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

pprreeffiixx-mmeettaa ((EESSCC))

Metafy the next character typed. EESSCC ff is equivalent to MMeettaa-ff.

uunnddoo ((CC-,, CC-xx CC-uu))

Incremental undo, separately remembered for each line.

rreevveerrtt-lliinnee ((MM-rr))

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

ttiillddee-eexxppaanndd ((MM-&&))

Perform tilde expansion on the current word.

sseett-mmaarrkk ((CC-@@,, MM-<>))

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

eexxcchhaannggee-ppooiinntt-aanndd-mmaarrkk ((CC-xx CC-xx))

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.

cchhaarraacctteerr-sseeaarrcchh ((CC-]]))

A character is read and point is moved to the next occurrence of

that character. A negative count searches for previous occur-

rences.

cchhaarraacctteerr-sseeaarrcchh-bbaacckkwwaarrdd ((MM-CC-]]))

A character is read and point is moved to the previous occur-

rence of that character. A negative count searches for subse-

quent occurrences.

iinnsseerrtt-ccoommmmeenntt ((MM-##))

Without a numeric argument, the value of the readline ccoomm-

mmeenntt-bbeeggiinn 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 ccoommmmeenntt-bbeeggiinn, the value is inserted, other-

wise the characters in ccoommmmeenntt-bbeeggiinn are deleted from the begin-

ning of the line. In either case, the line is accepted as if a

newline had been typed. The default value of ccoommmmeenntt-bbeeggiinn

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.

gglloobb-ccoommpplleettee-wwoorrdd ((MM-gg))

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.

gglloobb-eexxppaanndd-wwoorrdd ((CC-xx **))

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.

gglloobb-lliisstt-eexxppaannssiioonnss ((CC-xx gg))

The list of expansions that would have been generated by

gglloobb-eexxppaanndd-wwoorrdd is displayed, and the line is redrawn. If a

numeric argument is supplied, an asterisk is appended before pathname expansion.

dduummpp-ffuunnccttiioonnss

Print all of the functions and their key bindings to the read-

line output stream. If a numeric argument is supplied, the out-

put is formatted in such a way that it can be made part of an inputrc file.

dduummpp-vvaarriiaabblleess

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.

dduummpp-mmaaccrrooss

Print all of the readline key sequences bound to macros and the

strings they ouput. If a numeric argument is supplied, the out-

put is formatted in such a way that it can be made part of an inputrc file.

ddiissppllaayy-sshheellll-vveerrssiioonn ((CC-xx CC-vv))

Display version information about the current instance of bbaasshh.

PPrrooggrraammmmaabbllee CCoommpplleettiioonn When word completion is attempted for an argument to a command for which a completion specification (a compspec) has been defined using

the ccoommpplleettee builtin (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below), the pro-

grammable completion facilities are invoked. First, the command name is identified. If a compspec has been defined for that command, the compspec is used to generate the list of possible completions for the word. If the command word is a full pathname, a compspec for the full pathname is searched for first. If no compspec is found for the full pathname, an attempt is made to find a compspec

for the portion following the final slash.

Once a compspec has been found, it is used to generate the list of

matching words. If a compspec is not found, the default bbaasshh comple-

tion as described above under CCoommpplleettiinngg is performed. First, the actions specified by the compspec are used. Only matches which are prefixed by the word being completed are returned. When the

-ff or -dd option is used for filename or directory name completion, the

shell variable FFIIGGNNOORREE is used to filter the matches.

Any completions specified by a filename expansion pattern to the -GG

option are generated next. The words generated by the pattern need not

match the word being completed. The GGLLOOBBIIGGNNOORREE shell variable is not

used to filter the matches, but the FFIIGGNNOORREE variable is used.

Next, the string specified as the argument to the -WW option is consid-

ered. The string is first split using the characters in the IIFFSS spe-

cial variable as delimiters. Shell quoting is honored. Each word is then expanded using brace expansion, tilde expansion, parameter and variable expansion, command substitution, arithmetic expansion, and pathname expansion, as described above under EEXXPPAANNSSIIOONN. The results are split using the rules described above under WWoorrdd SSpplliittttiinngg. The

results of the expansion are prefix-matched against the word being com-

pleted, and the matching words become the possible completions.

After these matches have been generated, any shell function or command

specified with the -FF and -CC options is invoked. When the command or

function is invoked, the CCOOMMPPLLIINNEE and CCOOMMPPPPOOIINNTT variables are

assigned values as described above under SShheellll VVaarriiaabblleess. If a shell

function is being invoked, the CCOOMMPPWWOORRDDSS and CCOOMMPPCCWWOORRDD variables are also set. When the function or command is invoked, the first argument is the name of the command whose arguments are being completed, the second argument is the word being completed, and the third argument is the word preceding the word being completed on the current command line. No filtering of the generated completions against the word being completed is performed; the function or command has complete freedom in generating the matches.

Any function specified with -FF is invoked first. The function may use

any of the shell facilities, including the ccoommppggeenn builtin described

below, to generate the matches. It must put the possible completions in the CCOOMMPPRREEPPLLYY array variable.

Next, any command specified with the -CC option is invoked in an envi-

ronment equivalent to command substitution. It should print a list of

completions, one per line, to the standard output. Backslash may be

used to escape a newline, if necessary.

After all of the possible completions are generated, any filter speci-

fied with the -XX option is applied to the list. The filter is a pat-

tern as used for pathname expansion; a && in the pattern is replaced with the text of the word being completed. A literal && may be escaped

with a backslash; the backslash is removed before attempting a match.

Any completion that matches the pattern will be removed from the list.

A leading !! negates the pattern; in this case any completion not match-

ing the pattern will be removed.

Finally, any prefix and suffix specified with the -PP and -SS options are

added to each member of the completion list, and the result is returned to the readline completion code as the list of possible completions.

If the previously-applied actions do not generate any matches, and the

-oo ddiirrnnaammeess option was supplied to ccoommpplleettee when the compspec was

defined, directory name completion is attempted. By default, if a compspec is found, whatever it generates is returned to the completion code as the full set of possible completions. The

default bbaasshh completions are not attempted, and the readline default of

filename completion is disabled. If the -oo ddeeffaauulltt option was supplied

to ccoommpplleettee when the compspec was defined, readline's default comple-

tion will be performed if the compspec generates no matches. When a compspec indicates that directory name completion is desired,

the programmable completion functions force readline to append a slash

to completed names which are symbolic links to directories, subject to

the value of the mmaarrkk-ddiirreeccttoorriieess readline variable, regardless of the

setting of the mmaarrkk-ssyymmlliinnkkeedd-ddiirreeccttoorriieess readline variable.

HISTORY

When the -oo hhiissttoorryy option to the sseett builtin is enabled, the shell

provides access to the command history, the list of commands previously typed. The value of the HHIISSTTSSIIZZEE variable is used as the number of

commands to save in a history list. The text of the last HHIISSTTSSIIZZEE com-

mands (default 500) is saved. The shell stores each command in the

history list prior to parameter and variable expansion (see EEXXPPAANNSSIIOONN above) but after history expansion is performed, subject to the values

of the shell variables HHIISSTTIIGGNNOORREE and HHIISSTTCCOONNTTRROOLL.

On startup, the history is initialized from the file named by the vari-

able HHIISSTTFFIILLEE (default ~/.bashhistory). The file named by the value

of HHIISSTTFFIILLEE is truncated, if necessary, to contain no more than the ubr f ie seiid y h vle f HISTFILESIZE We a itr

active shell exits, the last $$HHIISSTTSSIIZZEE lines are copied from the his-

tory list to $$HHIISSTTFFIILLEE. If the hhiissttaappppeenndd shell option is enabled (see

the description of sshhoopptt under SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below), the lines

are appended to the history file, otherwise the history file is over-

written. If HHIISSTTFFIILLEE is unset, or if the history file is unwritable, the history is not saved. After saving the history, the history file s rnae t cnan o oe hn HISTFILESIZE ie. f HISTFILE SSIIZZEE is not set, no truncation is performed. The builtin command ffcc (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below) may be used

to list or edit and re-execute a portion of the history list. The hhiiss-

ttoorryy builtin may be used to display or modify the history list and

manipulate the history file. When using command-line editing, search

commands are available in each editing mode that provide access to the history list.

The shell allows control over which commands are saved on the history

list. The HHIISSTTCCOONNTTRROOLL and HHIISSTTIIGGNNOORREE variables may be set to cause the

shell to save only a subset of the commands entered. The ccmmddhhiisstt shell

option, if enabled, causes the shell to attempt to save each line of a

multi-line command in the same history entry, adding semicolons where

necessary to preserve syntactic correctness. The lliitthhiisstt shell option

causes the shell to save the command with embedded newlines instead of

semicolons. See the description of the sshhoopptt builtin below under SSHHEELLLL

BBUUIILLTTIINN CCOOMMMMAANNDDSS for information on setting and unsetting shell

options. HISTORY EXPANSION

The shell supports a history expansion feature that is similar to the

history expansion in ccsshh.. This section describes what syntax features

are available. This feature is enabled by default for interactive

shells, and can be disabled using the ++HH option to the sseett builtin com-

mand (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below). Non-interactive shells do not

perform history expansion by default. History expansions introduce words from the history list into the input stream, making it easy to repeat commands, insert the arguments to a previous command into the current input line, or fix errors in previous commands quickly. History expansion is performed immediately after a complete line is

read, before the shell breaks it into words. It takes place in two

parts. The first is to determine which line from the history list to use during substitution. The second is to select portions of that line for inclusion into the current one. The line selected from the history is the event, and the portions of that line that are acted upon are words. Various modifiers are available to manipulate the selected

words. The line is broken into words in the same fashion as when read-

ing input, so that several metacharacter-separated words surrounded by

quotes are considered one word. History expansions are introduced by the appearance of the history expansion character, which is !! by

default. Only backslash (\\) and single quotes can quote the history

expansion character.

Several shell options settable with the sshhoopptt builtin may be used to

tailor the behavior of history expansion. If the hhiissttvveerriiffyy shell

option is enabled (see the description of the sshhoopptt builtin), and rreeaadd-

lliinnee is being used, history substitutions are not immediately passed to

the shell parser. Instead, the expanded line is reloaded into the

rreeaaddlliinnee editing buffer for further modification. If rreeaaddlliinnee is being

used, and the hhiissttrreeeeddiitt shell option is enabled, a failed history sub-

stitution will be reloaded into the rreeaaddlliinnee editing buffer for correc-

tion. The -pp option to the hhiissttoorryy builtin command may be used to see

what a history expansion will do before using it. The -ss option to the

hhiissttoorryy builtin may be used to add commands to the end of the history list without actually executing them, so that they are available for subsequent recall.

The shell allows control of the various characters used by the history

expansion mechanism (see the description of hhiissttcchhaarrss above under SShheellll VVaarriiaabblleess). EEvveenntt DDeessiiggnnaattoorrss

An event designator is a reference to a command line entry in the his-

tory list. !! Start a history substitution, except when followed by a bbllaannkk, newline, = or (. !!n Refer to command line n.

!!-n Refer to the current command line minus n.

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

!!string Refer to the most recent command starting with string. !!??string[[??]]

Refer to the most recent command containing string. The trail-

ing ?? may be omitted if string is followed immediately by a new-

line. ^^string1^^string2^^ Quick substitution. Repeat the last command, replacing string1

with string2. Equivalent to ``!!:s/string1/string2/'' (see MMoodd-

iiffiieerrss below).

!!## The entire command line typed so far.

WWoorrdd DDeessiiggnnaattoorrss Word designators are used to select desired words from the event. A :: separates the event specification from the word designator. It may be

omitted if the word designator begins with a ^^, $$, **, -, or %%. Words

are numbered from the beginning of the line, with the first word being

denoted by 0 (zero). Words are inserted into the current line sepa-

rated by single spaces. 00 ((zzeerroo))

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.

xx** Abbreviates x-$.

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

If a word designator is supplied without an event specification, the previous command is used as the event. MMooddiiffiieerrss After the optional word designator, there may appear a sequence of one or more of the following modifiers, each preceded by a `:'. hh Remove a trailing file name component, leaving only the head. tt Remove all leading file name components, leaving the tail. rr Remove a trailing suffix of the form .xxx, leaving the basename. ee Remove all but the trailing suffix. pp Print the new command but do not execute it. qq Quote the substituted words, escaping further substitutions. xx Quote the substituted words as with qq, but break into words at bbllaannkkss and newlines. ss//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 sin-

gle backslash will quote the &. If old is null, it is set to

the last old substituted, or, if no previous history substitu-

tions took place, the last string in a !!??string[[??]] search. && Repeat the previous substitution. gg Cause changes to be applied over the entire event line. This is used in conjunction with `::ss' (e.g., `::ggss//old//new//') or `::&&'. If used with `::ss', any delimiter can be used in place of /, and the final delimiter is optional if it is the last character of the event line. SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS Unless otherwise noted, each builtin command documented in this section

as accepting options preceded by - accepts -- to signify the end of the

options. :: [arguments] No effect; the command does nothing beyond expanding arguments and performing any specified redirections. A zero exit code is returned. .. filename [arguments] ssoouurrccee filename [arguments]

Read and execute commands from filename in the current shell

environment and return the exit status of the last command exe-

cuted from filename. If filename does not contain a slash, file

names in PPAATTHH are used to find the directory containing file-

name. The file searched for in PPAATTHH need not be executable.

When bbaasshh is not in posix mode, the current directory is

searched if no file is found in PPAATTHH. If the ssoouurrcceeppaatthh option

to the sshhoopptt builtin command is turned off, the PPAATTHH is not

searched. If any arguments are supplied, they become the posi-

tional 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.

aalliiaass [-pp] [name[=value] ...]

AAlliiaass with no arguments or with the -pp option prints the list of

aliases in the form aalliiaass 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 sup-

plied, the name and value of the alias is printed. AAlliiaass returns true unless a name is given for which no alias has been defined. bbgg [jobspec] Resume the 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. bbgg jobspec returns 0 unless run when job control is disabled or, when run with job control

enabled, if jobspec was not found or started without job con-

trol.

bbiinndd [-mm keymap] [-llppssvvPPSSVV]

bbiinndd [-mm keymap] [-qq function] [-uu function] [-rr keyseq]

bbiinndd [-mm keymap] -ff filename

bbiinndd [-mm keymap] -xx keyseq:shell-command

bbiinndd [-mm keymap] keyseq:function-name

bbiinndd readline-command

Display current rreeaaddlliinnee key and function bindings, bind a key sequence to a rreeaaddlliinnee function or macro, or set a rreeaaddlliinnee

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:

-mm keymap

Use keymap as the keymap to be affected by the subsequent

bindings. Acceptable keymap names are emacs, emacs-stan-

dard, emacs-meta, emacs-ctlx, vi, vi-move, vi-command,

and vi-insert. vi is equivalent to vi-command; emacs is

equivalent to emacs-standard.

-ll List the names of all rreeaaddlliinnee functions.

-pp Display rreeaaddlliinnee function names and bindings in such a

way that they can be re-read.

-PP List current rreeaaddlliinnee function names and bindings.

-vv Display rreeaaddlliinnee variable names and values in such a way

that they can be re-read.

-VV List current rreeaaddlliinnee variable names and values.

-ss Display rreeaaddlliinnee key sequences bound to macros and the

strings they output in such a way that they can be re-

read.

-SS Display rreeaaddlliinnee key sequences bound to macros and the

strings they output.

-ff filename

Read key bindings from filename.

-qq function

Query about which keys invoke the named function.

-uu function

Unbind all keys bound to the named function.

-rr keyseq

Remove any current binding for keyseq.

-xx keyseq::shell-command

Cause shell-command to be executed whenever keyseq is

entered. The return value is 0 unless an unrecognized option is given or an error occurred. bbrreeaakk [n] Exit from within a ffoorr, wwhhiillee, uunnttiill, or sseelleecctt 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 0 unless the shell is not executing

a loop when bbrreeaakk is executed.

bbuuiillttiinn 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 func-

tionality of the builtin within the function. The ccdd builtin is commonly redefined this way. The return status is false if

shell-builtin is not a shell builtin command.

ccdd [-LL||-PP] [dir]

Change the current directory to dir. The variable HHOOMMEE is the default dir. The variable CCDDPPAATTHH defines the search path for the directory containing dir. Alternative directory names in CCDDPPAATTHH are separated by a colon (:). A null directory name in CCDDPPAATTHH is the same as the current directory, i.e., ``..''. If

dir begins with a slash (/), then CCDDPPAATTHH is not used. The -PP

option says to use the physical directory structure instead of

following symbolic links (see also the -PP option to the sseett

builtin command); the -LL option forces symbolic links to be fol-

lowed. An argument of - is equivalent to $$OOLLDDPPWWDD. The return

value is true if the directory was successfully changed; false otherwise.

ccoommmmaanndd [-ppVVvv] command [arg ...]

Run command with args suppressing the normal shell function

lookup. Only builtin commands or commands found in the PPAATTHH are

executed. If the -pp option is given, the search for command is

performed using a default value for PPAATTHH that is guaranteed to

find all of the standard utilities. If either the -VV or -vv

option is supplied, a description of command is printed. The -vv

option causes a single word indicating the command or file name

used to invoke command to be displayed; the -VV option produces a

more verbose description. If the -VV or -vv 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 can-

not be found, the exit status is 127. Otherwise, the exit sta-

tus of the ccoommmmaanndd builtin is the exit status of command. ccoommppggeenn [option] [word] Generate possible completion matches for word according to the options, which may be any option accepted by the ccoommpplleettee

builtin with the exception of -pp and -rr, and write the matches

to the standard output. When using the -FF or -CC 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 pro-

grammable completion code had generated them directly from a

completion specification with the same flags. If word is speci-

fied, only those completions matching word will be displayed. The return value is true unless an invalid option is supplied, or no matches were generated.

ccoommpplleettee [-aabbccddeeffggjjkkssuuvv] [-oo comp-option] [-AA action] [-GG globpat] [-WW

wordlist] [-PP prefix] [-SS suffix]

[-XX filterpat] [-FF function] [-CC command] name [name ...]

ccoommpplleettee -pprr [name ...]

Specify how arguments to each name should be completed. If the

-pp 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 -rr option removes a completion spec-

ification for each name, or, if no names are supplied, all com-

pletion specifications. The process of applying these completion specifications when

word completion is attempted is described above under PPrroo-

ggrraammmmaabbllee CCoommpplleettiioonn. Other options, if specified, have the following meanings. The

arguments to the -GG, -WW, and -XX options (and, if necessary, the

-PP and -SS options) should be quoted to protect them from expan-

sion before the ccoommpplleettee builtin is invoked.

-oo comp-option

The comp-option controls several aspects of the comp-

spec's behavior beyond the simple generation of comple-

tions. comp-option may be one of:

ddeeffaauulltt Use readline's default filename completion if the compspec generates no matches. ddiirrnnaammeess

Perform directory name completion if the comp-

spec generates no matches. ffiilleennaammeess

Tell readline that the compspec generates file-

names, so it can perform any filename-specific

processing (like adding a slash to directory

names or suppressing trailing spaces). Intended

to be used with shell functions.

nnoossppaaccee Tell readline not to append a space (the default) to words completed at the end of the line.

-AA action

The action may be one of the following to generate a list of possible completions:

aalliiaass Alias names. May also be specified as -aa.

aarrrraayyvvaarr Array variable names. bbiinnddiinngg RReeaaddlliinnee key binding names.

bbuuiillttiinn Names of shell builtin commands. May also be

specified as -bb.

ccoommmmaanndd Command names. May also be specified as -cc.

ddiirreeccttoorryy

Directory names. May also be specified as -dd.

ddiissaabblleedd

Names of disabled shell builtins.

eennaabblleedd Names of enabled shell builtins.

eexxppoorrtt Names of exported shell variables. May also be

specified as -ee.

ffiillee File names. May also be specified as -ff.

ffuunnccttiioonn

Names of shell functions.

ggrroouupp Group names. May also be specified as -gg.

hheellppttooppiicc Help topics as accepted by the hheellpp builtin. hhoossttnnaammee Hostnames, as taken from the file specified by

the HHOOSSTTFFIILLEE shell variable.

jjoobb Job names, if job control is active. May also

be specified as -jj.

kkeeyywwoorrdd Shell reserved words. May also be specified as

-kk.

rruunnnniinngg Names of running jobs, if job control is active.

sseerrvviiccee Service names. May also be specified as -ss.

sseettoopptt Valid arguments for the -oo option to the sseett

builtin.

sshhoopptt Shell option names as accepted by the sshhoopptt

builtin. ssiiggnnaall Signal names. ssttooppppeedd Names of stopped jobs, if job control is active.

uusseerr User names. May also be specified as -uu.

vvaarriiaabbllee

Names of all shell variables. May also be spec-

ified as -vv.

-GG globpat

The filename expansion pattern globpat is expanded to generate the possible completions.

-WW wordlist

The wordlist is split using the characters in the IIFFSS special variable as delimiters, and each resultant word is expanded. The possible completions are the members

of the resultant list which match the word being com-

pleted.

-CC command

command is executed in a subshell environment, and its

output is used as the possible completions.

-FF function

The shell function function is executed in the current

shell environment. When it finishes, the possible com-

pletions are retrieved from the value of the CCOOMMPPRREEPPLLYY array variable.

-XX filterpat

filterpat is a pattern as used for filename expansion.

It is applied to the list of possible completions gener-

ated by the preceding options and arguments, and each completion matching filterpat is removed from the list. A leading !! in filterpat negates the pattern; in this case, any completion not matching filterpat is removed.

-PP prefix

prefix is added at the beginning of each possible com-

pletion after all other options have been applied.

-SS suffix

suffix is appended to each possible completion after all other options have been applied. The return value is true unless an invalid option is supplied,

an option other than -pp or -rr is supplied without a name argu-

ment, an attempt is made to remove a completion specification for a name for which no specification exists, or an error occurs adding a completion specification. ccoonnttiinnuuee [n] Resume the next iteration of the enclosing ffoorr, wwhhiillee, uunnttiill, or sseelleecctt 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. The return value is 0 unless the shell is not

executing a loop when ccoonnttiinnuuee is executed.

ddeeccllaarree [-aaffFFiirrttxx] [-pp] [name[=value]]

ttyyppeesseett [-aaffFFiirrttxx] [-pp] [name[=value]]

Declare variables and/or give them attributes. If no names are

given then display the values of variables. The -pp option will

display the attributes and values of each name. When -pp is

used, additional options are ignored. The -FF option inhibits

the display of function definitions; only the function name and

attributes are printed. The -FF option implies -ff. The follow-

ing options can be used to restrict output to variables with the specified attribute or to give variables attributes:

-aa Each name is an array variable (see AArrrraayyss above).

-ff Use function names only.

-ii The variable is treated as an integer; arithmetic evalua-

tion (see AARRIITTHHMMEETTIICC EEVVAALLUUAATTIIOONN )) is performed when the variable is assigned a value.

-rr Make names readonly. These names cannot then be assigned

values by subsequent assignment statements or unset.

-tt Give each name the trace attribute. Traced functions

inherit the DDEEBBUUGG trap from the calling shell. The trace

attribute has no special meaning for variables.

-xx Mark names for export to subsequent commands via the

environment.

Using `+' instead of `-' turns off the attribute instead, with

the exception that ++aa may not be used to destroy an array vari-

able. When used in a function, makes each name local, as with the llooccaall command. The return value is 0 unless an invalid option is encountered, an attempt is made to define a function

using ``-f foo=bar'', an attempt is made to assign a value to a

readonly variable, an attempt is made to assign a value to an array variable without using the compound assignment syntax (see

AArrrraayyss above), one of the names is not a valid shell variable

name, an attempt is made to turn off readonly status for a read-

only variable, an attempt is made to turn off array status for

an array variable, or an attempt is made to display a non-exis-

tent function with -ff.

ddiirrss [[-ccllppvv]] [[++n]] [[-n]]

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 ppuusshhdd command; the ppooppdd command removes

entries from the list. ++n Displays the nth entry counting from the left of the list

shown by ddiirrss when invoked without options, starting with

zero.

-n Displays the nth entry counting from the right of the

list shown by ddiirrss when invoked without options, starting

with zero.

-cc Clears the directory stack by deleting all of the

entries.

-ll Produces a longer listing; the default listing format

uses a tilde to denote the home directory.

-pp Print the directory stack with one entry per line.

-vv Print the directory stack with one entry per line, pre-

fixing each entry with its index in the stack. The return value is 0 unless an invalid option is supplied or n indexes beyond the end of the directory stack.

ddiissoowwnn [-aarr] [-hh] [jobspec ...]

Without options, each jobspec is removed from the table of

active jobs. If the -hh option is given, each jobspec is not

removed from the table, but is marked so that SSIIGGHHUUPP is not sent

to the job if the shell receives a SSIIGGHHUUPP. If no jobspec is

present, and neither the -aa nor the -rr option is supplied, the

current job is used. If no jobspec is supplied, the -aa option

means to remove or mark all jobs; the -rr option without a job-

spec argument restricts operation to running jobs. The return value is 0 unless a jobspec does not specify a valid job.

eecchhoo [-nneeEE] [arg ...]

Output the args, separated by spaces, followed by a newline.

The return status is always 0. If -nn is specified, the trailing

newline is suppressed. If the -ee option is given, interpreta-

tion of the following backslash-escaped characters is enabled.

The -EE option disables the interpretation of these escape char-

acters, even on systems where they are interpreted by default.

The xxppggeecchhoo shell option may be used to dynamically determine

whether or not eecchhoo expands these escape characters by default.

eecchhoo does not interpret -- to mean the end of options. eecchhoo

interprets the following escape sequences: \\aa alert (bell) \\bb backspace \\cc suppress trailing newline \\ee an escape character \\ff form feed \\nn new line \\rr carriage return \\tt horizontal tab \\vv vertical tab

\\\\ backslash

\\00nnn the eight-bit character whose value is the octal value

nnn (zero to three octal digits)

\\nnn the eight-bit character whose value is the octal value

nnn (one to three octal digits)

\\xxHH the eight-bit character whose value is the hexadecimal

value HH (one or two hex digits)

eennaabbllee [-aaddnnppss] [-ff 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 -nn is used, each name is disabled; otherwise, names are

enabled. For example, to use the tteesstt binary found via the PPAATTHH

instead of the shell builtin version, run ``enable -n test''.

The -ff option means to load the new builtin command name from

shared object filename, on systems that support dynamic loading.

The -dd option will delete a builtin previously loaded with -ff.

If no name arguments are given, or if the -pp option is supplied,

a list of shell builtins is printed. With no other option argu-

ments, the list consists of all enabled shell builtins. If -nn

is supplied, only disabled builtins are printed. If -aa is sup-

plied, the list printed includes all builtins, with an indica-

tion of whether or not each is enabled. If -ss 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.

eevvaall [arg ...]

The args are read and concatenated together into a single com-

mand. This command is then read and executed by the shell, and

its exit status is returned as the value of eevvaall. If there are no args, or only null arguments, eevvaall returns 0.

eexxeecc [-ccll] [-aa 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 -ll option is supplied, the shell places a dash at the begin-

ning of the zeroth arg passed to command. This is what login(1)

does. The -cc option causes command to be executed with an empty

environment. If -aa 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 eexxeeccffaaiill is enabled, in which case it returns

failure. An interactive shell returns failure if the file can-

not 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. eexxiitt [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

EEXXIITT is executed before the shell terminates.

eexxppoorrtt [-ffnn] [name[=word]] ...

eexxppoorrtt -pp

The supplied names are marked for automatic export to the envi-

ronment of subsequently executed commands. If the -ff option is

given, the names refer to functions. If no names are given, or

if the -pp option is supplied, a list of all names that are

exported in this shell is printed. The -nn option causes the

export property to be removed from the named variables. eexxppoorrtt

returns an exit status of 0 unless an invalid option is encoun-

tered, one of the names is not a valid shell variable name, or

-ff is supplied with a name that is not a function.

ffcc [-ee ename] [-nnllrr] [first] [last]

ffcc -ss [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 cur-

rent 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 spec-

ified it is set to the previous command for editing and -16 for

listing.

The -nn option suppresses the command numbers when listing. The

-rr option reverses the order of the commands. If the -ll option

is given, the commands are listed on standard output. Other-

wise, the editor given by ename is invoked on a file containing those commands. If ename is not given, the value of the FFCCEEDDIITT variable is used, and the value of EEDDIITTOORR if FFCCEEDDIITT is not set.

If neither variable is set, vi is used. When editing is com-

plete, 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 com-

mand. 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 -ee 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-exe-

cuted, unless cmd does not specify a valid history line, in which case ffcc returns failure. ffgg [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 spec-

ify a valid job or jobspec specifies a job that was started without job control. ggeettooppttss optstring name [args]

ggeettooppttss is used by shell procedures to parse positional parame-

ters. optstring contains the option characters to be recog-

nized; 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, ggeettooppttss

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 OOPPTTIINNDD. OOPPTTIINNDD is initialized to

1 each time the shell or a shell script is invoked. When an

option requires an argument, ggeettooppttss places that argument into

the variable OOPPTTAARRGG. The shell does not reset OOPPTTIINNDD automati-

cally; it must be manually reset between multiple calls to

ggeettooppttss within the same shell invocation if a new set of parame-

ters is to be used. When the end of options is encountered, ggeettooppttss exits with a return value greater than zero. OOPPTTIINNDD is set to the index of

the first non-option argument, and nnaammee is set to ?.

ggeettooppttss normally parses the positional parameters, but if more arguments are given in args, ggeettooppttss parses those instead. ggeettooppttss 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 OOPPTTEERRRR is set to 0, no error messages will be dis-

played, even if the first character of optstring is not a colon. If an invalid option is seen, ggeettooppttss places ? into name and, if not silent, prints an error message and unsets OOPPTTAARRGG. If ggeettooppttss is silent, the option character found is placed in OOPPTTAARRGG and no diagnostic message is printed. If a required argument is not found, and ggeettooppttss is not silent, a question mark (??) is placed in name, OOPPTTAARRGG is unset, and a diagnostic message is printed. If ggeettooppttss is silent, then a colon (::) is placed in name and OOPPTTAARRGG is set to the option character found. ggeettooppttss returns true if an option, specified or unspecified, is found. It returns false if the end of options is encountered or an error occurs.

hhaasshh [-llrr] [-pp filename] [-ddtt] [name]

For each name, the full file name of the command is determined

by searching the directories in $$PPAATTHH and remembered. If the -pp

option is supplied, no path search is performed, and filename is

used as the full file name of the command. The -rr option causes

the shell to forget all remembered locations. The -dd option

causes the shell to forget the remembered location of each name.

If the -tt option is supplied, the full pathname to which each

name corresponds is printed. If multiple name arguments are

supplied with -tt, the name is printed before the hashed full

pathname. The -ll option causes output to be displayed in a for-

mat that may be reused as input. If no arguments are given, or

if only -ll 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.

hheellpp [-ss] [pattern]

Display helpful information about builtin commands. If pattern is specified, hheellpp gives detailed help on all commands matching

pattern; otherwise help for all the builtins and shell control

structures is printed. The -ss option restricts the information

displayed to a short usage synopsis. The return status is 0

unless no command matches pattern. hhiissttoorryy [[n]]

hhiissttoorryy -cc

hhiissttoorryy -dd offset

hhiissttoorryy -aannrrww [filename]

hhiissttoorryy -pp arg [arg ...]

hhiissttoorryy -ss arg [arg ...]

With no options, display the command history list with line num-

bers. Lines listed with a ** have been modified. An argument of n lists only the last n lines. If filename is supplied, it is

used as the name of the history file; if not, the value of HHIISSTT-

FFIILLEE is used. Options, if supplied, have the following mean-

ings:

-cc Clear the history list by deleting all the entries.

-dd offset

Delete the history entry at position offset.

-aa Append the ``new'' history lines (history lines entered

since the beginning of the current bbaasshh session) to the

history file.

-nn Read the history lines not already read from the history

file into the current history list. These are lines appended to the history file since the beginning of the

current bbaasshh session.

-rr Read the contents of the history file and use them as the

current history.

-ww Write the current history to the history file, overwrit-

ing the history file's contents.

-pp Perform history substitution on the following args and

display the result on the standard output. Does not store the results in the history list. Each arg must be quoted to disable normal history expansion.

-ss Store the args in the history list as a single entry.

The last command in the history list is removed before the args are added. The return value is 0 unless an invalid option is encountered, an error occurs while reading or writing the history file, an

invalid offset is supplied as an argument to -dd, or the history

expansion supplied as an argument to -pp fails.

jjoobbss [-llnnpprrss] [ jobspec ... ]

jjoobbss -xx command [ args ... ]

The first form lists the active jobs. The options have the fol-

lowing meanings:

-ll List process IDs in addition to the normal information.

-pp List only the process ID of the job's process group

leader.

-nn Display information only about jobs that have changed

status since the user was last notified of their status.

-rr Restrict output to running jobs.

-ss Restrict output to stopped jobs.

If jobspec is given, output is restricted to information about that job. The return status is 0 unless an invalid option is encountered or an invalid jobspec is supplied.

If the -xx option is supplied, jjoobbss replaces any jobspec found in

command or args with the corresponding process group ID, and executes command passing it args, returning its exit status.

kkiillll [-ss sigspec | -nn signum | -sigspec] [pid | jobspec] ...

kkiillll -ll [sigspec | exitstatus]

Send the signal named by sigspec or signum to the processes named by pid or jobspec. sigspec is either a signal name such as SSIIGGKKIILLLL or a signal number; signum is a signal number. If sigspec is a signal name, the name may be given with or without the SSIIGG prefix. If sigspec is not present, then SSIIGGTTEERRMM is

assumed. An argument of -ll lists the signal names. If any

arguments are supplied when -ll is given, the names of the sig-

nals corresponding to the arguments are listed, and the return

status is 0. The exitstatus argument to -ll is a number speci-

fying either a signal number or the exit status of a process

terminated by a signal. kkiillll returns true if at least one sig-

nal was successfully sent, or false if an error occurs or an invalid option is encountered. lleett arg [arg ...]

Each arg is an arithmetic expression to be evaluated (see AARRIITTHH-

MMEETTIICC EEVVAALLUUAATTIIOONN). If the last arg evaluates to 0, lleett returns 1; 0 is returned otherwise. llooccaall [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 ddeeccllaarree. When llooccaall is used within a function, it causes the

variable name to have a visible scope restricted to that func-

tion and its children. With no operands, llooccaall writes a list of local variables to the standard output. It is an error to use llooccaall when not within a function. The return status is 0 unless llooccaall is used outside a function, an invalid name is supplied, or name is a readonly variable.

llooggoouutt Exit a login shell.

ppooppdd [-nn] [+n] [-n]

Removes entries from the directory stack. With no arguments, removes the top directory from the stack, and performs a ccdd to

the new top directory. Arguments, if supplied, have the follow-

ing meanings: ++n Removes the nth entry counting from the left of the list

shown by ddiirrss, starting with zero. For example: ``popd

+0'' removes the first directory, ``popd +1'' the second.

-n Removes the nth entry counting from the right of the list

shown by ddiirrss, starting with zero. For example: ``popd

-0'' removes the last directory, ``popd -1'' the next to

last.

-nn Suppresses the normal change of directory when removing

directories from the stack, so that only the stack is manipulated. If the ppooppdd command is successful, a ddiirrss is performed as well, and the return status is 0. ppooppdd returns false if an invalid

option is encountered, the directory stack is empty, a non-exis-

tent directory stack entry is specified, or the directory change fails. pprriinnttff format [arguments] Write the formatted arguments to the standard output under the control of the format. 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 for-

mat specifications, each of which causes printing of the next

successive argument. In addition to the standard printf(1) for-

mats, %%bb causes pprriinnttff to expand backslash escape sequences in

the corresponding argument, and %%qq causes pprriinnttff to output the

corresponding argument in a format that can be reused as shell

input.

The format is reused as necessary to consume all of the argu-

ments. If the format requires more arguments than are supplied, the extra format specifications behave as if a zero value or null string, as appropriate, had been supplied. The return

value is zero on success, non-zero on failure.

ppuusshhdd [-nn] [dir]

ppuusshhdd [-nn] [+n] [-n]

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: ++n Rotates the stack so that the nth directory (counting

from the left of the list shown by ddiirrss, starting with

zero) is at the top.

-n Rotates the stack so that the nth directory (counting

from the right of the list shown by ddiirrss, starting with

zero) is at the top.

-nn Suppresses the normal change of directory when adding

directories to the stack, so that only the stack is manipulated. dir Adds dir to the directory stack at the top, making it the new current working directory.

If the ppuusshhdd command is successful, a ddiirrss is performed as well.

If the first form is used, ppuusshhdd returns 0 unless the cd to dir

fails. With the second form, ppuusshhdd returns 0 unless the direc-

tory stack is empty, a non-existent directory stack element is

specified, or the directory change to the specified new current directory fails.

ppwwdd [-LLPP]

Print the absolute pathname of the current working directory.

The pathname printed contains no symbolic links if the -PP option

is supplied or the -oo pphhyyssiiccaall option to the sseett builtin command

is enabled. If the -LL 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.

rreeaadd [-eerrss] [-uu fd] [-tt timeout] [-aa aname] [-pp prompt] [-nn nchars] [-dd

delim] [name ...] One line is read from the standard input, or from the file

descriptor fd supplied as an argument to the -uu 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 interven-

ing 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 IIFFSS 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 fol-

lowing meanings:

-aa aname

The words are assigned to sequential indices of the array variable aname, starting at 0. aname is unset before any new values are assigned. Other name arguments are ignored.

-dd delim

The first character of delim is used to terminate the input line, rather than newline.

-ee If the standard input is coming from a terminal, rreeaaddlliinnee

(see RREEAADDLLIINNEE above) is used to obtain the line.

-nn nchars

rreeaadd returns after reading nchars characters rather than waiting for a complete line of input.

-pp prompt

Display prompt on standard error, without a trailing new-

line, before attempting to read any input. The prompt is displayed only if input is coming from a terminal.

-rr Backslash does not act as an escape character. The back-

slash is considered to be part of the line. In particu-

lar, a backslash-newline pair may not be used as a line

continuation.

-ss Silent mode. If input is coming from a terminal, charac-

ters are not echoed.

-tt timeout

Cause rreeaadd to time out and return failure if a complete line of input is not read within timeout seconds. This option has no effect if rreeaadd is not reading input from the terminal or a pipe.

-uu fd Read input from file descriptor fd.

If no names are supplied, the line read is assigned to the vari-

able RREEPPLLYY. The return code is zero, unless end-of-file is

encountered, rreeaadd times out, or an invalid file descriptor is

supplied as the argument to -uu.

rreeaaddoonnllyy [-aappff] [name ...]

The given names are marked readonly; the values of these names

may not be changed by subsequent assignment. If the -ff option

is supplied, the functions corresponding to the names are so

marked. The -aa option restricts the variables to arrays. If no

name arguments are given, or if the -pp option is supplied, a

list of all readonly names is printed. The -pp option causes

output to be displayed in a format that may be reused as input. The return status is 0 unless an invalid option is encountered,

one of the names is not a valid shell variable name, or -ff is

supplied with a name that is not a function. rreettuurrnn [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 .. (ssoouurrccee) 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.

sseett [--aabbeeffhhkkmmnnppttuuvvxxBBCCHHPP] [-oo option] [arg ...]

Without options, the name and value of each shell variable are

displayed in a format that can be reused as input. The output is sorted according to the current locale. When options are

specified, they set or unset shell attributes. Any arguments

remaining after the options are processed are treated as values

for the positional parameters and are assigned, in order, to $$11,

$$22, ...... $$n. Options, if specified, have the following mean-

ings:

-aa Automatically mark variables and functions which are

modified or created for export to the environment of subsequent commands.

-bb Report the status of terminated background jobs immedi-

ately, rather than before the next primary prompt. This is effective only when job control is enabled.

-ee Exit immediately if a simple command (see SSHHEELLLL GGRRAAMMMMAARR

above) exits with a non-zero status. The shell does not

exit if the command that fails is part of an until or while loop, part of an if statement, part of a &&&& or |||| list, or if the command's return value is being inverted via !!. A trap on EERRRR, if set, is executed before the

shell exits.

-ff Disable pathname expansion.

-hh Remember the location of commands as they are looked up

for execution. This is enabled by default.

-kk All arguments in the form of assignment statements are

placed in the environment for a command, not just those that precede the command name.

-mm Monitor mode. Job control is enabled. This option is

on by default for interactive shells on systems that

support it (see JJOOBB CCOONNTTRROOLL above). Background pro-

cesses run in a separate process group and a line con-

taining their exit status is printed upon their comple-

tion.

-nn Read commands but do not execute them. This may be used

to check a shell script for syntax errors. This is

ignored by interactive shells.

-oo option-name

The option-name can be one of the following:

aalllleexxppoorrtt

Same as -aa.

bbrraacceeeexxppaanndd

Same as -BB.

eemmaaccss Use an emacs-style command line editing inter-

face. This is enabled by default when the shell

is interactive, unless the shell is started with

the --nnooeeddiittiinngg option.

eerrrreexxiitt Same as -ee.

hhaasshhaallll Same as -hh.

hhiisstteexxppaanndd

Same as -HH.

hhiissttoorryy Enable command history, as described above under

HISTORY Ti oto i o b dfut n ne-

active shells.

iiggnnoorreeeeooff

The effect is as if the shell command

``IGNOREEOF=10'' had been executed (see SShheellll VVaarriiaabblleess above).

kkeeyywwoorrdd Same as -kk.

mmoonniittoorr Same as -mm.

nnoocclloobbbbeerr

Same as -CC.

nnooeexxeecc Same as -nn.

nnoogglloobb Same as -ff. nnoolloogg Currently ignored.

nnoottiiffyy Same as -bb.

nnoouunnsseett Same as -uu.

oonneeccmmdd Same as -tt.

pphhyyssiiccaall

Same as -PP.

ppoossiixx Change the behavior of bbaasshh where the default

operation differs from the POSIX 1003.2 standard to match the standard (posix mode). pprriivviilleeggeedd

Same as -pp.

vveerrbboossee Same as -vv.

vvii Use a vi-style command line editing interface.

xxttrraaccee Same as -xx.

If -oo is supplied with no option-name, the values of the

current options are printed. If ++oo is supplied with no

option-name, a series of sseett commands to recreate the

current option settings is displayed on the standard output.

-pp Turn on privileged mode. In this mode, the $$EENNVV and

$$BBAASSHHEENNVV files are not processed, shell functions are

not inherited from the environment, and the SSHHEELLLLOOPPTTSS variable, if it appears in the environment, is ignored.

If the shell is started with the effective user (group)

id not equal to the real user (group) id, and the -pp

option is not supplied, these actions are taken and the

effective user id is set to the real user id. If the -pp

option is supplied at startup, the effective user id is not reset. Turning this option off causes the effective user and group ids to be set to the real user and group ids.

-tt Exit after reading and executing one command.

-uu Treat unset variables as an error when performing param-

eter expansion. If expansion is attempted on an unset

variable, the shell prints an error message, and, if not

interactive, exits with a non-zero status.

-vv Print shell input lines as they are read.

-xx After expanding each simple command, display the

expanded value of PPSS44, followed by the command and its expanded arguments.

-BB The shell performs brace expansion (see BBrraaccee EExxppaannssiioonn

above). This is on by default.

-CC If set, bbaasshh does not overwrite an existing file with

the >>, >>&&, and <<>> redirection operators. This may be

overridden when creating output files by using the redi-

rection operator >>|| instead of >>.

-HH Enable !! style history substitution. This option is on

by default when the shell is interactive.

-PP If set, the shell does not follow symbolic links when

executing commands such as ccdd that change the current working directory. It uses the physical directory

structure instead. By default, bbaasshh follows the logical

chain of directories when performing commands which change the current directory.

-- If no arguments follow this option, then the positional

parameters are unset. Otherwise, the positional parame-

ters are set to the args, even if some of them begin

with a -.

- Signal the end of options, cause all remaining args to

be assigned to the positional parameters. The -xx and -vv

options are turned off. If there are no args, the posi-

tional parameters remain unchanged. The options are off by default unless otherwise noted. Using +

rather than - causes these options to be turned off. The

options can also be specified as arguments to an invocation of

the shell. The current set of options may be found in $$-. The

return status is always true unless an invalid option is encoun-

tered.

sshhiifftt [n]

The positional parameters from n+1 ... are renamed to $$11 ........

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.

sshhoopptt [-ppqqssuu] [-oo] [optname ...]

Toggle the values of variables controlling optional shell behav-

ior. With no options, or with the -pp option, a list of all set-

table options is displayed, with an indication of whether or not

each is set. The -pp option causes output to be displayed in a

form that may be reused as input. Other options have the fol-

lowing meanings:

-ss Enable (set) each optname.

-uu Disable (unset) each optname.

-qq Suppresses normal output (quiet mode); the return status

indicates whether the optname is set or unset. If multi-

ple optname arguments are given with -qq, the return sta-

tus is zero if all optnames are enabled; non-zero other-

wise.

-oo Restricts the values of optname to be those defined for

the -oo option to the sseett builtin.

If either -ss or -uu is used with no optname arguments, the dis-

play is limited to those options which are set or unset, respec-

tively. Unless otherwise noted, the sshhoopptt options are disabled

(unset) by default. The return status when listing options is zero if all optnames

are enabled, non-zero otherwise. When setting or unsetting

options, the return status is zero unless an optname is not a

valid shell option.

The list of sshhoopptt options is:

ccddaabblleevvaarrss If set, an argument to the ccdd builtin command that is not a directory is assumed to be the name of a variable whose value is the directory to change to.

ccddssppeellll If set, minor errors in the spelling of a directory com-

ponent in a ccdd command will be corrected. The errors

checked for are transposed characters, a missing charac-

ter, and one character too many. If a correction is

found, the corrected file name is printed, and the com-

mand proceeds. This option is only used by interactive

shells.

cchheecckkhhaasshh

If set, bbaasshh checks that a command found in the hash ta-

ble exists before trying to execute it. If a hashed

command no longer exists, a normal path search is per-

formed. cchheecckkwwiinnssiizzee

If set, bbaasshh checks the window size after each command

and, if necessary, updates the values of LLIINNEESS and CCOOLL-

UUMMNNSS.

ccmmddhhiisstt If set, bbaasshh attempts to save all lines of a multiple-

line command in the same history entry. This allows

easy re-editing of multi-line commands.

ddoottgglloobb If set, bbaasshh includes filenames beginning with a `.' in

the results of pathname expansion. eexxeeccffaaiill

If set, a non-interactive shell will not exit if it can-

not execute the file specified as an argument to the

eexxeecc builtin command. An interactive shell does not

exit if eexxeecc fails. eexxppaannddaalliiaasseess If set, aliases are expanded as described above under

AALLIIAASSEESS. This option is enabled by default for interac-

tive shells.

eexxttgglloobb If set, the extended pattern matching features described above under PPaatthhnnaammee EExxppaannssiioonn are enabled. hhiissttaappppeenndd If set, the history list is appended to the file named

by the value of the HHIISSTTFFIILLEE variable when the shell

exits, rather than overwriting the file. hhiissttrreeeeddiitt If set, and rreeaaddlliinnee is being used, a user is given the

opportunity to re-edit a failed history substitution.

hhiissttvveerriiffyy

If set, and rreeaaddlliinnee is being used, the results of his-

tory substitution are not immediately passed to the

shell parser. Instead, the resulting line is loaded

into the rreeaaddlliinnee editing buffer, allowing further modi-

fication. hhoossttccoommpplleettee

If set, and rreeaaddlliinnee is being used, bbaasshh will attempt to

perform hostname completion when a word containing a @@ is being completed (see CCoommpplleettiinngg under RREEAADDLLIINNEE above). This is enabled by default. hhuuppoonneexxiitt

If set, bbaasshh will send SSIIGGHHUUPP to all jobs when an inter-

active login shell exits.

iinntteerraaccttiivveeccoommmmeennttss

If set, allow a word beginning with ## to cause that word

and all remaining characters on that line to be ignored

in an interactive shell (see CCOOMMMMEENNTTSS above). This

option is enabled by default.

lliitthhiisstt If set, and the ccmmddhhiisstt option is enabled, multi-line

commands are saved to the history with embedded newlines rather than using semicolon separators where possible.

llooggiinnsshheellll

The shell sets this option if it is started as a login

shell (see IINNVVOOCCAATTIIOONN above). The value may not be

changed. mmaaiillwwaarrnn

If set, and a file that bbaasshh is checking for mail has

been accessed since the last time it was checked, the

message ``The mail in mailfile has been read'' is dis-

played. nnooeemmppttyyccmmddccoommpplleettiioonn

If set, and rreeaaddlliinnee is being used, bbaasshh will not

attempt to search the PPAATTHH for possible completions when completion is attempted on an empty line. nnooccaasseegglloobb

If set, bbaasshh matches filenames in a case-insensitive

fashion when performing pathname expansion (see PPaatthhnnaammee

EExxppaannssiioonn above). nnuullllgglloobb

If set, bbaasshh allows patterns which match no files (see

PPaatthhnnaammee EExxppaannssiioonn above) to expand to a null string, rather than themselves. pprrooggccoommpp

If set, the programmable completion facilities (see PPrroo-

ggrraammmmaabbllee CCoommpplleettiioonn above) are enabled. This option is enabled by default. pprroommppttvvaarrss If set, prompt strings undergo variable and parameter expansion after being expanded as described in PPRROOMMPPTTIINNGG above. This option is enabled by default.

rreessttrriicctteeddsshheellll

The shell sets this option if it is started in

restricted mode (see RREESSTTRRIICCTTEEDD SSHHEELLLL below). The value may not be changed. This is not reset when the startup

files are executed, allowing the startup files to dis-

cover whether or not a shell is restricted.

sshhiiffttvveerrbboossee

If set, the sshhiifftt builtin prints an error message when

the shift count exceeds the number of positional parame-

ters. ssoouurrcceeppaatthh If set, the ssoouurrccee (..) builtin uses the value of PPAATTHH to find the directory containing the file supplied as an argument. This option is enabled by default. xxppggeecchhoo

If set, the eecchhoo builtin expands backslash-escape

sequences by default.

ssuussppeenndd [-ff]

Suspend the execution of this shell until it receives a SSIIGGCCOONNTT

signal. The -ff option says not to complain if this is a login

shell; just suspend anyway. The return status is 0 unless the

shell is a login shell and -ff is not supplied, or if job control

is not enabled. tteesstt 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 CCOONNDDIITTIIOONNAALL EEXXPPRREESSSSIIOONNSS. Expressions may be combined using the following operators, listed in decreasing order of precedence. !! expr True if expr is false. (( expr )) Returns the value of expr. This may be used to override the normal precedence of operators.

expr1 -aa expr2

True if both expr1 and expr2 are true.

expr1 -oo expr2

True if either expr1 or expr2 is true. tteesstt and [[ evaluate conditional expressions using a set of rules based on the number of arguments. 0 arguments The expression is false. 1 argument The expression is true if and only if the argument is not null. 2 arguments If the first argument is !!, the expression is true if and

only if the second argument is null. If the first argu-

ment is one of the unary conditional operators listed above under CCOONNDDIITTIIOONNAALL EEXXPPRREESSSSIIOONNSS, the expression is true if the unary test is true. If the first argument is not a valid unary conditional operator, the expression is false. 3 arguments If the second argument is one of the binary conditional operators listed above under CCOONNDDIITTIIOONNAALL EEXXPPRREESSSSIIOONNSS, the result of the expression is the result of the binary test using the first and third arguments as operands. If the first argument is !!, the value is the negation of the

two-argument test using the second and third arguments.

If the first argument is exactly (( and the third argument

is exactly )), the result is the one-argument test of the

second argument. Otherwise, the expression is false.

The -aa and -oo operators are considered binary operators

in this case. 4 arguments If the first argument is !!, the result is the negation of

the three-argument expression composed of the remaining

arguments. Otherwise, the expression is parsed and eval-

uated according to precedence using the rules listed above. 5 or more arguments The expression is parsed and evaluated according to precedence using the rules listed above.

ttiimmeess Print the accumulated user and system times for the shell and

for processes run from the shell. The return status is 0.

ttrraapp [-llpp] [arg] [sigspec ...]

The command arg is to be read and executed when the shell

receives signal(s) sigspec. If arg is absent or -, all speci-

fied signals are reset to their original values (the values they

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 -pp has been

supplied, then the trap commands associated with each sigspec

are displayed. If no arguments are supplied or if only -pp is

given, ttrraapp prints the list of commands associated with each signal number. Each sigspec is either a signal name defined in , or a signal number. If a sigspec is EEXXIITT (0) the

command arg is executed on exit from the shell. If a sigspec is

DDEEBBUUGG, the command arg is executed after every simple command (see SSHHEELLLL GGRRAAMMMMAARR above). If a sigspec is EERRRR, the command arg

is executed whenever a simple command has a non-zero exit sta-

tus. The EERRRR trap is not executed if the failed command is part of an until or while loop, part of an if statement, part of a &&&& or |||| list, or if the command's return value is being inverted

via !!. The -ll option causes the shell to print a list of signal

names and their corresponding numbers. Signals ignored upon

entry to the shell cannot be trapped or reset. Trapped signals

are reset to their original values in a child process when it is created. The return status is false if any sigspec is invalid; otherwise ttrraapp returns true.

ttyyppee [-aaffttppPP] name [name ...]

With no options, indicate how each name would be interpreted if

used as a command name. If the -tt option is used, ttyyppee 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 -pp option is used, ttyyppee either returns the

name of the disk file that would be executed if name were speci-

fied as a command name, or nothing if ``type -t name'' would not

return file. The -PP option forces a PPAATTHH search for each name,

even if ``type -t name'' would not return file. If a command is

hashed, -pp and -PP print the hashed value, not necessarily the

file that appears first in PPAATTHH. If the -aa option is used, ttyyppee

prints all of the places that contain an executable named name.

This includes aliases and functions, if and only if the -pp

option is not also used. The table of hashed commands is not

consulted when using -aa. The -ff option suppresses shell func-

tion lookup, as with the ccoommmmaanndd builtin. ttyyppee returns true if any of the arguments are found, false if none are found.

uulliimmiitt [-SSHHaaccddffllmmnnppssttuuvv [limit]]

Provides control over the resources available to the shell and

to processes started by it, on systems that allow such control.

The -HH and -SS options specify that the hard or soft limit is set

for the given resource. A hard limit cannot be increased once it is set; a soft limit may be increased up to the value of the

hard limit. If neither -HH nor -SS 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 hhaarrdd, ssoofftt, or uunnlliimmiitteedd, 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 -HH 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 fol-

lows:

-aa All current limits are reported

-cc The maximum size of core files created

-dd The maximum size of a process's data segment

-ff The maximum size of files created by the shell

-ll The maximum size that may be locked into memory

-mm The maximum resident set size

-nn The maximum number of open file descriptors (most systems

do not allow this value to be set)

-pp The pipe size in 512-byte blocks (this may not be set)

-ss The maximum stack size

-tt The maximum amount of cpu time in seconds

-uu The maximum number of processes available to a single

user

-vv The maximum amount of virtual memory available to the

shell

If limit is given, it is the new value of the specified resource

(the -aa option is display only). If no option is given, then -ff

is assumed. Values are in 1024-byte increments, except for -tt,

which is in seconds, -pp, which is in units of 512-byte blocks,

and -nn and -uu, which are unscaled values. The return status is

0 unless an invalid option or argument is supplied, or an error occurs while setting a new limit.

uummaasskk [-pp] [-SS] [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 -SS option causes the mask to be printed in sym-

bolic form; the default output is an octal number. If the -pp

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.

uunnaalliiaass [-aa] [name ...]

Remove each name from the list of defined aliases. If -aa is

supplied, all alias definitions are removed. The return value is true unless a supplied name is not a defined alias.

uunnsseett [-ffvv] [name ...]

For each name, remove the corresponding variable or function.

If no options are supplied, or the -vv option is given, each name

refers to a shell variable. Read-only variables may not be

unset. If -ff is specifed, 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

omns I ay f RANDOM SECONDS, LINENO HISTCMD, FUNCNAME

GGRROOUUPPSS, or DDIIRRSSTTAACCKK are unset, they lose their special proper-

ties, even if they are subsequently reset. The exit status is true unless a name does not exist or is readonly. wwaaiitt [n]

Wait for the specified process and return its termination sta-

tus. 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. Other-

wise, the return status is the exit status of the last process or job waited for. RREESSTTRRIICCTTEEDD SSHHEELLLL

If bbaasshh is started with the name rrbbaasshh, or the -rr option is supplied at

invocation, the shell becomes restricted. A restricted shell is used

to set up an environment more controlled than the standard shell. It

behaves identically to bbaasshh with the exception that the following are

disallowed or not performed: +o changing directories with ccdd +o setting or unsetting the values of SSHHEELLLL, PPAATTHH, EENNVV, or BBAASSHHEENNVV +o specifying command names containing // +o specifying a file name containing a // as an argument to the .. builtin command

+o Specifying a filename containing a slash as an argument to the

-pp option to the hhaasshh builtin command

+o importing function definitions from the shell environment at

startup

+o parsing the value of SSHHEELLLLOOPPTTSS from the shell environment at

startup

+o redirecting output using the >, >|, <>, >&, &>, and >> redirect-

ion operators

+o using the eexxeecc builtin command to replace the shell with another

command

+o adding or deleting builtin commands with the -ff and -dd options

to the eennaabbllee builtin command

+o Using the eennaabbllee builtin command to enable disabled shell

builtins

+o specifying the -pp option to the ccoommmmaanndd builtin command

+o turning off restricted mode with sseett ++rr or sseett ++oo rreessttrriicctteedd. These restrictions are enforced after any startup files are read.

When a command that is found to be a shell script is executed (see CCOOMM-

MMAANNDD EEXXEECCUUTTIIOONN above), rrbbaasshh turns off any restrictions in the shell

spawned to execute the script.

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 Utili-

ties, IEEE

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

emacs(1), vi(1) readline(3) FILES

/bin/bash

The bbaasshh executable

/etc/profile

The systemwide initialization file, executed for login shells

~/.bashprofile

The personal initialization file, executed for login shells

~/.bashrc

The individual per-interactive-shell startup file

~/.bashlogout

The individual login shell cleanup file, executed when a login

shell exits

~/.inputrc Individual readline initialization file AUTHORS Brian Fox, Free Software Foundation bfox@gnu.org Chet Ramey, Case Western Reserve University chet@ins.CWRU.Edu BBUUGG RREEPPOORRTTSS

If you find a bug in bbaasshh,, you should report it. But first, you should

make sure that it really is a bug, and that it appears in the latest

version of bbaasshh that you have.

Once you have determined that a bug actually exists, use the bashbug

command to submit a bug report. If you have a fix, you are encouraged to mail that as well! Suggestions and `philosophical' bug reports may

be mailed to bug-bash@gnu.org or posted to the Usenet newsgroup

ggnnuu..bbaasshh..bbuugg.

ALL bug reports should include:

The version number of bbaasshh

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

bashbug inserts the first three items automatically into the template

it provides for filing a bug report.

Comments and bug reports concerning this manual page should be directed

to chet@ins.CWRU.Edu.

BUGS

It's too big and too slow.

There are some subtle differences between bbaasshh and traditional versions

of sshh, mostly because of the PPOOSSIIXX specification.

Aliases are confusing in some uses. Shell builtin commands and functions are not stoppable/restartable. Compound commands and command sequences of the form `a ; b ; c' are not handled gracefully when process suspension is attempted. When a

process is stopped, the shell immediately executes the next command in

the sequence. It suffices to place the sequence of commands between

parentheses to force it into a subshell, which may be stopped as a

unit.

Commands inside of $$((...)) command substitution are not parsed until

substitution is attempted. This will delay error reporting until some time after the command is entered. Array variables may not (yet) be exported.