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Bash Reference Manual
This text is a brief description of the features that are present in
the Bash shell (version 3.0, 27 July 2004)..
This is Edition 3.0, last updated 27 July 2004,
of
The GNU Bash Reference Manual
,
for
Bash
, Version 3.0.
Bash contains features that appear in other popular shells, and some
features that only appear in Bash.  Some of the shells that Bash has
borrowed concepts from are the Bourne Shell (
`sh'
), the Korn Shell
(
`ksh'
), and the C-shell (
`csh'
and its successor,
`tcsh'
). The following menu breaks the features up into
categories based upon which one of these other shells inspired the
feature.
This manual is meant as a brief introduction to features found in
Bash.  The Bash manual page should be used as the definitive
reference on shell behavior.
bashref.html#SEC1
1. Introduction
An introduction to the shell.
bashref.html#SEC4
2. Definitions
Some definitions used in the rest of this
manual.
bashref.html#SEC5
3. Basic Shell Features
The shell "building blocks".
bashref.html#SEC56
4. Shell Builtin Commands
Commands that are a part of the shell.
bashref.html#SEC61
5. Shell Variables
Variables used or set by Bash.
bashref.html#SEC64
6. Bash Features
Features found only in Bash.
bashref.html#SEC87
7. Job Control
A chapter describing what job control is
and how Bash allows you to use it.
bashref.html#SEC115
9. Using History Interactively
Chapter dealing with history expansion
rules.
bashref.html#SEC91
8. Command Line Editing
Chapter describing the command line
editing features.
bashref.html#SEC122
10. Installing Bash
How to build and install Bash on your system.
bashref.html#SEC131
A. Reporting Bugs
How to report bugs in Bash.
bashref.html#SEC132
B. Major Differences From The Bourne Shell
A terse list of the differences
between Bash and historical
versions of /bin/sh.
bashref.html#SEC134
C. Copying This Manual
Copying this manual.
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Index of Shell Builtin Commands
Index of Bash builtin commands.
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Index of Shell Reserved Words
Index of Bash reserved words.
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Parameter and Variable Index
Quick reference helps you find the
variable you want.
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Function Index
Index of bindable Readline functions.
bashref.html#SEC141
Concept Index
General index for concepts described in
this manual.
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1. Introduction
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1.1 What is Bash?
A short description of Bash.
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1.2 What is a shell?
A brief introduction to shells.
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1.1 What is Bash?
Bash is the shell, or command language interpreter,
for the GNU operating system.
The name is an acronym for the
`Bourne-Again SHell'
,
a pun on Stephen Bourne, the author of the direct ancestor of
the current Unix shell
sh
,
which appeared in the Seventh Edition Bell Labs Research version
of Unix.
Bash is largely compatible with
sh
and incorporates useful
features from the Korn shell
ksh
and the C shell
csh
.
It is intended to be a conformant implementation of the IEEE
POSIX Shell and Tools specification (IEEE Working Group 1003.2).
It offers functional improvements over
sh
for both interactive and
programming use.
While the GNU operating system provides other shells, including
a version of
csh
, Bash is the default shell.
Like other GNU software, Bash is quite portable.  It currently runs
on nearly every version of Unix and a few other operating systems -
independently-supported ports exist for MS-DOS, OS/2,
and Windows platforms.
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1.2 What is a shell?
At its base, a shell is simply a macro processor that executes
commands.  The term macro processor means functionality where text
and symbols are expanded to create larger expressions.
A Unix shell is both a command interpreter and a programming
language.  As a command interpreter, the shell provides the user
interface to the rich set of GNU utilities.  The programming
language features allow these utilitites to be combined.
Files containing commands can be created, and become
commands themselves.  These new commands have the same status as
system commands in directories such as
`/bin'
, allowing users
or groups to establish custom environments to automate their common
tasks.
Shells may be used interactively or non-interactively.  In
interactive mode, they accept input typed from the keyboard.
When executing non-interactively, shells execute commands read
from a file.
A shell allows execution of GNU commands, both synchronously and
asynchronously.
The shell waits for synchronous commands to complete before accepting
more input; asynchronous commands continue to execute in parallel
with the shell while it reads and executes additional commands.
The
redirection
constructs permit
fine-grained control of the input and output of those commands.
Moreover, the shell allows control over the contents of commands'
environments.
Shells also provide a small set of built-in
commands (
builtins
) implementing functionality impossible
or inconvenient to obtain via separate utilities.
For example,
cd
,
break
,
continue
, and
exec
) cannot be implemented outside of the shell because
they directly manipulate the shell itself.
The
history
,
getopts
,
kill
, or
pwd
builtins, among others, could be implemented in separate utilities,
but they are more convenient to use as builtin commands.
All of the shell builtins are described in
subsequent sections.
While executing commands is essential, most of the power (and
complexity) of shells is due to their embedded programming
languages.  Like any high-level language, the shell provides
variables, flow control constructs, quoting, and functions.
Shells offer features geared specifically for
interactive use rather than to augment the programming language.
These interactive features include job control, command line
editing, command history and aliases.  Each of these features is
described in this manual.
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2. Definitions
These definitions are used throughout the remainder of this manual.
POSIX
A family of open system standards based on Unix.  Bash
is concerned with POSIX 1003.2, the Shell and Tools Standard.
blank
A space or tab character.
builtin
A command that is implemented internally by the shell itself, rather
than by an executable program somewhere in the file system.
control operator
A
word
that performs a control function.  It is a
newline
or one of the following:
`||'
,
`&&'
,
`&'
,
`;'
,
`;;'
,
`|'
,
`('
, or
`)'
.
exit status
The value returned by a command to its caller.  The value is restricted
to eight bits, so the maximum value is 255.
field
A unit of text that is the result of one of the shell expansions.  After
expansion, when executing a command, the resulting fields are used as
the command name and arguments.
filename
A string of characters used to identify a file.
job
A set of processes comprising a pipeline, and any processes descended
from it, that are all in the same process group.
job control
A mechanism by which users can selectively stop (suspend) and restart
(resume) execution of processes.
metacharacter
A character that, when unquoted, separates words.  A metacharacter is
a
blank
or one of the following characters:
`|'
,
`&'
,
`;'
,
`('
,
`)'
,
`<'
, or
`>'
.
name
A
word
consisting solely of letters, numbers, and underscores,
and beginning with a letter or underscore.
Name
s are used as
shell variable and function names.
Also referred to as an
identifier
.
operator
A
control operator
or a
redirection operator
.
See section
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3.6 Redirections
, for a list of redirection operators.
process group
A collection of related processes each having the same process
group ID.
process group ID
A unique identifer that represents a
process group
during its lifetime.
reserved word
A
word
that has a special meaning to the shell.  Most reserved
words introduce shell flow control constructs, such as
for
and
while
.
return status
A synonym for
exit status
.
signal
A mechanism by which a process may be notified by the kernel
of an event occurring in the system.
special builtin
A shell builtin command that has been classified as special by the
POSIX 1003.2 standard.
token
A sequence of characters considered a single unit by the shell.  It is
either a
word
or an
operator
.
word
A
token
that is not an
operator
.
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3. Basic Shell Features
Bash is an acronym for
`Bourne-Again SHell'
.
The Bourne shell is
the traditional Unix shell originally written by Stephen Bourne.
All of the Bourne shell builtin commands are available in Bash,
The rules for evaluation and quoting are taken from the POSIX
specification for the `standard' Unix shell.
This chapter briefly summarizes the shell's `building blocks':
commands, control structures, shell functions, shell
parameters
,
shell expansions,
redirections
, which are a way to direct input and output from
and to named files, and how the shell executes commands.
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3.1 Shell Syntax
What your input means to the shell.
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3.2 Shell Commands
The types of commands you can use.
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3.3 Shell Functions
Grouping commands by name.
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3.4 Shell Parameters
How the shell stores values.
bashref.html#SEC27
3.5 Shell Expansions
How Bash expands parameters and the various
expansions available.
bashref.html#SEC38
3.6 Redirections
A way to control where input and output go.
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3.7 Executing Commands
What happens when you run a command.
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3.8 Shell Scripts
Executing files of shell commands.
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3.1 Shell Syntax
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3.1.1 Shell Operation
The basic operation of the shell.
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3.1.2 Quoting
How to remove the special meaning from characters.
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3.1.3 Comments
How to specify comments.
When the shell reads input, it proceeds through a
sequence of operations.  If the input indicates the beginning of a
comment, the shell ignores the comment symbol (
`#'
), and the rest
of that line.
Otherwise, roughly speaking,  the shell reads its input and
divides the input into words and operators, employing the quoting rules
to select which meanings to assign various words and characters.
The shell then parses these tokens into commands and other constructs,
removes the special meaning of certain words or characters, expands
others, redirects input and output as needed, executes the specified
command, waits for the command's exit status, and makes that exit status
available for further inspection or processing.
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3.1.1 Shell Operation
The following is a brief description of the shell's operation when it
reads and executes a command.  Basically, the shell does the
following:
Reads its input from a file (see section
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3.8 Shell Scripts
), from a string
supplied as an argument to the
`-c'
invocation option
(see section
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6.1 Invoking Bash
), or from the user's terminal.
Breaks the input into words and operators, obeying the quoting rules
described in
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3.1.2 Quoting
.  These tokens are separated by
metacharacters
.  Alias expansion is performed by this step
(see section
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6.6 Aliases
).
Parses the tokens into simple and compound commands
(see section
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3.2 Shell Commands
).
Performs the various shell expansions (see section
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3.5 Shell Expansions
), breaking
the expanded tokens into lists of filenames (see section
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3.5.8 Filename Expansion
)
and commands and arguments.
Performs any necessary redirections (see section
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3.6 Redirections
) and removes
the redirection operators and their operands from the argument list.
Executes the command (see section
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3.7 Executing Commands
).
Optionally waits for the command to complete and collects its exit
status (see section
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3.7.5 Exit Status
).
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3.1.2 Quoting
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3.1.2.1 Escape Character
How to remove the special meaning from a single
character.
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3.1.2.2 Single Quotes
How to inhibit all interpretation of a sequence
of characters.
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3.1.2.3 Double Quotes
How to suppress most of the interpretation of a
sequence of characters.
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3.1.2.4 ANSI-C Quoting
How to expand ANSI-C sequences in quoted strings.
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3.1.2.5 Locale-Specific Translation
How to translate strings into different languages.
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 shell metacharacters (see section
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2. Definitions
)
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
history expansion
character, usually
`!'
, must be quoted
to prevent history expansion.  See section
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9.1 Bash History Facilities
, for
more details concerning history expansion.
There are three quoting mechanisms: the
escape character
, single quotes, and double quotes.
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3.1.2.1 Escape Character
A non-quoted backslash
`\'
is the Bash escape character.
It preserves the literal value of the next character that follows,
with the exception of
newline
.  If a
\newline
pair
appears, and the backslash itself is not quoted, the
\newline
is treated as a line continuation (that is, it is removed from
the input stream and effectively ignored).
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3.1.2.2 Single Quotes
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.
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3.1.2.3 Double Quotes
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 (see section
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3.5 Shell Expansions
).
The backslash retains its special meaning only when followed by one of
the following characters:
`$'
,
``'
,
`"'
,
`\'
, or
newline
.
Within double quotes, backslashes that are followed by one of these
characters are removed.  Backslashes preceding characters without a
special meaning are left unmodified.
A double quote may be quoted within double quotes by preceding it with
a backslash.
When command history is being used, the double quote may not be used to
quote the history expansion character.
The special parameters
`*'
and
`@'
have special meaning
when in double quotes (see section
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3.5.3 Shell Parameter Expansion
).
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3.1.2.4 ANSI-C Quoting
Words of the form
$'
string
'
are treated specially.  The
word expands to
string
, with backslash-escaped characters replaced
as specified by the ANSI C standard.  Backslash escape sequences, if
present, are decoded as follows:
\a
alert (bell)
\b
backspace
\e
an escape character (not ANSI C)
\f
form feed
\n
newline
\r
carriage return
\t
horizontal tab
\v
vertical tab
\\
backslash
\'
single quote
\
nnn
the eight-bit character whose value is the octal value
nnn
(one to three digits)
\x
HH
the eight-bit character whose value is the hexadecimal value
HH
(one or two hex digits)
\c
x
a control-
x
character
The expanded result is single-quoted, as if the dollar sign had not
been present.
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3.1.2.5 Locale-Specific Translation
A double-quoted string preceded by a dollar sign (
`$'
) will cause
the string to be translated according to the current locale.
If the current locale is
C
or
POSIX
, the dollar sign
is ignored.
If the string is translated and replaced, the replacement is
double-quoted.
Some systems use the message catalog selected by the
LC_MESSAGES
shell variable.  Others create the name of the message catalog from the
value of the
TEXTDOMAIN
shell variable, possibly adding a
suffix of
`.mo'
.  If you use the
TEXTDOMAIN
variable, you
may need to set the
TEXTDOMAINDIR
variable to the location of
the message catalog files.  Still others use both variables in this
fashion:
TEXTDOMAINDIR
/
LC_MESSAGES
/LC_MESSAGES/
TEXTDOMAIN
.mo.
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3.1.3 Comments
In a non-interactive shell, or an interactive shell in which the
interactive_comments
option to the
shopt
builtin is enabled (see section
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4.2 Bash Builtin Commands
),
a word beginning with
`#'
causes that word and all remaining characters on that line to
be ignored.  An interactive shell without the
interactive_comments
option enabled does not allow comments.  The
interactive_comments
option is on by default in interactive shells.
See section
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6.3 Interactive Shells
, for a description of what makes
a shell interactive.
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3.2 Shell Commands
A simple shell command such as
echo a b c
consists of the command
itself followed by arguments, separated by spaces.
More complex shell commands are composed of simple commands arranged together
in a variety of ways: in a pipeline in which the output of one command
becomes the input of a second, in a loop or conditional construct, or in
some other grouping.
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3.2.1 Simple Commands
The most common type of command.
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3.2.2 Pipelines
Connecting the input and output of several
commands.
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3.2.3 Lists of Commands
How to execute commands sequentially.
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3.2.4 Compound Commands
Shell commands for control flow.
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3.2.1 Simple Commands
A simple command is the kind of command encountered most often.
It's just a sequence of words separated by
blank
s, terminated
by one of the shell's control operators (see section
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2. Definitions
).  The
first word generally specifies a command to be executed, with the
rest of the words being that command's arguments.
The return status (see section
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3.7.5 Exit Status
) of a simple command is
its exit status as provided
by the POSIX 1003.1
waitpid
function, or 128+
n
if
the command was terminated by signal
n
.
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3.2.2 Pipelines
A
pipeline
is a sequence of simple commands separated by
`|'
.
The format for a pipeline is
[
time
[
-p
]] [
!
]
command1
[
|
command2
...
]
The output of each command in the pipeline is connected via a pipe
to the input of the next command.
That is, each command reads the previous command's output.
The reserved word
time
causes timing statistics
to be printed for the pipeline once it finishes.
The statistics currently consist of elapsed (wall-clock) time and
user and system time consumed by the command's execution.
The
`-p'
option changes the output format to that specified
by POSIX.
The
TIMEFORMAT
variable may be set to a format string that
specifies how the timing information should be displayed.
See section
bashref.html#SEC63
5.2 Bash Variables
, for a description of the available formats.
The use of
time
as a reserved word permits the timing of
shell builtins, shell functions, and pipelines.  An external
time
command cannot time these easily.
If the pipeline is not executed asynchronously (see section
bashref.html#SEC18
3.2.3 Lists of Commands
), the
shell waits for all commands in the pipeline to complete.
Each command in a pipeline is executed in its own subshell
(see section
bashref.html#SEC51
3.7.3 Command Execution Environment
).  The exit
status of a pipeline is the exit status of the last command in the
pipeline, unless the
pipefail
option is enabled
(see section
bashref.html#SEC59
4.3 The Set Builtin
).
If
pipefail
is enabled, the pipeline's return status is the
value of the last (rightmost) command to exit with a non-zero status,
or zero if all commands exit successfully.
If the reserved word
`!'
precedes the pipeline, the
exit status is the logical negation of the exit status as described
above.
The shell waits for all commands in the pipeline to terminate before
returning a value.
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3.2.3 Lists of Commands
A
list
is a sequence of one or more pipelines separated by one
of the operators
`;'
,
`&'
,
`&&'
, or
`||'
,
and optionally terminated by one of
`;'
,
`&'
, or a
newline
.
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
to delimit commands, equivalent to a semicolon.
If a command is terminated by the control operator
`&'
,
the shell executes the command asynchronously in a subshell.
This is known as executing the command in the
background
.
The shell does not wait for the command to finish, and the return
status is 0 (true).
When job control is not active (see section
bashref.html#SEC87
7. Job Control
),
the standard input for asynchronous commands, in the absence of any
explicit redirections, is redirected from
/dev/null
.
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, respectively.
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.
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3.2.4 Compound Commands
bashref.html#SEC20
3.2.4.1 Looping Constructs
Shell commands for iterative action.
bashref.html#SEC21
3.2.4.2 Conditional Constructs
Shell commands for conditional execution.
bashref.html#SEC22
3.2.4.3 Grouping Commands
Ways to group commands.
Compound commands are the shell programming constructs.
Each construct begins with a reserved word or control operator and is
terminated by a corresponding reserved word or operator.
Any redirections (see section
bashref.html#SEC38
3.6 Redirections
) associated with a compound command
apply to all commands within that compound command unless explicitly overridden.
Bash provides looping constructs, conditional commands, and mechanisms
to group commands and execute them as a unit.
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3.2.4.1 Looping Constructs
Bash supports the following looping constructs.
Note that wherever a
`;'
appears in the description of a
command's syntax, it may be replaced with one or more newlines.
until
The syntax of the
until
command is:
until
test-commands
; do
consequent-commands
; done
Execute
consequent-commands
as long as
test-commands
has an exit status which is not zero.
The return status is the exit status of the last command executed
in
consequent-commands
, or zero if none was executed.
while
The syntax of the
while
command is:
while
test-commands
; do
consequent-commands
; done
Execute
consequent-commands
as long as
test-commands
has an exit status of zero.
The return status is the exit status of the last command executed
in
consequent-commands
, or zero if none was executed.
for
The syntax of the
for
command is:
for
name
[in
words
...
]; do
commands
; done
Expand
words
, and execute
commands
once for each member
in the resultant list, with
name
bound to the current member.
If
`in
words
'
is not present, the
for
command
executes the
commands
once for each positional parameter that is
set, as if
`in "$@"'
had been specified
(see section
bashref.html#SEC26
3.4.2 Special Parameters
).
The return status is the exit status of the last command that executes.
If there are no items in the expansion of
words
, no commands are
executed, and the return status is zero.
An alternate form of the
for
command is also supported:
for ((
expr1
;
expr2
;
expr3
)) ; do
commands
; done
First, the arithmetic expression
expr1
is evaluated according
to the rules described below (see section
bashref.html#SEC79
6.5 Shell Arithmetic
).
The arithmetic expression
expr2
is then evaluated repeatedly
until it evaluates to zero.
Each time
expr2
evaluates to a non-zero value,
commands
are
executed and the arithmetic expression
expr3
is evaluated.
If any expression is omitted, it behaves as if it evaluates to 1.
The return value is the exit status of the last command in
list
that is executed, or false if any of the expressions is invalid.
The
break
and
continue
builtins (see section
bashref.html#SEC57
4.1 Bourne Shell Builtins
)
may be used to control loop execution.
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3.2.4.2 Conditional Constructs
if
The syntax of the
if
command is:
if
test-commands
; then
consequent-commands
;
[elif
more-test-commands
; then
more-consequents
;]
[else
alternate-consequents
;]
fi
The
test-commands
list is executed, and if its return status is zero,
the
consequent-commands
list is executed.
If
test-commands
returns a non-zero status, each
elif
list
is executed in turn, and if its exit status is zero,
the corresponding
more-consequents
is executed and the
command completes.
If
`else
alternate-consequents
'
is present, and
the final command in the final
if
or
elif
clause
has a non-zero exit status, then
alternate-consequents
is executed.
The return status is the exit status of the last command executed, or
zero if no condition tested true.
case
The syntax of the
case
command is:
case
word
in [ [(]
pattern
[|
pattern
]
...
)
command-list
;;]
...
esac
case
will selectively execute the
command-list
corresponding to
the first
pattern
that matches
word
.
The
`|'
is used to separate multiple patterns, and the
`)'
operator terminates a pattern list.
A list of patterns and an associated command-list is known
as a
clause
.  Each clause must be terminated with
`;;'
.
The
word
undergoes tilde expansion, parameter expansion, command
substitution, arithmetic expansion, and quote removal before matching is
attempted.  Each
pattern
undergoes tilde expansion, parameter
expansion, command substitution, and arithmetic expansion.
There may be an arbitrary number of
case
clauses, each terminated
by a
`;;'
.  The first pattern that matches determines the
command-list that is executed.
Here is an example using
case
in a script that could be used to
describe one interesting feature of an animal:
echo -n "Enter the name of an animal: "
read ANIMAL
echo -n "The $ANIMAL has "
case $ANIMAL in
horse | dog | cat) echo -n "four";;
man | kangaroo ) echo -n "two";;
*) echo -n "an unknown number of";;
esac
echo " legs."
The return status is zero if no
pattern
is matched.  Otherwise, the
return status is the exit status of the
command-list
executed.
select
The
select
construct allows the easy generation of menus.
It has almost the same syntax as the
for
command:
select
name
[in
words
...
]; do
commands
; done
The list of words following
in
is expanded, generating a list
of items.  The set of expanded words is printed on the standard
error output stream, each preceded by a number.  If the
`in
words
'
is omitted, the positional parameters are printed,
as if
`in "$@"'
had been specifed.
The
PS3
prompt is then displayed and a line is read from the
standard input.
If the line consists of a number corresponding to one of the displayed
words, then the value of
name
is set to that word.
If the line is empty, the words and prompt are displayed again.
If
EOF
is read, the
select
command completes.
Any other value read causes
name
to be set to null.
The line read is saved in the variable
REPLY
.
The
commands
are executed after each selection until a
break
command is executed, at which
point the
select
command completes.
Here is an example that allows the user to pick a filename from the
current directory, and displays the name and index of the file
selected.
select fname in *;
do
echo you picked $fname \($REPLY\)
break;
done
((
...
))
((
expression
))
The arithmetic
expression
is evaluated according to the rules
described below (see section
bashref.html#SEC79
6.5 Shell Arithmetic
).
If the value of the expression is non-zero, the return status is 0;
otherwise the return status is 1.  This is exactly equivalent to
let "
expression
"
See section
bashref.html#SEC58
4.2 Bash Builtin Commands
, for a full description of the
let
builtin.
[[
...
]]
[[
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 in
bashref.html#SEC78
6.4 Bash Conditional Expressions
.
Word splitting and filename expansion are not performed on the words
between the
`[['
and
`]]'
; tilde expansion, parameter and
variable expansion, arithmetic expansion, command substitution, process
substitution, and quote removal are performed.
Conditional operators such as
`-f'
must be unquoted to be recognized
as primaries.
When 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 in
bashref.html#SEC36
3.5.8.1 Pattern Matching
.
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.
An additional binary operator,
`=~'
, is available, with the same
precedence as
`=='
and
`!='
.
When it is used, the string to the right of the operator is considered
an extended regular expression and matched accordingly (as in
regex
3)).
The return value is 0 if the string matches
the pattern, and 1 otherwise.
If the regular expression is syntactically incorrect, the conditional
expression's return value is 2.
If the shell option
nocaseglob
(see the description of
shopt
in
bashref.html#SEC58
4.2 Bash Builtin Commands
)
is enabled, the match is performed without regard to the case
of alphabetic characters.
Substrings matched by parenthesized subexpressions within the regular
expression are saved in the array variable
BASH_REMATCH
.
The element of
BASH_REMATCH
with index 0 is the portion of the string
matching the entire regular expression.
The element of
BASH_REMATCH
with index
n
is the portion of the
string matching the
n
th parenthesized subexpression.
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.
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3.2.4.3 Grouping Commands
Bash provides two ways to group a list of commands to be executed
as a unit.  When commands are grouped, redirections may be applied
to the entire command list.  For example, the output of all the
commands in the list may be redirected to a single stream.
()
(
list
)
Placing a list of commands between parentheses causes a subshell
environment to be created (see section
bashref.html#SEC51
3.7.3 Command Execution Environment
), and each
of the commands in
list
to be executed in that subshell.  Since the
list
is executed in a subshell, variable assignments do not remain in
effect after the subshell completes.
{}
{
list
; }
Placing a list of commands between curly braces causes the list to
be executed in the current shell context.  No subshell is created.
The semicolon (or newline) following
list
is required.
In addition to the creation of a subshell, there is a subtle difference
between these two constructs due to historical reasons.  The braces
are
reserved words
, so they must be separated from the
list
by
blank
s.  The parentheses are
operators
, and are
recognized as separate tokens by the shell even if they are not separated
from the
list
by whitespace.
The exit status of both of these constructs is the exit status of
list
.
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3.3 Shell Functions
Shell functions are a way to group commands for later execution
using a single name for the group.  They are executed just like
a "regular" command.
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.
Shell functions are executed in the current
shell context; no new process is created to interpret them.
Functions are declared using this syntax:
[
function
]
name
()
compound-command
[
redirections
]
This defines a shell function named
name
.  The reserved
word
function
is optional.
If the
function
reserved
word is supplied, the parentheses are optional.
The
body
of the function is the compound command
compound-command
(see section
bashref.html#SEC19
3.2.4 Compound Commands
).
That command is usually a
list
enclosed between { and }, but
may be any compound command listed above.
compound-command
is executed whenever
name
is specified as the
name of a command.
Any redirections (see section
bashref.html#SEC38
3.6 Redirections
) associated with the shell function
are performed when the function is executed.
The exit status of a function definition is zero unless a syntax error
occurs or a readonly function with the same name already exists.
When executed, the exit status of a function is the exit status of the
last command executed in the body.
Note that for historical reasons, in the most common usage the curly braces
that surround the body of the function must be separated from the body by
blank
s or newlines.
This is because the braces are reserved words and are only recognized
as such when they are separated by whitespace.
Also, when using the braces, the
list
must be terminated by a semicolon,
a
`&'
, or a newline.
When a function is executed, the arguments to the
function become the positional parameters
during its execution (see section
bashref.html#SEC25
3.4.1 Positional Parameters
).
The special parameter
`#'
that expands to the number of
positional parameters is updated to reflect the change.
Special parameter
0
is unchanged.
The first element of the
FUNCNAME
variable is set to the
name of the function while the function is executing.
All other aspects of the shell execution
environment are identical between a function and its caller
with the exception that the
DEBUG
trap
below) is not inherited unless the function has been given the
trace
attribute using the
declare
builtin or
the
-o functrace
option has been enabled with
the
set
builtin,
(in which case all functions inherit the
DEBUG
trap).
See section
bashref.html#SEC57
4.1 Bourne Shell Builtins
, for the description of the
trap
builtin.
If the builtin command
return
is executed in a function, the function completes and
execution resumes with the next command after the function
call.
Any command associated with the
RETURN
trap is executed
before execution resumes.
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.  If a numeric argument is given to
return
,
that is the function's return status; otherwise the function's
return status is the exit status of the last command executed
before the
return
.
Variables local to the function may be declared with the
local
builtin.  These variables are visible only to
the function and the commands it invokes.
Function names and definitions may be listed with the
`-f'
option to the
declare
or
typeset
builtin commands (see section
bashref.html#SEC58
4.2 Bash Builtin Commands
).
The
`-F'
option to
declare
or
typeset
will list the function names only
(and optionally the source file and line number, if the
extdebug
shell option is enabled).
Functions may be exported so that subshells
automatically have them defined with the
`-f'
option to the
export
builtin
(see section
bashref.html#SEC57
4.1 Bourne Shell Builtins
).
Note that shell functions and variables with the same name may result
in multiple identically-named entries in the environment passed to the
shell's children.
Care should be taken in cases where this may cause a problem.
Functions may be recursive.  No limit is placed on the number of
recursive  calls.
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3.4 Shell Parameters
bashref.html#SEC25
3.4.1 Positional Parameters
The shell's command-line arguments.
bashref.html#SEC26
3.4.2 Special Parameters
Parameters denoted by special characters.
A
parameter
is an entity that stores values.
It can be a
name
, a number, or one of the special characters
listed below.
A
variable
is a parameter denoted by a
name
.
A variable has a
value
and zero or more
attributes
.
Attributes are assigned using the
declare
builtin command
(see the description of the
declare
builtin in
bashref.html#SEC58
4.2 Bash Builtin Commands
).
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
unset
builtin command.
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
value
s undergo tilde expansion, parameter and variable expansion,
command substitution, arithmetic expansion, and quote
removal (detailed below).  If the variable has its
integer
attribute set, then
value
is evaluated as an arithmetic expression even if the
$((
...
))
expansion is not used (see section
bashref.html#SEC32
3.5.5 Arithmetic Expansion
).
Word splitting is not performed, with the exception
of
"$@"
as explained below.
Filename expansion is not performed.
Assignment statements may also appear as arguments to the
alias
,
declare
,
typeset
,
export
,
readonly
,
and
local
builtin commands.
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3.4.1 Positional Parameters
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
set
builtin command.
Positional parameter
N
may be referenced as
${N}
, or
as
$N
when
N
consists of a single digit.
Positional parameters may not be assigned to with assignment statements.
The
set
and
shift
builtins are used to set and
unset them (see section
bashref.html#SEC56
4. Shell Builtin Commands
).
The positional parameters are
temporarily replaced when a shell function is executed
(see section
bashref.html#SEC23
3.3 Shell Functions
).
When a positional parameter consisting of more than a single
digit is expanded, it must be enclosed in braces.
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3.4.2 Special Parameters
The shell treats several parameters specially.  These parameters may
only be referenced; assignment to them is not allowed.
*
Expands to the positional parameters, starting from one.  When the
expansion occurs within double quotes, it expands to a single word
with the value of each parameter separated by the first character
of the
IFS
special variable.  That is,
"$*"
is equivalent
to
"$1
c
$2
c
...
"
, where
c
is the first character of the value of the
IFS
variable.
If
IFS
is unset, the parameters are separated by spaces.
If
IFS
is null, the parameters are joined without intervening
separators.
@
Expands to the positional parameters, starting from one.  When the
expansion occurs within double quotes, each parameter expands to a
separate word.  That is,
"$@"
is equivalent to
"$1" "$2"
...
.
When there are no positional parameters,
"$@"
and
$@
expand to nothing (i.e., they are removed).
#
Expands to the number of positional parameters in decimal.
?
Expands to the exit status of the most recently executed foreground
pipeline.
-
(A hyphen.)  Expands to the current option flags as specified upon
invocation, by the
set
builtin command, or those set by the shell itself
(such as the
`-i'
option).
$
Expands to the process ID of the shell.  In a
()
subshell, it
expands to the process ID of the invoking shell, not the subshell.
!
Expands to the process ID of the most recently executed background
(asynchronous) command.
0
Expands to the name of the shell or shell script.  This is set at
shell initialization.  If Bash is invoked with a file of commands
(see section
bashref.html#SEC55
3.8 Shell Scripts
),
$0
is set to the name of that file.
If Bash is started with the
`-c'
option (see section
bashref.html#SEC65
6.1 Invoking Bash
),
then
$0
is set to the first argument after the string to be
executed, if one is present.  Otherwise, it is set
to the filename used to invoke Bash, as given by argument zero.
_
(An underscore.)
At shell startup, set to the absolute filename of the shell or shell
script being executed as passed in the argument list.
Subsequently, expands to the last argument to the previous command,
after expansion.
Also set to the full pathname 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.
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3.5 Shell Expansions
Expansion is performed on the command line after it has been split into
token
s.  There are seven kinds of expansion performed:
brace expansion
tilde expansion
parameter and variable expansion
command substitution
arithmetic expansion
word splitting
filename expansion
bashref.html#SEC28
3.5.1 Brace Expansion
Expansion of expressions within braces.
bashref.html#SEC29
3.5.2 Tilde Expansion
Expansion of the ~ character.
bashref.html#SEC30
3.5.3 Shell Parameter Expansion
How Bash expands variables to their values.
bashref.html#SEC31
3.5.4 Command Substitution
Using the output of a command as an argument.
bashref.html#SEC32
3.5.5 Arithmetic Expansion
How to use arithmetic in shell expansions.
bashref.html#SEC33
3.5.6 Process Substitution
A way to write and read to and from a
command.
bashref.html#SEC34
3.5.7 Word Splitting
How the results of expansion are split into separate
arguments.
bashref.html#SEC35
3.5.8 Filename Expansion
A shorthand for specifying filenames matching patterns.
bashref.html#SEC37
3.5.9 Quote Removal
How and when quote characters are removed from
words.
The order of expansions is: brace expansion, tilde expansion,
parameter, variable, and arithmetic expansion and
command substitution
(done in a left-to-right fashion), word splitting, and filename
expansion.
On systems that can support it, there is an additional expansion
available:
process substitution
.  This is performed at the
same time as parameter, variable, and arithmetic expansion and
command substitution.
Only brace expansion, word splitting, and filename 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
"$@"
(see section
bashref.html#SEC26
3.4.2 Special Parameters
) and
"${
name
[@]}"
(see section
bashref.html#SEC81
6.7 Arrays
).
After all expansions,
quote removal
(see section
bashref.html#SEC37
3.5.9 Quote Removal
)
is performed.
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3.5.1 Brace Expansion
Brace expansion is a mechanism by which arbitrary strings may be generated.
This mechanism is similar to
filename expansion
(see section
bashref.html#SEC35
3.5.8 Filename Expansion
),
but the file names generated need not exist.
Patterns to be brace expanded take the form of an optional
preamble
,
followed by either a series of comma-separated strings or a sequnce expression
between a pair of braces,
followed by an optional
postscript
.
The preamble is prefixed to each string contained within the braces, and
the postscript is then appended to each resulting string, expanding left
to right.
Brace expansions may be nested.
The results of each expanded string are not sorted; left to right order
is preserved.
For example,
bash$ echo a{d,c,b}e
ade ace abe
A sequence expression takes the form
{
x
..
y
}
,
where
x
and
y
are either integers or single characters.
When integers are supplied, the expression expands to each number between
x
and
y
, inclusive.
When characters are supplied, the expression expands to each character
lexicographically between
x
and
y
, inclusive.  Note that
both
x
and
y
must be of the same type.
Brace expansion is performed before any other expansions,
and any characters special to other expansions are preserved
in the result.  It is strictly textual.  Bash
does not apply any syntactic interpretation to the context of the
expansion or the text between the braces.
To avoid conflicts with parameter expansion, the string
`${'
is not considered eligible for brace expansion.
A correctly-formed brace expansion must contain unquoted opening
and closing braces, and at least one unquoted comma or a valid
sequence expression.
Any incorrectly formed brace expansion is left unchanged.
A { or
`,'
may be quoted with a backslash to prevent its
being considered part of a brace expression.
To avoid conflicts with parameter expansion, the string
`${'
is not considered 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?.?*,how_ex}}
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3.5.2 Tilde Expansion
If a word begins with an unquoted tilde character (
`~'
), all of the
characters up to 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
HOME
shell variable.
If
HOME
is unset, the home directory of the user executing the
shell is substituted instead.
Otherwise, the tilde-prefix is replaced with the home directory
associated with the specified login name.
If the tilde-prefix is
`~+'
, the value of
the shell variable
PWD
replaces the tilde-prefix.
If the tilde-prefix is
`~-'
, the value of the shell variable
OLDPWD
, if it is set, is substituted.
If the characters 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
dirs
builtin invoked with the characters following tilde
in the tilde-prefix as an argument (see section
bashref.html#SEC82
6.8 The Directory Stack
).
If the tilde-prefix, sans the tilde, consists of a number without a
leading
`+'
or
`-'
,
`+'
is assumed.
If the login name is invalid, or the tilde expansion fails, the word is
left unchanged.
Each variable assignment is checked for unquoted tilde-prefixes immediately
following a
`:'
or
`='
.
In these cases, tilde expansion is also performed.
Consequently, one may use file names with tildes in assignments to
PATH
,
MAILPATH
, and
CDPATH
,
and the shell assigns the expanded value.
The following table shows how Bash treats unquoted tilde-prefixes:
~
The value of
$HOME
~/foo
`$HOME/foo'
~fred/foo
The subdirectory
foo
of the home directory of the user
fred
~+/foo
`$PWD/foo'
~-/foo
`${OLDPWD-'~-'}/foo'
~
N
The string that would be displayed by
`dirs +
N
'
~+
N
The string that would be displayed by
`dirs +
N
'
~-
N
The string that would be displayed by
`dirs -
N
'
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3.5.3 Shell Parameter Expansion
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 parameter
expansion.
The basic form of parameter expansion is ${
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 that 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.
Bash uses the value of the variable 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 exceptions to this are the expansions of ${!
prefix*
}
and ${!
name
[@]}
described below.
The exclamation point must immediately follow the left brace in order to
introduce indirection.
In each of the cases below,
word
is subject to tilde expansion,
parameter expansion, command substitution, and arithmetic expansion.
When not performing substring expansion, Bash tests for a parameter
that is unset or null; omitting the colon results in a test only for a
parameter that is unset.  Put another way, if the colon is included,
the operator tests for both existence and that the value is not null;
if the colon is omitted, the operator tests only for existence.
${
parameter
:-
word
}
If
parameter
is unset or null, the expansion of
word
is substituted.  Otherwise, the value of
parameter
is substituted.
${
parameter
:=
word
}
If
parameter
is unset or null, the expansion of
word
is assigned to
parameter
.
The value of
parameter
is then substituted.
Positional parameters and special parameters may not be assigned to
in this way.
${
parameter
:?
word
}
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
}
If
parameter
is null or unset, nothing is substituted, otherwise the expansion of
word
is substituted.
${
parameter
:
offset
}
${
parameter
:
offset
:
length
}
Expands to up to
length
characters of
parameter
starting at the character specified by
offset
.
If
length
is omitted, expands to the substring of
parameter
starting at the character specified by
offset
.
length
and
offset
are arithmetic expressions
(see section
bashref.html#SEC79
6.5 Shell Arithmetic
).
This is referred to as Substring Expansion.
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
*}
${!
prefix
@}
Expands to the names of variables whose names begin with
prefix
,
separated by the first character of the
IFS
special variable.
${!
name
[@]}
${!
name
[*]}
If
name
is an array variable, expands to the list of array indices
(keys) assigned in
name
.
If
name
is not an array, expands to 0 if
name
is set and null
otherwise.
When
`@'
is used and the expansion appears within double quotes, each
key expands to a separate word.
${#
parameter
}
The length in characters of the expanded value of
parameter
is
substituted.
If
parameter
is
`*'
or
`@'
, the value substituted
is the number of positional parameters.
If
parameter
is an array name subscripted by
`*'
or
`@'
,
the value substituted is the number of elements in the array.
${
parameter
#
word
}
${
parameter
##
word
}
The
word
is expanded to produce a pattern just as in filename
expansion (see section
bashref.html#SEC35
3.5.8 Filename Expansion
).  If the pattern matches
the beginning of the expanded value of
parameter
,
then the result of the expansion is the expanded value of
parameter
with the shortest matching pattern (the
`#'
case) or the
longest matching pattern (the
`##'
case) deleted.
If
parameter
is
`@'
or
`*'
,
the pattern removal operation is applied to each positional
parameter in turn, and the expansion is the resultant list.
If
parameter
is an array variable subscripted with
`@'
or
`*'
,
the pattern removal operation is applied to each member of the
array in turn, and the expansion is the resultant list.
${
parameter
%
word
}
${
parameter
%%
word
}
The
word
is expanded to produce a pattern just as in
filename expansion.
If the pattern matches a trailing portion of the expanded value of
parameter
, then the result of the expansion is the value of
parameter
with the shortest matching pattern (the
`%'
case)
or the longest matching pattern (the
`%%'
case) deleted.
If
parameter
is
`@'
or
`*'
,
the pattern removal operation is applied to each positional
parameter in turn, and the expansion is the resultant list.
If
parameter
is an array variable subscripted with
`@'
or
`*'
,
the pattern removal operation is applied to each member of the
array in turn, and the expansion is the resultant list.
${
parameter
/
pattern
/
string
}
${
parameter
//
pattern
/
string
}
The
pattern
is expanded to produce a pattern just as in
filename expansion.
Parameter
is expanded and the longest match of
pattern
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 expansion is the resultant list.
If
parameter
is an array variable subscripted with
`@'
or
`*'
,
the substitution operation is applied to each member of the
array in turn, and the expansion is the resultant list.
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3.5.4 Command Substitution
Command substitution allows the output of a command to replace
the command itself.
Command substitution occurs when a command is enclosed as follows:
$(
command
)
or
`
command
`
Bash performs the expansion by executing
command
and
replacing the command 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
$(cat
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 substitution.
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
filename expansion are not performed on the results.
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3.5.5 Arithmetic Expansion
Arithmetic expansion allows the evaluation of an arithmetic expression
and the substitution of the result.  The format for arithmetic expansion 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, command
substitution, and quote removal.
Arithmetic expansions may be nested.
The evaluation is performed according to the rules listed below
(see section
bashref.html#SEC79
6.5 Shell Arithmetic
).
If the expression is invalid, Bash prints a message indicating
failure to the standard error and no substitution occurs.
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3.5.6 Process Substitution
Process substitution is supported on systems that support named
pipes (FIFOs) or the
`/dev/fd'
method of naming open files.
It takes the form of
<(
list
)
or
>(
list
)
The process
list
is run with its input or output connected to a
FIFO or some file in
`/dev/fd'
.  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 provide input for
list
.  If the
<(
list
)
form is used, the file passed as an
argument should be read to obtain the output of
list
.
Note that no space may appear between the
<
or
>
and the left parenthesis, otherwise the construct would be interpreted
as a redirection.
When available, process substitution is performed simultaneously with
parameter and variable expansion, command substitution, and arithmetic
expansion.
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3.5.7 Word Splitting
The shell scans the results of parameter expansion, command substitution,
and arithmetic expansion that did not occur within double quotes for
word splitting.
The shell treats each character of
$IFS
as a delimiter, and splits the results of the other
expansions into words on these characters.  If
IFS
is unset, or its value is exactly
<space><tab><newline>
,
the default, then any sequence of
IFS
characters serves to delimit words.  If
IFS
has a value other than the default, then sequences of
the whitespace characters
space
and
tab
are ignored at the beginning and end of the
word, as long as the whitespace character is in the
value of
IFS
(an
IFS
whitespace character).
Any character in
IFS
that is not
IFS
whitespace, along with any adjacent
IFS
whitespace characters, delimits a field.  A sequence of
IFS
whitespace characters is also treated as a delimiter.
If the value of
IFS
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.
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3.5.8 Filename Expansion
bashref.html#SEC36
3.5.8.1 Pattern Matching
How the shell matches patterns.
After word splitting, unless the
`-f'
option has been set
(see section
bashref.html#SEC59
4.3 The Set Builtin
), Bash 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
nullglob
is disabled, the word is left
unchanged.
If the
nullglob
option is set, and no matches are found, the word
is removed.
If the
failglob
shell option is set, and no matches are found,
an error message is printed and the command is not executed.
If the shell option
nocaseglob
is enabled, the match is performed
without regard to the case of alphabetic characters.
When a pattern is used for filename generation, the character
`.'
at the start of a filename or immediately following a slash
must be matched explicitly, unless the shell option
dotglob
is set.
When matching a file name, the slash character must always be
matched explicitly.
In other cases, the
`.'
character is not treated specially.
See the description of
shopt
in
bashref.html#SEC58
4.2 Bash Builtin Commands
,
for a description of the
nocaseglob
,
nullglob
,
failglob
, and
dotglob
options.
The
GLOBIGNORE
shell variable may be used to restrict the set of filenames matching a
pattern.  If
GLOBIGNORE
is set, each matching filename that also matches one of the patterns in
GLOBIGNORE
is removed from the list of matches.  The filenames
`.'
and
`..'
are always ignored when
GLOBIGNORE
is set and not null.
However, setting
GLOBIGNORE
to a non-null value has the effect of
enabling the
dotglob
shell option, so all other filenames beginning with a
`.'
will match.
To get the old behavior of ignoring filenames beginning with a
`.'
, make
`.*'
one of the patterns in
GLOBIGNORE
.
The
dotglob
option is disabled when
GLOBIGNORE
is unset.
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3.5.8.1 Pattern Matching
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.
A backslash escapes the following character; the
escaping backslash is discarded when matching.
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 characters
separated by a hyphen denotes a
range expression
;
any character 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.  A
`-'
may be matched by including it as the first or last character
in the set.  A
`]'
may be matched by including it as the first
character in the set.
The sorting order of characters in range expressions is determined by
the current locale and the value of the
LC_COLLATE
shell variable,
if set.
For example, in the default C locale,
`[a-dx-z]'
is equivalent to
`[abcdxyz]'
.  Many locales sort characters in dictionary order, and in
these locales
`[a-dx-z]'
is typically not equivalent to
`[abcdxyz]'
;
it might be equivalent to
`[aBbCcDdxXyYz]'
, for example.  To obtain
the traditional interpretation of ranges in bracket expressions, you can
force the use of the C locale by setting the
LC_COLLATE
or
LC_ALL
environment variable to the value
`C'
.
Within
`['
and
`]'
,
character classes
can be specified
using the syntax
[:
class
:]
, where
class
is one of the
following classes defined in the POSIX 1003.2 standard:
alnum   alpha   ascii   blank   cntrl   digit   graph   lower
print   punct   space   upper   word    xdigit
A character class matches any character belonging to that class.
The
word
character class matches letters, digits, and the character
`_'
.
Within
`['
and
`]'
, an
equivalence class
can be
specified using the syntax
[=
c
=]
, which
matches all characters with the same collation weight (as defined
by the current locale) as the character
c
.
Within
`['
and
`]'
, the syntax
[.
symbol
.]
matches the collating symbol
symbol
.
If the
extglob
shell option is enabled using the
shopt
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 following
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.
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3.5.9 Quote Removal
After the preceding expansions, all unquoted occurrences of the
characters
`\'
,
`''
, and
`"'
that did not
result from one of the above expansions are removed.
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3.6 Redirections
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
omitted, and the first character of the redirection operator is
`<'
, the redirection 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
descriptions, unless otherwise noted, is subjected to brace expansion,
tilde expansion, parameter expansion, command substitution, arithmetic
expansion, quote removal, filename expansion, and word splitting.
If it expands to more than one word, Bash reports an error.
Note that the order of redirections is significant.  For example,
the command
ls >
dirlist
2>&1
directs both standard output (file descriptor 1) and standard error
(file descriptor 2) 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
.
Bash handles several filenames specially when they are used in
redirections, as described in the following table:
/dev/fd/
fd
If
fd
is a valid integer, file descriptor
fd
is duplicated.
/dev/stdin
File descriptor 0 is duplicated.
/dev/stdout
File descriptor 1 is duplicated.
/dev/stderr
File descriptor 2 is duplicated.
/dev/tcp/
host
/
port
If
host
is a valid hostname or Internet address, and
port
is an integer port number or service name, Bash attempts to open a TCP
connection to the corresponding socket.
/dev/udp/
host
/
port
If
host
is a valid hostname or Internet address, and
port
is an integer port number or service name, Bash attempts to open a UDP
connection to the corresponding socket.
A failure to open or create a file causes the redirection to fail.
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3.6.1 Redirecting Input
Redirection of input causes the file whose name results from
the expansion 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
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3.6.2 Redirecting Output
Redirection of output causes the file whose name results from
the expansion of
word
to be opened for writing 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;
if it does exist it is truncated to zero size.
The general format for redirecting output is:
[
n
]>[|]
word
If the redirection operator is
`>'
, and the
noclobber
option to the
set
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
noclobber
option is not enabled, the redirection
is attempted even if the file named by
word
exists.
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3.6.3 Appending Redirected Output
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
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3.6.4 Redirecting Standard Output and Standard Error
Bash allows both the
standard output (file descriptor 1) and
the standard 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 equivalent to
>
word
2>&1
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3.6.5 Here Documents
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 filename 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,
command substitution, and arithmetic expansion.  In the latter
case, the character sequence
\newline
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.
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3.6.6 Here Strings
A variant of here documents, the format is:
<<<
word
The
word
is expanded and supplied to the command on its standard
input.
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3.6.7 Duplicating File Descriptors
The redirection operator
[
n
]<&
word
is used to duplicate input file descriptors.
If
word
expands to one or more digits, the file descriptor denoted by
n
is made to be a copy of that file descriptor.
If the digits in
word
do not specify a file descriptor open for
input, a redirection error occurs.
If
word
evaluates 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 redirection 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.
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3.6.8 Moving File Descriptors
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.
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3.6.9 Opening File Descriptors for Reading and Writing
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.
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3.7 Executing Commands
bashref.html#SEC49
3.7.1 Simple Command Expansion
How Bash expands simple commands before
executing them.
bashref.html#SEC50
3.7.2 Command Search and Execution
How Bash finds commands and runs them.
bashref.html#SEC51
3.7.3 Command Execution Environment
The environment in which Bash
executes commands that are not
shell builtins.
bashref.html#SEC52
3.7.4 Environment
The environment given to a command.
bashref.html#SEC53
3.7.5 Exit Status
The status returned by commands and how Bash
interprets it.
bashref.html#SEC54
3.7.6 Signals
What happens when Bash or a command it runs
receives a signal.
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3.7.1 Simple Command Expansion
When a simple command is executed, the shell performs the following
expansions, assignments, and redirections, from left to right.
The words that the parser has marked as variable assignments (those
preceding the command name) and redirections are saved for later
processing.
The words that are not variable assignments or redirections are
expanded (see section
bashref.html#SEC27
3.5 Shell Expansions
).
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.
Redirections are performed as described above (see section
bashref.html#SEC38
3.6 Redirections
).
The text after the
`='
in each variable assignment undergoes tilde
expansion, parameter expansion, command substitution, arithmetic expansion,
and quote removal before being assigned to the variable.
If no command name results, the variable assignments affect the current
shell environment.  Otherwise, the variables are added to the environment
of the executed command and do not affect the current shell environment.
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 expansions
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.
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3.7.2 Command Search and Execution
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 in
bashref.html#SEC23
3.3 Shell Functions
.
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, Bash searches each element of
$PATH
for a directory containing an executable file
by that name.  Bash uses a hash table to remember the full
pathnames of executable files to avoid multiple
PATH
searches
(see the description of
hash
in
bashref.html#SEC57
4.1 Bourne Shell Builtins
).
A full search of the directories in
$PATH
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 execution environment.
Argument 0 is set to the name given, and the remaining arguments
to the command are set to the arguments supplied, 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
and the shell executes it as described in
bashref.html#SEC55
3.8 Shell Scripts
.
If the command was not begun asynchronously, the shell waits for
the command to complete and collects its exit status.
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3.7.3 Command Execution Environment
The shell has an
execution environment
, which consists of the
following:
open files inherited by the shell at invocation, as modified by
redirections supplied to the
exec
builtin
the current working directory as set by
cd
,
pushd
, or
popd
, or inherited by the shell at invocation
the file creation mode mask as set by
umask
or inherited from
the shell's parent
current traps set by
trap
shell parameters that are set by variable assignment or with
set
or inherited from the shell's parent in the environment
shell functions defined during execution or inherited from the shell's
parent in the environment
options enabled at invocation (either by default or with command-line
arguments) or by
set
options enabled by
shopt
shell aliases defined with
alias
(see section
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6.6 Aliases
)
various process IDs, including those of background jobs
(see section
bashref.html#SEC18
3.2.3 Lists of Commands
), the value of
$$
, and the value of
$PPID
When a simple command other than a builtin or shell function
is to be executed, it
is invoked in a separate execution environment that consists of
the following.  Unless otherwise noted, the values are inherited
from the shell.
the shell's open files, plus any modifications and additions specified
by redirections to the command
the current working directory
the file creation mode mask
shell variables and functions marked for export, along with variables
exported for the command, passed in the environment (see section
bashref.html#SEC52
3.7.4 Environment
)
traps caught by the shell are reset to the values inherited from the
shell's parent, and traps ignored by the shell are ignored
A command invoked in this separate environment cannot affect the
shell's execution environment.
Command substitution, commands grouped with parentheses,
and asynchronous commands are invoked in a
subshell 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 environment.  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.
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3.7.4 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
.
Bash 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 processes.  Executed commands inherit the environment.
The
export
and
`declare -x'
commands allow parameters and functions to be added to and
deleted from the environment.  If the value of a parameter
in the environment 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 modified in the shell,
less any pairs removed by the
unset
and
`export -n'
commands, plus any additions via the
export
and
`declare -x'
commands.
The environment for any simple command
or function may be augmented temporarily by prefixing it with
parameter assignments, as described in
bashref.html#SEC24
3.4 Shell Parameters
.
These assignment statements affect only the environment seen
by that command.
If the
`-k'
option is set (see section
bashref.html#SEC59
4.3 The Set Builtin
), then all
parameter assignments are placed in the environment for a command,
not just those that precede the command name.
When Bash invokes an external command, the variable
`$_'
is set to the full path name of the command and passed to that
command in its environment.
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3.7.5 Exit Status
For the shell's purposes, a command which exits with a
zero exit status has succeeded.
A non-zero exit status indicates failure.
This seemingly counter-intuitive scheme is used so there
is one well-defined way to indicate success and a variety of
ways to indicate various failure modes.
When a command terminates on a fatal signal whose number is
N
,
Bash uses the value 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.
The exit status is used by the Bash conditional commands
(see section
bashref.html#SEC21
3.2.4.2 Conditional Constructs
) and some of the list
constructs (see section
bashref.html#SEC18
3.2.3 Lists of Commands
).
All of the Bash builtins return an exit status of zero if they succeed
and a non-zero status on failure, so they may be used by the
conditional and list constructs.
All builtins return an exit status of 2 to indicate incorrect usage.
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3.7.6 Signals
When Bash is interactive, in the absence of any traps, it ignores
SIGTERM
(so that
`kill 0'
does not kill an interactive shell),
and
SIGINT
is caught and handled (so that the
wait
builtin is interruptible).
When Bash receives a
SIGINT
, it breaks out of any executing loops.
In all cases, Bash ignores
SIGQUIT
.
If job control is in effect (see section
bashref.html#SEC87
7. Job Control
), Bash
ignores
SIGTTIN
,
SIGTTOU
, and
SIGTSTP
.
Non-builtin commands started by Bash have signal handlers set to the
values inherited by the shell from its parent.
When job control is not in effect, asynchronous commands
ignore
SIGINT
and
SIGQUIT
in addition to these inherited
handlers.
Commands run as a result of
command substitution ignore the keyboard-generated job control signals
SIGTTIN
,
SIGTTOU
, and
SIGTSTP
.
The shell exits by default upon receipt of a
SIGHUP
.
Before exiting, an interactive shell resends the
SIGHUP
to
all jobs, running or stopped.
Stopped jobs are sent
SIGCONT
to ensure that they receive
the
SIGHUP
.
To prevent the shell from sending the
SIGHUP
signal to a
particular job, it should be removed
from the jobs table with the
disown
builtin (see section
bashref.html#SEC89
7.2 Job Control Builtins
) or marked
to not receive
SIGHUP
using
disown -h
.
If the
huponexit
shell option has been set with
shopt
(see section
bashref.html#SEC58
4.2 Bash Builtin Commands
), Bash sends a
SIGHUP
to all jobs when
an interactive login shell exits.
If Bash is waiting for a command to complete and receives a signal
for which a trap has been set, the trap will not be executed until
the command completes.
When Bash is waiting for an asynchronous
command via the
wait
builtin, the reception of a signal for
which a trap has been set will cause the
wait
builtin to return
immediately with an exit status greater than 128, immediately after
which the trap is executed.
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3.8 Shell Scripts
A shell script is a text file containing shell commands.  When such
a file is used as the first non-option argument when invoking Bash,
and neither the
`-c'
nor
`-s'
option is supplied
(see section
bashref.html#SEC65
6.1 Invoking Bash
),
Bash reads and executes commands from the file, then exits.  This
mode of operation creates a non-interactive shell.  The shell first
searches for the file in the current directory, and looks in the
directories in
$PATH
if not found there.
When Bash runs
a shell script, it sets the special parameter
0
to the name
of the file, rather than the name of the shell, and the positional
parameters are set to the remaining arguments, if any are given.
If no additional arguments are supplied, the positional parameters
are unset.
A shell script may be made executable by using the
chmod
command
to turn on the execute bit.  When Bash finds such a file while
searching the
$PATH
for a command, it spawns a subshell to
execute it.  In other words, executing
filename
arguments
is equivalent to executing
bash filename
arguments
if
filename
is an executable shell script.
This subshell reinitializes itself, so that the effect is as if a
new shell had been invoked to interpret the script, with the
exception that the locations of commands remembered by the parent
(see the description of
hash
in
bashref.html#SEC57
4.1 Bourne Shell Builtins
)
are retained by the child.
Most versions of Unix make this a part of the operating system's command
execution mechanism.  If the first line of a script begins with
the two characters
`#!'
, the remainder of the line specifies
an interpreter for the program.
Thus, you can specify Bash,
awk
, Perl, or some other
interpreter and write the rest of the script file in that language.
The arguments to the interpreter
consist of a single optional argument following the interpreter
name on the first line of the script file, followed by the name of
the script file, followed by the rest of the arguments.  Bash
will perform this action on operating systems that do not handle it
themselves.  Note that some older versions of Unix limit the interpreter
name and argument to a maximum of 32 characters.
Bash scripts often begin with
#! /bin/bash
(assuming that
Bash has been installed in
`/bin'
), since this ensures that
Bash will be used to interpret the script, even if it is executed
under another shell.
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4. Shell Builtin Commands
bashref.html#SEC57
4.1 Bourne Shell Builtins
Builtin commands inherited from the Bourne
Shell.
bashref.html#SEC58
4.2 Bash Builtin Commands
Table of builtins specific to Bash.
bashref.html#SEC59
4.3 The Set Builtin
This builtin is so overloaded it
deserves its own section.
bashref.html#SEC60
4.4 Special Builtins
Builtin commands classified specially by
POSIX.2.
Builtin commands are contained within the shell itself.
When the name of a builtin command is used as the first word of
a simple command (see section
bashref.html#SEC16
3.2.1 Simple Commands
), the shell executes
the command directly, without invoking another program.
Builtin commands are necessary to implement functionality impossible
or inconvenient to obtain with separate utilities.
This section briefly the builtins which Bash inherits from
the Bourne Shell, as well as the builtin commands which are unique
to or have been extended in Bash.
Several builtin commands are described in other chapters:  builtin
commands which provide the Bash interface to the job control
facilities (see section
bashref.html#SEC89
7.2 Job Control Builtins
), the directory stack
(see section
bashref.html#SEC83
6.8.1 Directory Stack Builtins
), the command history
(see section
bashref.html#SEC117
9.2 Bash History Builtins
), and the programmable completion
facilities (see section
bashref.html#SEC114
8.7 Programmable Completion Builtins
).
Many of the builtins have been extended by POSIX or Bash.
Unless otherwise noted, each builtin command documented as accepting
options preceded by
`-'
accepts
`--'
to signify the end of the options.
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4.1 Bourne Shell Builtins
The following shell builtin commands are inherited from the Bourne Shell.
These commands are implemented as specified by the POSIX 1003.2 standard.
:    (a colon)
: [
arguments
]
Do nothing beyond expanding
arguments
and performing redirections.
The return status is zero.
.    (a period)
.
filename
[
arguments
]
Read and execute commands from the
filename
argument in the
current shell context.  If
filename
does not contain a slash,
the
PATH
variable is used to find
filename
.
When Bash is not in POSIX mode, the current directory is searched
if
filename
is not found in
$PATH
.
If any
arguments
are supplied, they become the positional
parameters when
filename
is executed.  Otherwise the positional
parameters are unchanged.
The return status is the exit status of the last command executed, or
zero if no commands are executed.  If
filename
is not found, or
cannot be read, the return status is non-zero.
This builtin is equivalent to
source
.
break
break [
n
]
Exit from a
for
,
while
,
until
, or
select
loop.
If
n
is supplied, the
n
th enclosing loop is exited.
n
must be greater than or equal to 1.
The return status is zero unless
n
is not greater than or equal to 1.
cd
cd [-L|-P] [
directory
]
Change the current working directory to
directory
.
If
directory
is not given, the value of the
HOME
shell
variable is used.
If the shell variable
CDPATH
exists, it is used as a search path.
If
directory
begins with a slash,
CDPATH
is not used.
The
`-P'
option means to not follow symbolic links; symbolic
links are followed by default or with the
`-L'
option.
If
directory
is
`-'
, it is equivalent to
$OLDPWD
.
If a non-empty directory name from
CDPATH
is used, or if
`-'
is the first argument, and the directory change is
successful, the absolute pathname of the new working directory is
written to the standard output.
The return status is zero if the directory is successfully changed,
non-zero otherwise.
continue
continue [
n
]
Resume the next iteration of an enclosing
for
,
while
,
until
, or
select
loop.
If
n
is supplied, the execution of the
n
th enclosing loop
is resumed.
n
must be greater than or equal to 1.
The return status is zero unless
n
is not greater than or equal to 1.
eval
eval [
arguments
]
The arguments are concatenated together into a single command, which is
then read and executed, and its exit status returned as the exit status
of
eval
.
If there are no arguments or only empty arguments, the return status is
zero.
exec
exec [-cl] [-a
name
] [
command
[
arguments
]]
If
command
is supplied, it replaces the shell without creating a new process.
If the
`-l'
option is supplied, the shell places a dash at the
beginning of the zeroth arg passed to
command
.
This is what the
login
program does.
The
`-c'
option causes
command
to be executed with an empty
environment.
If
`-a'
is supplied, the shell passes
name
as the zeroth
argument to
command
.
If no
command
is specified, redirections may be used to affect
the current shell environment.  If there are no redirection errors, the
return status is zero; otherwise the return status is non-zero.
exit
exit [
n
]
Exit the shell, returning a status of
n
to the shell's parent.
If
n
is omitted, the exit status is that of the last command executed.
Any trap on
EXIT
is executed before the shell terminates.
export
export [-fn] [-p] [
name
[=
value
]]
Mark each
name
to be passed to child processes
in the environment.  If the
`-f'
option is supplied, the
name
s
refer to shell functions; otherwise the names refer to shell variables.
The
`-n'
option means to no longer mark each
name
for export.
If no
names
are supplied, or if the
`-p'
option is given, a
list of exported names is displayed.
The
`-p'
option displays output in a form that may be reused as input.
If a variable name is followed by =
value
, the value of
the variable is set to
value
.
The return status is zero unless an invalid option is supplied, one of
the names is not a valid shell variable name, or
`-f'
is supplied
with a name that is not a shell function.
getopts
getopts
optstring
name
[
args
]
getopts
is used by shell scripts to parse positional parameters.
optstring
contains the option characters to be recognized; if a
character is followed by a colon, the option is expected to have an
argument, which should be separated from it by white space.
The colon (
`:'
) and question mark (
`?'
) may not be
used as option characters.
Each time it is invoked,
getopts
places the next option in the shell variable
name
, initializing
name
if it does not exist,
and the index of the next argument to be processed into the
variable
OPTIND
.
OPTIND
is initialized to 1 each time the shell or a shell script
is invoked.
When an option requires an argument,
getopts
places that argument into the variable
OPTARG
.
The shell does not reset
OPTIND
automatically; it must be manually
reset between multiple calls to
getopts
within the same shell
invocation if a new set of parameters is to be used.
When the end of options is encountered,
getopts
exits with a
return value greater than zero.
OPTIND
is set to the index of the first non-option argument,
and
name
is set to
`?'
.
getopts
normally parses the positional parameters, but if more arguments are
given in
args
,
getopts
parses those instead.
getopts
can report errors in two ways.  If the first character of
optstring
is a colon,
silent
error reporting is used.  In normal operation diagnostic messages
are printed when invalid options or missing option arguments are
encountered.
If the variable
OPTERR
is set to 0, no error messages will be displayed, even if the first
character of
optstring
is not a colon.
If an invalid option is seen,
getopts
places
`?'
into
name
and, if not silent,
prints an error message and unsets
OPTARG
.
If
getopts
is silent, the option character found is placed in
OPTARG
and no diagnostic message is printed.
If a required argument is not found, and
getopts
is not silent, a question mark (
`?'
) is placed in
name
,
OPTARG
is unset, and a diagnostic message is printed.
If
getopts
is silent, then a colon (
`:'
) is placed in
name
and
OPTARG
is set to the option character found.
hash
hash [-'r] [-p
filename
] [-dt] [
name
]
Remember the full pathnames of commands specified as
name
arguments,
so they need not be searched for on subsequent invocations.
The commands are found by searching through the directories listed in
$PATH
.
The
`-p'
option inhibits the path search, and
filename
is
used as the location of
name
.
The
`-r'
option causes the shell to forget all remembered locations.
The
`-d'
option causes the shell to forget the remembered location
of each
name
.
If the
`-t'
option is supplied, the full pathname to which each
name
corresponds is printed.  If multiple
name
arguments are
supplied with
`-t'
the
name
is printed before the hashed
full pathname.
The
`-l'
option causes output to be displayed in a format
that may be reused as input.
If no arguments are given, or if only
`-l'
is supplied,
information about remembered commands is printed.
The return status is zero unless a
name
is not found or an invalid
option is supplied.
pwd
pwd [-LP]
Print the absolute pathname of the current working directory.
If the
`-P'
option is supplied, the pathname printed will not
contain symbolic links.
If the
`-L'
option is supplied, the pathname printed may contain
symbolic links.
The return status is zero unless an error is encountered while
determining the name of the current directory or an invalid option
is supplied.
readonly
readonly [-apf] [
name
[=
value
]]
...
Mark each
name
as readonly.
The values of these names may not be changed by subsequent assignment.
If the
`-f'
option is supplied, each
name
refers to a shell
function.
The
`-a'
option means each
name
refers to an array variable.
If no
name
arguments are given, or if the
`-p'
option is supplied, a list of all readonly names is printed.
The
`-p'
option causes output to be displayed in a format that
may be reused as input.
If a variable name is followed by =
value
, the value of
the variable is set to
value
.
The return status is zero unless an invalid option is supplied, one of
the
name
arguments is not a valid shell variable or function name,
or the
`-f'
option is supplied with a name that is not a shell function.
return
return [
n
]
Cause a shell function to exit with the return value
n
.
If
n
is not supplied, the return value is the exit status of the
last command executed in the function.
This may also be used to terminate execution of a script being executed
with the
.
(or
source
) builtin, returning either
n
or
the exit status of the last command executed within the script as the exit
status of the script.
Any command associated with the
RETURN
trap is executed
before execution resumes after the function or script.
The return status is non-zero if
return
is used outside a function
and not during the execution of a script by
.
or
source
.
shift
shift [
n
]
Shift the positional parameters to the left by
n
.
The positional parameters from
n
+1
...
$#
are
renamed to
$1
...
$#
-
n
+1.
Parameters represented by the numbers
$#
to
n
+1 are unset.
n
must be a non-negative number less than or equal to
$#
.
If
n
is zero or greater than
$#
, the positional parameters
are not changed.
If
n
is not supplied, it is assumed to be 1.
The return status is zero unless
n
is greater than
$#
or
less than zero, non-zero otherwise.
test
[
Evaluate a conditional expression
expr
.
Each operator and operand must be a separate argument.
Expressions are composed of the primaries described below in
bashref.html#SEC78
6.4 Bash Conditional Expressions
.
When the
[
form is used, the last argument to the command must
be a
]
.
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
-a
expr2
True if both
expr1
and
expr2
are true.
expr1
-o
expr2
True if either
expr1
or
expr2
is true.
The
test
and
[
builtins 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 argument is one of the unary conditional operators
(see section
bashref.html#SEC78
6.4 Bash Conditional Expressions
), the expression
is true if the unary test is true.
If the first argument is not a valid unary operator, the expression is
false.
3 arguments
If the second argument is one of the binary conditional
operators (see section
bashref.html#SEC78
6.4 Bash Conditional Expressions
), 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
`-a'
and
`-o'
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 evaluated 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.
times
times
Print out the user and system times used by the shell and its children.
The return status is zero.
trap
trap [-lp] [
arg
] [
sigspec
...
]
The commands in
arg
are to be read and executed when the
shell receives signal
sigspec
.  If
arg
is absent (and
there is a single
sigspec
) or
equal to
`-'
, each specified signal's disposition is reset
to the value it had when the shell was started.
If
arg
is the null string, then the signal specified by
each
sigspec
is ignored by the shell and commands it invokes.
If
arg
is not present and
`-p'
has been supplied,
the shell displays the trap commands associated with each
sigspec
.
If no arguments are supplied, or
only
`-p'
is given,
trap
prints the list of commands
associated with each signal number in a form that may be reused as
shell input.
The
`-l'
option causes the shell to print a list of signal names
and their corresponding numbers.
Each
sigspec
is either a signal name or a signal number.
Signal names are case insensitive and the
SIG
prefix is optional.
If a
sigspec
is
0
or
EXIT
,
arg
is executed when the shell exits.
If a
sigspec
is
DEBUG
, the command
arg
is executed
before every simple command,
for
command,
case
command,
select
command, every arithmetic
for
command, and before
the first command executes in a shell function.
Refer to the description of the
extglob
option to the
shopt
builtin (see section
bashref.html#SEC58
4.2 Bash Builtin Commands
) for details of its
effect on the
DEBUG
trap.
If a
sigspec
is
ERR
, the command
arg
is executed whenever a simple command has a non-zero exit status,
subject to the following conditions.
The
ERR
trap is not executed if the failed command is part of the
command list immediately following an
until
or
while
keyword,
part of the test in an
if
statement,
part of a
&&
or
||
list, or if the command's return
status is being inverted using
!
.
These are the same conditions obeyed by the
errexit
option.
If a
sigspec
is
RETURN
, the command
arg
is executed
each time a shell function or a script executed with the
.
or
source
builtins finishes executing.
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 zero unless a
sigspec
does not specify a
valid signal.
umask
umask [-p] [-S] [
mode
]
Set the shell process's file creation mask to
mode
.  If
mode
begins with a digit, it is interpreted as an octal number;
if not, it is interpreted as a symbolic mode mask similar
to that accepted by the
chmod
command.  If
mode
is
omitted, the current value of the mask is printed.  If the
`-S'
option is supplied without a
mode
argument, the mask is printed
in a symbolic format.
If the
`-p'
option is supplied, and
mode
is omitted, the output is in a form that may be reused as input.
The return status is zero if the mode is successfully changed or if
no
mode
argument is supplied, and non-zero otherwise.
Note that when the mode is interpreted as an octal number, each number
of the umask is subtracted from
7
.  Thus, a umask of
022
results in permissions of
755
.
unset
unset [-fv] [
name
]
Each variable or function
name
is removed.
If no options are supplied, or the
`-v'
option is given, each
name
refers to a shell variable.
If the
`-f'
option is given, the
name
s refer to shell
functions, and the function definition is removed.
Readonly variables and functions may not be unset.
The return status is zero unless a
name
is readonly.
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4.2 Bash Builtin Commands
This section describes builtin commands which are unique to
or have been extended in Bash.
Some of these commands are specified in the POSIX 1003.2 standard.
alias
alias [
-p
] [
name
[=
value
]
...
]
Without arguments or with the
`-p'
option,
alias
prints
the list of aliases on the standard output in a form that allows
them to be reused as input.
If arguments are supplied, an alias is defined for each
name
whose
value
is given.  If no
value
is given, the name
and value of the alias is printed.
Aliases are described in
bashref.html#SEC80
6.6 Aliases
.
bind
bind [-m
keymap
] [-lpsvPSV]
bind [-m
keymap
] [-q
function
] [-u
function
] [-r
keyseq
]
bind [-m
keymap
] -f
filename
bind [-m
keymap
] -x
keyseq:shell-command
bind [-m
keymap
]
keyseq:function-name
bind
readline-command
Display current Readline (see section
bashref.html#SEC91
8. Command Line Editing
)
key and function bindings,
bind a key sequence to a Readline function or macro,
or set a Readline variable.
Each non-option argument is a command as it would appear in a
a Readline initialization file (see section
bashref.html#SEC99
8.3 Readline Init File
),
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:
-m
keymap
Use
keymap
as the keymap to be affected by
the subsequent bindings.  Acceptable
keymap
names are
emacs
,
emacs-standard
,
emacs-meta
,
emacs-ctlx
,
vi
,
vi-move
,
vi-command
, and
vi-insert
.
vi
is equivalent to
vi-command
;
emacs
is equivalent to
emacs-standard
.
-l
List the names of all Readline functions.
-p
Display Readline function names and bindings in such a way that they
can be used as input or in a Readline initialization file.
-P
List current Readline function names and bindings.
-v
Display Readline variable names and values in such a way that they
can be used as input or in a Readline initialization file.
-V
List current Readline variable names and values.
-s
Display Readline key sequences bound to macros and the strings they output
in such a way that they can be used as input or in a Readline
initialization file.
-S
Display Readline key sequences bound to macros and the strings they output.
-f
filename
Read key bindings from
filename
.
-q
function
Query about which keys invoke the named
function
.
-u
function
Unbind all keys bound to the named
function
.
-r
keyseq
Remove any current binding for
keyseq
.
-x
keyseq:shell-command
Cause
shell-command
to be executed whenever
keyseq
is
entered.
The return status is zero unless an invalid option is supplied or an
error occurs.
builtin
builtin [
shell-builtin
[
args
]]
Run a shell builtin, passing it
args
, and return its exit status.
This is useful when defining a shell function with the same
name as a shell builtin, retaining the functionality of the builtin within
the function.
The return status is non-zero if
shell-builtin
is not a shell
builtin command.
caller
caller [
expr
]
Returns the context of any active subroutine call (a shell function or
a script executed with the
.
or
source
builtins).
Without
expr
,
caller
displays the line number and source
filename of the current subroutine call.
If a non-negative integer is supplied as
expr
,
caller
displays the line number, subroutine name, and source file corresponding
to that position in the current execution call stack.  This extra
information may be used, for example, to print a stack trace.  The
current frame is frame 0.
The return value is 0 unless the shell is not executing a subroutine
call or
expr
does not correspond to a valid position in the
call stack.
command
command [-pVv]
command
[
arguments
...
]
Runs
command
with
arguments
ignoring any shell function
named
command
.
Only shell builtin commands or commands found by searching the
PATH
are executed.
If there is a shell function named
ls
, running
`command ls'
within the function will execute the external command
ls
instead of calling the function recursively.
The
`-p'
option means to use a default value for
PATH
that is guaranteed to find all of the standard utilities.
The return status in this case is 127 if
command
cannot be
found or an error occurred, and the exit status of
command
otherwise.
If either the
`-V'
or
`-v'
option is supplied, a
description of
command
is printed.  The
`-v'
option
causes a single word indicating the command or file name used to
invoke
command
to be displayed; the
`-V'
option produces
a more verbose description.  In this case, the return status is
zero if
command
is found, and non-zero if not.
declare
declare [-afFirtx] [-p] [
name
[=
value
]
...
]
Declare variables and give them attributes.  If no
name
s
are given, then display the values of variables instead.
The
`-p'
option will display the attributes and values of each
name
.
When
`-p'
is used, additional options are ignored.
The
`-F'
option inhibits the display of function definitions;
only the function name and attributes are printed.
If the
extdebug
shell option is enabled using
shopt
(see section
bashref.html#SEC58
4.2 Bash Builtin Commands
), the source file name and line number where
the function is defined are displayed as well.
`-F'
implies
`-f'
.
The following options can be used to restrict output to variables with
the specified attributes or to give variables attributes:
-a
Each
name
is an array variable (see section
bashref.html#SEC81
6.7 Arrays
).
-f
Use function names only.
-i
The variable is to be treated as
an integer; arithmetic evaluation (see section
bashref.html#SEC79
6.5 Shell Arithmetic
) is
performed when the variable is assigned a value.
-r
Make
name
s readonly.  These names cannot then be assigned values
by subsequent assignment statements or unset.
-t
Give each
name
the
trace
attribute.
Traced functions inherit the
DEBUG
trap from the calling shell.
The trace attribute has no special meaning for variables.
-x
Mark each
name
for export to subsequent commands via
the environment.
Using
`+'
instead of
`-'
turns off the attribute instead.
When used in a function,
declare
makes each
name
local,
as with the
local
command.  If a variable name is followed by
=
value
, the value of the variable is set to
value
.
The return status is zero 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 section
bashref.html#SEC81
6.7 Arrays
),
one of the
names
is not a valid shell variable name,
an attempt is made to turn off readonly status for a readonly variable,
an attempt is made to turn off array status for an array variable,
or an attempt is made to display a non-existent function with
`-f'
.
echo
echo [-neE] [
arg
...
]
Output the
arg
s, separated by spaces, terminated with a
newline.
The return status is always 0.
If
`-n'
is specified, the trailing newline is suppressed.
If the
`-e'
option is given, interpretation of the following
backslash-escaped characters is enabled.
The
`-E'
option disables the interpretation of these escape characters,
even on systems where they are interpreted by default.
The
xpg_echo
shell option may be used to
dynamically determine whether or not
echo
expands these
escape characters by default.
echo
interprets the following escape sequences:
\a
alert (bell)
\b
backspace
\c
suppress trailing newline
\e
escape
\f
form feed
\n
new line
\r
carriage return
\t
horizontal tab
\v
vertical tab
\\
backslash
\0
nnn
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)
\x
HH
the eight-bit character whose value is the hexadecimal value
HH
(one or two hex digits)
enable
enable [-n] [-p] [-f
filename
] [-ads] [
name
...
]
Enable and disable builtin shell commands.
Disabling a builtin allows a disk command which has the same name
as a shell builtin to be executed without specifying a full pathname,
even though the shell normally searches for builtins before disk commands.
If
`-n'
is used, the
name
s become disabled.  Otherwise
name
s are enabled.  For example, to use the
test
binary
found via
$PATH
instead of the shell builtin version, type
`enable -n test'
.
If the
`-p'
option is supplied, or no
name
arguments appear,
a list of shell builtins is printed.  With no other arguments, the list
consists of all enabled shell builtins.
The
`-a'
option means to list
each builtin with an indication of whether or not it is enabled.
The
`-f'
option means to load the new builtin command
name
from shared object
filename
, on systems that support dynamic loading.
The
`-d'
option will delete a builtin loaded with
`-f'
.
If there are no options, a list of the shell builtins is displayed.
The
`-s'
option restricts
enable
to the POSIX special
builtins.  If
`-s'
is used with
`-f'
, the new builtin becomes
a special builtin (see section
bashref.html#SEC60
4.4 Special Builtins
).
The return status is zero unless a
name
is not a shell builtin
or there is an error loading a new builtin from a shared object.
help
help [-s] [
pattern
]
Display helpful information about builtin commands.
If
pattern
is specified,
help
gives detailed help
on all commands matching
pattern
, otherwise a list of
the builtins is printed.
The
`-s'
option restricts the information displayed to a short
usage synopsis.
The return status is zero unless no command matches
pattern
.
let
let
expression
[
expression
]
The
let
builtin allows arithmetic to be performed on shell
variables.  Each
expression
is evaluated according to the
rules given below in
bashref.html#SEC79
6.5 Shell Arithmetic
.  If the
last
expression
evaluates to 0,
let
returns 1;
otherwise 0 is returned.
local
local [
option
]
name
[=
value
]
...
For each argument, a local variable named
name
is created,
and assigned
value
.
The
option
can be any of the options accepted by
declare
.
local
can only be used within a function; it makes the variable
name
have a visible scope restricted to that function and its
children.  The return status is zero unless
local
is used outside
a function, an invalid
name
is supplied, or
name
is a
readonly variable.
logout
logout [
n
]
Exit a login shell, returning a status of
n
to the shell's
parent.
printf
printf
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
format specifications, each of which causes printing of the next successive
argument
.
In addition to the standard
printf(1)
formats,
`%b'
causes
printf
to expand backslash escape sequences in the corresponding
argument
,
(except that
`\c'
terminates output, backslashes in
`\''
,
`\"'
, and
`\?'
are not removed, and octal escapes
beginning with
`\0'
may contain up to four digits),
and
`%q'
causes
printf
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
arguments
.
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.
read
read [-ers] [-a
aname
] [-d
delim
] [-n
nchars
] [-p
prompt
] [-t
timeout
] [-u
fd
] [
name
...
]
One line is read from the standard input, or from the file descriptor
fd
supplied as an argument to the
`-u'
option, and the first word
is assigned to the first
name
, the second word to the second
name
,
and so on, with leftover words and their intervening separators assigned
to the last
name
.
If there are fewer words read from the input stream than names,
the remaining names are assigned empty values.
The characters in the value of the
IFS
variable
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.
If no names are supplied, the line read is assigned to the
variable
REPLY
.
The return code is zero, unless end-of-file is encountered,
read
times out, or an invalid file descriptor is supplied as the argument to
`-u'
.
Options, if supplied, have the following meanings:
-a
aname
The words are assigned to sequential indices of the array variable
aname
, starting at 0.
All elements are removed from
aname
before the assignment.
Other
name
arguments are ignored.
-d
delim
The first character of
delim
is used to terminate the input line,
rather than newline.
-e
Readline (see section
bashref.html#SEC91
8. Command Line Editing
) is used to obtain the line.
-n
nchars
read
returns after reading
nchars
characters rather than
waiting for a complete line of input.
-p
prompt
Display
prompt
, without a trailing newline, before attempting
to read any input.
The prompt is displayed only if input is coming from a terminal.
-r
If this option is given, backslash does not act as an escape character.
The backslash is considered to be part of the line.
In particular, a backslash-newline pair may not be used as a line
continuation.
-s
Silent mode.  If input is coming from a terminal, characters are
not echoed.
-t
timeout
Cause
read
to time out and return failure if a complete line of
input is not read within
timeout
seconds.
This option has no effect if
read
is not reading input from the
terminal or a pipe.
-u
fd
Read input from file descriptor
fd
.
shopt
shopt [-pqsu] [-o] [
optname
...
]
Toggle the values of variables controlling optional shell behavior.
With no options, or with the
`-p'
option, a list of all settable
options is displayed, with an indication of whether or not each is set.
The
`-p'
option causes output to be displayed in a form that
may be reused as input.
Other options have the following meanings:
-s
Enable (set) each
optname
.
-u
Disable (unset) each
optname
.
-q
Suppresses normal output; the return status
indicates whether the
optname
is set or unset.
If multiple
optname
arguments are given with
`-q'
,
the return status is zero if all
optnames
are enabled;
non-zero otherwise.
-o
Restricts the values of
optname
to be those defined for the
`-o'
option to the
set
builtin (see section
bashref.html#SEC59
4.3 The Set Builtin
).
If either
`-s'
or
`-u'
is used with no
optname
arguments, the display is limited to
those options which are set or unset, respectively.
Unless otherwise noted, the
shopt
options are disabled (off)
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
shopt
options is:
cdable_vars
If this is set, an argument to the
cd
builtin command that
is not a directory is assumed to be the name of a variable whose
value is the directory to change to.
cdspell
If set, minor errors in the spelling of a directory component in a
cd
command will be corrected.
The errors checked for are transposed characters,
a missing character, and a character too many.
If a correction is found, the corrected path is printed,
and the command proceeds.
This option is only used by interactive shells.
checkhash
If this is set, Bash checks that a command found in the hash
table exists before trying to execute it.  If a hashed command no
longer exists, a normal path search is performed.
checkwinsize
If set, Bash checks the window size after each command
and, if necessary, updates the values of
LINES
and
COLUMNS
.
cmdhist
If set, Bash
attempts to save all lines of a multiple-line
command in the same history entry.  This allows
easy re-editing of multi-line commands.
dotglob
If set, Bash includes filenames beginning with a `.' in
the results of filename expansion.
execfail
If this is set, a non-interactive shell will not exit if
it cannot execute the file specified as an argument to the
exec
builtin command.  An interactive shell does not exit if
exec
fails.
expand_aliases
If set, aliases are expanded as described below under Aliases,
bashref.html#SEC80
6.6 Aliases
.
This option is enabled by default for interactive shells.
extdebug
If set, behavior intended for use by debuggers is enabled:
The
`-F'
option to the
declare
builtin (see section
bashref.html#SEC58
4.2 Bash Builtin Commands
)
displays the source file name and line number corresponding to each function
name supplied as an argument.
If the command run by the
DEBUG
trap returns a non-zero value, the
next command is skipped and not executed.
If the command run by the
DEBUG
trap returns a value of 2, and the
shell is executing in a subroutine (a shell function or a shell script
executed by the
.
or
source
builtins), a call to
return
is simulated.
extglob
If set, the extended pattern matching features described above
(see section
bashref.html#SEC36
3.5.8.1 Pattern Matching
) are enabled.
extquote
If set,
$'
string
'
and
$"
string
"
quoting is
performed within
${
parameter
}
expansions
enclosed in double quotes.  This option is enabled by default.
failglob
If set, patterns which fail to match filenames during pathname expansion
result in an expansion error.
force_fignore
If set, the suffixes specified by the
FIGNORE
shell variable
cause words to be ignored when performing word completion even if
the ignored words are the only possible completions.
See section
bashref.html#SEC63
5.2 Bash Variables
, for a description of
FIGNORE
.
This option is enabled by default.
gnu_errfmt
If set, shell error messages are written in the standard GNU error
message format.
histappend
If set, the history list is appended to the file named by the value
of the
HISTFILE
variable when the shell exits, rather than overwriting the file.
histreedit
If set, and Readline
is being used, a user is given the opportunity to re-edit a
failed history substitution.
histverify
If set, and Readline
is being used, the results of history substitution are not immediately
passed to the shell parser.  Instead, the resulting line is loaded into
the Readline editing buffer, allowing further modification.
hostcomplete
If set, and Readline is being used, Bash will attempt to perform
hostname completion when a word containing a
`@'
is being
completed (see section
bashref.html#SEC109
8.4.6 Letting Readline Type For You
).  This option is enabled
by default.
huponexit
If set, Bash will send
SIGHUP
to all jobs when an interactive
login shell exits (see section
bashref.html#SEC54
3.7.6 Signals
).
interactive_comments
Allow a word beginning with
`#'
to cause that word and all remaining characters on that
line to be ignored in an interactive shell.
This option is enabled by default.
lithist
If enabled, and the
cmdhist
option is enabled, multi-line commands are saved to the history with
embedded newlines rather than using semicolon separators where possible.
login_shell
The shell sets this option if it is started as a login shell
(see section
bashref.html#SEC65
6.1 Invoking Bash
).
The value may not be changed.
mailwarn
If set, and a file that Bash is checking for mail has been
accessed since the last time it was checked, the message
"The mail in
mailfile
has been read"
is displayed.
no_empty_cmd_completion
If set, and Readline is being used, Bash will not attempt to search
the
PATH
for possible completions when completion is attempted
on an empty line.
nocaseglob
If set, Bash matches filenames in a case-insensitive fashion when
performing filename expansion.
nullglob
If set, Bash allows filename patterns which match no
files to expand to a null string, rather than themselves.
progcomp
If set, the programmable completion facilities
(see section
bashref.html#SEC113
8.6 Programmable Completion
) are enabled.
This option is enabled by default.
promptvars
If set, prompt strings undergo
parameter expansion, command substitution, arithmetic
expansion, and quote removal after being expanded
as described below (see section
bashref.html#SEC84
6.9 Controlling the Prompt
).
This option is enabled by default.
restricted_shell
The shell sets this option if it is started in restricted mode
(see section
bashref.html#SEC85
6.10 The Restricted Shell
).
The value may not be changed.
This is not reset when the startup files are executed, allowing
the startup files to discover whether or not a shell is restricted.
shift_verbose
If this is set, the
shift
builtin prints an error message when the shift count exceeds the
number of positional parameters.
sourcepath
If set, the
source
builtin uses the value of
PATH
to find the directory containing the file supplied as an argument.
This option is enabled by default.
xpg_echo
If set, the
echo
builtin expands backslash-escape sequences
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.
source
source
filename
A synonym for
.
(see section
bashref.html#SEC57
4.1 Bourne Shell Builtins
).
type
type [-afptP] [
name
...
]
For each
name
, indicate how it would be interpreted if used as a
command name.
If the
`-t'
option is used,
type
prints a single word
which is one of
`alias'
,
`function'
,
`builtin'
,
`file'
or
`keyword'
,
if
name
is an alias, shell function, shell builtin,
disk file, or shell reserved word, respectively.
If the
name
is not found, then nothing is printed, and
type
returns a failure status.
If the
`-p'
option is used,
type
either returns the name
of the disk file that would be executed, or nothing if
`-t'
would not return
`file'
.
The
`-P'
option forces a path search for each
name
, even if
`-t'
would not return
`file'
.
If a command is hashed,
`-p'
and
`-P'
print the hashed value,
not necessarily the file that appears first in
$PATH
.
If the
`-a'
option is used,
type
returns all of the places
that contain an executable named
file
.
This includes aliases and functions, if and only if the
`-p'
option
is not also used.
If the
`-f'
option is used,
type
does not attempt to find
shell functions, as with the
command
builtin.
The return status is zero if any of the
names
are found, non-zero
if none are found.
typeset
typeset [-afFrxi] [-p] [
name
[=
value
]
...
]
The
typeset
command is supplied for compatibility with the Korn
shell; however, it has been deprecated in favor of the
declare
builtin command.
ulimit
ulimit [-acdflmnpstuvSH] [
limit
]
ulimit
provides control over the resources available to processes
started by the shell, on systems that allow such control.  If an
option is given, it is interpreted as follows:
-S
Change and report the soft limit associated with a resource.
-H
Change and report the hard limit associated with a resource.
-a
All current limits are reported.
-c
The maximum size of core files created.
-d
The maximum size of a process's data segment.
-f
The maximum size of files created by the shell.
-l
The maximum size that may be locked into memory.
-m
The maximum resident set size.
-n
The maximum number of open file descriptors.
-p
The pipe buffer size.
-s
The maximum stack size.
-t
The maximum amount of cpu time in seconds.
-u
The maximum number of processes available to a single user.
-v
The maximum amount of virtual memory available to the process.
If
limit
is given, it is the new value of the specified resource;
the special
limit
values
hard
,
soft
, and
unlimited
stand for the current hard limit, the current soft limit,
and no limit, respectively.
Otherwise, the current value of the soft limit for the specified resource
is printed, unless the
`-H'
option is supplied.
When setting new limits, if neither
`-H'
nor
`-S'
is supplied,
both the hard and soft limits are set.
If no option is given, then
`-f'
is assumed.  Values are in 1024-byte
increments, except for
`-t'
, which is in seconds,
`-p'
,
which is in units of 512-byte blocks, and
`-n'
and
`-u'
, which
are unscaled values.
The return status is zero unless an invalid option or argument is supplied,
or an error occurs while setting a new limit.
unalias
unalias [-a] [
name
...
]
Remove each
name
from the list of aliases.  If
`-a'
is
supplied, all aliases are removed.
Aliases are described in
bashref.html#SEC80
6.6 Aliases
.
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4.3 The Set Builtin
This builtin is so complicated that it deserves its own section.
set
set [--abefhkmnptuvxBCHP] [-o
option
] [
argument
...
]
If no options or arguments are supplied,
set
displays the names
and values of all shell variables and functions, sorted according to the
current locale, in a format that may be reused as input.
When options are supplied, they set or unset shell attributes.
Options, if specified, have the following meanings:
-a
Mark variables and function which are modified or created for export
to the environment of subsequent commands.
-b
Cause the status of terminated background jobs to be reported
immediately, rather than before printing the next primary prompt.
-e
Exit immediately if a simple command (see section
bashref.html#SEC16
3.2.1 Simple Commands
) exits
with a non-zero status, unless the command that fails is part of the
command list immediately following a
while
or
until
keyword, part of the test in an
if
statement,
part of a
&&
or
||
list, or if the command's return
status is being inverted using
!
.
A trap on
ERR
, if set, is executed before the shell exits.
-f
Disable file name generation (globbing).
-h
Locate and remember (hash) commands as they are looked up for execution.
This option is enabled by default.
-k
All arguments in the form of assignment statements are placed
in the environment for a command, not just those that precede
the command name.
-m
Job control is enabled (see section
bashref.html#SEC87
7. Job Control
).
-n
Read commands but do not execute them; this may be used to check a
script for syntax errors.
This option is ignored by interactive shells.
-o
option-name
Set the option corresponding to
option-name
:
allexport
Same as
-a
.
braceexpand
Same as
-B
.
emacs
Use an
emacs
-style line editing interface (see section
bashref.html#SEC91
8. Command Line Editing
).
errexit
Same as
-e
.
errtrace
Same as
-E
.
functrace
Same as
-T
.
hashall
Same as
-h
.
histexpand
Same as
-H
.
history
Enable command history, as described in
bashref.html#SEC116
9.1 Bash History Facilities
.
This option is on by default in interactive shells.
ignoreeof
An interactive shell will not exit upon reading EOF.
keyword
Same as
-k
.
monitor
Same as
-m
.
noclobber
Same as
-C
.
noexec
Same as
-n
.
noglob
Same as
-f
.
nolog
Currently ignored.
notify
Same as
-b
.
nounset
Same as
-u
.
onecmd
Same as
-t
.
physical
Same as
-P
.
pipefail
If set, the return value of a pipeline is the value of the last
(rightmost) command to exit with a non-zero status, or zero if all
commands in the pipeline exit successfully.
This option is disabled by default.
posix
Change the behavior of Bash where the default operation differs
from the POSIX 1003.2 standard to match the standard
(see section
bashref.html#SEC86
6.11 Bash POSIX Mode
).
This is intended to make Bash behave as a strict superset of that
standard.
privileged
Same as
-p
.
verbose
Same as
-v
.
vi
Use a
vi
-style line editing interface.
xtrace
Same as
-x
.
-p
Turn on privileged mode.
In this mode, the
$BASH_ENV
and
$ENV
files are not
processed, shell functions are not inherited from the environment,
and the
SHELLOPTS
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
-p
option is not supplied, these actions
are taken and the effective user id is set to the real user id.
If the
-p
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.
-t
Exit after reading and executing one command.
-u
Treat unset variables as an error when performing parameter expansion.
An error message will be written to the standard error, and a non-interactive
shell will exit.
-v
Print shell input lines as they are read.
-x
Print a trace of simple commands, \fBfor\fP commands, \fBcase\fP
commands, \fBselect\fP commands, and arithmetic \fBfor\fP commands
and their arguments or associated word lists after they are
expanded and before they are executed.  The value of the
PS4
variable is expanded and the resultant value is printed before
the command and its expanded arguments.
-B
The shell will perform brace expansion (see section
bashref.html#SEC28
3.5.1 Brace Expansion
).
This option is on by default.
-C
Prevent output redirection using
`>'
,
`>&'
, and
`<>'
from overwriting existing files.
-E
If set, any trap on
ERR
is inherited by shell functions, command
substitutions, and commands executed in a subshell environment.
The
ERR
trap is normally not inherited in such cases.
-H
Enable
`!'
style history substitution (see section
bashref.html#SEC118
9.3 History Expansion
).
This option is on by default for interactive shells.
-P
If set, do not follow symbolic links when performing commands such as
cd
which change the current directory.  The physical directory
is used instead.  By default, Bash follows
the logical chain of directories when performing commands
which change the current directory.
For example, if
`/usr/sys'
is a symbolic link to
`/usr/local/sys'
then:
$ cd /usr/sys; echo $PWD
/usr/sys
$ cd ..; pwd
/usr
If
set -P
is on, then:
$ cd /usr/sys; echo $PWD
/usr/local/sys
$ cd ..; pwd
/usr/local
-T
If set, any trap on
DEBUG
is inherited by shell functions, command
substitutions, and commands executed in a subshell environment.
The
DEBUG
trap is normally not inherited in such cases.
--
If no arguments follow this option, then the positional parameters are
unset.  Otherwise, the positional parameters are set to the
arguments
, even if some of them begin with a
`-'
.
-
Signal the end of options, cause all remaining
arguments
to be assigned to the positional parameters.  The
`-x'
and
`-v'
options are turned off.
If there are no arguments, the positional parameters remain unchanged.
Using
`+'
rather than
`-'
causes these options to be
turned off.  The options can also be used upon invocation of the
shell.  The current set of options may be found in
$-
.
The remaining N
arguments
are positional parameters and are
assigned, in order, to
$1
,
$2
,
...
$N
.
The special parameter
#
is set to N.
The return status is always zero unless an invalid option is supplied.
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4.4 Special Builtins
For historical reasons, the POSIX 1003.2 standard has classified
several builtin commands as
special
.
When Bash is executing in POSIX mode, the special builtins
differ from other builtin commands in three respects:
Special builtins are found before shell functions during command lookup.
If a special builtin returns an error status, a non-interactive shell exits.
Assignment statements preceding the command stay in effect in the shell
environment after the command completes.
When Bash is not executing in POSIX mode, these builtins behave no
differently than the rest of the Bash builtin commands.
The Bash POSIX mode is described in
bashref.html#SEC86
6.11 Bash POSIX Mode
.
These are the POSIX special builtins:
break : . continue eval exec exit export readonly return set
shift trap unset
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5. Shell Variables
bashref.html#SEC62
5.1 Bourne Shell Variables
Variables which Bash uses in the same way
as the Bourne Shell.
bashref.html#SEC63
5.2 Bash Variables
List of variables that exist in Bash.
This chapter describes the shell variables that Bash uses.
Bash automatically assigns default values to a number of variables.
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5.1 Bourne Shell Variables
Bash uses certain shell variables in the same way as the Bourne shell.
In some cases, Bash assigns a default value to the variable.
CDPATH
A colon-separated list of directories used as a search path for
the
cd
builtin command.
HOME
The current user's home directory; the default for the
cd
builtin
command.
The value of this variable is also used by tilde expansion
(see section
bashref.html#SEC29
3.5.2 Tilde Expansion
).
IFS
A list of characters that separate fields; used when the shell splits
words as part of expansion.
MAIL
If this parameter is set to a filename and the
MAILPATH
variable
is not set, Bash informs the user of the arrival of mail in
the specified file.
MAILPATH
A colon-separated list of filenames which the shell periodically checks
for new mail.
Each list entry can specify the message that is printed when new mail
arrives in the mail file 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 mail file.
OPTARG
The value of the last option argument processed by the
getopts
builtin.
OPTIND
The index of the last option argument processed by the
getopts
builtin.
PATH
A colon-separated list of directories in which the shell looks for
commands.
A zero-length (null) directory name in the value of
PATH
indicates the
current directory.
A null directory name may appear as two adjacent colons, or as an initial
or trailing colon.
PS1
The primary prompt string.  The default value is
`\s-\v\$ '
.
See section
bashref.html#SEC84
6.9 Controlling the Prompt
, for the complete list of escape
sequences that are expanded before
PS1
is displayed.
PS2
The secondary prompt string.  The default value is
`> '
.
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5.2 Bash Variables
These variables are set or used by Bash, but other shells
do not normally treat them specially.
A few variables used by Bash are described in different chapters:
variables for controlling the job control facilities
(see section
bashref.html#SEC90
7.3 Job Control Variables
).
BASH
The full pathname used to execute the current instance of Bash.
BASH_ARGC
An array variable whose values are the number of parameters in each
frame of the current bash execution call stack.  The number of
parameters to the current subroutine (shell function or script executed
with
.
or
source
) is at the top of the stack.  When a
subroutine is executed, the number of parameters passed is pushed onto
BASH_ARGC
.
BASH_ARGV
An array variable containing all of the parameters in the current bash
execution call stack.  The final parameter of the last subroutine call
is at the top of the stack; the first parameter of the initial call is
at the bottom.  When a subroutine is executed, the parameters supplied
are pushed onto
BASH_ARGV
.
BASH_COMMAND
The command currently being executed or about to be executed, unless the
shell is executing a command as the result of a trap,
in which case it is the command executing at the time of the trap.
BASH_ENV
If this variable is set when Bash is invoked to execute a shell
script, its value is expanded and used as the name of a startup file
to read before executing the script.  See section
bashref.html#SEC66
6.2 Bash Startup Files
.
BASH_EXECUTION_STRING
The command argument to the
`-c'
invocation option.
BASH_LINENO
An array variable whose members are the line numbers in source files
corresponding to each member of
FUNCNAME
.
${BASH_LINENO[$i]}
is the line number in the source file where
${FUNCNAME[$i + 1]}
was called.
The corresponding source file name is
${BASH_SOURCE[$i + 1]}
.
Use
LINENO
to obtain the current line number.
BASH_REMATCH
An array variable whose members are assigned by the
`=~'
binary
operator to the
[[
conditional command
(see section
bashref.html#SEC21
3.2.4.2 Conditional Constructs
).
The element with index 0 is the portion of the string
matching the entire regular expression.
The element with index
n
is the portion of the
string matching the
n
th parenthesized subexpression.
This variable is read-only.
BASH_SOURCE
An array variable whose members are the source filenames corresponding
to the elements in the
FUNCNAME
array variable.
BASH_SUBSHELL
Incremented by one each time a subshell or subshell environment is spawned.
The initial value is 0.
BASH_VERSINFO
A readonly array variable (see section
bashref.html#SEC81
6.7 Arrays
)
whose members hold version information for this instance of Bash.
The values assigned to the array members are as follows:
BASH_VERSINFO[0]
The major version number (the
release
).
BASH_VERSINFO[1]
The minor version number (the
version
).
BASH_VERSINFO[2]
The patch level.
BASH_VERSINFO[3]
The build version.
BASH_VERSINFO[4]
The release status (e.g.,
beta1
).
BASH_VERSINFO[5]
The value of
MACHTYPE
.
BASH_VERSION
The version number of the current instance of Bash.
COLUMNS
Used by the
select
builtin command to determine the terminal width
when printing selection lists.  Automatically set upon receipt of a
SIGWINCH
.
COMP_CWORD
An index into
${COMP_WORDS}
of the word containing the current
cursor position.
This variable is available only in shell functions invoked by the
programmable completion facilities (see section
bashref.html#SEC113
8.6 Programmable Completion
).
COMP_LINE
The current command line.
This variable is available only in shell functions and external
commands invoked by the
programmable completion facilities (see section
bashref.html#SEC113
8.6 Programmable Completion
).
COMP_POINT
The index of the current cursor position relative to the beginning of
the current command.
If the current cursor position is at the end of the current command,
the value of this variable is equal to
${#COMP_LINE}
.
This variable is available only in shell functions and external
commands invoked by the
programmable completion facilities (see section
bashref.html#SEC113
8.6 Programmable Completion
).
COMP_WORDBREAKS
The set of characters that the Readline library treats as word
separators when performing word completion.
If
COMP_WORDBREAKS
is unset, it loses its special properties,
even if it is subsequently reset.
COMP_WORDS
An array variable consisting of the individual
words in the current command line.
This variable is available only in shell functions invoked by the
programmable completion facilities (see section
bashref.html#SEC113
8.6 Programmable Completion
).
COMPREPLY
An array variable from which Bash reads the possible completions
generated by a shell function invoked by the programmable completion
facility (see section
bashref.html#SEC113
8.6 Programmable Completion
).
DIRSTACK
An array variable containing the current contents of the directory stack.
Directories appear in the stack in the order they are displayed by the
dirs
builtin.
Assigning to members of this array variable may be used to modify
directories already in the stack, but the
pushd
and
popd
builtins must be used to add and remove directories.
Assignment to this variable will not change the current directory.
If
DIRSTACK
is unset, it loses its special properties, even if
it is subsequently reset.
EMACS
If Bash finds this variable in the environment when the shell
starts with value
`t'
, it assumes that the shell is running in an
emacs shell buffer and disables line editing.
EUID
The numeric effective user id of the current user.  This variable
is readonly.
FCEDIT
The editor used as a default by the
`-e'
option to the
fc
builtin command.
FIGNORE
A colon-separated list of suffixes to ignore when performing
filename completion.
A file name whose suffix matches one of the entries in
FIGNORE
is excluded from the list of matched file names.  A sample
value is
`.o:~'
FUNCNAME
An array variable containing the names of all shell functions
currently in the execution call stack.
The element with index 0 is the name of any currently-executing
shell function.
The bottom-most element is "main".
This variable exists only when a shell function is executing.
Assignments to
FUNCNAME
have no effect and return an error status.
If
FUNCNAME
is unset, it loses its special properties, even if
it is subsequently reset.
GLOBIGNORE
A colon-separated list of patterns defining the set of filenames to
be ignored by filename expansion.
If a filename matched by a filename expansion pattern also matches one
of the patterns in
GLOBIGNORE
, it is removed from the list
of matches.
GROUPS
An array variable containing the list of groups of which the current
user is a member.
Assignments to
GROUPS
have no effect and return an error status.
If
GROUPS
is unset, it loses its special properties, even if it is
subsequently reset.
histchars
Up to three characters which control history expansion, quick
substitution, and tokenization (see section
bashref.html#SEC118
9.3 History Expansion
).
The first character is the
history expansion
character, that is, the character which signifies the
start of a history expansion, normally
`!'
.  The second character is the
character which signifies `quick substitution' when seen as the first
character on a line, normally
`^'
.  The optional third character is the
character which indicates that the remainder of the line is a comment when
found as the first character of a word, usually
`#'
.  The history
comment character causes history substitution to be skipped for the
remaining words on the line.  It does not necessarily cause the shell
parser to treat the rest of the line as a comment.
HISTCMD
The history number, or index in the history list, of the current
command.  If
HISTCMD
is unset, it loses its special properties,
even if it is subsequently reset.
HISTCONTROL
A colon-separated list of values controlling how commands are saved on
the history list.
If the list of values includes
`ignorespace'
, lines which begin
with a space character are not saved in the history list.
A value of
`ignoredups'
causes lines which match the previous
history entry to not be saved.
A value of
`ignoreboth'
is shorthand for
`ignorespace'
and
`ignoredups'
.
A value of
`erasedups'
causes all previous lines matching the
current line to be removed from the history list before that line
is saved.
Any value not in the above list is ignored.
If
HISTCONTROL
is unset, or does not include a valid value,
all lines read by the shell parser are saved on the history list,
subject to the value of
HISTIGNORE
.
The second and subsequent lines of a multi-line compound command are
not tested, and are added to the history regardless of the value of
HISTCONTROL
.
HISTFILE
The name of the file to which the command history is saved.  The
default value is
`~/.bash_history'
.
HISTFILESIZE
The maximum number of lines contained in the history file.  When this
variable is assigned a value, the history file is truncated, if
necessary, to contain no more than that number of lines.
The history file is also truncated to this size after
writing it when an interactive shell exits.
The default value is 500.
HISTIGNORE
A colon-separated list of patterns used to decide which command
lines should be saved on the history list.  Each pattern is
anchored at the beginning of the line and must match the complete
line (no implicit
`*'
is appended).  Each pattern is tested
against the line after the checks specified by
HISTCONTROL
are applied.  In addition to the normal shell pattern matching
characters,
`&'
matches the previous history line.
`&'
may be escaped using a backslash; the backslash is removed
before attempting a match.
The second and subsequent lines of a multi-line compound command are
not tested, and are added to the history regardless of the value of
HISTIGNORE
.
HISTIGNORE
subsumes the function of
HISTCONTROL
.  A
pattern of
`&'
is identical to
ignoredups
, and a
pattern of
`[ ]*'
is identical to
ignorespace
.
Combining these two patterns, separating them with a colon,
provides the functionality of
ignoreboth
.
HISTSIZE
The maximum number of commands to remember on the history list.
The default value is 500.
HISTTIMEFORMAT
If this variable is set and not null, its value is used as a format string
for
strftime
to print the time stamp associated with each history
entry displayed by the
history
builtin.
If this variable is set, time stamps are written to the history file so
they may be preserved across shell sessions.
HOSTFILE
Contains the name of a file in the same format as
`/etc/hosts'
that
should be read when the shell needs to complete a hostname.
The list of possible hostname completions may be changed while the shell
is running;
the next time hostname completion is attempted after the
value is changed, Bash adds the contents of the new file to the
existing list.
If
HOSTFILE
is set, but has no value, Bash attempts to read
`/etc/hosts'
to obtain the list of possible hostname completions.
When
HOSTFILE
is unset, the hostname list is cleared.
HOSTNAME
The name of the current host.
HOSTTYPE
A string describing the machine Bash is running on.
IGNOREEOF
Controls the action of the shell on receipt of an
EOF
character
as the sole input.  If set, the value denotes the number
of consecutive
EOF
characters that can be read as the
first character on an input line
before the shell will exit.  If the variable exists but does not
have a numeric value (or has no value) then the default is 10.
If the variable does not exist, then
EOF
signifies the end of
input to the shell.  This is only in effect for interactive shells.
INPUTRC
The name of the Readline initialization file, overriding the default
of
`~/.inputrc'
.
LANG
Used to determine the locale category for any category not specifically
selected with a variable starting with
LC_
.
LC_ALL
This variable overrides the value of
LANG
and any other
LC_
variable specifying a locale category.
LC_COLLATE
This variable determines the collation order used when sorting the
results of filename expansion, and
determines the behavior of range expressions, equivalence classes,
and collating sequences within filename expansion and pattern matching
(see section
bashref.html#SEC35
3.5.8 Filename Expansion
).
LC_CTYPE
This variable determines the interpretation of characters and the
behavior of character classes within filename expansion and pattern
matching (see section
bashref.html#SEC35
3.5.8 Filename Expansion
).
LC_MESSAGES
This variable determines the locale used to translate double-quoted
strings preceded by a
`$'
(see section
bashref.html#SEC13
3.1.2.5 Locale-Specific Translation
).
LC_NUMERIC
This variable determines the locale category used for number formatting.
LINENO
The line number in the script or shell function currently executing.
LINES
Used by the
select
builtin command to determine the column length
for printing selection lists.  Automatically set upon receipt of a
SIGWINCH
.
MACHTYPE
A string that fully describes the system type on which Bash
is executing, in the standard GNU
cpu-company-system
format.
MAILCHECK
How often (in seconds) that the shell should check for mail in the
files specified in the
MAILPATH
or
MAIL
variables.
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.
OLDPWD
The previous working directory as set by the
cd
builtin.
OPTERR
If set to the value 1, Bash displays error messages
generated by the
getopts
builtin command.
OSTYPE
A string describing the operating system Bash is running on.
PIPESTATUS
An array variable (see section
bashref.html#SEC81
6.7 Arrays
)
containing a list of exit status values from the processes
in the most-recently-executed foreground pipeline (which may
contain only a single command).
POSIXLY_CORRECT
If this variable is in the environment when
bash
starts, the shell
enters POSIX mode (see section
bashref.html#SEC86
6.11 Bash POSIX Mode
) before reading the
startup files, as if the
`--posix'
invocation option had been supplied.
If it is set while the shell is running,
bash
enables POSIX mode,
as if the command
set -o posix
had been executed.
PPID
The process ID of the shell's parent process.  This variable
is readonly.
PROMPT_COMMAND
If set, the value is interpreted as a command to execute
before the printing of each primary prompt (
$PS1
).
PS3
The value of this variable is used as the prompt for the
select
command.  If this variable is not set, the
select
command prompts with
`#? '
PS4
The value is the prompt printed before the command line is echoed
when the
`-x'
option is set (see section
bashref.html#SEC59
4.3 The Set Builtin
).
The first character of
PS4
is replicated multiple times, as
necessary, to indicate multiple levels of indirection.
The default is
`+ '
.
PWD
The current working directory as set by the
cd
builtin.
RANDOM
Each time this parameter is referenced, a random integer
between 0 and 32767 is generated.  Assigning a value to this
variable seeds the random number generator.
REPLY
The default variable for the
read
builtin.
SECONDS
This variable expands to the number of seconds since the
shell was started.  Assignment to this variable resets
the count to the value assigned, and the expanded value
becomes the value assigned plus the number of seconds
since the assignment.
SHELL
The full pathname to the shell is kept in this environment variable.
If it is not set when the shell starts,
Bash assigns to it the full pathname of the current user's login shell.
SHELLOPTS
A colon-separated list of enabled shell options.  Each word in
the list is a valid argument for the
`-o'
option to the
set
builtin command (see section
bashref.html#SEC59
4.3 The Set Builtin
).
The options appearing in
SHELLOPTS
are those reported
as
`on'
by
`set -o'
.
If this variable is in the environment when Bash
starts up, each shell option in the list will be enabled before
reading any startup files.  This variable is readonly.
SHLVL
Incremented by one each time a new instance of Bash is started.  This is
intended to be a count of how deeply your Bash shells are nested.
TIMEFORMAT
The value of this parameter is used as a format string specifying
how the timing information for pipelines prefixed with the
time
reserved word should be displayed.
The
`%'
character introduces an
escape sequence that is expanded to a time value or other
information.
The escape sequences and their meanings are as
follows; the braces denote optional portions.
%%
A literal
`%'
.
%[
p
][l]R
The elapsed time in seconds.
%[
p
][l]U
The number of CPU seconds spent in user mode.
%[
p
][l]S
The number of CPU seconds spent in system mode.
%P
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
l
specifies a longer format, including minutes, of
the form
MM
m
SS
.
FF
s.
The value of
p
determines whether or not the fraction is included.
If this variable is not set, Bash acts as if it had the value
$'\nreal\t%3lR\nuser\t%3lU\nsys\t%3lS'
If the value is null, no timing information is displayed.
A trailing newline is added when the format string is displayed.
TMOUT
If set to a value greater than zero,
TMOUT
is treated as the
default timeout for the
read
builtin (see section
bashref.html#SEC58
4.2 Bash Builtin Commands
).
The
select
command (see section
bashref.html#SEC21
3.2.4.2 Conditional Constructs
) terminates
if input does not arrive after
TMOUT
seconds when input is coming
from a terminal.
In an interative shell, the value is interpreted as
the number of seconds to wait for input after issuing the primary
prompt when the shell is interactive.
Bash terminates after that number of seconds if input does
not arrive.
UID
The numeric real user id of the current user.  This variable is readonly.
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6. Bash Features
This section describes features unique to Bash.
bashref.html#SEC65
6.1 Invoking Bash
Command line options that you can give
to Bash.
bashref.html#SEC66
6.2 Bash Startup Files
When and how Bash executes scripts.
bashref.html#SEC74
6.3 Interactive Shells
What an interactive shell is.
bashref.html#SEC78
6.4 Bash Conditional Expressions
Primitives used in composing expressions for
the
test
builtin.
bashref.html#SEC79
6.5 Shell Arithmetic
Arithmetic on shell variables.
bashref.html#SEC80
6.6 Aliases
Substituting one command for another.
bashref.html#SEC81
6.7 Arrays
Array Variables.
bashref.html#SEC82
6.8 The Directory Stack
History of visited directories.
bashref.html#SEC84
6.9 Controlling the Prompt
Controlling the PS1 string.
bashref.html#SEC85
6.10 The Restricted Shell
A more controlled mode of shell execution.
bashref.html#SEC86
6.11 Bash POSIX Mode
Making Bash behave more closely to what
the POSIX standard specifies.
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6.1 Invoking Bash
bash [long-opt] [-ir] [-abefhkmnptuvxdBCDHP] [-o
option
] [-O
shopt_option
] [
argument
...
]
bash [long-opt] [-abefhkmnptuvxdBCDHP] [-o
option
] [-O
shopt_option
] -c
string
[
argument
...
]
bash [long-opt] -s [-abefhkmnptuvxdBCDHP] [-o
option
] [-O
shopt_option
] [
argument
...
]
In addition to the single-character shell command-line options
(see section
bashref.html#SEC59
4.3 The Set Builtin
), there are several multi-character
options that you can use.  These options must appear on the command
line before the single-character options to be recognized.
--debugger
Arrange for the debugger profile to be executed before the shell
starts.  Turns on extended debugging mode (see
bashref.html#SEC58
4.2 Bash Builtin Commands
for a description of the
extdebug
option to the
shopt
builtin) and shell function tracing
(see
bashref.html#SEC59
4.3 The Set Builtin
for a description of the
-o functrace
option).
--dump-po-strings
A list of all double-quoted strings preceded by
`$'
is printed on the standard ouput
in the GNU
gettext
PO (portable object) file format.
Equivalent to
`-D'
except for the output format.
--dump-strings
Equivalent to
`-D'
.
--help
Display a usage message on standard output and exit sucessfully.
--init-file
filename
--rcfile
filename
Execute commands from
filename
(instead of
`~/.bashrc'
)
in an interactive shell.
--login
Equivalent to
`-l'
.
--noediting
Do not use the GNU Readline library (see section
bashref.html#SEC91
8. Command Line Editing
)
to read  command lines when the shell is interactive.
--noprofile
Don't load the system-wide startup file
`/etc/profile'
or any of the personal initialization files
`~/.bash_profile'
,
`~/.bash_login'
, or
`~/.profile'
when Bash is invoked as a login shell.
--norc
Don't read the
`~/.bashrc'
initialization file in an
interactive shell.  This is on by default if the shell is
invoked as
sh
.
--posix
Change the behavior of Bash where the default operation differs
from the POSIX 1003.2 standard to match the standard.  This
is intended to make Bash behave as a strict superset of that
standard.  See section
bashref.html#SEC86
6.11 Bash POSIX Mode
, for a description of the Bash
POSIX mode.
--restricted
Make the shell a restricted shell (see section
bashref.html#SEC85
6.10 The Restricted Shell
).
--verbose
Equivalent to
`-v'
.  Print shell input lines as they're read.
--version
Show version information for this instance of
Bash on the standard output and exit successfully.
There are several single-character options that may be supplied at
invocation which are not available with the
set
builtin.
-c
string
Read and execute commands from
string
after processing the
options, then exit.  Any remaining arguments are assigned to the
positional parameters, starting with
$0
.
-i
Force the shell to run interactively.  Interactive shells are
described in
bashref.html#SEC74
6.3 Interactive Shells
.
-l
Make this shell act as if it had been directly invoked by login.
When the shell is interactive, this is equivalent to starting a
login shell with
`exec -l bash'
.
When the shell is not interactive, the login shell startup files will
be executed.
`exec bash -l'
or
`exec bash --login'
will replace the current shell with a Bash login shell.
See section
bashref.html#SEC66
6.2 Bash Startup Files
, for a description of the special behavior
of a login shell.
-r
Make the shell a restricted shell (see section
bashref.html#SEC85
6.10 The Restricted Shell
).
-s
If this option is present, or if no arguments remain after option
processing, then commands are read from the standard input.
This option allows the positional parameters to be set
when invoking an interactive shell.
-D
A list of all double-quoted strings preceded by
`$'
is printed on the standard ouput.
These are the strings that
are subject to language translation when the current locale
is not
C
or
POSIX
(see section
bashref.html#SEC13
3.1.2.5 Locale-Specific Translation
).
This implies the
`-n'
option; no commands will be executed.
[-+]O [
shopt_option
]
shopt_option
is one of the shell options accepted by the
shopt
builtin (see section
bashref.html#SEC56
4. Shell Builtin Commands
).
If
shopt_option
is present,
`-O'
sets the value of that option;
`+O'
unsets it.
If
shopt_option
is not supplied, the names and values of the shell
options accepted by
shopt
are printed on the standard output.
If the invocation option is
`+O'
, the output is displayed in a format
that may be reused as input.
--
A
--
signals the end of options and disables further option
processing.
Any arguments after the
--
are treated as filenames and arguments.
A
login
shell is one whose first character of argument zero is
`-'
, or one invoked with the
`--login'
option.
An
interactive
shell is one started without non-option arguments,
unless
`-s'
is specified,
without specifying the
`-c'
option, and whose input and output are both
connected to terminals (as determined by
isatty(3)
), or one
started with the
`-i'
option.  See section
bashref.html#SEC74
6.3 Interactive Shells
, for more
information.
If arguments remain after option processing, and neither the
`-c'
nor the
`-s'
option has been supplied, the first argument is assumed to
be the name of a file containing shell commands (see section
bashref.html#SEC55
3.8 Shell Scripts
).
When Bash is invoked in this fashion,
$0
is set to the name of the file, and the positional parameters
are set to the remaining arguments.
Bash reads and executes commands from this file, then exits.
Bash's exit status is the exit status of the last command executed
in the script.  If no commands are executed, the exit status is 0.
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6.2 Bash Startup Files
This section describs how Bash executes its startup files.
If any of the files exist but cannot be read, Bash reports an error.
Tildes are expanded in file names as described above under
Tilde Expansion (see section
bashref.html#SEC29
3.5.2 Tilde Expansion
).
Interactive shells are described in
bashref.html#SEC74
6.3 Interactive Shells
.
Invoked as an interactive login shell, or with
`--login'
When Bash is invoked as an interactive login shell, or as a
non-interactive shell with the
`--login'
option, it first reads and
executes commands from the file
`/etc/profile'
, if that file exists.
After reading that file, it looks for
`~/.bash_profile'
,
`~/.bash_login'
, and
`~/.profile'
, in that order, and reads
and executes commands from the first one that exists and is readable.
The
`--noprofile'
option may be used when the shell is started to
inhibit this behavior.
When a login shell exits, Bash reads and executes commands from
the file
`~/.bash_logout'
, if it exists.
Invoked as an interactive non-login shell
When an interactive shell that is not a login shell is started, Bash
reads and executes commands from
`~/.bashrc'
, if that file exists.
This may be inhibited by using the
`--norc'
option.
The
`--rcfile
file
'
option will force Bash to read and
execute commands from
file
instead of
`~/.bashrc'
.
So, typically, your
`~/.bash_profile'
contains the line
if [ -f ~/.bashrc ]; then . ~/.bashrc; fi
after (or before) any login-specific initializations.
Invoked non-interactively
When Bash is started non-interactively, to run a shell script,
for example, it looks for the variable
BASH_ENV
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.  Bash behaves as if the
following command were executed:
if [ -n "$BASH_ENV" ]; then . "$BASH_ENV"; fi
but the value of the
PATH
variable is not used to search for the
file name.
As noted above, if a non-interactive shell is invoked with the
`--login'
option, Bash attempts to read and execute commands from the
login shell startup files.
Invoked with name
sh
If Bash is invoked with the name
sh
, it tries to mimic the
startup behavior of historical versions of
sh
as closely as
possible, while conforming to the POSIX standard as well.
When invoked as an interactive login shell, or as a non-interactive
shell with the
`--login'
option, it first attempts to read
and execute commands from
`/etc/profile'
and
`~/.profile'
, in
that order.
The
`--noprofile'
option may be used to inhibit this behavior.
When invoked as an interactive shell with the name
sh
, Bash
looks for the variable
ENV
, 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
sh
does not attempt to read and execute
commands from any other startup files, the
`--rcfile'
option has
no effect.
A non-interactive shell invoked with the name
sh
does not attempt
to read any other startup files.
When invoked as
sh
, Bash enters POSIX mode after
the startup files are read.
Invoked in POSIX mode
When Bash is started in POSIX mode, as with the
`--posix'
command line option, it follows the POSIX standard
for startup files.
In this mode, interactive shells expand the
ENV
variable
and commands are read and executed from the file whose name is the
expanded value.
No other startup files are read.
Invoked by remote shell daemon
Bash attempts to determine when it is being run by the remote shell
daemon, usually
rshd
.  If Bash 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
sh
.
The
`--norc'
option may be used to inhibit this behavior, and the
`--rcfile'
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.
Invoked with unequal effective and real UID/GIDs
If Bash is started with the effective user (group) id not equal to the
real user (group) id, and the
-p
option is not supplied, no startup
files are read, shell functions are not inherited from the environment,
the
SHELLOPTS
variable, if it appears in the environment, is ignored,
and the effective user id is set to the real user id.
If the
-p
option is supplied at invocation, the startup behavior is
the same, but the effective user id is not reset.
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6.3 Interactive Shells
bashref.html#SEC75
6.3.1 What is an Interactive Shell?
What determines whether a shell is Interactive.
bashref.html#SEC76
6.3.2 Is this Shell Interactive?
How to tell if a shell is interactive.
bashref.html#SEC77
6.3.3 Interactive Shell Behavior
What changes in a interactive shell?
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6.3.1 What is an Interactive Shell?
An interactive shell
is one started without non-option arguments, unless
`-s'
is
specified, without specifiying the
`-c'
option, and
whose input and error output are both
connected to terminals (as determined by
isatty(3)
),
or one started with the
`-i'
option.
An interactive shell generally reads from and writes to a user's
terminal.
The
`-s'
invocation option may be used to set the positional parameters
when an interactive shell is started.
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6.3.2 Is this Shell Interactive?
To determine within a startup script whether or not Bash is
running interactively,
test the value of the
`-'
special parameter.
It contains
i
when the shell is interactive.  For example:
case "$-" in
*i*)	echo This shell is interactive ;;
*)	echo This shell is not interactive ;;
esac
Alternatively, startup scripts may examine the variable
PS1
; it is unset in non-interactive shells, and set in
interactive shells.  Thus:
if [ -z "$PS1" ]; then
echo This shell is not interactive
else
echo This shell is interactive
fi
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6.3.3 Interactive Shell Behavior
When the shell is running interactively, it changes its behavior in
several ways.
Startup files are read and executed as described in
bashref.html#SEC66
6.2 Bash Startup Files
.
Job Control (see section
bashref.html#SEC87
7. Job Control
) is enabled by default.  When job
control is in effect, Bash ignores the keyboard-generated job control
signals
SIGTTIN
,
SIGTTOU
, and
SIGTSTP
.
Bash expands and displays
PS1
before reading the first line
of a command, and expands and displays
PS2
before reading the
second and subsequent lines of a multi-line command.
Bash executes the value of the
PROMPT_COMMAND
variable as a command
before printing the primary prompt,
$PS1
(see section
bashref.html#SEC63
5.2 Bash Variables
).
Readline (see section
bashref.html#SEC91
8. Command Line Editing
) is used to read commands from
the user's terminal.
Bash inspects the value of the
ignoreeof
option to
set -o
instead of exiting immediately when it receives an
EOF
on its
standard input when reading a command (see section
bashref.html#SEC59
4.3 The Set Builtin
).
Command history (see section
bashref.html#SEC116
9.1 Bash History Facilities
)
and history expansion (see section
bashref.html#SEC118
9.3 History Expansion
)
are enabled by default.
Bash will save the command history to the file named by
$HISTFILE
when an interactive shell exits.
Alias expansion (see section
bashref.html#SEC80
6.6 Aliases
) is performed by default.
In the absence of any traps, Bash ignores
SIGTERM
(see section
bashref.html#SEC54
3.7.6 Signals
).
In the absence of any traps,
SIGINT
is caught and handled
((see section
bashref.html#SEC54
3.7.6 Signals
).
SIGINT
will interrupt some shell builtins.
An interactive login shell sends a
SIGHUP
to all jobs on exit
if the
hupoxexit
shell option has been enabled (see section
bashref.html#SEC54
3.7.6 Signals
).
The
`-n'
invocation option is ignored, and
`set -n'
has
no effect (see section
bashref.html#SEC59
4.3 The Set Builtin
).
Bash will check for mail periodically, depending on the values of the
MAIL
,
MAILPATH
, and
MAILCHECK
shell variables
(see section
bashref.html#SEC63
5.2 Bash Variables
).
Expansion errors due to references to unbound shell variables after
`set -u'
has been enabled will not cause the shell to exit
(see section
bashref.html#SEC59
4.3 The Set Builtin
).
The shell will not exit on expansion errors caused by
var
being unset
or null in
${
var
:?
word
}
expansions
(see section
bashref.html#SEC30
3.5.3 Shell Parameter Expansion
).
Redirection errors encountered by shell builtins will not cause the
shell to exit.
When running in POSIX mode, a special builtin returning an error
status will not cause the shell to exit (see section
bashref.html#SEC86
6.11 Bash POSIX Mode
).
A failed
exec
will not cause the shell to exit
(see section
bashref.html#SEC57
4.1 Bourne Shell Builtins
).
Parser syntax errors will not cause the shell to exit.
Simple spelling correction for directory arguments to the
cd
builtin is enabled by default (see the description of the
cdspell
option to the
shopt
builtin in
bashref.html#SEC58
4.2 Bash Builtin Commands
).
The shell will check the value of the
TMOUT
variable and exit
if a command is not read within the specified number of seconds after
printing
$PS1
(see section
bashref.html#SEC63
5.2 Bash Variables
).
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6.4 Bash Conditional Expressions
Conditional expressions are used by the
[[
compound command
and the
test
and
[
builtin commands.
Expressions may be unary or binary.
Unary expressions are often used to examine the status of a file.
There are string operators and numeric comparison operators as well.
If the
file
argument to one of the primaries 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.
-a
file
True if
file
exists.
-b
file
True if
file
exists and is a block special file.
-c
file
True if
file
exists and is a character special file.
-d
file
True if
file
exists and is a directory.
-e
file
True if
file
exists.
-f
file
True if
file
exists and is a regular file.
-g
file
True if
file
exists and its set-group-id bit is set.
-h
file
True if
file
exists and is a symbolic link.
-k
file
True if
file
exists and its "sticky" bit is set.
-p
file
True if
file
exists and is a named pipe (FIFO).
-r
file
True if
file
exists and is readable.
-s
file
True if
file
exists and has a size greater than zero.
-t
fd
True if file descriptor
fd
is open and refers to a terminal.
-u
file
True if
file
exists and its set-user-id bit is set.
-w
file
True if
file
exists and is writable.
-x
file
True if
file
exists and is executable.
-O
file
True if
file
exists and is owned by the effective user id.
-G
file
True if
file
exists and is owned by the effective group id.
-L
file
True if
file
exists and is a symbolic link.
-S
file
True if
file
exists and is a socket.
-N
file
True if
file
exists and has been modified since it was last read.
file1
-nt
file2
True if
file1
is newer (according to modification date)
than
file2
, or if
file1
exists and
file2
does not.
file1
-ot
file2
True if
file1
is older than
file2
,
or if
file2
exists and
file1
does not.
file1
-ef
file2
True if
file1
and
file2
refer to the same device and
inode numbers.
-o
optname
True if shell option
optname
is enabled.
The list of options appears in the description of the
`-o'
option to the
set
builtin (see section
bashref.html#SEC59
4.3 The Set Builtin
).
-z
string
True if the length of
string
is zero.
-n
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
OP
arg2
OP
is one of
`-eq'
,
`-ne'
,
`-lt'
,
`-le'
,
`-gt'
, or
`-ge'
.
These arithmetic binary operators return true if
arg1
is equal to, not equal to, less than, less than or equal to,
greater than, or greater than or equal to
arg2
,
respectively.
Arg1
and
arg2
may be positive or negative integers.
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6.5 Shell Arithmetic
The shell allows arithmetic expressions to be evaluated, as one of
the shell expansions or by the
let
and the
`-i'
option
to the
declare
builtins.
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, associativity, and values
are the same as in the C language.
The following list of operators is grouped into levels of
equal-precedence operators.
The levels are listed in order of decreasing 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 operator
= *= /= %= += -= <<= >>= &= ^= |=
assignment
expr1 , expr2
comma
Shell variables are allowed as operands; parameter expansion is
performed before the expression is evaluated.
Within an expression, shell variables may also be referenced by name
without using the parameter expansion syntax.
A shell variable that is null or unset evaluates to 0 when referenced
by name without using the parameter expansion syntax.
The value of a variable is evaluated as an arithmetic expression
when it is referenced, or when a variable which has been given the
integer
attribute using
`declare -i'
is assigned a value.
A null value evaluates to 0.
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
omitted, 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.
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6.6 Aliases
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
alias
and
unalias
builtin commands.
The first word of each simple 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 characters
`/'
,
`$'
,
``'
,
`='
and any of the
shell metacharacters or quoting characters listed above may not appear
in an alias name.
The replacement text may contain any valid
shell input, including shell metacharacters.
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
ls
to
"ls -F"
,
for instance, and Bash does not try to recursively expand the
replacement text. If the last character of the alias value is a
space or tab character, then the next command word following the
alias is also checked for alias expansion.
Aliases are created and listed with the
alias
command, and removed with the
unalias
command.
There is no mechanism for using arguments in the replacement text,
as in
csh
.
If arguments are needed, a shell function should be used
(see section
bashref.html#SEC23
3.3 Shell Functions
).
Aliases are not expanded when the shell is not interactive,
unless the
expand_aliases
shell option is set using
shopt
(see section
bashref.html#SEC58
4.2 Bash Builtin Commands
).
The rules concerning the definition and use of aliases are
somewhat confusing.  Bash
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 compound 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
alias
in compound commands.
For almost every purpose, shell functions are preferred over aliases.
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6.7 Arrays
Bash provides one-dimensional array variables.  Any variable may be used as
an array; the
declare
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 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
declare -a
name
The syntax
declare -a
name
[
subscript
]
is also accepted; the
subscript
is ignored.  Attributes may be
specified for an array variable using the
declare
and
readonly
builtins.  Each attribute applies to all members of
an array.
Arrays are assigned to using compound assignments of the form
name=(value
1
...
value
n
)
where each
value
is of the form
[[
subscript
]=]
string
.  If
the optional subscript is 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
declare
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 the shell's filename expansion operators.  If the
subscript
is
`@'
or
`*'
, the word expands to all members
of the array
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
IFS
variable, and
${name[@]}
expands each element of
name
to a separate word.  When there are no array members,
${name[@]}
expands to nothing.  This is analogous to the
expansion of the special parameters
`@'
and
`*'
.
${#name[
subscript
]}
expands to the length of
${name[
subscript
]}
.
If
subscript
is
`@'
or
`*'
, the expansion is the number of elements in the array.
Referencing an array variable without a subscript is equivalent to
referencing element zero.
The
unset
builtin is used to destroy arrays.
unset
name
[
subscript
]
destroys the array element at index
subscript
.
unset
name
, where
name
is an array, removes the
entire array. A subscript of
`*'
or
`@'
also removes the
entire array.
The
declare
,
local
, and
readonly
builtins each accept a
`-a'
option to specify an array.  The
read
builtin accepts a
`-a'
option to assign a list of words read from the standard input
to an array, and can read values from the standard input into
individual array elements.  The
set
and
declare
builtins display array values in a way that allows them to be
reused as input.
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6.8 The Directory Stack
bashref.html#SEC83
6.8.1 Directory Stack Builtins
Bash builtin commands to manipulate
the directory stack.
The directory stack is a list of recently-visited directories.  The
pushd
builtin adds directories to the stack as it changes
the current directory, and the
popd
builtin removes specified
directories from the stack and changes the current directory to
the directory removed.  The
dirs
builtin displays the contents
of the directory stack.
The contents of the directory stack are also visible
as the value of the
DIRSTACK
shell variable.
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6.8.1 Directory Stack Builtins
dirs
dirs [+
N
| -
N
] [-clpv]
Display the list of currently remembered directories.  Directories
are added to the list with the
pushd
command; the
popd
command removes directories from the list.
+
N
Displays the
N
th directory (counting from the left of the
list printed by
dirs
when invoked without options), starting
with zero.
-
N
Displays the
N
th directory (counting from the right of the
list printed by
dirs
when invoked without options), starting
with zero.
-c
Clears the directory stack by deleting all of the elements.
-l
Produces a longer listing; the default listing format uses a
tilde to denote the home directory.
-p
Causes
dirs
to print the directory stack with one entry per
line.
-v
Causes
dirs
to print the directory stack with one entry per
line, prefixing each entry with its index in the stack.
popd
popd [+
N
| -
N
] [-n]
Remove the top entry from the directory stack, and
cd
to the new top directory.
When no arguments are given,
popd
removes the top directory from the stack and
performs a
cd
to the new top directory.  The
elements are numbered from 0 starting at the first directory listed with
dirs
; i.e.,
popd
is equivalent to
popd +0
.
+
N
Removes the
N
th directory (counting from the left of the
list printed by
dirs
), starting with zero.
-
N
Removes the
N
th directory (counting from the right of the
list printed by
dirs
), starting with zero.
-n
Suppresses the normal change of directory when removing directories
from the stack, so that only the stack is manipulated.
pushd
pushd [
dir
|
+N
|
-N
] [-n]
Save the current directory on the top of the directory stack
and then
cd
to
dir
.
With no arguments,
pushd
exchanges the top two directories.
+
N
Brings the
N
th directory (counting from the left of the
list printed by
dirs
, starting with zero) to the top of
the list by rotating the stack.
-
N
Brings the
N
th directory (counting from the right of the
list printed by
dirs
, starting with zero) to the top of
the list by rotating the stack.
-n
Suppresses the normal change of directory when adding directories
to the stack, so that only the stack is manipulated.
dir
Makes the current working directory be the top of the stack, and then
executes the equivalent of `
cd
dir
'.
cd
s to
dir
.
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6.9 Controlling the Prompt
The value of the variable
PROMPT_COMMAND
is examined just before
Bash prints each primary prompt.  If
PROMPT_COMMAND
is set and
has a non-null value, then the
value is executed just as if it had been typed on the command line.
In addition, the following table describes the special characters which
can appear in the prompt variables:
\a
A bell character.
\d
The date, in "Weekday Month Date" format (e.g., "Tue May 26").
\D{
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.
\e
An escape character.
\h
The hostname, up to the first `.'.
\H
The hostname.
\j
The number of jobs currently managed by the shell.
\l
The basename of the shell's terminal device name.
\n
A newline.
\r
A carriage return.
\s
The name of the shell, the basename of
$0
(the portion
following the final slash).
\t
The time, in 24-hour HH:MM:SS format.
\T
The time, in 12-hour HH:MM:SS format.
\@
The time, in 12-hour am/pm format.
\A
The time, in 24-hour HH:MM format.
\u
The username of the current user.
\v
The version of Bash (e.g., 2.00)
\V
The release of Bash, version + patchlevel (e.g., 2.00.0)
\w
The current working directory, with
$HOME
abbreviated with a tilde.
\W
The basename of
$PWD
, with
$HOME
abbreviated with a tilde.
\!
The history number of this command.
\#
The command number of this command.
\$
If the effective uid is 0,
#
, otherwise
$
.
\
nnn
The character whose ASCII code is the octal value
nnn
.
\\
A backslash.
\[
Begin a sequence of non-printing characters.  This could be used to
embed a terminal control sequence into the prompt.
\]
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 may include commands restored from the history file
(see section
bashref.html#SEC116
9.1 Bash History Facilities
), 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 substitution, arithmetic
expansion, and quote removal, subject to the value of the
promptvars
shell option (see section
bashref.html#SEC58
4.2 Bash Builtin Commands
).
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6.10 The Restricted Shell
If Bash is started with the name
rbash
, or the
`--restricted'
or
`-r'
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.
A restricted shell behaves identically to
bash
with the exception that the following are disallowed or not performed:
Changing directories with the
cd
builtin.
Setting or unsetting the values of the
SHELL
,
PATH
,
ENV
, or
BASH_ENV
variables.
Specifying command names containing slashes.
Specifying a filename containing a slash as an argument to the
.
builtin command.
Specifying a filename containing a slash as an argument to the
`-p'
option to the
hash
builtin command.
Importing function definitions from the shell environment at startup.
Parsing the value of
SHELLOPTS
from the shell environment at startup.
Redirecting output using the
`>'
,
`>|'
,
`<>'
,
`>&'
,
`&>'
, and
`>>'
redirection operators.
Using the
exec
builtin to replace the shell with another command.
Adding or deleting builtin commands with the
`-f'
and
`-d'
options to the
enable
builtin.
Using the
enable
builtin command to enable disabled shell builtins.
Specifying the
`-p'
option to the
command
builtin.
Turning off restricted mode with
`set +r'
or
`set +o restricted'
.
These restrictions are enforced after any startup files are read.
When a command that is found to be a shell script is executed
(see section
bashref.html#SEC55
3.8 Shell Scripts
),
rbash
turns off any restrictions in
the shell spawned to execute the script.
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6.11 Bash POSIX Mode
Starting Bash with the
`--posix'
command-line option or executing
`set -o posix'
while Bash is running will cause Bash to conform more
closely to the POSIX 1003.2 standard by changing the behavior to
match that specified by POSIX in areas where the Bash default differs.
When invoked as
sh
, Bash enters POSIX mode after reading the
startup files.
The following list is what's changed when `POSIX mode' is in effect:
When a command in the hash table no longer exists, Bash will re-search
$PATH
to find the new location.  This is also available with
`shopt -s checkhash'
.
The message printed by the job control code and builtins when a job
exits with a non-zero status is `Done(status)'.
The message printed by the job control code and builtins when a job
is stopped is `Stopped(
signame
)', where
signame
is, for
example,
SIGTSTP
.
Reserved words may not be aliased.
The POSIX 1003.2
PS1
and
PS2
expansions of
`!'
to
the history number and
`!!'
to
`!'
are enabled,
and parameter expansion is performed on the values of
PS1
and
PS2
regardless of the setting of the
promptvars
option.
The POSIX 1003.2 startup files are executed (
$ENV
) rather than
the normal Bash files.
Tilde expansion is only performed on assignments preceding a command
name, rather than on all assignment statements on the line.
The default history file is
`~/.sh_history'
(this is the
default value of
$HISTFILE
).
The output of
`kill -l'
prints all the signal names on a single line,
separated by spaces, without the
`SIG'
prefix.
The
kill
builtin does not accept signal names with a
`SIG'
prefix.
Non-interactive shells exit if
filename
in
.
filename
is not found.
Non-interactive shells exit if a syntax error in an arithmetic expansion
results in an invalid expression.
Redirection operators do not perform filename expansion on the word
in the redirection unless the shell is interactive.
Redirection operators do not perform word splitting on the word in the
redirection.
Function names must be valid shell
name
s.  That is, they may not
contain characters other than letters, digits, and underscores, and
may not start with a digit.  Declaring a function with an invalid name
causes a fatal syntax error in non-interactive shells.
POSIX 1003.2 `special' builtins are found before shell functions
during command lookup.
If a POSIX 1003.2 special builtin returns an error status, a
non-interactive shell exits.  The fatal errors are those listed in
the POSIX.2 standard, and include things like passing incorrect options,
redirection errors, variable assignment errors for assignments preceding
the command name, and so on.
If the
cd
builtin finds a directory to change to
using
$CDPATH
, the
value it assigns to the
PWD
variable does not contain any
symbolic links, as if
`cd -P'
had been executed.
If
CDPATH
is set, the
cd
builtin will not implicitly
append the current directory to it.  This means that
cd
will
fail if no valid directory name can be constructed from
any of the entries in
$CDPATH
, even if the a directory with
the same name as the name given as an argument to
cd
exists
in the current directory.
A non-interactive shell exits with an error status if a variable
assignment error occurs when no command name follows the assignment
statements.
A variable assignment error occurs, for example, when trying to assign
a value to a readonly variable.
A non-interactive shell exits with an error status if the iteration
variable in a
for
statement or the selection variable in a
select
statement is a readonly variable.
Process substitution is not available.
Assignment statements preceding POSIX 1003.2 special builtins
persist in the shell environment after the builtin completes.
Assignment statements preceding shell function calls persist in the
shell environment after the function returns, as if a POSIX
special builtin command had been executed.
The
export
and
readonly
builtin commands display their
output in the format required by POSIX 1003.2.
The
trap
builtin displays signal names without the leading
SIG
.
The
trap
builtin doesn't check the first argument for a possible
signal specification and revert the signal handling to the original
disposition if it is, unless that argument consists solely of digits and
is a valid signal number.  If users want to reset the handler for a given
signal to the original disposition, they should use
`-'
as the
first argument.
The
.
and
source
builtins do not search the current directory
for the filename argument if it is not found by searching
PATH
.
Subshells spawned to execute command substitutions inherit the value of
the
`-e'
option from the parent shell.  When not in POSIX mode,
Bash clears the
`-e'
option in such subshells.
Alias expansion is always enabled, even in non-interactive shells.
When the
alias
builtin displays alias definitions, it does not
display them with a leading
`alias '
unless the
`-p'
option
is supplied.
When the
set
builtin is invoked without options, it does not display
shell function names and definitions.
When the
set
builtin is invoked without options, it displays
variable values without quotes, unless they contain shell metacharacters,
even if the result contains nonprinting characters.
When the
cd
builtin is invoked in
logical
mode, and the pathname
constructed from
$PWD
and the directory name supplied as an argument
does not refer to an existing directory,
cd
will fail instead of
falling back to
physical
mode.
There is other POSIX 1003.2 behavior that Bash does not implement.
Specifically:
Assignment statements affect the execution environment of all
builtins, not just special ones.
When a subshell is created to execute a shell script with execute permission,
but without a leading
`#!'
, Bash sets
$0
to the full pathname of
the script as found by searching
$PATH
, rather than the command as
typed by the user.
When using
`.'
to source a shell script found in
$PATH
, bash
checks execute permission bits rather than read permission bits, just as
if it were searching for a command.
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7. Job Control
This chapter discusses what job control is, how it works, and how
Bash allows you to access its facilities.
bashref.html#SEC88
7.1 Job Control Basics
How job control works.
bashref.html#SEC89
7.2 Job Control Builtins
Bash builtin commands used to interact
with job control.
bashref.html#SEC90
7.3 Job Control Variables
Variables Bash uses to customize job
control.
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7.1 Job Control Basics
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 Bash.
The shell associates a
job
with each pipeline.  It keeps a
table of currently executing jobs, which may be listed with the
jobs
command.  When Bash starts a job
asynchronously, 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.  Bash 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
SIGINT
.
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-generated
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
SIGTTIN
(
SIGTTOU
) signal by the terminal driver, which, unless
caught, suspends the process.
If the operating system on which Bash is running supports
job control, Bash contains facilities to use it.  Typing the
suspend
character (typically
`^Z'
, Control-Z) while a
process is running causes that process to be stopped and returns
control to Bash.  Typing the
delayed suspend
character
(typically
`^Y'
, Control-Y) causes the process to be stopped
when it attempts to read input from the terminal, and control to
be returned to Bash.  The user then manipulates the state of
this job, using the
bg
command to continue it in the
background, the
fg
command to continue it in the
foreground, or the
kill
command to kill it.  A
`^Z'
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
character
`%'
introduces a job name.
Job number
n
may be referred to as
`%n'
.
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 background.  The
previous job may be referenced using
`%-'
.  In output
pertaining to jobs (e.g., the output of the
jobs
command),
the current job is always flagged with a
`+'
, and the
previous job with a
`-'
.
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 example,
`%ce'
refers
to a stopped
ce
job. Using
`%?ce'
, on the
other hand, refers to any job containing the string
`ce'
in
its command line.  If the prefix or substring matches more than one job,
Bash reports an error.
Simply naming a job can be used to bring it into the foreground:
`%1'
is a synonym for
`fg %1'
, bringing job 1 from the
background into the foreground.  Similarly,
`%1 &'
resumes
job 1 in the background, equivalent to
`bg %1'
The shell learns immediately whenever a job changes state.
Normally, Bash 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
`-b'
option to the
set
builtin is enabled,
Bash reports such changes immediately (see section
bashref.html#SEC59
4.3 The Set Builtin
).
Any trap on
SIGCHLD
is executed for each child process
that exits.
If an attempt to exit Bash is made while jobs are stopped, the
shell prints a message warning that there are stopped jobs.
The
jobs
command may then be used to inspect their status.
If a second attempt to exit is made without an intervening command,
Bash does not print another warning, and the stopped jobs are terminated.
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7.2 Job Control Builtins
bg
bg [
jobspec
]
Resume the suspended job
jobspec
in the background, as if it
had been started with
`&'
.
If
jobspec
is not supplied, the current job is used.
The return status is zero unless it is run when job control is not
enabled, or, when run with job control enabled, if
jobspec
was
not found or
jobspec
specifies a job that was started without
job control.
fg
fg [
jobspec
]
Resume the job
jobspec
in the foreground and make it the current job.
If
jobspec
is not supplied, the current job is used.
The return status is that of the command placed into the foreground,
or non-zero if run when job control is disabled or, when run with
job control enabled,
jobspec
does not specify a valid job or
jobspec
specifies a job that was started without job control.
jobs
jobs [-lnprs] [
jobspec
]
jobs -x
command
[
arguments
]
The first form lists the active jobs.  The options have the
following meanings:
-l
List process IDs in addition to the normal information.
-n
Display information only about jobs that have changed status since
the user was last notified of their status.
-p
List only the process ID of the job's process group leader.
-r
Restrict output to running jobs.
-s
Restrict output to stopped jobs.
If
jobspec
is given,
output is restricted to information about that job.
If
jobspec
is not supplied, the status of all jobs is
listed.
If the
`-x'
option is supplied,
jobs
replaces any
jobspec
found in
command
or
arguments
with the
corresponding process group ID, and executes
command
,
passing it
argument
s, returning its exit status.
kill
kill [-s
sigspec
] [-n
signum
] [-
sigspec
]
jobspec
or
pid
kill -l [
exit_status
]
Send a signal specified by
sigspec
or
signum
to the process
named by job specification
jobspec
or process ID
pid
.
sigspec
is either a case-insensitive signal name such as
SIGINT
(with or without the
SIG
prefix)
or a signal number;
signum
is a signal number.
If
sigspec
and
signum
are not present,
SIGTERM
is used.
The
`-l'
option lists the signal names.
If any arguments are supplied when
`-l'
is given, the names of the
signals corresponding to the arguments are listed, and the return status
is zero.
exit_status
is a number specifying a signal number or the exit
status of a process terminated by a signal.
The return status is zero if at least one signal was successfully sent,
or non-zero if an error occurs or an invalid option is encountered.
wait
wait [
jobspec
or
pid
]
Wait until the child process specified by process ID
pid
or job
specification
jobspec
exits and return the exit status of the last
command waited for.
If a job spec is given, all processes in the job are waited for.
If no arguments are given, all currently active child processes are
waited for, and the return status is zero.
If neither
jobspec
nor
pid
specifies an active child process
of the shell, the return status is 127.
disown
disown [-ar] [-h] [
jobspec
...
]
Without options, each
jobspec
is removed from the table of
active jobs.
If the
`-h'
option is given, the job is not removed from the table,
but is marked so that
SIGHUP
is not sent to the job if the shell
receives a
SIGHUP
.
If
jobspec
is not present, and neither the
`-a'
nor
`-r'
option is supplied, the current job is used.
If no
jobspec
is supplied, the
`-a'
option means to remove or
mark all jobs; the
`-r'
option without a
jobspec
argument restricts operation to running jobs.
suspend
suspend [-f]
Suspend the execution of this shell until it receives a
SIGCONT
signal.  The
`-f'
option means to suspend
even if the shell is a login shell.
When job control is not active, the
kill
and
wait
builtins do not accept
jobspec
arguments.  They must be
supplied process IDs.
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7.3 Job Control Variables
auto_resume
This variable controls how the shell interacts with the user and
job control.  If this variable exists then single word simple
commands without redirections are treated as candidates for resumption
of an existing job.  There is no ambiguity allowed; if there is
more than one job beginning with the string typed, then
the most recently accessed job will be selected.
The name of a stopped job, in this context, is the command line
used to start it.  If this variable is set to the value
`exact'
,
the string supplied must match the name of a stopped job exactly;
if set to
`substring'
,
the string supplied needs to match a substring of the name of a
stopped job.  The
`substring'
value provides functionality
analogous to the
`%?'
job ID (see section
bashref.html#SEC88
7.1 Job Control Basics
).
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 ID.
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8. Command Line Editing
This chapter describes the basic features of the GNU
command line editing interface.
Command line editing is provided by the Readline library, which is
used by several different programs, including Bash.
bashref.html#SEC92
8.1 Introduction to Line Editing
Notation used in this text.
bashref.html#SEC93
8.2 Readline Interaction
The minimum set of commands for editing a line.
bashref.html#SEC99
8.3 Readline Init File
Customizing Readline from a user's view.
bashref.html#SEC103
8.4 Bindable Readline Commands
A description of most of the Readline commands
available for binding
bashref.html#SEC112
8.5 Readline vi Mode
A short description of how to make Readline
behave like the vi editor.
bashref.html#SEC113
8.6 Programmable Completion
How to specify the possible completions for
a specific command.
bashref.html#SEC114
8.7 Programmable Completion Builtins
Builtin commands to specify how to
complete arguments for a particular command.
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8.1 Introduction to Line Editing
The following paragraphs describe the notation used to represent
keystrokes.
The text
C-k
is read as `Control-K' and describes the character
produced when the
k
key is pressed while the Control key
is depressed.
The text
M-k
is read as `Meta-K' and describes the character
produced when the Meta key (if you have one) is depressed, and the
k
key is pressed.
The Meta key is labeled
ALT
on many keyboards.
On keyboards with two keys labeled
ALT
(usually to either side of
the space bar), the
ALT
on the left side is generally set to
work as a Meta key.
The
ALT
key on the right may also be configured to work as a
Meta key or may be configured as some other modifier, such as a
Compose key for typing accented characters.
If you do not have a Meta or
ALT
key, or another key working as
a Meta key, the identical keystroke can be generated by typing
ESC
first
, and then typing
k
.
Either process is known as
metafying
the
k
key.
The text
M-C-k
is read as `Meta-Control-k' and describes the
character produced by
metafying
C-k
.
In addition, several keys have their own names.  Specifically,
DEL
,
ESC
,
LFD
,
SPC
,
RET
, and
TAB
all
stand for themselves when seen in this text, or in an init file
(see section
bashref.html#SEC99
8.3 Readline Init File
).
If your keyboard lacks a
LFD
key, typing
C-j
will
produce the desired character.
The
RET
key may be labeled
Return
or
Enter
on
some keyboards.
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8.2 Readline Interaction
Often during an interactive session you type in a long line of text,
only to notice that the first word on the line is misspelled.  The
Readline library gives you a set of commands for manipulating the text
as you type it in, allowing you to just fix your typo, and not forcing
you to retype the majority of the line.  Using these editing commands,
you move the cursor to the place that needs correction, and delete or
insert the text of the corrections.  Then, when you are satisfied with
the line, you simply press
RET
.  You do not have to be at the
end of the line to press
RET
; the entire line is accepted
regardless of the location of the cursor within the line.
bashref.html#SEC94
8.2.1 Readline Bare Essentials
The least you need to know about Readline.
bashref.html#SEC95
8.2.2 Readline Movement Commands
Moving about the input line.
bashref.html#SEC96
8.2.3 Readline Killing Commands
How to delete text, and how to get it back!
bashref.html#SEC97
8.2.4 Readline Arguments
Giving numeric arguments to commands.
bashref.html#SEC98
8.2.5 Searching for Commands in the History
Searching through previous lines.
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8.2.1 Readline Bare Essentials
In order to enter characters into the line, simply type them.  The typed
character appears where the cursor was, and then the cursor moves one
space to the right.  If you mistype a character, you can use your
erase character to back up and delete the mistyped character.
Sometimes you may mistype a character, and
not notice the error until you have typed several other characters.  In
that case, you can type
C-b
to move the cursor to the left, and then
correct your mistake.  Afterwards, you can move the cursor to the right
with
C-f
.
When you add text in the middle of a line, you will notice that characters
to the right of the cursor are `pushed over' to make room for the text
that you have inserted.  Likewise, when you delete text behind the cursor,
characters to the right of the cursor are `pulled back' to fill in the
blank space created by the removal of the text.  A list of the bare
essentials for editing the text of an input line follows.
C-b
Move back one character.
C-f
Move forward one character.
DEL
or
Backspace
Delete the character to the left of the cursor.
C-d
Delete the character underneath the cursor.
Printing characters
Insert the character into the line at the cursor.
C-_
or
C-x C-u
Undo the last editing command.  You can undo all the way back to an
empty line.
(Depending on your configuration, the
Backspace
key be set to
delete the character to the left of the cursor and the
DEL
key set
to delete the character underneath the cursor, like
C-d
, rather
than the character to the left of the cursor.)
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8.2.2 Readline Movement Commands
The above table describes the most basic keystrokes that you need
in order to do editing of the input line.  For your convenience, many
other commands have been added in addition to
C-b
,
C-f
,
C-d
, and
DEL
.  Here are some commands for moving more rapidly
about the line.
C-a
Move to the start of the line.
C-e
Move to the end of the line.
M-f
Move forward a word, where a word is composed of letters and digits.
M-b
Move backward a word.
C-l
Clear the screen, reprinting the current line at the top.
Notice how
C-f
moves forward a character, while
M-f
moves
forward a word.  It is a loose convention that control keystrokes
operate on characters while meta keystrokes operate on words.
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8.2.3 Readline Killing Commands
Killing
text means to delete the text from the line, but to save
it away for later use, usually by
yanking
(re-inserting)
it back into the line.
(`Cut' and `paste' are more recent jargon for `kill' and `yank'.)
If the description for a command says that it `kills' text, then you can
be sure that you can get the text back in a different (or the same)
place later.
When you use a kill command, the text is saved in a
kill-ring
.
Any number of consecutive kills save all of the killed text together, so
that when you yank it back, you get it all.  The kill
ring is not line specific; the text that you killed on a previously
typed line is available to be yanked back later, when you are typing
another line.
Here is the list of commands for killing text.
C-k
Kill the text from the current cursor position to the end of the line.
M-d
Kill from the cursor 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
M-f
.
M-
DEL
Kill from the cursor the start of the current word, or, if between
words, to the start of the previous word.
Word boundaries are the same as those used by
M-b
.
C-w
Kill from the cursor to the previous whitespace.  This is different than
M-
DEL
because the word boundaries differ.
Here is how to
yank
the text back into the line.  Yanking
means to copy the most-recently-killed text from the kill buffer.
C-y
Yank the most recently killed text back into the buffer at the cursor.
M-y
Rotate the kill-ring, and yank the new top.  You can only do this if
the prior command is
C-y
or
M-y
.
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8.2.4 Readline Arguments
You can pass numeric arguments to Readline commands.  Sometimes the
argument acts as a repeat count, other times it is the
sign
of the
argument that is significant.  If you pass a negative argument to a
command which normally acts in a forward direction, that command will
act in a backward direction.  For example, to kill text back to the
start of the line, you might type
`M-- C-k'
.
The general way to pass numeric arguments to a command is to type meta
digits before the command.  If the first `digit' typed is a minus
sign (
`-'
), then the sign of the argument will be negative.  Once
you have typed one meta digit to get the argument started, you can type
the remainder of the digits, and then the command.  For example, to give
the
C-d
command an argument of 10, you could type
`M-1 0 C-d'
,
which will delete the next ten characters on the input line.
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8.2.5 Searching for Commands in the History
Readline provides commands for searching through the command history
(see section
bashref.html#SEC116
9.1 Bash History Facilities
)
for lines containing a specified string.
There are 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, Readline 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.
To search backward in the history for a particular string, type
C-r
.  Typing
C-s
searches forward through the history.
The characters present in the value of the
isearch-terminators
variable
are used to terminate an incremental search.
If that variable has not been assigned a value, the
ESC
and
C-J
characters will terminate an incremental search.
C-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
C-r
or
C-s
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
RET
will terminate the search and accept
the line, thereby executing the command from the history list.
A movement command will terminate the search, make the last line found
the current line, and begin editing.
Readline remembers the last incremental search string.  If two
C-r
s 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.
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8.3 Readline Init File
Although the Readline library comes with a set of Emacs-like
keybindings installed by default, it is possible to use a different set
of keybindings.
Any user can customize programs that use Readline by putting
commands in an
inputrc
file, conventionally in his home directory.
The name of this
file is taken from the value of the shell variable
INPUTRC
.  If
that variable is unset, Readline will read both
`/etc/inputrc'
and
`~/.inputrc'
.
When a program which uses the Readline library starts up, the
init file is read, and the key bindings are set.
In addition, the
C-x C-r
command re-reads this init file, thus
incorporating any changes that you might have made to it.
bashref.html#SEC100
8.3.1 Readline Init File Syntax
Syntax for the commands in the inputrc file.
bashref.html#SEC101
8.3.2 Conditional Init Constructs
Conditional key bindings in the inputrc file.
bashref.html#SEC102
8.3.3 Sample Init File
An example inputrc file.
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8.3.1 Readline Init File Syntax
There are only a few basic constructs allowed in the
Readline init file.  Blank lines are ignored.
Lines beginning with a
`#'
are comments.
Lines beginning with a
`$'
indicate conditional
constructs (see section
bashref.html#SEC101
8.3.2 Conditional Init Constructs
).  Other lines
denote variable settings and key bindings.
Variable Settings
You can modify the run-time behavior of Readline by
altering the values of variables in Readline
using the
set
command within the init file.
The syntax is simple:
set
variable
value
Here, for example, is how to
change from the default Emacs-like key binding to use
vi
line editing commands:
set editing-mode vi
Variable names and values, where appropriate, are recognized without regard
to case.
The
bind -V
command lists the current Readline variable names
and values.  See section
bashref.html#SEC58
4.2 Bash Builtin Commands
.
A great deal of run-time behavior is changeable with the following
variables.
bell-style
Controls what happens when Readline wants to ring the terminal bell.
If set to
`none'
, Readline never rings the bell.  If set to
`visible'
, Readline uses a visible bell if one is available.
If set to
`audible'
(the default), Readline attempts to ring
the terminal's bell.
comment-begin
The string to insert at the beginning of the line when the
insert-comment
command is executed.  The default value
is
"#"
.
completion-ignore-case
If set to
`on'
, Readline performs filename matching and completion
in a case-insensitive fashion.
The default value is
`off'
.
completion-query-items
The number of possible completions that determines when the user is
asked whether the list of possibilities should be displayed.
If the number of possible completions is greater than this value,
Readline will ask the user whether or not he wishes to view
them; otherwise, they are simply listed.
This variable must be set to an integer value greater than or equal to 0.
The default limit is
100
.
convert-meta
If set to
`on'
, Readline will convert characters with the
eighth bit set to an ASCII key sequence by stripping the eighth
bit and prefixing an
ESC
character, converting them to a
meta-prefixed key sequence.  The default value is
`on'
.
disable-completion
If set to
`On'
, Readline will inhibit word completion.
Completion  characters will be inserted into the line as if they had
been mapped to
self-insert
.  The default is
`off'
.
editing-mode
The
editing-mode
variable controls which default set of
key bindings is used.  By default, Readline starts up in Emacs editing
mode, where the keystrokes are most similar to Emacs.  This variable can be
set to either
`emacs'
or
`vi'
.
enable-keypad
When set to
`on'
, Readline will try to enable the application
keypad when it is called.  Some systems need this to enable the
arrow keys.  The default is
`off'
.
expand-tilde
If set to
`on'
, tilde expansion is performed when Readline
attempts word completion.  The default is
`off'
.
If set to
`on'
, the history code attempts to place point at the
same location on each history line retrieved with
previous-history
or
next-history
.
horizontal-scroll-mode
This variable can be set to either
`on'
or
`off'
.  Setting it
to
`on'
means that the text of the lines being edited will scroll
horizontally on a single screen line when they are longer than the width
of the screen, instead of wrapping onto a new screen line.  By default,
this variable is set to
`off'
.
input-meta
If set to
`on'
, Readline will enable eight-bit input (it
will not clear the eighth bit in the characters it reads),
regardless of what the terminal claims it can support.  The
default value is
`off'
.  The name
meta-flag
is a
synonym for this variable.
isearch-terminators
The string of characters that should terminate an incremental search without
subsequently executing the character as a command (see section
bashref.html#SEC98
8.2.5 Searching for Commands in the History
).
If this variable has not been given a value, the characters
ESC
and
C-J
will terminate an incremental search.
keymap
Sets Readline's idea of the current keymap for key binding commands.
Acceptable
keymap
names are
emacs
,
emacs-standard
,
emacs-meta
,
emacs-ctlx
,
vi
,
vi-move
,
vi-command
, and
vi-insert
.
vi
is equivalent to
vi-command
;
emacs
is
equivalent to
emacs-standard
.  The default value is
emacs
.
The value of the
editing-mode
variable also affects the
default keymap.
mark-directories
If set to
`on'
, completed directory names have a slash
appended.  The default is
`on'
.
mark-modified-lines
This variable, when set to
`on'
, causes Readline to display an
asterisk (
`*'
) at the start of history lines which have been modified.
This variable is
`off'
by default.
mark-symlinked-directories
If set to
`on'
, completed names which are symbolic links
to directories have a slash appended (subject to the value of
mark-directories
).
The default is
`off'
.
match-hidden-files
This variable, when set to
`on'
, 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.
This variable is
`on'
by default.
output-meta
If set to
`on'
, Readline will display characters with the
eighth bit set directly rather than as a meta-prefixed escape
sequence.  The default is
`off'
.
page-completions
If set to
`on'
, Readline uses an internal
more
-like pager
to display a screenful of possible completions at a time.
This variable is
`on'
by default.
print-completions-horizontally
If set to
`on'
, Readline will display completions with matches
sorted horizontally in alphabetical order, rather than down the screen.
The default is
`off'
.
show-all-if-ambiguous
This alters the default behavior of the completion functions.  If
set to
`on'
,
words which have more than one possible completion cause the
matches to be listed immediately instead of ringing the bell.
The default value is
`off'
.
show-all-if-unmodified
This alters the default behavior of the completion functions in
a fashion similar to
show-all-if-ambiguous
.
If set to
`on'
,
words which have more than one possible completion without any
possible partial completion (the possible completions don't share
a common prefix) cause the matches to be listed immediately instead
of ringing the bell.
The default value is
`off'
.
visible-stats
If set to
`on'
, a character denoting a file's type
is appended to the filename when listing possible
completions.  The default is
`off'
.
Key Bindings
The syntax for controlling key bindings in the init file is
simple.  First you need to find the name of the command that you
want to change.  The following sections contain tables of the command
name, the default keybinding, if any, and a short description of what
the command does.
Once you know the name of the command, simply place on a line
in the init file the name of the key
you wish to bind the command to, a colon, and then the name of the
command.  The name of the key
can be expressed in different ways, depending on what you find most
comfortable.
In addition to command names, readline allows keys to be bound
to a string that is inserted when the key is pressed (a
macro
).
The
bind -p
command displays Readline function names and
bindings in a format that can put directly into an initialization file.
See section
bashref.html#SEC58
4.2 Bash Builtin Commands
.
keyname
:
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
universal-argument
,
M-DEL
is bound to the function
backward-kill-word
, 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).
A number of symbolic character names are recognized while
processing this key binding syntax:
DEL
,
ESC
,
ESCAPE
,
LFD
,
NEWLINE
,
RET
,
RETURN
,
RUBOUT
,
SPACE
,
SPC
,
and
TAB
.
"
keyseq
":
function-name
or
macro
keyseq
differs from
keyname
above in that strings
denoting an entire key sequence can be specified, by placing
the key sequence in double quotes.  Some GNU Emacs style key
escapes can be used, as in the following example, but the
special character names are not recognized.
"\C-u": universal-argument
"\C-x\C-r": re-read-init-file
"\e[11~": "Function Key 1"
In the above example,
C-u
is again bound to the function
universal-argument
(just as it was in the first example),
`
C-x
C-r
'
is bound to the function
re-read-init-file
,
and
`
ESC
[
1
1
~
'
is bound to insert
the text
`Function Key 1'
.
The following GNU Emacs style escape sequences are available when
specifying key sequences:
\C-
control prefix
\M-
meta prefix
\e
an escape character
\\
backslash
\"
"
, a double quotation mark
\'
'
, a single quote or apostrophe
In addition to the GNU Emacs style escape sequences, a second
set of backslash escapes is available:
\a
alert (bell)
\b
backspace
\d
delete
\f
form feed
\n
newline
\r
carriage return
\t
horizontal tab
\v
vertical tab
\
nnn
the eight-bit character whose value is the octal value
nnn
(one to three digits)
\x
HH
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 function name.
In the macro body, the backslash escapes described above are expanded.
Backslash will quote any other character in the macro text,
including
`"'
and
`''
.
For example, the following binding will make
`
C-x
\'
insert a single
`\'
into the line:
"\C-x\\": "\\"
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8.3.2 Conditional Init Constructs
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.
$if
The
$if
construct allows bindings to be made based on the
editing mode, the terminal being used, or the application using
Readline.  The text of the test extends to the end of the line;
no characters are required to isolate it.
mode
The
mode=
form of the
$if
directive is used to test
whether Readline is in
emacs
or
vi
mode.
This may be used in conjunction
with the
`set keymap'
command, for instance, to set bindings in
the
emacs-standard
and
emacs-ctlx
keymaps only if
Readline is starting out in
emacs
mode.
term
The
term=
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 both the full name of the terminal and
the portion of the terminal name before the first
`-'
.  This
allows
sun
to match both
sun
and
sun-cmd
,
for instance.
application
The
application
construct is used to include
application-specific settings.  Each program using the Readline
library sets the
application name
, and you 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:
$if Bash
# Quote the current or previous word
"\C-xq": "\eb\"\ef\""
$endif
$endif
This command, as seen in the previous example, terminates an
$if
command.
$else
Commands in this branch of the
$if
directive are executed if
the test fails.
$include
This directive takes a single filename as an argument and reads commands
and bindings from that file.
For example, the following directive reads from
`/etc/inputrc'
:
$include /etc/inputrc
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8.3.3 Sample Init File
Here is an example of an
inputrc
file.  This illustrates key
binding, variable assignment, and conditional syntax.
# This file controls the behaviour of line input editing for
# programs that use the GNU Readline library.  Existing
# programs include FTP, Bash, and GDB.
#
# You can re-read the inputrc file with C-x C-r.
# Lines beginning with '#' are comments.
#
# First, include any systemwide bindings and variable
# assignments from /etc/Inputrc
$include /etc/Inputrc
#
# Set various bindings for emacs mode.
set editing-mode emacs
$if mode=emacs
Meta-Control-h:	backward-kill-word	Text after the function name is ignored
#
# Arrow keys in keypad mode
#
#"\M-OD":        backward-char
#"\M-OC":        forward-char
#"\M-OA":        previous-history
#"\M-OB":        next-history
#
# Arrow keys in ANSI mode
#
"\M-[D":        backward-char
"\M-[C":        forward-char
"\M-[A":        previous-history
"\M-[B":        next-history
#
# Arrow keys in 8 bit keypad mode
#
#"\M-\C-OD":       backward-char
#"\M-\C-OC":       forward-char
#"\M-\C-OA":       previous-history
#"\M-\C-OB":       next-history
#
# Arrow keys in 8 bit ANSI mode
#
#"\M-\C-[D":       backward-char
#"\M-\C-[C":       forward-char
#"\M-\C-[A":       previous-history
#"\M-\C-[B":       next-history
C-q: quoted-insert
$endif
# An old-style binding.  This happens to be the default.
TAB: complete
# Macros that are convenient for shell interaction
$if Bash
# edit the path
"\C-xp": "PATH=${PATH}\e\C-e\C-a\ef\C-f"
# prepare to type a quoted word --
# insert open and close double quotes
# and move to just after the open quote
"\C-x\"": "\"\"\C-b"
# insert a backslash (testing backslash escapes
# in sequences and macros)
"\C-x\\": "\\"
# Quote the current or previous word
"\C-xq": "\eb\"\ef\""
# Add a binding to refresh the line, which is unbound
"\C-xr": redraw-current-line
# Edit variable on current line.
"\M-\C-v": "\C-a\C-k$\C-y\M-\C-e\C-a\C-y="
$endif
# use a visible bell if one is available
set bell-style visible
# don't strip characters to 7 bits when reading
set input-meta on
# allow iso-latin1 characters to be inserted rather
# than converted to prefix-meta sequences
set convert-meta off
# display characters with the eighth bit set directly
# rather than as meta-prefixed characters
set output-meta on
# if there are more than 150 possible completions for
# a word, ask the user if he wants to see all of them
set completion-query-items 150
# For FTP
$if Ftp
"\C-xg": "get \M-?"
"\C-xt": "put \M-?"
"\M-.": yank-last-arg
$endif
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8.4 Bindable Readline Commands
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8.4.1 Commands For Moving
Moving about the line.
bashref.html#SEC105
8.4.2 Commands For Manipulating The History
Getting at previous lines.
bashref.html#SEC106
8.4.3 Commands For Changing Text
Commands for changing text.
bashref.html#SEC107
8.4.4 Killing And Yanking
Commands for killing and yanking.
bashref.html#SEC108
8.4.5 Specifying Numeric Arguments
Specifying numeric arguments, repeat counts.
bashref.html#SEC109
8.4.6 Letting Readline Type For You
Getting Readline to do the typing for you.
bashref.html#SEC110
8.4.7 Keyboard Macros
Saving and re-executing typed characters
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
Other miscellaneous commands.
This section describes Readline commands that may be bound to key
sequences.
You can list your key bindings by executing
bind -P
or, for a more terse format, suitable for an
inputrc
file,
bind -p
.  (See section
bashref.html#SEC58
4.2 Bash Builtin Commands
.)
Command names without an accompanying key sequence are unbound by default.
In the following descriptions,
point
refers to the current cursor
position, and
mark
refers to a cursor position saved by the
set-mark
command.
The text between the point and mark is referred to as the
region
.
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8.4.1 Commands For Moving
beginning-of-line (C-a)
Move to the start of the current line.
end-of-line (C-e)
Move to the end of the line.
forward-char (C-f)
Move forward a character.
backward-char (C-b)
Move back a character.
forward-word (M-f)
Move forward to the end of the next word.  Words are composed of
letters and digits.
backward-word (M-b)
Move back to the start of the current or previous word.  Words are
composed of letters and digits.
clear-screen (C-l)
Clear the screen and redraw the current line,
leaving the current line at the top of the screen.
redraw-current-line ()
Refresh the current line.  By default, this is unbound.
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8.4.2 Commands For Manipulating The History
accept-line (Newline or Return)
Accept the line regardless of where the cursor is.
If this line is
non-empty, add it to the history list according to the setting of
the
HISTCONTROL
and
HISTIGNORE
variables.
If this line is a modified history line, then restore the history line
to its original state.
previous-history (C-p)
Move `back' through the history list, fetching the previous command.
next-history (C-n)
Move `forward' through the history list, fetching the next command.
beginning-of-history (M-<)
Move to the first line in the history.
end-of-history (M->)
Move to the end of the input history, i.e., the line currently
being entered.
reverse-search-history (C-r)
Search backward starting at the current line and moving `up' through
the history as necessary.  This is an incremental search.
forward-search-history (C-s)
Search forward starting at the current line and moving `down' through
the the history as necessary.  This is an incremental search.
non-incremental-reverse-search-history (M-p)
Search backward starting at the current line and moving `up'
through the history as necessary using a non-incremental search
for a string supplied by the user.
non-incremental-forward-search-history (M-n)
Search forward starting at the current line and moving `down'
through the the history as necessary using a non-incremental search
for a string supplied by the user.
history-search-forward ()
Search forward through the history for the string of characters
between the start of the current line and the point.
This is a non-incremental search.
By default, this command is unbound.
history-search-backward ()
Search backward through the history for the string of characters
between the start of the current line and the point.  This
is a non-incremental search.  By default, this command is unbound.
yank-nth-arg (M-C-y)
Insert the first argument to the previous command (usually
the second word on the previous line) at point.
With an argument
n
,
insert the
n
th word from the previous command (the words
in the previous command begin with word 0).  A negative argument
inserts the
n
th word from the end of the previous command.
yank-last-arg (M-. or M-_)
Insert last argument to the previous command (the last word of the
previous history entry).  With an
argument, behave exactly like
yank-nth-arg
.
Successive calls to
yank-last-arg
move back through the history
list, inserting the last argument of each line in turn.
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8.4.3 Commands For Changing Text
delete-char (C-d)
Delete the character at point.  If point is at the
beginning of the line, there are no characters in the line, and
the last character typed was not bound to
delete-char
, then
return EOF.
backward-delete-char (Rubout)
Delete the character behind the cursor.  A numeric argument means
to kill the characters instead of deleting them.
forward-backward-delete-char ()
Delete the character under the cursor, unless the cursor is at the
end of the line, in which case the character behind the cursor is
deleted.  By default, this is not bound to a key.
quoted-insert (C-q or C-v)
Add the next character typed to the line verbatim.  This is
how to insert key sequences like
C-q
, for example.
self-insert (a, b, A, 1, !,
...
)
Insert yourself.
transpose-chars (C-t)
Drag the character before the cursor forward over
the character at the cursor, moving the
cursor forward as well.  If the insertion point
is at the end of the line, then this
transposes the last two characters of the line.
Negative arguments have no effect.
transpose-words (M-t)
Drag the word before point past the word after point,
moving point past that word as well.
If the insertion point is at the end of the line, this transposes
the last two words on the line.
upcase-word (M-u)
Uppercase the current (or following) word.  With a negative argument,
uppercase the previous word, but do not move the cursor.
downcase-word (M-l)
Lowercase the current (or following) word.  With a negative argument,
lowercase the previous word, but do not move the cursor.
capitalize-word (M-c)
Capitalize the current (or following) word.  With a negative argument,
capitalize the previous word, but do not move the cursor.
overwrite-mode ()
Toggle overwrite mode.  With an explicit positive numeric argument,
switches to overwrite mode.  With an explicit non-positive numeric
argument, switches to insert mode.  This command affects only
emacs
mode;
vi
mode does overwrite differently.
Each call to
readline()
starts in insert mode.
In overwrite mode, characters bound to
self-insert
replace
the text at point rather than pushing the text to the right.
Characters bound to
backward-delete-char
replace the character
before point with a space.
By default, this command is unbound.
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8.4.4 Killing And Yanking
kill-line (C-k)
Kill the text from point to the end of the line.
backward-kill-line (C-x Rubout)
Kill backward to the beginning of the line.
unix-line-discard (C-u)
Kill backward from the cursor to the beginning of the current line.
kill-whole-line ()
Kill all characters on the current line, no matter where point is.
By default, this is unbound.
kill-word (M-d)
Kill from point to the end of the current word, or if between
words, to the end of the next word.
Word boundaries are the same as
forward-word
.
backward-kill-word (M-
DEL
)
Kill the word behind point.
Word boundaries are the same as
backward-word
.
unix-word-rubout (C-w)
Kill the word behind point, using white space as a word boundary.
The killed text is saved on the kill-ring.
unix-filename-rubout ()
Kill the word behind point, using white space and the slash character
as the word boundaries.
The killed text is saved on the kill-ring.
delete-horizontal-space ()
Delete all spaces and tabs around point.  By default, this is unbound.
kill-region ()
Kill the text in the current region.
By default, this command is unbound.
copy-region-as-kill ()
Copy the text in the region to the kill buffer, so it can be yanked
right away.  By default, this command is unbound.
copy-backward-word ()
Copy the word before point to the kill buffer.
The word boundaries are the same as
backward-word
.
By default, this command is unbound.
copy-forward-word ()
Copy the word following point to the kill buffer.
The word boundaries are the same as
forward-word
.
By default, this command is unbound.
yank (C-y)
Yank the top of the kill ring into the buffer at point.
yank-pop (M-y)
Rotate the kill-ring, and yank the new top.  You can only do this if
the prior command is
yank
or
yank-pop
.
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8.4.5 Specifying Numeric Arguments
digit-argument (
M-0
,
M-1
,
...
M--
)
Add this digit to the argument already accumulating, or start a new
argument.
M--
starts a negative argument.
universal-argument ()
This is another way to specify an argument.
If this command is followed by one or more digits, optionally with a
leading minus sign, those digits define the argument.
If the command is followed by digits, executing
universal-argument
again ends the numeric argument, but is otherwise ignored.
As a special case, if this command is immediately followed by a
character that is neither a digit or minus sign, the argument count
for the next command is multiplied by four.
The argument count is initially one, so executing this function the
first time makes the argument count four, a second time makes the
argument count sixteen, and so on.
By default, this is not bound to a key.
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8.4.6 Letting Readline Type For You
complete (
TAB
)
Attempt to perform completion on the text before point.
The actual completion performed is application-specific.
Bash attempts completion treating the text as a variable (if the
text begins with
`$'
), username (if the text begins with
`~'
), hostname (if the text begins with
`@'
), or
command (including aliases and functions) in turn.  If none
of these produces a match, filename completion is attempted.
possible-completions (M-?)
List the possible completions of the text before point.
insert-completions (M-*)
Insert all completions of the text before point that would have
been generated by
possible-completions
.
menu-complete ()
Similar to
complete
, but replaces the word to be completed
with a single match from the list of possible completions.
Repeated execution of
menu-complete
steps through the list
of possible completions, inserting each match in turn.
At the end of the list of completions, the bell is rung
(subject to the setting of
bell-style
)
and the original text is restored.
An argument of
n
moves
n
positions forward in the list
of matches; a negative argument may be used to move backward
through the list.
This command is intended to be bound to
TAB
, but is unbound
by default.
delete-char-or-list ()
Deletes the character under the cursor if not at the beginning or
end of the line (like
delete-char
).
If at the end of the line, behaves identically to
possible-completions
.
This command is unbound by default.
complete-filename (M-/)
Attempt filename completion on the text before point.
possible-filename-completions (C-x /)
List the possible completions of the text before point,
treating it as a filename.
complete-username (M-~)
Attempt completion on the text before point, treating
it as a username.
possible-username-completions (C-x ~)
List the possible completions of the text before point,
treating it as a username.
complete-variable (M-$)
Attempt completion on the text before point, treating
it as a shell variable.
possible-variable-completions (C-x $)
List the possible completions of the text before point,
treating it as a shell variable.
complete-hostname (M-@)
Attempt completion on the text before point, treating
it as a hostname.
possible-hostname-completions (C-x @)
List the possible completions of the text before point,
treating it as a hostname.
complete-command (M-!)
Attempt completion on the text before point, treating
it as a command name.  Command completion attempts to
match the text against aliases, reserved words, shell
functions, shell builtins, and finally executable filenames,
in that order.
possible-command-completions (C-x !)
List the possible completions of the text before point,
treating it as a command name.
dynamic-complete-history (M-
TAB
)
Attempt completion on the text before point, comparing
the text against lines from the history list for possible
completion matches.
complete-into-braces (M-{)
Perform filename completion and insert the list of possible completions
enclosed within braces so the list is available to the shell
(see section
bashref.html#SEC28
3.5.1 Brace Expansion
).
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8.4.7 Keyboard Macros
start-kbd-macro (C-x ()
Begin saving the characters typed into the current keyboard macro.
end-kbd-macro (C-x ))
Stop saving the characters typed into the current keyboard macro
and save the definition.
call-last-kbd-macro (C-x e)
Re-execute the last keyboard macro defined, by making the characters
in the macro appear as if typed at the keyboard.
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8.4.8 Some Miscellaneous Commands
re-read-init-file (C-x C-r)
Read in the contents of the
inputrc
file, and incorporate
any bindings or variable assignments found there.
abort (C-g)
Abort the current editing command and
ring the terminal's bell (subject to the setting of
bell-style
).
do-uppercase-version (M-a, M-b, M-
x
,
...
)
If the metafied character
x
is lowercase, run the command
that is bound to the corresponding uppercase character.
prefix-meta (
ESC
)
Metafy the next character typed.  This is for keyboards
without a meta key.  Typing
`
ESC
f'
is equivalent to typing
M-f
.
undo (C-_ or C-x C-u)
Incremental undo, separately remembered for each line.
revert-line (M-r)
Undo all changes made to this line.  This is like executing the
undo
command enough times to get back to the beginning.
tilde-expand (M-&)
Perform tilde expansion on the current word.
set-mark (C-@)
Set the mark to the point.  If a
numeric argument is supplied, the mark is set to that position.
exchange-point-and-mark (C-x C-x)
Swap the point with the mark.  The current cursor position is set to
the saved position, and the old cursor position is saved as the mark.
character-search (C-])
A character is read and point is moved to the next occurrence of that
character.  A negative count searches for previous occurrences.
character-search-backward (M-C-])
A character is read and point is moved to the previous occurrence
of that character.  A negative count searches for subsequent
occurrences.
insert-comment (M-#)
Without a numeric argument, the value of the
comment-begin
variable is inserted at the beginning of the current line.
If a numeric argument is supplied, this command acts as a toggle:  if
the characters at the beginning of the line do not match the value
of
comment-begin
, the value is inserted, otherwise
the characters in
comment-begin
are deleted from the beginning of
the line.
In either case, the line is accepted as if a newline had been typed.
The default value of
comment-begin
causes this command
to make the current line a shell comment.
If a numeric argument causes the comment character to be removed, the line
will be executed by the shell.
dump-functions ()
Print all of the functions and their key bindings to the
Readline output stream.  If a numeric argument is supplied,
the output is formatted in such a way that it can be made part
of an
inputrc
file.  This command is unbound by default.
dump-variables ()
Print all of the settable 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.  This command is unbound by default.
dump-macros ()
Print all of the Readline key sequences bound to macros and the
strings they output.  If a numeric argument is supplied,
the output is formatted in such a way that it can be made part
of an
inputrc
file.  This command is unbound by default.
glob-complete-word (M-g)
The word before point is treated as a pattern for pathname expansion,
with an asterisk implicitly appended.  This pattern is used to
generate a list of matching file names for possible completions.
glob-expand-word (C-x *)
The word before point is treated as a pattern for pathname expansion,
and the list of matching file names is inserted, replacing the word.
If a numeric argument is supplied, a
`*'
is appended before
pathname expansion.
glob-list-expansions (C-x g)
The list of expansions that would have been generated by
glob-expand-word
is displayed, and the line is redrawn.
If a numeric argument is supplied, a
`*'
is appended before
pathname expansion.
display-shell-version (C-x C-v)
Display version information about the current instance of Bash.
shell-expand-line (M-C-e)
Expand the line as the shell does.
This performs alias and history expansion as well as all of the shell
word expansions (see section
bashref.html#SEC27
3.5 Shell Expansions
).
history-expand-line (M-^)
Perform history expansion on the current line.
magic-space ()
Perform history expansion on the current line and insert a space
(see section
bashref.html#SEC118
9.3 History Expansion
).
alias-expand-line ()
Perform alias expansion on the current line (see section
bashref.html#SEC80
6.6 Aliases
).
history-and-alias-expand-line ()
Perform history and alias expansion on the current line.
insert-last-argument (M-. or M-_)
A synonym for
yank-last-arg
.
operate-and-get-next (C-o)
Accept the current line for execution and fetch the next line
relative to the current line from the history for editing.  Any
argument is ignored.
edit-and-execute-command (C-xC-e)
Invoke an editor on the current command line, and execute the result as shell
commands.
Bash attempts to invoke
$VISUAL
,
$EDITOR
, and
emacs
as the editor, in that order.
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8.5 Readline vi Mode
While the Readline library does not have a full set of
vi
editing functions, it does contain enough to allow simple editing
of the line.  The Readline
vi
mode behaves as specified in
the POSIX 1003.2 standard.
In order to switch interactively between
emacs
and
vi
editing modes, use the
`set -o emacs'
and
`set -o vi'
commands (see section
bashref.html#SEC59
4.3 The Set Builtin
).
The Readline default is
emacs
mode.
When you enter a line in
vi
mode, you are already placed in
`insertion' mode, as if you had typed an
`i'
.  Pressing
ESC
switches you into `command' mode, where you can edit the text of the
line with the standard
vi
movement keys, move to previous
history lines with
`k'
and subsequent lines with
`j'
, and
so forth.
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8.6 Programmable Completion
When word completion is attempted for an argument to a command for
which a completion specification (a
compspec
) has been defined
using the
complete
builtin (see section
bashref.html#SEC114
8.7 Programmable Completion Builtins
),
the programmable 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 Bash completion
described above (see section
bashref.html#SEC109
8.4.6 Letting Readline Type For You
) 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
`-f'
or
`-d'
option is used for filename or
directory name completion, the shell variable
FIGNORE
is
used to filter the matches.
See section
bashref.html#SEC63
5.2 Bash Variables
, for a description of
FIGNORE
.
Any completions specified by a filename expansion pattern to the
`-G'
option are generated next.
The words generated by the pattern need not match the word being completed.
The
GLOBIGNORE
shell variable is not used to filter the matches,
but the
FIGNORE
shell variable is used.
Next, the string specified as the argument to the
`-W'
option
is considered.
The string is first split using the characters in the
IFS
special 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 (see section
bashref.html#SEC27
3.5 Shell Expansions
).
The results are split using the rules described above
(see section
bashref.html#SEC34
3.5.7 Word Splitting
).
The results of the expansion are prefix-matched against the word being
completed, and the matching words become the possible completions.
After these matches have been generated, any shell function or command
specified with the
`-F'
and
`-C'
options is invoked.
When the command or function is invoked, the
COMP_LINE
and
COMP_POINT
variables are assigned values as described above
(see section
bashref.html#SEC63
5.2 Bash Variables
).
If a shell function is being invoked, the
COMP_WORDS
and
COMP_CWORD
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
`-F'
is invoked first.
The function may use any of the shell facilities, including the
compgen
builtin described below
(see section
bashref.html#SEC114
8.7 Programmable Completion Builtins
), to generate the matches.
It must put the possible completions in the
COMPREPLY
array
variable.
Next, any command specified with the
`-C'
option is invoked
in an environment 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
specified with the
`-X'
option is applied to the list.
The filter is a pattern 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 matching the pattern will be removed.
Finally, any prefix and suffix specified with the
`-P'
and
`-S'
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
`-o dirnames'
option was supplied to
complete
when the
compspec was defined, directory name completion is attempted.
If the
`-o plusdirs'
option was supplied to
complete
when
the compspec was defined, directory name completion is attempted and any
matches are added to the results of the other actions.
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 Bash completions are not attempted, and the Readline default
of filename completion is disabled.
If the
`-o bashdefault'
option was supplied to
complete
when
the compspec was defined, the default Bash completions are attempted
if the compspec generates no matches.
If the
`-o default'
option was supplied to
complete
when the
compspec was defined, Readline's default completion will be performed
if the compspec (and, if attempted, the default Bash completions)
generate 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
mark-directories
Readline variable, regardless
of the setting of the
mark-symlinked-directories
Readline variable.
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8.7 Programmable Completion Builtins
Two builtin commands are available to manipulate the programmable completion
facilities.
compgen
compgen [
option
] [
word
]
Generate possible completion matches for
word
according to
the
option
s, which may be any option accepted by the
complete
builtin with the exception of
`-p'
and
`-r'
, and write
the matches to the standard output.
When using the
`-F'
or
`-C'
options, the various shell variables
set by the programmable completion facilities, while available, will not
have useful values.
The matches will be generated in the same way as if the programmable
completion code had generated them directly from a completion specification
with the same flags.
If
word
is specified, only those completions matching
word
will be displayed.
The return value is true unless an invalid option is supplied, or no
matches were generated.
complete
complete [-abcdefgjksuv] [-o
comp-option
] [-A
action
] [-G
globpat
] [-W
wordlist
]
[-P
prefix
] [-S
suffix
] [-X
filterpat
] [-F
function
]
[-C
command
]
name
[
name
...
]
complete -pr [
name
...
]
Specify how arguments to each
name
should be completed.
If the
`-p'
option is supplied, or if no options are supplied, existing
completion specifications are printed in a way that allows them to be
reused as input.
The
`-r'
option removes a completion specification for
each
name
, or, if no
name
s are supplied, all
completion specifications.
The process of applying these completion specifications when word completion
is attempted is described above (see section
bashref.html#SEC113
8.6 Programmable Completion
).
Other options, if specified, have the following meanings.
The arguments to the
`-G'
,
`-W'
, and
`-X'
options
(and, if necessary, the
`-P'
and
`-S'
options)
should be quoted to protect them from expansion before the
complete
builtin is invoked.
-o
comp-option
The
comp-option
controls several aspects of the compspec's behavior
beyond the simple generation of completions.
comp-option
may be one of:
bashdefault
Perform the rest of the default Bash completions if the compspec
generates no matches.
default
Use Readline's default filename completion if the compspec generates
no matches.
dirnames
Perform directory name completion if the compspec generates no matches.
filenames
Tell Readline that the compspec generates filenames, so it can perform any
filename-specific processing (like adding a slash to directory names or
suppressing trailing spaces).  This option is intended to be used with
shell functions specified with
`-F'
.
nospace
Tell Readline not to append a space (the default) to words completed at
the end of the line.
-A
action
The
action
may be one of the following to generate a list of possible
completions:
alias
Alias names.  May also be specified as
`-a'
.
arrayvar
Array variable names.
binding
Readline key binding names (see section
bashref.html#SEC103
8.4 Bindable Readline Commands
).
builtin
Names of shell builtin commands.  May also be specified as
`-b'
.
command
Command names.  May also be specified as
`-c'
.
directory
Directory names.  May also be specified as
`-d'
.
disabled
Names of disabled shell builtins.
enabled
Names of enabled shell builtins.
export
Names of exported shell variables.  May also be specified as
`-e'
.
file
File names.  May also be specified as
`-f'
.
function
Names of shell functions.
group
Group names.  May also be specified as
`-g'
.
helptopic
Help topics as accepted by the
help
builtin (see section
bashref.html#SEC58
4.2 Bash Builtin Commands
).
hostname
Hostnames, as taken from the file specified by the
HOSTFILE
shell variable (see section
bashref.html#SEC63
5.2 Bash Variables
).
job
Job names, if job control is active.  May also be specified as
`-j'
.
keyword
Shell reserved words.  May also be specified as
`-k'
.
running
Names of running jobs, if job control is active.
service
Service names.  May also be specified as
`-s'
.
setopt
Valid arguments for the
`-o'
option to the
set
builtin
(see section
bashref.html#SEC59
4.3 The Set Builtin
).
shopt
Shell option names as accepted by the
shopt
builtin
(see section
bashref.html#SEC58
4.2 Bash Builtin Commands
).
signal
Signal names.
stopped
Names of stopped jobs, if job control is active.
user
User names.  May also be specified as
`-u'
.
variable
Names of all shell variables.  May also be specified as
`-v'
.
-G
globpat
The filename expansion pattern
globpat
is expanded to generate
the possible completions.
-W
wordlist
The
wordlist
is split using the characters in the
IFS
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 completed.
-C
command
command
is executed in a subshell environment, and its output is
used as the possible completions.
-F
function
The shell function
function
is executed in the current shell
environment.
When it finishes, the possible completions are retrieved from the value
of the
COMPREPLY
array variable.
-X
filterpat
filterpat
is a pattern as used for filename expansion.
It is applied to the list of possible completions generated 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.
-P
prefix
prefix
is added at the beginning of each possible completion
after all other options have been applied.
-S
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
`-p'
or
`-r'
is supplied without a
name
argument, 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.
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9. Using History Interactively
This chapter describes how to use the GNU History Library
interactively, from a user's standpoint.
It should be considered a user's guide.
For information on using the GNU History Library in other programs,
see the GNU Readline Library Manual.
bashref.html#SEC116
9.1 Bash History Facilities
How Bash lets you manipulate your command
history.
bashref.html#SEC117
9.2 Bash History Builtins
The Bash builtin commands that manipulate
the command history.
bashref.html#SEC118
9.3 History Expansion
What it feels like using History as a user.
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9.1 Bash History Facilities
When the
`-o history'
option to the
set
builtin
is enabled (see section
bashref.html#SEC59
4.3 The Set Builtin
),
the shell provides access to the
command history
,
the list of commands previously typed.
The value of the
HISTSIZE
shell variable is used as the
number of commands to save in a history list.
The text of the last
$HISTSIZE
commands (default 500) is saved.
The shell stores each command in the history list prior to
parameter and variable expansion
but after history expansion is performed, subject to the
values of the shell variables
HISTIGNORE
and
HISTCONTROL
.
When the shell starts up, the history is initialized from the
file named by the
HISTFILE
variable (default
`~/.bash_history'
).
The file named by the value of
HISTFILE
is truncated, if
necessary, to contain no more than the number of lines specified by
the value of the
HISTFILESIZE
variable.
When an interactive shell exits, the last
$HISTSIZE
lines are copied from the history list to the file
named by
$HISTFILE
.
If the
histappend
shell option is set (see section
bashref.html#SEC58
4.2 Bash Builtin Commands
),
the lines are appended to the history file,
otherwise the history file is overwritten.
If
HISTFILE
is unset, or if the history file is unwritable, the history is
not saved.  After saving the history, the history file is truncated
to contain no more than
$HISTFILESIZE
lines.  If
HISTFILESIZE
is not set, no truncation is performed.
If the
HISTTIMEFORMAT
is set, the time stamp information
associated with each history entry is written to the history file.
The builtin command
fc
may be used to list or edit and re-execute
a portion of the history list.
The
history
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 (see section
bashref.html#SEC105
8.4.2 Commands For Manipulating The History
).
The shell allows control over which commands are saved on the history
list.  The
HISTCONTROL
and
HISTIGNORE
variables may be set to cause the shell to save only a subset of the
commands entered.
The
cmdhist
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
lithist
shell option causes the shell to save the command with embedded newlines
instead of semicolons.
The
shopt
builtin is used to set these options.
See section
bashref.html#SEC58
4.2 Bash Builtin Commands
, for a description of
shopt
.
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9.2 Bash History Builtins
Bash provides two builtin commands which manipulate the
history list and history file.
fc
fc [-e
ename
] [-nlr] [
first
] [
last
]
fc -s [
pat
=
rep
] [
command
]
Fix Command.  In the first form, a range of commands from
first
to
last
is selected from the history list.  Both
first
and
last
may be specified as a string (to locate the most recent
command beginning with that string) or as a number (an index into the
history list, where a negative number is used as an offset from the
current command number).  If
last
is not specified it is set to
first
.  If
first
is not specified it is set to the previous
command for editing and -16 for listing.  If the
`-l'
flag is
given, the commands are listed on standard output.  The
`-n'
flag
suppresses the command numbers when listing.  The
`-r'
flag
reverses the order of the listing.  Otherwise, the editor given by
ename
is invoked on a file containing those commands.  If
ename
is not given, the value of the following variable expansion
is used:
${FCEDIT:-${EDITOR:-vi}}
.  This says to use the
value of the
FCEDIT
variable if set, or the value of the
EDITOR
variable if that is set, or
vi
if neither is set.
When editing is complete, the edited commands are echoed and executed.
In the second form,
command
is re-executed after each instance
of
pat
in the selected command is replaced by
rep
.
A useful alias to use with the
fc
command is
r='fc -s'
, so
that typing
`r cc'
runs the last command beginning with
cc
and typing
`r'
re-executes the last command (see section
bashref.html#SEC80
6.6 Aliases
).
history
history [
n
]
history -c
history -d
offset
history [-anrw] [
filename
]
history -ps
arg
With no options, display the history list with line numbers.
Lines prefixed with a
`*'
have been modified.
An argument of
n
lists only the last
n
lines.
If the shell variable
HISTTIMEFORMAT
is set and not null,
it is used as a format string for
strftime
to display
the time stamp associated with each displayed history entry.
No intervening blank is printed between the formatted time stamp
and the history line.
Options, if supplied, have the following meanings:
-c
Clear the history list.  This may be combined
with the other options to replace the history list completely.
-d
offset
Delete the history entry at position
offset
.
offset
should be specified as it appears when the history is
displayed.
-a
Append the new
history lines (history lines entered since the beginning of the
current Bash session) to the history file.
-n
Append the history lines not already read from the history file
to the current history list.  These are lines appended to the history
file since the beginning of the current Bash session.
-r
Read the current history file and append its contents to
the history list.
-w
Write out the current history to the history file.
-p
Perform history substitution on the
arg
s and display the result
on the standard output, without storing the results in the history list.
-s
The
arg
s are added to the end of
the history list as a single entry.
When any of the
`-w'
,
`-r'
,
`-a'
, or
`-n'
options is
used, if
filename
is given, then it is used as the history file.  If not, then
the value of the
HISTFILE
variable is used.
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9.3 History Expansion
The History library provides a history expansion feature that is similar
to the history expansion provided by
csh
.  This section
describes the syntax used to manipulate the history information.
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 takes place in two parts.  The first is to determine
which line from the history list should be used during substitution.
The second is to select portions of that line for inclusion into the
current one.  The line selected from the history is called the
event
, and the portions of that line that are acted upon are
called
words
.  Various
modifiers
are available to manipulate
the selected words.  The line is broken into words in the same fashion
that Bash does, so that several 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
`\'
and
`''
may be used to escape the history expansion
character.
Several shell options settable with the
shopt
builtin (see section
bashref.html#SEC58
4.2 Bash Builtin Commands
) may be used to tailor
the behavior of history expansion.  If the
histverify
shell option is enabled, and Readline
is being used, history substitutions are not immediately passed to
the shell parser.
Instead, the expanded line is reloaded into the Readline
editing buffer for further modification.
If Readline is being used, and the
histreedit
shell option is enabled, a failed history expansion will be
reloaded into the Readline editing buffer for correction.
The
`-p'
option to the
history
builtin command
may be used to see what a history expansion will do before using it.
The
`-s'
option to the
history
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.
This is most useful in conjunction with Readline.
The shell allows control of the various characters used by the
history expansion mechanism with the
histchars
variable.
bashref.html#SEC119
9.3.1 Event Designators
How to specify which history line to use.
bashref.html#SEC120
9.3.2 Word Designators
Specifying which words are of interest.
bashref.html#SEC121
9.3.3 Modifiers
Modifying the results of substitution.
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9.3.1 Event Designators
An event designator is a reference to a command line entry in the
history list.
!
Start a history substitution, except when followed by a space, tab,
the end of the line,
`='
or
`('
(when the
extglob
shell option is enabled using the
shopt
builtin).
!
n
Refer to command line
n
.
!-
n
Refer to the command
n
lines back.
!!
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 trailing
`?'
may be omitted if the
string
is followed immediately by
a newline.
^
string1
^
string2
^
Quick Substitution.  Repeat the last command, replacing
string1
with
string2
.  Equivalent to
!!:s/
string1
/
string2
/
.
!#
The entire command line typed so far.
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9.3.2 Word Designators
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
`^'
,
`$'
,
`*'
,
`-'
, or
`%'
.  Words are numbered from the beginning
of the line, with the first word being denoted by 0 (zero).  Words are
inserted into the current line separated by single spaces.
For example,
!!
designates the preceding command.  When you type this, the preceding
command is repeated in toto.
!!:$
designates the last argument of the preceding command.  This may be
shortened to
!$
.
!fi:2
designates the second argument of the most recent command starting with
the letters
fi
.
Here are the word designators:
0 (zero)
The
0
th word.  For many applications, this is the command word.
n
The
n
th 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, except the
0
th.  This is a synonym for
`1-$'
.
It is not an error to use
`*'
if there is just one word in the event;
the empty string is returned in that case.
x
*
Abbreviates
`
x
-$'
x
-
Abbreviates
`
x
-$'
like
`
x
*'
, but omits the last word.
If a word designator is supplied without an event specification, the
previous command is used as the event.
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9.3.3 Modifiers
After the optional word designator, you can add a sequence of one or more
of the following modifiers, each preceded by a
`:'
.
h
Remove a trailing pathname component, leaving only the head.
t
Remove all leading  pathname  components, leaving the tail.
r
Remove a trailing suffix of the form
`.
suffix
'
, leaving
the basename.
e
Remove all but the trailing suffix.
p
Print the new command but do not execute it.
q
Quote the substituted words, escaping further substitutions.
x
Quote the substituted words as with
`q'
,
but break into words at spaces, tabs, and newlines.
s/
old
/
new
/
Substitute
new
for the first occurrence of
old
in the
event line.  Any delimiter may be used in place of
`/'
.
The delimiter may be quoted in
old
and
new
with a single backslash.  If
`&'
appears in
new
,
it is replaced by
old
.  A single backslash will quote
the
`&'
.  The final delimiter is optional if it is the last
character on the input line.
&
Repeat the previous substitution.
g
a
Cause changes to be applied over the entire event line.  Used in
conjunction with
`s'
, as in
gs/
old
/
new
/
,
or with
`&'
.
G
Apply the following
`s'
modifier once to each word in the event.
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10. Installing Bash
This chapter provides basic instructions for installing Bash on
the various supported platforms.  The distribution supports the
GNU operating systems, nearly every version of Unix, and several
non-Unix systems such as BeOS and Interix.
Other independent ports exist for
MS-DOS, OS/2, and Windows platforms.
bashref.html#SEC123
10.1 Basic Installation
Installation instructions.
bashref.html#SEC124
10.2 Compilers and Options
How to set special options for various
systems.
bashref.html#SEC125
10.3 Compiling For Multiple Architectures
How to compile Bash for more
than one kind of system from
the same source tree.
bashref.html#SEC126
10.4 Installation Names
How to set the various paths used by the installation.
bashref.html#SEC127
10.5 Specifying the System Type
How to configure Bash for a particular system.
bashref.html#SEC128
10.6 Sharing Defaults
How to share default configuration values among GNU
programs.
bashref.html#SEC129
10.7 Operation Controls
Options recognized by the configuration program.
bashref.html#SEC130
10.8 Optional Features
How to enable and disable optional features when
building Bash.
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10.1 Basic Installation
These are installation instructions for Bash.
The simplest way to compile Bash is:
cd
to the directory containing the source code and type
`./configure'
to configure Bash for your system.  If you're
using
csh
on an old version of System V, you might need to
type
`sh ./configure'
instead to prevent
csh
from trying
to execute
configure
itself.
Running
configure
takes some time.
While running, it prints messages telling which features it is
checking for.
Type
`make'
to compile Bash and build the
bashbug
bug
reporting script.
Optionally, type
`make tests'
to run the Bash test suite.
Type
`make install'
to install
bash
and
bashbug
.
This will also install the manual pages and Info file.
The
configure
shell script attempts to guess correct
values for various system-dependent variables used during
compilation.  It uses those values to create a
`Makefile'
in
each directory of the package (the top directory, the
`builtins'
,
`doc'
, and
`support'
directories,
each directory under
`lib'
, and several others).  It also creates a
`config.h'
file containing system-dependent definitions.
Finally, it creates a shell script named
config.status
that you
can run in the future to recreate the current configuration, a
file
`config.cache'
that saves the results of its tests to
speed up reconfiguring, and a file
`config.log'
containing
compiler output (useful mainly for debugging
configure
).
If at some point
`config.cache'
contains results you don't want to keep, you
may remove or edit it.
To find out more about the options and arguments that the
configure
script understands, type
bash-2.04$ ./configure --help
at the Bash prompt in your Bash source directory.
If you need to do unusual things to compile Bash, please
try to figure out how
configure
could check whether or not
to do them, and mail diffs or instructions to
mailto:bash-maintainers@gnu.org
bash-maintainers@gnu.org
so they can be
considered for the next release.
The file
`configure.in'
is used to create
configure
by a program called Autoconf.  You only need
`configure.in'
if you want to change it or regenerate
configure
using a newer version of Autoconf.  If
you do this, make sure you are using Autoconf version 2.50 or
newer.
You can remove the program binaries and object files from the
source code directory by typing
`make clean'
.  To also remove the
files that
configure
created (so you can compile Bash for
a different kind of computer), type
`make distclean'
.
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10.2 Compilers and Options
Some systems require unusual options for compilation or linking
that the
configure
script does not know about.  You can
give
configure
initial values for variables by setting
them in the environment.  Using a Bourne-compatible shell, you
can do that on the command line like this:
CC=c89 CFLAGS=-O2 LIBS=-lposix ./configure
On systems that have the
env
program, you can do it like this:
env CPPFLAGS=-I/usr/local/include LDFLAGS=-s ./configure
The configuration process uses GCC to build Bash if it
is available.
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10.3 Compiling For Multiple Architectures
You can compile Bash for more than one kind of computer at the
same time, by placing the object files for each architecture in their
own directory.  To do this, you must use a version of
make
that
supports the
VPATH
variable, such as GNU
make
.
cd
to the
directory where you want the object files and executables to go and run
the
configure
script from the source directory.  You may need to
supply the
`--srcdir=PATH'
argument to tell
configure
where the
source files are.
configure
automatically checks for the
source code in the directory that
configure
is in and in `..'.
If you have to use a
make
that does not supports the
VPATH
variable, you can compile Bash for one architecture at a
time in the source code directory.  After you have installed
Bash for one architecture, use
`make distclean'
before
reconfiguring for another architecture.
Alternatively, if your system supports symbolic links, you can use the
`support/mkclone'
script to create a build tree which has
symbolic links back to each file in the source directory.  Here's an
example that creates a build directory in the current directory from a
source directory
`/usr/gnu/src/bash-2.0'
:
bash /usr/gnu/src/bash-2.0/support/mkclone -s /usr/gnu/src/bash-2.0 .
The
mkclone
script requires Bash, so you must have already built
Bash for at least one architecture before you can create build
directories for other architectures.
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10.4 Installation Names
By default,
`make install'
will install into
`/usr/local/bin'
,
`/usr/local/man'
, etc.  You can
specify an installation prefix other than
`/usr/local'
by
giving
configure
the option
`--prefix=
PATH
'
,
or by specifying a value for the
DESTDIR
`make'
variable when running
`make install'
.
You can specify separate installation prefixes for
architecture-specific files and architecture-independent files.
If you give
configure
the option
`--exec-prefix=
PATH
'
,
`make install'
will use
PATH
as the prefix for installing programs and libraries.
Documentation and other data files will still use the regular prefix.
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10.5 Specifying the System Type
There may be some features
configure
can not figure out
automatically, but need to determine by the type of host Bash
will run on.  Usually
configure
can figure that
out, but if it prints a message saying it can not guess the host
type, give it the
`--host=TYPE'
option.
`TYPE'
can
either be a short name for the system type, such as
`sun4'
,
or a canonical name with three fields:
`CPU-COMPANY-SYSTEM'
(e.g.,
`i386-unknown-freebsd4.2'
).
See the file
`support/config.sub'
for the possible
values of each field.
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10.6 Sharing Defaults
If you want to set default values for
configure
scripts to
share, you can create a site shell script called
config.site
that gives default values for variables like
CC
,
cache_file
, and
prefix
.
configure
looks for
`PREFIX/share/config.site'
if it exists, then
`PREFIX/etc/config.site'
if it exists.  Or, you can set the
CONFIG_SITE
environment variable to the location of the site
script.  A warning: the Bash
configure
looks for a site script,
but not all
configure
scripts do.
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10.7 Operation Controls
configure
recognizes the following options to control how it
operates.
--cache-file=
file
Use and save the results of the tests in
file
instead of
`./config.cache'
.  Set
file
to
`/dev/null'
to disable caching, for debugging
configure
.
--help
Print a summary of the options to
configure
, and exit.
--quiet
--silent
-q
Do not print messages saying which checks are being made.
--srcdir=
dir
Look for the Bash source code in directory
dir
.  Usually
configure
can determine that directory automatically.
--version
Print the version of Autoconf used to generate the
configure
script, and exit.
configure
also accepts some other, not widely used, boilerplate
options.
`configure --help'
prints the complete list.
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10.8 Optional Features
The Bash
configure
has a number of
`--enable-
feature
'
options, where
feature
indicates an optional part of Bash.
There are also several
`--with-
package
'
options,
where
package
is something like
`bash-malloc'
or
`purify'
.
To turn off the default use of a package, use
`--without-
package
'
.  To configure Bash without a feature
that is enabled by default, use
`--disable-
feature
'
.
Here is a complete list of the
`--enable-'
and
`--with-'
options that the Bash
configure
recognizes.
--with-afs
Define if you are using the Andrew File System from Transarc.
--with-bash-malloc
Use the Bash version of
malloc
in
`lib/malloc/malloc.c'
.  This is not the same
malloc
that appears in GNU libc, but an older version
derived from the 4.2 BSD
malloc
.  This
malloc
is
very fast, but wastes some space on each allocation.
This option is enabled by default.
The
`NOTES'
file contains a list of systems for
which this should be turned off, and
configure
disables this
option automatically for a number of systems.
--with-curses
Use the curses library instead of the termcap library.  This should
be supplied if your system has an inadequate or incomplete termcap
database.
--with-gnu-malloc
A synonym for
--with-bash-malloc
.
--with-installed-readline[=
PREFIX
]
Define this to make Bash link with a locally-installed version of Readline
rather than the version in
`lib/readline'
.  This works only with
Readline 4.3 and later versions.  If
PREFIX
is
yes
or not
supplied,
configure
uses the values of the make variables
includedir
and
libdir
, which are subdirectories of
prefix
by default, to find the installed version of Readline if it is not in
the standard system include and library directories.
If
PREFIX
is
no
, Bash links with the version in
`lib/readline'
.
If
PREFIX
is set to any other value,
configure
treats it as
a directory pathname and looks for
the installed version of Readline in subdirectories of that directory
(include files in
PREFIX
/
include
and the library in
PREFIX
/
lib
).
--with-purify
Define this to use the Purify memory allocation checker from Rational
Software.
--enable-minimal-config
This produces a shell with minimal features, close to the historical
Bourne shell.
There are several
`--enable-'
options that alter how Bash is
compiled and linked, rather than changing run-time features.
--enable-largefile
Enable support for
http://www.sas.com/standards/large_file/x_open.20Mar96.html
large files
if the operating system requires special compiler options
to build programs which can access large files.  This is enabled by
default, if the operating system provides large file support.
--enable-profiling
This builds a Bash binary that produces profiling information to be
processed by
gprof
each time it is executed.
--enable-static-link
This causes Bash to be linked statically, if
gcc
is being used.
This could be used to build a version to use as root's shell.
The
`minimal-config'
option can be used to disable all of
the following options, but it is processed first, so individual
options may be enabled using
`enable-
feature
'
.
All of the following options except for
`disabled-builtins'
and
`xpg-echo-default'
are
enabled by default, unless the operating system does not provide the
necessary support.
--enable-alias
Allow alias expansion and include the
alias
and
unalias
builtins (see section
bashref.html#SEC80
6.6 Aliases
).
--enable-arith-for-command
Include support for the alternate form of the
for
command
that behaves like the C language
for
statement
(see section
bashref.html#SEC20
3.2.4.1 Looping Constructs
).
--enable-array-variables
Include support for one-dimensional array shell variables
(see section
bashref.html#SEC81
6.7 Arrays
).
--enable-bang-history
Include support for
csh
-like history substitution
(see section
bashref.html#SEC118
9.3 History Expansion
).
--enable-brace-expansion
Include
csh
-like brace expansion
(
b{a,b}c
==>
bac bbc
).
See
bashref.html#SEC28
3.5.1 Brace Expansion
, for a complete description.
--enable-command-timing
Include support for recognizing
time
as a reserved word and for
displaying timing statistics for the pipeline following
time
(see section
bashref.html#SEC17
3.2.2 Pipelines
).
This allows pipelines as well as shell builtins and functions to be timed.
--enable-cond-command
Include support for the
[[
conditional command.
(see section
bashref.html#SEC21
3.2.4.2 Conditional Constructs
).
--enable-cond-regexp
Include support for matching POSIX regular expressions using the
`=~'
binary operator in the
[[
conditional command.
(see section
bashref.html#SEC21
3.2.4.2 Conditional Constructs
).
--enable-directory-stack
Include support for a
csh
-like directory stack and the
pushd
,
popd
, and
dirs
builtins
(see section
bashref.html#SEC82
6.8 The Directory Stack
).
--enable-disabled-builtins
Allow builtin commands to be invoked via
`builtin xxx'
even after
xxx
has been disabled using
`enable -n xxx'
.
See
bashref.html#SEC58
4.2 Bash Builtin Commands
, for details of the
builtin
and
enable
builtin commands.
--enable-dparen-arithmetic
Include support for the
((
...
))
command
(see section
bashref.html#SEC21
3.2.4.2 Conditional Constructs
).
--enable-extended-glob
Include support for the extended pattern matching features described
above under
bashref.html#SEC36
3.5.8.1 Pattern Matching
.
--enable-help-builtin
Include the
help
builtin, which displays help on shell builtins and
variables (see section
bashref.html#SEC58
4.2 Bash Builtin Commands
).
--enable-history
Include command history and the
fc
and
history
builtin commands (see section
bashref.html#SEC116
9.1 Bash History Facilities
).
--enable-job-control
This enables the job control features (see section
bashref.html#SEC87
7. Job Control
),
if the operating system supports them.
--enable-multibyte
This enables support for multibyte characters if the operating
system provides the necessary support.
--enable-net-redirections
This enables the special handling of filenames of the form
/dev/tcp/
host
/
port
and
/dev/udp/
host
/
port
when used in redirections (see section
bashref.html#SEC38
3.6 Redirections
).
--enable-process-substitution
This enables process substitution (see section
bashref.html#SEC33
3.5.6 Process Substitution
) if
the operating system provides the necessary support.
--enable-prompt-string-decoding
Turn on the interpretation of a number of backslash-escaped characters
in the
$PS1
,
$PS2
,
$PS3
, and
$PS4
prompt
strings.  See
bashref.html#SEC84
6.9 Controlling the Prompt
, for a complete list of prompt
string escape sequences.
--enable-progcomp
Enable the programmable completion facilities
(see section
bashref.html#SEC113
8.6 Programmable Completion
).
If Readline is not enabled, this option has no effect.
--enable-readline
Include support for command-line editing and history with the Bash
version of the Readline library (see section
bashref.html#SEC91
8. Command Line Editing
).
--enable-restricted
Include support for a
restricted shell
.  If this is enabled, Bash,
when called as
rbash
, enters a restricted mode.  See
bashref.html#SEC85
6.10 The Restricted Shell
, for a description of restricted mode.
--enable-select
Include the
select
builtin, which allows the generation of simple
menus (see section
bashref.html#SEC21
3.2.4.2 Conditional Constructs
).
--enable-usg-echo-default
A synonym for
--enable-xpg-echo-default
.
--enable-xpg-echo-default
Make the
echo
builtin expand backslash-escaped characters by default,
without requiring the
`-e'
option.
This sets the default value of the
xpg_echo
shell option to
on
,
which makes the Bash
echo
behave more like the version specified in
the Single Unix Specification, version 2.
See section
bashref.html#SEC58
4.2 Bash Builtin Commands
, for a description of the escape sequences that
echo
recognizes.
The file
`config-top.h'
contains C Preprocessor
`#define'
statements for options which are not settable from
configure
.
Some of these are not meant to be changed; beware of the consequences if
you do.
Read the comments associated with each definition for more
information about its effect.
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A. Reporting Bugs
Please report all bugs you find in Bash.
But first, you should
make sure that it really is a bug, and that it appears in the latest
version of Bash.
The latest version of Bash is always available for FTP from
ftp://ftp.gnu.org/pub/bash/
ftp://ftp.gnu.org/pub/bash/
.
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
mailto:bug-bash@gnu.org
bug-bash@gnu.org
or posted to the Usenet
newsgroup
gnu.bash.bug
.
All bug reports should include:
The version number of Bash.
The hardware and operating system.
The compiler used to compile Bash.
A description of the bug behaviour.
A short script or `recipe' which exercises the bug and may be used
to reproduce it.
bashbug
inserts the first three items automatically into
the template it provides for filing a bug report.
Please send all reports concerning this manual to
mailto:chet@po.CWRU.Edu
chet@po.CWRU.Edu
.
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B. Major Differences From The Bourne Shell
Bash implements essentially the same grammar, parameter and
variable expansion, redirection, and quoting as the Bourne Shell.
Bash uses the POSIX 1003.2 standard as the specification of
how these features are to be implemented.  There are some
differences between the traditional Bourne shell and Bash; this
section quickly details the differences of significance.  A
number of these differences are explained in greater depth in
previous sections.
This section uses the version of
sh
included in SVR4.2 as
the baseline reference.
Bash is POSIX-conformant, even where the POSIX specification
differs from traditional
sh
behavior (see section
bashref.html#SEC86
6.11 Bash POSIX Mode
).
Bash has multi-character invocation options (see section
bashref.html#SEC65
6.1 Invoking Bash
).
Bash has command-line editing (see section
bashref.html#SEC91
8. Command Line Editing
) and
the
bind
builtin.
Bash provides a programmable word completion mechanism
(see section
bashref.html#SEC113
8.6 Programmable Completion
), and two builtin commands,
complete
and
compgen
, to manipulate it.
Bash has command history (see section
bashref.html#SEC116
9.1 Bash History Facilities
) and the
history
and
fc
builtins to manipulate it.
The Bash history list maintains timestamp information and uses the
value of the
HISTTIMEFORMAT
variable to display it.
Bash implements
csh
-like history expansion
(see section
bashref.html#SEC118
9.3 History Expansion
).
Bash has one-dimensional array variables (see section
bashref.html#SEC81
6.7 Arrays
), and the
appropriate variable expansions and assignment syntax to use them.
Several of the Bash builtins take options to act on arrays.
Bash provides a number of built-in array variables.
The
$'
...
'
quoting syntax, which expands ANSI-C
backslash-escaped characters in the text between the single quotes,
is supported (see section
bashref.html#SEC12
3.1.2.4 ANSI-C Quoting
).
Bash supports the
$"
...
"
quoting syntax to do
locale-specific translation of the characters between the double
quotes.  The
`-D'
,
`--dump-strings'
, and
`--dump-po-strings'
invocation options list the translatable strings found in a script
(see section
bashref.html#SEC13
3.1.2.5 Locale-Specific Translation
).
Bash implements the
!
keyword to negate the return value of
a pipeline (see section
bashref.html#SEC17
3.2.2 Pipelines
).
Very useful when an
if
statement needs to act only if a test fails.
Bash has the
time
reserved word and command timing (see section
bashref.html#SEC17
3.2.2 Pipelines
).
The display of the timing statistics may be controlled with the
TIMEFORMAT
variable.
Bash implements the
for ((
expr1
;
expr2
;
expr3
))
arithmetic for command, similar to the C language (see section
bashref.html#SEC20
3.2.4.1 Looping Constructs
).
Bash includes the
select
compound command, which allows the
generation of simple menus (see section
bashref.html#SEC21
3.2.4.2 Conditional Constructs
).
Bash includes the
[[
compound command, which makes conditional
testing part of the shell grammar (see section
bashref.html#SEC21
3.2.4.2 Conditional Constructs
).
Bash includes brace expansion (see section
bashref.html#SEC28
3.5.1 Brace Expansion
) and tilde
expansion (see section
bashref.html#SEC29
3.5.2 Tilde Expansion
).
Bash implements command aliases and the
alias
and
unalias
builtins (see section
bashref.html#SEC80
6.6 Aliases
).
Bash provides shell arithmetic, the
((
compound command
(see section
bashref.html#SEC21
3.2.4.2 Conditional Constructs
),
and arithmetic expansion (see section
bashref.html#SEC79
6.5 Shell Arithmetic
).
Variables present in the shell's initial environment are automatically
exported to child processes.  The Bourne shell does not normally do
this unless the variables are explicitly marked using the
export
command.
Bash includes the POSIX pattern removal
`%'
,
`#'
,
`%%'
and
`##'
expansions to remove leading or trailing substrings from
variable values (see section
bashref.html#SEC30
3.5.3 Shell Parameter Expansion
).
The expansion
${#xx}
, which returns the length of
${xx}
,
is supported (see section
bashref.html#SEC30
3.5.3 Shell Parameter Expansion
).
The expansion
${var:
offset
[:
length
]}
,
which expands to the substring of
var
's value of length
length
, beginning at
offset
, is present
(see section
bashref.html#SEC30
3.5.3 Shell Parameter Expansion
).
The expansion
${var/[/]
pattern
[/
replacement
]}
,
which matches
pattern
and replaces it with
replacement
in
the value of
var
, is available (see section
bashref.html#SEC30
3.5.3 Shell Parameter Expansion
).
The expansion
${!
prefix}*
expansion, which expands to
the names of all shell variables whose names begin with
prefix
,
is available (see section
bashref.html#SEC30
3.5.3 Shell Parameter Expansion
).
Bash has
indirect
variable expansion using
${!word}
(see section
bashref.html#SEC30
3.5.3 Shell Parameter Expansion
).
Bash can expand positional parameters beyond
$9
using
${
num
}
.
The POSIX
$()
form of command substitution
is implemented (see section
bashref.html#SEC31
3.5.4 Command Substitution
),
and preferred to the Bourne shell's
"
(which
is also implemented for backwards compatibility).
Bash has process substitution (see section
bashref.html#SEC33
3.5.6 Process Substitution
).
Bash automatically assigns variables that provide information about the
current user (
UID
,
EUID
, and
GROUPS
), the current host
(
HOSTTYPE
,
OSTYPE
,
MACHTYPE
, and
HOSTNAME
),
and the instance of Bash that is running (
BASH
,
BASH_VERSION
, and
BASH_VERSINFO
).  See section
bashref.html#SEC63
5.2 Bash Variables
,
for details.
The
IFS
variable is used to split only the results of expansion,
not all words (see section
bashref.html#SEC34
3.5.7 Word Splitting
).
This closes a longstanding shell security hole.
Bash implements the full set of POSIX 1003.2 filename expansion operators,
including
character classes
,
equivalence classes
, and
collating symbols
(see section
bashref.html#SEC35
3.5.8 Filename Expansion
).
Bash implements extended pattern matching features when the
extglob
shell option is enabled (see section
bashref.html#SEC36
3.5.8.1 Pattern Matching
).
It is possible to have a variable and a function with the same name;
sh
does not separate the two name spaces.
Bash functions are permitted to have local variables using the
local
builtin, and thus useful recursive functions may be written
(see section
bashref.html#SEC58
4.2 Bash Builtin Commands
).
Variable assignments preceding commands affect only that command, even
builtins and functions (see section
bashref.html#SEC52
3.7.4 Environment
).
In
sh
, all variable assignments
preceding commands are global unless the command is executed from the
file system.
Bash performs filename expansion on filenames specified as operands
to input and output redirection operators (see section
bashref.html#SEC38
3.6 Redirections
).
Bash contains the
`<>'
redirection operator, allowing a file to be
opened for both reading and writing, and the
`&>'
redirection
operator, for directing standard output and standard error to the same
file (see section
bashref.html#SEC38
3.6 Redirections
).
Bash treats a number of filenames specially when they are
used in redirection operators (see section
bashref.html#SEC38
3.6 Redirections
).
Bash can open network connections to arbitrary machines and services
with the redirection operators (see section
bashref.html#SEC38
3.6 Redirections
).
The
noclobber
option is available to avoid overwriting existing
files with output redirection (see section
bashref.html#SEC59
4.3 The Set Builtin
).
The
`>|'
redirection operator may be used to override
noclobber
.
The Bash
cd
and
pwd
builtins (see section
bashref.html#SEC57
4.1 Bourne Shell Builtins
)
each take
`-L'
and
`-P'
options to switch between logical and
physical modes.
Bash allows a function to override a builtin with the same name, and provides
access to that builtin's functionality within the function via the
builtin
and
command
builtins (see section
bashref.html#SEC58
4.2 Bash Builtin Commands
).
The
command
builtin allows selective disabling of functions
when command lookup is performed (see section
bashref.html#SEC58
4.2 Bash Builtin Commands
).
Individual builtins may be enabled or disabled using the
enable
builtin (see section
bashref.html#SEC58
4.2 Bash Builtin Commands
).
The Bash
exec
builtin takes additional options that allow users
to control the contents of the environment passed to the executed
command, and what the zeroth argument to the command is to be
(see section
bashref.html#SEC57
4.1 Bourne Shell Builtins
).
Shell functions may be exported to children via the environment
using
export -f
(see section
bashref.html#SEC23
3.3 Shell Functions
).
The Bash
export
,
readonly
, and
declare
builtins can
take a
`-f'
option to act on shell functions, a
`-p'
option to
display variables with various attributes set in a format that can be
used as shell input, a
`-n'
option to remove various variable
attributes, and
`name=value'
arguments to set variable attributes
and values simultaneously.
The Bash
hash
builtin allows a name to be associated with
an arbitrary filename, even when that filename cannot be found by
searching the
$PATH
, using
`hash -p'
(see section
bashref.html#SEC57
4.1 Bourne Shell Builtins
).
Bash includes a
help
builtin for quick reference to shell
facilities (see section
bashref.html#SEC58
4.2 Bash Builtin Commands
).
The
printf
builtin is available to display formatted output
(see section
bashref.html#SEC58
4.2 Bash Builtin Commands
).
The Bash
read
builtin (see section
bashref.html#SEC58
4.2 Bash Builtin Commands
)
will read a line ending in
`\'
with
the
`-r'
option, and will use the
REPLY
variable as a
default if no non-option arguments are supplied.
The Bash
read
builtin
also accepts a prompt string with the
`-p'
option and will use
Readline to obtain the line when given the
`-e'
option.
The
read
builtin also has additional options to control input:
the
`-s'
option will turn off echoing of input characters as
they are read, the
`-t'
option will allow
read
to time out
if input does not arrive within a specified number of seconds, the
`-n'
option will allow reading only a specified number of
characters rather than a full line, and the
`-d'
option will read
until a particular character rather than newline.
The
return
builtin may be used to abort execution of scripts
executed with the
.
or
source
builtins
(see section
bashref.html#SEC57
4.1 Bourne Shell Builtins
).
Bash includes the
shopt
builtin, for finer control of shell
optional capabilities (see section
bashref.html#SEC58
4.2 Bash Builtin Commands
), and allows these options
to be set and unset at shell invocation (see section
bashref.html#SEC65
6.1 Invoking Bash
).
Bash has much more optional behavior controllable with the
set
builtin (see section
bashref.html#SEC59
4.3 The Set Builtin
).
The
`-x'
(
xtrace
) option displays commands other than
simple commands when performing an execution trace
(see section
bashref.html#SEC59
4.3 The Set Builtin
).
The
test
builtin (see section
bashref.html#SEC57
4.1 Bourne Shell Builtins
)
is slightly different, as it implements the POSIX algorithm,
which specifies the behavior based on the number of arguments.
Bash includes the
caller
builtin, which displays the context of
any active subroutine call (a shell function or a script executed with
the
.
or
source
builtins).  This supports the bash
debugger.
The
trap
builtin (see section
bashref.html#SEC57
4.1 Bourne Shell Builtins
) allows a
DEBUG
pseudo-signal specification, similar to
EXIT
.
Commands specified with a
DEBUG
trap are executed before every
simple command,
for
command,
case
command,
select
command, every arithmetic
for
command, and before
the first command executes in a shell function.
The
DEBUG
trap is not inherited by shell functions unless the
function has been given the
trace
attribute or the
functrace
option has been enabled using the
shopt
builtin.
The
extdebug
shell option has additional effects on the
DEBUG
trap.
The
trap
builtin (see section
bashref.html#SEC57
4.1 Bourne Shell Builtins
) allows an
ERR
pseudo-signal specification, similar to
EXIT
and
DEBUG
.
Commands specified with an
ERR
trap are executed after a simple
command fails, with a few exceptions.
The
ERR
trap is not inherited by shell functions unless the
-o errtrace
option to the
set
builtin is enabled.
The
trap
builtin (see section
bashref.html#SEC57
4.1 Bourne Shell Builtins
) allows a
RETURN
pseudo-signal specification, similar to
EXIT
and
DEBUG
.
Commands specified with an
RETURN
trap are executed before
execution resumes after a shell function or a shell script executed with
.
or
source
returns.
The
RETURN
trap is not inherited by shell functions.
The Bash
type
builtin is more extensive and gives more information
about the names it finds (see section
bashref.html#SEC58
4.2 Bash Builtin Commands
).
The Bash
umask
builtin permits a
`-p'
option to cause
the output to be displayed in the form of a
umask
command
that may be reused as input (see section
bashref.html#SEC57
4.1 Bourne Shell Builtins
).
Bash implements a
csh
-like directory stack, and provides the
pushd
,
popd
, and
dirs
builtins to manipulate it
(see section
bashref.html#SEC82
6.8 The Directory Stack
).
Bash also makes the directory stack visible as the value of the
DIRSTACK
shell variable.
Bash interprets special backslash-escaped characters in the prompt
strings when interactive (see section
bashref.html#SEC84
6.9 Controlling the Prompt
).
The Bash restricted mode is more useful (see section
bashref.html#SEC85
6.10 The Restricted Shell
);
the SVR4.2 shell restricted mode is too limited.
The
disown
builtin can remove a job from the internal shell
job table (see section
bashref.html#SEC89
7.2 Job Control Builtins
) or suppress the sending
of
SIGHUP
to a job when the shell exits as the result of a
SIGHUP
.
The SVR4.2 shell has two privilege-related builtins
(
mldmode
and
priv
) not present in Bash.
Bash does not have the
stop
or
newgrp
builtins.
Bash does not use the
SHACCT
variable or perform shell accounting.
The SVR4.2
sh
uses a
TIMEOUT
variable like Bash uses
TMOUT
.
More features unique to Bash may be found in
bashref.html#SEC64
6. Bash Features
.
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B.1 Implementation Differences From The SVR4.2 Shell
Since Bash is a completely new implementation, it does not suffer from
many of the limitations of the SVR4.2 shell.  For instance:
Bash does not fork a subshell when redirecting into or out of
a shell control structure such as  an
if
or
while
statement.
Bash does not allow unbalanced quotes.  The SVR4.2 shell will silently
insert a needed closing quote at
EOF
under certain circumstances.
This can be the cause of some hard-to-find errors.
The SVR4.2 shell uses a baroque memory management scheme based on
trapping
SIGSEGV
.  If the shell is started from a process with
SIGSEGV
blocked (e.g., by using the
system()
C library
function call), it misbehaves badly.
In a questionable attempt at security, the SVR4.2 shell,
when invoked without the
`-p'
option, will alter its real
and effective UID and GID if they are less than some
magic threshold value, commonly 100.
This can lead to unexpected results.
The SVR4.2 shell does not allow users to trap
SIGSEGV
,
SIGALRM
, or
SIGCHLD
.
The SVR4.2 shell does not allow the
IFS
,
MAILCHECK
,
PATH
,
PS1
, or
PS2
variables to be unset.
The SVR4.2 shell treats
`^'
as the undocumented equivalent of
`|'
.
Bash allows multiple option arguments when it is invoked (
-x -v
);
the SVR4.2 shell allows only one option argument (
-xv
).  In
fact, some versions of the shell dump core if the second argument begins
with a
`-'
.
The SVR4.2 shell exits a script if any builtin fails; Bash exits
a script only if one of the POSIX 1003.2 special builtins fails, and
only for certain failures, as enumerated in the POSIX 1003.2 standard.
The SVR4.2 shell behaves differently when invoked as
jsh
(it turns on job control).
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C. Copying This Manual
bashref.html#SEC135
C.1 GNU Free Documentation License
License for copying this manual.
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C.1 GNU Free Documentation License
Version 1.2, November 2002
Copyright (C) 2000,2001,2002 Free Software Foundation, Inc.
59 Temple Place, Suite 330, Boston, MA  02111-1307, USA
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
PREAMBLE
The purpose of this License is to make a manual, textbook, or other
functional and useful document
free
in the sense of freedom: to
assure everyone the effective freedom to copy and redistribute it,
with or without modifying it, either commercially or noncommercially.
Secondarily, this License preserves for the author and publisher a way
to get credit for their work, while not being considered responsible
for modifications made by others.
This License is a kind of "copyleft", which means that derivative
works of the document must themselves be free in the same sense.  It
complements the GNU General Public License, which is a copyleft
license designed for free software.
We have designed this License in order to use it for manuals for free
software, because free software needs free documentation: a free
program should come with manuals providing the same freedoms that the
software does.  But this License is not limited to software manuals;
it can be used for any textual work, regardless of subject matter or
whether it is published as a printed book.  We recommend this License
principally for works whose purpose is instruction or reference.
APPLICABILITY AND DEFINITIONS
This License applies to any manual or other work, in any medium, that
contains a notice placed by the copyright holder saying it can be
distributed under the terms of this License.  Such a notice grants a
world-wide, royalty-free license, unlimited in duration, to use that
work under the conditions stated herein.  The "Document", below,
refers to any such manual or work.  Any member of the public is a
licensee, and is addressed as "you".  You accept the license if you
copy, modify or distribute the work in a way requiring permission
under copyright law.
A "Modified Version" of the Document means any work containing the
Document or a portion of it, either copied verbatim, or with
modifications and/or translated into another language.
A "Secondary Section" is a named appendix or a front-matter section
of the Document that deals exclusively with the relationship of the
publishers or authors of the Document to the Document's overall
subject (or to related matters) and contains nothing that could fall
directly within that overall subject.  (Thus, if the Document is in
part a textbook of mathematics, a Secondary Section may not explain
any mathematics.)  The relationship could be a matter of historical
connection with the subject or with related matters, or of legal,
commercial, philosophical, ethical or political position regarding
them.
The "Invariant Sections" are certain Secondary Sections whose titles
are designated, as being those of Invariant Sections, in the notice
that says that the Document is released under this License.  If a
section does not fit the above definition of Secondary then it is not
allowed to be designated as Invariant.  The Document may contain zero
Invariant Sections.  If the Document does not identify any Invariant
Sections then there are none.
The "Cover Texts" are certain short passages of text that are listed,
as Front-Cover Texts or Back-Cover Texts, in the notice that says that
the Document is released under this License.  A Front-Cover Text may
be at most 5 words, and a Back-Cover Text may be at most 25 words.
A "Transparent" copy of the Document means a machine-readable copy,
represented in a format whose specification is available to the
general public, that is suitable for revising the document
straightforwardly with generic text editors or (for images composed of
pixels) generic paint programs or (for drawings) some widely available
drawing editor, and that is suitable for input to text formatters or
for automatic translation to a variety of formats suitable for input
to text formatters.  A copy made in an otherwise Transparent file
format whose markup, or absence of markup, has been arranged to thwart
or discourage subsequent modification by readers is not Transparent.
An image format is not Transparent if used for any substantial amount
of text.  A copy that is not "Transparent" is called "Opaque".
Examples of suitable formats for Transparent copies include plain
ASCII without markup, Texinfo input format, LaTeX input
format,
SGML
or
XML
using a publicly available
DTD
, and standard-conforming simple
HTML
,
PostScript or
PDF
designed for human modification.  Examples
of transparent image formats include
PNG
,
XCF
and
JPG
.  Opaque formats include proprietary formats that can be
read and edited only by proprietary word processors,
SGML
or
XML
for which the
DTD
and/or processing tools are
not generally available, and the machine-generated
HTML
,
PostScript or
PDF
produced by some word processors for
output purposes only.
The "Title Page" means, for a printed book, the title page itself,
plus such following pages as are needed to hold, legibly, the material
this License requires to appear in the title page.  For works in
formats which do not have any title page as such, "Title Page" means
the text near the most prominent appearance of the work's title,
preceding the beginning of the body of the text.
A section "Entitled XYZ" means a named subunit of the Document whose
title either is precisely XYZ or contains XYZ in parentheses following
text that translates XYZ in another language.  (Here XYZ stands for a
specific section name mentioned below, such as "Acknowledgements",
"Dedications", "Endorsements", or "History".)  To "Preserve the Title"
of such a section when you modify the Document means that it remains a
section "Entitled XYZ" according to this definition.
The Document may include Warranty Disclaimers next to the notice which
states that this License applies to the Document.  These Warranty
Disclaimers are considered to be included by reference in this
License, but only as regards disclaiming warranties: any other
implication that these Warranty Disclaimers may have is void and has
no effect on the meaning of this License.
VERBATIM COPYING
You may copy and distribute the Document in any medium, either
commercially or noncommercially, provided that this License, the
copyright notices, and the license notice saying this License applies
to the Document are reproduced in all copies, and that you add no other
conditions whatsoever to those of this License.  You may not use
technical measures to obstruct or control the reading or further
copying of the copies you make or distribute.  However, you may accept
compensation in exchange for copies.  If you distribute a large enough
number of copies you must also follow the conditions in section 3.
You may also lend copies, under the same conditions stated above, and
you may publicly display copies.
COPYING IN QUANTITY
If you publish printed copies (or copies in media that commonly have
printed covers) of the Document, numbering more than 100, and the
Document's license notice requires Cover Texts, you must enclose the
copies in covers that carry, clearly and legibly, all these Cover
Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
the back cover.  Both covers must also clearly and legibly identify
you as the publisher of these copies.  The front cover must present
the full title with all words of the title equally prominent and
visible.  You may add other material on the covers in addition.
Copying with changes limited to the covers, as long as they preserve
the title of the Document and satisfy these conditions, can be treated
as verbatim copying in other respects.
If the required texts for either cover are too voluminous to fit
legibly, you should put the first ones listed (as many as fit
reasonably) on the actual cover, and continue the rest onto adjacent
pages.
If you publish or distribute Opaque copies of the Document numbering
more than 100, you must either include a machine-readable Transparent
copy along with each Opaque copy, or state in or with each Opaque copy
a computer-network location from which the general network-using
public has access to download using public-standard network protocols
a complete Transparent copy of the Document, free of added material.
If you use the latter option, you must take reasonably prudent steps,
when you begin distribution of Opaque copies in quantity, to ensure
that this Transparent copy will remain thus accessible at the stated
location until at least one year after the last time you distribute an
Opaque copy (directly or through your agents or retailers) of that
edition to the public.
It is requested, but not required, that you contact the authors of the
Document well before redistributing any large number of copies, to give
them a chance to provide you with an updated version of the Document.
MODIFICATIONS
You may copy and distribute a Modified Version of the Document under
the conditions of sections 2 and 3 above, provided that you release
the Modified Version under precisely this License, with the Modified
Version filling the role of the Document, thus licensing distribution
and modification of the Modified Version to whoever possesses a copy
of it.  In addition, you must do these things in the Modified Version:
Use in the Title Page (and on the covers, if any) a title distinct
from that of the Document, and from those of previous versions
(which should, if there were any, be listed in the History section
of the Document).  You may use the same title as a previous version
if the original publisher of that version gives permission.
List on the Title Page, as authors, one or more persons or entities
responsible for authorship of the modifications in the Modified
Version, together with at least five of the principal authors of the
Document (all of its principal authors, if it has fewer than five),
unless they release you from this requirement.
State on the Title page the name of the publisher of the
Modified Version, as the publisher.
Preserve all the copyright notices of the Document.
Add an appropriate copyright notice for your modifications
adjacent to the other copyright notices.
Include, immediately after the copyright notices, a license notice
giving the public permission to use the Modified Version under the
terms of this License, in the form shown in the Addendum below.
Preserve in that license notice the full lists of Invariant Sections
and required Cover Texts given in the Document's license notice.
Include an unaltered copy of this License.
Preserve the section Entitled "History", Preserve its Title, and add
to it an item stating at least the title, year, new authors, and
publisher of the Modified Version as given on the Title Page.  If
there is no section Entitled "History" in the Document, create one
stating the title, year, authors, and publisher of the Document as
given on its Title Page, then add an item describing the Modified
Version as stated in the previous sentence.
Preserve the network location, if any, given in the Document for
public access to a Transparent copy of the Document, and likewise
the network locations given in the Document for previous versions
it was based on.  These may be placed in the "History" section.
You may omit a network location for a work that was published at
least four years before the Document itself, or if the original
publisher of the version it refers to gives permission.
For any section Entitled "Acknowledgements" or "Dedications", Preserve
the Title of the section, and preserve in the section all the
substance and tone of each of the contributor acknowledgements and/or
dedications given therein.
Preserve all the Invariant Sections of the Document,
unaltered in their text and in their titles.  Section numbers
or the equivalent are not considered part of the section titles.
Delete any section Entitled "Endorsements".  Such a section
may not be included in the Modified Version.
Do not retitle any existing section to be Entitled "Endorsements" or
to conflict in title with any Invariant Section.
Preserve any Warranty Disclaimers.
If the Modified Version includes new front-matter sections or
appendices that qualify as Secondary Sections and contain no material
copied from the Document, you may at your option designate some or all
of these sections as invariant.  To do this, add their titles to the
list of Invariant Sections in the Modified Version's license notice.
These titles must be distinct from any other section titles.
You may add a section Entitled "Endorsements", provided it contains
nothing but endorsements of your Modified Version by various
parties--for example, statements of peer review or that the text has
been approved by an organization as the authoritative definition of a
standard.
You may add a passage of up to five words as a Front-Cover Text, and a
passage of up to 25 words as a Back-Cover Text, to the end of the list
of Cover Texts in the Modified Version.  Only one passage of
Front-Cover Text and one of Back-Cover Text may be added by (or
through arrangements made by) any one entity.  If the Document already
includes a cover text for the same cover, previously added by you or
by arrangement made by the same entity you are acting on behalf of,
you may not add another; but you may replace the old one, on explicit
permission from the previous publisher that added the old one.
The author(s) and publisher(s) of the Document do not by this License
give permission to use their names for publicity for or to assert or
imply endorsement of any Modified Version.
COMBINING DOCUMENTS
You may combine the Document with other documents released under this
License, under the terms defined in section 4 above for modified
versions, provided that you include in the combination all of the
Invariant Sections of all of the original documents, unmodified, and
list them all as Invariant Sections of your combined work in its
license notice, and that you preserve all their Warranty Disclaimers.
The combined work need only contain one copy of this License, and
multiple identical Invariant Sections may be replaced with a single
copy.  If there are multiple Invariant Sections with the same name but
different contents, make the title of each such section unique by
adding at the end of it, in parentheses, the name of the original
author or publisher of that section if known, or else a unique number.
Make the same adjustment to the section titles in the list of
Invariant Sections in the license notice of the combined work.
In the combination, you must combine any sections Entitled "History"
in the various original documents, forming one section Entitled
"History"; likewise combine any sections Entitled "Acknowledgements",
and any sections Entitled "Dedications".  You must delete all
sections Entitled "Endorsements."
COLLECTIONS OF DOCUMENTS
You may make a collection consisting of the Document and other documents
released under this License, and replace the individual copies of this
License in the various documents with a single copy that is included in
the collection, provided that you follow the rules of this License for
verbatim copying of each of the documents in all other respects.
You may extract a single document from such a collection, and distribute
it individually under this License, provided you insert a copy of this
License into the extracted document, and follow this License in all
other respects regarding verbatim copying of that document.
AGGREGATION WITH INDEPENDENT WORKS
A compilation of the Document or its derivatives with other separate
and independent documents or works, in or on a volume of a storage or
distribution medium, is called an "aggregate" if the copyright
resulting from the compilation is not used to limit the legal rights
of the compilation's users beyond what the individual works permit.
When the Document is included an aggregate, this License does not
apply to the other works in the aggregate which are not themselves
derivative works of the Document.
If the Cover Text requirement of section 3 is applicable to these
copies of the Document, then if the Document is less than one half of
the entire aggregate, the Document's Cover Texts may be placed on
covers that bracket the Document within the aggregate, or the
electronic equivalent of covers if the Document is in electronic form.
Otherwise they must appear on printed covers that bracket the whole
aggregate.
TRANSLATION
Translation is considered a kind of modification, so you may
distribute translations of the Document under the terms of section 4.
Replacing Invariant Sections with translations requires special
permission from their copyright holders, but you may include
translations of some or all Invariant Sections in addition to the
original versions of these Invariant Sections.  You may include a
translation of this License, and all the license notices in the
Document, and any Warranty Disclaimers, provided that you also include
the original English version of this License and the original versions
of those notices and disclaimers.  In case of a disagreement between
the translation and the original version of this License or a notice
or disclaimer, the original version will prevail.
If a section in the Document is Entitled "Acknowledgements",
"Dedications", or "History", the requirement (section 4) to Preserve
its Title (section 1) will typically require changing the actual
title.
TERMINATION
You may not copy, modify, sublicense, or distribute the Document except
as expressly provided for under this License.  Any other attempt to
copy, modify, sublicense or distribute the Document is void, and will
automatically terminate your rights under this License.  However,
parties who have received copies, or rights, from you under this
License will not have their licenses terminated so long as such
parties remain in full compliance.
FUTURE REVISIONS OF THIS LICENSE
The Free Software Foundation may publish new, revised versions
of the GNU Free Documentation License from time to time.  Such new
versions will be similar in spirit to the present version, but may
differ in detail to address new problems or concerns.  See
http://www.gnu.org/copyleft/
http://www.gnu.org/copyleft/
.
Each version of the License is given a distinguishing version number.
If the Document specifies that a particular numbered version of this
License "or any later version" applies to it, you have the option of
following the terms and conditions either of that specified version or
of any later version that has been published (not as a draft) by the
Free Software Foundation.  If the Document does not specify a version
number of this License, you may choose any version ever published (not
as a draft) by the Free Software Foundation.
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C.1.1 ADDENDUM: How to use this License for your documents
To use this License in a document you have written, include a copy of
the License in the document and put the following copyright and
license notices just after the title page:
Copyright (C)
year
your name
.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.2
or any later version published by the Free Software Foundation;
with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
A copy of the license is included in the section entitled ``GNU
Free Documentation License''.
If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
replace the "with...Texts." line with this:
with the Invariant Sections being
list their titles
, with
the Front-Cover Texts being
list
, and with the Back-Cover Texts
being
list
.
If you have Invariant Sections without Cover Texts, or some other
combination of the three, merge those two alternatives to suit the
situation.
If your document contains nontrivial examples of program code, we
recommend releasing these examples in parallel under your choice of
free software license, such as the GNU General Public License,
to permit their use in free software.
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Index of Shell Builtin Commands
Jump to:
bashref.html#bt_.
.
bashref.html#bt_:
:
bashref.html#bt_[
[
bashref.html#bt_A
A
bashref.html#bt_B
B
bashref.html#bt_C
C
bashref.html#bt_D
D
bashref.html#bt_E
E
bashref.html#bt_F
F
bashref.html#bt_G
G
bashref.html#bt_H
H
bashref.html#bt_J
J
bashref.html#bt_K
K
bashref.html#bt_L
L
bashref.html#bt_P
P
bashref.html#bt_R
R
bashref.html#bt_S
S
bashref.html#bt_T
T
bashref.html#bt_U
U
bashref.html#bt_W
W
Index Entry
Section
.
bashref.html#IDX69
.
bashref.html#SEC57
4.1 Bourne Shell Builtins
:
bashref.html#IDX68
:
bashref.html#SEC57
4.1 Bourne Shell Builtins
[
bashref.html#IDX84
[
bashref.html#SEC57
4.1 Bourne Shell Builtins
A
bashref.html#IDX89
alias
bashref.html#SEC58
4.2 Bash Builtin Commands
B
bashref.html#IDX273
bg
bashref.html#SEC89
7.2 Job Control Builtins
bashref.html#IDX90
bind
bashref.html#SEC58
4.2 Bash Builtin Commands
bashref.html#IDX70
break
bashref.html#SEC57
4.1 Bourne Shell Builtins
bashref.html#IDX91
builtin
bashref.html#SEC58
4.2 Bash Builtin Commands
C
bashref.html#IDX92
caller
bashref.html#SEC58
4.2 Bash Builtin Commands
bashref.html#IDX71
cd
bashref.html#SEC57
4.1 Bourne Shell Builtins
bashref.html#IDX93
command
bashref.html#SEC58
4.2 Bash Builtin Commands
bashref.html#IDX501
compgen
bashref.html#SEC114
8.7 Programmable Completion Builtins
bashref.html#IDX502
complete
bashref.html#SEC114
8.7 Programmable Completion Builtins
bashref.html#IDX72
continue
bashref.html#SEC57
4.1 Bourne Shell Builtins
D
bashref.html#IDX94
declare
bashref.html#SEC58
4.2 Bash Builtin Commands
bashref.html#IDX270
dirs
bashref.html#SEC83
6.8.1 Directory Stack Builtins
bashref.html#IDX278
disown
bashref.html#SEC89
7.2 Job Control Builtins
E
bashref.html#IDX95
echo
bashref.html#SEC58
4.2 Bash Builtin Commands
bashref.html#IDX96
enable
bashref.html#SEC58
4.2 Bash Builtin Commands
bashref.html#IDX73
eval
bashref.html#SEC57
4.1 Bourne Shell Builtins
bashref.html#IDX74
exec
bashref.html#SEC57
4.1 Bourne Shell Builtins
bashref.html#IDX75
exit
bashref.html#SEC57
4.1 Bourne Shell Builtins
bashref.html#IDX76
export
bashref.html#SEC57
4.1 Bourne Shell Builtins
F
bashref.html#IDX504
fc
bashref.html#SEC117
9.2 Bash History Builtins
bashref.html#IDX274
fg
bashref.html#SEC89
7.2 Job Control Builtins
G
bashref.html#IDX77
getopts
bashref.html#SEC57
4.1 Bourne Shell Builtins
H
bashref.html#IDX78
hash
bashref.html#SEC57
4.1 Bourne Shell Builtins
bashref.html#IDX97
help
bashref.html#SEC58
4.2 Bash Builtin Commands
bashref.html#IDX505
history
bashref.html#SEC117
9.2 Bash History Builtins
J
bashref.html#IDX275
jobs
bashref.html#SEC89
7.2 Job Control Builtins
K
bashref.html#IDX276
kill
bashref.html#SEC89
7.2 Job Control Builtins
L
bashref.html#IDX98
let
bashref.html#SEC58
4.2 Bash Builtin Commands
bashref.html#IDX99
local
bashref.html#SEC58
4.2 Bash Builtin Commands
bashref.html#IDX100
logout
bashref.html#SEC58
4.2 Bash Builtin Commands
P
bashref.html#IDX271
popd
bashref.html#SEC83
6.8.1 Directory Stack Builtins
bashref.html#IDX101
printf
bashref.html#SEC58
4.2 Bash Builtin Commands
bashref.html#IDX272
pushd
bashref.html#SEC83
6.8.1 Directory Stack Builtins
bashref.html#IDX79
pwd
bashref.html#SEC57
4.1 Bourne Shell Builtins
R
bashref.html#IDX102
read
bashref.html#SEC58
4.2 Bash Builtin Commands
bashref.html#IDX80
readonly
bashref.html#SEC57
4.1 Bourne Shell Builtins
bashref.html#IDX81
return
bashref.html#SEC57
4.1 Bourne Shell Builtins
S
bashref.html#IDX109
set
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4.3 The Set Builtin
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shift
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4.1 Bourne Shell Builtins
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shopt
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4.2 Bash Builtin Commands
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source
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4.2 Bash Builtin Commands
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suspend
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7.2 Job Control Builtins
T
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test
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4.1 Bourne Shell Builtins
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times
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4.1 Bourne Shell Builtins
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trap
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4.1 Bourne Shell Builtins
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type
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4.2 Bash Builtin Commands
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typeset
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4.2 Bash Builtin Commands
U
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ulimit
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4.2 Bash Builtin Commands
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umask
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4.1 Bourne Shell Builtins
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unalias
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4.2 Bash Builtin Commands
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unset
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4.1 Bourne Shell Builtins
W
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wait
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7.2 Job Control Builtins
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bashref.html#rw_C
C
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D
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E
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F
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Index Entry
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3.2.2 Pipelines
[
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[[
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3.2.4.2 Conditional Constructs
]
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]]
bashref.html#SEC21
3.2.4.2 Conditional Constructs
{
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{
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3.2.4.3 Grouping Commands
}
bashref.html#IDX44
}
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3.2.4.3 Grouping Commands
C
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case
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3.2.4.2 Conditional Constructs
D
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do
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3.2.4.1 Looping Constructs
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done
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3.2.4.1 Looping Constructs
E
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elif
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3.2.4.2 Conditional Constructs
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else
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3.2.4.2 Conditional Constructs
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esac
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3.2.4.2 Conditional Constructs
F
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fi
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3.2.4.2 Conditional Constructs
bashref.html#IDX31
for
bashref.html#SEC20
3.2.4.1 Looping Constructs
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function
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3.3 Shell Functions
I
bashref.html#IDX32
if
bashref.html#SEC21
3.2.4.2 Conditional Constructs
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in
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3.2.4.2 Conditional Constructs
S
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select
bashref.html#SEC21
3.2.4.2 Conditional Constructs
T
bashref.html#IDX33
then
bashref.html#SEC21
3.2.4.2 Conditional Constructs
bashref.html#IDX24
time
bashref.html#SEC17
3.2.2 Pipelines
U
bashref.html#IDX27
until
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3.2.4.1 Looping Constructs
W
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while
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3.2.4.1 Looping Constructs
Jump to:
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]
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C
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D
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F
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I
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*
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0
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?
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A
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Index Entry
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3.4.2 Special Parameters
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!
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3.4.2 Special Parameters
#
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#
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3.4.2 Special Parameters
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#
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3.4.2 Special Parameters
$
bashref.html#IDX56
$
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3.4.2 Special Parameters
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$
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3.4.2 Special Parameters
*
bashref.html#IDX46
*
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3.4.2 Special Parameters
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*
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3.4.2 Special Parameters
-
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-
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3.4.2 Special Parameters
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-
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3.4.2 Special Parameters
0
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0
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3.4.2 Special Parameters
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0
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3.4.2 Special Parameters
?
bashref.html#IDX52
?
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3.4.2 Special Parameters
bashref.html#IDX53
?
bashref.html#SEC26
3.4.2 Special Parameters
@
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@
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3.4.2 Special Parameters
bashref.html#IDX49
@
bashref.html#SEC26
3.4.2 Special Parameters
_
bashref.html#IDX62
_
bashref.html#SEC26
3.4.2 Special Parameters
bashref.html#IDX63
_
bashref.html#SEC26
3.4.2 Special Parameters
A
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auto_resume
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7.3 Job Control Variables
bashref.html#IDX281
auto_resume
bashref.html#SEC90
7.3 Job Control Variables
B
bashref.html#IDX130
BASH
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX131
BASH
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX132
BASH_ARGC
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5.2 Bash Variables
bashref.html#IDX133
BASH_ARGC
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5.2 Bash Variables
bashref.html#IDX134
BASH_ARGV
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5.2 Bash Variables
bashref.html#IDX135
BASH_ARGV
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX136
BASH_COMMAND
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5.2 Bash Variables
bashref.html#IDX137
BASH_COMMAND
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX138
BASH_ENV
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX139
BASH_ENV
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5.2 Bash Variables
bashref.html#IDX140
BASH_EXECUTION_STRING
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX141
BASH_EXECUTION_STRING
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX142
BASH_LINENO
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX143
BASH_LINENO
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX144
BASH_REMATCH
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX145
BASH_REMATCH
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX146
BASH_SOURCE
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX147
BASH_SOURCE
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX148
BASH_SUBSHELL
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX149
BASH_SUBSHELL
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX150
BASH_VERSINFO
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX151
BASH_VERSINFO
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX152
BASH_VERSION
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX153
BASH_VERSION
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX287
bell-style
bashref.html#SEC100
8.3.1 Readline Init File Syntax
C
bashref.html#IDX110
CDPATH
bashref.html#SEC62
5.1 Bourne Shell Variables
bashref.html#IDX111
CDPATH
bashref.html#SEC62
5.1 Bourne Shell Variables
bashref.html#IDX154
COLUMNS
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX155
COLUMNS
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX288
comment-begin
bashref.html#SEC100
8.3.1 Readline Init File Syntax
bashref.html#IDX156
COMP_CWORD
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX157
COMP_CWORD
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX158
COMP_LINE
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX159
COMP_LINE
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX160
COMP_POINT
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX161
COMP_POINT
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX162
COMP_WORDBREAKS
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX163
COMP_WORDBREAKS
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX164
COMP_WORDS
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX165
COMP_WORDS
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX289
completion-query-items
bashref.html#SEC100
8.3.1 Readline Init File Syntax
bashref.html#IDX166
COMPREPLY
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX167
COMPREPLY
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX290
convert-meta
bashref.html#SEC100
8.3.1 Readline Init File Syntax
D
bashref.html#IDX168
DIRSTACK
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX169
DIRSTACK
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX291
disable-completion
bashref.html#SEC100
8.3.1 Readline Init File Syntax
E
bashref.html#IDX292
editing-mode
bashref.html#SEC100
8.3.1 Readline Init File Syntax
bashref.html#IDX170
EMACS
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX171
EMACS
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX293
enable-keypad
bashref.html#SEC100
8.3.1 Readline Init File Syntax
bashref.html#IDX172
EUID
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX173
EUID
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX294
expand-tilde
bashref.html#SEC100
8.3.1 Readline Init File Syntax
F
bashref.html#IDX174
FCEDIT
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX175
FCEDIT
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX176
FIGNORE
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX177
FIGNORE
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX178
FUNCNAME
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX179
FUNCNAME
bashref.html#SEC63
5.2 Bash Variables
G
bashref.html#IDX180
GLOBIGNORE
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX181
GLOBIGNORE
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX182
GROUPS
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX183
GROUPS
bashref.html#SEC63
5.2 Bash Variables
H
bashref.html#IDX184
histchars
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX185
histchars
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX186
HISTCMD
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX187
HISTCMD
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX188
HISTCONTROL
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX189
HISTCONTROL
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX190
HISTFILE
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX191
HISTFILE
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX192
HISTFILESIZE
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX193
HISTFILESIZE
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX194
HISTIGNORE
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX195
HISTIGNORE
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX295
history-preserve-point
bashref.html#SEC100
8.3.1 Readline Init File Syntax
bashref.html#IDX196
HISTSIZE
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX197
HISTSIZE
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX198
HISTTIMEFORMAT
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX199
HISTTIMEFORMAT
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX112
HOME
bashref.html#SEC62
5.1 Bourne Shell Variables
bashref.html#IDX113
HOME
bashref.html#SEC62
5.1 Bourne Shell Variables
bashref.html#IDX296
horizontal-scroll-mode
bashref.html#SEC100
8.3.1 Readline Init File Syntax
bashref.html#IDX200
HOSTFILE
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX201
HOSTFILE
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX202
HOSTNAME
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX203
HOSTNAME
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX204
HOSTTYPE
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX205
HOSTTYPE
bashref.html#SEC63
5.2 Bash Variables
I
bashref.html#IDX114
IFS
bashref.html#SEC62
5.1 Bourne Shell Variables
bashref.html#IDX115
IFS
bashref.html#SEC62
5.1 Bourne Shell Variables
bashref.html#IDX206
IGNOREEOF
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX207
IGNOREEOF
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX297
input-meta
bashref.html#SEC100
8.3.1 Readline Init File Syntax
bashref.html#IDX208
INPUTRC
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX209
INPUTRC
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX299
isearch-terminators
bashref.html#SEC100
8.3.1 Readline Init File Syntax
K
bashref.html#IDX300
keymap
bashref.html#SEC100
8.3.1 Readline Init File Syntax
L
bashref.html#IDX210
LANG
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX211
LANG
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX212
LC_ALL
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX213
LC_ALL
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX214
LC_COLLATE
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX215
LC_COLLATE
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX216
LC_CTYPE
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX217
LC_CTYPE
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX21
LC_MESSAGES
bashref.html#SEC13
3.1.2.5 Locale-Specific Translation
bashref.html#IDX218
LC_MESSAGES
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX219
LC_MESSAGES
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX220
LC_NUMERIC
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX221
LC_NUMERIC
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX222
LINENO
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX223
LINENO
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX224
LINES
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX225
LINES
bashref.html#SEC63
5.2 Bash Variables
M
bashref.html#IDX226
MACHTYPE
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX227
MACHTYPE
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX116
MAIL
bashref.html#SEC62
5.1 Bourne Shell Variables
bashref.html#IDX117
MAIL
bashref.html#SEC62
5.1 Bourne Shell Variables
bashref.html#IDX228
MAILCHECK
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX229
MAILCHECK
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX118
MAILPATH
bashref.html#SEC62
5.1 Bourne Shell Variables
bashref.html#IDX119
MAILPATH
bashref.html#SEC62
5.1 Bourne Shell Variables
bashref.html#IDX301
mark-modified-lines
bashref.html#SEC100
8.3.1 Readline Init File Syntax
bashref.html#IDX302
mark-symlinked-directories
bashref.html#SEC100
8.3.1 Readline Init File Syntax
bashref.html#IDX303
match-hidden-files
bashref.html#SEC100
8.3.1 Readline Init File Syntax
bashref.html#IDX298
meta-flag
bashref.html#SEC100
8.3.1 Readline Init File Syntax
O
bashref.html#IDX230
OLDPWD
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX231
OLDPWD
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX120
OPTARG
bashref.html#SEC62
5.1 Bourne Shell Variables
bashref.html#IDX121
OPTARG
bashref.html#SEC62
5.1 Bourne Shell Variables
bashref.html#IDX232
OPTERR
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX233
OPTERR
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX122
OPTIND
bashref.html#SEC62
5.1 Bourne Shell Variables
bashref.html#IDX123
OPTIND
bashref.html#SEC62
5.1 Bourne Shell Variables
bashref.html#IDX234
OSTYPE
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX235
OSTYPE
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX304
output-meta
bashref.html#SEC100
8.3.1 Readline Init File Syntax
P
bashref.html#IDX305
page-completions
bashref.html#SEC100
8.3.1 Readline Init File Syntax
bashref.html#IDX124
PATH
bashref.html#SEC62
5.1 Bourne Shell Variables
bashref.html#IDX125
PATH
bashref.html#SEC62
5.1 Bourne Shell Variables
bashref.html#IDX236
PIPESTATUS
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX237
PIPESTATUS
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX238
POSIXLY_CORRECT
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX239
POSIXLY_CORRECT
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX240
PPID
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX241
PPID
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX242
PROMPT_COMMAND
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX243
PROMPT_COMMAND
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX126
PS1
bashref.html#SEC62
5.1 Bourne Shell Variables
bashref.html#IDX127
PS1
bashref.html#SEC62
5.1 Bourne Shell Variables
bashref.html#IDX128
PS2
bashref.html#SEC62
5.1 Bourne Shell Variables
bashref.html#IDX129
PS2
bashref.html#SEC62
5.1 Bourne Shell Variables
bashref.html#IDX244
PS3
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX245
PS3
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX246
PS4
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX247
PS4
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX248
PWD
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX249
PWD
bashref.html#SEC63
5.2 Bash Variables
R
bashref.html#IDX250
RANDOM
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX251
RANDOM
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX252
REPLY
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX253
REPLY
bashref.html#SEC63
5.2 Bash Variables
S
bashref.html#IDX254
SECONDS
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX255
SECONDS
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX256
SHELL
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX257
SHELL
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX258
SHELLOPTS
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX259
SHELLOPTS
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX260
SHLVL
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX261
SHLVL
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX306
show-all-if-ambiguous
bashref.html#SEC100
8.3.1 Readline Init File Syntax
bashref.html#IDX307
show-all-if-unmodified
bashref.html#SEC100
8.3.1 Readline Init File Syntax
T
bashref.html#IDX22
TEXTDOMAIN
bashref.html#SEC13
3.1.2.5 Locale-Specific Translation
bashref.html#IDX23
TEXTDOMAINDIR
bashref.html#SEC13
3.1.2.5 Locale-Specific Translation
bashref.html#IDX262
TIMEFORMAT
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX263
TIMEFORMAT
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX264
TMOUT
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX265
TMOUT
bashref.html#SEC63
5.2 Bash Variables
U
bashref.html#IDX266
UID
bashref.html#SEC63
5.2 Bash Variables
bashref.html#IDX267
UID
bashref.html#SEC63
5.2 Bash Variables
V
bashref.html#IDX308
visible-stats
bashref.html#SEC100
8.3.1 Readline Init File Syntax
Jump to:
bashref.html#vr_!
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bashref.html#vr_0
0
bashref.html#vr_?
?
bashref.html#vr_@
@
bashref.html#vr__
_
bashref.html#vr_A
A
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B
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[
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<
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>
]
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Top
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[
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Contents
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Function Index
Jump to:
bashref.html#fn_A
A
bashref.html#fn_B
B
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C
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D
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E
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F
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G
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H
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U
bashref.html#fn_Y
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Index Entry
Section
A
bashref.html#IDX449
abort (C-g)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX450
abort (C-g)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX325
accept-line (Newline or Return)
bashref.html#SEC105
8.4.2 Commands For Manipulating The History
bashref.html#IDX326
accept-line (Newline or Return)
bashref.html#SEC105
8.4.2 Commands For Manipulating The History
bashref.html#IDX491
alias-expand-line ()
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX492
alias-expand-line ()
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
B
bashref.html#IDX315
backward-char (C-b)
bashref.html#SEC104
8.4.1 Commands For Moving
bashref.html#IDX316
backward-char (C-b)
bashref.html#SEC104
8.4.1 Commands For Moving
bashref.html#IDX353
backward-delete-char (Rubout)
bashref.html#SEC106
8.4.3 Commands For Changing Text
bashref.html#IDX354
backward-delete-char (Rubout)
bashref.html#SEC106
8.4.3 Commands For Changing Text
bashref.html#IDX375
backward-kill-line (C-x Rubout)
bashref.html#SEC107
8.4.4 Killing And Yanking
bashref.html#IDX376
backward-kill-line (C-x Rubout)
bashref.html#SEC107
8.4.4 Killing And Yanking
bashref.html#IDX383
backward-kill-word (M-
DEL
)
bashref.html#SEC107
8.4.4 Killing And Yanking
bashref.html#IDX384
backward-kill-word (M-
DEL
)
bashref.html#SEC107
8.4.4 Killing And Yanking
bashref.html#IDX319
backward-word (M-b)
bashref.html#SEC104
8.4.1 Commands For Moving
bashref.html#IDX320
backward-word (M-b)
bashref.html#SEC104
8.4.1 Commands For Moving
bashref.html#IDX331
beginning-of-history (M-&#60;)
bashref.html#SEC105
8.4.2 Commands For Manipulating The History
bashref.html#IDX332
beginning-of-history (M-&#60;)
bashref.html#SEC105
8.4.2 Commands For Manipulating The History
bashref.html#IDX309
beginning-of-line (C-a)
bashref.html#SEC104
8.4.1 Commands For Moving
bashref.html#IDX310
beginning-of-line (C-a)
bashref.html#SEC104
8.4.1 Commands For Moving
C
bashref.html#IDX445
call-last-kbd-macro (C-x e)
bashref.html#SEC110
8.4.7 Keyboard Macros
bashref.html#IDX446
call-last-kbd-macro (C-x e)
bashref.html#SEC110
8.4.7 Keyboard Macros
bashref.html#IDX369
capitalize-word (M-c)
bashref.html#SEC106
8.4.3 Commands For Changing Text
bashref.html#IDX370
capitalize-word (M-c)
bashref.html#SEC106
8.4.3 Commands For Changing Text
bashref.html#IDX465
character-search (C-])
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX466
character-search (C-])
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX467
character-search-backward (M-C-])
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX468
character-search-backward (M-C-])
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX321
clear-screen (C-l)
bashref.html#SEC104
8.4.1 Commands For Moving
bashref.html#IDX322
clear-screen (C-l)
bashref.html#SEC104
8.4.1 Commands For Moving
bashref.html#IDX407
complete (
TAB
)
bashref.html#SEC109
8.4.6 Letting Readline Type For You
bashref.html#IDX408
complete (
TAB
)
bashref.html#SEC109
8.4.6 Letting Readline Type For You
bashref.html#IDX433
complete-command (M-!)
bashref.html#SEC109
8.4.6 Letting Readline Type For You
bashref.html#IDX434
complete-command (M-!)
bashref.html#SEC109
8.4.6 Letting Readline Type For You
bashref.html#IDX417
complete-filename (M-/)
bashref.html#SEC109
8.4.6 Letting Readline Type For You
bashref.html#IDX418
complete-filename (M-/)
bashref.html#SEC109
8.4.6 Letting Readline Type For You
bashref.html#IDX429
complete-hostname (M-@)
bashref.html#SEC109
8.4.6 Letting Readline Type For You
bashref.html#IDX430
complete-hostname (M-@)
bashref.html#SEC109
8.4.6 Letting Readline Type For You
bashref.html#IDX439
complete-into-braces (M-{)
bashref.html#SEC109
8.4.6 Letting Readline Type For You
bashref.html#IDX440
complete-into-braces (M-{)
bashref.html#SEC109
8.4.6 Letting Readline Type For You
bashref.html#IDX421
complete-username (M-~)
bashref.html#SEC109
8.4.6 Letting Readline Type For You
bashref.html#IDX422
complete-username (M-~)
bashref.html#SEC109
8.4.6 Letting Readline Type For You
bashref.html#IDX425
complete-variable (M-$)
bashref.html#SEC109
8.4.6 Letting Readline Type For You
bashref.html#IDX426
complete-variable (M-$)
bashref.html#SEC109
8.4.6 Letting Readline Type For You
bashref.html#IDX395
copy-backward-word ()
bashref.html#SEC107
8.4.4 Killing And Yanking
bashref.html#IDX396
copy-backward-word ()
bashref.html#SEC107
8.4.4 Killing And Yanking
bashref.html#IDX397
copy-forward-word ()
bashref.html#SEC107
8.4.4 Killing And Yanking
bashref.html#IDX398
copy-forward-word ()
bashref.html#SEC107
8.4.4 Killing And Yanking
bashref.html#IDX393
copy-region-as-kill ()
bashref.html#SEC107
8.4.4 Killing And Yanking
bashref.html#IDX394
copy-region-as-kill ()
bashref.html#SEC107
8.4.4 Killing And Yanking
D
bashref.html#IDX351
delete-char (C-d)
bashref.html#SEC106
8.4.3 Commands For Changing Text
bashref.html#IDX352
delete-char (C-d)
bashref.html#SEC106
8.4.3 Commands For Changing Text
bashref.html#IDX415
delete-char-or-list ()
bashref.html#SEC109
8.4.6 Letting Readline Type For You
bashref.html#IDX416
delete-char-or-list ()
bashref.html#SEC109
8.4.6 Letting Readline Type For You
bashref.html#IDX389
delete-horizontal-space ()
bashref.html#SEC107
8.4.4 Killing And Yanking
bashref.html#IDX390
delete-horizontal-space ()
bashref.html#SEC107
8.4.4 Killing And Yanking
bashref.html#IDX403
digit-argument (
M-0
,
M-1
, <small>...</small>
M--
)
bashref.html#SEC108
8.4.5 Specifying Numeric Arguments
bashref.html#IDX404
digit-argument (
M-0
,
M-1
, <small>...</small>
M--
)
bashref.html#SEC108
8.4.5 Specifying Numeric Arguments
bashref.html#IDX483
display-shell-version (C-x C-v)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX484
display-shell-version (C-x C-v)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX451
do-uppercase-version (M-a, M-b, M-
x
, <small>...</small>)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX452
do-uppercase-version (M-a, M-b, M-
x
, <small>...</small>)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX367
downcase-word (M-l)
bashref.html#SEC106
8.4.3 Commands For Changing Text
bashref.html#IDX368
downcase-word (M-l)
bashref.html#SEC106
8.4.3 Commands For Changing Text
bashref.html#IDX471
dump-functions ()
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX472
dump-functions ()
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX475
dump-macros ()
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX476
dump-macros ()
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX473
dump-variables ()
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX474
dump-variables ()
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX437
dynamic-complete-history (M-
TAB
)
bashref.html#SEC109
8.4.6 Letting Readline Type For You
bashref.html#IDX438
dynamic-complete-history (M-
TAB
)
bashref.html#SEC109
8.4.6 Letting Readline Type For You
E
bashref.html#IDX499
edit-and-execute-command (C-xC-e)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX500
edit-and-execute-command (C-xC-e)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX443
end-kbd-macro (C-x ))
bashref.html#SEC110
8.4.7 Keyboard Macros
bashref.html#IDX444
end-kbd-macro (C-x ))
bashref.html#SEC110
8.4.7 Keyboard Macros
bashref.html#IDX333
end-of-history (M-&#62;)
bashref.html#SEC105
8.4.2 Commands For Manipulating The History
bashref.html#IDX334
end-of-history (M-&#62;)
bashref.html#SEC105
8.4.2 Commands For Manipulating The History
bashref.html#IDX311
end-of-line (C-e)
bashref.html#SEC104
8.4.1 Commands For Moving
bashref.html#IDX312
end-of-line (C-e)
bashref.html#SEC104
8.4.1 Commands For Moving
bashref.html#IDX463
exchange-point-and-mark (C-x C-x)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX464
exchange-point-and-mark (C-x C-x)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
F
bashref.html#IDX355
forward-backward-delete-char ()
bashref.html#SEC106
8.4.3 Commands For Changing Text
bashref.html#IDX356
forward-backward-delete-char ()
bashref.html#SEC106
8.4.3 Commands For Changing Text
bashref.html#IDX313
forward-char (C-f)
bashref.html#SEC104
8.4.1 Commands For Moving
bashref.html#IDX314
forward-char (C-f)
bashref.html#SEC104
8.4.1 Commands For Moving
bashref.html#IDX337
forward-search-history (C-s)
bashref.html#SEC105
8.4.2 Commands For Manipulating The History
bashref.html#IDX338
forward-search-history (C-s)
bashref.html#SEC105
8.4.2 Commands For Manipulating The History
bashref.html#IDX317
forward-word (M-f)
bashref.html#SEC104
8.4.1 Commands For Moving
bashref.html#IDX318
forward-word (M-f)
bashref.html#SEC104
8.4.1 Commands For Moving
G
bashref.html#IDX477
glob-complete-word (M-g)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX478
glob-complete-word (M-g)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX479
glob-expand-word (C-x *)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX480
glob-expand-word (C-x *)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX481
glob-list-expansions (C-x g)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX482
glob-list-expansions (C-x g)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
H
bashref.html#IDX493
history-and-alias-expand-line ()
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX494
history-and-alias-expand-line ()
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX487
history-expand-line (M-^)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX488
history-expand-line (M-^)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX345
history-search-backward ()
bashref.html#SEC105
8.4.2 Commands For Manipulating The History
bashref.html#IDX346
history-search-backward ()
bashref.html#SEC105
8.4.2 Commands For Manipulating The History
bashref.html#IDX343
history-search-forward ()
bashref.html#SEC105
8.4.2 Commands For Manipulating The History
bashref.html#IDX344
history-search-forward ()
bashref.html#SEC105
8.4.2 Commands For Manipulating The History
I
bashref.html#IDX469
insert-comment (M-#)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX470
insert-comment (M-#)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX411
insert-completions (M-*)
bashref.html#SEC109
8.4.6 Letting Readline Type For You
bashref.html#IDX412
insert-completions (M-*)
bashref.html#SEC109
8.4.6 Letting Readline Type For You
bashref.html#IDX495
insert-last-argument (M-. or M-_)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX496
insert-last-argument (M-. or M-_)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
K
bashref.html#IDX373
kill-line (C-k)
bashref.html#SEC107
8.4.4 Killing And Yanking
bashref.html#IDX374
kill-line (C-k)
bashref.html#SEC107
8.4.4 Killing And Yanking
bashref.html#IDX391
kill-region ()
bashref.html#SEC107
8.4.4 Killing And Yanking
bashref.html#IDX392
kill-region ()
bashref.html#SEC107
8.4.4 Killing And Yanking
bashref.html#IDX379
kill-whole-line ()
bashref.html#SEC107
8.4.4 Killing And Yanking
bashref.html#IDX380
kill-whole-line ()
bashref.html#SEC107
8.4.4 Killing And Yanking
bashref.html#IDX381
kill-word (M-d)
bashref.html#SEC107
8.4.4 Killing And Yanking
bashref.html#IDX382
kill-word (M-d)
bashref.html#SEC107
8.4.4 Killing And Yanking
M
bashref.html#IDX489
magic-space ()
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX490
magic-space ()
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX413
menu-complete ()
bashref.html#SEC109
8.4.6 Letting Readline Type For You
bashref.html#IDX414
menu-complete ()
bashref.html#SEC109
8.4.6 Letting Readline Type For You
N
bashref.html#IDX329
next-history (C-n)
bashref.html#SEC105
8.4.2 Commands For Manipulating The History
bashref.html#IDX330
next-history (C-n)
bashref.html#SEC105
8.4.2 Commands For Manipulating The History
bashref.html#IDX341
non-incremental-forward-search-history (M-n)
bashref.html#SEC105
8.4.2 Commands For Manipulating The History
bashref.html#IDX342
non-incremental-forward-search-history (M-n)
bashref.html#SEC105
8.4.2 Commands For Manipulating The History
bashref.html#IDX339
non-incremental-reverse-search-history (M-p)
bashref.html#SEC105
8.4.2 Commands For Manipulating The History
bashref.html#IDX340
non-incremental-reverse-search-history (M-p)
bashref.html#SEC105
8.4.2 Commands For Manipulating The History
O
bashref.html#IDX497
operate-and-get-next (C-o)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX498
operate-and-get-next (C-o)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX371
overwrite-mode ()
bashref.html#SEC106
8.4.3 Commands For Changing Text
bashref.html#IDX372
overwrite-mode ()
bashref.html#SEC106
8.4.3 Commands For Changing Text
P
bashref.html#IDX435
possible-command-completions (C-x !)
bashref.html#SEC109
8.4.6 Letting Readline Type For You
bashref.html#IDX436
possible-command-completions (C-x !)
bashref.html#SEC109
8.4.6 Letting Readline Type For You
bashref.html#IDX409
possible-completions (M-?)
bashref.html#SEC109
8.4.6 Letting Readline Type For You
bashref.html#IDX410
possible-completions (M-?)
bashref.html#SEC109
8.4.6 Letting Readline Type For You
bashref.html#IDX419
possible-filename-completions (C-x /)
bashref.html#SEC109
8.4.6 Letting Readline Type For You
bashref.html#IDX420
possible-filename-completions (C-x /)
bashref.html#SEC109
8.4.6 Letting Readline Type For You
bashref.html#IDX431
possible-hostname-completions (C-x @)
bashref.html#SEC109
8.4.6 Letting Readline Type For You
bashref.html#IDX432
possible-hostname-completions (C-x @)
bashref.html#SEC109
8.4.6 Letting Readline Type For You
bashref.html#IDX423
possible-username-completions (C-x ~)
bashref.html#SEC109
8.4.6 Letting Readline Type For You
bashref.html#IDX424
possible-username-completions (C-x ~)
bashref.html#SEC109
8.4.6 Letting Readline Type For You
bashref.html#IDX427
possible-variable-completions (C-x $)
bashref.html#SEC109
8.4.6 Letting Readline Type For You
bashref.html#IDX428
possible-variable-completions (C-x $)
bashref.html#SEC109
8.4.6 Letting Readline Type For You
bashref.html#IDX453
prefix-meta (
ESC
)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX454
prefix-meta (
ESC
)
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8.4.8 Some Miscellaneous Commands
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previous-history (C-p)
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8.4.2 Commands For Manipulating The History
bashref.html#IDX328
previous-history (C-p)
bashref.html#SEC105
8.4.2 Commands For Manipulating The History
Q
bashref.html#IDX357
quoted-insert (C-q or C-v)
bashref.html#SEC106
8.4.3 Commands For Changing Text
bashref.html#IDX358
quoted-insert (C-q or C-v)
bashref.html#SEC106
8.4.3 Commands For Changing Text
R
bashref.html#IDX447
re-read-init-file (C-x C-r)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX448
re-read-init-file (C-x C-r)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX323
redraw-current-line ()
bashref.html#SEC104
8.4.1 Commands For Moving
bashref.html#IDX324
redraw-current-line ()
bashref.html#SEC104
8.4.1 Commands For Moving
bashref.html#IDX335
reverse-search-history (C-r)
bashref.html#SEC105
8.4.2 Commands For Manipulating The History
bashref.html#IDX336
reverse-search-history (C-r)
bashref.html#SEC105
8.4.2 Commands For Manipulating The History
bashref.html#IDX457
revert-line (M-r)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX458
revert-line (M-r)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
S
bashref.html#IDX359
self-insert (a, b, A, 1, !, <small>...</small>)
bashref.html#SEC106
8.4.3 Commands For Changing Text
bashref.html#IDX360
self-insert (a, b, A, 1, !, <small>...</small>)
bashref.html#SEC106
8.4.3 Commands For Changing Text
bashref.html#IDX461
set-mark (C-@)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX462
set-mark (C-@)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX485
shell-expand-line (M-C-e)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX486
shell-expand-line (M-C-e)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX441
start-kbd-macro (C-x ()
bashref.html#SEC110
8.4.7 Keyboard Macros
bashref.html#IDX442
start-kbd-macro (C-x ()
bashref.html#SEC110
8.4.7 Keyboard Macros
T
bashref.html#IDX459
tilde-expand (M-&#38;)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX460
tilde-expand (M-&#38;)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX361
transpose-chars (C-t)
bashref.html#SEC106
8.4.3 Commands For Changing Text
bashref.html#IDX362
transpose-chars (C-t)
bashref.html#SEC106
8.4.3 Commands For Changing Text
bashref.html#IDX363
transpose-words (M-t)
bashref.html#SEC106
8.4.3 Commands For Changing Text
bashref.html#IDX364
transpose-words (M-t)
bashref.html#SEC106
8.4.3 Commands For Changing Text
U
bashref.html#IDX455
undo (C-_ or C-x C-u)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX456
undo (C-_ or C-x C-u)
bashref.html#SEC111
8.4.8 Some Miscellaneous Commands
bashref.html#IDX405
universal-argument ()
bashref.html#SEC108
8.4.5 Specifying Numeric Arguments
bashref.html#IDX406
universal-argument ()
bashref.html#SEC108
8.4.5 Specifying Numeric Arguments
bashref.html#IDX387
unix-filename-rubout ()
bashref.html#SEC107
8.4.4 Killing And Yanking
bashref.html#IDX388
unix-filename-rubout ()
bashref.html#SEC107
8.4.4 Killing And Yanking
bashref.html#IDX377
unix-line-discard (C-u)
bashref.html#SEC107
8.4.4 Killing And Yanking
bashref.html#IDX378
unix-line-discard (C-u)
bashref.html#SEC107
8.4.4 Killing And Yanking
bashref.html#IDX385
unix-word-rubout (C-w)
bashref.html#SEC107
8.4.4 Killing And Yanking
bashref.html#IDX386
unix-word-rubout (C-w)
bashref.html#SEC107
8.4.4 Killing And Yanking
bashref.html#IDX365
upcase-word (M-u)
bashref.html#SEC106
8.4.3 Commands For Changing Text
bashref.html#IDX366
upcase-word (M-u)
bashref.html#SEC106
8.4.3 Commands For Changing Text
Y
bashref.html#IDX399
yank (C-y)
bashref.html#SEC107
8.4.4 Killing And Yanking
bashref.html#IDX400
yank (C-y)
bashref.html#SEC107
8.4.4 Killing And Yanking
bashref.html#IDX349
yank-last-arg (M-. or M-_)
bashref.html#SEC105
8.4.2 Commands For Manipulating The History
bashref.html#IDX350
yank-last-arg (M-. or M-_)
bashref.html#SEC105
8.4.2 Commands For Manipulating The History
bashref.html#IDX347
yank-nth-arg (M-C-y)
bashref.html#SEC105
8.4.2 Commands For Manipulating The History
bashref.html#IDX348
yank-nth-arg (M-C-y)
bashref.html#SEC105
8.4.2 Commands For Manipulating The History
bashref.html#IDX401
yank-pop (M-y)
bashref.html#SEC107
8.4.4 Killing And Yanking
bashref.html#IDX402
yank-pop (M-y)
bashref.html#SEC107
8.4.4 Killing And Yanking
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G
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H
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M
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Up
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Top
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Contents
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Concept Index
Jump to:
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A
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B
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C
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D
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E
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F
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H
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Index Entry
Section
A
bashref.html#SEC80
alias expansion
bashref.html#SEC80
6.6 Aliases
bashref.html#SEC79
arithmetic evaluation
bashref.html#SEC79
6.5 Shell Arithmetic
bashref.html#SEC32
arithmetic expansion
bashref.html#SEC32
3.5.5 Arithmetic Expansion
bashref.html#SEC79
arithmetic, shell
bashref.html#SEC79
6.5 Shell Arithmetic
bashref.html#SEC81
arrays
bashref.html#SEC81
6.7 Arrays
B
bashref.html#SEC88
background
bashref.html#SEC88
7.1 Job Control Basics
bashref.html#SEC123
Bash configuration
bashref.html#SEC123
10.1 Basic Installation
bashref.html#SEC123
Bash installation
bashref.html#SEC123
10.1 Basic Installation
bashref.html#SEC5
Bourne shell
bashref.html#SEC5
3. Basic Shell Features
bashref.html#SEC28
brace expansion
bashref.html#SEC28
3.5.1 Brace Expansion
bashref.html#IDX2
builtin
bashref.html#SEC4
2. Definitions
C
bashref.html#SEC94
command editing
bashref.html#SEC94
8.2.1 Readline Bare Essentials
bashref.html#SEC50
command execution
bashref.html#SEC50
3.7.2 Command Search and Execution
bashref.html#SEC49
command expansion
bashref.html#SEC49
3.7.1 Simple Command Expansion
bashref.html#SEC116
command history
bashref.html#SEC116
9.1 Bash History Facilities
bashref.html#SEC50
command search
bashref.html#SEC50
3.7.2 Command Search and Execution
bashref.html#SEC31
command substitution
bashref.html#SEC31
3.5.4 Command Substitution
bashref.html#IDX26
command timing
bashref.html#SEC17
3.2.2 Pipelines
bashref.html#SEC19
commands, compound
bashref.html#SEC19
3.2.4 Compound Commands
bashref.html#SEC21
commands, conditional
bashref.html#SEC21
3.2.4.2 Conditional Constructs
bashref.html#SEC22
commands, grouping
bashref.html#SEC22
3.2.4.3 Grouping Commands
bashref.html#SEC18
commands, lists
bashref.html#SEC18
3.2.3 Lists of Commands
bashref.html#SEC20
commands, looping
bashref.html#SEC20
3.2.4.1 Looping Constructs
bashref.html#SEC17
commands, pipelines
bashref.html#SEC17
3.2.2 Pipelines
bashref.html#SEC15
commands, shell
bashref.html#SEC15
3.2 Shell Commands
bashref.html#SEC16
commands, simple
bashref.html#SEC16
3.2.1 Simple Commands
bashref.html#SEC14
comments, shell
bashref.html#SEC14
3.1.3 Comments
bashref.html#SEC114
completion builtins
bashref.html#SEC114
8.7 Programmable Completion Builtins
bashref.html#SEC123
configuration
bashref.html#SEC123
10.1 Basic Installation
bashref.html#IDX3
control operator
bashref.html#SEC4
2. Definitions
D
bashref.html#SEC82
directory stack
bashref.html#SEC82
6.8 The Directory Stack
E
bashref.html#SEC94
editing command lines
bashref.html#SEC94
8.2.1 Readline Bare Essentials
bashref.html#SEC52
environment
bashref.html#SEC52
3.7.4 Environment
bashref.html#SEC79
evaluation, arithmetic
bashref.html#SEC79
6.5 Shell Arithmetic
bashref.html#SEC119
event designators
bashref.html#SEC119
9.3.1 Event Designators
bashref.html#SEC51
execution environment
bashref.html#SEC51
3.7.3 Command Execution Environment
bashref.html#IDX4
exit status
bashref.html#SEC4
2. Definitions
bashref.html#SEC53
exit status
bashref.html#SEC53
3.7.5 Exit Status
bashref.html#SEC27
expansion
bashref.html#SEC27
3.5 Shell Expansions
bashref.html#SEC32
expansion, arithmetic
bashref.html#SEC32
3.5.5 Arithmetic Expansion
bashref.html#SEC28
expansion, brace
bashref.html#SEC28
3.5.1 Brace Expansion
bashref.html#IDX64
expansion, filename
bashref.html#SEC35
3.5.8 Filename Expansion
bashref.html#SEC30
expansion, parameter
bashref.html#SEC30
3.5.3 Shell Parameter Expansion
bashref.html#IDX65
expansion, pathname
bashref.html#SEC35
3.5.8 Filename Expansion
bashref.html#SEC29
expansion, tilde
bashref.html#SEC29
3.5.2 Tilde Expansion
bashref.html#SEC79
expressions, arithmetic
bashref.html#SEC79
6.5 Shell Arithmetic
bashref.html#SEC78
expressions, conditional
bashref.html#SEC78
6.4 Bash Conditional Expressions
F
bashref.html#IDX507
FDL, GNU Free Documentation License
bashref.html#SEC135
C.1 GNU Free Documentation License
bashref.html#IDX5
field
bashref.html#SEC4
2. Definitions
bashref.html#IDX6
filename
bashref.html#SEC4
2. Definitions
bashref.html#IDX66
filename expansion
bashref.html#SEC35
3.5.8 Filename Expansion
bashref.html#SEC88
foreground
bashref.html#SEC88
7.1 Job Control Basics
bashref.html#SEC23
functions, shell
bashref.html#SEC23
3.3 Shell Functions
H
bashref.html#SEC117
history builtins
bashref.html#SEC117
9.2 Bash History Builtins
bashref.html#IDX506
history events
bashref.html#SEC119
9.3.1 Event Designators
bashref.html#SEC118
history expansion
bashref.html#SEC118
9.3 History Expansion
bashref.html#SEC116
history list
bashref.html#SEC116
9.1 Bash History Facilities
bashref.html#IDX503
History, how to use
bashref.html#SEC114
8.7 Programmable Completion Builtins
I
bashref.html#IDX11
identifier
bashref.html#SEC4
2. Definitions
bashref.html#SEC99
initialization file, readline
bashref.html#SEC99
8.3 Readline Init File
bashref.html#SEC123
installation
bashref.html#SEC123
10.1 Basic Installation
bashref.html#SEC93
interaction, readline
bashref.html#SEC93
8.2 Readline Interaction
bashref.html#IDX269
interactive shell
bashref.html#SEC65
6.1 Invoking Bash
bashref.html#SEC74
interactive shell
bashref.html#SEC74
6.3 Interactive Shells
bashref.html#SEC13
internationalization
bashref.html#SEC13
3.1.2.5 Locale-Specific Translation
J
bashref.html#IDX7
job
bashref.html#SEC4
2. Definitions
bashref.html#IDX8
job control
bashref.html#SEC4
2. Definitions
bashref.html#SEC88
job control
bashref.html#SEC88
7.1 Job Control Basics
K
bashref.html#IDX285
kill ring
bashref.html#SEC96
8.2.3 Readline Killing Commands
bashref.html#IDX283
killing text
bashref.html#SEC96
8.2.3 Readline Killing Commands
L
bashref.html#SEC13
localization
bashref.html#SEC13
3.1.2.5 Locale-Specific Translation
bashref.html#IDX268
login shell
bashref.html#SEC65
6.1 Invoking Bash
M
bashref.html#SEC36
matching, pattern
bashref.html#SEC36
3.5.8.1 Pattern Matching
bashref.html#IDX9
metacharacter
bashref.html#SEC4
2. Definitions
N
bashref.html#IDX10
name
bashref.html#SEC4
2. Definitions
bashref.html#SEC13
native languages
bashref.html#SEC13
3.1.2.5 Locale-Specific Translation
bashref.html#SEC94
notation, readline
bashref.html#SEC94
8.2.1 Readline Bare Essentials
O
bashref.html#IDX12
operator, shell
bashref.html#SEC4
2. Definitions
P
bashref.html#SEC30
parameter expansion
bashref.html#SEC30
3.5.3 Shell Parameter Expansion
bashref.html#SEC24
parameters
bashref.html#SEC24
3.4 Shell Parameters
bashref.html#SEC25
parameters, positional
bashref.html#SEC25
3.4.1 Positional Parameters
bashref.html#SEC26
parameters, special
bashref.html#SEC26
3.4.2 Special Parameters
bashref.html#IDX67
pathname expansion
bashref.html#SEC35
3.5.8 Filename Expansion
bashref.html#SEC36
pattern matching
bashref.html#SEC36
3.5.8.1 Pattern Matching
bashref.html#SEC17
pipeline
bashref.html#SEC17
3.2.2 Pipelines
bashref.html#IDX1
POSIX
bashref.html#SEC4
2. Definitions
bashref.html#SEC86
POSIX Mode
bashref.html#SEC86
6.11 Bash POSIX Mode
bashref.html#IDX13
process group
bashref.html#SEC4
2. Definitions
bashref.html#IDX14
process group ID
bashref.html#SEC4
2. Definitions
bashref.html#SEC33
process substitution
bashref.html#SEC33
3.5.6 Process Substitution
bashref.html#SEC113
programmable completion
bashref.html#SEC113
8.6 Programmable Completion
bashref.html#SEC84
prompting
bashref.html#SEC84
6.9 Controlling the Prompt
Q
bashref.html#SEC8
quoting
bashref.html#SEC8
3.1.2 Quoting
bashref.html#SEC12
quoting, ANSI
bashref.html#SEC12
3.1.2.4 ANSI-C Quoting
R
bashref.html#IDX282
Readline, how to use
bashref.html#SEC90
7.3 Job Control Variables
bashref.html#SEC38
redirection
bashref.html#SEC38
3.6 Redirections
bashref.html#IDX15
reserved word
bashref.html#SEC4
2. Definitions
bashref.html#SEC85
restricted shell
bashref.html#SEC85
6.10 The Restricted Shell
bashref.html#IDX16
return status
bashref.html#SEC4
2. Definitions
S
bashref.html#SEC79
shell arithmetic
bashref.html#SEC79
6.5 Shell Arithmetic
bashref.html#SEC23
shell function
bashref.html#SEC23
3.3 Shell Functions
bashref.html#SEC55
shell script
bashref.html#SEC55
3.8 Shell Scripts
bashref.html#SEC24
shell variable
bashref.html#SEC24
3.4 Shell Parameters
bashref.html#SEC74
shell, interactive
bashref.html#SEC74
6.3 Interactive Shells
bashref.html#IDX17
signal
bashref.html#SEC4
2. Definitions
bashref.html#SEC54
signal handling
bashref.html#SEC54
3.7.6 Signals
bashref.html#IDX18
special builtin
bashref.html#SEC4
2. Definitions
bashref.html#SEC60
special builtin
bashref.html#SEC60
4.4 Special Builtins
bashref.html#SEC66
startup files
bashref.html#SEC66
6.2 Bash Startup Files
bashref.html#SEC88
suspending jobs
bashref.html#SEC88
7.1 Job Control Basics
T
bashref.html#SEC29
tilde expansion
bashref.html#SEC29
3.5.2 Tilde Expansion
bashref.html#IDX19
token
bashref.html#SEC4
2. Definitions
bashref.html#SEC13
translation, native languages
bashref.html#SEC13
3.1.2.5 Locale-Specific Translation
V
bashref.html#SEC24
variable, shell
bashref.html#SEC24
3.4 Shell Parameters
bashref.html#IDX286
variables, readline
bashref.html#SEC100
8.3.1 Readline Init File Syntax
W
bashref.html#IDX20
word
bashref.html#SEC4
2. Definitions
bashref.html#SEC34
word splitting
bashref.html#SEC34
3.5.7 Word Splitting
Y
bashref.html#IDX284
yanking text
bashref.html#SEC96
8.2.3 Readline Killing Commands
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A
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D
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F
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[
bashref.html#SEC_Top
Top
]
[
bashref.html#SEC_Contents
Contents
]
[Index]
[
bashref.html#SEC_About
?
]
Table of Contents
bashref.html#SEC1
1. Introduction
bashref.html#SEC2
1.1 What is Bash?
bashref.html#SEC3
1.2 What is a shell?
bashref.html#SEC4
2. Definitions
bashref.html#SEC5
3. Basic Shell Features
bashref.html#SEC6
3.1 Shell Syntax
bashref.html#SEC7
3.1.1 Shell Operation
bashref.html#SEC8
3.1.2 Quoting
bashref.html#SEC9
3.1.2.1 Escape Character
bashref.html#SEC10
3.1.2.2 Single Quotes
bashref.html#SEC11
3.1.2.3 Double Quotes
bashref.html#SEC12
3.1.2.4 ANSI-C Quoting
bashref.html#SEC13
3.1.2.5 Locale-Specific Translation
bashref.html#SEC14
3.1.3 Comments
bashref.html#SEC15
3.2 Shell Commands
bashref.html#SEC16
3.2.1 Simple Commands
bashref.html#SEC17
3.2.2 Pipelines
bashref.html#SEC18
3.2.3 Lists of Commands
bashref.html#SEC19
3.2.4 Compound Commands
bashref.html#SEC20
3.2.4.1 Looping Constructs
bashref.html#SEC21
3.2.4.2 Conditional Constructs
bashref.html#SEC22
3.2.4.3 Grouping Commands
bashref.html#SEC23
3.3 Shell Functions
bashref.html#SEC24
3.4 Shell Parameters
bashref.html#SEC25
3.4.1 Positional Parameters
bashref.html#SEC26
3.4.2 Special Parameters
bashref.html#SEC27
3.5 Shell Expansions
bashref.html#SEC28
3.5.1 Brace Expansion
bashref.html#SEC29
3.5.2 Tilde Expansion
bashref.html#SEC30
3.5.3 Shell Parameter Expansion
bashref.html#SEC31
3.5.4 Command Substitution
bashref.html#SEC32
3.5.5 Arithmetic Expansion
bashref.html#SEC33
3.5.6 Process Substitution
bashref.html#SEC34
3.5.7 Word Splitting
bashref.html#SEC35
3.5.8 Filename Expansion
bashref.html#SEC36
3.5.8.1 Pattern Matching
bashref.html#SEC37
3.5.9 Quote Removal
bashref.html#SEC38
3.6 Redirections
bashref.html#SEC39
3.6.1 Redirecting Input
bashref.html#SEC40
3.6.2 Redirecting Output
bashref.html#SEC41
3.6.3 Appending Redirected Output
bashref.html#SEC42
3.6.4 Redirecting Standard Output and Standard Error
bashref.html#SEC43
3.6.5 Here Documents
bashref.html#SEC44
3.6.6 Here Strings
bashref.html#SEC45
3.6.7 Duplicating File Descriptors
bashref.html#SEC46
3.6.8 Moving File Descriptors
bashref.html#SEC47
3.6.9 Opening File Descriptors for Reading and Writing
bashref.html#SEC48
3.7 Executing Commands
bashref.html#SEC49
3.7.1 Simple Command Expansion
bashref.html#SEC50
3.7.2 Command Search and Execution
bashref.html#SEC51
3.7.3 Command Execution Environment
bashref.html#SEC52
3.7.4 Environment
bashref.html#SEC53
3.7.5 Exit Status
bashref.html#SEC54
3.7.6 Signals
bashref.html#SEC55
3.8 Shell Scripts
bashref.html#SEC56
4. Shell Builtin Commands
bashref.html#SEC57
4.1 Bourne Shell Builtins
bashref.html#SEC58
4.2 Bash Builtin Commands
bashref.html#SEC59
4.3 The Set Builtin
bashref.html#SEC60
4.4 Special Builtins
bashref.html#SEC61
5. Shell Variables
bashref.html#SEC62
5.1 Bourne Shell Variables
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5.2 Bash Variables
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6. Bash Features
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6.1 Invoking Bash
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6.2 Bash Startup Files
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6.3 Interactive Shells
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6.3.1 What is an Interactive Shell?
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6.3.2 Is this Shell Interactive?
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6.3.3 Interactive Shell Behavior
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6.4 Bash Conditional Expressions
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6.5 Shell Arithmetic
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6.6 Aliases
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6.7 Arrays
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6.8 The Directory Stack
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6.8.1 Directory Stack Builtins
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6.9 Controlling the Prompt
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6.10 The Restricted Shell
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6.11 Bash POSIX Mode
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7. Job Control
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7.1 Job Control Basics
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7.2 Job Control Builtins
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7.3 Job Control Variables
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8. Command Line Editing
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8.1 Introduction to Line Editing
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8.2 Readline Interaction
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8.2.1 Readline Bare Essentials
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8.2.2 Readline Movement Commands
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8.2.3 Readline Killing Commands
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8.2.4 Readline Arguments
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8.2.5 Searching for Commands in the History
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8.3 Readline Init File
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8.3.1 Readline Init File Syntax
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8.3.2 Conditional Init Constructs
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8.3.3 Sample Init File
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8.4 Bindable Readline Commands
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8.4.1 Commands For Moving
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8.4.2 Commands For Manipulating The History
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8.4.3 Commands For Changing Text
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8.4.4 Killing And Yanking
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8.4.5 Specifying Numeric Arguments
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8.4.6 Letting Readline Type For You
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8.4.7 Keyboard Macros
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8.4.8 Some Miscellaneous Commands
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8.5 Readline vi Mode
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8.6 Programmable Completion
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8.7 Programmable Completion Builtins
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9. Using History Interactively
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9.1 Bash History Facilities
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9.2 Bash History Builtins
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9.3 History Expansion
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9.3.1 Event Designators
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9.3.2 Word Designators
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9.3.3 Modifiers
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10. Installing Bash
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10.1 Basic Installation
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10.2 Compilers and Options
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10.3 Compiling For Multiple Architectures
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10.4 Installation Names
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10.5 Specifying the System Type
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10.6 Sharing Defaults
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10.7 Operation Controls
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10.8 Optional Features
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A. Reporting Bugs
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B. Major Differences From The Bourne Shell
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B.1 Implementation Differences From The SVR4.2 Shell
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C. Copying This Manual
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C.1 GNU Free Documentation License
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C.1.1 ADDENDUM: How to use this License for your documents
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Index of Shell Builtin Commands
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Index of Shell Reserved Words
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Parameter and Variable Index
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Function Index
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Concept Index
[
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Top
]
[
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Contents
]
[Index]
[
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?
]
Short Table of Contents
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1. Introduction
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2. Definitions
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3. Basic Shell Features
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4. Shell Builtin Commands
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5. Shell Variables
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6. Bash Features
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7. Job Control
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8. Command Line Editing
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9. Using History Interactively
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10. Installing Bash
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A. Reporting Bugs
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B. Major Differences From The Bourne Shell
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C. Copying This Manual
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Index of Shell Builtin Commands
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Index of Shell Reserved Words
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Parameter and Variable Index
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Function Index
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Concept Index
[
bashref.html#SEC_Top
Top
]
[
bashref.html#SEC_Contents
Contents
]
[Index]
[
bashref.html#SEC_About
?
]
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