features that only appear in Bash. Some of the shells that Bash has
borrowed concepts from are the Bourne Shell (@file{sh}), the Korn Shell
(@file{ksh}), and the C-shell (@file{csh} and its successor,
-@file{tcsh}). The following menu breaks the features up into
+@file{tcsh}). The following menu breaks the features up into
categories based upon which one of these other shells inspired the
feature.
@cindex command timing
The format for a pipeline is
@example
-[@code{time} [@code{-p}]] [@code{!}] @var{command1} [ [@code{|} or @code{|&}] @var{command2} @dots{}]
+[time [-p]] [!] @var{command1} [ | or |& @var{command2} ] @dots{}
@end example
@noindent
connection is performed before any redirections specified by the
command.
-If @samp{|&} is used, the standard error of @var{command1} is connected to
-@var{command2}'s standard input through the pipe; it is shorthand for
-@code{2>&1 |}. This implicit redirection of the standard error is
+If @samp{|&} is used, @var{command1}'s standard output and standard error
+are connected to
+@var{command2}'s standard input through the pipe;
+it is shorthand for @code{2>&1 |}.
+This implicit redirection of the standard error is
performed after any redirections specified by the command.
The reserved word @code{time} causes timing statistics
@rwindex do
@rwindex done
The syntax of the @code{until} command is:
+
@example
until @var{test-commands}; do @var{consequent-commands}; done
@end example
+
Execute @var{consequent-commands} as long as
@var{test-commands} has an exit status which is not zero.
The return status is the exit status of the last command executed
@item while
@rwindex while
The syntax of the @code{while} command is:
+
@example
while @var{test-commands}; do @var{consequent-commands}; done
@end example
@example
for @var{name} [ [in [@var{words} @dots{}] ] ; ] do @var{commands}; done
@end example
+
Expand @var{words}, and execute @var{commands} once for each member
in the resultant list, with @var{name} bound to the current member.
If @samp{in @var{words}} is not present, the @code{for} command
@example
for (( @var{expr1} ; @var{expr2} ; @var{expr3} )) ; do @var{commands} ; done
@end example
+
First, the arithmetic expression @var{expr1} is evaluated according
to the rules described below (@pxref{Shell Arithmetic}).
The arithmetic expression @var{expr2} is then evaluated repeatedly
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 @var{commands}
that is executed, or false if any of the expressions is invalid.
-
@end table
The @code{break} and @code{continue} builtins (@pxref{Bourne Shell Builtins})
The syntax of the @code{case} command is:
@example
-@code{case @var{word} in [ [(] @var{pattern} [| @var{pattern}]@dots{}) @var{command-list} ;;]@dots{} esac}
+case @var{word} in [ [(] @var{pattern} [| @var{pattern}]@dots{}) @var{command-list} ;;]@dots{} esac
@end example
@code{case} will selectively execute the @var{command-list} corresponding to
@item @var{expression1} || @var{expression2}
True if either @var{expression1} or @var{expression2} is true.
@end table
+
@noindent
-The @code{&&} and @code{||} operators do not evaluate @var{expression2} if the
+The @code{&&} and @code{||} operators do not evaluate @var{[Bexpression2} if the
value of @var{expression1} is sufficient to determine the return
value of the entire conditional expression.
-
@end table
@node Command Grouping
The format for a coprocess is:
@example
-@code{coproc} [@var{NAME}] @var{command} [@var{redirections}]
+coproc [@var{NAME}] @var{command} [@var{redirections}]
@end example
@noindent
command (@pxref{Simple Commands}); otherwise, it is interpreted as
the first word of the simple command.
-When the coproc is executed, the shell creates an array variable
+When the coprocess is executed, the shell creates an array variable
(@pxref{Arrays})
-named @var{NAME} in the context of the executing shell.
+named @env{NAME} in the context of the executing shell.
The standard output of @var{command}
is connected via a pipe to a file descriptor in the executing shell,
-and that file descriptor is assigned to @var{NAME}[0].
+and that file descriptor is assigned to @env{NAME}[0].
The standard input of @var{command}
is connected via a pipe to a file descriptor in the executing shell,
-and that file descriptor is assigned to @var{NAME}[1].
+and that file descriptor is assigned to @env{NAME}[1].
This pipe is established before any redirections specified by the
command (@pxref{Redirections}).
The file descriptors can be utilized as arguments to shell commands
and redirections using standard word expansions.
The process ID of the shell spawned to execute the coprocess is
-available as the value of the variable @var{NAME}_PID.
+available as the value of the variable @env{NAME}_PID.
The @code{wait}
builtin command may be used to wait for the coprocess to terminate.
Functions are declared using this syntax:
@rwindex function
@example
-@var{name} () @var{compound-command} [ @var{redirections} ]@*or@*
-@code{function} @var{name} [()] @var{compound-command} [ @var{redirections} ]
+@var{name} () @var{compound-command} [ @var{redirections} ]
+@end example
+
+or
+
+@example
+function @var{name} [()] @var{compound-command} [ @var{redirections} ]
@end example
This defines a shell function named @var{name}. The reserved
the function and the commands it invokes.
Function names and definitions may be listed with the
-@option{-f} option to the @code{declare} or @code{typeset}
-builtin commands (@pxref{Bash Builtins}).
+@option{-f} option to the @code{declare} (@code{typeset})
+builtin command (@pxref{Bash Builtins}).
The @option{-F} option to @code{declare} or @code{typeset}
will list the function names only
(and optionally the source file and line number, if the @code{extdebug}
Expansion is performed on the command line after it has been split into
@code{token}s. There are seven kinds of expansion performed:
+
@itemize @bullet
@item brace expansion
@item tilde expansion
Brace expansion is a mechanism by which arbitrary strings may be generated.
This mechanism is similar to
@var{filename expansion} (@pxref{Filename Expansion}),
-but the file names generated need not exist.
+but the filenames generated need not exist.
Patterns to be brace expanded take the form of an optional @var{preamble},
followed by either a series of comma-separated strings or a sequence expression
between a pair of braces,
Each variable assignment is checked for unquoted tilde-prefixes immediately
following a @samp{:} or the first @samp{=}.
In these cases, tilde expansion is also performed.
-Consequently, one may use file names with tildes in assignments to
+Consequently, one may use filenames with tildes in assignments to
@env{PATH}, @env{MAILPATH}, and @env{CDPATH},
and the shell assigns the expanded value.
@item ~-@var{N}
The string that would be displayed by @samp{dirs -@var{N}}
-
@end table
@node Shell Parameter Expansion
is an array variable subscripted with @samp{@@} or @samp{*},
the case modification operation is applied to each member of the
array in turn, and the expansion is the resultant list.
-
@end table
@node Command Substitution
If one of these characters appears, then the word is
regarded as a @var{pattern},
and replaced with an alphabetically sorted list of
-file names matching the pattern (@pxref{Pattern Matching}).
-If no matching file names are found,
+filenames matching the pattern (@pxref{Pattern Matching}).
+If no matching filenames are found,
and the shell option @code{nullglob} is disabled, the word is left
unchanged.
If the @code{nullglob} option is set, and no matches are found, the word
When a pattern is used for filename expansion, the character @samp{.}
at the start of a filename or immediately following a slash
must be matched explicitly, unless the shell option @code{dotglob} is set.
-When matching a file name, the slash character must always be
+When matching a filename, the slash character must always be
matched explicitly.
In other cases, the @samp{.} character is not treated specially.
If @var{host} is a valid hostname or Internet address, and @var{port}
is an integer port number or service name, Bash attempts to open a UDP
connection to the corresponding socket.
-
@end table
A failure to open or create a file causes the redirection to fail.
@var{delimiter}
@end example
-No parameter expansion, command substitution, arithmetic expansion,
-or filename expansion is performed on
+No parameter and variable expansion, command substitution,
+arithmetic expansion, or filename expansion is performed on
@var{word}. If any characters in @var{word} are quoted, the
@var{delimiter} is the result of quote removal on @var{word},
and the lines in the here-document are not expanded.
<<< @var{word}
@end example
-The @var{word}
-is expanded as described above, with the exception that
-pathname expansion is not applied, and supplied as a single string
-to the command on its standard input.
+The @var{word} undergoes
+brace expansion, tilde expansion, parameter and variable expansion,
+command substitution, arithmetic expansion, and quote removal.
+Pathname expansion word splitting are not performed.
+The result is supplied as a single string to the command on its
+standard input.
@subsection Duplicating File Descriptors
The redirection operator
not just those that precede the command name.
When Bash invokes an external command, the variable @samp{$_}
-is set to the full path name of the command and passed to that
+is set to the full pathname of the command and passed to that
command in its environment.
@node Exit Status
@var{waitpid} system call or equivalent function. Exit statuses
fall between 0 and 255, though, as explained below, the shell may
use values above 125 specially. Exit statuses from shell builtins and
-compound commands are also limited to this range. Under certain
+compound commands are also limited to this range. Under certain
circumstances, the shell will use special values to indicate specific
failure modes.
@example
: [@var{arguments}]
@end example
+
Do nothing beyond expanding @var{arguments} and performing redirections.
The return status is zero.
@example
. @var{filename} [@var{arguments}]
@end example
+
Read and execute commands from the @var{filename} argument in the
current shell context. If @var{filename} does not contain a slash,
the @env{PATH} variable is used to find @var{filename}.
@example
break [@var{n}]
@end example
+
Exit from a @code{for}, @code{while}, @code{until}, or @code{select} loop.
If @var{n} is supplied, the @var{n}th enclosing loop is exited.
@var{n} must be greater than or equal to 1.
@example
cd [-L|[-P [-e]]] [@var{directory}]
@end example
+
Change the current working directory to @var{directory}.
If @var{directory} is not given, the value of the @env{HOME} shell
variable is used.
@example
continue [@var{n}]
@end example
+
Resume the next iteration of an enclosing @code{for}, @code{while},
@code{until}, or @code{select} loop.
If @var{n} is supplied, the execution of the @var{n}th enclosing loop
@example
eval [@var{arguments}]
@end example
+
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 @code{eval}.
@example
exec [-cl] [-a @var{name}] [@var{command} [@var{arguments}]]
@end example
+
If @var{command}
is supplied, it replaces the shell without creating a new process.
If the @option{-l} option is supplied, the shell places a dash at the
environment.
If @option{-a} is supplied, the shell passes @var{name} as the zeroth
argument to @var{command}.
+If @var{command}
+cannot be executed for some reason, a non-interactive shell exits,
+unless the @code{execfail} shell option
+is enabled. In that case, it returns failure.
+An interactive shell returns failure if the file cannot be executed.
If no @var{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.
@example
exit [@var{n}]
@end example
+
Exit the shell, returning a status of @var{n} to the shell's parent.
If @var{n} is omitted, the exit status is that of the last command executed.
Any trap on @code{EXIT} is executed before the shell terminates.
@example
export [-fn] [-p] [@var{name}[=@var{value}]]
@end example
+
Mark each @var{name} to be passed to child processes
in the environment. If the @option{-f} option is supplied, the @var{name}s
refer to shell functions; otherwise the names refer to shell variables.
The @option{-n} option means to no longer mark each @var{name} for export.
If no @var{names} are supplied, or if the @option{-p} option is given, a
-list of exported names is displayed.
+list of names of all exported variables is displayed.
The @option{-p} option displays output in a form that may be reused as input.
If a variable name is followed by =@var{value}, the value of
the variable is set to @var{value}.
@example
getopts @var{optstring} @var{name} [@var{args}]
@end example
+
@code{getopts} is used by shell scripts to parse positional parameters.
@var{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.
+argument, which should be separated from it by whitespace.
The colon (@samp{:}) and question mark (@samp{?}) may not be
used as option characters.
Each time it is invoked, @code{getopts}
@code{getopts} can report errors in two ways. If the first character of
@var{optstring} is a colon, @var{silent}
-error reporting is used. In normal operation diagnostic messages
+error reporting is used. In normal operation, diagnostic messages
are printed when invalid options or missing option arguments are
encountered.
If the variable @env{OPTERR}
@example
hash [-r] [-p @var{filename}] [-dt] [@var{name}]
@end example
+
Each time @code{hash} is invoked, it remembers the full pathnames of the
commands specified as @var{name} arguments,
so they need not be searched for on subsequent invocations.
@example
pwd [-LP]
@end example
+
Print the absolute pathname of the current working directory.
If the @option{-P} option is supplied, the pathname printed will not
contain symbolic links.
@example
readonly [-aAf] [-p] [@var{name}[=@var{value}]] @dots{}
@end example
+
Mark each @var{name} as readonly.
The values of these names may not be changed by subsequent assignment.
If the @option{-f} option is supplied, each @var{name} refers to a shell
@example
return [@var{n}]
@end example
-Cause a shell function to exit with the return value @var{n}.
+
+Cause a shell function to stop executing and return the value @var{n}
+to its caller.
If @var{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 @code{.} (or @code{source}) builtin, returning either @var{n} or
+@code{return} may also be used to terminate execution of a script
+being executed with the @code{.} (@code{source}) builtin,
+returning either @var{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 @code{RETURN} trap is executed
@example
shift [@var{n}]
@end example
+
Shift the positional parameters to the left by @var{n}.
The positional parameters from @var{n}+1 @dots{} @code{$#} are
renamed to @code{$1} @dots{} @code{$#}-@var{n}.
The return status is zero unless @var{n} is greater than @code{$#} or
less than zero, non-zero otherwise.
-@item test
+@item test[B
@itemx [
@btindex test
@btindex [
-Evaluate a conditional expression @var{expr}.
+@example
+test @var{expr}
+@end example
+
+Evaluate a conditional expression @var{expr} and return a status of 0
+(true) or 1 (false).
Each operator and operand must be a separate argument.
Expressions are composed of the primaries described below in
@ref{Bash Conditional Expressions}.
@example
times
@end example
+
Print out the user and system times used by the shell and its children.
The return status is zero.
@example
trap [-lp] [@var{arg}] [@var{sigspec} @dots{}]
@end example
+
The commands in @var{arg} are to be read and executed when the
shell receives signal @var{sigspec}. If @var{arg} is absent (and
there is a single @var{sigspec}) or
@example
umask [-p] [-S] [@var{mode}]
@end example
+
Set the shell process's file creation mask to @var{mode}. If
@var{mode} begins with a digit, it is interpreted as an octal number;
if not, it is interpreted as a symbolic mode mask similar
@example
unset [-fv] [@var{name}]
@end example
-Each variable or function @var{name} is removed.
+
+Remove each variable or function @var{name}.
If the @option{-v} option is given, each
@var{name} refers to a shell variable and that variable is remvoved.
If the @option{-f} option is given, the @var{name}s refer to shell
@item alias
@btindex alias
@example
-alias [@code{-p}] [@var{name}[=@var{value}] @dots{}]
+alias [-p] [@var{name}[=@var{value}] @dots{}]
@end example
Without arguments or with the @option{-p} option, @code{alias} prints
@example
builtin [@var{shell-builtin} [@var{args}]]
@end example
+
Run a shell builtin, passing it @var{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
@example
caller [@var{expr}]
@end example
+
Returns the context of any active subroutine call (a shell function or
a script executed with the @code{.} or @code{source} builtins).
@example
command [-pVv] @var{command} [@var{arguments} @dots{}]
@end example
+
Runs @var{command} with @var{arguments} ignoring any shell function
named @var{command}.
Only shell builtin commands or commands found by searching the
@item declare
@btindex declare
@example
-declare [-aAfFilrtux] [-p] [@var{name}[=@var{value}] @dots{}]
+declare [-aAfFgilrtux] [-p] [@var{name}[=@var{value}] @dots{}]
@end example
Declare variables and give them attributes. If no @var{name}s
may not be used to destroy an array variable and @samp{+r} will not
remove the readonly attribute.
When used in a function, @code{declare} makes each @var{name} local,
-as with the @code{local} command, unless the @samp{-g} option is used.
+as with the @code{local} command, unless the @option{-g} option is used.
If a variable name is followed by =@var{value}, the value of the variable
is set to @var{value}.
@example
echo [-neE] [@var{arg} @dots{}]
@end example
+
Output the @var{arg}s, separated by spaces, terminated with a
newline.
The return status is 0 unless a write error occurs.
@example
enable [-a] [-dnps] [-f @var{filename}] [@var{name} @dots{}]
@end example
+
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,
@example
help [-dms] [@var{pattern}]
@end example
+
Display helpful information about builtin commands.
If @var{pattern} is specified, @code{help} gives detailed help
on all commands matching @var{pattern}, otherwise a list of
@item let
@btindex let
@example
-let @var{expression} [@var{expression}]
+let @var{expression} [@var{expression} @dots{}]
@end example
+
The @code{let} builtin allows arithmetic to be performed on shell
variables. Each @var{expression} is evaluated according to the
rules given below in @ref{Shell Arithmetic}. If the
@example
local [@var{option}] @var{name}[=@var{value}] @dots{}
@end example
+
For each argument, a local variable named @var{name} is created,
and assigned @var{value}.
The @var{option} can be any of the options accepted by @code{declare}.
@example
logout [@var{n}]
@end example
+
Exit a login shell, returning a status of @var{n} to the shell's
parent.
@item mapfile
@btindex mapfile
@example
-mapfile [-n @var{count}] [-O @var{origin}] [-s @var{count}] [-t] [-u @var{fd}] [
--C @var{callback}] [-c @var{quantum}] [@var{array}]
+mapfile [-n @var{count}] [-O @var{origin}] [-s @var{count}] [-t] [-u @var{fd}]
+ [-C @var{callback}] [-c @var{quantum}] [@var{array}]
@end example
+
Read lines from the standard input into the indexed array variable @var{array},
or from file descriptor @var{fd}
if the @option{-u} option is supplied.
The variable @code{MAPFILE} is the default @var{array}.
Options, if supplied, have the following meanings:
+
@table @code
@item -n
@example
printf [-v @var{var}] @var{format} [@var{arguments}]
@end example
+
Write the formatted @var{arguments} to the standard output under the
control of the @var{format}.
The @option{-v} option causes the output to be assigned to the variable
@table @code
@item %b
-causes @code{printf} to expand backslash escape sequences in the
+Causes @code{printf} to expand backslash escape sequences in the
corresponding @var{argument},
-(except that @samp{\c} terminates output, backslashes in
+except that @samp{\c} terminates output, backslashes in
@samp{\'}, @samp{\"}, and @samp{\?} are not removed, and octal escapes
-beginning with @samp{\0} may contain up to four digits).
+beginning with @samp{\0} may contain up to four digits.
@item %q
-causes @code{printf} to output the
+Causes @code{printf} to output the
corresponding @var{argument} in a format that can be reused as shell input.
@item %(@var{datefmt})T
-causes @code{printf} to output the date-time string resulting from using
+Causes @code{printf} to output the date-time string resulting from using
@var{datefmt} as a format string for @code{strftime}(3). The corresponding
@var{argument} is an integer representing the number of seconds since the
epoch. Two special argument values may be used: -1 represents the current
@item read
@btindex read
@example
-read [-ers] [-a @var{aname}] [-d @var{delim}] [-i @var{text}] [-n @var{nchars}] [-N @var{nchars}] [-p @var{prompt}] [-t @var{timeout}] [-u @var{fd}] [@var{name} @dots{}]
+read [-ers] [-a @var{aname}] [-d @var{delim}] [-i @var{text}] [-n @var{nchars}]
+ [-N @var{nchars}] [-p @var{prompt}] [-t @var{timeout}] [-u @var{fd}] [@var{name} @dots{}]
@end example
+
One line is read from the standard input, or from the file descriptor
@var{fd} supplied as an argument to the @option{-u} option, and the first word
is assigned to the first @var{name}, the second word to the second @var{name},
This option is only effective if @code{read} is reading input from a
terminal, pipe, or other special file; it has no effect when reading
from regular files.
-If @var{timeout} is 0, @code{read} returns success if input is available on
-the specified file descriptor, failure otherwise.
+If @var{timeout} is 0, @code{read} returns immediately, without trying to
+read and data. The exit status is 0 if input is available on
+the specified file descriptor, non-zero otherwise.
The exit status is greater than 128 if the timeout is exceeded.
@item -u @var{fd}
Read input from file descriptor @var{fd}.
-
@end table
@item readarray
@btindex readarray
@example
-readarray [-n @var{count}] [-O @var{origin}] [-s @var{count}] [-t] [-u @var{fd}] [
--C @var{callback}] [-c @var{quantum}] [@var{array}]
+readarray [-n @var{count}] [-O @var{origin}] [-s @var{count}] [-t] [-u @var{fd}]
+ [-C @var{callback}] [-c @var{quantum}] [@var{array}]
@end example
+
Read lines from the standard input into the indexed array variable @var{array},
or from file descriptor @var{fd}
if the @option{-u} option is supplied.
@example
source @var{filename}
@end example
+
A synonym for @code{.} (@pxref{Bourne Shell Builtins}).
@item type
@example
type [-afptP] [@var{name} @dots{}]
@end example
+
For each @var{name}, indicate how it would be interpreted if used as a
command name.
@option{-t} would not return @samp{file}.
If a command is hashed, @option{-p} and @option{-P} print the hashed value,
-not necessarily the file that appears first in @code{$PATH}.
+which is not necessarily the file that appears first in @code{$PATH}.
If the @option{-a} option is used, @code{type} returns all of the places
that contain an executable named @var{file}.
@item typeset
@btindex typeset
@example
-typeset [-afFrxi] [-p] [@var{name}[=@var{value}] @dots{}]
+typeset [-afFgrxilrtux] [-p] [@var{name}[=@var{value}] @dots{}]
@end example
+
The @code{typeset} command is supplied for compatibility with the Korn
-shell; however, it has been deprecated in favor of the @code{declare}
-builtin command.
+shell.
+It is a synonym for the @code{declare} builtin command.
@item ulimit
@btindex ulimit
@example
ulimit [-abcdefilmnpqrstuvxHST] [@var{limit}]
@end example
+
@code{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:
+
@table @code
@item -S
Change and report the soft limit associated with a resource.
@item -T
The maximum number of threads.
-
@end table
-If @var{limit} is given, it is the new value of the specified resource;
-the special @var{limit} values @code{hard}, @code{soft}, and
+If @var{limit} is given, and the @option{-a} option is not used,
+@var{limit} is the new value of the specified resource.
+The special @var{limit} values @code{hard}, @code{soft}, and
@code{unlimited} stand for the current hard limit, the current soft limit,
and no limit, respectively.
A hard limit cannot be increased by a non-root user once it is set;
When setting new limits, if neither @option{-H} nor @option{-S} is supplied,
both the hard and soft limits are set.
If no option is given, then @option{-f} is assumed. Values are in 1024-byte
-increments, except for @option{-t}, which is in seconds, @option{-p},
-which is in units of 512-byte blocks, and @option{-n} and @option{-u}, which
-are unscaled values.
+increments, except for @option{-t}, which is in seconds; @option{-p},
+which is in units of 512-byte blocks; and @option{-T}, @option{-b},
+@option{-n} and @option{-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.
Remove each @var{name} from the list of aliases. If @option{-a} is
supplied, all aliases are removed.
Aliases are described in @ref{Aliases}.
-
@end table
@node Modifying Shell Behavior
and the @env{SHELLOPTS}, @env{BASHOPTS}, @env{CDPATH} and @env{GLOBIGNORE}
variables, if they appear in the environment, are ignored.
If the shell is started with the effective user (group) id not equal to the
-real user (group) id, and the @code{-p} option is not supplied, these actions
+real user (group) id, and the @option{-p} option is not supplied, these actions
are taken and the effective user id is set to the real user id.
-If the @code{-p} option is supplied at startup, the effective user id is
+If the @option{-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.
@example
shopt [-pqsu] [-o] [@var{optname} @dots{}]
@end example
+
Toggle the values of variables controlling optional shell behavior.
With no options, or with the @option{-p} option, a list of all settable
options is displayed, with an indication of whether or not each is set.
@end table
If either @option{-s} or @option{-u}
-is used with no @var{optname} arguments, the display is limited to
+is used with no @var{optname} arguments, @code{shopt} shows only
those options which are set or unset, respectively.
Unless otherwise noted, the @code{shopt} options are disabled (off)
quoted. This is the behavior of @sc{posix} mode through version 4.1.
The default Bash behavior remains as in previous versions.
+@item complete_fullquote
+If set, Bash
+quotes all shell metacharacters in filenames and directory names when
+performing completion.
+If not set, Bash
+removes metacharacters such as the dollar sign from the set of
+characters that will be quoted in completed filenames
+when these metacharacters appear in shell variable references in words to be
+completed.
+This means that dollar signs in variable names that expand to directories
+will not be quoted;
+however, any dollar signs appearing in filenames will not be quoted, either.
+This is active only when bash is using backslashes to quote completed
+filenames.
+This variable is set by default, which is the default Bash behavior in
+versions through 4.2.
+
@item direxpand
If set, Bash
replaces directory names with the results of word expansion when performing
If set, prompt strings undergo
parameter expansion, command substitution, arithmetic
expansion, and quote removal after being expanded
-as described below (@pxref{Printing a Prompt}).
+as described below (@pxref{Controlling the Prompt}).
This option is enabled by default.
@item restricted_shell
are enabled, non-zero otherwise.
When setting or unsetting options, the return status is zero unless an
@var{optname} is not a valid shell option.
-
@end table
@node Special Builtins
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
+arrives in the mail file by separating the filename from the message with
a @samp{?}.
When used in the text of the message, @code{$_} expands to the name of
the current mail file.
@item PS1
The primary prompt string. The default value is @samp{\s-\v\$ }.
-@xref{Printing a Prompt}, for the complete list of escape
+@xref{Controlling the Prompt}, for the complete list of escape
sequences that are expanded before @env{PS1} is displayed.
@item PS2
@item BASH_VERSINFO[5]
The value of @env{MACHTYPE}.
-
@end table
@item BASH_VERSION
@item FIGNORE
A colon-separated list of suffixes to ignore when performing
filename completion.
-A file name whose suffix matches one of the entries in
+A filename whose suffix matches one of the entries in
@env{FIGNORE}
-is excluded from the list of matched file names. A sample
+is excluded from the list of matched filenames. A sample
value is @samp{.o:~}
@item FUNCNAME
contain only a single command).
@item POSIXLY_CORRECT
-If this variable is in the environment when @code{bash} starts, the shell
+If this variable is in the environment when Bash starts, the shell
enters @sc{posix} mode (@pxref{Bash POSIX Mode}) before reading the
startup files, as if the @option{--posix} invocation option had been supplied.
-If it is set while the shell is running, @code{bash} enables @sc{posix} mode,
+If it is set while the shell is running, Bash enables @sc{posix} mode,
as if the command
@example
@code{set -o posix}
@item PROMPT_DIRTRIM
If set to a number greater than zero, the value is used as the number of
trailing directory components to retain when expanding the @code{\w} and
-@code{\W} prompt string escapes (@pxref{Printing a Prompt}).
+@code{\W} prompt string escapes (@pxref{Controlling the Prompt}).
Characters removed are replaced with an ellipsis.
@item PS3
@node Bash Features
@chapter Bash Features
-This section describes features unique to Bash.
+This chapter describes features unique to Bash.
@menu
* Invoking Bash:: Command line options that you can give
* Aliases:: Substituting one command for another.
* Arrays:: Array Variables.
* The Directory Stack:: History of visited directories.
-* Printing a Prompt:: Controlling the PS1 string.
+* Controlling the Prompt:: Customizing the various prompt strings.
* The Restricted Shell:: A more controlled mode of shell execution.
* Bash POSIX Mode:: Making Bash behave more closely to what
the POSIX standard specifies.
@item --version
Show version information for this instance of
Bash on the standard output and exit successfully.
-
@end table
There are several single-character options that may be supplied at
A @code{--} signals the end of options and disables further option
processing.
Any arguments after the @code{--} are treated as filenames and arguments.
-
@end table
@cindex login shell
This section describes 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
+Tildes are expanded in filenames as described above under
Tilde Expansion (@pxref{Tilde Expansion}).
Interactive shells are described in @ref{Interactive Shells}.
@end example
@noindent
but the value of the @env{PATH} variable is not used to search for the
-file name.
+filename.
As noted above, if a non-interactive shell is invoked with the
@option{--login} option, Bash attempts to read and execute commands from the
@subsubheading Invoked with unequal effective and real @sc{uid/gid}s
If Bash is started with the effective user (group) id not equal to the
-real user (group) id, and the @code{-p} option is not supplied, no startup
+real user (group) id, and the @option{-p} option is not supplied, no startup
files are read, shell functions are not inherited from the environment,
the @env{SHELLOPTS}, @env{BASHOPTS}, @env{CDPATH}, and @env{GLOBIGNORE}
variables, if they appear in the environment, are ignored, and the effective
user id is set to the real user id.
-If the @code{-p} option is supplied at invocation, the startup behavior is
+If the @option{-p} option is supplied at invocation, the startup behavior is
the same, but the effective user id is not reset.
@node Interactive Shells
greater than, or greater than or equal to @var{arg2},
respectively. @var{Arg1} and @var{arg2}
may be positive or negative integers.
-
@end table
@node Shell Arithmetic
is not expanded a second time.
This means that one may alias @code{ls} to @code{"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
+replacement text.
+If the last character of the alias value is a
+@var{blank}, then the next command word following the
alias is also checked for alias expansion.
Aliases are created and listed with the @code{alias}
An indexed array is created automatically if any variable is assigned to
using the syntax
@example
-name[@var{subscript}]=@var{value}
+@var{name}[@var{subscript}]=@var{value}
@end example
@noindent
@noindent
is also accepted; the @var{subscript} is ignored.
+@noindent
Associative arrays are created using
@example
declare -A @var{name}.
Arrays are assigned to using compound assignments of the form
@example
-name=(value@var{1} @dots{} value@var{n})
+@var{name}=(@var{value1} @var{value2} @dots{} )
@end example
@noindent
where each
@var{value} is of the form @code{[@var{subscript}]=}@var{string}.
-Indexed array assignments do not require the bracket and subscript.
+Indexed array assignments do not require anything but @var{string}.
When assigning to indexed arrays, if
the optional subscript is supplied, that index is assigned to;
otherwise the index of the element assigned is the last index assigned
This syntax is also accepted by the @code{declare}
builtin. Individual array elements may be assigned to using the
-@code{name[}@var{subscript}@code{]=}@var{value} syntax introduced above.
+@code{@var{name}[@var{subscript}]=@var{value}} syntax introduced above.
Any element of an array may be referenced using
-@code{$@{name[}@var{subscript}@code{]@}}.
+@code{$@{@var{name}[@var{subscript}]@}}.
The braces are required to avoid
conflicts with the shell's filename expansion operators. If the
@var{subscript} is @samp{@@} or @samp{*}, the word expands to all members
of the array @var{name}. These subscripts differ only when the word
appears within double quotes.
If the word is double-quoted,
-@code{$@{name[*]@}} expands to a single word with
+@code{$@{@var{name}[*]@}} expands to a single word with
the value of each array member separated by the first character of the
-@env{IFS} variable, and @code{$@{name[@@]@}} expands each element of
+@env{IFS} variable, and @code{$@{@var{name}[@@]@}} expands each element of
@var{name} to a separate word. When there are no array members,
-@code{$@{name[@@]@}} expands to nothing.
+@code{$@{@var{name}[@@]@}} expands to nothing.
If the double-quoted expansion occurs within a word, the expansion of
the first parameter is joined with the beginning part of the original
word, and the expansion of the last parameter is joined with the last
part of the original word.
This is analogous to the
expansion of the special parameters @samp{@@} and @samp{*}.
-@code{$@{#name[}@var{subscript}@code{]@}} expands to the length of
-@code{$@{name[}@var{subscript}@code{]@}}.
+@code{$@{#@var{name}[@var{subscript}]@}} expands to the length of
+@code{$@{@var{name}[@var{subscript}]@}}.
If @var{subscript} is @samp{@@} or
@samp{*}, the expansion is the number of elements in the array.
Referencing an array variable without a subscript is equivalent to
value. The null string is a valid value.
The @code{unset} builtin is used to destroy arrays.
-@code{unset} @var{name}[@var{subscript}]
+@code{unset @var{name}[@var{subscript}]}
destroys the array element at index @var{subscript}.
Care must be taken to avoid unwanted side effects caused by filename
expansion.
-@code{unset} @var{name}, where @var{name} is an array, removes the
-entire array. A subscript of @samp{*} or @samp{@@} also removes the
+@code{unset @var{name}}, where @var{name} is an array, removes the
+entire array. A subscript of @samp{*} or @samp{@@} also removes the
entire array.
The @code{declare}, @code{local}, and @code{readonly}
@item dirs
@btindex dirs
@example
-dirs [+@var{N} | -@var{N}] [-clpv]
+dirs [-clpv] [+@var{N} | -@var{N}]
@end example
+
Display the list of currently remembered directories. Directories
are added to the list with the @code{pushd} command; the
@code{popd} command removes directories from the list.
+
@table @code
-@item +@var{N}
-Displays the @var{N}th directory (counting from the left of the
-list printed by @code{dirs} when invoked without options), starting
-with zero.
-@item -@var{N}
-Displays the @var{N}th directory (counting from the right of the
-list printed by @code{dirs} when invoked without options), starting
-with zero.
@item -c
Clears the directory stack by deleting all of the elements.
@item -l
-Produces a longer listing; the default listing format uses a
-tilde to denote the home directory.
+Produces a listing using full pathnames;
+the default listing format uses a tilde to denote the home directory.
@item -p
Causes @code{dirs} to print the directory stack with one entry per
line.
@item -v
Causes @code{dirs} to print the directory stack with one entry per
line, prefixing each entry with its index in the stack.
+@item +@var{N}
+Displays the @var{N}th directory (counting from the left of the
+list printed by @code{dirs} when invoked without options), starting
+with zero.
+@item -@var{N}
+Displays the @var{N}th directory (counting from the right of the
+list printed by @code{dirs} when invoked without options), starting
+with zero.
@end table
@item popd
@btindex popd
@example
-popd [+@var{N} | -@var{N}] [-n]
+popd [-n] [+@var{N} | -@var{N}]
@end example
Remove the top entry from the directory stack, and @code{cd}
removes the top directory from the stack and
performs a @code{cd} to the new top directory. The
elements are numbered from 0 starting at the first directory listed with
-@code{dirs}; i.e., @code{popd} is equivalent to @code{popd +0}.
+@code{dirs}; that is, @code{popd} is equivalent to @code{popd +0}.
+
@table @code
+@item -n
+Suppresses the normal change of directory when removing directories
+from the stack, so that only the stack is manipulated.
@item +@var{N}
Removes the @var{N}th directory (counting from the left of the
list printed by @code{dirs}), starting with zero.
@item -@var{N}
Removes the @var{N}th directory (counting from the right of the
list printed by @code{dirs}), starting with zero.
-@item -n
-Suppresses the normal change of directory when removing directories
-from the stack, so that only the stack is manipulated.
@end table
@btindex pushd
@item pushd
@example
-pushd [-n] [@var{+N} | @var{-N} | @var{dir} ]
+pushd [-n] [@var{+N} | @var{-N} | @var{dir}]
@end example
Save the current directory on the top of the directory stack
list printed by @code{dirs}, starting with zero) to the top of
the list by rotating the stack.
@item @var{dir}
-Makes the current working directory be the top of the stack, and then
-executes the equivalent of `@code{cd} @var{dir}'.
-@code{cd}s to @var{dir}.
+Makes the current working directory be the top of the stack, making
+it the new current directory as if it had been supplied as an argument
+to the @code{cd} builtin.
@end table
-
@end table
-@node Printing a Prompt
+@node Controlling the Prompt
@section Controlling the Prompt
@cindex prompting
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:
+can appear in the prompt variables @env{PS1} to @env{PS4}:
@table @code
@item \a
may not start with a digit. Declaring a function with an invalid name
causes a fatal syntax error in non-interactive shells.
+@item
+Function names may not be the same as one of the @sc{posix} special
+builtins.
+
@item
@sc{posix} special builtins are found before shell functions
during command lookup.
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, @samp{%ce} refers
-to a stopped @code{ce} job. Using @samp{%?ce}, on the
+to a stopped @code{ce} job. Using @samp{%?ce}, on the
other hand, refers to any job containing the string @samp{ce} in
its command line. If the prefix or substring matches more than one job,
Bash reports an error.
@example
bg [@var{jobspec} @dots{}]
@end example
+
Resume each suspended job @var{jobspec} in the background, as if it
had been started with @samp{&}.
If @var{jobspec} is not supplied, the current job is used.
@example
fg [@var{jobspec}]
@end example
+
Resume the job @var{jobspec} in the foreground and make it the current job.
If @var{jobspec} is not supplied, the current job is used.
The return status is that of the command placed into the foreground,
List only the process @sc{id} of the job's process group leader.
@item -r
-Restrict output to running jobs.
+Display only running jobs.
@item -s
-Restrict output to stopped jobs.
+Display only stopped jobs.
@end table
If @var{jobspec} is given,
kill [-s @var{sigspec}] [-n @var{signum}] [-@var{sigspec}] @var{jobspec} or @var{pid}
kill -l [@var{exit_status}]
@end example
+
Send a signal specified by @var{sigspec} or @var{signum} to the process
named by job specification @var{jobspec} or process @sc{id} @var{pid}.
@var{sigspec} is either a case-insensitive signal name such as
@item wait
@btindex wait
@example
-wait [@var{jobspec} or @var{pid} ...]
+wait [@var{jobspec} or @var{pid} @dots{}]
@end example
+
Wait until the child process specified by each process @sc{id} @var{pid}
or job specification @var{jobspec} exits and return the exit status of the
last command waited for.
@example
disown [-ar] [-h] [@var{jobspec} @dots{}]
@end example
-Without options, each @var{jobspec} is removed from the table of
+
+Without options, remove each @var{jobspec} from the table of
active jobs.
If the @option{-h} option is given, the job is not removed from the table,
but is marked so that @code{SIGHUP} is not sent to the job if the shell
@example
suspend [-f]
@end example
+
Suspend the execution of this shell until it receives a
@code{SIGCONT} signal.
A login shell cannot be suspended; the @option{-f}
option can be used to override this and force the suspension.
-
@end table
When job control is not active, the @code{kill} and @code{wait}
@item --enable-prompt-string-decoding
Turn on the interpretation of a number of backslash-escaped characters
in the @env{$PS1}, @env{$PS2}, @env{$PS3}, and @env{$PS4} prompt
-strings. See @ref{Printing a Prompt}, for a complete list of prompt
+strings. See @ref{Controlling the Prompt}, for a complete list of prompt
string escape sequences.
@item --enable-readline
the Single Unix Specification, version 3.
@xref{Bash Builtins}, for a description of the escape sequences that
@code{echo} recognizes.
-
@end table
The file @file{config-top.h} contains C Preprocessor
builtin (@pxref{The Set Builtin}).
@item
-The @samp{-x} (@code{xtrace}) option displays commands other than
+The @samp{-x} (@option{xtrace}) option displays commands other than
simple commands when performing an execution trace
(@pxref{The Set Builtin}).
@item
Bash interprets special backslash-escaped characters in the prompt
-strings when interactive (@pxref{Printing a Prompt}).
+strings when interactive (@pxref{Controlling the Prompt}).
@item
The Bash restricted mode is more useful (@pxref{The Restricted Shell});
projects / thirdparty / bash.git / blobdiff