bash: The Shopt Builtin
4.3.2 The Shopt Builtin
-----------------------
This builtin allows you to change additional shell optional behavior.
'shopt'
shopt [-pqsu] [-o] [OPTNAME ...]
Toggle the values of settings controlling optional shell behavior.
The settings can be either those listed below, or, if the '-o'
option is used, those available with the '-o' option to the 'set'
builtin command (
The Set Builtin). 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 (The Set Builtin).
If either '-s' or '-u' is used with no OPTNAME arguments, 'shopt'
shows only 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:
'autocd'
If set, a command name that is the name of a directory is
executed as if it were the argument to the 'cd' command. This
option is only used by interactive shells.
'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.
'checkjobs'
If set, Bash lists the status of any stopped and running jobs
before exiting an interactive shell. If any jobs are running,
this causes the exit to be deferred until a second exit is
attempted without an intervening command (Job
Control). The shell always postpones exiting if any jobs
are stopped.
'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.
'compat31'
If set, Bash changes its behavior to that of version 3.1 with
respect to quoted arguments to the conditional command's '=~'
operator and with respect to locale-specific string comparison
when using the '[[' conditional command's '<' and '>'
operators. Bash versions prior to bash-4.1 use ASCII
collation and strcmp(3); bash-4.1 and later use the current
locale's collation sequence and strcoll(3).
'compat32'
If set, Bash changes its behavior to that of version 3.2 with
respect to locale-specific string comparison when using the
'[[' conditional command's '<' and '>' operators (see previous
item) and the effect of interrupting a command list. Bash
versions 3.2 and earlier continue with the next command in the
list after one terminates due to an interrupt.
'compat40'
If set, Bash changes its behavior to that of version 4.0 with
respect to locale-specific string comparison when using the
'[[' conditional command's '<' and '>' operators (see
description of 'compat31') and the effect of interrupting a
command list. Bash versions 4.0 and later interrupt the list
as if the shell received the interrupt; previous versions
continue with the next command in the list.
'compat41'
If set, Bash, when in POSIX mode, treats a single quote in a
double-quoted parameter expansion as a special character. The
single quotes must match (an even number) and the characters
between the single quotes are considered quoted. This is the
behavior of POSIX mode through version 4.1. The default Bash
behavior remains as in previous versions.
'compat42'
If set, Bash does not process the replacement string in the
pattern substitution word expansion using quote removal.
'compat43'
If set, Bash does not print a warning message if an attempt is
made to use a quoted compound array assignment as an argument
to 'declare', makes word expansion errors non-fatal errors
that cause the current command to fail (the default behavior
is to make them fatal errors that cause the shell to exit),
and does not reset the loop state when a shell function is
executed (this allows 'break' or 'continue' in a shell
function to affect loops in the caller's context).
'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.
'direxpand'
If set, Bash replaces directory names with the results of word
expansion when performing filename completion. This changes
the contents of the readline editing buffer. If not set, Bash
attempts to preserve what the user typed.
'dirspell'
If set, Bash attempts spelling correction on directory names
during word completion if the directory name initially
supplied does not exist.
'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,
Aliases. This option is enabled by default for
interactive shells.
'extdebug'
If set at shell invocation, arrange to execute the debugger
profile before the shell starts, identical to the '--debugger'
option. If set after invocation, behavior intended for use by
debuggers is enabled:
Builtins::) displays the source file name and line number
corresponding to each function name supplied as an
argument.
2. If the command run by the 'DEBUG' trap returns a non-zero
value, the next command is skipped and not executed.
3. 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), the shell simulates a call to
'return'.
4. 'BASH_ARGC' and 'BASH_ARGV' are updated as described in
their descriptions (Bash Variables).
5. Function tracing is enabled: command substitution, shell
functions, and subshells invoked with '( COMMAND )'
inherit the 'DEBUG' and 'RETURN' traps.
6. Error tracing is enabled: command substitution, shell
functions, and subshells invoked with '( COMMAND )'
inherit the 'ERR' trap.
'extglob'
If set, the extended pattern matching features described above
(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 filename
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.
Bash Variables, for a description of 'FIGNORE'. This option
is enabled by default.
'globasciiranges'
If set, range expressions used in pattern matching bracket
expressions (Pattern Matching) behave as if in the
traditional C locale when performing comparisons. That is,
the current locale's collating sequence is not taken into
account, so 'b' will not collate between 'A' and 'B', and
upper-case and lower-case ASCII characters will collate
together.
'globstar'
If set, the pattern '**' used in a filename expansion context
will match all files and zero or more directories and
subdirectories. If the pattern is followed by a '/', only
directories and subdirectories match.
'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 (Commands For Completion). This
option is enabled by default.
'huponexit'
If set, Bash will send 'SIGHUP' to all jobs when an
interactive login shell exits (Signals).
'inherit_errexit'
If set, command substitution inherits the value of the
'errexit' option, instead of unsetting it in the subshell
environment. This option is enabled when POSIX mode is
enabled.
'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.
'lastpipe'
If set, and job control is not active, the shell runs the last
command of a pipeline not executed in the background in the
current shell environment.
'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
(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.
'nocasematch'
If set, Bash matches patterns in a case-insensitive fashion
when performing matching while executing 'case' or '[['
conditional commands, when performing pattern substitution
word expansions, or when filtering possible completions as
part of programmable completion.
'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 (
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 (Controlling the
Prompt). This option is enabled by default.
'restricted_shell'
The shell sets this option if it is started in restricted mode
(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.
Info Catalog
bash: The Set Builtin
bash: Modifying Shell Behavior