Classic Shell Scripting

The bash shopt Command

The bash shell, besides using the set command with long and short options, has a separate shopt command for enabling and disabling options.

shopt (bash)

Usage

shopt [ -pqsu ] [ -o ] [ option-name ... ]

Purpose

To centralize control of shell options as they're added to bash, instead of proliferating set options or shell variables.

Major options

 

-o

Limit options to those that can be set with set -o.

-p

Print output in a form suitable for rereading.

-q

Quiet mode. The exit status indicates if the option is set. With multiple options, the status is zero if they are all enabled, nonzero otherwise.

-s

Set (enable) the given option.

-u

Unset (disable) the given option.

For -s and -u without named options, the display lists those options which are set or unset, respectively.

Behavior

Control the settings of various internal shell options. With no option or -p, print the settings. Use -p to print the settings in a form that can be reread later.

Caveats

Only in bash, not in ksh.

The list of options for bash version 3.0 follows. For each option, we describe the behavior when the option is set (enabled):

cdable_vars

When an argument to cd isn't a directory, bash treats it as a variable name, whose value is the target directory.

cdspell

If a cd to a directory fails, bash attempts several minor spelling corrections to see if it can find the real directory. If it finds a correction, it prints the name and changes to the computed directory. This option works only in interactive shells.

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