getopt1

Usage

Overview

The getopt utility cannot handle option arguments containing whitespace; consider using the standard getopts shell built-in instead.

getopt is used to break up options in command lines for easy parsing by shell procedures, and to check for legal options. optstring is a string of recognized option letters (see getopt(3)); if a letter is followed by a colon, the option is expected to have an argument which may or may not be separated from it by whitespace. However, if a letter is followed by two colons, the argument is optional and may not be separated by whitespace - this is an extension not covered by POSIX. The special option ‘--’ is used to delimit the end of the options. getopt will place ‘--’ in the arguments at the end of the options, or recognize it if used explicitly. The shell arguments ($1, $2, ...) are reset so that each option is preceded by a ‘-’ and in its own shell argument; each option argument is also in its own shell argument.

Examples

The following code fragment shows how one might process the arguments for a command that can take the options -a and -b, and the option -o, which requires an argument.

args=`getopt abo: $*`
if [ $? -ne 0 ]
then
	echo 'Usage: ...'
	exit 2
fi
set -- $args
while [ $# -ne 0 ]
do
	case "$1"
	in
		-a|-b)
			flag="$1"; shift;;
		-o)
			oarg="$2"; shift; shift;;
		--)
			shift; break;;
	esac
done

This code will accept any of the following as equivalent:

cmd -aoarg file file
cmd -a -o arg file file
cmd -oarg -a file file
cmd -a -oarg -- file file

Diagnostics

getopt prints an error message on the standard error output when it encounters an option letter not included in optstring.

Caveats

Note that the construction

set -- `getopt optstring $*`

is not recommended, as the exit value from set will prevent the exit value from getopt from being determined.