getopt
GETOPT(1) General Commands Manual GETOPT(1)
NAME
getopt – parse command options
SYNOPSIS
args=`getopt optstring $*` ; errcode=$?; set -- $args
DESCRIPTION
The getopt utility 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 white space. The special option ‘--’ is
used to delimit the end of the options. The getopt utility 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: $*`
# you should not use `getopt abo: "$@"` since that would parse
# the arguments differently from what the set command below does.
if [ $? != 0 ]
then
echo 'Usage: ...'
exit 2
fi
set -- $args
# You cannot use the set command with a backquoted getopt directly,
# since the exit code from getopt would be shadowed by those of set,
# which is zero by definition.
for i
do
case "$i"
in
-a|-b)
echo flag $i set; sflags="${i#-}$sflags";
shift;;
-o)
echo oarg is "'"$2"'"; oarg="$2"; shift;
shift;;
--)
shift; break;;
esac
done
echo single-char flags: "'"$sflags"'"
echo oarg is "'"$oarg"'"
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
SEE ALSO
sh(1), getopt(3)
DIAGNOSTICS
The getopt utility prints an error message on the standard error output and
exits with status > 0 when it encounters an option letter not included in
optstring.
HISTORY
Written by Henry Spencer, working from a Bell Labs manual page. Behavior
believed identical to the Bell version. Example changed in FreeBSD version
3.2 and 4.0.
BUGS
Whatever getopt(3) has.
Arguments containing white space or embedded shell metacharacters generally
will not survive intact; this looks easy to fix but isn't. People trying
to fix getopt or the example in this manpage should check the history of
this file in FreeBSD.
The error message for an invalid option is identified as coming from getopt
rather than from the shell procedure containing the invocation of getopt;
this again is hard to fix.
The precise best way to use the set command to set the arguments without
disrupting the value(s) of shell options varies from one shell version to
another.
Each shellscript has to carry complex code to parse arguments halfway
correcty (like the example presented here). A better getopt-like tool would
move much of the complexity into the tool and keep the client shell scripts
simpler.
macOS 12.1 April 3, 1999 macOS 12.1