GETOPT(1)               FreeBSD 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.

EXIT STATUS
     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.

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 [ $? -ne 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.
           while :; do
                   case "$1" in
                   -a|-b)
                           echo "flag $1 set"; sflags="${1#-}$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 file1 file2
           cmd -a -o arg file1 file2
           cmd -oarg -a file1 file2
           cmd -a -oarg -- file1 file2

SEE ALSO
     getopts(1), sh(1), getopt(3)

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 is not.
     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
     correctly (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.

FreeBSD 13.1-RELEASE-p6         August 1, 2015         FreeBSD 13.1-RELEASE-p6