GETOPT(1)                    General Commands Manual                   GETOPT(1)

     getopt – parse command options

     args=`getopt optstring $*` ; errcode=$?; set -- $args

     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.

     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 ]
                   echo 'Usage: ...'
                   exit 2
           set -- $args
           # You cannot use the set command with a backquoted getopt directly,
           # since the exit code from getopt would be shadowed by those of set,
           # which is zero by definition.
           for i
                   case "$i"
                                   echo flag $i set; sflags="${i#-}$sflags";
                                   echo oarg is "'"$2"'"; oarg="$2"; shift;
                                   shift; break;;
           echo single-char flags: "'"$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

     sh(1), getopt(3)

     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

     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.

     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

     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

macOS 12.1                        April 3, 1999                       macOS 12.1