Updated: 2021/Apr/14

GETOPT(1)                   General Commands Manual                  GETOPT(1)

     getopt - parse command options

     args=`getopt optstring $*`

     set -- `getopt optstring $*`

     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 white space.  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.

     getopt should not be used in new scripts; use the shell builtin getopts

     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 [c],
     which requires an argument.

           args=`getopt abc: $*`
           if [ $? -ne 0 ]; then
                   echo 'Usage: ...'
                   exit 2
           set -- $args
           while [ $# -gt 0 ]; do
                   case "$1" in
                                   carg=$2; shift
                                   shift; break

     This code will accept any of the following as equivalent:

           cmd -acarg file file
           cmd -a -c arg file file
           cmd -carg -a file file
           cmd -a -carg -- file file

     IEEE Std 1003.2 ("POSIX.2") mandates that the sh(1) set command return
     the value of 0 for the exit status.  Therefore, the exit status of the
     getopt command is lost when getopt and the sh(1) set command are used on
     the same line.  The example given is one way to detect errors found by

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

     sh(1), getopt(3)

     Written by Henry Spencer, working from a Bell Labs manual page.  Behavior
     believed identical to the Bell version.

     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.

     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

NetBSD 9.99                    November 28, 2009                   NetBSD 9.99