getopt man page on OpenBSD

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GETOPT(1)		   OpenBSD Reference Manual		     GETOPT(1)

NAME
     getopt - parse command options

SYNOPSIS
     args=`getopt optstring $*`; set -- $args

DESCRIPTION
     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.

     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.

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 [ $# -ge 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].

SEE ALSO
     sh(1), getopt(3)

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

BUGS
     Whatever getopt(3) has.

     Arguments containing whitespace 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
     another.

OpenBSD 4.9		       October 28, 2010			   OpenBSD 4.9
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