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GETOPT(1)		  BSD 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 op-
     tion is preceded by a `-' and in its own shell argument; each option ar-
     gument is also in its own shell argument.

     The getopt	utility	prints an error	message	on the standard	error output
     and exits with status > 0 when it encounters an option letter not in-
     cluded in optstring.

     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
	   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
			   echo	"flag $1 set"; sflags="${1#-}$sflags"
			   echo	"oarg is '$2'";	oarg="$2"
			   shift; shift
			   shift; break
	   echo	"single-char flags: '$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

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

     Written by	Henry Spencer, working from a Bell Labs	manual page.  Behavior
     believed identical	to the Bell version.  Example changed in FreeBSD ver-
     sion 3.2 and 4.0.

     Whatever getopt(3)	has.

     Arguments containing white	space or embedded shell	metacharacters gener-
     ally 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 his-
     tory 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
     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.

BSD				August 1, 2015				   BSD


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