getopt(3C)							    getopt(3C)

NAME    [Toc]    [Back]

     getopt - get option letter	from argument vector

SYNOPSIS    [Toc]    [Back]

     #include <unistd.h>

     int getopt	(int argc, char	* const	argv[],	const char *optstring);

     extern char *optarg;

     extern int	optind,	opterr,	optopt;

     extern void getoptreset (void);

DESCRIPTION    [Toc]    [Back]

     getopt returns the	next option letter in argv that	matches	a letter in
     optstring.	 It supports all the rules of the command syntax standard [see
     intro(1)].	 Since all new commands	are intended to	adhere to the command
     syntax standard, they should use getopts(1), getopt(3C), or getsubopt(3C)
     to	parse positional parameters and	check for options that are legal for
     that command.

     optstring must contain the	option letters that the	command	using getopt
     will recognize.  If a letter is followed by a colon, the option is
     expected to have an argument, or group of arguments, which	may be
     separated from it by white	space.	optarg is set to point to the start of
     the option	argument on return from	getopt.

     getopt places in optind the argv index of the next	argument to be
     processed.	 optind	is external and	is initialized to 1 before the first
     call to getopt.  When all options have been processed (i.e., up to	the
     first non-option argument), getopt	returns	-1.  The special option	``--''
     (two hyphens) may be used to delimit the end of the options; when it is
     encountered, -1 is	returned and ``--'' is skipped.	This is	useful in
     delimiting	non-option arguments that begin	with ``-'' (hyphen).

     getoptreset can be	used to	reset all the internal state of	getopt so that
     it	may be used again on a different set of	arguments.

EXAMPLE    [Toc]    [Back]

     The following code	fragment shows how one might process the arguments for
     a command that can	take the mutually exclusive options a and b, and the
     option o, which requires an argument:

     #include <unistd.h>

     main (int argc, char *argv[])
     {
	  int c;
	  extern char *optarg;
	  extern int optind;
	  int aflg = 0;



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getopt(3C)							    getopt(3C)



	 int bflg = 0;
	  int errflg = 0;
	  char *ofile =	NULL;

	  while	((c = getopt(argc, argv, "abo:")) != -1)
	       switch (c) {
	       case 'a':
		    if (bflg)
			 errflg++;
		    else
			 aflg++;
		    break;
	       case 'b':
		    if (aflg)
			 errflg++;
		    else
			 bflg++;
		    break;
	       case 'o':
		    ofile = optarg;
		    (void)printf("ofile	= %s\n", ofile);
		    break;
	       case '?':
		    errflg++;
	       }
	  if (errflg) {
	       (void)fprintf(stderr,
		    "usage: cmd	[-a|-b]	[-o<file>] files...\n");
	       exit (2);
	  }
	  for (	; optind < argc; optind++)
	       (void)printf("%s\n", argv[optind]);
	  return 0;
     }

FILES    [Toc]    [Back]

     /usr/lib/locale/locale<b>/LC_MESSAGES/uxlibc
	  language-specific message file [See LANG on environ(5).]

SEE ALSO    [Toc]    [Back]

     getopts(1), intro(1), getsubopt(3C), pfmt(3C), setlabel(3C)

RETURN VALUE    [Toc]    [Back]

     The getopt	function returns the next option character specified on	the
     command line.

     A colon character ``:''  is returned if getopt detects a missing argument
     and the first character of	optstring was a	colon character	``:''.

     A question	mark character ``?''  is returned if getopt encounters an
     option character not in optstring or detects a missing argument and the
     first character of	optstring was not a colon character ``:''.



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getopt(3C)							    getopt(3C)



     Otherwise getopt returns -1 when all command line options are parsed.

DIAGNOSTICS    [Toc]    [Back]

     If	getopt detects a missing option-argument, it returns the ``:''	colon
     character if the first character of optstring was a colon,	or a ``?''
     (question mark) character otherwise.  If the application has not set the
     variable opterr to	zero and the first character of	optstring is not a
     colon, getopt also	prints a diagnostic message in the standard error
     format.  The value	of the character that caused the error is in optopt.

     The label defined by a call to setlabel(3C) will be used if available;
     otherwise the name	of the utility (argv[0]) will be used.	Remember to
     set the environment variable (NOMSGSEVERITY=1) for	X/Open conformance.
     Also, the environment variable (NOMSGLABEL) must be not defined in	order
     for setlabel(3C) to print labels.

NOTES    [Toc]    [Back]

     The library routine getopt	does not fully check for mandatory arguments.
     That is, given an option string a:b and the input -a -b, getopt assumes
     that -b is	the mandatory argument to the option -a	and not	that -a	is
     missing a mandatory argument.

     It	is a violation of the command syntax standard [see intro(1)] for
     options with arguments to be grouped with other options, as in cmd
     -aboxxx file, where a and b are options, o	is an option that requires an
     argument, and xxx is the argument to o.  Although this syntax is
     permitted in the current implementation, it should	not be used because it
     may not be	supported in future releases. The correct syntax is cmd	-ab -o
     xxx file.


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