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GETOPT(3)	       FreeBSD Library Functions Manual		     GETOPT(3)

NAME
     getopt -- get option character from command line argument list

LIBRARY
     Standard C	Library	(libc, -lc)

SYNOPSIS
     #include <unistd.h>

     extern char *optarg;
     extern int	optind;
     extern int	optopt;
     extern int	opterr;
     extern int	optreset;

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

DESCRIPTION
     The getopt() function incrementally parses	a command line argument	list
     argv and returns the next known option character.	An option character is
     known if it has been specified in the string of accepted option charac-
     ters, optstring.

     The option	string optstring may contain the following elements: individ-
     ual characters, and characters followed by	a colon	to indicate an option
     argument is to follow.  For example, an option string "x" recognizes an
     option ``-x'', and	an option string "x:" recognizes an option and argu-
     ment ``-x argument''.  It does not	matter to getopt() if a	following
     argument has leading white	space.

     On	return from getopt(), optarg points to an option argument, if it is
     anticipated, and the variable optind contains the index to	the next argv
     argument for a subsequent call to getopt().  The variable optopt saves
     the last known option character returned by getopt().

     The variables opterr and optind are both initialized to 1.	 The optind
     variable may be set to another value before a set of calls	to getopt() in
     order to skip over	more or	less argv entries.

     In	order to use getopt() to evaluate multiple sets	of arguments, or to
     evaluate a	single set of arguments	multiple times,	the variable optreset
     must be set to 1 before the second	and each additional set	of calls to
     getopt(), and the variable	optind must be reinitialized.

     The getopt() function returns -1 when the argument	list is	exhausted.
     The interpretation	of options in the argument list	may be cancelled by
     the option	`--' (double dash) which causes	getopt() to signal the end of
     argument processing and return -1.	 When all options have been processed
     (i.e., up to the first non-option argument), getopt() returns -1.

RETURN VALUES
     The getopt() function returns the next known option character in
     optstring.	 If getopt() encounters	a character not	found in optstring or
     if	it detects a missing option argument, it returns `?' (question mark).
     If	optstring has a	leading	`:' then a missing option argument causes `:'
     to	be returned instead of `?'.  In	either case, the variable optopt is
     set to the	character that caused the error.  The getopt() function
     returns -1	when the argument list is exhausted.

EXAMPLES
     #include <unistd.h>
     int bflag,	ch, fd;

     bflag = 0;
     while ((ch	= getopt(argc, argv, "bf:")) !=	-1) {
	     switch (ch) {
	     case 'b':
		     bflag = 1;
		     break;
	     case 'f':
		     if	((fd = open(optarg, O_RDONLY, 0)) < 0) {
			     (void)fprintf(stderr,
				 "myname: %s: %s\n", optarg, strerror(errno));
			     exit(1);
		     }
		     break;
	     case '?':
	     default:
		     usage();
	     }
     }
     argc -= optind;
     argv += optind;

DIAGNOSTICS
     If	the getopt() function encounters a character not found in the string
     optstring or detects a missing option argument it writes an error message
     to	the stderr and returns `?'.  Setting opterr to a zero will disable
     these error messages.  If optstring has a leading `:' then	a missing
     option argument causes a `:' to be	returned in addition to	suppressing
     any error messages.

     Option arguments are allowed to begin with	``-''; this is reasonable but
     reduces the amount	of error checking possible.

SEE ALSO
     getopt(1),	getopt_long(3),	getsubopt(3)

STANDARDS
     The optreset variable was added to	make it	possible to call the getopt()
     function multiple times.  This is an extension to the IEEE	Std 1003.2
     (``POSIX.2'') specification.

HISTORY
     The getopt() function appeared in 4.3BSD.

BUGS
     The getopt() function was once specified to return	EOF instead of -1.
     This was changed by IEEE Std 1003.2-1992 (``POSIX.2'') to decouple
     getopt() from <stdio.h>.

     A single dash ``-'' may be	specified as a character in optstring, however
     it	should never have an argument associated with it.  This	allows
     getopt() to be used with programs that expect ``-'' as an option flag.
     This practice is wrong, and should	not be used in any current develop-
     ment.  It is provided for backward	compatibility only.  Care should be
     taken not to use `-' as the first character in optstring to avoid a
     semantic conflict with GNU	getopt(), which	assigns	different meaning to
     an	optstring that begins with a `-'.  By default, a single	dash causes
     getopt() to return	-1.

     It	is also	possible to handle digits as option letters.  This allows
     getopt() to be used with programs that expect a number (``-3'') as	an
     option.  This practice is wrong, and should not be	used in	any current
     development.  It is provided for backward compatibility only.  The	fol-
     lowing code fragment works	in most	cases.

	   int ch;
	   long	length;
	   char	*p, *ep;

	   while ((ch =	getopt(argc, argv, "0123456789")) != -1)
		   switch (ch) {
		   case	'0': case '1': case '2': case '3': case	'4':
		   case	'5': case '6': case '7': case '8': case	'9':
			   p = argv[optind - 1];
			   if (p[0] == '-' && p[1] == ch && !p[2]) {
				   length = ch - '0';
				   ep =	"";
			   } else if (argv[optind] && argv[optind][1] == ch) {
				   length = strtol((p =	argv[optind] + 1),
				       &ep, 10);
				   optind++;
				   optreset = 1;
			   } else
				   usage();
			   if (*ep != '\0')
				   errx(EX_USAGE, "illegal number -- %s", p);
			   break;
		   }

FreeBSD	6.0			April 27, 1995			   FreeBSD 6.0

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | EXAMPLES | DIAGNOSTICS | SEE ALSO | STANDARDS | HISTORY | BUGS

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