Standard C Library Functions			       getopt(3C)



NAME
     getopt - get option letter	from argument vector

SYNOPSIS
     #include <stdlib.h>

     int getopt(int argc, char * const *argv,  const  char  *opt-
     string);
     extern char *optarg;
     extern int	optind,	opterr,	optopt;

DESCRIPTION
     The getopt() function 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 syn-
     tax 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.

     The optstring argument must contain the option  letters  the
     command  using  getopt() will recognize; if a letter is fol-
     lowed by a	colon, the option is expected to  have	an  argu-
     ment,  or group of	arguments, which may be	separated from it
     by	white space.  The optarg argument is set to point to  the
     start of the option argument on return from getopt().

     The getopt() function 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 (that is, up	to the first non-
     option argument), getopt()	returns	EOF. The  special  option
     "--"  (two	 hyphens)  may	be used	to delimit the end of the
     options; when it is encountered, EOF is returned  and  "--"'
     is	 skipped.   This is useful in delimiting non-option argu-
     ments that	begin with "-" (hyphen).

RETURN VALUES
     The getopt() function prints an error message on  the  stan-
     dard  error  and  returns	a  "?"	(question  mark)  when it
     encounters	an option letter not included in optstring or  no
     argument  after  an option	that expects one. This error mes-
     sage may be disabled by setting  opterr to	0. The	value  of
     the character that	caused the error is in optopt.

USAGE
     If	the application	is  linked  with  -lintl,  then	 messages
     printed from this function	are in the native language speci-
     fied by the LC_MESSAGES locale category; see setlocale(3C).

     The getopt() function does	not  fully  check  for	mandatory
     arguments;	that is, given an option string	a:b and	the input



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Standard C Library Functions			       getopt(3C)



     -a	-b, getopt() assumes that -b is	the mandatory argument to
     the  -a  option and not that -a is	missing	a mandatory argu-
     ment.

     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 -abo filename , where a and  b  are
     options,
      o	is an option that requires an argument,	and  filename  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 to
     use is:

	  cmd -ab -o filename.


EXAMPLES
     Example 1:	Example	on how one might  process  the	arguments
     for a command.

     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  argu-
     ment:

     #include <stdlib.h>
     #include <stdio.h>

     main (int argc, char **argv)
     {
	int c;
	extern char *optarg;
	extern int optind;
	int aflg = 0;
	int bflg = 0;
	int errflg = 0;
	char *ofile = NULL;

	while ((c = getopt(argc, argv, "abo:"))	!= EOF)
	   switch (c) {
	   case	'a':
	      if (bflg)
		 errflg++;
	      else
		 aflg++;
	      break;
	   case	'b':
	      if (aflg)
		 errflg++;
	      else
		 bflg++;



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Standard C Library Functions			       getopt(3C)



	      break;
	   case	'o':
	      ofile = optarg;
	      (void)printf("ofile = %s\n", ofile);
	      break;
	   case	'?':
	      errflg++;
	   }
	if (errflg) {
	   (void)fprintf(stderr,
	      "usage: cmd [-a|-b] [-o <filename>] files...\n");
	   exit	(2);
	    }
	    for	( ; optind < argc; optind++)
	  (void)printf("%s\n", argv[optind]);
	return 0;
     }

ATTRIBUTES
     See attributes(5) for descriptions	of the	following  attri-
     butes:

     ____________________________________________________________
    |	    ATTRIBUTE TYPE	  |	  ATTRIBUTE VALUE	|
    |_____________________________|_____________________________|
    | MT-Level			  | Unsafe			|
    |_____________________________|_____________________________|


SEE ALSO
     intro(1),	   getopts(1),	   getopt(3C),	   getsubopt(3C),
     setlocale(3C), gettext(3C), attributes(5)























SunOS 5.8	    Last change: 29 Dec	1996			3