GETOPT(3C)                           SysV                           GETOPT(3C)



NAME
     getopt - get option letter from argument vector

SYNOPSIS
     int getopt (argc, argv, optstring)
     int argc;
     char **argv, *opstring;

     extern char *optarg;
     extern int optind, opterr;

DESCRIPTION
     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)).  So all new commands will adhere to the command syntax
     standard, they should use getopts(1) or getopt(3C) to parse positional
     parameters and check for options that are legal for that command.

     optstring must contain the option letters 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 must 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 (that is, up to the first non-option
     argument), getopt returns -1.  The special option "--" may be used to
     delimit the end of the options; when it is encountered, -1 will be
     returned, and "--" will be skipped.

DIAGNOSTICS
     getopt prints an error message on standard error and returns a question
     mark (?)  when it encounters an option letter not included in optstring
     or no option-argument after an option that expects one.  This error
     message may be disabled by setting opterr to zero.

EXAMPLE
     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 option-argument:

     main (argc, argv)
     int argc;
     char **argv;
     {
          int c;
          extern char *optarg;
          extern int optind;
          .
          .
          while ((c = getopt(argc, argv, "abo:")) != -1)
               switch (c) {
               case 'a':
                    if (bflg)
                         errflg++;
                    else

                         aflg++;
                    break;
               case 'b':
                    if (aflg)
                         errflg++;
                    else
                         bproc( );
                    break;
               case 'o':
                    ofile = optarg;
                    break;
               case '?':
                    errflg++;
               }
          if (errflg) {
               (void)fprintf(stderr, "usage: . . . ");
               exit (2);
          }
          for ( ; optind < argc; optind++) {
          .    if (access(argv[optind], 4)) {
          .
     }

WARNING
     Although the following command syntax rule (see intro(1)) relaxations are
     permitted under the current implementation, they should not be used
     because they may not be supported in future releases of the system.  As
     in the EXAMPLE section above, a and b are options, and the option o
     requires an option-argument:

          cmd -aboxxx file  (Rule 5 violation:  options with
                option-arguments must not be grouped with other options)
          cmd -ab -oxxx file  (Rule 6 violation:  there must be
                white space after an option that takes an option-argument)

     Changing the value of the variable optind, or calling getopt with
     different values of argv, may lead to unexpected results.

SEE ALSO
     getopts(1), intro(1) in the SysV Command Reference.