The following example shows how you might process the arguments
      for a utility that can take the mutually exclusive options a
      and b and the options f and o, both of which require arguments:

 #include <unistd.h>

 int main (int argc, char *argv[ ])
 {
          int c;
          int bflg, aflg, errflg;
          char *ifile;
          char *ofile;
          extern char *optarg;
          extern int optind, optopt;
          .
          .
          .
          while ((c = getopt(argc, argv, ":abf:o:)) != -1) {

                 switch (c) {
                 case 'a':
                         if (bflg)
                                 errflg++;
                         else
                                 aflg++;
                         break;
                 case 'b':
                         if (aflg)
                                errflg++;
                         else {
                                bflg++;
                                bproc();
                         }

                         break;
                 case 'f':
                         ifile = optarg;
                         break;
                 case 'o':
                         ofile = optarg;
                         break;
                 case ':':      /* -f or -o without operand */
                         fprintf (stderr,
                          "Option -%c requires an operand\n"' optopt);
                         errflg++;
                         break;
                 case '?':
                         fprintf (stderr,
                                 "Unrecognized option -%c\n"' optopt);
                         errflg++;
                 }
          }
          if (errflg) {
                 fprintf (stderr, "usage: ...");
                 exit(2);
          }
          for ( ; optind < argc; optind++)  {
                 if (access(argv[optind], R_OK)) {
          .
          .
          .
 }

      This sample code accepts any of the following as equivalent:

        cmd -ao arg path path
        cmd -a -o arg path path
        cmd -o arg -a path path
        cmd -a -o arg -- path path
        cmd -a -oarg path path
        cmd -aoarg path path