getopt

getopt is a GNU library used to parse command-line options.

It is used with the

#include <getopt.h>

include line.

Example

      #include <stdio.h>     /* for printf */
      #include <stdlib.h>    /* for exit */
      #include <getopt.h>
      int
      main (int argc, char **argv) {
          int c;
          int digit_optind = 0;
          while (1) {
              int this_option_optind = optind ? optind : 1;
              int option_index = 0;
              static struct option long_options[] = {
                  {"add", 1, 0, 0},
                  {"append", 0, 0, 0},
                  {"delete", 1, 0, 0},
                  {"verbose", 0, 0, 0},
                  {"create", 1, 0, 'c'},
                  {"file", 1, 0, 0},
                  {NULL, 0, NULL, 0}
              };
              c = getopt_long (argc, argv, "abc:d:012",
                       long_options, &option_index);
              if (c == -1)
                  break;
              switch (c) {
              case 0:
                  printf ("option %s", long_options[option_index].name);
                  if (optarg)
                      printf (" with arg %s", optarg);
                  printf ("\n");
                  break;
              case '0':
              case '1':
              case '2':
                  if (digit_optind != 0 && digit_optind != this_option_optind)
                    printf ("digits occur in two different argv-elements.\n");
                 digit_optind = this_option_optind;
                  printf ("option %c\n", c);
                  break;
               if (long_options[option_index].name == "longoption1") 
               {
                       printf ("longoption1 without a short alias detected \n");
                       break;
               }
               if (long_options[option_index].name == "longoption2") 
               {
                       printf ("longoption2 detected with value '%s'\n", optarg);
                       break;
              }
              case 'a':
                  printf ("option a\n");
                  break;
              case 'b':
                  printf ("option b\n");
                  break;
              case 'c':
                  printf ("option c with value '%s'\n", optarg);
                  break;
              case 'd':
                  printf ("option d with value '%s'\n", optarg);
                  break;
              case '?':
                  break;
              default:
                  printf ("?? getopt returned character code 0%o ??\n", c);
              }
          }
          if (optind < argc) {
              printf ("non-option ARGV-elements: ");
              while (optind < argc)
                  printf ("%s ", argv[optind++]);
              printf ("\n");
          }
          exit (0);
      }

External links

• getopt manual