Opt parsing in C

compile.sh

#!/bin/sh

gcc optparse_example.c -o optparse_example
gcc optparse_long_example.c -o optparse_long_example

optparse_example.c

//http://www.gnu.org/savannah-checkouts/gnu/libc/manual/html_node/Example-of-Getopt.html#Example-of-Getopt
#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int main (int argc, char **argv) {
 int   aflag  = 0;
 int   bflag  = 0;
 char *cvalue = NULL;
 int   index;
 int   c;

       opterr = 0;

 while ((c = getopt (argc, argv, "abc:")) != -1)
   switch (c) {
     case 'a':
       aflag = 1;
       break;
     case 'b':
       bflag = 1;
       break;
     case 'c':
       cvalue = optarg;
       break;
     case '?':
       if (optopt == 'c')
         fprintf (stderr, "Option -%c requires an argument.\n", optopt);
       else if (isprint (optopt))
         fprintf (stderr, "Unknown option `-%c'.\n", optopt);
       else
         fprintf (stderr, "Unknown option character `\\x%x'.\n", optopt);
       return 1;
     default:
       abort ();
   }

printf ("aflag = %d, bflag = %d, cvalue = %s\n",
         aflag, bflag, cvalue);

  for (index = optind; index < argc; index++) {
    printf ("Non-option argument %s\n", argv[index]);
  }
  return 0;
}

optparse_long_example.c

//http://www.gnu.org/savannah-checkouts/gnu/libc/manual/html_node/Getopt-Long-Option-Example.html#Getopt-Long-Option-Example

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

/* Flag set by ‘--verbose’. */
static int verbose_flag;

int main (int argc, char **argv) {
  int c;

  while (1){
    static struct option long_options[] = {
      /* These options set a flag. */
      {"verbose", no_argument,       &verbose_flag, 1},
      {"brief",   no_argument,       &verbose_flag, 0},
      /* These options don't set a flag.
         We distinguish them by their indices. */
      {"add",     no_argument,       0, 'a'},
      {"append",  no_argument,       0, 'b'},
      {"delete",  required_argument, 0, 'd'},
      {"create",  required_argument, 0, 'c'},
      {"file",    required_argument, 0, 'f'},
      {0, 0, 0, 0}
    };
    /* getopt_long stores the option index here. */
    int option_index = 0;

    c = getopt_long (argc, argv, "abc:d:f:",
        long_options, &option_index);

    /* Detect the end of the options. */
    if (c == -1)
      break;

    switch (c) {
      case 0:
        /* If this option set a flag, do nothing else now. */
        if (long_options[option_index].flag != 0)
          break;
        printf ("option %s", long_options[option_index].name);
        if (optarg) {
          printf (" with arg %s", optarg);
        }
        printf ("\n");
        break;

      case 'a':
        puts ("option -a\n");
        break;

      case 'b':
        puts ("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 'f':
        printf ("option -f with value `%s'\n", optarg);
        break;

      case '?':
        /* getopt_long already printed an error message. */
        break;

      default:
        abort ();
    }
  }

  /* Instead of reporting ‘--verbose’
     and ‘--brief’ as they are encountered,
     we report the final status resulting from them. */
  if (verbose_flag)
    puts ("verbose flag is set");

  /* Print any remaining command line arguments (not options). */
  if (optind < argc) {
    printf ("non-option ARGV-elements: ");
    while (optind < argc)
      printf ("%s ", argv[optind++]);
    putchar ('\n');
  }

  exit (0);
}