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

int main (int argc, char **argv)
{
  int flag_a = 0;
  int flag_b = 0;
  char *value_c = NULL;
  int option;

  opterr = 0;

  // options:  -a, -b, -c value (defined by "abc:")
  while ((option = getopt (argc, argv, "abc:")) != -1)
    switch (option)
      {
      case 'a':      // option -a was set
        flag_a = 1;
        break;
      case 'b':      // option -b was set
        flag_b = 1;
        break;
      case 'c':      // option -c was set with value
        value_c = optarg;
        break;
     default:
        fprintf (stderr, "Usage: %s -a -b -c value\n", argv[0]);
	exit (1) ;
      }

  printf ("flag_a = %d, flag_b = %d, value_c = %s\n",
          flag_a, flag_b, value_c);

  return 0;
}