#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;
}