#include <stdio.h>
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <getopt.h>

#define	OPTLIST		"df:n:"

int main(int argc, char *argv[])
{
    int  opt;
    bool dflag   = false;
    char *filenm = NULL;
    int  value   = DEFAULT_VALUE;

    opterr	= 0;
    while((opt = getopt(argc, argv, OPTLIST)) != -1)   {  
//  ACCEPT A BOOLEAN ARGUMENT
	if(opt == 'd') {
            dflag  =  !dflag;
        }
//  ACCEPT A STRING ARGUMENT
	else if(opt == 'f') {
            filenm  =  strdup(optarg);
        }
//  ACCEPT A INTEGER ARGUMENT
	else if(opt == 'n') {
            value  =  atoi(optarg);
        }
//  OOPS - AN UNKNOWN ARGUMENT
        else {
            argc = -1;
        }
    }

    if(argc <= 0) {    //  display program's usage/help   
        usage(1);
    }
    argc  -= optind;
    argv  += optind;
    .....
    return 0;
}