#include <stdio.h>#include <unistd.h>int main(int argc, char *argv[]){    int opt;    while((opt = getopt(argc, argv, "if:lr")) != -1) {        switch(opt) {        case 'i':        case 'l':        case 'r':            printf("option: %c\n", opt);            break;        case 'f':            printf("filename: %s\n", optarg);            break;        case ':':            printf("option needs a value\n");            break;        case '?':            printf("unknown option: %c\n", optopt);            break;        }    }    for(; optind < argc; optind++)        printf("argument: %s\n", argv[optind]);    exit(0);}