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

char *optarg = NULL;    // global argument pointer
int   optind = 0;     // global argv index

int getopt(int argc, char *argv[], char *optstring) {
    static char *next = NULL;
    char c;
    char *cp = NULL;
    
    if (optind == 0)
        next = NULL;

    optarg = NULL;

    if (next == NULL || *next == '\0') {
        if (optind == 0)
            optind++;

        if (optind >= argc || argv[optind][0] != '-' || argv[optind][1] == '\0') {
            optarg = NULL;
            if (optind < argc)
                optarg = argv[optind];
            return EOF;
        }

        if (strncmp(argv[optind], "--", 2) == 0) {
            optind++;
            optarg = NULL;
            if (optind < argc)
                optarg = argv[optind];
            return EOF;
        }

        next = argv[optind];
        next++;        // skip past -
        optind++;
    }

    c = *next++;
    cp = strchr(optstring, c);

    if (cp == NULL || c == ':')
        return '?';

    cp++;
    if (*cp == ':') {
        if (*next != '\0') {
            optarg = next;
            next = NULL;
        }
        else if (optind < argc) {
            optarg = argv[optind];
            optind++;
        }
        else {
            return '?';
        }
    }
    return c;
}