getopt.c


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

/* getopt() external variables */
extern char *optarg;
extern int optind, opterr, optopt;

int main(int argc, char **argv)
{
    int opt;
    int fname_f = 0, random_f = 0; /* options' flags */
    char *fname_a = NULL;

    while ((opt = getopt(argc, argv, "o::c")) != -1)
    {
        switch (opt)
        {
        case 'o':
            fname_f = 1;
#if 0       /* optional args to an option can only be of this format: -ofile.txt */
            if (optarg)
                fname_a = strdup(optarg);
#endif      /* we will check optind in the end and that should be the filename */
            break;
        case 'c':
            random_f = 1;
            break;
        default: /* '?' */
            fprintf(stderr, "usage: %s [-o fname] [-c]\n", argv[0]);
            exit(EXIT_FAILURE);
        }
    }

    if (argv[optind])
        fname_a = strdup(argv[optind]);

    printf("fname_f = %d\nfname_a = %s\nrandom_f = %d\noptind = %d\n", fname_f,
           fname_a, random_f, optind);

    printf("optind = %s\n", argv[optind]);

    return 0;
}