Correct or decent getopts_long usage?

Question

What it the correct usage if I want this behaviour:

$ ./a.out --help for printing help information

$ ./a.out --version for printing the program version

I managed to code this so that it takes the arguments but I don't know a good / correct way to separate the messages since they are the same case.

static struct option long_options[] = {
        {"help",  no_argument,       0,  0 },
        {"version", no_argument,       0,  0 },
        {0,         0,                 0,  0 }
};


int main(int argc, char *argv[]) {


    while (1) {
        int this_option_optind = optind ? optind : 1;
        int option_index = 0;


        c = getopt_long(argc, argv, "",
                        long_options, &option_index);
        if (c == -1)
            break;

        switch (c) {
            case 0:
                printf("option %s", long_options[option_index].name);
                if (optarg)
                    printf(" with arg %s", optarg);
                printf("\n");
                return 0;

            case '0':
            case '1':
            case '2':
                if (digit_optind != 0 && digit_optind != this_option_optind)
                    printf("digits occur in two different argv-elements.\n");
                digit_optind = this_option_optind;
                printf("option 2 2 %c\n", c);
                return 0;

            case 'a':
                printf("option a\n");
                break;

            case 'b':
                printf("option b\n");
                break;

            case 'c':
                printf("option c with value '%s'\n", optarg);
                break;

            case 'd':
                printf("option d with value '%s'\n", optarg);
                break;

            case '?':
                break;

            default:
                printf("?? getopt returned character code 0%o ??\n", c);
        }
    }

    if (optind < argc) {
        printf("non-option ARGV-elements: ");
        while (optind < argc)
            printf("%s ", argv[optind++]);
        printf("\n");
    }

...

Answer 1

Here you have an example:

while (1)
{
    int option_index = 0;
    static struct option long_options[] = {
        {"with_param", required_argument, 0, 'p'},
        {"version", no_argument, 0, 'v'},
        {"help", no_argument, 0, 'h'},
        {0, 0, 0, 0}
    };

    option = getopt_long(argc, argv, "p:vh",
                         long_options, &option_index);
    if (option == -1)
        break;

    switch (option) {
    case 'p':
    {
        store_parameter(optarg);
        break;
    }
    case 'v':
    {
        print_version();
        break;
    }
    case 'h':
    {
        print_help();
        exit(EXIT_SUCCESS);
        break;
    }
    default:
    {
        fprintf(stderr, "Error (%s): unrecognized option.\n", __FUNCTION__);
        print_help();
        exit(EXIT_FAILURE);
        break;
    }
    } /* end switch */
}

Notice the string "p:vh" as parameter of getopt_long, which allows you to also use short options. (":" follows options with a required argument)