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

static struct option const long_options[] =
{
    {"portal", required_argument, NULL, 'p'},
    {"discover", no_argument, NULL, 'D'},
    {NULL, 0, NULL, 0},
};

static char *short_options = "Dp:";

int main(int argc, char **argv)
{
    int ch, longindex;
    optopt = 0;
    while ((ch = getopt_long(argc, argv, short_options, long_options, &longindex)) >= 0) {
        switch (ch) {
        case 'D':
            printf("D\n");
            break;
        case 'p':
            printf("p\n");
        }
    }

    if (optopt)
        printf("unrecognized character '%c'\n", optopt);
}