c++ och användning av argp.

#include <argp.h>
#include <stdlib.h>
#include <stdio.h>

struct app_state {
    int   is_kalle_set;
    char *pelle_arg;
};

error_t
parse_opts(int key, char *arg, struct argp_state *state)
{
    struct app_state *app_s = state->input;
    switch (key)
    {
    case 'k':
        app_s->is_kalle_set = 1;
        break;
    case 'p':
        app_s->pelle_arg = arg;
	break;
    }
    return 0;
}

int main(int argc, char *argv[])
{
    struct argp_option opts[] = {
	{ "kalle", 'k', NULL,     0,    "The kalle option", 0 },
	{ "pelle", 'p', "pelle_arg", 0, "The pelle option, requires argument", 0 },
        { NULL, 0, NULL, 0, NULL, 0 }
    };
    struct argp a = {
	.options     = opts,
	.parser      = parse_opts,
	.args_doc    = "Text printed at the end of 'Usage' line",
        .doc         = "Text printed after 'Usage' but before first option",
	.children    = NULL,
	.help_filter = NULL,
	.argp_domain = NULL
    };
    struct app_state state = {
	.is_kalle_set = 0,
	.pelle_arg    = NULL
    };

    argp_parse(&a, argc, argv, 0, 0, &state);
    printf("kalle: %d\n", state.is_kalle_set);
    printf("pelle arg: %s\n", state.pelle_arg);
}

$ ./argp -?
Usage: argp [OPTION...] Text printed at the end of 'Usage' line
Text printed after 'Usage' but before first option

  -k, --kalle                The kalle option
  -p, --pelle=pelle_arg      The pelle option, requires argument
  -?, --help                 Give this help list
      --usage                Give a short usage message

Mandatory or optional arguments to long options are also mandatory or optional
for any corresponding short options.