/*************************************************************************\
*                  Copyright (C) Michael Kerrisk, 2026.                   *
*                                                                         *
* This program is free software. You may use, modify, and redistribute it *
* under the terms of the GNU General Public License as published by the   *
* Free Software Foundation, either version 3 or (at your option) any      *
* later version. This program is distributed without any warranty.  See   *
* the file COPYING.gpl-v3 for details.                                    *
\*************************************************************************/

/* t_getopt.c

   Demonstrate the use of getopt(3) to parse command-line options.
*/
#include <ctype.h>
#include "tlpi_hdr.h"

#define printable(ch) (isprint((unsigned char) ch) ? ch : '#')

#ifdef __GNUC__
__attribute__((noreturn))       /* Prevent "this statement may fall through"
                                   warnings from "gcc -Wimplicit-fallthrough"
                                   in switch() statement in main(). */
#endif
static void             /* Print "usage" message and exit */
usageError(char *progName, char *msg, int opt)
{
    if (msg != NULL && opt != 0)
        fprintf(stderr, "%s (-%c)\n", msg, printable(opt));
    fprintf(stderr, "Usage: %s [-p arg] [-x]\n", progName);
    exit(EXIT_FAILURE);
}

int
main(int argc, char *argv[])
{
    int opt, xfnd;
    char *pstr;

    xfnd = 0;
    pstr = NULL;

    while ((opt = getopt(argc, argv, ":p:x")) != -1) {
        printf("opt =%3d (%c); optind = %d", opt, printable(opt), optind);
        if (opt == '?' || opt == ':')
            printf("; optopt =%3d (%c)", optopt, printable(optopt));
        printf("\n");

        switch (opt) {
        case 'p': pstr = optarg;        break;
        case 'x': xfnd++;               break;
        case ':': usageError(argv[0], "Missing argument", optopt);
        case '?': usageError(argv[0], "Unrecognized option", optopt);
        default:  fatal("Unexpected case in switch()");
        }
    }

    if (xfnd != 0)
        printf("-x was specified (count=%d)\n", xfnd);
    if (pstr != NULL)
        printf("-p was specified with the value \"%s\"\n", pstr);
    if (optind < argc)
        printf("First nonoption argument is \"%s\" at argv[%d]\n",
                argv[optind], optind);
    exit(EXIT_SUCCESS);
}