/*************************************************************************\
*                  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.                                    *
\*************************************************************************/

/* psem_create.c

   Create a POSIX named semaphore.

   Usage as shown in usageError().

   On Linux, named semaphores are supported with kernel 2.6 or later, and
   a glibc that provides the NPTL threading implementation.
*/
#include <semaphore.h>
#include <sys/stat.h>
#include <fcntl.h>
#include "tlpi_hdr.h"

static void
usageError(const char *progName)
{
    fprintf(stderr, "Usage: %s [-cx] name [octal-perms [value]]\n", progName);
    fprintf(stderr, "    -c   Create semaphore (O_CREAT)\n");
    fprintf(stderr, "    -x   Create exclusively (O_EXCL)\n");
    exit(EXIT_FAILURE);
}

int
main(int argc, char *argv[])
{
    int flags, opt;
    mode_t perms;
    unsigned int value;
    sem_t *sem;

    flags = 0;
    while ((opt = getopt(argc, argv, "cx")) != -1) {
        switch (opt) {
        case 'c':   flags |= O_CREAT;           break;
        case 'x':   flags |= O_EXCL;            break;
        default:    usageError(argv[0]);
        }
    }

    if (optind >= argc)
        usageError(argv[0]);

    /* Default permissions are rw-------; default semaphore initialization
       value is 0 */

    perms = (argc <= optind + 1) ? (S_IRUSR | S_IWUSR) :
                getInt(argv[optind + 1], GN_BASE_8, "octal-perms");
    value = (argc <= optind + 2) ? 0 : getInt(argv[optind + 2], 0, "value");

    sem = sem_open(argv[optind], flags, perms, value);
    if (sem == SEM_FAILED)
        errExit("sem_open");

    exit(EXIT_SUCCESS);
}