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

/* svmsg_ls.c

   Display a list of all System V message queues on the system.

   This program is Linux-specific.
*/
#define _GNU_SOURCE
#include <sys/types.h>
#include <sys/msg.h>
#include "tlpi_hdr.h"

int
main(int argc, char *argv[])
{
    int maxind, ind, msqid;
    struct msqid_ds ds;
    struct msginfo msginfo;

    /* Obtain size of kernel 'entries' array */

    maxind = msgctl(0, MSG_INFO, (struct msqid_ds *) &msginfo);
    if (maxind == -1)
        errExit("msgctl-MSG_INFO");

    printf("maxind: %d\n\n", maxind);
    printf("index     id       key      messages\n");

    /* Retrieve and display information from each element of 'entries' array */

    for (ind = 0; ind <= maxind; ind++) {
        msqid = msgctl(ind, MSG_STAT, &ds);
        if (msqid == -1) {
            if (errno != EINVAL && errno != EACCES)
                errMsg("msgctl-MSG_STAT");              /* Unexpected error */
            continue;                                   /* Ignore this item */
        }

        printf("%4d %8d  0x%08lx %7ld\n", ind, msqid,
                (unsigned long) ds.msg_perm.__key, (long) ds.msg_qnum);
    }

    exit(EXIT_SUCCESS);
}