#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <mqueue.h>
#include <errno.h>
#include <fcntl.h>

int main() {
    struct mq_attr attrs;
    attrs.mq_maxmsg = 10;
    attrs.mq_msgsize = sizeof(int);

    const char name[] = "/test-queue";

    mqd_t q = mq_open(name, O_CREAT | O_RDWR, 0600, &attrs);
    if (q == (mqd_t)-1) {
        perror("mq_open");
        exit(EXIT_FAILURE);
    }

    if (fork()) {
        int msg = 666;
        if (mq_send(q, (const char *)&msg, sizeof(msg), 1)) {
            perror("mq_send");
            exit(EXIT_FAILURE);
        }
    } else {
        int msg;
        unsigned priority;
        if (mq_receive(q, (char *)&msg, sizeof(msg), &priority) == -1) {
            perror("mq_receive");
            exit(EXIT_FAILURE);
        }
        printf("%d\n", msg);
    }

    mq_unlink(name);
    mq_close(q);

    return 0;
}