/* touch queue; gcc -Wall -Wextra -pedantic -std=c99 -o a a.c && a */
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/msg.h>
#include <sys/wait.h>
#include <unistd.h>

typedef struct Mymsg {
    long mtype;     /* Message type */
    char mtext[20]; /* Message body */
} Mymsg;


int main() {
    key_t key = ftok("queue", 'x');
    int id = msgget(key, IPC_CREAT);
    if (id == -1) {
        printf("msgget error");
        exit(EXIT_FAILURE);
    }

    pid_t child_pid = fork();
    if (child_pid == -1) {
        perror("fork");
        exit(EXIT_FAILURE);
    }

    if (child_pid == 0) {
        printf("CHILD PROCESS\n");

        Mymsg message;
        message.mtype = 1;
        strcpy(message.mtext, "test");
        if (msgsnd(id, &message, sizeof(message)-sizeof(long), 0) == -1) {
            perror("msgsnd");
            exit(EXIT_FAILURE);
        }

        exit(EXIT_SUCCESS);
    }
    else
    {
        int status;
        if (waitpid(child_pid, &status, 0) == -1) {
            perror("waitpid");
            exit(EXIT_FAILURE);
        }
        if (WIFSIGNALED(status)) {
            fprintf(stderr, "Child killed by signal %d\n", WTERMSIG(status));
            exit(EXIT_FAILURE);
        }
        if (!WEXITSTATUS(status)) {
            fprintf(stderr, "Child exited with error %d\n", WEXITSTATUS(status));
            exit(EXIT_FAILURE);
        }

        printf("PARENT PROCESS\n");

        Mymsg message;
        if (msgrcv(id, &message, sizeof(message)-sizeof(long), 1, 0) == -1) {
            perror("msgrcv");
            exit(EXIT_FAILURE);
        }

        printf("READ: %s\n", message.mtext);

        if (msgctl(id, IPC_RMID, 0) == -1) {
            perror("msgctl");
            exit(EXIT_FAILURE);
        }

        exit(EXIT_SUCCESS);
    }
}