/*
 * private-queue-hello-world.c  - a "hello world" example in which a single
 *                                process creates a message queue and sends
 *                                itself a "hello world" message via this queue.
 */

#include <stdio.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/msg.h>
struct msgbuf {
       long mtype;     /* message type, must be > 0 */
       char mtext[1];  /* message data */
            };

int main(int argc, char* argv[])
{
    /* create a private message queue, with access only to the owner. */

    int queue_id = msgget(IPC_PRIVATE, 0600);
    struct msgbuf* msg;
    struct msgbuf* recv_msg;
    int rc;

    if (queue_id == -1) {
	perror("main: msgget");
	exit(1);
    }
    printf("IPC_PRIVATE=%d\n",IPC_PRIVATE);
    printf("message queue created, queue id '%d'.\n", queue_id);
    msg = (struct msgbuf*)malloc(sizeof(struct msgbuf)+strlen("hello world"));
    msg->mtype = 1;
    strcpy(msg->mtext, "hello world");
    rc = msgsnd(queue_id, msg, strlen(msg->mtext)+1, 0);
    if (rc == -1) {
	perror("main: msgsnd");
	exit(1);
    }
    free(msg);
    printf("message placed on the queue successfully.\n");
    recv_msg = (struct msgbuf*)malloc(sizeof(struct msgbuf)+strlen("hello world"));
    rc = msgrcv(queue_id, recv_msg, strlen("hello world")+1, 0, 0);
    if (rc == -1) {
	perror("main: msgrcv");
	exit(1);
    }

    printf("msgrcv: received message: mtype '%d'; mtext '%s'\n",
	   recv_msg->mtype, recv_msg->mtext);
    
    return 0;
}