message-queue-interchange

// prog1.c

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

#include <sys/ipc.h>
#include <sys/msg.h>
#include <sys/stat.h>

int main() {
    int msqid;
    char pathname[] = "prog1.c";
    key_t  key;
    int i, len, maxlen;

    struct mymsgbuf
    {
       long mtype;
       struct info {
          char mtext[81];
          int count;
       } a;
    } mybuf;

    /* Create or attach message queue  */

    key = ftok(pathname, 0);

    (void) umask(0000);
    if ((msqid = msgget(key, 0666 | IPC_CREAT)) < 0){
       printf("Can\'t get msqid\n");
       exit(-1);
    }

    /* Send information */

    for (i = 1; i <= 5; i++) {
       mybuf.mtype = 1;
       strcpy(mybuf.a.mtext, "Hi, second. I'm first\n");
       len = sizeof(struct info);

       if (msgsnd(msqid, (struct msgbuf*) &mybuf, len, 0) < 0) {
         printf("Can\'t send message to queue\n");
         msgctl(msqid, IPC_RMID, (struct msqid_ds *) NULL);
         exit(-1);
       }

       maxlen = len;

       if ((len = msgrcv(msqid, (struct msgbuf *) &mybuf, maxlen, 2, 0)) < 0) {
         printf("Can\'t receive message from queue\n");
         exit(-1);
       }

       printf("I am first and I found string: %s", mybuf.a.mtext);
    }

    return 0;
}



// prog2.c

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

#include <sys/ipc.h>
#include <sys/msg.h>
#include <sys/stat.h>

int main() {
    int msqid;
    char pathname[] = "prog1.c";
    key_t  key;
    int i, len, maxlen;

    struct mymsgbuf
    {
       long mtype;
       struct info {
          char mtext[81];
          int count;
       } a;
    } mybuf;

    /* Create or attach message queue  */

    key = ftok(pathname, 0);

    (void) umask(0000);
    if ((msqid = msgget(key, 0666 | IPC_CREAT)) < 0){
       printf("Can\'t get msqid\n");
       exit(-1);
    }

    /* Send information */

    for (i = 1; i <= 5; i++) {
       mybuf.mtype = 2;
       strcpy(mybuf.a.mtext, "Hi, first. I'm second\n");
       len = sizeof(struct info);

       if (msgsnd(msqid, (struct msgbuf*) &mybuf, len, 0) < 0) {
         printf("Can\'t send message to queue\n");
         msgctl(msqid, IPC_RMID, (struct msqid_ds *) NULL);
         exit(-1);
       }

       maxlen = len;

       if ((len = msgrcv(msqid, (struct msgbuf *) &mybuf, maxlen, 1, 0)) < 0) {
         printf("Can\'t receive message from queue\n");
         exit(-1);
       }

       printf("I am second and I found string: %s", mybuf.a.mtext);
    }

    return 0;
}