Queue Sender Program

/* * queue_sender.c - a program that reads messages with one of 3 identifiers * to a message queue. */
#include <stdio.h> /* standard I/O functions. */
#include <stdlib.h> /* malloc(), free() etc. */
#include <sys/types.h> /* various type definitions. */
#include <sys/ipc.h> /* general SysV IPC structures */
#include <sys/msg.h> /* message queue functions and structs. */

#define MAX_MSG_SIZE 200  /* size (in bytes) of largest message we'll send.   */
#define NUM_MESSAGES 50  /* number of messages the sender program will send. */
struct mymsgbuf{
  long int mtype;
  char mtext[128];
};
int main(int argc, char* argv[]) {
  int queue_id;                                 /* ID of the created queue. */
  struct mymsgbuf* msg;                         /* structure used for sent messages. */
/*struct msgbuf* recv_msg;*/
  int i;                                     /* loop counter */
  int rc;                                   /* error code retuend by system calls. */
/* create a public message queue, with access only to the owning user. */
  queue_id = msgget((key_t)1234, 0666 | IPC_CREAT);
  if (queue_id == -1) { perror("main: msgget"); exit(1); }
  printf("Message queue created, queue id '%d'.\n", queue_id);
  msg = (struct mymsgbuf*)malloc((sizeof(struct mymsgbuf)));
/* form a loop of creating messages and sending them. */
  for (i=1; i <= NUM_MESSAGES; i++) {
    msg->mtype = (i % 3) + 1;               /* create message type between '1' and '3' */
    sprintf(msg->mtext, "Hello - %d", i);
    rc = msgsnd(queue_id, msg, strlen(msg->mtext)+1, 0);
    if (rc == -1) { perror("main: msgsnd"); exit(1); }
  }
/* free allocated memory. */
  free(msg);
  printf("Generated %d messages, exiting.\n", NUM_MESSAGES);
  return 0;
}