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

#define MSGQ_KEY 0x1234
#define PERM 0660

struct mymsg {
  long mtype;
  char mtext[1];
};

int
main()
{
  int msg_id; /* message Queue id. */
  struct mymsg msg; /* message to send. */
  int nmsg; /* number of msg send. */
  int status; /* status returned by msgsnd(). */

  /*
   * Create Message Queue
   */
  if ( (msg_id = msgget (MSGQ_KEY, PERM | IPC_CREAT)) == -1 ) {
    perror ("msgget: ");
    exit (EXIT_FAILURE);
  }
  /*
   * now write message one by one until Queue is full
   */
  msg.mtype = 1;
  msg.mtext[0] = 'A';
  nmsg = 0;
  do {
    status = msgsnd (msg_id, &msg, sizeof(msg.mtext), IPC_NOWAIT);
    nmsg++;
    printf ("Sent msg #%d\r", nmsg);
  }
  while ( status == 0 );
  
  if (errno != EAGAIN ) { /* eh? we didn't overflow? */
    perror ("msgsnd: ");
    exit (EXIT_FAILURE);
  }
  
  printf ("Queue full, sent %d messages\n", nmsg-1);
  exit (EXIT_SUCCESS);
}