epoll.c

int main(){

  /**
   * Create the epoll() 
   *
   * From man pages
   * Since Linux 2.6.8, the
   * size argument is ignored, 
   * but must be greater than zero;
   */
  int epoll_fd = epoll_create(1);

  /* Double-array of fds for the pipe() */
  int **fds = malloc(2 * sizeof(int *));

  /* Each process needs its own epoll struct */
  struct epoll_event event[2];

  /* Create two processs */
  int i;
  for (i = 0; i < 2; i++){

    /* Create a pipe */
    fds[i] = malloc(2 * sizeof(int));
    pipe(fds[i]);

    int read_fd = fds[i][0];
    int write_fd = fds[i][1];

    /* Generates a new process */
    pid_t pid = fork();

    /* child */
    if (pid == 0){

      close(read_fd);

      if (i == 0) { child_one_func(write_fd); }
      else if (i == 1) { child_two_func(write_fd); }

      /* Closes child */
      exit(0);

    }else{
      close(write_fd);
    }

    /* Setup the epoll_event for this process */
    event[i].events = EPOLLIN;

    /* Parent process listening to read file descriptor */
    event[i].data.fd = read_fd;

    /* Add read_fd to event[i] or (Read) event on epoll_fds -- event[i] */
    epoll_ctl( epoll_fd, EPOLL_CTL_ADD, read_fd, &event[i]);
  }

  /**
   * Read data via epoll_wait() 
   * It prints out the data as it comes in.
   */
  while(1){

    struct epoll_event ev;
    epoll_wait(epoll_fd, &ev, 1, -1);

    char str[10];
    ssize_t bytes = read(ev.data.fd, &str, 10);

    /* If the ev.data.fd has bytes added print, else wait */
    if(bytes > 0)
      printf("Read: %s\n", str);
    else
      epoll_ctl(epoll_fd, EPOLL_CTL_DEL, ev.data.fd, NULL);
    if(strcmp(str, "D - 4") == 0)
      return 0;
  }