#include <unistd.h>
#include <signal.h>
#include <stdio.h>
#define __USE_GNU
#include <fcntl.h>

/* mjp@pilcrow.madison.wi.us; 15 Nov 2001 */

/* gcc -o fasync-tty fasync-tty.c */

sig_atomic_t flag_io = 0;

void sigio(int signo) {
  flag_io = 1;
}

void pdie(char *errtag) {
  perror(errtag);
  exit(1);
}

int main() {
  int fd;
  char buf[512];
  char * tty;

  if (signal(SIGIO, sigio) == SIG_ERR)
    pdie("signal");

  tty = ttyname(fileno(stdin));
  if (!tty)
    pdie("tty/stdin");

  fd = open(tty, O_ASYNC|O_RDONLY);
  if (fd == -1)
    pdie("open");

  if (fcntl(fd, F_SETOWN, getpid()) == -1)
    pdie("F_SETOWN");

  printf("%s open()d O_ASYNC, F_SETOWN'd\n", tty);

  printf("A line of input, please...\n");
  (void) fgets(buf, 512, stdin);

  printf("O_ASYNC set? %s\n",
         (fcntl(fd, F_GETFL) & O_ASYNC) ? "Yes" : "No");

  printf("O_ASYNC respected? %s\n",
         flag_io ? "Yes" : "No (bummer)");
  exit(0);
}