#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>

int main (int argc, char *argv[])
{
  FILE *f;
  int fd;
  struct flock lck;

  if (argc != 3)
  {
    fprintf (stderr, "Usage: tfcntl <file> <sleeptime>\n");
    exit (1);
  }

  f = fopen (argv[1], "r+b");
  if (f == NULL)
  {
    fprintf (stderr, "tfcntl: can't open file %s\n", argv[1]);
    perror ("tfnctl");
    exit (2);
  }
  fd = fileno (f);

  memset (&lck, 0, sizeof (struct flock));
  lck.l_type = F_WRLCK;
  lck.l_whence = SEEK_SET;
  if (fcntl (fd, F_SETLK, &lck) == -1)
  {
    fprintf (stderr, "tfcntl: lock failed (errno = %d)\n", errno);
    perror ("tfnctl");
    exit (3);
  }

  sleep(atoi(argv[2]));

  memset (&lck, 0, sizeof (struct flock));
  lck.l_type = F_UNLCK;
  lck.l_whence = SEEK_SET;
  fcntl (fd, F_SETLK, &lck);

  return 0;
}