#include <stdio.h>
#include <sys/fcntl.h>

#define filename "flock.txt"

int main(int argc, char *argv[])
{
  FILE *fp;
  char s[100];
  int c;

  fp = fopen(filename, "r+");
  printf("%d", flock(fileno(fp), LOCK_EX));
  fgets(s, 100, fp);
  c = atoi(s);
  if ((argc > 1) && (! strcmp(argv[1], "-sleep")))
  {
    //printf("%s", argv[1]);
    sleep(5);
  }
  c++;
  rewind(fp);
  fprintf(fp, "%d", c);
  fflush(fp);
  flock(fp, LOCK_UN);
  fclose(fp);
  return 0;
}