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

void die(char *s)
{
  fprintf(stderr,"fatal: %s: %s\n",s,strerror(errno));
  exit(111);
}

int main(void)
{
  FILE *f;

  f = fopen("alreadyran.dat","r");
  if (f) { printf("Hello again\n"); exit(0); }

  if (errno != ENOENT) die("unable to read alreadyran.dat");

  printf("Hello\n");
  f = fopen("alreadyran.dat","w");
  if (!f) die("unable to write alreadyran.dat");

  exit(0);
}