if (res == 0) { fprintf (stderr, "Error writing\n"); perror ("read"); exit (1); }
if (res == 0) err (1, "write");
efwrite (const void *ptr, size_t size, size_t nitems, FILE *stream){     size_t res;     res = fwrite (ptr, size, nitems, stream);     if (res == 0) {	  fprintf (stderr, "Error writing\n");	  perror ("read");	  exit (1);     }     return res;}