rem: return err;
add: return ok;
context: read_char (int *c){  int err = 0;  *c = EOF;  while (in_stream != NULL)	/* EOF.  */    {      *c = fgetc (in_stream);      if (*c != EOF)	break;      err |= check_and_close ();      err |= open_next_file ();    }  return err;}