rem: int r = stat (filename, &finfo); if (r == 0)
add: bool ok = (stat (filename, &finfo) == 0); if (ok)
context: age_of (char *filename, time_t *age){  struct stat finfo;  int r = stat (filename, &finfo);  if (r == 0)    *age = finfo.st_mtime;  return r;}