static TailFile tailFileLinewiseFromPosition(File file, int interval, long position, IVF1<S> onData, ISleeper sleeper default defaultSleeper()) {
  if (file == null) null;
  TailFile tf = new TailFile(file, interval, vfAppendToLineBuffer(new LineBuffer(toVF1(onData))));
  tf.sleeper(sleeper);
  tf.l = position;
  tf.start();
  ret tf;
}