static Lock appendToFile_lock = lock();

static void appendToFile(S path, S s) ctex {
  lock appendToFile_lock; // Let's just generally synchronize this to be safe.
  new File(path).getParentFile().mkdirs();
  //print("[Logging to " + path + "]");
  Writer writer = new BufferedWriter(new OutputStreamWriter(
    newFileOutputStream(path, true), "UTF-8"));
  writer.write(s);
  writer.close();
}
  
static void appendToFile(File path, String s) {
  if (path != null)
    appendToFile(path.getPath(), s);
}