!7

import java.nio.channels.*;
import java.nio.file.*;
import java.nio.*;

p {
  File path = programFile("lockfile");
  FileChannel channel = FileChannel.open(toPath(path), StandardOpenOption.CREATE, StandardOpenOption.WRITE);
  repeat with sleep 1 {
    {
      temp FileLock lock = channel.tryLock();
      if (lock == null) print("Couldn't lock.");
      else {
        print("Locked!");
        //appendToFile(path, "test\n");
        long size = channel.size();
        print("Size=" + size);
        channel.position(size);
        channel.write(ByteBuffer.wrap(toUtf8("test\n")));
        print("New size=" + channel.size());
        sleepSeconds(1);
      }
    }
  }
}

Began life as a copy of #1016917