I think you're right about that. It seems a risky way to accomplish what can easily be done with a temp file. I feel that unless there is some compelling reason to take such a risk, you're far better off just creating a temporary file and renaming it when you're done. I'm not even sure what the advantage might be to using the same filename for input and output. Just seems like you're asking for trouble. In my experience, trouble always manages to find me without my having to go looking for it.