Check file is in Use

[tbscope]

Not in Qt.
Search the forum, this question has been asked before. There are a couple of techniques you can try like getting an exclusive lock on the file. If it works, you're the only one using it. If the exclusive lock fails, someone else already opened the file. But thats just a guess as I never tried this. And it might not work on all operating systems.

[wysota]

It will certainly not work on all operating systems. In Unix environment you need superuser privileges to know if a file is opened by some other process.