How to synchronize file I/O of many independent applications on Linux?

I'm writing a software for Linux which would actively work with user's files in background concurrently with other applications that I don't control. I want to make my background application to not overwrite changes made by other applications. But there is a problem - unlike Windows Linux doesn't provide mandatory file locking capability which creates possibility of ruining user's work due to race conditions which I'd like to avoid. I'm writing a software for Linux which would ac