If so stop it and use a library. A library will do all the necessary checks anyways, atomically. And you need to handle API errors anyways. So checking ahead of time just would be a waste of time.
But in the end it's irrelevant. This all seems like premature optimization at best and optimizing the wrong thing at worst. You shouldn't need to open thousands of files a second to save a game and if you don't then the cost of all this checking is essentially zero.
And if you are actually bound by the speed of opening files then you should investigate ways to open fewer files (or not closing files that you know will be needed later).