Do not you hate it when you break or snag a finger nail? It's annoying and dangerous. Anyone that has cut their nose with a rough nail knows this. Do not even go near your eye - ouch! No file - no problem. I learned years ago how to take care of a rough nail without a nail file. Call me cheap or call me ingenious - I do not care. My methods work.
It is easiest if you are staying in a hotel to find an alternative to a nail file. And is not this when you need a file the most - away from home? It's hiding in that nice big bathroom that you do not have to clean. It comes in many colors and many sizes. It always works and will not only cure the rough edges but can help reshape the nail. Shower tiles, or more specifically, the grout between the tiles are nail-wonderful. All you need to do is rub your nail along the grout line and viola - smooth again. You can take the drive-by approach or attend to that snag in the shower - whatever fits your time line. Best of all - you know the shower is cleaned daily. Of course, this works in your own shower if you can not find a file.
The other no-file approach I find helpful is the underside of desks or stone counter tops. One is wood one is stone. Either will work in a pinch. Usually the tops of both are as smooth as glass. But the bottoms are a goldmine. File away. This will keep you from hurting yourself until you find a file.
Just pick clean places to file your nails. Do not try these tricks in the subway or in the airplane bathroom. You never know what will work. Remember, you do not need a nail file to file that nail.