Not technically related to atomicity, but I was looking for a way to do arbitrary filesystem operations based on some condition (like adding a file to a directory, and having some operation be performed on it). The usual recommendation for this is to use inotify/watchman, but something about it seems clunky to me. I want to write a virtual filesystem, where you pass it a trigger condition and a function, and it applies the function to all files based on the trigger condition. Does something like this exist?