FSentry is an Elixir module for spawning FS sentries. It is implemented as a port driver that streams FS event messages to a designated PID.
Based on Inotify. macOS and BSD users should install libinotify-kqueue, Windows users are currently out of luck (although it would be nice to have a Win32 Inotify implementation).
Unlike synrc/fs, FSentry doesn't spawn external processes and doesn't have any runtime dependencies. It also can listen on individual files rather than just folders.