filenotify

Filenotify is a generic term for software that monitors changes to files or directories and emits notifications to an application. It enables reactive behavior such as automatic reloading, synchronization, or auditing when content changes.

Most systems rely on platform-specific facilities: Linux uses inotify (and the newer fanotify for certain operations), macOS uses FSEvents, and Windows uses ReadDirectoryChangesW (often via the USN Journal). Cross-platform libraries wrap these APIs to provide a consistent interface and, in many cases, a higher-level event stream.

Key features include watching a single path or multiple paths, recursive watching of directories, and events such as create, modify, delete, and rename. Some implementations distinguish between pre- and post-events, while others group events into batches. Common techniques include debouncing and optional polling fallback when native facilities are unavailable.

Limitations and caveats include platform differences in event semantics, the possibility of missed events during heavy I/O, resource limits, and race conditions. Security considerations include appropriate permission checks and careful handling of symlinks and mounted volumes.

Uses include development workflows such as live-reload, file synchronization, and log monitoring. Notable libraries and tools include chokidar (JavaScript), watchdog (Python), and fsnotify (Go), all of which implement filenotify concepts to various degrees.