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Native access to MacOS FSEvents in Node.js
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Native access to MacOS FSEvents in Node.js

The FSEvents API in MacOS allows applications to register for notifications of changes to a given directory tree. It is a very fast and lightweight alternative to kqueue.

This is a low-level library. For a cross-platform file watching module that uses fsevents, check out Chokidar.


npm install fsevents


const fsevents = require('fsevents');
const stop =, (path, flags, id) => {
  const info = fsevents.getInfo(path, flags, id);
}); // To start observation
stop(); // To end observation

The callback passed as the second parameter to .watch get's called whenever the operating system detects a a change in the file system. It takes three arguments:

(path: String, flags: Number, id: String) => {}

  • path - the item in the filesystem that have been changed
  • flags - a numeric value describing what the change was
  • id - an unique-id identifying this specific event
fsevents.getInfo(path, flags, id): FsEventInfo => {}

The getInfo function takes the path, flags and id arguments and converts those parameters into a structure that is easier to digest to determine what the change was.

The FsEventsInfo has the following shape:

 * @typedef {'created'|'modified'|'deleted'|'moved'|'root-changed'|'unknown'} FsEventsEvent
 * @typedef {'file'|'directory'|'symlink'} FsEventsType
  "event": "created",
  "path": "file.txt", // {FsEventsEvent}
  "type": "file",    // {FsEventsType}
  "changes": {
    "inode": true,   // Had iNode Meta-Information changed
    "finder": false, // Had Finder Meta-Data changed
    "access": false, // Had access permissions changed
    "xattrs": false  // Had xAttributes changed
  "flags": 0x100000000


The MIT License Copyright (C) 2010-2018 by Philipp Dunkel, Ben Noordhuis, Elan Shankar — see LICENSE file.

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