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Chokidar Weekly downloads

Minimal and efficient cross-platform file watching library

Why?

There are many reasons to prefer Chokidar to raw fs.watch / fs.watchFile in 2024:

Chokidar relies on the Node.js core fs module, but when using fs.watch and fs.watchFile for watching, it normalizes the events it receives, often checking for truth by getting file stats and/or dir contents. The fs.watch-based implementation is the default, which avoids polling and keeps CPU usage down. Be advised that chokidar will initiate watchers recursively for everything within scope of the paths that have been specified, so be judicious about not wasting system resources by watching much more than needed. For some cases, fs.watchFile, which utilizes polling and uses more resources, is used.

Made for Brunch in 2012, it is now used in ~30 million repositories and has proven itself in production environments.

Sep 2024 update: v4 is out! It decreases dependency count from 13 to 1, removes support for globs, adds support for ESM / Common.js modules, and bumps minimum node.js version from v8 to v14. Check out upgrading.

Getting started

Install with npm:

npm install chokidar

Use it in your code:

import chokidar from 'chokidar';

// One-liner for current directory
chokidar.watch('.').on('all', (event, path) => {
  console.log(event, path);
});


// Extended options
// ----------------

// Initialize watcher.
const watcher = chokidar.watch('file, dir, or array', {
  ignored: (path, stats) => stats?.isFile() && !path.endsWith('.js'), // only watch js files
  persistent: true
});

// Something to use when events are received.
const log = console.log.bind(console);
// Add event listeners.
watcher
  .on('add', path => log(`File ${path} has been added`))
  .on('change', path => log(`File ${path} has been changed`))
  .on('unlink', path => log(`File ${path} has been removed`));

// More possible events.
watcher
  .on('addDir', path => log(`Directory ${path} has been added`))
  .on('unlinkDir', path => log(`Directory ${path} has been removed`))
  .on('error', error => log(`Watcher error: ${error}`))
  .on('ready', () => log('Initial scan complete. Ready for changes'))
  .on('raw', (event, path, details) => { // internal
    log('Raw event info:', event, path, details);
  });

// 'add', 'addDir' and 'change' events also receive stat() results as second
// argument when available: https://nodejs.org/api/fs.html#fs_class_fs_stats
watcher.on('change', (path, stats) => {
  if (stats) console.log(`File ${path} changed size to ${stats.size}`);
});

// Watch new files.
watcher.add('new-file');
watcher.add(['new-file-2', 'new-file-3']);

// Get list of actual paths being watched on the filesystem
let watchedPaths = watcher.getWatched();

// Un-watch some files.
await watcher.unwatch('new-file');

// Stop watching. The method is async!
await watcher.close().then(() => console.log('closed'));

// Full list of options. See below for descriptions.
// Do not use this example!
chokidar.watch('file', {
  persistent: true,

  // ignore .txt files
  ignored: (file) => file.endsWith('.txt'),
  // watch only .txt files
  // ignored: (file, _stats) => _stats?.isFile() && !file.endsWith('.txt'),

  awaitWriteFinish: true, // emit single event when chunked writes are completed
  atomic: true, // emit proper events when "atomic writes" (mv _tmp file) are used

  // The options also allow specifying custom intervals in ms
  // awaitWriteFinish: {
  //   stabilityThreshold: 2000,
  //   pollInterval: 100
  // },
  // atomic: 100,

  interval: 100,
  binaryInterval: 300,

  cwd: '.',
  depth: 99,

  followSymlinks: true,
  ignoreInitial: false,
  ignorePermissionErrors: false,
  usePolling: false,
  alwaysStat: false,
});

chokidar.watch(paths, [options])

Persistence

Path filtering

Performance

Errors

Methods & Events

chokidar.watch() produces an instance of FSWatcher. Methods of FSWatcher:

CLI

Check out third party chokidar-cli, which allows to execute a command on each change, or get a stdio stream of change events.

Troubleshooting

Sometimes, Chokidar runs out of file handles, causing EMFILE and ENOSP errors:

There are two things that can cause it.

  1. Exhausted file handles for generic fs operations
    • Can be solved by using graceful-fs, which can monkey-patch native fs module used by chokidar: let fs = require('fs'); let grfs = require('graceful-fs'); grfs.gracefulify(fs);
    • Can also be solved by tuning OS: echo fs.inotify.max_user_watches=524288 | sudo tee -a /etc/sysctl.conf && sudo sysctl -p.
  2. Exhausted file handles for fs.watch
    • Can't seem to be solved by graceful-fs or OS tuning
    • It's possible to start using usePolling: true, which will switch backend to resource-intensive fs.watchFile

All fsevents-related issues (WARN optional dep failed, fsevents is not a constructor) are solved by upgrading to v4+.

Changelog

Upgrading

If you've used globs before and want do replicate the functionality with v4:

// v3
chok.watch('**/*.js');
chok.watch("./directory/**/*");

// v4
chok.watch('.', {
  ignored: (path, stats) => stats?.isFile() && !path.endsWith('.js'), // only watch js files
});
chok.watch('./directory');

// other way
import { glob } from 'node:fs/promises';
const watcher = watch(await Array.fromAsync(glob('**/*.js')));

// unwatching
// v3
chok.unwatch('**/*.js');
// v4
chok.unwatch(await glob('**/*.js'));

Also

Why was chokidar named this way? What's the meaning behind it?

Chowkidar is a transliteration of a Hindi word meaning 'watchman, gatekeeper', चौकीदार. This ultimately comes from Sanskrit _ चतुष्क_ (crossway, quadrangle, consisting-of-four). This word is also used in other languages like Urdu as (چوکیدار) which is widely used in Pakistan and India.

License

MIT (c) Paul Miller (https://paulmillr.com), see LICENSE file.