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1# Chokidar [![Weekly downloads](https://img.shields.io/npm/dw/chokidar.svg)](https://github.com/paulmillr/chokidar) [![Yearly downloads](https://img.shields.io/npm/dy/chokidar.svg)](https://github.com/paulmillr/chokidar)
2
3> Minimal and efficient cross-platform file watching library
4
5[![NPM](https://nodei.co/npm/chokidar.png)](https://www.npmjs.com/package/chokidar)
6
7## Why?
8
9Node.js `fs.watch`:
10
11* Doesn't report filenames on MacOS.
12* Doesn't report events at all when using editors like Sublime on MacOS.
13* Often reports events twice.
14* Emits most changes as `rename`.
15* Does not provide an easy way to recursively watch file trees.
16* Does not support recursive watching on Linux.
17
18Node.js `fs.watchFile`:
19
20* Almost as bad at event handling.
21* Also does not provide any recursive watching.
22* Results in high CPU utilization.
23
24Chokidar resolves these problems.
25
26Initially made for **[Brunch](https://brunch.io/)** (an ultra-swift web app build tool), it is now used in
27[Microsoft's Visual Studio Code](https://github.com/microsoft/vscode),
28[gulp](https://github.com/gulpjs/gulp/),
29[karma](https://karma-runner.github.io/),
30[PM2](https://github.com/Unitech/PM2),
31[browserify](http://browserify.org/),
32[webpack](https://webpack.github.io/),
33[BrowserSync](https://www.browsersync.io/),
34and [many others](https://www.npmjs.com/browse/depended/chokidar).
35It has proven itself in production environments.
36
37Version 3 is out! Check out our blog post about it: [Chokidar 3: How to save 32TB of traffic every week](https://paulmillr.com/posts/chokidar-3-save-32tb-of-traffic/)
38
39## How?
40
41Chokidar does still rely on the Node.js core `fs` module, but when using
42`fs.watch` and `fs.watchFile` for watching, it normalizes the events it
43receives, often checking for truth by getting file stats and/or dir contents.
44
45On MacOS, chokidar by default uses a native extension exposing the Darwin
46`FSEvents` API. This provides very efficient recursive watching compared with
47implementations like `kqueue` available on most \*nix platforms. Chokidar still
48does have to do some work to normalize the events received that way as well.
49
50On most other platforms, the `fs.watch`-based implementation is the default, which
51avoids polling and keeps CPU usage down. Be advised that chokidar will initiate
52watchers recursively for everything within scope of the paths that have been
53specified, so be judicious about not wasting system resources by watching much
54more than needed.
55
56## Getting started
57
58Install with npm:
59
60```sh
61npm install chokidar
62```
63
64Then `require` and use it in your code:
65
66```javascript
67const chokidar = require('chokidar');
68
69// One-liner for current directory
70chokidar.watch('.').on('all', (event, path) => {
71 console.log(event, path);
72});
73```
74
75## API
76
77```javascript
78// Example of a more typical implementation structure
79
80// Initialize watcher.
81const watcher = chokidar.watch('file, dir, glob, or array', {
82 ignored: /(^|[\/\\])\../, // ignore dotfiles
83 persistent: true
84});
85
86// Something to use when events are received.
87const log = console.log.bind(console);
88// Add event listeners.
89watcher
90 .on('add', path => log(`File ${path} has been added`))
91 .on('change', path => log(`File ${path} has been changed`))
92 .on('unlink', path => log(`File ${path} has been removed`));
93
94// More possible events.
95watcher
96 .on('addDir', path => log(`Directory ${path} has been added`))
97 .on('unlinkDir', path => log(`Directory ${path} has been removed`))
98 .on('error', error => log(`Watcher error: ${error}`))
99 .on('ready', () => log('Initial scan complete. Ready for changes'))
100 .on('raw', (event, path, details) => { // internal
101 log('Raw event info:', event, path, details);
102 });
103
104// 'add', 'addDir' and 'change' events also receive stat() results as second
105// argument when available: https://nodejs.org/api/fs.html#fs_class_fs_stats
106watcher.on('change', (path, stats) => {
107 if (stats) console.log(`File ${path} changed size to ${stats.size}`);
108});
109
110// Watch new files.
111watcher.add('new-file');
112watcher.add(['new-file-2', 'new-file-3', '**/other-file*']);
113
114// Get list of actual paths being watched on the filesystem
115var watchedPaths = watcher.getWatched();
116
117// Un-watch some files.
118await watcher.unwatch('new-file*');
119
120// Stop watching.
121// The method is async!
122watcher.close().then(() => console.log('closed'));
123
124// Full list of options. See below for descriptions.
125// Do not use this example!
126chokidar.watch('file', {
127 persistent: true,
128
129 ignored: '*.txt',
130 ignoreInitial: false,
131 followSymlinks: true,
132 cwd: '.',
133 disableGlobbing: false,
134
135 usePolling: false,
136 interval: 100,
137 binaryInterval: 300,
138 alwaysStat: false,
139 depth: 99,
140 awaitWriteFinish: {
141 stabilityThreshold: 2000,
142 pollInterval: 100
143 },
144
145 ignorePermissionErrors: false,
146 atomic: true // or a custom 'atomicity delay', in milliseconds (default 100)
147});
148
149```
150
151`chokidar.watch(paths, [options])`
152
153* `paths` (string or array of strings). Paths to files, dirs to be watched
154recursively, or glob patterns.
155 - Note: globs must not contain windows separators (`\`),
156 because that's how they work by the standard —
157 you'll need to replace them with forward slashes (`/`).
158 - Note 2: for additional glob documentation, check out low-level
159 library: [picomatch](https://github.com/micromatch/picomatch).
160* `options` (object) Options object as defined below:
161
162#### Persistence
163
164* `persistent` (default: `true`). Indicates whether the process
165should continue to run as long as files are being watched. If set to
166`false` when using `fsevents` to watch, no more events will be emitted
167after `ready`, even if the process continues to run.
168
169#### Path filtering
170
171* `ignored` ([anymatch](https://github.com/es128/anymatch)-compatible definition)
172Defines files/paths to be ignored. The whole relative or absolute path is
173tested, not just filename. If a function with two arguments is provided, it
174gets called twice per path - once with a single argument (the path), second
175time with two arguments (the path and the
176[`fs.Stats`](https://nodejs.org/api/fs.html#fs_class_fs_stats)
177object of that path).
178* `ignoreInitial` (default: `false`). If set to `false` then `add`/`addDir` events are also emitted for matching paths while
179instantiating the watching as chokidar discovers these file paths (before the `ready` event).
180* `followSymlinks` (default: `true`). When `false`, only the
181symlinks themselves will be watched for changes instead of following
182the link references and bubbling events through the link's path.
183* `cwd` (no default). The base directory from which watch `paths` are to be
184derived. Paths emitted with events will be relative to this.
185* `disableGlobbing` (default: `false`). If set to `true` then the strings passed to `.watch()` and `.add()` are treated as
186literal path names, even if they look like globs.
187
188#### Performance
189
190* `usePolling` (default: `false`).
191Whether to use fs.watchFile (backed by polling), or fs.watch. If polling
192leads to high CPU utilization, consider setting this to `false`. It is
193typically necessary to **set this to `true` to successfully watch files over
194a network**, and it may be necessary to successfully watch files in other
195non-standard situations. Setting to `true` explicitly on MacOS overrides the
196`useFsEvents` default. You may also set the CHOKIDAR_USEPOLLING env variable
197to true (1) or false (0) in order to override this option.
198* _Polling-specific settings_ (effective when `usePolling: true`)
199 * `interval` (default: `100`). Interval of file system polling, in milliseconds. You may also
200 set the CHOKIDAR_INTERVAL env variable to override this option.
201 * `binaryInterval` (default: `300`). Interval of file system
202 polling for binary files.
203 ([see list of binary extensions](https://github.com/sindresorhus/binary-extensions/blob/master/binary-extensions.json))
204* `useFsEvents` (default: `true` on MacOS). Whether to use the
205`fsevents` watching interface if available. When set to `true` explicitly
206and `fsevents` is available this supercedes the `usePolling` setting. When
207set to `false` on MacOS, `usePolling: true` becomes the default.
208* `alwaysStat` (default: `false`). If relying upon the
209[`fs.Stats`](https://nodejs.org/api/fs.html#fs_class_fs_stats)
210object that may get passed with `add`, `addDir`, and `change` events, set
211this to `true` to ensure it is provided even in cases where it wasn't
212already available from the underlying watch events.
213* `depth` (default: `undefined`). If set, limits how many levels of
214subdirectories will be traversed.
215* `awaitWriteFinish` (default: `false`).
216By default, the `add` event will fire when a file first appears on disk, before
217the entire file has been written. Furthermore, in some cases some `change`
218events will be emitted while the file is being written. In some cases,
219especially when watching for large files there will be a need to wait for the
220write operation to finish before responding to a file creation or modification.
221Setting `awaitWriteFinish` to `true` (or a truthy value) will poll file size,
222holding its `add` and `change` events until the size does not change for a
223configurable amount of time. The appropriate duration setting is heavily
224dependent on the OS and hardware. For accurate detection this parameter should
225be relatively high, making file watching much less responsive.
226Use with caution.
227 * *`options.awaitWriteFinish` can be set to an object in order to adjust
228 timing params:*
229 * `awaitWriteFinish.stabilityThreshold` (default: 2000). Amount of time in
230 milliseconds for a file size to remain constant before emitting its event.
231 * `awaitWriteFinish.pollInterval` (default: 100). File size polling interval, in milliseconds.
232
233#### Errors
234
235* `ignorePermissionErrors` (default: `false`). Indicates whether to watch files
236that don't have read permissions if possible. If watching fails due to `EPERM`
237or `EACCES` with this set to `true`, the errors will be suppressed silently.
238* `atomic` (default: `true` if `useFsEvents` and `usePolling` are `false`).
239Automatically filters out artifacts that occur when using editors that use
240"atomic writes" instead of writing directly to the source file. If a file is
241re-added within 100 ms of being deleted, Chokidar emits a `change` event
242rather than `unlink` then `add`. If the default of 100 ms does not work well
243for you, you can override it by setting `atomic` to a custom value, in
244milliseconds.
245
246### Methods & Events
247
248`chokidar.watch()` produces an instance of `FSWatcher`. Methods of `FSWatcher`:
249
250* `.add(path / paths)`: Add files, directories, or glob patterns for tracking.
251Takes an array of strings or just one string.
252* `.on(event, callback)`: Listen for an FS event.
253Available events: `add`, `addDir`, `change`, `unlink`, `unlinkDir`, `ready`,
254`raw`, `error`.
255Additionally `all` is available which gets emitted with the underlying event
256name and path for every event other than `ready`, `raw`, and `error`. `raw` is internal, use it carefully.
257* `.unwatch(path / paths)`: Stop watching files, directories, or glob patterns.
258Takes an array of strings or just one string.
259* `.close()`: **async** Removes all listeners from watched files. Asynchronous, returns Promise. Use with `await` to ensure bugs don't happen.
260* `.getWatched()`: Returns an object representing all the paths on the file
261system being watched by this `FSWatcher` instance. The object's keys are all the
262directories (using absolute paths unless the `cwd` option was used), and the
263values are arrays of the names of the items contained in each directory.
264
265## CLI
266
267If you need a CLI interface for your file watching, check out
268[chokidar-cli](https://github.com/kimmobrunfeldt/chokidar-cli), allowing you to
269execute a command on each change, or get a stdio stream of change events.
270
271## Install Troubleshooting
272
273* `npm WARN optional dep failed, continuing fsevents@n.n.n`
274 * This message is normal part of how `npm` handles optional dependencies and is
275 not indicative of a problem. Even if accompanied by other related error messages,
276 Chokidar should function properly.
277
278* `TypeError: fsevents is not a constructor`
279 * Update chokidar by doing `rm -rf node_modules package-lock.json yarn.lock && npm install`, or update your dependency that uses chokidar.
280
281* Chokidar is producing `ENOSP` error on Linux, like this:
282 * `bash: cannot set terminal process group (-1): Inappropriate ioctl for device bash: no job control in this shell`
283 `Error: watch /home/ ENOSPC`
284 * This means Chokidar ran out of file handles and you'll need to increase their count by executing the following command in Terminal:
285 `echo fs.inotify.max_user_watches=524288 | sudo tee -a /etc/sysctl.conf && sudo sysctl -p`
286
287## Changelog
288
289For more detailed changelog, see [`full_changelog.md`](.github/full_changelog.md).
290- **v3.5 (Jan 6, 2021):** Support for ARM Macs with Apple Silicon. Fixes for deleted symlinks.
291- **v3.4 (Apr 26, 2020):** Support for directory-based symlinks. Fixes for macos file replacement.
292- **v3.3 (Nov 2, 2019):** `FSWatcher#close()` method became async. That fixes IO race conditions related to close method.
293- **v3.2 (Oct 1, 2019):** Improve Linux RAM usage by 50%. Race condition fixes. Windows glob fixes. Improve stability by using tight range of dependency versions.
294- **v3.1 (Sep 16, 2019):** dotfiles are no longer filtered out by default. Use `ignored` option if needed. Improve initial Linux scan time by 50%.
295- **v3 (Apr 30, 2019):** massive CPU & RAM consumption improvements; reduces deps / package size by a factor of 17x and bumps Node.js requirement to v8.16 and higher.
296- **v2 (Dec 29, 2017):** Globs are now posix-style-only; without windows support. Tons of bugfixes.
297- **v1 (Apr 7, 2015):** Glob support, symlink support, tons of bugfixes. Node 0.8+ is supported
298- **v0.1 (Apr 20, 2012):** Initial release, extracted from [Brunch](https://github.com/brunch/brunch/blob/9847a065aea300da99bd0753f90354cde9de1261/src/helpers.coffee#L66)
299
300## Also
301
302Why was chokidar named this way? What's the meaning behind it?
303
304>Chowkidar is a transliteration of a Hindi word meaning 'watchman, gatekeeper', चौकीदार. This ultimately comes from Sanskrit _ चतुष्क_ (crossway, quadrangle, consisting-of-four).
305
306## License
307
308MIT (c) Paul Miller (<https://paulmillr.com>), see [LICENSE](LICENSE) file.
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