| # Chokidar [](https://github.com/paulmillr/chokidar) [](https://github.com/paulmillr/chokidar) |
| |
| > A neat wrapper around node.js fs.watch / fs.watchFile / FSEvents. |
| |
| [](https://www.npmjs.com/package/chokidar) |
| |
| Version 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/) |
| |
| ## Why? |
| Node.js `fs.watch`: |
| |
| * Doesn't report filenames on MacOS. |
| * Doesn't report events at all when using editors like Sublime on MacOS. |
| * Often reports events twice. |
| * Emits most changes as `rename`. |
| * Does not provide an easy way to recursively watch file trees. |
| |
| Node.js `fs.watchFile`: |
| |
| * Almost as bad at event handling. |
| * Also does not provide any recursive watching. |
| * Results in high CPU utilization. |
| |
| Chokidar resolves these problems. |
| |
| Initially made for **[Brunch](http://brunch.io)** (an ultra-swift web app build tool), it is now used in |
| [Microsoft's Visual Studio Code](https://github.com/microsoft/vscode), |
| [gulp](https://github.com/gulpjs/gulp/), |
| [karma](http://karma-runner.github.io), |
| [PM2](https://github.com/Unitech/PM2), |
| [browserify](http://browserify.org/), |
| [webpack](http://webpack.github.io/), |
| [BrowserSync](http://www.browsersync.io/), |
| and [many others](https://www.npmjs.org/browse/depended/chokidar/). |
| It has proven itself in production environments. |
| |
| ## How? |
| Chokidar does still rely 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. |
| |
| On MacOS, chokidar by default uses a native extension exposing the Darwin |
| `FSEvents` API. This provides very efficient recursive watching compared with |
| implementations like `kqueue` available on most \*nix platforms. Chokidar still |
| does have to do some work to normalize the events received that way as well. |
| |
| On other platforms, 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. |
| |
| ## Getting started |
| Install with npm: |
| |
| ```sh |
| npm install chokidar |
| ``` |
| |
| Then `require` and use it in your code: |
| |
| ```javascript |
| const chokidar = require('chokidar'); |
| |
| // One-liner for current directory |
| chokidar.watch('.').on('all', (event, path) => { |
| console.log(event, path); |
| }); |
| ``` |
| |
| ## API |
| |
| ```javascript |
| // Example of a more typical implementation structure: |
| |
| // Initialize watcher. |
| const watcher = chokidar.watch('file, dir, glob, or array', { |
| ignored: /(^|[\/\\])\../, // ignore dotfiles |
| 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: http://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', '**/other-file*']); |
| |
| // Get list of actual paths being watched on the filesystem |
| var watchedPaths = watcher.getWatched(); |
| |
| // Un-watch some files. |
| watcher.unwatch('new-file*'); |
| |
| // Stop watching. |
| watcher.close(); |
| |
| // Full list of options. See below for descriptions. |
| // Do not use this example! |
| chokidar.watch('file', { |
| persistent: true, |
| |
| ignored: '*.txt', |
| ignoreInitial: false, |
| followSymlinks: true, |
| cwd: '.', |
| disableGlobbing: false, |
| |
| usePolling: false, |
| interval: 100, |
| binaryInterval: 300, |
| alwaysStat: false, |
| depth: 99, |
| awaitWriteFinish: { |
| stabilityThreshold: 2000, |
| pollInterval: 100 |
| }, |
| |
| ignorePermissionErrors: false, |
| atomic: true // or a custom 'atomicity delay', in milliseconds (default 100) |
| }); |
| |
| ``` |
| |
| `chokidar.watch(paths, [options])` |
| |
| * `paths` (string or array of strings). Paths to files, dirs to be watched |
| recursively, or glob patterns. |
| - Note: globs must not contain windows separators (`\`), |
| because that's how they work by the standard — |
| you'll need to replace them with forward slashes (`/`). |
| - Note 2: for additional glob documentation, check out low-level |
| library: [picomatch](https://github.com/micromatch/picomatch). |
| * `options` (object) Options object as defined below: |
| |
| #### Persistence |
| |
| * `persistent` (default: `true`). Indicates whether the process |
| should continue to run as long as files are being watched. If set to |
| `false` when using `fsevents` to watch, no more events will be emitted |
| after `ready`, even if the process continues to run. |
| |
| #### Path filtering |
| |
| * `ignored` ([anymatch](https://github.com/es128/anymatch)-compatible definition) |
| Defines files/paths to be ignored. The whole relative or absolute path is |
| tested, not just filename. If a function with two arguments is provided, it |
| gets called twice per path - once with a single argument (the path), second |
| time with two arguments (the path and the |
| [`fs.Stats`](http://nodejs.org/api/fs.html#fs_class_fs_stats) |
| object of that path). |
| * `ignoreInitial` (default: `false`). If set to `false` then `add`/`addDir` events are also emitted for matching paths while |
| instantiating the watching as chokidar discovers these file paths (before the `ready` event). |
| * `followSymlinks` (default: `true`). When `false`, only the |
| symlinks themselves will be watched for changes instead of following |
| the link references and bubbling events through the link's path. |
| * `cwd` (no default). The base directory from which watch `paths` are to be |
| derived. Paths emitted with events will be relative to this. |
| * `disableGlobbing` (default: `false`). If set to `true` then the strings passed to `.watch()` and `.add()` are treated as |
| literal path names, even if they look like globs. |
| |
| #### Performance |
| |
| * `usePolling` (default: `false`). |
| Whether to use fs.watchFile (backed by polling), or fs.watch. If polling |
| leads to high CPU utilization, consider setting this to `false`. It is |
| typically necessary to **set this to `true` to successfully watch files over |
| a network**, and it may be necessary to successfully watch files in other |
| non-standard situations. Setting to `true` explicitly on MacOS overrides the |
| `useFsEvents` default. You may also set the CHOKIDAR_USEPOLLING env variable |
| to true (1) or false (0) in order to override this option. |
| * _Polling-specific settings_ (effective when `usePolling: true`) |
| * `interval` (default: `100`). Interval of file system polling, in milliseconds. You may also |
| set the CHOKIDAR_INTERVAL env variable to override this option. |
| * `binaryInterval` (default: `300`). Interval of file system |
| polling for binary files. |
| ([see list of binary extensions](https://github.com/sindresorhus/binary-extensions/blob/master/binary-extensions.json)) |
| * `useFsEvents` (default: `true` on MacOS). Whether to use the |
| `fsevents` watching interface if available. When set to `true` explicitly |
| and `fsevents` is available this supercedes the `usePolling` setting. When |
| set to `false` on MacOS, `usePolling: true` becomes the default. |
| * `alwaysStat` (default: `false`). If relying upon the |
| [`fs.Stats`](http://nodejs.org/api/fs.html#fs_class_fs_stats) |
| object that may get passed with `add`, `addDir`, and `change` events, set |
| this to `true` to ensure it is provided even in cases where it wasn't |
| already available from the underlying watch events. |
| * `depth` (default: `undefined`). If set, limits how many levels of |
| subdirectories will be traversed. |
| * `awaitWriteFinish` (default: `false`). |
| By default, the `add` event will fire when a file first appears on disk, before |
| the entire file has been written. Furthermore, in some cases some `change` |
| events will be emitted while the file is being written. In some cases, |
| especially when watching for large files there will be a need to wait for the |
| write operation to finish before responding to a file creation or modification. |
| Setting `awaitWriteFinish` to `true` (or a truthy value) will poll file size, |
| holding its `add` and `change` events until the size does not change for a |
| configurable amount of time. The appropriate duration setting is heavily |
| dependent on the OS and hardware. For accurate detection this parameter should |
| be relatively high, making file watching much less responsive. |
| Use with caution. |
| * *`options.awaitWriteFinish` can be set to an object in order to adjust |
| timing params:* |
| * `awaitWriteFinish.stabilityThreshold` (default: 2000). Amount of time in |
| milliseconds for a file size to remain constant before emitting its event. |
| * `awaitWriteFinish.pollInterval` (default: 100). File size polling interval, in milliseconds. |
| |
| #### Errors |
| * `ignorePermissionErrors` (default: `false`). Indicates whether to watch files |
| that don't have read permissions if possible. If watching fails due to `EPERM` |
| or `EACCES` with this set to `true`, the errors will be suppressed silently. |
| * `atomic` (default: `true` if `useFsEvents` and `usePolling` are `false`). |
| Automatically filters out artifacts that occur when using editors that use |
| "atomic writes" instead of writing directly to the source file. If a file is |
| re-added within 100 ms of being deleted, Chokidar emits a `change` event |
| rather than `unlink` then `add`. If the default of 100 ms does not work well |
| for you, you can override it by setting `atomic` to a custom value, in |
| milliseconds. |
| |
| ### Methods & Events |
| |
| `chokidar.watch()` produces an instance of `FSWatcher`. Methods of `FSWatcher`: |
| |
| * `.add(path / paths)`: Add files, directories, or glob patterns for tracking. |
| Takes an array of strings or just one string. |
| * `.on(event, callback)`: Listen for an FS event. |
| Available events: `add`, `addDir`, `change`, `unlink`, `unlinkDir`, `ready`, |
| `raw`, `error`. |
| Additionally `all` is available which gets emitted with the underlying event |
| name and path for every event other than `ready`, `raw`, and `error`. `raw` is internal, use it carefully. |
| * `.unwatch(path / paths)`: Stop watching files, directories, or glob patterns. |
| Takes an array of strings or just one string. |
| * `.close()`: Removes all listeners from watched files. |
| * `.getWatched()`: Returns an object representing all the paths on the file |
| system being watched by this `FSWatcher` instance. The object's keys are all the |
| directories (using absolute paths unless the `cwd` option was used), and the |
| values are arrays of the names of the items contained in each directory. |
| |
| ## CLI |
| |
| If you need a CLI interface for your file watching, check out |
| [chokidar-cli](https://github.com/kimmobrunfeldt/chokidar-cli), allowing you to |
| execute a command on each change, or get a stdio stream of change events. |
| |
| ## Install Troubleshooting |
| |
| * `npm WARN optional dep failed, continuing fsevents@n.n.n` |
| * This message is normal part of how `npm` handles optional dependencies and is |
| not indicative of a problem. Even if accompanied by other related error messages, |
| Chokidar should function properly. |
| |
| * `TypeError: fsevents is not a constructor` |
| * Update chokidar by doing `rm -rf node_modules package-lock.json yarn.lock && npm install`, or update your dependency that uses chokidar. |
| |
| * Chokidar is producing `ENOSP` error on Linux, like this: |
| * `bash: cannot set terminal process group (-1): Inappropriate ioctl for device bash: no job control in this shell` |
| `Error: watch /home/ ENOSPC` |
| * This means Chokidar ran out of file handles and you'll need to increase their count by executing the following command in Terminal: |
| `echo fs.inotify.max_user_watches=524288 | sudo tee -a /etc/sysctl.conf && sudo sysctl -p` |
| |
| ## Changelog |
| |
| For more detailed changelog, see [`full_changelog.md`](.github/full_changelog.md). |
| |
| - **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. |
| - **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%. |
| - **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. |
| - **v2 (Dec 29, 2017):** Globs are now posix-style-only; without windows support. Tons of bugfixes. |
| - **v1 (Apr 7, 2015):** Glob support, symlink support, tons of bugfixes. Node 0.8+ is supported |
| - **v0.1 (Apr 20, 2012):** Initial release, extracted from [Brunch](https://github.com/brunch/brunch/blob/9847a065aea300da99bd0753f90354cde9de1261/src/helpers.coffee#L66) |
| |
| ## License |
| |
| MIT (c) Paul Miller (https://paulmillr.com), see LICENSE file. |