309 lines
14 KiB
Markdown
309 lines
14 KiB
Markdown
# Chokidar [](https://github.com/paulmillr/chokidar) [](https://github.com/paulmillr/chokidar)
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> Minimal and efficient cross-platform file watching library
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[](https://www.npmjs.com/package/chokidar)
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## Why?
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Node.js `fs.watch`:
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* Doesn't report filenames on MacOS.
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* Doesn't report events at all when using editors like Sublime on MacOS.
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* Often reports events twice.
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* Emits most changes as `rename`.
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* Does not provide an easy way to recursively watch file trees.
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* Does not support recursive watching on Linux.
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Node.js `fs.watchFile`:
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* Almost as bad at event handling.
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* Also does not provide any recursive watching.
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* Results in high CPU utilization.
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Chokidar resolves these problems.
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Initially made for **[Brunch](https://brunch.io/)** (an ultra-swift web app build tool), it is now used in
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[Microsoft's Visual Studio Code](https://github.com/microsoft/vscode),
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[gulp](https://github.com/gulpjs/gulp/),
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[karma](https://karma-runner.github.io/),
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[PM2](https://github.com/Unitech/PM2),
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[browserify](http://browserify.org/),
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[webpack](https://webpack.github.io/),
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[BrowserSync](https://www.browsersync.io/),
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and [many others](https://www.npmjs.com/browse/depended/chokidar).
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It has proven itself in production environments.
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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/)
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## How?
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Chokidar does still rely on the Node.js core `fs` module, but when using
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`fs.watch` and `fs.watchFile` for watching, it normalizes the events it
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receives, often checking for truth by getting file stats and/or dir contents.
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On MacOS, chokidar by default uses a native extension exposing the Darwin
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`FSEvents` API. This provides very efficient recursive watching compared with
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implementations like `kqueue` available on most \*nix platforms. Chokidar still
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does have to do some work to normalize the events received that way as well.
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On most other platforms, the `fs.watch`-based implementation is the default, which
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avoids polling and keeps CPU usage down. Be advised that chokidar will initiate
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watchers recursively for everything within scope of the paths that have been
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specified, so be judicious about not wasting system resources by watching much
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more than needed.
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## Getting started
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Install with npm:
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```sh
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npm install chokidar
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```
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Then `require` and use it in your code:
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```javascript
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const chokidar = require('chokidar');
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// One-liner for current directory
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chokidar.watch('.').on('all', (event, path) => {
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console.log(event, path);
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});
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```
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## API
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```javascript
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// Example of a more typical implementation structure
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// Initialize watcher.
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const watcher = chokidar.watch('file, dir, glob, or array', {
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ignored: /(^|[\/\\])\../, // ignore dotfiles
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persistent: true
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});
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// Something to use when events are received.
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const log = console.log.bind(console);
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// Add event listeners.
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watcher
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.on('add', path => log(`File ${path} has been added`))
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.on('change', path => log(`File ${path} has been changed`))
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.on('unlink', path => log(`File ${path} has been removed`));
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// More possible events.
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watcher
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.on('addDir', path => log(`Directory ${path} has been added`))
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.on('unlinkDir', path => log(`Directory ${path} has been removed`))
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.on('error', error => log(`Watcher error: ${error}`))
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.on('ready', () => log('Initial scan complete. Ready for changes'))
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.on('raw', (event, path, details) => { // internal
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log('Raw event info:', event, path, details);
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});
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// 'add', 'addDir' and 'change' events also receive stat() results as second
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// argument when available: https://nodejs.org/api/fs.html#fs_class_fs_stats
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watcher.on('change', (path, stats) => {
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if (stats) console.log(`File ${path} changed size to ${stats.size}`);
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});
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// Watch new files.
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watcher.add('new-file');
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watcher.add(['new-file-2', 'new-file-3', '**/other-file*']);
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// Get list of actual paths being watched on the filesystem
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var watchedPaths = watcher.getWatched();
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// Un-watch some files.
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await watcher.unwatch('new-file*');
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// Stop watching.
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// The method is async!
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watcher.close().then(() => console.log('closed'));
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// Full list of options. See below for descriptions.
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// Do not use this example!
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chokidar.watch('file', {
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persistent: true,
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ignored: '*.txt',
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ignoreInitial: false,
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followSymlinks: true,
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cwd: '.',
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disableGlobbing: false,
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usePolling: false,
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interval: 100,
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binaryInterval: 300,
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alwaysStat: false,
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depth: 99,
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awaitWriteFinish: {
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stabilityThreshold: 2000,
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pollInterval: 100
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},
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ignorePermissionErrors: false,
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atomic: true // or a custom 'atomicity delay', in milliseconds (default 100)
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});
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```
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`chokidar.watch(paths, [options])`
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* `paths` (string or array of strings). Paths to files, dirs to be watched
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recursively, or glob patterns.
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- Note: globs must not contain windows separators (`\`),
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because that's how they work by the standard —
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you'll need to replace them with forward slashes (`/`).
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- Note 2: for additional glob documentation, check out low-level
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library: [picomatch](https://github.com/micromatch/picomatch).
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* `options` (object) Options object as defined below:
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#### Persistence
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* `persistent` (default: `true`). Indicates whether the process
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should continue to run as long as files are being watched. If set to
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`false` when using `fsevents` to watch, no more events will be emitted
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after `ready`, even if the process continues to run.
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#### Path filtering
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* `ignored` ([anymatch](https://github.com/es128/anymatch)-compatible definition)
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Defines files/paths to be ignored. The whole relative or absolute path is
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tested, not just filename. If a function with two arguments is provided, it
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gets called twice per path - once with a single argument (the path), second
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time with two arguments (the path and the
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[`fs.Stats`](https://nodejs.org/api/fs.html#fs_class_fs_stats)
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object of that path).
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* `ignoreInitial` (default: `false`). If set to `false` then `add`/`addDir` events are also emitted for matching paths while
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instantiating the watching as chokidar discovers these file paths (before the `ready` event).
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* `followSymlinks` (default: `true`). When `false`, only the
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symlinks themselves will be watched for changes instead of following
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the link references and bubbling events through the link's path.
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* `cwd` (no default). The base directory from which watch `paths` are to be
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derived. Paths emitted with events will be relative to this.
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* `disableGlobbing` (default: `false`). If set to `true` then the strings passed to `.watch()` and `.add()` are treated as
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literal path names, even if they look like globs.
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#### Performance
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* `usePolling` (default: `false`).
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Whether to use fs.watchFile (backed by polling), or fs.watch. If polling
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leads to high CPU utilization, consider setting this to `false`. It is
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typically necessary to **set this to `true` to successfully watch files over
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a network**, and it may be necessary to successfully watch files in other
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non-standard situations. Setting to `true` explicitly on MacOS overrides the
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`useFsEvents` default. You may also set the CHOKIDAR_USEPOLLING env variable
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to true (1) or false (0) in order to override this option.
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* _Polling-specific settings_ (effective when `usePolling: true`)
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* `interval` (default: `100`). Interval of file system polling, in milliseconds. You may also
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set the CHOKIDAR_INTERVAL env variable to override this option.
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* `binaryInterval` (default: `300`). Interval of file system
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polling for binary files.
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([see list of binary extensions](https://github.com/sindresorhus/binary-extensions/blob/master/binary-extensions.json))
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* `useFsEvents` (default: `true` on MacOS). Whether to use the
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`fsevents` watching interface if available. When set to `true` explicitly
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and `fsevents` is available this supercedes the `usePolling` setting. When
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set to `false` on MacOS, `usePolling: true` becomes the default.
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* `alwaysStat` (default: `false`). If relying upon the
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[`fs.Stats`](https://nodejs.org/api/fs.html#fs_class_fs_stats)
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object that may get passed with `add`, `addDir`, and `change` events, set
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this to `true` to ensure it is provided even in cases where it wasn't
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already available from the underlying watch events.
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* `depth` (default: `undefined`). If set, limits how many levels of
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subdirectories will be traversed.
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* `awaitWriteFinish` (default: `false`).
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By default, the `add` event will fire when a file first appears on disk, before
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the entire file has been written. Furthermore, in some cases some `change`
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events will be emitted while the file is being written. In some cases,
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especially when watching for large files there will be a need to wait for the
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write operation to finish before responding to a file creation or modification.
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Setting `awaitWriteFinish` to `true` (or a truthy value) will poll file size,
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holding its `add` and `change` events until the size does not change for a
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configurable amount of time. The appropriate duration setting is heavily
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dependent on the OS and hardware. For accurate detection this parameter should
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be relatively high, making file watching much less responsive.
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Use with caution.
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* *`options.awaitWriteFinish` can be set to an object in order to adjust
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timing params:*
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* `awaitWriteFinish.stabilityThreshold` (default: 2000). Amount of time in
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milliseconds for a file size to remain constant before emitting its event.
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* `awaitWriteFinish.pollInterval` (default: 100). File size polling interval, in milliseconds.
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#### Errors
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* `ignorePermissionErrors` (default: `false`). Indicates whether to watch files
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that don't have read permissions if possible. If watching fails due to `EPERM`
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or `EACCES` with this set to `true`, the errors will be suppressed silently.
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* `atomic` (default: `true` if `useFsEvents` and `usePolling` are `false`).
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Automatically filters out artifacts that occur when using editors that use
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"atomic writes" instead of writing directly to the source file. If a file is
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re-added within 100 ms of being deleted, Chokidar emits a `change` event
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rather than `unlink` then `add`. If the default of 100 ms does not work well
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for you, you can override it by setting `atomic` to a custom value, in
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milliseconds.
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### Methods & Events
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`chokidar.watch()` produces an instance of `FSWatcher`. Methods of `FSWatcher`:
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* `.add(path / paths)`: Add files, directories, or glob patterns for tracking.
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Takes an array of strings or just one string.
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* `.on(event, callback)`: Listen for an FS event.
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Available events: `add`, `addDir`, `change`, `unlink`, `unlinkDir`, `ready`,
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`raw`, `error`.
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Additionally `all` is available which gets emitted with the underlying event
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name and path for every event other than `ready`, `raw`, and `error`. `raw` is internal, use it carefully.
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* `.unwatch(path / paths)`: Stop watching files, directories, or glob patterns.
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Takes an array of strings or just one string.
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* `.close()`: **async** Removes all listeners from watched files. Asynchronous, returns Promise. Use with `await` to ensure bugs don't happen.
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* `.getWatched()`: Returns an object representing all the paths on the file
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system being watched by this `FSWatcher` instance. The object's keys are all the
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directories (using absolute paths unless the `cwd` option was used), and the
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values are arrays of the names of the items contained in each directory.
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## CLI
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If you need a CLI interface for your file watching, check out
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[chokidar-cli](https://github.com/open-cli-tools/chokidar-cli), allowing you to
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execute a command on each change, or get a stdio stream of change events.
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## Install Troubleshooting
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* `npm WARN optional dep failed, continuing fsevents@n.n.n`
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* This message is normal part of how `npm` handles optional dependencies and is
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not indicative of a problem. Even if accompanied by other related error messages,
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Chokidar should function properly.
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* `TypeError: fsevents is not a constructor`
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* Update chokidar by doing `rm -rf node_modules package-lock.json yarn.lock && npm install`, or update your dependency that uses chokidar.
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* Chokidar is producing `ENOSP` error on Linux, like this:
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* `bash: cannot set terminal process group (-1): Inappropriate ioctl for device bash: no job control in this shell`
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`Error: watch /home/ ENOSPC`
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* This means Chokidar ran out of file handles and you'll need to increase their count by executing the following command in Terminal:
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`echo fs.inotify.max_user_watches=524288 | sudo tee -a /etc/sysctl.conf && sudo sysctl -p`
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## Changelog
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For more detailed changelog, see [`full_changelog.md`](.github/full_changelog.md).
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- **v3.5 (Jan 6, 2021):** Support for ARM Macs with Apple Silicon. Fixes for deleted symlinks.
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- **v3.4 (Apr 26, 2020):** Support for directory-based symlinks. Fixes for macos file replacement.
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- **v3.3 (Nov 2, 2019):** `FSWatcher#close()` method became async. That fixes IO race conditions related to close method.
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- **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.
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- **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%.
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- **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.
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- **v2 (Dec 29, 2017):** Globs are now posix-style-only; without windows support. Tons of bugfixes.
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- **v1 (Apr 7, 2015):** Glob support, symlink support, tons of bugfixes. Node 0.8+ is supported
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- **v0.1 (Apr 20, 2012):** Initial release, extracted from [Brunch](https://github.com/brunch/brunch/blob/9847a065aea300da99bd0753f90354cde9de1261/src/helpers.coffee#L66)
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## Also
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Why was chokidar named this way? What's the meaning behind it?
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>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.
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## License
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MIT (c) Paul Miller (<https://paulmillr.com>), see [LICENSE](LICENSE) file.
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