A neat wrapper around Node.js fs.watch / fs.watchFile / FSEvents.
Version 3 is out! Check out our blog post about it: Chokidar 3: How to save 32TB of traffic every week
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 (an ultra-swift web app build tool), it is now used in Microsoft's Visual Studio Code, gulp, karma, PM2, browserify, webpack, BrowserSync, and many others. It has proven itself in production environments.
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.
Install with npm:
npm install chokidar
Then require
and use it in your code:
const chokidar = require('chokidar');
// One-liner for current directory
chokidar.watch('.').on('all', (event, path) => {
console.log(event, path);
});
// 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: 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', '**/other-file*']);
// Get list of actual paths being watched on the filesystem
var watchedPaths = watcher.getWatched();
// Un-watch some files.
await watcher.unwatch('new-file*');
// Stop watching.
// The method is async!
watcher.close().then(() => console.log('closed'));
// 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 โ you'll need to replace them with forward slashes (/
). - Note 2: for additional glob documentation, check out low-level library: picomatch.
- Note: globs must not contain windows separators (
options
(object) Options object as defined below:
persistent
(default:true
). Indicates whether the process should continue to run as long as files are being watched. If set tofalse
when usingfsevents
to watch, no more events will be emitted afterready
, even if the process continues to run.
ignored
(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 thefs.Stats
object of that path).ignoreInitial
(default:false
). If set tofalse
thenadd
/addDir
events are also emitted for matching paths while instantiating the watching as chokidar discovers these file paths (before theready
event).followSymlinks
(default:true
). Whenfalse
, 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 watchpaths
are to be derived. Paths emitted with events will be relative to this.disableGlobbing
(default:false
). If set totrue
then the strings passed to.watch()
and.add()
are treated as literal path names, even if they look like globs.
usePolling
(default:false
). Whether to use fs.watchFile (backed by polling), or fs.watch. If polling leads to high CPU utilization, consider setting this tofalse
. It is typically necessary to set this totrue
to successfully watch files over a network, and it may be necessary to successfully watch files in other non-standard situations. Setting totrue
explicitly on MacOS overrides theuseFsEvents
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)
useFsEvents
(default:true
on MacOS). Whether to use thefsevents
watching interface if available. When set totrue
explicitly andfsevents
is available this supercedes theusePolling
setting. When set tofalse
on MacOS,usePolling: true
becomes the default.alwaysStat
(default:false
). If relying upon thefs.Stats
object that may get passed withadd
,addDir
, andchange
events, set this totrue
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, theadd
event will fire when a file first appears on disk, before the entire file has been written. Furthermore, in some cases somechange
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. SettingawaitWriteFinish
totrue
(or a truthy value) will poll file size, holding itsadd
andchange
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.
ignorePermissionErrors
(default:false
). Indicates whether to watch files that don't have read permissions if possible. If watching fails due toEPERM
orEACCES
with this set totrue
, the errors will be suppressed silently.atomic
(default:true
ifuseFsEvents
andusePolling
arefalse
). 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 achange
event rather thanunlink
thenadd
. If the default of 100 ms does not work well for you, you can override it by settingatomic
to a custom value, in milliseconds.
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
. Additionallyall
is available which gets emitted with the underlying event name and path for every event other thanready
,raw
, anderror
.raw
is internal, use it carefully..unwatch(path / paths)
: async Stop watching files, directories, or glob patterns. Takes an array of strings or just one string. Use withawait
to ensure bugs don't happen..close()
: Removes all listeners from watched files. Asynchronous, returns Promise..getWatched()
: Returns an object representing all the paths on the file system being watched by thisFSWatcher
instance. The object's keys are all the directories (using absolute paths unless thecwd
option was used), and the values are arrays of the names of the items contained in each directory.
If you need a CLI interface for your file watching, check out chokidar-cli, allowing you to execute a command on each change, or get a stdio stream of change events.
-
npm WARN optional dep failed, continuing [email protected]
- 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.
- This message is normal part of how
-
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.
- Update chokidar by doing
-
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
For more detailed changelog, see full_changelog.md
.
- v3.3 (Nov 2, 2019):
FSWatcher#close()
method became async. - 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
MIT (c) Paul Miller (https://paulmillr.com), see LICENSE file.