Node.js: fs-extra

fs-extra adds file system methods that aren't included in the native fs module. It is a drop in replacement for fs.

NOTE (2016-01-13): Node v0.10 will be unsupported AFTER Ubuntu LTS releases their next version AND Amazon Lambda upgrades its Node.js runtime from v0.10. I anticipate this will happen around late spring / summer 2016. Please prepare accordingly. After this, we'll make a strong push for a 1.0.0 release.

Why?

I got tired of including mkdirp, rimraf, and cp -r in most of my projects.

Installation

npm install --save fs-extra

Usage

fs-extra is a drop in replacement for native fs. All methods in fs are unmodified and attached to fs-extra.

You don't ever need to include the original fs module again:

var fs = require('fs') // this is no longer necessary

you can now do this:

var fs = require('fs-extra')

or if you prefer to make it clear that you're using fs-extra and not fs, you may want to name your fs variable fse like so:

var fse = require('fs-extra')

you can also keep both, but it's redundant:

var fs = require('fs')
var fse = require('fs-extra')

Sync vs Async

Most methods are async by default (they take a callback with an Error as first argument).

Sync methods on the other hand will throw if an error occurs.

Example:

var fs = require('fs-extra')

fs.copy('/tmp/myfile', '/tmp/mynewfile', function (err) {
  if (err) return console.error(err)
  console.log("success!")
});

try {
  fs.copySync('/tmp/myfile', '/tmp/mynewfile')
  console.log("success!")
} catch (err) {
  console.error(err)
}

Methods

• copy
• copySync
• createOutputStream
• emptyDir
• emptyDirSync
• ensureFile
• ensureFileSync
• ensureDir
• ensureDirSync
• ensureLink
• ensureLinkSync
• ensureSymlink
• ensureSymlinkSync
• mkdirs
• mkdirsSync
• move
• outputFile
• outputFileSync
• outputJson
• outputJsonSync
• readJson
• readJsonSync
• remove
• removeSync
• walk
• writeJson
• writeJsonSync

NOTE: You can still use the native Node.js methods. They are copied over to fs-extra.

copy()

copy(src, dest, [options], callback)

Copy a file or directory. The directory can have contents. Like cp -r.

Options:

• clobber (boolean): overwrite existing file or directory
• preserveTimestamps (boolean): will set last modification and access times to the ones of the original source files, default is false.
• filter: Function or RegExp to filter copied files. If function, return true to include, false to exclude. If RegExp, same as function, where filter is filter.test.

Sync: copySync()

Example:

var fs = require('fs-extra')

fs.copy('/tmp/myfile', '/tmp/mynewfile', function (err) {
  if (err) return console.error(err)
  console.log("success!")
}) // copies file

fs.copy('/tmp/mydir', '/tmp/mynewdir', function (err) {
  if (err) return console.error(err)
  console.log('success!')
}) // copies directory, even if it has subdirectories or files

createOutputStream(file, [options])

Exactly like createWriteStream, but if the directory does not exist, it's created.

Examples:

var fs = require('fs-extra')

// if /tmp/some does not exist, it is created
var ws = fs.createOutputStream('/tmp/some/file.txt')
ws.write('hello\n')

Note on naming: you'll notice that fs-extra has some methods like fs.outputJson, fs.outputFile, etc that use the word output to denote that if the containing directory does not exist, it should be created. If you can think of a better succinct nomenclature for these methods, please open an issue for discussion. Thanks.

emptyDir(dir, [callback])

Ensures that a directory is empty. Deletes directory contents if the directory is not empty. If the directory does not exist, it is created. The directory itself is not deleted.

Alias: emptydir()

Sync: emptyDirSync(), emptydirSync()

Example:

var fs = require('fs-extra')

// assume this directory has a lot of files and folders
fs.emptyDir('/tmp/some/dir', function (err) {
  if (!err) console.log('success!')
})

ensureFile(file, callback)

Ensures that the file exists. If the file that is requested to be created is in directories that do not exist, these directories are created. If the file already exists, it is NOT MODIFIED.

Alias: createFile()

Sync: createFileSync(),ensureFileSync()

Example:

var fs = require('fs-extra')

var file = '/tmp/this/path/does/not/exist/file.txt'
fs.ensureFile(file, function (err) {
  console.log(err) // => null
  // file has now been created, including the directory it is to be placed in
})

ensureDir(dir, callback)

Ensures that the directory exists. If the directory structure does not exist, it is created.

Sync: ensureDirSync()

Example:

var fs = require('fs-extra')

var dir = '/tmp/this/path/does/not/exist'
fs.ensureDir(dir, function (err) {
  console.log(err) // => null
  // dir has now been created, including the directory it is to be placed in
})

ensureLink(srcpath, dstpath, callback)

Ensures that the link exists. If the directory structure does not exist, it is created.

Sync: ensureLinkSync()

Example:

var fs = require('fs-extra')

var srcpath = '/tmp/file.txt'
var dstpath = '/tmp/this/path/does/not/exist/file.txt'
fs.ensureLink(srcpath, dstpath, function (err) {
  console.log(err) // => null
  // link has now been created, including the directory it is to be placed in
})

ensureSymlink(srcpath, dstpath, [type], callback)

Ensures that the symlink exists. If the directory structure does not exist, it is created.

Sync: ensureSymlinkSync()

Example:

var fs = require('fs-extra')

var srcpath = '/tmp/file.txt'
var dstpath = '/tmp/this/path/does/not/exist/file.txt'
fs.ensureSymlink(srcpath, dstpath, function (err) {
  console.log(err) // => null
  // symlink has now been created, including the directory it is to be placed in
})

mkdirs(dir, callback)

Creates a directory. If the parent hierarchy doesn't exist, it's created. Like mkdir -p.

Alias: mkdirp()

Sync: mkdirsSync() / mkdirpSync()

Examples:

var fs = require('fs-extra')

fs.mkdirs('/tmp/some/long/path/that/prob/doesnt/exist', function (err) {
  if (err) return console.error(err)
  console.log("success!")
})

fs.mkdirsSync('/tmp/another/path')

move(src, dest, [options], callback)

Moves a file or directory, even across devices.

Options:

• clobber (boolean): overwrite existing file or directory
• limit (number): number of concurrent moves, see ncp for more information

Example:

var fs = require('fs-extra')

fs.move('/tmp/somefile', '/tmp/does/not/exist/yet/somefile', function (err) {
  if (err) return console.error(err)
  console.log("success!")
})

outputFile(file, data, [options], callback)

Almost the same as writeFile (i.e. it overwrites), except that if the parent directory does not exist, it's created. options are what you'd pass to fs.writeFile().

Sync: outputFileSync()

Example:

var fs = require('fs-extra')
var file = '/tmp/this/path/does/not/exist/file.txt'

fs.outputFile(file, 'hello!', function (err) {
  console.log(err) // => null

  fs.readFile(file, 'utf8', function (err, data) {
    console.log(data) // => hello!
  })
})

outputJson(file, data, [options], callback)

Almost the same as writeJson, except that if the directory does not exist, it's created. options are what you'd pass to jsonFile.writeFile().

Alias: outputJSON()

Sync: outputJsonSync(), outputJSONSync()

Example:

var fs = require('fs-extra')
var file = '/tmp/this/path/does/not/exist/file.txt'

fs.outputJson(file, {name: 'JP'}, function (err) {
  console.log(err) // => null

  fs.readJson(file, function(err, data) {
    console.log(data.name) // => JP
  })
})

readJson(file, [options], callback)

Reads a JSON file and then parses it into an object. options are the same that you'd pass to jsonFile.readFile.

Alias: readJSON()

Sync: readJsonSync(), readJSONSync()

Example:

var fs = require('fs-extra')

fs.readJson('./package.json', function (err, packageObj) {
  console.log(packageObj.version) // => 0.1.3
})

readJsonSync() can take a throws option set to false and it won't throw if the JSON is invalid. Example:

var fs = require('fs-extra')
var file = path.join('/tmp/some-invalid.json')
var data = '{not valid JSON'
fs.writeFileSync(file, data)

var obj = fs.readJsonSync(file, {throws: false})
console.log(obj) // => null

remove(dir, callback)

Removes a file or directory. The directory can have contents. Like rm -rf.

Sync: removeSync()

Examples:

var fs = require('fs-extra')

fs.remove('/tmp/myfile', function (err) {
  if (err) return console.error(err)

  console.log('success!')
})

fs.removeSync('/home/jprichardson') //I just deleted my entire HOME directory.

walk()

walk(dir, [streamOptions])

The function walk() from the module klaw.

Returns a Readable stream that iterates through every file and directory starting with dir as the root. Every read() or data event returns an object with two properties: path and stats. path is the full path of the file and stats is an instance of fs.Stats.

Streams 1 (push) example:

var items = [] // files, directories, symlinks, etc
fse.walk(TEST_DIR)
  .on('data', function (item) {
    items.push(item.path)
  })
  .on('end', function () {
    console.dir(items) // => [ ... array of files]
  })

Streams 2 & 3 (pull) example:

var items = [] // files, directories, symlinks, etc
fse.walk(TEST_DIR)
  .on('readable', function () {
    var item
    while ((item = this.read())) {
      items.push(item.path)
    }
  })
  .on('end', function () {
    console.dir(items) // => [ ... array of files]
  })

If you're not sure of the differences on Node.js streams 1, 2, 3 then I'd recommend this resource as a good starting point: https://strongloop.com/strongblog/whats-new-io-js-beta-streams3/.

See klaw documentation for more detailed usage.

writeJson(file, object, [options], callback)

Writes an object to a JSON file. options are the same that you'd pass to jsonFile.writeFile().

Alias: writeJSON()

Sync: writeJsonSync(), writeJSONSync()

Example:

var fs = require('fs-extra')
fs.writeJson('./package.json', {name: 'fs-extra'}, function (err) {
  console.log(err)
})

Third Party

Promises

Use Bluebird. See https://github.com/petkaantonov/bluebird/blob/master/API.md#promisification. fs-extra is explicitly listed as supported.

var Promise = require('bluebird')
var fs = Promise.promisifyAll(require('fs-extra'))

Or you can use the package fs-extra-promise that marries the two together.

TypeScript

If you like TypeScript, you can use fs-extra with it: https://github.com/borisyankov/DefinitelyTyped/tree/master/fs-extra

File / Directory Watching

If you want to watch for changes to files or directories, then you should use chokidar.

Misc.

• mfs - Monitor your fs-extra calls.

Hacking on fs-extra

Wanna hack on fs-extra? Great! Your help is needed! fs-extra is one of the most depended upon Node.js packages. This project uses JavaScript Standard Style - if the name or style choices bother you, you're gonna have to get over it :) If standard is good enough for npm, it's good enough for fs-extra.

What's needed?

• First, take a look at existing issues. Those are probably going to be where the priority lies.
• More tests for edge cases. Specifically on different platforms. There can never be enough tests.
• Really really help with the Windows tests. See appveyor outputs for more info.
• Improve test coverage. See coveralls output for more info.
• A directory walker. Probably this one: https://github.com/thlorenz/readdirp imported into fs-extra.
• After the directory walker is integrated, any function that needs to traverse directories like copy, remove, or mkdirs should be built on top of it.

Note: If you make any big changes, you should definitely post an issue for discussion first.

Naming

I put a lot of thought into the naming of these functions. Inspired by @coolaj86's request. So he deserves much of the credit for raising the issue. See discussion(s) here:

• jprichardson#2
• flatiron/utile#11
• ryanmcgrath/wrench-js#29
• https://github.com/substack/node-mkdirp/issues/17

First, I believe that in as many cases as possible, the Node.js naming schemes should be chosen. However, there are problems with the Node.js own naming schemes.

For example, fs.readFile() and fs.readdir(): the F is capitalized in File and the d is not capitalized in dir. Perhaps a bit pedantic, but they should still be consistent. Also, Node.js has chosen a lot of POSIX naming schemes, which I believe is great. See: fs.mkdir(), fs.rmdir(), fs.chown(), etc.

We have a dilemma though. How do you consistently name methods that perform the following POSIX commands: cp, cp -r, mkdir -p, and rm -rf?

My perspective: when in doubt, err on the side of simplicity. A directory is just a hierarchical grouping of directories and files. Consider that for a moment. So when you want to copy it or remove it, in most cases you'll want to copy or remove all of its contents. When you want to create a directory, if the directory that it's suppose to be contained in does not exist, then in most cases you'll want to create that too.

So, if you want to remove a file or a directory regardless of whether it has contents, just call fs.remove(path). If you want to copy a file or a directory whether it has contents, just call fs.copy(source, destination). If you want to create a directory regardless of whether its parent directories exist, just call fs.mkdirs(path) or fs.mkdirp(path).

Credit

fs-extra wouldn't be possible without using the modules from the following authors:

• Isaac Shlueter
• Charlie McConnel
• James Halliday
• Andrew Kelley

License

Licensed under MIT

Copyright (c) 2011-2016 JP Richardson