What is fs-extra?
The fs-extra package is a file system module for Node.js that extends the built-in 'fs' module. It provides additional methods and simplifies certain file operations, such as copying, moving, deleting files and directories, and more. It also adds promise support to the fs methods.
What are fs-extra's main functionalities?
Copying files and directories
This feature allows you to copy files and directories from one location to another. The method returns a promise that resolves when the operation is complete.
const fs = require('fs-extra');
fs.copy('/path/to/source', '/path/to/dest')
.then(() => console.log('Copy successful!'))
.catch(err => console.error(err));
Moving files and directories
This feature enables you to move files and directories to a new location. Like copy, it returns a promise and provides a simple API for a task that would otherwise require multiple steps.
const fs = require('fs-extra');
fs.move('/path/to/source', '/path/to/dest')
.then(() => console.log('Move successful!'))
.catch(err => console.error(err));
Removing files and directories
This feature is used to delete files and directories. It is a safer and more powerful alternative to the standard 'fs.unlink' and 'fs.rmdir' methods, as it can remove non-empty directories.
const fs = require('fs-extra');
fs.remove('/path/to/dir')
.then(() => console.log('Removal successful!'))
.catch(err => console.error(err));
Reading and writing JSON files
This feature simplifies the process of reading and writing JSON files. It automatically handles stringifying objects when writing and parsing JSON data when reading.
const fs = require('fs-extra');
const myData = { name: 'fs-extra' };
fs.writeJson('/path/to/file.json', myData)
.then(() => console.log('Write successful!'))
.catch(err => console.error(err));
Ensuring a file or directory exists
This feature checks if a file or directory exists, and if it does not, it is created. This is useful for making sure that a given file or directory is present before performing operations on it.
const fs = require('fs-extra');
fs.ensureFile('/path/to/file.txt')
.then(() => console.log('File exists!'))
.catch(err => console.error(err));
Other packages similar to fs-extra
rimraf
Rimraf is a Node.js package that provides a simple way to delete files and directories with a UNIX command 'rm -rf' like functionality. It is less feature-rich compared to fs-extra, which provides a broader set of file system operations.
mkdirp
Mkdirp is a package that allows you to create a new directory and its parent directories if they do not exist (similar to the 'mkdir -p' command in UNIX). It is more focused than fs-extra, which includes this functionality as part of a larger suite of file system tools.
graceful-fs
Graceful-fs is a drop-in replacement for the fs module that makes file system operations more robust by queuing them and retrying on certain types of errors. It does not add new methods like fs-extra but improves the reliability of existing ones.
node-fs-extra
Node-fs-extra is a fork of fs-extra that aims to provide the same functionality. However, fs-extra is more commonly used and actively maintained, making it the preferred choice for most developers.
fs-extra
adds file system methods that aren't included in the native fs
module and adds promise support to the fs
methods. It also uses graceful-fs
to prevent EMFILE
errors. It should be a drop in replacement for fs
.
Why?
I got tired of including mkdirp
, rimraf
, and ncp
in most of my projects.
Installation
npm install fs-extra
Usage
CommonJS
fs-extra
is a drop in replacement for native fs
. All methods in fs
are attached to fs-extra
. All fs
methods return promises if the callback isn't passed.
You don't ever need to include the original fs
module again:
const fs = require('fs')
you can now do this:
const 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:
const fse = require('fs-extra')
you can also keep both, but it's redundant:
const fs = require('fs')
const fse = require('fs-extra')
ESM
There is also an fs-extra/esm
import, that supports both default and named exports. However, note that fs
methods are not included in fs-extra/esm
; you still need to import fs
and/or fs/promises
seperately:
import { readFileSync } from 'fs'
import { readFile } from 'fs/promises'
import { outputFile, outputFileSync } from 'fs-extra/esm'
Default exports are supported:
import fs from 'fs'
import fse from 'fs-extra/esm'
but you probably want to just use regular fs-extra
instead of fs-extra/esm
for default exports:
import fs from 'fs-extra'
Sync vs Async vs Async/Await
Most methods are async by default. All async methods will return a promise if the callback isn't passed.
Sync methods on the other hand will throw if an error occurs.
Also Async/Await will throw an error if one occurs.
Example:
const fs = require('fs-extra')
fs.copy('/tmp/myfile', '/tmp/mynewfile')
.then(() => console.log('success!'))
.catch(err => console.error(err))
fs.copy('/tmp/myfile', '/tmp/mynewfile', 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)
}
async function copyFiles () {
try {
await fs.copy('/tmp/myfile', '/tmp/mynewfile')
console.log('success!')
} catch (err) {
console.error(err)
}
}
copyFiles()
Methods
Async
Sync
NOTE: You can still use the native Node.js methods. They are promisified and copied over to fs-extra
. See notes on fs.read()
, fs.write()
, & fs.writev()
What happened to walk()
and walkSync()
?
They were removed from fs-extra
in v2.0.0. If you need the functionality, walk
and walkSync
are available as separate packages, klaw
and klaw-sync
.
Third Party
CLI
fse-cli allows you to run fs-extra
from a console or from npm scripts.
TypeScript
If you like TypeScript, you can use fs-extra
with it: https://github.com/DefinitelyTyped/DefinitelyTyped/tree/master/types/fs-extra
File / Directory Watching
If you want to watch for changes to files or directories, then you should use chokidar.
Obtain Filesystem (Devices, Partitions) Information
fs-filesystem allows you to read the state of the filesystem of the host on which it is run. It returns information about both the devices and the partitions (volumes) of the system.
Misc.
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.
- Improve test coverage.
Note: If you make any big changes, you should definitely file an issue for discussion first.
Running the Test Suite
fs-extra contains hundreds of tests.
npm run lint
: runs the linter (standard)npm run unit
: runs the unit testsnpm run unit-esm
: runs tests for fs-extra/esm
exportsnpm test
: runs the linter and all tests
When running unit tests, set the environment variable CROSS_DEVICE_PATH
to the absolute path of an empty directory on another device (like a thumb drive) to enable cross-device move tests.
Windows
If you run the tests on the Windows and receive a lot of symbolic link EPERM
permission errors, it's
because on Windows you need elevated privilege to create symbolic links. You can add this to your Windows's
account by following the instructions here: http://superuser.com/questions/104845/permission-to-make-symbolic-links-in-windows-7
However, I didn't have much luck doing this.
Since I develop on Mac OS X, I use VMWare Fusion for Windows testing. I create a shared folder that I map to a drive on Windows.
I open the Node.js command prompt
and run as Administrator
. I then map the network drive running the following command:
net use z: "\\vmware-host\Shared Folders"
I can then navigate to my fs-extra
directory and run the tests.
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:
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:
License
Licensed under MIT
Copyright (c) 2011-2017 JP Richardson