memfs

[![][chat-badge]][chat] [![][npm-badge]][npm-url] [![][travis-badge]][travis-url]

In-memory file-system with [Node's fs API](https://nodejs.org/api/fs.html).

• Node's fs API implemented, see [_old API Status_](./docs/api-status.md), missing list, [missing opendir](https://github.com/streamich/memfs/issues/663)
• Stores files in memory, in Buffers
• Throws sameish\* errors as Node.js
• Has concept of _i-nodes_
• Implements _hard links_
• Implements _soft links_ (aka symlinks, symbolic links)
• Permissions may\* be implemented in the future
• Can be used in browser, see [memfs-webpack](https://github.com/streamich/memfs-webpack)

Install

shell
npm install --save memfs

Usage

js
import { fs } from 'memfs';

fs.writeFileSync('/hello.txt', 'World!');
fs.readFileSync('/hello.txt', 'utf8'); // World!

Create a file system from a plain JSON:

js
import { fs, vol } from 'memfs';

const json = {
  './README.md': '1',
  './src/index.js': '2',
  './node_modules/debug/index.js': '3',
};
vol.fromJSON(json, '/app');

fs.readFileSync('/app/README.md', 'utf8'); // 1
vol.readFileSync('/app/src/index.js', 'utf8'); // 2

Export to JSON:

js
vol.writeFileSync('/script.sh', 'sudo rm -rf *');
vol.toJSON(); // {"/script.sh": "sudo rm -rf *"}

Use it for testing:

js
vol.writeFileSync('/foo', 'bar');
expect(vol.toJSON()).toEqual({ '/foo': 'bar' });

Create as many filesystem volumes as you need:

js
import { Volume } from 'memfs';

const vol = Volume.fromJSON({ '/foo': 'bar' });
vol.readFileSync('/foo'); // bar

const vol2 = Volume.fromJSON({ '/foo': 'bar 2' });
vol2.readFileSync('/foo'); // bar 2

Use memfs together with [unionfs][unionfs] to create one filesystem from your in-memory volumes and the real disk filesystem:

js
import * as fs from 'fs';
import { ufs } from 'unionfs';

ufs.use(fs).use(vol);

ufs.readFileSync('/foo'); // bar

Use [fs-monkey][fs-monkey] to monkey-patch Node's require function:

js
import { patchRequire } from 'fs-monkey';

vol.writeFileSync('/index.js', 'console.log("hi world")');
patchRequire(vol);
require('/index'); // hi world

Docs

• [Reference](./docs/reference.md)
• [Relative paths](./docs/relative-paths.md)
• [API status](./docs/api-status.md)
• [Dependencies](./docs/dependencies.md)

See also

• [spyfs][spyfs] - spies on filesystem actions
• [unionfs][unionfs] - creates a union of multiple filesystem volumes
• [linkfs][linkfs] - redirects filesystem paths
• [fs-monkey][fs-monkey] - monkey-patches Node's fs module and require function
• [libfs](https://github.com/streamich/full-js/blob/master/src/lib/fs.ts) - real filesystem (that executes UNIX system calls) implemented in JavaScript

[chat]: https://onp4.com/@vadim/~memfs [chat-badge]: https://img.shields.io/badge/Chat-%F0%9F%92%AC-green?style=flat&logo=chat&link=https://onp4.com/@vadim/~memfs [npm-url]: https://www.npmjs.com/package/memfs [npm-badge]: https://img.shields.io/npm/v/memfs.svg [travis-url]: https://travis-ci.org/streamich/memfs [travis-badge]: https://travis-ci.org/streamich/memfs.svg?branch=master [memfs]: https://github.com/streamich/memfs [unionfs]: https://github.com/streamich/unionfs [linkfs]: https://github.com/streamich/linkfs [spyfs]: https://github.com/streamich/spyfs [fs-monkey]: https://github.com/streamich/fs-monkey

License

[Unlicense](./LICENSE) - public domain.