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memfs

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In-memory file-system with Node's fs API.

Package Exports

  • memfs
  • memfs/lib/node
  • memfs/lib/promises
  • memfs/lib/volume

This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (memfs) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

Readme

memfs

In-memory file-system with Node's fs API.

  • Node's fs API implemented, see API Status
  • 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

Install

npm install --save memfs

Usage

import { fs } from 'memfs';

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

Create a file system from a plain JSON:

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:

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

Use it for testing:

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

Create as many filesystem volumes as you need:

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 to create one filesystem from your in-memory volumes and the real disk filesystem:

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

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

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

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

import { patchRequire } from 'fs-monkey';

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

Docs

See also

  • spyfs - spies on filesystem actions
  • unionfs - creates a union of multiple filesystem volumes
  • linkfs - redirects filesystem paths
  • fs-monkey - monkey-patches Node's fs module and require function
  • libfs - real filesystem (that executes UNIX system calls) implemented in JavaScript

License

Unlicense - public domain.