# memfs 2.0

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

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

 - 100% of Node's `fs` API implemented, see [*API Status*](./docs/api-status.md)
 - Stores files in memory, in `Buffer`s
 - Throws same* errors as Node.js
 - Has concept of *i-nodes*
 - Implements *hard links*
 - Implements *soft links* (aka symlinks, symbolic links)
 - More testing coming soon*
 - 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)


## 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


## Dependencies

This package depends on the following Node modules: `buffer`, `events`,
`streams`, `path`.

It also uses `process` and `setImmediate` globals, but mocks them, if not
available.

[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.