# File system

## Introduction

Custom operators for working with files

## Usage

### Nabu

When using the Nabu storage engine, File system operators are included by default.

### Memory storage engine

If you are using the memory storage engine the fs plugin must be configured

```typescript
import Memory from '@tashmet/memory';
import mingo from '@tashmet/mingo';
import fs from '@tashmet/fs';

const store = Memory
  .configure({})
  .use(mingo())
  .use(fs())
  .bootstrap();
```

## Expression operators

### $lstat

`{ $lstat: <expression> }`

### $fileExists

`{ $fileExists: <expression> }`

Expression operator that resolves to `true` if the file specified in the expression exists on the file system.

### $readFile

`{ $readFile: <expression> }`

Expression operator that resolves to the content of the file specied in the expression

### $basename

`{ $basename: <path> | [<path>, <suffix>] }`

Expression operator that returns the last portion of a path, similar to the Unix basename command.

See: <https://nodejs.org/api/path.html#pathbasenamepath-suffix>

### $extname

`{ $basename: <path> }`

See: <https://nodejs.org/api/path.html#pathextnamepath>

### $dirname

`{ $dirname: <expression> }`

### $relativePath

`{ $dirname: <expression> }`

### $joinPaths

`{ $joinPaths: <expression> }`

***

## Aggregation stages

### $writeFile

Write each document in the stream to file

```typescript
{
  $writeFile: {
    content: 'content to write (expression or actual data)',
    path: 'path to file',
    overwrite: 'true if file should be overwritten if it exists',
  }
}
```

### $glob

`{ $glob: <expression> }`

### $globMatch

`{ $globMatch: <expression> }`