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@license Apache-2.0

Copyright (c) 2018 The Stdlib Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

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distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# stdin

> Read data from [`stdin`][@stdlib/streams/node/stdin].

<section class="usage">

## Usage

```javascript
var stdin = require( '@stdlib/process/read-stdin' );
```

#### stdin( \[encoding,] clbk )

Reads data from [`stdin`][@stdlib/streams/node/stdin].

<!-- run-disable -->

```javascript
function onRead( error, data ) {
    if ( error ) {
        return console.error( 'Error: %s', error.message );
    }
    console.log( data.toString() );
    // => '...'
}

stdin( onRead );
```

By default, returned `data` is a [`Buffer`][buffer]. To return a `string` of a specified encoding, provide an `encoding` parameter.

<!-- run-disable -->

```javascript
function onRead( error, data ) {
    if ( error ) {
        return console.error( 'Error: %s', error.message );
    }
    console.log( data );
    // => '...'
}

stdin( 'utf8', onRead );
```

When a file's calling Node.js process is running in a [TTY][tty] context (i.e., no [`stdin`][@stdlib/streams/node/stdin]), `data` will either be an empty [`Buffer`][buffer] (no encoding provided) or an empty `string` (encoding provided).

<!-- run-disable -->

```javascript
var stream = require( '@stdlib/streams/node/stdin' );

function onRead( error, data ) {
    if ( error ) {
        return console.error( 'Error: %s', error.message );
    }
    console.log( data );
    // => ''
}

stream.isTTY = true;

stdin( 'utf8', onRead );
```

</section>

<!-- /.usage -->

<section class="examples">

## Examples

<!-- run-disable -->

<!-- eslint no-undef: "error" -->

```javascript
var string2buffer = require( '@stdlib/buffer/from-string' );
var stream = require( '@stdlib/streams/node/stdin' );
var stdin = require( '@stdlib/process/read-stdin' );

function onRead( error, data ) {
    if ( error ) {
        console.error( 'Error: %s', error.message );
    } else {
        console.log( data.toString() );
        // => 'beep boop'
    }
}

// Fake not being in a terminal context:
stream.isTTY = false;

// Provide a callback to consume all data from `stdin`:
stdin( onRead );

// Push some data to `stdin`:
stream.push( string2buffer( 'beep' ) );
stream.push( string2buffer( ' ' ) );
stream.push( string2buffer( 'boop' ) );

// End the stream:
stream.push( null );
```

</section>

<!-- /.examples -->

<section class="links">

[buffer]: https://nodejs.org/api/buffer.html

[tty]: https://nodejs.org/api/tty.html#tty_tty

[@stdlib/streams/node/stdin]: https://www.npmjs.com/package/@stdlib/streams-node-stdin

</section>

<!-- /.links -->