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			# first-chunk-stream [![Build Status](https://travis-ci.org/sindresorhus/first-chunk-stream.svg?branch=master)](https://travis-ci.org/sindresorhus/first-chunk-stream)

			> Transform the first chunk in a stream

			Useful if you want to do something to the first chunk.

			You can also set the minimum size of that chunk.


			## Install

			```sh
			$ npm install --save first-chunk-stream
			```


			## Usage

			```js
			var fs = require('fs');
			var concat = require('concat-stream');
			var firstChunk = require('first-chunk-stream');

			// unicorn.txt => unicorn rainbow
			// `highWaterMark: 1` means it will only read 1 byte at the time
			fs.createReadStream('unicorn.txt', {highWaterMark: 1})
			.pipe(firstChunk({minSize: 7}, function (chunk, enc, cb) {
			this.push(chunk.toUpperCase());
			cb();
			}))
			.pipe(concat(function (data) {
			console.log(data);
			//=> UNICORN rainbow
			}));
			```


			## API

			### firstChunk([options], transform)

			#### options.minSize

			Type: `number`

			The minimum size of the first chunk.

			#### transform(chunk, encoding, callback)

			Required
			Type: `function`

			The [function](http://nodejs.org/docs/latest/api/stream.html#stream_transform_transform_chunk_encoding_callback) that gets the first chunk.

			### firstChunk.ctor()

			Instead of returning a [stream.Transform](http://nodejs.org/docs/latest/api/stream.html#stream_class_stream_transform_1) instance, `firstChunk.ctor()` returns a constructor for a custom Transform. This is useful when you want to use the same transform logic in multiple instances.


			## License

			MIT © [Sindre Sorhus](http://sindresorhus.com)