stream-line-reader

Read through a stream of lines on-demand

Installation

$ npm install stream-line-reader

Usage

const { spawn } = require('child_process');
const { StreamLineReader } = require('stream-line-reader');

async function example () {
  const child = spawn('my-calculator-program');
  const lines = new StreamLineReader(child.stdout);

  console.log(await lines.readUntil('Done startup'));
  // -> ['Starting...', 'Done startup']

  child.stdin.write('1+2\n');
  console.log(await lines.readUntil(/^Answer:/));
  // -> ['Question: 1+2', 'Calculating...', 'Answer: 3']

  child.stdin.write('3+4\n');
  console.log(await lines.readUntil(line => line.startsWith('Answer:')));
  // -> ['Question: 3+4', 'Calculating...', 'Answer: 7']

  child.stdin.end();
  console.log(await lines.readRemaining());
  // -> ['Bye!', '', '']
}

Instance can be created with a single stream, or an array of streams, in which case they are merged (interleaved), to be read as one stream.

If during a call to .readUntil() the stream ends without emitting a matching line, an error will be raised with details for debugging.

Instances also have a .readBuffered() method for when some time has passed and you just want to read whatever lines have become available. It takes no arguments and returns synchronously an array of lines.