Read through a stream of lines on-demand
$ npm install stream-line-reader
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.