stream.pipeline & pump with process.stdout 🤔

random.js

'use strict'

const {randomBytes} = require('crypto')
const {Readable, PassThrough, pipeline} = require('stream')
const pump = require('pump')

const random = (amount) => {
	let bytes = 0
	function read (size) {
		size = Math.min(size, amount - bytes)
		bytes += size
		const end = bytes === amount

		const that = this
		setTimeout(() => {
			that.push(randomBytes(size))
			if (end) that.push(null)
		}, 100)
	}
	return new Readable({read})
}

const printRandom = (pipeFn, wrapStdout, cb) => {
	console.error('pipeFn', pipeFn.name, 'wrapStdout', wrapStdout)

	let dest = process.stdout
	if (wrapStdout) {
		dest = new PassThrough()
		dest.pipe(process.stdout)
	}

	pipeFn(
		random(10 * 1024), // 10kb
		dest,
		(err) => {
			if (err) {
				console.error(err)
				process.exit(1)
			}
			console.error('done')
			cb()
		},
	)
}

const pipeFn = ({pipeline, pump})[process.argv[2]]
const wrapStdout = process.argv[3] === 'true'

printRandom(pipeFn, wrapStdout, () => {
	printRandom(pipeFn, wrapStdout, () => {
		printRandom(pipeFn, wrapStdout, () => {})
	})
})

test.sh

#!/bin/sh

node -v
# v15.5.0

node random.js pipeline false | wc -c
# pipeFn pipeline wrapStdout false
# done
# pipeFn pipeline wrapStdout false
#    10240

node random.js pipeline true | wc -c
# pipeFn pipeline wrapStdout true
# done
# pipeFn pipeline wrapStdout true
# done
# pipeFn pipeline wrapStdout true
# done
#    30720

node random.js pump false | wc -c
# pipeFn pump wrapStdout false
#    10240

node random.js pump true | wc -c
# pipeFn pump wrapStdout true
# done
# pipeFn pump wrapStdout true
# done
# pipeFn pump wrapStdout true
# done
#    30720