spawncommand

spawnCommand

yarn add -E spawncommand

This package is a wrapper around child_process.spawn methods to set .promise property on the returned ChildProcess instances. The promise will be fulfilled on process exit with an object consisting of code, stdout and stderr properties, where:

• code is the exit code
• stdout is all data the process wrote to stdout
• stderr is all data the process wrote to stderr

The promise will be rejected if an error was encountered when trying to spawn the process.

/* yarn example/spawncommand.js */
import spawnCommand from 'spawncommand'

(async () => {
  const { promise } = spawnCommand('echo', ['hello world'])
  const { stderr, stdout, code } =  await promise

  console.log(stderr) // undefined
  console.log(stdout) // hello world\n
  console.log(code) // 0
})()

Because the returned object is a ChildProcess, all its properties can be accessed.

/* yarn example/pipe.js */
import spawnCommand from 'spawncommand'

(async () => {
  const { stdout, promise } = spawnCommand('echo', ['hello world'])

  stdout.pipe(process.stdout)
  await promise
})()

fork

It is also possible to fork a Node.js process and execute a module in it.

/* yarn example/fork.js */
import { resolve } from 'path'
import { fork } from 'spawncommand'

const MODULE_PATH = resolve(__dirname, 'example/spawn.js')

;(async () => {
  const { promise } = fork('example/spawn.js', [], {
    stdio: 'pipe',
  })
  const { stdout } =  await promise
  console.log(stdout) // same output as example/spawn.js
})()

Make sure to pass pipe option to be able to gather stderr and stdout streams (or an array for versions of Node.js when this does not work).

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(c) Art Deco Code 2018