spawncommand

spawnCommand

SpawnCommand will run the spawn or fork methods from the child_process module, and add a promise property to the returned process instance. The promise will be resolved on process exit with an object consisting of code, stdout and stderr properties.

yarn add -E spawncommand

Table Of Contents

• Table Of Contents
• API
  • Types
    • ChildProcessWithPromise
    • PromiseResult
  • spawn(module: string, args: string[], options?: SpawnOptions): ChildProcessWithPromise
  • fork(module: string, args: string[], options?: ForkOptions): ChildProcessWithPromise
• Copyright

API

SpawnCommand can be used by importing the default spawn and named fork exports.

import spawn, { fork } from 'spawncommand'

Types

The package's main type is ChildProcessWithPromise which enriches the standard ChildProcess with a promise property.

import('child_process').ChildProcess ChildProcess

ChildProcess ChildProcessWithPromise: A child process with an extra promise property.

Name	Type	Description	Default
promise*	Promise.<PromiseResult>	A promise resolved when the process exits.	-

PromiseResult

Name	Type	Description	Default
stdout*	string	The accumulated result of the stdout stream.	-
stderr*	string	The accumulated result of the stderr stream.	-
code*	number	The code with which the process exited.	-

spawn(
  module: string,
  args: string[],
  options?: SpawnOptions,
): ChildProcessWithPromise

Spawns a command and returns a ChildProcess instance with the promise property resolved on exit. The promise will be rejected if an error was encountered when trying to spawn the process.

import('child_process').SpawnOptions SpawnOptions

import spawn from 'spawncommand'

(async () => {
  const { promise } = spawn('echo', ['hello world'])
  const { stderr, stdout, code } =  await promise
  console.log(JSON.stringify({
    stderr, stdout, code,
  }, null, 2))
})()

{
  "stderr": "",
  "stdout": "hello world\n",
  "code": 0
}

The returned object is a ChildProcess and all of its properties can be accessed in the standard way.

import spawnCommand from 'spawncommand'

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

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

hello world

fork(
  module: string,
  args: string[],
  options?: ForkOptions,
): ChildProcessWithPromise

Forks a Node.js module and adds a promise property to the returned ChildProcess.

import { fork } from 'spawncommand'

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

{
  "stderr": "",
  "stdout": "hello world\n",
  "code": 0
}

The pipe option needs to be set in order to gather the output of the stderr and stdout streams (or an array for older versions of Node.js when this does not work).

Copyright

(c) Art Deco 2018

Changelog

2.1.0

• [feature] Correct JSDoc for the ForkOptions and SpawnOptions.
• [doc] Compile with documentary.
• [build] Build with alamode

15 May 2018