async-child-process

A simple Promise-based API for working with ChildProcesses.

Usage

npm install --save async-child-process

join(child: ChildProcess): Promise<Result>

Waits for child to exit.

Returns a Promise that:

• will resolve {code: 0} if child exits with code 0
• with reject with an error otherwise
  • error.code will be the exit code if the child exited normally
  • error.signal will be the signal the child was terminated with, if any
  • Note: if child emits an error, it may be the rejection reason and it may not have code or signal

Example:

import {exec} from 'child_process'
import {join} from 'async-child-process'

async function test() {
  await join(exec('echo hello world'))
}

kill(child: ChildProcess, signal?: string): Promise<void>

Sends a signal to child and waits for it to exit.

Returns a Promise that:

• will resolve once child is killed
• will reject with an error if child emits one

Example:

import {exec} from 'child_process'
import {kill} from 'async-child-process'

async function test() {
  const child = exec(`node -e 'setTimeout(() => console.log("finally!"), 1e11)'`)
  await kill(child)
}

childPrinted(child: ChildProcess, predicate: (output: string) => boolean | RegExp, stream?: 'stdout' | 'stderr'): Promise<string>

Waits for child to print something to its stdout and/or stderr. Returns a promise that:

• will resolve with the message that matched predicate or
• will reject if child exited or errored before printing a message that matched predicate

Arguments:

• child: the ChildProcess to listen to
• predicate: childPrinted will wait until child's stream(s) output a message matching the predicate
• stream: which of child's streams to listen to, omit to listen to both stdout and stderr

Example:

import {exec} from 'child_process'
import {childPrinted} from 'async-child-process'

async function test() {
  const child = exec(`webpack --config webpack.config.dev.js`)
  await childPrinted(child, /webpack built in \d+ ms/)
}

execAsync(command: string, options?: Object): Promise<Result>

Like exec, but returns a Promise that:

• will resolve with {stdout: string, stderr: string} from running command if it exited with code 0
• will reject with an error otherwise
  • error.code will be the exit code if the child exited normally
  • error.signal will be the signal the child was terminated with, if any
  • Note: if child emits an error, it may be the rejection reason and it may not have code or signal

Example:

import {execAsync} from 'async-child-process'

async function test() {
  const {stdout} = await execAsync('docker-compose port webapp 80')
  const testUrl = stdout.trim()
}