seriously like the best async child process library
Based upon child-process-async,
but more thorough, because that package doesn't seem very actively maintained.
promisify-child-process provides a drop-in replacement for the
original child_process functions, not just duplicate methods that
return a Promise. So when you call exec(...) we still return a
ChildProcess instance, just with .then(), .catch(), and .finally() added to
make it promise-friendly.
npm install --save promisify-child-processIf you are using a old version of Node without built-in Promises or
Object.create, you will need to use polyfills (e.g. @babel/polyfill).
// OLD:
const { exec, spawn, fork, execFile } = require('child_process')
// NEW:
const { exec, spawn, fork, execFile } = require('promisify-child-process')You must now pass maxBuffer or encoding to spawn/fork if you want to
capture stdout or stderr.
The child process promise will only resolve if the process exits with a code of 0.
If it exits with any other code, is killed by a signal, or emits an 'error' event,
the promise will reject.
exec and execFile capture stdout and stderr by default. But spawn and
fork don't capture stdout and stderr unless you pass an encoding or
maxBuffer option:
const { spawn } = require('promisify-child-process');
async function() {
// captures output
const { stdout, stderr } = await spawn('ls', [ '-al' ], {encoding: 'utf8'});
const { stdout, stderr } = await spawn('ls', [ '-al' ], {maxBuffer: 200 * 1024});
// BUG, DOESN'T CAPTURE OUTPUT:
const { stdout, stderr } = await spawn('ls', [ '-al' ]);
}If the child process promise rejects, the error may have the following additional properties:
code- the process' exit code (if it exited)signal- the signal the process was killed with (if it was killed)stdout- the capturedstdout(if output capturing was enabled)stderr- the capturedstderr(if output capturing was enabled)
If for any reason you need to wrap a ChildProcess you didn't create,
you can use the exported promisifyChildProcess function:
const { promisifyChildProcess } = require('promisify-child-process');
async function() {
const { stdout, stderr } = await promisifyChildProcess(
some3rdPartyFunctionThatReturnsChildProcess(),
{ encoding: 'utf8' }
)
}async function() {
const { stdout, stderr } = await exec('ls -al');
// OR:
const child = exec('ls -al', {});
// do whatever you want with `child` here - it's a ChildProcess instance just
// with promise-friendly `.then()` & `.catch()` functions added to it!
child.stdin.write(...);
child.stdout.pipe(...);
child.stderr.on('data', (data) => ...);
const { stdout, stderr } = await child;
}async function() {
const { stdout, stderr, code } = await spawn('ls', [ '-al' ], {encoding: 'utf8'});
// OR:
const child = spawn('ls', [ '-al' ], {});
// do whatever you want with `child` here - it's a ChildProcess instance just
// with promise-friendly `.then()` & `.catch()` functions added to it!
child.stdin.write(...);
child.stdout.pipe(...);
child.stderr.on('data', (data) => ...);
const { stdout, stderr, code } = await child;
}
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