How to execute shell command in Javascript

I don't know why the previous answers gave all sorts of complicated solutions. If you just want to execute a quick command like ls, you don't need async/await or callbacks or anything. Here's all you need - execSync:

const execSync = require('child_process').execSync;
// import { execSync } from 'child_process';  // replace ^ if using ES modules

const output = execSync('ls', { encoding: 'utf-8' });  // the default is 'buffer'
console.log('Output was:\n', output);

For error handling, add a try/catch block around the statement.

If you're running a command that takes a long time to complete, then yes, look at the asynchronous exec function.

function exec(cmd, handler = function(error, stdout, stderr){console.log(stdout);if(error !== null){console.log(stderr)}})
{
    const childfork = require('child_process');
    return childfork.exec(cmd, handler);
}

This function can be easily used like:

exec('echo test');
//output:
//test

exec('echo test', function(err, stdout){console.log(stdout+stdout+stdout)});
//output:
//testtesttest

If you are using npm you can use the shelljs package

To install: npm install [-g] shelljs

var shell = require('shelljs');
shell.ls('*.js').forEach(function (file) {
// do something
});

See more: https://www.npmjs.com/package/shelljs

Another post on this topic with a nice jQuery/Ajax/PHP solution:

shell scripting and jQuery

As far as I can tell, there is no built-in function, method or otherwise, in the official ECMAScript specification to run an external process. That said, extensions are allowed, see this note from the spec, for example:

NOTE Examples of built-in functions include parseInt and Math.exp. A host or implementation may provide additional built-in functions that are not described in this specification.

One such "host" is Node.js which has the child_process module. Let's try this code to execute the Linux shell command ps -aux, saved in runps.js, based on the child_process documentation:

const { spawn } = require('child_process');
const ps = spawn('ps', ['-aux']);

ps.stdout.on('data', (data) => {
  console.log(`stdout: ${data}`);
});

ps.stderr.on('data', (data) => {
  console.error(`stderr: ${data}`);
});

ps.on('close', (code) => {
  console.log(`child process exited with code ${code}`);
});

Which produces the following example output, running it in docker:

$ docker run --rm -v "$PWD":/usr/src/app -w /usr/src/app node:17-bullseye node ./runps.js
stdout: USER         PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root           1  0.0  0.8 319312 33888 ?        Ssl  11:08   0:00 node ./runps.js
root          13  0.0  0.0   6700  2844 ?        R    11:08   0:00 ps -aux

child process exited with code 0

The thing I like about this module, is that it's included with the Node.js distribution, no npm install ... needed.

If you search the Node.js code in github for spawn you will find references to the implementation in C or C++ in the engine. Modern browsers like Firefox and Chrome would be reluctant to extend JavaScript with such features, for obvious security reasons, even if the underlying engine such as V8 supports it.

On that note, it's better not to run our container as root, let's try the above example again, adding a random user this time.

$ docker run --rm -u 7000 -v "$PWD":/usr/src/app -w /usr/src/app node:17-bullseye node ./runps.js
stdout: USER         PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
7000           1  5.0  0.8 319312 33812 ?        Ssl  11:19   0:00 node ./runps.js
7000          13  0.0  0.0   6700  2832 ?        R    11:19   0:00 ps -aux

child process exited with code 0

Of course that's better but not enough. If this approach is used at all, more precautions must be taken, such as ensuring that no arbitrary user commands can be executed.

Windows 10

My version of Windows 10 still has Windows Script Host which can run JScript on the console with the wscript.exe or cscript.exe programs, i.e. no browser needed. To try it out you can open a PowerShell Windows Terminal. Save the following code into a file which you can call shell.js:

WScript.StdOut.WriteLine("Hallo, ECMAScript on Windows!");
WScript.CreateObject("WScript.Shell").run("C://Windows//system32//mspaint.exe");

And on the command line, run:

cscript .\shell.js

Which shows the following and opens Paint:

Microsoft (R) Windows Script Host Version 5.812
Copyright (C) Microsoft Corporation. All rights reserved.

Hallo, ECMAScript on Windows!

Other variations exist. Find the documentation applicable to your preferred JavaScript runtime environment.