Execute and get the output of a shell command in node.js

In a node.js, I'd like to find a way to obtain the output of a Unix terminal command. Is there any way to do this?

function getCommandOutput(commandString){
    // now how can I implement this function?
    // getCommandOutput("ls") should print the terminal output of the shell command "ls"
}

This is the method I'm using in a project I am currently working on.

var exec = require('child_process').exec;
function execute(command, callback){
    exec(command, function(error, stdout, stderr){ callback(stdout); });
};

Example of retrieving a git user:

module.exports.getGitUser = function(callback){
    execute("git config --global user.name", function(name){
        execute("git config --global user.email", function(email){
            callback({ name: name.replace("\n", ""), email: email.replace("\n", "") });
        });
    });
};

If you're using node later than 7.6 and you don't like the callback style, you can also use node-util's promisify function with async / await to get shell commands which read cleanly. Here's an example of the accepted answer, using this technique:

const { promisify } = require('util');
const exec = promisify(require('child_process').exec)

module.exports.getGitUser = async function getGitUser () {
  // Exec output contains both stderr and stdout outputs
  const nameOutput = await exec('git config --global user.name')
  const emailOutput = await exec('git config --global user.email')

  return { 
    name: nameOutput.stdout.trim(), 
    email: emailOutput.stdout.trim()
  }
};

This also has the added benefit of returning a rejected promise on failed commands, which can be handled with try / catch inside the async code.

You're looking for child_process

var exec = require('child_process').exec;
var child;

child = exec(command,
   function (error, stdout, stderr) {
      console.log('stdout: ' + stdout);
      console.log('stderr: ' + stderr);
      if (error !== null) {
          console.log('exec error: ' + error);
      }
   });

As pointed out by Renato, there are some synchronous exec packages out there now too, see sync-exec that might be more what yo're looking for. Keep in mind though, node.js is designed to be a single threaded high performance network server, so if that's what you're looking to use it for, stay away from sync-exec kinda stuff unless you're only using it during startup or something.