How to out output live console.log with exec in node

Question

Is there a way to run a command line command from within a node app and get the output to be live?

eg:

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

exec( 'nightwatch --config nightwatch_dev.json  ', function( error, stdout, stderr ){
    console.log( stdout );
});

or:

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

exec( 'rsync -avz /some/folder/ john@8.8.8.8:/some/folder/', function( error, stdout, stderr ){
    console.log( stdout );
});

There are many many instances where it would be nice and easy to script something up in node but the output is only dumped to the terminal after the command has finished.

Cheers J

Answer 1

If you want results as they occur, then you should use spawn() instead of exec(). exec() buffers the output and then gives it to you all at once when the process has finished. spawn() returns an event emitter and you get the output as it happens.

Examples here in the node.js doc for .spawn():