How to see stdout of a phantomjs child process using node.js?

Question

In the following node.js code, I normally have to wait for the phantomjs child process to terminate to get the stdout. I am wondering if there is any way to see the stdout while the phantomjs child process is running?

var path = require('path')
var childProcess = require('child_process')
var phantomjs = require('phantomjs')
var binPath = phantomjs.path

var childArgs = [
  path.join(__dirname, 'phantomjs-script.js'),
]

childProcess.execFile(binPath, childArgs, function(err, stdout, stderr) {
  // handle results 
})

Answer 1

You can spawn PhantomJS as a child process and subscribe to its stdout and stderr streams to get data realtime (whereas exec only returns buffered result after program execution).

var path = require('path');
var phantomjs = require('phantomjs');
var spawn = require('child_process').spawn;

var childArgs = [
  path.join(__dirname, 'phantomjs-script.js'),
];
var child = spawn(phantomjs.path, childArgs);

child.stdout.on('data', function (data) {
  console.log('stdout: ' + data);
});

child.stderr.on('data', function (data) {
  console.log('stderr: ' + data);
});

child.on('close', function (code) {
  console.log('child process exited with code ' + code);
});