title: get execFile stdOut on chunks
body: <p>I am trying to use execFile and log the stdOut that gives the percentage done on the task, but the callback function:</p>
  
  <pre><code>var child = require('child_process');
  
  child.execFile("path/to/the/file", options, function (error, stdout, stderr) {
      console.log('stdout: ' + stdout);
  });
  </code></pre>
  
  <p>Waits until the process is done and then logs everything at once. 
  How do i get the info while is being processed and log it in parts?, I have try this:</p>
  
  <pre><code>child.stdout.on('data', function (data) {
    console.log(data);
  });
  </code></pre>
  
  <p>But i get this error: <code>Cannot read property 'on' of undefined"</code></p>