title: Node.js Piping-how to write?
body: <p>I need to figure out how I can give exec permissions to write.</p>
  
  <pre><code>var exec = require('child_process').exec;
  exec('ffmpeg -i file.ogv -f mp4 file.mp4', function(err, stdout, stderr){
  });
  // ffmpeg converts one video file to another.
  </code></pre>
  
  <p>How can I do this?</p>