title: tricky POS printer design question
body: <p>I'm looking at designing an application to run on POS terminals in addition to the software already installed. I'd like it to receive POS printer commands and then on some of them intercept and modify them. So for example when a receipt is printed, we'd like to add a custom reference number in the middle of it without having to modify the third party POS applications. </p>
  
  <p>I'd love to hear peoples suggestions on the best way to approach this as reading through the POS specs, it doesn't seem trivial.</p>