Occasionally there's something you need to achieve, which would be really easy if only you could have it performed via Drush - some script that could be run on the server during an update or migration process, perhaps. But it all looks a bit too scary, right? "The task is tricky enough already, let's just do it some other way"?
Well, it's actually surprisingly easy to write your own Drush commands, and it's totally something worth learning. Let's take a look.