I’m sure everybody reading this knows that you can invoke elisp commands from the eshell command line but if you’re like me you tend to forget it in the heat of the moment. That’s too bad because it’s often possible to mix a bit of elisp with a “normal” Unix shell command to produce a result more refined than possible with the standard command line alone.
Over at the Emacs subreddit, yubrshen has a nice example. The value in his post is not the specific task he implemented—there are plenty of ways of doing that—but in using elisp to generate intermediate data for the rest of the command. It’s worth taking a look at his example if only to help you remember to make use of it in the future.