Shameless Self Promotion

— The Aaron Brady Story

Sun, Sep 25, 2016

I got a new job in a new place, and with that job comes a new set of programming languages.

I’ve been lucky to be able to mostly code in Python for the last few years. It’s my default language and the closest to the way that I think, but this has meant I’ve let other language skills that I have atrophy a bit. The most relevant of these is Ruby.

I posted before about, it’s a great way to get up and running with a new language, especially if you’re already a programmer or have a little experience. Generally speaking the solutions to the problems you’re given take you on a bit of a trip around the core concepts of each language and its standard library.

That being said, I was still reaching for Python and not for Ruby when solving problems. So I’ve decided that those those little “helper” things I would have done in Python will now be done in Ruby. I had to do a similar thing when I learned C (after BASIC); I kept sliding back to BASIC for tasks until I forced myself.

I’ve got a new broadband supplier and a new router set up. I was previously terminating my PPPoE on a Raspberry Pi, but now I’m just using the supplier’s router. Also my IP is way more unstable on this supplier, so I keep not being able to SSH in to my house - updating my record by hand isn’t going to cut it.

Previously I had this script:

IP=$(ip a | grep 'inet.*ppp0' | awk '{print $2}')
nsupdate -k /root/ddns.txt <<EOF
update delete 300 a
update add 300 a $IP

It relied on a BIND TSIG key being in /root/ddns.txt. Not having the IP terminate on the router means I’m going to have to use a third party service to find out my IP. I’ve chosen

The first draft of the code is pretty basic. It has hardcoded everything and doesn’t handle any errors, but it worked. A few commits later and the final version is over twice as long, mainly due to argument parsing and trying to be clever about our inputs.

It also gets an (almost) clean bill of health from Rubocop. It sports a Gemfile (for bundler) and a gemspec, so I can publish it on

To use it, you’ll need a BIND master server for your zone with a TSIG key configured. There’s examples in the README

I suspect not that many people run their own BIND for a small installation, but I much prefer using an RFC-ed protocol over just some proprietary or jerry-rigged REST API.