One example was being able to write native gems so that I integrate ruby directly with other C based services. Writing ruby code that directly interacts with mail servers, databases in a thread safe manor was quite useful.

Like learning assembly, sometimes it’s not directly useful, but it does make you write better code; since you understand more of what’s under the hood.

Lol. 20k.

I was a competent programmer and a Linux user, but system stuff always seemed like black magic.

With this book I was able to tackle much harder problems