Comment by tonysdg

I'd add that The C Programming Language should be seen as a tutorial (albeit an older one that no longer is fully up-to-date in best practices, in my experience) that can serve as a reference in a pinch (it skimps a bit on the corner cases if memory serves). Advanced Programming in the Unix Environment, conversely, should be seen as a reference book with fantastic examples and discussion on error handling -- yes, you can use it as a tutorial, but it's a tad dense and you'll likely never need a lot of it.