The Unix Programming Environment

This is the Kernighan and Pike classic.

Although it is getting old and is incomplete (no reference to Perl, for example), this is still a valuable and useful book. More than just command listings, it really gets into the philosophy of why Unix is the way it is, and that understanding can help you tremendously.

Don't let the "Programming" scare you away if you aren't into C. A lot of this is shell programming, using sed and awk, that sort of thing.

I recently lost my ancient copy, and the moment I realized that, I ordered a new copy. That ought to say something.