1. W.R. Stevens books on Unix and Tcp/ip.
2. Rochkind's Advanced UNIX Programming.
3. Most of the Unix/Linux manual pages.
4. Bash FAQ
As a Unix systems programmer I would choose
1. Mythical Man Month
2. Jon Bentley's Programming Pearls.
3. K&R C and Stroustrup C++
4. A recent Java reference and Bloch's Java Puzzlers
5. a reference and cookbook for the language of your choice -- Python, Ruby, Perl, etc.
6. Google's style guides
As a Unix systems engineer, I would choose
As a Unix systems programmer I would choose