sed & awk: UNIX Power Tools (Nutshell Handbooks)
Bash Pocket Reference: Help for Power Users and Sys Admins
Classic Shell Scripting: Hidden Commands that Unlock the Power of Unix
Learning the vi and Vim Editors: Text Processing at Maximum Speed and Power
bash Cookbook: Solutions and Examples for bash Users
grep Pocket Reference: A Quick Pocket Reference for a Utility Every Unix User Needs (Pocket Reference (O'Reilly))
Wicked Cool Shell Scripts, 2nd Edition: 101 Scripts for Linux, OS X, and UNIX Systems
Managing Projects with GNU Make: The Power of GNU Make for Building Anything (Nutshell Handbooks)
Learning the Unix Operating System: A Concise Guide for the New User (In a Nutshell)
Linux Command Line and Shell Scripting Bible