Bash useful resources:
- Advanced Bash-Scripting Guide
- Bash Guide for Beginners by Machtelt Garrels
- BASH Programming- Mike G mikkey
- Getting Started with BASH
- Google Shell Style Guide
- Learning the bash Shell
- Lhunath’s Bash Guide
- The Command Line Crash Course (also a Powershell reference)
- Conquering the Command Line - Mark Bates