Arnold Robbins 
bash Quick Reference [PDF ebook] 

In this quick reference, you’ll find everything you need to know about the bash shell. Whether you print it out or read it on the screen, this PDF gives you the answers to the annoying questions that always come up when you’re writing shell scripts: What characters do you need to quote? How do you get variable substitution to do exactly what you want? How do you use arrays? It’s also helpful for interactive use.If you’re a Unix user or programmer, or if you’re using bash on Windows, you’ll find this quick reference indispensable.