Shell Parameters (Bash Reference Manual)| www.gnu.org
Tilde Expansion (Bash Reference Manual)| www.gnu.org
The Shopt Builtin (Bash Reference Manual)| www.gnu.org
Learn how to do math arithmetic with integer and floating-point in Bash. Includes addition, subtraction, division, multiplication, and also floating-point precision.| Shell Tips!
4 Patterns| raimonster.com