bash

• bash Idioms. Write Powerful, Flexible, Readable Shell Scripts by Carl Albing and JP Vossen - 200 pages
• Effective Shell
• Amber The Programming Language compiled to Bash.
  • SecurityLab.ru / Amber: ваша новая суперсила в мире непонятных bash-скриптов
• freeCodeCamp.org / Bash Array – How to Declare an Array of Strings in a Bash Script

Wikipedia

• Shebang (Unix)

LOLZ

• This second form (function_name () { command... }) will cheer the hearts of C programmers.

Pipelines

Dr. Donald Knuth, the legendary computer scientist and Stanford University Professor was asked to write a program that:

• Reads a text file and determines n frequently used words
• Prints out a sorted list of words along with their frequencies

Knuth's solution was a ten-page Pascal program! Doug McIlroy realized the same with just the following shell script:

tr -cs A-Za-z ' n ' | tr A-Z a-z | sor t | uniq -c | sort -rn | sed ${1}q

So much for the power of command composition.