Bash
Some useful links to explain the concepts of Bash Scripting
Concepts
http://www.thegeekstuff.com/2010/08/bash-shell-builtin-commands/
https://dev.to/awwsmm/101-bash-commands-and-tips-for-beginners-to-experts-30je
Conditional Statements, Loops
http://bencane.com/2014/01/27/8-examples-of-bash-if-statements-to-get-you-started/
https://superuser.com/questions/615043/while-loop-in-bash-until-file-size-does-not-change
https://unix.stackexchange.com/questions/247187/bash-if-not-multiple-conditions-without-subshell
https://www.cyberciti.biz/faq/howto-check-if-a-directory-exists-in-a-bash-shellscript/