BASH, aka Bourne Again SHell, is probably the most wide-spread shell for *nix like systems (no discussions about this, please; if you prefer some other, just enjoy, I’m not making anyone use bash).
There are many intros out there, but most of them are more about syntax etc., with just a little practical use.
I wrote quite a few bash scripts, but it’s not my primary “language” of choice; so I often need a fast reminder, rather than textbook. That’s why I compiled this simple “list” or “intro” to use as a reference. Maybe someone else will find this useful also.