Can you still write Bash scripts and aliases in macos High Sierra?

You can still write Bash v3.2.57 scripts and assign aliases in your dot startup files (e.g. .bash_profile, .bashrc). I mentioned the Bash version because most of the examples of Bash syntax on the web are from those using Bash v4.n on Linux. Bash v4 unique features are not backwards compatible.

alias tt='open -a Textastic "$@"'

tt ~/Desktop/foo.py

Where Textastic is an advanced programmer's editor available from the Mac App Store.

Oh, about 32 years ago on SunOS. ;-). Or via Google search. Creating Bash Aliases.

Here is a downloadable link to the Bash-3.2 documentation. Double-click on this gzipped content in the Finder and you will have a bash-doc-3.2 folder containing several PDF including the Bash 3.2 Reference Manual.

https://tiswww.case.edu/php/chet/bash/bashref.html

N to sure I know that you need, but on Aliases,,,

https://discussions.apple.com/thread/8577757

https://scriptingosx.com/2017/04/about-bash_profile-and-bashrc-on-macos/