Superuser question: How do I learn bash shell scripting? – a useful list of resources
Bash Scripting Tutorial – Linux Shell Script and Command Line for Beginners – a single page guide
https://tldp.org/LDP/Bash-Beginners-Guide/html/index.html
https://www.makeuseof.com/tag/beginners-guide-mac-terminal/
grep
grep -r 'text goes here' path_goes_here
Bash HereDoc Tutorial With Examples
bashrc vs. bash_profile: What Is the Difference?
– also interactive vs non-interactive and log-in vs non-log-in