Bash has had some nice minor features and syntax sugar added, but the fundamentals are entirely the same. All the examples in the book work just the same today as they did when it was written.

What was added in 4.X or 5.x that you can’t live without? What do you think has changed that merits inclusion?

It’s a 36 y/o language, mate. I still reference my copy all the time, and found it to be a great definitive resource when I was learning.

How many bash 4/5 features are you seriously using on a regular basis? What do you think is out-of-date?

I highly recommend O’Reilly’s Learning the Bash Shell in paperback form: https://www.oreilly.com/library/view/learning-the-bash/0596009658/.

The other responses you’ve received so far don’t offer much insight into the historical background and underlying mechanics of the shell, which are crucial to understanding the "Why?"s of command-line quirkiness.

For anyone who missed it, the Windows Terminal team is infamous for claiming that it would require PhD level expertise to implement some basic optimizations suggested in a Github thread. Within a few hours, another developer countered that claim by submitting a functioning PR with said improvements implemented.

Windows Terminal team lead Dustin Howett then went on to double down on the original claim that said optimizations were unfeasable, and publicly attacked the author of the original suggestion thread on Hacker News. He issued an extremely half-assed apology and is still a Micro$haft employee to this day.

https://blog.royalsloth.eu/posts/it-takes-a-phd-to-develop-that/

Synology runs a proprietary OS OOTB that’s had multiple sloppy vulns exposing full remote access to users’ files. Putting your data in the hands of fuckups who have and will continue to leak it is the opposite of total control.

It’s completely trivial to store any data you want to in a cloud provider 100% securely just by piping it through openssl before uploading.