Fair enough point but for many years I wasn't aware of what bash COULD do. I mean one should get to learn more about [[]] and how it does regexps and while read

Fair enough point but for many years I wasn't aware of what bash COULD do. I mean one should get to learn more about [[]] and how it does regexps and while read loops: ls *.txt | { while read FILENAME; do <something> to $FILENAME; done; } and so on. Once you know, you can get a lot done on e.g. a docker image, without having to install lots of other things first.