learnbyexample

Why would it print the colon?

Regex syntax and features vary between implementations. \d isn't supported by BRE/ERE flavors.

GNU grep supports PCRE, so you can use grep -oP '/dev/loop\d' or grep -o '/dev/loop[0-9]' if you are matching only one digit character.

Thanks a lot for the feedback :)

Already done grep, sed, coreutils, cli basics and more. See https://learnbyexample.github.io/learn_gnuawk/buy.html#book-list for links.

Well, I'm not going to even try understanding the various features used in that sed command. I do know how to use basic loops with labels, but I never bothered with all the buffer manipulation stuff. I'd rather use awk/perl/python for those cases.

This might work, but I think it is best to not tinker further if you already have a working script (especially one that you understand and can modify further if needed).

perl -pe 's/\[[^]]+\]\((?!https?)[^#]*#\K[^)]+(?=\))/lc $&=~s:%20|\d\K\.(?=\d):-:gr/ge'

Hmm, OP mentioned "Only edit what’s between parentheses" - don't see anywhere that whole URL shouldn't be changed...

Here's a solution with perl (assuming you don't want to change http/https after the start of ( instead of start of a line):

perl -pe 's/\[[^]]+\]\(\K(?!https?)[^)]+(?=\))/lc $&=~s|%20|-|gr/ge' ip.txt

• e flag allows you to use Perl code in the substitution portion.
• \[[^]]+\]\(\K match square brackets and use \K to mark the start of matching portion (text before that won't be part of $&)
• (?!https?) don't match if http or https is found
• [^)]+(?=\)) match non ) characters and assert that ) is present after those characters
• $&=~s|%20|-|gr change %20 to - for the matching portion found, the r flag is used to return the modified string instead of change $& itself
• lc is a function to change text to lowercase

GNU datamash (https://www.gnu.org/software/datamash/alternatives/) - handy tool for data munching. There's also https://github.com/BurntSushi/xsv

Check out my chapter on GNU grep BRE/ERE for those wanting to learn this regex flavor: https://learnbyexample.github.io/learn_gnugrep_ripgrep/breere-regular-expressions.html (there's also another chapter for PCRE)

See also https://github.com/TomWright/dasel

I use Vim ;)

Python itself provides IDLE, which is good enough for beginners. https://thonny.org/ is another good one for beginners.

As mentioned by others, Jetbrains is good for many languages. https://www.kdevelop.org/ is another option.