Extended vs Perl regular expressions in episode 2 about library-shell-deprecated

[danmichaelo]

Probably because -P is not available in BSD grep (as found on e.g. Macs). And funnily enough, BSD grep does support \d with -E.. so the best cross-platform solution is probably ranges. Or keep the two solutions, but explain better.

In any case, the exercise requires knowledge of something that hasn't been teached (\d or [0-9]) afaics, so I wonder if it would be good to provide a hint.

[weaverbel]

@mawds We don't go into Perl at all, and I don't see us going there either so I would rather use terms that are comptaible with the shell, which we are teaching.

[mawds]

Thanks @danmichaelo . I didn't realise it was so different on the Mac!

Character classes are already covered. Extending this to include ranges might be a way of covering the material needed for the exercise? Let me know if you'd like me to submit a PR doing this.