30 Oct
2017
30 Oct
'17
9:26 a.m.
-------- Original Message -------- The first line is essentially random, the second line will be all the same character of a limited number of possibles (=, - and maybe a couple more). The lines can probably be required to be the same length but it would be nice if they didn't have to be. It would be OK to have multiple REs, one for each possible 'underline' character.
Context is everything. Why are you trying to do this with a regular expression and what implementation will you be using?
Something like /([-_=])\1{3,}/ will match the underline part (the rest is straightforward) in some implementations but not all allow you to use backrefs in the match.
/.{4,}\n([-_=])\1{3,}/ ought to match what you've described. Again... it depends ;)
Steve