[COFF] Re: Requesting thoughts on extended regular expressions in grep.

Hi Grant, If you want to understand: - the maths of regular expressions, - the syntax of regexps which these days expresses more than REs, and - the regexp engines in programs, the differences in how they work and what they match, and - how to efficiently steer an engine's internals then I recommend Jeffrey Friedl's Mastering Regular Expressions. http://regex.info/book.html Do you want speed of matching with some false positives or validation by regexp rather than post-lexing logic and to what depth, e.g. does this month have a ‘31st’? /^... .. ..:..:../ You'd said egrep, which is NDFA, but in other engines, alternation order can matter, e.g. ‘J’ starts the most months and some months have more days than others. /^(J(an|u[nl])|Ma[ry]|A(ug|pr)|Oct|Dec|... -- Cheers, Ralph.