Re: Documentation request: sed, grep and other regexs

[Karl Berry]

    Somewhere, it would be good to have a comparison of the regular
    expressions of the various tools - sed, awk, grep, perl - to teach
    the differences, if any, and commonalities.

I fully agree.

FWIW, many years ago I helped make a standalone regex distribution,
including an extensive manual.  It was aimed at programmers more than
users, but it could serve as a starting point.  (It is certainly very
much out of date by now, so would need plenty of updating anyway.)
ftp://ftp.gnu.org/gnu/regex

Another possible place for such a section would be the libc manual,
although of course that is also aimed at programmers.

Perhaps a separate manual on user-level regular expressions is the way to go.

Here's a web page that may be of interest (there's a summary of what
supports what near the end):
http://sitescooper.org/tao_regexps.html

Regards,
karl