Re: Egrep does not support \A, \Z, \s

[Karl Berry]

    Thus your regepxs are malformed.

Well, that seems a bit draconian.  POSIX is not the be-all and end-all
of what is ok.  As I know you know, Andreas, GNU has always supported
many useful extensions, not to mention every other real-world program.
That POSIX does not live in the real world does not obviate the fact
that we do :).

    > echo "hi" | egrep "\Ah"
    > echo "hi | egrep "i\Z"
    > echo "h i" | egrep "\s"

However, in this case, I surmise you were expecting the Perl definitions
for \A, \Z, and \s.  These have never been supported by GNU (e)grep (or
any other GNU program that I can think of).  GNU grep relatively
recently acquired a --perl-regexp option to interpret regexps as Perl,
but I gather the support is rather flaky.  If you want Perl regexps, I
advise using Perl.

The comparable GNU extensions are \< and \> for \A and \Z.  And the
standard [[:space:]] is comparable to \s.

BTW, using \ inside "double quotes" on the command line is risky,
because shells also interpret some \-sequences .  Better to use
'single quotes'.

Regards,
Karl