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Date:      Fri, 24 Jan 2014 09:23:36 -0800
From:      <dteske@FreeBSD.org>
To:        "'Warren Block'" <wblock@wonkity.com>, "'Devin Teske'" <dteske@FreeBSD.org>
Cc:        'RW' <rwmaillists@googlemail.com>, freebsd-questions@freebsd.org
Subject:   RE: awk programming question
Message-ID:  <050a01cf1929$051c0670$0f541350$@FreeBSD.org>
In-Reply-To: <alpine.BSF.2.00.1401231904410.82598@wonkity.com>
References:  <F01EB9CE742DEB17DB6B51C7@localhost> <alpine.BSF.2.00.1401230900270.76961@wonkity.com> <20140123185604.4cbd7611@gumby.homeunix.com> <04a201cf1878$8ebce540$ac36afc0$@FreeBSD.org> <alpine.BSF.2.00.1401231346520.80613@wonkity.com> <04aa01cf187e$cfcf9ef0$6f6edcd0$@FreeBSD.org> <alpine.BSF.2.00.1401231537260.80613@wonkity.com> <04d201cf1895$20956890$61c039b0$@FreeBSD.org> <alpine.BSF.2.00.1401231904410.82598@wonkity.com>

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> -----Original Message-----
> From: Warren Block [mailto:wblock@wonkity.com]
> Sent: Thursday, January 23, 2014 6:23 PM
> To: 'Devin Teske'
> Cc: 'RW'; freebsd-questions@freebsd.org
> Subject: RE: awk programming question
> 
> On Thu, 23 Jan 2014, dteske@FreeBSD.org wrote:
> 
> >> No, the non-greedy modifier to a standard quantifier:
> >>
> >> echo "abczabczabcz" | perl -ne '/(a.*z)/; print "$1\n"'
> >> abczabczabcz
> >>
> >> echo "abczabczabcz" | perl -ne '/(a.*?z)/; print "$1\n"'
> >> abcz
> >
> > Craziness! Wonder when that crept in.
> 
> I've been using it for at least a decade, so it's probably been around at
least
> twice that long.  ...So probably came out about twenty years after the sed
> and awk feature sets were frozen. :)
> 
> > I'm not entirely sure how I feel about that -- in terms of
> > readability, I'm not sure if the following is more readable:
> >
> > 	/(a[^z]*z)/
> 
> Wait till you see the other PCRE stuff.  There are lots of things that
really
> make it much more powerful.  perlre(1) covers it all, sketchily and not
really
> in order.
> 
> I've said elsewhere, and will repeat again: "Mastering Regular
Expressions"
> by Jeffrey E. F. Friedl (the owl book) is amazing.  My first edition
(1997) does
> not have some of the newer Perl stuff, but it's now up to a third edition:
> 
> http://shop.oreilly.com/product/9780596528126.do

Does it cover "back references" ? Definitely one of the more powerful but
esoteric regular expressions (e.g., you want to match a string that starts
with
a quote and has a matching terminating quote, but not match a string that
has
a quote without matching termination).

If-so, I'm totally buying that book.
-- 
Devin

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