Date: Mon, 18 Jan 2010 20:14:30 +0100 (CET) From: Oliver Fromme <olli@lurza.secnetix.de> To: freebsd-hackers@FreeBSD.ORG, david@catwhisker.org, yanefbsd@gmail.com Subject: Re: User error or awk bug? Message-ID: <201001181914.o0IJEUXV000789@lurza.secnetix.de> In-Reply-To: <7d6fde3d1001151402m74d999e5off14be9a99b5d187@mail.gmail.com>
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Garrett Cooper wrote:
> David Wolfskill wrote:
> > How about:
> >
> > d254(6.4-S)[10] echo //////// | awk '{ gsub (/\/\/+/, "/"); print }'
> > /
> > d254(6.4-S)[11]
> >
> > then?
>
> This works very well. Is the expression quantifier operator [ `{'
> ] not supported in awk like perl, python, tcl, etc?
awk is quite old. It implements the historical behaviour
of egrep which did not support braces (this is mentioned
in the manual page). Braces are a relatively new feature
in egrep. They were probably never added to awk because
of compatibility issues with existing scripts.
By the way, you can use strings as regular expressions
so you don't have to enclose them in slashes. This saves
you from the ugly escaping with backslashes:
echo //////// | awk '{gsub ("/+", "/"); print}'
will do what you want. On the other hand, the typical
tool for simple search+replace tasks is sed:
echo //////// | sed 's=//*=/=g'
By the way, when egrep parses brace expressions, it simply
translates them to standard expressions. So, when it sees
"/{2,}" it converts it to "//+" before creating the DFA.
Best regards
Oliver
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"The scanf() function is a large and complex beast that often does
something almost but not quite entirely unlike what you desired."
-- Chris Torek
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