Re: backrefs in regexps?

[Tim Nelson]

On Tue, 19 Oct 2004, martin f krafft wrote:

> Hi all, I am new to cfengine and thus, this may be a really dumb
> question. However, I went through the docs and I could not find the
> solution, honestly.
>
> I am trying to use editfiles/ReplaceAll and backreference into the
> search pattern, conceptually like so:
>
>  ReplaceAll "foo(.*)bar" With "bar$1foo"
>
> However, the $1 is replaced literally. Is there a way to do what
> I want/need?

	Looking at this and your other question, you need to carefully 
learn the differences between the three different types of Regex.  They 
are:

-       Basic (POSIX) Regex
-       Extended (POSIX) Regex
-       Perl Regex

	Basic Regex is the one used by most Unix utilities such as grep. 
Extended is supported by most of the same utilities (grep -E, or egrep). 
Perl regex is only supported by some tools (eg. Perl, the pcre library, 
PHP, and some others).  You'll notice that the cfengine Reference manual 
says "The regular expression matching functions are POSIX extended regular 
expressions".  For more information:

http://en.wikipedia.org/wiki/Regular_expression

        Anyway, to come back to your problem...

	In this e-mail, you may find that it works if you use \1 instead 
of $1.  If not, you'll need to do some more reading.

	In your other e-mail, you'll find that \s doesn't exist in eregex. 
You could use [[:space:]] (elegant but long-winded) or [ \n\t] (and maybe 
\r too).

        Hope this helps...

--
Tim Nelson
Server Administrator
WebAlive Technologies Global
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