From: Scott Morris (swm@emanon.com)
Date: Wed May 26 2004 - 17:17:27 GMT-3
The parentheses have some double meanings when trying to filter things.
From a regular expression point of view, just like in math, they're used to
isolate parts of the "equation" (e.g. solve here first). So the text
parsing engine processes the parenth.
At the same time, you want to use the parentheses to show searching for text
inside the confederation. In other words, the () actually show up in the
as-path set text string and you want to match on them. So that's why you
need the "\" to denote "upcoming special character, process as part of text,
not part of parsing equation"
So if we were to pretend that the < > represented a grouping of text
equations, your expression would look like:
^<(.*)>?$
The "?" character means 0 or 1 of the preceeding item. Since you had the <
> (pretend change) around that part of the equation, that is the item that
repeats 0 or 1 times. It could be in a confederation, or could not be in the
confederation.
Hope that helps,
Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, CISSP,
JNCIP, et al.
IPExpert CCIE Program Manager
IPExpert Sr. Technical Instructor
swm@emanon.com/smorris@ipexpert.net
http://www.ipexpert.net
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Yasser Aly
Sent: Wednesday, May 26, 2004 3:57 PM
To: ccielab@groupstudy.com
Subject: Regular expression inside confederation
Hello,
I am confused on the meaning of the following regular expressions that can
be used inside a confederation and appreciate if someone can help in
explaining what do they mean and how ?
The expressions are:
^\(.*\)$
^(\(.*\))?$
Regards,
Yasser
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