From: Ammar Ali <ammarabuali@...>
Date: 2010-10-26T23:54:24+09:00
Subject: Re: Change captured values in a regexp

On Tue, Oct 26, 2010 at 4:47 PM, Bruno Sousa <brgsousa@gmail.com> wrote:
> Hi everyone!
> Supposing there is a string like this:
> Oct 22 06:25:35 machine kernel: [271182.956004] IN= OUT=eth0
> SRC=10.8.0.248 DST=192.5.5.241
>
> I am using the following regexp to capture time:
> /Oct (\d{2}) (\d{2}:\d{2}:\d{2})/
>
> How can I alter the hour value only and keep it in the result returned?
> I want to decrease 3 hours.
> Instead of #<MatchData "Oct 22 06:25:35" 1:"22" 2:"06:25:35">
> It should return  #<MatchData "Oct 22 06:25:35" 1:"22" 2:"03:25:35">

That's not a job for regular expressions. You need to handle this by
yourself. Once you have the hour match, convert it into a Time object
(see http://ruby-doc.org/core/classes/Time.html#M000305) and then
offset it as you need.

HTH,
Ammar