From: Dan Zwell <dzwell@...>
Date: 2007-06-12T16:20:41+09:00
Subject: Re: extracting numbers from a string

Matt Jones wrote:
> I have filenames from various digital cameras:  DSC_1234.jpg,
> CRW1234.jpg, etc.  What I really want is the numeric portion of that
> filename.  How would I extract just that portion?
> 
> 
> I expect it to involve the regex /\d+/, but I'm unclear how to extract a
> portion of a string matching a regex.
> 
> Thank you
> 

This may be the simplest (and arguably the most ruby-esque):
str = "DSC_1234.jpg"
num = str.scan(/\d+/)[0]

Other ways to do it:
num = str.match(/\d+/)[0]

OR
num = (/\d+/).match(str)[0]

OR
num = str.scan(/\d+/) {|match| match}

OR
num = str =~ /(\d+)/ ? $1 : nil

That is,
num = if str =~ /(\d+)/
   $1
else
   nil
end

OR
if str =~ /\d+/
   num = $~[0]
end

Some proponents of ruby have said that perl's "There is more than one 
way to do it," is a curse. But the same is true of ruby. However, it 
seems to me that most people learn reasonable idioms and common sense 
prevails.

Dan