From: Nikolai Weibull <mailing-lists.ruby-talk@...>
Date: 2005-06-16T07:36:39+09:00
Subject: Re: Regex help

Ezra Zygmuntowicz wrote:

>     Could someone help me do a little regex conversion? I've got a  
> few perl compatible regexes from a php script I am trying to port to  
> ruby but I need a little help. Here are the php functions:
> 
>  $buffer = preg_replace("#(?<!\"|http:\/\/)www\.(?:[a-zA-Z0-9\-]+\.)* 
> [a-zA-Z]{2,4}(?:/[^ \n\r\"\'<]+)?#", "http://$0", $buffer);
>  $buffer = preg_replace("#(?<!\"|href=|href\s=\s|href=\s|href\s=) 
> (?:http:\/\/|https:\/\/|ftp:\/\/)(?:[a-zA-Z0-9\-]+\.)+[a-zA-Z]{2,4} 
> (?::[0-9]+)?(?:/[^ \n\r\"\'<]+)?#", "<a href=\"$0\" target=\"_blank\"> 
> $0</a>", $buffer);
> $buffer = preg_replace("#(?<=[\n ])([a-z0-9\-_.]+?)@([^,< \n\r]+)#i",  
> "<a href=\"mailto:$0\">$0</a>", $buffer);

OK, this wins my newly instated prize for _worst regexes ever_.  Inefficient,
inconclusive, inconsistent, and just plain wrong.  I really hope you
don’t have to work with a lot of code like this.

Nonetheless, here’s my solution:

domain = /(?:[[:alnum:]\-]+\.)/
tld = /[[:alpha:]]{2,4}/
buffer.gsub!(/(?<!"|http:\/\/)www\.#{domain_part}*#{tld}/, 'http://\0')
buffer.gsub!(/(?<!\"|href=|href\s=\s|href=\s|href\s=)
              (?:https?|ftp):\/\/#{domain_part}+#{tld}
              (?::\d+)?(?:\/[^\s"'<]+)?/x,
             '<a href="\0" target="_blank">\0</a>')
buffer.gsub!(/(?<=\s)[[:alnum:]\-_.]+@[^,<\s]+/i,
             '<a href="mailto:\0">\0</a>')

Totally untested, but at least it’s somewhat easier to understand and a
bit more correct.  There are better ways to extract URLs and email
addresses from an input than this, mind you,
        nikolai

-- 
Nikolai Weibull: now available free of charge at http://bitwi.se/!
Born in Chicago, IL USA; currently residing in Gothenburg, Sweden.
main(){printf(&linux["\021%six\012\0"],(linux)["have"]+"fun"-97);}