From: Ben Giddings <bg-rubytalk@...>
Date: 2009-08-21T23:28:03+09:00
Subject: Re: How to convert string "/regexp/i" to /regexp/i - ?

On Aug 21, 2009, at 06:04, Joao Silva wrote:
> I tried this, but it's totally unsafe way (these strings are  
> provided by
> user).

If the strings are provided by an untrusted source, don't use any  
solution that uses eval().

Instead, use a solution that recognizes the string contains a regexp  
and then uses a regexp constructor after pulling the relevant data out  
of the string.  Something along the lines of:

def parse_input(str)
   if md = %r{^/(.*)+/(.*)*$}.match(str)
     #it's a regexp
     pattern = md[1]
     if md[2]
       # deal with the flags
       flags = deal_with(md[2]
     end
     Regexp.new(pattern, flags)
   else
     ...
   end
end

Ben