Netmask to CIDR in ruby

Question

I\'ve been using the ip-address gem and it doesn\'t seem to have the ability to convert from a netmask of the form

255.255.255.0 

into the

Answer 1

Here is a way to do it without the IPAddr gem

(('1'*cidr)+('0'*(32-cidr))).scan(/.{8}/m).map{|e|e.to_i(2)}.join('.')