How do I check whether a value in a string is an IP address

Question

when I do this

ip = request.env["REMOTE_ADDR"] 

I get the client's IP address it it. But what if I want to validate whether the value in the variable is really an IP? How do I do that?

Please help. Thanks in advance. And sorry if this question is repeated, I didn't take the effort of finding it...

EDIT

What about IPv6 IP's??

Answer 1

Ruby has already the needed Regex in the standard library. Checkout resolv.

require "resolv"  "192.168.1.1"   =~ Resolv::IPv4::Regex ? true : false #=> true "192.168.1.500" =~ Resolv::IPv4::Regex ? true : false #=> false  "ff02::1"    =~ Resolv::IPv6::Regex ? true : false #=> true "ff02::1::1" =~ Resolv::IPv6::Regex ? true : false #=> false 

If you like it the short way ...

require "resolv"  !!("192.168.1.1"   =~ Resolv::IPv4::Regex) #=> true !!("192.168.1.500" =~ Resolv::IPv4::Regex) #=> false  !!("ff02::1"    =~ Resolv::IPv6::Regex) #=> true !!("ff02::1::1" =~ Resolv::IPv6::Regex) #=> false 

Have fun!

Update (2018-10-08):

From the comments below i love the very short version:

!!(ip_string =~ Regexp.union([Resolv::IPv4::Regex, Resolv::IPv6::Regex])) 

Very elegant with rails (also an answer from below):

validates :ip,           :format => {             :with => Regexp.union(Resolv::IPv4::Regex, Resolv::IPv6::Regex)           }