Script to find IPs that belong in a list of subnets

findip.rb

#!/usr/bin/env ruby
require 'ipaddr'

def usage
    puts "#{$0} supernets file"
    puts "Checks if a file full of ip-addresses is part of a supernet \n\n"
    puts "Supernets: A comma-separated list of CIDR-noted networks. NO SPACES!\n\n"
    puts "Example:"
    puts "#{$0} 10.0.0.0/8,172.16.0.0/12 badguys.txt"
    Process.exit
end

ARGV.count == 2 or usage

(rawips, filename) = ARGV

unless rawips =~ /^[0-9\.,\/]+$/
    puts "Illegal value of supernets"
    usage
end

myrawranges = rawips.split(',')

firstoctets = myrawranges.collect { |x| x.match(/^(\d+)\./)[1] rescue nil } # extract first octet
begin
    fh = File.new(filename)
rescue => e
    puts "Couldn't open file #{filename} - #{e}"
    usage
    Process.exit
end

myranges = Array.new

myrawranges.each do |addr|
    myranges << IPAddr.new(addr, Socket::AF_INET) 
end


ips = Array.new # Initialize the array of IPs gathered from file

fh.each_line do |line|
    firstoctets.each do |oct|
        if line =~ /^#{oct}\./ # only add IPs that actually match on the first octet.
            ips << line.chomp
        end
    end
end


ips.each do |ip|
    myranges.each do |range|
        begin
            o_ip = IPAddr.new("#{ip}/32", Socket::AF_INET)
        rescue
            # just skip entries that are not real ip addresses
        end
        if range.include?(o_ip)
            puts ip
        end
    end
end