GeoIP database queries in Ruby

geoip_lookup.rb

#!/usr/bin/env ruby

require 'csv'
require 'maxminddb'

db = MaxMindDB.new('./GeoLite2-City.mmdb')
CSV.open('results.csv', 'w') do |output|
  output << ['IP', 'City', 'Subdivision', 'Country', 'Latitude', 'Longitude']
  File.new('ips.txt','r').each_line do |line|
    line.chomp!
    result = db.lookup(line)
    next if result.city.geoname_id.nil?
    sub = ['CA','US'].include?(result.country.iso_code) ? result.subdivisions.most_specific.iso_code : result.subdivisions.most_specific.name
    output << [line, result.city.name, sub, result.country.name, result.location.latitude, result.location.longitude]
    $stderr.puts result.city.name
  end
end