twitter-friends.rb

require 'csv'
require 'twitter'

def twitter_client
  @twitter_client ||= Twitter::REST::Client.new do |config|
    config.consumer_key = 'XXXXXX'
    config.consumer_secret = 'XXXXXX'
    config.access_token = 'XXXXXX'
    config.access_token_secret = 'XXXXXX'
  end
end

SLICE_SIZE = 100

def fetch_all_friends(twitter_username)
  CSV.open("#{twitter_username}_friends_list.txt", 'w') do |csv|
    twitter_client.friend_ids(twitter_username).each_slice(SLICE_SIZE).with_index do |slice, i|
      twitter_client.users(slice).each_with_index do |f, j|
        csv << [i * SLICE_SIZE + j + 1, f.name, f.screen_name, f.url, f.followers_count, f.location.gsub(/\n+/, ' '), f.created_at, f.description.gsub(/\n+/, ' '), f.lang, f.time_zone, f.verified, f.profile_image_url, f.website, f.statuses_count, f.profile_background_image_url, f.profile_banner_url]
      end
    end
  end
end

fetch_all_friends("screen_name_of_twitter_user")