pigeon.rb

require 'rubygems'
require 'twitter'

target = ''
next_cursor = -1

Twitter.configure do |config|
    config.consumer_key = ''
    config.consumer_secret = ''
    config.oauth_token = ''
    config.oauth_token_secret = ''
end

fp = open(target + '.txt', 'w')

while next_cursor != 0 do
    a = Twitter.follower_ids(target, {:cursor => next_cursor})
    fp.print a.attrs[:ids].join("\n")
    fp.print "\n"
    next_cursor = a.attrs[:next_cursor]
end

fp.close