namespace :admin do
  desc "Create a user"
  task :add_user => :environment do
    username    = ENV['username']
    password    = ENV['password']

    ### do stuff  
  end

  desc "Batch add users."
  task :add_users => :environment do
    USER_FILE  = ENV['user_file'] || "/tmp/users.txt"

    ### def open_file

    open_file(USER_FILE) do |f|
      until f.eof do

      ### do stuff
      ENV['username'] = username
      ENV['password'] = password
      Rake::Task[ "admin:add_user" ].execute
    end
  end
end