db:createuser.rake.rb

  desc "a task which creates the database user"
  task(:createuser) do
    require 'yaml'
    require 'erb'
    path = File.join(Rails.root, 'config', 'database.yml')
    config = YAML::load(ERB.new((IO.read(path))).result)
    config = config[Rails.env] || config
    adapter = config['adapter']
    username = config['username']
    password = config['password']

    case adapter
      when /postgres/
        require 'pty'
        require 'expect'
        command = "createuser --superuser #{ username.inspect }"
        command += " --password" if password
        PTY.spawn(command) do |r,w,pid|
          w.sync = true
          if password
            r.expect(/^\s*password:\s*/i)
            w.puts(password)
          end
          while r.gets
          end
        end

      when /mysql/
        warn "you should be using postgresql!"
    end
  end
  task('db:create' => %w( db:createuser )){}