setup_pager

# File lib/rdoc/ri/driver.rb, line 1442
  def setup_pager
    return if @use_stdout

    jruby = Object.const_defined?(:RUBY_ENGINE) && RUBY_ENGINE == 'jruby'

    pagers = [ENV['RI_PAGER'], ENV['PAGER'], 'pager', 'less', 'more']

    pagers.compact.uniq.each do |pager|
      next unless pager

      pager_cmd = pager.split.first

      next unless in_path? pager_cmd

      if jruby then
        case io = find_pager_jruby(pager)
        when nil   then break
        when false then next
        else            io
        end
      else
        io = IO.popen(pager, 'w') rescue next
      end

      next if $? and $?.pid == io.pid and $?.exited? # pager didn't work

      @paging = true

      return io
    end

    @use_stdout = true

    nil
  end