Rolling output window in a terminal - a little snippet for command line tools

rolling_output_buffer.rb

class RollingOutputBuffer
  def initialize(max_lines = 10)
    @max_lines = max_lines
    @lines = []
    @last_printed = 0
  end

  def <<(line)
    @lines << line
    shift if @lines.size > @max_lines
  end

  def shift
    @lines.shift
  end

  def unshift(line)
    @lines.unshift(line)
  end

  def print
    if @last_printed > 0
      $stdout.print "\e[#{@last_printed}A"
    end

    $stdout.print "\e[0J#{@lines.join("\n")}\n"
    @last_printed = @lines.size
  end

  def clear
    $stdout.print "\e[#{@last_printed}A" if @last_printed > 0
    $stdout.print "\e[0J"
    @last_printed = 0
    @lines = []
  end
end