command-line animation

animation_prompt.rb

# Forked from gist: 148765
#
# Removed question and default value
# Renamed main method
# Put the 'ensure' clause within its own begin/end block
# Added a constant
#
# TO DO: increase animation speed

require 'rubygems'
require 'termios'

ANIMATION = %W{- / | \\}
 
def animate_with_timeout(seconds)
  print 'Press any key to exit: '
  begin
    with_unbuffered_input($stdin) do
      countdown_from(seconds) do |seconds_left|
        write_then_erase_prompt(seconds_left) do
          wait_for_input($stdin, seconds_left % 1) do
            return 'bye...'
          end
        end
      end
    end
  ensure
    $stdout.puts
  end
end # ask_with_countdown_to_default
 
def with_unbuffered_input(input = $stdin)
  begin
    old_attributes = Termios.tcgetattr(input)
    new_attributes = old_attributes.dup
    new_attributes.lflag &= ~Termios::ECHO
    new_attributes.lflag &= ~Termios::ICANON
    Termios::tcsetattr(input, Termios::TCSANOW, new_attributes)
  
    yield
  ensure
    Termios::tcsetattr(input, Termios::TCSANOW, old_attributes)
  end
end # with_unbuffered_input
 
def countdown_from(seconds_left)
  start_time = Time.now
  end_time = start_time + seconds_left
  begin
    yield(seconds_left)
    seconds_left = end_time - Time.now
  end while seconds_left > 0.0
end # countdown_from
 
def write_then_erase_prompt(seconds_left)
  prompt = ANIMATION[ seconds_left.to_i % 4 ]
  prompt_length = prompt.length
  $stdout.write(prompt)
  $stdout.flush
 
  yield
 
  $stdout.write("\b" * prompt_length)
  $stdout.flush
end # write_then_erase_prompt
 
def wait_for_input(input, timeout)
  # Wait until input is available
  if select([input], [], [], timeout)
    yield
  end
end # wait_for_input
 
# :SAMPLE: usage
puts animate_with_timeout(60.0)