Heroku style spinner

interruptible_sleep.rb

# Shamelessly stolen from https://gist.github.com/ileitch/1459987

module InterruptibleSleep
  def interruptible_sleep(seconds)
    @sleep_check, @sleep_interrupt = IO.pipe
    IO.select([@sleep_check], nil, nil, seconds)
  end

  def interrupt_sleep
    @sleep_interrupt.close if @sleep_interrupt
  end
end

spinner.rb

require 'interruptible_sleep'

class Spinner
  include InterruptibleSleep
  GLYPHS = %w(⣾ ⣷ ⣯ ⣟ ⡿ ⢿ ⣻ ⣽).reverse
  INTERVAL_DURATION = 0.07

  def initialize
    @current_glyph = 0
  end

  def progress
    loop do
      increment
      print "\r#{glyph} "
      interruptible_sleep(INTERVAL_DURATION)
    end
  end

  def stop
    print "\r"
    interrupt_sleep
  end

  def self.show_progress(&block)
    process = fork(&block)

    progress = fork do
      progress_indicator = Spinner.new
      progress_indicator.progress
    end

    Process.wait(process)
    Process.kill("HUP", progress)
    print "\r"
  end

  private

  def increment
    @current_glyph = @current_glyph + 1
    @current_glyph = 0 if @current_glyph >= GLYPHS.length
  end

  def glyph
    GLYPHS[@current_glyph]
  end
end

Use it with:

Spinner.show_progress do
  sleep 1
end
puts "Finished!"