a.rb

require 'io/console'

$stdin.raw do
  $stdin.noecho do
    loop do
      print "\r"
      begin
        c =  $stdin.read_nonblock(1)
        p c
        exit if c == ?;
      rescue => e
        p e
        a, *_ = IO.select([$stdin], [], [], 1)
        p a
      end
      sleep 0.1
    end
  end
end