act.rb

w_r, w_w = IO.pipe
t_r, t_w = IO.pipe

work = Thread.new { block.call; w_w.write('.') }
timeout = Thread.new{ sleep 10; t_w.write('.') }

io = IO.select [w_r, t_r]

if io == t_r
  #Timeout
else
  #No timeout
end