DouKaku?

#load "unix.cma";;
open Unix;;

(*エコー、行バッファoff*)
let x = tcgetattr Unix.stdout in
  tcsetattr Unix.stdout TCSADRAIN {x with
    c_icanon = false;  c_vmin = 1; c_echo = false; };
  at_exit (fun () -> tcsetattr Unix.stdout TCSADRAIN x;);

(*一秒ごとのa*)
Sys.set_signal Sys.sigalrm (Sys.Signal_handle 
  (fun _ -> print_char 'a'; flush Pervasives.stdout));

(*本編*)
let t = ref (setitimer ITIMER_REAL {it_interval=1.0; it_value=1.0}) in
  while true do
    match input_char Pervasives.stdin with
    | 'q' -> exit 0
    | 'p' -> t := setitimer ITIMER_REAL !t
    | _ -> ()
  done;;