Re: [Caml-list] catch keypressed

[Gerd Stolpmann <info@gerd-stolpmann.de>]

On 2002.05.02 12:23 Vincent Barichard wrote:
> 
> Hello,
> 
> I would like to catch the hit of a key without being in graphic
> mode. Something like :
> 
> while not keypressed() do
>   print_string "Hit a key";
> done;
> 
> Is a fonction of this kind exists in CAML ??
> And if it doesn't exist, is there a way to simulate its effect ??
> The read_int fonction blocks until user enter a value so it is not
> suitable for my problem.
> 
> thanks for your help
> 
> Vincent

Quite simple: Turn the "canonical mode" of stdin off, and keypresses
are reported immediately:

open Unix;;
let waitkey() =
  let m = tcgetattr stdin in
  tcsetattr stdin TCSAFLUSH { m with c_icanon = false };  
  let s = String.create 1 in
  ignore(read stdin s 0 1);
  tcsetattr stdin TCSAFLUSH m;
  s.[0]
;;

Maybe you also want to turn off echo mode (c_echo=false). Changing the
terminal mode is dangerous, because it is a property of the terminal
emulator, and is not automatically reset if the program stops for any
reason. Because of this, it is a good idea to register an at_exit function
that restores the terminal mode when the program terminates, and to catch
also the various signals that might lead to termination.

And if the cursor has vanished: type "stty sane" to reset the terminal
modes from the shell.

Gerd
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Gerd Stolpmann      Telefon: +49 6151 997705 (privat)
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