Sorry,

> let wait ?(delay_time = 0.01) pid idle x =
>   let rec wait' () =
>     idle x;
>     delay delay_time;
>     let pid = try fst (Unix.waitpid [Unix.WNOHANG] pid) with 
> _  -> 1 in
>       if pid <> 0 then wait' ()
>   in wait' ()
this code is wrong, my original code was:

let rec wait' () =
      idle x;
      delay delay_time;
     let wpid = try fst( Unix.waitpid [Unix.WNOHANG] pid) with _ -> pid in
       if pid <> wpid then wait' ()
    in wait' ()

Christoph Bauer