Re: [Caml-list] Unix.wait: strange behavior

[Remi VANICAT <vanicat@labri.u-bordeaux.fr>]

Yang Shouxun <yangsx@fltrp.com> writes:

> Hi,
>
> I'm reading ocaml-book English version. On p. 611:
> ----8<----
> match Unix.fork () with
>      0 -> Printf.printf "fair Marquise " ; flush stdout
>    | _  -> ignore (Unix.wait ()) ;
>            match Unix.fork () with
>                0 -> Printf.printf "your beautiful eyes " ; flush stdout
>              | _ -> ignore (Unix.wait ()) ;
>                    match Unix.fork () with
>                        0 -> Printf.printf "make me die " ; flush stdout
>                      | _ -> ignore (Unix.wait ()) ;
>                     Printf.printf "of love\n" ;
>                     flush stdout
> ----8<----
> this is intended to show the use of Unix.wait to wait for the
> termination of the child.
>
> Strangely, when I input at the Ocaml toplevel, it does not print "fair
> Marquise your beautiful eyes make me die of love", but only "fair
> Marquise". The forked processes did not terminate for some reason,
> which I don't understand why. Is this a bug?

Mmm, Don't know if this a bug or not, but the problem is that after
forking, you have two toplevel, so personally I've something like :

# match Unix.fork () with
       0 -> Printf.printf "fair Marquise " ; flush stdout
[....]
fair Marquise - : unit = ()
# #quit
  ;;
your beautiful eyes - : unit = ()
# #quit ;;
make me die - : unit = ()
# #quit ;;
of love
- : unit = ()
# 


>
> Guessing that the child processes will not automatically exit, I added
> "; exit 0" to the lines for newly forked processes, and I got "your
> beautiful eyes make me die of love" printed before the return of the
> expression and then "fair Marquise " printed.

Strange, I've the waited output.
-- 
Rémi Vanicat
vanicat@labri.u-bordeaux.fr
http://dept-info.labri.u-bordeaux.fr/~vanicat
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