Unix.waitpid

Unix.waitpid

[Bauer, Christoph]

Hi,

my app should wait for some processes. This is done 
by my function wait, which gets a pid, a idle function (e.g. ignore)
+ its value and a delay time between polling:


let delay s = ignore (Unix.select [] [] [] s)

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' ()

It works mostly, but in some rare, non-deterministic cases wait loops
forever.
In a seconds round it works without problems. I saw this behaviour on Linux
and Windows. Can anybody help me?

Thanks!

Christoph Bauer
Dipl. Inf.

LMS Deutschland GmbH
Luxemburgerstr. 7
D-67657 Kaiserslautern

T +49 631 303 22 152

mailto:Christoph.Bauer@lms-gmbh.de
http://www.lmsintl.com 

Re: [Caml-list] Unix.waitpid

[Oliver Bandel]

On Thu, Jun 30, 2005 at 02:09:51PM +0200, Bauer, Christoph wrote:
> Hi,
> 
> my app should wait for some processes. This is done 
> by my function wait, which gets a pid, a idle function (e.g. ignore)
> + its value and a delay time between polling:
> 
> 
> let delay s = ignore (Unix.select [] [] [] s)
> 
> 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' ()

Does you have a valid pid (as calling parameter)?
You may better use 0 or -1 in the call to Unix.waitpid.

Maybe WUNTRACED would also makes sense as flag.
Maybe better not testing with "_" in try-with.


P.S.: Documentation could be better.
I had to look in the C-API manpage to know what parameters
the Unix.aitpid awaits.
That the one arg is the pid is mentioned in the documentation, but there
is no function call example, to identify the second arg as the wpid.


Ciao,
   Oliver Bandel