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Date: Mon, 24 Mar 2014 23:55:58 +0100
From: oliver <oliver@first.in-berlin.de>
To: Johan Grande <johan.grande@ens-cachan.org>
Cc: caml users <caml-list@inria.fr>
Message-ID: <20140324225558.GA13355@siouxsie>
References: <53307809.80202@ens-cachan.org>
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User-Agent: Mutt/1.5.20 (2009-06-14)
Subject: Re: [Caml-list] Child process doesn't terminate

Hello,

On Mon, Mar 24, 2014 at 07:23:05PM +0100, Johan Grande wrote:
> Hi,
> 
> In the following program, the child process "cat" never terminates.
> I don't understand why; can anyone tell me?
> 
> ~~~
> let _ =
>   let open Unix in
>   let indescr, outdescr = pipe () in
>   let outchan = out_channel_of_descr outdescr in
>   let pid =
>     create_process "/bin/cat" [|"cat"|]
>       indescr  stdout  stderr
>   in
>   Printf.fprintf outchan "Hello!\n%!";
>   close indescr;
>   close outdescr;
>   ignore (waitpid [] pid)  (* stuck here *)
> ~~~


"cat" does not terminate.


With

  create_process "/bin/cat" [| "cat"; "/etc/passwd" |]

cat would terminate after cat'ing the file,
otherwise it reads from input until Ctrl-D arrives,
before printing the data and then terminates.

So you can wait in vain with your waitpid-call,
if you call it as you did.


Ciao,
   Oliver