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Date:	Wed, 7 Jun 2017 19:31:53 +0200
From:	Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To:	cygwin AT cygwin DOT com
Subject:	Re: PPID in ps -efW not accurate
Message-ID:	<20170607173153.GC13513@calimero.vinschen.de>
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On Jun  7 13:10, Erik Soderquist wrote:
> The information exists in Windows somewhere, but either does not seem
> to be available to ps, or is not fetched by ps, and I don't know
> enough to know which...
>=20
> I tested with both elevated and non-elevated bash sessions, and ps
> -efW shows 0 (zero) as the PPID for all Windows processes

This is accurate because Windows does not maintain a parent-child
relationship between processes.  That's why there's no Windows functions
to fetch a parent process PID or handle.

The only information available is the PID of a process this process
inherits handles from.  In the POSIX context that's equivalent with a
parent process, but not on Windows.  Therefore this info is only
available in the lower NT API(*).

Worse, given the fact that Windows reuses PIDs quickly after a process
died, this information can be totally wrong.


Corinna

(*) NtQueryInformationProcess(ProcessBasicInformation)

--=20
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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