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Message-ID: <4271E5C6.876A373D@dessent.net>
Date: Fri, 29 Apr 2005 00:44:06 -0700
From: Brian Dessent <brian AT dessent DOT net>
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To: cygwin AT cygwin DOT com
Subject: Re: Help understanding process tree
References: <4270F2F5 DOT 5010000 AT agilent DOT com> <20050428150258 DOT GB13295 AT trixie DOT casa DOT cgf DOT cx> <20050429072631 DOT GC3112 AT efn DOT org>
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Yitzchak Scott-Thoennes wrote:

> > Right.  cmd is a non-cygwin program so it needs a cygwin stub to handle
> > being "execed".  sleep is a cygwin program and does not require any
> > hand holding.
> 
> Now go back and reread the sentence where he says "I'd like help
> understanding why..." :)

I was under the impression that the reason that Cygwin processes often
appear as orphans and not part of the process tree (from the standpoint
of a native win32 app that is) is due to supporting exec().  AFAIK there
is no direct way in the win32 API to replace a process with another, so
in order to exec() the parent must create a new process and then itself
exit - thus leaving the child with no parent process.

This is also the reason why Cygwin must maintain its own PID translation
table, since the above process results in the exec()'d process with a
new PID.  But exec() is supposed to replace a process, and not change
its PID, so Cygwin has to invent the notion of Cygwin PIDs that can
differ from Windows PIDs.

I could be off in my understanding of the above, however.

To the original poster... Try "procps aux --forest" if you want an
accurate picture of the Cygwin process tree, since procps is a Cygwin
program and thus will use Cygwin PIDs.

Brian

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