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From: zemon@fritz.UUCP (Art Zemon)
Newsgroups: net.unix-wizards,net.unix
Subject: Re: UNIX question
Message-ID: <4324@fritz.UUCP>
Date: Mon, 9-Dec-85 20:36:45 EST
Article-I.D.: fritz.4324
Posted: Mon Dec  9 20:36:45 1985
Date-Received: Thu, 12-Dec-85 05:19:58 EST
References: <156@uw-june>
Reply-To: zemon@fritz.UUCP (Art Zemon)
Organization: FileNet Corp., Costa Mesa, CA
Lines: 34
Keywords: zombies, wait()
Xref: watmath net.unix-wizards:16063 net.unix:6600
Summary: use wait()

In article <156@uw-june> pjs@uw-june (Philip J. Schneider) writes:
>
>
>I have a C program which, during the course of its execution, spawns(forks)
>child processes. I should mention that a process is spawned, it lives
>for a while, then exits, and then sometime later the same thing happens,
>and so on.  This all happens within the lifetime of the parent, and I
>would like to do this an arbitrary number of times.  Sometimes, two or
>more child processes exist at once, but the upper limit on child
>processes that exist concurrently is low, and a group of such children
>exit before the next process begins.
>
>Since UNIX only allows one a certain number of processes at a time,
>eventually during the course of execution of the parent I run out of
>processes.  If I temporarily stop the parent process execution and
>do a 'ps', the child processes show up in the list with a 'Z' status.
>They do not completely disappear until the parent process exits.  As some
>of you probably already know, these useless ex-processes can't even
>be completely gotten rid of with a 'kill' command.  The result is that
>these processes are taking up my process quota, even though they are
>dead in all practical terms (in that they finished their work and exited
>properly).  Of course, they do go away completely once the parent exits.

The child processes have gone away properly and are waiting for
someone (some process) to collect their exit statuses with a
wait() or a wait3().  They cannot be kill()-ed because they are
already dead.

They go away after the parent exits because init inherits them
and does enough wait()s to get rid of all of them.
-- 
	-- Art Zemon
	   FileNet Corp.
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