Date: Tue, 23 Oct 2007 10:06:41 -0400
From: Rob <bitabyss@gmail.com>
To: FreeBSD Questions <freebsd-questions@freebsd.org>
Subject: Re: defend from -> :() { :&:; } ;:
Message-ID: <471DFFF1.3010209@gmail.com>
In-Reply-To: <200710222031.58924.mike.jeays@rogers.com>
References: <123275.56819.qm@web30812.mail.mud.yahoo.com> <471D00EB.2030903@lazlarlyricon.com> <200710222031.58924.mike.jeays@rogers.com>
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Mike Jeays wrote:
>>> Please do not try to execute this: :() { :&:; } ;: on your BSD machine.
>> What does it do?
>
> It is easier to understand when you replace the ":" by a more conventional
> subroutine name.
>
> myproc () {
> myproc &
> myproc
> }
>
> myproc
>
> It recursively generates useless processes that clog up the machine. Mine
> ground to a halt and froze after a few seconds.
Interesting, if not annoying ;) Thanks for the explanation, Mike. I edited /etc/login.conf and changed maxproc=unlimited to maxproc=200. Then tried it. Took a second or so to start spewing "Cannot fork: Resource temporarily unavailable". I'd opened a 2nd session, and ps wasn't even able to give me full info on what was happening. Luckily, is was easily interruptible and the system seemed to recover.
-Rob
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