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To: Dag-Erling =?iso-8859-1?Q?Sm=F8rgrav?= <des@des.no>
References: <47B90868.7000900@electron-tube.net> <86odae5rgr.fsf@ds4.des.no>
From: Lowell Gilbert <freebsd-bugs-local@be-well.ilk.org>
Date: Mon, 18 Feb 2008 22:26:42 -0500
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Cc: freebsd-fs@freebsd.org
Subject: Re: How to take down a system to the point of requiring a newfs
	with one line of C (userland)
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Dag-Erling Sm=F8rgrav <des@des.no> writes:

> Jim Bryant <freebsd@electron-tube.net> writes:
>> #include <stdio.h>
>> #include <stdlib.h>
>>
>> int main(int argc, char **argv) { int i; char buf[1024]; bzero(buf, 1024=
); for(i =3D 0; i < 10000; i++) { sprintf(buf, "touch %s%05d\n", argv[1], i=
); system((const char *)buf);} return(0);}
>
> Subject should be "how to take down a system [...] with three lines of
> badly written C, provided you have root privileges already and are too
> lazy to just dd if=3D/dev/zero of=3D/dev/ad0s1 count=3D100", which would
> accomplish the job much faster.

I don't really see that argument, given that I can't understand *why*
this code would produce the specific symptoms described in the
original message.=20=20

For the record, I've been unable to reproduce the problem, so I'm
unwilling to get too excited about it.

> Purely in the interest of showing off, here is my version.  It is 81
> bytes shorter than yours, it is valid C99 with POSIX extensions (yours
> is not), and it produces 11,450 files in about 0.2% of the time yours
> takes to produce 10,000.
>
> #include <unistd.h>
> #define b(i,v) for(int v=3D48;v<127;++v){f[i]=3Dv;
> #define a(i) b(i,v##i)
> int main(void){char f[5]=3D{'/'};a(1)a(2)a(3)truncate(f,0);}}}}

Entertaining, but not enough so to win the Obfuscated C contest.=20=20

I'm a pretty dedicated C user, but on this subject I've been using
shell scripts for testing.