On 03-Nov-04 Daniel Silverstone wrote:

On Wed, 2004-11-03 at 22:47 +0100, Wayne Stallwood wrote:

...

When typed into a bash prompt :(){ :|:&};: I have been told it does bad things so don't try it, is it folklore or does it really do something nasty ?

It's a fork bomb.. read fully it is:

define function called ':' as being the result of calling ':' piped through ':' put into the background. Then call the function ':'

Rapidly spirals into doom.

A common alternative you see floating around is:

_(){_&_}_

Another subtle bomb is

cat < /dev/tty0

If you don't like what happens, you can try killing it from another console.

This one is relatively less disastrous, in that it is possible to close it down. Just how, is left as an exercise for the reader[1].

Best wishes to all, Ted.

[1] Hint: X

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On Wed, Nov 03, 2004 at 10:01:14PM +0000, Brett Parker wrote:

On Wed, Nov 03, 2004 at 10:47:12PM +0100, Wayne Stallwood wrote:

...

When typed into a bash prompt

:(){ :|:&};:

I have been told it does bad things so don't try it, is it folklore or does it really do something nasty ?

Looking at it, I'd say it creates a function called : and then recursively executes itself through itself... probably ends in an infinite loop, with lots and lots and lots of forks.

Though, I could be wrong :)

If anyone else can see anything obvious, that I've missed, I'd be interested.

Thanks,

Note to self: when you think it's going to fork lots, and you've posted this to the list, at least give it 5 mins for Daniel to confirm it *before* you decide to randomly try it to see what happens

Note number2: process limit myself so that I can't cause such pain and unclean reboots again

Note number3: XFS rocks, the machine came back cleanly, and fast :)

Thanks,