Question

397

Why did the command ":(){ :|: & };:" make my system lag so badly I had to reboot?

rated 0 times [ 397] [ 0] / answers: 1 / hits: 304714 / 2 Years ago, sun, october 16, 2022, 9:15:45

DANGER!

Do not run this command to 'test' it unless you are prepared for a crash and/or force-rebooting your system.

I was in my Virtualbox running 12.04 trying to compile an app, and while waiting I happened to chance upon a forum where a comment said:

Try :(){ :|: & };:

Fun, too, and doesn't need root.

Without thinking, I ran it in my gnome-terminal. It made my 12.04(in Virtualbox) lag so badly, I had to shut it down.

My question is what does this command do?

:(){ :|: & };:

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eving

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1 Year ago

answered 2 Years ago intssive · Accepted Answer

This is called a fork bomb.

:() means you are defining a function called :

{:|: &} is the : function's body. It calls the function : recursively and sends (pipes) its output to another call of :. And & means the created process must run in the background.

The ; is a command separator.

The final : runs the function the first time.

Essentially you are creating a function that calls itself twice every call and doesn't have any way to terminate itself. It will keep doubling up until you run out of system resources.

Running in Virtualbox was quite sensible really otherwise you would have had to restart your pc.