How does this combined command :() { :|:& }; : work? (CAUTION: don't try, cause system halted)

Question

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How does this bash fork bomb work?

Today one of my friend told me a funny thing, that this such command cause system halted:

:() { :|:& }; :

But, I just don't understand how does this command work and cause such a disaster. Any one comes up with this thing?

Thanks,

Xi

Google forkbomb, this is not an original question. – richo Jan 19 '12 at 03:33 — richo, Jan 19 '12 at 03:33

score 2 · Accepted Answer · answered Jan 19 '12 at 03:35

In short,

:() { :|:& }; :
|     |       ` Invoke the function
|     ` Run itself twice, once in a subshell, once for each invocation
` Create a new function called :

Which basically means that for each call of :, two instances of : are created, each of which create two more, etc.

The correct solution is sane ulimits.

How does this combined command :() { :|:& }; : work? (CAUTION: don't try, cause system halted)

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