Why is the following command killing a system?

Question

Anyone understand the following code , running in bash ?

:(){ :|:& };:

It seems to be a "fork" bomb on Linux.

Answer 1

It's not that difficult to decipher in fact.

This piece of code just defines a function named : which calls two instances of itself in a pipeline: :|:&. After the definition an instance of this function is started.

This leads to a fast increasing number of subshell processes. Unprotected systems (systems without a process number limit per user) will be severely affected by such fork bombs since legitimate processes will quickly be outnumbered and thus deprived of most CPU resources.