Specifically, kill()ing pid 0 kills every process in the process group of the calling process. Pid 0 is more like a NULL pointer. You can put something in memor

Specifically, kill()ing pid 0 kills every process in the process group of the calling process. Pid 0 is more like a NULL pointer. You can put something in memory there, but a lot of systems will treat it as an invalid identifier for their own purposes. I had some ruby code that called kill(str.to_i) and killed every process when the string wasn't an integer, which is when I painfully found out that to_i returns 0 on invalid strings and kill(0) kills (potentially) a lot of processes.