[talk] kill -0

[Jan Schaumann]

Raul Cuza <raulcuza at gmail.com> wrote:
 
> I just had someone submit a shell script using `kill -0 ${PID}` to
> test if a process is running. It exits non-zero if ${PID} isn't a
> running process and zero otherwise. But...
> 
> http://nixdoc.net/man-pages/FreeBSD/kill.1.html says nothing about it.

kill(2) describes this behavior:

"sig may be one of the signals specified in
sigaction(2) or it may be 0, in which case error
checking is performed but no signal is actually sent.
This can be used to check the validity of pid."

-Jan