killpg - send signal to all members of a process group.
pidgrp, int signal);
The killpg() function causes signal signal to
be sent to all the processes in the process group
pidgrp or to the processes' own process group if
pidgrp is equal to zero.
It is equivalent to
The value returned is -1 on error, or 0 for
Errors are returned in errno and can be one of the
for an invalid signal,
for a process group which does not exist, and
if the userid of the calling process is not equal to that of
the process the signal is sent to, and the userid is not
that of the superuser.