kill
Sends a signal to one or more processes or process groups.
The first argument is the signal, specified either as a name
('TERM', 'HUP', with or without SIG prefix) or as a number.
The remaining arguments are PIDs to signal.
If the signal is negative, the absolute value is sent to the
process group identified by each PID (using kill(-sig, -abs(pid))).
Signal 0 does not actually send a signal but checks whether the
process exists and is reachable (permission check).
Returns the number of processes successfully signaled.
Synopsis
kill 'TERM', $pid; # send SIGTERM by name
kill 15, $pid; # send SIGTERM by number
kill 'TERM', $pid1, $pid2; # signal multiple processes
kill 0, $pid; # check if process exists
kill -15, $pgrp; # signal a process group