terminate or signal processes (POSIX)
kill [-signal_name | -signal_number] pid... kill -l
A pid of zero sends the signal to all processes owned by the user in the current shell's process group.
Don't use a pid of zero when logged on as root. Signalling all the background processes owned by superuser and any current superuser foreground processes (e.g. backups in progress) may produce unpredictable results.
Any of the commands:
kill -9 100 -16 kill -sigkill 100 -16 kill -KILL 100 -16
sends the SIGKILL signal to the process whose process ID is 100 and to all processes whose process groupid is 16, assuming the sending process has permission to send that signal to the specified processes, and that they exist.
The kill utility sends a signal to the process(es) specified by each pid operand. By default, kill sends the SIGTERM signal, but you may override this default by naming a signal to be sent.
To print out the list of signals that may be sent, use kill with the -l option:
The kill command is available both as a standalone utility and as a shell built-in.