kill

kill sends a signal to a process. Despite the name, a signal is not always fatal — it is a message, and some signals ask a process to do something other than stop.

kill [options] pid...

$ kill 4821                 # ask process 4821 to terminate
$ kill -KILL 4821           # force it to stop

A pid is a process identifier — the number a running process is known by.

Signals

With no option, kill sends TERM — a polite request to shut down, which a well-behaved process honours by cleaning up and exiting. The signals you will reach for most:

Signal	Meaning
`TERM`	Terminate. The default — a request to stop cleanly.
`KILL`	Stop immediately. Cannot be caught or ignored, so it cannot be refused — but the process gets no chance to clean up. The last resort.
`HUP`	Hang up. Conventionally tells a long-running service to reload its configuration.
`INT`	Interrupt — the signal a terminal sends on Ctrl-C.
`STOP` / `CONT`	Suspend the process / resume a suspended one.

Option	Effect
`-s`, `--signal=SIGNAL`	Send `SIGNAL` instead of `TERM`.
`-SIGNAL`	A shorthand — `-KILL` or `-9` both send `KILL`.
`-l`, `--list`	List the signal names.
`-L`, `--table`	List the signals as a table of numbers and names.

Reach for KILL only when TERM has failed. A process killed outright cannot save its work or release what it holds.

Exit status

Code	Meaning
`0`	Every signal was sent.
`1`	A signal could not be sent — a process that does not exist, or one you are not permitted to signal.

Signals #

Exit status #

See also

Signals

Exit status