kill

sends a signal to a process, usually to stop it

TLDR

Terminate a program using the default SIGTERM signal

$ kill [process_id]

List available signal names

$ kill -l

Terminate a background job

$ kill %[job_id]

Send SIGHUP signal (reload for many daemons)

$ kill -HUP [process_id]

Send SIGINT signal (like Ctrl+C)

$ kill -INT [process_id]

Force kill a program (SIGKILL)

$ kill -9 [process_id]

Pause a program (SIGSTOP)

$ kill -STOP [process_id]

Send signal to all processes with a group ID

$ kill -SIGUSR1 -[group_id]

DESCRIPTION

kill sends a signal to a process, usually to stop it. All signals except SIGKILL and SIGSTOP can be intercepted by the process to perform a clean exit. By default, SIGTERM is sent.

PARAMETERS

-l, --list

List signal names, or convert signal number to name

-L, --table

List signal names and numbers in a table

-s signal

Specify signal to send

-signal

Specify signal by name or number (e.g., -9, -KILL, -SIGKILL)

-p, --pid

Print the process ID only; do not send a signal

-q, --queue value

Send the signal using sigqueue(3) with the accompanying integer value

pid

Process ID to signal. A PID of 0 signals all processes in the current process group. A PID of -1 signals all processes with PID > 1.

%job_id

Job ID from shell job control

SIGTERM (15): Request termination (default)SIGKILL (9): Force immediate termination (cannot be caught)SIGHUP (1): Hang up; often used to reload configurationSIGINT (2): Interrupt (Ctrl+C)SIGSTOP (19): Pause process (cannot be caught)SIGCONT (18): Continue paused process

CAVEATS

SIGKILL (-9) should be used as a last resort as it doesn't allow the process to clean up. Use SIGTERM first and give the process time to exit gracefully.

HISTORY

Part of standard Unix since early versions. The kill command has been available since Version 4 AT&T UNIX (1973).