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📛 NAME

kill — send a signal to processes, causing them to terminate or otherwise act upon receiving the signal; or list information about signals.

🚀 Quick Reference

Use Case	Command	Description
Terminate process by PID (default TERM)	kill 1234	Send SIGTERM to process 1234
Force kill (cannot be caught/ignored)	kill -9 1234 kill -KILL 1234	Send SIGKILL
Hang up (reload config, close terminal)	kill -HUP 1234	Send SIGHUP
Send signal to a process group	kill -TERM -1234	Send to all processes in group 1234
Test if process exists (no signal sent)	kill -0 1234	Success if process 1234 is alive
List all signal names	kill -l	Show one name per line
Get the number for a signal name	kill -l HUP	Print the numeric value (e.g., 1)
Show a table of signals with descriptions	kill -t	Outputs number, name, description
Avoid shell builtin/wrapper	env kill ...	Call the real kill binary directly

📋 Synopsis

kill [-s SIGNAL | --signal SIGNAL | -SIGNAL] PID...
kill [-l | --list | -t | --table] [SIGNAL]...

📖 Description

Due to shell aliases and built-in kill functions, using an unadorned kill interactively or in a script may get you different functionality than described here. Invoke it via env (i.e., env kill ...) to avoid interference from the shell.

🔹 First Form: Sending a Signal

The first form sends a signal to all PID arguments. The default signal is TERM. The special signal number 0 does not denote a valid signal, but can be used to test whether the PID arguments specify processes to which a signal could be sent.

If PID is positive, the signal is sent to the process with that ID. If PID is zero, the signal is sent to all processes in the process group of the current process. If PID is -1, the signal is sent to all processes for which the user has permission to send a signal. If PID is less than -1, the signal is sent to all processes in the process group whose absolute value equals PID.

If PID is not positive, a system‑dependent set of system processes is excluded from the list.

If a negative PID argument is desired as the first one, it should be preceded by --. However, as a common extension to POSIX, -- is not required with kill -SIGNAL -PID. The following commands are equivalent:

kill -15 -1
kill -TERM -1
kill -s TERM -- -1
kill -- -1

The first form succeeds if every PID argument specifies at least one process that the signal was sent to.

🔹 Second Form: Listing Signals

Either the -l/--list option or the -t/--table option must be specified. Without any SIGNAL argument, all supported signals are listed. The output of -l or --list is a list of the signal names, one per line; if SIGNAL is already a name, the signal number is printed instead. The output of -t or --table is a table of signal numbers, names, and descriptions. This form succeeds if all SIGNAL arguments are valid and if there is no output error.

🔹 Signal Specifications

A SIGNAL may be a signal name like HUP, or a signal number like 1, or an exit status of a process terminated by the signal. A signal name can be given in canonical form or prefixed by SIG. The case of the letters is ignored, except for the -SIGNAL option which must use upper case to avoid ambiguity with lower case option letters.

See Signal specifications for a list of supported signal names and numbers.

⚙️ Options

The following options are available:

• -s SIGNAL, --signal=SIGNAL — Specify the signal to send. SIGNAL can be a name (e.g., HUP) or a number (e.g., 1).
• -SIGNAL — Equivalent to -s SIGNAL. Must be in upper‑case to avoid conflicts with lower‑case option letters (e.g., -KILL).
• -l, --list — List signal names. With an argument SIGNAL, print its number.
• -t, --table — Print a table of signal numbers, names, and descriptions.
• --help — Display usage information and exit.
• --version — Output version information and exit.

These are described in more detail under Common options.

🔗 See Also

Common options for --help and --version behavior, Signal specifications for a complete list of signal names and numbers.

📛 NAME 🚀 Quick Reference 📋 Synopsis 📖 Description ⚙️ Options 🔗 See Also