# The kill builtin command

## Synopsis

    kill [-s SIGNAL | -n SIGNALNUMBER | -SIGNAL] PID|JOB

    kill -l|-L [SIGNAL...]

## Description

The `kill` command is used to send signals to processes specified by
their `PID` or their `JOB`-specification.

The signal(s) to be specified can have the following formats:

-   Numerical: The signal is specified using its constant numeric value.
    Be aware that not all systems have identical numbers for the
    signals.
-   Symbolic (long): The signal is specified using the same name that is
    used for the constant/macro in the C API (`SIG<name>`)
-   Symbolic (short): The signal is specified using the name from the C
    API without the `SIG`-prefix (`<name>`)

Without any specified signal, the command sends the `SIGTERM`-signal.

The `kill` command is a Bash builtin command instead of relying on the
external `kill` command of the operating system to

-   be able to use shell job specifications instead of Unix process IDs
-   be able to send signals ("kill something") also, when your process
    limit is reached

### Options

|Option|Description|
|------|-----------|
|`-s SIGNAL`|specifies the signal to send|
|`-n SIGNALNUMBER`|specifies the signal to send|
|`-SIGNAL`|specifies the signal to send|
|`-l [SIGNAL...]`|Lists supported/known signal numbers and their symbolic name. If `SIGNAL` is given, only list this signal, translated (if a number is given the symbolic name is printed, and vice versa)|
|`-L [SIGNAL...]`|Same as `-l [SIGNAL]` (compatiblity option)|

### Return status

|Status|Reason|
|------|------|
|0|no error/success|
|!=0|invalid option|
|!=0|invalid signal specification|
|!=0|error returned by the system function (e.g. insufficient permissions to send to a specific process)|

## Examples

### List supported signals

    kill -l

### Send KILL to a process ID

    kill -9 12345

    kill -KILL 12345

    kill -SIGKILL 12345

## Portability considerations

-   POSIX(R) and ISO C only standardize symbolic signal names (no
    numbers) and a default action

## See also