The kill builtin command [Bash Hackers Wiki]

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====== The kill builtin command ======

===== Synopsis =====
<code>kill [-s SIGNAL | -n SIGNALNUMBER | -SIGNAL] PID|JOB</code>
<code>kill -l|-L [SIGNAL...]</code>

===== 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 ====

<code>
kill -l
</code>

==== Send KILL to a process ID ====

<code>
kill -9 12345
</code>

<code>
kill -KILL 12345
</code>

<code>
kill -SIGKILL 12345
</code>

===== Portability considerations =====

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

===== See also =====