kill invocation (GNU Coreutils 9.0)
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24.1 kill: Send a signal to processes
The kill
command sends a signal to processes, causing them to terminate or otherwise act upon receiving the signal in some way. Alternatively, it lists information about signals. Synopses:
kill [-s signal | --signal signal | -signal] pid… kill [-l | --list | -t | --table] [signal]…
Due to shell aliases and built-in kill
functions, using an unadorned kill
interactively or in a script may get you different functionality than that described here. Invoke it via env
(i.e., env kill …
) to avoid interference from the shell.
The first form of the kill
command sends a signal to all pid
arguments. The default signal to send if none is specified 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 the process ID pid
. 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 that equals the absolute value of pid
.
If pid
is not positive, a system-dependent set of system processes is excluded from the list of processes to which the signal is sent.
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 of the kill
command succeeds if every pid
argument specifies at least one process that the signal was sent to.
The second form of the kill
command lists signal information. Either the -l
or --list
option, or the -t
or --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 of the kill
command succeeds if all signal
arguments are valid and if there is no output error.
The kill
command also supports the --help
and --version
options. See Common options.
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.
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