kill(1) — Linux manual page


KILL(1)                       User Commands                      KILL(1)

NAME         top

       kill - terminate a process

SYNOPSIS         top

       kill [-signal|-s signal|-p] [-q value] [-a] [--timeout
       milliseconds signal] [--] pid|name...
       kill -l [number] | -L

DESCRIPTION         top

       The command kill sends the specified signal to the specified
       processes or process groups.

       If no signal is specified, the TERM signal is sent.  The default
       action for this signal is to terminate the process.  This signal
       should be used in preference to the KILL signal (number 9), since
       a process may install a handler for the TERM signal in order to
       perform clean-up steps before terminating in an orderly fashion.
       If a process does not terminate after a TERM signal has been
       sent, then the KILL signal may be used; be aware that the latter
       signal cannot be caught, and so does not give the target process
       the opportunity to perform any clean-up before terminating.

       Most modern shells have a builtin kill command, with a usage
       rather similar to that of the command described here.  The --all,
       --pid, and --queue options, and the possibility to specify
       processes by command name, are local extensions.

       If signal is 0, then no actual signal is sent, but error checking
       is still performed.

ARGUMENTS         top

       The list of processes to be signaled can be a mixture of names
       and PIDs.

       pid    Each pid can be expressed in one of the following ways:

              n      where n is larger than 0.  The process with PID n
                     is signaled.

              0      All processes in the current process group are

              -1     All processes with a PID larger than 1 are

              -n     where n is larger than 1.  All processes in process
                     group n are signaled.  When an argument of the form
                     '-n' is given, and it is meant to denote a process
                     group, either a signal must be specified first, or
                     the argument must be preceded by a '--' option,
                     otherwise it will be taken as the signal to send.

       name   All processes invoked using this name will be signaled.

OPTIONS         top

       -s, --signal signal
              The signal to send.  It may be given as a name or a

       -l, --list [number]
              Print a list of signal names, or convert the given signal
              number to a name.  The signals can be found in /usr/

       -L, --table
              Similar to -l, but it will print signal names and their
              corresponding numbers.

       -a, --all
              Do not restrict the command-name-to-PID conversion to
              processes with the same UID as the present process.

       -p, --pid
              Only print the process ID (PID) of the named processes, do
              not send any signals.

              Print PID(s) that will be signaled with kill along with
              the signal.

       -q, --queue value
              Send the signal using sigqueue(3) rather than kill(2).
              The value argument is an integer that is sent along with
              the signal.  If the receiving process has installed a
              handler for this signal using the SA_SIGINFO flag to
              sigaction(2), then it can obtain this data via the
              si_sigval field of the siginfo_t structure.

       --timeout milliseconds signal
              Send a signal defined in the usual way to a process,
              followed by an additional signal after a specified delay.
              The --timeout option causes kill to wait for a period
              defined in milliseconds before sending a follow-up signal
              to the process.  This feature is implemented using the
              Linux kernel PID file descriptor feature in order to
              guarantee that the follow-up signal is sent to the same
              process or not sent if the process no longer exists.

              Note that the operating system may re-use PIDs and
              implementing an equivalent feature in a shell using kill
              and sleep would be subject to races whereby the follow-up
              signal might be sent to a different process that used a
              recycled PID.

              The --timeout option can be specified multiple times: the
              signals are sent sequentially with the specified timeouts.
              The --timeout option can be combined with the --queue

              As an example, the following command sends the signals
              QUIT, TERM and KILL in sequence and waits for 1000
              milliseconds between sending the signals:

                  kill --verbose --timeout 1000 TERM --timeout 1000 KILL \
                          --signal QUIT 12345

EXIT STATUS         top

       kill has the following exit status values:

              0      success
              1      failure
              64     partial success (when more than one process

NOTES         top

       Although it is possible to specify the TID (thread ID, see
       gettid(2)) of one of the threads in a multithreaded process as
       the argument of kill, the signal is nevertheless directed to the
       process (i.e., the entire thread group).  In other words, it is
       not possible to send a signal to an explicitly selected thread in
       a multithreaded process.  The signal will be delivered to an
       arbitrarily selected thread in the target process that is not
       blocking the signal.  For more details, see signal(7) and the
       description of CLONE_THREAD in clone(2).

       Various shells provide a builtin kill command that is preferred
       in relation to the kill(1) executable described by this manual.
       The easiest way to ensure one is executing the command described
       in this page is to use the full path when calling the command,
       for example: /bin/kill --version

AUTHORS         top

       Salvatore Valente ⟨⟩
       Karel Zak ⟨⟩

       The original version was taken from BSD 4.4.

SEE ALSO         top

       bash(1), tcsh(1), sigaction(2), kill(2), sigqueue(3), signal(7)

AVAILABILITY         top

       The kill command is part of the util-linux package and is
       available from Linux Kernel Archive 

COLOPHON         top

       This page is part of the util-linux (a random collection of Linux
       utilities) project.  Information about the project can be found
       at ⟨⟩.  If you
       have a bug report for this manual page, send it to  This page was obtained from the
       project's upstream Git repository
       ⟨git://⟩ on
       2021-03-21.  (At that time, the date of the most recent commit
       that was found in the repository was 2021-03-19.)  If you
       discover any rendering problems in this HTML version of the page,
       or you believe there is a better or more up-to-date source for
       the page, or you have corrections or improvements to the
       information in this COLOPHON (which is not part of the original
       manual page), send a mail to

util-linux                    November 2019                      KILL(1)

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