kill(1) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | ARGUMENTS | OPTIONS | EXIT STATUS | NOTES | AUTHORS | SEE ALSO | AVAILABILITY | COLOPHON

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
                     signaled.

              -1     All processes with a PID larger than 1 are signaled.

              -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 number.

       -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/include/
              linux/signal.h.

       -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.

       --verbose
              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 option.

              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 specified)

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 ⟨svalente@mit.edu⟩
       Karel Zak ⟨kzak@redhat.com⟩

       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 
       ⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩.

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 
       ⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩.  If you have a
       bug report for this manual page, send it to
       util-linux@vger.kernel.org.  This page was obtained from the
       project's upstream Git repository
       ⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
       2020-06-09.  (At that time, the date of the most recent commit that
       was found in the repository was 2020-06-08.)  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
       man-pages@man7.org

util-linux                      November 2019                        KILL(1)

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