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KILL(1)                          User Commands                         KILL(1)

NAME
       kill - terminate a process

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

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

       pid    Each pid can be one of four things:

              n      where n is larger than 0.  The process with PID n is sig‐
                     naled.

              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
       -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/sig‐
              nal.h

       -L, --table
              Similar to -l, but it will print signal names and  their  corre‐
              sponding 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 sig‐
              nal.

       -q, --queue value
              Use 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 the usual way  to  a  process.   --timeout
              will  make  kill  to  wait  for a period defined in milliseconds
              before sending follow-up signal to  process.   This  feature  is
              implemented by PID file-descriptor and guaranties that follow-up
              signals are sent to the same process or not sent if the  process
              no  more  exist.  Note that the operating system may re-use PIDs
              and implement the same feature in a shell by kill and sleep com‐
              mands  sequence may introduce a race.  This option can be speci‐
              fied more than  once  than  signals  are  sent  sequentially  in
              defined  timeouts.   The  --timeout  option can be combined with
              --queue option.

              Example.  Send signals QUIT, TERM and KILL in sequence and  wait
              for 1000 milliseconds between the signals
              kill  --verbose --timeout 1000 TERM --timeout 1000 KILL --signal
              QUIT 12345

NOTES
       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  have  provide  an internal kill implementation that is
       preferred in relation to the kill(1) executable described by this  man‐
       ual.   Easiest  way to ensure one is executing the executable is to use
       full path when calling the command, for example: /bin/kill --version

RETURN CODES
       kill has the following return codes:

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

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

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

       The original version was taken from BSD 4.4.

AVAILABILITY
       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/⟩.

util-linux                       November 2019                         KILL(1)