.\"	$OpenBSD: kill.1,v 1.40 2020/02/09 00:21:01 jsg Exp $
.\"	$NetBSD: kill.1,v 1.8 1995/09/07 06:30:26 jtc Exp $
.\"
.\" Copyright (c) 1980, 1990, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" This code is derived from software contributed to Berkeley by
.\" the Institute of Electrical and Electronics Engineers, Inc.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"	@(#)kill.1	8.2 (Berkeley) 4/28/95
.\"
.Dd $Mdocdate: February 9 2020 $
.Dt KILL 1
.Os
.Sh NAME
.Nm kill
.Nd terminate or signal a process
.Sh SYNOPSIS
.Nm kill
.Op Fl s Ar signal_name
.Ar pid ...
.Nm kill
.Fl l
.Op Ar exit_status
.Nm kill
.Fl Ar signal_name
.Ar pid ...
.Nm kill
.Fl Ar signal_number
.Ar pid ...
.Sh DESCRIPTION
The
.Nm
utility sends a signal to the process(es) specified
by the
.Ar pid
operand(s).
If no signal is specified,
.Dv SIGTERM
is used.
.Pp
Only the superuser may send signals to other users' processes.
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl l Op Ar exit_status
Display the name of the signal corresponding to
.Ar exit_status .
.Ar exit_status
may be the exit status of a command killed by a signal
(see the
special
.Xr sh 1
parameter
.Sq ?\& )
or a signal number.
.Pp
If no operand is given, display the names of all the signals.
.It Fl s Ar signal_name
A symbolic signal name specifying the signal to be sent instead of the
default
.Dv SIGTERM .
.It Fl Ar signal_name
A symbolic signal name specifying the signal to be sent instead of the
default
.Dv SIGTERM .
.It Fl Ar signal_number
A non-negative decimal integer specifying the signal to be sent instead
of the default
.Dv SIGTERM .
.El
.Pp
The following PIDs have special meanings:
.Bl -tag -width Ds -offset indent
.It \-1
If superuser, broadcast the signal to all processes; otherwise, broadcast
to all processes belonging to the user.
.It 0
Send the signal to all processes whose group ID is equal to the
process group ID of the sender, and for which the process has permission.
.It \- Ns Ar pgid
Send the signal to all processes within the specified process group.
.El
.Pp
Some of the more commonly used signals:
.Pp
.Bl -tag -width Ds -compact -offset indent
.It 1
HUP (hang up)
.It 2
INT (interrupt)
.It 3
QUIT (quit)
.It 6
ABRT (abort)
.It 9
KILL (non-catchable, non-ignorable kill)
.It 14
ALRM (alarm clock)
.It 15
TERM (software termination signal)
.El
.Pp
For a more complete list, consult the
.Xr sigaction 2
manual page.
.Pp
A signal number of 0
.Pq Li kill \-0 pid
checks the validity of a certain PID, to see if it exists.
An exit code of 0 means that the specified process exists.
.Sh EXIT STATUS
.Ex -std kill
.Sh EXAMPLES
Forcibly terminate process ID 1234:
.Pp
.Dl $ kill -9 1234
.Pp
Send the
.Xr init 8
process the hangup signal, instructing it to re-read
.Xr ttys 5 :
.Pp
.Dl # kill -HUP 1
.Sh SEE ALSO
.Xr csh 1 ,
.Xr ksh 1 ,
.Xr pkill 1 ,
.Xr ps 1 ,
.Xr kill 2 ,
.Xr sigaction 2
.Sh STANDARDS
The
.Nm
utility is compliant with the
.St -p1003.1-2008
specification.
.Pp
The
.Fl Ar signal_name
and
.Fl Ar signal_number
syntax is marked by
.St -p1003.1-2008
as being an
X/Open System Interfaces
option.
.Pp
.Nm
also exists as a built-in to
.Xr csh 1
and
.Xr ksh 1 ,
though with a different syntax.
.Sh HISTORY
A
.Nm
command appeared in
.At v3 .