1.\" Copyright (c) 1980, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)kill.2 8.3 (Berkeley) 4/19/94 29.\" $FreeBSD: src/lib/libc/sys/kill.2,v 1.10.2.7 2001/12/14 18:34:01 ru Exp $ 30.\" 31.Dd November 26, 2016 32.Dt KILL 2 33.Os 34.Sh NAME 35.Nm kill 36.Nd send signal to a process 37.Sh LIBRARY 38.Lb libc 39.Sh SYNOPSIS 40.In sys/types.h 41.In signal.h 42.Ft int 43.Fn kill "pid_t pid" "int sig" 44.Sh DESCRIPTION 45The 46.Fn kill 47function sends the signal given by 48.Fa sig 49to 50.Fa pid , 51a 52process or a group of processes. 53.Fa Sig 54may be one of the signals specified in 55.Xr sigaction 2 56or it may be 0, in which case 57error checking is performed but no 58signal is actually sent. 59This can be used to check the validity of 60.Fa pid . 61.Pp 62For a process to have permission to send a signal to a process designated 63by 64.Fa pid , 65the real or effective user ID of the receiving process must match 66that of the sending process or the user must have appropriate privileges 67(such as given by a set-user-ID program or the user is the super-user). 68A single exception is the signal 69.Dv SIGCONT , 70which may always be sent to any descendant of the current process. 71.Bl -tag -width Ds 72.It \&If Fa pid No \&is greater than zero : 73.Fa Sig 74is sent to the process whose ID is equal to 75.Fa pid . 76.It \&If Fa pid No \&is zero : 77.Fa Sig 78is sent to all processes whose group ID is equal 79to the process group ID of the sender, and for which the 80process has permission; 81this is a variant of 82.Xr killpg 3 . 83.It \&If Fa pid No \&is -1 : 84If the user has super-user privileges, 85the signal is sent to all processes excluding 86system processes 87(with 88.Dv P_SYSTEM 89flag set), 90process with ID 1 91(usually 92.Xr init 8 ) , 93and the process sending the signal. 94If the user is not the super user, the signal is sent to all processes 95with the same uid as the user excluding the process sending the signal. 96No error is returned if any process could be signaled. 97.El 98.Pp 99For compatibility with System V, 100if the process number is negative but not -1, 101the signal is sent to all processes whose process group ID 102is equal to the absolute value of the process number. 103This is a variant of 104.Xr killpg 3 . 105.Sh RETURN VALUES 106.Rv -std kill 107.Sh ERRORS 108.Fn Kill 109will fail and no signal will be sent if: 110.Bl -tag -width Er 111.It Bq Er EINVAL 112.Fa Sig 113is not a valid signal number. 114.It Bq Er ESRCH 115No process can be found corresponding to that specified by 116.Fa pid . 117.It Bq Er ESRCH 118The process id was given as 0 119but the sending process does not have a process group. 120.It Bq Er EPERM 121The sending process is not the super-user and its effective 122user id does not match the effective user-id of the receiving process. 123When signaling a process group, this error is returned if any members 124of the group could not be signaled. 125.El 126.Sh SEE ALSO 127.Xr getpgrp 2 , 128.Xr getpid 2 , 129.Xr lwp_kill 2 , 130.Xr sigaction 2 , 131.Xr killpg 3 , 132.Xr raise 3 , 133.Xr init 8 134.Sh STANDARDS 135The 136.Fn kill 137function call is expected to conform to 138.St -p1003.1-90 . 139.Sh HISTORY 140A 141.Fn kill 142function call appeared in 143.At v7 . 144