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.\" $DragonFly: src/lib/libc/sys/kill.2,v 1.4 2007/12/08 23:20:29 swildner Exp $ 31.\" 32.Dd April 19, 1994 33.Dt KILL 2 34.Os 35.Sh NAME 36.Nm kill 37.Nd send signal to a process 38.Sh LIBRARY 39.Lb libc 40.Sh SYNOPSIS 41.In sys/types.h 42.In signal.h 43.Ft int 44.Fn kill "pid_t pid" "int sig" 45.Sh DESCRIPTION 46The 47.Fn kill 48function sends the signal given by 49.Fa sig 50to 51.Fa pid , 52a 53process or a group of processes. 54.Fa Sig 55may be one of the signals specified in 56.Xr sigaction 2 57or it may be 0, in which case 58error checking is performed but no 59signal is actually sent. 60This can be used to check the validity of 61.Fa pid . 62.Pp 63For a process to have permission to send a signal to a process designated 64by 65.Fa pid , 66the real or effective user ID of the receiving process must match 67that of the sending process or the user must have appropriate privileges 68(such as given by a set-user-ID program or the user is the super-user). 69A single exception is the signal 70.Dv SIGCONT , 71which may always be sent to any descendant of the current process. 72.Bl -tag -width Ds 73.It \&If Fa pid No \&is greater than zero : 74.Fa Sig 75is sent to the process whose ID is equal to 76.Fa pid . 77.It \&If Fa pid No \&is zero : 78.Fa Sig 79is sent to all processes whose group ID is equal 80to the process group ID of the sender, and for which the 81process has permission; 82this is a variant of 83.Xr killpg 2 . 84.It \&If Fa pid No \&is -1 : 85If the user has super-user privileges, 86the signal is sent to all processes excluding 87system processes 88(with 89.Dv P_SYSTEM 90flag set), 91process with ID 1 92(usually 93.Xr init 8 ) , 94and the process sending the signal. 95If the user is not the super user, the signal is sent to all processes 96with the same uid as the user excluding the process sending the signal. 97No error is returned if any process could be signaled. 98.El 99.Pp 100For compatibility with System V, 101if the process number is negative but not -1, 102the signal is sent to all processes whose process group ID 103is equal to the absolute value of the process number. 104This is a variant of 105.Xr killpg 2 . 106.Sh RETURN VALUES 107.Rv -std kill 108.Sh ERRORS 109.Fn Kill 110will fail and no signal will be sent if: 111.Bl -tag -width Er 112.It Bq Er EINVAL 113.Fa Sig 114is not a valid signal number. 115.It Bq Er ESRCH 116No process can be found corresponding to that specified by 117.Fa pid . 118.It Bq Er ESRCH 119The process id was given as 0 120but the sending process does not have a process group. 121.It Bq Er EPERM 122The sending process is not the super-user and its effective 123user id does not match the effective user-id of the receiving process. 124When signaling a process group, this error is returned if any members 125of the group could not be signaled. 126.El 127.Sh SEE ALSO 128.Xr getpgrp 2 , 129.Xr getpid 2 , 130.Xr killpg 2 , 131.Xr lwp_kill 2 , 132.Xr sigaction 2 , 133.Xr raise 3 , 134.Xr init 8 135.Sh STANDARDS 136The 137.Fn kill 138function call is expected to conform to 139.St -p1003.1-90 . 140.Sh HISTORY 141A 142.Fn kill 143function call appeared in 144.At v7 . 145