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. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)kill.2 8.3 (Berkeley) 4/19/94 33.\" $FreeBSD$ 34.\" 35.Dd April 19, 1994 36.Dt KILL 2 37.Os BSD 4 38.Sh NAME 39.Nm kill 40.Nd send signal to a process 41.Sh SYNOPSIS 42.Fd #include <sys/types.h> 43.Fd #include <signal.h> 44.Ft int 45.Fn kill "pid_t pid" "int sig" 46.Sh DESCRIPTION 47The 48.Fn kill 49function sends the signal given by 50.Fa sig 51to 52.Fa pid , 53a 54process or a group of processes. 55.Fa Sig 56may be one of the signals specified in 57.Xr sigaction 2 58or it may be 0, in which case 59error checking is performed but no 60signal is actually sent. 61This can be used to check the validity of 62.Fa pid . 63.Pp 64For a process to have permission to send a signal to a process designated 65by 66.Fa pid , 67the real or effective user ID of the receiving process must match 68that of the sending process or the user must have appropriate privileges 69(such as given by a set-user-ID program or the user is the super-user). 70A single exception is the signal SIGCONT, which may always be sent 71to 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.Pq with Dv P_SYSTEM flag set , 89process with ID 1 90.Pq usually Xr init 8 , 91and the process sending the signal. 92If the user is not the super user, the signal is sent to all processes 93with the same uid as the user excluding the process sending the signal. 94No error is returned if any process could be signaled. 95.El 96.Pp 97For compatibility with System V, 98if the process number is negative but not -1, 99the signal is sent to all processes whose process group ID 100is equal to the absolute value of the process number. 101This is a variant of 102.Xr killpg 2 . 103.Sh RETURN VALUES 104Upon successful completion, a value of 0 is returned. 105Otherwise, a value of -1 is returned and 106.Va errno 107is set to indicate the error. 108.Sh ERRORS 109.Fn Kill 110will fail and no signal will be sent if: 111.Bl -tag -width [EINVAL] 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 sigaction 2 , 132.Xr init 8 133.Sh STANDARDS 134The 135.Fn kill 136function call is expected to conform to 137.St -p1003.1-90 . 138.Sh HISTORY 139A 140.Fn kill 141function call appeared in 142.At v7 . 143