1.\" Copyright (c) 1980, 1991 Regents of the University of California. 2.\" 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.\" from: @(#)kill.2 6.6 (Berkeley) 3/10/91 33.\" $Id: kill.2,v 1.3 1993/11/25 00:39:12 jtc Exp $ 34.\" 35.Dd March 10, 1991 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/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 receving 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 SIGCONT, which may always be sent 70to 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 2 . 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. If the user is not the super user, 87the signal is sent to all processes with the same uid as the user 88except the process sending the signal. 89No error is returned if any process could be signaled. 90.El 91.Pp 92For compatibility with System V, 93if the process number is negative but not -1, 94the signal is sent to all processes whose process group ID 95is equal to the absolute value of the process number. 96This is a variant of 97.Xr killpg 2 . 98.Sh RETURN VALUES 99Upon successful completion, a value of 0 is returned. 100Otherwise, a value of -1 is returned and 101.Va errno 102is set to indicate the error. 103.Sh ERRORS 104.Fn Kill 105will fail and no signal will be sent if: 106.Bl -tag -width [EINVAL] 107.It Bq Er EINVAL 108.Fa Sig 109is not a valid signal number. 110.It Bq Er ESRCH 111No process can be found corresponding to that specified by 112.Fa pid . 113.It Bq Er ESRCH 114The process id was given as 0 115but the sending process does not have a process group. 116.It Bq Er EPERM 117The sending process is not the super-user and its effective 118user id does not match the effective user-id of the receiving process. 119When signaling a process group, this error is returned if any members 120of the group could not be signaled. 121.El 122.Sh SEE ALSO 123.Xr getpid 2 , 124.Xr getpgrp 2 , 125.Xr killpg 2 , 126.Xr sigaction 2 127.Sh STANDARDS 128The 129.Fn kill 130function is expected to conform to 131.St -p1003.1-88 . 132