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 1.6 1994/01/10 23:54:22 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/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. If the user is not the super user, 88the signal is sent to all processes with the same uid as the user 89except the process sending the signal. 90No error is returned if any process could be signaled. 91.El 92.Pp 93For compatibility with System V, 94if the process number is negative but not -1, 95the signal is sent to all processes whose process group ID 96is equal to the absolute value of the process number. 97This is a variant of 98.Xr killpg 2 . 99.Sh RETURN VALUES 100Upon successful completion, a value of 0 is returned. 101Otherwise, a value of -1 is returned and 102.Va errno 103is set to indicate the error. 104.Sh ERRORS 105.Fn Kill 106will fail and no signal will be sent if: 107.Bl -tag -width Er 108.It Bq Er EINVAL 109.Fa Sig 110is not a valid signal number. 111.It Bq Er ESRCH 112No process can be found corresponding to that specified by 113.Fa pid . 114.It Bq Er ESRCH 115The process id was given as 0 116but the sending process does not have a process group. 117.It Bq Er EPERM 118The sending process is not the super-user and its effective 119user id does not match the effective user-id of the receiving process. 120When signaling a process group, this error is returned if any members 121of the group could not be signaled. 122.El 123.Sh SEE ALSO 124.Xr getpid 2 , 125.Xr getpgrp 2 , 126.Xr killpg 2 , 127.Xr sigaction 2 128.Sh STANDARDS 129The 130.Fn kill 131function is expected to conform to 132.St -p1003.1-88 . 133