1.\" $NetBSD: kill.2,v 1.7 1995/02/27 12:33:53 cgd Exp $ 2.\" 3.\" Copyright (c) 1980, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the University of 17.\" California, Berkeley and its contributors. 18.\" 4. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" @(#)kill.2 8.3 (Berkeley) 4/19/94 35.\" 36.Dd April 19, 1994 37.Dt KILL 2 38.Os BSD 4 39.Sh NAME 40.Nm kill 41.Nd send signal to a process 42.Sh SYNOPSIS 43.Fd #include <signal.h> 44.Ft int 45.Fo kill 46.Fa "pid_t pid" 47.Fa "int sig" 48.Fc 49.Sh DESCRIPTION 50The 51.Fn kill 52function sends the signal specified by 53.Fa sig 54to 55.Fa pid , 56a 57process or a group of processes. 58Typically, 59.Fa Sig 60will be one of the signals specified in 61.Xr sigaction 2 . 62A value of 0, however, 63will cause error checking to be performed (with no signal being sent). 64This can be used to check the validity of 65.Fa pid . 66.Pp 67For a process to have permission to send a signal to a process designated 68by 69.Fa pid , 70the real or effective user ID of the receiving process must match 71that of the sending process or the user must have appropriate privileges 72(such as given by a set-user-ID program or the user is the super-user). 73A single exception is the signal SIGCONT, 74which may always be sent to any descendant of the current process. 75.Bl -tag -width Ds 76.It \&If Fa pid No \&is greater than zero : 77.Fa Sig 78is sent to the process whose ID is equal to 79.Fa pid. 80.It \&If Fa pid No \&is zero : 81.Fa Sig 82is sent to all processes whose group ID is equal 83to the process group ID of the sender, 84and for which the process has permission; 85this is a variant of 86.Xr killpg 2 . 87.It \&If Fa pid No \&is -1 : 88If the user has super-user privileges, 89the signal is sent to all processes excluding 90system processes and the process sending the signal. 91If the user is not the super user, 92the signal is sent to all processes with the same uid as the user, 93excluding 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 Er 112.\" ========== 113.It Bq Er EINVAL 114.Fa Sig 115is not a valid, supported signal number. 116.\" ========== 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.\" ========== 123.It Bq Er ESRCH 124No process or process group can be found 125corresponding to that specified by 126.Fa pid . 127.\" ========== 128.It Bq Er ESRCH 129The process id was given as 0, 130but the sending process does not have a process group. 131.El 132.Sh SEE ALSO 133.Xr getpgrp 2 , 134.Xr getpid 2 , 135.Xr killpg 2 , 136.Xr sigaction 2 137.Sh STANDARDS 138The 139.Fn kill 140function is expected to conform to 141.St -p1003.1-88 . 142