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 38.Sh NAME 39.Nm kill 40.Nd send signal to a process 41.Sh LIBRARY 42.Lb libc 43.Sh SYNOPSIS 44.Fd #include <sys/types.h> 45.Fd #include <signal.h> 46.Ft int 47.Fn kill "pid_t pid" "int sig" 48.Sh DESCRIPTION 49The 50.Fn kill 51function sends the signal given by 52.Fa sig 53to 54.Fa pid , 55a 56process or a group of processes. 57.Fa Sig 58may be one of the signals specified in 59.Xr sigaction 2 60or it may be 0, in which case 61error checking is performed but no 62signal is actually sent. 63This can be used to check the validity of 64.Fa pid . 65.Pp 66For a process to have permission to send a signal to a process designated 67by 68.Fa pid , 69the real or effective user ID of the receiving process must match 70that of the sending process or the user must have appropriate privileges 71(such as given by a set-user-ID program or the user is the super-user). 72A single exception is the signal SIGCONT, which may always be sent 73to any descendant of the current process. 74.Bl -tag -width Ds 75.It \&If Fa pid No \&is greater than zero : 76.Fa Sig 77is sent to the process whose ID is equal to 78.Fa pid . 79.It \&If Fa pid No \&is zero : 80.Fa Sig 81is sent to all processes whose group ID is equal 82to the process group ID of the sender, and for which the 83process has permission; 84this is a variant of 85.Xr killpg 2 . 86.It \&If Fa pid No \&is -1 : 87If the user has super-user privileges, 88the signal is sent to all processes excluding 89system processes 90.Pq with Dv P_SYSTEM flag set , 91process with ID 1 92.Pq usually Xr init 8 , 93and the process sending the signal. 94If the user is not the super user, the signal is sent to all processes 95with the same uid as the user excluding the process sending the signal. 96No error is returned if any process could be signaled. 97.El 98.Pp 99For compatibility with System V, 100if the process number is negative but not -1, 101the signal is sent to all processes whose process group ID 102is equal to the absolute value of the process number. 103This is a variant of 104.Xr killpg 2 . 105.Sh RETURN VALUES 106Upon successful completion, a value of 0 is returned. 107Otherwise, a value of -1 is returned and 108.Va errno 109is set to indicate the error. 110.Sh ERRORS 111.Fn Kill 112will fail and no signal will be sent if: 113.Bl -tag -width Er 114.It Bq Er EINVAL 115.Fa Sig 116is not a valid signal number. 117.It Bq Er ESRCH 118No process can be found corresponding to that specified by 119.Fa pid . 120.It Bq Er ESRCH 121The process id was given as 0 122but the sending process does not have a process group. 123.It Bq Er EPERM 124The sending process is not the super-user and its effective 125user id does not match the effective user-id of the receiving process. 126When signaling a process group, this error is returned if any members 127of the group could not be signaled. 128.El 129.Sh SEE ALSO 130.Xr getpgrp 2 , 131.Xr getpid 2 , 132.Xr killpg 2 , 133.Xr sigaction 2 , 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