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Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)kill.2 8.3 (Berkeley) 4/19/94 29.\" $FreeBSD: src/lib/libc/sys/kill.2,v 1.10.2.7 2001/12/14 18:34:01 ru Exp $ 30.\" 31.Dd November 26, 2016 32.Dt KILL 2 33.Os 34.Sh NAME 35.Nm kill 36.Nd send signal to a process 37.Sh LIBRARY 38.Lb libc 39.Sh SYNOPSIS 40.In sys/types.h 41.In signal.h 42.Ft int 43.Fn kill "pid_t pid" "int sig" 44.Sh DESCRIPTION 45The 46.Fn kill 47function sends the signal given by 48.Fa sig 49to 50.Fa pid , 51a 52process or a group of processes. 53.Fa Sig 54may be one of the signals specified in 55.Xr sigaction 2 56or it may be 0, in which case 57error checking is performed but no 58signal is actually sent. 59This can be used to check the validity of 60.Fa pid . 61.Pp 62For a process to have permission to send a signal to a process designated 63by 64.Fa pid , 65the real or effective user ID of the receiving process must match 66that of the sending process or the user must have appropriate privileges 67(such as given by a set-user-ID program or the user is the super-user). 68A single exception is the signal 69.Dv SIGCONT , 70which may always be sent to 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 3 . 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 87(with 88.Dv P_SYSTEM 89flag set), 90process with ID 1 91(usually 92.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 99NOTE! If the sending process is restricted by a reaper, the signal is 100further restricted to processes only within or under that reaper. 101The reaper itself can only be signalled directly. 102.Pp 103For compatibility with System V, 104if the process number is negative but not -1, 105the signal is sent to all processes whose process group ID 106is equal to the absolute value of the process number. 107This is a variant of 108.Xr killpg 3 . 109.Sh RETURN VALUES 110.Rv -std kill 111.Sh ERRORS 112.Fn Kill 113will fail and no signal will be sent if: 114.Bl -tag -width Er 115.It Bq Er EINVAL 116.Fa Sig 117is not a valid signal number. 118.It Bq Er ESRCH 119No process can be found corresponding to that specified by 120.Fa pid . 121.It Bq Er ESRCH 122The process id was given as 0 123but the sending process does not have a process group. 124.It Bq Er EPERM 125The sending process is not the super-user and its effective 126user id does not match the effective user-id of the receiving process. 127When signaling a process group, this error is returned if any members 128of the group could not be signaled. 129.El 130.Sh SEE ALSO 131.Xr getpgrp 2 , 132.Xr getpid 2 , 133.Xr lwp_kill 2 , 134.Xr sigaction 2 , 135.Xr killpg 3 , 136.Xr raise 3 , 137.Xr init 8 138.Sh STANDARDS 139The 140.Fn kill 141function call is expected to conform to 142.St -p1003.1-90 . 143.Sh HISTORY 144A 145.Fn kill 146function call appeared in 147.At v7 . 148