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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: src/lib/libc/sys/kill.2,v 1.10.2.7 2001/12/14 18:34:01 ru Exp $ 34.\" $DragonFly: src/lib/libc/sys/kill.2,v 1.4 2007/12/08 23:20:29 swildner Exp $ 35.\" 36.Dd April 19, 1994 37.Dt KILL 2 38.Os 39.Sh NAME 40.Nm kill 41.Nd send signal to a process 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.In sys/types.h 46.In signal.h 47.Ft int 48.Fn kill "pid_t pid" "int sig" 49.Sh DESCRIPTION 50The 51.Fn kill 52function sends the signal given by 53.Fa sig 54to 55.Fa pid , 56a 57process or a group of processes. 58.Fa Sig 59may be one of the signals specified in 60.Xr sigaction 2 61or it may be 0, in which case 62error checking is performed but no 63signal is actually 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 74.Dv SIGCONT , 75which may always be sent to any descendant of the current process. 76.Bl -tag -width Ds 77.It \&If Fa pid No \&is greater than zero : 78.Fa Sig 79is sent to the process whose ID is equal to 80.Fa pid . 81.It \&If Fa pid No \&is zero : 82.Fa Sig 83is sent to all processes whose group ID is equal 84to the process group ID of the sender, and for which the 85process has permission; 86this is a variant of 87.Xr killpg 2 . 88.It \&If Fa pid No \&is -1 : 89If the user has super-user privileges, 90the signal is sent to all processes excluding 91system processes 92(with 93.Dv P_SYSTEM 94flag set), 95process with ID 1 96(usually 97.Xr init 8 ) , 98and the process sending the signal. 99If the user is not the super user, the signal is sent to all processes 100with the same uid as the user excluding the process sending the signal. 101No error is returned if any process could be signaled. 102.El 103.Pp 104For compatibility with System V, 105if the process number is negative but not -1, 106the signal is sent to all processes whose process group ID 107is equal to the absolute value of the process number. 108This is a variant of 109.Xr killpg 2 . 110.Sh RETURN VALUES 111.Rv -std kill 112.Sh ERRORS 113.Fn Kill 114will fail and no signal will be sent if: 115.Bl -tag -width Er 116.It Bq Er EINVAL 117.Fa Sig 118is not a valid signal number. 119.It Bq Er ESRCH 120No process can be found corresponding to that specified by 121.Fa pid . 122.It Bq Er ESRCH 123The process id was given as 0 124but the sending process does not have a process group. 125.It Bq Er EPERM 126The sending process is not the super-user and its effective 127user id does not match the effective user-id of the receiving process. 128When signaling a process group, this error is returned if any members 129of the group could not be signaled. 130.El 131.Sh SEE ALSO 132.Xr getpgrp 2 , 133.Xr getpid 2 , 134.Xr killpg 2 , 135.Xr lwp_kill 2 , 136.Xr sigaction 2 , 137.Xr raise 3 , 138.Xr init 8 139.Sh STANDARDS 140The 141.Fn kill 142function call is expected to conform to 143.St -p1003.1-90 . 144.Sh HISTORY 145A 146.Fn kill 147function call appeared in 148.At v7 . 149