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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 1.2 2003/06/17 04:26:47 dillon 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 SIGCONT, which may always be sent 74to 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, and for which the 84process 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 91(with 92.Dv P_SYSTEM 93flag set), 94process with ID 1 95(usually 96.Xr init 8 ) , 97and the process sending the signal. 98If the user is not the super user, the signal is sent to all processes 99with the same uid as the user excluding the process sending the signal. 100No error is returned if any process could be signaled. 101.El 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 2 . 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 killpg 2 , 134.Xr sigaction 2 , 135.Xr raise 3 , 136.Xr init 8 137.Sh STANDARDS 138The 139.Fn kill 140function call is expected to conform to 141.St -p1003.1-90 . 142.Sh HISTORY 143A 144.Fn kill 145function call appeared in 146.At v7 . 147