.\" $NetBSD: kill.2,v 1.7 1995/02/27 12:33:53 cgd Exp $ .\" .\" Copyright (c) 1980, 1991, 1993 .\" The Regents of the University of California. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. All advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" This product includes software developed by the University of .\" California, Berkeley and its contributors. .\" 4. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" @(#)kill.2 8.3 (Berkeley) 4/19/94 .\" .Dd April 19, 1994 .Dt KILL 2 .Os BSD 4 .Sh NAME .Nm kill .Nd send signal to a process .Sh SYNOPSIS .Fd #include <signal.h> .Ft int .Fo kill .Fa "pid_t pid" .Fa "int sig" .Fc .Sh DESCRIPTION The .Fn kill function sends the signal specified by .Fa sig to .Fa pid , a process or a group of processes. Typically, .Fa Sig will be one of the signals specified in .Xr sigaction 2 . A value of 0, however, will cause error checking to be performed (with no signal being sent). This can be used to check the validity of .Fa pid . .Pp For a process to have permission to send a signal to a process designated by .Fa pid , the real or effective user ID of the receiving process must match that of the sending process or the user must have appropriate privileges (such as given by a set-user-ID program or the user is the super-user). A single exception is the signal SIGCONT, which may always be sent to any descendant of the current process. .Bl -tag -width Ds .It \&If Fa pid No \&is greater than zero : .Fa Sig is sent to the process whose ID is equal to .Fa pid. .It \&If Fa pid No \&is zero : .Fa Sig is sent to all processes whose group ID is equal to the process group ID of the sender, and for which the process has permission; this is a variant of .Xr killpg 2 . .It \&If Fa pid No \&is -1 : If the user has super-user privileges, the signal is sent to all processes excluding system processes and the process sending the signal. If the user is not the super user, the signal is sent to all processes with the same uid as the user, excluding the process sending the signal. No error is returned if any process could be signaled. .El .Pp For compatibility with System V, if the process number is negative but not -1, the signal is sent to all processes whose process group ID is equal to the absolute value of the process number. This is a variant of .Xr killpg 2 . .Sh RETURN VALUES Upon successful completion, a value of 0 is returned. Otherwise, a value of -1 is returned and .Va errno is set to indicate the error. .Sh ERRORS .Fn Kill will fail and no signal will be sent if: .Bl -tag -width Er .\" ========== .It Bq Er EINVAL .Fa Sig is not a valid, supported signal number. .\" ========== .It Bq Er EPERM The sending process is not the super-user and its effective user id does not match the effective user-id of the receiving process. When signaling a process group, this error is returned if any members of the group could not be signaled. .\" ========== .It Bq Er ESRCH No process or process group can be found corresponding to that specified by .Fa pid . .\" ========== .It Bq Er ESRCH The process id was given as 0, but the sending process does not have a process group. .El .Sh SEE ALSO .Xr getpgrp 2 , .Xr getpid 2 , .Xr killpg 2 , .Xr sigaction 2 .Sh STANDARDS The .Fn kill function is expected to conform to .St -p1003.1-88 .