159 lines
4.5 KiB
Groff
159 lines
4.5 KiB
Groff
.\" Copyright (c) 1980, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)kill.2 8.3 (Berkeley) 4/19/94
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.\"
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.Dd December 1, 2019
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.Dt KILL 2
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.Os
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.Sh NAME
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.Nm kill
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.Nd send signal to a process
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In sys/types.h
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.In signal.h
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.Ft int
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.Fn kill "pid_t pid" "int sig"
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.Sh DESCRIPTION
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The
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.Fn kill
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system call sends the signal given by
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.Fa sig
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to
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.Fa pid ,
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a
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process or a group of processes.
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The
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.Fa sig
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argument
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may be one of the signals specified in
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.Xr sigaction 2
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or it may be 0, in which case
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error checking is performed but no
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signal is actually sent.
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This can be used to check the validity of
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.Fa pid .
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.Pp
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For a process to have permission to send a signal to a process designated
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by
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.Fa pid ,
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the user must be the super-user, or
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the real or saved user ID of the receiving process must match
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the real or effective user ID of the sending process.
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A single exception is the signal SIGCONT, which may always be sent
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to any process with the same session ID as the sender.
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In addition, if the
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.Va security.bsd.conservative_signals
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.Xr sysctl 9
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is set to 1, the user is not a super-user, and
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the receiver is set-uid, then
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only job control and terminal control signals may
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be sent (in particular, only SIGKILL, SIGINT, SIGTERM, SIGALRM,
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SIGSTOP, SIGTTIN, SIGTTOU, SIGTSTP, SIGHUP, SIGUSR1, SIGUSR2).
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.Bl -tag -width Ds
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.It \&If Fa pid No \&is greater than zero :
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The
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.Fa sig
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signal
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is sent to the process whose ID is equal to
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.Fa pid .
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.It \&If Fa pid No \&is zero :
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The
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.Fa sig
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signal
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is sent to all processes whose group ID is equal
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to the process group ID of the sender, and for which the
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process has permission;
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this is a variant of
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.Xr killpg 2 .
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.It \&If Fa pid No \&is -1 :
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If the user has super-user privileges,
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the signal is sent to all processes excluding
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system processes
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(with
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.Dv P_SYSTEM
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flag set),
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process with ID 1
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(usually
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.Xr init 8 ) ,
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and the process sending the signal.
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If the user is not the super user, the signal is sent to all processes
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which the caller has permissions to, excluding the process sending the signal.
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No error is returned if any process could be signaled.
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.El
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.Pp
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If the process number is negative but not -1,
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the signal is sent to all processes whose process group ID
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is equal to the absolute value of the process number.
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This is a variant of
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.Xr killpg 2 .
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.Sh RETURN VALUES
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.Rv -std kill
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.Sh ERRORS
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The
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.Fn kill
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system call
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will fail and no signal will be sent if:
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.Bl -tag -width Er
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.It Bq Er EINVAL
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The
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.Fa sig
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argument
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is not a valid signal number.
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.It Bq Er ESRCH
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No process or process group can be found corresponding to that specified by
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.Fa pid .
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.It Bq Er EPERM
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The sending process does not have permission to send
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.Va sig
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to any receiving process.
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.El
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.Sh SEE ALSO
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.Xr getpgrp 2 ,
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.Xr getpid 2 ,
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.Xr killpg 2 ,
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.Xr sigaction 2 ,
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.Xr sigqueue 2 ,
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.Xr raise 3 ,
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.Xr init 8
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.Sh STANDARDS
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The
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.Fn kill
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system call is expected to conform to
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.St -p1003.1-90 .
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.Sh HISTORY
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A version of the
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.Fn kill
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function appeared in
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.At v3 .
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The signal number was added to the
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.Fn kill
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function in
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.At v4 .
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