0cc9fb7551
As mandated by POSIX. Also clarify the kill(2) manpage. While there, restructure the code in killpg1() to use helper which keeps overall state of the process list iteration in the killpg1_ctx structued, later used to infer the error returned. Reported by: amdmi3 Reviewed by: jilles Sponsored by: The FreeBSD Foundation MFC after: 2 weeks Differential revision: https://reviews.freebsd.org/D22621
160 lines
4.5 KiB
Groff
160 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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.\" $FreeBSD$
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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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