2fe8fb192f
There is important information about booting non-ack images in docs/UPDATING. ack/aout-format images can't be built any more, and booting clang/ELF-format ones is a little different. Updating to the new boot monitor is recommended. Changes in this commit: . drop boot monitor -> allowing dropping ack support . facility to copy ELF boot files to /boot so that old boot monitor can still boot fairly easily, see UPDATING . no more ack-format libraries -> single-case libraries . some cleanup of OBJECT_FMT, COMPILER_TYPE, etc cases . drop several ack toolchain commands, but not all support commands (e.g. aal is gone but acksize is not yet). . a few libc files moved to netbsd libc dir . new /bin/date as minix date used code in libc/ . test compile fix . harmonize includes . /usr/lib is no longer special: without ack, /usr/lib plays no kind of special bootstrapping role any more and bootstrapping is done exclusively through packages, so releases depend even less on the state of the machine making them now. . rename nbsd_lib* to lib* . reduce mtree
191 lines
5.6 KiB
Groff
191 lines
5.6 KiB
Groff
.\" $NetBSD: signal.3,v 1.24 2004/06/13 19:17:06 lha Exp $
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.\"
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.\" 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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.\" @(#)signal.3 8.3 (Berkeley) 4/19/94
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.\"
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.Dd June 11, 2004
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.Dt SIGNAL 3
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.Os
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.Sh NAME
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.Nm signal
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.Nd simplified software signal facilities
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In signal.h
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.\" The following is Quite Ugly, but syntactically correct. Don't try to
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.\" fix it.
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.Ft void \*(lp*
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.Fn signal "int sig" "void \*(lp*func\*(rp\*(lpint\*(rp\*(rp\*(rp\*(lpint"
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.Sh DESCRIPTION
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This
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.Fn signal
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facility
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is a simplified interface to the more general
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.Xr sigaction 2
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facility.
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.Pp
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Signals allow the manipulation of a process from outside its
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domain as well as allowing the process to manipulate itself or
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copies of itself (children).
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There are two general types of signals:
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those that cause termination of a process and those that do not.
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Signals which cause termination of a program might result from
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an irrecoverable error or might be the result of a user at a terminal
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typing the `interrupt' character.
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Signals are used when a process is stopped because it wishes to access
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its control terminal while in the background (see
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.Xr tty 4 ) .
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Signals are optionally generated
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when a process resumes after being stopped,
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when the status of child processes changes,
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or when input is ready at the control terminal.
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Most signals result in the termination of the process receiving them
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if no action
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is taken; some signals instead cause the process receiving them
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to be stopped, or are simply discarded if the process has not
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requested otherwise.
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Except for the
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.Dv SIGKILL
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and
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.Dv SIGSTOP
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signals, the
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.Fn signal
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function allows for a signal to be caught, to be ignored, or to generate
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an interrupt.
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See
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.Xr signal 7
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for comprehensive list of supported signals.
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.Pp
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The
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.Fa func
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procedure allows a user to choose the action upon receipt of a signal.
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To set the default action of the signal to occur as listed above,
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.Fa func
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should be
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.Dv SIG_DFL .
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A
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.Dv SIG_DFL
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resets the default action.
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To ignore the signal
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.Fa func
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should be
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.Dv SIG_IGN .
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This will cause subsequent instances of the signal to be ignored
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and pending instances to be discarded.
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If
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.Dv SIG_IGN
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is not used,
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further occurrences of the signal are
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automatically blocked and
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.Fa func
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is called.
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.Pp
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The handled signal is unblocked when the
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function returns and
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the process continues from where it left off when the signal occurred.
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.Bf -symbolic
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Unlike previous signal facilities, the handler
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func() remains installed after a signal has been delivered.
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.Ef
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.Pp
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For some system calls, if a signal is caught while the call is
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executing and the call is prematurely terminated,
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the call is automatically restarted.
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(The handler is installed using the
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.Dv SA_RESTART
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flag with
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.Xr sigaction 2 ) .
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The affected system calls include
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.Xr read 2 ,
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.Xr write 2 ,
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.Xr sendto 2 ,
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.Xr recvfrom 2 ,
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.Xr sendmsg 2
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and
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.Xr recvmsg 2
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on a communications channel or a low speed device
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and during a
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.Xr ioctl 2
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or
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.Xr wait 2 .
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However, calls that have already committed are not restarted,
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but instead return a partial success (for example, a short read count).
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.Pp
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When a process which has installed signal handlers forks,
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the child process inherits the signals.
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All caught signals may be reset to their default action by a call
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to the
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.Xr execve 2
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function;
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ignored signals remain ignored.
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.Pp
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Only functions that are async-signal-safe can safely be used in signal
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handlers, see
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.Xr signal 7
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for a complete list.
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.Sh RETURN VALUES
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The previous action is returned on a successful call.
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Otherwise,
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.Dv SIG_ERR
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is returned and the global variable
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.Va errno
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is set to indicate the error.
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.Sh ERRORS
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.Fn signal
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will fail and no action will take place if one of the following occur:
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.Bl -tag -width Er
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.It Bq Er EINVAL
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Specified
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.Em sig
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is not a valid signal number.
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.It Bq Er EINVAL
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An attempt is made to ignore or supply a handler for
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.Dv SIGKILL
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or
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.Dv SIGSTOP .
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.El
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.Sh SEE ALSO
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.Xr kill 1 ,
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.Xr kill 2 ,
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.Xr ptrace 2 ,
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.Xr sigaction 2 ,
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.Xr sigaltstack 2 ,
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.Xr sigprocmask 2 ,
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.Xr sigsuspend 2 ,
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.Xr psignal 3 ,
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.Xr setjmp 3 ,
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.Xr strsignal 3 ,
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.Xr tty 4 ,
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.Xr signal 7
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.Sh HISTORY
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This
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.Fn signal
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facility appeared in
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.Bx 4.0 .
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