fbbd9655e5
Renumber cluase 4 to 3, per what everybody else did when BSD granted them permission to remove clause 3. My insistance on keeping the same numbering for legal reasons is too pedantic, so give up on that point. Submitted by: Jan Schaumann <jschauma@stevens.edu> Pull Request: https://github.com/freebsd/freebsd/pull/96
343 lines
10 KiB
Groff
343 lines
10 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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.\" @(#)sigvec.2 8.2 (Berkeley) 4/19/94
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.\" $FreeBSD$
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.\"
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.Dd April 19, 1994
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.Dt SIGVEC 2
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.Os
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.Sh NAME
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.Nm sigvec
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.Nd 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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.Bd -literal
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struct sigvec {
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void (*sv_handler)();
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int sv_mask;
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int sv_flags;
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};
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.Ed
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.Ft int
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.Fn sigvec "int sig" "struct sigvec *vec" "struct sigvec *ovec"
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.Sh DESCRIPTION
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.Bf -symbolic
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This interface is made obsolete by
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.Xr sigaction 2 .
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.Ef
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.Pp
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The system defines a set of signals that may be delivered to a process.
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Signal delivery resembles the occurrence of a hardware interrupt:
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the signal is blocked from further occurrence, the current process
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context is saved, and a new one is built.
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A process may specify a
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.Em handler
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to which a signal is delivered, or specify that a signal is to be
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.Em blocked
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or
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.Em ignored .
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A process may also specify that a default action is to be taken
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by the system when a signal occurs.
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Normally, signal handlers execute on the current stack
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of the process.
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This may be changed, on a per-handler basis,
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so that signals are taken on a special
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.Em "signal stack" .
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.Pp
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All signals have the same
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.Em priority .
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Signal routines execute with the signal that caused their
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invocation
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.Em blocked ,
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but other signals may yet occur.
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A global
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.Em "signal mask"
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defines the set of signals currently blocked from delivery
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to a process.
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The signal mask for a process is initialized
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from that of its parent (normally 0).
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It
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may be changed with a
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.Xr sigblock 2
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or
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.Xr sigsetmask 2
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call, or when a signal is delivered to the process.
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.Pp
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When a signal
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condition arises for a process, the signal is added to a set of
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signals pending for the process.
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If the signal is not currently
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.Em blocked
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by the process then it is delivered to the process.
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When a signal
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is delivered, the current state of the process is saved,
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a new signal mask is calculated (as described below),
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and the signal handler is invoked.
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The call to the handler
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is arranged so that if the signal handling routine returns
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normally the process will resume execution in the context
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from before the signal's delivery.
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If the process wishes to resume in a different context, then it
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must arrange to restore the previous context itself.
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.Pp
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When a signal is delivered to a process a new signal mask is
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installed for the duration of the process' signal handler
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(or until a
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.Xr sigblock 2
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or
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.Xr sigsetmask 2
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call is made).
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This mask is formed by taking the current signal mask,
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adding the signal to be delivered, and
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.Em or Ns 'ing
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in the signal mask associated with the handler to be invoked.
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.Pp
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The
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.Fn sigvec
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function
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assigns a handler for a specific signal.
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If
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.Fa vec
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is non-zero, it
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specifies a handler routine and mask
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to be used when delivering the specified signal.
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Further, if the
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.Dv SV_ONSTACK
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bit is set in
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.Fa sv_flags ,
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the system will deliver the signal to the process on a
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.Em "signal stack" ,
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specified with
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.Xr sigaltstack 2 .
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If
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.Fa ovec
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is non-zero, the previous handling information for the signal
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is returned to the user.
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.Pp
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The following is a list of all signals
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with names as in the include file
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.In signal.h :
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.Bl -column SIGVTALARMXX "create core imagexxx"
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.It Sy "NAME Default Action Description"
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.It Dv SIGHUP No " terminate process" " terminal line hangup"
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.It Dv SIGINT No " terminate process" " interrupt program"
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.It Dv SIGQUIT No " create core image" " quit program"
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.It Dv SIGILL No " create core image" " illegal instruction"
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.It Dv SIGTRAP No " create core image" " trace trap"
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.It Dv SIGABRT No " create core image" Ta Xr abort 3
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call (formerly
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.Dv SIGIOT )
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.It Dv SIGEMT No " create core image" " emulate instruction executed"
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.It Dv SIGFPE No " create core image" " floating-point exception"
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.It Dv SIGKILL No " terminate process" " kill program"
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.It Dv SIGBUS No " create core image" " bus error"
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.It Dv SIGSEGV No " create core image" " segmentation violation"
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.It Dv SIGSYS No " create core image" " non-existent system call invoked"
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.It Dv SIGPIPE No " terminate process" " write on a pipe with no reader"
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.It Dv SIGALRM No " terminate process" " real-time timer expired"
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.It Dv SIGTERM No " terminate process" " software termination signal"
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.It Dv SIGURG No " discard signal" " urgent condition present on socket"
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.It Dv SIGSTOP No " stop process" " stop (cannot be caught or ignored)"
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.It Dv SIGTSTP No " stop process" " stop signal generated from keyboard"
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.It Dv SIGCONT No " discard signal" " continue after stop"
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.It Dv SIGCHLD No " discard signal" " child status has changed"
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.It Dv SIGTTIN No " stop process" " background read attempted from control terminal"
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.It Dv SIGTTOU No " stop process" " background write attempted to control terminal"
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.It Dv SIGIO No " discard signal" Tn " I/O"
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is possible on a descriptor (see
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.Xr fcntl 2 )
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.It Dv SIGXCPU No " terminate process" " cpu time limit exceeded (see"
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.Xr setrlimit 2 )
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.It Dv SIGXFSZ No " terminate process" " file size limit exceeded (see"
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.Xr setrlimit 2 )
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.It Dv SIGVTALRM No " terminate process" " virtual time alarm (see"
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.Xr setitimer 2 )
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.It Dv SIGPROF No " terminate process" " profiling timer alarm (see"
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.Xr setitimer 2 )
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.It Dv SIGWINCH No " discard signal" " Window size change"
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.It Dv SIGINFO No " discard signal" " status request from keyboard"
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.It Dv SIGUSR1 No " terminate process" " User defined signal 1"
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.It Dv SIGUSR2 No " terminate process" " User defined signal 2"
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.El
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.Pp
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Once a signal handler is installed, it remains installed
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until another
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.Fn sigvec
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call is made, or an
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.Xr execve 2
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is performed.
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A signal-specific default action may be reset by
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setting
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.Fa sv_handler
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to
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.Dv SIG_DFL .
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The defaults are process termination, possibly with core dump;
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no action; stopping the process; or continuing the process.
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See the above signal list for each signal's default action.
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If
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.Fa sv_handler
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is
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.Dv SIG_IGN
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current and pending instances
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of the signal are ignored and discarded.
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.Pp
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If a signal is caught during the system calls listed below,
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the call is normally restarted.
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The call can be forced to terminate prematurely with an
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.Er EINTR
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error return by setting the
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.Dv SV_INTERRUPT
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bit in
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.Fa sv_flags .
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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 slow device (such as a terminal,
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but not a regular file)
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and during a
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.Xr wait 2
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or
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.Xr ioctl 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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After a
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.Xr fork 2
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or
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.Xr vfork 2
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all signals, the signal mask, the signal stack,
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and the restart/interrupt flags are inherited by the child.
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.Pp
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The
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.Xr execve 2
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system call reinstates the default
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action for all signals which were caught and
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resets all signals to be caught on the user stack.
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Ignored signals remain ignored;
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the signal mask remains the same;
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signals that interrupt system calls continue to do so.
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.Sh NOTES
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The mask specified in
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.Fa vec
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is not allowed to block
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.Dv SIGKILL
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or
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.Dv SIGSTOP .
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This is done silently by the system.
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.Pp
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The
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.Dv SV_INTERRUPT
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flag is not available in
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.Bx 4.2 ,
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hence it should not be used if backward compatibility is needed.
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.Sh RETURN VALUES
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.Rv -std sigvec
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.Sh EXAMPLES
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On the
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.Tn VAX\-11
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The handler routine can be declared:
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.Bd -literal -offset indent
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void handler(sig, code, scp)
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int sig, code;
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struct sigcontext *scp;
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.Ed
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.Pp
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Here
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.Fa sig
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is the signal number, into which the hardware faults and traps are
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mapped as defined below.
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The
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.Fa code
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argument
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is either a constant
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as given below or, for compatibility mode faults, the code provided by
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the hardware (Compatibility mode faults are distinguished from the
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other
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.Dv SIGILL
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traps by having
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.Dv PSL_CM
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set in the psl).
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The
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.Fa scp
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argument
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is a pointer to the
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.Fa sigcontext
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structure (defined in
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.In signal.h ) ,
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used to restore the context from before the signal.
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.Sh ERRORS
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The
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.Fn sigvec
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function
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will fail and no new signal handler will be installed if one
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of the following occurs:
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.Bl -tag -width Er
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.It Bq Er EFAULT
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Either
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.Fa vec
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or
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.Fa ovec
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points to memory that is not a valid part of the process
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address space.
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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 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 sigblock 2 ,
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.Xr sigpause 2 ,
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.Xr sigprocmask 2 ,
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.Xr sigsetmask 2 ,
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.Xr sigsuspend 2 ,
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.Xr setjmp 3 ,
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.Xr siginterrupt 3 ,
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.Xr signal 3 ,
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.Xr sigsetops 3 ,
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.Xr tty 4
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.Sh BUGS
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This manual page is still confusing.
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