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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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.\" 4. 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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