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SIGVEC(3)	       FreeBSD Library Functions Manual		     SIGVEC(3)

     sigvec -- software	signal facilities

     #include <signal.h>

     struct sigvec {
	     void     (*sv_handler)();
	     int      sv_mask;
	     int      sv_flags;

     sigvec(int	sig, struct sigvec *vec, struct	sigvec *ovec);

     This interface is made obsolete by	sigaction(2).

     The system	defines	a set of signals that may be delivered to a process.
     Signal delivery resembles the occurrence of a hardware interrupt: the
     signal is blocked from further occurrence,	the current process context is
     saved, and	a new one is built.  A process may specify a handler to	which
     a signal is delivered, or specify that a signal is	to be blocked or
     ignored.  A process may also specify that a default action	is to be taken
     by	the system when	a signal occurs.  A signal may also be blocked,	in
     which case	its delivery is	postponed until	it is unblocked.  The action
     to	be taken on delivery is	determined at the time of delivery.  Normally,
     signal handlers execute on	the current stack of the process.  This	may be
     changed, on a per-handler basis, so that signals are taken	on a special
     signal stack.

     All signals have the same priority.  Signal routines execute with the
     signal that caused	their invocation blocked, but other signals may	yet
     occur.  A global signal mask defines the set of signals currently blocked
     from delivery to a	process.  The signal mask for a	process	is initialized
     from that of its parent (normally 0).  It may be changed with a
     sigblock(3) or sigsetmask(3) call,	or when	a signal is delivered to the

     When a signal condition arises for	a process, the signal is added to a
     set of signals pending for	the process.  If the signal is not currently
     blocked by	the process then it is delivered to the	process.  When a
     caught signal is delivered, the current state of the process is saved, a
     new signal	mask is	calculated (as described below), and the signal	han-
     dler is invoked.  The call	to the handler is arranged so that if the sig-
     nal handling routine returns normally the process will resume execution
     in	the context from before	the signal's delivery.	If the process wishes
     to	resume in a different context, then it must arrange to restore the
     previous context itself.

     When a signal is delivered	to a process a new signal mask is installed
     for the duration of the process' signal handler (or until a sigblock(3)
     or	sigsetmask(3) call is made).  This mask	is formed by taking the	union
     of	the current signal mask, the signal to be delivered, and the signal
     mask associated with the handler to be invoked.

     sigvec() assigns a	handler	for a specific signal.	If vec is non-zero, it
     specifies an action (SIG_DFL, SIG_IGN, or a handler routine) and mask to
     be	used when delivering the specified signal.  If ovec is non-zero, the
     previous handling information for the signal is returned to the user.

     Once a signal handler is installed, it remains installed until another
     sigvec() call is made, or an execve(2) is performed.  A signal-specific
     default action may	be reset by setting sv_handler to SIG_DFL.  The	de-
     faults are	process	termination, possibly with core	dump; no action; stop-
     ping the process; or continuing the process.  See the signal list below
     for each signal's default action.	If sv_handler is set to	SIG_IGN, the
     default action for	the signal is to discard the signal, and if a signal
     is	pending, the pending signal is discarded even if the signal is masked.
     If	sv_handler is set to SIG_IGN, current and pending instances of the
     signal are	ignored	and discarded.

     Options may be specified by setting sv_flags.  If the SV_ONSTACK bit is
     set in sv_flags, the system will deliver the signal to the	process	on a
     signal stack, specified with sigaltstack(2).

     If	a signal is caught during the system calls listed below, the call may
     be	restarted, the call may	return with a data transfer shorter than re-
     quested, or the call may be forced	to terminate with the error EINTR.
     Interrupting of pending calls is requested	by setting the SV_INTERRUPT
     bit in sv_flags.  The affected system calls include open(2), read(2),
     write(2), sendto(2), recvfrom(2), sendmsg(2) and recvmsg(2) on a communi-
     cations channel or	a slow device (such as a terminal, but not a regular
     file) and during a	wait(2)	or ioctl(2).  However, calls that have already
     committed are not restarted, but instead return a partial success (for
     example, a	short read count).

     After a fork(2) or	vfork(2) all signals, the signal mask, the signal
     stack, and	the interrupt/restart flags are	inherited by the child.

     execve(2) reinstates the default action for all signals which were	caught
     and resets	all signals to be caught on the	user stack.  Ignored signals
     remain ignored; the signal	mask remains the same; signals that interrupt
     pending system calls continue to do so.

     The following is a	list of	all signals with names as in the include file

     Name	  Default Action       Description
     SIGHUP	  terminate process    terminal	line hangup
     SIGINT	  terminate process    interrupt program
     SIGQUIT	  create core image    quit program
     SIGILL	  create core image    illegal instruction
     SIGTRAP	  create core image    trace trap
     SIGABRT	  create core image    abort(3)	call (formerly SIGIOT)
     SIGEMT	  create core image    emulate instruction executed
     SIGFPE	  create core image    floating-point exception
     SIGKILL	  terminate process    kill program (cannot be caught or
     SIGBUS	  create core image    bus error
     SIGSEGV	  create core image    segmentation violation
     SIGSYS	  create core image    system call given invalid argument
     SIGPIPE	  terminate process    write on	a pipe with no reader
     SIGALRM	  terminate process    real-time timer expired
     SIGTERM	  terminate process    software	termination signal
     SIGURG	  discard signal       urgent condition	present	on socket
     SIGSTOP	  stop process	       stop (cannot be caught or ignored)
     SIGTSTP	  stop process	       stop signal generated from keyboard
     SIGCONT	  discard signal       continue	after stop
     SIGCHLD	  discard signal       child status has	changed
     SIGTTIN	  stop process	       background read attempted from control
     SIGTTOU	  stop process	       background write	attempted to control
     SIGIO	  discard signal       I/O is possible on a descriptor (see
     SIGXCPU	  terminate process    CPU time	limit exceeded (see
     SIGXFSZ	  terminate process    file size limit exceeded	(see
     SIGVTALRM	  terminate process    virtual time alarm (see setitimer(2))
     SIGPROF	  terminate process    profiling timer alarm (see
     SIGWINCH	  discard signal       window size change
     SIGINFO	  discard signal       status request from keyboard
     SIGUSR1	  terminate process    user-defined signal 1
     SIGUSR2	  terminate process    user-defined signal 2

     The mask specified	in vec is not allowed to block SIGKILL or SIGSTOP.
     This is enforced silently by the system.

     The SV_INTERRUPT flag is not available in 4.2BSD, hence it	should not be
     used if backward compatibility is needed.

     A 0 value indicated that the call succeeded.  A -1	return value indicates
     an	error occurred and errno is set	to indicated the reason.

     For an example of signal handler declarations, see	sigaction(2).

     sigvec() will fail	and no new signal handler will be installed if one of
     the following occurs:

     [EFAULT]		Either vec or ovec points to memory that is not	a
			valid part of the process address space.

     [EINVAL]		sig is not a valid signal number.

     [EINVAL]		An attempt is made to ignore or	supply a handler for

     kill(1), kill(2), ptrace(2), sigaction(2),	sigaltstack(2),
     sigprocmask(2), sigsuspend(2), setjmp(3), sigaddset(3), sigblock(3),
     siginterrupt(3), sigpause(3), sigsetmask(3), tty(4)

     A sigvec()	system call first appeared in 4.2BSD.  It was reimplemented as
     a wrapper around sigaction(2) in 4.3BSD-Reno.  The	old system call	was
     kept for compatibility until OpenBSD 4.9.

FreeBSD	13.0			 May 29, 2017			  FreeBSD 13.0


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