sigvec - software signal facilities
#include <signal.h>
struct sigvec {
void (*sv_handler)();
int sv_mask;
int sv_flags;
};
int
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
process.
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 handler
is invoked. The call to the handler is arranged so
that if the signal
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 defaults
are process termination, possibly with core dump; no
action; stopping
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 sigstack(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 requested,
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 communications
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
<signal.h>:
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
ignored)
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 terminal
SIGTTOU stop process background write attempted to
control terminal
SIGIO discard signal I/O is possible on a
descriptor
(see fcntl(2))
SIGXCPU terminate process CPU time limit exceeded (see
setrlimit(2))
SIGXFSZ terminate process file size limit exceeded (see
setrlimit(2))
SIGVTALRM terminate process virtual time alarm
(see
setitimer(2))
SIGPROF terminate process profiling timer
alarm (see
setitimer(2))
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
SIGKILL or SIGSTOP.
kill(1), kill(2), ptrace(2), sigaction(2), sigaltstack(2),
sigprocmask(2), sigstack(2), sigsuspend(2), setjmp(3), sigblock(3),
siginterrupt(3), sigpause(3), sigsetmask(3), sigsetops(3),
tty(4)
OpenBSD 3.6 April 29, 1991
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