BSD SIGVEC(3) Programmer's Manual SIGVEC(3)
NAME
sigvec - software signal facilities
SYNOPSIS
#include <signal.h>
struct sigvec {
void (*sv_handler)();
sigset_t sv_mask;
int sv_flags;
};
sigvec(int sig, struct sigvec *vec, struct sigvec *ovec);
DESCRIPTION
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. 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 sig-
nal that caused their invocation blocked, but other signals may yet oc-
cur. 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 sig-
block(2) or sigsetmask(2) call, or when a signal is delivered to the pro-
cess.
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 sig-
nal is delivered, the current state of the process is saved, a new signal
mask is calculated (as described below), and the signal handler is in-
voked. The call to the handler is arranged so that if the signal han-
dling routine returns normally the process will resume execution in the
context from before the signal's delivery. If the process wishes to re-
sume 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 or
sigsetmask call is made). This mask is formed by taking the current sig-
nal mask, adding the signal to be delivered, and or'ing in 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 a handler routine and mask to be used when delivering the spec-
ified signal. Further, if the SV_ONSTACK bit is set in sv_flags, the
system will deliver the signal to the process on a signal stack, speci-
fied with sigstack(2). If ovec is non-zero, the previous handling infor-
mation for the signal is returned to the user.
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(2) call (formerly SIGIOT)
SIGEMT create core image emulate instruction executed
SIGFPE create core image floating-point exception
SIGKILL terminate process kill program
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 signal discard 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
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 above signal list
for each signal's default action. If sv_handler is SIG_IGN current and
pending instances of the signal are ignored and discarded.
If a signal is caught during the system calls listed below, the call is
normally restarted. The call can be forced to terminate prematurely with
an EINTR error return by setting the SV_INTERRUPT bit in sv_flags. The
affected system calls include 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 restart/interrupt 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 t...