sigvec(3UCB) SunOS/BSD Compatibility Library Functions sigvec(3UCB)NAMEsigvec - software signal facilities
SYNOPSIS
/usr/ucb/cc [ flag ... ] file...
#include <signal.h>
int sigvec(sig, nvec, ovec)
int sig;
struct sigvec *nvec, *ovec;
DESCRIPTION
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
signal that caused their invocation to be blocked, but other signals
may yet occur. A global signal mask defines the set of signals cur‐
rently 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() or sigsetmask() call, or when a signal is
delivered to the process.
A process may also specify a set of flags for a signal that affect the
delivery of that signal.
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
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()
or sigsetmask() call is made). This mask is formed by taking the cur‐
rent signal mask, adding the signal to be delivered, and ORing in the
signal mask associated with the handler to be invoked.
The action to be taken when the signal is delivered is specified by a
sigvec() structure, which includes the following members:
void (*sv_handler)(); /* signal handler */
int sv_mask; /* signal mask to apply */
int sv_flags; /* see signal options */
#define SV_ONSTACK /* take signal on signal stack */
#define SV_INTERRUPT /* do not restart system on signal
return */
#define SV_RESETHAND /* reset handler to SIG_DFL when
signal taken*/
If the SV_ONSTACK bit is set in the flags for that signal, the system
will deliver the signal to the process on the signal stack specified
with sigstack(3UCB) rather than delivering the signal on the current
stack.
If nvec is not a NULL pointer, sigvec() assigns the handler specified
by sv_handler(), the mask specified by sv_mask(), and the flags speci‐
fied by sv_flags() to the specified signal. If nvec is a NULL pointer,
sigvec() does not change the handler, mask, or flags for the specified
signal.
The mask specified in nvec is not allowed to block SIGKILL, SIGSTOP, or
SIGCONT. The system enforces this restriction silently.
If ovec is not a NULL pointer, the handler, mask, and flags in effect
for the signal before the call to sigvec() are returned to the user. A
call to sigvec() with nvec a NULL pointer and ovec not a NULL pointer
can be used to determine the handling information currently in effect
for a signal without changing that information.
The following is a list of all signals with names as in the include
file <signal.h>:
SIGHUP hangup
SIGINT interrupt
SIGQUIT* quit
SIGILL* illegal instruction
SIGTRAP* trace trap
SIGABRT* abort (generated by abort(3C) routine)
SIGEMT* emulator trap
SIGFPE* arithmetic exception
SIGKILL kill (cannot be caught, blocked, or ignored)
SIGBUS* bus error
SIGSEGV* segmentation violation
SIGSYS* bad argument to function
SIGPIPE write on a pipe or other socket with no one to read it
SIGALRM alarm clock
SIGTERM software termination signal
SIGURG* urgent condition present on socket
SIGSTOP** stop (cannot be caught, blocked, or ignored)
SIGTSTP** stop signal generated from keyboard
SIGCONT* continue after stop (cannot be blocked)
SIGCHLD* child status has changed
SIGTTIN** background read attempted from control terminal
SIGTTOU** background write attempted to control terminal
SIGIO* I/O is possible on a descriptor (see fcntl(2))
SIGXCPU cpu time limit exceeded (see getrlimit(2))
SIGXFSZ file size limit exceeded (see getrlimit(2))
SIGVTALRM virtual time alarm; see setitimer() on getitimer(2)
SIGPROF profiling timer alarm; see setitimer() on getitimer(2)
SIGWINCH* window changed (see termio(7I))
SIGLOST resource lost (see lockd(1M))
SIGUSR1 user-defined signal 1
SIGUSR2 user-defined signal 2
The starred signals in the list above cause a core image if not caught
or ignored.
Once a signal handler is installed, it remains installed until another
sigvec() call is made, or an execve(2) is performed, unless the
SV_RESETHAND bit is set in the flags for that signal. In that case,
the value of the handler for the caught signal will be set to SIG_DFL
before entering the signal-catching function, unless the signal is SIG‐
ILL, SIGPWR, or SIGTRAP. Also, if this bit is set, the bit for that
signal in the signal mask will not be set; unless the signal mask asso‐
ciated with that signal blocks that signal, further occurrences of that
signal will not be blocked. The SV_RESETHAND flag is not available in
4.2BSD, hence it should not be used if backward compatibility is
needed.
The default action for a signal may be reinstated by setting the sig‐
nal's handler to SIG_DFL; this default is termination except for sig‐
nals marked with * or **. Signals marked with * are discarded if the
action is SIG_DFL; signals marked with ** cause the process to stop. If
the process is terminated, a "core image" will be made in the current
working directory of the receiving process if the signal is one for
which an asterisk appears in the above list (see core(4)).
If the handler for that signal is SIG_IGN, the signal is subsequently
ignored, and pending instances of the signal are discarded.
If a caught signal occurs during certain functions, the call is nor‐
mally restarted. The call can be forced to terminate prematurely with
an EINTR error return by setting the SV_INTERRUPT bit in the flags for
that signal. The SV_INTERRUPT flag is not available in 4.2BSD, hence it
should not be used if backward compatibility is needed. The affected
functions are read(2) or write(2) on a slow device (such as a terminal
or pipe or other socket, but not a file) and during a wait(3C).
After a fork(2) or vfork(2) the child inherits all signals, the signal
mask, the signal stack, and the restart/interrupt and reset-signal-han‐
dler flags.
The execve(2) call resets all caught signals to default action and
resets all signals to be caught on the user stack. Ignored signals
remain ignored; the signal mask remains the same; signals that inter‐
rupt functions continue to do so.
The accuracy of addr is machine dependent. For example, certain
machines may supply an address that is on the same page as the address
that caused the fault. If an appropriate addr cannot be computed it
will be set to SIG_NOADDR.
RETURN VALUES
A 0 value indicates that the call succeeded. A −1 return value indi‐
cates that an error occurred and errno is set to indicate the reason.
ERRORSsigvec() will fail and no new signal handler will be installed if one
of the following occurs:
EFAULT Either nvec or ovec is not a NULL pointer and points to mem‐
ory that is not a valid part of the process address space.
EINVAL sig is not a valid signal number, or, SIGKILL, or SIGSTOP.
SEE ALSOcc(1B), intro(2), exec(2), fcntl(2), fork(2), getitimer(2), getr‐
limit(2), ioctl(2), kill(2), read(2), umask(2), vfork(2), write(2),
ptrace(3C), setjmp(3C)sigblock(3UCB), signal(3C), signal(3UCB),
sigstack(3UCB), wait(3C), wait(3UCB), core(4), streamio(7I), termio(7I)NOTES
Use of these interfaces should be restricted to only applications writ‐
ten on BSD platforms. Use of these interfaces with any of the system
libraries or in multi-thread applications is unsupported.
SIGPOLL is a synonym for SIGIO. A SIGIO will be issued when a file
descriptor corresponding to a STREAMS (see intro(2)) file has a
"selectable" event pending. Unless that descriptor has been put into
asynchronous mode (see fcntl(2)), a process may specifically request
that this signal be sent using the I_SETSIG ioctl(2) call (see
streamio(7I)). Otherwise, the process will never receive SIGPOLLs0.
The handler routine can be declared:
void handler(int sig, int code, struct sigcontext *scp,
char *addr);
Here sig is the signal number; code is a parameter of certain signals
that provides additional detail; scp is a pointer to the sigcontext
structure (defined in signal.h), used to restore the context from
before the signal; and addr is additional address information.
The signals SIGKILL, SIGSTOP, and SIGCONT cannot be ignored.
SunOS 5.10 30 Oct 2007 sigvec(3UCB)
