sigvec(3UCB)					     SunOS/BSD Compatibility Library Functions					      sigvec(3UCB)

NAME

       sigvec - 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  han-
       dler 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 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() or sigsetmask() call, or when a signal is deliv-
       ered 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  cur-
       rently  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  sig-
       block() or sigsetmask() call is made).  This mask is formed by taking the current 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 spec-
       ified by sv_flags() to the specified signal.  If nvec is a NULL pointer, sigvec() does not change the handler, mask, or flags for the spec-
       ified 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 SIGILL, 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 associated 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 signal'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 normally 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-
       handler 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 interrupt 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 indicates that an error occurred and errno is set to indicate the reason.

ERRORS

       sigvec() 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 memory that is not a valid part of the process address space.

       EINVAL	 sig is not a valid signal number, or, SIGKILL, or SIGSTOP.

SEE ALSO

       cc(1B),	Intro(2),  exec(2),  fcntl(2),	fork(2),  getitimer(2),  getrlimit(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 written 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 5.11							    30 Oct 2007 						      sigvec(3UCB)