thr_sigsetmask(3thread)                      thr_sigsetmask(3thread)


       NAME
             thr_sigsetmask - change or examine the signal mask of a thread

       SYNOPSIS
             cc [options] -Kthread file
             #include <thread.h>
             int thr_sigsetmask(int how, const sigset_t *set, sigset_t *oset);

          Parameters
             how  SIG_BLOCK, SIG_UNBLOCK, or SIG_SETMASK

             set  pointer to a set of signals to be blocked or unblocked

             oset pointer to the value of the previous signal mask (set by
                  thr_sigsetmask)

       DESCRIPTION
             thr_sigsetmask changes or examines the calling thread's signal
             mask according to the way how and set are set.

             If there are any pending unblocked signals after the call to
             thr_sigsetmask, at least one of those signals will be
             delivered before the call to thr_sigsetmask returns.

             In this implementation, changing the signal mask of the thread
             will also change the signal mask of the lightweight process
             (LWP) running the thread.

          how Parameter
             how determines how set is interpreted.  Set how to one of the
             following values:

             SIG_BLOCK       Add the set of signals denoted by set to the
                             current signal mask.

             SIG_UNBLOCK     Remove the set of signals denoted by set from
                             the current signal mask.

             SIG_SETMASK     Replace the current signal mask with the set
                             of signals denoted by set.
             Note that 0 is not a valid value for how.

          set Parameter
             set points to a set of signals to be blocked or unblocked
             (according to the value of how) in the current thread.  set is
             usually constructed with the routines described on


                           Copyright 1994 Novell, Inc.               Page 1

      thr_sigsetmask(3thread)                      thr_sigsetmask(3thread)


            sigsetops(3C).  If set is NULL, the value of how is not
            significant, and the thread's signal mask will not be changed.

            It is not possible to block those signals that cannot be
            ignored [see sigaction(2)]; this restriction is silently
            imposed by the system.

         oset Parameter
            If oset is not NULL, thr_sigsetmask stores the value of the
            previous mask in that location.  If set is NULL and oset is
            not NULL, oset will point to the value of the thread's current
            signal mask.

         Return Values
            thr_sigsetmask returns zero for success and an error number
            for failure, as described below.

            If thr_sigsetmask fails, the thread's signal mask is not
            changed.

         Errors
            If any of the following conditions occurs, thr_sigsetmask
            returns the corresponding value:

            EINVAL   The value of how is not equal to one of the defined
                     values.

      USAGE
         Portability Considerations
            Threads should use thr_sigsetmask rather than sigprocmask(2).
            In some implementations, sigprocmask may be trapped and
            behaves identically to thr_sigsetmask, but for portability,
            thr_sigsetmask should be used.

         Performance Considerations
            In this implementation, an application running multiplexed
            threads with different signal masks may observe a performance
            degradation.  Therefore for optimal performance, all
            multiplexing threads in a process should use the same signal
            mask.  Applications needing threads that will run frequently
            with signal masks different from other threads in the process,
            should consider creating those threads as bound threads for
            better performance.





                          Copyright 1994 Novell, Inc.               Page 2

       thr_sigsetmask(3thread)                      thr_sigsetmask(3thread)


          Style Considerations
             The preferred coding style is to mask all signals and use
             sigwait synchronously.

       REFERENCES
             kill(2), sigaction(2), signal(5), sigprocmask(2), sigsend(2),
             sigsetops(3C), sigwait(2), thr_kill(3thread), thread(3thread)









































                           Copyright 1994 Novell, Inc.               Page 3