sigprocmask(2)                                        sigprocmask(2)


       NAME
             sigprocmask - change or examine signal mask

       SYNOPSIS
             #include <signal.h>
             int sigprocmask(int how, const sigset_t *set, sigset_t *oset);

       DESCRIPTION
             The sigprocmask function is used to examine and/or change the
             calling process's signal mask.  If the value is SIG_BLOCK, the
             set pointed to by the argument set is added to the current
             signal mask.  If the value is SIG_UNBLOCK, the set pointed by
             the argument set is removed from the current signal mask.  If
             the value is SIG_SETMASK, the current signal mask is replaced
             by the set pointed to by the argument set.  If the argument
             oset is not NULL, the previous mask is stored in the space
             pointed to by oset.  If the value of the argument set is NULL,
             the value how is not significant and the process's signal mask
             is unchanged; thus, the call can be used to enquire about
             currently blocked signals.

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

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

             If sigprocmask fails, the process's signal mask is not
             changed.

          Return Values
             On success, sigprocmask returns 0.  On failure, sigprocmask
             returns -1 and sets errno to identify the error.

          Errors
             In the following conditions, sigprocmask fails and sets errno
             to:

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

             EFAULT         The value of set or oset points outside the
                            process's allocated address space.



                           Copyright 1994 Novell, Inc.               Page 1

      sigprocmask(2)                                        sigprocmask(2)


      REFERENCES
            sigaction(2), signal(2), signal(5), sigsetops(3C)

      NOTICES
         Considerations for Threads Programming
            Signal masks are maintained per thread.  See signal(5) for
            further details.

         Considerations for Lightweight Processes
            Signal masks are internally maintained per LWP.  The Threads
            Library has a wrapper function for this system call to make
            its effect per thread.




































                          Copyright 1994 Novell, Inc.               Page 2