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.

         sigprocmask fails if any of the following is true:

         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.

   SEE ALSO
         sigaction(2), signal(2), sigsetopts(3C), signal(5).

   DIAGNOSTICS
         On success, sigprocmask returns zero.  On failure, it returns -1 and
         sets errno to indicate the error.









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