sigprocmask(2)                   UNIX System V                   sigprocmask(2)


NAME
      sigprocmask - change or examine signal mask

SYNOPSIS
      #include <signal.h>

      int sigprocmask(int how, const sigsett *set, sigsett *oset);

DESCRIPTION
      The sigprocmask function is used to examine and/or change the calling
      process's signal mask.  If the value is SIGBLOCK, the set pointed to by
      the argument set is added to the current signal mask.  If the value is
      SIGUNBLOCK, the set pointed by the argument set is removed from the
      current signal mask.  If the value is SIGSETMASK, 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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