sigprocmask(2)							System Calls Manual						    sigprocmask(2)

NAME

       sigprocmask() - examine and change blocked signals

SYNOPSIS

DESCRIPTION

       The function allows the calling thread to examine and/or change its signal mask.

       If the argument set is not a null pointer, it points to a set of signals to be used to change the currently blocked set.

       The argument how indicates the way in which the set is changed and consists of one of the following values:

	      The resulting set will be the union
				of the current set and the signal set pointed to by set.

	      The resulting set will be the signal set pointed to by set.

	      The resulting set will be the intersection of the
				current set and the complement of the signal set pointed to by set.

       If  the argument oset is not a null pointer, the previous mask is stored in the location pointed to by oset.  If set is a null pointer, the
       value of the argument how is not significant and the thread's signal mask is unchanged; thus the call can be used  to  inquire  about  cur-
       rently blocked signals.

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

       It  is  not  possible  to  block  those	signals  which cannot  be  ignored.  This is enforced by the system without causing an error to be
       indicated.

       If any of the or signals are generated while they are blocked, the result is undefined, unless the signal was generated by a call to or

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

RETURN VALUE

       Upon successful completion, returns 0.  Otherwise -1 is returned, is set to indicate the error,	and  the  thread's  signal  mask  will	be
       unchanged.

ERRORS

       The function will fail if:

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

	      set	     or oset points to an invalid address.  The reliable detection of this error is implementation dependent.

APPLICATION USAGE

   Threads Considerations
       Each thread maintains its own blocked signal mask.  In a single-threaded process, modifies only the calling thread's blocked signal mask.

       Use of this function is unspecified in a multithreaded process.

       For more information regarding signals and threads, refer to signal(5).

   LWP (Lightweight Processes) Considerations
       modifies only the calling LWP's blocked signal mask.

AUTHOR

       was derived from the IEEE POSIX 1003.1-1988 Standard.

SEE ALSO

       sigaction(2), sigpending(2), sigsuspend(2), sigsetops(3C), pthread_sigmask(3T), signal(5).

STANDARDS CONFORMANCE

																    sigprocmask(2)