sigprocmask(3) [ultrix man page]

sigprocmask(3)						     Library Functions Manual						    sigprocmask(3)

Name
       sigprocmask - examine and change blocked signals (POSIX)

Syntax
       #include <signal.h>

       int sigprocmask(how, set, oset)
       int how;
       sigset_t *set, *oset;

Description
       The system call is used to examine and/or change the calling process's signal mask. If the value of the argument set is not NULL, it points
       to a set of signals that will be used to change the currently blocked set.

       The value of the argument how indicates the manner in which the set is changed as defined by the following values, defined in <signal.h>:

       SIG_BLOCK
	      The resulting signal set is the union of the current set and the signal set pointed to by the argument set.

       SIG_UNBLOCK
	      The resulting signal set is the intersection of the current set and the complement of the signal set pointed to by the argument set.

       SIG_SETMASK
	      The resulting signal set is the signal 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 process's signal mask is unchanged; thus, the function can be used to enquire about currently blocked signals.

       The signal masks used as arguments to this function are manipulated using the functions.

       As a system restriction, SIGKILL and SIGSTOP cannot be blocked.

Return Values
       A 0 return value indicates a successful call.  A -1 return value indicates an error and errno is set to indicated the reason.

Diagnostics
       The function fails and the signal mask remains unchanged if the follow occurs:

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

See Also
       kill(2), sigsetmask(2), sigvec(2), sigblock(2), sigsetops(3)

																    sigprocmask(3)

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)