SIGPROCMASK(2)		   Linux Programmers Manual	       SIGPROCMASK(2)



NAME
       sigprocmask - examine and change blocked signals

SYNOPSIS
       #include 

       int sigprocmask(int how, const sigset_t *set, sigset_t *oldset);

DESCRIPTION
       sigprocmask()  is  used to change the signal mask, the set of currently
       blocked signals.  The behavior of the call is dependent on the value of
       how, as follows.

       SIG_BLOCK
	      The  set	of blocked signals is the union of the current set and
	      the set argument.

       SIG_UNBLOCK
	      The signals in set are removed from the current set  of  blocked
	      signals.	It is permissible to attempt to unblock a signal which
	      is not blocked.

       SIG_SETMASK
	      The set of blocked signals is set to the argument set.

       If oldset is non-null, the previous value of the signal mask is	stored
       in oldset.

       If  set	is  NULL,  then  the  signal  mask  is unchanged (i.e., how is
       ignored), but the current value of  the	signal	mask  is  nevertheless
       returned in oldset (it is not NULL).

       The use of sigprocmask() is unspecified in a multithreaded process; see
       pthread_sigmask(3).

RETURN VALUE
       sigprocmask() returns 0 on success and -1 on error.

ERRORS
       EINVAL The value specified in how was invalid.

CONFORMING TO
       POSIX.1-2001.

NOTES
       It is not possible to block SIGKILL or SIGSTOP.	Attempts to do so  are
       silently ignored.

       If  SIGBUS,  SIGFPE,  SIGILL,  or  SIGSEGV are generated while they are
       blocked, the result is undefined, unless the signal  was  generated  by
       the kill(2), sigqueue(2), or raise(3).

       See sigsetops(3) for details on manipulating signal sets.

SEE ALSO
       kill(2), pause(2), sigaction(2), signal(2), sigpending(2), sigqueue(2),
       sigsuspend(2), pthread_sigmask(3), sigsetops(3), signal(7)

COLOPHON
       This page is part of release 3.05 of the Linux  man-pages  project.   A
       description  of	the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.



Linux				  2005-09-15			SIGPROCMASK(2)