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SIGPROCMASK(2)		       System Calls Manual		  SIGPROCMASK(2)

NAME
     sigprocmask -- manipulate current signal mask

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <signal.h>

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

DESCRIPTION
     The  sigprocmask()  system  call examines and/or changes the current signal
     mask (those signals that are blocked from delivery).  Signals  are  blocked
     if they are members of the current signal mask set.

     If set is not null, the action of sigprocmask() depends on the value of the
     how  argument.   The  signal mask is changed as a function of the specified
     set and the current mask.	The function is specified by how  using  one  of
     the following values from <signal.h>:

     SIG_BLOCK	  The  new  mask is the union of the current mask and the speci-
		  fied set.

     SIG_UNBLOCK  The new mask is the intersection of the current mask	and  the
		  complement of the specified set.

     SIG_SETMASK  The current mask is replaced by the specified set.

     If  oset  is  not null, it is set to the previous value of the signal mask.
     When set is null, the value of how is insignificant and  the  mask  remains
     unset providing a way to examine the signal mask without modification.

     The system quietly disallows SIGKILL or SIGSTOP to be blocked.

     In  threaded  applications, pthread_sigmask(3) must be used instead of sig-
     procmask().

RETURN VALUES
     The sigprocmask() function returns the value 0 if successful; otherwise the
     value -1 is returned and the global variable errno is set to  indicate  the
     error.

ERRORS
     The  sigprocmask()  system  call  will fail and the signal mask will be un-
     changed if one of the following occurs:

     [EINVAL]		The how argument has a value  other  than  those  listed
			here.

SEE ALSO
     kill(2),	 sigaction(2),	 sigpending(2),   sigsuspend(2),   fpsetmask(3),
     pthread_sigmask(3), sigsetops(3)

STANDARDS
     The sigprocmask() system call is expected to conform to ISO/IEC 9945-1:1990
     ("POSIX.1").

FreeBSD ports 15.quarterly	   May 7, 2010			  SIGPROCMASK(2)

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