SIGPROCMASK(2)		   Linux Programmer's Manual		SIGPROCMASK(2)

NAME
       sigprocmask - examine and change blocked signals

SYNOPSIS
       #include <signal.h>

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

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       sigprocmask(): _POSIX_C_SOURCE >= 1 || _XOPEN_SOURCE || _POSIX_SOURCE

DESCRIPTION
       sigprocmask()  is  used	to  fetch and/or change the signal mask of the
       calling thread.	The signal mask is the set of signals  whose  delivery
       is  currently  blocked  for  the  caller  (see  also signal(7) for more
       details).

       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 (if 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
       EFAULT the  set	or  oldset argument points outside the process's allo-
	      cated address space.

       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.

       Each of the threads in a process has its own signal mask.

       A  child  created  via  fork(2)	inherits a copy of its parent's signal
       mask; the signal mask is preserved across execve(2).

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

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

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

COLOPHON
       This  page  is  part of release 3.44 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				  2012-04-15			SIGPROCMASK(2)