sigprocmask

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

NAME

     sigprocmask - manipulate current signal mask

SYNOPSIS

     #include <signal.h>

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

DESCRIPTION

     The sigprocmask() function 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 parameter how, which can be one of the following constants defined in
     <sys/signal.h>:

     SIG_BLOCK    The new mask is the union of the current mask and the
                  specified 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
     unchanged, providing a way to examine the signal mask without
     modification.

     The system quietly disallows SIGKILL or SIGSTOP to be blocked.

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() call will fail and the signal mask will be unchanged if
     one of the following occurs:

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

SEE ALSO

     kill(2), sigaction(2), sigsuspend(2), sigsetops(3)

STANDARDS

     The sigprocmask() function call is expected to conform to IEEE Std
     1003.1-2008 (``POSIX.1'').

OpenBSD 5.1                     April 26, 2011                     OpenBSD 5.1