sigprocmask - manipulate current signal mask
sigprocmask(int how, const sigset_t *set, sigset_t *oset);
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. 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 <sys/signal.h>:
SIG_BLOCK The new mask is the union of the current mask
and the specified
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
If oset is not null, it is set to the previous value of the
When set is null, the value of how is insignificant and the
unset providing a way to examine the signal mask without
The system quietly disallows SIGKILL or SIGSTOP to be
A 0 value indicated that the call succeeded. A -1 return
an error occurred and errno is set to indicated the reason.
The sigprocmask() call will fail and the signal mask will be
one of the following occurs:
[EINVAL] how has a value other than those listed here.
kill(2), sigaction(2), sigsuspend(2), sigsetops(3)
The sigprocmask() function call is expected to conform to
OpenBSD 3.6 June 4, 1993
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