SIGPROCMASK(2) BSD System Calls Manual SIGPROCMASK(2)
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, which can be one of the following values:
SIG_BLOCK The new mask is the union of the current mask and the speci-
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 modifica-
The system quietly disallows SIGKILL or SIGSTOP to be blocked.
Upon successful completion, the value 0 is returned; otherwise the
value -1 is returned and the global variable errno is set to indicate the
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.
kill(2), sigaction(2), sigsuspend(2), sigsetops(3)
The sigprocmask() function call is expected to conform to IEEE Std
BSD April 29, 2017 BSD