sigprocmask - change and/or examine caller's signal mask
int sigprocmask(int how, const sigset_t *set, sigset_t
The sigprocmask() function is used to examine and/or change
the caller's signal mask. If the value is SIG_BLOCK, the
set pointed to by the set argument is added to the current
signal mask. If the value is SIG_UNBLOCK, the set pointed
by the set argument is removed from the current signal
mask. If the value is SIG_SETMASK, the current signal mask
is replaced by the set pointed to by the set argument. If
the oset argument is not NULL, the previous mask is stored
in the space pointed to by oset. If the value of the
set argument is NULL, the value how is not significant
and the caller's signal mask is unchanged; thus, the call
can be used to inquire about currently blocked signals.
If there are any pending unblocked signals after the call to
sigprocmask(), at least one of those signals will be
delivered before the call to sigprocmask() returns.
It is not possible to block those signals that cannot be
ignored this restriction is silently imposed by the system.
If sigprocmask() fails, the caller's signal mask is not
Upon successful completion, 0 is returned. Otherwise, -1 is
returned and errno is set to indicate the error.
The sigprocmask() function will fail if:
The set or oset argument points to an illegal
The value of the how argument is not equal to one of
the defined values.
See attributes(5) for descriptions of the following attri-
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
| MT-Level | Async-Signal-Safe |
sigaction(2), signal(3C), sigsetops(3C),
thr_sigsetmask(3THR), attributes(5), signal(3HEAD)
In a multithreaded program, the call to sigpromask()
impacts only the calling thread's signal mask and is there-
fore identical to a call to thr_sigsetmask(3THR).
Signals that are generated synchronously should not be
masked. If such a signal is blocked and delivered, the
receiving process is killed.
Man(1) output converted with