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 values:
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.
Only signals which are in the pending state will be blocked. Signals that are explicitly ignored or for which no handler has been installed and where the default action is to discard the signal are not held as pending and will be discarded regardless of the signal mask.
Blocked signals remain in the pending state
until another call to
sigprocmask()
removes the pending signal(s) from the mask. If there are unblocked signals
that are pending after the signal mask is updated, at least one will be
delivered before sigprocmask() returns.
RETURN VALUES
Upon successful completion, the value 0 is returned; 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), sigpending(2), sigsuspend(2), sigaddset(3)
STANDARDS
The sigprocmask() function conforms to
IEEE Std 1003.1-2008 (“POSIX.1”).