system call 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.
is not null, the action of
depends on the value of the
The signal mask is changed as a function of the specified
and the current mask.
The function is specified by
using one of the following values from
.In signal.h :
The new mask is the union of the current mask and the specified
The new mask is the intersection of the current mask
and the complement of the specified
The current mask is replaced by the specified
is not null, it is set to
the previous value of the signal mask.
the value of
is insignificant and the mask remains unset
providing a way to examine the signal mask without modification.
to be blocked.
In threaded applications,
must be used instead of