temporarily replaces the signal mask of the calling process with the
mask given by
and then suspends the process until delivery of a signal whose
action is to invoke a signal handler or to terminate a process.
If the signal terminates the process, then
does not return.
If the signal is caught, then
returns after the signal handler returns,
and the signal mask is restored to the state before the call to
It is not possible to block
specifying these signals in
has no effect on the process's signal mask.
always returns -1, normally with the error
points to memory which is not a valid part of the process address space.
The call was interrupted by a signal.
is used in conjunction with
in order to prevent delivery of a signal during the execution of a
critical code section.
The caller first blocks the signals with
When the critical code has completed, the caller then waits for the
signals by calling
with the signal mask that was returned by
for details on manipulating signal sets.