The sigtimedwait function behaves the same as the sigwaitinfo
    function except that if none of the signals specified by set are
    pending, sigtimedwait waits for the time interval specified in
    the timespec structure referenced by timeout. If the timespec
    structure pointed to by timeout is zero-valued and if none of the
    signals specified by set are pending, then sigtimedwait returns
    immediately with an error.

    See also sigwait and sigwaitinfo.

    See the "Error and Signal Handling" chapter of the HP C RTL
    Reference Manual for more information on signal handling.