sigtimedwait( ) shall wait for the time interval specified in the timespec structure referenced by timeout, if none of the signals specified by set are pending, sigtimedwait( ) shall return immediately with an error, if the timespec structure pointed to by timeout is7 zero-valued and if none of the signals specified by set are pending. The CLOCK_MONOTONIC clock shall be used to measure the time interval specified by the timeout argument, if the Monotonic Clock option is supported. sigtimedwait( ) shall return the selected signal number, upon successful completion sigtimedwait() shall return a value of -1 upon unsuccessful completion. sigtimedwait() shall set errno to [EAGAIN] if no signal specified by set was generated within the specified timeout period.