Since this scripts output is usually redirected, put error messages
on standard error and exit with error code if no data is found.
Signed-off-by: NStephen Hemminger <shemminger@vyatta.com>
Acked-by: NArjan van de Ven <arjan@linux.intel.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>