You'll need the DateTime::Event::Sunrise module, on debian based
systems the package will be called libdatetime-event-sunrise-perl.
Copy the sunwait script to somewhere on your path.
The script sleeps until sunset or sunrise. Useful in cron if you need something to happen in sync with the sun. For example, doing your bitcoin mining operations while the sun provides the electricity :-)
Usage: sunwait --lat=xxx.yyy --long=aaa.bbb [--offset=60] [--debug] rise|set
You can also provide an offset to alter the time, in case you don't want it to be exactly in time with the sunrise/sunset. The offset is specified in minutes and can be negative or positive.
The --debug option will show when the script is run and the time it is
going to wait for.
Example usage in cron:
# wait for an hour after sunrise and start mining those coins!
00 03 * * * sunwait --lat=40.71 --long=-74.01 --offset=60 rise && bitcoin_mine_start.sh
# an hour before sunset, turn off the miner
15 00 * * * sunwait --lat=40.71 --long=-74.01 --offset=-60 set && bitcoin_mine_stop.sh