This is a simple little shell script scheduled by cron meand to run tarsnap for daily backup.
After Tarsnap has been compiled; move tarsnap.conf to /usr/local/etc/ (that's where it likes to be),
daily-tarsnap.sh to /opt/local/bin/; and copy-paste the contents of crontab into sudo crontab -e.
You also need to mkdir /var/log/backups and cd /var/log/backups && touch tarsnap_backups.log && touch tarsnap_daily.log.