how can i do this in a loop?

I need to put little script in cron-tab which will take actual logs and put them in log-1 file. Rename log-1 file to log-2 file ... Bassicaly i need to have week old log files, sorted in log-1 to log-7 logs, where log-7 is day log 7 days ago and updated daily.

Bassicaly i need this in a little loop and have a problem with syntax:

```
mv log-6 log-7
mv log-5 log-6
mv log-4 log-5
mv log-3 log-4
mv log-2 log-3
mv log-1 log-2
mv logactual log-1

```