Script comments are clear, it is no longer a long-winded.
Forget it, or say one more thing, right, after the design is complete script, you can join a scheduled task, allowing the computer to help you work out.
Note: For scheduled tasks crontab, I will write a special note.
Most last sentence,
find $BACKUP -mtime +10 -name "*" -exec rm -fr {} \;
This statement is meant to change the time to find the backup files in more than 10 days, and then perform the removal.