Question: It's hard to explain in the title.

I have a bash script that runs daily to backup one folder into a zip file. The zip files are named **world**`YYYYMMDD`**.zip** with `YYYYMMDD` being the date of backup. What I want to do is delete all but the 5 most recent backups. Sorting the files alphabetically will list the oldest ones first, so I basically need to delete all but the last 5 files when sorted in alphabetical order.

Answer: 
How about this:

```
find /your/directory -name 'world*.zip' -mtime +5 | xargs rm

```

Test it before. This should remove all `world*.zip` files older than 5 days. So a different logic than you have.
I can't test it right now because I don't have a Linux machine, but I think it should be:

```
rm `ls -A | head -5`

```