Linux – From what context is a cron task executed

I am asking this question after royally destroying a Linux box. Let me give you some background so you know where I am coming from.

I currently have (well… did have) a RedHat Linux box running Apache with Phusion Passenger added for running Ruby Apps under Apache. The app acts as a service to serve cached files to Kiosks in the Cincinnati area on a regular basis. The web app worked great and the only part left was to set up a cron task to retrieve all the information that needed to be cached and package that into a few different update packages for serving to the kiosks. To accomplish this I wrote a Ruby script that would handle the fetching and packaging of data. To setup the cron task, I just used the built-in crontab. The script looked like so:

#!/bin/bash

cd ../lib
ruby pdf_cache.rb
ruby pdf_prepare.rb
ruby rss_cache.rb
ruby nightly-pack.rb 
cd ..
chown -R www.www *

This script was located in the cron folder and the directory structure looked like so:

.
|-- cron
|-- feeds
|-- lib
|   `-- trash
|-- logs
|-- nightly-packs
|-- pdf
|   `-- tank
|-- public
`-- tmp

and I ran crontab -e as root with the following contents:

0 3 * * * /usr/local/apache2/ruby_projects/kiosk/cron/schedule_job

Which should execute the script every day at 3am. The next day after scheduling this cron task, I got a very unfortunate surprise. The cron task was executed in the root and I assume that most of the commands failed, with the exception of chmod -R www.www * which changed ownership of everything in the system to the www user.

My question is; what is the proper way to implement a cron-task and from what context is the cron-task run from? I realize now that I probably should not be running this under the root account, and I am not sure how to run it under the www account as that user has no shell and you can't successfully su to the www user.