You can use rsync with an ssh key for password-less transfers. This is useful for doing unattended backups using a cron job and a script or to keep your website in line with a local copy.

First you will need to generate the Private and Public Keys on the device you want to run the script on.

you can do this by following my blog entry found here.

Once you have the keys and you have added the public key to the target server you can configure an ssh config file.

$ nano ~/.ssh/config 
Host targetserver
HostName <hostname or IP address of target server>
User <username>
IdentityFile /path/to/private_key (usually in ~/.ssh/id_rsa)

You can then use rsync to transfer files.

$ rsync [options] [SOURCE] [DESTINATION]

$ rsync -e ssh -aPvh <username>@<hostname or IP address of target server>:/home/user/directory/ /home/user/directory

Or you can use the name from the Host line above

$ rsync -e ssh -aPvh targetserver::/home/user/directory/ /home/user/directory