Upgrading Wordpress
From HostThyself
Simple step to upgrade Wordpress on the shell
Download from the website
wget http://wordpress.org/latest.tar.gz
Untar
tar -xzf latest.tar.gz
Check for difference on the current installation with diff.
diff -qr wordpress/ public_html/
Make sure that you do not have any file that you do not want to overwrite. Use the cp command to copy and overwrite the old files.
cp -R wordpress/* public_html/
Visit the Wordpress Upgrading page for specific instruction for each version.