Here is the list of  Database connection file locations of various CMS in cPanel. If you are installing it on Plesk the public_html will become httpdocs. 

(1) Wordpress                       :       public_html/wp-config.php

(2) OSCommerce                  :       public_html/catalog/includes/configure.php
      OS Commerce Admin   :       admin/includes/configure.php

(3) Joomla                              :       public_html/configuration.php

(4) Drupal                              :       public_html/settings.php

Public_html is the default root location for the cPanel and httpdocs is the default root location for Plesk. Suppose, your application is hosted on the blog directory inside public_html, the path will become as below.

(1) Wordpress                       :       public_html/blog/wp-config.php

(2) OSCommerce                  :       public_html/blog/catalog/includes/configure.php
      OS Commerce Admin   :       admin/includes/configure.php

(3) Joomla                              :       public_html/blog/configuration.php

(4) Drupal                              :       public_html/blog/settings.php