how to know if a directory is normal one or subdomain?

there are 2 directiries under public_html directory:

public_html/images
public_html/pictures

"images" is a normal directory (uploaded by ftp) and "pictures" is a subdomain (created in cPanel).

if using cpanel, I know "pictures" is subdomain because it is displayed as subdomain in cpanel.

but:
How can I know a directory is subdomain programmatically? I mean, kowning it from C++ program, I am sure that there must be info about subdomain stored in some files, do you know the info files? where are they?

If I know the info files, i may read subdomian info from them by c++.

try using "grep -R pictures *"

this will show you all files that have "pictures" in the config directory of the application.
One of those files is what you need.