View HowTo Find the Path to Your System Directory
Question: How can I find the full path to my EE system directory? I want to use that instead of a virtual path.
Answer: In your control panel, open the PHP info page.
Control Panel Home > Admin > PHP Info
Search for the following: document_root

Example from one of my sites.
Take the value stored there and add your system directory name to it.
Replace .\system in the path.php with:
/dir1/sitename/public_html/system/
Where dir1 and sitename are the actual values you found when viewing the PHPInfo page.
You can use this in your subdomain versions of path.php.