To add up to this, there's an article on how to do this (compatible with 12.6, but I doubt that aspect of PB has changed that much)

https://community.appeon.com/index.php/articles-blogs/tutorials-articles/2-powerbuilder/155-how-to-get-the-application-path

The C++ constant MAX_PATH has a value of 260 so I would use that when allocating the buffer instead of 255. I don't think it is necessary to pass one less to the function. It will truncate the output to nSize - 1 if it needs to. Some functions (not this one) will accept up to 32,767.

I want to add a tip about configuring App Path in PowerServer 2022:

If you use the default app launcher, "Allow the user to change the path" is not selected by default, the path %appdata%\pbapps\ will be the installing path of the cloud apps. So the install path of a specified app (E.g.: %appdata%\pbapps\Applications\demo.appeon.com_googlecharts) is basically fixed on the Client by default.

If you want to customize the Cloud App launcher, please refer to: https://docs.appeon.com/ps2022/Customize_cloud_app_launcher.html