Where does APPDATA get initialized in the default docker-compose.override file

Question

Below I will show the default docker-compose.override.yml file that was created for me when added orchestration to my ASP.NET application. This is using .NET Core 3.1. I right clicked on the project file -> Add -> Container Orchestrator Support... and the docker-compose project was added to my solution. (Obviously I chose Docker Compose in the options).

I would like to know where the variable APPDATA is being initialized so that I can understand the full path. I understand how the volumes work; I'm simply interested in knowing how and where APPDATA is initialized.

version: '3.4'

services:
  myproject:
    environment:
      - ASPNETCORE_ENVIRONMENT=Development
      - ASPNETCORE_URLS=https://+:443;http://+:80
    ports:
      - "80"
      - "443"
    volumes:
      - ${APPDATA}/Microsoft/UserSecrets:C:\Users\ContainerUser\AppData\Roaming\Microsoft\UserSecrets:ro
      - ${APPDATA}/ASP.NET/Https:C:\Users\ContainerUser\AppData\Roaming\ASP.NET\Https:ro

Answer 1

I know this is an old post and you probably figure it out but, APPDATA is variable built in with Windows.

If you open Windows Explorer or Run and paste APPDATA with % before and after you will get path.