# Evaluating container environment variables in Dockerfile commands

Hello,

Docker in Linux environments knows to evaluate environment variables in `Dockerfile` commands like `ENV` or `ENTRYPOINT`. For example, the following command line in `Dockerfile` that generates linux platform container image is perfectly legal:

``````ENV PATH \$PATH:/usr/bin/myapp
``````

However, it is impossible to write such line for Windows platform container. In case of Windows the resulted value of the `PATH` variable for the line

``````ENV PATH %PATH%;c:\myapp
``````

will be `%PATH%;c:\myapp`

Does anyone know how to achieve the functionality when docker evaluates the environment variables in the context of the container?
And for which commands of the `Dockerfile` it is possible to do?

Thank you,
L

Check out the reference to =\$env:variable_name

https://technet.microsoft.com/en-us/library/ff730964.aspx