Get Environment Variable from Docker Container

Question

What\'s the simplest way to get an environment variable from a docker container that has not been declared in the Dockerfile?

For instance, an environment v

Answer 1

None of the above answers show you how to extract a variable from a non-running container (if you use the echo approach with run, you won't get any output).

Simply run with printenv, like so:

docker run --rm  printenv 

(Note that docker-compose instead of docker works too)