How to use environment in Dockerfile?

Question

LXC

Hello!
Is it possible to use environment variables in Dockerfile using docker-compose?
For example I have docker-compose.yml

app:
  build: ./
  env_file: dc.env

dc.env file:
MY_VAR="my_var"
and Dockerfile:

FROM ubuntu
RUN echo "$MY_VAR"

In this example, echo does not show what I expect, but I would like to see my_varhow to be?
Grateful for any information.
Thank you!

Answer 1

The fact is that the variables from env_file are initialized after the deployment of the container.
Try setting them in the Dockerfile itself:

ADD dc.env dc.env
RUN export `cat dc.env`

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