How to do variable substitution in env_file?

问题

I am using docker-compose and I want my env_file to have variable subsitution. I would like to define one variable in the file and then use it in other variables:

APP_ENV=dev-foo
LOCALPATH=/tmp/builddir/${APP_ENV}
GIT_URL=git@github.com:some-org/${APP_ENV}

What is the supported form of variable substitutions in env_file???

回答1:

Variable substitution is not supported in env_file.

Your options are:

• use variables in the environment: section (although you wont be able to do your example because setting a value in environment only sets it for the container environment, and substitution happens on the host).
• use host variables by specifying an environment variable without a value (ex: LOCALPATH=), which may be in either the env_file or environment section.

来源：https://stackoverflow.com/questions/35277472/how-to-do-variable-substitution-in-env-file