Conditional Logic In Dockerfile
Sometimes when running a Dockerfile you need to run some conditional logic based upon an ARG variable. This can be handy in the instance you want to run a production build or development build or need to run an extra step for production, etc.
When running this you need to pass in the argument ENV as part of your docker build command:
Read this Stackoverflow answer about it here. It should be noted that using conditional logic in a Dockerfile forces the Dockerfile to be built each time when normally if nothing changed it would be changed. Because this build-arg is dynamic the Docker build step cannot be cached. In short, using conditional logic in your Dockerfile will slow down the build.