What takes precedence when setting an environment variable in Docker?

When setting an environment variable in Docker, the value set in the shell takes precedence. This is because when you run a Docker container, the environment variables defined in the shell or terminal where the Docker command is executed will override any other specified values, including those defined in a .env file or any default values configured inline. This behavior ensures that any existing configurations or settings in the user's environment can affect the running container, allowing for dynamic adjustments to be made without modifying the Docker configurations themselves.

Usually, the values provided through the shell are intended to be more immediate and context-specific, which is why they are given higher priority. This allows for flexibility in controlling application behavior based on the environment the container is being run in, enhancing usability in different environments or deployment scenarios.

The other options refer to values that are defined within the container’s configuration or in external files, but once the container is initialized with the shell values, they are effectively bypassed in favor of whatever the shell directs.