How do you set environment variables for a Docker container?

Setting environment variables for a Docker container can be effectively done using the -e option. This allows you to specify individual environment variables directly in the docker run command. For example, you can pass environment variables like this: docker run -e VAR_NAME=value image_name. This flexibility is crucial when you need to configure your application behaviors at runtime without altering the container's image.

The -e option is particularly useful for defining variables in a straightforward manner, enabling the application running within the container to access those variables via standard methods for retrieving environment variables, such as using the operating system's environment variable functions or libraries.

While there are other methods for setting environment variables, such as using the --env flag, which is an equivalent way to specify environment variables, the -e option is frequently used in practice due to its brevity. Using the --env-file option can allow you to specify an entire file of environment variables, which is also effective but may be less convenient for specifying individual variables on the fly. The -v option, on the other hand, is typically used for mounting volumes, so it does not apply to setting environment variables.