What is the scope of variables in Docker Compose?

What is the scope of variables in Docker Compose?

In Docker Compose, variables can be defined in different scopes: global, service, and environment. Global variables are accessible throughout the entire Compose file, while service-specific variables are only available to the service they are defined in. Environment variables can be set in the shell or in an .env file.

Can you give me an example of how to define a global variable?

Sure! You can define a global variable in the 'x-' section of your Docker Compose file. For example:

x-variables:
  my_global_var: value
services:
  my_service:
    image: my_image
    environment:
      - MY_VAR=${my_global_var}

What about service-specific variables?

Service-specific variables are defined under the service's configuration. For example:

services:
  my_service:
    image: my_image
    environment:
      - MY_SERVICE_VAR=value

How do I use environment variables in Docker Compose?

You can use environment variables by referencing them in your Compose file. For instance, if you have an .env file with MY_ENV_VAR=value, you can use it like this:

services:
  my_service:
    image: my_image
    environment:
      - MY_VAR=${MY_ENV_VAR}