Substitute environment variables in Docker Compose files using interpolation syntax.| Docker Documentation
How to set, use, and manage variables in your Compose file with interpolation| Docker Documentation
Compose pre-defined environment variables| Docker Documentation
Scenario overview illustrating how environment variables are resolved in Compose| Docker Documentation
Explore all the attributes the services top-level element can have.| Docker Documentation
Bash Variables (Bash Reference Manual)| www.gnu.org