How do you define a default value in Docker Compose interpolation?
Experience Level: Senior
Tags: Docker Compose
Answer
Use the following syntax with default value after dash:
version: "3.9"
services:
my-service:
image: "postgres:${POSTGRES_VERSION:-1.0.0}"
If the environment variable POSTGRES_VERSION is not defined, the image version will fall back to postgres:1.0.0.
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