Documentation's example is not working

[AndreiBadescu]

Is this a docs issue?

• My issue is about the documentation content or website

Type of issue

Information is incorrect

Description

https://docs.docker.com/compose/how-tos/startup-order/

healthcheck: test: ["CMD-SHELL", "pg_isready -U ${POSTGRES_USER} -d ${POSTGRES_DB}"]

This is not working, I think it should be with $$ (e.g. $${POSTGRES_USER}).

Am I right?

Location

https://docs.docker.com/compose/how-tos/startup-order/

Suggestion

Transform $ into $$

AND IMPROVE DOCS REGARDING ENVIRONMENT VARIABLES DURING HEALTHCHECK (Spent 2h debugging the issue and I'm still not sure how it works exactly).

[AndreiBadescu]

https://docs.docker.com/reference/compose-file/interpolation/

Also found this where it says:

The way this is being expressed is very confusing for me. I barely understand.

PLEASE also improve this section.