CODEWITHSUNDEEP
docker-compose
chrish
chrish

Reputation: 2432

How to do variable substitution in env_file?

I am using docker-compose and I want my env_file to have variable subsitution. I would like to define one variable in the file and then use it in other variables:

APP_ENV=dev-foo
LOCALPATH=/tmp/builddir/${APP_ENV}
[email protected]:some-org/${APP_ENV}

What is the supported form of variable substitutions in env_file???

Upvotes: 17

Views: 6564

Answers (1)

Francesco Belladonna
Francesco Belladonna

Reputation: 11709

Variable substitution is now supported in docker compose

The syntax is similar to shell substitution.

Direct substitution

${VAR} -> value of VAR

Default value

${VAR:-default} -> value of VAR if set and non-empty, otherwise default
${VAR-default} -> value of VAR if set, otherwise default

Required value

${VAR:?error} -> value of VAR if set and non-empty, otherwise exit with error
${VAR?error} -> value of VAR if set, otherwise exit with error

Alternative value

${VAR:+replacement} -> replacement if VAR is set and non-empty, otherwise empty
${VAR+replacement} -> replacement if VAR is set, otherwise empty

EDIT: Do notice that using docker-compose is deprecated and will not use the latest version. Use docker compose (no dash), which will use the latest compose version.

Upvotes: 5

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