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Review/Refactor of precedence table 

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Ulysses Souza 2022-08-19 02:07:52 +02:00 committed by dockertopia
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compose/envvars-precedence.md
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@ -5,15 +5,15 @@ keywords: compose, environment, env file
---
## Order of precedence
1. Passed from the command-line [`docker compose run --env <KEY[=VAL]>`](../../engine/reference/commandline/compose_run/#options).
2. Passed from/set in `compose.yaml` service's configuration, [from the environment key](../../compose/compose-file/#environment).
3. Passed from/set in `compose.yaml` service's configuration, [from the env_file key](../../compose/compose-file/#env_file).
4. Passed from/set in Container Image [in ENV directive](../../engine/reference/builder/#env).
1. Passed from the command-line [`docker compose run --env <KEY[=[VAL]]>`](../../engine/reference/commandline/compose_run/#options).
2. Passed from/set in `compose.yaml` service's configuration, from the [environment key](../../compose/compose-file/#environment).
3. Passed from/set in `compose.yaml` service's configuration, from the [env_file key](../../compose/compose-file/#env_file).
4. Passed from/set in Container Image in [ENV directive](../../engine/reference/builder/#env).
### Precedence quick overview table
The table below provides a quick overview of how interpolation works when using all environment variables on Compose, using `TAG`, an environmental variable defining the version for an image, as an example.
Each row represents a scenario and each columns represents a context where you can be setting or passing an environment variable.
Each row represents a scenario and each column represents a context where you can be setting or passing an environment variable.
| # | `.env` file | `compose.yaml`:`env_file` key | `compose.yaml`:`environment` key | CMD | Image | OS | Resolved as |
|:-:|:--------------------------:|:-----------------------------:|:---------------------------------:|:------------:|:-------------:|:------------:|:-----------------:|
@ -35,8 +35,12 @@ Each row represents a scenario and each columns represents a context where you c
| 16| Unset | Unset | `TAG=1.7` | Unset | `TAG=1.6` | `TAG=1.4` | `TAG=1.4` |
Description for each column:
* `.env` file - `.env` file on the project root (or, with higher precedence, the file passed via `docker compose -–env-file <FILE>`).
* `OS` environment - OS Environment variable
* Image - `ENV` directive in the Dockerfile
* .env file - `.env` file on the project root (or, with higher precedence, the file passed via `docker compose -–env-file <FILE>`).
* Command line - environmental variable passed via `docker compose run -e <KEY[=VAL]>`.
* Compose file - in `environment` key from the service section in the `compose.yaml`.
* Compose file - in `env_file key` from the service section in the `compose.yaml`.
* Compose file - In `env_file` key from the service section in the `compose.yaml`.
* Compose file - In `environment` key from the service section in the `compose.yaml`.
* Command line - Environmental variable passed via `docker compose run -e <KEY[=[VAL]]>`.
* Resolved as - This column expresses the result available in the container.
**Note that the "`OS`" has precedence over "`.env` file" column for variable resolution in the other columns.**