mirror of https://github.com/docker/docs.git
86 lines
3.4 KiB
Markdown
86 lines
3.4 KiB
Markdown
---
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description: Define environment variables
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keywords: Python, service, environment, service
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redirect_from:
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- /docker-cloud/getting-started/python/6_define_environment_variables/
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- /docker-cloud/getting-started/golang/6_define_environment_variables/
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title: Define environment variables
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---
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Docker lets you store data such as configuration settings, encryption keys, and external resource addresses in environment variables. Docker Cloud makes it easy to define, share, and update the environment variables for your services.
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At runtime, environment variables are exposed to the application inside the container.
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## Look inside your deployed app
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Let's look inside the app you just deployed.
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### Python quickstart
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Open the file in `quickstart-python/app.py`, and look at the return statement in the method *hello()*. The code uses **os.getenv('NAME', "world")** to get the environment variable
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**NAME**.
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```python
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return html.format(name=os.getenv('NAME', "world"), hostname=socket.gethostname(), visits=visits)
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```
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### Go quickstart
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Open the file in `quickstart-go/main.go`, and look at the *fmt.Fprintf* call in the *indexHandler* method. The code uses **os.Getenv("NAME")** to get the environment variable **NAME**.
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```go
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fmt.Fprintf(w, "<h1>hello, %s</h1>\n<b>Hostname: </b>%s<br><b>MongoDB Status: </b>%s", os.Getenv("NAME"), hostname, mongostatus)
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```
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## Edit an environment variable
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If you modify the environment variable, the message the app shows when you curl or visit the service webpage changes accordingly. Let's try it!
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Run the following command to change the **NAME** variable, and then redeploy the `web` service.
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```bash
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$ docker-cloud service set --env NAME="Friendly Users" --redeploy web
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```
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## Check endpoint status
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Execute `docker-cloud container ps` again to see the container's new endpoint.
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You should now see two `web-1` containers, one with a status of **terminated**
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(that's the original container) and another one either **starting** or already
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**running**.
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```none
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$ docker-cloud container ps
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NAME UUID STATUS IMAGE RUN COMMAND EXIT CODE DEPLOYED PORTS
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web-1 a2ff2247 ✘ Terminated my-username/quickstart-python:latest python app.py 40 minutes ago web-1.my-username.cont.dockerapp.io:49165->80/tcp
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web-1 ae20d960 ▶ Running my-username/quickstart-python:latest python app.py 20 seconds ago web-1.my-username.cont.dockerapp.io:49166->80/tcp
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```
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Now curl the new endpoint to see the updated greeting.
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> **Note**: If `docker-cloud container ps` doesn't show an endpoint for the container yet, wait until the container status changes to **running**.
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```none
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$ curl web-1.$DOCKER_ID_USER.cont.dockerapp.io:49162
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Hello Friendly Users!</br>Hostname: e360d05cdb81</br>Counter: Redis Cache not found, counter disabled.%
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```
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Your service now returns `Hello Friendly Users!`. Great! You've modified your service using environment variables!
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### Environment Variables and the Dockerfile
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Environment variables can also be set in the Dockerfile, and modified at runtime
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(like you just did).
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Wondering where the default value for the **NAME** environment variable is set?
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Look in the quickstart's Dockerfile.
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```none
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# Environment Variables
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ENV NAME World
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```
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## What's Next?
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Next, we [scale the service](7_scale_the_service.md).
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