Menu
If I pass an environment variable which is set inside of the container as an argument to docker run, my shell evaluates it. For example:
I want my container to print the value of $FOO which is bar. None of these will work:
# Prints blank line
$ docker run -e FOO=bar ubuntu echo $FOO
# Prints '$FOO'
$ docker run -r FOO=bar ubuntu echo \$FOO
689
Dockerfile provides a dedicated variable type ENV to create an environment variable. We can access ENV values during the build, as well as once the container runs.
Fetch Using docker exec Command Here, we are executing the /usr/bin/env utility inside the Docker container. Using this utility, you can view all the environment variables set inside Docker containers.
The ENV command sets environment variables within the image both when it is built and when it is executed. These variables can be overridden when you launch your image. An environment variable is a name-value pair, which can be accessed by any script or application that runs from the image.
You can pass the values of environment variables from the host to your containers without much effort. Simply don't specify a value in the command line, and make sure that the environment variable is named the same as the variable the containerized app expects: $ docker run -e var_name (...)
It works if you run echo in a shell:
$ sudo docker run --rm -e FOO=bar ubuntu bash -c 'echo $FOO'
bar
This is because echo is a command (/bin/echo), but it's the shell that does the variable substitution.
50
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
