Creating a launch script for a docker container

    Let's say we wanted to use UCG generate a launch script for a local jupyter datascience notebook container. This HowTo walks you through creating a UCG file that can generate a script to launch the container.

    First lets define some docker configuration values that we'll use later.

    let container_conf = {
        port = 8888,
        hostMount = "~/iJulia/notebooks",
        mountPoint = "/var/iJulia/notebooks",

    Then we can define a helper function for creating our host and port mappings

    // A little helper func for creating our host and port mappings.
    let map_to_container = func (host, container) => {
        result = "@:@" % (host, container)
    let publish = map_to_container(container_conf.port, container_conf.port);
    let volumes = map_to_container(container_conf.hostMount, container_conf.mountPoint);

    Now we set up our docker run flags.

    let docker_flags = {
        // d because we want this container to daemonize.
        d = NULL, // no value for this one.
        // We provide the container name from the environment.
        name = env.CONTAINER_NAME,
        // We use our generated publish and volume mappings from above.
        publish = publish.result,
        volume = volumes.result,

    Finally we are ready to define our jupyter specific flags.

    let jupyter_flags = {
        notebook-dir = container_conf.mountPoint

    Finally we tie it all together into a script and output it as a bash script using the exec converter.

    let script = {
        command = "docker",
        args = [
            "run", "--rm", docker_flags,
            "jupyter", "notebook", jupyter_flags,
    out exec script;

    The script tuple above will generate the following bash script:

    #!/usr/bin/env bash
    # Turn on unofficial Bash-Strict-Mode
    set -euo pipefail
    exec docker run --rm -d --name '<from-env>' --publish '8888:8888' --volume '~/iJulia/notebooks:/var/iJulia/notebooks' jupyter/datascience-notebook jupyter notebook --notebook-dir '/var/iJulia/notebooks'

    The items in the args should be either strings or tuples. The tuples are turned into flags using the builtin flag converter.