clk

A very opinionated framework to ease the creation of command line interfaces

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Sometimes you want a group of commands to share configuration through environment variables. This is useful when you have bash subcommands that need access to values computed or validated by the parent Python command.

For example, imagine you have a deployment tool where you select an environment (dev, staging, prod) once, and all subcommands should use that environment.

First, create a Python command group:

clk command create python myenv --group --description "Commands that work with a specific environment"

Then edit it to add the option and set environment variables:

import click

from clk.config import config
from clk.decorators import group, option


@group()
@option("--env", "-e", type=click.Choice(["dev", "staging", "prod"]), default="dev", help="The environment to use")
def myenv(env):
    "Commands that work with a specific environment"
    config.override_env["MYENV_NAME"] = env
    config.override_env["MYENV_URL"] = f"https://{env}.example.com"
    config.init()

The key line is config.override_env["MYENV_NAME"] = env. This makes the MYENV_NAME environment variable available to all subcommands, including bash commands.

Now let’s add a bash subcommand that uses these environment variables.

clk command create bash myenv.status --description "Show the current environment status" --body '
echo "Environment: ${MYENV_NAME}"
echo "URL: ${MYENV_URL}"
echo "Checking status..."
# In real life, you might do: curl -s "${MYENV_URL}/health"
echo "Status: OK"
'

Let’s test it.

clk myenv status

Environment: dev
URL: https://dev.example.com
Checking status...
Status: OK

clk myenv --env prod status

Environment: prod
URL: https://prod.example.com
Checking status...
Status: OK

The bash command automatically has access to MYENV_NAME and MYENV_URL because the parent group set them in config.override_env.

Let’s add another bash command that deploys to the selected environment.

clk myenv --env staging deploy

Deploying to staging at https://staging.example.com...
Deployment complete!

This pattern is particularly useful when: