Pass shell command results to Dockerfile from docker-compose

Question

i trying to pass user group ID from my Linux environment to Dockerfile throught docker-compose. I know about about "args" in docker-compose.yml, but i need to find method for getting group id by executing shell commang "getent group mygroup | cut -d: -f3". This is a mandatory requirement, because then the container will be distributed in different environments where the name of the group is known, and the id will be different.

Here is what i talking about:

    version: '3.3'
    services:
    ...
        php:
            build:
                context: './php-fpm'
                args:
                    - GROUP_ID=<HERE I NEED TO GET SHELL COMMAND RESULTS>
            container_name: php-fpm
    ...

Is any methods to do that?

Answer 1

Is something like this what you're after

$groupid = getent group mygroup | cut -d: -f3
docker-compose up --build --build-arg GROUP_ID=$groupid

or are you hoping to have the groupid command in the docker-compose script

Answer 2

Not exactly what you asked for.

You could set an environment variable before running your wrapper script. e.g.

export GROUP_ID=`getent group mygroup | cut -d: -f3`
run wrapper script to call your docker-compose file

Then you can retrieve the GROUP_ID inside your docker-compose file:

                args:
                    - GROUP_ID=${GROUP_ID}