Send variables into docker container to use in a script - shell

Question

I am running a script in the CI/CD of the pipeline. The goal is to get a string to work with.
When I get that result, I save it into a variable and save result in the yaml file of the dockerfile.
I am wanting to pass that variable from the CI environment, into the docker-compose container. So, I am trying to export this like another things are exported, however it doesn't work:
ci/pdf/jenkins-changes.sh
LOG="$(cat ".log")"
export LOG
I have added a variables.env file that looks like this:
LOG=LOG
And then modified the docker-compose.yaml to read the var :
pdf:
image: thisimage/this
build:
context: ../
dockerfile: ./docker/Dockerfile.name
args:
git_branch: ${GIT_BRANCH}
env_file:
- variables.env
environment:
- LOG=${LOG}
volumes:
- do-build:/src/do-build
And in the script that finally runs the docker-container, I have also
Declared it:
FROM ubuntu:16.04 as pdf-builder
ARG log
ENV log=${log}
RUN LOG=${log}
RUN export $LOG
And right after, I run the script.sh that requires the variable, however, it returns Unbound variable and breaks.
LOG=${log}
echo ${LOG}

Answer 1

The answer to this question was:
ci/pdf/jenkins-changes.sh
LOG="$(cat ".log")"
export LOG
Then pass it as an argument, instead of a variable:
pdf:
image: thisimage/this
build:
context: ../
dockerfile: ./docker/Dockerfile.name
args:
git_branch: ${GIT_BRANCH}
env_file:
- variables.env
environment:
- LOG=${LOG}
volumes:
- do-build:/src/do-build
And then, in the dockerfile call it and define it.
ARG log
This should leave it global for any script to use it.