Makefile remove stopped Docker containers

Question

I'm new to Makefiles, I'm trying to use one to help me automate the build of my docker images.

I'm struggling to write, what feels like, a simple recipe that does the following:

• Check to see if there are running containers (docker ps -a -q)
• If running containers exist remove them (docker rm $(docker ps -a -q))

This is what I've manage to cobble together so far through various Google searches:

DOCKER_CONTAINER_LIST := $(shell docker ps -a -q)

clean-docker:
    if [[ ! $(DOCKER_CONTAINER_LIST) == "" ]];then \ 
        docker rm $$(docker ps -a -q) \ 
    fi

Which yields the following output:

if [[ de6e694da4f9 == "" ]];then \
/bin/sh: -c: line 0: conditional binary operator expected
/bin/sh: -c: line 0: syntax error near 'de6e694da4f9'
/bin/sh: -c: line 0: 'if [[ de6e694da4f9 == "" ]];then \ '
make: *** [clean-docker] Error 2

Would be great if someone could show me how to achieve this please

UPDATE

Thank @I0b0 for your answer, I think I'm almost there now. The Makefile now looks like this:

DOCKER_CONTAINER_LIST := $(shell docker ps -a -q)

clean-docker:
    if [ -n "$(DOCKER_CONTAINER_LIST)" ] \
    then \
        docker rm "$(DOCKER_CONTAINER_LIST)" \
    fi

But I get the following error when running it:

if [ -n "6778d35e5c95" ] \
then \
docker rm "6778d35e5c95" \
fi
/usr/bin/sh: -c: line 4: syntax error: unexpected end of file
make: *** [clean-docker] Error 1

I had a look at this answer regarding line endings, but that made no difference. I am using Makefile on both Mac and Windows.

Answer 1

It can be done with:

# for images
docker rmi $(shell docker images -a -q)

# for containers
docker rm $(shell docker ps -a -q)

# for volumes
docker volume rm $(shell docker volume ls -q)

PS. macOS

Answer 2

if [ -n "$(DOCKER_CONTAINER_LIST)" ] should do it:

• -n is the standard test for a non-empty string
• Use More Quotes™ never gets old
• [[ is a bashism, but sh is not bash

Bonus points for reusing the variable with docker rm "$(DOCKER_CONTAINER_LIST)".

---

After the update the problem is related to a fundamental difference between scripts and makefiles: the latter cannot be broken into lines in the exact same way as scripts by just adding backslashes before the end of line. What you've ended up with is a single line if [ -n "$(DOCKER_CONTAINER_LIST)" ] then docker rm "$(DOCKER_CONTAINER_LIST)" fi. Because newlines in a makefile don't work like ; in a shell script you have to add two:

if [ -n "$(DOCKER_CONTAINER_LIST)" ]; \
then \
    docker rm "$(DOCKER_CONTAINER_LIST)"; \
fi

Answer 3

I couldn't figure out how to divide those commands into multiple lines either, but ugly oneliners work for me.

So what you were asking about would be something like this

DOCKER_CONTAINER_LIST := $(shell docker ps -a -q)

clean_docker:
    @if [ -n "$(DOCKER_CONTAINER_LIST)" ]; then echo "Removing docker containers" && docker rm "$(DOCKER_CONTAINER_LIST)"; else echo "No containers found"; fi;