Is there an elegant way to use a Dockerfile argument to tag an image?

Question

I use and argument (ARG) in my Dockerfile to download a particular version of an application. I would like to tag my image with that version number. I end up writing something like that:

sh$ PHPBB_VERSION=3.2.4 &&
    sudo docker build --build-arg PHPBB_VERSION=${PHPBB_VERSION} \
                      --tag phpbb:${PHPBB_VERSION} - < dockerfiles/bootstrap

But I don't find that very elegant since you have to type the word PHPBB_VERSION no less than four times in this command, with all the possible errors introduced by a typo.

So, is there a more elegant solution to tag an image with the value of a Dockerfile argument?

---

FWIW, here is the relevant part of my Dockerfile:

sh$ cat dockerfiles/bootstrap
FROM php:7.2-cli

ARG PHPBB_VERSION
RUN echo "You are building phpBB version ${PHPBB_VERSION:?undefined}"
...
RUN wget -nv -O- \
      https://github.com/phpbb/phpbb/archive/release-${PHPBB_VERSION}.tar.gz | \
    tar xzf - --strip-components=1

Answer 1

You can use a Makefile for this:

PHPBB_VERSION := 3.2.4

build:
    docker build \
        --build-arg PHPBB_VERSION=${PHPBB_VERSION} \
        --tag phpbb:${PHPBB_VERSION} - < Dockerfile

Dockerfile:

FROM php:7.2-cli                                                                           

ARG PHPBB_VERSION                                                                          

RUN wget -nv -O- https://github.com/phpbb/phpbb/archive/release-${PHPBB_VERSION}.tar.gz | \
    tar xzf - --strip-components=1                                                         

Then, in a shell: make build.

Answer 2

Why would you want to pass ARG as docker tag? Obviously it will at least be two times, first time with --build-arg and second time with --tag. So what you can do is that run this command inside a shell script so that you don't type this command again and again and just change value of $PHPBB_VETSION and run shell script.