CODEWITHSUNDEEP
dockerdockerfile
Jan Nowak
Jan Nowak

Reputation: 129

Nesting parameters in --build-arg of docker build command

lets start by example. I have a simple Dockerfile:

ARG arg1
ARG arg2
RUN echo "$arg1 $arg2"

And what i expect when i call the command

docker build --build-arg arg1=abc --build-arg arg2=${arg1} .

Is that i got the abc abc as the outbut, but i got abc. So is the result that i want possible? And how can I achieve it?

Upvotes: 1

Views: 1282

Answers (1)

Javier Buzzi
Javier Buzzi

Reputation: 6828

Do this in your Dockerfile

FROM alpine
ARG arg1
ARG arg2
RUN 

echo "$arg1 ${arg2:-$arg1}"

You can now call it like this:

docker build --build-arg arg1=abc --build-arg arg2= .

output:

...truncated...
Step 4/4 : RUN echo "$arg1 ${arg2:-$arg1}"
 ---> Running in e65458b9ba6e
abc abc

or like this:

docker build --build-arg arg1=abc --build-arg arg2=override .

output:

...truncated...
Step 4/4 : RUN echo "$arg1 ${arg2:-$arg1}"
 ---> Running in e65458b9ba6e
abc override

(old answer)

Based on the little info you've provided. I would say:

arg1=abc; docker build --build-arg arg1=$arg1 --build-arg arg2=$arg1

should give you what you want.

Upvotes: 1

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