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I'm having some trouble with passing argument value to dockerfile.

Running docker in Windows Server 2016

My docker version info is

PS C:\Users\Administrator\Desktop> docker version
Client: Docker Engine - Enterprise
 Version:           19.03.4
 API version:       1.40
 Go version:        go1.12.10
 Git commit:        9e27c76fe0
 Built:             10/17/2019 23:42:50
 OS/Arch:           windows/amd64
 Experimental:      false

Server: Docker Engine - Enterprise
 Engine:
  Version:          19.03.4
  API version:      1.40 (minimum version 1.24)
  Go version:       go1.12.10
  Git commit:       9e27c76fe0
  Built:            10/17/2019 23:41:23
  OS/Arch:          windows/amd64
  Experimental:     false

and powershell opened as administrator.

My reference is this.

But it not worked for me.

So this is my dockerfile.

FROM microsoft/iis

ARG a_version
RUN echo $a_version

Also i tried many different types of echo value Such as 

RUN echo "$a_version"
RUN echo ${a_version}
RUN echo "${a_version}"

And this is my execute command.

docker build . --build-arg a_version=1234

My expected result was print 1234

But actual result was

PS C:\Users\Administrator\Desktop> docker build . --build-arg a_version=1234
Sending build context to Docker daemon  14.04MB
Step 1/3 : FROM microsoft/iis
 ---> 595015675977
Step 2/3 : ARG a_version
 ---> Running in 91698d9e71da
Removing intermediate container 91698d9e71da
 ---> 2bad94a2ce74
Step 3/3 : RUN echo $a_version
 ---> Running in 3fe25ecb813c
$a_version

Why it happens? How can is fix it?

stories2
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    can you try with `RUN echo %a_version%` – Adiii Nov 05 '19 at 07:39
  • @Adiii Wow! It works! You are so genius. Why %a_version% works? What is mean? – stories2 Nov 05 '19 at 07:51
  • this is because your base image is a window and you need to use command-prompt syntax. – Adiii Nov 05 '19 at 07:57
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    It doesn't work. It prints out the literal with the percent signs and all. This is completely broken in docker for windows, and there no way to get an ARG or an ENV of any kind to the RUN command. May as well build the dockerfiles dynamically with hard-coded values because there's no working way to pass arguments to the file or the RUN statement. – Triynko Aug 30 '21 at 22:12

2 Answers2

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In Windows Command-Prompt the syntax is echo %a_version% as your base image is based on window.

how-can-i-display-the-contents-of-an-environment-variable-from-the-command-promp

So you can change this to

FROM microsoft/iis
ARG a_version
RUN echo %a_version%

env in window dockerfile

Adiii
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1

I had to do something simmilar and this is a piece of code that worked for me.

ARG PORT_SITE
ENV PORT_SITE ${PORT_SITE}

and then I refer it in the entrypoint as following

$env:PORT_SITE

That's the way I did it, but i suppose that you can ommit the env variable and just refer to the arg value using

${PORT_SITE}
Elmer Real
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