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Pass in Arguments when Doing a Docker Run – CentOS

If I have the following Dockfile

FROM centos:8
RUN yum update -y
RUN yum install -y python38-pip
COPY . /app
WORKDIR /app
RUN pip3 install -r requirements.txt
ENTRYPOINT ["python3"]
CMD ["app.py"]

With app being the following:

#!/usr/bin/python
import sys
print('Here is your param: ', sys.argv[0])

When I call docker run -it (myimg), how can I pass in a parameter so the output would be the param?

ex:

docker run -it (myparam) "testfoo"

would print 

Here is your param: testfoo
Tags:

2

Answers


  1. 0

    Anything you provide after the image name in the docker run command line replaces the CMD from the Dockerfile, and then that gets appended to the ENTRYPOINT to form a complete command.

    Since you put the script name in CMD, you need to repeat that in the docker run invocation:

    docker run -it myimg app.py testfoo

    (This split of ENTRYPOINT and CMD seems odd to me. I’d make sure the script starts with a line like #!/usr/bin/env python3 and is executable, so you can directly run ./app.py; make that be the CMD and remove the ENTRYPOINT entirely.)

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  2. 0

    sys.argv[0] refer to the FileName so you can not expect testfoo when you run docker run -it my_image testfoo

    The first item in the list, sys.argv[0], is the name of the Python script. The rest of the list elements, sys.argv[1] to sys.argv[n], are the command line arguments 2 through n

    print('Here is your param: file Name', sys.argv[0],'args testfoo:',sys.argv[1])

    So you can just replace the entrypoint to below then you are good to pass runtime argument testfoo

    ENTRYPOINT ["python3","app.py"]

    Now pass argument testfoo

    docker run -it --rm my_image testfoo
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