Running Docker on Mac, build works, run errors: : /bin/sh: 1: [: missing ]

Question

Running Docker on Mac, I can build my image, but on running, I get the following error:

/bin/sh: 1: [: missing ]

I create the image in a local directory with a dockerfile, requirements.txt and a python script file. - 3 files- using docker build

Dockerfile:

FROM python
COPY "requirements.txt"
RUN pip install -r requirements.txt
COPY "quandlData.py"
CMD [ "python", "./quandlData.py" 

-simple script that gets some data from quandl API and writes-gets from a redis server- which is running. To run, I just use docker run image_name

Answer 1

CMD [ "python", "./quandlData.py"

is being parsed as a shell command, not an array -- and the [ command (when invoked that way, rather than by its alternate name test) requires its last argument to be ].

In this case, however, adding a trailing ] will cause your CMD to parse as an array describing arguments to pass to python, not a [ command at all -- which it should be.

---

Thus, you can do either of these two things:

# BETTER: Fix your JSON array
CMD [ "python", "./quandlData.py" ]

...or...

# WORSE: Pass a valid shell command
CMD python ./quandlData.py