Why can't I write to a (/tmp or /user_created) folder from inside a container using the microservice docker image example?

I'm exploring the micro-magic microservice docker image example and was able to successfully the run the original example on localhost as well as on AWS. But as a next step, I modified it to write the results to a simple txt file using the following commands:

outputFile = '/tmpdata/dummy.txt'

fileID = fopen(outputFile,'w+');

fprintf(fileID, 'Output of MyMagic: \n');

fprintf(fileID,'%d %d %d %d \n', magic(x));

But, I'm seeing an error: Invalid file identifier. Use fopen to generate a valid file identifier.

I suspect I'm running into problems that are connected to the WRITE permissions to any folder within the container from the runtime. Any ideas on how to fix this, and enable writing to a local folder on the container?

Thanks.

Answer 1

[Linda]

@escape road city 2 the issue is likely due to write permission problems inside the Docker container—specifically, the path /tmpdata/dummy.txt may not exist, or your container doesn't have permission to write there.