Investigate a docker container's file system

investigate.sh

# build the container
# consider removing the entrypoint/cmd from the dockerfile if the container errors and stops running
docker build -t ncc:testing -f Dockerfile-build --target runtime .
  
# run the container
docker run --name wtf -itd ncc:testing

# connect to shell inside the running container
docker exec -ti wtf /bin/sh

# OR ###############################

# copy file from (running or stopped) container
docker cp wtf:/var/www/app/current/ncc/index.js ncc/index.js