docker view directory within container

You'll first need to know the name of the instance running?

$ docker ps

CONTAINER ID  IMAGE        COMMAND  CREATED  STATUS  PORTS  NAMES
36029...      image/image  ...      1 sec..  Up..    ...    some-container

Now, get inside the container and look for what you need. Assuming the container name is, some-image.

$ docker exec -it some-container /bin/bash

root@1f3420c939:/var/www/html#

If you already know the folder:

docker exec -it some-container ls /path/to/file

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EDIT:

as noted by @Konrad Botor it's possible to use also the container id instead of the container name and more importantly not all images have bash installed (alpine is the most popular image not using it).

Here's an example with alpine:

docker run -d \
    --rm \
    --name my_alpine_container \
    alpine \
    sleep 3600

CONTAINER_ID=$( docker ps -q my_alpine_container )

# to "enter" the container:
docker exec -it $CONTAINER_ID sh