How to map a docker containers directory to the host with docker-compose?

Reading from: Dockers Volume Page

Volumes have several advantages over bind mounts:

New volumes can have their content pre-populated by a container.

---

So a simple docker-compose (inside a folder called nginx):

version: "3.7"
volumes:
  xmpl:

services:
  testnginx:
    image: nginx:stable
    volumes:
      - xmpl:/etc/nginx

Will yield all the files on the host system via:

$ docker-compose up
$ docker inspect nginx_xmpl
...
"Mountpoint": "/var/lib/docker/volumes/nginx_xmpl/_data"

And you can then view the files on the host:

# ls /var/lib/docker/volumes/nginx_xmpl/_data                               
  conf.d       fastcgi_params koi-utf    koi-win  
  mime.types   modules        nginx.conf scgi_params    
  uwsgi_params win-utf

And finally to use it from ./config:

# ln -s /var/lib/docker/volumes/nginx_xmpl/_data ./config
# ls config
  conf.d       fastcgi_params koi-utf    koi-win  
  mime.types   modules        nginx.conf scgi_params    
  uwsgi_params win-utf