You can get container IP by inspecting the container ID or tag name.
# docker inspect <containerIDorName> | grep \"IPAddress\":
docker inspect test4 | grep \"IPAddress\":
You can also get container ID by entering the container with exec command and running
docker exec -it test4 /bin/sh
Now run
$ hostname
$ hostname -i
Outputs:
28c9b44ab6b3 172.17.0.3