Getting a Docker container's dynamic port on the command line
Generally I like to map my Docker containers to dynamic ports to avoid port collisions, so I’ll build my containers like this:
docker run --name some-container-name -d -p 80 some-image
Here, Docker will find a free port and map it to port 80 on the container.
Although not foolproof, the following code will tell you what that port is:
PORT="$(docker ps|grep some-container-name|sed \
's/.*0.0.0.0://g'|sed 's/->.*//g')"
And, if you’re using docker-compose, you can run, for example:
PORT=$(docker-compose port web 80)
This will give you something like 0.0.0.0:32790.