How to determine Docker version [duplicate]

Question

When I run:

$ docker -v

the output is:

Docker version 18.06.1-ce, build e68fc7a

What version they mean when the write

If you use Docker 1.13 or higher, use --cpus instead.

Asking because the difference between 18 and 1 is too big to me. Can the docu be so old? Or do the docker versions increase so fast?

Answer 1

docker -v only shows the client version. docker version will show both client and server version. 1.13 wasn't that long ago, docker just decided to jump their version numbers rapidly.