Empty Git submodule folder when repo cloned

Question

I have one repo hosted at https://github.com/aikiframework/json. On my local copy, I added a submodule using the command:

git submodule add git@github.com:jcubic/json-rpc.git json-rpc

Then I did a commit and push, and the changes appear on GitHub (I can click on it). But when I clone the repo:

git clone https://github.com/aikiframework/json.git

the submodule folder json-rpc is empty.

What am I missing here? Did I forget about something? Why is that folder empty?

Answer 1

OK I found it, needed to add --recursive when cloning the repo.

So the clone command ends up as:

git clone https://github.com/aikiframework/json.git --recursive

Note that if you forgot the --recursive flag you can do (thanks to @Amber):

git submodule update --init

Note that when submodules have other submodules you need recursive option (thanks for @cpprust):

git submodule update --init --recursive