Getting endpoint states of robot

edit

I'm using a Baxter and I want to get the endpoint states of my robot. The endpoint states are located in the topic

/robot/limb/left/endpoint_state

and on the terminal I can echo this topic to get the endpoint states. Running this would yield:

pose:
position:
x: some double
y: some double
z: some double
orientation:
...

I only need the pose x y and z position data. My guess is to get this, I need to subscribe to this topic, but I'm not sure how I would subscribe to it to get just that data.