Is there any API MacBook to get clamshell mode?

Question

I want to make a small utility which makes my MacBook to get clamshell mode. Is there any usable API?

---(edit)---

I'm afraid of the term 'clamshell' may send wrong meaning. I used it for 'only external monitor on mode'. This is the behaviors what I want.

1. Both of internal/external monitors on
2. Use the utility
3. Internal monitor off/externals on.

Answer 1

Call pmset from your code.