Is there any API MacBook to get clamshell mode?

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

Clamshell means 'only external monitor on mode'.

This is the behaviors wha开发者_开发百科t I want.

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

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Call pmset from your code.