dig for domain registration

[Scott Haneda]

Hello, I want to do some spring cleaning on my dns.  WHOIS seems to  
throttle me back with too many checks, how can I use dig to check for  
registration of a domains?

If I do `dig NS example.com` and grep out my NS, does that suffice for  
making sure my primary and secondary are listed?

What about if I want to check if a domain is registered, regardless of  
NS's listed?  Just omit the specific grep and I would accomplish that?

Thank you
--
Scott