Whois or nslookup.. for domain availability?

Hi, i want to make linux bash script which will periodically check for certain domain availability, i mean like every 100miliseconds.

I want to ask which command i need to use, so the result is not cached and i dont cause any inappropriate overload?

i see:
whois domainname.com (when No entries found., domain is available)
nslookup -type=ns domainname.com (when cant find nameservers, domain is expired or available)

So my questions what kind of command do you please suggest?

Does these whois providers have any limits above which they ban your IP?

Yes providers of public whois data usually set daily query limits per Ip4 address unless you have a contract with them. Usually less than 100 queries a day.