Mapped subdomains and robots.txt

Sorry if this has been covered before but a quick search didn't yield any answers, though I'm not sure what the question should be!

I have a main domain > mydomain.com that has wordpress installed

My hosting allows me to have subdirectories, e.g., mydomain.com/sub1 and mydomain.com/sub2 - both with their own wordpress installations.

sub1 and sub2 are not at all related to mydomain.com but are instead mapped to myotherdomain1.com and myotherdomain2.com

My question is how do I construct the robots.txt file, as I can only have one version in the mydomain.com main directory, correct? Or can I have one in each subdirectory, that is myotherdomain1.com/robots.txt and myotherdomain2.com/robots.txt?

As they cover completely different subjects I don't want the search engines to crawl and index them as one site.

Hope that makes sense!
Thanks for any advice.
Nick

 

robots.txt can only works for current host name

 

Since Google considers directories and subdomains as seperate domains, you can have two different robots.txt files for your websites.