.htaccess mod_rewrite help

[Misterer <rd_ree@xxxxxxxxx>]

Hello,

I'm trying to create certain functionality using .htaccess files only.

Suppose we have a domain and a subdomain with document roots as follows:

domain.com -> /home/user/public_html
sub.domain.com -> /home/user/public_html/sub

The contents of /home/user/public_html are as follows ([]'s are directories):

[something]
[something_else]
[sub]
main.file
sub.file

What I'd like to do is this:

• Make all domain.com requests that do not request an actual filename go to main.file file.
  
• Make all sub.domain.com requests that do not request an actual filename go to main.file file.

I can do what I want using VirtualHosts easily (one for domain.com and another for sub.domain.com) but I'm not sure about .htaccess here. How would you do this?