There is a second approach where pointed domains and subdomains become automatic, meaning no specific code is required for each pointer. While this method is much easier to use and does not need to be modified when adding more domains or subdomains, note that there are some restrictions when using this method.

Domains and subdomains are treated exactly the same. The pointing is based on the first argument of the url (except www if used).

You must create a subdirectory under htdocs with a - at the front for every domain and subdomain you wish to be pointed. The directory name must match the first argument in the url (except for www if used). For example, domain.com would have htdocs/-domain and sub.domain.com would have htdocs/-sub and domain2.com would have htdocs/-domain2 etc.

The first argument in the url, and therefore the directory name, must be unique. You cannot have two subdomains with the same name. sub.domain1.com and sub.domain2.com will both go to the directory htdocs/-sub

You cannot have any other directory names that start with a - character.
It defaults to allow www. as a prefix on any domain or subdomain.
The htdocs directory is the “drop through” for any domain or subdomain not found. You may want to put an error not found page as the default page. Or, you could choose to have your main website be the “drop through” and just leave that one in htdocs.

RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_URI} !^/-
RewriteCond %{HTTP_HOST} ^(www\.)?([^\.]+)
RewriteCond %{DOCUMENT_ROOT}/-%2 -d
RewriteRule ^(.*)$ -%2/$1 [L]

The htaccess code works this way. The first two lines set up the Apache server rewrite process. The first RewriteCond allows www. to be a prefix and captures the request name. The second RewriteCond checks for the existence of a subdirectory with the request name. The third RewriteCond ensures we are not caught in a looping operation. The RewriteRule rewrites the request with the subdirectory name (which was already verified).