Please help with determining absolute paths using RewriteCond and RewriteRule

Hi, all! I am tearing my hair out here...

I want to rewrite some URLs based on the absolute path and whether the
resulting thing being looked for is actually a real file or directory or
not. The Apache mod_rewrite documentation is pretty good and so is the
companion rewriting guide, but they are lacking some details that I need
to understand.

Question: It seems to me that REQUEST_URI, REQUEST_FILENAME, and
SCRIPT_FILENAME all contain the exact same information. Unfortunately,
none of these contain the absolute path to the resource. What CGI variable
accessible to mod_rewrite can be used for this? I need the FULL path that
mod_rewrite thinks leads to the resulting resource.

I don't want to use %{DOCUMENT_ROOT}%{REQUEST_URI} or type in the start of
the path a la /home/webmaster/public_html%{REQUEST_URI} because sometimes
the start of the path is not DOCUMENT_ROOT or the hard-coded stuff before
REQUEST_URI. As in the case of a user's home directory accessed in the
tilde-username style - e.g. http://myserver/~jeff/test.php .

How can mod_rewrite get the full path from, say, the last URL example --
http://myserver/~jeff/test.php ??

I hope I have made this clear. Please let me know how I can further
clarify.

Thanks in advance!

--
Jeffrey D. Silverman | jeffreyPANTS@jhu.edu **
Website | http://www.newtnotes.com

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