Embedding Google Analytics on Every Page

I wanted to embed Google Analytics on every page of this site, including all possible error pages. This site is pretty heterogenous, in that not all pages are managed by the same content generator. So if I were to use some template-based footer that included this, I'd have to duplicate in various places and keep track of duplications manually.

Alternatively, I could use .htaccess to setup each page so it is parsed as PHP, which automatically appends the code snippet. But, seriously? PHP?

So it turns out Apache has a built-in module called mod_substitute, which is basically sed. I have the following defined for my virtual host:

<VirtualHost *:80>
    ...
    <Location />
        AddOutputFilterByType SUBSTITUTE text/html text/plain
        Substitute "s|</body>|<script type='text/javascript'>var gaJsHost = (('https:' == document.location.protocol) ? 'https://ssl.': 'http://www.');document.write(unescape('%3Cscript src=\'' + gaJsHost + 'google-analytics.com/ga.js\' type=\'text/javascript\'%3E%3C/script%3E'));</script><script type='text/javascript'>try {var pageTracker = _gat._getTracker('UA-12849586-1');pageTracker._setDomainName('.oliverzheng.com');pageTracker._trackPageview();} catch(err) {}</script></body>|i"
    </Location>
</VirtualHost>

With that, each page is sed'ed on the fly just before it is given to the client browser. My code snippet is inserted right before </body>. Yes, all that has to be on one line (it's sed) and, yes, that quote escaping is ugly, but it works simply and quickly.