If I'm understanding your quandary: you can replace values in files "in place" with sed. See the manpages for
sed(1) -- the -i option (which can be used with or without making a backup).
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I replied with that info after looking at a FBSD 6.3 box. The 7.0 manpages are slightly different, so you may really need the -I option if you're running 7.