bill, i'm not sure what you mean by 'port', but i'm pretty sure there is a weewx port (i.e., package) for freebsd:
https://reviews.freebsd.org/D6324 the cmon extension has to deal with many platform-specific operations. at first i wrote it using /sys and /proc, but then i discovered the python package psutil: https://github.com/giampaolo/psutil i still have not done the bsd collector, but using psutil made it *much* easier to do the macosx collector. we cannot make weewx depend on psutil, but you might want to look at the psutil source code to see how they do platform-specific system calls in a platform agnostic way. m
