courtenay /tmp $ sysctl -ah
kern.ostype: FreeBSD
kern.osrelease: 6.1-RELEASE-p10
kern.osrevision: 199506
kern.version: FreeBSD 6.1-RELEASE-p10 #0: Wed Nov  1 00:46:06 EST 2006
    root@rm-1005-14.serve.com:/usr/obj/usr/src/sys/GENERIC

 ... snip ..

courtenay /tmp $ sudo gem install sys-proctable
Password:
Bulk updating Gem source index for: http://gems.rubyforge.org
Select which gem to install for your platform (i386-freebsd6)
 1. sys-proctable 0.7.5 (ruby)
 2. sys-proctable 0.7.5 (mswin32)
 3. sys-proctable 0.7.4 (mswin32)
 4. sys-proctable 0.7.4 (ruby)
 5. Skip this gem
 6. Cancel installation
> 1
Building native extensions.  This could take a while...
ERROR:  While executing gem ... (Gem::Installer::ExtensionBuildError)
    ERROR: Failed to build gem native extension.

ruby extconf.rb install sys-proctable
checking for rb_pid_t... yes
checking for main() in -lkvm... yes
checking for struct kinfo_proc.kp_proc... no
checking for struct kinfo_proc.kp_eproc... no
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers.  Check the mkmf.log file for more
details.  You may need configuration options.

Provided configuration options:
        --with-opt-dir
        --without-opt-dir
        --with-opt-include
        --without-opt-include=${opt-dir}/include
        --with-opt-lib
        --without-opt-lib=${opt-dir}/lib
        --with-make-prog
        --without-make-prog
        --srcdir=.
        --curdir
        --ruby=/usr/local/bin/ruby18
        --with-kvmlib
        --without-kvmlib


Gem files will remain installed in /usr/local/lib/ruby/gems/1.8/gems/sys-proctable-0.7.5 for inspection.
Results logged to /usr/local/lib/ruby/gems/1.8/gems/sys-proctable-0.7.5/ext/gem_make.out
courtenay /tmp $