Gentoolkit
# equery depends openmotif [ Searching for packages depending on openmotif... ] app-text/xpdf-3.01-r3 #
# equery belongs /usr/bin/ruby18 [ Searching for file(s) /usr/bin/ruby18 in *... ] dev-lang/ruby-1.8.3 (/usr/bin/ruby18) #
# equery depends openmotif [ Searching for packages depending on openmotif... ] app-text/xpdf-3.01-r3 #
# equery belongs /usr/bin/ruby18 [ Searching for file(s) /usr/bin/ruby18 in *... ] dev-lang/ruby-1.8.3 (/usr/bin/ruby18) #