Doing a "man emerge" gives information about the target update and talks about an option called --world. To my knowledge there is no target named update but an option called --update with a target for "system" or "world". Therefor I think that the section "update" should be rewritten, and renamed to "--update".
the manpage in emerge, which is contained in sys-apps/portage-1.9.6_pre1 is incorrect. the section for --usepkg, -k states that we should set the environment variable $DISTDIR, when, in fact, it shoud be $PKGDIR which is set.
*** This bug has been marked as a duplicate of 2347 ***