pkg_add -u von NetBSD:
If the package that's being installed is already installed,
either in the same or a different version, an update is per-
formed. If this is specified twice, then any dependant packages
that are too old will also be updated to fulfill the dependency.
....
If the package that's being installed is already installed,
either in the same or a different version, an update is per-
formed. If this is specified twice, then any dependant packages
that are too old will also be updated to fulfill the dependency.
....