groupmod(8) on OpenBSD

The text 36edb3396c8b, as OpenBSD 4.1, OpenBSD 4.0, OpenBSD 3.9, OpenBSD 3.8, OpenBSD 3.7, OpenBSD 3.6, OpenBSD 3.5, OpenBSD 3.4 shipped it.

modify an existing group on the system

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