ftp(1) on OpenBSD
The text 9e4b68634dfc, as OpenBSD 6.0, OpenBSD 5.9 shipped it.
Internet file transfer program
Flags it lists
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-4 -
-6 -
-A -
-C -
-D -
-E -
-M -
-P -
-S -
-U -
-V -
-a -
-c -
-d -
-e -
-g -
-i -
-k -
-m -
-n -
-o -
-p -
-r -
-s -
-t -
-v