telnet(1) on FreeBSD
The text 57edfa89feb8, as FreeBSD 11.2-RELEASE shipped it.
user interface to the TELNET protocol
Flags it lists
-
-4 -
-6 -
-8 -
-B -
-E -
-F -
-K -
-L -
-N -
-S -
-X -
-a -
-c -
-d -
-e -
-f -
-input -
-k -
-l -
-n -
-output -
-r -
-s -
-u -
-x -
-y