link4.0

link end1 end2 <breed> end1 end2

Given the who numbers of the endpoints, reports the link connecting the turtles. If there is no such link reports nobody. To refer to breeded links you must use the singular breed form with the endpoints.

ask link 0 1 [ set color green ]
;; unbreeded link connecting turtle 0 and turtle 1 will turn green
ask directed-link 0 1 [ set color red ]
;; directed link connecting turtle 0 and turtle 1 will turn red

See also patch-at.