DirectedGraphQ

DirectedGraphQ[g] yields True if graph g is a directed graph and False otherwise.

Examples

Check if graph is directed:

DirectedGraphQ[Graph[{1 -> 2, 2 -> 3}]]
(* True *)

DirectedGraphQ[Graph[{1 <-> 2, 2 <-> 3}]]
(* False *)

Complete graphs are undirected:

DirectedGraphQ[CompleteGraph[5]]
(* False *)

Please visit the official Wolfram Language Reference for more details.