diff --git a/app/main.ml b/app/main.ml
index 425b9aa..23a472a 100644
--- a/app/main.ml
+++ b/app/main.ml
@@ -13,10 +13,17 @@ let read_file file =
 
 let () =
   match Sys.argv with
-  | [| _ ; file |] ->
+  | [| _ ; output_format; file |] -> (
     let switch = read_file file in
     let data = OpamFile.SwitchExport.read_from_string switch in
-    Opam_graph.dependencies data
+    let graph = Opam_graph.dependencies data in
+    match output_format with
+    | "text" -> Format.printf "%a" Opam_graph.pp_graph graph
+    | "dot" ->
+      let dot = Opam_graph.Dot.of_graph graph in
+      Format.printf "%a" Opam_graph.Dot.pp dot
+    | _ -> failwith "Unsupported output format"
+  )
   | _ ->
     print_endline "expecting exactly one argument";
     exit 1
diff --git a/src/dune b/src/dune
index 0f484b0..07548d8 100644
--- a/src/dune
+++ b/src/dune
@@ -1,4 +1,6 @@
 (library
  (name opam_graph)
  (public_name opam-graph)
- (libraries opam-core opam-format))
\ No newline at end of file
+ (libraries opam-core opam-format dot)
+ (flags (:standard (-w -27-26)))
+ )
diff --git a/src/opam_graph.ml b/src/opam_graph.ml
index 471de3e..5f2f92e 100644
--- a/src/opam_graph.ml
+++ b/src/opam_graph.ml
@@ -74,5 +74,38 @@ let dependencies (switch : OpamFile.SwitchExport.t) =
       in
       find_deps graph work
   in
-  let graph = find_deps graph (Name_set.singleton top) in
-  Format.printf "%a" pp_graph graph
+  find_deps graph (Name_set.singleton top)
+
+module Dot = struct
+
+  type t = Odot.graph
+
+  let of_graph (graph:graph) : t =
+    let open Odot in
+    let stmt_list =
+      Name_map.fold (fun pkg deps acc ->
+        let stmt =
+          let pkg_id = Double_quoted_id (OpamPackage.Name.to_string pkg) in
+          let pkg_point = Edge_node_id (pkg_id, None) in
+          let deps_points =
+            Name_set.elements deps
+            |> List.map (fun p -> 
+              let id = Double_quoted_id (OpamPackage.Name.to_string p) in
+              Edge_node_id (id, None)
+            )
+          in
+          let edge = pkg_point, deps_points, [] in
+          Stmt_edge edge
+        in
+        stmt :: acc
+      ) graph.nodes []
+    in
+    { strict = false; (*todo test params*)
+      kind = Digraph;
+      id = None;
+      stmt_list }
+
+  let pp ppf dot =
+    Format.fprintf ppf "%s" (Odot.string_of_graph dot)
+
+end