diff --git a/tools/gen_signatures_registry.ml b/tools/gen_signatures_registry.ml
index dc6a8ede..b1bb4663 100644
--- a/tools/gen_signatures_registry.ml
+++ b/tools/gen_signatures_registry.ml
@@ -54,27 +54,17 @@ end
 let url =
   "https://git-www.gnunet.org/gana.git/plain/gnunet-signatures/registry.rec"
 
-let registry_file = "registry.rec"
-
-let download () =
+let download url =
   let open Bos in
   let res =
-    OS.Cmd.run
-      Cmd.(
-        v "curl"
-        % "--silent"
-        % "--show-error"
-        % "-o"
-        % registry_file
-        % "-X"
-        % "GET"
-        % url)
+    OS.Cmd.(
+      to_string
+        (run_out
+           Cmd.(v "curl" % "--silent" % "--show-error" % "-X" % "GET" % url)))
   in
   match res with
   | Error (`Msg s) -> Fmt.failwith "download failure: %s" s
-  | Ok () -> ()
-
-let read_file file = In_channel.with_open_bin file In_channel.input_all
+  | Ok registry_rec -> registry_rec
 
 type purpose = {
   number: int32;
@@ -100,19 +90,23 @@ let parse_purposes records =
       | _ -> None)
   |> List.filter (fun v -> v.number >= 1000_l)
 
-let () =
-  download ();
-  let content = read_file registry_file in
-  match Recfile.parse content with
+let print_module purposes =
+  let header =
+    {|(* This file was generated from the GANA database:
+   https://git-www.gnunet.org/gana.git/tree/gnunet-signatures/registry.rec *)|}
+  in
+  let pp ppf { number; name; comment } =
+    Fmt.pf ppf "(** %s *)\nlet %s : int32 = %ld_l\n\n" comment name number
+  in
+  Fmt.pr "%s\n\n%a@." header (Fmt.list ~sep:Fmt.nop pp) purposes;
+  ()
+
+let main () =
+  let registry_rec = download url in
+  match Recfile.parse registry_rec with
   | Error msg -> Fmt.failwith "Recfile parse error: %s" msg
   | Ok records ->
-      let purposes = parse_purposes records in
-      let header =
-        {|(* This file was generated from the GANA database:
-   https://git-www.gnunet.org/gana.git/tree/gnunet-signatures/registry.rec *)|}
-      in
-      let pp ppf { number; name; comment } =
-        Fmt.pf ppf "(** %s *)\nlet %s : int32 = %ld_l\n\n" comment name number
-      in
-      Fmt.pr "%s\n\n%a@." header (Fmt.list ~sep:Fmt.nop pp) purposes;
+      print_module (parse_purposes records);
       ()
+
+let () = main ()