#load "unix.cma"

let mkdir_p ~path ~perms =
  let ps = String.split_on_char '/' path in
  let rec aux acc = function [] -> ()
  | p::ps ->
      let this = String.concat Filename.dir_sep (List.rev (p::acc)) in
      Unix.mkdir this perms;
      aux (p::acc) ps
  in
  aux [] ps

let () =
  mkdir_p "path/to/dir" 0o700