(* foo_program.ml -- the program using foolib *) open Swig (* Give access to the swig library *) open Foolib (* This is the name of your swig output *) let results = _foo '() (* Function names are prefixed with _ in order to make them lex as identifiers in ocaml. Consider that uppercase identifiers are module names in ocaml. NOTE: the '() syntax is part of swigp4. You can do: let results = _foo C_void *) (* Since your function has a return value in addition to the string output, you'll need to match them as a list *) let result_string = match results with C_list [ C_string result_string ; C_int 0 ] -> (* The return value is last when out arguments appear, but this too can be customized. We're also checking that the function succeeded. *) result_string | _ -> raise (Failure "Expected string, int reply from _foo") let _ = print_endline result_string