+/* val defvar : t -> string -> string option -> int option */
+CAMLprim value
+ocaml_augeas_defvar (value tv, value namev, value exprv)
+{
+ CAMLparam3 (tv, namev, exprv);
+ CAMLlocal2 (optv, v);
+ augeas_t t = Augeas_t_val (tv);
+ const char *name = String_val (namev);
+ const char *expr = Optstring_val (exprv);
+ int r;
+
+ r = aug_defvar (t, name, expr);
+ if (r > 0) { /* Return Some val */
+ v = Val_int (r);
+ optv = caml_alloc (1, 0);
+ Field (optv, 0) = v;
+ } else if (r == 0) /* Return None */
+ optv = Val_int (0);
+ else if (r == -1) /* Error or multiple matches */
+ raise_error (t, "Augeas.defvar");
+ else
+ caml_failwith ("Augeas.defvar: bad return value");
+
+ CAMLreturn (optv);
+}
+