let get_field s pos field =
let f = field^": " in
let len = String.length f in
let re = Str.regexp_string f in
let p = Str.search_forward re s pos in
let p2 = String.index_from s p ';' in
let res = (p2, String.sub s (p+len) (p2 - p - len)) in
(* prerr_endline (Printf.sprintf "get_field: %s=%s" field (snd res));*)
res