let mkostemp ?(suffix = "") ?(flags = []) prefix =
let prefixlen = String.length prefix in
let suffixlen = String.length suffix in
let len = (prefixlen + 6) + suffixlen in
let s = String.create len
in
(String.blit prefix 0 s 0 prefixlen;
String.blit "XXXXXX" 0 s prefixlen 6;
String.blit suffix 0 s (prefixlen + 6) suffixlen;
let fd = internal_mkostemps s suffixlen flags in (fd, s))