PerlIO *
PerlIO_fdupopen(pTHX_ PerlIO *f, CLONE_PARAMS *param, int flags)
{
#if defined(PERL_MICRO) || defined(__SYMBIAN32__)
    return NULL;
#else
#ifdef PERL_IMPLICIT_SYS
    return PerlSIO_fdupopen(f);
#else
#ifdef WIN32
    return win32_fdupopen(f);
#else
    if (f) {
	const int fd = PerlLIO_dup(PerlIO_fileno(f));
	if (fd >= 0) {
	    char mode[8];
#ifdef DJGPP
	    const int omode = djgpp_get_stream_mode(f);
#else
	    const int omode = fcntl(fd, F_GETFL);
#endif
	    PerlIO_intmode2str(omode,mode,NULL);
	    /* the r+ is a hack */
	    return PerlIO_fdopen(fd, mode);
	}
	return NULL;
    }
    else {
	SETERRNO(EBADF, SS_IVCHAN);
    }
#endif
    return NULL;
#endif
#endif
}


##</code><code>##

     The object referenced by the descriptor does not distinguish between
     fildes and fildes2 in any way.  Thus if fildes2 and fildes are duplicate
     references to an open file, read(2), write(2) and lseek(2) calls all move
     a single pointer into the file, and append mode, non-blocking I/O and
     asynchronous I/O options are shared between the references.  If a sepa-
     rate pointer into the file is desired, a different object reference to
     the file must be obtained by issuing an additional open(2) call.  The
     close-on-exec flag on the new file descriptor is unset.