On 18/09/2011, at 9:29 PM, Joseph Wright wrote:

> That's easy to do, leaving only the question of what happens with
> 
>  \iow_new:N \l_my_stream
>  \iow_open:N \l_my_stream { <file> }
>  ...
>  \iow_close:N \l_my_stream
>  ..
>  \iow_open:N \l_my_stream { <file> }
> 
> The easiest approach is that we just overwrite the <file>.

That's the logical behaviour, I think. If you want to keep appending, then you don't close the file. If you absolutely must close the file and still want to append, then the catchfile package can be used to read it in again. But I'd say we needn't add that feature to expl3 until it seems like there's a pressing need...

Cheers,
-- Will