Re: [LaTeX-team] \showstream oddity

That behaviour for -1 is the documented behaviour in the pdftex manual, so
I'm not sure the behaviour could change (although the format could
initialise it to 128 if we wanted)

The special casing for negative stream numbers used by `\write` just
doesn't (apparently) apply to \show(stream) so the behaviour of default of
-1 seems OK.

David

On Tue, 16 Sept 2025 at 20:27, Joseph Wright <[email protected]> wrote:

> Hello all,
>
> We've just spotted an oddity with \showstream. Consider the example
>
> \immediate\openout1=test.txt
> \immediate\write1{test}
> %\showstream1   % A real file
> %\showstream16  % or 128 for LuaTeX
> \show\foo
> \immediate\write\showstream{^^Jbong}
> \bye
>
> With the file as-is, the \show output appears in the terminal and the
> log, but the \write only goes to the (log the standard setting for
> \showstream is -1). Setting \showstream to 1 sends everything to the
> real file, and to 16 (or in LuaTeX 128) sends everything to the terminal.
>
> The default behaviour is puzzling. It seems that \show more-or-less
> ignores \showstream there, or special cases, as it does *not* only send
> to the .log. My feeling is that the engines should be setting
> \showstream to a default that gives predictable but unchanged behaviour
> (e.g. 16+ or LuaTeX 128+) - but there is an alternative interpretation.
>
> Regards,
>
> Joseph
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