Re: \showstream oddity

On Tue, 16 Sept 2025 at 22:13, Karl Berry <[email protected]> wrote:

> Hi Joseph,
>
>     The default behaviour is puzzling. It seems that \show more-or-less
>     ignores \showstream there
>
> Yes. As I recall, the idea was to make the default behavior be what
> happened for the several decades before \showstream was invented.
>

The suggestion was not to change the default behaviour but to make
\showstream/show have the same three options as \write
that is:

allocated stream: write to stream
unallocated non-negative stream: write to log and terminal
unallocated negative stream  write to log

Currently \show doesn't distinguish negative values, which means you can't
do

\write\showstream{some preamble text}
\show\foo

and know the preamble will be printed to the same places as the \show.

With no engine change if we set \showstream to a large positive value in
the format
then the above will work as long as a user never sets it negative, but an
engine change
to make negative values only write to the log could also be considered but
it may
be too late for an incompatible change as the pdftex manual has suggested
-1 with the current behaviour for years





> If you think there should be a change here, we can discuss. As David
> already replied, changing the default in the format might be the way to
> go. --best, karl.
>