# [NTG-pdftex] [Dev-luatex] Looking at a PDF/DVI while it is being produced

Taco Hoekwater taco at elvenkind.com
Sat Mar 8 09:54:16 CET 2008

Hi,

David Kastrup wrote:
> Hi, sometimes on a long run one would like to be able to take a look at
> the current state of a PDF being produced.
>
> I don't know whether there is something like a progressive PDF format:
> likely not.

I doubt it would be possible to do, that even with changes to pdftex.
In any case you end up with either no embedded fonts at all, or a
rather massive PDF with each page having its own font subsets and
images.

> But if I could send a signal to my PDFTeX/LuaTeX process, and this would
> cause it (at least if it would not currently be in a \shipout) to flush
> the current buffers, create a copy of the current PDF/DVI file under a
> snapshot name, properly finish/close it (writing reference table/DVI
> trailers) and then resume regular work, this would be quite dandy.

The idea is interesting, but I have absolutely no time to implement it.
I fear that getting the details right may take quite some time (forking
is easy, the tricky bit is duplicating the open files and file handles).

> I often have the situation of starting a dead slow 1400 page compilation
> where I really need the full output, but can probably see after looking
> at a dozen pages whether or not the whole compilation will be rubbish,
> needs some minor change and restart.

Can't you just interrupt tex always and at the error prompt "I\end" ?
If the PDF turns out to be OK after all, you will have to generate
1414 or so pages, a 10% overhead, not that bad compared to generating 2800.

Best wishes,
Taco