# Auto incremented document number

Philip Taylor P.Taylor at Hellenic-Institute.Uk
Fri Feb 19 20:44:19 CET 2021

Jerry wrote:
>
>> I may be missing something obvious, but why can you not (a) open a
>> tracker file for reading, and note if it is empty; then, (b) if it is
>> not empty, read an integer from it, increment the integer, close the
>> file for reading, open it for writing, and write the augmented integer
>> back.  If it was empty, treat it as if it contained zero.
> Perhaps I am misunderstanding you, but that sounds like a like more
> work than I want to invest. I was looking for an automated system.

In that case, I am very very confused !  The system /is/ "automated";
all you have to do is to add a tiny bit of code to your TeX source.  The
following is written without testing, but it should be pretty close to a
solution:

\newwrite \trackerout

\newcount \seqno

\openin \trackerin = tracker.txt

\ifeof \trackerin

\seqno = 0

\else

\seqno = \seqtmp

\fi

\closein \trackerin

\message {New sequence number = \number \seqno}

\immediate \openout \trackerout = tracker.txt

\immediate \write \trackerout {\number \seqno}

\immediate \closeout \trackerout

\end

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