# [tex-k] TeX error exit upon \showthe

Reinhard Kotucha reinhard.kotucha at web.de
Tue Feb 10 00:20:51 CET 2004

>>>>> "Olaf" == Olaf Weber <olaf at infovore.xs4all.nl> writes:

> Hartmut Henkel writes:
>> I'm wondering about the following, in TeX and pdfTeX: Upon
>> \showthe\wd0 one gets e. g.

>>> 5.55994pt.
>> l.13 \showthe\wd0

>> ? h This isn't an error message; I'm just \showing something.

>> So it's only an informal message, harmless, definitely not an
>> error! But in tex.web still the procedure error is called from
>> procedure show_whatever. Consequently TeX or pdfTeX end with
>> uexit(1), which means FAIL, so that e. g. a make would quit
>> after such a TeX run. It looks wrong to me, but it is in the
>> TeX core... Can anybody give me a short hint about this? Thanks
>> a lot.

> Well, it _is_ in the TeX core, in the sense that even after a
> \show* the error history has become "tainted".  And the core TeX
> code (that is, DEK's code) doesn't signal to the 'error' routine
> that this was intentional and harmless...

Hi Olaf,
do you think that it shouldn't be changed because it's in the core?  I
mentioned this behaviour when we met in Bremen last year, you said
that if I think it is a bug I should send you a mail.

Though I think that this behaviour is wrong if the operating system
has a concept of "exit codes",  I found it quite convenient sometimes.

If you run tex from the commandline the exit status doesn't matter.
If your makefile runs LaTeX three times to get cross references right,
it is probably better if it aborts after the first run if you forgot
to remove the \show or \showthe.

I think that the behaviour can be changed because it is definitely
operating system dependant.  On the other hand, I doubt that it is
worth the trouble.

What is more important is that TeX exits with status 1 in certain
cases.  For instance, if an \input file is not found, TeX ends up in
an endless loop.  LaTeX's x.tex breakes this loop but the exit status
was 0 because it just executed \end.  In the next LaTeX release it
will call \errmessage{} before.  \errmessage sets the exit status to 1.

x.tex is designed to work with plain TeX as well, but it would be nice
if we would have something for metapost and metafont as well.

For metapost I use a file x.mp
------------------------------
batchmode;
errmessage "";
end;
------------------------------

The same file will work for metafont if it is called x.mf.

It would be nice if those two little files would be part of future TeX
disributions.

Regards,
Reinhard

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