Clarification for http://tex.stackexchange.com/questions/325969/converting-a-tikz-length-into-a-tex-length

output

Running `LaTeX' on `test' with ``include-tex-file test.tex test.tex; latex -file-line-error --synctex=1 -src-specials  -interaction=nonstopmode "\input" test.tex''
Subfile test not an \include, no need to add to \includeonly
This is pdfTeX, Version 3.1415926-2.5-1.40.14 (TeX Live 2013/Debian)
 restricted \write18 enabled.
 Source specials enabled.
entering extended mode
LaTeX2e <2011/06/27>
Babel <3.9h> and hyphenation patterns for 78 languages loaded.
(./test.tex (/usr/share/texlive/texmf-dist/tex/latex/base/article.cls
Document Class: article 2007/10/19 v1.4h Standard LaTeX document class
(/usr/share/texlive/texmf-dist/tex/latex/base/size10.clo))
(/usr/share/texmf/tex/latex/pgf/frontendlayer/tikz.sty
(/usr/share/texmf/tex/latex/pgf/basiclayer/pgf.sty
(/usr/share/texmf/tex/latex/pgf/utilities/pgfrcs.sty
(/usr/share/texmf/tex/generic/pgf/utilities/pgfutil-common.tex)
(/usr/share/texmf/tex/generic/pgf/utilities/pgfutil-latex.def
(/usr/share/texlive/texmf-dist/tex/latex/ms/everyshi.sty))
(/usr/share/texmf/tex/generic/pgf/utilities/pgfrcs.code.tex))
(/usr/share/texmf/tex/latex/pgf/basiclayer/pgfcore.sty
(/usr/share/texlive/texmf-dist/tex/latex/graphics/graphicx.sty
(/usr/share/texlive/texmf-dist/tex/latex/graphics/keyval.sty)
(/usr/share/texlive/texmf-dist/tex/latex/graphics/graphics.sty
(/usr/share/texlive/texmf-dist/tex/latex/graphics/trig.sty)
(/usr/share/texlive/texmf-dist/tex/latex/latexconfig/graphics.cfg)
(/usr/share/texlive/texmf-dist/tex/latex/graphics/dvips.def)))
(/usr/share/texmf/tex/latex/pgf/systemlayer/pgfsys.sty
(/usr/share/texmf/tex/generic/pgf/systemlayer/pgfsys.code.tex
(/usr/share/texmf/tex/generic/pgf/utilities/pgfkeys.code.tex
(/usr/share/texmf/tex/generic/pgf/utilities/pgfkeysfiltered.code.tex))
(/usr/share/texmf/tex/generic/pgf/systemlayer/pgf.cfg)
(/usr/share/texmf/tex/generic/pgf/systemlayer/pgfsys-dvips.def
(/usr/share/texmf/tex/generic/pgf/systemlayer/pgfsys-common-postscript.def)))
(/usr/share/texmf/tex/generic/pgf/systemlayer/pgfsyssoftpath.code.tex)
(/usr/share/texmf/tex/generic/pgf/systemlayer/pgfsysprotocol.code.tex))
(/usr/share/texmf/tex/latex/xcolor/xcolor.sty
(/usr/share/texlive/texmf-dist/tex/latex/latexconfig/color.cfg))
(/usr/share/texmf/tex/generic/pgf/basiclayer/pgfcore.code.tex
(/usr/share/texmf/tex/generic/pgf/math/pgfmath.code.tex
(/usr/share/texmf/tex/generic/pgf/math/pgfmathcalc.code.tex
(/usr/share/texmf/tex/generic/pgf/math/pgfmathutil.code.tex)
(/usr/share/texmf/tex/generic/pgf/math/pgfmathparser.code.tex)
(/usr/share/texmf/tex/generic/pgf/math/pgfmathfunctions.code.tex
(/usr/share/texmf/tex/generic/pgf/math/pgfmathfunctions.basic.code.tex)
(/usr/share/texmf/tex/generic/pgf/math/pgfmathfunctions.trigonometric.code.tex)
(/usr/share/texmf/tex/generic/pgf/math/pgfmathfunctions.random.code.tex)
(/usr/share/texmf/tex/generic/pgf/math/pgfmathfunctions.comparison.code.tex)
(/usr/share/texmf/tex/generic/pgf/math/pgfmathfunctions.base.code.tex)
(/usr/share/texmf/tex/generic/pgf/math/pgfmathfunctions.round.code.tex)
(/usr/share/texmf/tex/generic/pgf/math/pgfmathfunctions.misc.code.tex)))
(/usr/share/texmf/tex/generic/pgf/math/pgfmathfloat.code.tex))
(/usr/share/texmf/tex/generic/pgf/basiclayer/pgfcorepoints.code.tex)
(/usr/share/texmf/tex/generic/pgf/basiclayer/pgfcorepathconstruct.code.tex)
(/usr/share/texmf/tex/generic/pgf/basiclayer/pgfcorepathusage.code.tex)
(/usr/share/texmf/tex/generic/pgf/basiclayer/pgfcorescopes.code.tex)
(/usr/share/texmf/tex/generic/pgf/basiclayer/pgfcoregraphicstate.code.tex)
(/usr/share/texmf/tex/generic/pgf/basiclayer/pgfcoretransformations.code.tex)
(/usr/share/texmf/tex/generic/pgf/basiclayer/pgfcorequick.code.tex)
(/usr/share/texmf/tex/generic/pgf/basiclayer/pgfcoreobjects.code.tex)
(/usr/share/texmf/tex/generic/pgf/basiclayer/pgfcorepathprocessing.code.tex)
(/usr/share/texmf/tex/generic/pgf/basiclayer/pgfcorearrows.code.tex)
(/usr/share/texmf/tex/generic/pgf/basiclayer/pgfcoreshade.code.tex)
(/usr/share/texmf/tex/generic/pgf/basiclayer/pgfcoreimage.code.tex
(/usr/share/texmf/tex/generic/pgf/basiclayer/pgfcoreexternal.code.tex))
(/usr/share/texmf/tex/generic/pgf/basiclayer/pgfcorelayers.code.tex)
(/usr/share/texmf/tex/generic/pgf/basiclayer/pgfcoretransparency.code.tex)
(/usr/share/texmf/tex/generic/pgf/basiclayer/pgfcorepatterns.code.tex)))
(/usr/share/texmf/tex/generic/pgf/modules/pgfmoduleshapes.code.tex)
(/usr/share/texmf/tex/generic/pgf/modules/pgfmoduleplot.code.tex)
(/usr/share/texmf/tex/latex/pgf/compatibility/pgfcomp-version-0-65.sty)
(/usr/share/texmf/tex/latex/pgf/compatibility/pgfcomp-version-1-18.sty))
(/usr/share/texmf/tex/latex/pgf/utilities/pgffor.sty
(/usr/share/texmf/tex/latex/pgf/utilities/pgfkeys.sty
(/usr/share/texmf/tex/generic/pgf/utilities/pgfkeys.code.tex))
(/usr/share/texmf/tex/generic/pgf/utilities/pgffor.code.tex))
(/usr/share/texmf/tex/generic/pgf/frontendlayer/tikz/tikz.code.tex
(/usr/share/texmf/tex/generic/pgf/libraries/pgflibraryplothandlers.code.tex)
(/usr/share/texmf/tex/generic/pgf/modules/pgfmodulematrix.code.tex)
(/usr/share/texmf/tex/generic/pgf/frontendlayer/tikz/libraries/tikzlibrarytopaths.code.tex))) (./test.aux) ABD: EveryShipout initializing macros
> 1.0pt.
l.12   \showthe\@tempdima
                         %
[1] (./test.aux) )
(see the transcript file for additional information)
Output written on test.dvi (1 page, 5152 bytes).
SyncTeX written on test.synctex.gz.
Transcript written on test.log.

LaTeX exited abnormally with code 1 at Mon Aug 22 18:38:34

test.tex

\documentclass{article}
\usepackage{tikz}

\begin{document}

\makeatletter

\begin{tikzpicture}
  \def\length{1}%
  \pgfpoint{0pt}{\length}% Notice pt after 0 for consistency
  \@tempdima\pgf@y% 
  \showthe\@tempdima%
\end{tikzpicture}

\end{document}