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+% \iffalse meta-comment
+%
+% extract package by Hendri Adriaens.
+%
+% Extract package files and examples and create documentation:
+%    latex extract.dtx
+%    latex extract.dtx
+%    bibtex extract
+%    makeindex -s gglo.ist -o extract.gls extract.glo
+%    makeindex -s gind.ist -o extract.ind extract.idx
+%    latex extract.dtx
+%    latex extract.dtx
+%
+% To finish the installation you have to move the following
+% file into a directory searched by LaTeX:
+%    extract.sty
+%
+%% ---------------------------------------
+%% Copyright (C) 2004-2005 Hendri Adriaens
+%% ---------------------------------------
+%%
+%% This work may be distributed and/or modified under the
+%% conditions of the LaTeX Project Public License, either version 1.3
+%% of this license or (at your option) any later version.
+%% The latest version of this license is in
+%%   http://www.latex-project.org/lppl.txt
+%% and version 1.3 or later is part of all distributions of LaTeX
+%% version 2003/12/01 or later.
+%%
+%% This work has the LPPL maintenance status "maintained".
+%%
+%% This Current Maintainer of this work is Hendri Adriaens.
+%%
+%% This work consists of the file extract.dtx and the derived files
+%% extract.sty, xtrex1.tex, xtrex2.tex, xtrex3.tex, xtrex4.tex,
+%% xtrex5.tex, xtrex6.tex and xtrex7.tex.
+%%
+%% The following files constitute the extract package and must be
+%% distributed as a whole: readme, extract.dtx, extract.pdf and
+%% extract.sty.
+%%
+%<*batchfile>
+\begingroup
+\input docstrip
+\keepsilent
+\preamble
+\endpreamble
+\askforoverwritefalse
+\generate{
+  \file{extract.sty}{\from{extract.dtx}{extract}}
+  \file{xtrex1.tex}{\from{extract.dtx}{xtrex1}}
+  \file{xtrex2.tex}{\from{extract.dtx}{xtrex2}}
+  \file{xtrex3.tex}{\from{extract.dtx}{xtrex3}}
+  \file{xtrex4.tex}{\from{extract.dtx}{xtrex4}}
+  \file{xtrex5.tex}{\from{extract.dtx}{xtrex5}}
+  \file{xtrex6.tex}{\from{extract.dtx}{xtrex6}}
+  \file{xtrex7.tex}{\from{extract.dtx}{xtrex7}}
+  \file{xtrpream.ble}{\from{extract.dtx}{preamble}}
+  \file{extract.bib}{\from{extract.dtx}{bib}}
+}
+\endgroup
+%</batchfile>
+%<*driver>
+\documentclass[a4paper]{ltxdoc}
+\input{xtrpream.ble}
+\begin{document}
+\DocInput{extract.dtx}
+\let\Section\section\def\section*#1{\Section*{#1}\addcontentsline{toc}{section}{#1}}
+\bibliographystyle{plain}
+\bibliography{extract}
+\PrintChangesX
+\PrintIndex
+\end{document}
+%</driver>
+% \fi
+%
+% \changes{v1.0}{2004/12/19}{Initial release}
+% \changes{v1.1}{2005/01/01}{Added conditional extraction using labels}
+% \changes{v1.1}{2005/01/01}{Revised documentation}
+% \changes{v1.2}{2005/01/06}{Fixed \ci{AfterEndEnv} hook for nested environments}
+% \changes{v1.2}{2005/01/06}{Simplified optional argument check for \texttt{extract} environment}
+% \changes{v1.2}{2005/01/06}{Increased efficiency of the package}
+% \changes{v1.3}{2005/01/12}{Removed some input checks for more flexibility}
+% \changes{v1.3}{2005/01/12}{Added \ci{extractline}}
+% \changes{v1.3}{2005/01/12}{Added line extraction method for commands}
+% \changes{v1.3}{2005/01/12}{Simplified package}
+% \changes{v1.3}{2005/01/12}{Added \texttt{document-handles} option}
+% \changes{v1.3}{2005/01/12}{Added examples and documentation}
+% \changes{v1.3}{2005/01/12}{Updated license information}
+% \changes{v1.4}{2005/02/06}{Adjusted options section for \pf{xkeyval} (\ci{XKV@tkey} not defined anymore)}
+% \changes{v1.4}{2005/02/06}{Added \texttt{extractskip} environment}
+% \changes{v1.4}{2005/02/06}{Allow for any filename}
+% \changes{v1.4}{2005/02/06}{Changed temp extension to \texttt{.xtr}}
+% \changes{v1.5}{2005/02/08}{Solved bug in options section}
+% \changes{v1.5}{2005/02/08}{Avoid using counters for conditional extraction with numbers}
+% \changes{v1.6}{2005/02/14}{Improved options section}
+% \changes{v1.6}{2005/02/14}{Added optional header for extracted files}
+%
+% \GetFileInfo{extract.sty}
+%
+% \CheckSum{989}
+%
+% \DoNotIndex{\@backslashchar,\@bsphack,\@checkend,\@currenvir,
+% \@currenvline,\@doendpe,\@eha,\@ehc,\@empty,\@endpefalse,\@esphack,
+% \@expandtwoargs,\@for,\@ifundefined,\@ignorefalse,\@latex@error,
+% \@makeother,\@namedef,\@ne,\@nil,\@nnil,\@temptokena,\@testopt,
+% \active,\advance,\AtBeginDocument,\AtEndDocument,\begin,\begingroup,
+% \catcode,\closeout,\csname,\CurrentOption,\DeclareOptionX,\def,\do,
+% \dospecials,\edef,\else,\end,\endcsname,\endgroup,\expandafter,\fi,
+% \g@addto@macro,\global,\if@endpe,\if@ignore,\ifcat,\ifin@,\ifnum,\ifx,
+% \ignorespaces,\immediate,\in@,\input,\jobname,\lccode,\let,\lowercase,
+% \m@ne,\NeedsTeXFormat,\newcount,\newif,\newwrite,\noexpand,\on@line,
+% \openout,\ProcessOptionsXi,\ProvidesPackage,\relax,\RequirePackage,
+% \reserved@a,\romannumeral,\string,\the,\write,\XTR@activefalse,
+% \XTR@activetrue,\XTR@handlestrue,\XTR@resa,\XTR@tempa,\XTR@tempb,\z@,
+% \PackageError,\gdef,\count@,\day,\divide,\month,\multiply,\space,
+% \time,\xdef,\year}
+%
+% \CharacterTable
+%  {Upper-case    \A\B\C\D\E\F\G\H\I\J\K\L\M\N\O\P\Q\R\S\T\U\V\W\X\Y\Z
+%   Lower-case    \a\b\c\d\e\f\g\h\i\j\k\l\m\n\o\p\q\r\s\t\u\v\w\x\y\z
+%   Digits        \0\1\2\3\4\5\6\7\8\9
+%   Exclamation   \!     Double quote  \"     Hash (number) \#
+%   Dollar        \$     Percent       \%     Ampersand     \&
+%   Acute accent  \'     Left paren    \(     Right paren   \)
+%   Asterisk      \*     Plus          \+     Comma         \,
+%   Minus         \-     Point         \.     Solidus       \/
+%   Colon         \:     Semicolon     \;     Less than     \<
+%   Equals        \=     Greater than  \>     Question mark \?
+%   Commercial at \@     Left bracket  \[     Backslash     \\
+%   Right bracket \]     Circumflex    \^     Underscore    \_
+%   Grave accent  \`     Left brace    \{     Vertical bar  \|
+%   Right brace   \}     Tilde         \~}
+%
+%\title{The \pf{extract} package
+%\thanks{This package can be downloaded from the CTAN mirrors:
+%\texttt{/macros/latex/contrib/extract}. See \texttt{extract.dtx} for
+%information on installing \pf{extract} into your \LaTeX\
+%distribution and for the license of this package.}}
+%\author{Hendri Adriaens\\\url{http://stuwww.uvt.nl/~hendri}}
+%\date{\fileversion\ (\filedate)}
+%\maketitle
+%
+%\begin{abstract}\noindent
+%This package can be used to (conditionally) extract specific
+%commands and environments from a source file and write them to a
+%target file. This can be done without significant changes to the
+%source document, but labels inside the source can be used for more
+%flexibility. The package also provides environments to write code
+%directly to the target file or use code in both the source and the
+%target file. These tools allow one to generate ready-to-run files
+%from a source document, containing only the extracted material, in
+%an otherwise ordinary \LaTeX\ run.
+%\end{abstract}
+%
+%\tableofcontents
+%
+%\section{Introduction}\label{sec:intro}
+%I created this package when I was working on some lecture notes with
+%exercises in the text and wanted to generate an exercises book on
+%the fly. The package heavily uses the \pf{verbatim} package
+%\cite{verbatim} by Rainer Sch\"opf and uses the \pf{xkeyval} package
+%\cite{xkeyval} to provide a simple and easy interface\footnote{And
+%some tools like \ci{XKV@ifundefined} and \ci{XKV@sp@deflist}. See
+%section~\ref{sec:imple} for more information.}.
+%
+%There are other packages around that provide tools for conditionally
+%typesetting material or writing material to an external file. Let me list a few.
+%\begin{description}
+%\item[\pf{askinclude} \cite{askinclude}, \pf{excludeonly} \cite{excludeonly}]\indent\\
+%These packages enhance \LaTeX's |\include| and |\includeonly|
+%system to select the files that should be included in typesetting.
+%\item[\pf{comment} \cite{comment}, \pf{verbatim} \cite{verbatim}, \pf{xcomment} \cite{xcomment}]\indent\\
+%The first two packages define the |comment| environment and the
+%third the |xcomment| environment. These environments ignore their
+%body. But if the command |\xcomment| is used and supplied with a
+%list of environments, these environments will be typeset when they
+%appear in the body of the |xcomment| environment. The \pf{comment}
+%package provides the commands |\includecomment| and
+%|\excludecomment| to do a similar job.
+%\item[\pf{optional} \cite{optional}, \pf{version} \cite{version}, \pf{versions} \cite{versions}]\indent\\
+%These packages define some commands with which you can
+%control which material should be typeset.
+%\item[\pf{pagesel} \cite{pagesel}, \pf{pdfpages} \cite{pdfpages}, \pf{selectp} \cite{selectp}]\indent\\
+%These packages only typeset certain pages.
+%\item[\pf{fancyvrb} \cite{fancyvrb}, \pf{listings} \cite{listings}]\indent\\
+%These packages (among others) provide tools to write text to an
+%external file.
+%\end{description}
+%
+%The \pf{extract} package differs from all these packages since it
+%extracts content and leaves the typeset version of the original
+%document untouched. Furthermore, for simple extraction jobs, it is
+%not necessary to make any changes to the document other than adding
+%the |\usepackage| command. This allows for conditional extraction of
+%commands and environments based on the number of the command or
+%environment counted from the beginning of the document. More
+%flexible conditional extraction can be achieved by adding labels to
+%the source document. How all of this works will be explained in the
+%sections to come.
+%
+%\section{Environment extraction}\label{sec:envxtr}
+%The following provides an example of the user interface of the package.
+%\begin{example}
+% \usepackage[
+%   active,
+%   generate=file,
+%   extract-env={figure,table}
+% ]{extract}
+%\end{example}
+%\DescribeOptions{active,generate,extract-env}
+%If the |active| option is not specified, the package does nothing
+%and no files are generated. If the option is specified, the package
+%will redefine the environments |figure| and |table| so that they
+%write their bodies (the content of the environment) to the file
+%indicated with the |generate| option, here |file.tex|\footnote{If a
+%file extension is lacking, \texttt{.tex} will be used.}, including
+%the |\begin{figure}| and |\end{figure}| commands. Besides that, the
+%environments will be executed as usual. Most environments are
+%supported (known exception is the |document| environment). When the
+%package encounters |\begin{document}| or |\end{document}| in the
+%source file, by default\footnote{See section~\ref{sec:misc} for the
+%the \texttt{document-handles} option.}, it will also write these
+%commands to the target file, such that, if a suitable preamble is
+%added, the file is ready to be run by \LaTeX. See
+%listing~\vref{list:env} for an example.\footnote{See
+%section~\ref{sec:tools} for the \texttt{extract} environment and
+%section~\ref{sec:sande} how to obtain example files.}
+%\begin{Listing}\caption{Environment extraction.}\label{list:env}
+%\begin{minipage}[t]{.49\linewidth}
+%\hfill |xtrex1.tex|
+%\begin{example}
+% \documentclass[10pt]{article}
+% \usepackage[
+%   active,
+%   generate=file,
+%   extract-env=equation
+% ]{extract}
+% \begin{extract}
+% \documentclass[11pt]{article}
+% \end{extract}
+% \begin{document}
+% Some text.
+% \begin{equation}
+% a^2+b^2=c^2
+% \end{equation}
+% Some text.
+% \begin{equation}
+% x^2+y^2=z^2
+% \end{equation}
+% Some text.
+% \end{document}
+%\end{example}
+%\end{minipage}
+%\hfill
+%\begin{minipage}[t]{.49\linewidth}
+%\hfill |file.tex|
+%\begin{example}
+% \documentclass[11pt]{article}
+%
+% \begin{document}
+%
+% \begin{equation}
+% a^2+b^2=c^2
+% \end{equation}
+%
+% \begin{equation}
+% x^2+y^2=z^2
+% \end{equation}
+%
+% \end{document}
+%\end{example}
+%\end{minipage}
+%\end{Listing}
+%The package will also write a header to the target file with some
+%information about the source and time of generation of the target
+%file. This header can be turned off with the |no-header| option.
+%See also section~\ref{sec:misc}.
+%
+%\section{Command extraction}\label{sec:cmdxtr}
+%\DescribeOptions{extract-cmd,extract-cmdline}
+%This package can also extract commands. It supplies two methods to
+%do this. See the example below.
+%\begin{example}
+% \usepackage[
+%   active,
+%   generate=file,
+%   extract-cmd=section,
+%   extract-cmdline=label
+% ]{extract}
+%\end{example}
+%The first method (accessed with the |extract-cmd| option) is based
+%on the particular syntax of the command and hence only supports
+%particular commands. It will read it arguments and write them,
+%together with the original command, to the target file. Besides
+%that, the command will be executed as usual. Currently, the commands
+%|\chapter|, |\section|, |\subsection|, and |\subsubsection| in the
+%standard \LaTeX\ classes (and classes or packages derived from
+%those) are supported. An optional argument to these commands, like
+%|\chapter[short]{long}| is supported. However, the starred version
+%|\chapter*{title}| will not be written to the file due to technical
+%limitations. Sections~\ref{sec:how} and~\ref{sec:imple} will explain
+%this in more detail.
+%
+%The second method (accessed with the |extract-cmdline| option) will
+%redefine commands to write themselves and all the text following on
+%the same line to the target file and will also execute the entire
+%line as with an ordinary \LaTeX\ run. This allows to redefine any
+%command that is not supported by the first method, but should be
+%applied with care. If the command is used internally in a class or
+%style file, your document might fail to run. In particular, one
+%should not redefine one of the commands supported by the first
+%method with this method. See listing~\vref{list:cmd} for a working
+%example of both methods.
+%\begin{Listing}\caption{Command extraction.}\label{list:cmd}
+%\begin{minipage}[t]{.49\linewidth}
+%\hfill |xtrex2.tex|
+%\begin{example}
+% \documentclass{article}
+% \usepackage[
+%   active,
+%   generate=file,
+%   extract-env=exercise,
+%   extract-cmd=section,
+%   extract-cmdline=label
+% ]{extract}
+% \newtheorem{exercise}{Exercise}
+% \begin{extract}
+% \documentclass{article}
+% \end{extract}
+% \begin{document}
+% \section{Theory}
+% \label{sec:1}
+% Some text.
+% \section{Exercises}
+% \begin{exercise}
+% Use the results from section
+% \ref{sec:1} to show that\dots
+% \end{exercise}
+% Some text.
+% \end{document}
+%\end{example}
+%\end{minipage}
+%\hfill
+%\begin{minipage}[t]{.49\linewidth}
+%\hfill |file.tex|
+%\begin{example}
+% \documentclass{article}
+%
+% \begin{document}
+%
+% \section{Theory}
+%
+% \label{sec:1}
+%
+% \section{Exercises}
+%
+% \begin{exercise}
+% Use the results from section
+% \ref{sec:1} to show that\dots
+% \end{exercise}
+%
+% \end{document}
+%\end{example}
+%\end{minipage}
+%\end{Listing}
+%
+%\section{Conditional extraction}\label{sec:conditional}
+%\subsection{Extraction with numbers}
+%\DescribeOptions{-nrs}
+%It is also possible to conditionally extract environments and
+%commands. After the options |extract-env|, |extract-cmd| and
+%|exstract-cmdline| are used, for each environment or command
+%specified there, there will be a new option with the name of that
+%environment or command and the |-nrs| postfix. This option can take
+%a comma separated list in which you can specify which environments
+%or macros (counting from the |\usepackage{extract}|
+%command\footnote{Notice that starred commands like \ci{chapter*},
+%which won't be redefined by the \texttt{extract-cmd} option, will
+%also not be counted.}) should be extracted. Table~\vref{tab:syntax} lists
+%the syntax that can be used in the comma separated list. The term
+%`item' is used for `command or environment'.
+%\begin{table}[htb]\centering
+%\begin{tabular}{cp{8.5cm}}
+%Syntax&Meaning\\\hline
+%$\meta{x}$&Item $\meta{x}$ will be extracted.\\
+%-$\meta{x}$&All items up to and including item $\meta{x}$ will be extracted.\\
+%$\meta{x}$-&All items from and including item $\meta{x}$ will be extracted.\\
+%$\meta{x}$-$\meta{y}$&All items in between $\meta{x}$ and $\meta{y}$, including
+%$\meta{x}$ and $\meta{y}$ will be extracted.
+%\end{tabular}
+%\caption{Syntax for conditional extraction with numbers.}\label{tab:syntax}
+%\end{table}
+%See an example in the listing below.
+%\begin{example}
+% \documentclass{book}
+% \usepackage[
+%   active,
+%   generate=file,
+%   extract-env={figure,table},
+%   figure-nrs={-2,4-},
+%   extract-cmd=chapter,
+%   chapter-nrs={3-5,7}
+% ]{extract}
+% \begin{document}
+% ...
+% \end{document}
+%\end{example}
+%This example, when completed with content, will extract all |table|
+%environments, |figure| environments 1, 2, and all figures from (and
+%including) figure 4. It will also extract chapters 3 to 5 and
+%chapter 7.
+%
+%\subsection{Extraction with labels}
+%\DescribeOptions{-labels}
+%Conditional extraction is also possible with labels. The advantage of
+%using labels is that output does not change (in comparison to using
+%numbers) when commands or environments are added. The drawback is
+%that one needs to modify the source document and add labels in the
+%text.
+%
+%Labels are declared with the following command.
+%\begin{command}
+% `\ci{extractionlabel}\marg{name}'
+%\end{command}
+%A label should be declared just before the command or environment
+%that you want to extract. For instance
+%\begin{example}
+% \extractionlabel{exer-a}
+% \begin{exercise}
+% ...
+% \end{exercise}
+%\end{example}
+%You can reuse the same label multiple times and you can specify
+%which items should be extracted by the options with a |-labels|
+%prefix. This works in the same way as with numbers.
+%\begin{example}
+% \documentclass{book}
+% \usepackage[
+%   active,
+%   generate=file,
+%   extract-env=exercise,
+%   exercise-labels={exer-a,exer-c}
+% ]{extract}
+% \begin{document}
+% ...
+% \end{document}
+%\end{example}
+%This example will only extract exercises that have been preceded by
+%the declaration |\extractionlabel{exer-a}| or
+%|\extractionlabel{exer-c}|.
+%
+%When using both conditional extraction with numbers and with labels,
+%the command or environment at hand will be extracted when at least
+%on of the conditions is true. Find an example in listing~\vref{list:cond}.
+%\begin{Listing}\caption{Conditional extraction.}\label{list:cond}
+%\begin{minipage}[t]{.49\linewidth}
+%\hfill |xtrex3.tex|
+%\begin{example}
+% \documentclass{article}
+% \usepackage[
+%   active,
+%   generate=file,
+%   extract-env=figure,
+%   figure-nrs={1,3},
+%   figure-labels={fig-a,fig-b}
+% ]{extract}
+% \begin{extract}
+% \documentclass{article}
+% \end{extract}
+% \begin{document}
+% Some text.
+% \begin{figure}
+% Figure 1.
+% \end{figure}
+% Some text.
+% \extractionlabel{fig-a}
+% \begin{figure}
+% Figure 2.
+% \end{figure}
+% Some text.
+% \extractionlabel{fig-b}
+% \begin{figure}
+% Figure 3.
+% \end{figure}
+% Some text.
+% \extractionlabel{fig-c}
+% \begin{figure}
+% Figure 4.
+% \end{figure}
+% \end{document}
+%\end{example}
+%\end{minipage}
+%\hfill
+%\begin{minipage}[t]{.49\linewidth}
+%\hfill |file.tex|
+%\begin{example}
+% \documentclass{article}
+%
+% \begin{document}
+%
+% \begin{figure}
+% Figure 1.
+% \end{figure}
+%
+% \begin{figure}
+% Figure 2.
+% \end{figure}
+%
+% \begin{figure}
+% Figure 3.
+% \end{figure}
+%
+% \end{document}
+%\end{example}
+%\end{minipage}
+%\end{Listing}
+%
+%\section{Extraction tools}\label{sec:tools}
+%\subsection{Manual extraction}
+%\DescribeEnv{extract}
+%The package provides the environment |extract|
+%\begin{command}
+% `\ci{begin\char`\{extract\char`\}}'
+% `\meta{body}'
+% `\ci{end\char`\{extract\char`\}}'
+%\end{command}
+%This environment writes only its body to the target file. This can
+%be used to generate a preamble in the target file so that you can
+%run the generated file through \LaTeX\ immediately after creation.
+%See the examples in sections~\ref{sec:envxtr} and~\ref{sec:cmdxtr}
+%and the example below.
+%
+%\DescribeEnv{extract*}
+%There exists also a starred version of the |extract| environment.
+%\begin{command}
+% `\ci{begin\char`\{extract*\char`\}}'
+% `\meta{body}'
+% `\ci{end\char`\{extract*\char`\}}'
+%\end{command}
+%This environment will not only write the body to the target file,
+%but will also execute the code in the source document. This can be
+%used to create a common preamble which holds packages and commands
+%that will be used in both the source and the target file. See
+%listing~\vref{list:xtrenv} for an example.
+%\begin{Listing}\caption{Extract environments.}\label{list:xtrenv}
+%\begin{minipage}[t]{.49\linewidth}
+%\hfill |xtrex4.tex|
+%\begin{example}
+% \documentclass{article}
+% \usepackage[
+%   active,
+%   generate=file,
+%   extract-env=equation*
+% ]{extract}
+% \begin{extract}
+% \documentclass{article}
+% \end{extract}
+% \begin{extract*}
+% \usepackage{amsmath}
+% \end{extract*}
+% \begin{document}
+% Some text.
+% \begin{equation*}
+% x^2+y^2=z^2
+% \end{equation*}
+% Some text.
+% \end{document}
+%\end{example}
+%\end{minipage}
+%\hfill
+%\begin{minipage}[t]{.49\linewidth}
+%\hfill |file.tex|
+%\begin{example}
+% \documentclass{article}
+% \usepackage{amsmath}
+%
+% \begin{document}
+%
+% \begin{equation*}
+% x^2+y^2=z^2
+% \end{equation*}
+%
+% \end{document}
+%\end{example}
+%\end{minipage}
+%\end{Listing}
+%
+%\DescribeMacro{\extractline}
+%\DescribeMacro{\extractline*}
+%The package also provides a command that extracts the current line.
+%\begin{command}
+% `\ci{extractline}'
+% `\ci{extractline*}'
+%\end{command}
+%The starred version also executes the code at that line. See the
+%example below.
+%\begin{example}
+% \extractline This should be extracted.
+% \extractline*This should be executed and extracted.
+%\end{example}
+%Notice that a space is following |\extractline| and that no space is
+%following |\extractline*|. In the first line, \LaTeX\ will eat this
+%space, but it won't do that in the second line. If we add a space
+%there in between the |*| and |This|, this space will be executed and
+%extracted as well.
+%
+%\newpage\DescribeMacro{\extractline}
+%\DescribeMacro{\extractline*}
+%\DescribeEnvs{extract,extract*}
+%The |extract| and |extract*| environments and the commands
+%|\extractionlabel| and |\extractionlabel*| have an optional argument
+%for specifying the label directly.
+%\begin{command}
+% `\ci{begin\char`\{extract\char`\}}\oarg{name}'
+% `\ci{begin\char`\{extract*\char`\}}\oarg{name}'
+% `\ci{extractlabel}\oarg{name}'
+% `\ci{extractlabel*}\oarg{name}'
+%\end{command}
+%
+%\DescribeOptions{extract-labels,line-labels,extract-nrs,line-nrs}
+%The options |extract-labels| and |line-labels| can be used to
+%control conditional extraction of these environments and commands
+%using labels. Moreover, one can do conditional extractions with
+%numbers for these commands and environments as well. Use the options
+%|extract-nrs| and |line-nrs| for that purpose.
+%
+%See an example in listing~\vref{list:optlab}.
+%This example will demonstrate that only certain lines and environments
+%are extracted. Note that, when running |xtrex5.tex| with \LaTeX,
+%the output, |xtrex5.dvi|, will contain the following.
+%\begin{example}
+% line 2
+% line 4
+% line 5
+%\end{example}
+%\begin{Listing}\caption{Optional labels.}\label{list:optlab}
+%\begin{minipage}[t]{.49\linewidth}
+%\hfill |xtrex5.tex|
+%\begin{example}
+% \documentclass{article}
+% \usepackage[
+%   active,
+%   generate=file,
+%   extract-labels=type-a,
+%   line-labels={type-a,type-c},
+%   line-nrs=3
+% ]{extract}
+% \begin{extract}[type-a]
+% \documentclass{article}
+% \end{extract}
+% \begin{extract}[type-b]
+% \documentclass{book}
+% \end{extract}
+% \begin{document}
+% \parindent0pt
+% \extractline[type-a]line 1\\
+% \extractline*line 2\\
+% \extractline line 3\\
+% \extractline*[type-a]line 4\\
+% \extractline*[type-c]line 5\\
+% \extractline line 6\\
+% \end{document}
+%\end{example}
+%\end{minipage}
+%\hfill
+%\begin{minipage}[t]{.49\linewidth}
+%\hfill |file.tex|
+%\begin{example}
+% \documentclass{article}
+%
+% \begin{document}
+% line 1\\
+% line 3\\
+% line 4\\
+% line 5\\
+%
+% \end{document}
+%\end{example}
+%\end{minipage}
+%\end{Listing}
+%
+%\subsection{Skipping content}
+%\DescribeEnv{extractskip}
+%The package also provides the |extractskip| environment.
+%\begin{command}
+% `\ci{begin\char`\{extractskip\char`\}}\oarg{name}'
+% `\meta{body}'
+% `\ci{end\char`\{extractskip\char`\}}'
+%\end{command}
+%The body of this environment will not be written to the target file,
+%but will be executed. This environment can be used to skip material
+%in an environment which extracts its entire body. This could be the
+%|extract| environment, but also an environment that has been
+%redefined to be extracted using the |extract-env| option. The argument
+%\meta{name} is optional and contains the label; see below.
+%
+%\DescribeOptions{extractskip-nrs,extractskip-labels}
+%This environment can also operate conditionally as has been
+%described in section~\ref{sec:conditional} using the options
+%|extractskip-nrs| and |extractskip-labels|. Listings~\vref{list:skip1}
+%and~\vref{list:skip2} will demonstrate this environment.
+%\begin{Listing}\caption{Skipping extraction.}\label{list:skip1}
+%\begin{minipage}[t]{.49\linewidth}
+%\hfill |xtrex6.tex|
+%\begin{example}
+% \documentclass{article}
+% \usepackage[
+%   active,
+%   generate=file,
+%   extract-env=figure
+% ]{extract}
+% \begin{extract}
+% \documentclass{article}
+% \end{extract}
+% \begin{document}
+% \begin{figure}[!h]
+% \begin{extractskip}
+% \fbox{figure 1}
+% \end{extractskip}
+% \fbox{figure 2}
+% \end{figure}
+% \begin{extract*}
+% \begin{itemize}
+% \item 1
+% \item 2
+% a\begin{extractskip}b
+% \item 3
+% c\end{extractskip}d
+% \item 4
+% \begin{extractskip}
+% \item 5
+% \end{extractskip}
+% \end{itemize}
+% \end{extract*}
+% \end{document}
+%\end{example}
+%\end{minipage}
+%\hfill
+%\begin{minipage}[t]{.49\linewidth}
+%\hfill |file.tex|
+%\begin{example}
+% \documentclass{article}
+%
+% \begin{document}
+%
+% \begin{figure}[!h]
+% \fbox{figure 2}
+% \end{figure}
+% \begin{itemize}
+% \item 1
+% \item 2
+% a
+% d
+% \item 4
+% \end{itemize}
+%
+% \end{document}
+%\end{example}
+%\end{minipage}
+%\end{Listing}
+%\begin{Listing}\caption{Skipping extraction conditionally.}\label{list:skip2}
+%\begin{minipage}[t]{.49\linewidth}
+%\hfill |xtrex7.tex|
+%\begin{example}
+% \documentclass{article}
+% \usepackage[
+%   active,
+%   generate=file,
+%   extractskip-labels=skipb
+% ]{extract}
+% \begin{extract}
+% \documentclass{article}
+% \end{extract}
+% \begin{document}
+% \begin{extract*}
+% \begin{itemize}
+% \begin{extractskip}[skipa]
+% \item 1
+% \end{extractskip}
+% \begin{extractskip}[skipb]
+% \item 2
+% \end{extractskip}
+% \begin{extractskip}[skipc]
+% \item 3
+% \end{extractskip}
+% \end{itemize}
+% \end{extract*}
+% \end{document}
+%\end{example}
+%\end{minipage}
+%\hfill
+%\begin{minipage}[t]{.49\linewidth}
+%\hfill |file.tex|
+%\begin{example}
+% \documentclass{article}
+%
+% \begin{document}
+% \begin{itemize}
+% \item 1
+% \item 3
+% \end{itemize}
+%
+% \end{document}
+%\end{example}
+%\end{minipage}
+%\end{Listing}
+%
+%\subsection{Miscellaneous options}\label{sec:misc}
+%\DescribeOption{document-handles} The package provides the
+%option |document-handles|. This option can be set to |true| or
+%|false| and controls whether the package will write
+%|\begin{document}| and |\end{document}| to the target file when it
+%encounters these commands in the source document. By default, this
+%option is set to |true|. When the option is set to |false|, the
+%generated file can be |\input|ed or |\include|d by another file
+%immediately after production.
+%
+%\DescribeOption{no-header} When specifying the |no-header| option,
+%no header will be written to the target file. If the option is not
+%specified or set to |true|, the package will write a header to the
+%target file including information on when the target file was generated
+%and which source file was used.
+%
+%\section{How it works, limitations}\label{sec:how}
+%The package works as follows. When an environment is asked to be
+%extracted, the package will first make a backup of the environment
+%with the |XTR| prefix, for instance, |XTRequation*|. After that, the
+%package will redefine the environment to read the lines of its body
+%verbatim (without executing), parse the lines to locate
+%|extractskip| environments and write all lines to a temporary file
+%and the lines that are not in an |extractskip| environment to a
+%temporary file. After the environment is finished, the temporary
+%file, containing for instance
+%\begin{example}
+% \begin{XTRequation*}
+% x^2+y^2=z^2
+% \end{XTRequation*}
+%\end{example}
+%will be inserted in the source document using |\input|. This works,
+%at least in theory, with most environments. Notice that this method
+%does require a change to the |\begin| and |\end| macros provided by
+%the \LaTeX\ kernel \cite{LaTeXbase}. I had to add a hook to these
+%commands to be able to collect code to be executed after the current
+%environment is ended. In particular, this package will use those
+%hooks to |\input| the original code after finishing the current
+%group. See section~\ref{sec:imple} for more details.
+%
+%Commands require a different approach. As a command can have a very
+%specific argument structure, redefining commands safely, without
+%distorting its original behavior, is not possible in general. I have
+%chosen to support the most basic document structure commands as
+%provided by standard \LaTeX\ classes, like \pf{book} and
+%\pf{article}. Other classes, like provided by the \pf{koma-script}
+%bundle, might work, but there is no guarantee.
+%
+%To be more precise: when requested, the macros |\@chapter| and
+%|\@sect| will be redefined. These commands are at the basis of all
+%chapters and sections. When \pf{extract} redefines one of these
+%commands, it first makes a backup, like |\XTR@chapter|. After that,
+%it will redefine the original command to read its argument(s),
+%export them to the target file and execute the backup with the
+%proper arguments.
+%
+%An alternative to this, rather restricted method is the method
+%accessed by the |extract-cmdline| option which redefines the
+%commands listed there to read the entire line of text, write that to
+%the target file and afterwards execute it with a backup copy of the
+%original command. This methods too has its drawbacks though as you
+%can't redefine commands that are used internally in other macros.
+%
+%More details on the package code can be found in
+%section~\ref{sec:imple}.
+%
+%\section{Source and examples}\label{sec:sande}
+%To generate this documentation, find the source of this
+%package, |extract.dtx| in your local \LaTeX\ installation or on CTAN
+%and perform the following steps.
+%\begin{example}
+% latex extract.dtx
+% latex extract.dtx
+% bibtex extract
+% makeindex -s gglo.ist -o extract.gls extract.glo
+% makeindex -s gind.ist -o extract.ind extract.idx
+% latex extract.dtx
+% latex extract.dtx
+%\end{example}
+%
+%If you only want to produce the package and example files from the
+%source, then the first step is sufficient. This step will generate
+%the package file |extract.sty| and the example files |xtrex1.tex|,
+%|xtrex2.tex|, |xtrex3.tex|, |xtrex4.tex|, |xtrex5.tex|, |xtrex6.tex|
+%and |xtrex7.tex|.
+%
+%\StopEventually{}
+%
+% \section{Implementation}\label{sec:imple}
+% Initializations.
+%    \begin{macrocode}
+%<*extract>
+\NeedsTeXFormat{LaTeX2e}[1995/12/01]
+\ProvidesPackage{extract}[2005/02/14 v1.6 extract content from document (HA)]
+\RequirePackage{verbatim}
+\RequirePackage{xkeyval}
+\newwrite\XTR@out
+\newwrite\XTR@tmp
+\newif\ifXTR@st
+\newif\ifXTR@skip
+\newif\ifXTR@active
+\newif\ifXTR@extract
+\newif\ifXTR@header\XTR@headertrue
+\newif\ifXTR@handles\XTR@handlestrue
+%    \end{macrocode}
+% \begin{macro}{\XTR@err}
+% Error macro.
+%    \begin{macrocode}
+\def\XTR@err#1{\PackageError{extract}{#1}\@ehc}
+%    \end{macrocode}
+% \end{macro}
+% \begin{macro}{\XTR@namelet}
+% Version of |\let| for two command sequence names.
+%    \begin{macrocode}
+\def\XTR@namelet#1#2{\expandafter\let\csname#1\expandafter\endcsname\csname#2\endcsname}
+%    \end{macrocode}
+% \end{macro}
+% Options section, powered by \pf{xkeyval}.
+% \DescribeOption{active}
+% Control extraction with one switch.
+%    \begin{macrocode}
+\DeclareOptionX[XTR]{active}{\XTR@activetrue}
+%    \end{macrocode}
+% \DescribeOption{generate}
+% Entry point for the target file name.
+%    \begin{macrocode}
+\DeclareOptionX[XTR]{generate}{\lowercase{\def\XTR@file{#1}}}
+%    \end{macrocode}
+% \DescribeOption{no-header}
+% Do not create a header in the target file.
+%    \begin{macrocode}
+\DeclareOptionX[XTR]{no-header}[false]{\XKV@setbool{XTR@header}{#1}}
+%    \end{macrocode}
+% \DescribeOption{document-handles}
+% Extract |\begin{document}| and |\end{document}| or not.
+%    \begin{macrocode}
+\DeclareOptionX[XTR]{document-handles}[true]{\XKV@setbool{XTR@handles}{#1}}
+%    \end{macrocode}
+% \DescribeOption{extract-env}
+% Environments that should be extracted.
+%    \begin{macrocode}
+\DeclareOptionX[XTR]{extract-env}{%
+  \def\XTR@envs{#1}%
+  \@for\XTR@tempa:=\XTR@envs\do\XTR@tempb
+}
+%    \end{macrocode}
+% \DescribeOption{extract-cmd}
+% Commands that should be extracted with the `arguments method'.
+%    \begin{macrocode}
+\DeclareOptionX[XTR]{extract-cmd}{%
+  \def\XTR@cmdsargs{#1}%
+  \@for\XTR@tempa:=\XTR@cmdsargs\do\XTR@tempb
+}
+%    \end{macrocode}
+% \DescribeOption{extract-cmdline}
+% Commands that should be extracted with the `line method'.
+%    \begin{macrocode}
+\DeclareOptionX[XTR]{extract-cmdline}{%
+  \def\XTR@cmdsline{#1}%
+  \@for\XTR@tempa:=\XTR@cmdsline\do\XTR@tempb
+}
+\def\XTR@tempb{%
+%    \end{macrocode}
+% \DescribeOptions{-nrs,-labels}
+% For each environment or command provide new package options that
+% save the argument to a list cleared from redundant spaces. The
+% |-nrs| options also create a `counter' for counting the commands or
+% environments. The lists and counters will be used for conditional
+% extraction. Note that |\XTR@tkey| contains the key name inside
+% the option macro (due to the use of |\ProcessOptionsXi|).
+%    \begin{macrocode}
+  \DeclareOptionX[XTR]{\XTR@tempa-nrs}{%
+    \expandafter\XKV@sp@deflist\csname XTR@\XKV@tkey\endcsname{##1}%
+    \XTR@namelet{XTR@\XKV@tkey @cnt}{z@}%
+  }%
+  \DeclareOptionX[XTR]{\XTR@tempa-labels}{%
+    \expandafter\XKV@sp@deflist\csname XTR@\XKV@tkey\endcsname{##1}%
+  }%
+}
+%    \end{macrocode}
+% \DescribeOptions{line-nrs,line-labels}
+% Generate options for |\extractline| commands.
+%    \begin{macrocode}
+\def\XTR@tempa{line}\XTR@tempb
+%    \end{macrocode}
+% \DescribeOptions{extract-nrs,extract-labels}
+% Generate options for |extract| environments.
+%    \begin{macrocode}
+\def\XTR@tempa{extract}\XTR@tempb
+%    \end{macrocode}
+% \DescribeOptions{extractskip-nrs,extractskip-labels}
+% Generate options for |extractskip| environments.
+%    \begin{macrocode}
+\def\XTR@tempa{extractskip}\XTR@tempb
+%    \end{macrocode}
+% Generate an error for unknown options.
+%    \begin{macrocode}
+\DeclareOptionX*{\XTR@err{Unknown option `\CurrentOption'}}
+%    \end{macrocode}
+% Process options.
+%    \begin{macrocode}
+\ProcessOptionsX[XTR]
+%    \end{macrocode}
+% \begin{macro}{\XTR@opentmp}
+% \begin{macro}{\XTR@writetmp}
+% \begin{macro}{\XTR@closetmp}
+% \begin{macro}{\XTR@writeout}
+% Shortcut macros for much used command sequences.
+%    \begin{macrocode}
+\def\XTR@opentmp{\immediate\openout\XTR@tmp\jobname.xtr\relax}
+\def\XTR@writetmp{\immediate\write\XTR@tmp}
+\def\XTR@closetmp{\immediate\closeout\XTR@tmp}
+\def\XTR@writeout{\immediate\write\XTR@out}
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% Perform some checks on the input. Notice the use of |\XKV@ifundefined|
+% which is equal to |\@ifundefined| if no $\varepsilon$-\TeX\ engine
+% is available and which uses |\ifcsname| when it is. In the latter
+% case, testing whether commands are defined does not create an
+% entry in \TeX's hash table.
+%    \begin{macrocode}
+\ifXTR@active
+  \XKV@ifundefined{XTR@file}{
+    \XTR@activefalse
+    \XTR@err{no file to generate; extract deactivated}
+  }{}
+  \XTR@opentmp
+  \XTR@writetmp{\string\lowercase{\string\def\string\XTR@tempa{\jobname}}}
+  \XTR@closetmp
+  \input{\jobname.xtr}
+  \ifx\XTR@tempa\XTR@file
+    \XTR@activefalse
+    \XTR@err{attempt to overwrite source file; extract deactivated}
+  \fi
+\fi
+%    \end{macrocode}
+% \begin{macro}{\@envdepth}
+% Counter for depth of environments.
+%    \begin{macrocode}
+\newcount\@envdepth\@envdepth\z@
+%    \end{macrocode}
+% \end{macro}
+% \begin{macro}{\begin}
+% Modify the macro |\begin| to allow adding code to a level specific
+% hook which can be executed after |\endgroup| in |\end|. See for
+% more info on this macro the \LaTeX\ source~\cite{LaTeXbase}.
+%    \begin{macrocode}
+\def\begin#1{%
+  \@ifundefined{#1}%
+    {\def\reserved@a{\@latex@error{Environment #1 undefined}\@eha}}%
+    {\def\reserved@a{\def\@currenvir{#1}%
+     \edef\@currenvline{\on@line}%
+     \csname #1\endcsname}}%
+  \@ignorefalse
+  \begingroup\@endpefalse
+%    \end{macrocode}
+% Advance depth level.
+%    \begin{macrocode}
+  \global\advance\@envdepth\@ne
+%    \end{macrocode}
+% Initialize the hook for this level.
+%    \begin{macrocode}
+  \global\@namedef{@afterendenvhook@\romannumeral\@envdepth}{}%
+  \reserved@a}
+%    \end{macrocode}
+% \end{macro}
+% \begin{macro}{\end}
+% Modify |\end| to execute the code collected in the hook.
+%    \begin{macrocode}
+\def\end#1{%
+  \csname end#1\endcsname\@checkend{#1}%
+  \expandafter\endgroup\if@endpe\@doendpe\fi
+%    \end{macrocode}
+% Copy current hook code to a temporary macro.
+%    \begin{macrocode}
+  \expandafter\let\expandafter\reserved@a
+    \csname @afterendenvhook@\romannumeral\@envdepth\endcsname
+%    \end{macrocode}
+% Decrease the depth.
+%    \begin{macrocode}
+  \global\advance\@envdepth\m@ne
+%    \end{macrocode}
+% Execute the hook of the current environment. This is done after
+% decreasing the depth as to avoid level mixing problems when the
+% hook contains another environment. This environment has to be
+% executed at the same level as the environment in which the hook was
+% defined since it is executed after the group and does not below
+% anymore to the environment in which the hook was defined.
+%    \begin{macrocode}
+  \reserved@a\relax
+  \if@ignore\@ignorefalse\ignorespaces\fi}
+%    \end{macrocode}
+% \end{macro}
+% \begin{macro}{\AfterEndEnv}
+% Adds code to the macros |\@afterendenvhook@i|, |ii|, etc. which will
+% be executed after the group of the current environment.
+%    \begin{macrocode}
+\def\AfterEndEnv{%
+  \expandafter\g@addto@macro
+    \csname @afterendenvhook@\romannumeral\@envdepth\endcsname
+}
+%    \end{macrocode}
+% \end{macro}
+% \begin{macro}{\XTR@checkxtr}
+% Checks whether a certain environment or command should be extracted.
+%    \begin{macrocode}
+\def\XTR@checkxtr#1#2{%
+  \@nameuse{XTR@#1false}%
+  \XTR@namelet{XTR@maketrue}{XTR@#1true}%
+%    \end{macrocode}
+% First check whether, for this macro or environment, some method of
+% conditional extraction is used. If not, just extract.
+%    \begin{macrocode}
+  \XKV@ifundefined{XTR@#2-nrs}{%
+    \XKV@ifundefined{XTR@#2-labels}\XTR@maketrue{}%
+  }{%
+%    \end{macrocode}
+% Advance the `counter'.
+%    \begin{macrocode}
+    \begingroup
+      \expandafter\count@\csname XTR@#2-nrs@cnt\endcsname
+      \advance\count@\@ne
+      \edef\XTR@resa{\expandafter\noexpand\expandafter\gdef\expandafter
+        \noexpand\csname XTR@#2-nrs@cnt\endcsname{\the\count@}}%
+    \expandafter\endgroup\XTR@resa
+  }%
+  \@nameuse{ifXTR@#1}\else
+    \XKV@ifundefined{XTR@#2-labels}{}{%
+%    \end{macrocode}
+% If the current label is in the list for extraction, extract it.
+%    \begin{macrocode}
+      \ifx\XTR@currentlabel\relax\else
+        \@expandtwoargs\in@{,\XTR@currentlabel,}{,\csname XTR@#2-labels\endcsname,}%
+        \ifin@\XTR@maketrue\fi
+      \fi
+    }%
+  \fi
+  \@nameuse{ifXTR@#1}\else
+    \XKV@ifundefined{XTR@#2-nrs}{}{%
+%    \end{macrocode}
+% If the current command or environment number is in the list, extract it.
+%    \begin{macrocode}
+      \expandafter\XTR@ch@ckxtr\csname XTR@#2-nrs\expandafter
+        \endcsname\csname XTR@#2-nrs@cnt\endcsname
+    }%
+  \fi
+%    \end{macrocode}
+% Redefine |\XTR@currentlabel| to avoid extracting all following
+% environments of this type.
+%    \begin{macrocode}
+  \global\let\XTR@currentlabel\relax
+}
+%    \end{macrocode}
+% \end{macro}
+% \begin{macro}{\XTR@ch@ckxtr}
+% Parse the list and compare each item with the counter in |#2|.
+%    \begin{macrocode}
+\def\XTR@ch@ckxtr#1#2{%
+  \@for\XTR@resa:=#1\do{\expandafter\XTR@ch@ck@tr\XTR@resa--\@nil#2}%
+}
+%    \end{macrocode}
+% \end{macro}
+% \begin{macro}{\XTR@ch@ck@tr}
+% Parse an element of the list. Basically, decide whether we have |x|
+% |x-y|, |x-| or |-y| and act accordingly.
+%    \begin{macrocode}
+\def\XTR@ch@ck@tr#1-#2-#3\@nil#4{%
+  \ifx\@empty#1\@empty
+    \ifnum#4>#2 \else\XTR@maketrue\fi
+  \else
+    \ifx\@empty#2\@empty
+      \ifx\@empty#3\@empty
+        \ifnum#4=#1 \XTR@maketrue\fi
+      \else
+        \ifnum#4<#1 \else\XTR@maketrue\fi
+      \fi
+    \else
+      \ifnum#4<#1 \else\ifnum#4>#2 \else\XTR@maketrue\fi\fi
+    \fi
+  \fi
+}
+%    \end{macrocode}
+% \end{macro}
+% \begin{macro}{\extractionlabel}
+% \changes{v1.3}{2005/01/12}{Was \ci{extractlabel}}
+% \begin{macro}{\XTR@currentlabel}
+% |\extractionlabel| saves its argument (after removing redundant spaces).
+% This label will be used for conditional extraction. |\XTR@currentlabel|
+% is initialized.
+%    \begin{macrocode}
+\def\extractionlabel{\KV@@sp@def\XTR@currentlabel}
+\let\XTR@currentlabel\relax
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+% \begin{macro}{\extract}
+% \begin{macro}{\extract*}
+% Define environments that write verbatim to the target file. The
+% starred version also executes the code by writing it to a temp file
+% and inputting it |\AfterEndEnv|, just as with redefining existing
+% environments. When the package is inactive, |extract| is equivalent
+% to the |comment| environment and |extract*| takes its body out of the
+% group and executes it hence acting as if |\begin{extract*}| and
+% |\end{extract*}| were never typed.
+%    \begin{macrocode}
+\def\extract{\XTR@stfalse\XTR@extract}
+\@namedef{extract*}{\XTR@sttrue\XTR@extract}
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+% \begin{macro}{\XTR@extract}
+% Prepare verbatim reading and check for an optional argument.
+%    \begin{macrocode}
+\def\XTR@extract{%
+  \@bsphack
+  \let\do\@makeother\dospecials\catcode`\^^M\active
+  \@testopt\XTR@@xtract\@nil
+}
+%    \end{macrocode}
+% \end{macro}
+% \begin{macro}{\XTR@@xtract}
+% Process the optional label, define line processing and start reading
+% verbatim. Do not extract when the package is not active. Use a
+% temporary file to extract the body to in case this needs to be
+% executed in the source document (|extract*| environment).
+%    \begin{macrocode}
+\def\XTR@@xtract[#1]{%
+%    \end{macrocode}
+% Check state.
+%    \begin{macrocode}
+  \ifXTR@active
+    \def\XTR@tempa{#1}%
+    \ifx\XTR@tempa\@nnil\else
+      \KV@@sp@def\XTR@currentlabel{#1}%
+    \fi
+    \XTR@checkxtr{extract}{extract}%
+  \else
+    \XTR@extractfalse
+  \fi
+  \ifXTR@st\XTR@opentmp\fi
+  \let\verbatim@processline\XTR@processline@begin
+  \verbatim@start
+}
+%    \end{macrocode}
+% \end{macro}
+%    \begin{macrocode}
+\begingroup
+  \lccode`\!=`\\ \lccode`\(=`\{ \lccode`\)=`\}
+\lowercase{\endgroup
+%    \end{macrocode}
+% \begin{macro}{\XTR@processline@begin}
+% This macro starts the reparsing of a line read by \pf{verbatim}. It
+% is possible to have |\begin{extractskip}| and |\end{extractskip}|
+% on the same line.
+%    \begin{macrocode}
+\def\XTR@processline@begin{%
+%    \end{macrocode}
+% Initialize |\@temptokena| (used for temp file) and |\verbatim@line|
+% (used for output file).
+%    \begin{macrocode}
+  \@temptokena{}%
+  \expandafter\verbatim@line\expandafter{\expandafter}\expandafter
+    \XTR@testbegin\the\verbatim@line!begin(extractskip)\@nil
+}
+%    \end{macrocode}
+% \end{macro}
+% \begin{macro}{\XTR@testbegin}
+% Checks whether |\begin{extractskip}| occurs.
+%    \begin{macrocode}
+\def\XTR@testbegin#1!begin(extractskip)#2\@nil{%
+  \@temptokena\expandafter{\the\@temptokena#1}%
+  \verbatim@line\expandafter{\the\verbatim@line#1}%
+  \def\XTR@tempa{#2}%
+%    \end{macrocode}
+% If |#2| empty, there is no |\begin{extractskip}|. Just write the
+% content to file.
+%    \begin{macrocode}
+  \ifx\XTR@tempa\@empty\XTR@processline@write\else\XKV@afterfi
+%    \end{macrocode}
+% Check the label.
+%    \begin{macrocode}
+    \XTR@skiplabel#2[]\@nil
+%    \end{macrocode}
+% Should we skip the |extractskip| environment or not?
+%    \begin{macrocode}
+    \XTR@checkxtr{skip}{extractskip}%
+%    \end{macrocode}
+% Switch to scanning for |\end{extractskip}| in the next line.
+%    \begin{macrocode}
+    \let\verbatim@processline\XTR@processline@end
+%    \end{macrocode}
+% Remove some stuff that we added and continue scanning for |\end{extractskip}|
+% on the current line.
+%    \begin{macrocode}
+    \ifx\XTR@tempa\@nnil\XKV@afterelsefi
+      \XTR@t@stbegin#2\@nil
+    \else\XKV@afterfi
+      \expandafter\XTR@t@stbegin\XTR@tempa\@nil
+    \fi
+  \fi
+}
+%    \end{macrocode}
+% \end{macro}
+% \begin{macro}{\XKV@skiplabel}
+% This macro checks whether a label is present and sets |\XTR@currentlabel|
+% if necessary.
+%    \begin{macrocode}
+\def\XTR@skiplabel#1[#2]#3\@nil{%
+  \def\XTR@tempa{#1}%
+  \def\XTR@tempb{#2}%
+  \ifx\XTR@tempa\@empty
+    \ifx\XTR@tempb\@empty
+      \let\XTR@tempa\@nnil
+    \else
+      \KV@@sp@def\XTR@currentlabel{#2}%
+      \XTR@sk@plabel#3\@nil
+    \fi
+  \else
+    \let\XTR@tempa\@nnil
+  \fi
+}
+%    \end{macrocode}
+% \end{macro}
+% \begin{macro}{\XTR@sk@plabel}
+% Remove extra brackets from input.
+%    \begin{macrocode}
+\def\XTR@sk@plabel#1[]\@nil{\def\XTR@tempa{#1}}
+%    \end{macrocode}
+% \end{macro}
+% \begin{macro}{\XTR@t@stbegin}
+% Remove the extra |\begin{extractskip}| and start scanning for
+% |\end{extractskip}| in the current line.
+%    \begin{macrocode}
+\def\XTR@t@stbegin#1!begin(extractskip)\@nil{\XTR@testend#1!end(extractskip)\@nil}
+%    \end{macrocode}
+% \end{macro}
+% \begin{macro}{\XTR@processline@end}
+% Starts scanning for |\end{extractskip}| in case this was not on one
+% line with |\begin{extractskip}|.
+%    \begin{macrocode}
+\def\XTR@processline@end{%
+  \@temptokena{}%
+  \expandafter\verbatim@line\expandafter{\expandafter}\expandafter
+    \XTR@testend\the\verbatim@line!end(extractskip)\@nil
+}
+%    \end{macrocode}
+% \end{macro}
+% \begin{macro}{\XTR@testend}
+% Check whether |\end{extractskip}| occurs in the line.
+%    \begin{macrocode}
+\def\XTR@testend#1!end(extractskip)#2\@nil{%
+  \@temptokena\expandafter{\the\@temptokena#1}%
+%    \end{macrocode}
+% Skip material conditionally on labels or numbers.
+%    \begin{macrocode}
+  \ifXTR@skip\else\verbatim@line\expandafter{\the\verbatim@line#1}\fi
+  \def\XTR@tempa{#2}%
+  \ifx\XTR@tempa\@empty\XTR@processline@write\else\XKV@afterfi
+%    \end{macrocode}
+% Switch to scanning for |\begin{extractskip}| in the next line.
+%    \begin{macrocode}
+    \let\verbatim@processline\XTR@processline@begin
+%    \end{macrocode}
+% Continue scanning for |\begin{extractskip}| in the current line.
+%    \begin{macrocode}
+    \XTR@t@stend#2\@nil
+  \fi
+}
+%    \end{macrocode}
+% \end{macro}
+% \begin{macro}{\XTR@t@stend}
+% Remove the redundant |\end{extractskip}| and continue scanning for
+% |\begin{extractskip}| in this line.
+%    \begin{macrocode}
+\def\XTR@t@stend#1!end(extractskip)\@nil{\XTR@testbegin#1!begin(extractskip)\@nil}
+%    \end{macrocode}
+% \end{macro}
+% \begin{macro}{\XTR@processline@write}
+% Writes the material to the appropriate file.
+%    \begin{macrocode}
+\def\XTR@processline@write{%
+  \ifXTR@st\ifcat$\the\@temptokena$\else
+      \XTR@writetmp{\the\@temptokena}%
+  \fi\fi
+  \ifXTR@extract\ifcat$\the\verbatim@line$\else
+      \XTR@writeout{\the\verbatim@line}%
+  \fi\fi
+}}
+%    \end{macrocode}
+% \end{macro}
+% \begin{macro}{\endextract}
+% \begin{macro}{\endextract*}
+% Stop reading verbatim and if necessary execute the body of the
+% environment after the |extract*| environment.
+%    \begin{macrocode}
+\def\endextract{\XTR@stfalse\XTR@endextract}
+\@namedef{endextract*}{\XTR@sttrue\XTR@endextract}
+\def\XTR@endextract{%
+  \@esphack
+  \ifXTR@st
+    \XTR@closetmp
+    \AfterEndEnv{\input{\jobname.xtr}}%
+  \fi
+}
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+% \begin{macro}{\extractskip}
+% \begin{macro}{\endextractskip}
+% The |extractskip| environment when it is not used inside an environment
+% that is redefined to be extracted. Hence this environment makes itself
+% disappear, just as |extract*|, but doesn't write to the output file.
+% The trick with |XTR@activefalse| will remain local.
+%    \begin{macrocode}
+\@namedef{extractskip}{\XTR@activefalse\@nameuse{extract*}}
+\XTR@namelet{endextractskip}{endextract*}
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+% \begin{macro}{\extractline}
+% This macro extracts all text after the macro and at the same line.
+% First we check for an optional star.
+%    \begin{macrocode}
+\def\extractline{%
+  \XKV@ifstar{\XTR@sttrue\XTR@extractline}{\XTR@stfalse\XTR@extractline}%
+}
+%    \end{macrocode}
+% \end{macro}
+% \begin{macro}{\XTR@extractline}
+% Start the group and reset all catcodes for verbatim reading.
+%    \begin{macrocode}
+\def\XTR@extractline{%
+  \begingroup
+    \let\do\@makeother\dospecials\catcode`\^^M\active
+%    \end{macrocode}
+% Test for an optional argument. Note that, due to reset catcodes,
+% macros won't work in the optional argument, but that is not a real
+% restriction, while it saves some tokens and memory. If we want to
+% allow for macro arguments, we need an extra macro for the check.
+%    \begin{macrocode}
+    \@testopt\XTR@@xtractline\@nil
+}
+%    \end{macrocode}
+% \end{macro}
+% \begin{macro}{\XTR@@xtractline}
+% The workhorse that reads input until the end of the line. Use the
+% |\lowercase| trick for the definition.
+%    \begin{macrocode}
+\begingroup
+  \catcode`\~=\active\lccode`\~=`\^^M
+\lowercase{\endgroup
+  \def\XTR@@xtractline[#1]#2~{%
+%    \end{macrocode}
+% Check state.
+%    \begin{macrocode}
+      \ifXTR@active
+        \def\XTR@tempa{#1}%
+        \ifx\XTR@tempa\@nnil\else
+          \KV@@sp@def\XTR@currentlabel{#1}%
+        \fi
+        \XTR@checkxtr{extract}{line}%
+      \else
+        \XTR@extractfalse
+      \fi
+      \ifXTR@extract\XTR@writeout{#2}\fi
+%    \end{macrocode}
+% If we need to execute the line, the catcodes are wrong, so write it
+% to the temporary file and insert it again when the catcodes are
+% reset by |\endgroup|.
+%    \begin{macrocode}
+      \ifXTR@st\XTR@opentmp\XTR@writetmp{#2}\XTR@closetmp\fi
+    \endgroup
+%    \end{macrocode}
+% Insert original content.
+%    \begin{macrocode}
+    \ifXTR@st
+      \input{\jobname.xtr}%
+    \fi
+  }%
+}
+%    \end{macrocode}
+% \end{macro}
+% Only define the following macros when the package is active. This
+% branch also performs redefinitions of the macros and environments
+% that should be extracted.
+%    \begin{macrocode}
+\ifXTR@active
+%    \end{macrocode}
+% Start writing the target file.
+%    \begin{macrocode}
+\immediate\openout\XTR@out\XTR@file\relax
+%    \end{macrocode}
+% Write header to the target file.
+%    \begin{macrocode}
+\ifXTR@header
+  \begingroup
+%    \end{macrocode}
+% Save the \% character.
+%    \begin{macrocode}
+    \catcode`\%=12
+    \gdef\XTR@tempa{%%\space}
+%    \end{macrocode}
+% Compute the time.
+%    \begin{macrocode}
+    \@tempcnta\time
+    \divide\@tempcnta 60
+    \edef\XTR@tempb{\the\year/\the\month/\the\day, \the\@tempcnta:}
+    \multiply\@tempcnta 60
+    \@tempcntb\time
+    \advance\@tempcntb-\@tempcnta
+    \ifnum\@tempcntb<10
+      \xdef\XTR@tempb{\XTR@tempb0\the\@tempcntb}
+    \else
+      \xdef\XTR@tempb{\XTR@tempb\the\@tempcntb}
+    \fi
+  \endgroup
+%    \end{macrocode}
+% Write all information to the target file.
+%    \begin{macrocode}
+  \XTR@writeout{\XTR@tempa}
+  \filename@parse\XTR@file
+  \ifx\filename@ext\relax\def\filename@ext{tex}\fi
+  \XTR@writeout{\XTR@tempa This is file, `\filename@base.\filename@ext',}
+  \XTR@writeout{\XTR@tempa generated with the extract package.^^J\XTR@tempa}
+  \XTR@writeout{\XTR@tempa Generated on : \space\XTR@tempb}
+  \filename@parse\jobname
+  \ifx\filename@ext\relax\def\filename@ext{tex}\fi
+  \XTR@writeout{\XTR@tempa From source \space: \space\filename@base.\filename@ext}
+  \XTR@writeout{\XTR@tempa Using options: \space\csname opt@extract.sty\endcsname}
+  \XTR@writeout{\XTR@tempa}
+\fi
+%    \end{macrocode}
+% Perform redefinitions at the beginning of the document.
+%    \begin{macrocode}
+\AtBeginDocument{%
+  \ifXTR@handles
+    \XTR@writeout{}%
+    \XTR@writeout{\string\begin{document}}%
+  \fi
+%    \end{macrocode}
+% Redefine environments.
+%    \begin{macrocode}
+  \XKV@ifundefined{XTR@envs}{}{%
+    \@for\XTR@tempa:=\XTR@envs\do{%
+%    \end{macrocode}
+% Check whether the environment is defined.
+%    \begin{macrocode}
+      \XKV@ifundefined\XTR@tempa{%
+        \XTR@err{environment `\XTR@tempa' not defined; extraction canceled}%
+      }{%
+%    \end{macrocode}
+% Backup the beginning of the environment.
+%    \begin{macrocode}
+        \XTR@namelet{XTR\XTR@tempa}{\XTR@tempa}%
+%    \end{macrocode}
+% Redefine the beginning of the environment. This uses \pf{verbatim}
+% internally.
+%    \begin{macrocode}
+        \@namedef{\XTR@tempa\expandafter}\expandafter{\expandafter
+          \def\expandafter\XTR@tempa\expandafter{\XTR@tempa}%
+%    \end{macrocode}
+% Check whether the current environment should be extracted. Note
+% that |\XTR@tempa| contains the current environment name.
+%    \begin{macrocode}
+          \XTR@checkxtr{extract}\XTR@tempa
+          \ifXTR@extract
+%    \end{macrocode}
+% If extraction is required, write to the target file and to a temporary
+% file for inclusion afterwards.
+%    \begin{macrocode}
+            \XTR@writeout{}\XTR@opentmp
+            \@bsphack
+            \let\do\@makeother\dospecials\catcode`\^^M\active
+%    \end{macrocode}
+% \begin{macro}{\verbatim@processline}
+% \changes{v1.1}{2005/01/01}{Made to write content on same line as
+% environment heading if so in source file}
+% Process macro for \pf{verbatim}.
+%    \begin{macrocode}
+            \def\verbatim@processline{%
+%    \end{macrocode}
+% |\verbatim@processline| is redefined here since the first line is
+% treated specially, see below.
+%    \begin{macrocode}
+              \let\verbatim@processline\XTR@processline@begin
+%    \end{macrocode}
+% Write the content to the files.
+%    \begin{macrocode}
+              \XTR@writeout{\string\begin{\XTR@tempa}\the\verbatim@line}%
+              \XTR@writetmp{\string\begin{XTR\XTR@tempa}\the\verbatim@line}%
+            }%
+%    \end{macrocode}
+% \end{macro}
+%    \begin{macrocode}
+            \XTR@sttrue\let\XTR@tempb\verbatim@
+          \else
+%    \end{macrocode}
+% Else, execute the backup of the current environment.
+%    \begin{macrocode}
+            \edef\XTR@tempb{\noexpand\begin{XTR\XTR@tempa}}%
+          \fi
+          \XTR@tempb
+        }%
+%    \end{macrocode}
+% Backup the end of the environment.
+%    \begin{macrocode}
+        \XTR@namelet{endXTR\XTR@tempa}{end\XTR@tempa}%
+%    \end{macrocode}
+% Redefine the end of the environment.
+%    \begin{macrocode}
+        \@namedef{end\XTR@tempa\expandafter}\expandafter{\expandafter
+          \def\expandafter\XTR@tempa\expandafter{\XTR@tempa}%
+          \ifXTR@extract
+            \@esphack
+%    \end{macrocode}
+% Finalize writing and add the |\input| to the hook at the end of the
+% current environment.
+%    \begin{macrocode}
+            \XTR@writeout{\string\end{\XTR@tempa}}%
+            \XTR@writetmp{\string\end{XTR\XTR@tempa}}%
+            \XTR@closetmp
+            \AfterEndEnv{\input{\jobname.xtr}}%
+          \else
+%    \end{macrocode}
+% If not extracting, execute the backup of the end of the environment.
+%    \begin{macrocode}
+            \edef\XTR@tempa{\noexpand\end{XTR\XTR@tempa}}%
+            \expandafter\XTR@tempa
+          \fi
+        }%
+      }%
+    }%
+  }%
+%    \end{macrocode}
+% Redefine commands using the arguments.
+%    \begin{macrocode}
+  \XKV@ifundefined{XTR@cmdsargs}{}{%
+%    \end{macrocode}
+% Once backup the current definitions.
+%    \begin{macrocode}
+    \let\XTR@sect\@sect
+    \let\XTR@chapter\@chapter
+    \def\XTR@tempb{chapter}%
+%    \end{macrocode}
+% Redefine a list of macros to write themselves to the target file.
+% Chapters and section are treated differently since they are
+% constructed differently. |\chapter*| will not extract itself since
+% this gives technical difficulties due to the fact that this macro
+% is reused at several places inside other macros, taking none-character
+% input in its argument.
+%    \begin{macrocode}
+    \@for\XTR@tempa:=\XTR@cmdsargs\do{%
+      \XKV@ifundefined\XTR@tempa{%
+        \XTR@err{command `\@backslashchar\XTR@tempa' not defined; extraction canceled}%
+      }{%
+%    \end{macrocode}
+% Check whether allowed or not.
+%    \begin{macrocode}
+        \@expandtwoargs\in@{,\XTR@tempa,}{,chapter,section,subsection,subsubsection,}%
+        \ifin@
+          \ifx\XTR@tempa\XTR@tempb
+            \def\@chapter[#1]#2{%
+%    \end{macrocode}
+% Check whether to extract this chapter or not.
+%    \begin{macrocode}
+              \XTR@checkxtr{extract}{chapter}%
+              \ifXTR@extract
+                \XTR@writeout{}%
+                \def\XTR@tempa{#1}%
+                \def\XTR@tempb{#2}%
+                \ifx\XTR@tempa\XTR@tempb
+                  \@temptokena{{#2}}%
+                \else
+                  \@temptokena{[#1]{#2}}%
+                \fi
+%    \end{macrocode}
+% Write to file.
+%    \begin{macrocode}
+                \XTR@writeout{\string\chapter\the\@temptokena}%
+              \fi
+%    \end{macrocode}
+% Typeset the chapter.
+%    \begin{macrocode}
+              \XTR@chapter[#1]{#2}%
+            }%
+          \else
+%    \end{macrocode}
+% We do a similar thing for sections created with |\@sect|.
+%    \begin{macrocode}
+            \def\@sect#1#2#3#4#5#6[#7]#8{%
+              \@expandtwoargs\in@{,#1,}{,\XTR@cmdsargs,}%
+              \ifin@
+                \XTR@checkxtr{extract}{#1}%
+                \ifXTR@extract
+                  \XTR@writeout{}%
+                  \def\XTR@tempa{#7}%
+                  \def\XTR@tempb{#8}%
+                  \ifx\XTR@tempa\XTR@tempb
+                    \@temptokena{{#8}}%
+                  \else
+                    \@temptokena{[#7]{#8}}%
+                  \fi
+                  \XTR@writeout{\expandafter
+                    \string\csname#1\endcsname\the\@temptokena}%
+                \fi
+              \fi
+              \XTR@sect{#1}{#2}{#3}{#4}{#5}{#6}[#7]{#8}%
+            }%
+          \fi
+        \else
+          \XTR@err{unsupported command `\XTR@tempa'; try the `extract-cmdline option}%
+        \fi
+      }%
+    }%
+  }%
+  \XKV@ifundefined{XTR@cmdsline}{}{%
+%    \end{macrocode}
+% Redefine a list of commands to write themselves and the text on the
+% same line to the target file. This works similar to |\extractline|.
+%    \begin{macrocode}
+    \@for\XTR@tempa:=\XTR@cmdsline\do{%
+      \XKV@ifundefined\XTR@tempa{%
+%    \end{macrocode}
+% Check whether the command is defined.
+%    \begin{macrocode}
+        \XTR@err{command `\@backslashchar\XTR@tempa' not defined; extraction canceled}%
+      }{%
+%    \end{macrocode}
+% Check whether allowed or not.
+%    \begin{macrocode}
+        \@expandtwoargs\in@{,\XTR@tempa,}{,chapter,section,subsection,subsubsection,}%
+        \ifin@
+          \XTR@err{use the `extract-cmd' option for command `\XTR@tempa'}%
+        \else
+%    \end{macrocode}
+% Backup the command.
+%    \begin{macrocode}
+          \XTR@namelet{XTR\XTR@tempa}{\XTR@tempa}%
+%    \end{macrocode}
+% Redefine the command. Note that, inside the definition of the command,
+% |\XTR@tempa| contains the command name.
+%    \begin{macrocode}
+          \@namedef{\XTR@tempa\expandafter}\expandafter{\expandafter
+            \def\expandafter\XTR@tempa\expandafter{\XTR@tempa}%
+%    \end{macrocode}
+% Check whether this command should be extracted.
+%    \begin{macrocode}
+            \XTR@checkxtr{extract}\XTR@tempa
+              \begingroup
+                \let\do\@makeother\dospecials\catcode`\^^M\active
+                \XTR@extractcmdline
+          }%
+        \fi
+      }%
+    }%
+    \begingroup
+      \catcode`\~=\active\lccode`\~=`\^^M
+%    \end{macrocode}
+% \begin{macro}{\XTR@extractcmdline}
+% \changes{v1.4}{2005/02/06}{Changed temp macro to token register}
+% Workhorse for the command line extraction method. This macros reads
+% until the next end of line and saves the content in |\XTR@tempb|.
+%    \begin{macrocode}
+    \lowercase{\endgroup
+      \def\XTR@extractcmdline#1~{\verbatim@line{#1}\XTR@@xtractcmdline}%
+    }%
+%    \end{macrocode}
+% \end{macro}
+% \begin{macro}{\XTR@@xtractcmdline}
+% Finalize the operation with the content of the current line. We write
+% it to a target file and to a temporary file for execution in the
+% current document. Note that |\XTR@tempa| still contains the current
+% command name.
+%    \begin{macrocode}
+    \def\XTR@@xtractcmdline{%
+        \XTR@writeout{}%
+        \XTR@writeout{\expandafter\string\csname\XTR@tempa\endcsname\the\verbatim@line}%
+        \XTR@opentmp
+        \XTR@writetmp{\expandafter\string\csname XTR\XTR@tempa\endcsname\the\verbatim@line}%
+        \XTR@closetmp
+      \endgroup
+      \input{\jobname.xtr}%
+    }%
+  }%
+}
+%    \end{macrocode}
+% \end{macro}
+% Finalize writing the target file.
+%    \begin{macrocode}
+\AtEndDocument{%
+  \ifXTR@handles
+    \XTR@writeout{}%
+    \XTR@writeout{\string\end{document}}%
+  \fi
+  \immediate\closeout\XTR@out
+}
+\fi
+%</extract>
+%    \end{macrocode}
+% \Finale
+% \endinput
+% \iffalse
+%<*xtrex1>
+\documentclass[10pt]{article}
+\usepackage[
+  active,
+  generate=file,
+  extract-env=equation
+]{extract}
+\begin{extract}
+\documentclass[11pt]{article}
+\end{extract}
+\begin{document}
+Some text.
+\begin{equation}
+a^2+b^2=c^2
+\end{equation}
+Some text.
+\begin{equation}
+x^2+y^2=z^2
+\end{equation}
+Some text.
+\end{document}
+%</xtrex1>
+%
+%<*xtrex2>
+\documentclass{article}
+\usepackage[
+  active,
+  generate=file,
+  extract-env=exercise,
+  extract-cmd=section,
+  extract-cmdline=label
+]{extract}
+\newtheorem{exercise}{Exercise}
+\begin{extract}
+\documentclass{article}
+\end{extract}
+\begin{document}
+\section{Theory}
+\label{sec:1}
+Some text.
+\section{Exercises}
+\begin{exercise}
+Use the results from section
+\ref{sec:1} to show that\dots
+\end{exercise}
+Some text.
+\end{document}
+%</xtrex2>
+%
+%<*xtrex3>
+\documentclass{article}
+\usepackage[
+  active,
+  generate=file,
+  extract-env=figure,
+  figure-nrs={1,3},
+  figure-labels={fig-a,fig-b}
+]{extract}
+\begin{extract}
+\documentclass{article}
+\end{extract}
+\begin{document}
+Some text.
+\begin{figure}
+Figure 1.
+\end{figure}
+Some text.
+\extractionlabel{fig-a}
+\begin{figure}
+Figure 2.
+\end{figure}
+Some text.
+\extractionlabel{fig-b}
+\begin{figure}
+Figure 3.
+\end{figure}
+Some text.
+\extractionlabel{fig-c}
+\begin{figure}
+Figure 4.
+\end{figure}
+\end{document}
+%</xtrex3>
+%
+%<*xtrex4>
+\documentclass{article}
+\usepackage[
+  active,
+  generate=file,
+  extract-env=equation*
+]{extract}
+\begin{extract}
+\documentclass{article}
+\end{extract}
+\begin{extract*}
+\usepackage{amsmath}
+\end{extract*}
+\begin{document}
+Some text.
+\begin{equation*}
+x^2+y^2=z^2
+\end{equation*}
+Some text.
+\end{document}
+%</xtrex4>
+%
+%<*xtrex5>
+\documentclass{article}
+\usepackage[
+  active,
+  generate=file,
+  extract-labels=type-a,
+  line-labels={type-a,type-c},
+  line-nrs=3
+]{extract}
+\begin{extract}[type-a]
+\documentclass{article}
+\end{extract}
+\begin{extract}[type-b]
+\documentclass{book}
+\end{extract}
+\begin{document}
+\parindent0pt
+\extractline[type-a]line 1\\
+\extractline*line 2\\
+\extractline line 3\\
+\extractline*[type-a]line 4\\
+\extractline*[type-c]line 5\\
+\extractline line 6\\
+\end{document}
+%</xtrex5>
+%
+%<*xtrex6>
+\documentclass{article}
+\usepackage[
+  active,
+  generate=file,
+  extract-env=figure
+]{extract}
+\begin{extract}
+\documentclass{article}
+\end{extract}
+\begin{document}
+\begin{figure}[!h]
+\begin{extractskip}
+\fbox{figure 1}
+\end{extractskip}
+\fbox{figure 2}
+\end{figure}
+\begin{extract*}
+\begin{itemize}
+\item 1
+\item 2
+a\begin{extractskip}b
+\item 3
+c\end{extractskip}d
+\item 4
+\begin{extractskip}
+\item 5
+\end{extractskip}
+\end{itemize}
+\end{extract*}
+\end{document}
+%</xtrex6>
+%
+%<*xtrex7>
+\documentclass{article}
+\usepackage[
+  active,
+  generate=file,
+  extractskip-labels=skipb
+]{extract}
+\begin{extract}
+\documentclass{article}
+\end{extract}
+\begin{document}
+\begin{extract*}
+\begin{itemize}
+\begin{extractskip}[skipa]
+\item 1
+\end{extractskip}
+\begin{extractskip}[skipb]
+\item 2
+\end{extractskip}
+\begin{extractskip}[skipc]
+\item 3
+\end{extractskip}
+\end{itemize}
+\end{extract*}
+\end{document}
+%</xtrex7>
+%
+%<*preamble>
+\usepackage{url}
+\usepackage{extract}
+\usepackage{xcolor}
+\usepackage{varioref}
+\def\reftextafter{on page~\thevpagerefnum}
+\def\reftextbefore{on page~\thevpagerefnum}
+\def\reftextfaceafter{on page~\thevpagerefnum}
+\def\reftextfacebefore{on page~\thevpagerefnum}
+\usepackage{listings}
+\lstnewenvironment{command}{%
+  \lstset{columns=flexible,frame=single,backgroundcolor=\color{yellow},%
+    xleftmargin=\fboxsep,xrightmargin=\fboxsep,escapeinside=`',gobble=1}}{}
+\lstnewenvironment{example}{%
+  \lstset{basicstyle=\footnotesize\ttfamily,columns=flexible,frame=single,%
+    backgroundcolor=\color{yellow!20},xleftmargin=\fboxsep,%
+    xrightmargin=\fboxsep,gobble=1}}{}
+\usepackage{float}
+\newfloat{Listing}{htb}{loe}
+\makeatletter
+\def\tableofcontents{%
+  \begin{multicols}{2}%
+  [\section*{Contents}%
+  \setlength{\columnseprule}{.4pt}%
+  \setlength{\columnsep}{18pt}]%
+  \@starttoc{toc}%
+  \end{multicols}%
+}
+\def\changes@#1#2#3{%
+  \protected@edef\@tempa{%
+    \noexpand\glossary{\textbf{#1}\hfill\emph{(#2)}%
+      \levelchar
+      \ifx\saved@macroname\@empty
+        \space\actualchar\generalname
+      \else
+        \expandafter\@gobble\saved@macroname
+        \actualchar\string\verb\quotechar*%
+        \verbatimchar\saved@macroname\verbatimchar
+      \fi
+      :\levelchar #3}%
+    }%
+  \@tempa\endgroup\@esphack
+}
+\def\DescribeOption#1{\leavevmode\@bsphack
+              \marginpar{\raggedleft\PrintDescribeOption{#1}}%
+              \SpecialOptionIndex{#1}\@esphack\ignorespaces}
+\def\PrintDescribeOption#1{\strut\emph{option}\\\MacroFont #1\ }
+\def\SpecialOptionIndex#1{\@bsphack
+    \index{#1\actualchar{\protect\ttfamily#1}
+           (option)\encapchar usage}%
+    \index{options:\levelchar#1\actualchar{\protect\ttfamily#1}\encapchar
+           usage}\@esphack}
+\def\DescribeOptions#1{\leavevmode\@bsphack
+  \marginpar{\raggedleft\strut\emph{options}%
+  \@for\@tempa:=#1\do{%
+    \\\strut\MacroFont\@tempa\SpecialOptionIndex\@tempa
+  }}\@esphack\ignorespaces}
+\def\DescribeEnv#1{\leavevmode\@bsphack
+              \marginpar{\raggedleft\PrintDescribeEnv{#1}}%
+              \SpecialEnvIndex{#1}\@esphack\ignorespaces}
+\def\PrintDescribeEnv#1{\strut\emph{environment}\\\MacroFont #1\ }
+\def\SpecialEnvIndex#1{\@bsphack
+    \index{#1\actualchar{\protect\ttfamily#1}
+           (environment)\encapchar usage}%
+    \index{environments:\levelchar#1\actualchar{\protect\ttfamily#1}\encapchar
+           usage}\@esphack}
+\def\SpecialMainEnvIndex#1{\@bsphack\special@index{%
+                                      #1\actualchar
+                                      {\string\ttfamily\space#1}
+                                      \encapchar main}%
+    \special@index{environments:\levelchar#1\actualchar{%
+                   \string\ttfamily\space#1}\encapchar
+           main}\@esphack}
+\def\DescribeEnvs#1{\leavevmode\@bsphack
+  \marginpar{\raggedleft\strut\emph{environments}%
+  \@for\@tempa:=#1\do{%
+    \\\strut\MacroFont\@tempa\SpecialEnvIndex\@tempa
+  }}\@esphack\ignorespaces}
+\makeatother
+\def\PrintChangesX{%
+  \begingroup
+  \let\efill\relax
+  \setlength{\columnsep}{18pt}%
+  \setlength{\columnseprule}{.4pt}%
+  \PrintChanges
+  \endgroup
+}
+\def\pf#1{\textsf{#1}}
+\def\bs{\symbol{'134}}
+\def\ci#1{\texttt{\bs#1}}
+\def\descriptionlabel{\hspace\labelsep\normalfont}
+\EnableCrossrefs
+\RecordChanges
+\GlossaryPrologue{\section*{Version history}}
+\CodelineIndex
+%</preamble>
+%
+%<*bib>
+@MISC{LaTeXbase,
+  author       = {Johannes Braams and David Carlisle and Alan Jeffrey and Leslie Lamport
+                    and Frank Mittelbach and Chris Rowley and Rainer Sch\"opf},
+  title        = {The {\LaTeXe} Sources},
+  howpublished = {\url{CTAN:/macros/latex/base}},
+  year         = 2003
+}
+
+@MISC{xkeyval,
+  author       = {Hendri Adriaens},
+  title        = {\pf{xkeyval} package, 2.1},
+  howpublished = {\url{CTAN:/macros/latex/contrib/xkeyval}},
+  year         = {2005/02/08}
+}
+
+@MISC{verbatim,
+  author       = {Rainer Sch\"opf},
+  title        = {\pf{verbatim} package, v1.5q},
+  howpublished = {\url{CTAN:/macros/latex/required/tools}},
+  year         = {2003/08/22}
+}
+
+@MISC{xcomment,
+  author       = {Timothy Van Zandt},
+  title        = {\pf{xcomment} package, v1.2},
+  howpublished = {\url{CTAN:/macros/latex/contrib/seminar}},
+  year         = {1993/02/12}
+}
+
+@MISC{askinclude,
+  author       = {{Pablo A. Straub}},
+  title        = {\pf{askinclude} package, v1.2e},
+  howpublished = {\url{CTAN:/macros/latex/contrib/misc}},
+  year         = {1994/11/11}
+}
+
+@MISC{excludeonly,
+  author       = {Dan Luecking},
+  title        = {\pf{excludeonly} package, v1.0},
+  howpublished = {\url{CTAN:/macros/latex/contrib/misc}},
+  year         = {2003/03/14}
+}
+
+@MISC{comment,
+  author       = {Victor Eijkhout},
+  title        = {\pf{comment} package, v3.6},
+  howpublished = {\url{CTAN:/macros/latex/contrib/comment}},
+  year         = {1999/10}
+}
+
+@MISC{optional,
+  author       = {Donald Arseneau},
+  title        = {\pf{optional} package, v2.2},
+  howpublished = {\url{CTAN:/macros/latex/contrib/misc}},
+  year         = {2001/09}
+}
+
+@MISC{version,
+  author       = {Stephen Bellantoni},
+  title        = {\pf{version} package},
+  howpublished = {\url{CTAN:/macros/latex/contrib/misc}},
+  year         = {1990}
+}
+
+@MISC{versions,
+  author       = {Uwe L\"uck},
+  title        = {\pf{versions} package, v0.51},
+  howpublished = {\url{CTAN:/macros/latex/contrib/versions}},
+  year         = {2003/10/15}
+}
+
+@MISC{pagesel,
+  author       = {Heiko Oberdiek},
+  title        = {\pf{pagesel} package, v1.1},
+  howpublished = {\url{CTAN:/macros/latex/contrib/oberdiek}},
+  year         = {1999/04/13}
+}
+
+@MISC{pdfpages,
+  author       = {Andreas Matthias},
+  title        = {\pf{pdfpages} package, v0.3e},
+  howpublished = {\url{CTAN:/macros/latex/contrib/pdfpages}},
+  year         = {2004/01/31}
+}
+
+@MISC{selectp,
+  author       = {Donald Arseneau},
+  title        = {\pf{selectp} package, v0.9},
+  howpublished = {\url{CTAN:/macros/latex/contrib/misc}},
+  year         = {1992/09/25}
+}
+
+@MISC{fancyvrb,
+  author       = {Timothy Van Zandt},
+  title        = {\pf{fancyvrb} package, v2.6},
+  howpublished = {\url{CTAN:/macros/latex/contrib/fancyvrb}},
+  year         = {1998/07/17}
+}
+
+@MISC{listings,
+  author       = {Carsten Heinz},
+  title        = {\pf{listings} package, v1.3},
+  howpublished = {\url{CTAN:/macros/latex/contrib/listings}},
+  year         = {2004/09/07}
+}
+%</bib>
+%
+% \fi