Guide to LaTeX (4th Edition) (Tools and Techniques

448 Appendix D. L AT E X Programming
which may be given in the preamble, even before \documentclass. It
causes a list of all input files to be printed at the end of the processing,
along with their version and release data. In this way, one has a record
of just which files were included, something that may be of use when
deciding to send a document file to another installation for processing
there. Since any non-standard files may also have to be included, these
may be more readily identified from such a listing.
For example, the simple document file
\documentclass{article}
\usepackage{ifthen}
\listfiles
\begin{document}
\input{mymacros}
This is \te.
\end{document}
produces the listing
*File List*
article.cls 2001/04/21 v1.4e Standard LaTeX document class
size10.clo 2001/04/21 v1.4e Standard LaTeX file (size option)
ifthen.sty 2001/05/26 v1.1c Standard LaTeX ifthen package
mymacros.tex
***********
In this case, the local file mymacros.tex contains no version information
because it is missing a \ProvidesFile command.
What should one do if a local file, such as mymacros.tex above, is
needed for the processing of a document file that is to be sent elsewhere?
One could send it along with the main file, but that requires giving the
recipient more instructions on what to do. Or, its contents could simply
be included in the main file, for shipping purposes. For a package file,
this is not so easy, since internal commands containing the @ sign would
cause trouble, and the options would not be handled properly. For this
purpose, we have the environment
\begin{filecontents}{file name}
file contents
\end{filecontents}
which may only appear at the very beginning of the document, before the
\documentclass command. It tests to see if there is a file on the system
with the name file name, and if not, it writes its contents literally to a file
of that name. This may be a package file that is subsequently input with
\usepackage. In this way, the missing non-standard files can be ported
together with the main document file.
If we extend the above simple example by including at the very start