Compile small piece of code without \begin{document} with modern tools like vscode

Question

I would like to compile piece of LaTeX code without \begin{document} and \end{document} (the preamble is, of course, fixed). The reason is that sometimes I only write small pieces of text and don't want to include the basic lines every time (not even with \input, etc.). For now the only way I know is by running shell code like the following one.

DIR="$( cd "$( dirname "$0" )" && pwd )"
cd $DIR

xelatex -interaction=batchmode \\documentclass{einfart}\\usepackage{ProjLib}\\begin{document}\\input{<filename>}\\end{document}

Is there a better way to do so? For example, I don't know if there is a compatible way with latexmk. Also, is it possible to achieve a similar effect with Visual Studio Code's extension "LaTeX Workshop"?

(I do realize that omitting the \begin{document} etc. is probably not a good idea. I'm just exploring the possibilities for the workflow.)

Answer 1

Just for reference, below is the shell script I'm currently using for compile files with extension .piece.tex, where .piece is a mark to tell that this is not a complete LaTeX code file.

DIR="$( cd "$( dirname "$0" )" && pwd )"
cd $DIR

mkdir -p .aux

filename=$(ls -t *.piece.tex | head -n1)

echo "\\documentclass[use boldface, theorem in new line, simple name, theorem numbering = *]{einfart}" > .aux/${filename%.piece.tex}.temp.tex
echo "\\usepackage{ProjLib}" >> .aux/${filename%.piece.tex}.temp.tex
echo "\\usepackage{tikz-cd}" >> .aux/${filename%.piece.tex}.temp.tex
echo "\\\\begin{document}"   >> .aux/${filename%.piece.tex}.temp.tex
echo "\\input{$filename}"    >> .aux/${filename%.piece.tex}.temp.tex
echo "\\end{document}"       >> .aux/${filename%.piece.tex}.temp.tex

latexmk -xelatex -silent -output-directory=.aux -jobname=${filename%.piece.tex} .aux/${filename%.piece.tex}.temp.tex

mv .aux/${filename%.piece.tex}.pdf ${filename%.piece.tex}.pdf

For example, if you have a Document.piece.tex with the content:

This is a test document.

\begin{theorem}\label{thm1}
    \blindtext
\end{theorem}

\begin{theorem}\label{thm2}
    \blindtext
\end{theorem}

\begin{definition}\label{def1}
    \blindtext
\end{definition}

\cref{thm1,def1,thm2}

\dnf

Then after running the script, you shall get a Document.pdf looks like:

---

Some explanations:

The first two lines change the directory to the current one containing the shell script:

DIR="$( cd "$( dirname "$0" )" && pwd )"
cd $DIR

Then make a .aux folder for storing auxiliary files.

mkdir -p .aux

The script shall now find the latest .piece.tex file for compilation.

filename=$(ls -t *.piece.tex | head -n1)

It will produce a same named .temp.tex file in the .aux folder for latexmk to work on.

echo "\\documentclass[use boldface, theorem in new line, simple name, theorem numbering = *]{einfart}" > .aux/${filename%.piece.tex}.temp.tex
echo "\\usepackage{ProjLib}" >> .aux/${filename%.piece.tex}.temp.tex
echo "\\usepackage{tikz-cd}" >> .aux/${filename%.piece.tex}.temp.tex
echo "\\\\begin{document}"   >> .aux/${filename%.piece.tex}.temp.tex
echo "\\input{$filename}"    >> .aux/${filename%.piece.tex}.temp.tex
echo "\\end{document}"       >> .aux/${filename%.piece.tex}.temp.tex

And finally, compile with latexmk and move the .pdf file to the current folder.

latexmk -xelatex -silent -output-directory=.aux -jobname=${filename%.piece.tex} .aux/${filename%.piece.tex}.temp.tex
mv .aux/${filename%.piece.tex}.pdf ${filename%.piece.tex}.pdf