\begin{sfragment}{Setting your MathHub Directory} One of \sTeX's features is a proper \emph{module system} of interconnected document snippets for mathematical content. Analogously to \emph{object-oriented programming}, it allows for ``object-oriented mathematics'' via individual combinable and, importantly, \emph{reusable} modules, developed collaboratively. To make use of such modules, the \sTeX system needs to be told where to find them. There are several ways to do so (see \sref[file=stex-mathhub]{sec:localmh}[in=../stex-manual, title={\href{\basedocurl/stex-manual.pdf}{the \sTeX{}3 Manual}}]), but the most convenient way to do so is via a system variable. To do so, create a directory \texttt{MathHub} somewhere on your local file system and set the environment variable \texttt{MATHHUB} to the file path to that directory. In linux, you can do so by writing \begin{lstlisting}[language=bash] export MATHHUB="/path/to/your/MathHub" \end{lstlisting} in your \verb|~/.profile| (for all shells) or \verb|~/.bashrc| (for the bash terminal only) file. \end{sfragment}