%%
%% The LaTeX Companion, 3ed
%%
%% Example 9-6-19 on page I-723 in "Stylistic features".
%%
%% Copyright (C) 2022 Frank Mittelbach
%%
%% It may be distributed and/or modified under the conditions
%% of the LaTeX Project Public License, either version 1.3c
%% of this license or (at your option) any later version.
%%
%% See https://www.latex-project.org/lppl.txt for details.
%%

\documentclass{tlc3exa}
\pagestyle{empty}
\setcounter{page}{6}
\setlength\textwidth{87.0pt}

  %!TEX program = lualatex

  \setlength\parindent{0pt}

%StartShownPreambleCommands
\usepackage{fontspec}  \setmainfont{XCharter}[Numbers=OldStyle]
%StopShownPreambleCommands

\begin{document}
123             \addfontfeature{RawFeature = +cv01} 123
                \addfontfeature{RawFeature = -cv01} 123            \\
\textsc{Gruß} ß \addfontfeature{RawFeature =  ss01} \textsc{Gruß} ß
\end{document}