\documentclass{article}
\directlua{
function sort_tdo (jobname)
file=io.open(jobname.."sorted", "w")
io.output(file)
io.close(file)
end
}
\directlua{
function shellescape()
if os.execute then
tex.write(os.execute())
end
end}
\directlua{sort_tdo("\jobname.tdo")
\makeatletter
%\def\pdf@shellescape{\directlua{tex.sprint(status.shell_escape .. " ")}} %works
\def\pdf@shellescape{\directlua{shellescape()}}% breaks
\ifnum\pdf@shellescape>0 %
\show\x
\fi
\begin{document}
\end{document}