\documentclass{article}
\usepackage{t1enc}
\usepackage{makeidx}\makeindex
\index{|run husort.pl -C novowelequiv -C groupheadings}
\begin{document}
Hello
\index{nos}
\index{oszt}
\index{\'olom}
\index{\"oleb}
\index{\H ofels\'ege}
\index{poszt}
World
\printindex
\end{document}
