I'm trying to use XeLaTeX, imakeidx and xindy for a german book with multiple indexes. Based on an answer on this page, (which works) I tried to switch to xelatex and imakeidx. Calling
xelatex --shell-escape test.tex
on this file test.tex:
\documentclass{article}
\usepackage{xltxtra}
\usepackage[xindy]{imakeidx}
\makeindex[options=-M texindy -L german-duden -C utf8]
\begin{document}
üäö
start
\index{a}\index{b}\index{ä}\index{ü}\index{ÖÖ}
end
\printindex
\end{document}
gives me the error message:
(require "tex/inputenc/utf8.xdy") ERROR: Could not find file "tex/inputenc/utf8.xdy" !
Leaving out xindy option "-C utf8" gives me an index with alll umlauts sorted under "O".
I just discovered that xindy does work when run separately, without being started from within xelatex per imakeidx, but from the command prompt:
$ xindy -M texindy -C utf8 -L german-duden test.idx
No nagging and no mention of "utf8.xdy" either.

\makeatletter \def\imki@progdefault{xindy} \makeatotherafter loading imakeidx. – Ulrike Fischer Apr 01 '14 at 11:58\makeindex[program=xindy ...]either. Thanks @Ulrike! – Blackface Apr 01 '14 at 12:12truexindyas soon as possible. But\makeindex[program=truexindy]should work. – egreg Apr 01 '14 at 12:15\makeindex[program=truexindy]works. – Blackface Apr 02 '14 at 11:38