I'm on windows 7... I tried cmd /U with java -Dfile.encoding=UTF8, but this does not work...
Hm, this is indeed a general terminal issue, which can't be solved from within BaseX. Instead, you could change the output encoding for XQuery results to match the console encoding. An example:
basex -sencoding=850 YourQuery.xq
…or (using the console mode)…
BaseX 6.5.1 [Standalone] Try "help" to get more information.
set serializer encoding=850
SERIALIZER: encoding=850
run YourQuery.xq
....
Hope this helps, Christian