Allowed characters in classnames?

[Thomas Neumann]

The fai-class manpage simply states:

"All class names should be written in uppercase letters (execpt the class
of the hostname). Do not use a dash, use an underscore."

Which says nothing about umlauts, diacrites and other 'strange' stuff.

Is there an official list of allowed characters? For me [a-zA-Z0-9_] would
be totally fine. I just want to make sure I'm not forgetting something. I
need this info to correctly untaint possible classnames inside a scripts/
perl script.

P.S.: The 'execpt' typo is not mine.