Question

What characters are allowed in Linux environment variable names? My cursory search of man pages and the web did only produce information about how to work with variables, but not which names are allowed.

I have a Java program that requires an defined environment variable containing a dot, like com.example.fancyproperty. With Windows I can set that variable, but I had no luck setting it in linux (tried in SuSE and Ubuntu). Is that variable name even allowed?

Answer 1

From The Open Group:

These strings have the form
name=value; names shall not contain
the character ‘=’. For values to be
portable across systems conforming to
IEEE Std 1003.1-2001, the value shall
be composed of characters from the
portable character set (except NUL
and as indicated below).

So names may contain any character except = and NUL, but:

Environment variable names used by the utilities in the Shell and
Utilities volume of IEEE Std
1003.1-2001 consist solely of uppercase letters, digits, and the ‘_’
(underscore) from the characters
defined in Portable Character Set and
do not begin with a digit. Other
characters may be permitted by an
implementation; applications shall
tolerate the presence of such names.

So while the names may be valid, your shell might not support anything besides letters, numbers, and underscores.