generating a user-specific string

[Qianqian Fang]

hi

I am working on an octave toolbox that requires to save
some intermediate outputs to a temporary directory (as returned
by tempdir). However, multiple users may write to tempdir
so they will face the permission conflict if the filenames are
the same. So, I am thinking to create sub-folders under tempdir
for each user, something like /tmp/session-user1/...

I don't know if it is possible for octave to return me a
unique string for each user, so, everyone will be able to
save to its own folder across multiple sessions.
tempname is not preferred as it changes everytime,
which presumably will leave a lot of folders under /tmp.

your feedback is very much appreciated.

Qianqian