[OS X TeX] problem with texdoc

[Alain Matthes]

Hello,

Sorry for posting the message twice, but I don't see the first one
_ perhaps we have too much snow in Paris :) _

I try yesterday $ texdoc texbytopic    

texbytopic.pdf is opened but I get

texdoc warning: Failed to create cache file in /Users/ego/Library/texlive/2010/texmf-var/texdoc/cache-tlpdb.lua:
texdoc warning: Permission denied.


$  kpsexpand '$TEXMFVAR'   gives 
/Users/ego/Library/texlive/2010/texmf-var

but the permissions for the texlive folder and all  the subfolders are

owner root
group staff

reading and writing for system
forbidden access for everyone

I can repair the problem but I don't know what bad action I made

Best regards

Alain Matthes