How to use global and user related files?

[Peter <volkov_peter list ru>]

Hello.

I have a problem, I don't know how to fight with. :) I want my application
to save big amount of data in ~/.appname dir. What is the best way to
achieve this? How to find user related dirrectory?

Also program may already have some data files in /usr/share/appname
dirrectory, so I need to check the existance of file there and if I do not
have file there create a new one in ~/.appname.

And at least may be even more. To add users possibility to look for files
in dirrectories that may be mentioned in some environment variable
(APPNAMEDIR="path1:path2").

Is there any technology in gtk+/gnome programming for thing like this? May
be I should save paths with gconf? Or may be there already exist some
parser to environment variables?

Sorry if this is very simple and not realated to gtk+ question. I'm
creating gui with gtk, so I don't know better list to ask questions...
May be you could point me there?

Thank you in advance for any help,
Peter.