Marc Weber wrote:

Is there a way to ask ghc-pkg to list all availible packages found in the user lib or system lib or lib given by path? If I have read the documentation corretly it says: no. Is there any reason for this restriction?

Can I query ghc-pkg to list pgk-config files (user/ system)?

"ghc-pkg list" tells you each of the config files it is using. You can say "ghc-pkg --global-conf=<file>" to use a different system config file. Does that help? Cheers, Simon