 group_data(?Field, 
?GroupData, ?Value)Value is the value for Field GroupData. 
Defined fields are:
group_data(?Field, 
?GroupData, ?Value)Value is the value for Field GroupData. 
Defined fields are:
- name
- Name of the user
- password
- Password hash of the user (or xif this is not accessible)
- gid
- Numeric group id of the group
- members
- List of user-names that are member of this group.