[Gambas-user] Program to use different group rights

[Rolf-Werner Eilert]

When a program needs to read from a file which could actually only be 
read if member of a special group, how would this be achieved?

I found that in order to read from /etc/shadow, a program needs to be 
member of the group "shadow". But when I start a password management 
program (in GUI) as an ordinary user, this program will be member of my 
own group only.

So how would such a program be able to read my hash from /etc/shadow to 
verify if I type the right old password first? The new password could be 
sent to passwd to form and save a new hash, but how to read the old one 
first?

Maybe someone here knows how this is achieved.

Regards
Rolf