There is no way to get this information. Furthermore user input in postinst should not be used and is a violation of the Ubuntu packaging principles. So this would always be a bug of the package itself. That is why there is debconf. Dist-upgrader and synaptic will show the terminal after a short timeout automatically.
f-prot-installer already seems to use debconf. But I assume that you don't run a default Ubuntu desktop? Please check if libgnome2-perl is installed on your system. So you can get a graphical representation of debconf questions. But it seems to be a bug here. That we don't show the terminal if there is only a text viewer for debconf. -- prompt required in terminal box https://launchpad.net/bugs/46778 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
