The problem with:
apt-get --yes install $something
is that it will ask for a manual confirmation if the package signature owner's public-key is not in the keyring, or some other conditions. to be sure it does not ask a confirmation just do this:
apt-get --yes --force-yes install $something
If you want to have these settings permanent, create a file in /etc/apt/apt.conf.d/, like /etc/apt/apt.conf.d/90forceyes with the following content:
APT::Get::Assume-Yes "true";
APT::Get::force-yes "true";