Gentoo leaves your (old) config files untouched after an update. Problem is, sometimes the old config files are incompatible with the new program.
This is a dialog code that shows the diffs and asks if the admin wants to accept the new file (almost always the case).

for line in $(find /etc/ -name "._cfg*")
do
origfile=$(echo $line|sed "s/\._cfg[0-9]*_//g");
echo $line "<=>" $origfile;
echo "Diff: ";
diff $origfile $line | less
echo -n "take it? [y|n] ";
read choice;
if [[ "$choice" == "y" ]]; then
mv $line $origfile;
else
echo "$line left as is.";
fi;
done

BTW: on Bash-ifs, the spaces around the comparator (e.g. ==) are necessary. If you leave them out, it is always true (String concatenation).