# Handle the incoming configuration files:
config() {
  NEW="$1"
  OLD="$(dirname $NEW)/$(basename $NEW .new)"
  # If there's no config file by that name, mv it over:
  if [ ! -r $OLD ]; then
    mv $NEW $OLD
  # use the new config files and backup the old one
  elif [ "$(cat $OLD | md5sum)" != "$(cat $NEW | md5sum)" ]; then
    cp $OLD $OLD.old
    mv $NEW $OLD
  # toss the redundant copy
  elif [ "$(cat $OLD | md5sum)" = "$(cat $NEW | md5sum)" ]; then
    cp $OLD $OLD.old # backup the old config (just in case)
    rm $NEW
  fi
  #  Otherwise, we leave the .new copy for the admin to consider...
}

config etc/nail.rc.new


.