#!/usr/local/bin/bash
#BUG: Need usage message if not two (or more?) arguments.

FIRSTONE=$1
SECONDONE=$2
if [ "`head -1 $FIRSTONE`" != "`head -1 $SECONDONE`" ];
then
  echo "$FIRSTONE and $SECONDONE are not union compatible."
else
  sed 1d $SECONDONE | cat $FIRSTONE -
fi