# redefine su command
su() {
  CHECKSU=0
  for FLAG in $*; do
    [[ $FLAG == "-" ]] && CHECKSU=1
    [[ $FLAG == "-l" ]] && CHECKSU=1
    [[ $FLAG == "--login" ]] && CHECKSU=1
  done
  if [[ $CHECKSU == 0 ]]; then
    echo "Use 'su -', Luke"
    /usr/bin/su - $*
  else
    /usr/bin/su $*
  fi
}