case语句：选择结构

case SWITCH in
value1)
   statement
   ...
   ;;
value2)
   statement
   ...
   ;;
*)
   statement
   ...
   ;;
esac

case $1 in
[0-9])
  echo "A digit." ;;
[a-z])
  echo "Lower" ;;
[A-Z])
  echo "upper" ;;
*)
  echo "Special character."
esac