shell编程-case语句中遇到问题

#!/bin/bash echo "Hit a key, then hit return." read Keypress case "$Keypress" in        [A-Z] ) echo "Uppercase letter";;        [a-z] ) echo "Lowercase letter";;        [0-9] ) echo "Digit";;        * ) echo "Punctuation, whitespace, or other";; esac   运行结果： [root@localhost shell实验]# ./s10 Hit a key, then hit return. a                                                     //输入小写字母 Lowercase letter                            //显示小写字母   [root@localhost shell实验]# ./s10 Hit a key, then hit return. b                                                  //输入小写字母 Uppercase letter                         //显示大写字母？？？？？？    [root@localhost shell实验]# ./s10 Hit a key, then hit return. d                                                  //再次验证：输入小写字母 Uppercase letter                           //显示大写字母？？？？？？ [root@localhost shell实验]# ./s10 Hit a key, then hit return. D Uppercase letter   真是邪门，上面代码到底出了什么问题，但是当输入小写a字母时，他能够正确检测，但是当输入小写字母b、d.....时，就不能显示出小写字母了，咋为事呢？？？？？？？？？？？？？