If the Case statement is not executed, let's see why ....

If the Case statement is not executed, let's see why .... -- Linux general technology-Linux programming and kernel information. The following is a detailed description. Today, I wrote a simple shell script to test the case statement and found a strange phenomenon. The procedure is as follows:

#! /Bin/sh
Echo 'hit a key, then Hit return .'
Read Keypress
Case "$ Keypress" in
[A-z]) echo "Lowercase letter ";;
[A-Z]) echo "Uppercase letter ";;
[0-9]) echo 'digit ';;
*) Echo 'punctuation, whitespace, or other ';;
Esac

When running, it is found that the second case is always not running, and the Lowercase letter is still printed when uppercase letters are entered.

When I change a-z]) echo "Lowercase letter"; and [A-Z]) echo "Uppercase letter, when you enter lower-case letters, the Uppercase letter is displayed!


Please help me to see what the problem is.

By the way, cat> hello <What is MY_PROMGRAM?

Thank you for your answers.