Shell script case in and regular expressions

case in Of pattern Some support simple regular expressions , say concretely , You can use the following formats ：

Format	explain
*	Represents any string .
[abc]	Express a、b、c Any one of the three characters . such as ,[15ZH] Express 1、5、Z、H Any of the four characters .
[m-n]	From m To n Any character of . such as ,[0-9] Represents any number ,[0-9a-zA-Z] Represents letters or numbers .
|	Indicates multiple selection , Similar to or operation in logical operation . such as ,abc | xyz Represents a matching string “abc” perhaps “xyz”.

If not explained ,Shell All values are strings ,expression and pattern It is also matched in the form of string ; The first code in this section seems to determine whether the numbers are equal , In fact, it is to judge whether the strings are equal .

The last branch *) It's not a grammatical rule , It's just a regular expression ,* Represents any string , So no matter expression What is the value of ,*) Always match successfully .

Code

#!/bin/bash
printf "Input a character: "
read -n 1 char
case $char in
    [a-zA-Z])
        printf "\nletter\n"
        ;;
    [0-9])
        printf "\nDigit\n"
        ;;
    [0-9])
        printf "\nDigit\n"
        ;;
    [,.?!])
        printf "\nPunctuation\n"
        ;;
    *)
        printf "\nerror\n"
esac

Output ：

 Running results 1：
Input integer number: S
letter

 Running results 2：
Input integer number: ,
Punctuation