Linux命令之条件判断-case

朱雀 2022-08-19 11:15 175阅读 0赞

case语句和判断语句\[if...elif...else\]功能类似;  
当在逻辑判断比较简单的情况下,比后者的代码量要少许多.  
匹配模式中可是使用方括号表示一个连续的范围，如\[0-9\]；使用竖杠符号“|”表示或。

语法:

var = xxx  
case $var in   
value1 )  
echo "input is value1"  
;;  
value2 )  
echo "input is value2"  
;;  
valuen )  
echo "input is valuen"  
;;  
\* )  
echo "i don't know"  
;;  
esac

说明:  
1、星号(\*)相当于其他语言中的default;  
2、双分号(;;)是必须的,相当于java中的break;  
3、竖线(|)用于分割多个模式,相当于or;

\#从实战中学习

#!/bin/bash 
    ###程序启动脚本
    case $1 in 
    	s | start )
    		echo "start..."
    		;;
    	stop | end )
    		echo "stop..."
    		;;
    	r | reload )
    		echo "reload..."
    		;;
    	*)
    		echo "Usage: $name [start|stop|reload]"
    		exit 1
    		;;
    esac

#!/bin/bash
    ###忽略大小写
    echo "Please input yes or no"
    read var
    case "$var" in
    	[yY][eE][sS] ) 
    		echo "input is yes"
    		;;
    	[nN][oO] )
    		echo "input is no"
    		;;
    	* )
    		echo "error input"
    		;;
    esac

#!/bin/bash
    #从键盘输入一个字符,判断该字符是否为字母、数字或者其他字符,并输出相应的提示信息
    read -p "press a key," key
    case $key in
    	[a-z] | [A-Z] )
    		echo "It's a letter."
    		;;
    	[0-9] )
    		echo "It's a number."
    		;;
    	* )
    		echo "other key."
    		;;
    esac

#!/bin/sh 
    ###判断操作系统类型
    var=`uname -s`
    case $var in
    	Linux )
    		echo "os is Linux"
    		;;
    	FreeBSD )
    		echo "os is FreeBSD"
    		;;
    	* )
    		echo "unknown os: $var"
    		;;
    esac