shell脚本之case用法

你会经常发现自己在尝试计算一个变量的值，在一组可能的值中寻找特定值。在这种情形下，

你不得不写出很长的if-then-else语句，就像下面这样。

$ cat test25.sh

#!/bin/bash

# looking for a possible value

#

if [ $USER = "rich" ]

then

echo "Welcome $USER"

echo "Please enjoy your visit"

elif [ $USER = "barbara" ]

then

echo "Welcome $USER"

echo "Please enjoy your visit"

elif [ $USER = "testing" ]

then

echo "Special testing account"

elif [ $USER = "jessica" ]

then

echo "Do not forget to logout when you're done"

else

echo "Sorry, you are not allowed here"

fi

$

$ ./test25.sh

Welcome rich

Please enjoy your visit

如上面的案例，我们需要做多个if判断来一一核对，代码量比较多，还容易乱，这时可以用case用法来减少代码量，

有了case命令，就不需要再写出所有的elif语句来不停地检查同一个变量的值了。case命

令会采用列表格式来检查单个变量的多个值。

#!/bin/bash
# using the case command
#
case $USER in
rich | barbara)
echo "Welcome, $USER"
echo "Please enjoy your visit";;
testing)
echo "Special testing account";;
jessica)
echo "Do not forget to log off when you're done";;
*)
echo "Sorry, you are not allowed here";;
esac

case 用法也常用于启动脚本中

#!/bin/sh

# Comments to support chkconfig on RedHat Linux
# chkconfig: 2345 80 50
# description: A very fast and reliable Tomcat.

export JAVA_HOME=/data/jdk8/

tomcat[1]="/data/Tomcat/"
project="/data/www/kstore/"
module="site boss mobile third open"
webinf="/htdocs/WEB-INF/"
war="/htdocs/war/"


start(){
    cache

    for i in ${tomcat[@]}
    do 
        ${i}/bin/startup.sh
        sleep 60
    done
    
    sleep 60
    
    test
}

stop(){
    for i in ${tomcat[@]}
    do 
        ${i}/bin/shutdown.sh
        rm -rf ${i}/work/Catalina/
        pid=$(ps -ef | grep ${i} | grep -v grep | awk '{print $2}')
        if [ "${pid}" != "" ];then
            kill -9 ${pid}
        fi
        
        sleep 5
    done
    
    cache
    
    test
}

test(){
    for i in ${tomcat[@]}
    do
        pid=$(ps -ef | grep ${i} | grep -v grep | awk '{print $2}')
        if [ "${pid}" != "" ];then
            echo "${i} is running!"
        else 
            echo "${i} may not be running!"
        fi 
    done
}

change(){
    transfer(){
        a=`find ~ -name "*.war" | wc -l`
        
        if [ ${a} -gt 0 ];then
            mv ${war}/*.war ${war}/backup/
            mv ~/*.war ${war}
        fi    
        
        for i in ${module[@]}
        do
            b=$(ls -A ${war} | grep "${i}")
            if [ "${b}" != "" ];then
                echo ${i}
            fi
        done
    }

    app=$(transfer)

    for i in ${app[@]}
    do
        rm -rf ${project}${i}
        mkdir ${project}${i}
        unzip -q ${war}/*${i}*.war -d ${project}${i}
        cp -rf ${webinf} ${project}${i}
        sed -i "/amq.destination/s/boss/${i}/g" ${project}/${i}/WEB-INF/classes/com/ningpai/web/config/amq.properties
    done
}

cache(){
    sync
    echo 3 > /proc/sys/vm/drop_caches
}



case "$1" in
    #startup tomcat
    start)
    start
    ;;
    #stop tomcat
    stop)
    stop
    ;;
    #restart tomcat
    restart)
    stop
    start
    ;;
    #reload tomcat
    reload)
    stop
    change
    start
    ;;
    #test tomcat 
    status)
    test
    ;;
    #load tomcat 
    load)
    change
    start
    ;;
    *)
    echo "Use tomcat start|stop|status|restart|reload|load"
    ;;
esac