Linux之shell脚本for、while、case语句的高级用法

1、case语句的用法：

[root@ELK-chaofeng test]# cat test3.sh
#!/bin/bash

while true ;do
read -p "please input the menu:cpu,mem,disk,quit: " variable
case $variable in
        cpu) lscpu
        break
        ;;
        mem) free -m
        break
        ;;
        disk) fdisk -l /dev/[shv]d[a-z][0-9]
        break
        ;;
        *) echo "error,again"
        ;;
esac
done

看一下效果

现在我们来编写一个服务框架：

[root@ELK-chaofeng init.d]# cat testservice 
#!/bin/bash
#
#chkconfig: 2345 60 60
#description: test service script
#
prog=$(basename $0)
lockfile=/var/lock/subsys/${prog}
case $1 in
start)
        if [ -f $lockfile ];then
                echo "service $prog is running"
        else
                touch $lockfile
                echo "service $prog start"
        fi
;;
stop)
        if [ -f $lockfile ];then
                rm -rf $lockfile
                echo "service $prog stop"
        else
                echo "service $prog stop"
        fi
;;
restart)
        if [ -f $lockfile ];then
                rm -rf $lockfile && touch $lockfile
                echo "service $prog restart"
        else
                touch $lockfile
                echo "service $prog start"
        fi
;;
status)
        if [ -f $lockfile ];then
                echo "service $prog is running"
        else
                echo "service $prog is not running"
        fi
;;
*)
        echo "usage: $prog {start|restart|stop|status}"
;;
esac

然后chkconfig添加至service服务管理。现在看一下效果：

[root@ELK-chaofeng init.d]# chkconfig --add testservice 
[root@ELK-chaofeng init.d]# chkconfig --list testservice 

Note: This output shows SysV services only and does not include native
      systemd services. SysV configuration data might be overridden by native
      systemd configuration.

      If you want to list systemd services use 'systemctl list-unit-files'.
      To see services enabled on particular target use
      'systemctl list-dependencies [target]'.

testservice     0:off   1:off   2:on    3:on    4:on    5:on    6:off
[root@ELK-chaofeng init.d]# service testservice status
service testservice is running
[root@ELK-chaofeng init.d]# service testservice stop
service testservice stop
[root@ELK-chaofeng init.d]# service testservice start
service testservice start
[root@ELK-chaofeng init.d]# service testservice status
service testservice is running
[root@ELK-chaofeng init.d]# service testservice stop
service testservice stop
[root@ELK-chaofeng init.d]# service testservice status
service testservice is not running
[root@ELK-chaofeng init.d]# service testservice restart
service testservice start
[root@ELK-chaofeng init.d]# service testservice status
service testservice is running

case总结：

　　case支持glob风格的通配符：、

　　　　*：任意长度的任意字符；

　　　　？：任意单个字符；

　　　　[ ]：范围内任意单个字符；

　　　　a|b：a或b

现在我们使用函数来改写上面的脚本：

#!/bin/bash
#
#chkconfig: 2345 60 60
#description: test service script
#
prog=$(basename $0)
lockfile=/var/lock/subsys/${prog}
start(){
        if [ -f $lockfile ];then
                echo "service $prog is running"
        else
                touch $lockfile
                echo "service $prog start"
        fi
}
stop() {
        if [ -f $lockfile ];then
                rm -rf $lockfile
                echo "service $prog stop"
        else
                echo "service $prog stop"
        fi
}
        else
                touch $lockfile
                echo "service $prog start"
        fi
}
stop() {
        if [ -f $lockfile ];then
                rm -rf $lockfile
                echo "service $prog stop"
        else
                echo "service $prog stop"
        fi
}
status() {
        if [ -f $lockfile ];then
                echo "service $prog is running"
        else
                echo "service $prog is not running"
        fi
}
usage () {
        echo "usage: $prog {start|restart|stop|status}"
}
case $1 in
start)
        start
;;
stop)
        stop
;;
restart)
        stop
        start
;;
status)
        status
;;
*)
        usage
;;
esac

2、for语句的高级用法：

#!/bin/bash
# print 9*9 
for ((k=1;k<=9;k++));do
        for ((i=1;i<=k;i++));do
                echo -e -n "${i}X${k}=$[${i}*${k}]	"
        done
        echo ""    #huan hang
done

看一下效果：

3、while语句的高级用法

#!/bin/bash
while read VARIABLE;do
        userID=`echo $VARIABLE | cut -d':' -f 3`
        userUS=`echo $VARIABLE | cut -d':' -f 1`
        usershell=`echo $VARIABLE | cut -d':' -f 7`
        if [ $[$userID%2] -eq 0 ];then
                echo "$userID,$userUS,$usershell"
        fi
done < /etc/passwd

看一下效果：