43.监控用户登陆脚本

思路：while 死循环加if判断语句30秒判断一次用户登陆信息
#!/bin/bash
read -p "please input a username : " user
while :
do
if who |grep -qw "$user" ;then  #grep -q 不显示输出信息 -w 精确查找
        echo "$user is login!"
        exit#退出循环
else
        echo -e "$user does not exist!\nMonitoring..."
fi
sleep 30#睡眠30秒
done