43.監控用戶登陸腳本

思路：while 死循環加if判斷語句30秒判斷一次用戶登陸信息
#!/bin/bash
read -p "please input a username : " user
while :
do
if who |grep -qw "$user" ;then  #grep -q 不顯示輸出信息 -w 精確查找
        echo "$user is login!"
        exit#退出循環
else
        echo -e "$user does not exist!\nMonitoring..."
fi
sleep 30#睡眠30秒
done