if [[ -z $(screen -list |grep tached) ]];then screen -dRU terminal;elif [[ -n $(screen -list |grep Detached) ]];then screen -dRU $(screen -list|grep Detached|tail -1|awk -F " " '{print $1}'|awk -F "." '{print $2}');else screen -dRU $(screen -list|grep -m 1 Attached|awk -F " " '{print $1}'|awk -F "." '{print $2}')-1;fi 说明： 1 ，没有，创建新的 2 ，有死，链接死的 3 ，否则，链接活着的-1
