Shell 编程 until语句

本篇主要写一些shell脚本until语句的使用。

计算1-50的和

#!/bin/bash  i=0  s=0  until [ $i -eq 51 ];do    let s+=i;let i++  done  echo $s  

[root@localhost ~]# vim sum.sh  [root@localhost ~]# chmod +x sum.sh  [root@localhost ~]# ./sum.sh  1275  

为指定用户发送在线消息

#!/bin/bash  username=$1  # 判断格式是否正确  if [ $# -lt 1 ] ;then    echo "Usage:`basename $0` <username> [message]"    exit 1  fi  # 判断用户是否存在  if grep "^$username:" /etc/passwd > /dev/null ;then :  else    echo "用户不存在"    exit 1  fi  # 判断用户是否在线，不在则每5s联系一次  until who|grep "$username" > /dev/null ;do    echo "用户不在线"    sleep 5  done  # 发送信息  mes=$*  echo $mes | write $username  

[root@localhost ~]# vim message.sh  [root@localhost ~]# chmod +x message.sh  [root@localhost ~]# ./message.sh  Usage:message.sh <username> [message]  [root@localhost ~]# ./message.sh zhangsan hello  用户不存在  [root@localhost ~]# useradd zhangsan && echo "000000" | passwd --stdin zhangsan  Changing password for user zhangsan.  passwd: all authentication tokens updated successfully.  [root@localhost ~]# ./message.sh zhangsan hello  用户不在线  用户不在线  ^C  

[zhangsan@localhost ~]$  

[root@localhost ~]# ./message.sh zhangsan hello  

[zhangsan@localhost ~]$  Message from root@localhost on pts/0 at 02:25 ...  zhangsan hello  EOF