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