[root@server0 ~]# vim  /root/3.sh 
#! /bin/bash
read -p "请输入用户名：" name
read -p  "请输入用户密码： " pass
if [ -z $name ];then
echo "用户不能为空"
exit
fi
pass=${pass:-123456}
echo -n "你输入是$name，你的密码是$pass，确认吗y/n："
read adb
if [ $adb == y ];then
useradd $name
echo $pass | passwd --stdin $name &>/dev/null
echo "创建成功"
fi

[root@server0 ~]# vim 8.sh 
read -p "请输入数字:" num
num=${num:-1}            #防止报错，默认值1
sum=0
for i in `seq $num`
do 
sum=$[sum+i]
done
echo $sum