1. for创建20用户
    用户前缀由用户输入
    用户初始密码由用户输入
    例如：test01,test10

[root@Server ~]# vim add_user20.sh
#!/bin/bash
read -p "please input username's prefix:" name_pre
read -p "please input user's passwd:" passwd
account=20
for name in ${name_pre}{01..20}
do
   useradd $name &>/dev/null
   if [ $? -eq 0 ]
   then
      echo $passwd | passwd --stdin $name &>/dev/null
   else
      echo "user $name already exists"
   fi
done
echo "created $account users successfully"

[root@Server ~]# sh -n add_user20.sh
[root@Server ~]# sh add_user20.sh
[root@Server ~]# tail -20 /etc/passwd

1. for ping测试子网段的主机
网段由用户输入，例如用户输入192.168.101 ，则ping 192.168.101.125 — 192.101.131
UP： /tmp/host_up.txt
Down: /tmp/host_down.txt

[root@Server ~]# vim ping_ip.sh
#!/bin/bash
read -p "请输入网段:" ip
for((i=125;i<=131;i++))
do
   IP="$ip"."$i"
   echo "$IP"
   if ping -c 2 -w 3 $IP &>/dev/null
   then
           echo "$IP is up" >> /tmp/host_up.txt

   else

           echo "$IP is down" >> /tmp/host_down.txt

   fi
done

echo "up is:" $(cat /tmp/host_up.txt)
echo "down is:" $(cat /tmp/host_down.txt)

[root@Server ~]# sh -n ping_ip.sh

[root@Server ~]# sh ping_ip.sh