1

[root@localhost ~]# vim for1.sh
#!/bin/bash
read -p "请输入用户的账户名前缀：" prefix
read -p "请输入账户的密码：" prefix
for ((i=1;i<=20;i++))
do
        user=$prefix$i
        if id -u $user &> /dev/null
        then
                echo "$user 已存在"
                else
                        useradd $user
                        echo "$passwd" | passwd --stdin $user &> /dev/null
                        echo "$user用户创建成功"
                fi
        done
[root@localhost ~]# bash for1.sh
请输入用户的账户名前缀：ko
请输入账户的密码：123456
useradd：无效的用户名“1234561”
1234561用户创建成功
useradd：无效的用户名“1234562”
1234562用户创建成功
useradd：无效的用户名“1234563”
1234563用户创建成功
useradd：无效的用户名“1234564”
1234564用户创建成功
useradd：无效的用户名“1234565”
1234565用户创建成功
useradd：无效的用户名“1234566”
1234566用户创建成功
useradd：无效的用户名“1234567”
1234567用户创建成功
useradd：无效的用户名“1234568”
1234568用户创建成功
useradd：无效的用户名“1234569”
1234569用户创建成功
useradd：无效的用户名“12345610”
12345610用户创建成功
useradd：无效的用户名“12345611”
12345611用户创建成功
useradd：无效的用户名“12345612”
12345612用户创建成功
useradd：无效的用户名“12345613”
12345613用户创建成功
useradd：无效的用户名“12345614”
12345614用户创建成功
useradd：无效的用户名“12345615”
12345615用户创建成功
useradd：无效的用户名“12345616”
12345616用户创建成功
useradd：无效的用户名“12345617”
12345617用户创建成功
useradd：无效的用户名“12345618”
12345618用户创建成功
useradd：无效的用户名“12345619”
12345619用户创建成功
useradd：无效的用户名“12345620”
12345620用户创建成功
[root@localhost ~]# 

2.

[root@localhost ~]# vim for2.sh
#!/bin/bash
read -p  "请输入网段:"  ip
for ((i=125;i<=135;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@localhost ~]# bash for2.sh
请输入网段:192.168.174
192.168.174,125
192.168.174,126
192.168.174,127
192.168.174,128
192.168.174,129
192.168.174,130
192.168.174,131
192.168.174,132
192.168.174,133
192.168.174,134
192.168.174,135
up is:
down is:
192.168.174,125 is down 
192.168.174,126 is down 
192.168.174,127 is down 
192.168.174,128 is down 
192.168.174,129 is down 
192.168.174,130 is down 
192.168.174,131 is down 
192.168.174,132 is down 
192.168.174,133 is down 
192.168.174,134 is down 
192.168.174,135 is down 
192.168.174,125 is down 
192.168.174,126 is down 
192.168.174,127 is down 
192.168.174,128 is down 
192.168.174,129 is down 
192.168.174,130 is down 
192.168.174,131 is down 
192.168.174,132 is down 
192.168.174,133 is down 
192.168.174,134 is down 
192.168.174,135 is down 

3.