假设局域网中有多台主机，只能开通ssh服务(端口22)，如果发现其他服务打开，则全部关闭。通过运行一个shell脚本，完成以上功能。在实际运维中，可以通过puppet等工具更快更好的完成这个功能，所以本案例仅仅用来练手，为了熟悉sed, awk, grep等常见的shell命令而已。
1、通过nmap命令查询局域网中所有主机打开的端口，并存入文件nmap1.txt中。
# 通过nmap命令查询局域网中所有主机打开的端口，并存入文件nmap1.txt中
mkdir -p /wuhao/sh/files
nmap $1 > /wuhao/sh/files/nmap1.txt
以nmap 192.168.20.1-10为例，输出结果为：
Starting Nmap 5.51 ( ) at 2016-03-03 16:37 CST
Nmap scan report for oos01 (192.168.20.1)
Host is up (0.0000040s latency).
Not shown: 997 closed ports
PORT STATE SERVICE
21/tcp open ftp
22/tcp open ssh
80/tcp filtered http
Nmap scan report for oos02 (192.168.20.2)
Host is up (0.000099s latency).
Not shown: 997 closed ports
PORT STATE SERVICE
22/tcp open ssh
80/tcp open http
3306/tcp open MySQL
MAC Address: 00:1C:42:FF:5A:B5 (Parallels)
Nmap scan report for oos03 (192.168.20.3)
Host is up (0.000097s latency).
Not shown: 997 closed ports
PORT STATE SERVICE
22/tcp open ssh
80/tcp open http
3306/tcp open mysql
MAC Address: 00:1C:42:38:94:3C (Parallels)
Nmap done: 10 IP addresses (3 hosts up) scanned in 1.57 seconds
2、从文件nmap1.txt中提取出需要的信息(主机ip，以及端口状态)。
# 从文件nmap1.txt中提取出需要的信息(主机ip，以及端口状态)
sed -n '/\(Nmap scan report for\|^[0-9]\+\/\)/p' /wuhao/sh/files/nmap1.txt > /wuhao/sh/files/nmap2.txt
hosts=($(grep -on '(.*)' /wuhao/sh/files/nmap2.txt | sed -n 's/(\|)//gp'))
declare -i len=${#hosts[*]}
declare -i i=0
while [[ $i -lt $len ]]
do
lines[$i]=$(echo ${hosts[$i]} | awk -F ':' '{print $1}')
ips[$i]=$(echo ${hosts[$i]} | awk -F ':' '{print $2}')
i=$i+1
done
# echo ${lines[*]}=1 5 9
# echo ${ips[*]}=192.168.20.1 192.168.20.2 192.168.20.3
3、在端口状态行首添加所对应的主机ip信息，并将结果保存到文件nmap2.txt中。
# 在端口状态行首添加所对应的主机ip信息
declare -i j=0
while [[ $j -lt $len ]]
do
declare -i k=$j+1
if [ $j -ne $(($len-1)) ]; then
sed -i "$((${lines[$j]}+1)),$((${lines[$k]}-1))s/^/${ips[$j]} /" /wuhao/sh/files/nmap2.txt
else
sed -i "$((${lines[$j]}+1)),$""s/^/${ips[$j]} /" /wuhao/sh/files/nmap2.txt
fi
j=$j+1
done
# 将多个空格以及/替换为一个空格
sed -i 's/ \+\|\// /g' /wuhao/sh/files/nmap2.txt
nmap2.txt文件内容为：
Nmap scan report for oos01 (192.168.20.1)
192.168.20.1 21 tcp open ftp
192.168.20.1 22 tcp open ssh
192.168.20.1 80 tcp filtered http
Nmap scan report for oos02 (192.168.20.2)
192.168.20.2 22 tcp open ssh
192.168.20.2 80 tcp open http
192.168.20.2 3306 tcp open mysql
Nmap scan report for oos03 (192.168.20.3)
192.168.20.3 22 tcp open ssh
192.168.20.3 80 tcp open http
192.168.20.3 3306 tcp open mysql
4、提取出需要关闭的端口(除了端口22之外，其余端口全部关闭)。通过sshpass远程登录到各主机，并且在iptables执行关闭端口命令。
# 提取出需要关闭的端口(除了端口22之外，其余端口如果打开则全部关闭)
awk '{if($4~/open/ && $2!=22) print $0}' /wuhao/sh/files/nmap2.txt > /wuhao/sh/files/nmap3.txt
hostip=($(awk -F " " '{print $1}' /wuhao/sh/files/nmap3.txt))
port=($(awk -F " " '{print $2}' /wuhao/sh/files/nmap3.txt))
protocol=($(awk -F " " '{print $3}' /wuhao/sh/files/nmap3.txt))
# 通过sshpass远程登录到各主机，并且在iptables执行关闭端口命令
for((m=0;m<${#hostip[*]};m=m+1))
do
sshpass -p 123456 ssh root@${hostip[$m]} "iptables -A INPUT -p ${protocol[$m]} --dport ${port[$m]} -j DROP;service iptables save;service iptables restart;exit"
done
echo "success!"
5、运行脚本，查看结果。
[root@oos01 sh]# sh shutdownport.sh 192.168.20.1-10
iptables: Saving firewall rules to /etc/sysconfig/iptables: [ OK ]
iptables: Setting chains to policy ACCEPT: filter [ OK ]
iptables: Flushing firewall rules: [ OK ]
iptables: Unloading modules: [ OK ]
iptables: Applying firewall rules: [ OK ]
iptables: Saving firewall rules to /etc/sysconfig/iptables: [ OK ]
iptables: Setting chains to policy ACCEPT: filter [ OK ]
iptables: Flushing firewall rules: [ OK ]
iptables: Unloading modules: [ OK ]
iptables: Applying firewall rules: [ OK ]
iptables: Saving firewall rules to /etc/sysconfig/iptables: [ OK ]
iptables: Setting chains to policy ACCEPT: filter [ OK ]
iptables: Flushing firewall rules: [ OK ]
iptables: Unloading modules: [ OK ]
iptables: Applying firewall rules: [ OK ]
iptables: Saving firewall rules to /etc/sysconfig/iptables: [ OK ]
iptables: Setting chains to policy ACCEPT: filter [ OK ]
iptables: Flushing firewall rules: [ OK ]
iptables: Unloading modules: [ OK ]
iptables: Applying firewall rules: [ OK ]
iptables: Saving firewall rules to /etc/sysconfig/iptables: [ OK ]
iptables: Setting chains to policy ACCEPT: filter [ OK ]
iptables: Flushing firewall rules: [ OK ]
iptables: Unloading modules: [ OK ]
iptables: Applying firewall rules: [ OK ]
success!
更多Nmap相关教程见以下内容：