檢查是否在腳本中的系統上設置了 iptables

我正在用 bash 編寫腳本，我需要檢查是否設置了 iptables ……我有這個：

if [ `iptables-save | grep '^\-' | wc -l` > 0 ]
then
   echo "Iptables already set, skipping..........!"
else
   Here the iptables get set

但它沒有按預期工作……

問題：

我做到了iptables-save，它創造了這個：

$iptables-save
# Generated by iptables-save v1.6.0 on Tue Oct 16 02:48:41 2018
*filter
:INPUT ACCEPT [2:266]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [2:116]
COMMIT
# Completed on Tue Oct 16 02:48:41 2018

因此，如果我執行測試，它會發現它們已經設置好了……就像這裡：

(root@notemDEB78)-(03:12:20)-(/home/something78/Bash_Programming_2018)
$s.sh
Iptables already set....skipping!!!!!
(root@notemDEB78)-(03:12:25)-(/home/something78/Bash_Programming_2018)
$iptables -L
Chain INPUT (policy ACCEPT)
target     prot opt source               destination         

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination         

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination 

(root@notemDEB78)-(03:16:41)-(/home/something78/Bash_Programming_2018)
$iptables-save | grep '^\-' | wc -l
0

問題：

• 為什麼它總是發現 iptables 顯然沒有設置
• 你有更好/工作的方法來檢查是否iptables已設置….我的系統是Debian 9

bash -version GNU bash，版本 4.4.12(1)-release (x86_64-pc-linux-gnu) 版權所有 (C) 2016 Free Software Foundation, Inc. 許可證 GPLv3+：GNU GPL 版本 3 或更高版本http://gnu。 org/licenses/gpl.html

至於可能的重複：

這個問題還詢問是否有人有更好的方法來檢查是否為 bash 中的腳本設置了 iptables….

編輯：

通過設置，我的意思是 iptables 已設置如下：

if [[ `iptables-save | grep '^\-' | wc -l` > 0 ]]
   then
       echo "Iptables already set....skipping!!!!!"
   else
       if [ "$PORT" = "" ]
       then
           echo "Port not set for iptables exiting"
           echo -n "Setting port now, insert portnumber: "
           read port
           PORT=$port
       fi
       if [ ! -f /etc/iptables.test.rules ]
       then
           touch /etc/iptables.test.rules
       else
           cat /dev/null > /etc/iptables.test.rules
       fi

       cat << EOT >> /etc/iptables.test.rules
       *filter

       # Allows all loopback (lo0) traffic and drop all traffic to 127/8 that doesn't use lo0
       -A INPUT -i lo -j ACCEPT
       -A INPUT ! -i lo -d 127.0.0.0/8 -j REJECT

       # Accepts all established inOAUTH_TOKEN=d6637f7ccf109a0171a2f55d21b6ca43ff053616bound connections
       -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

       # Allows all outbound traffic
       # You could modify this to only allow certain traffic
       -A OUTPUT -j ACCEPT

       # Allows HTTP and HTTPS connections from anywhere (the normal ports for websites)
       -A INPUT -p tcp --dport 80 -j ACCEPT
       -A INPUT -p tcp --dport 443 -j ACCEPT

       # Allows SSH connections
       # The --dport number is the same as in /etc/ssh/sshd_config
       -A INPUT -p tcp -m state --state NEW --dport $PORT -j ACCEPT

       # Now you should read up on iptables rules and consider whether ssh access
       # for everyone is really desired. Most likely you will only allow access from certain IPs.

       # Allow ping
       #  note that blocking other types of icmp packets is considered a bad idea by some
       #  remove -m icmp --icmp-type 8 from this line to allow all kinds of icmp:
       #  https://security.stackexchange.com/questions/22711
       -A INPUT -p icmp -m icmp --icmp-type 8 -j ACCEPT

       # log iptables denied calls (access via dmesg command)
       -A INPUT -m limit --limit 5/min -j LOG --log-prefix "iptables denied: " --log-level 7

       # Reject all other inbound - default deny unless explicitly allowed policy:
       -A INPUT -j REJECT
       -A FORWARD -j REJECT

       COMMIT
EOT
       sed "s/^[ \t]*//" -i /etc/iptables.test.rules ## remove tabs and spaces
       /sbin/iptables-restore < /etc/iptables.test.rules || echo "iptables-restore failed"; exit 127
       /sbin/iptables-save > /etc/iptables.up.rules || echo "iptables-save failed"; exit 127
       printf "#!/bin/bash\n/sbin/iptables-restore < /etc/iptables.up.rules" > /etc/network/if-pre-up.d/iptables ## create a script to run iptables on startup
       chmod +x /etc/network/if-pre-up.d/iptables || echo "cmod +x failed"; exit 127
   fi

一種可能的簡化是使用grep自身的返回作為條件，grep僅當存在匹配時才會以程式碼 0（表示“成功”）退出。由於您正在尋找任何匹配項，因此無需計算行數。

此外，您不需要-用 a轉義\，因為它不是 grep 正則表達式的元字元。

您可以傳遞grep一個-q參數，因此它不會列印匹配的行（僅使用適當的退出程式碼退出，具體取決於是否有任何行匹配。）

if /sbin/iptables-save | grep -q '^-'; then
   echo "Iptables already set....skipping!!!!!"
else
   # set up iptables here
fi

我認為檢查輸出iptables-save以檢查是否設置了任何規則是可以的，我想不出另一種可靠或更簡單的方法。

引用自：https://unix.stackexchange.com/questions/475710