netcat 命令的结果不合逻辑地匹配字符串

发布于 2024-11-27 05:53:30 字数 807 浏览 4 评论 0原文

我想测试哪个远程端口已打开，以了解我是否必须使用 telnet VNC Teamviewer 或其他设备进行连接。

我将有大约 10 个端口要测试，我正在为其编写一个脚本。此时，我已经提供了以下代码：

function testPort(){
        res=`nc -v $1 $2 < /dev/null`
        echo $res
        if [[ "$res" == *refused* ]]
        then
                echo "refused"
                return 0
        else
                echo "accepted"
                return 1
        fi

}

if test -z "$1"
then
        echo "What's the adress?"
        read IP
else
        IP="$1"
fi

testPort $IP 80

echo $res 的结果类似于：

nc: connect to 192.168.0.110 port 80 (tcp) failed: Connection refused
RFB 003.889 Connection to 192.168.0.110 5900 port [tcp/vnc-server] succeeded!

但在任何情况下，我都会显示“已接受”。我不明白为什么。有人可以解释我的错误在哪里吗？

原文

I'm wanting to test wich distant port is open to know if I have to connect with telnet VNC Teamviewer or whatever.

I'll have about 10 ports to test, and I'm doing a script for it.
At this point I've come with this code:

function testPort(){
        res=`nc -v $1 $2 < /dev/null`
        echo $res
        if [[ "$res" == *refused* ]]
        then
                echo "refused"
                return 0
        else
                echo "accepted"
                return 1
        fi

}

if test -z "$1"
then
        echo "What's the adress?"
        read IP
else
        IP="$1"
fi

testPort $IP 80

The result of echo $res is something like:

nc: connect to 192.168.0.110 port 80 (tcp) failed: Connection refused
RFB 003.889 Connection to 192.168.0.110 5900 port [tcp/vnc-server] succeeded!

But in any case I got the "accepted" displayed. I can't figure out why. Can someone explain me where's my mistake?

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君勿笑 2024-12-04 05:53:30

这是因为 netcat 将其消息写入标准错误，而不是标准输出。因此，变量 res 为空，并且与 *refused* 不匹配。

您在控制台上看到 netcat 消息的原因不是因为 echo $res 行，而是因为您没有捕获标准错误，因此它会发送到控制台。

如果将 testPort 的第一行更改为：

    res=`nc -v $1 $2 < /dev/null 2>&1`

它应该可以工作。

It's because netcat writes its message to standard error, not standard output. So, the variable res is empty, and doesn't match *refused*.

The reason you see the netcat message on the console is not because of the echo $res line, but because you aren't capturing standard error, so it's going to the console.

If you change the first line of testPort to: