SED：在hosts文件替换IP，使用主机名模式 [英] sed: replace ip in hosts file, using hostname as pattern

问题描述

我学习sed的，但对我来说很困难的理解。

I'm learning about sed but it is very difficult to me understand it.

我有一个动态IP的ADSL等等，我希望把当前的IP主机上的文件。

I have adsl with dynamic ip so and i want to put current ip on hosts file.

这下面的脚本只是告诉我目前的广域网IP地址，并没有更多的：

This following script just tells me the current wan ip address and no more:

IP=$(dig +short myip.opendns.com @resolver1.opendns.com)
echo $IP

结果：

192.42.7.73

所以，我对主机的符合旧的IP地址文件：

So, i have a line on hosts file with the old ip address:

190.42.44.22   peep.strudel.com

和我想更新这样的主机文件：

and i want to update host file like this:

192.42.7.73    peep.strudel.com

我该怎么办呢？我想我可以使用主机名作为模式...

How can i do it? I think i can use the hostname as pattern...

这样做的原因是因为我的服务器是我的路由器的客户，所以它访问网络直通其网关而不是直接。和Postfix总是登录我说：未知[X.X.X.X]连接（其中X.X.X.X是我的广域网IP！），它无法解析IP地址。我想，也许，如果我指定这个与我的FQDN主机/域有关，在hosts文件，将更好地工作。

The reason of doing this is because my server is a client of my router, so it access the internet thru its gateway and not directly. And postfix always is logging me that "connect from unknown [x.x.x.x]" (where x.x.x.x is my wan ip!) and it can't resolve that ip. I think that maybe if i specify this relating with my fqdn host/domain, on hosts file it will works better.

谢谢
塞尔吉奥。

Thanks Sergio.

推荐答案

使用的sed

sed -r "s/^ *[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+( +peep.strudel.com)/$IP\1/"

。
[0-9] + \\。发现1个或多个数字与此模式匹配的所有行然后连续4次模式 peep.strudel.com 周围的图案.The括号 peep.strudel.com 另存为 \\ 1 然后更换整个彭定康与你的变量，并为新的IP。

. [0-9]+\. find all lines that matches 1 or more digits with this pattern 4 consecutive times then pattern peep.strudel.com .The parenthesis around the pattern peep.strudel.com save it as \1 then replace the whole patten with your variable and your new ip.

另一种方法：而不是保存模式来命名的IP变量，可以执行sed命令行里的命令行来获得新的IP

another approach:instead of saving pattern to a variable named IP, you can execute your command line inside sed command line to get the new IP .

   sed -r "s/^ *[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+( +peep.strudel.com)/$(dig +short myip.opendns.com @resolver1.opendns.com)\1/"

使用GAWK

gawk -v IP=$IP '/ *[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+( +peep.strudel.com).*/{print gensub(/ *[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+( +peep.strudel.com)/,IP"\\1","g")}'

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