我如何一行文本添加到使用bash文件的中间？ [英] How do I add a line of text to the middle of a file using bash?

问题描述

我试图一行文本添加到一个bash脚本的文本文件的中间。特别是我想一个域名服务器添加到我的/etc/resolv.conf文件。因为它的立场，resolv.conf的是这样的：

I'm trying to add a line of text to the middle of a text file in a bash script. Specifically I'm trying add a nameserver to my /etc/resolv.conf file. As it stands, resolv.conf looks like this:

# Generated by NetworkManager
domain dhcp.example.com
search dhcp.example.com
nameserver 10.0.0.1
nameserver 10.0.0.2
nameserver 10.0.0.3

我的目标是添加域名服务器127.0.0.1 所有其他名称服务器线上方，但低于上述的任何文字。最后，我想我的resolve.conf文件看起来是这样的：

My goal is to add nameserver 127.0.0.1 above all other nameserver lines, but below any text above that. In the end I want to my resolve.conf file to look like this:

# Generated by NetworkManager
domain dhcp.example.com
search dhcp.example.com
nameserver 127.0.0.1
nameserver 10.0.0.1
nameserver 10.0.0.2
nameserver 10.0.0.3

如何通过bash脚本，这可能吗？这是不是awk或者sed可以做什么？或将创意greping重新创建该文件是我最好的举动？

How is this possible via a bash script? Is this something sed or awk can do? Or would creative greping to recreate the file be my best move?

推荐答案

下面是一个使用SED的解决方案：

Here is a solution using sed:

$ sed -n 'H;${x;s/nameserver .*\n/nameserver 127.0.0.1\
&/;p;}' resolv.conf

# Generated by NetworkManager
domain dhcp.example.com
search dhcp.example.com
nameserver 127.0.0.1
nameserver 10.0.0.1
nameserver 10.0.0.2
nameserver 10.0.0.3

它是如何工作的：第一，SUP preSS与 -n 标记的sed的输出。然后，对于每个行，我们追加行保留空间，他们用换行分隔：

How it works: first, suppress the output of sed with the -n flag. Then, for each line, we append the line to the hold space, separating them with newlines:

H

当我们来到文件（ $ 处理）结束时，我们移动保持空间模式空间的内容：

When we come to the end of the file (addressed by $) we move the content of the hold space to the pattern space:

x

然后我们替换第一行含有域名服务器127.0.0.1 A线，新的生产线与域名服务器启动（重新由 psented \\ $ p $跟着一个换行符 - 也许你的sed版本支持 \\ n ，而不是... ）和原线（通过重新psented $ p $ ＆安培; ）

Then we replace the first line starting with nameserver by a line containing nameserver 127.0.0.1, a new line (represented by \ followed by a newline - maybe your sed version supports \n instead...) and the original line (represented by &):

s/nameserver .*\n/nameserver 127.0.0.1\
&/

现在，我们只需要打印结果：

Now we just need to print the results:

p

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