Linux 如何使用 sed 替换配置文件的变量？
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How to use sed to replace a config file's variable?
提问by SomeGuyOnAComputer
I've been looking online for this answer and cannot seem to find it.
我一直在网上寻找这个答案，但似乎找不到。
I have a config file that contains:
我有一个配置文件，其中包含：
VAR1=VALUE1
VAR2=VALUE2
VAR3=VALUE3
VAR4=VALUE4
VAR5=VALUE5
VAR6=VALUE6
And I want to change VAR5's value from VALUE5 to VALUE10. Unfortunately, I do not know the value of VALUE5 so I cannot search for it. So basically I need to use sed (or whatever) to replace the value of VAR5 to whatever value I want to replace it with.
我想将 VAR5 的值从 VALUE5 更改为 VALUE10。不幸的是，我不知道 VALUE5 的值，所以我无法搜索它。所以基本上我需要使用 sed （或其他）将 VAR5 的值替换为我想替换的任何值。
采纳答案by anubhava
You can try this sed:
你可以试试这个 sed：
sed -i.bak 's/^\(VAR5=\).*/VALUE10/' file
It gives:
它给：
VAR1=VALUE1
VAR2=VALUE2
VAR3=VALUE3
VAR4=VALUE4
VAR5=VALUE10
VAR6=VALUE6
回答by devnull
You can say:
你可以说：
sed '/^VAR5=/s/=.*/=VALUE10/' filename
To make in the change to the file in-place, use the -ioption:
要对文件进行就地更改，请使用以下-i选项：
sed -i '/^VAR5=/s/=.*/=VALUE10/' filename
回答by Vlad.Bachurin
Try the following
尝试以下
sed -r 's/^(VAR5=).*/\1REPLACEMENT/'
sed -r 's/^(VAR5=).*/\1REPLACEMENT/'
The value of VAR5 will be replaced with REPLACEMENT.
VAR5 的值将替换为 REPLACEMENT。
回答by NeronLeVelu
sed '/\(^VAR5=\).*/ s//VALUE10/' YourFile
Under AIX/KSH
在 AIX/KSH 下
$ cat sample.txt
VAR1=VALUE1
VAR2=VALUE2
VAR3=VALUE3
VAR4=VALUE4
VAR5=VALUE5
VAR6=VALUE6
$ sed '/\(^VAR5=\).*/ s//VALUE10/' sample.txt
VAR1=VALUE1
VAR2=VALUE2
VAR3=VALUE3
VAR4=VALUE4
VAR5=VALUE10
VAR6=VALUE6
and for replacement in file
并在文件中替换
cat <> YourFile | sed '/\(^VAR5=\).*/ s//VALUE10/'
$ cat <> sample.txt | sed '/\(^VAR5=\).*/ s//VALUE10/'
$ cat sample.txt
VAR1=VALUE1
VAR2=VALUE2
VAR3=VALUE3
VAR4=VALUE4
VAR5=VALUE10
VAR6=VALUE6
To be POSIX (on sedpart, not cat) compliant (sed --posixon gnu sed and natively traditionnal sed on non linux system)
符合 POSIX（sed部分，不cat）兼容（--posixgnu sed 上的 sed 和非 linux 系统上的本机传统 sed）
回答by Kannan Ramamoorthy
Even though the answer has been added to the question. I spent some time on how it works, I would like add some facts and my version of the answer,
即使答案已添加到问题中。我花了一些时间研究它是如何工作的，我想添加一些事实和我的答案版本，
sed -i 's,^\(THISISMYVARIABLE[ ]*=\).*,'THISISMYVALUE',g' config.cfg
Explanation:
解释：
- As a basic of
sed 's/find_this/replace_with/', we are saying sed to search and replace. Also remember there are multiple other delimiters that we can use instead of/. Here,is used. - Here we find the line that matches
^\(THISISMYVARIABLE[ ]*=\).*. This means we are grouping the matchTHISISMYVARIABLE[ ]*=. ([ ]*to cover if there are any spaces after the key) - In replace section
\1is a back-reference. We are referencing the first group in the regular expression that we used for match.
- 作为 的基础
sed 's/find_this/replace_with/'，我们说 sed 来搜索和替换。还要记住，我们可以使用多个其他分隔符来代替/. 这里,使用。 - 在这里我们找到匹配的行
^\(THISISMYVARIABLE[ ]*=\).*。这意味着我们正在对比赛进行分组THISISMYVARIABLE[ ]*=。（[ ]*如果键后有空格，则覆盖） - 在替换部分
\1是一个反向引用。我们正在引用我们用于匹配的正则表达式中的第一组。
