Golang正则表达式匹配并替换某个字符串后的第一个匹配项

问题描述：

Following up on my previous question about using Golang's regex to replace between strings. I now have a bit of complexity added to it. Here is what the contexts of my file looks like:

foo:
    blahblah
    MYSTRING=*
bar:
    blah
    blah
    MYSTRING=*

I need to replace what's between MYSTRING= and with a string of my choice (like previous stated in the original post). I can do that with:

var re = regexp.MustCompile(`(MYSTRING=).*`)
s := re.ReplaceAllString(content, `${1}stringofmychoice`)

But now I need to match and replace only after a certain occurrence. So that the contents of my file can look something like this:

foo:
    blahblah
    MYSTRING=foostring
bar:
    blah
    blah
    MYSTRING=barstring

ReplaceAllString obviously replaces everything, which is not what I want. Is there a way to only match and replace the first occurrence after a certain string?

For a bit of background about all of this. I'm trying to write a program to edit the contents of a given docker-compose.yml file and its environment variables. I need to edit the environment variable MYSTRING differently depending on what service it's listed under. In the example above, the two different services would be foo and bar.

紧随我之前的有关使用Golang的正则表达式替换字符串之间的问题。现在，我增加了一些复杂性。这是我文件的上下文： p>

  foo：
 blahblah 
 MYSTRING = * 
bar：
 blah 
 blah 
 MYSTRING = * \  n  code>  pre> 
 
 我需要用我选择的字符串替换 MYSTRING =  code>和 
  code>之间的内容（例如上一个 在原始帖子中说明）。 我可以这样： p> 
 
 
  var re = regexp.MustCompile（`（MYSTRING =）。*`）
s：= re.ReplaceAllString（content，`$ {1  } stringofmychoice`）
  code>  pre> 
 
 但是现在我只需要匹配并替换就可以了。 这样我的文件内容就可以像这样： p> 
 
 
  foo：
 blahblah 
 MYSTRING = foostring 
bar：
 blah 
 blah 
 MYSTRING =  barstring 
  code>  pre> 
 
   ReplaceAllString  code>显然替换了所有内容，这不是我想要的。 有没有办法只匹配并替换某个字符串后的第一个匹配项？ p> 
 
 

有关所有这些的一些背景知识。 我正在尝试编写一个程序来编辑给定 docker-compose.yml  code>文件及其环境变量的内容。 我需要根据下面列出的服务来不同地编辑环境变量 MYSTRING  code>。 在上面的示例中，两个不同的服务将是 foo  code>和 bar  code>。 p> 
  div>

答

You may use ReplaceAllStringFunc and use a regex like

(?m)^bar:(?:
\s{4}.*)+

See the regex demo. It will match a bar block indented with four whitespaces. Then, after a match is obtained, you may use a regular ReplaceAllString on the match.

See the Go demo:

package main

import (
    "fmt"
    "regexp"
)

const sample = `foo:
    blahblah
    MYSTRING=*
bar:
    blah
    blah
    MYSTRING=*`

func main() {
    re := regexp.MustCompile(`(?m)^bar:(?:
\s{4}.*)+`)
    re_2 := regexp.MustCompile(`(MYSTRING=).*`)
    s := re.ReplaceAllStringFunc(sample, func(m string) string {
                return re_2.ReplaceAllString(m, `${1}stringofmychoice`)
        })
    fmt.Println(s)
}

Here, the second occurrence is changed in the bar block:

foo:
    blahblah
    MYSTRING=*
bar:
    blah
    blah
    MYSTRING=stringofmychoice

Golang正则表达式匹配并替换某个字符串后的第一个匹配项

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