使用 Powershell 中的函数替换 [英] Use a function in Powershell replace

问题描述

我正在尝试替换 Powershell 中的部分字符串.但是，替换字符串不是硬编码的，它是从函数计算出来的:

I'm trying to replace part of a string in Powershell. However, the replacement string is not hardcoded, it's calculated from a function:

$text = "the image is -12345-"
$text = $text -replace "-(\d*)-", 'This is the image: $1'
Write-Host $text

这给了我正确的结果:这是图像:12345"

This gives me the correct result: "This is the image: 12345"

现在，我想包含 base64 编码的图像.我可以从 id 中读取图像.我希望以下内容有效，但没有:

Now, I want to include the base64 encoded image. I can read the image from the id. I was hoping the following would work, but it doesn't:

function Get-Base64($path)
{
    [convert]::ToBase64String((get-content $path -encoding byte))
}
$text -replace "-(\d*)-", "This is the image: $(Get-Base64 '$1')"

它不工作的原因是因为它首先将 $1(字符串，而不是 $1 的值)传递给函数，执行它并且只执行然后它做替换.我想做的是

The reason that it doesn't work, is because it first passes $1 (the string, not the value of $1) to the function, executes it and only then does it do the replace. What I want to do is

• 找出模式的出现
• 用模式替换每次出现
• 对于每次替换:
• 将捕获组传递给函数
• 使用捕获组的值获取base64图像
• 将 base64 图像注入到替换中

推荐答案

您可以使用静态<[regex] 类中的 code>Replace 方法:

You can use the static Replace method from the [regex] class:

[regex]::Replace($text,'-(\d*)-',{param($match) "This is the image: $(Get-Base64 $match.Groups[1].Value)"})

或者，您可以定义一个 regex 对象并使用该对象的 Replace 方法:

Alternatively you can define a regex object and use the Replace method of that object:

$re = [regex]'-(\d*)-'
$re.Replace($text, {param($match) "This is the image: $(Get-Base64 $match.Groups[1].Value)"})

为了更好的可读性，您可以在单独的变量中定义回调函数(脚本块)并在替换中使用它:

For better readability you could define the callback function (the scriptblock) in a separate variable and use that in the replacement:

$callback = {
  param($match)
  'This is the image: ' + (Get-Base64 $match.Groups[1].Value)
}

$re = [regex]'-(\d*)-'
$re.Replace($text, $callback)

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