如何在 PowerShell 中使用变量作为正则表达式的一部分 [英] How to use a variable as part of a regular expression in PowerShell

问题描述

我想Select-String 文件路径的一部分，以包含在变量中的字符串值开始.让我用一个抽象的例子来解释这一点.

I want to Select-String parts of a file path starting at a string value that is contained in a variable. Let me explain this in an abstracted example.

让我们假设这个路径:/docs/reports/testreports/document1.docx

Let's assume this path: /docs/reports/test reports/document1.docx

使用正则表达式，我可以获得所需的字符串，如下所示:'^.*(?=\/test\s)'

Using a regular expression I can get the required string like so: '^.*(?=\/test\s)'

https://regex101.com/r/6mBhLX/5

结果字符串是'/test reports/document1.docx'.

The resulting string is '/test reports/document1.docx'.

现在，为了让它起作用，我必须使用文字字符串test".但是，我想知道如何使用包含test"的变量，例如$myString.

Now, for this to work I have to use the literal string 'test'. However, I would like to know how to use a variable that contains 'test', e.g. $myString.

我已经看过怎么做您在正则表达式中使用了变量吗?，但我不知道如何为 PowerShell 进行调整.

I already looked at How do you use a variable in a regular expression?, but I couldn't figure out how to adapt this for PowerShell.

推荐答案

我建议在双引号字符串文字中使用 $([regex]::escape($myString)):

I suggest using $([regex]::escape($myString)) inside a double quoted string literal:

$myString="[test]"
$pattern = "^.*(?=/$([regex]::escape($myString))\s)"

或者，如果您不想担心额外的转义，请使用 + 运算符使用常规连接:

Or, in case you do not want to worry with additional escaping, use a regular concatenation using + operator:

$pattern = '^.*(?=/' + [regex]::escape($myString) +'\s)'

结果 $pattern 看起来像 ^.*(?=/\[test]\s).由于 $myString 变量是一个文字字符串，您需要转义所有可能在其中的特殊正则表达式元字符(使用 [regex]::escape())正则表达式引擎将其解释为文字字符.

The resulting $pattern will look like ^.*(?=/\[test]\s). Since the $myString variable is a literal string, you need to escape all special regex metacharacters (with [regex]::escape()) that may be inside it for the regex engine to interpret it as literal chars.

在你的情况下，你可以使用

In your case, you may use

$s = '/docs/reports/test reports/document1.docx'
$myString="test"
$pattern = "^.*(?=/$([regex]::escape($myString))\s)"
$s -replace $pattern

结果:/test reports/document1.docx

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