在替换期间强制立即评估反向引用 [英] Force immediate evaluation of backreference during replace

问题描述

我遇到了一个错误，我将字符串连接在一起以获得我想要替换的字段.

I am running into an error where I am concatenating strings together to obtain the field I want replaced.

以下是我的脚本正在执行的操作的示例:

Below is an example of what my script is doing:

$TEXTTOREPLACEWITH= '6Q'

(Get-Content testfile.html) | ForEach-Object { $_ -replace '(.*)\$\(STRINGTOREPLACE\)(.*)', ('$1' +$TEXTTOREPLACEWITH+'$2')

如果我对一个输入如下的文件运行这个:

If I ran this against a file that had a line input as follows:

abc$(STRINGTOREPLACE)xyz

我希望得到以下输出:

abc6Qxyz

相反，当我运行此脚本时，输出如下所示:

INSTEAD, When I run this script the output looks as follows:

$16Qxyz

我假设这是因为在字符串连接完成之前不能解析反向引用.在 PowerShell 中是否有任何方法可以立即解决这些反向引用并避免我看到的输出?

I'm assuming this is due to the fact that back-references must not be resolved until string concatenation is complete. Is there any way in PowerShell to go ahead and resolve these back-references immediately and avoid the output that I am seeing?

推荐答案

1st，漏点，答案已替换...

当连接 '$1' 和 '6Q' 时(在传递给正则表达式引擎之前)你得到 $16Q 并且没有要替换的第 16 个 捕获.

When concatenate '$1' and '6Q' (before being passed to the regex engine) you get $16Q and there is no 16^th capture to replace.

为避免这种情况，请在匹配中使用命名组 ((?)) 并在替换字符串中使用 ${name}.

To avoid this, use named groups in the match ((?<name>)) and ${name} in the replacement string.

请参阅文档，并注意:

如果 number 未指定在正则表达式模式中定义的有效捕获组，则 $number 将被解释为用于替换每个匹配项的文字字符序列.

If number does not specify a valid capturing group defined in the regular expression pattern, $number is interpreted as a literal character sequence that is used to replace each match.

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