使用Regular Expression和lookahead从字符串中提取版本

Question

我有以下字符串作为示例，预计版本号将来会发生变化，并且可能会添加订单更改或其他类型）

Flash Player 12.0.0.38 (Internet Explorer); 12.0.0.43 (Plugin-based browsers)

我想用以下方式用RegEx解析它：

• 查找（Internet Explorer）并捕获其前面的版本（12.0.0.38）
• 查找（基于插件的浏览器）并捕获其前面的版本

到目前为止我的尝试：

$text = "Flash Player 12.0.0.38 (Internet Explorer); 12.0.0.43 (Plugin-based browsers)"
[RegEx]::Match($text, ".*(?=\(Internet\040Explorer\))").Value

返回Flash Player 12.0.0.38

所以我认为我需要过滤“一个或多个单词”而不是捕获它们，然后捕获“一个或多个数字或”。当我跟着（Internet Explorer）我试过：

[RegEx]::Match($text, "(?:\w+)[\d\.]+(?=\(Internet\040Explorer\))").Value

但是那不匹配，订单是不正确的？所以我正在寻找正确的正则表达式，并附上一个小解释。

Answer 1

$text = "Flash Player 12.0.0.38 (Internet Explorer); 12.0.0.43 (Plugin-based browsers)"
$Regex = '[\d\.]+';
$Matches = [Regex]::Matches($text, $Regex);

$Matches[0].Value;
$Matches[1].Value;

结果如下：

12.0.0.38
12.0.0.43

编辑：我修改了正则表达式以匹配，无论顺序如何。

Clear-Host;

$matches = $null;
$Regex = '(?<=Flash Player\s)(?<FlashIE>[\d\.]+)(?:.*?)(?<FlashPlugin>[\d\.]+)(?=\s\(Plu)|(?<FlashPlugin>[\d\.]+)(?=\s\(Plu)(?:.*?)(?<=Flash Player\s)(?<FlashIE>[\d\.]+)';

# 1. Example string
$text = "Flash Player 12.0.0.38 (Internet Explorer); 12.0.0.43 (Plugin-based browsers)"
$MatchList = [Regex]::Matches($text, $Regex);
$MatchList[0].Groups['FlashIE'].Value;
$MatchList[0].Groups['FlashPlugin'].Value;

# 2. Reversed example string
$text = "; 12.0.0.43 (Plugin-based browsers);Flash Player 12.0.0.38 (Internet Explorer)"
$MatchList = [Regex]::Matches($text, $Regex);
$MatchList[0].Groups['FlashIE'].Value;
$MatchList[0].Groups['FlashPlugin'].Value;

# NOTE: Both of these yield the exact, same output, because we are using named groups.

结果：

12.0.0.38
12.0.0.43
12.0.0.38
12.0.0.43

Answer 2

命名组有一点改进：

if ($text -cmatch '(?<plugin>(?:\d\.?)+) (?=\(Plugin-based browsers\))|(?<internet>(?:\d\.?)+) (?=\(Internet Explorer\))') {
    $PluginBrowsers = $matches['plugin']
    $InternetExplorer = $matches['internet']
}

你可以试试这个（没有经过测试）：

使用两个正则表达式：

if ($subject -cmatch '((?:\d\.?)+) (?=\(Internet Explorer\))') {
   $result = $matches[1]
} else {
   $result = ''
}

if ($subject -cmatch '((?:\d\.?)+) (?=\(Plugin-based browsers\))') {
   $result = $matches[1]
} else {
   $result = ''
}

或者只有一个：

if ($subject -cmatch '((?:\d\.?)+) ((?=\(Plugin-based browsers\))|(?=\(Internet Explorer\)))') {
   $result = $matches[1]
} else {
   $result = ''
}

Answer 3

原因 (?:\w+)[\d\.]+(?=\(Internet\040Explorer\))不匹配是因为[\d\.]+(?=\(Internet\040Explorer\))部分不期望版本号与(Internet Explorer)之间的空格

无论顺序如何，此表达式都将捕获所需的两个值：

(?=^.*?([\d\.]+)(?=(?> *)(?:\(Internet\040Explorer\))))(?=^.*?([\d\.]+)(?=(?> *)(?:\(Plugin-based browsers\))))

在powershell中：

$text = "Flash Player 12.0.0.38 (Internet Explorer); 12.0.0.43 (Plugin-based browsers)"
$regex = "(?=^.*?([\d\.]+)(?=(?> *)(?:\(Internet\040Explorer\))))(?=^.*?([\d\.]+)(?=(?> *)(?:\(Plugin-based browsers\))))"
$matches  = [RegEx]::Match($text, $regex)
echo $Matches.Groups[1].value  #Outputs 12.0.0.38
echo $Matches.Groups[2].value  #Outputs 12.0.0.43

示例顺序：

Flash Player 12.0.0.38 (Internet Explorer); 12.0.0.43 (Plugin-based browsers)
[Match number 1]
Matched: '' at character 1
[Capture Group 1] '12.0.0.38' found at character 14
[Capture Group 2] '12.0.0.43' found at character 45

反向示例顺序：

12.0.0.43 (Plugin-based browsers); Flash Player 12.0.0.38 (Internet Explorer)
[Match number 1]
Matched: '' at character 1
[Capture Group 1] '12.0.0.38' found at character 49
[Capture Group 2] '12.0.0.43' found at character 1

Answer 4

如果你不确定他们的订单是什么：

$text = "Flash Player 12.0.0.38 (Internet Explorer); 12.0.0.43 (Plugin-based browsers)"

$IE_Version = $text -replace '.+\s([0-9.]+)\s\(Internet Explorer\).*','$1'
$Plugin_Version = $text -replace '.+\s([0-9.]+)\s\(Plugin-based browsers\).*','$1'

$IE_Version
$Plugin_Version

12.0.0.38
12.0.0.43

简而言之，正则表达式逻辑是：

搜索字符串，直到找到一个空格，后跟一大堆数字和点，然后是另一个空格，然后是文字字符串（Internet Explorer）。捕获一堆数字和点，并用这个捕获替换整个字符串。重复文字字符串（基于插件的浏览器）。

Answer 5

试试这个：

([0-9.]*)(?: (\(Internet Explorer\)|\(Plugin-based browsers\)))

Debuggex Demo

测试here。