正则表达式包括结果中应该是非捕获组 [英] Regex including what is supposed to be non-capturing group in result

问题描述

我有以下简单测试，在这里我试图获取Regex模式，以使其抽取不带后缀".exe"的可执行文件名称.
 
看来我的非捕获组设置(?:\\.exe)不起作用，或者我误解了它的工作原理.
 
regex101 和 regexstorm.net 显示相同的结果，而前者确认(?:\.exe)"是非捕获性匹配.
 
对我在做什么错有任何想法吗?

I have the following simple test where i'm trying to get the Regex pattern such that it yanks the executable name without the ".exe" suffix.
 
It appears my non-capturing group setting (?:\\.exe) isn't working or i'm misunderstanding how its intended to work.
 
Both regex101 and regexstorm.net show the same result and the former confirms that "(?:\.exe)" is a non-capturing match.
 
Any thoughts on what i'm doing wrong?

// test variable for what i would otherwise acquire from Environment.CommandLine
var testEcl = "\"D:\\src\\repos\\myprj\\bin\\Debug\\MyApp.exe\" /?"
var asmName = Regex.Match(testEcl, @"[^\\]+(?:\.exe)", RegexOptions.IgnoreCase).Value;
// expecting "MyApp" but I get "MyApp.exe"

我已经能够通过使用定义了组名的匹配模式来提取我想要的值，如下所示，但是我想了解为什么非捕获组设置方法无法按我期望的方式工作

I have been able to extract the value i wanted by using a matching pattern with group names defined, as shown in the following, but would like to understand why non-capturing group setting approach didn't work the way i expected it to.

// test variable for what i would otherwise acquire from Environment.CommandLine
var testEcl = "\"D:\\src\\repos\\myprj\\bin\\Debug\\MyApp.exe\" /?"
var asmName = Regex.Match(Environment.CommandLine, @"(?<fname>[^\\]+)(?<ext>\.exe)", 
    RegexOptions.IgnoreCase).Groups["fname"].Value;
// get the desired "MyApp" result

/eoq

推荐答案

(?:...)是一个非捕获组，可匹配并且仍使用文本.这意味着该组匹配的文本部分仍会添加到总体匹配值中.

A (?:...) is a non-capturing group that matches and still consumes the text. It means the part of text this group matches is still added to the overall match value.

通常，如果您想匹配某件商品但不消费，则需要使用环顾四周.因此，如果需要匹配后跟特定字符串的内容，请使用正向超前，(?=...)构造:

In general, if you want to match something but not consume, you need to use lookarounds. So, if you need to match something that is followed with a specific string, use a positive lookahead, (?=...) construct:

some_pattern(?=specific string) // if specific string comes immmediately after pattern
some_pattern(?=.*specific string) // if specific string comes anywhere after pattern

如果您需要匹配，但之前需要排除匹配"某些特定文本，请使用正向查找:

If you need to match but "exclude from match" some specific text before, use a positive lookbehind:

(?<=specific string)some_pattern // if specific string comes immmediately before pattern
(?<=specific string.*?)some_pattern // if specific string comes anywhere before pattern

请注意，.*?或.*-即具有*，+，?，{2,}甚至是{1,3}量词的模式-正则表达式引擎并不总是支持后向模式但是，C#.NET正则表达式引擎幸运地支持它们. Python PyPi regex模块，Vim，JGSoft软件以及现在符合ECMAScript 2018的JavaScript环境也支持它们.

Note that .*? or .* - that is, patterns with *, +, ?, {2,} or even {1,3} quantifiers - in lookbehind patterns are not always supported by regex engines, however, C# .NET regex engine luckily supports them. They are also supported by Python PyPi regex module, Vim, JGSoft software and now by ECMAScript 2018 compliant JavaScript environments.

在这种情况下，您可以捕获需要获取的内容，而仅匹配上下文而不捕获:

In this case, you may capture what you need to get and just match the context without capturing:

var testEcl = "\"D:\\src\\repos\\myprj\\bin\\Debug\\MyApp.exe\" /?";
var asmName = string.Empty; 
var m = Regex.Match(testEcl, @"([^\\]+)\.exe", RegexOptions.IgnoreCase);
if (m.Success)
{
    asmName = m.Groups[1].Value;
}
Console.WriteLine(asmName);

请参见 C#演示

详细信息

• ([^\\]+)-捕获组1 :\
以外的一个或多个字符
• \.-文字点
• exe-文字exe子字符串.

• ([^\\]+) - Capturing group 1: one or more chars other than \
• \. - a literal dot
• exe - a literal exe substring.

由于我们只对捕获第1组的内容感兴趣，因此我们获取m.Groups[1].Value，而不是整个m.Value(包含.exe).

Since we are only interested in capturing group #1 contents, we grab m.Groups[1].Value, and not the whole m.Value (that contains .exe).

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