参考 - 这个正则表达式意味着什么？

Question

这是什么？

这是一个常见的Q＆amp; A的集合。这也是一个社区维基，所以每个人都被邀请参与维护。

为什么会这样？

regex正在遭受给我ze代码类型的问题和糟糕的答案，没有任何解释。此参考旨在提供质量Q＆amp; A的链接。

范围是什么？

此引用适用于以下语言：php，perl，javascript，python，ruby，java，{{ 3}}

这可能过于宽泛，但这些语言共享相同的语法。对于特定功能，它背后的语言标签，例如：

• 什么是正则表达式平衡组？ .net

Answer 1

Stack Overflow正则表达式常见问题解答

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在线教程

• RegexOne
• Regular Expressions Info

<强>量词

• 零或多：*:greedy，*?:reluctant，*+:possessive
• 一个或多个：+:greedy，+?:reluctant，++:possessive
• ?:optional (zero-or-one)
• 最低/最高范围（全包）：{n,m}:between n & m，{n,}:n-or-more，{n}:exactly n
• 贪婪，不情愿（a.k.a。＆＃34;懒惰＆＃34;，＆＃34; ungreedy＆＃34;）和占有量词之间的差异：
  • Greedy vs. Reluctant vs. Possessive Quantifiers
  • In-depth discussion on the differences between greedy versus non-greedy
  • What's the difference between {n} and {n}?
  • Can someone explain Possessive Quantifiers to me? php，perl，java，ruby
  • Emulating possessive quantifiers .net
  • 非堆叠溢出参考：来自Oracle，regular-expressions.info

字符类

• What is the difference between square brackets and parentheses?
• [...]：任何一个字符，[^...]：否定/任何字符，但
• [^] matches any one character including newlines javascript
• [\w-[\d]] / [a-z-[qz]]：设置减法.net，xml-schema，xpath，JGSoft
• [\w&&[^\d]]: set intersection java，ruby 1.9 +
• [[:alpha:]]：POSIX字符类
• Why do [^\\D2], [^[^0-9]2], [^2[^0-9]] get different results in Java? java
• 简写：
  • 数字：\d:digit，\D:non-digit
  • 单词字符（字母，数字，下划线）：\w:word character，\W:non-word character
  • 空白：\s:whitespace，\S:non-whitespace
• Unicode categories (\p{L}, \P{L}, etc.)

转义序列

• 水平空格：\h:space-or-tab，\t:tab
• 换行：
  • \r, \n:carriage return and line feed
  • \R:generic newline php
• 否定的空格序列：\H:Non horizontal whitespace character, \V:Non vertical whitespace character, \N:Non line feed character pcre php5 java-8
• 其他：\v:vertical tab，\e:the escape character

<强>锚

• ^:start of line/input，\b:word boundary, and \B:non-word boundary，$:end of line/input
• \A:start of input, \Z:end of input php，perl，ruby
• \z:the very end of input（Python中的\Z）.net，php，pcre，java，ruby，{{3 }}，icu，swift
• objective-c \G:start of match，php，perl

（另请参阅＆＃34;风味特定信息→Java→Matcher＆＃34;中的功能）

<强>组

• ruby，(...):capture group
  • (?:):non-capture group
• Why is my repeating capturing group only capturing the last match?
  • \1:backreference and capture-group reference, $1:capture group reference
  • What's the meaning of a number after a backslash in a regular expression? \g<1>123:How to follow a numbered capture group, such as \1, with a number?:
• python
• What does a subpattern (?i:regex) mean?
• What does the 'P' in (?P<group_name>regexp) mean?或(?>):atomic group，independent group
  • (?|):branch reset Equivalent of branch reset in .NET/C#
• 命名捕获组：
  • .net
  • General named capturing group reference at regular-expressions.info：(?<groupname>regex)：java和Overview （非堆叠溢出链接）
  • 其他语言：naming rules (?P<groupname>regex)，python (?<groupname>regex)，.net (?<groupname>regex)，(?P<groupname>regex)和(?<groupname>regex) perl

<强> Lookarounds

• Lookaheads：php，(?=...):positive
• Lookbehinds：(?!...):negative，(?<=...):positive（(?<!...):negative不支持）
• Lookbehind限制：
  • javascript Lookbehinds need to be constant-length，php，perl，python
  • ruby Lookarounds of limited length {0,n}
  • java Variable length lookbehinds are allowed
• Lookbehind替代方案：
  • .net Using \K，php（perl）
  • Flavors that support \K Alternative regex module for Python
    • python
    • The hacky way ^{JavaScript negative lookbehind equivalents}

<强>调节剂

• 大多数口味：External link，g:global，i:case-insensitive，u:unicode
• x:whitespace-extended c:current position perl e:expression php perl o:once
• ruby m:multiline php perl python javascript .net，java m:(non)multiline < / LI>
• ruby（s:single line或javascript不支持），ruby s workaround
• javascript S:study php U:ungreedy php
• r
• How to convert preg_replace e to preg_replace_callback?
• What are inline modifiers?

其他

• What is '?-mix' in a Ruby Regular Expression，|:alternation (OR) operator，.:any character
• [.]:literal dot character
• 控制动词（What special characters must be escaped?和php）：perl，(*PRUNE)，(*SKIP)
  仅限
  • (*FAIL) and (*F)：php
• 递归（(*BSR_ANYCRLF)和php）：perl，(?R)，(?0) and (?1)，(?-1)

常见任务

• (?&groupname)
• Get a string between two curly braces: {...}
• Match (or replace) a pattern except in situations s1, s2, s3...
• 验证：
  • 互联网：How do I find all YouTube video ids in a string using a regex?，email addresses（主机/端口：URLs和regex替代方案），non-regex
  • 数字：passwords，a number，min-max ranges (such as 1-31)，phone numbers
  • 使用正则表达式解析HTML：请参阅＆＃34;一般信息＆gt;何时不使用Regex＆＃34;

高级正则表达式

• 字符串和数字：
  • date
  • Regular expression to match a line that doesn't contain a word?
  • How does this PCRE pattern detect palindromes?
  • Match strings whose length is a fourth power
  • How does this regex find triangular numbers?
  • How to determine if a number is a prime with regex?
• 其他：
  • How to match the middle character in a string with regex?
  • 匹配嵌套括号
    • How can we match a^n b^n with Java regex? Using a recursive pattern，php
    • perl Using balancing groups
  • .net
  • “Vertical” regex matching in an ASCII “image”
  • List of highly up-voted regex questions on Code Golf
  • How to make two quantifiers repeat the same number of times?
  • An impossible-to-match regular expression: (?!a)a
  • Match/delete/replace this except in contexts A, B and C

风味特定信息

（除了标有*的内容外，此部分包含非Stack Overflow链接。）

• 爪哇
  • 官方文档：Match nested brackets with regex without using recursion or balancing groups?，Pattern Javadoc
  • Oracle's regular expressions tutorial中函数之间的差异：
    • java.util.regex.Matcher）：匹配必须锚定到input-start和-end
    • matches()）：匹配可以是输入字符串中的任何位置（子字符串）
    • find()：匹配必须锚定到仅输入 -
    • （一般情况下，锚点见＆＃34; Anchors＆＃34;）
  • 唯一接受正则表达式的lookingAt()函数：java.lang.String，matches(s)，replaceAll(s,s)，replaceFirst(s,s)，split(s)
  • * split(s,i)
• .NET
  • An (opinionated and) detailed discussion of the disadvantages of and missing features in java.util.regex
• 官方文件：
  • 提升正则表达式引擎：How to read a .NET regex with look-ahead, look-behind, capturing groups and back-references mixed together?，General syntax （由TextPad使用，Sublime Text，UltraEdit，...... ???）
  • JavaScript 1.5 Perl syntax和general info
  • RegExp object .NET MySQL Oracle
  • PHP：Perl5 version 18.2，pattern syntax
  • Python：preg_match，Regular expression operations，search vs match
  • Splunk：how-to和regex terminology and syntax
  • Tcl：regex command，regex syntax，manpage
  • regexp command

一般信息

（标有*的链接是非Stack Overflow链接。）

• 其他常规文档资源：Visual Studio Find and Replace，* Learning Regular Expressions，* Regular-expressions.info，* Wikipedia entry，RexEgg
• Open-Directory Project
• DFA versus NFA
• 图书：Jeffrey Friedl的 Generating Strings matching regex
• 何时不使用正则表达式：
  • Mastering Regular Expressions （由Some people, when confronted with a problem, think "I know, I'll use regular expressions." Now they have two problems.创始人撰写的博客文章）*
  • 不要使用正则表达式来解析HTML：
    • Stack Overflow。 Don't
    • Please, just don't（此问题的其他答案也不错）

可能导致正则表达式引擎失败的正则表达式示例

• Well, maybe...if you're really determined

工具：测试人员和解说员

（此部分包含非Stack Overflow链接。）

• 在线（*包括替换测试仪，+包括分割测试仪）：

  • Why does this regular expression kill the Java regex engine?（还有一个有用的正则表达式存储库）Debuggex，javascript，python
  • * pcre Regular Expressions 101，php，pcre，python
  • javascript， Regex Pal regular-expressions.info
  • javascript Rubular ruby RegExr Regex Hero
  • * + dotnet regexstorm.net
  • * RegexPlanet：.net Java，java Go，go Haskell，haskell JavaScript， javascript .NET，dotnet Perl perl php PCRE，php Python，{{ 3}} python，Ruby ruby
  • XRegExp xregexp
  • * + freeformatter.com xregexp PCRE和POSIX，regex.larsolavtorvik.com
  • php javascript Refiddle javascript

• 离线：

  • Microsoft Windows：ruby（分析），.net（创建），RegexBuddy（分析，创建，免费）