参考 – 这个正则表达式是什么意思？

这是什么？

这是一个常见的Q& A的集合。这也是一个社区Wiki，所以大家被邀请参与维护它。

为什么是这样？

regex是给我我的代码类型的问题和穷人的答案，没有解释。此引用意在提供到质量问答的链接。

范围是什么？

此引用适用于以下语言：php,perl,javascript,python,ruby,java,.net。

这可能过于宽泛，但这些语言具有相同的语法。对于特定的功能，有它背后的语言的标签，例如：

>什么是正则表达式平衡组？ .net

堆栈溢出正则表达式常见问题

量词

>零或更多：*:greedy，[*？：不愿] [需要链接]，*+:possessive
>一个或多个：+:greedy，[？：reluctant] [需要链接]，++:possessive
> ?:optional (zero-or-one)
>最小/最大范围(全部)：{n,m}:between n & m,{n,}:n-or-more,{n}:exactly n
>贪婪，勉强(又名“懒惰”，“不y”)和占有量词的区别：

> 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stackoverflow参考：从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
> [^] 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
>短手：

> Digit：\d:digit，\D:non-digit
>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

>水平空白：\h:space-or-tab，\t:tab
>换行：

> \r,\n:carriage return and line feed
> \R:generic newline php

>否定空白序列：\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

锚点

> ^: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，python，ruby
> \G:start of match php，perl，ruby

(另请参见“风味特定信息> Java>在Matcher中的函数”)

组

> (...):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

> \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?
> (?>):atomic group或independent group,(?|):branch reset

> Equivalent of branch reset in .NET/C# .net

>命名捕获组：

> java：(？< groupname> regex)：Overview和naming rules(Non stackoverflow links)
>其他语言：(?P<groupname>regex) python,(?<groupname>regex) .net,(?<groupname>regex) perl，(< group name> regex)和(？< groupname> regex)php

环境

> Lookaheads：(?=...):positive，(?!...):negative
> Lookbehinds：(?<=...):positive，(?<!...):negative(不受javascript 支持)
> Lookbehind限制：

> Lookbehinds need to be constant-length php，perl，python，ruby
> Lookarounds of limited length {0,n} java
> Variable length lookbehinds are allowed .net

> Lookbehind替代方案：

> Using \K php，perl(Flavors that support \K)
> Alternative regex module for python python

> The hacky way
> Javascript negative lookbehind equivalents External link

修饰符

>最多风味：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 ruby
> s:single line(不支持 javascript或ruby)，s workaround javascript
> S:study php r
> How to convert preg_replace e to preg_replace_callback?
> What are inline modifiers?
> What is ‘?-mix’ in a Ruby Regular Expression

其他：

> |:alternation (OR) operator，.:any character，[.]:literal dot character
> What special characters must be escaped?
>控制动词(php和perl)：(*PRUNE),(*SKIP),(*FAIL) and (*F)

> php only：(*BSR_ANYCRLF)

>递归(php和perl)：(?R)，(?0) and (?1)，(?-1)，(?&groupname)

常见任务

> Get a string between two curly braces: {...}
> Match (or replace) a pattern except in situations s1,s2,s3…
> How to find all Youtube video ids in a string using a regex?
>验证：

> Internet：email addresses,urls(主机/端口：regex和non-regex替代方案)，passwords
> Numeric：a number，min-max ranges (such as 1-31)，phone numbers，date
>使用regex解析HTML：请参见“常规信息>何时不使用Regex”

高级Regex-Fu

>字符串和数字：

> @L_502_180@
> 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?
> How to match the middle character in a string with regex?

>其他：

> How can we match a^n b^n with Java regex?
>匹配嵌套括号

> 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

风味特异性信息

(除了那些用*标记的部分，这部分包含非堆栈溢出链接。)

> Java

>官方文档：Pattern Javadoc,Oracle’s regular expressions tutorial
> java.util.regex.Matcher中的功能之间的区别：

> matches())：匹配必须锚定到input-start和-end
> find())：匹配可以在输入字符串(子串)中的任何位置
> lookingAt()：匹配必须仅锚定到输入启动
>(对于锚，一般来说，参见“锚点”一节)