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：
> Regular expression to match 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?
> 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)
>接受正则表达式的唯一的java.lang.String函数：matches(s)，replaceAll(s,s)，replaceFirst(s,s)，split(s)，split(s,i)
> * An (opinionated and) detailed discussion of the disadvantages of and missing features in java.util.regex
> .NET
> How to read a .NET regex with look-ahead,look-behind,capturing groups and back-references mixed together?
>官方文档：
> Boost regex引擎：General syntax,Perl syntax(由TextPad，Sublime Text，UltraEdit，…使用)
> JavaScript 1.5 general info和RegExp object
> .NET MySQL Oracle Perl5 version 18.2
> PHP：pattern syntax，preg_match
> Python：Regular expression operations，search vs match，how-to
> Splunk：regex terminology and syntax和regex command
> Tcl：regex syntax,manpage,regexp command
一般信息
(标有*的链接是非堆栈溢出链接。)
>其他一般文档资源：Learning Regular Expressions，* Regular-expressions.info，* Wikipedia entry，* RexEgg，Open-Directory Project
> DFA versus NFA
> Generating Strings matching regex
>图书：Jeffrey Friedl’s * Mastering Regular Expressions
>何时不使用正则表达式：
> * Some people,when confronted with a problem,think “I know,I’ll use regular expressions.” Now they have two problems.(博客由Stack Overflow的创始人写)
>不要使用正则表达式来解析HTML：
> Don’t.Please,just don’t
> Well,maybe…if you’re really determined(这个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
> Why does this regular expression kill the Java regex engine?
工具：测试者和解释者
(此部分包含非Stack Overflow链接。)
>在线(*包括更换测试仪，包括分体测试仪)：
> Debuggex(还有一个有用的正则表达式库)javascript，python，pcre
> * Regular Expressions 101 php，pcre，python，javascript
> Regex Pal，* regular-expressions.info javascript
> Rubular ruby RegExr Regex Hero dotnet
> * regexstorm.net .net
> * RegexPlanet：Java java,Go go，Haskell haskell,php javascript,.NET dotnet,Perl perl php PCRE php,Python python,Ruby ruby,XRegExp xregexp
> freeformatter.com xregexp
> * regex.larsolavtorvik.com php PCRE和POSIX，javascript
> Refiddle javascript ruby .net
>离线：
> Microsoft Windows：RegexBuddy(分析)，RegexMagic(创建)，Expresso(分析，创建，免费)
