正则表达式前端使用手册

小灰灰 2022-09-29 06:13 159阅读 0赞

1.  [导读][Link 1]
2.  [回顾历史][Link 2]
3.  [正则表达式的定义][Link 3]
    
    1.  [元字符][Link 4]
    2.  [反义元字符][Link 5]
    3.  [重复限定符][Link 6]
    4.  [字符组][Link 7]
    5.  [排除性字符组][Link 8]
    6.  [多选结构][Link 9]
    7.  [括号][Link 10]
    8.  [转义字符][Link 11]
    9.  [操作符的运算优先级][Link 12]
    10. [测试][Link 13]
4.  [修饰符][Link 14]
5.  [常用的正则表达式][Link 15]
    
    1.  [密码验证][Link 16]
6.  [正则的几大家族][Link 17]
    
    1.  [正则表达式分类][Link 18]
    2.  [正则表达式比较][Link 19]
7.  [linux/osx下常用命令与正则表达式的关系][linux_osx]
    
    1.  [grep , egrep , sed , awk 正则表达式特点][grep _ egrep _ sed _ awk]
8.  [正则表达式初阶技能][Link 20]
    
    1.  [贪婪模式与非贪婪模式][Link 21]
        
        1.  [区间量词的非贪婪模式][Link 22]
    2.  [分组][Link 23]
    3.  [捕获性分组][Link 24]
    4.  [非捕获性分组][Link 25]
    5.  [命名分组][Link 26]
    6.  [固化分组][Link 27]
9.  [正则表达式高阶技能-零宽断言][-]
    
    1.  [场景回顾][Link 28]
        
        1.  [获取html片段][html]
        2.  [千位分割符][Link 29]
10. [正则表达式在JS中的应用][JS]
    
    1.  [ES6对正则的扩展][ES6]
        
        1.  [UCS-2字节码][UCS-2]
        2.  [附: ES6新增的处理4字节码的函数][ES6_4]
    2.  [RegExp][]
        
        1.  [compile][]
        2.  [test][]
        3.  [exec][]
    3.  [String][]
11. [正则表达式在H5中的应用][H5]
12. [正则引擎][Link 30]
13. [总结][Link 31]

### 导读 ###

你有没有在搜索文本的时候绞尽脑汁, 试了一个又一个表达式, 还是不行.

你有没有在表单验证的时候, 只是做做样子(只要不为空就好), 然后烧香拜佛, 虔诚祈祷, 千万不要出错.

你有没有在使用sed 和 grep 命令的时候, 感觉莫名其妙, 明明应该支持的元字符, 却就是匹配不到.

甚至, 你压根没遇到过上述情况, 你只是一遍又一遍的调用 replace 而已 (把非搜索文本全部替换为空, 然后就只剩搜索文本了), 面对别人家的简洁高效的语句, 你只能在心中呐喊, replace 大法好.

为什么要学正则表达式. 有位网友这么说: 江湖传说里, 程序员的正则表达式和医生的处方, 道士的鬼符齐名, 曰: 普通人看不懂的三件神器. 这个传说至少向我们透露了两点信息: 一是正则表达式很牛, 能和医生的处方, 道士的鬼符齐名, 并被大家提起, 可见其江湖地位. 二是正则表达式很难, 这也从侧面说明了, 如果你可以熟练的掌握并应用它, 在装逼的路上, 你将如日中天 (别问我中天是谁……) !

显然, 有关正则表达的介绍, 无须我多言. 这里就借助 Jeffrey Friedl 的《精通正则表达式》一书的序言正式抛个砖.

>  “如果罗列计算机软件领域的伟大发明, 我相信绝对不会超过二十项, 在这个名单当中, 当然应该包括分组交换网络, Web, Lisp, 哈希算法, UNIX, 编译技术, 关系模型, 面向对象, XML这些大名鼎鼎的家伙, 而正则表达式也绝对不应该被漏掉.
> 
>  对很多实际工作而言, 正则表达式简直是灵丹妙药, 能够成百倍的提高开发效率和程序质量, 正则表达式在生物信息学和人类基因图谱的研究中所发挥的关键作用, 更是被传为佳话. CSDN的创始人蒋涛先生在早年开发专业软件产品时, 就曾经体验过这一工具的巨大威力, 并且一直印象深刻.”

因此, 我们没有理由不去了解正则表达式, 甚至是熟练掌握并运用它.

本文以正则基础语法开篇, 结合具体实例, 逐步讲解正则表达式匹配原理. 代码实例使用语言包括 js, php, python, java(因有些匹配模式, js并未支持, 需要借助其他语言讲解). 内容包括初阶技能和高阶技能, 适合新手学习和进阶. 本文力求简单通俗易懂, 同时为求全面, 涉及知识较多, 共计12k字, 篇幅较长, 请耐心阅读, 如有阅读障碍请及时[联系我][Link 32].

### 回顾历史 ###

要论正则表达式的渊源, 最早可以追溯至对人类神经系统如何工作的早期研究. Warren McCulloch 和 Walter Pitts 这两位神经大咖 (神经生理学家) 研究出一种数学方式来描述这些神经网络.

1956 年, 一位叫 Stephen Kleene 的数学家在 McCulloch 和 Pitts 早期工作的基础上, 发表了一篇标题为”神经网事件的表示法”的论文, 引入了正则表达式的概念.

随后, 发现可以将这一工作应用于使用 Ken Thompson 的计算搜索算法的一些早期研究中. 而 Ken Thompson 又是 Unix 的主要发明人. 因此半个世纪以前的Unix 中的 qed 编辑器(1966 qed编辑器问世) 成了第一个使用正则表达式的应用程序.

至此之后, 正则表达式成为家喻户晓的文本处理工具, 几乎各大编程语言都以支持正则表达式作为卖点, 当然 JavaScript 也不例外.

### 正则表达式的定义 ###

正则表达式是由普通字符和特殊字符(也叫元字符或限定符)组成的文字模板. 如下便是简单的匹配连续数字的正则表达式:

“\\d” 就是元字符, 而 “+” 则是限定符.

#### 元字符 ####

#### 反义元字符 ####

可以看出正则表达式严格区分大小写.

#### 重复限定符 ####

限定符共有6个, 假设重复次数为x次, 那么将有如下规则:

#### 字符组 ####

\[…\] 匹配中括号内字符之一. 如: \[xyz\] 匹配字符 x, y 或 z. 如果中括号中包含元字符, 则元字符降级为普通字符, 不再具有元字符的功能, 如 \[+.?\] 匹配 加号, 点号或问号.

#### 排除性字符组 ####

\[^…\] 匹配任何未列出的字符,. 如: \[^x\] 匹配除x以外的任意字符.

#### 多选结构 ####

| 就是或的意思, 表示两者中的一个. 如: a|b 匹配a或者b字符.

#### 括号 ####

括号 常用来界定重复限定符的范围, 以及将字符分组. 如: (ab)+ 可以匹配abab..等, 其中 ab 便是一个分组.

#### 转义字符 ####

\\ 即转义字符, 通常 \\ \* + ? | \{ \[ ( ) \] \}^ $ . \# 和 空白 这些字符都需要转义.

#### 操作符的运算优先级 ####

1.  \\ 转义符
2.  (), (?:), (?=), \[\] 圆括号或方括号
3.  \*, +, ?, \{n\}, \{n,\}, \{n,m\} 限定符
4.  ^, $ 位置
5.  | “或” 操作

#### 测试 ####

我们来测试下上面的知识点, 写一个匹配手机号码的正则表达式, 如下:

① “\\+86” 匹配文本 “+86”, 后面接元字符问号, 表示可匹配1次或0次, 合起来表示 “(\\+86)?” 匹配 “+86” 或者 “”.

② 普通字符”1” 匹配文本 “1”.

③ 元字符 “\\d” 匹配数字0到9, 区间量词 “\{10\}” 表示匹配 10 次, 合起来表示 “\\d\{10\}” 匹配连续的10个数字.

以上, 匹配结果如下:

[![regexp01.png][]][regexp01.png]

### 修饰符 ###

javaScript中正则表达式默认有如下五种修饰符:

*  g (全文查找), 如上述截图, 实际上就开启了全文查找模式.
 *  i (忽略大小写查找)
 *  m (多行查找)
 *  y (ES6新增的粘连修饰符)
 *  u (ES6新增)

### 常用的正则表达式 ###

1.  汉字: ^\[\\u4e00-\\u9fa5\]\{0,\}$
2.  Email: ^\\w+(\[-+.\]\\w+)\*@\\w+(\[-.\]\\w+)\*\\.\\w+(\[-.\]\\w+)\*$
3.  URL: ^https?://(\[\\w-\]+.)+\[\\w-\]+(/\[\\w-./?%&=\]\*)?$
4.  手机号码: ^1\\d\{10\}$
5.  身份证号: ^(\\d\{15\}|\\d\{17\}(\\d|X))$
6.  中国邮政编码: \[1-9\]\\d\{5\}(?!\\d) (邮政编码为6位数字)

#### 密码验证 ####

密码验证是常见的需求, 一般来说, 常规密码大致会满足规律: 6-16位, 数字, 字母, 字符至少包含两种, 同时不能包含中文和空格. 如下便是常规密码验证的正则描述:

### 正则的几大家族 ###

#### 正则表达式分类 ####

在 linux 和 osx 下, 常见的正则表达式, 至少有以下三种:

*  基本的正则表达式( Basic Regular Expression 又叫 Basic RegEx 简称 BREs )
 *  扩展的正则表达式( Extended Regular Expression 又叫 Extended RegEx 简称 EREs )
 *  Perl 的正则表达式( Perl Regular Expression 又叫 Perl RegEx 简称 PREs )

#### 正则表达式比较 ####

<table style="margin:15px 0px; padding:0px; border:1px solid rgb(222,222,222); outline:0px; font-family:微软雅黑,HelveticaNeue-Light,&quot;Helvetica Neue Light&quot;,&quot;Helvetica Neue&quot;,Helvetica,Arial,sans-serif; font-size:16px; vertical-align:middle; border-collapse:collapse; border-spacing:0px; width:933px"> 
 <thead style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline"> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px; background:rgb(248,248,248)"> 
   <th style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-weight:400; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; text-align:left"> 字符</th> 
   <th style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-weight:400; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; text-align:left"> 说明</th> 
   <th style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-weight:400; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; text-align:left"> Basic RegEx</th> 
   <th style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-weight:400; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; text-align:left"> Extended RegEx</th> 
   <th style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-weight:400; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; text-align:left"> python RegEx</th> 
   <th style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-weight:400; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; text-align:left"> Perl regEx</th> 
  </tr> 
 </thead> 
 <tbody style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline"> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 转义</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> &nbsp;</td> 
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   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> &nbsp;</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> &nbsp;</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> &nbsp;</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> ^</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配行首，例如’^dog’匹配以字符串dog开头的行（注意：awk 指令中，’^’则是匹配字符串的开始）</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> ^</td> 
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  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> $</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配行尾，例如：’^、dog\$’ 匹配以字符串 dog 为结尾的行（注意：awk 指令中，’$’则是匹配字符串的结尾）</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> $</td> 
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  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
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   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配空行</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> ^$</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> ^$</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> ^$</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> ^$</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> ^string$</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配行，例如：’^dog$’匹配只含一个字符串 dog 的行</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> ^string$</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> ^string$</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> ^string$</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> ^string$</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \&lt;</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配单词，例如：’\&lt;frog’ （等价于’\bfrog’），匹配以 frog 开头的单词</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \&lt;</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \&lt;</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span></td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span>（但可以使用\b来匹配单词，例如：’\bfrog’）</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> &gt;</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配单词，例如：’frog&gt;‘（等价于’frog\b ‘），匹配以 frog 结尾的单词</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> &gt;</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> &gt;</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span></td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span>（但可以使用\b来匹配单词，例如：’frog\b’）</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配一个单词或者一个特定字符，例如：’\‘（等价于’\bfrog\b’）、’\‘</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span></td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span>（但可以使用\b来匹配单词，例如：’\bfrog\b’</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> ()</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配表达式，例如：不支持’（frog）’</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span>（但可以使用，如：dog</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> ()</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> ()</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> ()</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> &nbsp;</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配表达式，例如：不支持’（frog）’</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> &nbsp;</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span>（同())</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span>（同())</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span>（同())</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> ？</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配前面的子表达式 0 次或 1 次（等价于{0,1}），例如：where(is)?能匹配”where” 以及”whereis”</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span>（同\?)</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> ？</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> ？</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> ？</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \?</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配前面的子表达式 0 次或 1 次（等价于’{0,1}‘），例如：’whereis\? ‘能匹配 “where”以及”whereis”</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \?</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span>（同?)</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span>（同?)</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span>（同?)</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> ?</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 当该字符紧跟在任何一个其他限制符（*, +, ?, {n},{n,}, {n,m}） 后面时，匹配模式是非贪婪的。非贪婪模式尽可能少的匹配所搜索的字符串，而默认的贪婪模式则尽可能多的匹配所搜索的字符串。例如，对于字符串 “oooo”，’o+?’ 将匹配单个”o”，而 ‘o+’ 将匹配所有 ‘o’</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span></td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span></td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span></td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span></td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> .</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配除换行符（’\n’）之外的任意单个字符（注意：awk 指令中的句点能匹配换行符）</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> .</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> .（如果要匹配包括“\n”在内的任何一个字符，请使用: [\s\S]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> .</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> .（如果要匹配包括“\n”在内的任何一个字符，请使用：’ [.\n] ‘</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> *</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配前面的子表达式 0 次或多次（等价于{0, }），例如：zo* 能匹配 “z”以及 “zoo”</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> *</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> *</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> *</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> *</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> +</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配前面的子表达式 1 次或多次（等价于’{1, }‘），例如：’whereis+ ‘能匹配 “whereis”以及”whereisis”</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> +</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span>（同+)</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span>（同+)</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span>（同+)</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> +</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配前面的子表达式 1 次或多次（等价于{1, }），例如：zo+能匹配 “zo”以及 “zoo”，但不能匹配 “z”</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span>（同\+)</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> +</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> +</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> +</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> {n}</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> n 必须是一个 0 或者正整数，匹配子表达式 n 次，例如：zo{2}能匹配</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span>（同\{n\})</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> {n}</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> {n}</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> {n}</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> {n,}</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> “zooz”，但不能匹配 “Bob”n 必须是一个 0 或者正整数，匹配子表达式大于等于 n次，例如：go{2,}</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span>（同\{n,\})</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> {n,}</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> {n,}</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> {n,}</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> {n,m}</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 能匹配 “good”，但不能匹配 godm 和 n 均为非负整数，其中 n &lt;= m，最少匹配 n 次且最多匹配 m 次 ，例如：o{1,3}将配”fooooood” 中的前三个 o（请注意在逗号和两个数之间不能有空格）</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span>（同\{n,m\})</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> {n,m}</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> {n,m}</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> {n,m}</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> x l y</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配 x 或 y</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span>（同x \l y</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> x l y</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> x l y</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> x l y</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [0-9]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配从 0 到 9 中的任意一个数字字符（注意：要写成递增）</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [0-9]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [0-9]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [0-9]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [0-9]</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [xyz]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 字符集合，匹配所包含的任意一个字符，例如：’[abc]’可以匹配”lay” 中的 ‘a’（注意：如果元字符，例如：. *等，它们被放在[ ]中，那么它们将变成一个普通字符）</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [xyz]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [xyz]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [xyz]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [xyz]</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [^xyz]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 负值字符集合，匹配未包含的任意一个字符（注意：不包括换行符），例如：’[^abc]’ 可以匹配 “Lay” 中的’L’（注意：[^xyz]在awk 指令中则是匹配未包含的任意一个字符+换行符）</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [^xyz]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [^xyz]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [^xyz]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [^xyz]</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [A-Za-z]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配大写字母或者小写字母中的任意一个字符（注意：要写成递增）</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [A-Za-z]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [A-Za-z]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [A-Za-z]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [A-Za-z]</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [^A-Za-z]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配除了大写与小写字母之外的任意一个字符（注意：写成递增）</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [^A-Za-z]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [^A-Za-z]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [^A-Za-z]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [^A-Za-z]</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \d</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配从 0 到 9 中的任意一个数字字符（等价于 [0-9]）</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span></td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span></td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \d</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \d</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \D</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配非数字字符（等价于 [^0-9]）</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span></td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span></td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \D</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \D</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \S</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配任何非空白字符（等价于[^\f\n\r\t\v]）</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span></td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span></td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \S</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \S</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \s</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配任何空白字符，包括空格、制表符、换页符等等（等价于[ \f\n\r\t\v]）</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span></td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span></td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \s</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \s</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \W</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配任何非单词字符 (等价于[^A-Za-z0-9_])</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \W</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \W</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \W</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \W</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \w</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配包括下划线的任何单词字符（等价于[A-Za-z0-9_]）</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \w</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \w</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \w</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \w</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \B</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配非单词边界，例如：’er\B’ 能匹配 “verb” 中的’er’，但不能匹配”never” 中的’er’</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \B</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \B</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \B</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \B</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \b</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配一个单词边界，也就是指单词和空格间的位置，例如： ‘er\b’ 可以匹配”never” 中的 ‘er’，但不能匹配 “verb” 中的’er’</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \b</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \b</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \b</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \b</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \t</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配一个横向制表符（等价于 \x09和 \cI）</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span></td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span></td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \t</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \t</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \v</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配一个垂直制表符（等价于 \x0b和 \cK）</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span></td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span></td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \v</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \v</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \n</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配一个换行符（等价于 \x0a 和\cJ）</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span></td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span></td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \n</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \n</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \f</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配一个换页符（等价于\x0c 和\cL）</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span></td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span></td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \f</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \f</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \r</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配一个回车符（等价于 \x0d 和\cM）</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span></td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span></td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \r</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \r</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配转义字符本身”\”</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \cx</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配由 x 指明的控制字符，例如：\cM匹配一个Control-M 或回车符，x 的值必须为A-Z 或 a-z 之一，否则，将 c 视为一个原义的 ‘c’ 字符</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span></td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span></td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> &nbsp;</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \cx</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \xn</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配 n，其中 n 为十六进制转义值。十六进制转义值必须为确定的两个数字长，例如：’\x41’ 匹配 “A”。’\x041’ 则等价于’\x04’ &amp; “1”。正则表达式中可以使用 ASCII 编码</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span></td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span></td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> &nbsp;</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \xn</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \num</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配 num，其中 num是一个正整数。表示对所获取的匹配的引用</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:700; font-style:inherit; font-family:inherit; vertical-align:baseline">不支持</span></td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \num</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> \num</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> &nbsp;</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:alnum:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配任何一个字母或数字（[A-Za-z0-9]），例如：’[[:alnum:]] ‘</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:alnum:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:alnum:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:alnum:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:alnum:]</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:alpha:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配任何一个字母（[A－Za－z]）， 例如：’ [[:alpha:]] ‘</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:alpha:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:alpha:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:alpha:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:alpha:]</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:digit:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配任何一个数字（[0-9]），例如：’[[:digit:]] ‘</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:digit:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:digit:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:digit:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:digit:]</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:lower:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配任何一个小写字母（[a-z]）， 例如：’ [[:lower:]] ‘</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:lower:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:lower:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:lower:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:lower:]</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:upper:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 匹配任何一个大写字母（[A-Z]）</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:upper:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:upper:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:upper:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:upper:]</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:space:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 任何一个空白字符： 支持制表符、空格，例如：’ [[:space:]] ‘</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:space:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:space:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:space:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:space:]</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:blank:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 空格和制表符（横向和纵向），例如：’[[:blank:]]’ó’[\s\t\v]’</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:blank:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:blank:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:blank:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:blank:]</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:graph:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 任何一个可以看得见的且可以打印的字符（注意：不包括空格和换行符等），例如：’[[:graph:]] ‘</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:graph:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:graph:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:graph:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:graph:]</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:print:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 任何一个可以打印的字符（注意：不包括：[:cntrl:]、字符串结束符’\0’、EOF 文件结束符（-1）， 但包括空格符号），例如：’[[:print:]] ‘</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:print:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:print:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:print:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:print:]</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:cntrl:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 任何一个控制字符（ASCII 字符集中的前 32 个字符，即：用十进制表示为从 0 到31，例如：换行符、制表符等等），例如：’ [[:cntrl:]]’</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:cntrl:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:cntrl:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:cntrl:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:cntrl:]</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:punct:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 任何一个标点符号（不包括：[:alnum:]、[:cntrl:]、[:space:]这些字符集）</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:punct:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:punct:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:punct:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:punct:]</td> 
  </tr> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:xdigit:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> 任何一个十六进制数（即：0-9，a-f，A-F）</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:xdigit:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:xdigit:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:xdigit:]</td> 
   <td style="margin:0px; padding:0px 10px; border:1px solid rgb(222,222,222); outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> [:xdigit:]</td> 
  </tr> 
 </tbody> 
</table>

注意

*  js中支持的是EREs.
 *  当使用 BREs ( 基本正则表达式 ) 时，必须在下列这些符号(?,+,|,\{,\},(,))前加上转义字符 \\ .
 *  上述\[\[:xxxx:\]\] 形式的正则表达式, 是php中内置的通用字符簇, js中并不支持.

### linux/osx下常用命令与正则表达式的关系 ###

我曾经尝试在 grep 和 sed 命令中书写正则表达式, 经常发现不能使用元字符, 而且有时候需要转义, 有时候不需要转义, 始终不能摸清它的规律. 如果恰好你也有同样的困惑, 那么请往下看, 相信应该能有所收获.

#### grep , egrep , sed , awk 正则表达式特点 ####

1.  grep 支持：BREs、EREs、PREs 正则表达式
    
    grep 指令后不跟任何参数, 则表示要使用 “BREs”
    
    grep 指令后跟 ”-E” 参数, 则表示要使用 “EREs”
    
    grep 指令后跟 “-P” 参数, 则表示要使用 “PREs”
2.  egrep 支持：EREs、PREs 正则表达式
    
    egrep 指令后不跟任何参数, 则表示要使用 “EREs”
    
    egrep 指令后跟 “-P” 参数, 则表示要使用 “PREs”
3.  sed 支持: BREs、EREs
    
    sed 指令默认是使用 “BREs”
    
    sed 指令后跟 “-r” 参数 , 则表示要使用“EREs”
4.  awk 支持 EREs, 并且默认使用 “EREs”

### 正则表达式初阶技能 ###

#### 贪婪模式与非贪婪模式 ####

默认情况下, 所有的限定词都是贪婪模式, 表示尽可能多的去捕获字符; 而在限定词后增加?, 则是非贪婪模式, 表示尽可能少的去捕获字符. 如下:

实际上, 非贪婪模式非常有效, 特别是当匹配html标签时. 比如匹配一个配对出现的div, 方案一可能会匹配到很多的div标签对, 而方案二则只会匹配一个div标签对.

##### 区间量词的非贪婪模式 #####

一般情况下, 非贪婪模式, 我们使用的是”\*?”, 或 “+?” 这种形式, 还有一种是 “\{n,m\}?”.

区间量词”\{n,m\}” 也是匹配优先, 虽有匹配次数上限, 但是在到达上限之前, 它依然是尽可能多的匹配, 而”\{n,m\}?” 则表示在区间范围内, 尽可能少的匹配.

需要注意的是:

*  能达到同样匹配结果的贪婪与非贪婪模式, 通常是贪婪模式的匹配效率较高.
 *  所有的非贪婪模式, 都可以通过修改量词修饰的子表达式, 转换为贪婪模式.
 *  贪婪模式可以与`固化分组`(后面会讲到)结合，提升匹配效率，而非贪婪模式却不可以.

#### 分组 ####

正则的分组主要通过小括号来实现, 括号包裹的子表达式作为一个分组, 括号后可以紧跟限定词表示重复次数. 如下, 小括号内包裹的abc便是一个分组:

那么分组有什么用呢? 一般来说, 分组是为了方便的表示重复次数, 除此之外, 还有一个作用就是用于捕获, 请往下看.

#### 捕获性分组 ####

捕获性分组, 通常由一对小括号加上子表达式组成. 捕获性分组会创建反向引用, 每个反向引用都由一个编号或名称来标识, js中主要是通过 `$+编号` 或者 `\+编号` 表示法进行引用. 如下便是一个捕获性分组的例子.

以上, (\\d+) 表示一个捕获性分组, `RegExp.$1` 指向该分组捕获的内容. `$+编号` 这种引用通常在正则表达式之外使用. `\+编号` 这种引用却可以在正则表达式中使用, 可用于匹配不同位置相同部分的子串.

以上, 相同部分的”google”字符串只被替换一次.

#### 非捕获性分组 ####

非捕获性分组, 通常由一对括号加上”?:”加上子表达式组成, 非捕获性分组不会创建反向引用, 就好像没有括号一样. 如下:

以上, (?:\\d+) 表示一个非捕获性分组, 由于分组不捕获任何内容, 所以, `RegExp.$1` 就指向了空字符串.

同时, 由于`$1` 的反向引用不存在, 因此最终它被当成了普通字符串进行替换.

实际上, 捕获性分组和无捕获性分组在搜索效率方面也没什么不同, 没有哪一个比另一个更快.

#### 命名分组 ####

语法: (?…)

命名分组也是捕获性分组, 它将匹配的字符串捕获到一个组名称或编号名称中, 在获得匹配结果后, 可通过分组名进行获取. 如下是一个python的命名分组的例子.

python的命名分组表达式与标准格式相比, 在 ? 后多了一大写的 P 字符, 并且python通过“\\g<命名>”表示法进行引用. (如果是捕获性分组, python通过”\\g<编号>”表示法进行引用)

与python不同的是, javaScript 中并不支持命名分组.

#### 固化分组 ####

固化分组, 又叫原子组.

语法: (?>…)

如上所述, 我们在使用非贪婪模式时, 匹配过程中可能会进行多次的回溯, 回溯越多, 正则表达式的运行效率就越低. 而固化分组就是用来减少回溯次数的.

实际上, 固化分组(?>…)的匹配与正常的匹配并无分别, 它并不会改变匹配结果. 唯一的不同就是: 固化分组匹配结束时, 它匹配到的文本已经固化为一个单元, 只能作为整体而保留或放弃, 括号内的子表达式中未尝试过的备用状态都会被放弃, 所以回溯永远也不能选择其中的状态(因此不能参与回溯). 下面我们来通过一个例子更好地理解固化分组.

假如要处理一批数据, 原格式为 123.456, 因为浮点数显示问题, 部分数据格式会变为123.456000000789这种, 现要求只保留小数点后2~3位, 但是最后一位不能为0, 那么这个正则怎么写呢?

以上的正则, 对于”123.456” 这种格式的数据, 将白白处理一遍. 为了提高效率, 我们将正则最后的一个”\*”改为”+”. 如下:

此时, “\\d\\d\[1-9\]?” 子表达式, 匹配是 “45”, 而不是 “456”, 这是因为正则末尾使用了”+”, 表示末尾至少要匹配一个数字, 因此末尾的子表达式”\\d+” 匹配到了 “6”. 显然 “123.45” 不是我们期望的匹配结果, 那我们应该怎么做呢? 能否让 “\[1-9\]?” 一旦匹配成功, 便不再进行回溯, 这里就要用到我们上面说的固化分组.

“(\\.\\d\\d(?>\[1-9\]?))\\d+” 便是上述正则的固化分组形式. 由于字符串 “123.456” 不满足该固化分组的正则, 所以, 匹配会失败, 符合我们期望.

下面我们来分析下固化分组的正则 (\\.\\d\\d(?>\[1-9\]?))\\d+ 为什么匹配不到字符串”123.456”.

很明显, 对于上述固化分组, 只存在两种匹配结果.

情况①: 若 \[1-9\] 匹配失败, 正则会返回 ? 留下的备用状态. 然后匹配脱离固化分组, 继续前进到\[\\d+\]. 当控制权离开固化分组时, 没有备用状态需要放弃(因固化分组中根本没有创建任何备用状态).

情况②: 若 \[1-9\] 匹配成功, 匹配脱离固化分组之后, ? 保存的备用状态仍然存在, 但是, 由于它属于已经结束的固化分组, 所以会被抛弃.

对于字符串 “123.456”, 由于 \[1-9\] 能够匹配成功, 所以它符合情况②. 下面我们来还原情况②的执行现场.

1.  匹配所处的状态: 匹配已经走到了 “6” 的位置, 匹配将继续前进;==>
2.  子表达式 \\d+ 发现无法匹配, 正则引擎便尝试回溯;==>
3.  查看是否存在备用状态以供回溯?==>
4.  “?” 保存的备用状态属于已经结束的固化分组, 所以该备用状态会被放弃;==>
5.  此时固化分组匹配到的 “6”, 便不能用于正则引擎的回溯;==>
6.  尝试回溯失败;==>
7.  正则匹配失败.==>
8.  文本 “123.456” 没有被正则表达式匹配上, 符合预期.

相应的流程图如下:

[![正则表达式流程图][regexp02.png]][regexp02.png]

遗憾的是, javaScript, java 和 python中并不支持固化分组的语法, 不过, 它在php和.NET中表现良好. 下面提供了一个php版的固化分组形式的正则表达式, 以供尝试.

不仅如此, php还提供了占有量词优先的语法. 如下:

虽然java不支持固化分组的语法, 但java也提供了占有量词优先的语法, 同样能够避免正则回溯. 如下:

值得注意的是: java中 replaceAll 方法需要转义反斜杠.

### 正则表达式高阶技能-零宽断言 ###

如果说正则分组是写轮眼, 那么零宽断言就是万花筒写轮眼终极奥义-须佐能乎(这里借火影忍术打个比方). 合理地使用零宽断言, 能够能分组之不能, 极大地增强正则匹配能力, 它甚至可以帮助你在匹配条件非常模糊的情况下快速地定位文本.

零宽断言, 又叫环视. 环视只进行子表达式的匹配, 匹配到的内容不保存到最终的匹配结果, 由于匹配是零宽度的, 故最终匹配到的只是一个位置.

环视按照方向划分, 有顺序和逆序两种(也叫前瞻和后瞻), 按照是否匹配有肯定和否定两种, 组合之, 便有4种环视. 4种环视并不复杂, 如下便是它们的描述.

非捕获性分组由于结构与环视相似, 故列在表中, 以做对比. 以上4种环视中, 目前 javaScript 中只支持前两种, 也就是只支持 顺序肯定环视 和 顺序否定环视. 下面我们通过实例来帮助理解下:

<table style="margin:0px; padding:0px; border:none; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; border-collapse:collapse; border-spacing:0px; width:auto"> 
 <tbody style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline"> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px; border:none; outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <pre style="margin-top:0px; margin-bottom:0px; padding:0px 20px 0px 0px; border:none; outline:0px; font-weight:inherit; font-style:inherit; font-family:&quot;Source Code Pro&quot;,Consolas,Monaco,Menlo,Consolas,monospace; font-size:10px; vertical-align:baseline; overflow:auto; background:rgb(60,60,60); color:rgb(102,102,102); line-height:22.4px; text-align:right">
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      1
     
      
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     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      2
     
      
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     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      3
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      4
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      5
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      6
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      7
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      8
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      9
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      10
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      11
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      12
     
      
     </div></pre> </td> 
   <td style="margin:0px; padding:0px; border:none; outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <pre style="margin-top:0px; margin-bottom:0px; padding:0px; border:none; outline:0px; font-weight:inherit; font-style:inherit; font-family:&quot;Source Code Pro&quot;,Consolas,Monaco,Menlo,Consolas,monospace; font-size:10px; vertical-align:baseline; overflow:auto; background:rgb(60,60,60); color:rgb(255,255,255); line-height:22.4px">
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(102,217,239)">var</span> str = 
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(230,219,116)">"123abc789"</span>,s;
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(117,113,94)">//没有使用环视,abc直接被替换</span>
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      s = str.replace(
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline">/abc/</span>,
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(113,99,215)">456</span>);
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(166,226,46)">console</span>.log(s); 
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(117,113,94)">//123456789</span>
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px"></div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(117,113,94)">//使用了顺序肯定环视,捕获到了a前面的位置,所以abc没有被替换,只是将3替换成了3456</span>
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      s = str.replace(
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline">/3(?=abc)/</span>,
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(113,99,215)">3456</span>);
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(166,226,46)">console</span>.log(s); 
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(117,113,94)">//123456abc789</span>
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px"></div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(117,113,94)">//使用了顺序否定环视,由于3后面跟着abc,不满意条件,故捕获失败,所以原字符串没有被替换</span>
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      s = str.replace(
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline">/3(?!abc)/</span>,
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(113,99,215)">3456</span>);
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(166,226,46)">console</span>.log(s); 
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(117,113,94)">//123abc789</span>
     
      
     </div></pre> </td> 
  </tr> 
 </tbody> 
</table>

下面通过python来演示下 逆序肯定环视 和 逆序否定环视 的用法.

<table style="margin:0px; padding:0px; border:none; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; border-collapse:collapse; border-spacing:0px; width:auto"> 
 <tbody style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline"> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px; border:none; outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <pre style="margin-top:0px; margin-bottom:0px; padding:0px 20px 0px 0px; border:none; outline:0px; font-weight:inherit; font-style:inherit; font-family:&quot;Source Code Pro&quot;,Consolas,Monaco,Menlo,Consolas,monospace; font-size:10px; vertical-align:baseline; overflow:auto; background:rgb(60,60,60); color:rgb(102,102,102); line-height:22.4px; text-align:right">
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      1
     
      
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     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      2
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      3
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      4
     
      
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     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      5
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      6
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      7
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      8
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      9
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      10
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      11
     
      
     </div></pre> </td> 
   <td style="margin:0px; padding:0px; border:none; outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <pre style="margin-top:0px; margin-bottom:0px; padding:0px; border:none; outline:0px; font-weight:inherit; font-style:inherit; font-family:&quot;Source Code Pro&quot;,Consolas,Monaco,Menlo,Consolas,monospace; font-size:10px; vertical-align:baseline; overflow:auto; background:rgb(60,60,60); color:rgb(255,255,255); line-height:22.4px">
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(102,217,239)">import</span> re
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      data = 
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(230,219,116)">"123abc789"</span>
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(117,113,94)"># 使用了逆序肯定环视,替换左边为123的连续的小写英文字母,匹配成功,故abc被替换为456</span>
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      regExp = 
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(230,219,116)">r"(?&lt;=123)[a-z]+"</span>
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      replaceString = 
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(230,219,116)">"456"</span>
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(102,217,239)">print</span> re.sub(regExp,replaceString,data) 
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(117,113,94)"># 123456789</span>
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px"></div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(117,113,94)"># 使用了逆序否定环视,由于英文字母左侧不能为123,故子表达式[a-z]+捕获到bc,最终bc被替换为456</span>
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      regExp = 
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(230,219,116)">r"(?&lt;!123)[a-z]+"</span>
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      replaceString = 
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(230,219,116)">"456"</span>
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(102,217,239)">print</span> re.sub(regExp,replaceString,data) 
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(117,113,94)"># 123a456789</span>
     
      
     </div></pre> </td> 
  </tr> 
 </tbody> 
</table>

需要注意的是: python 和 perl 语言中的 逆序环视 的子表达式只能使用定长的文本. 比如将上述 “(?<=123)” (逆序肯定环视)子表达式写成 “(?<=\[0-9\]+)”, python解释器将会报错: “error: look-behind requires fixed-width pattern”.

#### 场景回顾 ####

##### 获取html片段 #####

假如现在, js 通过 ajax 获取到一段 html 代码如下:

现我们需要替换img标签的src 属性中的 “dev”字符串 为 “test” 字符串.

① 由于上述 responseText 字符串中包含至少两个子字符串 “dev”, 显然不能直接 replace 字符串 “dev”为 “test”.

② 同时由于 js 中不支持逆序环视, 我们也不能在正则中判断前缀为 “src=’”, 然后再替换”dev”.

③ 我们注意到 img 标签的 src 属性以 “.png” 结尾, 基于此, 就可以使用顺序肯定环视. 如下:

当然, 以上不止顺序肯定环视一种解法, 捕获性分组同样可以做到. 那么环视高级在哪里呢? 环视高级的地方就在于它通过一次捕获就可以定位到一个位置, 对于复杂的文本替换场景, 常有奇效, 而分组则需要更多的操作. 请往下看.

##### 千位分割符 #####

> 千位分隔符, 顾名思义, 就是数字中的逗号. 参考西方的习惯, 数字之中加入一个符号, 避免因数字太长难以直观的看出它的值. 故而数字之中, 每隔三位添加一个逗号, 即千位分隔符.

那么怎么将一串数字转化为千位分隔符形式呢?

如上, `toLocaleString()` 返回当前对象的”本地化”字符串形式.

*  如果该对象是Number类型, 那么将返回该数值的按照特定符号分割的字符串形式.
 *  如果该对象是Array类型, 那么先将数组中的每项转化为字符串, 然后将这些字符串以指定分隔符连接起来并返回.

`toLocaleString` 方法特殊, 有本地化特性, 对于天朝, 默认的分隔符是英文逗号. 因此使用它恰好可以将数值转化为千位分隔符形式的字符串. 如果考虑到国际化, 以上方法就有可能会失效了.

我们尝试使用环视来处理下.

上述使用到的正则分为两块. `(?!^)` 和 `(?=([0-9]{3})+$)`. 我们先来看后面的部分, 然后逐步分析之.

1.  “\[0-9\]\{3\}” 表示连续3位数字.
2.  “(\[0-9\]\{3\})+” 表示连续3位数字至少出现一次或更多次.
3.  “(\[0-9\]\{3\})+$” 表示连续3的正整数倍的数字, 直到字符串末尾.
4.  那么 `(?=([0-9]{3})+$)` 就表示匹配一个零宽度的位置, 并且从这个位置到字符串末尾, 中间拥有3的正整数倍的数字.
5.  正则表达式使用全局匹配g, 表示匹配到一个位置后, 它会继续匹配, 直至匹配不到.
6.  将这个位置替换为逗号, 实际上就是每3位数字添加一个逗号.
7.  当然对于字符串”123456”这种刚好拥有3的正整数倍的数字的, 当然不能在1前面添加逗号. 那么使用 `(?!^)` 就指定了这个替换的位置不能为起始位置.

千位分隔符实例, 展示了环视的强大, 一步到位.

### 正则表达式在JS中的应用 ###

#### ES6对正则的扩展 ####

ES6对正则扩展了又两种修饰符(其他语言可能不支持):

*  y (粘连sticky修饰符), 与g类似, 也是全局匹配, 并且下一次匹配都是从上一次匹配成功的下一个位置开始, 不同之处在于, g修饰符只要剩余位置中存在匹配即可, 而y修饰符确保匹配必须从剩余的第一个位置开始.

<table style="margin:0px; padding:0px; border:none; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; border-collapse:collapse; border-spacing:0px; width:auto"> 
 <tbody style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline"> 
  <tr style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; height:35px"> 
   <td style="margin:0px; padding:0px; border:none; outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <pre style="margin-top:0px; margin-bottom:0px; padding:0px 20px 0px 0px; border:none; outline:0px; font-weight:inherit; font-style:inherit; font-family:&quot;Source Code Pro&quot;,Consolas,Monaco,Menlo,Consolas,monospace; font-size:10px; vertical-align:baseline; overflow:auto; background:rgb(60,60,60); color:rgb(102,102,102); line-height:22.4px; text-align:right">
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      1
     
      
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      3
     
      
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      4
     
      
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      5
     
      
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      6
     
      
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      7
     
      
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     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      8
     
      
     </div></pre> </td> 
   <td style="margin:0px; padding:0px; border:none; outline:0px; font-style:inherit; font-family:inherit; font-size:16px; vertical-align:middle; height:35px"> <pre style="margin-top:0px; margin-bottom:0px; padding:0px; border:none; outline:0px; font-weight:inherit; font-style:inherit; font-family:&quot;Source Code Pro&quot;,Consolas,Monaco,Menlo,Consolas,monospace; font-size:10px; vertical-align:baseline; overflow:auto; background:rgb(60,60,60); color:rgb(255,255,255); line-height:22.4px">
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(102,217,239)">var</span> s = 
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(230,219,116)">"abc_ab_a"</span>;
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(102,217,239)">var</span> r1 = 
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline">/[a-z]+/g</span>;
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(102,217,239)">var</span> r2 = 
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline">/[a-z]+/y</span>;
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(166,226,46)">console</span>.log(r1.exec(s),r1.lastIndex); 
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(117,113,94)">// ["abc", index: 0, input: "abc_ab_a"] 3</span>
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(166,226,46)">console</span>.log(r2.exec(s),r2.lastIndex); 
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(117,113,94)">// ["abc", index: 0, input: "abc_ab_a"] 3</span>
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px"></div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(166,226,46)">console</span>.log(r1.exec(s),r1.lastIndex); 
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(117,113,94)">// ["ab", index: 4, input: "abc_ab_a"] 6</span>
     
      
     </div>
     
      
     <div style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; font-size:15px; vertical-align:baseline; height:15px">
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(166,226,46)">console</span>.log(r2.exec(s),r2.lastIndex); 
      
       
      <span style="margin:0px; padding:0px; border:0px; outline:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(117,113,94)">// null 0</span>
     
      
     </div></pre> </td> 
  </tr> 
 </tbody> 
</table>

如上, 由于第二次匹配的开始位置是下标3, 对应的字符串是 “\_”, 而使用y修饰符的正则对象r2, 需要从剩余的第一个位置开始, 所以匹配失败, 返回null.

正则对象的 sticky 属性, 表示是否设置了y修饰符. 这点将会在后面讲到.

*  u 修饰符, 提供了对正则表达式添加4字节码点的支持. 比如 “

[Link 1]: http://louiszhai.github.io/2016/06/13/regexp/#导读
[Link 2]: http://louiszhai.github.io/2016/06/13/regexp/#回顾历史
[Link 3]: http://louiszhai.github.io/2016/06/13/regexp/#正则表达式的定义
[Link 4]: http://louiszhai.github.io/2016/06/13/regexp/#元字符
[Link 5]: http://louiszhai.github.io/2016/06/13/regexp/#反义元字符
[Link 6]: http://louiszhai.github.io/2016/06/13/regexp/#重复限定符
[Link 7]: http://louiszhai.github.io/2016/06/13/regexp/#字符组
[Link 8]: http://louiszhai.github.io/2016/06/13/regexp/#排除性字符组
[Link 9]: http://louiszhai.github.io/2016/06/13/regexp/#多选结构
[Link 10]: http://louiszhai.github.io/2016/06/13/regexp/#括号
[Link 11]: http://louiszhai.github.io/2016/06/13/regexp/#转义字符
[Link 12]: http://louiszhai.github.io/2016/06/13/regexp/#操作符的运算优先级
[Link 13]: http://louiszhai.github.io/2016/06/13/regexp/#测试
[Link 14]: http://louiszhai.github.io/2016/06/13/regexp/#修饰符
[Link 15]: http://louiszhai.github.io/2016/06/13/regexp/#常用的正则表达式
[Link 16]: http://louiszhai.github.io/2016/06/13/regexp/#密码验证
[Link 17]: http://louiszhai.github.io/2016/06/13/regexp/#正则的几大家族
[Link 18]: http://louiszhai.github.io/2016/06/13/regexp/#正则表达式分类
[Link 19]: http://louiszhai.github.io/2016/06/13/regexp/#正则表达式比较
[linux_osx]: http://louiszhai.github.io/2016/06/13/regexp/#linux-osx下常用命令与正则表达式的关系
[grep _ egrep _ sed _ awk]: http://louiszhai.github.io/2016/06/13/regexp/#grep-egrep-sed-awk-正则表达式特点
[Link 20]: http://louiszhai.github.io/2016/06/13/regexp/#正则表达式初阶技能
[Link 21]: http://louiszhai.github.io/2016/06/13/regexp/#贪婪模式与非贪婪模式
[Link 22]: http://louiszhai.github.io/2016/06/13/regexp/#区间量词的非贪婪模式
[Link 23]: http://louiszhai.github.io/2016/06/13/regexp/#分组
[Link 24]: http://louiszhai.github.io/2016/06/13/regexp/#捕获性分组
[Link 25]: http://louiszhai.github.io/2016/06/13/regexp/#非捕获性分组
[Link 26]: http://louiszhai.github.io/2016/06/13/regexp/#命名分组
[Link 27]: http://louiszhai.github.io/2016/06/13/regexp/#固化分组
[-]: http://louiszhai.github.io/2016/06/13/regexp/#正则表达式高阶技能-零宽断言
[Link 28]: http://louiszhai.github.io/2016/06/13/regexp/#场景回顾
[html]: http://louiszhai.github.io/2016/06/13/regexp/#获取html片段
[Link 29]: http://louiszhai.github.io/2016/06/13/regexp/#千位分割符
[JS]: http://louiszhai.github.io/2016/06/13/regexp/#正则表达式在JS中的应用
[ES6]: http://louiszhai.github.io/2016/06/13/regexp/#ES6对正则的扩展
[UCS-2]: http://louiszhai.github.io/2016/06/13/regexp/#UCS-2字节码
[ES6_4]: http://louiszhai.github.io/2016/06/13/regexp/#附-ES6新增的处理4字节码的函数
[RegExp]: http://louiszhai.github.io/2016/06/13/regexp/#RegExp
[compile]: http://louiszhai.github.io/2016/06/13/regexp/#compile
[test]: http://louiszhai.github.io/2016/06/13/regexp/#test
[exec]: http://louiszhai.github.io/2016/06/13/regexp/#exec
[String]: http://louiszhai.github.io/2016/06/13/regexp/#String
[H5]: http://louiszhai.github.io/2016/06/13/regexp/#正则表达式在H5中的应用
[Link 30]: http://louiszhai.github.io/2016/06/13/regexp/#正则引擎
[Link 31]: http://louiszhai.github.io/2016/06/13/regexp/#总结
[Link 32]: http://louiszhai.github.io/2016/06/13/regexp/#respond
[regexp01.png]: /images/20220708/62190548d155445684ea47c26ded9190.png
[regexp02.png]: /images/20220708/46c7700322654fafabb580d98a4ccdea.png