LINUX学习之正则表达式(十二)

淡淡的烟草味﹌ 2023-09-24 16:21 33阅读 0赞

## 普通正则 ##

### 元字符 ###

<table> 
 <thead> 
  <tr> 
   <th>元字符</th> 
   <th>匹配描述</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td><code>.</code></td> 
   <td>匹配除了换行符以外的任意单个字符</td> 
  </tr> 
  <tr> 
   <td><code>*</code></td> 
   <td>前导字符出现0次或连续多次</td> 
  </tr> 
  <tr> 
   <td><code>.*</code></td> 
   <td>任意长度字符</td> 
  </tr> 
  <tr> 
   <td><code>^</code></td> 
   <td>行首(以…开头)</td> 
  </tr> 
  <tr> 
   <td><code>$</code></td> 
   <td>行尾(以…结尾)</td> 
  </tr> 
  <tr> 
   <td><code>^$</code></td> 
   <td>空行</td> 
  </tr> 
  <tr> 
   <td><code>[]</code></td> 
   <td>匹配括号里任意单个字符或一组单个字符</td> 
  </tr> 
  <tr> 
   <td><code>[^]</code></td> 
   <td>匹配不包含括号里任一单个字符或一组单个字符</td> 
  </tr> 
  <tr> 
   <td><code>^[]</code></td> 
   <td>匹配以括号里任意单个字符或一组单个字符开头</td> 
  </tr> 
  <tr> 
   <td><code>^[^]</code></td> 
   <td>匹配非括号里任意单个字符或一组单个字符开头</td> 
  </tr> 
  <tr> 
   <td><code>&lt;</code></td> 
   <td>取单词的头</td> 
  </tr> 
  <tr> 
   <td><code>&gt;</code></td> 
   <td>取单词的尾</td> 
  </tr> 
  <tr> 
   <td><code>&lt; &gt;</code></td> 
   <td>精确匹配</td> 
  </tr> 
 </tbody> 
</table>

### 实例演示 ###

创建test.txt文件用于正则匹配操作, 文件内容如下:

ggle
    gogle
    google
    gooogle
    goooooogle
    gooooooogle
    taobao.com
    taotaobaobao.com
    
    jingdong.com
    dingdingdongdong.com
    10.1.1.1
    Adfjd8789JHfdsdf/
    a87fdjfkdLKJK
    7kdjfd989KJK;
    bSKJjkksdjf878.
    cidufKJHJ6576,
    
    hello world
    helloworld yourself

\*\*1.匹配包含'go'的字符串: \`grep 'go' test.txt\`\*\*

![image-20221018232926698][]

\*\*2.匹配以'g'开头的字符串: \`grep '^g' test.txt\`\*\*

![image-20221018233400385][]

\*\*3.匹配以'g'开头,后接一个任意字符的字符串:\`grep '^g.' test.txt\`\*\*

![image-20221020102121356][]

\*\*4.匹配以'g'开头,后接多个任意字符的字符串: \`grep '^g.\*' test.txt\`\*\*

![image-20221020102435071][]

\*\*5.匹配所有字符: \`grep '.\*' test.txt\`\*\*

![image-20221020102645393][]

\*\*6.匹配以'gle'结尾的字符串: \`grep 'gle$' test.txt\`\*\*

![image-20221020102939310][]

**7.匹配以’gle’结尾的所有字符串: `grep '.*gle$' test.txt`**

![image-20221020103415245][]

\*\*8.匹配以字符'a','b','c'开头的字符串: \`grep '^\[abc\]' test.txt\` \*\*

![image-20221020103755646][]

\*\*9.匹配非字符'a','b','c'开头的字符串: \`grep '^\[^abc\]' test.txt\`\*\*

![image-20221020104042127][]

\*\*10.匹配含有字符'a','b','c'的字符串: \`grep '\[abc\]' test.txt\`\*\*

![image-20221020104625050][]

## 扩展正则 ##

### 扩展元字符 ###

<table> 
 <thead> 
  <tr> 
   <th>扩展元字符(需用<code>grep -E</code>或<code>egrep</code>)</th> 
   <th>功能</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>+</td> 
   <td>匹配一个或多个前导字符</td> 
  </tr> 
  <tr> 
   <td>?</td> 
   <td>匹配零个或一个前导字符</td> 
  </tr> 
  <tr> 
   <td>|</td> 
   <td>或</td> 
  </tr> 
  <tr> 
   <td>()</td> 
   <td>将字符组合成一个整体</td> 
  </tr> 
  <tr> 
   <td>{n}</td> 
   <td>前导字符重复n次</td> 
  </tr> 
  <tr> 
   <td>{n,}</td> 
   <td>前导字符重复至少n次</td> 
  </tr> 
  <tr> 
   <td>{n,m}</td> 
   <td>前导字符重复n到m次</td> 
  </tr> 
 </tbody> 
</table>

<table> 
 <thead> 
  <tr> 
   <th>扩展元字符(需用<code>grep -P</code>)</th> 
   <th>功能</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>\d</td> 
   <td>匹配数字, 等价于<code>[0-9]</code></td> 
  </tr> 
  <tr> 
   <td>\w</td> 
   <td>匹配字母数字下划线, 等价于<code>[a-zA-Z0-9_]</code></td> 
  </tr> 
  <tr> 
   <td>\s</td> 
   <td>匹配空格、制表符、换页符, 等价于<code>[\t\r\n]</code></td> 
  </tr> 
 </tbody> 
</table>

### 实例演示 ###

**1.`grep -E 'o+gle' test.txt`**

![image-20221020141052127][]

\*\*2. \`grep -E 'o?gle' test.txt\`\*\*

![image-20221020141520613][]

\*\*3.匹配前导字符‘o’至少出现两次的字符串: \`grep -E 'go\{2,\}' test.txt\` \*\*

![image-20221020141809380][]

\*\*4.匹配前导字符'tao'至少出现两次的字符串: \`grep -E '(tao)\{2,\}' test.txt\`\*\*

![image-20221020142042456][]

\*\*5.匹配包含'hello'或'jingdong'的字符串:\`grep -E '(hello|jingdong)' test.txt\`\*\*

![image-20221020142345370][]

\*\*6.匹配IP格式的字符串: \`grep -E '\[0-9\]\{1,3\}\\.\[0-9\]\{1,3\}\\.\[0-9\]\{1,3\}.\[0-9\]\{1,3\}' test.txt\` 或 \`grep -P '(\\d)\{1,3\}\\.(\\d)\{1,3\}\\.(\\d)\{1,3\}.(\\d)\{1,3\}' test.txt\`\*\*

> 此处要注意对特殊字符的转义, 例如这里就对`.`使用了转义符号

![image-20221020144411057][]

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