1、正则表达式概述
正则表达式就是处理字符串的方法，它以行为单位来进行字符串的处理操作，正则表达式通过一些特殊字符的辅助，可以让用户轻易的完成查找、删除、替换某些特定字符串的处理过程
2、常用特殊符号
| 特殊字符 | 含义 |
|---|---|
| ^word | 指定字符开头 |
| word$ | 指定字符结尾 |
| . | 一个任意字符 |
| * | 零到多个*前面的字符 |
| [list] | 包含集合里面的任意字符 |
| [n1 - n2] | 包含n1到n2之间任意字符 |
| [^list] | 不包含集合中的字符 |
| \{n,m\} | 连续 n 到 m 个前面的字符 |
| [:alnum:] | 大小写字符及数字，即 0-9、 A-Z、a-z |
| [:alpha:] | 大小写字母，即 A-Z、 a-z |
| [:blank:] | 空格键与【TAB】键 |
| [:cntrl:] | 键盘上的控制按键，包括 CR、LF、Tab、Del等 |
| [:digit:] | 数字，即 0 - 9 |
| [:graph:] | 除了空格符（空格键与【TAB】键）以外的所有按键 |
| [:lower:] | 所有小写字母，即 a-z |
| [:print:] | 任何可以被打印出来的字符 |
| [:punct:] | 标点符号，即：" ' ? ! ; : # $等 |
| [:upper:] | 大写字母，即 A-Z |
| [:space:] | 空白字符，包括空白鍵、[Tab]、 CR 等 |
| [:xdigit:] | 十六进制字符，包括： 0-9、A-F、 a-f |
3、grep
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作用
根据模式搜索文本，并将包含关键字的行显示出来
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语法
grep [选项] 文件
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常用选项
-a：将二进制文件以文本的方式查找数据
-c：统计 '查找字符' 的数量
-E：扩展正则表达式
-i：忽略大小写
-n：显示行号
-v：显示不包含关键字的行
--color=auto：加亮显示 -
示例用文本
1 "Open Source" is a good mechanism to develop programs. 2 apple is my favorite food. 3 Football game is not use feet only. 4 this dress doesn't fit me. 5 However, this dress is about $ 3183 dollars.^M 6 GNU is free air not free beer.^M 7 Her hair is very beauty.^M 8 I can't finish the test.^M 9 Oh! The soup taste good.^M 10 motorcycle is cheap than car. 11 This window is clear. 12 the symbol '*' is represented as start. 13 Oh!^IMy god! 14 The gd software is a library for drafting programs.^M 15 You are the best is mean you are the no. 1. 16 The world <Happy> is the same with "glad". 17 I like dog. 18 google is the best tools for search keyword. 19 goooooogle yes! 20 go! go! Let's go. 21 # I am VBird 22 -
使用示例
# 查找特定字符 [root@localhost ~]# grep -n 'the' test.txt 8:I can't finish the test. 12:the symbol '*' is represented as start. 15:You are the best is mean you are the no. 1. 16:The world <Happy> is the same with "glad". 18:google is the best tools for search keyword. # 查找不包含特定字符 [root@localhost ~]# grep -nv 'the' test.txt # 查找包含[]中任意字符 ## 在[]中只需要匹配到任意一个即可 [root@localhost ~]# grep -n 't[ae]st' test.txt 8:I can't finish the test. 9:Oh! The soup taste good. # 排除以特定符号开头的字符 [root@localhost ~]# grep -n '[^t]oo' test.txt 1:"Open Source" is a good mechanism to develop programs. 2:apple is my favorite food. 3:Football game is not use feet only. 9:Oh! The soup taste good. 18:google is the best tools for search keyword. 19:goooooogle yes! # 查找包含数字的行 [root@localhost ~]# grep -n [0-9] test.txt [root@localhost ~]# grep -n [[:digit:]] test.txt 5:However, this dress is about $ 3183 dollars. 15:You are the best is mean you are the no. 1. # 查找特定字符开头的行（小写字母开头） [root@localhost ~]# grep -n ^[a-z] test.txt [root@localhost ~]# grep -n ^[[:lower:]] test.txt 2:apple is my favorite food. 4:this dress doesn't fit me. 10:motorcycle is cheap than car. 12:the symbol '*' is represented as start. 18:google is the best tools for search keyword. 19:goooooogle yes! 20:go! go! Let's go. # 查找特定字符结尾的行 [root@localhost ~]# grep -n '\.$' test.txt 1:"Open Source" is a good mechanism to develop programs. 2:apple is my favorite food. 3:Football game is not use feet only. 4:this dress doesn't fit me. 10:motorcycle is cheap than car. 11:This window is clear. 12:the symbol '*' is represented as start. 15:You are the best is mean you are the no. 1. 16:The world <Happy> is the same with "glad". 17:I like dog. 18:google is the best tools for search keyword. 20:go! go! Let's go. # 查找空白行 [root@localhost ~]# grep -n '^$' test.txt 22: # 使用“.”查找指定长度并包含指定开头与结尾的字符 [root@localhost ~]# grep -n 'g..d' test.txt 1:"Open Source" is a good mechanism to develop programs. 9:Oh! The soup taste good. 16:The world <Happy> is the same with "glad". # 使用“*”查找包含任意多个*前面字符的行 ## w*：表示包含零个到任意多个w [root@localhost ~]# grep -n 'go*d' test.txt 1:"Open Source" is a good mechanism to develop programs. 9:Oh! The soup taste good. 13:Oh! My god! 14:The gd software is a library for drafting programs. # 使用{}查找g与g之间包含指定个数o的字符 [root@localhost ~]# grep -n 'go\{2,5\}g' test.txt 18:google is the best tools for search keyword. [root@localhost ~]# grep -n 'go\{2,\}g' test.txt 18:google is the best tools for search keyword. 19:goooooogle yes!