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不同语系下，字符的编码数据可能不同。
LANG=C：012……ABC……abc……
LANG=zh_CN：012……aAbB……
因此，使用[A-Z]时，搜索到的字符也不一样。
| 特殊符号 | 代表意义 |
| [:alnum:] | 大小写字符及数字，0-9，A-Z，a-z |
| [:alpha:] | 英文大小写字符 |
| [:blank:] | 空格键与tab键 |
| [:cntrl:] | 控制按键，CR，LF，TAB，DEL等 |
| [:digit:] | 代表数字 |
| [:graph:] | 除空格符（空格和Tab）外其他按键 |
| [:lower:] | 小写字符 |
| [:print:] | 可以被打印出来的字符 |
| [:punct:] | 标点字符，" ‘ ? ; : # $ |
| [:upper:] | 大写字符 |
| [:space:] | 任何会产生空白的字符 |
| [:xdigit:] | 十六进制数字 |
除了上一章介绍的基本用法，grep还有一些高级用法。
grep [-A] [-B] [--color=auto} ‘搜寻字符串‘ filename
参数：
-A：后面可加数字n，为after的意思，除了列出该列，后面的n列也列出来
-B：后面可加数字n，为after的意思，除了列出该列，前面的n列也列出来
--color=auto：对正确选取的数据着色
//-n用于显示行号 [root@localhost 桌面]# dmesg | grep -n --color=auto ‘eth‘ 1730:[ 10.210383] e1000 0000:02:01.0 eth0: (PCI:66MHz:32-bit) 00:0c:29:7f:dd:91 1731:[ 10.210404] e1000 0000:02:01.0 eth0: Intel(R) PRO/1000 Network Connection
注：grep搜索到字符串后都是以整行为单位显示。
以下是练习文本
[root@localhost 桌面]# cat regular_express.txt "Open Source" is a good mechanism to develop programs. apple is my favorite food. Football game is not use feet only. this dress doesn‘t fit me. However, this dress is about $ 3183 dollars. GNU is free air not free beer. Her hair is very beauty. I can‘t finish the test. Oh! The soup taste good. motorcycle is cheap than car. This window is clear. the symbol ‘*‘ is represented as start. Oh! My god! The gd software is a library for drafting programs. You are the best is mean you are the no. 1. The world <Happy> is the same with "glad". I like dog. google is the best tools for search keyword. goooooogle yes! go! go! Let‘s go. # I am VBird [root@localhost 桌面]#
例题一：查找特定字符串
//查找含有the的行 [root@localhost 桌面]# grep -n ‘the‘ regular_express.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. //查找不含有the的行 [root@localhost 桌面]# grep -vn ‘the‘ regular_express.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. 5:However, this dress is about $ 3183 dollars. 6:GNU is free air not free beer. 7:Her hair is very beauty. 9:Oh! The soup taste good. 10:motorcycle is cheap than car. 11:This window is clear. 13:Oh! My god! 14:The gd software is a library for drafting programs. 17:I like dog. 19:goooooogle yes! 20:go! go! Let‘s go. 21:# I am VBird 22: [root@localhost 桌面]#
例题二：利用中括号[]来查找集合字符
//查找tast或test字符串 [root@localhost 桌面]# grep -n ‘t[ae]st‘ regular_express.txt 8:I can‘t finish the test. 9:Oh! The soup taste good. //查找不是以g开头的oo字符串 [root@localhost 桌面]# grep -n ‘[^g]oo‘ regular_express.txt 2:apple is my favorite food. 3:Football game is not use feet only. 18:google is the best tools for search keyword. 19:goooooogle yes! //查找数字 [root@localhost 桌面]# grep -n ‘[0-9]‘ regular_express.txt 5:However, this dress is about $ 3183 dollars. 15:You are the best is mean you are the no. 1. 查找不是以小写字母开头的oo字符串 [root@localhost 桌面]# grep -n ‘[^[:lower:]]oo‘ regular_express.txt 3:Football game is not use feet only. [root@localhost 桌面]#
例题三：行首与行尾字符^$
//以the开头的行 [root@localhost 桌面]# grep -n ‘^the‘ regular_express.txt 12:the symbol ‘*‘ is represented as start. //以小写字母开头的行 [root@localhost 桌面]# grep -n ‘^[a-z]‘ regular_express.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. //以小数点结尾的（需要转义） [root@localhost 桌面]# grep -n ‘\.$‘ regular_express.txt 1:"Open Source" is a good mechanism to develop programs. 2:apple is my favorite food. 3:Football game is not use feet only. 4:this dress doesn‘t fit me. 10:motorcycle is cheap than car. 11:This window is clear. 12:the symbol ‘*‘ is represented as start. 15:You are the best is mean you are the no. 1. 16:The world <Happy> is the same with "glad". 17:I like dog. 18:google is the best tools for search keyword. 20:go! go! Let‘s go. //查找空白行 [root@localhost 桌面]# grep -n ‘^$‘ regular_express.txt 22: [root@localhost 桌面]#
例题四：任意字符.和重复字符*
.（小数点）：代表一定有一个任意字符的意思
*：代表重复前一个0到无穷的意思
//查找以g开头，d结尾，中间两个字符的字符 [root@localhost 桌面]# grep -n ‘g..d‘ regular_express.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". //查找至少含有两个o，后面跟0到无穷个o的字符 [root@localhost 桌面]# grep -n ‘ooo*‘ regular_express.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! [root@localhost 桌面]#
例题五：限定连续RE字符范围{}
{}必须转义
//查找o重复两次的字符 [root@localhost 桌面]# grep -n ‘o\{2\}‘ regular_express.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o重复2到5次的字符 [root@localhost 桌面]# grep -n ‘o\{2,5\}‘ regular_express.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o重复两次以上的 [root@localhost 桌面]# grep -n ‘go\{2,\}g‘ regular_express.txt 18:google is the best tools for search keyword. 19:goooooogle yes! [root@localhost 桌面]#
经过上节的五个例题，可将基础的正则表达式总结如下：
| RE字符 | 意义 | |
| ^word | 带查找的字符串在行首 | |
| word$ | 待查找的字符串在行尾 | |
| . | 代表一定有一个任意字符的字符 | |
| \ | 转义字符 | |
| * | 重复零到无穷多个前一个字符 | |
| [list] | 从字符集合的RE字符里找到想要选取的字符 | |
| [n1-n2] | 从字符集合的RE字符里找到想要选取的字符范围 | |
| [^list] |
|
|
| \{n,m\} | 前一个字符重复n到m次 |
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原文地址：http://www.cnblogs.com/wuchaodzxx/p/5678709.html
