基础正则表达式

语系对正则表达式的影响

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。

grep的一些高级参数

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
[[email protected] 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。

基础正则表达式练习

以下是练习文本

[[email protected] 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

[[email protected] 桌面]# 

例题一：查找特定字符串

//查找含有the的行
[[email protected] 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
[[email protected] 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:
[[email protected] 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
[[email protected] 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
[[email protected] 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
[[email protected] 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
[[email protected] 桌面]# grep -n ‘[^[:lower:]]oo‘ regular_express.txt
3:Football game is not use feet only.
[[email protected] 桌面]# 

例题三：行首与行尾字符^$

//以the开头的行
[[email protected] 桌面]# grep -n ‘^the‘ regular_express.txt
12:the symbol ‘*‘ is represented as start.

//以小写字母开头的行
[[email protected] 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）
[[email protected] 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
[[email protected] 桌面]# grep -n ‘^$‘ regular_express.txt
22:
[[email protected] 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
[[email protected] 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
[[email protected] 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!
[[email protected] 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
[[email protected] 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
[[email protected] 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
[[email protected] 桌面]# grep -n ‘go\{2,\}g‘ regular_express.txt
18:google is the best tools for search keyword.
19:goooooogle yes!
[[email protected] 桌面]# 

基础正则表达式字符

经过上节的五个例题，可将基础的正则表达式总结如下：