基础正则表达式及grep的使用

regular_express.txt文件内容

<span style="font-size:14px;">"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.^M
GNU is free air not free beer.^M
Her hair is very beauty.^M
I can't finish the test.^M
Oh! The soup taste good.^M
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.^M
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

</span>

1.查找特定字符

--color=auto 关键字显示颜色

grep  -n --color=auto'the' regular_express.txt

8:I can't finish <span style="color:#FF0000;">the</span> test.
12:<span style="color:#FF0000;">the</span> symbol '*' is represented as start.
15:You are <span style="color:#FF0000;">the</span> best is mean you are <span style="color:#FF0000;">the</span> no. 1.
16:The world <Happy> is <span style="color:#FF0000;">the</span> same with "glad".
18:google is <span style="color:#FF0000;">the</span> best tools for search keyword.

2.该行没有特定字符串时显示

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:

3.忽略大小写

grep -in 'the' regular_express.txt

8:I can't finish <span style="color:#FF0000;">the</span> test.
9:Oh! <span style="color:#FF0000;">The</span> soup taste good.
12:<span style="color:#FF0000;">the</span> symbol '*' is represented as start.
14:<span style="color:#FF0000;">The</span> gd software is a library for drafting programs.
15:You are <span style="color:#FF0000;">the</span> best is mean you are <span style="color:#FF0000;">the</span> no. 1.
16:<span style="color:#FF0000;">The</span> world <Happy> is <span style="color:#FF0000;">the</span> same with "glad".
18:google is <span style="color:#FF0000;">the</span> best tools for search keyword.

4.关键字的前面n行或后面n行

-A2 后续的2行也列出来

-B2 前面的2行也列出来

 grep -n -A2 -B2 'do' regular_express.txt

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.
12-the symbol '*' is represented as start.
13-Oh!	My god!
--
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!

5.统计有多少行

 grep -c 'the' regular_express.txt

5

6.利用中括号[]来查找集合字符

[]里面不论有几个字符，它都只代表某“一个”字符。

 grep -n 't[ae]st' regular_express.txt

8:I can't finish the <span style="color:#FF0000;">test</span>.
9:Oh! The soup <span style="color:#FF0000;">tast</span>e good.

7.反向查找集合字符

[^]反向选择查找

 grep -n '[^g]oo' regular_express.txt

<span style="color:#000000;">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!</span>

8.[a-z][A-Z][0-9]

当我们在一组集合字符中，如果该字符组是连续的，例如大写英文/小写英文/数字等，就可以使用[A-Z][a-z][0-9]等方式书写，如果要求字符串是

数字与英文，则写成[a-zA-Z0-9]

grep -n '[^a-z]oo' regular_express.txt

<span style="color:#000000;">3:Football game is not use feet only.
</span>

9.行首与行尾字符 ^ $

让查询的字符串在行首列出。

grep -n '^the' regular_express.txt

<span style="color:#000000;">12:the symbol '*' is represented as start.</span>

grep -n '^[a-z]' regular_express.txt

<span style="color:#000000;">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.</span>

^ 符号在字符集中(中括号[])之内与之外是不同的！在[]内代表“反向选择”，在[]之外则代表定位在行首的意义。
10 行尾字符 $

找出行尾结束字符为小数点(.)的那一行

grep -n '\.$' regular_express.txt

<span style="color:#000000;">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.</span>

查询空白符号  ^$开头和结尾即空白

grep -n '^$' regular_express.txt 

<span style="color:#000000;">22:</span>

去除空白行和注释行显示

grep -v '^$' export-1.sh |grep -v '^#'
11.任意一个字符. 与重复字符*

.(小数点):代表绝对有一个字符的意思

*(星号)：代表重复前一个0到无穷多次意思，为组合形态

查询g与d之间一定存在两个字符的行

<span style="color:#000000;">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".
</span>

因为*代表的是重复0个或多个前面的RE字符的意义，因此，“o*”
代表的是具有空字符或一个o以上的字符，特别注意，因为允许空字符(没有字符都可以的意思)，因此，

“grep -n 'o*' regular_express.txt” 将会把所有的数据都打印到屏幕上。

那如果是“oo*”呢？则第一个o肯定必须要存在，第二个o则是可有可无的多个oo，所以凡是含有o，oo，ooo，oooo等，都可以被列出来

同理，当我们需要至少两个o以上的字符串时，就需要ooo*,即

grep -n 'ooo*' regular_express.txt

<span style="color:#000000;">19:goooooogle yes!
zghw@zghw-Lenovo-B40-30:~/Desktop/bashdemo$ 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!</span>

.*组合则代表零个或多个任意字符的意思。

grep -n 'g.*g' regular_express.txt

<span style="color:#000000;">1:"Open Source" is a good mechanism to develop programs.
14:The gd software is a library for drafting programs.
18:google is the best tools for search keyword.
19:goooooogle yes!
20:go! go! Let's go.</span>

12.限定连续的RE字符范围 {}

限制一个范围区间内的重复字符数。

因为{与}的符号在shell是有特殊意义的，因此，我们必须要使用转义字符\来让它失去特殊意义才行。

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!

 grep -n 'go\{2,5\}g' regular_express.txt

18:google is the best tools for search keyword.

grep -n 'go\{2,\}g' regular_express.txt

18:google is the best tools for search keyword.
19:goooooogle yes!

基础正则表达式字符

RE字符	意义与范例
^word	意义：待查找的字符串(word)在行首 范例：查找行首为#开始的那一行，并列出行号 grep -n '^#' regular_express.txt
word$	意义：待查找的字符串(word)在行尾 范例：将行尾为！的那一行打印出来，并列出行号 grep -n '!$' regular_express.txt
.	意义：代表一定有一个任意字符的字符 范例：查找的字符从可以是(eve)(eae)(eee)(ee),但不能仅有(ee) 即e与e中间“一定”仅有一个字符，而空格符也是字符 grep -n 'e.e' regular_express.txt
\	意义：转义字符，将特殊符号的特殊意义去除 范例：查找含有单引号'的那一行 grep -n \' regular_express.txt
*	意义：重复零个或无穷多个的前一个字符 范例：找出含有(es)(ess)(esss)等的字符串，注意，因为*可以是0个，所以es也是符合待查找字符串。另外，因为*为重复“前一个RE字符”的符号，因此，在*之前必须要紧接着一个RE字符哦！例如任意字符“.*” grep -n 'ess*' regular_express.txt
[list]	意义：从字符集合的RE字符里面找出想要选取的字符 范例：查找含有(gl)或者(gd)的那一行，需要特别留意的是，在[]当中代表一个待查找的字符，例如“a[afl]y”代表查找的字符串可以是aay，afy，aly，即[afl]代表a或f或l的意思 grep -n 'g[ld]' regular_express.txt
[n1-n2]	意义：从字符集合的RE字符里面找出想要选取的字符范围 范例：查找含有任意数字的那一行。需特别留意，在字符集合[]中的减号-是有特殊意义的，它代表两个字符之间的所有连续字符。但这个连续与否与ASCII编码有官，因此，你的编码需要设置正确（在bash当中，需要确定LANG与LANGUAGE的变量是否正确）！例如所有大写字符则为[A-Z] grep -n '[a-zA-Z0-9]' regular_express.txt
[^list]	意义：从字符集合的RE字符里面找出不要的字符或范围 范例：查找的字符串可以是(oog)(ood) 但不能是（oot），那个^在[]内时代表的意义是“反向选择”的意思。例如我不要大写字符，则为[^A-Z]。但是需要特别注意的是，如果以grep -n [^A-Z] regular_express.txt来查找，却发现该文件内的所有行都被列出来，为什么？因为这个[^A-Z]是“非大写字符”的意思，因为每一行均有非大写字符 grep -n 'oo[^t]' regular_express.txt
\{n,m\}^	意义：连续n到m个的前一个RE字符，若为\{n\}则是连续n个的前一个RE字符，若为\{n,\}则是连续n个以上的前一个RE字符 范例：在g与g之间有2个到3个的o存在的字符串。即(goog)(gooog) grep -n 'go\{2,3\}g' regular_express.txt