grep真是一个很棒的工具，不解释，体验下。

实例文件：

regular_express.txt

例题1：查找特定字符串

查找包括“the”的

[zhouforme@zhouforme ~]$ 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.

不区分大小写

[zhouforme@zhouforme ~]$ grep -in 'the' regular_express.txt

8:I can't finish the test.

9:Oh! The soup taste good.

12:the symbol '*' is represented as start.

14:The gd software is a library for drafting programs.

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.

查找不包括“the”的（反向查找）

[zhouforme@zhouforme ~]$ grep -vn 'the' regular_express.txt

例题2：利用中括号[]来查找集合字符

比如要查找test或taste，它们有共同的“t？st”

[zhouforme@zhouforme ~]$ grep -n 't[ae]st' regular_express.txt

8:I can't finish the test.

9:Oh! The soup taste good.

如果想要查找有oo字符时，

[zhouforme@zhouforme ~]$ grep -n 'oo' 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!

如果不想要oo前面有g，

[zhouforme@zhouforme ~]$ 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!

如果不想要oo前面有小写字符，

[zhouforme@zhouforme ~]$ grep -n '[^a-z]oo' regular_express.txt

3:Football game is not use feet only.

或者

[zhouforme@zhouforme ~]$ grep -n '[^[:lower:]]oo' regular_express.txt

3:Football game is not use feet only.

对于数字，

[zhouforme@zhouforme ~]$ 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.

或者

[zhouforme@zhouforme ~]$ grep -n '[[:digit:]]' regular_express.txt

5:However, this dress is about $ 3183 dollars.

15:You are the best is mean you are the no. 1.

例题3：行首与行尾字符^$

如果只显示在行首出现the的，

[zhouforme@zhouforme ~]$ grep -n '^the' regular_express.txt

12:the symbol '*' is represented as start.

如果要开头是小写字符的，

[zhouforme@zhouforme ~]$ 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.

或者

[zhouforme@zhouforme ~]$ grep -n '^[[:lower:]]' 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.

NOTE: 注意与上面的区别！^在[]内代表“反向选择”，在[]外则代表定位在行首的意义！

如果不想开头是英文字符，

[zhouforme@zhouforme ~]$ grep -n '^[^a-zA-Z]' regular_express.txt

1:"Open Source" is a good mechanism to develop programs.

21:# I am Vbird.

或者

[zhouforme@zhouforme ~]$ grep -n '^[^[:alpha:]]' regular_express.txt

1:"Open Source" is a good mechanism to develop programs.

21:# I am Vbird.