Question

Grep 与正则表达式

其实学过正则表达式之后这些就不算啥事儿了，建议先学一下正则然后再来看。

不过直接看下面的更功利一些，毕竟看完了就可以直接用了。

下面这个是测试文的内容:

➤ cat -n fortune
    1    All generalizations are false, including this one.
    2            -- Mark Twain
    3    Many pages make a thick book, except for pocket Bibles which are on very
    4    very thin paper.
    5    
    6    Remark of Dr. Baldwin's concerning upstarts: We don't care to eat toadstools
    7    that think they are truffles.
    8            -- Mark Twain, "Pudd'nhead Wilson's Calendar"
    9    
    10    Sheriff Chameleotoptor sighed with an air of weary sadness, and then
    11    turned to Doppelgutt and said 'The Senator must really have been on a
    12    bender this time -- he left a party in Cleveland, Ohio, at 11:30 last
    13    night, and they found his car this morning in the smokestack of a British
    14    aircraft carrier in the Formosa Straits.'
    15            -- Grand Panjandrum's Special Award, 1985 Bulwer-Lytton

匹配句首 '^'

➤ grep -ni '^A' fortune
1:All generalizations are false, including this one.
14:aircraft carrier in the Formosa Straits.'

-n 的意思是显示行号

匹配句尾 '$'

➤ grep -ni '\.$' fortune
1:All generalizations are false, including this one.
4:very thin paper.
7:that think they are truffles.

这里的 '\.$' 是以 . 字符结尾的意思，中间的反斜杠是逃逸字符，起转义的效果

匹配空行 '^$'

➤ grep '^$' fortune -n
5:
9:

任意单个字符 '.'

➤ grep -n '.re' fortune
1:All generalizations are false, including this one.
3:Many pages make a thick book, except for pocket Bibles which are on very
6:Remark of Dr. Baldwin's concerning upstarts: We don't care to eat toadstools
7:that think they are truffles.
11:turned to Doppelgutt and said 'The Senator must really have been on a

\b 的意思是单词分界线，也许是空格，也许是 tab

➤ grep -n '\b.re\b' fortune
1:All generalizations are false, including this one.
3:Many pages make a thick book, except for pocket Bibles which are on very
7:that think they are truffles.

零次或多次重复 '*'

➤ grep -n 'l*' fortune
1:All generalizations are false, including this one.
2:        -- Mark Twain
3:Many pages make a thick book, except for pocket Bibles which are on very
4:very thin paper.
5:
6:Remark of Dr. Baldwin's concerning upstarts: We don't care to eat toadstools
7:that think they are truffles.
8:        -- Mark Twain, "Pudd'nhead Wilson's Calendar"
9:
10:Sheriff Chameleotoptor sighed with an air of weary sadness, and then
11:turned to Doppelgutt and said 'The Senator must really have been on a
12:bender this time -- he left a party in Cleveland, Ohio, at 11:30 last
13:night, and they found his car this morning in the smokestack of a British
14:aircraft carrier in the Formosa Straits.'
15:        -- Grand Panjandrum's Special Award, 1985 Bulwer-Lytton

显示的不是很好，因为没有高亮什么的。

其实这一部分完全可以当做正则来讲，毕竟正则才是核心, grep 只是一个工具，怎么用，还是看你的能力如何了。

曾经看过一个 30 分钟入门正则表达式，个人感觉挺不错的，因为我也是从那里入的门，所以也推荐看这一部分的人也去搜下那个，作者写的够简单易懂了。

这一段写的有点长，但是，当你学会正则的时候你就会发现，这东西真棒! (这是我 BB 的，跟原作者无关哈...)

扩展阅读

• 正则与 Grep (part I)
• 正则与 Grep (part II)

本书简介：

• Linux 进阶技巧
• 巧妙的命令组合
• Bash 某些技巧
• 一共一百零一个（包括充数的)
• 最后有个奖励章（额外技巧)