Linux大神养成之正则表达式（grep，sed）

秒速五厘米 2022-08-03 04:27 133阅读 0赞

## Linux大神养成之正则表达式 ##

### grep命令 ###

参数：

*  \-A后面加数字，代表after，表示把该行的后续n行也列出来
 *  \-B后面加数字，代表befer，表示把改行的前面n行也列出来

$ dmesg | grep -n -A3 -B2 --color=auto 'eth'

1.  **查找特定字符串**

$ cat -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.
     5  However, this dress is about $ 3183 dollars.^M
     6  GNU is free air not free beer.^M
     7  Her hair is very beauty.^M
     8  I can't finish the test.^M
     9  Oh! The soup taste good.^M
    10  motorcycle is cheap than car.
    11  This window is clear.
    12  the symbol '*' is represented as start.
    13  Oh!     My god!
    14  The gd software is a library for drafting programs.^M
    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!
    20  go! go! Let's go.
    21  # I am VBird

$ grep -n 'the' regular_express.txt

> 8:I can’t finish the test.^M  
> 12:the symbol ‘\*’ is represented as start.  
> 15:You are the best is mean you are the no. 1.  
> 16:The world is the same with “glad”.  
> 18:google is the best tools for search keyword.

2.**利用中括号来查找集合字符**

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

> 8:I can’t finish the test.^M  
> 9:Oh! The soup taste good.^M  
> 查找包含tast或test的字符的句子

$ 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!  
> ^反向选择，即非的意思，就是oo的前面的字母不是g的

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

> 3:Football game is not use feet only.  
> oo前面是非小写的

3.**行首与行尾符^$**  
`$ 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.  
> ^放在外面表示行首的意思，表示选出以小写字母开始的行

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

> 1:”Open Source” is a good mechanism to develop programs.  
> 21:\# I am VBird  
> 不是以字母开头的行

$ 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 is the same with “glad”.  
> 17:I like dog.  
> 18:google is the best tools for search keyword.  
> 20:go! go! Let’s go.  
> $表示行尾，表示以 ‘.’ 结尾的行，其中 ‘\\’ 是转义符

$ grep -v '^$' /etc/syslog.conf | grep  '^#'

> \# Log all kernel messages to the console.  
> \# Logging much else clutters up the screen.  
> \#kern.\* /dev/console  
> \# Log anything (except mail) of level info or higher.  
> \# Don’t log private authentication messages!  
> \# The authpriv file has restricted access.  
> \# Log all the mail messages in one place.  
> \# Log cron stuff  
> \# Everybody gets emergency messages  
> \# Save news errors of level crit and higher in a special file.  
> \# Save boot messages also to boot.log  
> 选出非空行的，然后在选出以\#开头的文字

4.**任意一个.和重复的\***

`$ grep -n 'g..d' regular_express.txt`

> 1:”Open Source” is a good mechanism to develop programs.  
> 9:Oh! The soup taste good.^M  
> 16:The world is the same with “glad”.  
> ‘g..d’表示g和d中间有两个连续任意字符的都可以匹配

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

> 18:google is the best tools for search keyword.  
> 19:goooooogle yes!  
> ‘goo\*g’前一个o必须有，后一个’o \*’表示一个或多个，所以为至少一个o

$ grep -n g.*g regular_express.txt

> 1:”Open Source” is a good mechanism to develop programs.  
> 14:The gd software is a library for drafting programs.^M  
> 18:google is the best tools for search keyword.  
> 19:goooooogle yes!  
> 20:go! go! Let’s go.  
> 表示由g开头g结尾的行

$ grep -n '[0-9][0-9]*' regular_express.txt

> 5:However, this dress is about $ 3183 dollars.^M  
> 15:You are the best is mean you are the no. 1.  
> 表示以数字开头，后面有0个到任意个数字的行

5.限定连续RE字符的范围\{\}

`$ 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.^M  
> 18:google is the best tools for search keyword.  
> 19:goooooogle yes!  
> 表示包含两个‘o’的行

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

> 18:google is the best tools for search keyword.  
> 19:goooooogle yes!  
> g和g中间包含两个以上的o

### sed工具 ###

参数：

*  \-n 安静模式，只列出经过特殊处理的行
 *  \-i 直接修改文件内容，而不是屏幕输出
 *  \-e 直接在命令行模式上sed动作编辑
 *  \-f sed动作写在一个文件中
 *  \-r扩展正则语法

函数参数;

*  a 新增
 *  c 替换
 *  d 删除
 *  i 插入
 *  p打印
 *  s 替换（和c的不同看练习）
    
    1.以行为单位进行**新增/删除**

$ nl /etc/passwd | sed '2,5d'

>     1 root:x:0:0:root:/root:/bin/bash
>      6  sync:x:5:0:sync:/sbin:/bin/sync
>      7  shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
>      8  halt:x:7:0:halt:/sbin:/sbin/halt
>      9  mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
>      PS:表示删除第2-5行

$ nl /etc/passwd | sed '2a Drink tea or .....\ 
    > drink bear ?'

> 1 root:x:0:0:root:/root:/bin/bash  
> 2 bin:x:1:1:bin:/bin:/sbin/nologin  
> Drink tea or …..  
> drink bear ?  
> 3 daemon:x:2:2:daemon:/sbin:/sbin/nologin  
> 4 adm:x:3:4:adm:/var/adm:/sbin/nologin  
> 5 lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin  
> PS:给第二行之后添加后面的字符串，用’\\’表示新行进行增加

2.以行为单位进行**替换**显示的功能  
`$ nl /etc/passwd | sed '2,5c No 2-5 number'`

> 1 root:x:0:0:root:/root:/bin/bash  
> No 2-5 number  
> 6 sync:x:5:0:sync:/sbin:/bin/sync  
> 7 shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown  
> PS:将2-5行替换成‘No 2-5 number’

$ nl /etc/passwd | sed -n '2,5p'

>     2 bin:x:1:1:bin:/bin:/sbin/nologin
>      3  daemon:x:2:2:daemon:/sbin:/sbin/nologin
>      4  adm:x:3:4:adm:/var/adm:/sbin/nologin
>      5  lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
>      PS：注意这里 '-n' 安静模式，只列出特殊处理的行

$ /sbin/ifconfig eth1

> eth1 Link encap:Ethernet HWaddr 6C:AE:8B:21:98:9B  
> inet addr:10.209.102.43 Bcast:10.209.102.127 Mask:255.255.255.128  
> UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1  
> RX packets:47103902950 errors:0 dropped:7743 overruns:7743 frame:0  
> TX packets:11073405019 errors:0 dropped:0 overruns:0 carrier:0  
> collisions:0 txqueuelen:1000  
> RX bytes:59771891524541 (54.3 TiB) TX bytes:810933823454 (755.2 GiB)

$ /sbin/ifconfig eth1  | grep 'inet addr'

>     inet addr:10.209.102.43  Bcast:10.209.102.127  Mask:255.255.255.128

$ /sbin/ifconfig eth1  | grep 'inet addr' | sed 's/^.*addr://g'

> 10.209.102.43 Bcast:10.209.102.127 Mask:255.255.255.128  
> PS:”sed ‘s/要替换字符/新字符/g’”

$ /sbin/ifconfig eth1  | grep 'inet addr' | sed 's/^.*addr://g' | sed 's/Bcast.*//g'

> 10.209.102.43  
> PS:其实就相当于hostname -i

$ cat /etc/man.config | grep 'MAN' | sed 's/#.*$//g' | sed '/^$/d'

> MANPATH /usr/share/man  
> MANPATH /usr/man  
> MANPATH /usr/local/share/man  
> MANPATH /usr/local/man  
> MANPATH /usr/X11R6/man  
> MANPATH\_MAP /bin /usr/share/man  
> MANPATH\_MAP /sbin /usr/share/man  
> MANPATH\_MAP /usr/bin /usr/share/man  
> MANPATH\_MAP /usr/sbin /usr/share/man  
> PS:先选出包含‘MAN’的行，然后替换掉’\#’开头的，即注释，然后把空行删除，注意最后的空行表示是写在一对 **‘/ /’**中

*  直接修改文件（危险操作）

$ sed -i 's/\.$/\!/g' regular_express.txt

> PS:直接把原文件中的‘.’结尾的全部替换成‘！’

$ sed -i '$a # This is a tese' regular_express.txt

> PS:给文章的最后一行添加一句话