linux基础学习-10.4-正则表达式练习题

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linux基础学习-10.4-正则表达式练习题
一、基础正则

环境准备
```
[root@oldboyedu42-lnb oldboy]# cat /oldboy/re.txt
I am oldboy teacher!
I teach linux.
I like badminton ball ,billiard ball and chinese chess!
my blog is 
http://oldboy.blog.51cto.com

our size is 
http://blog.oldboyedu.com

my qq is 49000448
not 4900000448.
my god ,i am not oldbey,but OLDBOY!
```
1、^ ^m 表示以....开头的行

[root@oldboyedu42-lnb oldboy]# grep '^m' re.txt

my blog is http://oldboy.blog.51cto.com

my qq is 49000448

my god ,i am not oldbey,but OLDBOY!

2、 $ m$ 表示以....结尾的行

[root@oldboyedu42-lnb oldboy]# cat -A re.txt

I am oldboy teacher!$

I teach linux.$

$

I like badminton ball ,billiard ball and chinese chess!$

my blog is http://oldboy.blog.51cto.com $ #注意此处结尾是空格不是m

$

our size is http://blog.oldboyedu.com $ #注意此处结尾是空格不是m

$

my qq is 49000448$

$

not 4900000448.$

my god ,i am not oldbey,but OLDBOY!$

#删除结尾的空格

[root@oldboyedu42-lnb oldboy]# vim re.txt

I am oldboy teacher!

I teach linux.

I like badminton ball ,billiard ball and chinese chess!

my blog is http://oldboy.blog.51cto.com

our size is http://blog.oldboyedu.com

my qq is 49000448

not 4900000448.

my god ,i am not oldbey,but OLDBOY!

#检查是否修改成功

[root@oldboyedu42-lnb oldboy]# cat -A re.txt

I am oldboy teacher!$

I teach linux.$

$

I like badminton ball ,billiard ball and chinese chess!$

my blog is http://oldboy.blog.51cto.com$

$

our size is http://blog.oldboyedu.com$

$

my qq is 49000448$

$

not 4900000448.$

my god ,i am not oldbey,but OLDBOY!$

[root@oldboyedu42-lnb oldboy]#

[root@oldboyedu42-lnb oldboy]# grep 'm$' re.txt

my blog is http://oldboy.blog.51cto.com

our size is http://blog.oldboyedu.com

cat -A #显示出文件中所有的符号 $这一行的结尾

[root@oldboyedu42-lnb oldboy]# grep ' ' re.txt

I am oldboy teacher!

I teach linux.

I like badminton ball ,billiard ball and chinese chess!

my blog is http://oldboy.blog.51cto.com

our size is http://blog.oldboyedu.com

my qq is 49000448

not 4900000448.

my god ,i am not oldbey,but OLDBOY!

3、 ^$ 空行这一行里面什么都没有

[root@oldboyedu42-lnb oldboy]# grep -n '^$' re.txt

3:

6:

8:

10:

练习题:排查文件中的空行

[root@oldboyedu42-lnb oldboy]# grep -v '^$' re.txt

I am oldboy teacher!

I teach linux.

I like badminton ball ,billiard ball and chinese chess!

my blog is http://oldboy.blog.51cto.com

our size is http://blog.oldboyedu.com

my qq is 49000448

not 4900000448.

my god ,i am not oldbey,but OLDBOY!

4、 . 任意一个字符不会匹配空行

#grep -o '.' re.txt

#-o 显示grep的执行过程，grep每一次找出什么

grep -o '.' re.txt

#-o 显示grep的执行过程，grep每一次找出什么

#-o 的结果中每一行表示 grep每次找出什么

[root@oldboyedu42-lnb oldboy]# grep '0' re.txt

my qq is 49000448

not 4900000448.

[root@oldboyedu42-lnb oldboy]# grep -o '0' re.txt

0

0

0

0

0

0

0

0

[root@oldboyedu42-lnb oldboy]# grep '00' re.txt

my qq is 49000448

not 4900000448.

[root@oldboyedu42-lnb oldboy]# grep -o '00' re.txt

00

00

00

说明：如果匹配的内容在一行中有多处，grep会从左到右匹配到最后一个，多多益善

提示：点（.）的特殊含义小结：

1、当前目录

2、使得文件生效相当于source

3、隐藏文件的开头

4、任意一个字符

5、撬棍转义字符去掉符号特殊含义脱掉马甲，打回原形

显示出文件中以.结尾的行？

[root@oldboyedu42-lnb oldboy]# grep '.$' re.txt

I teach linux.

not 4900000448.

撬棍系列转义字符系列

====== 回车

6、 * 前一个字符连续出现0次或0次以上

[root@oldboyedu42-lnb oldboy]# grep '0*' re.txt

I am oldboy teacher!

I teach linux.

I like badminton ball ,billiard ball and chinese chess!

my blog is http://oldboy.blog.51cto.com

our size is http://blog.oldboyedu.com

my qq is 49000448

not 4900000448.

my god ,i am not oldbey,but OLDBOY!

[root@oldboyedu42-lnb oldboy]#

[root@oldboyedu42-lnb oldboy]# grep '0*' re.txt -o

000

00000

#连续出现

#正则表示连续出现的时候，会尽可能的匹配（吃）更多的符号贪婪性

[root@oldboyedu42-lnb oldboy]# #0* 表示0连续出现0次

[root@oldboyedu42-lnb oldboy]# #0* 表示0连续出现1次及1次以上

[root@oldboyedu42-lnb oldboy]# #0

[root@oldboyedu42-lnb oldboy]# #000

[root@oldboyedu42-lnb oldboy]# #0000000

[root@oldboyedu42-lnb oldboy]# #0* 表示0连续出现0次

[root@oldboyedu42-lnb oldboy]# #'0*' 只出现0次的时候 ====== ''

[root@oldboyedu42-lnb oldboy]# #会把整个文件的内容都显示出来

[root@oldboyedu42-lnb oldboy]# grep '' re.txt

I am oldboy teacher!

I teach linux.

I like badminton ball ,billiard ball and chinese chess!

my blog is http://oldboy.blog.51cto.com

our size is http://blog.oldboyedu.com

my qq is 49000448

not 4900000448.

my god ,i am not oldbey,but OLDBOY!

小结正则之*：

1]] 贪婪性

2]] 连续出现

7、 .* 所有任何符号

#在正则中表示连续出现表示所有贪婪性

找出文件中以字母m开头的行并且以m结尾的行

[root@oldboyedu42-lnb oldboy]# grep '^m' re.txt

my blog is http://oldboy.blog.51cto.com

my qq is 49000448

my god ,i am not oldbey,but OLDBOY!

[root@oldboyedu42-lnb oldboy]# grep '^m' re.txt |grep 'm$'

my blog is http://oldboy.blog.51cto.com

[root@oldboyedu42-lnb oldboy]# grep '^m.*m$' re.txt

my blog is http://oldboy.blog.51cto.com

[root@oldboyedu42-lnb oldboy]# grep '^.*m$' re.txt

my blog is http://oldboy.blog.51cto.com

our size is http://blog.oldboyedu.com

[root@oldboyedu42-lnb oldboy]# grep 'm$' re.txt

my blog is http://oldboy.blog.51cto.com

our size is http://blog.oldboyedu.com

[root@oldboyedu-42mvp ~]# grep '.*m' re.txt

8、 [] [abc] 表示一个整体，a或b或c任意一个字符

[root@oldboyedu42-lnb oldboy]# grep '[abc]' re.txt

I am oldboy teacher!

I teach linux.

I like badminton ball ,billiard ball and chinese chess!

my blog is http://oldboy.blog.51cto.com

our size is http://blog.oldboyedu.com

my god ,i am not oldbey,but OLDBOY!

grep '[abc]' re.txt -o

===>从哪里来，到哪里去用的是-

[root@oldboyedu42-lnb oldboy]# grep '[a-z]' re.txt

I am oldboy teacher!

I teach linux.

I like badminton ball ,billiard ball and chinese chess!

my blog is http://oldboy.blog.51cto.com

our size is http://blog.oldboyedu.com

my qq is 49000448

not 4900000448.

my god ,i am not oldbey,but OLDBOY!

[root@oldboyedu42-lnb oldboy]# grep '[A-Z]' re.txt

I am oldboy teacher!

I teach linux.

I like badminton ball ,billiard ball and chinese chess!

my god ,i am not oldbey,but OLDBOY!

[root@oldboyedu42-lnb oldboy]# grep '[a-zA-Z]' re.txt

I am oldboy teacher!

I teach linux.

I like badminton ball ,billiard ball and chinese chess!

my blog is http://oldboy.blog.51cto.com

our size is http://blog.oldboyedu.com

my qq is 49000448

not 4900000448.

my god ,i am not oldbey,but OLDBOY!

#找出文件中以m或n开头的行

[root@oldboyedu42-lnb oldboy]# #第1个里程碑-m或n

[root@oldboyedu42-lnb oldboy]# grep '[mn]' re.txt

I am oldboy teacher!

I teach linux.

I like badminton ball ,billiard ball and chinese chess!

my blog is http://oldboy.blog.51cto.com

our size is http://blog.oldboyedu.com

my qq is 49000448

not 4900000448.

my god ,i am not oldbey,but OLDBOY!

[root@oldboyedu42-lnb oldboy]# #第2个里程碑-以m或n开头的行

[root@oldboyedu42-lnb oldboy]# grep '^[mn]' re.txt

my blog is http://oldboy.blog.51cto.com

my qq is 49000448

not 4900000448.

my god ,i am not oldbey,but OLDBOY!

grep '[a-z]' re.txt

grep '[A-Z]' re.txt

grep '[0-9]' re.txt

9、 [^] 排除 [^abc]

[root@oldboyedu42-lnb ~]# grep '[^abc]' /oldboy/re.txt

I am oldboy teacher!

I teach linux.

I like badminton ball ,billiard ball and chinese chess!

my blog is http://oldboy.blog.51cto.com

our size is http://blog.oldboyedu.com

my qq is 49000448

not 4900000448.

my god ,i am not oldbey,but OLDBOY!

||||||||||||||||||000000000

二、扩展正则

1、 + 前一个字符连续出现1次或多次

[root@oldboyedu42-lnb oldboy]# egrep '0+' re.txt

my qq is 49000448

not 4900000448.

[root@oldboyedu42-lnb oldboy]# egrep '0' re.txt

my qq is 49000448

not 4900000448.

[root@oldboyedu42-lnb oldboy]# egrep '0+' re.txt -o

000

00000

#+可以把连续的字符变为一个整体

[root@oldboyedu42-lnb oldboy]# egrep '0' re.txt -o

0

0

0

0

0

0

0

0

[root@oldboyedu42-lnb oldboy]# #连续出现

取出文件中连续出现的小写字母

[root@oldboyedu42-lnb oldboy]# #取出文件中连续出现的小写字母

[root@oldboyedu42-lnb oldboy]# egrep '小写字母+' re.txt

[root@oldboyedu42-lnb oldboy]# egrep '[a-z]+' re.txt

I am oldboy teacher!

I teach linux.

I like badminton ball ,billiard ball and chinese chess!

my blog is http://oldboy.blog.51cto.com

our size is http://blog.oldboyedu.com

my qq is 49000448

not 4900000448.

my god ,i am not oldbey,but OLDBOY!

[root@oldboyedu42-lnb oldboy]# egrep '[a-z]+' re.txt -o

am

oldboy

teacher

teach

linux

like

badminton

ball

billiard

ball

and

chinese

chess

my

blog

is

http

oldboy

blog

cto

com

our

size

is

http

blog

oldboyedu

com

my

qq

is

not

my

god

i

am

not

oldbey

but

小结:

1.+连续出现 1次及多次
1. 可以把连续的字符变为一个整体，一次取出来(-o)
2. +一般与[]配合
#1.找出规律

#2.中英文符号

#3.区分大小写

[root@oldboyedu42-lnb oldboy]# egrep '^[0-9]+$' id.txt

440304199604012792

130528197108126121

342923198310042132

330900199806382320

654126197703092303

131127197105115662

[root@oldboyedu42-lnb oldboy]# egrep '^[0-9]+X$' id.txt

61242619860416291X

[root@oldboyedu42-lnb oldboy]# egrep '^[0-9]+[0-9X]$' id.txt

440304199604012792

130528197108126121

342923198310042132

61242619860416291X

330900199806382320

654126197703092303

131127197105115662

2、 | 或者

[root@oldboyedu42-lnb oldboy]# egrep 'linux或oldboy' re.txt

[root@oldboyedu42-lnb oldboy]# egrep 'linux|oldboy' re.txt

I am oldboy teacher!

I teach linux.

my blog is http://oldboy.blog.51cto.com

our size is http://blog.oldboyedu.com

3、 () 变成一个整体反向引用后向引用

#先乘除后加减，有括号的先算括号里面的

[root@oldboyedu42-lnb oldboy]# egrep 'oldbo|ey' re.txt

I am oldboy teacher!

my blog is http://oldboy.blog.51cto.com

our size is http://blog.oldboyedu.com

my god ,i am not oldbey,but OLDBOY!

[root@oldboyedu42-lnb oldboy]# egrep 'oldb(o|e)y' re.txt

I am oldboy teacher!

my blog is http://oldboy.blog.51cto.com

our size is http://blog.oldboyedu.com

my god ,i am not oldbey,but OLDBOY!

#反向引用后向引用 sed

##先通过()把你想要的内容保护起来，然后再使用

echo 123456|xxxxxxx

<123456>

[root@oldboyedu42-lnb oldboy]# echo 123456

123456

[root@oldboyedu42-lnb oldboy]# echo 123456|sed -r 's#(.*)#1#g'

123456

[root@oldboyedu42-lnb oldboy]# echo 123456|sed -r 's#(.*)#<1>#g'

<123456>

echo 123456

34

[root@oldboyedu42-lnb oldboy]# echo 123456

123456

[root@oldboyedu42-lnb oldboy]# echo 123456|sed -r 's#12(34)56#1#g'

34

[root@oldboyedu42-lnb oldboy]# echo 123456|sed -r 's#(1)2(34)5(6)#2#g'

34

[root@oldboyedu42-lnb oldboy]# echo 123456|sed -r 's#(.).(..)..#2#g'

34

小结:

1.()小括号 []中括号 {}大括号花括号

2.后向引用（sed）

4、 {} 花括号

0{n,m} 前一个字符连续出现至少n次，最多m次 >=n && <=m

0{n} 前一个字符连续出现n次 ==n

0{n,} 前一个字符连续出现至少n次 >=n

0{,m} 前一个字符连续出现最多m次 <=m

[root@oldboyedu42-lnb oldboy]# egrep '0{1,4}' re.txt

my qq is 49000448

not 4900000448.

[root@oldboyedu42-lnb oldboy]# egrep '0{1,4}' re.txt -o

000

0000

0

[root@oldboyedu42-lnb oldboy]# egrep '0{2,4}' re.txt

my qq is 49000448

not 4900000448.

[root@oldboyedu42-lnb oldboy]# egrep '0{2,4}' re.txt -o

000

0000

#取出文件中连续出现8次到10次的数字

[root@oldboyedu42-lnb oldboy]# #取出文件中连续出现8次到10次的数字

[root@oldboyedu42-lnb oldboy]# egrep '[0-9]{8,10}' re.txt

my qq is 49000448

not 4900000448.

[root@oldboyedu42-lnb oldboy]# egrep '^[0-9]{17}[0-9X]$' id.txt

440304199604012792

130528197108126121

342923198310042132

61242619860416291X

330900199806382320

330900199806382320

654126197703092303

三、取出ip地址(ifconfig ip）

方法1-sed

[root@oldboyedu42-lnb oldboy]# ifconfig eth0|sed -n '2p'
```
      inet addr:10.0.0.200  Bcast:10.0.0.255  Mask:255.255.255.0
```
[root@oldboyedu42-lnb oldboy]# ifconfig eth0|sed -n '2p'|sed 's#^.*:##g'

255.255.255.0

[root@oldboyedu42-lnb oldboy]# ifconfig eth0|sed -n '2p'|sed 's#^.*addr:##g'

10.0.0.200 Bcast:10.0.0.255 Mask:255.255.255.0

[root@oldboyedu42-lnb oldboy]# ifconfig eth0|sed -n '2p'|sed 's#^.*addr:##g'|sed 's# Bc.*$##g'

10.0.0.200

#方法2-sed-后向引用

[root@oldboyedu42-lnb oldboy]# ifconfig eth0|sed -n '2p'
```
      inet addr:10.0.0.200  Bcast:10.0.0.255  Mask:255.255.255.0
```
[root@oldboyedu42-lnb oldboy]# ifconfig eth0|sed -n '2p'|sed -r 's#^.*dr:(.*) Bc.*$#1#g'

10.0.0.200

#方法3-awk-指定多个分隔符

[root@oldboyedu42-lnb oldboy]# ifconfig eth0|awk 'NR==2'
```
      inet addr:10.0.0.200  Bcast:10.0.0.255  Mask:255.255.255.0
```
[root@oldboyedu42-lnb oldboy]# ifconfig eth0|awk 'NR==2'|awk -F "[ :]+" '{print $4}'

10.0.0.200

[root@oldboyedu42-lnb oldboy]# ifconfig eth0|awk 'NR==2'|egrep '[ :]'
```
      inet addr:10.0.0.200  Bcast:10.0.0.255  Mask:255.255.255.0
```
[root@oldboyedu42-lnb oldboy]# ifconfig eth0|awk 'NR==2'|egrep '[ :]+'
```
      inet addr:10.0.0.200  Bcast:10.0.0.255  Mask:255.255.255.0
```
#方法4-awk-'条件{命令}'

[root@oldboyedu42-lnb ~]# ifconfig eth0|awk 'NR==2'
```
      inet addr:10.0.0.200  Bcast:10.0.0.255  Mask:255.255.255.0
```
[root@oldboyedu42-lnb ~]# ifconfig eth0|awk 'NR==2'|awk '{print $2}'

addr:10.0.0.200

[root@oldboyedu42-lnb ~]# #awk '找谁{干啥}'

[root@oldboyedu42-lnb ~]# #awk '条件{命令}'

[root@oldboyedu42-lnb ~]# ifconfig eth0|awk 'NR==2{print $2}'

addr:10.0.0.200

[root@oldboyedu42-lnb ~]# #错误 ifconfig eth0|awk -F"[ :]+" 'NR==2{print $2}'

[root@oldboyedu42-lnb ~]# ifconfig eth0|awk -F "[ :]+" 'NR==2{print $4}'

10.0.0.200

#方法5-sed

sed -nr '2s#^.*dr:(.*) Bc.*$#1#gp'

sed -n '2s#inet#oldboy#gp'

[root@oldboyedu42-lnb ~]# ifconfig eth0|sed -n '2s#inet#oldboy#gp'
```
      oldboy addr:10.0.0.200  Bcast:10.0.0.255  Mask:255.255.255.0
```
老男孩IT教育出品-sed命令反向引用取出网卡ip地址详解

https://www.processon.com/view/link/59fa9baae4b0f84f8975eefe

#方法6

[root@oldboyedu42-lnb ~]# ip a s eth0 |awk 'NR==3'
```
inet 10.0.0.200/24 brd 10.0.0.255 scope global eth0
```
[root@oldboyedu42-lnb ~]# ip a s eth0 |awk 'NR==3'|awk -F"[ /]+" '{print $3}'

10.0.0.200

#方法7

[root@oldboyedu42-lnb ~]# ip a s eth0 |sed -n '3p'
```
inet 10.0.0.200/24 brd 10.0.0.255 scope global eth0
```
[root@oldboyedu42-lnb ~]# ip a s eth0 |sed -n '3p'|sed -r 's#^.* (.*)/##g'

24 brd 10.0.0.255 scope global eth0

[root@oldboyedu42-lnb ~]# ip a s eth0 |sed -n '3p'|sed -r 's#^.* ([0-9.]+)/.*$#1#g'

10.0.0.200

四、取出文件权限

#方法1

[root@oldboyedu42-lnb ~]# stat /etc/hosts |awk -F "[(/]" 'NR==4'

Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)

[root@oldboyedu42-lnb ~]# stat /etc/hosts |awk -F "[(/]" 'NR==4{print $2}'

0644

#方法2-sed

[root@oldboyedu42-lnb ~]# stat /etc/hosts |sed -n '4p'

Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)

[root@oldboyedu42-lnb ~]# stat /etc/hosts |sed -n '4p'|sed -r 's#^.*(0.*/##g'

root)

[root@oldboyedu42-lnb ~]# stat /etc/hosts |sed -n '4p'|sed -r 's#^.*(0(.*)/-##g'

rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)

[root@oldboyedu42-lnb ~]# stat /etc/hosts |sed -n '4p'|sed -r 's#^.*(0(.*)/-.*$##g'

[root@oldboyedu42-lnb ~]# stat /etc/hosts |sed -n '4p'|sed -r 's#^.*(0(.*)/-.*$#1#g'

644

https://www.processon.com/view/link/59fbc9c0e4b0f84f89765231

#方法3

[root@oldboyedu42-lnb ~]# stat /etc/hosts |awk 'NR==4'|sed -r 's#^.*(0|/.*$##g'

644

#方法4-stat

[root@oldboyedu42-lnb ~]# stat -c%a /etc/hosts

644

[root@oldboyedu42-lnb ~]# #命令的结果中有你想要的

练习题：

1、取ip地址

2、取文件权限
查看全文

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原文地址：https://www.cnblogs.com/Klanti/p/9143253.html

linux基础学习-10.4-正则表达式练习题

一、基础正则

环境准备

1、^ ^m 表示以....开头的行

2、 $ m$ 表示以....结尾的行

3、 ^$ 空行 这一行里面什么都没有

4、 . 任意一个字符 不会匹配空行

5、 撬棍 转义字符 去掉符号特殊含义 脱掉马甲，打回原形

6、 * 前一个字符连续出现0次或0次以上

7、 .* 所有 任何符号

8、 [] [abc] 表示一个整体，a或b或c任意一个字符

9、 [^] 排除 [^abc]

二、扩展正则

1、 + 前一个字符连续出现1次或多次

2、 | 或者

3、 () 变成一个整体 反向引用 后向引用

4、 {} 花括号

三、取出ip地址(ifconfig ip）

方法1-sed

#方法2-sed-后向引用

#方法3-awk-指定多个分隔符

#方法4-awk-'条件{命令}'

#方法5-sed

#方法6

#方法7

四、取出文件权限

#方法1

#方法2-sed

#方法3

#方法4-stat

练习题：

3、 ^$ 空行这一行里面什么都没有

4、 . 任意一个字符不会匹配空行

5、撬棍转义字符去掉符号特殊含义脱掉马甲，打回原形

7、 .* 所有任何符号

3、 () 变成一个整体反向引用后向引用