RH134-01 配合grep使用正则表达式

第二章、配合grep使用正则表达式

2.1 正则表达式基础

介绍shell中的常用正则表达式

^   以什么开头             ^#

$   以什么结尾              y$

.   匹配任意一个字符

.*匹配0个或若干个字符

h*匹配0个h或若干个h

h+匹配1个或更多个h

h?匹配0个或1个h

h{2}  匹配 hh (两个hh)

[abc]匹配a或b或c

[a-z]匹配所有的小写字符

[A-Z]匹配大写字母

[a-Z]匹配所有字符

[0-9]匹配所有数字

练习：匹配 IP地址的格式，但无需判断IP是否合理。格式要求满足 以 "."分割是四组数字,每组数字可以1~3位数

0.0.0.0- 255.255.255.255

[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}

2.2、使用grep匹配数据

使用grep和正则表达式过滤文件内容和需要的日志内容

练习：建立一个文本/tmp/cats.txt，文本内容如下

cat

caaat

catdog

cat2dog

catanddog

dogcat

ccat

catdogcccc

c123t

c45678t

Cat

cAt

catdogDogCAT

#this is a cat

;this is a dog

$ grep "cat"/tmp/cats.txt

$ grep -i "cat"/tmp/cats.txt  忽略大小写

$ grep  ^cat /tmp/cats.txt

$ grep  dog$ /tmp/cats.txt

$ grep ^catdog$  /tmp/cats.txt

$ grep ^cat.*dog$  /tmp/cats.txt

$ grep ^cat.dog$  /tmp/cats.txt

$ grep ^cat...dog$  /tmp/cats.txt

$ grep -E^cat.{3}dog$  /tmp/cats.txt  中间3个任意字符

$ grep ^c[0-9]*t$/tmp/cats.txt  [0-9]*  匹配0个或若干个数字

$ grep -E^"[#;]" /tmp/cats.txt 以# ;开头的

$ grep -e ^"#"-e ^";" /tmp/cats.txt  作用同上，-e 可以通过指定多个表达式

练习1：过去日志，把 August 8 sometime between 1:00pm and 3:00pm 时间段的日志找到

http://classroom.example.com/pub/materials/awesome_logs/door.log

$ grep "Aug  8 1[34]"  door.log

=========================================================================

2.2

上课笔记

2．2

[[email protected] tmp]$ cat cats.txt

t

catdog

cat2dog

catanddog

dogcat

ccat

catdogcccc

c123t

c45678t

Cat

cAt

catdogDogCAT

#this is a cat

;this is a dog

[[email protected] tmp]$

[[email protected] tmp]$

[[email protected] tmp]$ grep"cat" /tmp/cats.txt

[[email protected] tmp]$ grep"cat" /tmp/cats.txt

catdog

cat2dog

catanddog

dogcat

ccat

catdogcccc

catdogDogCAT

#this is a cat

[[email protected] tmp]$ grep -i"cat" /tmp/cats.txt

catdog

cat2dog

catanddog

dogcat

ccat

catdogcccc

Cat

cAt

catdogDogCAT

#this is a cat

[[email protected] tmp]$

[[email protected] tmp]$ grep ^cat/tmp/cats.txt

catdog

cat2dog

catanddog

catdogcccc

catdogDogCAT

[[email protected] tmp]$

可以对要找的内容加双 引号，也可以不加

[[email protected] tmp]$ grep ^cat /tmp/cats.txt

catdog

cat2dog

catanddog

catdogcccc

catdogDogCAT

[[email protected] tmp]$ ^C

[[email protected] tmp]$ grep"^cat" /tmp/cats.txt

catdog

cat2dog

catanddog

catdogcccc

catdogDogCAT

[[email protected] tmp]$

[[email protected] tmp]$ grep dog$/tmp/cats.txt

catdog

cat2dog

catanddog

;this is a dog

[[email protected] tmp]$ grep ^catdog$/tmp/cats.txt

catdog

[[email protected] tmp]$

[[email protected] tmp]$ grep ^cat.*dog$/tmp/cats.txt

catdog

cat2dog

catanddog

[[email protected] tmp]$

.*0个或 若干个其他字符

[[email protected] tmp]$ grep ^cat.dog$/tmp/cats.txt

cat2dog

[[email protected] tmp]$

.表示一个字符

[[email protected] tmp]$ grep -E^cat.{3}dog$ /tmp/cats.txt

catanddog

[[email protected] tmp]$ grep ^cat...dog$/tmp/cats.txt

catanddog

[[email protected] tmp]$

以上两种相同，前者显得更专业

[[email protected] tmp]$  grep ^c[0-9]*t$ /tmp/cats.txt

c123t

c45678t

ct也可以匹配

$ grep -E^"[#;]" /tmp/cats.txt 以# ;开头的

[[email protected] tmp]$ grep -E^"[#;]" /tmp/cats.txt

#this is a cat

;this is a dog

[[email protected] tmp]$ ifconfig | grep[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}

对输出结果进行查找

练习：

先下载 下来

[[email protected] tmp]$ wget -O/tmp/door.log  http://classroom.example.co

m/pub/materials/awesome_logs/door.log

--2017-06-25 12:22:01-- http://classroom.example.com/pub/materials/awesome_logs/door.log

Resolving classroom.example.com(classroom.example.com)... 172.25.254.254

Connecting to classroom.example.com(classroom.example.com)|172.25.254.254|:80... connected.

HTTP request sent, awaiting response... 200OK

Length: 58722 (57K) [text/plain]

Saving to: ‘/tmp/door.log’

100%[======================================>]58,722      --.-K/s   in 0.001s

2017-06-25 12:22:02 (43.6 MB/s) -‘/tmp/door.log’ saved [58722/58722]

[[email protected] tmp]$

grep -E "Aug  8 1[34]" /tmp/door.log

Aug 8之间是两个空格。

考题：

Grep  “UUID” /etc/fstab  > /tmp/find.txt