一、正则表达式 RE regular expression
1、什么是正则 为何用它？
你可以通过什么方法选出这里面的身份证号码。
440304199604012792
130528197108126121
3605sss98304033896
342923198310042132
1404ddddddddd5694X
61242619860416291X
5002xxxxxx04279521
330900199806382320
654126197703092303
131127197105115662
数字与X(在最后一位)
通过符号匹配查找出各种文字。
正则表达式通过特殊符号 ^ $ [] . * 表示各种各样的文字。
方便我们处理文本（日志）。
2、正则使用范围
谁可以使用正则？
三剑客正则(grep sed awk )
python java
3、正则表达式与通配符区别
正则-----在文件中进行过滤（查找文件内容） 三剑客支持
通配符---找出文件（文件名） 大部分命令都可以使用
4、使用正则注意事项
1) 正则默认是按照行为单位处理。
2) 一定要注意不要使用中文符号。
. ‘‘""^ `` ( ) {} [] <>
。‘’“”……??（ ）{}【】《》
3) 给grep/egrep加上别名
cat >>/etc/profile<<EOF
alias grep=‘grep --color=auto‘
alias egrep=‘egrep --color=auto‘
EOF
source /etc/profile
5、正则分类
基础正则: ^ $ . * []
扩展正则: + | () {} ?
基本正则 grep sed
扩展的正则 egrep sed -r awk
适合linux三剑客
以行为单位处理
cat >>/etc/profile<<EOF
alias egrep=‘egrep --color=auto‘
alias grep=‘grep --color=auto‘
EOF
source /etc/profile
export LC_ALL=C
测试文件
cat >>~/test/oldboy.log<<EOF
I am oldboy teacher!
I teach linux.
I like badminton ball ,billiard ball and chinese chess!
my blog ishttp://oldboy.blog.51cto.com
our site ishttp://www.etiantian.org
my qq num is 49000448.
not 4900000448.
my god ,i am not oldbey,but OLDBOY!
gd
good
god
goood
gooood
oldboy1
EOF
二、基础正则
基础正则(BRE)第一波字符说明
1、 ^word 匹配开头word
2、 word$ 匹配word结尾
3、 ^$ 匹配开头结尾 即空行
[[email protected] test]# grep "^m" oldboy.log
my blog ishttp://oldboy.blog.51cto.com
my qq num is 49000448.
my god ,i am not oldbey,but OLDBOY!
[[email protected] test]# grep "m$" oldboy.log
my blog ishttp://oldboy.blog.51cto.com
[[email protected] test]# grep -n "^$" oldboy.log
3:
8:
[[email protected] test]# grep "^m" oldboy.log
my blog ishttp://oldboy.blog.51cto.com
my qq num is 49000448.
my god ,i am not oldbey,but OLDBOY!
[[email protected] test]# grep -n "^$" oldboy.log
3:
8:
[[email protected] test]# grep "oldboy" oldboy.log
I am oldboy teacher!
my blog ishttp://oldboy.blog.51cto.com
[[email protected] test]# grep "oldb.y" oldboy.log
I am oldboy teacher!
my blog ishttp://oldboy.blog.51cto.com
my god ,i am not oldbey,but OLDBOY!
[[email protected] test]# grep "oldb.y" oldboy.log -o
oldboy
oldboy
oldbey
[[email protected] test]# grep ".$" oldboy.log
I teach linux.
my qq num is 49000448.
not 4900000448.
基础正则（BRE）第二波字符说明
. 代表且只能代表任意一个字符
转译符号，特殊字符还原本意
\n 表示换行
\n 在 echo sed awk 中使用
* 匹配前面的一个字符0次或多次（任意多次）
.* 匹配任意一个字符任意多次（任意字符串）
^.* 匹配开头任意字符串
[[email protected] test]# grep "^.*o" oldboy.log
I am oldboy teacher!
I like badminton ball ,billiard ball and chinese chess!
my blog ishttp://oldboy.blog.51cto.com
our site ishttp://www.etiantian.org
not 4900000448.
my god ,i am not oldbey,but OLDBOY!
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
[[email protected] test]# grep -n "." oldboy.log
2:I teach linux.
5:my blog ishttp://oldboy.blog.51cto.com
6:our site ishttp://www.etiantian.org
7:my qq num is 49000448.
9:not 4900000448.
[[email protected] test]# grep -n "." oldboy.log
1:I am oldboy teacher!
2:I teach linux.
4:I like badminton ball ,billiard ball and chinese chess!
5:my blog ishttp://oldboy.blog.51cto.com
6:our site ishttp://www.etiantian.org
7:my qq num is 49000448.
9:not 4900000448.
10:my god ,i am not oldbey,but OLDBOY!
[[email protected] test]# grep -n ".*" oldboy.log
1:I am oldboy teacher!
2:I teach linux.
3:
4:I like badminton ball ,billiard ball and chinese chess!
5:my blog ishttp://oldboy.blog.51cto.com
6:our site ishttp://www.etiantian.org
7:my qq num is 49000448.
8:
9:not 4900000448.
10:my god ,i am not oldbey,but OLDBOY!
基础正则（BRE）第三波字符说明
[abc] 匹配a、b、c任意一个字符
[^abc] 匹配非a、非b、非c 任意一个字符
a{n,m} 匹配a这个字符 n到m次
a{n,} 匹配a这个字符至少n次
a{n} 匹配a这个字符n次
a{,m} 匹配a这个字符最多m次
注意： 上面的 是转义 ，但是在 egrep (grep -E) 或 sed -r 或 awk {} 不需要转义
[[email protected] test]# grep -n "[abc]" oldboy.log
1:I am oldboy teacher!
2:I teach linux.
4:I like badminton ball ,billiard ball and chinese chess!
5:my blog ishttp://oldboy.blog.51cto.com
6:our site ishttp://www.etiantian.org
10:my god ,i am not oldbey,but OLDBOY!
[[email protected] test]# grep -n "[^abc]" oldboy.log
1:I am oldboy teacher!
2:I teach linux.
4:I like badminton ball ,billiard ball and chinese chess!
5:my blog ishttp://oldboy.blog.51cto.com
6:our site ishttp://www.etiantian.org
7:my qq num is 49000448.
9:not 4900000448.
10:my god ,i am not oldbey,but OLDBOY!
[[email protected] test]# grep -n "[a-Z0-9]" oldboy.log
1:I am oldboy teacher!
2:I teach linux.
4:I like badminton ball ,billiard ball and chinese chess!
5:my blog ishttp://oldboy.blog.51cto.com
6:our site ishttp://www.etiantian.org
7:my qq num is 49000448.
9:not 4900000448.
10:my god ,i am not oldbey,but OLDBOY!
[[email protected] test]# grep -n "^[abc]" oldboy.log
[[email protected] test]# grep -n "[^abc]" oldboy.log
1:I am oldboy teacher!
2:I teach linux.
4:I like badminton ball ,billiard ball and chinese chess!
5:my blog ishttp://oldboy.blog.51cto.com
6:our site ishttp://www.etiantian.org
7:my qq num is 49000448.
9:not 4900000448.
10:my god ,i am not oldbey,but OLDBOY!
[[email protected] test]# grep -n "^[^abc]" oldboy.log
1:I am oldboy teacher!
2:I teach linux.
4:I like badminton ball ,billiard ball and chinese chess!
5:my blog ishttp://oldboy.blog.51cto.com
6:our site ishttp://www.etiantian.org
7:my qq num is 49000448.
9:not 4900000448.
10:my god ,i am not oldbey,but OLDBOY!
[[email protected] test]# grep "[^a-z]" oldboy.log
I am oldboy teacher!
I teach linux.
I like badminton ball ,billiard ball and chinese chess!
my blog ishttp://oldboy.blog.51cto.com
our site ishttp://www.etiantian.org
my qq num is 49000448.
not 4900000448.
my god ,i am not oldbey,but OLDBOY!
[[email protected] test]# grep "[^0-9]" oldboy.log
I am oldboy teacher!
I teach linux.
I like badminton ball ,billiard ball and chinese chess!
my blog ishttp://oldboy.blog.51cto.com
our site ishttp://www.etiantian.org
my qq num is 49000448.
not 4900000448.
my god ,i am not oldbey,but OLDBOY!
[[email protected] test]# grep "[^0-9]" oldboy.log
I am oldboy teacher!
I teach linux.
I like badminton ball ,billiard ball and chinese chess!
my blog ishttp://oldboy.blog.51cto.com
our site ishttp://www.etiantian.org
my qq num is 49000448.
not 4900000448.
my god ,i am not oldbey,but OLDBOY!
[[email protected] test]# grep -v "[0-9]" oldboy.log
I am oldboy teacher!
I teach linux.
I like badminton ball ,billiard ball and chinese chess!
our site ishttp://www.etiantian.org
my god ,i am not oldbey,but OLDBOY!
[[email protected] test]# grep "[0-9]" oldboy.log
my blog ishttp://oldboy.blog.51cto.com
my qq num is 49000448.
not 4900000448.
[[email protected] test]# grep "0{2,3}" oldboy.log
my qq num is 49000448.
not 4900000448.
[[email protected] test]# grep -o "0{2,3}" oldboy.log
000
000
00
[[email protected] test]# grep "0{1,5}" oldboy.log
my qq num is 49000448.
not 4900000448.
[[email protected] test]# grep -o "0{1,5}" oldboy.log
000
00000
[[email protected] test]# egrep "0{1,5}" oldboy.log
my qq num is 49000448.
not 4900000448.
[[email protected] test]# egrep -o "0{1,5}" oldboy.log
000
00000
三、扩展正则
. 匹配前面一个字符一次或多次
a+ 匹配a这个字符一次或多次
? 匹配前面一个字符0次或1次
a? 匹配a这个字符0次或1次
| 表示或者 用于同时过滤多个
( ) 分组 后向引用
egrep "0+" oldboy.txt
egrep -o "0+" oldboy.txt
egrep -o "[a-z]+" oldboy.txt
egrep "[a-z]+" oldboy.txt
egrep -o "[a-z]+" oldboy.txt
egrep -o "[a-zA-Z]+" oldboy.txt
egrep -o "[a-Z]+" oldboy.txt
[[email protected] test]# egrep "go?d" oldboy.log
my god ,i am not oldbey,but OLDBOY!
gd
god
[[email protected] test]# egrep "go+d" oldboy.log
my god ,i am not oldbey,but OLDBOY!
good
god
goood
gooood
[[email protected] test]# egrep "go*d" oldboy.log
my god ,i am not oldbey,but OLDBOY!
gd
good
god
goood
gooood
[[email protected] test]# egrep "go{0,3}d" oldboy.log
my god ,i am not oldbey,but OLDBOY!
gd
good
god
goood
[[email protected] test]# dumpe2fs /dev/sda1 |grep -i "inode size"
dumpe2fs 1.41.12 (17-May-2010)
Inode size: 128
[[email protected] test]# dumpe2fs /dev/sda1 |grep -i "block size"
dumpe2fs 1.41.12 (17-May-2010)
Block size: 1024
[[email protected] test]# dumpe2fs /dev/sda1 |grep -i "inode count"
dumpe2fs 1.41.12 (17-May-2010)
Inode count: 51200
[[email protected] test]# dumpe2fs /dev/sda1 |grep -i "block count"
dumpe2fs 1.41.12 (17-May-2010)
Block count: 204800
Reserved block count: 10240
[[email protected] ~]# echo "##**##@@##@##*#[email protected]@@@@@@2**@@@**##**" |egrep "[#@*]+"
##**##@@##@##*#[email protected]@@@@@@2**@@@**##**
[[email protected] ~]# echo "##**##@@##@##*#[email protected]@@@@@@2**@@@**##**" |egrep "[#@*]+" -o
##**##@@##@##*#
@@@@@@@
**@@@**##**
[[email protected] test]# egrep "oldb(o|e)y" oldboy.log
I am oldboy teacher!
my blog ishttp://oldboy.blog.51cto.com
my god ,i am not oldbey,but OLDBOY!
oldboy1
[[email protected] test]# dumpe2fs /dev/sda1 |egrep -i "(inode|block) size"
dumpe2fs 1.41.12 (17-May-2010)
Block size: 1024
Inode size: 128
[[email protected] test]# dumpe2fs /dev/sda1 |egrep -i "(inode|block) count"
dumpe2fs 1.41.12 (17-May-2010)
Inode count: 51200
Block count: 204800
Reserved block count: 10240
[[email protected] test]# dumpe2fs /dev/sda1 |egrep -i "(inode|block) (size|count)"
dumpe2fs 1.41.12 (17-May-2010)
Inode count: 51200
Block count: 204800
Reserved block count: 10240
Block size: 1024
Inode size: 128
练习题：
1、什么是正则及正则的作用？
2、基础正则的相关符号
3、扩展正则的相关符号
原文地址：https://www.cnblogs.com/Klanti/p/9143248.html