shell 正则

正则的主要作用 处理文本内容

基础正则

^ 定位起始头的

[root@RainGod ~]# grep '^y' /etc/passwd
yt03:x:1002:1002::/home/yt03:/bin/bash
yt01:x:1003:1003::/home/yt01:/bin/bash
yt02:x:1004:1004::/home/yt02:/bin/bash

$ 定位结束尾部信息

[root@RainGod ~]# grep 'n$' /etc/passwd
bin:x:1:1:bin:/bin:/sbin/nologin
daemon:x:2:2:daemon:/sbin:/sbin/nologin
adm:x:3:4:adm:/var/adm:/sbin/nologin

^$ 空行

[root@RainGod ~]# cat test.txt 
11



22
[root@RainGod ~]# grep '^$' test.txt 



[root@RainGod ~]# grep -v '^$' test.txt 
11
22

. 点 匹配任意一个字符

[root@RainGod ~]# cat test.txt 
11

22
[root@RainGod ~]# grep "." test.txt -o 
1
1
2
2

* 匹配*号前面的字符出现0次或者多次

[root@RainGod ~]# cat test.txt 
11



22
[root@RainGod ~]# grep ".*" test.txt -o 
11
22

.* 匹配所有内容

[root@RainGod ~]# cat test.txt 
11
i  like fsfs  fsf   ball
22
[root@RainGod ~]# grep "i.*ball" test.txt 
i  like fsfs  fsf   ball   fsdfsd  fsdfsd 
[root@RainGod ~]# grep "i.*ball" test.txt  -o
i  like fsfs  fsf   ball

\ 转义符

[root@RainGod ~]# grep '.' test.txt 
11 .
i  like fsfs  fsf   ball   fsdfsd  fsdfsd .
22
[root@RainGod ~]# grep '\.' test.txt 
11 .
i  like fsfs  fsf   ball   fsdfsd  fsdfsd .

[] 或者的意思 匹配多个信息 按照每一个字符匹配

[root@RainGod ~]# grep '.' test.txt 
11 .
i  like fsfs  fsf   ball   fsdfsd  fsdfsd .
22
[root@RainGod ~]# grep '\.' test.txt 
11 .
i  like fsfs  fsf   ball   fsdfsd  fsdfsd .
[root@RainGod ~]# grep "[1]"  test.txt 
11 .
[root@RainGod ~]# grep "[1i]"  test.txt 
11 .
i  like fsfs  fsf   ball   fsdfsd  fsdfsd .

[]取反

[root@RainGod ~]# grep "^[^#]" /etc/selinux/config 
SELINUX=disabled
SELINUXTYPE=targeted 
[root@RainGod ~]# awk '/^[^#]/' /etc/selinux/config 
SELINUX=disabled
SELINUXTYPE=targeted 
[root@RainGod ~]# sed -n '/^[^#]/p' /etc/selinux/config 
SELINUX=disabled
SELINUXTYPE=targeted 

扩展正则

+ 表示前面一个字符连续出现1次及以上 *表示前面一个字符连续出现0次及以上

[root@RainGod ~]# egrep 'l+' test.txt  -o
l
ll
[root@RainGod ~]# grep 'l*' test.txt 
11 .

i  like fsfs  fsf   ball   fsdfsd  fsdfsd .

22
[root@famous-machine-1 ~]# egrep "[0-9]+" test.txt -o
110102199805296211
110102199805299877
110102199805299076
110102199805298559
110102199805296836
11010219980529817

| 匹配多个信息时 当做或者使用

[root@famous-machine-1 ~]# egrep "oldboy|oldgirl" test.txt 
冯   oldboy
oldgirl

() 把括号里的内容当做一个整体

[root@famous-machine-1 ~]# egrep "(oldboy|oldgirl)" test.txt 
冯   oldboy
oldgirl

{n,m} 花括号指定匹配的次数 最少出现n次 最多出现m次

[root@RainGod ~]# cat test.txt 
o
o
oo
ooo
oooo
ooooo
[root@RainGod ~]# egrep "o{1,4}" test.txt  -o
o
o
oo
ooo
oooo
oooo
o

? 匹配0次或一次

[root@RainGod ~]# grep "go*d" test1.txt  -o
gd
god
good
goood
gooood
[root@RainGod ~]# egrep "go+d" test1.txt  -o
god
good
goood
gooood
[root@RainGod ~]# egrep "go?d" test1.txt  -o
gd
god

正则取ip

grep 
[root@famous-machine-1 ~]# ip a s eth0|grep inet|egrep "([0-9]+\.?){4}" -o|head -n 1
206.190.238.90
awk
[root@famous-machine-1 ~]# ip a s eth0|awk -F"[ /]+" 'NR==3{print $3}'
206.190.238.90
sed
[root@famous-machine-1 ~]# ip a s eth0|sed -rn 's#.*net (.*)/22.*#\1#gp'
206.190.238.90