Linux 正则表达式
文章目录
正则表达式介绍
- 正则表达式作为一个 pattern，将 pattern 与要搜索的字符串进行匹配，以便查找一个或多个字符串。
- 正则表达式，自成体系，由普通字符 （例如字符 a 到 z）和元字符组成的文字模式。
- 正则表达式，工具（vim、grep、less...）和程序语言都使用正则表达式。
正则表达式分类
- 普通正则表达式
- 扩展正则表示，支持更多的元字符
准备环境
bash
[root@server ~ 14:11:25]# vim words
[root@server ~ 14:13:16]# cat words
cat
category
acat
concatenate
cbt
c1t
cCt
c-t
c.t
dog字符集
bash
#匹配除换行符（\n、\r）之外的任何单个字符
[root@server ~ 14:12:19]# cat words | grep .
cat
category
acat
concatenate
cbt
c1t
cCt
c-t
c.t
dog
[root@server ~ 14:16:28]# cat words | grep 'cat'
cat
category
acat
concatenate
[root@server ~ 14:19:25]# cat words | grep 'c.t'
cat
category
acat
concatenate
cbt
c1t
cCt
c-t
c.t
[root@server ~ 14:19:33]# cat words | grep 'c[ab]t'
cat
category
acat
concatenate
cbt
[root@server ~ 14:19:57]# cat words | grep 'c[a-z]t'
cat
category
acat
concatenate
cbt
[root@server ~ 14:20:04]# cat words | grep 'c[A-Z]t'
cCt
[root@server ~ 14:20:14]# cat words | grep 'c[a-z0-9]t'
cat
category
acat
concatenate
cbt
c1t
[root@server ~ 14:20:23]# cat words | grep 'c[a-zA-Z0-9]t'
cat
category
acat
concatenate
cbt
c1t
cCt
[root@server ~ 14:20:46]# cat words | grep 'c[-a-zA-Z0-9]t'
cat
category
acat
concatenate
cbt
c1t
cCt
c-t
[root@server ~ 14:20:59]# cat words | grep 'c[a-zA-Z0-9-]t'
cat
category
acat
concatenate
cbt
c1t
cCt
c-t
[root@server ~ 14:21:06]# cat words | grep 'c[^ab]t'
c1t
cCt
c-t
c.t
# ^放中间会被当做普通字符
[root@server ~ 14:21:22]# cat words | grep 'c[a^b]t'
cat
category
acat
concatenate
cbt
[root@server ~ 14:21:33]# cat words | grep 'c\.t'
c.t
[root@server ~ 14:23:12]# cat words | grep 'c.t'
cat
category
acat
concatenate
cbt
c1t
cCt
c-t
c.t
# 使用egrep或者grep -E 匹配
[root@server ~ 14:23:16]# cat words | egrep 'cat|dog'
cat
category
acat
concatenate
dog
[root@server ~ 14:24:04]# cat words | grep -E 'cat|dog'
cat
category
acat
concatenate
dog
bash
#查看十一月24日到今天的所有日志
[root@server ~ 15:13:15]# cat /var/log/messages | egrep '^Nov 2[4-9]|^Nov 30|^Dec 1'
#[[:punct:]]匹配标点符号非打印字符
bash
[root@server ~ 16:55:08]# cat words | grep '^cat'
cat
category
[root@server ~ 17:05:51]# cat words | grep 'cat$'
cat
acat
[root@server ~ 17:06:01]# echo hello cat kitty >> words
[root@server ~ 17:06:31]# cat words | grep '\bcat'
cat
category
hello cat kitty
[root@server ~ 17:06:43]# cat words | grep 'cat\b'
cat
acat
hello cat kitty
[root@server ~ 17:06:53]# cat words | grep '\bcat\b'
cat
hello cat kitty
[root@server ~ 17:07:00]# cat words | grep '\Bcat\B'
concatenate
[root@server ~ 17:07:14]# echo dg >> words
[root@server ~ 17:07:24]# echo doog >> words
[root@server ~ 17:07:28]# cat words | grep 'do*g'
dog
dg
doog
[root@server ~ 17:07:39]# cat words | egrep 'do+g'
dog
doog
[root@server ~ 17:07:47]# cat words | egrep 'do?g'
dog
dg
[root@server ~ 17:07:52]# cat words | egrep 'do{2}g'
doog
[root@server ~ 17:08:00]# echo dooog >> words
[root@server ~ 17:08:07]# echo doooog >> words
[root@server ~ 17:08:11]# cat words | egrep 'do{2,3}g'
doog
dooog
[root@server ~ 17:08:15]# cat words | egrep 'do{2,}g'
doog
dooog
doooog
[root@server ~ 17:08:24]# cat words | egrep 'do{,3}g'
dog
dg
doog
dooog
[root@server ~ 17:08:28]# echo dogdog >> words
[root@server ~ 17:08:51]# echo dogdogdog >> words
[root@server ~ 17:08:57]# cat words | egrep '(dog){2,3}'
dogdog
dogdogdog综合练习
bash
#如果所有启用的仓库都配置enabled=1
cd /etc/yum.repos.d
[root@server yum.repos.d 16:11:59]# cat *.repo | egrep -B8 -e enabled=1enabled=0
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
[epel]
name=Extra Packages for Enterprise Linux 7 - $basearch
baseurl=http://mirrors.aliyun.com/epel/7/$basearch
failovermethod=priority
enabled=1
[root@server yum.repos.d 16:12:32]# cat *.repo | egrep -B8 -e enabled=1 | grep '^\['
[epel]
#查询/etc/profile文件中有效行
[root@server ~ 15:46:21]# cat /etc/profile | egrep -v '^\s*#|^$'综合实验
bash
#准备环境
[root@server ~ 16:16:26]# cat ip.list
0.0.0.0
1.1.1.1
11.11.11.111
111.111.111.111
999.9.9.9
01.1.1.1
10.0.0.0
0.1.1.1
266.1.1.1
248.1.1.1
256.1.1.1
#过滤出所有有效IPv4地址
[root@server ~ 16:17:11]# cat ip.list | egrep '\b(([1-9]?[0-9])|(1[0-9]{2})|(2[0-4][0-9])|(25[0-4]))(\.(([1-9]?[0-9])|(1[0-9]{2})|(2[0-4][0-9])|(25[0-4]))){3}\b'
0.0.0.0
1.1.1.1
11.11.11.111
111.111.111.111
10.0.0.0
0.1.1.1
248.1.1.1
#0-255
[root@server ~ 16:54:44]# cat ip.list | egrep '^(([1-9]?[0-9])|(1[0-9]{2})|(2[0-4][0-9])|(25[0-5]))(\.(([1-9]?[0-9])|(1[0-9]{2})|(2[0-4][0-9])|(25[0-5]))){3}$'
0.0.0.0
1.1.1.1
11.11.11.111
111.111.111.111
10.0.0.0
0.1.1.1
248.1.1.1
#可访问https://tool.chinaz.com/regex/查看更多匹配规则10.0.0.0
0.1.1.1
248.1.1.1
#0-255
root@server \~ 16:54:44\]# cat ip.list \| egrep '\^((\[1-9\]?\[0-9\])\|(1\[0-9\]{2})\|(2\[0-4\]\[0-9\])\|(25\[0-5\]))(.((\[1-9\]?\[0-9\])\|(1\[0-9\]{2})\|(2\[0-4\]\[0-9\])\|(25\[0-5\]))){3}$' 0.0.0.0 1.1.1.1 11.11.11.111 111.111.111.111 10.0.0.0 0.1.1.1 248.1.1.1 #可访问https://tool.chinaz.com/regex/查看更多匹配规则 ``` ```