正则表达式是一种字符模式，用于在查找过程中匹配制定的字符。
元字符通常在Linux中分为两类：
Shell元字符，由Linux Shell进行解析；
正则表达式元字符，由vi/grep/sed/awk等文本处理工具进行解析；
正则表达式一般以文本行进行处理，在进行下面实例之前，先为grep命令设置--color参数：
[root@node01 mnt]# alias grep='grep --color=auto'
这样每次过滤出来的字符串都会带色彩了。
在开始之前还需要做一件事情，就是创建如下两个文件：
[root@node01 mnt]# cat re-file
I had a lovely time on our little picnic.
Lovers were all around us. It is springtime. Oh
love, how much I adore you. Do you know
the extent of my love? Oh, by the way, I think
I lost my gloves somewhere out in that field of
clover. Did you see them? I can only hope love
is forever. I live for you. It's hard to get back in the
groove.
[root@node01 mnt]# cat linux.txt
Linux is a good
god assdxw bcvnbvbjk
greatttttt wexcvxc
operaaaating dhfghfvx
gooodfs awrerdxxhkl
gdsystem awxxxx
glad
good
正则表达式元字符
| 元字符 | 功能 |
|---|---|
^ |
行以什么开头 |
$ |
行以什么结尾 |
. |
匹配任意单个字符 |
* |
匹配任意0次或多次字符串 |
[xy] |
匹配x或y中的任意单个字符 |
[x-y] |
匹配x~y范围内的任意单个字符 |
[^x-y] |
匹配不在x~y范围内的任意单个字符 |
\ |
转义字符 |
特殊的元字符
| 元字符 | 功能 |
|---|---|
< |
单词以什么开头 |
> |
单词以什么开头 |
() \1 |
标签匹配以后使用的字符串，最大支持9个 |
{n} |
匹配任意n次字符串 |
{n,} |
匹配任意n次或多次字符串 |
{n,m} |
匹配任意n次到m次字符串 |
扩展的正则表达式
| 元字符 | 功能 |
|---|---|
+ |
匹配任意1次或多次字符串 |
? |
匹配任意0次或1次字符串 |
| |
表示或 |
() |
分组过滤匹配 |
实例
- 匹配以love开头的所有行
[root@node01 mnt]# grep '^love' re-file
love, how much I adore you. Do you know
- 匹配以love结尾的所有行
[root@node01 mnt]# grep 'love$' re-file
clover. Did you see them? I can only hope love
- 匹配包含以l开头、中间包含两个字符、结尾是e的字符串的所有行
[root@node01 mnt]# grep 'l..e' re-file
I had a lovely time on our little picnic.
love, how much I adore you. Do you know
the extent of my love? Oh, by the way, I think
I lost my gloves somewhere out in that field of
clover. Did you see them? I can only hope love
is forever. I live for you. It's hard to get back in the
- 匹配包含0个或多个空行、后面是love的字符串的所有行
[root@node01 mnt]# grep ' *love' re-file
I had a lovely time on our little picnic.
love, how much I adore you. Do you know
the extent of my love? Oh, by the way, I think
I lost my gloves somewhere out in that field of
clover. Did you see them? I can only hope love
- 匹配包含love或Love的所有行
[root@node01 mnt]# grep '[lL]ove' re-file
I had a lovely time on our little picnic.
Lovers were all around us. It is springtime. Oh
love, how much I adore you. Do you know
the extent of my love? Oh, by the way, I think
I lost my gloves somewhere out in that field of
clover. Did you see them? I can only hope love
- 匹配包含以A-Z开头、后面是ove的字符串的所有行
[root@node01 mnt]# grep '[A-Z]ove' re-file
Lovers were all around us. It is springtime. Oh
- 匹配包含小写字符的所有行
[root@node01 mnt]# grep '[^A-Z]' re-file
I had a lovely time on our little picnic.
Lovers were all around us. It is springtime. Oh
love, how much I adore you. Do you know
the extent of my love? Oh, by the way, I think
I lost my gloves somewhere out in that field of
clover. Did you see them? I can only hope love
is forever. I live for you. It's hard to get back in the
groove.
- 匹配包含love的所有行
[root@node01 mnt]# grep 'love' re-file
I had a lovely time on our little picnic.
love, how much I adore you. Do you know
the extent of my love? Oh, by the way, I think
I lost my gloves somewhere out in that field of
clover. Did you see them? I can only hope love
- 匹配包含空格的所有行
[root@node01 mnt]# grep ' ' re-file
I had a lovely time on our little picnic.
Lovers were all around us. It is springtime. Oh
love, how much I adore you. Do you know
the extent of my love? Oh, by the way, I think
I lost my gloves somewhere out in that field of
clover. Did you see them? I can only hope love
is forever. I live for you. It's hard to get back in the
- 匹配包含任意字符的所有行
[root@node01 mnt]# grep '.*' re-file
I had a lovely time on our little picnic.
Lovers were all around us. It is springtime. Oh
love, how much I adore you. Do you know
the extent of my love? Oh, by the way, I think
I lost my gloves somewhere out in that field of
clover. Did you see them? I can only hope love
is forever. I live for you. It's hard to get back in the
groove.
- 匹配包含o重复2~4次的字符串的所有行
[root@node01 mnt]# grep -E 'o{2,4}' re-file
groove.
- 匹配包含重复o最少2次的字符串的所有行
[root@node01 mnt]# grep -E 'o{2,}' re-file
groove.
- 匹配包含重复o最多2次的字符串的所有行
[root@node01 mnt]# grep -E 'o{0,2}' re-file
I had a lovely time on our little picnic.
Lovers were all around us. It is springtime. Oh
love, how much I adore you. Do you know
the extent of my love? Oh, by the way, I think
I lost my gloves somewhere out in that field of
clover. Did you see them? I can only hope love
is forever. I live for you. It's hard to get back in the
groove.
- 匹配包含以g开头、重复o最少1次、以d结尾的字符串的所有行
[root@node01 mnt]# grep -E 'go+d' linux.txt
Linux is a good
god assdxw bcvnbvbjk
gooodfs awrerdxxhkl
good
- 匹配包含以g开头、重复o最多1次、以d结尾的字符串的所有行
[root@node01 mnt]# grep -E 'go?d' linux.txt
god assdxw bcvnbvbjk
gdsystem awxxxx
- 匹配包含gd或good的所有行
[root@node01 mnt]# grep -E 'gd|good' linux.txt
Linux is a good
gdsystem awxxxx
good
- 匹配包含glad或good的所有行
[root@node01 mnt]# grep -E 'g(la|oo)d' linux.txt
Linux is a good
glad
good
- 匹配包含以g开头和结尾的字符串的所有行
[root@node01 mnt]# grep -E '(g).*\1' linux.txt
operaaaating dhfghfvx
常用正则表达式公式总结
一、校验数字的表达式
- 数字：
^[0-9]*$ - n位的数字：
^d{n}$ - 至少n位的数字：
^d{n,}$ - m~n位的数字：
^d{m,n}$ - 零和非零开头的数字：
^(0|[1-9][0-9]*)$ - 非零开头的最多带两位小数的数字：
^([1-9][0-9]*)+(.[0-9]{1,2})?$ - 带1~2位小数的正数或负数：
^(-)?d+(.d{1,2})$ - 正数、负数、和小数：
^(-|+)?d+(.d+)?$ - 有两位小数的正实数：
^[0-9]+(.[0-9]{2})?$ - 有1~3位小数的正实数：
^[0-9]+(.[0-9]{1,3})?$ - 非零的正整数：
^[1-9]d*$或^([1-9][0-9]*){1,3}$或^+?[1-9][0-9]*$ - 非零的负整数：
^-[1-9][]0-9"*$或^-[1-9]d*$ - 非负整数：
^d+$或^[1-9]d*|0$ - 非正整数：
^-[1-9]d*|0$或^((-d+)|(0+))$ - 非负浮点数：
^d+(.d+)?$或^[1-9]d*.d*|0.d*[1-9]d*|0?.0+|0$ - 非正浮点数：
^((-d+(.d+)?)|(0+(.0+)?))$或^(-([1-9]d*.d*|0.d*[1-9]d*))|0?.0+|0$ - 正浮点数：
^[1-9]d*.d*|0.d*[1-9]d*$或^(([0-9]+.[0-9]*[1-9][0-9]*)|([0-9]*[1-9][0-9]*.[0-9]+)|([0-9]*[1-9][0-9]*))$ - 负浮点数：
^-([1-9]d*.d*|0.d*[1-9]d*)$或^(-(([0-9]+.[0-9]*[1-9][0-9]*)|([0-9]*[1-9][0-9]*.[0-9]+)|([0-9]*[1-9][0-9]*)))$ - 浮点数：
^(-?d+)(.d+)?$或^-?([1-9]d*.d*|0.d*[1-9]d*|0?.0+|0)$
二、校验字符的表达式
- 汉字：
^[一-龥]{0,}$ - 英文和数字：
^[A-Za-z0-9]+$或^[A-Za-z0-9]{4,40}$ - 长度为3~20的所有字符：
^.{3,20}$ - 由26个英文字母组成的字符串：
^[A-Za-z]+$ - 由26个大写英文字母组成的字符串：
^[A-Z]+$ - 由26个小写英文字母组成的字符串：
^[a-z]+$ - 由数字和26个英文字母组成的字符串：
^[A-Za-z0-9]+$ - 由数字、26个英文字母或者下划线组成的字符串：
^w+$或^w{3,20}$ - 中文、英文、数字包括下划线：
^[一-龥A-Za-z0-9_]+$ - 中文、英文、数字但不包括下划线等符号：
^[一-龥A-Za-z0-9]+$或^[一-龥A-Za-z0-9]{2,20}$ - 禁止输入含有~的字符：
[^~"]+
三、特殊需求表达式
- Email地址：
^w+([-+.]w+)*@w+([-.]w+)*.w+([-.]w+)*$ - 域名：
[a-zA-Z0-9][-a-zA-Z0-9]{0,62}(/.[a-zA-Z0-9][-a-zA-Z0-9]{0,62})+/.? - InternetURL：
[a-zA-z]+://[^s]*或^http://([w-]+.)+[w-]+(/[w-./?%&=]*)?$ - 手机号码：
^(13[0-9]|14[5|7]|15[0|1|2|3|5|6|7|8|9]|18[0|1|2|3|5|6|7|8|9])d{8}$ - 国内电话号码（0511-4405222、021-87888822）：
d{3}-d{8}|d{4}-d{7} - 电话号码（支持手机号码，34位区号，78位直播号码，1~4位分机号）：
((d{11})|^((d{7,8})|(d{4}|d{3})-(d{7,8})|(d{4}|d{3})-(d{7,8})-(d{4}|d{3}|d{2}|d{1})|(d{7,8})-(d{4}|d{3}|d{2}|d{1}))$) - 身份证号（15位、18位数字），最后一位是校验位，可能为数字或字符X：
(^d{15}$)|(^d{18}$)|(^d{17}(d|X|x)$) - 帐号是否合法（字母开头，允许5~16字节，允许字母数字下划线）：
^[a-zA-Z][a-zA-Z0-9_]{4,15}$ - 密码（以字母开头，长度在6~18之间，只能包含字母、数字和下划线）：
^[a-zA-Z]w{5,17}$ - 强密码（必须包含大小写字母和数字的组合，不能使用特殊字符，长度在8~10之间）：
^(?=.*d)(?=.*[a-z])(?=.*[A-Z])[a-zA-Z0-9]{8,10}$ - 强密码（必须包含大小写字母和数字的组合，可以使用特殊字符，长度在8~10之间）：
^(?=.*d)(?=.*[a-z])(?=.*[A-Z]).{8,10}$ - 日期格式：
^d{4}-d{1,2}-d{1,2}$ - 一年的12个月(0109和112)：
^(0?[1-9]|1[0-2])$ - 一个月的31天(0109和131)：
^((0?[1-9])|((1|2)[0-9])|30|31)$ - XML文件：
^([a-zA-Z]+-?)+[a-zA-Z0-9]+\.[x|X][m|M][l|L]$ - 中文字符：
^[一-龥]$ - 空白行：
s* - HTML标记：
<(S*?)[^>]*>.*?|<.*? /> - 腾讯QQ号：
[1-9][0-9]{4,} - 中国邮政编码：
[1-9]d{5}(?!d) - IP地址：
((?:(?:25[0-5]|2[0-4]\d|[01]?\d?\d)\.){3}(?:25[0-5]|2[0-4]\d|[01]?\d?\d))
正则表达式在线测试