Appendix C: Common Regex Patterns

This appendix presents some practical regex patterns that you can use for common matching and validation tasks.

Table C-1: IP Address *^(([0-1]?\d{1,2}\.)|(2[0-4]\d\.)|(25[0-5]\.)){3} (([0-1]?\d{1,2})|(2[0-4]\d)|(25[0-5]))*$
Regex	Description
^	Beginning of line
(	A group consisting of
(	A subgroup consisting of
[0-1]?	Zero or one, both optional, followed by
\d	Any digit
{1,2}	Repeated one or two times, followed by
\.	A period
)	Close subgroup
\|	Or
(	A subgroup consisting of
2	The digit 2, followed by
[0-4]	Any digit from 0 to 4, followed by
\d	Any digit, followed by
\.	A period
)	Close subgroup
\|	Or
(	A subgroup consisting of
2	The digit 2, followed by
5	The digit 5, followed by
[0-5]	Any digit from 0 to 5, followed by
\.	A period
)	Close subgroup
)	Close group
{3}	Repeated three times, followed by
(	A group consisting of
(	A subgroup consisting of
[0-1]?	Zero or one, both optional, followed by
\d{1,2}	Any two digits
)	Close subgroup
\|	Or
(	A subgroup consisting of
2	The digit 2, followed by
[0-4]	Any digit from 0 to 4, followed by
\d	Any digit
)	Close subgroup
\|	Or
(	A subgroup consisting of
2	The digit 2, followed by
5	The digit 5, followed by
[0-5]	Any digit from 0 to 5, followed by
)	Close subgroup
)	Subgroup
$	End of line
* In English: Three sets of three digits separated by periods, each ranging from 0 to 255, followed by three digits, each ranging from 0 to 255.

Note

The following pattern also matches the IP address, but all the groups have been marked as noncapturing:

(?:(?:[0-1]?\d{1,2}\.)|(?:2[0-4]\d\.)|(?:25[0-5]\.)){3}(?:(?:[0-1]?\
d{1,2})|(?:2[0-4]\d)|(?:25[0-5]))

This is slightly more efficient than the previous pattern, but it's less legible.

Table C-2: Simple E-mail *^(\p{Alnum}+(\.|\_|\-)?)*\p{Alnum}@(\p{Alnum}+ (\.|\_|\-)?)*\p{Alpha}*$
Regex	Description
^	Beginning of line
(	A group consisting of
\p{Alnum}	A letter or a digit
+	Repeated one or more times, followed by
(	A subgroup consisting of
\.	A period
\|	Or
\_	An underscore
\|	Or
\-	A hyphen
)	Close subgroup
?	The preceding punctuation is optional
)	Close group
*	The previous group can be repeated zero or more times,
	followed by
\p{Alnum}	A letter or a digit, followed by
@	An @ symbol, followed by
\p{Alnum}	A letter or a digit
+	Repeated one or more times, followed by
(	A group consisting of
\.	A period
\|	Or
\_	An underscore
\|	Or
\-	A hyphen
)	Close group
?	The preceding punctuation is optional
\p{Alpha}	An upper- or lowercase letter
$	End of line
* In English: Any number of alphanumeric characters followed by single hyphens, periods, or underscores, but ending in an alphanumeric character; followed by an @ symbol; followed by any number of alphanumeric characters; followed by single hyphens, periods, or underscores, but ending in an upper- or lowercase character.

Note

The following pattern matches the previous one exactly, except that it allows an IP address as well:

^(\p{Alnum}+(\.|\_|\-)?)*\p{Alnum}@(((\p{Alnum}+(\.|\_|\-)?)*
\p{Alpha})|((([0-1]?\d{1,2}\.)|(2[0-4]\d\.)|(25[0-5]\.)){3}(([0-1]?\d{1,2})|
(2[0-4]\d)|(25[0-5]))))$

For a breakdown of the IP address pattern, please see Table C-1.

Table C-3: Digit Repeated Exactly n Times *\d{n}*, Where n Is the Number of Digits Needed
Regex	Description
\d	Any number
{n}	Repeated n times
* In English: n digits. Thus, if n was equal to 4, any four digits.

Table C-4: Characters Repeated Exactly n Times *\w{n}*, Where n Is the Number of Characters Needed
Regex	Description
\w	Any number, any digit, or an underscore symbol
{n}	Repeated n times
* In English: n characters. Thus, if n was equal to 4, any four characters.

Table C-5: Characters Repeated n to m Times *\w{n.m}*, Where n Is the Number of Characters Needed
Regex	Description
\w	Any number, any digit, or an underscore symbol
{n	Repeated n times
m}	But not more than m times
* In English: n characters. Thus, if n was equal to 4 and m was equal to 9, any four, five, six, seven, eight, or nine characters.

Table C-6: Credit Cards: Visa, MasterCard, American Express, and Discover *^((4\d{3})|(5[1-5]\d{2})|(6011))-?\d{4}-?\d{4}-?\d{4}|3[4,7]\d{13}*$
Regex	Description
^	Beginning of line
(	A group consisting of
(	A subgroup consisting of
4	the digit four, followed by
\d[3]	Any three digits
)	Close subgroup
\|	Or
(	A subgroup consisting of
5	The digit 5, followed by
[1-5]	Any digit ranging from 1 to 5, followed by
\d[2]	Any two digits
)	Close subgroup
\|	Or
(	A subgroup consisting of
6001	The digits 6, 0, 0, 1
)	Close subgroup, followed by
-?	An optional hyphen, followed by
\d{4]	Any four digits, followed by
-?	An optional hyphen, followed by
\d{4]	Any four digits, followed by
-?	An optional hyphen, followed by
\d{4]	Any four digits, followed by
-?	An optional hyphen
\|	Or
3	The digit 3, followed by
[4,7]	A 4 or a 7, followed by
\d{13]	Any thirteen digits, followed by
$	End of line
* In English: A number starting with 4 and three digits, or 5 and three digits, or 6011, followed by a hyphen, followed by three sets of four digits, or 34 and thirteen digits, or 37 and thirteen digits.

Note

This regex does not, and cannot, conform to mod 10 verification. To find a Java program that does, please visit http://www.influxs.com.

Table C-7: Real Number *^[+-]?\d+(\.\d+)?*$
Regex	Description
^	Beginning of line, followed by
[+-]?	An optional plus or a minus sign
\d+	Followed by one or more digits, followed by
(	A group consisting of
\.	A period, followed by
\d+	One or more digits
)?	Close group, and make it optional
$	End of line
* In English: Any number of digits followed by an optional decimal component.