Regular Expressions 101

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Community Patterns

10

MikroTik FireWall

PCRE (PHP <7.3)
Regex used in Splunk to extract fields from Mikrotik FW. NOTES: Mikrotik must be configured to use "BSD Syslog" format FW rules must add, as log prefix, the action: drop accep...
Submitted by HappyIdeasMaker - 10 years ago
10

If-Then-Else Conditionals

PCRE (PHP <7.3)
no description available
Submitted by anonymous - 9 years ago
10

money: either 0 or 2 dp

ECMAScript (JavaScript)
no description available
Submitted by anonymous - 9 years ago
238

Matching email addresses per RFC5322

PCRE (PHP <7.3)
The BNF rules from RFC 5322 transformed to PCRE by Nikita Popov and described in the post http://nikic.github.io/2012/06/15/The-true-power-of-regular-expressions.html.
Submitted by Michael Musson - 11 years ago
483

regex101.com permalink id grabber

PCRE (PHP <7.3)
Grabs the ID for the regex101.com permalink code. If a revision number is provided, grab that as well.
Submitted by chris mccoy - 11 years ago (Last modified 8 months ago)
9

Fixo LDN CSP e SEM CSP

PCRE (PHP <7.3)
no description available
Submitted by Marcos Müller - 10 years ago
13

US Currency Format

ECMAScript (JavaScript)
no description available
Submitted by anonymous - 9 years ago
15

us postal/zip

ECMAScript (JavaScript)
no description available
Submitted by jay johnson - 11 years ago
84

Distinguish torrent files (series vs movies)

Python
A neat regex for finding out whether a given torrent name is a series or a movie. Returns the full name of the series with the separator needed to make it pretty (ie, replace it with space or what you want). Also returns the season number or the year for the movie/series, depending on what was prev...
Submitted by Firas Dib - 10 years ago (Last modified a year ago)
8

IP Address (with 0s)

ECMAScript (JavaScript)
Matches all valid IP addresses from 0.0.0.0 to 255.255.255.255
Submitted by Ryan Plummer - 9 years ago
10

entity

Python
no description available
Submitted by anonymous - 9 years ago
6

Quartz Cron Validation

PCRE (PHP <7.3)
http://stackoverflow.com/questions/2362985/verifying-a-cron-expression-is-valid-in-java
Submitted by anonymous - 9 years ago
6

Find and extract email domain

Python
Find and extract email domain. Ex: test@example.pt -> extract 'example.pt'
Submitted by Fnxk - 9 years ago
25

grab valid css rules and properties

ECMAScript (JavaScript)
no description available
Submitted by Pavel Dominguez - 10 years ago
11

UUID

ECMAScript (JavaScript)
no description available
Submitted by anonymous - 10 years ago
11

IPv4 Validator

PCRE (PHP <7.3)
no description available
Submitted by anonymous - 4 years ago (Last modified a year ago)
15

Email regex validation

ECMAScript (JavaScript)
RegEx email /^((?!\.)[\w-_.]*)(@\w+)(\.\w+(\.\w+)?)$/gim; Just playing with Reg Ex. This to validate emails in following ways ...
Submitted by https://www.linkedin.com/in/peralta-steve-atileon/ - 6 years ago (Last modified a year ago)
12

Find Reddit Threads

Python
Simply searches for the thread-id in any kind of valid reddit-URL.
Submitted by Mio - 10 years ago
10

extract subdomain(if available) or domain from URL

Python
This regex should extract the subdomain, if any, or the domain, if no subdomain is used, from an arbitrary URL
Submitted by trevi@twanda.com - 9 years ago
11

youtube url match

ECMAScript (JavaScript)
extract video id, index, play list id from youtube url
Submitted by anonymous - 9 years ago
1...899900901902

Community Library Entry

1

Regular Expression
PCRE2 (PHP >=7.3)

/
^( # Match only leap years \d\d[2468][048] # multiple of four but not 100 |\d\d[13579][26] # ... |\d\d0[48] # ... |[02468][048]00 # multiple of four hundred |[13579][26]00 # ... )$
/
gmux
Open regex in editor

Description

This will match all four-digit years that are leap years, using the "either (multiple of four but not a multiple of 100) OR (multiple of 400)" rule.

Explained

/
^(
  \d\d[2468][048]|\d\d[13579][26]|\d\d0[48]| # multiple of four but not 100
     [02468][048]00  |[13579][26]00          # multiple of four hundred
)$
/gmx

References

Test Cases

//	accept: multiple of four ()
0004
0008
0012
0016
0020
0024
0028
0032
0036
0040
0044
0048
0052
0056
0060
0064
0068
0072
0076
0080
0084
0088
0092
0096
1560
2004
2008
2012
2016
2020
2024
2028
2032
2036
2040
2044
9996
//	accept: Multiple of 400
0000
0400
0800
1200
1600
2000
2400
2800
3200
3600
4000
4400
4800
5200
5600
6000
6400
6800
7200
7600
8000
8400
8800
9200
9600
//	REJECT: Not a multiple of four
0101
0102
0103
1537
1538
2001
2002
2003
2021
2022
2023
2025
2026
2027
2029
2030
2031
2033
2034
2035
2037
2038
2039
2041
2042
2043
9997
9998
9999
//	REJECT: Multiple of 100 but not 400
0100
0200
0300
0500
0600
0700
0900
1000
1100
1500
2100
2200
2300
2500
2600
2700
2900
3000
3100
3300
3400
3500
3700
//	REJECT: Negative dates not accepted (malformed)
-2000
-0400
-0100
-0004
//	REJECT: Out of range date per RFC 3339
10000
Submitted by Philip Flip Kromer - 2 years ago (Last modified 2 months ago)