Regular Expressions 101

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Community Patterns

1

Extract URL, FTP, Mailto

ECMAScript (JavaScript)
extract url such as http, https:, ftp and mailto from a string
Submitted by Kumar Sundaram - 8 years ago
1

Months Regex

ECMAScript (JavaScript)
For Month Verification Works for January / Jan / Jan.
Submitted by F0123X - 8 years ago
1

Password minimum requirements

PCRE (PHP <7.3)
Password requirements (minimum length, character groups that must exist) can be easily validated AND extended using look-aheads.
Submitted by OnlineCop - 8 years ago
1

Floating Point number verifier and extractor with scientific notation support

PCRE (PHP <7.3)
The regex verifies floating point numbers in decimal or scientific notation with extensive error checking - however, there may be edge cases which i haven't addressed, so feel free to put in more unit tests!
Submitted by Tamoghna Chowdhury - 8 years ago
1

RFC-1034- and RFC-2181-compliant FQDN extractor

PCRE (PHP <7.3)
The specification for this regex is based upon the extracts from RFC 1034 and RFC 2181 below. It is also assumed that you are trying to extract the FQDN from a pipe-delimited string. If this is not the case then you will need to adjust the regex as necessary by either removing the pipe character o...
Submitted by 0jag - 8 years ago
1

Extract the only the Nth field from a delimited string

PCRE (PHP <7.3)
The aim of this regex is to extract only the Nth field from a delimited string. In the example provided the delimited is the pipe character. You will have to substitute the pipe character for whatever delimiter you are using.
Submitted by 0jag - 8 years ago
1

Remove Markdown Links

PCRE (PHP <7.3)
no description available
Submitted by anonymous - 8 years ago
1

Make PHP var_dump() output more compact

PCRE (PHP <7.3)
The PHP function var_dump() provides debugging output, but has more line-breaks than is needed for readability. This regex strips out the (in my eyes) unnecessary line-breaks. Good in a self written debugging method in combination with ob_start()and ob_get_contents().
Submitted by Doqnach - 8 years ago
1

URL Slugs Optimized

PCRE (PHP <7.3)
This slug regex is optimized using strictly my own opinions. Slugs: Should be english, alphanumeric phrases separated with a single dash. Should not contain single alpha character between dashes. ...
Submitted by Jordon Baade - 8 years ago
1

A revised e-mail validation regular expression

PCRE (PHP <7.3)
This one allows to begin with a digit, however, sometimes e-mail should begin with an *English letter *
Submitted by anonymous - 8 years ago
1

Date checker for X values

ECMAScript (JavaScript)
Work in progress
Submitted by anonymous - 8 years ago
1

Youtube ID Extractor

PCRE (PHP <7.3)
no description available
Submitted by anonymous - 8 years ago
1

Telegram bot deep linking

PCRE (PHP <7.3)
Telegram bot deep linking Telegram bots have a deep linking mechanism, that allows for passing additional parameters to the bot on startup. It could be a command that launches the bot — or an auth token to connect the user's Telegram account to their account on some external service. ...
Submitted by SadeghPM@gmail.com - 8 years ago
1

Phone numbers and/or extensions(relaxed)

ECMAScript (JavaScript)
Useful for phone number extraction
Submitted by hslayer - 7 years ago
1

Localhost/private ip origin check

PCRE (PHP <7.3)
Used by CORS to check for localhost/private IP origins Check out the unit tests at /r/2Ofume/1/tests
Submitted by ngokimphu - 7 years ago
1

Formatar CPF

PCRE (PHP <7.3)
Retorna um cpf no formato 123.456.789-11. Cpf de entrada deve conter apenas números
Submitted by anonymous - 7 years ago
1

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 - 7 years ago
1

Word Wrap examples

PCRE2 (PHP >=7.3)
Four examples of word wrapping at the 80 character mark, each one taking fewer steps than the last. Comment and uncomment lines with # to see the difference between versions. Optimization discussions welcome!
Submitted by OnlineCop - 7 years ago (Last modified a year ago)
1

Matching an Saudi Postal Code

PCRE (PHP <7.3)
Saudi Postal Code has five digits, if you would to have more information check the below: +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ First Digit (Postal Regions): "The postal region number is represented by the first digit of the postal code" ...
Submitted by Fares Alarabi - 7 years ago
1

Email matching with a grain of salt

PCRE (PHP <7.3)
Inspired by Micheal Musson entry Wich was hard to use in regex flavours that don't support recursion (C# engine doesn't) i've build my own simpler version wich matches what i would accept as validation entry
Submitted by Luigi Trabacchin - 7 years ago
1...760761762763764...902

Community Library Entry

1

Regular Expression
PCRE (PHP <7.3)

/
\|\K(?=.{1,253}\|)(?!.*--.*)(?P<fqdn>(?:(?!-)(?![0-9])[a-zA-Z0-9-]{1,63}(?<!-)\.){1,}(?:(?!-)[a-zA-Z0-9-]{1,63}(?<!-)))\|
/
gm
Open regex in editor

Description

The specification for this regex is based upon the extracts from RFC 1034 and RFC 2181 below.

It is also assumed that you are trying to extract the FQDN from a pipe-delimited string.

If this is not the case then you will need to adjust the regex as necessary by either removing the pipe character or replacing it with a different delimiter e.g. comma.

RFC 1034

3.5. Preferred name syntax

The labels must follow the rules for ARPANET host names. They must start with a letter, end with a letter or digit, and have as interior characters only letters, digits, and hyphen. There are also some restrictions on the length. Labels must be 63 characters or less.

RFC 2181

  1. Name Syntax

The DNS itself places only one restriction on the particular labels that can be used to identify resource records. That one restriction relates to the length of the label and the full name. The length of any one label is limited to between 1 and 63 octets. A full domain name is limited to 255 octets (including the separators).

Summary:

  • Valid characters [a-zA-Z0-9-]

  • FQDN length = 1-253

  • FQDN must not end with a dot.

  • Label length = 1-63

  • Labels must start with a letter.

  • Labels must not end with a hyphen.

  • Labels must not contain a double hyphen.

Submitted by 0jag - 8 years ago