Regular Expressions Quick Reference¶
A regular expression (also known as regex or regexp) is a special sequence of characters that defines a search pattern.
Example References¶
| Description | Regex Example | Match Example | Compatibility |
|---|---|---|---|
| Locate "foo" and "bar". | ^(?s)(?=.*foo)(?=.*bar) | Bar said "foo how are you doing today"? | PCRE |
| String starts with 79 and has a given date/time. | ^79|([a-zA-Z]+).*?\|2013-12-20 12:30:00 | 79|eng|813100|||TVPG|L|2013-12-20 12:30:00|30|0|0| |1|0|0|0|1|0|0|0||0|0|0|0|0|0|||0|0|0|0 | Notepad++ (POSIX) |
| String contains " (Mapped to: " and ends with a line feed (\n). | (Mapped to: .*?\n | ATMAX (Mapped to: MAXLAT | Notepad++ (POSIX) |
| Boundary Character Class (case in-sensitive) | /\bthe\b/i | The new music channel. | PHP, PCRE |
| Camel Case | ^[a-z]+(?:[A-Z][a-z]+)*$ | ||
| Email Address | /^\w+([\.-]?\w+)*@\w+([\.-]?\w+)*(\.\w{2,3})+$/ | foobar@example.com | PHP |
| Hostname | ^(([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9\-]*[a-zA-Z0-9])\.)*([A-Za-z0-9]|[A-Za-z0-9][A-Za-z0-9\-]*[A-Za-z0-9])$ | ||
| IPv4 Address | ^(([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.){3}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])$ | ||
| Postal Code | /^[a-z]\d[a-z] ?\d[a-z]\d$/i | S7H 0A1 | PHP |
| Longitude | /^[-]?((((1[0-7][0-9])|([0-9]?[0-9]))\.(\d+))|180(\.0+)?)$/ | -1.21321 | PHP |
| Latitude | /^[-]?(([0-8]?[0-9])\.(\d+))|(90(\.0+)?)$/ | -12.213213 | PHP |
| Longitude/Latitude | /^[-]?(([0-8]?[0-9])\.(\d+))|(90(\.0+)?);[-]?((((1[0-7][0-9])|([0-9]?[0-9])\.(\d+))|180(\.0+)?)$/ | -12.213213;-1.21321 | PHP. More Info |
| Multiple White space Characters | /\s+/ | How are you today? | PHP, PCRE |
| NIC MAC Address with Delimiters | /^[0-9a-fA-F]{2}(?=([:;.]?))(?:\\1[0-9a-fA-F]{2}){5}$/ | 1C:6F:65:34:A7:34 | PHP, PCRE |
| NIC MAC Address without Delimiter (case in-sensitive) | /^[0-9a-fA-F]{12}$/ | 1C6F6534a734 | PHP, PCRE |
| One and Two Character Words | /(?<!\S)\S{1,2}(?!\S)/ | He is the one who walks a line. | PHP, PCRE |
| Network IP v4 Address | /^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$/ | 127.0.0.1 | PHP, PCRE |
| Pascal Case | /^[A-Z][a-z0-9]*(?:[A-Z][a-z0-9]*)$/ | ||
| Punctuation and Symbols | /[[:punct:]]/ | He's doing fine. How are you? | PHP, PCRE |
| Semantic Version | ^(0|[1-9][0-9]*)\\.(0|[1-9][0-9]*)\\.(0|[1-9][0-9]*)(\\-[0-9A-Za-z-]+(\\.[0-9A-Za-z-]+)*)?(\\+[0-9A-Za-z-]+(\\.[0-9A-Za-z-]+)*)?$ | ||
| UUID | ^[0-9a-fA-F]{8}-([0-9a-fA-F]{4}-){3}[0-9a-fA-F]{12}\Z | b80a121a-51a6-11e5-a734-b827eb8df375 | Python, PCRE |
| USA Zip Code with optional dash/last 4 digits | /^[0-9]{5}(-[0-9]{4})?$/ | 12345 | PHP, PCRE |
| USA Zip Code 5 or 9 digit with dash | /^\d{5}([\-]\d{4}){0,1}$/ | PHP, PCRE |
In-depth Explanation¶
NIC MAC Address Explanation with Delimiters¶
^ => Match the beginning of the string
[0-9a-fA-F]{2} => Match the hexadecimal value
(?=([:;.]?)) => Lookahead (?=) and try to match the first delimiter (:;.). Storing the value matched in a backreference.
You'll note the [:;.] is inside "()" to capture the matched value. The "?" means matching the [:;.] is optional.
(?:\\1[0-9a-fA-F]{2}){5} => surrounding a pattern in () means group and capture the matched pattern in a backreference.
The ?: following the opening "(" means don't capture the pattern matched. Only group it.
The \\1 holds the value of the 1st backreference. In this case the delimiter. We try to match the delimiter we first
matched then a hexadecimal value 5 times ({5}).
$ => matches the end of the string.
Universally Unique Identifier (UUID)¶
Searching for UUIDs in text with regex