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Version vom 30. August 2021, 15:10 Uhr

Notes for RegEx respectively Regular Expressions and also some useful ressources.

General Rules

Meta Characters
Meta Character Example
Single Character .
Character class digit \d
Character class character \w

Character class whitespace
(Space, tab, new line, carriage return)

\s
Inversion of character classes (Not) \D, \W, \S
Word and text boundaries b ^ $
Ranges
Range Example
Character class range [a-c]
Inversion of character class range [^abc]
Quantifiers
Quantifier Example
Zero or one character ?
Zero or more characters (Kleene Star) *
One or more characters (Kleene Plus) +
Three characters {3}
Four to 20 characters {4,20}


White Space Characters
White Space Example
Space _
Tab \t
New line \n
Carriage return \r
Any white space character \s


Line start and end
Type Example
Start of line ^
End of line $


Groups and nested groups
Type String Expression Results
Group Example 1 IMG1000.png ^(IMG\d+\.png)$ IMG1000.png
Group Example 2 IMG1000.png ^(IMG\d+)\.png$ IMG1000
Nested group IMG1000.png ^(IMG(\d+))\.png$

Group 1: IMG1000
Group 2: 1000

Multiple groups 1920x1080 (\d+)x(\d+)

Group 1: IMG1000
Group 2: 1000

Grouping with alternatives Monday or Tuesday (Mon|Tues)day

Match 1: Monday
Group 1: Mon
Match 2: Tuesday
Group 2: Tues

Online Regex Tools

Tutorials and Guides

Guide (german): https://t3n.de/news/regex-guide-t3n-552858/

Quick Start Cheat Sheet: https://www.rexegg.com/regex-quickstart.html

Advanced tutorial: https://www.rexegg.com/regex-disambiguation.html

Practical tutorial: https://regexone.com/

Regex with JavaScript: https://www.freecodecamp.org/learn/javascript-algorithms-and-data-structures/#regular-expressions