About Regular Expressions
Regular expressions (regex) are patterns used to find matches in text strings. They are powerful tools for data validation, text search and replace, and information extraction.
Basic Metacharacters
Any character (except newline)
Zero or more occurrences
One or more occurrences
Zero or one occurrence (optional)
Start of string/line
End of string/line
Character Classes
Any digit [0-9]
Any word character [a-zA-Z0-9_]
Any whitespace
Any character in the set
Any character not in the set
Groups and Alternation
Capture group
Non-capture group
Alternation (a or b)
Usage Tips
Start with simple patterns and add complexity gradually. Use the 'i' flag for case-insensitive searches. Test your regex with various test cases, including edge cases. Remember to escape special characters like . * + ? etc. when you want to use them literally.