Regular expressions (regex) are a powerful tool for text processing and pattern matching. They are widely used in programming and data analysis. This guide provides an overview of regex syntax and usage.
Basic Syntax
- Pattern Matching: A regex pattern is used to match strings against a specific pattern.
- Characters: The characters in a regex pattern have special meanings. For example,
.matches any character except a newline, while*matches zero or more of the preceding element. - Quantifiers: Quantifiers specify how many times an element should occur. For example,
*matches zero or more,+matches one or more, and?matches zero or one.
Common Regex Symbols
.: Matches any character except a newline.*: Matches zero or more of the preceding element.+: Matches one or more of the preceding element.?: Matches zero or one of the preceding element.^: Matches the beginning of a line.$: Matches the end of a line.[]: Defines a character class, matching any of the enclosed characters.(): Groups elements for grouping and capturing.
Examples
.*: Matches any string.a.*b: Matches any string containing "a" followed by "b".[a-z]: Matches any lowercase letter.[a-z]*: Matches any string consisting of one or more lowercase letters.
Resources
For more information on regex, please visit our Regex Reference.