Regular expressions (regex) are a powerful tool for pattern matching in strings. They are used in various programming languages and text processing tools to search, find, and manipulate text.

What is a Regular Expression?

A regular expression is a sequence of characters that forms a search pattern. It can be used to search for specific patterns in strings, validate input, or manipulate text.

Syntax

Here's a basic syntax of a regular expression:

  • ^ - Start of the string
  • $ - End of the string
  • . - 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
  • [] - A character class; matches any one of the enclosed characters
  • () - Grouping; used to create subexpressions

Examples

Here are some examples of regex patterns:

  • ^hello - Matches any string that starts with "hello"
  • world$ - Matches any string that ends with "world"
  • a.*b - Matches any string that contains "a" followed by any characters and ends with "b"
  • [a-z] - Matches any lowercase letter

Resources

For more information on regular expressions, you can visit the following resources:

Regex Pattern