Welcome to the Regular Expression Tutorial! Regular expressions (regex) are a powerful tool used in programming to match patterns in text. They are widely used for tasks such as data validation, search and replace, and parsing.

What is a Regular Expression?

A regular expression is a sequence of characters that defines a search pattern. It can be used to search for specific patterns in text, or to perform operations on text that matches the pattern.

Basic Components of a Regular Expression

  • ** Literals **: Characters that match themselves (e.g., a, 1, *).
  • ** Metacharacters **: Special characters that have a special meaning (e.g., . matches any character, * matches zero or more of the preceding element).
  • ** Groups **: Used to combine multiple elements into a single unit (e.g., (a|b) matches either a or b).
  • ** Quantifiers **: Specify how many times an element should be repeated (e.g., * matches zero or more, + matches one or more).

Examples

  • To match any single character, use ..
  • To match any digit, use \d.
  • To match any letter, use [a-zA-Z].
  • To match a sequence of characters, use *.

Example 1: Matching Email Addresses

To match an email address, you can use the following regular expression:

[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}

This regex will match email addresses like example@example.com.

Example 2: Matching Phone Numbers

To match a phone number, you can use the following regular expression:

\+?1?\d{9,15}

This regex will match international phone numbers with up to 15 digits.

Resources

For more information on regular expressions, you can visit our Regular Expression Reference page.