Emacs: Regular Expression

What is Regular Expression

Regular Expression (aka regex) is a character sequence that represent a pattern for matching text. For example, you can use it to find all email addresses in a file by matching the email address pattern. Regex is used by many functions to check if a string contains certain pattern, or extract it, or replace it with other string.

Regex Commands

The most commonly used commands that use regex are:

• Alt+x list-matching-lines 〔see Emacs: List Matching Lines〕
• Alt+x query-replace-regexp 〔see Emacs: Find Replace in Current File〕