Emacs: Regular Expression

By Xah Lee. Date: . Last updated: .

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.

(video tutorial: xah talk show 2022-08-04 emacs regular expression)

Regex Commands

The most commonly used commands that use regex are:

Example:

  1. Open a file with many lines.
  2. Alt+x list-matching-lines
  3. type th.t

It will list all lines that contains the regex pattern th.t, which includes β€œthis”, β€œthat”. The dot . character in regex is a wildcard, matching any character.

Emacs Regular Expression

Regex in Emacs Lisp

Emacs Find Replace


Emacs Tutorial

Quick Start

Font

Split Window

File

Buffer

Find Replace

Copy/Paste

Unicode

Whitespace

Rectangle Edit

Line Wrap

Shell

View Special File

Editing Brackets

Org Mode

HTML

Emacs Efficiency

Misc