Emacs: Find and Replace Commands

By Xah Lee. Date: . Last updated: .

This page shows you how to use emacs to do find replace.

Find Replace Commands

Here are the most useful find replace commands. These are also under the menu 〖Edit ▸ Replace〗.

Interactive Find Replace Commands
Command NameKeyTargetPurpose
query-replaceAlt+%active region, or cursor point to endinteractive find/replace
query-replace-regexpCtrl+Alt+%active region, or cusor point to endinteractive find replace with regex pattern
dired-do-query-replace-regexpIn dired, 【Q】.marked files in diredinteractive find replace on multiple files

For example, call query-replace, then type your search string, then type your replacement string.

When a query command asks you for confirmation, here's the most common keys:

For detail on using dired-do-query-replace-regexp, see: Emacs: Find Replace Text in Directory.

Batch Replace

replace-string → find & replace in one shot, without asking for each. From cursor position to end of buffer, or, in a text selection.

replace-regexp → same as replace-string but with regex.

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Default Case Sensitivity: Smart

By default: If your search string contains a capital letter, search is automatically case-sensitive, otherwise it's not case-sensitive.

By default, the case of the replaced text is smartly dependent on the matched text. For example, suppose your search string is here, and your replacement string is dragon. Emacs will find any of {here, Here, HERE}. Now, when emacs found here, the replacement will be dragon, when emacs found Here, the replacement will be Dragon, when emacs found HERE, the replacement will be DRAGON.

If you want the letter case of your replacement string be exactly as you have it, you need to set the variable case-replace to nil. You can do so by calling set-variable.

Turn Off Smart Case Sensitivity

Call toggle-case-fold-search or menu 〖Options ▸ Case-Insensitive Search〗.

You can also give it a key such as F8. 〔➤see Emacs: How to Define Keys〕 Or you can give it a alias such as “tc” 〔➤see Emacs: Use Alias for Fast M-x

Force Case Change on Matched Text in Regex Match

If you are doing a regex search, and you want to force the replacement to upper case or lower case, in the replace prompt, give \,(upcase \1) or \,(downcase \1).

For example, suppose you have this text:

<p>once upon a time …</p>

<p>There is a dragon who lived in …</p>

<p>princess Tana is still waiting …</p>

Suppose you want all paragraphs to start with a capital letter. So, you use a pattern that catches the first letter after <p>, like this <p>\([a-z]\).

To make your captured pattern upper case, give your replacement string this expression: <p>\,(upcase \1). The \, tells emacs that what follows should be a lisp expression. The (upcase \1) is a lisp expression. The upcase is a lisp function and the \1 means the 1st captured string in your regex pattern.

For a more complex example in using the \, in replacement, see: Regex Replace with a Function in Emacs Lisp.

(info "(emacs) Search")

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