Emacs: Find Replace in Current File

By Xah Lee. Date: . Last updated: .

How to find replace?

Alt+x query-replaceAlt+%】. Emacs will prompt you for the find string and replace string.

Once emacs found a match, press

To undo, cancel search first, then Ctrl+_ to undo existing replacement.

Find Replace Commands

Here are the most useful find replace commands for current file.

Alt+x query-replaceAlt+%
Interactive find replace on text selection, or cursor position to end of buffer.
Alt+x query-replace-regexpCtrl+Alt+%
Interactive find replace with regex, on text selection, or cusor point to end of buffer. [see Emacs: Regular Expression]
Alt+x dired-do-query-replace-regexp (In dired, Q)
Interactive find replace on marked files in dired. See: Emacs: Interactive Find Replace Text in Directory.

How to Insert Literal Tab, Newline

In search prompt:

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 Alt+x set-variable.

Turn Off Smart Case Sensitivity

Alt+x 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: Alias]

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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