Emacs: Find Replace, by Regex

By Xah Lee. Date: . Last updated: .

Interactive Find Replace, by Regex Pattern

Alt+x query-replace-regexp

Replace String Special Characters

There are special syntax in the replacement string prompt.

\&

whole matched text.

\n

n is a digit. Means the nth capture in regex.

\?

prompt user to type text for each replacement.

\,lispExpr

execute the lispExpr and use its value as replacement string.

Inside the lispExpr,

  • \& → is the whole match (string type).
  • \n → is the nth capture (string type).
  • \#& → whole match, converted to number. (assume the match is a number)
  • \#n → nth capture converted to a number. (assume the match is a number)
  • \# → the number of replacements done so far (starting with zero).

If lispExpr is a Elisp: Symbol , write a space after it.

Example

Find Replace by Regex, with Word Boundary

Ctrl+u Alt+x query-replace-regexp

this saves you time of typing the regex word boundary chars. e.g. \bsomething\b

Find Replace All, by Regex, in One Shot

Alt+x replace-regexp