20.1.4 Special Input for Incremental Search

An upper-case letter in the search string makes the search case-sensitive. If you delete the upper-case character from the search string, it ceases to have this effect. See Search Case.

To search for a newline, type C-j. To search for another control character, such as control-S or carriage return, you must quote it by typing C-q first. This function of C-q is analogous to its use for insertion (see Inserting Text): it causes the following character to be treated the way any “ordinary” character is treated in the same context. You can also specify a character by its octal code: enter C-q followed by a sequence of octal digits.

M-% typed in incremental search invokes query-replace or query-replace-regexp (depending on search mode) with the current search string used as the string to replace. See Query Replace.

Entering <RET> when the search string is empty launches nonincremental search (see Nonincremental Search).

To customize the special characters that incremental search understands, alter their bindings in the keymap isearch-mode-map. For a list of bindings, look at the documentation of isearch-mode with C-h f isearch-mode <RET>.