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-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
C-h f isearch-mode <RET>.