Some of the characters you type during incremental search have special effects.
By default, incremental search performs lax space matching:
each space, or sequence of spaces, matches any sequence of one or more
spaces in the text. Hence, ‘foo bar’ matches ‘foo bar’,
‘foo bar’, ‘foo bar’, and so on (but not ‘foobar’).
More precisely, Emacs matches each sequence of space characters in the
search string to a regular expression specified by the variable
search-whitespace-regexp. For example, set it to
‘"[[:space:]\n]+"’ to make spaces match sequences of newlines as
well as spaces. To toggle lax space matching, type M-s SPC
isearch-toggle-lax-whitespace). To disable this feature
each space in the search string matches exactly one space
If the search string you entered contains only lower-case letters, the search is case-insensitive; as long as an upper-case letter exists in the search string, the search becomes 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 character, type C-j.
To search for other control characters, such as <control-S>,
quote it by typing C-q first (see Inserting Text). To
search for non-ASCII characters, you can either use
C-q and enter its octal code, or use an input method
(see Input Methods). If an input method is enabled in the current
buffer when you start the search, you can use it in the search string
also. While typing the search string, you can toggle the input method
with the command C-\ (
can also turn on a non-default input method with C-^
isearch-toggle-specified-input-method), which prompts for the
name of the input method. When an input method is active during
incremental search, the search prompt includes the input method
mnemonic, like this:
where im is the mnemonic of the active input method. Any input method you enable during incremental search remains enabled in the current buffer afterwards.
Typing M-% 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.
Typing M-<TAB> in incremental search invokes
isearch-complete, which attempts to complete the search string
using the search ring as a list of completion alternatives.
See Completion. In many operating systems, the M-<TAB>
key sequence is captured by the window manager; you then need to
isearch-complete to another key sequence if you want to
use it (see Rebinding).
When incremental search is active, you can type C-h C-h to
access interactive help options, including a list of special key
bindings. These key bindings are part of the keymap
isearch-mode-map (see Keymaps).