This section describes miscellaneous search-related customizations not described elsewhere.
The default search mode for the incremental search is specified by
search-default-mode. It can be
t, or a function. If it is
nil, the default mode is to
do literal searches without character folding, but with case folding
and lax-whitespace matches as determined by
search-whitespace-regexp, respectively (see Lax Matching During Searching). If the value is
t, incremental search defaults to
regexp searches. The default value specifies a function that only
performs case folding and lax-whitespace matching.
The current match of an on-going incremental search is highlighted
isearch face. This highlighting can be disabled by
setting the variable
When searching for regular expressions (with C-M-s, for
instance), subexpressions receive special highlighting depending on
search-highlight-submatches variable. If this variable’s
nil, no special highlighting is done, but if the value
nil, text that matches ‘\( … \)’ constructs
(a.k.a. “subexpressions”) in the regular expression will be
highlighted with distinct faces. By default, two distinct faces are
With these two faces, odd-numbered subexpressions will be highlighted
isearch-group-1 face and even-numbered subexpressions
will be highlighted using the
isearch-group-2 face. For
instance, when searching for ‘foo-\([0-9]+\)\([a-z]+\)’, the part
matched by ‘[0-9]+’ will be highlighted with the
isearch-group-1 face, and the part matched by ‘[a-z]+’
will be highlighted using
isearch-group-2. If you define
additional faces using the same numbering scheme, i.e.
isearch-group-4, …, then the face
isearch-group-M will be used to highlight the M’th,
subexpressions, where N is the total number of faces of the form
The other matches for the search string that are visible on display
are highlighted using the
lazy-highlight face. Setting the
nil disables this
highlighting. Here are some other variables that customize the lazy
Time in seconds to wait before highlighting visible matches.
Applies only if the search string is less than
lazy-highlight-no-delay-length characters long.
For search strings at least as long as the value of this variable, lazy highlighting of matches starts immediately.
Time in seconds between highlighting successive matches.
The maximum number of matches to highlight before checking for input. A large number can take some time to highlight, so if you want to continue searching and type C-s or C-r during that time, Emacs will not respond until it finishes highlighting all those matches. Thus, smaller values make Emacs more responsive.
Show the current match number and the total number of matches in the search prompt.
These two variables determine the format of showing the current and
the total number of matches for
Normally, entering RET within incremental search when the
search string is empty launches a nonincremental search. (Actually,
it lets you edit the search string, and the next RET does the
search.) However, if you customize the variable
nil, typing RET
will always exit the incremental search, even if the search string is
By default, incremental search and query-replace commands match
invisible text, but hide any such matches as soon as the current match
moves off the invisible text. If you customize the variable
nil, any invisible text
where matches were found stays on display until the search or the
replace command exits.
Searching incrementally on slow terminals, such as displays
connected to remote machines over slow connection, could be annoying
due to the need to redraw large portions of the display as the search
proceeds. Emacs provides a special display mode for slow terminals,
whereby search pops up a separate small window and displays the text
surrounding the match in that window. Small windows display faster,
so the annoying effect of slow speed is alleviated. The variable
search-slow-speed determines the baud rate threshold below
which Emacs will use this display mode. The variable
search-slow-window-lines controls the number of lines in the
window Emacs pops up for displaying the search results; the default is
1 line. Normally, this window will pop up at the bottom of the window
that displays the buffer where you start searching, but if the value
search-slow-window-lines is negative, that means to put the
window at the top and give it the number of lines that is the absolute