In addition, in some contexts, if you type a quotation using grave
accent and apostrophe `like this', it is converted to a form
‘like this’ using single quotation marks, even without C-x 8
commands. Similarly, typing a quotation ``like this'' using
double grave accent and apostrophe converts it to a form “like
this” using double quotation marks. See Quotation Marks.
8 The Minibuffer
The minibuffer is where Emacs commands read complicated
arguments, such as file names, buffer names, Emacs command names, or
Lisp expressions. We call it the “minibuffer” because it’s a
special-purpose buffer with a small amount of screen space. You can
use the usual Emacs editing commands in the minibuffer to edit the
argument text.
8.1 Using the Minibuffer
When the minibuffer is in use, it appears in the echo area, with a
cursor. The minibuffer starts with a prompt, usually ending
with a colon. The prompt states what kind of input is expected, and
how it will be used. The prompt is highlighted using the
minibuffer-prompt
face (see Text Faces).
The simplest way to enter a minibuffer argument is to type the text,
then RET to submit the argument and exit the minibuffer.
Alternatively, you can type C-g to exit the minibuffer by
canceling the command asking for the argument (see Quitting and Aborting).
Sometimes, the prompt shows a default argument, inside
parentheses before the colon. This default will be used as the
argument if you just type RET. For example, commands that read
buffer names usually show a buffer name as the default; you can type
RET to operate on that default buffer. You can customize how
the default argument is shown with the user option
minibuffer-default-prompt-format
.
If you enable Minibuffer Electric Default mode, a global minor mode,
Emacs hides the default argument as soon as you modify the contents of
the minibuffer (since typing RET would no longer submit that
default). If you ever bring back the original minibuffer text, the
prompt again shows the default. Furthermore, if you change the
variable minibuffer-eldef-shorten-default
to a non-nil
value, the default argument is displayed as ‘[default-arg]’
instead of ‘(default default-arg)’, saving some screen
space. To enable this minor mode, type M-x
minibuffer-electric-default-mode.
Since the minibuffer appears in the echo area, it can conflict with
other uses of the echo area. If an error message or an informative
message is emitted while the minibuffer is active, the message is
displayed in brackets after the minibuffer text for a few seconds, or
until you type something; then the message disappears. While the
minibuffer is in use, Emacs does not echo keystrokes.
While using the minibuffer, you can switch to a different frame,
perhaps to note text you need to enter (see Frame Commands). By
default, the active minibuffer moves to this new frame. If you set
the user option minibuffer-follows-selected-frame
to
nil
, then the minibuffer stays in the frame where you opened
it, and you must switch back to that frame in order to complete (or
abort) the current command. If you set that option to a value which
is neither nil
nor t
, the minibuffer moves frame only
after a recursive minibuffer has been opened in the current command
(see (elisp)Recursive Mini). This option is mainly to retain
(approximately) the behavior prior to Emacs 28.1. Note that the
effect of the command, when you finally finish using the minibuffer,
always takes place in the frame where you first opened it. The sole
exception is that when that frame no longer exists, the action takes
place in the currently selected frame.
8.2 Minibuffers for File Names
Commands such as C-x C-f (find-file
) use the minibuffer
to read a file name argument (see Files). When the
minibuffer is used to read a file name, it typically starts out with
some initial text ending in a slash. This is the default
directory. For example, it may start out like this:
Find file: /u2/emacs/src/
Here, ‘Find file: ’ is the prompt and ‘/u2/emacs/src/’ is
the default directory. If you now type buffer.c as input, that
specifies the file /u2/emacs/src/buffer.c. See File Names,
for information about the default directory.
Alternative defaults for the file name you may want are available by
typing M-n, see Minibuffer History.
You can specify a file in the parent directory with ..:
/a/b/../foo.el is equivalent to /a/foo.el.
Alternatively, you can use M-DEL to kill directory names
backwards (see Words).
To specify a file in a completely different directory, you can kill
the entire default with C-a C-k (see Editing in the Minibuffer).
Alternatively, you can ignore the default, and enter an absolute file
name starting with a slash or a tilde after the default directory.
For example, you can specify /etc/termcap as follows:
Find file: /u2/emacs/src//etc/termcap
A double slash causes Emacs to ignore everything before the
second slash in the pair. In the example above,
/u2/emacs/src/ is ignored, so the argument you supplied is
/etc/termcap. The ignored part of the file name is dimmed if
the terminal allows it. (To disable this dimming, turn off File Name
Shadow mode with the command M-x file-name-shadow-mode.)
When completing remote file names (see Remote Files), a double
slash behaves slightly differently: it causes Emacs to ignore only the
file-name part, leaving the rest (method, host and username, etc.)
intact. Typing three slashes in a row ignores everything in remote
file names. See File name completion in The Tramp Manual.
Emacs interprets ~/ as your home directory. Thus,
~/foo/bar.txt specifies a file named bar.txt, inside a
directory named foo, which is in turn located in your home
directory. In addition, ~user-id/ means the home
directory of a user whose login name is user-id. Any leading
directory name in front of the ~ is ignored: thus,
/u2/emacs/~/foo/bar.txt is equivalent to ~/foo/bar.txt.
On MS-Windows and MS-DOS systems, where a user doesn’t always have a
home directory, Emacs uses several alternatives. For MS-Windows, see
HOME and Startup Directories on MS-Windows; for MS-DOS, see
File Names on MS-DOS.
On these systems, the ~user-id/ construct is supported
only for the current user, i.e., only if user-id is the current
user’s login name.
To prevent Emacs from inserting the default directory when reading
file names, change the variable insert-default-directory
to
nil
. In that case, the minibuffer starts out empty.
Nonetheless, relative file name arguments are still interpreted based
on the same default directory.
You can also enter remote file names in the minibuffer.
See Remote Files.
8.3 Editing in the Minibuffer
The minibuffer is an Emacs buffer, albeit a peculiar one, and the
usual Emacs commands are available for editing the argument text.
(The prompt, however, is read-only, and cannot be changed.)
Since RET in the minibuffer submits the argument, you can’t
use it to insert a newline. You can do that with C-q C-j, which
inserts a C-j control character, which is formally equivalent to
a newline character (see Inserting Text). Alternatively, you can
use the C-o (open-line
) command (see Blank Lines).
Inside a minibuffer, the keys TAB, SPC, and ? are
often bound to completion commands, which allow you to easily
fill in the desired text without typing all of it. See Completion.
As with RET, you can use C-q to insert a TAB,
SPC, or ‘?’ character.
For convenience, C-a (move-beginning-of-line
) in a
minibuffer moves point to the beginning of the argument text, not the
beginning of the prompt. For example, this allows you to erase the
entire argument with C-a C-k.
When the minibuffer is active, the echo area is treated much like an
ordinary Emacs window. For instance, you can switch to another window
(with C-x o), edit text there, then return to the minibuffer
window to finish the argument. You can even kill text in another
window, return to the minibuffer window, and yank the text into the
argument. There are some restrictions on the minibuffer window,
however: for instance, you cannot split it. See Multiple Windows.
Normally, the minibuffer window occupies a single screen line.
However, if you add two or more lines’ worth of text into the
minibuffer, it expands automatically to accommodate the text. The
variable resize-mini-windows
controls the resizing of the
minibuffer. The default value is grow-only
, which means the
behavior we have just described. If the value is t
, the
minibuffer window will also shrink automatically if you remove some
lines of text from the minibuffer, down to a minimum of one screen
line. If the value is nil
, the minibuffer window never changes
size automatically, but you can use the usual window-resizing commands
on it (see Multiple Windows).
The variable max-mini-window-height
controls the maximum
height for resizing the minibuffer window. A floating-point number
specifies a fraction of the frame’s height; an integer specifies the
maximum number of lines; nil
means do not resize the minibuffer
window automatically. The default value is 0.25.
The C-M-v command in the minibuffer scrolls the help text from
commands that display help text of any sort in another window. You
can also scroll the help text with M-PageUp and
M-PageDown (or, equivalently, M-prior and
M-next). This is especially useful with long lists of
possible completions. See Using Other Windows.
Emacs normally disallows most commands that use the minibuffer while
the minibuffer is active. To allow such commands in the minibuffer,
set the variable enable-recursive-minibuffers
to t
.
You might need also to enable minibuffer-depth-indicate-mode
to show the current recursion depth in the minibuffer prompt
on recursive use of the minibuffer.
When active, the minibuffer is usually in minibuffer-mode
.
This is an internal Emacs mode without any special features.
When not active, the minibuffer is in minibuffer-inactive-mode
,
and clicking mouse-1 there shows the *Messages* buffer.
If you use a dedicated frame for minibuffers, Emacs also recognizes
certain keys there, for example, n to make a new frame.
8.4 Completion
You can often use a feature called completion to help enter
arguments. This means that after you type part of the argument, Emacs
can fill in the rest, or some of it, based on what was typed so far.
When completion is available, certain keys (usually TAB,
RET, and SPC) are rebound in the minibuffer to special
completion commands (see Completion Commands). These commands
attempt to complete the text in the minibuffer, based on a set of
completion alternatives provided by the command that requested
the argument. You can usually type ? to see a list of
completion alternatives.
Although completion is usually done in the minibuffer, the feature
is sometimes available in ordinary buffers too. See Completion for Symbol Names.
8.4.1 Completion Example
A simple example may help here. M-x uses the minibuffer to
read the name of a command, so completion works by matching the
minibuffer text against the names of existing Emacs commands. Suppose
you wish to run the command auto-fill-mode
. You can do that by
typing M-x auto-fill-mode RET, but it is easier to use
completion.
If you type M-x a u TAB, the TAB looks for
completion alternatives (in this case, command names) that start with
‘au’. There are several, including auto-fill-mode
and
autoconf-mode
, but they all begin with auto
, so the
‘au’ in the minibuffer completes to ‘auto’. (More commands
may be defined in your Emacs session. For example, if a command
called authorize-me
was defined, Emacs could only complete
as far as ‘aut’.)
If you type TAB again immediately, it cannot determine the
next character; it could be ‘-’, ‘a’, or ‘c’. So it
does not add any characters; instead, TAB displays a list of all
possible completions in another window.
Next, type -f. The minibuffer now contains ‘auto-f’, and
the only command name that starts with this is auto-fill-mode
.
If you now type TAB, completion fills in the rest of the
argument ‘auto-fill-mode’ into the minibuffer.
Hence, typing just a u TAB - f TAB allows you to
enter ‘auto-fill-mode’.
8.4.2 Completion Commands
Here is a list of the completion commands defined in the minibuffer
when completion is allowed.
- TAB
Complete the text in the minibuffer as much as possible; if unable to
complete, display a list of possible completions
(minibuffer-complete
).
- SPC
Complete up to one word from the minibuffer text before point
(minibuffer-complete-word
). This command is not available for
arguments that often include spaces, such as file names.
- RET
Submit the text in the minibuffer as the argument, possibly completing
first (minibuffer-complete-and-exit
). See Completion Exit.
- ?
Display a list of completions (minibuffer-completion-help
).
TAB (minibuffer-complete
) is the most fundamental
completion command. It searches for all possible completions that
match the existing minibuffer text, and attempts to complete as much
as it can. See How Completion Alternatives Are Chosen, for how completion alternatives
are chosen.
SPC (minibuffer-complete-word
) completes like
TAB, but only up to the next hyphen or space. If you have
‘auto-f’ in the minibuffer and type SPC, it finds that the
completion is ‘auto-fill-mode’, but it only inserts ‘ill-’,
giving ‘auto-fill-’. Another SPC at this point completes
all the way to ‘auto-fill-mode’.
If TAB or SPC is unable to complete, it displays a list
of matching completion alternatives (if there are any) in another
window. You can display the same list with ?
(minibuffer-completion-help
). The following commands can be
used with the completion list:
-
- M-v
- PageUp
- prior
Typing M-v, while in the minibuffer, selects the window showing
the completion list (switch-to-completions
). This paves the
way for using the commands below. PageUp, prior and
M-g M-c does the same. You can also select the window in other
ways (see Multiple Windows).
- RET
- mouse-1
- mouse-2
While in the completion list buffer, this chooses the completion at
point (choose-completion
).
- TAB
- RIGHT
- n
While in the completion list buffer, these keys move point to the
following completion alternative (next-completion
).
- S-TAB
- LEFT
- p
While in the completion list buffer, these keys move point to the
previous completion alternative (previous-completion
).
- q
While in the completion list buffer, this quits the window showing it
and selects the window showing the minibuffer (quit-window
).
- z
While in the completion list buffer, kill it and delete the window
showing it (kill-current-buffer
).
8.4.3 Completion Exit
When a command reads an argument using the minibuffer with
completion, it also controls what happens when you type RET
(minibuffer-complete-and-exit
) to submit the argument. There
are four types of behavior:
- Strict completion accepts only exact completion matches. Typing
RET exits the minibuffer only if the minibuffer text is an exact
match, or completes to one. Otherwise, Emacs refuses to exit the
minibuffer; instead it tries to complete, and if no completion can be
done it momentarily displays ‘[No match]’ after the minibuffer
text. (You can still leave the minibuffer by typing C-g to
cancel the command.)
An example of a command that uses this behavior is M-x, since it
is meaningless for it to accept a non-existent command name.
- Cautious completion is like strict completion, except RET
exits only if the text is already an exact match. If the text
completes to an exact match, RET performs that completion but
does not exit yet; you must type a second RET to exit.
Cautious completion is used for reading file names for files that must
already exist, for example.
- Permissive completion allows any input; the completion
candidates are just suggestions. Typing RET does not complete,
it just submits the argument as you have entered it.
-
Permissive completion with confirmation is like permissive
completion, with an exception: if you typed TAB and this
completed the text up to some intermediate state (i.e., one that is not
yet an exact completion match), typing RET right afterward does
not submit the argument. Instead, Emacs asks for confirmation by
momentarily displaying ‘[Confirm]’ after the text; type RET
again to confirm and submit the text. This catches a common mistake,
in which one types RET before realizing that TAB did not
complete as far as desired.
You can tweak the confirmation behavior by customizing the variable
confirm-nonexistent-file-or-buffer
. The default value,
after-completion
, gives the behavior we have just described.
If you change it to nil
, Emacs does not ask for confirmation,
falling back on permissive completion. If you change it to any other
non-nil
value, Emacs asks for confirmation whether or not the
preceding command was TAB.
This behavior is used by most commands that read file names, like
C-x C-f, and commands that read buffer names, like C-x b.
8.4.4 How Completion Alternatives Are Chosen
Completion commands work by narrowing a large list of possible
completion alternatives to a smaller subset that matches what you
have typed in the minibuffer. In Completion Example, we gave a
simple example of such matching. The procedure of determining what
constitutes a match is quite intricate. Emacs attempts to offer
plausible completions under most circumstances.
Emacs performs completion using one or more completion
styles—sets of criteria for matching minibuffer text to completion
alternatives. During completion, Emacs tries each completion style in
turn. If a style yields one or more matches, that is used as the list
of completion alternatives. If a style produces no matches, Emacs
falls back on the next style.
The list variable completion-styles
specifies the completion
styles to use. Each list element is the name of a completion style (a
Lisp symbol). The available style symbols are stored in the variable
completion-styles-alist
(see Completion Variables in The Emacs Lisp Reference Manual). The default completion styles are
(in order):
basic
¶
A matching completion alternative must have the same beginning as the
text in the minibuffer before point. Furthermore, if there is any
text in the minibuffer after point, the rest of the completion
alternative must contain that text as a substring.
partial-completion
This aggressive completion style divides the minibuffer text into
words separated by hyphens or spaces, and completes each word
separately. (For example, when completing command names,
‘em-l-m’ completes to ‘emacs-lisp-mode’.)
Furthermore, a ‘*’ in the minibuffer text is treated as a
wildcard—it matches any string of characters at the
corresponding position in the completion alternative.
emacs22
¶
This completion style is similar to basic
, except that it
ignores the text in the minibuffer after point. It is so-named
because it corresponds to the completion behavior in Emacs 22.
The following additional completion styles are also defined, and you
can add them to completion-styles
if you wish
(see Customization):
substring
¶
A matching completion alternative must contain the text in the
minibuffer before point, and the text in the minibuffer after point,
as substrings (in that same order).
Thus, if the text in the minibuffer is ‘foobar’, with point
between ‘foo’ and ‘bar’, that matches
‘afoobbarc’, where a, b, and
c can be any string including the empty string.
flex
¶
This aggressive completion style, also known as flx
or
fuzzy
or scatter
completion, attempts to complete using
in-order substrings. For example, it can consider ‘foo’ to match
‘frodo’ or ‘fbarbazoo’.
initials
¶
This very aggressive completion style attempts to complete acronyms
and initialisms. For example, when completing command names, it
matches ‘lch’ to ‘list-command-history’.
There is also a very simple completion style called emacs21
.
In this style, if the text in the minibuffer is ‘foobar’,
only matches starting with ‘foobar’ are considered.
You can use different completion styles in different situations,
by setting the variable completion-category-overrides
.
For example, the default setting says to use only basic
and substring
completion for buffer names.
8.4.5 Completion Options
Case is significant when completing case-sensitive arguments, such
as command names. For example, when completing command names,
‘AU’ does not complete to ‘auto-fill-mode’. Case
differences are ignored when completing arguments in which case does
not matter.
When completing file names, case differences are ignored if the
variable read-file-name-completion-ignore-case
is
non-nil
. The default value is nil
on systems that have
case-sensitive file-names, such as GNU/Linux; it is non-nil
on
systems that have case-insensitive file-names, such as Microsoft
Windows. When completing buffer names, case differences are ignored
if the variable read-buffer-completion-ignore-case
is
non-nil
; the default is nil
.
When completing file names, Emacs usually omits certain alternatives
that are considered unlikely to be chosen, as determined by the list
variable completion-ignored-extensions
. Each element in the
list should be a string; any file name ending in such a string is
ignored as a completion alternative. Any element ending in a slash
(/) represents a subdirectory name. The standard value of
completion-ignored-extensions
has several elements including
".o"
, ".elc"
, and "~"
. For example, if a
directory contains ‘foo.c’ and ‘foo.elc’, ‘foo’
completes to ‘foo.c’. However, if all possible
completions end in otherwise-ignored strings, they are not ignored: in the
previous example, ‘foo.e’ completes to ‘foo.elc’. Emacs
disregards completion-ignored-extensions
when showing
completion alternatives in the completion list.
Shell completion is an extended version of filename completion,
see Shell Mode Options.
If completion-auto-help
is set to nil
, the completion
commands never display the completion list buffer; you must type
? to display the list. If the value is lazy
, Emacs only
shows the completion list buffer on the second attempt to complete.
In other words, if there is nothing to complete, the first TAB
echoes ‘Next char not unique’; the second TAB shows the
completion list buffer.
If completion-cycle-threshold
is non-nil
, completion
commands can cycle through completion alternatives. Normally, if
there is more than one completion alternative for the text in the
minibuffer, a completion command completes up to the longest common
substring. If you change completion-cycle-threshold
to
t
, the completion command instead completes to the first of
those completion alternatives; each subsequent invocation of the
completion command replaces that with the next completion alternative,
in a cyclic manner. If you give completion-cycle-threshold
a
numeric value n, completion commands switch to this cycling
behavior only when there are n or fewer alternatives.
When displaying completions, Emacs will normally pop up a new buffer
to display the completions. The completions will (by default) be
sorted in columns horizontally in alphabetical order, but this can be
changed by changing the completions-format
user option. If
vertical
, sort the completions vertically in columns instead,
and if one-column
, just use a single column.
8.5 Minibuffer History
Everything you type in the minibuffer is saved in a minibuffer
history list so you can easily use it again later. This includes
completion candidates (such as file names, buffer names, command
names, etc.) and any other kind of minibuffer input. You can use
the following commands to quickly fetch an earlier or alternative
response into the minibuffer:
- M-p
Move to the previous item in the minibuffer history, an earlier
argument (previous-history-element
).
- M-n
Move to the next item in the minibuffer history
(next-history-element
).
- UP
- DOWN
Like M-p and M-n, but move to the previous or next line of
a multi-line item before going to the previous history item
(previous-line-or-history-element
and
next-line-or-history-element
) .
- M-r regexp RET
Move to an earlier item in the minibuffer history that
matches regexp (previous-matching-history-element
).
- M-s regexp RET
Move to a later item in the minibuffer history that matches
regexp (next-matching-history-element
).
While in the minibuffer, M-p (previous-history-element
)
moves through the minibuffer history list, one item at a time. Each
M-p fetches an earlier item from the history list into the
minibuffer, replacing its existing contents. Typing M-n
(next-history-element
) moves through the minibuffer history
list in the opposite direction, fetching later entries into the
minibuffer.
If you type M-n in the minibuffer when there are no later
entries in the minibuffer history (e.g., if you haven’t previously
typed M-p), Emacs tries fetching from a list of default
arguments: values that you are likely to enter. You can think of this
as moving through the “future history”.
The “future history” for file names includes several possible
alternatives you may find useful, such as the file name or the URL at
point in the current buffer. The defaults put into the “future
history” in this case are controlled by the functions mentioned in
the value of the option file-name-at-point-functions
. By
default, its value invokes the ffap
package (see Finding Files and URLs at Point),
which tries to guess the default file or URL from the text around
point. To disable this guessing, customize the option to a nil
value, then the “future history” of file names will include only the
file, if any, visited by the current buffer, and the default
directory.
The arrow keys UP and DOWN work like
M-p and M-n, but if the current history item is longer
than a single line, they allow you to move to the previous or next
line of the current history item before going to the previous or next
history item.
If you edit the text inserted by the M-p or M-n
minibuffer history commands, this does not change its entry in the
history list. However, the edited argument does go at the end of the
history list when you submit it.
You can use M-r (previous-matching-history-element
) to
search through older elements in the history list, and M-s
(next-matching-history-element
) to search through newer
entries. Each of these commands asks for a regular expression
as an argument, and fetches the first matching entry into the
minibuffer. See Syntax of Regular Expressions, for an explanation of regular
expressions. A numeric prefix argument n means to fetch the
nth matching entry. These commands are unusual, in that they
use the minibuffer to read the regular expression argument, even
though they are invoked from the minibuffer. An upper-case letter in
the regular expression makes the search case-sensitive (see Lax Matching During Searching).
You can also search through the history using an incremental search.
See Searching the Minibuffer.
Emacs keeps separate history lists for several different kinds of
arguments. For example, there is a list for file names, used by all
the commands that read file names. Other history lists include buffer
names, command names (used by M-x), and command arguments (used
by commands like query-replace
).
The variable history-length
specifies the maximum length of a
minibuffer history list; adding a new element deletes the oldest
element if the list gets too long. If the value is t
, there is
no maximum length.
The variable history-delete-duplicates
specifies whether to
delete duplicates in history. If it is non-nil
, adding a new
element deletes from the list all other elements that are equal to it.
The default is nil
.
8.6 Repeating Minibuffer Commands
Every command that uses the minibuffer once is recorded on a special
history list, the command history, together with the values of
its arguments, so that you can repeat the entire command. In
particular, every use of M-x is recorded there, since M-x
uses the minibuffer to read the command name.
- C-x ESC ESC
Re-execute a recent minibuffer command from the command history
(repeat-complex-command
).
- M-x list-command-history
Display the entire command history, showing all the commands
C-x ESC ESC can repeat, most recent first.
C-x ESC ESC re-executes a recent command that used
the minibuffer. With no argument, it repeats the last such command.
A numeric argument specifies which command to repeat; 1 means the last
one, 2 the previous, and so on.
C-x ESC ESC works by turning the previous command
into a Lisp expression and then entering a minibuffer initialized with
the text for that expression. Even if you don’t know Lisp, it will
probably be obvious which command is displayed for repetition. If you
type just RET, that repeats the command unchanged. You can also
change the command by editing the Lisp expression before you execute
it. The executed command is added to the front of the command history
unless it is identical to the most recent item.
Once inside the minibuffer for C-x ESC ESC, you
can use the usual minibuffer history commands (see Minibuffer History) to move through the history list. After finding the desired
previous command, you can edit its expression as usual and then execute
it by typing RET.
Incremental search does not, strictly speaking, use the minibuffer.
Therefore, although it behaves like a complex command, it normally
does not appear in the history list for C-x ESC ESC.
You can make incremental search commands appear in the history by
setting isearch-resume-in-command-history
to a non-nil
value. See Incremental Search.
The list of previous minibuffer-using commands is stored as a Lisp
list in the variable command-history
. Each element is a Lisp
expression that describes one command and its arguments. Lisp programs
can re-execute a command by calling eval
with the
command-history
element.
8.7 Entering passwords
Sometimes, you may need to enter a password into Emacs. For instance,
when you tell Emacs to visit a file on another machine via a network
protocol such as FTP, you often need to supply a password to gain
access to the machine (see Remote Files).
Entering a password is similar to using a minibuffer. Emacs
displays a prompt in the echo area (such as ‘Password: ’); after
you type the required password, press RET to submit it. To
prevent others from seeing your password, every character you type is
displayed as an asterisk (‘*’) instead of its usual form.
Most of the features and commands associated with the minibuffer
cannot be used when entering a password. There is no history
or completion, and you cannot change windows or perform any other
action with Emacs until you have submitted the password.
While you are typing the password, you may press DEL to delete
backwards, removing the last character entered. C-u deletes
everything you have typed so far. C-g quits the password prompt
(see Quitting and Aborting). C-y inserts the current kill into the
password (see Killing and Moving Text). You may type either RET or
ESC to submit the password. Any other self-inserting character
key inserts the associated character into the password, and all other
input is ignored.
8.8 Yes or No Prompts
An Emacs command may require you to answer a yes-or-no question
during the course of its execution. Such queries come in two main
varieties.
For the first type of yes-or-no query, the prompt ends with
‘(y or n)’. You answer the query by typing a single key,
either ‘y’ or ‘n’, which immediately exits the minibuffer
and delivers the response. For example, if you type C-x C-w
(write-file) to save a buffer, and enter the name of an existing
file, Emacs issues a prompt like this:
File ‘foo.el’ exists; overwrite? (y or n)
The second type of yes-or-no query is typically employed if giving
the wrong answer would have serious consequences; it thus features a
longer prompt ending with ‘(yes or no)’. For example, if you
invoke C-x k (kill-buffer
) on a file-visiting buffer with
unsaved changes, Emacs activates the minibuffer with a prompt like
this:
Buffer foo.el modified; kill anyway? (yes or no)
To answer, you must type ‘yes’ or ‘no’ into the minibuffer,
followed by RET.
With both types of yes-or-no query the minibuffer behaves as described
in the previous sections; you can recenter the selected window with
C-l, scroll that window (C-v or PageDown scrolls
forward, M-v or PageUp scrolls backward), switch to
another window with C-x o, use the history commands M-p
and M-n, etc. Type C-g to dismiss the query, and quit the
minibuffer and the querying command (see Quitting and Aborting).
10 Help
Emacs provides a wide variety of help commands, all accessible
through the prefix key C-h (or, equivalently, the function key
F1). These help commands are described in the following
sections. You can also type C-h C-h to view a list of help
commands (help-for-help
). You can scroll the list with
SPC and DEL, then type the help command you want. To
cancel, type C-g.
Many help commands display their information in a special help
buffer. In this buffer, you can type SPC and DEL to
scroll and type RET to follow hyperlinks. See Help Mode Commands.
If you are looking for a certain feature, but don’t know what it is
called or where to look, we recommend three methods. First, try an
apropos command, then try searching the manual index, then look in the
FAQ and the package keywords.
- C-h a topics RET
This searches for commands whose names match the argument
topics. The argument can be a keyword, a list of keywords, or a
regular expression (see Syntax of Regular Expressions). See Apropos.
- C-h i d m emacs RET i topic RET
This searches for topic in the indices of the Emacs Info manual,
displaying the first match found. Press , to see subsequent
matches. You can use a regular expression as topic.
- C-h i d m emacs RET s topic RET
Similar, but searches the text of the manual rather than the
indices.
- C-h C-f
This displays the Emacs FAQ, using Info.
- C-h p
This displays the available Emacs packages based on keywords.
See Keyword Search for Packages.
C-h or F1 mean “help” in various other contexts as
well. For instance, you can type them after a prefix key to view a
list of the keys that can follow the prefix key. (You can also use
? in this context. A few prefix keys don’t support C-h
or ? in this way, because they define other meanings for those
inputs, but they all support F1.)
10.1 Help Summary
Here is a summary of help commands for accessing the built-in
documentation. Most of these are described in more detail in the
following sections.
- C-h a topics RET
Display a list of commands whose names match topics
(apropos-command
). See Apropos.
- C-h b
Display all active key bindings; minor mode bindings first, then those
of the major mode, then global bindings (describe-bindings
).
See Other Help Commands.
- C-h c key
Show the name of the command that the key sequence key is bound
to (describe-key-briefly
). Here c stands for
“character”. For more extensive information on key, use
C-h k. See Documentation for a Key.
- C-h d topics RET
Display the commands and variables whose documentation matches
topics (apropos-documentation
). See Apropos.
- C-h e
Display the *Messages* buffer
(view-echo-area-messages
). See Other Help Commands.
- C-h f function RET
Display documentation on the Lisp function named function
(describe-function
). Since commands are Lisp functions, this
works for commands too, but you can also use C-h x
. See Help by Command or Variable Name.
- C-h h
Display the HELLO file, which shows examples of various character
sets.
- C-h i
Run Info, the GNU documentation browser (info
). The Emacs
manual is available in Info. See Other Help Commands.
- C-h k key
Display the name and documentation of the command that key runs
(describe-key
). See Documentation for a Key.
- C-h l
Display a description of your last 300 keystrokes
(view-lossage
). See Other Help Commands.
- C-h m
Display documentation of the current major mode and minor modes
(describe-mode
). See Other Help Commands.
- C-h n
Display news of recent Emacs changes (view-emacs-news
).
See Help Files.
- C-h o symbol
Display documentation of the Lisp symbol named symbol
(describe-symbol
). This will show the documentation of all
kinds of symbols: functions, variables, and faces. See Help by Command or Variable Name.
- C-h p
Find packages by topic keyword (finder-by-keyword
).
See Keyword Search for Packages. This lists packages using a package menu
buffer. See Emacs Lisp Packages.
- C-h P package RET
Display documentation about the specified package
(describe-package
). See Keyword Search for Packages.
- C-h r
Display the Emacs manual in Info (info-emacs-manual
).
- C-h s
Display the contents of the current syntax table
(describe-syntax
). See Other Help Commands. The syntax table says
which characters are opening delimiters, which are parts of words, and
so on. See Syntax Tables in The Emacs Lisp
Reference Manual, for details.
- C-h t
Enter the Emacs interactive tutorial (help-with-tutorial
).
- C-h v var RET
Display the documentation of the Lisp variable var
(describe-variable
). See Help by Command or Variable Name.
- C-h w command RET
Show which keys run the command named command (where-is
).
See Documentation for a Key.
- C-h x command RET
Display documentation on the named command
(describe-command
). See Help by Command or Variable Name.
- C-h C coding RET
Describe the coding system coding
(describe-coding-system
). See Coding Systems.
- C-h C RET
Describe the coding systems currently in use.
- C-h F command RET
Enter Info and go to the node that documents the Emacs command
command (Info-goto-emacs-command-node
). See Help by Command or Variable Name.
- C-h I method RET
Describe the input method method (describe-input-method
).
See Selecting an Input Method.
- C-h K key
Enter Info and go to the node that documents the key sequence
key (Info-goto-emacs-key-command-node
). See Documentation for a Key.
- C-h L language-env RET
Display information on the character sets, coding systems, and input
methods used in language environment language-env
(describe-language-environment
). See Language Environments.
- C-h S symbol RET
Display the Info documentation on symbol symbol according to the
programming language you are editing (info-lookup-symbol
).
See Other Help Commands.
- C-h .
Display the help message for a special text area, if point is in one
(display-local-help
). (These include, for example, links in
*Help* buffers.) See Help on Active Text and Tooltips.
10.2 Documentation for a Key
The help commands to get information about a key sequence are
C-h c (describe-key-briefly
) and C-h k
(describe-key
).
C-h c key displays in the echo area the name of the
command that key is bound to. For example, C-h c C-f
displays ‘forward-char’.
C-h k key is similar but gives more information: it
displays a help buffer containing the command’s documentation
string, which describes exactly what the command does.
C-h K key displays the section of the Emacs manual that
describes the command corresponding to key.
C-h c, C-h k and C-h K work for any sort of key
sequences, including function keys, menus, and mouse events (except
that C-h c ignores mouse movement events). For instance, after
C-h k you can select a menu item from the menu bar, to view the
documentation string of the command it runs.
C-h w command RET lists the keys that are bound to
command. It displays the list in the echo area. If it says the
command is not on any key, that means you must use M-x to run
it. C-h w runs the command where-is
.
Some modes in Emacs use various buttons (see Buttons in The
Emacs Lisp Reference Manual) and widgets
(see Introduction in Emacs Widgets) that can be clicked to
perform some action. To find out what function is ultimately invoked
by these buttons, Emacs provides the button-describe
and
widget-describe
commands, that should be run with point over
the button.
10.3 Help by Command or Variable Name
C-h x command RET (describe-command
)
displays the documentation of the named command, in a
window. For example,
displays the documentation of auto-fill-mode
. This is how you
would get the documentation of a command that is not bound to any key
(one which you would normally run using M-x).
C-h f function RET (describe-function
)
displays the documentation of Lisp function. This command is
intended for Lisp functions that you use in a Lisp program. For
example, if you have just written the expression
(make-vector len)
and want to check that you are using
make-vector
properly, type C-h f make-vector RET.
Additionally, since all commands are Lisp functions, you can also use
this command to view the documentation of any command.
If you type C-h f RET, it describes the function called
by the innermost Lisp expression in the buffer around point,
provided that function name is a valid, defined Lisp function.
(That name appears as the default while you enter the argument.) For
example, if point is located following the text ‘(make-vector
(car x)’, the innermost list containing point is the one that starts
with ‘(make-vector’, so C-h f RET describes the
function make-vector
.
C-h f is also useful just to verify that you spelled a
function name correctly. If the minibuffer prompt for C-h f
shows the function name from the buffer as the default, it means that
name is defined as a Lisp function. Type C-g to cancel the
C-h f command if you don’t really want to view the
documentation.
If you request help for an autoloaded function whose autoload
form (see Autoload in The Emacs Lisp Reference Manual)
doesn’t provide a doc string, the *Help* buffer won’t have any
doc string to display. In that case, if
help-enable-symbol-autoload
is non-nil
, Emacs will try
to load the file in which the function is defined to see whether
there’s a doc string there.
You can get an overview of functions relevant for a particular topic
by using the M-x shortdoc-display-group command. This will
prompt you for an area of interest, e.g., string
, and pop you
to a buffer where many of the functions relevant for handling strings
are listed.
C-h v (describe-variable
) is like C-h f but
describes Lisp variables instead of Lisp functions. Its default is
the Lisp symbol around or before point, if that is the name of a
defined Lisp variable. See Variables.
Help buffers that describe Emacs variables and functions normally
have hyperlinks to the corresponding source code, if you have the
source files installed (see Hyperlinking and Web Navigation Features).
To find a command’s documentation in a manual, use C-h F
(Info-goto-emacs-command-node
). This knows about various
manuals, not just the Emacs manual, and finds the right one.
C-h o (describe-symbol
) is like C-h f and
C-h v, but it describes any symbol, be it a function, a
variable, or a face. If the symbol has more than one definition, like
it has both definition as a function and as a variable, this command
will show the documentation of all of them, one after the other.
If the completions-detailed
user option is non-nil
,
some commands provide details about the possible values when
displaying completions. For instance, C-h o TAB will then
include the first line of the doc string, and will also say whether
each symbol is a function or a variable (and so on). Which details
are included varies depending on the command used.
10.4 Apropos
The apropos commands answer questions like, “What are the
commands for working with files?” More precisely, you specify an
apropos pattern, which means either a word, a list of words, or
a regular expression.
Each of the following apropos commands reads an apropos pattern in
the minibuffer, searches for items that match the pattern, and
displays the results in a different window.
- C-h a ¶
-
Search for commands (apropos-command
). With a prefix argument,
search for noninteractive functions too.
- M-x apropos ¶
Search for functions and variables. Both interactive functions
(commands) and noninteractive functions can be found by this.
- M-x apropos-user-option ¶
Search for user-customizable variables. With a prefix argument,
search for non-customizable variables too.
- M-x apropos-variable ¶
Search for variables. With a prefix argument, search for
customizable variables only.
- M-x apropos-local-variable ¶
Search for buffer-local variables.
- M-x apropos-value ¶
Search for variables whose values match the specified pattern. With a
prefix argument, search also for functions with definitions matching
the pattern, and Lisp symbols with properties matching the pattern.
- M-x apropos-local-value ¶
Search for buffer-local variables whose values match the specified
pattern.
- C-h d ¶
-
Search for functions and variables whose documentation strings match
the specified pattern (apropos-documentation
).
The simplest kind of apropos pattern is one word. Anything
containing that word matches the pattern. Thus, to find commands that
work on files, type C-h a file RET. This displays a list
of all command names that contain ‘file’, including
copy-file
, find-file
, and so on. Each command name
comes with a brief description and a list of keys you can currently
invoke it with. In our example, it would say that you can invoke
find-file
by typing C-x C-f.
For more information about a function definition, variable or symbol
property listed in an apropos buffer, you can click on it with
mouse-1 or mouse-2, or move there and type RET.
When you specify more than one word in the apropos pattern, a name
must contain at least two of the words in order to match. Thus, if
you are looking for commands to kill a chunk of text before point, you
could try C-h a kill back backward behind before RET. The
real command name kill-backward
will match that; if there were
a command kill-text-before
, it would also match, since it
contains two of the specified words.
For even greater flexibility, you can specify a regular expression
(see Syntax of Regular Expressions). An apropos pattern is interpreted as a regular
expression if it contains any of the regular expression special
characters, ‘^$*+?.\[’.
Following the conventions for naming Emacs commands, here are some
words that you’ll find useful in apropos patterns. By using them in
C-h a, you will also get a feel for the naming conventions.
char, line, word, sentence, paragraph, region, page, sexp, list, defun,
rect, buffer, frame, window, face, file, dir, register, mode, beginning, end,
forward, backward, next, previous, up, down, search, goto, kill, delete,
mark, insert, yank, fill, indent, case, change, set, what, list, find,
view, describe, default.
If the variable apropos-do-all
is non-nil
, most
apropos commands behave as if they had been given a prefix argument.
There is one exception: apropos-variable
without a prefix
argument will always search for all variables, no matter what the
value of apropos-do-all
is.
By default, all apropos commands except apropos-documentation
list their results in alphabetical order. If the variable
apropos-sort-by-scores
is non-nil
, these commands
instead try to guess the relevance of each result, and display the
most relevant ones first. The apropos-documentation
command
lists its results in order of relevance by default; to list them in
alphabetical order, change the variable
apropos-documentation-sort-by-scores
to nil
.
10.5 Help Mode Commands
Help buffers have Help mode as their major mode. Help mode provides
the same commands as View mode (see View Mode); for instance,
SPC scrolls forward, and DEL or S-SPC scrolls
backward. It also provides a few special commands:
- RET
Follow a cross reference at point (help-follow
).
- TAB
Move point forward to the next hyperlink (forward-button
).
- S-TAB
Move point back to the previous hyperlink (backward-button
).
- mouse-1
- mouse-2
Follow a hyperlink that you click on.
- C-c C-c
Show all documentation about the symbol at point
(help-follow-symbol
).
- C-c C-f
- r
Go forward to the next help topic (help-go-forward
).
- C-c C-b
- l
Go back to the previous help topic (help-go-back
).
- s
View the source of the current help topic (if any)
(help-view-source
).
- i
Look up the current topic in the manual(s) (help-goto-info
).
- c
Customize the variable or the face (help-customize
).
When a function name, variable name, or face name (see Text Faces)
appears in the documentation in the help buffer, it is normally an
underlined hyperlink. To view the associated documentation,
move point there and type RET (help-follow
), or click on
the hyperlink with mouse-1 or mouse-2. Doing so replaces
the contents of the help buffer; to retrace your steps, type C-c
C-b or l (help-go-back
). While retracing your steps,
you can go forward by using C-c C-f or r
(help-go-forward
).
A help buffer can also contain hyperlinks to Info manuals, source
code definitions, and URLs (web pages). The first two are opened in
Emacs, and the third using a web browser via the browse-url
command (see Following URLs).
In a help buffer, TAB (forward-button
) moves point
forward to the next hyperlink, while S-TAB
(backward-button
) moves point back to the previous hyperlink.
These commands act cyclically; for instance, typing TAB at the
last hyperlink moves back to the first hyperlink.
To view all documentation about any symbol in the text, move point
to the symbol and type C-c C-c (help-follow-symbol
).
This shows the documentation for all the meanings of the symbol—as a
variable, as a function, and/or as a face.
10.6 Keyword Search for Packages
Most optional features in Emacs are grouped into packages.
Emacs contains several hundred built-in packages, and more can be
installed over the network (see Emacs Lisp Packages).
To make it easier to find packages related to a topic, most packages
are associated with one or more keywords based on what they do.
Type C-h p (finder-by-keyword
) to bring up a list of
package keywords, together with a description of what the keywords
mean. To view a list of packages for a given keyword, type RET
on that line; this displays the list of packages in a Package Menu
buffer (see The Package Menu Buffer).
C-h P (describe-package
) prompts for the name of a
package (see Emacs Lisp Packages), and displays a help buffer describing the
attributes of the package and the features that it implements. The
buffer lists the keywords that relate to the package in the form of
buttons. Click on a button with mouse-1 or mouse-2 to see
the list of other packages related to that keyword.
10.7 Help for International Language Support
For information on a specific language environment (see Language Environments), type C-h L
(describe-language-environment
). This displays a help buffer
describing the languages supported by the language environment, and
listing the associated character sets, coding systems, and input
methods, as well as some sample text for that language environment.
The command C-h h (view-hello-file
) displays the file
etc/HELLO, which demonstrates various character sets by showing
how to say “hello” in many languages.
The command C-h I (describe-input-method
) describes an
input method—either a specified input method, or by default the
input method currently in use. See Input Methods.
The command C-h C (describe-coding-system
) describes
coding systems—either a specified coding system, or the ones
currently in use. See Coding Systems.
10.8 Other Help Commands
C-h i (info
) runs the Info program, which browses
structured documentation files. C-h 4 i
(info-other-window
) does the same, but shows the Info buffer in
another window. The entire Emacs manual is available within Info,
along with many other manuals for the GNU system. Type h after
entering Info to run a tutorial on using Info.
With a numeric argument n, C-h i selects the Info buffer
‘*info*<n>’. This is useful if you want to browse multiple
Info manuals simultaneously. If you specify just C-u as the
prefix argument, C-h i prompts for the name of a documentation
file, so you can browse a file which doesn’t have an entry in the
top-level Info menu.
The help commands C-h F function RET and C-h
K key, described above, enter Info and go straight to the
documentation of function or key.
When editing a program, if you have an Info version of the manual
for the programming language, you can use C-h S
(info-lookup-symbol
) to find an entry for a symbol (keyword,
function or variable) in the proper manual. The details of how this
command works depend on the major mode.
If something surprising happens, and you are not sure what you typed,
use C-h l (view-lossage
). C-h l displays your last
input keystrokes and the commands they invoked. By default, Emacs
stores the last 300 keystrokes; if you wish, you can change this number with
the command lossage-size
.
If you see commands that you are not familiar with, you can use C-h k or
C-h f to find out what they do.
To review recent echo area messages, use C-h e
(view-echo-area-messages
). This displays the buffer
*Messages*, where those messages are kept.
Each Emacs major mode typically redefines a few keys and makes other
changes in how editing works. C-h m (describe-mode
)
displays documentation on the current major mode, which normally
describes the commands and features that are changed in this mode, and
also its key bindings.
C-h b (describe-bindings
) and C-h s
(describe-syntax
) show other information about the current
environment within Emacs. C-h b displays a list of all the key
bindings now in effect: first the local bindings of the current minor
modes, then the local bindings defined by the current major mode, and
finally the global bindings (see Customizing Key Bindings). C-h s
displays the contents of the syntax table, with explanations of each
character’s syntax (see Syntax Tables in The
Emacs Lisp Reference Manual).
You can get a list of subcommands for a particular prefix key by
typing C-h, ?, or F1
(describe-prefix-bindings
) after the prefix key. (There are a
few prefix keys for which not all of these keys work—those that
provide their own bindings for that key. One of these prefix keys
is ESC, because ESC C-h and ESC ? are
actually C-M-h (mark-defun
) and M-?
(xref-find-references
), respectively. However,
ESC F1 works fine.)
Finally, M-x describe-keymap prompts for the name of a keymap,
with completion, and displays a listing of all key bindings in that
keymap.
10.9 Help Files
Apart from the built-in documentation and manuals, Emacs contains
several other files describing topics like copying conditions, release
notes, instructions for debugging and reporting bugs, and so forth.
You can use the following commands to view these files. Apart from
C-h g, they all have the form C-h C-char.
- C-h C-c
Display the rules under which you can copy and redistribute Emacs
(describe-copying
).
- C-h C-d
Display help for debugging Emacs (view-emacs-debugging
).
- C-h C-e
Display information about where to get external packages
(view-external-packages
).
- C-h C-f
Display the Emacs frequently-answered-questions list (view-emacs-FAQ
).
- C-h g
Visit the page with information about the GNU
Project (describe-gnu-project
).
- C-h C-m
Display information about ordering printed copies of Emacs manuals
(view-order-manuals
).
- C-h C-n
Display the news, which lists the new features in this
version of Emacs (view-emacs-news
).
- C-h C-o
Display how to order or download the latest version of
Emacs and other GNU software (describe-distribution
).
- C-h C-p
Display the list of known Emacs problems, sometimes with suggested
workarounds (view-emacs-problems
).
- C-h C-t
Display the Emacs to-do list (view-emacs-todo
).
- C-h C-w
Display the full details on the complete absence of warranty for GNU
Emacs (describe-no-warranty
).
10.10 Help on Active Text and Tooltips
In Emacs, stretches of active text (text that does something
special in response to mouse clicks or RET) often have
associated help text. This includes hyperlinks in Emacs buffers, as
well as parts of the mode line. On graphical displays, as well as
some text terminals which support mouse tracking, moving the mouse
over the active text displays the help text as a tooltip.
See Tooltips.
On terminals that don’t support mouse-tracking, you can display the
help text for active buffer text at point by typing C-h .
(display-local-help
). This shows the help text in the echo
area. To display help text automatically whenever it is available at
point, set the variable help-at-pt-display-when-idle
to
t
.
11 The Mark and the Region
Many Emacs commands operate on an arbitrary contiguous part of the
current buffer. To specify the text for such a command to operate on,
you set the mark at one end of it, and move point to the other
end. The text between point and the mark is called the region.
The region always extends between point and the mark, no matter which
one comes earlier in the text; each time you move point, the region
changes.
Setting the mark at a position in the text also activates it.
When the mark is active, we say also that the region is active; Emacs
indicates its extent by highlighting the text within it, using the
region
face (see Customizing Faces).
This is one of the few faces that has the :extend t
attribute
by default, which implies that the same face is used to highlight the
text and space between end of line and the window border. To
highlight only the text you could set this attribute to nil
.
After certain non-motion commands, including any command that
changes the text in the buffer, Emacs automatically deactivates
the mark; this turns off the highlighting. You can also explicitly
deactivate the mark at any time, by typing C-g
(see Quitting and Aborting).
The above default behavior is known as Transient Mark mode.
Disabling Transient Mark mode switches Emacs to an alternative
behavior, in which the region is usually not highlighted.
See Disabling Transient Mark Mode.
Setting the mark in one buffer has no effect on the marks in other
buffers. When you return to a buffer with an active mark, the mark is
at the same place as before. When multiple windows show the same
buffer, they can have different values of point, and thus different
regions, but they all share one common mark position. See Multiple Windows.
Ordinarily, only the selected window highlights its region; however,
if the variable highlight-nonselected-windows
is
non-nil
, each window highlights its own region.
There is another kind of region: the rectangular region.
See Rectangles.
11.1 Setting the Mark
Here are some commands for setting the mark:
- C-SPC
Set the mark at point, and activate it (set-mark-command
).
- C-@
The same.
- C-x C-x
Set the mark at point, and activate it; then move point where the mark
used to be (exchange-point-and-mark
).
- Drag-mouse-1
Set point and the mark around the text you drag across.
- mouse-3
Set the mark at point, then move point to where you click
(mouse-save-then-kill
).
- Shifted cursor motion keys
Set the mark at point if the mark is inactive, then move point.
See Shift Selection.
The most common way to set the mark is with C-SPC
(set-mark-command
)5. This sets the mark where point is,
and activates it. You can then move point away, leaving the mark
behind.
For example, suppose you wish to convert part of the buffer to upper
case. To accomplish this, go to one end of the desired text, type
C-SPC, and move point until the desired portion of text is
highlighted. Now type C-x C-u (upcase-region
). This
converts the text in the region to upper case, and then deactivates
the mark.
Whenever the mark is active, you can deactivate it by typing
C-g (see Quitting and Aborting). Most commands that operate on the
region also automatically deactivate the mark, like C-x C-u in
the above example.
Instead of setting the mark in order to operate on a region, you can
also use it to remember a position in the buffer (by typing
C-SPC C-SPC), and later jump back there (by typing
C-u C-SPC). See The Mark Ring, for details.
The command C-x C-x (exchange-point-and-mark
) exchanges
the positions of point and the mark. C-x C-x is useful when you
are satisfied with the position of point but want to move the other
end of the region (where the mark is). Using C-x C-x a second
time, if necessary, puts the mark at the new position with point back
at its original position. Normally, if the mark is inactive, this
command first reactivates the mark wherever it was last set, to ensure
that the region is left highlighted. However, if you call it with a
prefix argument, it leaves the mark inactive and the region
unhighlighted; you can use this to jump to the mark in a manner
similar to C-u C-SPC.
You can also set the mark with the mouse. If you press the left
mouse button (down-mouse-1) and drag the mouse across a range of
text, this sets the mark where you first pressed the mouse button and
puts point where you release it. Alternatively, clicking the right
mouse button (mouse-3) sets the mark at point and then moves
point to where you clicked. See Mouse Commands for Editing, for a more
detailed description of these mouse commands.
Finally, you can set the mark by holding down the shift key while
typing certain cursor motion commands (such as S-RIGHT,
S-C-f, S-C-n, etc.). This is called shift-selection.
It sets the mark at point before moving point, but only if there is no
active mark set via a previous shift-selection or mouse commands. The
mark set by mouse commands and by shift-selection behaves slightly
differently from the usual mark: any subsequent unshifted cursor motion
command deactivates it automatically. For details, see Shift Selection.
Many commands that insert text, such as C-y (yank
), set
the mark at the other end of the inserted text, without activating it.
This lets you easily return to that position (see The Mark Ring). You
can tell that a command does this when it shows ‘Mark set’ in the
echo area.
Under X, every time the active region changes, Emacs saves the text
in the region to the primary selection. This lets you insert
that text into other X applications with mouse-2 clicks.
See Cut and Paste with Other Window Applications.
11.2 Commands to Mark Textual Objects
Here are commands for placing point and the mark around a textual
object such as a word, list, paragraph or page:
- M-@
Set mark at the end of the next word (mark-word
). This does not
move point.
- C-M-@
Set mark after end of following balanced expression
(mark-sexp
). This does not move point.
- M-h
Move point to the beginning of the current paragraph, and set mark at
the end (mark-paragraph
).
- C-M-h
Move point to the beginning of the current defun, and set mark at the
end (mark-defun
).
- C-x C-p
Move point to the beginning of the current page, and set mark at the
end (mark-page
).
- C-x h
Move point to the beginning of the buffer, and set mark at the end
(mark-whole-buffer
).
M-@ (mark-word
) sets the mark at the end of the next
word (see Words, for information about words). Repeated
invocations of this command extend the region by advancing the mark
one word at a time. As an exception, if the mark is active and
located before point, M-@ moves the mark backwards from its
current position one word at a time.
This command also accepts a numeric argument n, which tells it
to advance the mark by n words. A negative argument
-n moves the mark back by n words.
Similarly, C-M-@ (mark-sexp
) puts the mark at the end
of the next balanced expression (see Expressions with Balanced Parentheses). Repeated
invocations extend the region to subsequent expressions, while
positive or negative numeric arguments move the mark forward or
backward by the specified number of expressions.
The other commands in the above list set both point and mark, so as
to delimit an object in the buffer. M-h (mark-paragraph
)
marks paragraphs (see Paragraphs), C-M-h (mark-defun
)
marks top-level definitions (see Moving by Defuns), and C-x
C-p (mark-page
) marks pages (see Pages). Repeated
invocations again play the same role, extending the region to
consecutive objects; similarly, numeric arguments specify how many
objects to move the mark by.
C-x h (mark-whole-buffer
) sets up the entire buffer as
the region, by putting point at the beginning and the mark at the end.
11.3 Operating on the Region
Once you have a region, here are some of the ways you can operate on
it:
Some commands have a default behavior when the mark is inactive, but
operate on the region if the mark is active. For example, M-$
(ispell-word
) normally checks the spelling of the word at
point, but it checks the text in the region if the mark is active
(see Checking and Correcting Spelling). Normally, such commands use their default
behavior if the region is empty (i.e., if mark and point are at the
same position). If you want them to operate on the empty region,
change the variable use-empty-active-region
to t
.
As described in Erasing Text, the DEL
(backward-delete-char
) and Delete
(delete-forward-char
) commands also act this way. If the mark
is active, they delete the text in the region. (As an exception, if
you supply a numeric argument n, where n is not one, these
commands delete n characters regardless of whether the mark is
active). If you change the variable delete-active-region
to
nil
, then these commands don’t act differently when the mark is
active. If you change the value to kill
, these commands
kill the region instead of deleting it (see Killing and Moving Text).
Other commands always operate on the region, and have no default
behavior. Such commands usually have the word region
in their
names, like C-w (kill-region
) and C-x C-u
(upcase-region
). If the mark is inactive, they operate on the
inactive region—that is, on the text between point and the
position at which the mark was last set (see The Mark Ring). To
disable this behavior, change the variable
mark-even-if-inactive
to nil
. Then these commands will
instead signal an error if the mark is inactive.
By default, text insertion occurs normally even if the mark is
active—for example, typing a inserts the character ‘a’,
then deactivates the mark. Delete Selection mode, a minor mode,
modifies this behavior: if you enable that mode, then inserting text
while the mark is active causes the text in the region to be deleted
first. To toggle Delete Selection mode on or off, type M-x
delete-selection-mode.
11.4 The Mark Ring
Each buffer remembers previous locations of the mark, in the
mark ring. Commands that set the mark also push the old mark
onto this ring. One of the uses of the mark ring is to remember spots
that you may want to go back to.
- C-SPC C-SPC
Set the mark, pushing it onto the mark ring, without activating it.
- C-u C-SPC
Move point to where the mark was, and restore the mark from the ring
of former marks.
The command C-SPC C-SPC is handy when you want to
use the mark to remember a position to which you may wish to return.
It pushes the current point onto the mark ring, without activating the
mark (which would cause Emacs to highlight the region). This is
actually two consecutive invocations of C-SPC
(set-mark-command
); the first C-SPC sets the mark,
and the second C-SPC deactivates it. (When Transient Mark
mode is off, C-SPC C-SPC instead activates Transient
Mark mode temporarily; see Disabling Transient Mark Mode.)
To return to a marked position, use set-mark-command
with a
prefix argument: C-u C-SPC. This moves point to where the
mark was, and deactivates the mark if it was active. Each subsequent
C-u C-SPC jumps to a prior position stored in the mark
ring. The positions you move through in this way are not lost; they
go to the end of the ring.
If you set set-mark-command-repeat-pop
to non-nil
,
then immediately after you type C-u C-SPC, you can type
C-SPC instead of C-u C-SPC to cycle through
the mark ring. By default, set-mark-command-repeat-pop
is
nil
.
Each buffer has its own mark ring. All editing commands use the
current buffer’s mark ring. In particular, C-u C-SPC
always stays in the same buffer.
The variable mark-ring-max
specifies the maximum number of
entries to keep in the mark ring. This defaults to 16 entries. If
that many entries exist and another one is pushed, the earliest one in
the list is discarded. Repeating C-u C-SPC cycles through
the positions currently in the ring.
If you want to move back to the same place over and over, the mark
ring may not be convenient enough. If so, you can record the position
in a register for later retrieval (see Saving
Positions in Registers).
11.5 The Global Mark Ring
In addition to the ordinary mark ring that belongs to each buffer,
Emacs has a single global mark ring. Each time you set a mark,
this is recorded in the global mark ring in addition to the current
buffer’s own mark ring, if you have switched buffers since the
previous mark setting. Hence, the global mark ring records a sequence
of buffers that you have been in, and, for each buffer, a place where
you set the mark. The length of the global mark ring is controlled by
global-mark-ring-max
, and is 16 by default.
The command C-x C-SPC (pop-global-mark
) jumps to
the buffer and position of the latest entry in the global ring. It also
rotates the ring, so that successive uses of C-x C-SPC take
you to earlier buffers and mark positions.
11.6 Shift Selection
If you hold down the shift key while typing a cursor motion command,
this sets the mark before moving point, so that the region extends
from the original position of point to its new position. This feature
is referred to as shift-selection. It is similar to the way
text is selected in other editors.
The mark set via shift-selection behaves a little differently from
what we have described above. Firstly, in addition to the usual ways
of deactivating the mark (such as changing the buffer text or typing
C-g), the mark is deactivated by any unshifted cursor
motion command. Secondly, any subsequent shifted cursor motion
command avoids setting the mark anew. Therefore, a series of shifted
cursor motion commands will continuously adjust the region.
Shift-selection only works if the shifted cursor motion key is not
already bound to a separate command (see Customization). For
example, if you bind S-C-f to another command, typing
S-C-f runs that command instead of performing a shift-selected
version of C-f (forward-char
).
A mark set via mouse commands behaves the same as a mark set via
shift-selection (see Setting the Mark). For example, if you specify a
region by dragging the mouse, you can continue to extend the region
using shifted cursor motion commands. In either case, any unshifted
cursor motion command deactivates the mark.
To turn off shift-selection, set shift-select-mode
to
nil
. Doing so does not disable setting the mark via mouse
commands. If you set shift-select-mode
to the value
permanent
, cursor motion keys that were not shift-translated
will not deactivate the mark, so, for example, the region set by prior
commands can be extended by shift-selection, and unshifted cursor
motion keys will extend the region set by shift-selection.
11.7 Disabling Transient Mark Mode
The default behavior of the mark and region, in which setting the
mark activates it and highlights the region, is called Transient Mark
mode. This is a minor mode that is enabled by default. It can be
toggled with M-x transient-mark-mode, or with the
‘Highlight Active Region’ menu item in the ‘Options’ menu.
Turning it off switches Emacs to an alternative mode of operation:
- Setting the mark, with commands like C-SPC or C-x
C-x, does not highlight the region. Therefore, you can’t tell by
looking where the mark is located; you have to remember.
The usual solution to this problem is to set the mark and then use it
soon, before you forget where it is. You can also check where the
mark is by using C-x C-x, which exchanges the positions of the
point and the mark (see Setting the Mark).
- Some commands, which ordinarily act on the region when the mark is
active, no longer do so. For example, normally M-%
(
query-replace
) performs replacements within the region, if the
mark is active. When Transient Mark mode is off, it always operates
from point to the end of the buffer. Commands that act this way are
identified in their own documentation.
While Transient Mark mode is off, you can activate it temporarily
using C-SPC C-SPC or C-u C-x C-x.
- C-SPC C-SPC ¶
Set the mark at point (like plain C-SPC) and enable
Transient Mark mode just once, until the mark is deactivated. (This
is not really a separate command; you are using the C-SPC
command twice.)
- C-u C-x C-x ¶
Exchange point and mark, activate the mark and enable Transient Mark
mode temporarily, until the mark is next deactivated. (This is the
C-x C-x command, exchange-point-and-mark
, with a prefix
argument.)
These commands set or activate the mark, and enable Transient Mark
mode only until the mark is deactivated. One reason you may want to
use them is that some commands operate on the entire buffer instead of
the region when Transient Mark mode is off. Enabling Transient Mark
mode momentarily gives you a way to use these commands on the region.
When you specify a region with the mouse (see Setting the Mark), or
with shift-selection (see Shift Selection), this likewise
activates Transient Mark mode temporarily and highlights the region.
12 Killing and Moving Text
In Emacs, killing means erasing text and copying it into the
kill ring. Yanking means bringing text from the kill ring
back into the buffer. (Some applications use the terms “cutting”
and “pasting” for similar operations.) The kill ring is so-named
because it can be visualized as a set of blocks of text arranged in a
ring, which you can access in cyclic order. See The Kill Ring.
Killing and yanking are the most common way to move or copy text
within Emacs. It is very versatile, because there are commands for
killing many different types of syntactic units.
12.1 Deletion and Killing
Most commands which erase text from the buffer save it in the kill
ring (see The Kill Ring). These are known as kill commands, and
their names normally contain the word ‘kill’ (e.g.,
kill-line
). The kill ring stores several recent kills, not
just the last one, so killing is a very safe operation: you don’t have
to worry much about losing text that you previously killed. The kill
ring is shared by all buffers, so text that is killed in one buffer
can be yanked into another buffer.
When you use C-/ (undo
) to undo a kill command
(see Undo), that brings the killed text back into the buffer, but
does not remove it from the kill ring.
On graphical displays, killing text also copies it to the system
clipboard. See “Cut and Paste” Operations on Graphical Displays.
Commands that erase text but do not save it in the kill ring are
known as delete commands; their names usually contain the word
‘delete’. These include C-d (delete-char
) and
DEL (delete-backward-char
), which delete only one
character at a time, and those commands that delete only spaces or
newlines. Commands that can erase significant amounts of nontrivial
data generally do a kill operation instead.
You can also use the mouse to kill and yank. See “Cut and Paste” Operations on Graphical Displays.
12.1.1 Deletion
Deletion means erasing text and not saving it in the kill ring. For
the most part, the Emacs commands that delete text are those that
erase just one character or only whitespace.
- DEL
- BACKSPACE
Delete the previous character, or the text in the region if it is
active (delete-backward-char
).
- Delete
Delete the next character, or the text in the region if it is active
(delete-forward-char
).
- C-d
Delete the next character (delete-char
).
- M-\
Delete spaces and tabs around point (delete-horizontal-space
).
- M-SPC
Delete spaces and tabs around point, leaving one space
(just-one-space
).
- C-x C-o
Delete blank lines around the current line (delete-blank-lines
).
- M-^
Join two lines by deleting the intervening newline, along with any
indentation following it (delete-indentation
).
We have already described the basic deletion commands DEL
(delete-backward-char
), delete
(delete-forward-char
), and C-d (delete-char
).
See Erasing Text. With a numeric argument, they delete the specified
number of characters. If the numeric argument is omitted or one,
DEL and delete delete all the text in the region if it is
active (see Operating on the Region).
The other delete commands are those that delete only whitespace
characters: spaces, tabs and newlines. M-\
(delete-horizontal-space
) deletes all the spaces and tab
characters before and after point. With a prefix argument, this only
deletes spaces and tab characters before point. M-SPC
(just-one-space
) does likewise but leaves a single space before
point, regardless of the number of spaces that existed previously
(even if there were none before). With a numeric argument n, it
leaves n spaces before point if n is positive; if n
is negative, it deletes newlines in addition to spaces and tabs,
leaving -n spaces before point. The command cycle-spacing
acts like a more flexible version of just-one-space
. It
does different things if you call it repeatedly in succession.
The first call acts like just-one-space
, the next removes
all whitespace, and a third call restores the original whitespace.
C-x C-o (delete-blank-lines
) deletes all blank lines
after the current line. If the current line is blank, it deletes all
blank lines preceding the current line as well (leaving one blank line,
the current line). On a solitary blank line, it deletes that line.
M-^ (delete-indentation
) joins the current line and the
previous line, by deleting a newline and all surrounding spaces, usually
leaving a single space. See M-^.
The command delete-duplicate-lines
searches the region for
identical lines, and removes all but one copy of each. Normally it
keeps the first instance of each repeated line, but with a C-u
prefix argument it keeps the last. With a C-u C-u prefix
argument, it only searches for adjacent identical lines. This is a
more efficient mode of operation, useful when the lines have already
been sorted. With a C-u C-u C-u prefix argument, it retains
repeated blank lines.
12.1.2 Killing by Lines
- C-k
Kill rest of line or one or more lines (kill-line
).
- C-S-backspace
Kill an entire line at once (kill-whole-line
)
The simplest kill command is C-k (kill-line
). If used
at the end of a line, it kills the line-ending newline character,
merging the next line into the current one (thus, a blank line is
entirely removed). Otherwise, C-k kills all the text from point
up to the end of the line; if point was originally at the beginning of
the line, this leaves the line blank.
Spaces and tabs at the end of the line are ignored when deciding
which case applies. As long as point is after the last non-whitespace
character in the line, you can be sure that C-k will kill the
newline. To kill an entire non-blank line, go to the beginning and
type C-k twice.
In this context, “line” means a logical text line, not a screen
line (see Continuation Lines).
When C-k is given a positive argument n, it kills
n lines and the newlines that follow them (text on the current
line before point is not killed). With a negative argument
-n, it kills n lines preceding the current line,
together with the text on the current line before point. C-k
with an argument of zero kills the text before point on the current
line.
If the variable kill-whole-line
is non-nil
, C-k at
the very beginning of a line kills the entire line including the
following newline. This variable is normally nil
.
C-S-backspace (kill-whole-line
) kills a whole line
including its newline, regardless of the position of point within the
line. Note that many text terminals will prevent you from typing the
key sequence C-S-backspace.
12.1.3 Other Kill Commands
- C-w
Kill the region (kill-region
).
- M-w
Copy the region into the kill ring (kill-ring-save
).
- M-d
Kill the next word (kill-word
). See Words.
- M-DEL
Kill one word backwards (backward-kill-word
).
- C-x DEL
Kill back to beginning of sentence (backward-kill-sentence
).
See Sentences.
- M-k
Kill to the end of the sentence (kill-sentence
).
- C-M-k
Kill the following balanced expression (kill-sexp
). See Expressions with Balanced Parentheses.
- M-z char
Kill through the next occurrence of char (zap-to-char
).
- M-x zap-up-to-char char
Kill up to, but not including, the next occurrence of char.
One of the commonly-used kill commands is C-w
(kill-region
), which kills the text in the region
(see The Mark and the Region). Similarly, M-w (kill-ring-save
) copies
the text in the region into the kill ring without removing it from the
buffer. If the mark is inactive when you type C-w or M-w,
the command acts on the text between point and where you last set the
mark (see Operating on the Region).
Emacs also provides commands to kill specific syntactic units:
words, with M-DEL and M-d (see Words); balanced
expressions, with C-M-k (see Expressions with Balanced Parentheses); and sentences,
with C-x DEL and M-k (see Sentences).
The command M-z (zap-to-char
) combines killing with
searching: it reads a character and kills from point up to (and
including) the next occurrence of that character in the buffer. A
numeric argument acts as a repeat count; a negative argument means to
search backward and kill text before point. A history of previously
used characters is maintained and can be accessed via the
M-p/M-n keystrokes. This is mainly useful if the
character to be used has to be entered via a complicated input method.
A similar command zap-up-to-char
kills from point up to, but
not including the next occurrence of a character, with numeric
argument acting as a repeat count.
12.1.4 Options for Killing
Some specialized buffers contain read-only text, which cannot
be modified and therefore cannot be killed. The kill commands work
specially in a read-only buffer: they move over text and copy it to
the kill ring, without actually deleting it from the buffer.
Normally, they also beep and display an error message when this
happens. But if you set the variable kill-read-only-ok
to a
non-nil
value, they just print a message in the echo area to
explain why the text has not been erased.
Before saving the kill to the kill ring, you can transform the
string using kill-transform-function
. It’s called with the
string to be killed, and it should return the string you want to be
saved. It can also return nil
, in which case the string won’t
be saved to the kill ring. For instance, if you never want to save
a pure white space string to the kill ring, you can say:
(setq kill-transform-function
(lambda (string)
(and (not (string-blank-p string))
string)))
If you change the variable kill-do-not-save-duplicates
to a
non-nil
value, identical subsequent kills yield a single
kill-ring entry, without duplication.
12.2 Yanking
Yanking means reinserting text previously killed. The usual
way to move or copy text is to kill it and then yank it elsewhere.
- C-y
Yank the last kill into the buffer, at point (yank
).
- M-y
Either replace the text just yanked with an earlier batch of killed
text (yank-pop
), or allow to select from the list of
previously-killed batches of text. See Yanking Earlier Kills.
- C-M-w
Cause the following command, if it is a kill command, to append to the
previous kill (append-next-kill
). See Appending Kills.
The basic yanking command is C-y (yank
). It inserts
the most recent kill, leaving the cursor at the end of the inserted
text. It also sets the mark at the beginning of the inserted text,
without activating the mark; this lets you jump easily to that
position, if you wish, with C-u C-SPC (see The Mark Ring).
With a plain prefix argument (C-u C-y), the command instead
leaves the cursor in front of the inserted text, and sets the mark at
the end. Using any other prefix argument specifies an earlier kill;
e.g., C-u 4 C-y reinserts the fourth most recent kill.
See Yanking Earlier Kills.
On graphical displays and on capable text-mode displays, C-y
first checks if another application has placed any text in the system
clipboard more recently than the last Emacs kill. If so, it inserts
the clipboard’s text instead. Thus, Emacs effectively treats “cut”
or “copy” clipboard operations performed in other applications like
Emacs kills, except that they are not recorded in the kill ring.
See “Cut and Paste” Operations on Graphical Displays, for details.
12.2.1 The Kill Ring
The kill ring is a list of blocks of text that were previously
killed. There is only one kill ring, shared by all buffers, so you
can kill text in one buffer and yank it in another buffer. This is
the usual way to move text from one buffer to another. (There are
several other methods: for instance, you could store the text in a
register; see Registers. See Accumulating Text, for some
other ways to move text around.)
The maximum number of entries in the kill ring is controlled by the
variable kill-ring-max
. The default is 60. If you make a new
kill when this limit has been reached, Emacs makes room by deleting
the oldest entry in the kill ring.
The actual contents of the kill ring are stored in a variable named
kill-ring
; you can view the entire contents of the kill ring
with C-h v kill-ring.
12.2.2 Yanking Earlier Kills
As explained in Yanking, you can use a numeric argument to
C-y to yank text that is no longer the most recent kill. This
is useful if you remember which kill ring entry you want. If you
don’t, you can use the M-y (yank-pop
) command to cycle
through the possibilities or to select one of the earlier kills.
If the previous command was a yank command, M-y takes the text
that was yanked and replaces it with the text from an earlier kill.
So, to recover the text of the next-to-the-last kill, first use
C-y to yank the last kill, and then use M-y to replace it
with the previous kill. This works only after a C-y
or another M-y. (If M-y is invoked after some other
command, it works differently, see below.)
You can understand this operation mode of M-y in terms of a
last-yank pointer which points at an entry in the kill ring. Each
time you kill, the last-yank pointer moves to the newly made entry at
the front of the ring. C-y yanks the entry which the last-yank
pointer points to. M-y after a C-y or another M-y
moves the last-yank pointer to the previous entry, and the text in the
buffer changes to match. Enough M-y commands one after another
can move the pointer to any entry in the ring, so you can get any
entry into the buffer. Eventually the pointer reaches the end of the
ring; the next M-y loops back around to the first entry again.
M-y moves the last-yank pointer around the ring, but it does
not change the order of the entries in the ring, which always runs from
the most recent kill at the front to the oldest one still remembered.
When used after C-y or M-y, M-y can take a numeric
argument, which tells it how many entries to advance the last-yank
pointer by. A negative argument moves the pointer toward the front of
the ring; from the front of the ring, it moves around to the last
entry and continues forward from there.
Once the text you are looking for is brought into the buffer, you
can stop doing M-y commands and the last yanked text will stay
there. It’s just a copy of the kill ring entry, so editing it in the
buffer does not change what’s in the ring. As long as no new killing
is done, the last-yank pointer remains at the same place in the kill
ring, so repeating C-y will yank another copy of the same
previous kill.
When you call C-y with a numeric argument, that also sets the
last-yank pointer to the entry that it yanks.
You can also invoke M-y after a command that is not a yank
command. In that case, M-y prompts you in the minibuffer for
one of the previous kills. You can use the minibuffer history
commands (see Minibuffer History) to navigate or search through
the entries in the kill ring until you find the one you want to
reinsert. Or you can use completion commands (see Completion Commands) to complete on an entry from the list of entries in the
kill ring or pop up the *Completions* buffer with the candidate
entries from which you can choose. After selecting the kill-ring
entry, you can optionally edit it in the minibuffer. Finally, type
RET to exit the minibuffer and insert the text of the selected
kill-ring entry. Like in case of M-y after another yank
command, the last-yank pointer is left pointing at the text you just
yanked, whether it is one of the previous kills or an entry from the
kill-ring that you edited before inserting it. (In the latter case,
the edited entry is added to the front of the kill-ring.) So here,
too, typing C-y will yank another copy of the text just
inserted.
When invoked with a plain prefix argument (C-u M-y) after a
command that is not a yank command, M-y leaves the cursor in
front of the inserted text, and sets the mark at the end, like
C-y does.
12.2.3 Appending Kills
Normally, each kill command pushes a new entry onto the kill ring.
However, two or more kill commands in a row combine their text into a
single entry, so that a single C-y yanks all the text as a unit,
just as it was before it was killed.
Thus, if you want to yank text as a unit, you need not kill all of it
with one command; you can keep killing line after line, or word after
word, until you have killed it all, and you can still get it all back at
once.
Commands that kill forward from point add onto the end of the previous
killed text. Commands that kill backward from point add text onto the
beginning. This way, any sequence of mixed forward and backward kill
commands puts all the killed text into one entry without rearrangement.
Numeric arguments do not break the sequence of appending kills. For
example, suppose the buffer contains this text:
This is a line ∗of sample text.
with point shown by ∗. If you type M-d M-DEL M-d
M-DEL, killing alternately forward and backward, you end up with
‘a line of sample’ as one entry in the kill ring, and
‘This is text.’ in the buffer. (Note the double space
between ‘is’ and ‘text’, which you can clean up with
M-SPC or M-q.)
Another way to kill the same text is to move back two words with
M-b M-b, then kill all four words forward with C-u M-d.
This produces exactly the same results in the buffer and in the kill
ring. M-f M-f C-u M-DEL kills the same text, all going
backward; once again, the result is the same. The text in the kill ring
entry always has the same order that it had in the buffer before you
killed it.
If a kill command is separated from the last kill command by other
commands (not just numeric arguments), it starts a new entry on the
kill ring. But you can force it to combine with the last killed text,
by typing C-M-w (append-next-kill
) right beforehand. The
C-M-w tells its following command, if it is a kill command, to
treat the kill as part of the sequence of previous kills. As usual,
the kill is appended to the previous killed text if the command kills
forward, and prepended if the command kills backward. In this way,
you can kill several separated pieces of text and accumulate them to
be yanked back in one place.
A kill command following M-w (kill-ring-save
) does not
append to the text that M-w copied into the kill ring.
12.3 “Cut and Paste” Operations on Graphical Displays
In most graphical desktop environments, you can transfer data
(usually text) between different applications using a system facility
called the clipboard. On X, two other similar facilities are
available: the primary selection and the secondary selection. When
Emacs is run on a graphical display, its kill and yank commands
integrate with these facilities, so that you can easily transfer text
between Emacs and other graphical applications.
By default, Emacs uses UTF-8 as the coding system for inter-program
text transfers. If you find that the pasted text is not what you
expected, you can specify another coding system by typing C-x
RET x or C-x RET X. You can also request a
different data type by customizing x-select-request-type
.
See Coding Systems for Interprocess Communication.
12.3.1 Using the Clipboard
The clipboard is the facility that most graphical applications
use for “cutting and pasting”. When the clipboard exists, the kill
and yank commands in Emacs make use of it.
When you kill some text with a command such as C-w
(kill-region
), or copy it to the kill ring with a command such
as M-w (kill-ring-save
), that text is also put in the
clipboard.
When an Emacs kill command puts text in the clipboard, the existing
clipboard contents are normally lost. Optionally, Emacs can save the
existing clipboard contents to the kill ring, preventing you from
losing the old clipboard data. If
save-interprogram-paste-before-kill
changed to a number, then
this data is copied over if it’s smaller (in characters) than this
number. If this variable is any other non-nil
value, it’s
always copied over—at the risk of high memory consumption if that
data turns out to be large.
Yank commands, such as C-y (yank
), also use the
clipboard. If another application “owns” the clipboard—i.e., if
you cut or copied text there more recently than your last kill command
in Emacs—then Emacs yanks from the clipboard instead of the kill
ring.
Normally, rotating the kill ring with M-y (yank-pop
)
does not alter the clipboard. However, if you change
yank-pop-change-selection
to t
, then M-y saves the
new yank to the clipboard.
To prevent kill and yank commands from accessing the clipboard,
change the variable select-enable-clipboard
to nil
.
Many X desktop environments support a feature called the
clipboard manager. If you exit Emacs while it is the current
“owner” of the clipboard data, and there is a clipboard manager
running, Emacs transfers the clipboard data to the clipboard manager
so that it is not lost. In some circumstances, this may cause a delay
when exiting Emacs; if you wish to prevent Emacs from transferring
data to the clipboard manager, change the variable
x-select-enable-clipboard-manager
to nil
.
Since strings containing NUL bytes are usually truncated when passed
through the clipboard, Emacs replaces such characters with “\0”
before transferring them to the system’s clipboard.
Prior to Emacs 24, the kill and yank commands used the primary
selection (see Cut and Paste with Other Window Applications), not the clipboard. If you
prefer this behavior, change select-enable-clipboard
to
nil
, select-enable-primary
to t
, and
mouse-drag-copy-region
to t
. In this case, you can use
the following commands to act explicitly on the clipboard:
clipboard-kill-region
kills the region and saves it to the
clipboard; clipboard-kill-ring-save
copies the region to the
kill ring and saves it to the clipboard; and clipboard-yank
yanks the contents of the clipboard at point.
12.3.2 Cut and Paste with Other Window Applications
Under the X Window System, there exists a primary selection
containing the last stretch of text selected in an X application
(usually by dragging the mouse). Typically, this text can be inserted
into other X applications by mouse-2 clicks. The primary
selection is separate from the clipboard. Its contents are more
fragile; they are overwritten each time you select text with the
mouse, whereas the clipboard is only overwritten by explicit cut
or copy commands.
Under X, whenever the region is active (see The Mark and the Region), the text in
the region is saved in the primary selection. This applies regardless
of whether the region was made by dragging or clicking the mouse
(see Mouse Commands for Editing), or by keyboard commands (e.g., by typing
C-SPC and moving point; see Setting the Mark).
If you change the variable select-active-regions
to
only
, Emacs saves only temporarily active regions to the
primary selection, i.e., those made with the mouse or with shift
selection (see Shift Selection). If you change
select-active-regions
to nil
, Emacs avoids saving active
regions to the primary selection entirely.
To insert the primary selection into an Emacs buffer, click
mouse-2 (mouse-yank-primary
) where you want to insert it.
See Mouse Commands for Editing. You can also use the normal Emacs yank command
(C-y) to insert this text if select-enable-primary
is set
(see Using the Clipboard).
MS-Windows provides no primary selection, but Emacs emulates it
within a single Emacs session by storing the selected text internally.
Therefore, all the features and commands related to the primary
selection work on Windows as they do on X, for cutting and pasting
within the same session, but not across Emacs sessions or with other
applications.
12.3.3 Secondary Selection
In addition to the primary selection, the X Window System provides a
second similar facility known as the secondary selection.
Nowadays, few X applications make use of the secondary selection, but
you can access it using the following Emacs commands:
-
- M-Drag-mouse-1
Set the secondary selection, with one end at the place where you press
down the button, and the other end at the place where you release it
(mouse-set-secondary
). The selected text is highlighted, using
the secondary-selection
face, as you drag. The window scrolls
automatically if you drag the mouse off the top or bottom of the
window, just like mouse-set-region
(see Mouse Commands for Editing).
This command does not alter the kill ring.
- M-mouse-1
Set one endpoint for the secondary selection
(mouse-start-secondary
); use M-mouse-3 to set the other
end and complete the selection. This command cancels any existing
secondary selection, when it starts a new one.
- M-mouse-3
Set the secondary selection (mouse-secondary-save-then-kill
),
with one end at the position you click M-mouse-3, and the other
at the position specified previously with M-mouse-1. This also
puts the selected text in the kill ring. A second M-mouse-3 at
the same place kills the text selected by the secondary selection just
made.
- M-mouse-2
Insert the secondary selection where you click, placing point at the
end of the yanked text (mouse-yank-secondary
).
Double or triple clicking of M-mouse-1 operates on words and
lines, much like mouse-1.
If mouse-yank-at-point
is non-nil
, M-mouse-2 yanks
at point. Then it does not matter precisely where you click, or even
which of the frame’s windows you click on. See Mouse Commands for Editing.
12.4 Accumulating Text
Usually we copy or move text by killing it and yanking it, but there
are other convenient methods for copying one block of text in many
places, or for copying many scattered blocks of text into one place.
Here we describe the commands to accumulate scattered pieces of text
into a buffer or into a file.
- M-x append-to-buffer
Append region to the contents of a specified buffer.
- M-x prepend-to-buffer
Prepend region to the contents of a specified buffer.
- M-x copy-to-buffer
Copy region into a specified buffer, deleting that buffer’s old contents.
- M-x insert-buffer
Insert the contents of a specified buffer into current buffer at point.
- M-x append-to-file
Append region to the contents of a specified file, at the end.
To accumulate text into a buffer, use M-x append-to-buffer.
This reads a buffer name, then inserts a copy of the region into the
buffer specified. If you specify a nonexistent buffer,
append-to-buffer
creates the buffer. The text is inserted
wherever point is in that buffer. If you have been using the buffer for
editing, the copied text goes into the middle of the text of the buffer,
starting from wherever point happens to be at that moment.
Point in that buffer is left at the end of the copied text, so
successive uses of append-to-buffer
accumulate the text in the
specified buffer in the same order as they were copied. Strictly
speaking, append-to-buffer
does not always append to the text
already in the buffer—it appends only if point in that buffer is at
the end. However, if append-to-buffer
is the only command you
use to alter a buffer, then point is always at the end.
M-x prepend-to-buffer is just like append-to-buffer
except that point in the other buffer is left before the copied text, so
successive uses of this command add text in reverse order. M-x
copy-to-buffer is similar, except that any existing text in the other
buffer is deleted, so the buffer is left containing just the text newly
copied into it.
The command C-x x i (insert-buffer
) can be used to
retrieve the accumulated text from another buffer. This prompts for
the name of a buffer, and inserts a copy of all the text in that
buffer into the current buffer at point, leaving point at the
beginning of the inserted text. It also adds the position of the end
of the inserted text to the mark ring, without activating the mark.
See Using Multiple Buffers, for background information on buffers.
Instead of accumulating text in a buffer, you can append text
directly into a file with M-x append-to-file. This prompts for
a filename, and adds the text of the region to the end of the
specified file. The file is changed immediately on disk.
You should use append-to-file
only with files that are
not being visited in Emacs. Using it on a file that you are
editing in Emacs would change the file behind Emacs’s back, which
can lead to losing some of your editing.
Another way to move text around is to store it in a register.
See Registers.
12.5 Rectangles
Rectangle commands operate on rectangular areas of the text:
all the characters between a certain pair of columns, in a certain
range of lines. Emacs has commands to kill rectangles, yank killed
rectangles, clear them out, fill them with blanks or text, or delete
them. Rectangle commands are useful with text in multicolumn formats,
and for changing text into or out of such formats.
To specify a rectangle for a command to work on, set the mark at one
corner and point at the opposite corner. The rectangle thus specified
is called the region-rectangle. If point and the mark are in
the same column, the region-rectangle is empty. If they are in the
same line, the region-rectangle is one line high.
The region-rectangle is controlled in much the same way as the
region is controlled. But remember that a given combination of point
and mark values can be interpreted either as a region or as a
rectangle, depending on the command that uses them.
A rectangular region can also be marked using the mouse: click and drag
C-M-mouse-1 from one corner of the rectangle to the opposite.
- C-x r k
Kill the text of the region-rectangle, saving its contents as the
last killed rectangle (kill-rectangle
).
- C-x r M-w
Save the text of the region-rectangle as the last killed rectangle
(copy-rectangle-as-kill
).
- C-x r d
Delete the text of the region-rectangle (delete-rectangle
).
- C-x r y
Yank the last killed rectangle with its upper left corner at point
(yank-rectangle
).
- C-x r o
Insert blank space to fill the space of the region-rectangle
(open-rectangle
). This pushes the previous contents of the
region-rectangle to the right.
- C-x r N
Insert line numbers along the left edge of the region-rectangle
(rectangle-number-lines
). This pushes the previous contents of
the region-rectangle to the right.
- C-x r c
Clear the region-rectangle by replacing all of its contents with spaces
(clear-rectangle
).
- M-x delete-whitespace-rectangle
Delete whitespace in each of the lines on the specified rectangle,
starting from the left edge column of the rectangle.
- C-x r t string RET
Replace rectangle contents with string on each line
(string-rectangle
).
- M-x string-insert-rectangle RET string RET
Insert string on each line of the rectangle.
- C-x SPC
Toggle Rectangle Mark mode (rectangle-mark-mode
).
When this mode is active, the region-rectangle is highlighted and can
be shrunk/grown, and the standard kill and yank commands operate on it.
The rectangle operations fall into two classes: commands to erase or
insert rectangles, and commands to make blank rectangles.
There are two ways to erase the text in a rectangle: C-x r d
(delete-rectangle
) to delete the text outright, or C-x r
k (kill-rectangle
) to remove the text and save it as the
last killed rectangle. In both cases, erasing the
region-rectangle is like erasing the specified text on each line of
the rectangle; if there is any following text on the line, it moves
backwards to fill the gap.
Killing a rectangle is not killing in the usual sense; the
rectangle is not stored in the kill ring, but in a special place that
only records the most recent rectangle killed. This is because
yanking a rectangle is so different from yanking linear text that
different yank commands have to be used. Yank-popping is not defined
for rectangles.
C-x r M-w (copy-rectangle-as-kill
) is the equivalent of
M-w for rectangles: it records the rectangle as the last
killed rectangle, without deleting the text from the buffer.
To yank the last killed rectangle, type C-x r y
(yank-rectangle
). The rectangle’s first line is inserted at
point, the rectangle’s second line is inserted at the same horizontal
position one line vertically below, and so on. The number of lines
affected is determined by the height of the saved rectangle.
For example, you can convert two single-column lists into a
double-column list by killing one of the single-column lists as a
rectangle, and then yanking it beside the other list.
You can also copy rectangles into and out of registers with C-x r
r r and C-x r i r. See Saving Rectangles in Registers.
There are two commands you can use for making blank rectangles:
C-x r c (clear-rectangle
) blanks out existing text in the
region-rectangle, and C-x r o (open-rectangle
) inserts a
blank rectangle.
M-x delete-whitespace-rectangle deletes horizontal whitespace
starting from a particular column. This applies to each of the lines
in the rectangle, and the column is specified by the left edge of the
rectangle. The right edge of the rectangle does not make any
difference to this command.
The command C-x r N (rectangle-number-lines
) inserts
line numbers along the left edge of the region-rectangle. Normally,
the numbering begins from 1 (for the first line of the rectangle).
With a prefix argument, the command prompts for a number to begin
from, and for a format string with which to print the numbers
(see Formatting Strings in The Emacs Lisp Reference
Manual).
The command C-x r t (string-rectangle
) replaces the
contents of a region-rectangle with a string on each line. The
string’s width need not be the same as the width of the rectangle. If
the string’s width is less, the text after the rectangle shifts left;
if the string is wider than the rectangle, the text after the
rectangle shifts right.
The command M-x string-insert-rectangle is similar to
string-rectangle
, but inserts the string on each line,
shifting the original text to the right.
The command C-x SPC (rectangle-mark-mode
) toggles
whether the region-rectangle or the standard region is highlighted
(first activating the region if necessary). When this mode is enabled,
commands that resize the region (C-f, C-n etc.) do
so in a rectangular fashion, and killing and yanking operate on the
rectangle. See Killing and Moving Text. The mode persists only as long as the
region is active.
The region-rectangle works only when the mark is active. In
particular, when Transient Mark mode is off (see Disabling Transient Mark Mode), in addition to typing C-x SPC you will need to
activate the mark.
Unlike the standard region, the region-rectangle can have its corners
extended past the end of buffer, or inside stretches of white space
that point normally cannot enter, like in the middle of a TAB
character.
When the region is active (see The Mark and the Region) and in rectangle-mark-mode,
C-x C-x runs the command
rectangle-exchange-point-and-mark
, which cycles between the
four corners of the region-rectangle. This comes in handy if you want
to modify the dimensions of the region-rectangle before invoking an
operation on the marked text.
12.6 CUA Bindings
The command M-x cua-mode sets up key bindings that are
compatible with the Common User Access (CUA) system used in many other
applications.
When CUA mode is enabled, the keys C-x, C-c, C-v,
and C-z invoke commands that cut (kill), copy, paste (yank), and
undo respectively. The C-x and C-c keys perform cut and
copy only if the region is active. Otherwise, they still act as
prefix keys, so that standard Emacs commands like C-x C-c still
work. Note that this means the variable mark-even-if-inactive
has no effect for C-x and C-c (see Operating on the Region).
To enter an Emacs command like C-x C-f while the mark is
active, use one of the following methods: either hold Shift
together with the prefix key, e.g., S-C-x C-f, or quickly type
the prefix key twice, e.g., C-x C-x C-f.
To disable the overriding of standard Emacs binding by CUA mode,
while retaining the other features of CUA mode described below, set
the variable cua-enable-cua-keys
to nil
.
CUA mode by default activates Delete-Selection mode (see Mouse Commands for Editing)
so that typed text replaces the active region. To use CUA without this
behavior, set the variable cua-delete-selection
to nil
.
CUA mode provides enhanced rectangle support with visible
rectangle highlighting. Use C-RET to start a rectangle,
extend it using the movement commands, and cut or copy it using
C-x or C-c. RET moves the cursor to the next
(clockwise) corner of the rectangle, so you can easily expand it in
any direction. Normal text you type is inserted to the left or right
of each line in the rectangle (on the same side as the cursor).
You can use this rectangle support without activating CUA by calling the
cua-rectangle-mark-mode
command. There’s also the standard command
rectangle-mark-mode
, see Rectangles.
With CUA you can easily copy text and rectangles into and out of
registers by providing a one-digit numeric prefix to the kill, copy,
and yank commands, e.g., C-1 C-c copies the region into register
1
, and C-2 C-v yanks the contents of register 2
.
CUA mode also has a global mark feature which allows easy moving and
copying of text between buffers. Use C-S-SPC to toggle the
global mark on and off. When the global mark is on, all text that you
kill or copy is automatically inserted at the global mark, and text
you type is inserted at the global mark rather than at the current
position.
For example, to copy words from various buffers into a word list in
a given buffer, set the global mark in the target buffer, then
navigate to each of the words you want in the list, mark it (e.g., with
S-M-f), copy it to the list with C-c or M-w, and
insert a newline after the word in the target list by pressing
RET.
13 Registers
Emacs registers are compartments where you can save text,
rectangles, positions, and other things for later use. Once you save
text or a rectangle in a register, you can copy it into the buffer
once or many times; once you save a position in a register, you can
jump back to that position once or many times.
Each register has a name that consists of a single character, which
we will denote by r; r can be a letter (such as ‘a’)
or a number (such as ‘1’); case matters, so register ‘a’ is
not the same as register ‘A’. You can also set a register in
non-alphanumeric characters, for instance ‘*’ or ‘C-d’.
Note, it’s not possible to set a register in ‘C-g’ or ‘ESC’,
because these keys are reserved for quitting (see Quitting and Aborting).
A register can store a position, a piece of text, a rectangle, a
number, a window configuration, or a file name, but only one thing at
any given time. Whatever you store in a register remains there until
you store something else in that register. To see what register
r contains, use M-x view-register:
- M-x view-register RET r
Display a description of what register r contains.
All of the commands that prompt for a register will display a
preview window that lists the existing registers (if there are
any) after a short delay. To change the length of the delay,
customize register-preview-delay
. To prevent this display, set
that option to nil
. You can explicitly request a preview
window by pressing C-h or F1.
Bookmarks record files and positions in them, so you can
return to those positions when you look at the file again. Bookmarks
are similar in spirit to registers, so they are also documented in
this chapter.
13.1 Saving Positions in Registers
- C-x r SPC r
Record the position of point and the current buffer in register
r (point-to-register
).
- C-x r j r
Jump to the position and buffer saved in register r
(jump-to-register
).
Typing C-x r SPC (point-to-register
), followed by
a character r, saves both the position of point and the
current buffer in register r. The register retains this
information until you store something else in it.
The command C-x r j r switches to the buffer recorded in
register r, pushes a mark, and moves point to the recorded
position. (The mark is not pushed if point was already at the
recorded position, or in successive calls to the command.) The
contents of the register are not changed, so you can jump to the saved
position any number of times.
If you use C-x r j to go to a saved position, but the buffer it
was saved from has been killed, C-x r j tries to create the buffer
again by visiting the same file. Of course, this works only for buffers
that were visiting files.
13.2 Saving Text in Registers
When you want to insert a copy of the same piece of text several
times, it may be inconvenient to yank it from the kill ring, since each
subsequent kill moves that entry further down the ring. An alternative
is to store the text in a register and later retrieve it.
- C-x r s r
Copy region into register r (copy-to-register
).
- C-x r i r
Insert text from register r (insert-register
).
- M-x append-to-register RET r
Append region to text in register r.
When register r contains text, you can use C-x r +
(increment-register
) to append to that register. Note that
command C-x r + behaves differently if r contains a
number. See Keeping Numbers in Registers.
- M-x prepend-to-register RET r
Prepend region to text in register r.
C-x r s r stores a copy of the text of the region into
the register named r. If the mark is inactive, Emacs first
reactivates the mark where it was last set. The mark is deactivated
at the end of this command. See The Mark and the Region. C-u C-x r s r,
the same command with a prefix argument, copies the text into register
r and deletes the text from the buffer as well; you can think of
this as moving the region text into the register.
M-x append-to-register RET r appends the copy of
the text in the region to the text already stored in the register
named r. If invoked with a prefix argument, it deletes the
region after appending it to the register. The command
prepend-to-register
is similar, except that it prepends
the region text to the text in the register instead of
appending it.
When you are collecting text using append-to-register
and
prepend-to-register
, you may want to separate individual
collected pieces using a separator. In that case, configure a
register-separator
and store the separator text in to that
register. For example, to get double newlines as text separator
during the collection process, you can use the following setting.
(setq register-separator ?+)
(set-register register-separator "\n\n")
C-x r i r inserts in the buffer the text from register
r. Normally it leaves point after the text and sets the mark
before, without activating it. With a prefix argument, it instead
puts point before the text and the mark after.
13.3 Saving Rectangles in Registers
A register can contain a rectangle instead of linear text.
See Rectangles, for basic information on how to specify a rectangle
in the buffer.
-
- C-x r r r
Copy the region-rectangle into register r
(copy-rectangle-to-register
). With prefix argument, delete it as
well.
- C-x r i r
Insert the rectangle stored in register r (if it contains a
rectangle) (insert-register
).
The C-x r i r (insert-register
) command,
previously documented in Saving Text in Registers, inserts a rectangle
rather than a text string, if the register contains a rectangle.
13.4 Saving Window Configurations in Registers
You can save the window configuration of the selected frame in a
register, or even the configuration of all windows in all frames, and
restore the configuration later. See Multiple Windows, for information
about window configurations.
- C-x r w r
Save the state of the selected frame’s windows in register r
(window-configuration-to-register
).
- C-x r f r
Save the state of all frames, including all their windows, in register
r (frameset-to-register
).
Use C-x r j r to restore a window or frame configuration.
This is the same command used to restore a cursor position. When you
restore a frame configuration, any existing frames not included in the
configuration become invisible. If you wish to delete these frames
instead, use C-u C-x r j r.
13.5 Keeping Numbers in Registers
There are commands to store a number in a register, to insert
the number in the buffer in decimal, and to increment it. These commands
can be useful in keyboard macros (see Keyboard Macros).
- C-u number C-x r n r ¶
-
Store number into register r (number-to-register
).
- C-u number C-x r + r ¶
-
If r contains a number, increment the number in that register by
number. Note that command C-x r +
(increment-register
) behaves differently if r contains
text. See Saving Text in Registers.
- C-x r i r
Insert the number from register r into the buffer.
C-x r i is the same command used to insert any other sort of
register contents into the buffer. C-x r + with no numeric
argument increments the register value by 1; C-x r n with no
numeric argument stores zero in the register.
13.6 Keeping File Names in Registers
If you visit certain file names frequently, you can visit them more
conveniently if you put their names in registers. Here’s the Lisp code
used to put a file name into register r:
(set-register r '(file . name))
For example,
(set-register ?z '(file . "/gd/gnu/emacs/19.0/src/ChangeLog"))
puts the file name shown in register ‘z’.
To visit the file whose name is in register r, type C-x r j
r. (This is the same command used to jump to a position or
restore a frame configuration.)
13.7 Keyboard Macro Registers
If you need to execute a keyboard macro (see Keyboard Macros)
frequently, it is more convenient to put it in a register or save it
(see Naming and Saving Keyboard Macros). C-x C-k x r
(kmacro-to-register
) stores the last keyboard macro in register
r.
To execute the keyboard macro in register r, type C-x r j
r. (This is the same command used to jump to a position or
restore a frameset.)
13.8 Bookmarks
Bookmarks are somewhat like registers in that they record
positions you can jump to. Unlike registers, they have long names, and
they persist automatically from one Emacs session to the next. The
prototypical use of bookmarks is to record where you were reading in
various files.
- C-x r m RET
Set the bookmark for the visited file, at point.
- C-x r m bookmark RET
Set the bookmark named bookmark at point (bookmark-set
).
- C-x r M bookmark RET
Like C-x r m, but don’t overwrite an existing bookmark.
- C-x r b bookmark RET
Jump to the bookmark named bookmark (bookmark-jump
).
- C-x r l
List all bookmarks (list-bookmarks
).
- M-x bookmark-save
Save all the current bookmark values in the default bookmark file.
To record the current position in the visited file, use the command
C-x r m, which sets a bookmark using the visited file name as
the default for the bookmark name. If you name each bookmark after
the file it points to, then you can conveniently revisit any of those
files with C-x r b, and move to the position of the bookmark at
the same time.
The command C-x r M (bookmark-set-no-overwrite
) works
like C-x r m, but it signals an error if the specified
bookmark already exists, instead of overwriting it.
To display a list of all your bookmarks in a separate buffer, type
C-x r l (list-bookmarks
). If you switch to that buffer,
you can use it to edit your bookmark definitions or annotate the
bookmarks. Type C-h m in the bookmark buffer for more
information about its special editing commands.
When you kill Emacs, Emacs saves your bookmarks, if
you have changed any bookmark values. You can also save the bookmarks
at any time with the M-x bookmark-save command. Bookmarks are
saved to the file ~/.emacs.d/bookmarks (for compatibility with
older versions of Emacs, if you have a file named ~/.emacs.bmk,
that is used instead). The bookmark commands load your default
bookmark file automatically. This saving and loading is how bookmarks
persist from one Emacs session to the next.
If you set the variable bookmark-save-flag
to 1, each command
that sets a bookmark will also save your bookmarks; this way, you
don’t lose any bookmark values even if Emacs crashes. The value, if
a number, says how many bookmark modifications should go by between
saving. If you set this variable to nil
, Emacs only
saves bookmarks if you explicitly use M-x bookmark-save.
The variable bookmark-default-file
specifies the file in
which to save bookmarks by default.
If you set the variable bookmark-use-annotations
to t
,
setting a bookmark will query for an annotation. If a bookmark has an
annotation, it is automatically shown in a separate window when you
jump to the bookmark.
Bookmark position values are saved with surrounding context, so that
bookmark-jump
can find the proper position even if the file is
modified slightly. The variable bookmark-search-size
says how
many characters of context to record on each side of the bookmark’s
position.
Here are some additional commands for working with bookmarks:
- M-x bookmark-load RET filename RET ¶
Load a file named filename that contains a list of bookmark
values. You can use this command, as well as bookmark-write
, to
work with other files of bookmark values in addition to your default
bookmark file.
- M-x bookmark-write RET filename RET ¶
Save all the current bookmark values in the file filename.
- M-x bookmark-delete RET bookmark RET ¶
Delete the bookmark named bookmark.
- M-x bookmark-insert-location RET bookmark RET ¶
Insert in the buffer the name of the file that bookmark bookmark
points to.
- M-x bookmark-insert RET bookmark RET ¶
Insert in the buffer the contents of the file that bookmark
bookmark points to.
14 Controlling the Display
Since only part of a large buffer fits in the window, Emacs has to
show only a part of it. This chapter describes commands and variables
that let you specify which part of the text you want to see, and how
the text is displayed.
14.1 Scrolling
If a window is too small to display all the text in its buffer, it
displays only a portion of it. Scrolling commands change which
portion of the buffer is displayed.
Scrolling forward or up advances the portion of the buffer
displayed in the window; equivalently, it moves the buffer text
upwards relative to the window. Scrolling backward or down
displays an earlier portion of the buffer, and moves the text
downwards relative to the window.
In Emacs, scrolling up or down refers to the direction that
the text moves in the window, not the direction that the window
moves relative to the text. This terminology was adopted by Emacs
before the modern meaning of “scrolling up” and “scrolling down”
became widespread. Hence, the strange result that PageDown
scrolls up in the Emacs sense.
The portion of a buffer displayed in a window always contains point.
If you move point past the bottom or top of the window, scrolling
occurs automatically to bring it back onscreen (see Automatic Scrolling). You can also scroll explicitly with these commands:
- C-v
- PageDown
- next
Scroll forward by nearly a full window (scroll-up-command
).
- M-v
- PageUp
- prior
Scroll backward (scroll-down-command
).
C-v (scroll-up-command
) scrolls forward by nearly the
whole window height. The effect is to take the two lines at the
bottom of the window and put them at the top, followed by lines that
were not previously visible. If point was in the text that scrolled
off the top, it ends up on the window’s new topmost line. The
PageDown (or next) key is equivalent to C-v.
M-v (scroll-down-command
) scrolls backward in a similar
way. The PageUp (or prior) key is equivalent to
M-v.
The number of lines of overlap left by these scroll commands is
controlled by the variable next-screen-context-lines
, whose
default value is 2. You can supply the commands with a numeric prefix
argument, n, to scroll by n lines; Emacs attempts to leave
point unchanged, so that the text and point move up or down together.
C-v with a negative argument is like M-v and vice versa.
By default, these commands signal an error (by beeping or flashing
the screen) if no more scrolling is possible, because the window has
reached the beginning or end of the buffer. If you change the
variable scroll-error-top-bottom
to t
, these commands
move point to the farthest possible position. If point is already
there, the commands signal an error.
Some users like scroll commands to keep point at the same screen
position, so that scrolling back to the same screen conveniently
returns point to its original position. You can enable this behavior
via the variable scroll-preserve-screen-position
. If the value
is t
, Emacs adjusts point to keep the cursor at the same screen
position whenever a scroll command moves it off-window, rather than
moving it to the topmost or bottommost line. With any other
non-nil
value, Emacs adjusts point this way even if the scroll
command leaves point in the window. This variable affects all the
scroll commands documented in this section, as well as scrolling with
the mouse wheel (see Mouse Commands for Editing); in general, it affects any
command that has a non-nil
scroll-command
property.
See Property Lists in The Emacs Lisp Reference Manual.
Sometimes, particularly when you hold down keys such as C-v
and M-v, activating keyboard auto-repeat, Emacs fails to keep up
with the rapid rate of scrolling requested; the display doesn’t update
and Emacs can become unresponsive to input for quite a long time. You
can counter this sluggishness by setting the variable
fast-but-imprecise-scrolling
to a non-nil
value. This
instructs the scrolling commands not to fontify (see Font Lock mode)
any unfontified text they scroll over, instead to assume it has the
default face. This can cause Emacs to scroll to somewhat wrong buffer
positions when the faces in use are not all the same size, even with
single (i.e., without auto-repeat) scrolling operations.
As an alternative to setting fast-but-imprecise-scrolling
you
might prefer to enable jit-lock deferred fontification (see Font Lock mode). To do this, customize jit-lock-defer-time
to a small
positive number such as 0.25, or even 0.1 if you type quickly. This
gives you less jerky scrolling when you hold down C-v, but the
window contents after any action which scrolls into a fresh portion of
the buffer will be momentarily unfontified.
Finally, a third alternative to these variables is
redisplay-skip-fontification-on-input
. If this variable is
non-nil
, skip some fontifications is there’s input pending.
This usually does not affect the display because redisplay is
completely skipped anyway if input was pending, but it can make
scrolling smoother by avoiding unnecessary fontification.
The commands M-x scroll-up and M-x scroll-down behave
similarly to scroll-up-command
and scroll-down-command
,
except they do not obey scroll-error-top-bottom
. Prior to
Emacs 24, these were the default commands for scrolling up and down.
The commands M-x scroll-up-line and M-x scroll-down-line
scroll the current window by one line at a time. If you intend to use
any of these commands, you might want to give them key bindings
(see Rebinding Keys in Your Init File).
14.2 Recentering
- C-l
Scroll the selected window so the current line is the center-most text
line; on subsequent consecutive invocations, make the current line the
top line, the bottom line, and so on in cyclic order. Possibly
redisplay the screen too (recenter-top-bottom
).
- C-M-S-l
Scroll the other window; this is equivalent to C-l acting on the
other window.
- M-x recenter
Scroll the selected window so the current line is the center-most text
line. Possibly redisplay the screen too.
- C-M-l
Scroll heuristically to bring useful information onto the screen
(reposition-window
).
The C-l (recenter-top-bottom
) command recenters
the selected window, scrolling it so that the current screen line is
exactly in the center of the window, or as close to the center as
possible.
Typing C-l twice in a row (C-l C-l) scrolls the window
so that point is on the topmost screen line. Typing a third C-l
scrolls the window so that point is on the bottom-most screen line.
Each successive C-l cycles through these three positions.
You can change the cycling order by customizing the list variable
recenter-positions
. Each list element should be the symbol
top
, middle
, or bottom
, or a number; an integer
means to move the line to the specified screen line, while a
floating-point number between 0.0 and 1.0 specifies a percentage of
the screen space from the top of the window. The default,
(middle top bottom)
, is the cycling order described above.
Furthermore, if you change the variable scroll-margin
to a
non-zero value n, C-l always leaves at least n
screen lines between point and the top or bottom of the window
(see Automatic Scrolling).
You can also give C-l a prefix argument. A plain prefix
argument, C-u C-l, simply recenters the line showing point. A
positive argument n moves line showing point n lines down
from the top of the window. An argument of zero moves point’s line to
the top of the window. A negative argument -n moves point’s
line n lines from the bottom of the window. When given an
argument, C-l does not clear the screen or cycle through
different screen positions.
If the variable recenter-redisplay
has a non-nil
value, each invocation of C-l also clears and redisplays the
screen; the special value tty
(the default) says to do this on
text-terminal frames only. Redisplaying is useful in case the screen
becomes garbled for any reason (see Garbage on the Screen).
The more primitive command M-x recenter behaves like
recenter-top-bottom
, but does not cycle among screen positions.
C-M-l (reposition-window
) scrolls the current window
heuristically in a way designed to get useful information onto the
screen. For example, in a Lisp file, this command tries to get the
entire current defun onto the screen if possible.
14.3 Automatic Scrolling
Emacs performs automatic scrolling when point moves out of the
visible portion of the text. Normally, automatic scrolling centers
point vertically in the window, but there are several ways to alter
this behavior.
If you set scroll-conservatively
to a small number n,
then moving point just a little off the screen (no more than n
lines) causes Emacs to scroll just enough to bring point back on
screen; if doing so fails to make point visible, Emacs scrolls just
far enough to center point in the window. If you set
scroll-conservatively
to a large number (larger than 100),
automatic scrolling never centers point, no matter how far point
moves; Emacs always scrolls text just enough to bring point into view,
either at the top or bottom of the window depending on the scroll
direction. By default, scroll-conservatively
is 0, which
means to always center point in the window.
This said, in minibuffer windows, scrolling is always conservative by
default because scroll-minibuffer-conservatively
is non-nil,
which takes precedence over scroll-conservatively
.
Another way to control automatic scrolling is to customize the
variable scroll-step
. Its value determines the number of lines
by which to automatically scroll, when point moves off the screen. If
scrolling by that number of lines fails to bring point back into view,
point is centered instead. The default value is zero, which (by
default) causes point to always be centered after scrolling.
A third way to control automatic scrolling is to customize the
variables scroll-up-aggressively
and
scroll-down-aggressively
, which directly specify the vertical
position of point after scrolling. The value of
scroll-up-aggressively
should be either nil
(the
default), or a floating point number f between 0 and 1. The
latter means that when point goes below the bottom window edge (i.e.,
scrolling forward), Emacs scrolls the window so that point is f
parts of the window height from the bottom window edge. Thus, larger
f means more aggressive scrolling: more new text is brought into
view. The default value, nil
, is equivalent to 0.5.
Likewise, scroll-down-aggressively
is used when point goes
above the top window edge (i.e., scrolling backward). The value
specifies how far point should be from the top margin of the window
after scrolling. Thus, as with scroll-up-aggressively
, a
larger value is more aggressive.
Note that the variables scroll-conservatively
,
scroll-step
, and scroll-up-aggressively
/
scroll-down-aggressively
control automatic scrolling in
contradictory ways. Therefore, you should pick no more than one of
these methods to customize automatic scrolling. In case you customize
multiple variables, the order of priority is:
scroll-conservatively
, then scroll-step
, and finally
scroll-up-aggressively
/ scroll-down-aggressively
.
The variable scroll-margin
restricts how close point can come
to the top or bottom of a window (even if aggressive scrolling
specifies a fraction f that is larger than the window portion
between the top and the bottom margins). Its value is a number of
screen lines; if point comes within that many lines of the top or
bottom of the window, Emacs performs automatic scrolling. By default,
scroll-margin
is 0. The effective margin size is limited to a
quarter of the window height by default, but this limit can be
increased up to half (or decreased down to zero) by customizing
maximum-scroll-margin
.
14.4 Horizontal Scrolling
Horizontal scrolling means shifting all the lines sideways
within a window, so that some of the text near the left margin is not
displayed. When the text in a window is scrolled horizontally, text
lines are truncated rather than continued (see Line Truncation).
If a window shows truncated lines, Emacs performs automatic horizontal
scrolling whenever point moves off the left or right edge of the
screen. By default, all the lines in the window are scrolled
horizontally together, but if you set the variable
auto-hscroll-mode
to the special value of current-line
,
only the line showing the cursor will be scrolled. To disable
automatic horizontal scrolling entirely, set the variable
auto-hscroll-mode
to nil
. Note that when the automatic
horizontal scrolling is turned off, if point moves off the edge of the
screen, the cursor disappears to indicate that. (On text terminals,
the cursor is left at the edge instead.)
The variable hscroll-margin
controls how close point can get
to the window’s left and right edges before automatic scrolling
occurs. It is measured in columns. For example, if the value is 5,
then moving point within 5 columns of an edge causes horizontal
scrolling away from that edge.
The variable hscroll-step
determines how many columns to
scroll the window when point gets too close to the edge. Zero, the
default value, means to center point horizontally within the window.
A positive integer value specifies the number of columns to scroll by.
A floating-point number (whose value should be between 0 and 1)
specifies the fraction of the window’s width to scroll by.
You can also perform explicit horizontal scrolling with the
following commands:
- C-x <
Scroll text in current window to the left (scroll-left
).
- C-x >
Scroll to the right (scroll-right
).
C-x < (scroll-left
) scrolls text in the selected window
to the left by the full width of the window, less two columns. (In
other words, the text in the window moves left relative to the
window.) With a numeric argument n, it scrolls by n
columns.
If the text is scrolled to the left, and point moves off the left
edge of the window, the cursor will freeze at the left edge of the
window, until point moves back to the displayed portion of the text.
This is independent of the current setting of
auto-hscroll-mode
, which, for text scrolled to the left, only
affects the behavior at the right edge of the window.
C-x > (scroll-right
) scrolls similarly to the right.
The window cannot be scrolled any farther to the right once it is
displayed normally, with each line starting at the window’s left
margin; attempting to do so has no effect. This means that you don’t
have to calculate the argument precisely for C-x >; any
sufficiently large argument will restore the normal display.
If you use those commands to scroll a window horizontally, that sets
a lower bound for automatic horizontal scrolling. Automatic scrolling
will continue to scroll the window, but never farther to the right
than the amount you previously set by scroll-left
. When
auto-hscroll-mode
is set to current-line
, all the lines
other than the one showing the cursor will be scrolled by that minimal
amount.
14.5 Narrowing
Narrowing means focusing in on some portion of the buffer,
making the rest temporarily inaccessible. The portion which you can
still get to is called the accessible portion. Canceling the
narrowing, which makes the entire buffer once again accessible, is
called widening. The bounds of narrowing in effect in a buffer
are called the buffer’s restriction.
Narrowing can make it easier to concentrate on a single subroutine or
paragraph by eliminating clutter. It can also be used to limit the
range of operation of a replace command or repeating keyboard macro.
- C-x n n
Narrow down to between point and mark (narrow-to-region
).
- C-x n w
Widen to make the entire buffer accessible again (widen
).
- C-x n p
Narrow down to the current page (narrow-to-page
).
- C-x n d
Narrow down to the current defun (narrow-to-defun
).
When you have narrowed down to a part of the buffer, that part appears
to be all there is. You can’t see the rest, you can’t move into it
(motion commands won’t go outside the accessible part), you can’t change
it in any way. However, it is not gone, and if you save the file all
the inaccessible text will be saved. The word ‘Narrow’ appears in
the mode line whenever narrowing is in effect.
The primary narrowing command is C-x n n (narrow-to-region
).
It sets the current buffer’s restrictions so that the text in the current
region remains accessible, but all text before the region or after the
region is inaccessible. Point and mark do not change.
Alternatively, use C-x n p (narrow-to-page
) to narrow
down to the current page. See Pages, for the definition of a page.
C-x n d (narrow-to-defun
) narrows down to the defun
containing point (see Top-Level Definitions, or Defuns).
The way to cancel narrowing is to widen with C-x n w
(widen
). This makes all text in the buffer accessible again.
You can get information on what part of the buffer you are narrowed down
to using the C-x = command. See Cursor Position Information.
Because narrowing can easily confuse users who do not understand it,
narrow-to-region
is normally a disabled command. Attempting to use
this command asks for confirmation and gives you the option of enabling it;
if you enable the command, confirmation will no longer be required for
it. See Disabling Commands.
14.6 View Mode
View mode is a minor mode that lets you scan a buffer by sequential
screenfuls. It provides commands for scrolling through the buffer
conveniently but not for changing it. Apart from the usual Emacs
cursor motion commands, you can type SPC to scroll forward one
windowful, S-SPC or DEL to scroll backward, and s to
start an incremental search.
Typing q (View-quit
) disables View mode, and switches
back to the buffer and position before View mode was enabled. Typing
e (View-exit
) disables View mode, keeping the current
buffer and position.
M-x view-buffer prompts for an existing Emacs buffer, switches
to it, and enables View mode. M-x view-file prompts for a file
and visits it with View mode enabled.
14.7 Follow Mode
Follow mode is a minor mode that makes two windows, both
showing the same buffer, scroll as a single tall virtual window.
To use Follow mode, go to a frame with just one window, split it into
two side-by-side windows using C-x 3, and then type M-x
follow-mode. From then on, you can edit the buffer in either of the
two windows, or scroll either one; the other window follows it.
In Follow mode, if you move point outside the portion visible in one
window and into the portion visible in the other window, that selects
the other window—again, treating the two as if they were parts of
one large window.
To turn off Follow mode, type M-x follow-mode a second time.
14.8 Text Faces
Emacs can display text in several different styles, called
faces. Each face can specify various face attributes,
such as the font, height, weight, slant, foreground and background
color, and underlining or overlining. Most major modes assign faces
to the text automatically, via Font Lock mode. See Font Lock mode, for
more information about how these faces are assigned.
To see what faces are currently defined, and what they look like,
type M-x list-faces-display. With a prefix argument, this
prompts for a regular expression, and displays only faces with names
matching that regular expression (see Syntax of Regular Expressions).
It’s possible for a given face to look different in different
frames. For instance, some text terminals do not support all face
attributes, particularly font, height, and width, and some support a
limited range of colors. In addition, most Emacs faces are defined so
that their attributes are different on light and dark frame
backgrounds, for reasons of legibility. By default, Emacs
automatically chooses which set of face attributes to display on each
frame, based on the frame’s current background color. However, you
can override this by giving the variable frame-background-mode
a non-nil
value. A value of dark
makes Emacs treat all
frames as if they have a dark background, whereas a value of
light
makes it treat all frames as if they have a light
background.
You can customize a face to alter its attributes, and save those
customizations for future Emacs sessions. See Customizing Faces,
for details.
The default
face is the default for displaying text, and all
of its attributes are specified. Its background color is also used as
the frame’s background color. See Colors for Faces.
Another special face is the cursor
face. On graphical
displays, the background color of this face is used to draw the text
cursor. None of the other attributes of this face have any effect;
the foreground color for text under the cursor is taken from the
background color of the underlying text. On text terminals, the
appearance of the text cursor is determined by the terminal, not by
the cursor
face.
You can also use X resources to specify attributes of any particular
face. See X Resources.
Emacs can display variable-width fonts, but some Emacs commands,
particularly indentation commands, do not account for variable
character display widths. Therefore, we recommend not using
variable-width fonts for most faces, particularly those assigned by
Font Lock mode.
14.9 Colors for Faces
Faces can have various foreground and background colors. When you
specify a color for a face—for instance, when customizing the face
(see Customizing Faces)—you can use either a color name
or an RGB triplet.
14.9.1 Color Names
A color name is a pre-defined name, such as ‘dark orange’ or
‘medium sea green’. To view a list of color names, type M-x
list-colors-display. To control the order in which colors are shown,
customize list-colors-sort
. If you run this command on a
graphical display, it shows the full range of color names known to
Emacs (these are the standard X11 color names, defined in X’s
rgb.txt file). If you run the command on a text terminal, it
shows only a small subset of colors that can be safely displayed on
such terminals. However, Emacs understands X11 color names even on
text terminals; if a face is given a color specified by an X11 color
name, it is displayed using the closest-matching terminal color.
14.9.2 RGB Triplets
An RGB triplet is a string of the form ‘#RRGGBB’. Each of the
primary color components is represented by a hexadecimal number
between ‘00’ (intensity 0) and ‘FF’ (the maximum intensity).
It is also possible to use one, three, or four hex digits for each
component, so ‘red’ can be represented as ‘#F00’,
‘#fff000000’, or ‘#ffff00000000’. The components must have
the same number of digits. For hexadecimal values A to F, either
upper or lower case are acceptable.
The M-x list-colors-display command also shows the equivalent
RGB triplet for each named color. For instance, ‘medium sea
green’ is equivalent to ‘#3CB371’.
You can change the foreground and background colors of a face with
M-x set-face-foreground and M-x set-face-background.
These commands prompt in the minibuffer for a face name and a color,
with completion, and then set that face to use the specified color.
They affect the face colors on all frames, but their effects do not
persist for future Emacs sessions, unlike using the customization
buffer or X resources. You can also use frame parameters to set
foreground and background colors for a specific frame; See Frame Parameters.
14.10 Standard Faces
Here are the standard faces for specifying text appearance. You can
apply them to specific text when you want the effects they produce.
default
This face is used for ordinary text that doesn’t specify any face.
Its background color is used as the frame’s background color.
bold
This face uses a bold variant of the default font.
italic
This face uses an italic variant of the default font.
bold-italic
This face uses a bold italic variant of the default font.
underline
This face underlines text.
fixed-pitch
This face forces use of a fixed-width font. It’s reasonable to
customize this face to use a different fixed-width font, if you like,
but you should not make it a variable-width font.
fixed-pitch-serif
This face is like fixed-pitch
, except the font has serifs and
looks more like traditional typewriting.
variable-pitch
This face forces use of a variable-width font.
shadow
This face is used for making the text less noticeable than the surrounding
ordinary text. Usually this can be achieved by using shades of gray in
contrast with either black or white default foreground color.
Here’s an incomplete list of faces used to highlight parts of the
text temporarily for specific purposes. (Many other modes define
their own faces for this purpose.)
highlight
This face is used for text highlighting in various contexts, such as
when the mouse cursor is moved over a hyperlink.
isearch
This face is used to highlight the current Isearch match
(see Incremental Search).
query-replace
This face is used to highlight the current Query Replace match
(see Replacement Commands).
lazy-highlight
This face is used to highlight lazy matches for Isearch and Query
Replace (matches other than the current one).
region
This face is used for displaying an active region (see The Mark and the Region).
When Emacs is built with GTK+ support, its colors are taken from the
current GTK+ theme.
secondary-selection
This face is used for displaying a secondary X selection (see Secondary Selection).
trailing-whitespace
The face for highlighting excess spaces and tabs at the end of a line
when show-trailing-whitespace
is non-nil
(see Useless Whitespace).
escape-glyph
The face for displaying control characters and escape sequences
(see How Text Is Displayed).
homoglyph
The face for displaying lookalike characters, i.e., characters that
look like but are not the characters being represented
(see How Text Is Displayed).
nobreak-space
The face for displaying no-break space characters (see How Text Is Displayed).
nobreak-hyphen
The face for displaying no-break hyphen characters (see How Text Is Displayed).
The following faces control the appearance of parts of the Emacs
frame:
mode-line
¶
-
This face is used for the mode line of the currently selected window,
and for menu bars when toolkit menus are not used. By default, it’s
drawn with shadows for a raised effect on graphical displays, and
drawn as the inverse of the default face on non-windowed terminals.
mode-line-inactive
¶
Like mode-line
, but used for mode lines of the windows other
than the selected one (if mode-line-in-non-selected-windows
is
non-nil
). This face inherits from mode-line
, so changes
in that face affect mode lines in all windows.
mode-line-highlight
¶
Like highlight
, but used for mouse-sensitive portions of text
on mode lines. Such portions of text typically pop up tooltips
(see Tooltips) when the mouse pointer hovers above them.
mode-line-buffer-id
¶
This face is used for buffer identification parts in the mode line.
Similar to mode-line
for a window’s header line, which appears
at the top of a window just as the mode line appears at the bottom.
Most windows do not have a header line—only some special modes, such
Info mode, create one.
Similar to highlight
and mode-line-highlight
, but used
for mouse-sensitive portions of text on header lines. This is a
separate face because the header-line
face might be customized
in a way that does not interact well with highlight
.
tab-line
¶
Similar to mode-line
for a window’s tab line, which appears
at the top of a window with tabs representing window buffers.
See Window Tab Line.
vertical-border
¶
This face is used for the vertical divider between windows on text
terminals.
minibuffer-prompt
¶
-
This face is used for the prompt strings displayed in the minibuffer.
By default, Emacs automatically adds this face to the value of
minibuffer-prompt-properties
, which is a list of text
properties (see Text Properties in the Emacs Lisp Reference
Manual) used to display the prompt text. (This variable takes effect
when you enter the minibuffer.)
fringe
¶
The face for the fringes to the left and right of windows on graphic
displays. (The fringes are the narrow portions of the Emacs frame
between the text area and the window’s right and left borders.)
See Window Fringes.
cursor
The :background
attribute of this face specifies the color of
the text cursor. See Displaying the Cursor.
tooltip
This face is used for tooltip text. By default, if Emacs is built
with GTK+ support, tooltips are drawn via GTK+ and this face has no
effect. See Tooltips.
mouse
This face determines the color of the mouse pointer.
The following faces likewise control the appearance of parts of the
Emacs frame, but only on text terminals, or when Emacs is built on X
with no toolkit support. (For all other cases, the appearance of the
respective frame elements is determined by system-wide settings.)
scroll-bar
This face determines the visual appearance of the scroll bar.
See Scroll Bars.
tool-bar
This face determines the color of tool bar icons. See Tool Bars.
tab-bar
This face determines the color of tab bar icons. See Tab Bars.
-
This face determines the colors and font of Emacs’s menus. See Menu Bars.
-
This face is used to display enabled menu items on text-mode
terminals.
tty-menu-disabled-face
This face is used to display disabled menu items on text-mode
terminals.
tty-menu-selected-face
This face is used to display on text-mode terminals the menu item that
would be selected if you click a mouse or press RET.
14.11 Text Scale
To increase the height of the default face in the current buffer,
type C-x C-+ or C-x C-=. To decrease it, type C-x
C--. To restore the default (global) face height, type C-x
C-0. These keys are all bound to the same command,
text-scale-adjust
, which looks at the last key typed to
determine which action to take.
Similarly, scrolling the mouse wheel with the Ctrl modifier
pressed, when the mouse pointer is above buffer text, will increase or
decrease the height of the default face, depending on the direction of
the scrolling.
The final key of these commands may be repeated without the leading
C-x. For instance, C-x C-= C-= C-= increases the face
height by three steps. Each step scales the text height by a factor
of 1.2; to change this factor, customize the variable
text-scale-mode-step
. A numeric argument of 0
to the text-scale-adjust
command restores the default height,
the same as typing C-x C-0.
The commands text-scale-increase
and
text-scale-decrease
increase or decrease the height of the
default face, just like C-x C-+ and C-x C-- respectively.
You may find it convenient to bind to these commands, rather than
text-scale-adjust
.
The command text-scale-set
scales the height of the default
face in the current buffer to an absolute level specified by its
prefix argument.
The above commands automatically enable the minor mode
text-scale-mode
if the current font scaling is other than 1,
and disable it otherwise.
14.12 Font Lock mode
Font Lock mode is a minor mode, always local to a particular buffer,
which assigns faces to (or fontifies) the text in the buffer.
Each buffer’s major mode tells Font Lock mode which text to fontify;
for instance, programming language modes fontify syntactically
relevant constructs like comments, strings, and function names.
Font Lock mode is enabled by default in major modes that support it.
To toggle it in the current buffer, type M-x font-lock-mode. A
positive numeric argument unconditionally enables Font Lock mode, and
a negative or zero argument disables it.
Type M-x global-font-lock-mode to toggle Font Lock mode in all
buffers. To impose this setting for future Emacs sessions, customize
the variable global-font-lock-mode
(see Easy Customization Interface), or add the following line to your init file:
(global-font-lock-mode 0)
If you have disabled Global Font Lock mode, you can still enable Font
Lock for specific major modes by adding the function
font-lock-mode
to the mode hooks (see Hooks). For example,
to enable Font Lock mode for editing C files, you can do this:
(add-hook 'c-mode-hook 'font-lock-mode)
Font Lock mode uses several specifically named faces to do its job,
including font-lock-string-face
, font-lock-comment-face
,
and others. The easiest way to find them all is to use M-x
customize-group RET font-lock-faces RET. You can then
use that customization buffer to customize the appearance of these
faces. See Customizing Faces.
You can customize the variable font-lock-maximum-decoration
to alter the amount of fontification applied by Font Lock mode, for
major modes that support this feature. The value should be a number
(with 1 representing a minimal amount of fontification; some modes
support levels as high as 3); or t
, meaning “as high as
possible” (the default). To be effective for a given file buffer,
the customization of font-lock-maximum-decoration
should be
done before the file is visited; if you already have the file
visited in a buffer when you customize this variable, kill the buffer
and visit the file again after the customization.
You can also specify different numbers for particular major modes; for
example, to use level 1 for C/C++ modes, and the default level
otherwise, use the value
'((c-mode . 1) (c++-mode . 1)))
Comment and string fontification (or “syntactic” fontification)
relies on analysis of the syntactic structure of the buffer text. For
the sake of speed, some modes, including Lisp mode, rely on a special
convention: an open-parenthesis or open-brace in the leftmost column
always defines the beginning of a defun, and is thus always outside
any string or comment. Therefore, you should avoid placing an
open-parenthesis or open-brace in the leftmost column, if it is inside
a string or comment. See Left Margin Convention, for details.
Font Lock highlighting patterns already exist for most modes, but
you may want to fontify additional patterns. You can use the function
font-lock-add-keywords
, to add your own highlighting patterns
for a particular mode. For example, to highlight ‘FIXME:’ words
in C comments, use this:
(add-hook 'c-mode-hook
(lambda ()
(font-lock-add-keywords nil
'(("\\<\\(FIXME\\):" 1
font-lock-warning-face t)))))
To remove keywords from the font-lock highlighting patterns, use the
function font-lock-remove-keywords
. See Search-based
Fontification in The Emacs Lisp Reference Manual.
Fontifying large buffers can take a long time. To avoid large
delays when a file is visited, Emacs initially fontifies only the
visible portion of a buffer. As you scroll through the buffer, each
portion that becomes visible is fontified as soon as it is displayed;
this type of Font Lock is called Just-In-Time (or JIT)
Lock. You can control how JIT Lock behaves, including telling it to
perform fontification while idle, by customizing variables in the
customization group ‘jit-lock’. See Customizing Specific Items.
14.13 Interactive Highlighting
Highlight Changes mode is a minor mode that highlights the parts
of the buffer that were changed most recently, by giving that text a
different face. To enable or disable Highlight Changes mode, use
M-x highlight-changes-mode.
Hi Lock mode is a minor mode that highlights text that matches
regular expressions you specify. For example, you can use it to
highlight all the references to a certain variable in a program source
file, highlight certain parts in a voluminous output of some program,
or highlight certain names in an article. To enable or disable Hi
Lock mode, use the command M-x hi-lock-mode. To enable Hi Lock
mode for all buffers, use M-x global-hi-lock-mode or place
(global-hi-lock-mode 1)
in your .emacs file.
Hi Lock mode works like Font Lock mode (see Font Lock mode), except
that you specify explicitly the regular expressions to highlight. You
can control them with the following commands. (The key bindings
below that begin with C-x w are deprecated in favor of the
global M-s h bindings, and will be removed in some future Emacs
version.)
- M-s h r regexp RET face RET ¶
- C-x w h regexp RET face RET
-
Highlight text that matches regexp using face face
(highlight-regexp
). The highlighting will remain as long as
the buffer is loaded. For example, to highlight all occurrences of
the word “whim” using the default face (a yellow background), type
M-s h r whim RET RET. Any face can be used for
highlighting, Hi Lock provides several of its own and these are
pre-loaded into a list of default values. While being prompted for a
face use M-n and M-p to cycle through them. A prefix
numeric argument limits the highlighting to the corresponding
subexpression.
Setting the option hi-lock-auto-select-face
to a non-nil
value causes this command (and other Hi Lock commands that read faces)
to automatically choose the next face from the default list without
prompting.
You can use this command multiple times, specifying various regular
expressions to highlight in different ways.
- M-s h u regexp RET ¶
- C-x w r regexp RET
-
Unhighlight regexp (unhighlight-regexp
). If you invoke
this from the menu, you select the expression to unhighlight from a
list. If you invoke this from the keyboard, you use the minibuffer.
It will show the most recently added regular expression; use M-n
to show the next older expression and M-p to select the next
newer expression. (You can also type the expression by hand, with
completion.) When the expression you want to unhighlight appears in
the minibuffer, press RET to exit the minibuffer and
unhighlight it.
- M-s h l regexp RET face RET ¶
- C-x w l regexp RET face RET
-
Highlight entire lines containing a match for regexp, using face
face (highlight-lines-matching-regexp
).
- M-s h p phrase RET face RET ¶
- C-x w p phrase RET face RET
-
Highlight matches of phrase, using face face
(highlight-phrase
). phrase can be any regexp,
but spaces will be replaced by matches to whitespace and
initial lower-case letters will become case insensitive.
- M-s h . ¶
- C-x w .
-
Highlight the symbol found near point, using the next available face
(highlight-symbol-at-point
).
- M-s h w ¶
- C-x w b
-
Insert all the current highlighting regexp/face pairs into the buffer
at point, with comment delimiters to prevent them from changing your
program. (This key binding runs the
hi-lock-write-interactive-patterns
command.)
These patterns are extracted from the comments, if appropriate, if you
invoke M-x hi-lock-find-patterns, or if you visit the file while
Hi Lock mode is enabled (since that runs hi-lock-find-patterns
).
- M-s h f ¶
- C-x w i
-
Extract regexp/face pairs from comments in the current buffer
(hi-lock-find-patterns
). Thus, you can enter patterns
interactively with highlight-regexp
, store them into the file
with hi-lock-write-interactive-patterns
, edit them (perhaps
including different faces for different parenthesized parts of the
match), and finally use this command (hi-lock-find-patterns
) to
have Hi Lock highlight the edited patterns.
The variable hi-lock-file-patterns-policy
controls whether Hi
Lock mode should automatically extract and highlight patterns found in a
file when it is visited. Its value can be nil
(never highlight),
ask
(query the user), or a function. If it is a function,
hi-lock-find-patterns
calls it with the patterns as argument; if
the function returns non-nil
, the patterns are used. The default
is ask
. Note that patterns are always highlighted if you call
hi-lock-find-patterns
directly, regardless of the value of this
variable.
Also, hi-lock-find-patterns
does nothing if the current major
mode’s symbol is a member of the list hi-lock-exclude-modes
.
14.14 Window Fringes
On graphical displays, each Emacs window normally has narrow
fringes on the left and right edges. The fringes are used to
display symbols that provide information about the text in the window.
You can type M-x fringe-mode to toggle display of the fringes or
to modify their width. This command affects fringes in all frames; to
modify fringes on the selected frame only, use M-x
set-fringe-style. You can make your changes to the fringes permanent
by customizing the variable fringe-mode
.
The most common use of the fringes is to indicate a continuation
line (see Continuation Lines). When one line of text is split
into multiple screen lines, the left fringe shows a curving arrow for
each screen line except the first, indicating that this is not the
real beginning. The right fringe shows a curving arrow for each
screen line except the last, indicating that this is not the real
end. If the line’s direction is right-to-left (see Bidirectional Editing), the meanings of the curving arrows in the fringes are
swapped.
The fringes indicate line truncation (see Line Truncation) with
short horizontal arrows meaning there’s more text on this line which
is scrolled horizontally out of view. Clicking the mouse on one of
the arrows scrolls the display horizontally in the direction of the
arrow.
The fringes can also indicate other things, such as buffer
boundaries (see Displaying Boundaries), unused lines near the end
of the window (see indicate-empty-lines), and where a program you
are debugging is executing (see Running Debuggers Under Emacs).
The fringe is also used for drawing the cursor, if the current line
is exactly as wide as the window and point is at the end of the line.
To disable this, change the variable
overflow-newline-into-fringe
to nil
; this causes Emacs
to continue or truncate lines that are exactly as wide as the window.
If you customize fringe-mode
to remove the fringes on one or
both sides of the window display, the features that display on the
fringe are not available. Indicators of line continuation and
truncation are an exception: when fringes are not available, Emacs
uses the leftmost and rightmost character cells to indicate
continuation and truncation with special ASCII characters, see
Continuation Lines, and Line Truncation. This reduces the
width available for displaying text on each line, because the
character cells used for truncation and continuation indicators are
reserved for that purpose. Since buffer text can include
bidirectional text, and thus both left-to-right and right-to-left
paragraphs (see Bidirectional Editing), removing only one of the
fringes still reserves two character cells, one on each side of the
window, for truncation and continuation indicators, because these
indicators are displayed on opposite sides of the window in
right-to-left paragraphs.
14.15 Displaying Boundaries
Emacs can display an indication of the fill-column
position
(see Explicit Fill Commands). The fill-column indicator is a useful
functionality especially in prog-mode
and its descendants
(see Major Modes) to indicate the position of a specific column
that has some special meaning for formatting the source code of a
program.
To activate the fill-column indication display, use the minor modes
display-fill-column-indicator-mode
and
global-display-fill-column-indicator-mode
, which enable
the indicator locally or globally, respectively.
Alternatively, you can set the two buffer-local variables
display-fill-column-indicator
and
display-fill-column-indicator-character
to activate the
indicator and control the character used for the indication. Note
that both variables must be non-nil
for the indication to be
displayed. (Turning on the minor mode sets both these variables.)
There are 2 buffer local variables and a face to customize this mode:
display-fill-column-indicator-column
¶
Specifies the column number where the indicator should be set. It can
take positive numerical values for the column, or the special value
t
, which means that the value of the variable
fill-column
will be used.
Any other value disables the indicator. The default value is t
.
display-fill-column-indicator-character
¶
Specifies the character used for the indicator. This character can be
any valid character including Unicode ones if the font supports them.
The value nil
disables the indicator. When the mode is enabled
through the functions display-fill-column-indicator-mode
or
global-display-fill-column-indicator-mode
, they will use the
character specified by this variable, if it is non-nil
;
otherwise Emacs will use the character U+2502 BOX DRAWINGS LIGHT VERTICAL,
falling back to ‘|’ if U+2502 cannot be displayed.
fill-column-indicator
¶
Specifies the face used to display the indicator. It inherits its
default values from the face shadow
, but without background
color. To change the indicator color, you need only set the foreground
color of this face.
On graphical displays, Emacs can indicate the buffer boundaries in
the fringes. If you enable this feature, the first line and the last
line are marked with angle images in the fringes. This can be
combined with up and down arrow images which say whether it is
possible to scroll the window.
The buffer-local variable indicate-buffer-boundaries
controls
how the buffer boundaries and window scrolling is indicated in the
fringes. If the value is left
or right
, both angle and
arrow bitmaps are displayed in the left or right fringe, respectively.
If value is an alist (see Association Lists in the Emacs
Lisp Reference Manual), each element (indicator .
position)
specifies the position of one of the indicators. The
indicator must be one of top
, bottom
, up
,
down
, or t
which specifies the default position for the
indicators not present in the alist. The position is one of
left
, right
, or nil
which specifies not to show
this indicator.
For example, ((top . left) (t . right))
places the top angle
bitmap in left fringe, the bottom angle bitmap in right fringe, and
both arrow bitmaps in right fringe. To show just the angle bitmaps in
the left fringe, but no arrow bitmaps, use ((top . left)
(bottom . left))
.
14.16 Useless Whitespace
It is easy to leave unnecessary spaces at the end of a line, or
empty lines at the end of a buffer, without realizing it. In most
cases, this trailing whitespace has no effect, but sometimes it
can be a nuisance.
You can make trailing whitespace at the end of a line visible by
setting the buffer-local variable show-trailing-whitespace
to
t
. Then Emacs displays trailing whitespace, using the face
trailing-whitespace
.
This feature does not apply when point is at the end of the line
containing the whitespace. Strictly speaking, that is trailing
whitespace nonetheless, but displaying it specially in that case
looks ugly while you are typing in new text. In this special case,
the location of point is enough to show you that the spaces are
present.
Type M-x delete-trailing-whitespace to delete all trailing
whitespace. This command deletes all extra spaces at the end of each
line in the buffer, and all empty lines at the end of the buffer; to
ignore the latter, change the variable delete-trailing-lines
to
nil
. If the region is active, the command instead deletes
extra spaces at the end of each line in the region.
On graphical displays, Emacs can indicate unused lines at the end of
the window with a small image in the left fringe (see Window Fringes).
The image appears for screen lines that do not correspond to any
buffer text, so blank lines at the end of the buffer stand out because
they lack this image. To enable this feature, set the buffer-local
variable indicate-empty-lines
to a non-nil
value. You
can enable or disable this feature for all new buffers by setting the
default value of this variable, e.g., (setq-default
indicate-empty-lines t)
.
Whitespace mode is a buffer-local minor mode that lets you
visualize many kinds of whitespace in the buffer, by either
drawing the whitespace characters with a special face or displaying
them as special glyphs. To toggle this mode, type M-x
whitespace-mode. The kinds of whitespace visualized are determined
by the list variable whitespace-style
. Individual elements in
that list can be toggled on or off in the current buffer by typing
M-x whitespace-toggle-options. Here is a partial list
of possible elements (see the variable’s documentation for the full
list):
face
Enable all visualizations which use special faces. This element has a
special meaning: if it is absent from the list, none of the other
visualizations take effect except space-mark
, tab-mark
,
and newline-mark
.
trailing
Highlight trailing whitespace.
tabs
Highlight tab characters.
spaces
Highlight space and non-breaking space characters.
lines
¶
Highlight lines longer than 80 columns. To change the column limit,
customize the variable whitespace-line-column
.
newline
Highlight newlines.
missing-newline-at-eof
Highlight the final character if the buffer doesn’t end with a newline
character.
empty
Highlight empty lines at the beginning and/or end of the buffer.
big-indent
¶
Highlight too-deep indentation. By default any sequence of at least 4
consecutive tab characters or 32 consecutive space characters is
highlighted. To change that, customize the regular expression
whitespace-big-indent-regexp
.
space-mark
Draw space and non-breaking characters with a special glyph.
tab-mark
Draw tab characters with a special glyph.
newline-mark
Draw newline characters with a special glyph.
Global Whitespace mode is a global minor mode that lets you visualize
whitespace in all buffers. To toggle individual features, use
M-x global-whitespace-toggle-options.
14.17 Selective Display
Emacs has the ability to hide lines indented more than a given
number of columns. You can use this to get an overview of a part of a
program.
To hide lines in the current buffer, type C-x $
(set-selective-display
) with a numeric argument n. Then
lines with at least n columns of indentation disappear from the
screen. The only indication of their presence is that three dots
(‘…’) appear at the end of each visible line that is
followed by one or more hidden ones.
The commands C-n and C-p move across the hidden lines as
if they were not there.
The hidden lines are still present in the buffer, and most editing
commands see them as usual, so you may find point in the middle of the
hidden text. When this happens, the cursor appears at the end of the
previous line, after the three dots. If point is at the end of the
visible line, before the newline that ends it, the cursor appears before
the three dots.
To make all lines visible again, type C-x $ with no argument.
If you set the variable selective-display-ellipses
to
nil
, the three dots do not appear at the end of a line that
precedes hidden lines. Then there is no visible indication of the
hidden lines. This variable becomes local automatically when set.
See also Outline Mode for another way to hide part of
the text in a buffer.
14.18 Optional Mode Line Features
The buffer percentage pos indicates the percentage of the
buffer above the top of the window. You can additionally display the
size of the buffer by typing M-x size-indication-mode to turn on
Size Indication mode. The size will be displayed immediately
following the buffer percentage like this:
Here size is the human readable representation of the number of
characters in the buffer, which means that ‘k’ for 10^3, ‘M’
for 10^6, ‘G’ for 10^9, etc., are used to abbreviate.
The current line number of point appears in the mode line when Line
Number mode is enabled. Use the command M-x line-number-mode to
turn this mode on and off; normally it is on. The line number appears
after the buffer percentage pos, with the letter ‘L’ to
indicate what it is.
Similarly, you can display the current column number by turning on
Column Number mode with M-x column-number-mode. The column
number is indicated by the letter ‘C’. However, when both of
these modes are enabled, the line and column numbers are displayed in
parentheses, the line number first, rather than with ‘L’ and
‘C’. For example: ‘(561,2)’. See Minor Modes, for more
information about minor modes and about how to use these commands.
In Column Number mode, the displayed column number counts from zero
starting at the left margin of the window. If you would prefer for
the displayed column number to count from one, you may set
column-number-indicator-zero-based
to nil
.
If you have narrowed the buffer (see Narrowing), the displayed
line number is relative to the accessible portion of the buffer.
Thus, it isn’t suitable as an argument to goto-line
. (The
command what-line
shows the line number relative to the whole
file.) You can use goto-line-relative
command to move point to
the line relative to the accessible portion of the narrowed buffer.
If the buffer is very large (larger than the value of
line-number-display-limit
), Emacs won’t compute the line
number, because that would be too slow; therefore, the line number
won’t appear on the mode-line. To remove this limit, set
line-number-display-limit
to nil
.
Line-number computation can also be slow if the lines in the buffer
are too long. For this reason, Emacs doesn’t display line numbers if
the average width, in characters, of lines near point is larger than
the value of line-number-display-limit-width
. The default
value is 200 characters.
Emacs can optionally display the time and system load in all mode
lines. To enable this feature, type M-x display-time or customize
the option display-time-mode
. The information added to the mode
line looks like this:
Here hh and mm are the hour and minute, followed always by
‘AM’ or ‘PM’. l.ll is the average number, collected
for the last few minutes, of processes in the whole system that were
either running or ready to run (i.e., were waiting for an available
processor). (Some fields may be missing if your operating system
cannot support them.) If you prefer time display in 24-hour format,
set the variable display-time-24hr-format
to t
.
The word ‘Mail’ appears after the load level if there is mail
for you that you have not read yet. On graphical displays, you can
use an icon instead of ‘Mail’ by customizing
display-time-use-mail-icon
; this may save some space on the
mode line. You can customize display-time-mail-face
to make
the mail indicator prominent. Use display-time-mail-file
to
specify the mail file to check, or set
display-time-mail-directory
to specify the directory to check
for incoming mail (any nonempty regular file in the directory is
considered to be newly arrived mail).
When running Emacs on a laptop computer, you can display the battery
charge on the mode-line, by using the command
display-battery-mode
or customizing the variable
display-battery-mode
. The variable
battery-mode-line-format
determines the way the battery charge
is displayed; the exact mode-line message depends on the operating
system, and it usually shows the current battery charge as a
percentage of the total charge.
On graphical displays, the mode line is drawn as a 3D box. If you
don’t like this effect, you can disable it by customizing the
mode-line
face and setting its box
attribute to
nil
. See Customizing Faces.
By default, the mode line of nonselected windows is displayed in a
different face, called mode-line-inactive
. Only the selected
window is displayed in the mode-line
face. This helps show
which window is selected. When the minibuffer is selected, since
it has no mode line, the window from which you activated the minibuffer
has its mode line displayed using mode-line
; as a result,
ordinary entry to the minibuffer does not change any mode lines.
You can disable use of mode-line-inactive
by setting variable
mode-line-in-non-selected-windows
to nil
; then all mode
lines are displayed in the mode-line
face.
You can customize the mode line display for each of the end-of-line
formats by setting each of the variables eol-mnemonic-unix
,
eol-mnemonic-dos
, eol-mnemonic-mac
, and
eol-mnemonic-undecided
to the strings you prefer.
14.19 How Text Is Displayed
Most characters are printing characters: when they appear in a
buffer, they are displayed literally on the screen. Printing
characters include ASCII numbers, letters, and punctuation
characters, as well as many non-ASCII characters.
The ASCII character set contains non-printing control
characters. Two of these are displayed specially: the newline
character (Unicode code point U+000A) is displayed by starting
a new line, while the tab character (U+0009) is displayed as a
space that extends to the next tab stop column (normally every 8
columns). The number of spaces per tab is controlled by the
buffer-local variable tab-width
, which must have an integer
value between 1 and 1000, inclusive. Note that the way the tab
character in the buffer is displayed has nothing to do with the
definition of TAB as a command.
Other ASCII control characters, whose codes are below
U+0020 (octal 40, decimal 32), are displayed as a caret
(‘^’) followed by the non-control version of the character, with
the escape-glyph
face. For instance, the ‘control-A’
character, U+0001, is displayed as ‘^A’.
The raw bytes with codes U+0080 (octal 200) through
U+009F (octal 237) are displayed as octal escape
sequences, with the escape-glyph
face. For instance,
character code U+0098 (octal 230) is displayed as ‘\230’.
If you change the buffer-local variable ctl-arrow
to
nil
, the ASCII control characters are also displayed
as octal escape sequences instead of caret escape sequences. (You can
also request that raw bytes be shown in hex, see display-raw-bytes-as-hex.)
Some non-ASCII characters have the same appearance as an
ASCII space or hyphen (minus) character. Such characters
can cause problems if they are entered into a buffer without your
realization, e.g., by yanking; for instance, source code compilers
typically do not treat non-ASCII spaces as whitespace
characters. To deal with this problem, Emacs displays such characters
specially: it displays U+00A0 NO-BREAK SPACE and other
characters from the Unicode horizontal space class with the
nobreak-space
face, and it displays U+00AD SOFT
HYPHEN, U+2010 HYPHEN, and U+2011 NON-BREAKING
HYPHEN with the nobreak-hyphen
face. To disable this, change
the variable nobreak-char-display
to nil
. If you give
this variable a non-nil
and non-t
value, Emacs instead
displays such characters as a highlighted backslash followed by a
space or hyphen.
You can customize the way any particular character code is displayed
by means of a display table. See Display Tables in The Emacs Lisp Reference Manual.
On graphical displays, some characters may have no glyphs in any of
the fonts available to Emacs. These glyphless characters are
normally displayed as boxes containing the hexadecimal character code.
Similarly, on text terminals, characters that cannot be displayed
using the terminal encoding (see Coding Systems for Terminal I/O) are normally
displayed as question signs. You can control the display method by
customizing the variable glyphless-char-display-control
. You
can also customize the glyphless-char
face to make these
characters more prominent on display. See Glyphless Character Display in The Emacs Lisp Reference Manual,
for details.
Emacs tries to determine if the curved quotes ‘ and ’
can be displayed on the current display. By default, if this seems to
be so, then Emacs will translate the ASCII quotes (‘`’ and ‘'’), when they appear in messages and help texts, to these
curved quotes. You can influence or inhibit this translation by
customizing the user option text-quoting-style
(see Keys in
Documentation in The Emacs Lisp Reference Manual).
If the curved quotes ‘, ’, “, and ” are
known to look just like ASCII characters, they are shown
with the homoglyph
face. Curved quotes that are known not to
be displayable are shown as their ASCII approximations
‘`’, ‘'’, and ‘"’ with the homoglyph
face.
14.20 Displaying the Cursor
On a text terminal, the cursor’s appearance is controlled by the
terminal, largely out of the control of Emacs. Some terminals offer
two different cursors: a visible static cursor, and a very
visible blinking cursor. By default, Emacs uses the very visible
cursor, and switches to it when you start or resume Emacs. If the
variable visible-cursor
is nil
when Emacs starts or
resumes, it uses the normal cursor.
On a graphical display, many more properties of the text cursor can
be altered. To customize its color, change the :background
attribute of the face named cursor
(see Customizing Faces). (The other attributes of this face have no effect;
the text shown under the cursor is drawn using the frame’s background
color.) To change its shape, customize the buffer-local variable
cursor-type
; possible values are box
(the default),
(box . size)
(box cursor becoming a hollow box under
masked images larger than size pixels in either dimension),
hollow
(a hollow box), bar
(a vertical bar), (bar
. n)
(a vertical bar n pixels wide), hbar
(a
horizontal bar), (hbar . n)
(a horizontal bar n
pixels tall), or nil
(no cursor at all).
By default, the cursor stops blinking after 10 blinks, if Emacs does
not get any input during that time; any input event restarts the
count. You can customize the variable blink-cursor-blinks
to
control that: its value says how many times to blink without input
before stopping. Setting that variable to a zero or negative value
will make the cursor blink forever. To disable cursor blinking
altogether, change the variable blink-cursor-mode
to nil
(see Easy Customization Interface), or add the line
to your init file. Alternatively, you can change how the cursor
looks when it blinks off by customizing the list variable
blink-cursor-alist
. Each element in the list should have the
form (on-type . off-type)
; this means that if the
cursor is displayed as on-type when it blinks on (where
on-type is one of the cursor types described above), then it is
displayed as off-type when it blinks off.
Some characters, such as tab characters, are extra wide. When
the cursor is positioned over such a character, it is normally drawn
with the default character width. You can make the cursor stretch to
cover wide characters, by changing the variable
x-stretch-cursor
to a non-nil
value.
The cursor normally appears in non-selected windows as a
non-blinking hollow box. (For a bar cursor, it instead appears as a
thinner bar.) To turn off cursors in non-selected windows, change the
variable cursor-in-non-selected-windows
to nil
.
To make the cursor even more visible, you can use HL Line mode, a
minor mode that highlights the line containing point. Use M-x
hl-line-mode to enable or disable it in the current buffer. M-x
global-hl-line-mode enables or disables the same mode globally.
14.21 Line Truncation
As an alternative to continuation (see Continuation Lines),
Emacs can display long lines by truncation. This means that all
the characters that do not fit in the width of the screen or window do
not appear at all. On graphical displays, a small straight arrow in
the fringe indicates truncation at either end of the line. On text
terminals, this is indicated with ‘$’ signs in the rightmost
and/or leftmost columns.
Horizontal scrolling automatically causes line truncation
(see Horizontal Scrolling). You can explicitly enable line
truncation for a particular buffer with the command C-x x t
(toggle-truncate-lines
). This works by locally changing the
variable truncate-lines
. If that variable is non-nil
,
long lines are truncated; if it is nil
, they are continued onto
multiple screen lines. Setting the variable truncate-lines
in
any way makes it local to the current buffer; until that time, the
default value, which is normally nil
, is in effect.
Since line truncation and word wrap (described in the next section)
are contradictory, toggle-truncate-lines
disables word wrap
when it turns on line truncation.
If a split window becomes too narrow, Emacs may automatically enable
line truncation. See Splitting Windows, for the variable
truncate-partial-width-windows
which controls this.
14.22 Visual Line Mode
Another alternative to ordinary line continuation is to use
word wrap. Here, each long logical line is divided into two or
more screen lines, like in ordinary line continuation. However, Emacs
attempts to wrap the line at word boundaries near the right window
edge. (If the line’s direction is right-to-left, it is wrapped at the
left window edge instead.) This makes the text easier to read, as
wrapping does not occur in the middle of words.
Word wrap is enabled by Visual Line mode, an optional minor mode.
To turn on Visual Line mode in the current buffer, type M-x
visual-line-mode; repeating this command turns it off. You can also
turn on Visual Line mode using the menu bar: in the Options menu,
select the ‘Line Wrapping in this Buffer’ submenu, followed by
the ‘Word Wrap (Visual Line mode)’ menu item. While Visual Line
mode is enabled, the mode line shows the string ‘wrap’ in the
mode display. The command M-x global-visual-line-mode toggles
Visual Line mode in all buffers.
Since word wrap and line truncation (described in the previous
section) are contradictory, turning on visual-line-mode
disables line truncation.
In Visual Line mode, some editing commands work on screen lines
instead of logical lines: C-a (beginning-of-visual-line
)
moves to the beginning of the screen line, C-e
(end-of-visual-line
) moves to the end of the screen line, and
C-k (kill-visual-line
) kills text to the end of the
screen line.
To move by logical lines, use the commands M-x
next-logical-line and M-x previous-logical-line. These move
point to the next logical line and the previous logical line
respectively, regardless of whether Visual Line mode is enabled. If
you use these commands frequently, it may be convenient to assign key
bindings to them. See Rebinding Keys in Your Init File.
By default, word-wrapped lines do not display fringe indicators.
Visual Line mode is often used to edit files that contain many long
logical lines, so having a fringe indicator for each wrapped line
would be visually distracting. You can change this by customizing the
variable visual-line-fringe-indicators
.
By default, Emacs only breaks lines after whitespace characters.
That produces incorrect results when CJK and Latin text are mixed
together (because CJK characters don’t use whitespace to separate
words). You can customize the option word-wrap-by-category
to
allow Emacs to break lines after any character with ‘|’ category
(see Categories in the Emacs Lisp Reference Manual), which
provides better support for CJK characters. Also, if this variable is
set using Customize, Emacs automatically loads kinsoku.el.
When kinsoku.el is loaded, Emacs respects kinsoku rules when
breaking lines. That means characters with the ‘>’ category don’t
appear at the beginning of a line (e.g., U+FF0C FULLWIDTH COMMA), and
characters with the ‘<’ category don’t appear at the end of a line
(e.g., U+300A LEFT DOUBLE ANGLE BRACKET). You can view the category
set of a character using the commands char-category-set
and
category-set-mnemonics
, or by typing C-u C-x = with point
on the character and looking at the “category” section in the
report. You can add categories to a character using the command
modify-category-entry
.
14.23 Customization of Display
This section describes variables that control miscellaneous aspects
of the appearance of the Emacs screen. Beginning users can skip it.
If you want to have Emacs display line numbers for every line in the
buffer, customize the buffer-local variable
display-line-numbers
; it is nil
by default. This
variable can have several different values to support various modes of
line-number display:
t
Display (an absolute) line number before each non-continuation screen
line that displays buffer text. If the line is a continuation line,
or if the entire screen line displays a display or an overlay string,
that line will not be numbered.
relative
Display relative line numbers before non-continuation lines which show
buffer text. The line numbers are relative to the line showing point,
so the numbers grow both up and down as lines become farther from the
current line.
visual
This value causes Emacs to count lines visually: only lines actually
shown on the display will be counted (disregarding any lines in
invisible parts of text), and lines which wrap to consume more than
one screen line will be numbered that many times. The displayed
numbers are relative, as with relative
value above. This is
handy in modes that fold text, such as Outline mode (see Outline Mode), and when you need to move by exact number of screen lines.
- anything else
Any other non-nil
value is treated as t
.
The command M-x display-line-numbers-mode provides a
convenient way to turn on display of line numbers. This mode has a globalized
variant, global-display-line-numbers-mode
. The user option
display-line-numbers-type
controls which sub-mode of
line-number display, described above, these modes will activate.
Note that line numbers are not displayed in the minibuffer and in the
tooltips, even if you turn on display-line-numbers-mode
globally.
When Emacs displays relative line numbers, you can control the number
displayed before the current line, the line showing point. By
default, Emacs displays the absolute number of the current line there,
even though all the other line numbers are relative. If you customize
the variable display-line-numbers-current-absolute
to a
nil
value, the number displayed for the current line will be
zero. This is handy if you don’t care about the number of the current
line, and want to leave more horizontal space for text in large
buffers.
In a narrowed buffer (see Narrowing) lines are normally numbered
starting at the beginning of the narrowing. However, if you customize
the variable display-line-numbers-widen
to a non-nil
value, line numbers will disregard any narrowing and will start at the
first character of the buffer.
If the value of display-line-numbers-offset
is non-zero, it is
added to each absolute line number, and lines are counted from the
beginning of the buffer, as if display-line-numbers-widen
were
non-nil
. It has no effect when set to zero, or when line
numbers are not absolute.
In selective display mode (see Selective Display), and other modes
that hide many lines from display (such as Outline and Org modes), you
may wish to customize the variables
display-line-numbers-width-start
and
display-line-numbers-grow-only
, or set
display-line-numbers-width
to a large enough value, to avoid
occasional miscalculations of space reserved for the line numbers.
The line numbers are displayed in a special face line-number
.
The current line number is displayed in a different face,
line-number-current-line
, so you can make the current line’s
number have a distinct appearance, which will help locating the line
showing point. Additional faces line-number-major-tick
and
line-number-minor-tick
can be used to highlight the line numbers
of lines which are a multiple of certain numbers. Customize
display-line-numbers-major-tick
and
display-line-numbers-minor-tick
respectively to set those
numbers.
If the variable visible-bell
is non-nil
, Emacs attempts
to make the whole screen blink when it would normally make an audible bell
sound. This variable has no effect if your terminal does not have a way
to make the screen blink.
The variable echo-keystrokes
controls the echoing of multi-character
keys; its value is the number of seconds of pause required to cause echoing
to start, or zero, meaning don’t echo at all. The value takes effect when
there is something to echo. See The Echo Area.
On graphical displays, Emacs displays the mouse pointer as an
hourglass if Emacs is busy. To disable this feature, set the variable
display-hourglass
to nil
. The variable
hourglass-delay
determines the number of seconds of busy
time before the hourglass is shown; the default is 1.
If the mouse pointer lies inside an Emacs frame, Emacs makes it
invisible each time you type a character to insert text, to prevent it
from obscuring the text. (To be precise, the hiding occurs when you
type a self-inserting character. See Inserting Text.) Moving
the mouse pointer makes it visible again. To disable this feature,
set the variable make-pointer-invisible
to nil
.
On graphical displays, the variable underline-minimum-offset
determines the minimum distance between the baseline and underline, in
pixels, for underlined text. By default, the value is 1; increasing
it may improve the legibility of underlined text for certain fonts.
(However, Emacs will never draw the underline below the current line
area.) The variable x-underline-at-descent-line
determines how
to draw underlined text. The default is nil
, which means to
draw it at the baseline level of the font; if you change it to
t
, Emacs draws the underline at the same height as the font’s
descent line. (If non-default line spacing was specified for the
underlined text, see Line Height in The Emacs Lisp
Reference Manual, Emacs draws the underline below the additional
spacing.)
The variable overline-margin
specifies the vertical position
of an overline above the text, including the height of the overline
itself, in pixels; the default is 2.
On some text terminals, bold face and inverse video together result
in text that is hard to read. Call the function
tty-suppress-bold-inverse-default-colors
with a non-nil
argument to suppress the effect of bold-face in this case.
Raw bytes are displayed in octal format by default, for example a
byte with a decimal value of 128 is displayed as \200
. To
change display to the hexadecimal format of \x80
, set the
variable display-raw-bytes-as-hex
to t
.
15 Searching and Replacement
Like other editors, Emacs has commands to search for occurrences of
a string. Emacs also has commands to replace occurrences of a string
with a different string. There are also commands that do the same
thing, but search for patterns instead of fixed strings.
You can also search multiple files under the control of xref
(see Searching and Replacing with Identifiers) or through the Dired A command
(see Operating on Files), or ask the grep
program to do it
(see Searching with Grep under Emacs).
15.1 Incremental Search
The principal search command in Emacs is incremental: it
begins searching as soon as you type the first character of the search
string. As you type in the search string, Emacs shows you where the
string (as you have typed it so far) would be found. When you have
typed enough characters to identify the place you want, you can stop.
Depending on what you plan to do next, you may or may not need to
terminate the search explicitly with RET.
- C-s
Incremental search forward (isearch-forward
).
- C-r
Incremental search backward (isearch-backward
).
You can also invoke incremental search from the menu bar’s
‘Edit->Search’ menu.
15.1.1 Basics of Incremental Search
- C-s
Begin incremental search (isearch-forward
).
- C-r
Begin reverse incremental search (isearch-backward
).
C-s (isearch-forward
) starts a forward incremental
search. It reads characters from the keyboard, and moves point just
past the end of the next occurrence of those characters in the buffer.
For instance, if you type C-s and then F, that puts the
cursor after the first ‘F’ that occurs in the buffer after the
starting point. If you then type O, the cursor moves to just
after the first ‘FO’; the ‘F’ in that ‘FO’ might not be
the first ‘F’ previously found. After another O, the
cursor moves to just after the first ‘FOO’.
At each step, Emacs highlights the current match—the buffer
text that matches the search string—using the isearch
face
(see Text Faces). See Tailoring Search to Your Needs, for various options
that customize this highlighting. The current search string is also
displayed in the echo area.
If you make a mistake typing the search string, type DEL
(isearch-delete-char
). Each DEL cancels the last input
item entered during the search. Emacs records a new input item
whenever you type a command that changes the search string, the
position of point, the success or failure of the search, the direction
of the search, the position of the other end of the current search
result, or the “wrappedness” of the search. See Errors in Incremental Search, for more about dealing with unsuccessful search.
When you are satisfied with the place you have reached, type
RET (isearch-exit
). This stops searching, leaving the
cursor where the search brought it. Also, any command not specially
meaningful in searches stops the searching and is then executed.
Thus, typing C-a exits the search and then moves to the
beginning of the line; typing one of the arrow keys exits the search
and performs the respective movement command; etc. RET is
necessary only if the next command you want to type is a printing
character, DEL, RET, or another character that is special
within searches (C-q, C-w, C-r, C-s,
C-y, M-y, M-r, M-c, M-e, and some others
described below). You can fine-tune the commands that exit the
search; see Not Exiting Incremental Search.
As a special exception, entering RET when the search string is
empty launches nonincremental search (see Nonincremental Search).
(This can be customized; see Tailoring Search to Your Needs.)
To abandon the search and return to the place where you started,
type ESC ESC ESC (isearch-cancel
) or
C-g C-g (isearch-abort
).
When you exit the incremental search, it adds the original value of
point to the mark ring, without activating the mark; you can thus use
C-u C-SPC or C-x C-x to return to where you were
before beginning the search. See The Mark Ring. (Emacs only does this
if the mark was not already active; if the mark was active when you
started the search, both C-u C-SPC and C-x C-x will
go to the mark.)
To search backwards, use C-r (isearch-backward
) instead
of C-s to start the search. A backward search finds matches
that end before the starting point, just as a forward search finds
matches that begin after it.
15.1.2 Repeating Incremental Search
Suppose you search forward for ‘FOO’ and find a match, but not
the one you expected to find: the ‘FOO’ you were aiming for
occurs later in the buffer. In this event, type another C-s
(isearch-repeat-forward
) to move to the next occurrence of the
search string, or C-r (isearch-repeat-backward
) to move
to the previous occurrence. You can repeat these commands any number
of times. Alternatively, you can supply a numeric prefix argument of
n to C-s and C-r to find the nth next or
previous occurrence. If you overshoot, you can cancel some C-s
commands with DEL. Similarly, each C-r
(isearch-repeat-backward
) in a backward incremental search
repeats the backward search.
If you pause for a little while during incremental search, Emacs
highlights all the other possible matches for the search string that
are present on the screen. This helps you anticipate where you can
get to by typing C-s or C-r to repeat the search. The
other matches are highlighted differently from the current match,
using the customizable face lazy-highlight
(see Text Faces). If
you don’t like this feature, you can disable it by setting
isearch-lazy-highlight
to nil
. For other customizations
related to highlighting matches, see Tailoring Search to Your Needs.
After exiting a search, you can search for the same string again by
typing just C-s C-s. The first C-s is the key that
invokes incremental search, and the second C-s means to search
again for the last search string. Similarly, C-r C-r searches
backward for the last search string. In determining the last search
string, it doesn’t matter whether that string was searched for with
C-s or C-r.
If you are searching forward but you realize you were looking for
something before the starting point, type C-r to switch to a
backward search, leaving the search string unchanged. Similarly,
C-s in a backward search switches to a forward search.
When you change the direction of a search, the first command you
type will, by default, remain on the same match, and the cursor will
move to the other end of the match. To move to another match
immediately, customize the variable
isearch-repeat-on-direction-change
to t
.
If a search is failing and you ask to repeat it by typing another
C-s, it starts again from the beginning of the buffer.
Repeating a failing reverse search with C-r starts again from
the end. This is called wrapping around, and ‘Wrapped’
appears in the search prompt once this has happened. If you keep on
going past the original starting point of the search, it changes to
‘Overwrapped’, which means that you are revisiting matches that
you have already seen.
You can control what happens when there are no more matches by
customizing the isearch-wrap-pause
user option. If it is
t
(the default), signal an error. (Repeating the search will
wrap around.) If no
, issue a ding
and wrap immediately
after reaching the last match. If no-ding
, wrap immediately,
but don’t ding
. Finally, if nil
, never wrap, but just
stop at the last match.
To reuse earlier search strings, use the search ring. The
commands M-p (isearch-ring-retreat
) and M-n
(isearch-ring-advance
) move through the ring to pick a search
string to reuse. These commands leave the selected search ring
element in the minibuffer, where you can edit it. Type
C-s/C-r or RET to accept the string and start
searching for it. The number of most recently used search strings
saved in the search ring is specified by the variable
search-ring-max
, 16 by default.
To edit the current search string in the minibuffer without
replacing it with items from the search ring, type M-e
(isearch-edit-string
) or click mouse-1 in the minibuffer.
Type RET, C-s or C-r to finish editing the string
and search for it. Type C-f or RIGHT to add to the
search string characters following point from the buffer from which
you started the search.
15.1.3 Isearch Yanking
In many cases, you will want to use text at or near point as your
search string. The commands described in this subsection let you do
that conveniently.
C-w (isearch-yank-word-or-char
) appends the next
character or word at point to the search string. This is an easy way
to search for another occurrence of the text at point. (The decision
of whether to copy a character or a word is heuristic.) With a prefix
numeric argument of n, append the next n characters or
words.
C-M-w (isearch-yank-symbol-or-char
) appends the next
character or symbol at point to the search string. This is an easy way
to search for another occurrence of the symbol at point. (The decision
of whether to copy a character or a symbol is heuristic.) With a prefix
numeric argument of n, append the next n characters or
symbols.
M-s C-e (isearch-yank-line
) appends the rest
of the current line to the search string. If point is already at the
end of a line, it appends the next line. With a prefix argument
n, it appends the next n lines.
Similarly, C-M-z (isearch-yank-until-char
) appends to
the search string everything from point until the next occurrence of
a specified character (not including that character). This is especially
useful for keyboard macros, for example in programming languages or
markup languages in which that character marks a token boundary. With
a prefix numeric argument of n, the command appends everything
from point to the nth occurrence of the specified character.
Within incremental search, C-y (isearch-yank-kill
)
appends the current kill to the search string. M-y
(isearch-yank-pop
), if called after C-y during
incremental search, replaces that appended text with an earlier kill,
similar to the usual M-y (yank-pop
) command. Clicking
mouse-2 in the echo area appends the current X selection
(see Cut and Paste with Other Window Applications) to the search string
(isearch-yank-x-selection
).
C-M-d (isearch-del-char
) deletes the last character
from the search string, and C-M-y (isearch-yank-char
)
appends the character after point to the search string. An
alternative method to add the character after point is to enter the
minibuffer with M-e (see Repeating Incremental Search) and type C-f
or RIGHT at the end of the search string in the
minibuffer. Each C-f or RIGHT you type adds another
character following point to the search string.
Normally, when the search is case-insensitive, text yanked into the
search string is converted to lower case, so that the search remains
case-insensitive (see case folding). However, if the
value of the variable search-upper-case
(see search-upper-case) is other than not-yanks
, that disables this
down-casing.
To begin a new incremental search with the text near point yanked
into the initial search string, type M-s M-. that runs the
command isearch-forward-thing-at-point
. If the region was
active, then it yanks the text from the region into the search string.
Otherwise, it tries to yank a URL, a symbol or an expression found
near point. What to yank is defined by the user option
isearch-forward-thing-at-point
.
15.1.4 Errors in Incremental Search
If your string is not found at all, the echo area says ‘Failing
I-Search’, and the cursor moves past the place where Emacs found as
much of your string as it could. Thus, if you search for ‘FOOT’,
and there is no ‘FOOT’, you might see the cursor after the
‘FOO’ in ‘FOOL’. In the echo area, the part of the search
string that failed to match is highlighted using the face
isearch-fail
.
At this point, there are several things you can do. If your string
was mistyped, use DEL to cancel a previous input item
(see Basics of Incremental Search), C-M-d to erase one character at a time,
or M-e to edit it. If you like the place you have found, you
can type RET to remain there. Or you can type C-g, which
removes from the search string the characters that could not be found
(the ‘T’ in ‘FOOT’), leaving those that were found (the
‘FOO’ in ‘FOOT’). A second C-g at that point cancels
the search entirely, returning point to where it was when the search
started.
The quit command, C-g, does special things during searches;
just what it does depends on the status of the search. If the search
has found what you specified and is waiting for input, C-g
cancels the entire search, moving the cursor back to where you started
the search. If C-g is typed when there are characters in the
search string that have not been found—because Emacs is still
searching for them, or because it has failed to find them—then the
search string characters which have not been found are discarded from
the search string. With them gone, the search is now successful and
waiting for more input, so a second C-g will cancel the entire
search.
15.1.5 Special Input for Incremental Search
In addition to characters described in the previous subsections,
some of the other characters you type during incremental search have
special effects. They are described here.
To toggle lax space matching (see lax space
matching), type M-s SPC.
To toggle case sensitivity of the search, type M-c or
M-s c. See case folding. If the search string
includes upper-case letters, the search is case-sensitive by default.
To toggle whether or not the search will consider similar and
equivalent characters as a match, type M-s '. See character folding. If the search string includes accented
characters, that disables character folding during that search.
To toggle whether or not invisible text is searched, type
M-s i (isearch-toggle-invisible
). See Outline Search.
To toggle between non-regexp and regexp incremental search, type
M-r or M-s r (isearch-toggle-regexp
).
See Regular Expression Search.
To toggle symbol mode, type M-s _. See Symbol Search.
To search for a newline character, type C-j as part of the
search string.
To search for non-ASCII characters, use one of the
following methods:
-
Type C-q (
isearch-quote-char
), followed by a non-graphic
character or a sequence of octal digits. This adds a character to the
search string, similar to inserting into a buffer using C-q
(see Inserting Text). For example, C-q C-s during
incremental search adds the ‘control-S’ character to the search
string.
-
Type C-x 8 RET (
isearch-char-by-name
), followed by
a Unicode name or code-point in hex. This adds the specified
character into the search string, similar to the usual
insert-char
command (see Inserting Text).
-
Use an input method (see Input Methods). If an input method is
enabled in the current buffer when you start the search, the same
method will be active in the minibuffer when you type the search
string. While typing the search string, you can toggle the input
method with C-\ (
isearch-toggle-input-method
). You 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. Finally, you can temporarily enable a
transient input method (see transient input method) with
C-x \ (isearch-transient-input-method
) to insert a single
character to the search string using an input method, and
automatically disable the input method afterwards.
Typing M-s o in incremental search invokes
isearch-occur
, which runs occur
with the current search
string. See occur.
Typing M-% (isearch-query-replace
) 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. A negative prefix argument means to replace
backward. See Query Replace. Typing C-M-%
(isearch-query-replace-regexp
) invokes
query-replace-regexp
with the current search string used as the
regexp to replace.
Typing M-TAB in incremental search invokes
isearch-complete
, which attempts to complete the search string
using the search ring (the previous search strings you used) 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 rebind isearch-complete
to another
key sequence if you want to use it (see Changing Key Bindings Interactively).
You can exit the search while leaving the matches highlighted by
typing M-s h r (isearch-highlight-regexp
). This runs
highlight-regexp
(see Interactive Highlighting), passing it
the regexp derived from the search string and prompting you for the face
to use for highlighting. To highlight whole lines containing
matches (rather than just the matches), type M-s h l
(isearch-highlight-lines-matching-regexp
). In either case, to
remove the highlighting, type M-s h u (unhighlight-regexp
).
When incremental search is active, you can type C-h C-h
(isearch-help-map
) 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).
When incremental search is active, typing M-s M-> will go to
the last occurrence of the search string, and M-s M-< will go to
the first occurrence. With a prefix numeric argument of n,
these commands will go to the nth occurrence of the search
string counting from the beginning or end of the buffer,
respectively.
15.1.6 Not Exiting Incremental Search
This subsection describes how to control whether typing a command not
specifically meaningful in searches exits the search before executing
the command. It also describes three categories of commands which you
can type without exiting the current incremental search, even though
they are not themselves part of incremental search.
Normally, typing a command that is not bound by the incremental
search exits the search before executing the command. Thus, the
command operates on the buffer from which you invoked the search.
However, if you customize the variable search-exit-option
to
append
, the characters which you type that are not interpreted by
the incremental search are simply appended to the search string. This
is so you could include in the search string control characters, such
as C-a, that would normally exit the search and invoke the
command bound to them on the buffer.
- Prefix Arguments ¶
-
In incremental search, when you type a command that specifies a
prefix argument (see Numeric Arguments), by default it will apply either
to the next action in the search or to the command that exits the
search. In other words, entering a prefix argument will not by itself
terminate the search.
In previous versions of Emacs, entering a prefix argument always
terminated the search. You can revert to this behavior by setting the
variable isearch-allow-prefix
to nil
.
When isearch-allow-scroll
is non-nil
(see below),
prefix arguments always have the default behavior described above,
i.e., they don’t terminate the search, even if
isearch-allow-prefix
is nil
.
- Scrolling Commands ¶
-
Normally, scrolling commands exit incremental search. If you change
the variable isearch-allow-scroll
to a non-nil
value,
that enables the use of the scroll-bar, as well as keyboard scrolling
commands like C-v, M-v, and C-l (see Scrolling).
This applies only to calling these commands via their bound key
sequences—typing M-x will still exit the search. You can give
prefix arguments to these commands in the usual way. This feature
normally won’t let you scroll the current match out of visibility; but
if you customize isearch-allow-scroll
to the special value
unlimited
, that restriction is lifted.
The isearch-allow-scroll
feature also affects some other
commands, such as C-x 2 (split-window-below
) and
C-x ^ (enlarge-window
), which don’t exactly scroll but do
affect where the text appears on the screen. It applies to any
command whose name has a non-nil
isearch-scroll
property. So you can control which commands are affected by changing
these properties.
For example, to make C-h l usable within an incremental search
in all future Emacs sessions, use C-h c to find what command it
runs (see Documentation for a Key), which is view-lossage
. Then you can
put the following line in your init file (see The Emacs Initialization File):
(put 'view-lossage 'isearch-scroll t)
This feature can be applied to any command that doesn’t permanently
change point, the buffer contents, the match data, the current buffer,
or the selected window and frame. The command must not itself attempt
an incremental search. This feature is disabled if
isearch-allow-scroll
is nil
(which it is by default).
Likewise, if you change the variable isearch-allow-motion
to a non-nil
value, this enables the use of the keyboard motion
commands M-<, M->, C-v and M-v, to move
respectively to the first occurrence of the current search string in
the buffer, the last one, the first one after the current window,
and the last one before the current window. The search direction
does not change when these motion commands are used, unless you change
the variable isearch-motion-changes-direction
to a non-nil
value, in which case the search direction is forward after M-< and
C-v, and backward after M-> and M-v.
- Motion Commands ¶
When isearch-yank-on-move
is customized to shift
,
you can extend the search string by holding down the shift key while
typing cursor motion commands. It will yank text that ends at the new
position after moving point in the current buffer.
When isearch-yank-on-move
is t
, you can extend the
search string without using the shift key for cursor motion commands,
but it applies only for certain motion command that have the
isearch-move
property on their symbols.
15.1.7 Searching the Minibuffer
If you start an incremental search while the minibuffer is active,
Emacs searches the contents of the minibuffer. Unlike searching an
ordinary buffer, the search string is not shown in the echo area,
because that is used to display the minibuffer.
If an incremental search fails in the minibuffer, it tries searching
the minibuffer history. See Minibuffer History. You can visualize
the minibuffer and its history as a series of pages, with the
earliest history element on the first page and the current minibuffer
on the last page. A forward search, C-s, searches forward to
later pages; a reverse search, C-r, searches backwards to
earlier pages. Like in ordinary buffer search, a failing search can
wrap around, going from the last page to the first page or vice versa.
When the current match is on a history element, that history element
is pulled into the minibuffer. If you exit the incremental search
normally (e.g., by typing RET), it remains in the minibuffer
afterwards. Canceling the search, with C-g, restores the
contents of the minibuffer when you began the search.
15.2 Nonincremental Search
Emacs also has conventional nonincremental search commands, which require
you to type the entire search string before searching begins.
- C-s RET string RET
Search for string.
- C-r RET string RET
Search backward for string.
To start a nonincremental search, first type C-s RET.
This enters the minibuffer to read the search string; terminate the
string with RET, and then the search takes place. If the string
is not found, the search command signals an error.
When you type C-s RET, the C-s invokes incremental
search as usual. That command is specially programmed to invoke the
command for nonincremental search, if the string you specify is empty.
(Such an empty argument would otherwise be useless.) C-r
RET does likewise, invoking the nonincremental
backward-searching command.
Nonincremental search can also be invoked from the menu bar’s
‘Edit->Search’ menu.
You can also use two simpler commands, M-x search-forward and
M-x search-backward. These commands look for the literal
strings you specify, and don’t support any of the lax-search features
(see Lax Matching During Searching) except case folding.
15.3 Word Search
A word search finds a sequence of words without regard to the
type of punctuation between them. For instance, if you enter a search
string that consists of two words separated by a single space, the
search matches any sequence of those two words separated by one or
more spaces, newlines, or other punctuation characters. This is
particularly useful for searching text documents, because you don’t
have to worry whether the words you are looking for are separated by
newlines or spaces. Note that major modes for programming languages
or other specialized modes can modify the definition of a word to suit
their syntactic needs.
- M-s w
If incremental search is active, toggle word search mode
(isearch-toggle-word
); otherwise, begin an incremental forward
word search (isearch-forward-word
).
- M-s w RET words RET
Search for words, using a forward nonincremental word search.
- M-s w C-r RET words RET
Search backward for words, using a nonincremental word search.
- M-s M-w
Search the Web for the text in region.
To begin a forward incremental word search, type M-s w. If
incremental search is not already active, this runs the command
isearch-forward-word
. If incremental search is already active
(whether a forward or backward search), M-s w runs the command
isearch-toggle-word
, which switches to a word search while
keeping the direction of the search and the current search string
unchanged. You can toggle word search back off by typing M-s w
again.
To begin a nonincremental word search, type M-s w RET
for a forward search, or M-s w C-r RET for a backward search.
These run the commands word-search-forward
and
word-search-backward
respectively.
Incremental and nonincremental word searches differ slightly in the
way they find a match. In a nonincremental word search, each word in
the search string must exactly match a whole word. In an incremental
word search, the matching is more lax: while you are typing the search
string, its first and last words need not match whole words. This is
so that the matching can proceed incrementally as you type. This
additional laxity does not apply to the lazy highlight
(see Incremental Search), which always matches whole words.
While you are typing the search string, ‘Pending’ appears in the
search prompt until you use a search repeating key like C-s.
The word search commands don’t perform character folding, and
toggling lax whitespace matching (see lax space
matching) has no effect on them.
To search the Web for the text in region, type M-s M-w. This
command performs an Internet search for the words in region using the
search engine whose URL is specified by the variable
eww-search-prefix
(see EWW in The Emacs Web
Wowser Manual). If the region is not active, or doesn’t contain any
words, this command prompts the user for a URL or keywords to search.
15.4 Symbol Search
A symbol search is much like an ordinary search, except that
the boundaries of the search must match the boundaries of a symbol.
The meaning of symbol in this context depends on the major mode,
and usually refers to a source code token, such as a Lisp symbol in
Emacs Lisp mode. For instance, if you perform an incremental symbol
search for the Lisp symbol forward-word
, it would not match
isearch-forward-word
. This feature is thus mainly useful for
searching source code.
- M-s _ ¶
If incremental search is active, toggle symbol search mode
(isearch-toggle-symbol
); otherwise, begin an incremental
forward symbol search (isearch-forward-symbol
).
- M-s .
Start a symbol incremental search forward with the symbol found near
point added to the search string initially.
- M-s _ RET symbol RET
Search forward for symbol, nonincrementally.
- M-s _ C-r RET symbol RET
Search backward for symbol, nonincrementally.
To begin a forward incremental symbol search, type M-s _ (or
M-s . if the symbol to search is near point). If incremental
search is not already active, M-s _ runs the command
isearch-forward-symbol
and M-s . runs the command
isearch-forward-symbol-at-point
. With a numeric prefix
argument of n, M-s . will search for the nthe next
occurrence of the symbol at point; negative values of n search
backwards. If incremental search is already active, M-s _
switches to a symbol search, preserving the direction of the search
and the current search string; you can disable symbol search by typing
M-s _ again. In incremental symbol search, while you are typing
the search string, only the beginning of the search string is required
to match the beginning of a symbol, and ‘Pending’ appears in the
search prompt until you use a search repeating key like C-s.
To begin a nonincremental symbol search, type M-s _ RET
for a forward search, or M-s _ C-r RET or a backward
search. In nonincremental symbol searches, the beginning and end of
the search string are required to match the beginning and end of a
symbol, respectively.
The symbol search commands don’t perform character folding, and
toggling lax whitespace matching (see lax space
matching) has no effect on them.
15.5 Regular Expression Search
A regular expression (or regexp for short) is a pattern
that denotes a class of alternative strings to match. Emacs
provides both incremental and nonincremental ways to search for a
match for a regexp. The syntax of regular expressions is explained in
the next section.
- C-M-s
Begin incremental regexp search (isearch-forward-regexp
).
- C-M-r
Begin reverse incremental regexp search (isearch-backward-regexp
).
Incremental search for a regexp is done by typing C-M-s
(isearch-forward-regexp
), by invoking C-s with a
prefix argument (whose value does not matter), or by typing M-r
within a forward incremental search. This command reads a
search string incrementally just like C-s, but it treats the
search string as a regexp rather than looking for an exact match
against the text in the buffer. Each time you add text to the search
string, you make the regexp longer, and the new regexp is searched
for. To search backward for a regexp, use C-M-r
(isearch-backward-regexp
), C-r with a prefix argument,
or M-r within a backward incremental search.
All of the special key sequences in an ordinary incremental search
(see Special Input for Incremental Search) do similar things in an incremental regexp
search. For instance, typing C-s immediately after starting the
search retrieves the last incremental search regexp used and searches
forward for it. Incremental regexp and non-regexp searches have
independent defaults. They also have separate search rings, which you
can access with M-p and M-n. The maximum number of search
regexps saved in the search ring is determined by the value of
regexp-search-ring-max
, 16 by default.
Unlike ordinary incremental search, incremental regexp search
does not use lax space matching by default. To toggle this feature
use M-s SPC (isearch-toggle-lax-whitespace
).
Then any SPC typed in incremental regexp search will match
any sequence of one or more whitespace characters. The variable
search-whitespace-regexp
specifies the regexp for the lax
space matching. See Special Input for Incremental Search.
Also unlike ordinary incremental search, incremental regexp search
cannot use character folding (see Lax Matching During Searching). (If you toggle
character folding during incremental regexp search with M-s ',
the search becomes a non-regexp search and the search pattern you
typed is interpreted as a literal string.)
In some cases, adding characters to the regexp in an incremental
regexp search can make the cursor move back and start again. For
example, if you have searched for ‘foo’ and you add ‘\|bar’,
the cursor backs up in case the first ‘bar’ precedes the first
‘foo’. See Syntax of Regular Expressions.
Forward and backward regexp search are not symmetrical, because
regexp matching in Emacs always operates forward, starting with the
beginning of the regexp. Thus, forward regexp search scans forward,
trying a forward match at each possible starting position. Backward
regexp search scans backward, trying a forward match at each possible
starting position. These search methods are not mirror images.
Nonincremental search for a regexp is done with the commands
re-search-forward
and re-search-backward
. You can
invoke these with M-x, or by way of incremental regexp search
with C-M-s RET and C-M-r RET. When you invoke
these commands with M-x, they search for the exact regexp you
specify, and thus don’t support any lax-search features (see Lax Matching During Searching) except case folding.
If you use the incremental regexp search commands with a prefix
argument, they perform ordinary string search, like
isearch-forward
and isearch-backward
. See Incremental Search.
15.6 Syntax of Regular Expressions
This section (and this manual in general) describes regular
expression features that users typically use. See Regular
Expressions in The Emacs Lisp Reference Manual, for additional
features used mainly in Lisp programs.
Regular expressions have a syntax in which a few characters are
special constructs and the rest are ordinary. An ordinary
character matches that same character and nothing else. The special
characters are ‘$^.*+?[\’. The character ‘]’ is special if
it ends a character alternative (see below). The character ‘-’
is special inside a character alternative. Any other character
appearing in a regular expression is ordinary, unless a ‘\’
precedes it. (When you use regular expressions in a Lisp program,
each ‘\’ must be doubled, see the example near the end of this
section.)
For example, ‘f’ is not a special character, so it is ordinary, and
therefore ‘f’ is a regular expression that matches the string
‘f’ and no other string. (It does not match the string
‘ff’.) Likewise, ‘o’ is a regular expression that matches
only ‘o’. (When case distinctions are being ignored, these regexps
also match ‘F’ and ‘O’, but we consider this a generalization
of “the same string”, rather than an exception.)
Any two regular expressions a and b can be concatenated.
The result is a regular expression which matches a string if a
matches some amount of the beginning of that string and b
matches the rest of the string. As a trivial example, concatenating
the regular expressions ‘f’ and ‘o’ gives the regular
expression ‘fo’, which matches only the string ‘fo’. To do
something less trivial, you need to use one of the special characters.
Here is a list of them.
- . (Period)
is a special character that matches any single character except a
newline. For example, the regular expressions ‘a.b’ matches any
three-character string that begins with ‘a’ and ends with
‘b’.
- *
is not a construct by itself; it is a postfix operator that means to
match the preceding regular expression repetitively any number of
times, as many times as possible. Thus, ‘o*’ matches any number
of ‘o’s, including no ‘o’s.
‘*’ always applies to the smallest possible preceding
expression. Thus, ‘fo*’ has a repeating ‘o’, not a repeating
‘fo’. It matches ‘f’, ‘fo’, ‘foo’, and so on.
The matcher processes a ‘*’ construct by matching, immediately,
as many repetitions as can be found. Then it continues with the rest
of the pattern. If that fails, backtracking occurs, discarding some
of the matches of the ‘*’-modified construct in case that makes
it possible to match the rest of the pattern. For example, in matching
‘ca*ar’ against the string ‘caaar’, the ‘a*’ first
tries to match all three ‘a’s; but the rest of the pattern is
‘ar’ and there is only ‘r’ left to match, so this try fails.
The next alternative is for ‘a*’ to match only two ‘a’s.
With this choice, the rest of the regexp matches successfully.
- +
is a postfix operator, similar to ‘*’ except that it must match
the preceding expression at least once. Thus, ‘ca+r’ matches the
strings ‘car’ and ‘caaaar’ but not the string ‘cr’,
whereas ‘ca*r’ matches all three strings.
- ?
is a postfix operator, similar to ‘*’ except that it can match
the preceding expression either once or not at all. Thus, ‘ca?r’
matches ‘car’ or ‘cr’, and nothing else.
- *?, +?, ?? ¶
are non-greedy variants of the operators above. The normal
operators ‘*’, ‘+’, ‘?’ match as much as they can, as
long as the overall regexp can still match. With a following
‘?’, they will match as little as possible.
Thus, both ‘ab*’ and ‘ab*?’ can match the string ‘a’
and the string ‘abbbb’; but if you try to match them both against
the text ‘abbb’, ‘ab*’ will match it all (the longest valid
match), while ‘ab*?’ will match just ‘a’ (the shortest
valid match).
Non-greedy operators match the shortest possible string starting at a
given starting point; in a forward search, though, the earliest
possible starting point for match is always the one chosen. Thus, if
you search for ‘a.*?$’ against the text ‘abbab’ followed by
a newline, it matches the whole string. Since it can match
starting at the first ‘a’, it does.
- \{n\}
is a postfix operator specifying n repetitions—that is, the
preceding regular expression must match exactly n times in a
row. For example, ‘x\{4\}’ matches the string ‘xxxx’ and
nothing else.
- \{n,m\}
is a postfix operator specifying between n and m
repetitions—that is, the preceding regular expression must match at
least n times, but no more than m times. If m is
omitted, then there is no upper limit, but the preceding regular
expression must match at least n times.
‘\{0,1\}’ is
equivalent to ‘?’.
‘\{0,\}’ is equivalent to
‘*’.
‘\{1,\}’ is equivalent to ‘+’.
- [ … ]
is a character set, beginning with ‘[’ and terminated by
‘]’.
In the simplest case, the characters between the two brackets are what
this set can match. Thus, ‘[ad]’ matches either one ‘a’ or
one ‘d’, and ‘[ad]*’ matches any string composed of just
‘a’s and ‘d’s (including the empty string). It follows that
‘c[ad]*r’ matches ‘cr’, ‘car’, ‘cdr’,
‘caddaar’, etc.
You can also include character ranges in a character set, by writing the
starting and ending characters with a ‘-’ between them. Thus,
‘[a-z]’ matches any lower-case ASCII letter. Ranges may be
intermixed freely with individual characters, as in ‘[a-z$%.]’,
which matches any lower-case ASCII letter or ‘$’, ‘%’ or
period. As another example, ‘[α-ωί]’ matches all lower-case
Greek letters.
You can also include certain special character classes in a
character set. A ‘[:’ and balancing ‘:]’ enclose a
character class inside a character alternative. For instance,
‘[[:alnum:]]’ matches any letter or digit. See Char Classes in The Emacs Lisp Reference Manual, for a list of character
classes.
To include a ‘]’ in a character set, you must make it the first character.
For example, ‘[]a]’ matches ‘]’ or ‘a’. To include a ‘-’,
write ‘-’ as the last character of the set, tho you can also put it first
or after a range. Thus, ‘[]-]’ matches both ‘]’ and ‘-’.
To include ‘^’ in a set, put it anywhere but at the beginning of
the set. (At the beginning, it complements the set—see below.)
When you use a range in case-insensitive search, you should write both
ends of the range in upper case, or both in lower case, or both should
be non-letters. The behavior of a mixed-case range such as ‘A-z’
is somewhat ill-defined, and it may change in future Emacs versions.
- [^ … ]
‘[^’ begins a complemented character set, which matches any
character except the ones specified. Thus, ‘[^a-z0-9A-Z]’ matches
all characters except ASCII letters and digits.
‘^’ is not special in a character set unless it is the first
character. The character following the ‘^’ is treated as if it
were first (in other words, ‘-’ and ‘]’ are not special there).
A complemented character set can match a newline, unless newline is
mentioned as one of the characters not to match. This is in contrast to
the handling of regexps in programs such as grep
.
- ^
is a special character that matches the empty string, but only at the
beginning of a line in the text being matched. Otherwise it fails to
match anything. Thus, ‘^foo’ matches a ‘foo’ that occurs at
the beginning of a line.
For historical compatibility reasons, ‘^’ can be used with this
meaning only at the beginning of the regular expression, or after
‘\(’ or ‘\|’.
- $
is similar to ‘^’ but matches only at the end of a line. Thus,
‘x+$’ matches a string of one ‘x’ or more at the end of a line.
For historical compatibility reasons, ‘$’ can be used with this
meaning only at the end of the regular expression, or before ‘\)’
or ‘\|’.
- \
has two functions: it quotes the special characters (including
‘\’), and it introduces additional special constructs.
Because ‘\’ quotes special characters, ‘\$’ is a regular
expression that matches only ‘$’, and ‘\[’ is a regular
expression that matches only ‘[’, and so on.
See the following section for the special constructs that begin
with ‘\’.
Note: for historical compatibility, special characters are treated as
ordinary ones if they are in contexts where their special meanings make no
sense. For example, ‘*foo’ treats ‘*’ as ordinary since there is
no preceding expression on which the ‘*’ can act. It is poor practice
to depend on this behavior; it is better to quote the special character anyway,
regardless of where it appears.
As a ‘\’ is not special inside a character alternative, it can
never remove the special meaning of ‘-’ or ‘]’. So you
should not quote these characters when they have no special meaning
either. This would not clarify anything, since backslashes can
legitimately precede these characters where they have special
meaning, as in ‘[^\]’ ("[^\\]"
for Lisp string syntax),
which matches any single character except a backslash.
15.7 Backslash in Regular Expressions
For the most part, ‘\’ followed by any character matches only
that character. However, there are several exceptions: two-character
sequences starting with ‘\’ that have special meanings. The
second character in the sequence is always an ordinary character when
used on its own. Here is a table of ‘\’ constructs.
- \|
specifies an alternative. Two regular expressions a and b
with ‘\|’ in between form an expression that matches some text if
either a matches it or b matches it. It works by trying to
match a, and if that fails, by trying to match b.
Thus, ‘foo\|bar’ matches either ‘foo’ or ‘bar’
but no other string.
‘\|’ applies to the largest possible surrounding expressions. Only a
surrounding ‘\( … \)’ grouping can limit the grouping power of
‘\|’.
Full backtracking capability exists to handle multiple uses of ‘\|’.
- \( … \)
is a grouping construct that serves three purposes:
- To enclose a set of ‘\|’ alternatives for other operations.
Thus, ‘\(foo\|bar\)x’ matches either ‘foox’ or ‘barx’.
- To enclose a complicated expression for the postfix operators ‘*’,
‘+’ and ‘?’ to operate on. Thus, ‘ba\(na\)*’ matches
‘bananana’, etc., with any (zero or more) number of ‘na’
strings.
- To record a matched substring for future reference.
This last application is not a consequence of the idea of a
parenthetical grouping; it is a separate feature that is assigned as a
second meaning to the same ‘\( … \)’ construct. In practice
there is usually no conflict between the two meanings; when there is
a conflict, you can use a shy group, described below.
- \(?: … \) ¶
specifies a shy group that does not record the matched substring;
you can’t refer back to it with ‘\d’ (see below). This is
useful in mechanically combining regular expressions, so that you can
add groups for syntactic purposes without interfering with the
numbering of the groups that are meant to be referred to.
- \d ¶
matches the same text that matched the dth occurrence of a
‘\( … \)’ construct. This is called a back
reference.
After the end of a ‘\( … \)’ construct, the matcher remembers
the beginning and end of the text matched by that construct. Then,
later on in the regular expression, you can use ‘\’ followed by the
digit d to mean “match the same text matched the dth time
by the ‘\( … \)’ construct”.
The strings matching the first nine ‘\( … \)’ constructs
appearing in a regular expression are assigned numbers 1 through 9 in
the order that the open-parentheses appear in the regular expression.
So you can use ‘\1’ through ‘\9’ to refer to the text matched
by the corresponding ‘\( … \)’ constructs.
For example, ‘\(.*\)\1’ matches any newline-free string that is
composed of two identical halves. The ‘\(.*\)’ matches the first
half, which may be anything, but the ‘\1’ that follows must match
the same exact text.
If a particular ‘\( … \)’ construct matches more than once
(which can easily happen if it is followed by ‘*’), only the last
match is recorded.
- \`
matches the empty string, but only at the beginning of the string or
buffer (or its accessible portion) being matched against.
- \'
matches the empty string, but only at the end of the string or buffer
(or its accessible portion) being matched against.
- \=
matches the empty string, but only at point.
- \b
matches the empty string, but only at the beginning or
end of a word. Thus, ‘\bfoo\b’ matches any occurrence of
‘foo’ as a separate word. ‘\bballs?\b’ matches
‘ball’ or ‘balls’ as a separate word.
‘\b’ matches at the beginning or end of the buffer
regardless of what text appears next to it.
- \B
matches the empty string, but not at the beginning or
end of a word.
- \<
matches the empty string, but only at the beginning of a word.
‘\<’ matches at the beginning of the buffer only if a
word-constituent character follows.
- \>
matches the empty string, but only at the end of a word. ‘\>’
matches at the end of the buffer only if the contents end with a
word-constituent character.
- \w
matches any word-constituent character. The syntax table determines
which characters these are. See Syntax Tables in The Emacs Lisp Reference Manual.
- \W
matches any character that is not a word-constituent.
- \_<
matches the empty string, but only at the beginning of a symbol.
A symbol is a sequence of one or more symbol-constituent characters.
A symbol-constituent character is a character whose syntax is either
‘w’ or ‘_’. ‘\_<’ matches at the beginning of the
buffer only if a symbol-constituent character follows. As with words,
the syntax table determines which characters are symbol-constituent.
- \_>
matches the empty string, but only at the end of a symbol. ‘\_>’
matches at the end of the buffer only if the contents end with a
symbol-constituent character.
- \sc
matches any character whose syntax is c. Here c is a
character that designates a particular syntax class: thus, ‘w’
for word constituent, ‘-’ or ‘ ’ for whitespace, ‘.’
for ordinary punctuation, etc. See Syntax Class Table in The Emacs Lisp Reference Manual.
- \Sc
matches any character whose syntax is not c.
- \cc
matches any character that belongs to the category c. For
example, ‘\cc’ matches Chinese characters, ‘\cg’ matches
Greek characters, etc. For the description of the known categories,
type M-x describe-categories RET.
- \Cc
matches any character that does not belong to category
c.
The constructs that pertain to words and syntax are controlled by
the setting of the syntax table. See Syntax Tables in The Emacs Lisp Reference Manual.
15.8 Regular Expression Example
Here is an example of a regexp—similar to the regexp that Emacs
uses, by default, to recognize the end of a sentence, not including
the following space (i.e., the variable sentence-end-base
):
This contains two parts in succession: a character set matching
period, ‘?’, or ‘!’, and a character set matching
close-brackets, quotes, or parentheses, repeated zero or more times.
15.9 Lax Matching During Searching
Normally, you’d want search commands to disregard certain minor
differences between the search string you type and the text being
searched. For example, sequences of whitespace characters of
different length are usually perceived as equivalent; letter-case
differences usually don’t matter; etc. This is known as
character equivalence.
This section describes the Emacs lax search features, and how to
tailor them to your needs.
By default, search commands perform lax space matching:
each space, or sequence of spaces, matches any sequence of one or more
whitespace characters in the text. (Incremental regexp search has a
separate default; see Regular Expression Search.) 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, to make spaces match
sequences of newlines as well as spaces, set it to the regular expression
‘[[:space:]\n]+’. The default value of this variable considers
any sequence of spaces and tab characters as whitespace.
If you want whitespace characters to match exactly, you can turn lax
space matching off by typing M-s SPC
(isearch-toggle-lax-whitespace
) within an incremental search.
Another M-s SPC turns lax space matching back on. To
disable lax whitespace matching for all searches, change
search-whitespace-regexp
to nil
; then each space in the
search string matches exactly one space.
Searches in Emacs by default ignore the case of the text they are
searching through, if you specify the search string in lower case.
Thus, if you specify searching for ‘foo’, then ‘Foo’ and
‘fOO’ also match. Regexps, and in particular character sets,
behave likewise: ‘[ab]’ matches ‘a’ or ‘A’ or ‘b’
or ‘B’. This feature is known as case folding, and it is
supported in both incremental and non-incremental search modes.
An upper-case letter anywhere in the search string makes the search
case-sensitive. Thus, searching for ‘Foo’ does not find
‘foo’ or ‘FOO’. This applies to regular expression search
as well as to literal string search. The effect ceases if you delete
the upper-case letter from the search string. The variable
search-upper-case
controls this: if it is non-nil
, an
upper-case character in the search string makes the search
case-sensitive; setting it to nil
disables this effect of
upper-case characters. The default value of this variable is
not-yanks
, which makes search case-sensitive if there are
upper-case letters in the search string, and also causes text yanked
into the search string (see Isearch Yanking) to be down-cased, so
that such searches are case-insensitive by default.
If you set the variable case-fold-search
to nil
, then
all letters must match exactly, including case. This is a per-buffer
variable; altering the variable normally affects only the current buffer,
unless you change its default value. See Local Variables.
This variable applies to nonincremental searches also, including those
performed by the replace commands (see Replacement Commands) and the minibuffer
history matching commands (see Minibuffer History).
Typing M-c or M-s c (isearch-toggle-case-fold
)
within an incremental search toggles the case sensitivity of that
search. The effect does not extend beyond the current incremental
search, but it does override the effect of adding or removing an
upper-case letter in the current search.
Several related variables control case-sensitivity of searching and
matching for specific commands or activities. For instance,
tags-case-fold-search
controls case sensitivity for
find-tag
. To find these variables, do M-x
apropos-variable RET case-fold-search RET.
Case folding disregards case distinctions among characters, making
upper-case characters match lower-case variants, and vice versa. A
generalization of case folding is character folding, which
disregards wider classes of distinctions among similar characters.
For instance, under character folding the letter a
matches all
of its accented cousins like ä
and á
, i.e., the
match disregards the diacritics that distinguish these
variants. In addition, a
matches other characters that
resemble it, or have it as part of their graphical representation,
such as U+00AA FEMININE ORDINAL INDICATOR and U+24D0
CIRCLED LATIN SMALL LETTER A (which looks like a small a
inside a circle).
Similarly, the ASCII double-quote character "
matches
all the other variants of double quotes defined by the Unicode
standard. Finally, character folding can make a sequence of one or
more characters match another sequence of a different length: for
example, the sequence of two characters ff
matches U+FB00
LATIN SMALL LIGATURE FF and the sequence (a)
matches
U+249C PARENTHESIZED LATIN SMALL LETTER A. Character sequences
that are not identical, but match under character folding are known as
equivalent character sequences.
Generally, search commands in Emacs do not by default perform
character folding in order to match equivalent character sequences.
You can enable this behavior by customizing the variable
search-default-mode
to char-fold-to-regexp
.
See Tailoring Search to Your Needs. Within an incremental search, typing
M-s ' (isearch-toggle-char-fold
) toggles character
folding, but only for that search. (Replace commands have a different
default, controlled by a separate option; see Replace Commands and Lax Matches.)
By default, typing an explicit variant of a character, such as
ä
, as part of the search string doesn’t match its base
character, such as a
. But if you customize the variable
char-fold-symmetric
to t
, then search commands treat
equivalent characters the same and use of any of a set of equivalent
characters in a search string finds any of them in the text being
searched, so typing an accented character ä
matches the
letter a
as well as all the other variants like á
.
You can add new foldings using the customizable variable
char-fold-include
, or remove the existing ones using the
customizable variable char-fold-exclude
.
15.10 Replacement Commands
Emacs provides several commands for performing search-and-replace
operations. In addition to the simple M-x replace-string
command, there is M-% (query-replace
), which presents
each occurrence of the search pattern and asks you whether to replace
it.
The replace commands normally operate on the text from point to the
end of the buffer. When the region is active, they operate on it
instead (see The Mark and the Region). The basic replace commands replace one
search string (or regexp) with one replacement string. It
is possible to perform several replacements in parallel, using the
command expand-region-abbrevs
(see Controlling Abbrev Expansion).
15.10.1 Unconditional Replacement
- M-x replace-string RET string RET newstring RET
Replace every occurrence of string with newstring.
To replace every instance of ‘foo’ after point with ‘bar’,
use the command M-x replace-string with the two arguments
‘foo’ and ‘bar’. Replacement happens only in the text after
point, so if you want to cover the whole buffer you must go to the
beginning first. All occurrences up to the end of the buffer are
replaced; to limit replacement to part of the buffer, activate the
region around that part. When the region is active, replacement is
limited to the region (see The Mark and the Region).
When replace-string
exits, it leaves point at the last
occurrence replaced. It adds the prior position of point (where the
replace-string
command was issued) to the mark ring, without
activating the mark; use C-u C-SPC to move back there.
See The Mark Ring.
A prefix argument restricts replacement to matches that are
surrounded by word boundaries.
See Replace Commands and Lax Matches, for details about
case-sensitivity and character folding in replace commands.
15.10.2 Regexp Replacement
The M-x replace-string command replaces exact matches for a
single string. The similar command M-x replace-regexp replaces
any match for a specified regular expression pattern (see Syntax of Regular Expressions).
- M-x replace-regexp RET regexp RET newstring RET
Replace every match for regexp with newstring.
In replace-regexp
, the newstring need not be constant:
it can refer to all or part of what is matched by the regexp.
‘\&’ in newstring stands for the entire match being
replaced. ‘\d’ in newstring, where d is a
digit starting from 1, stands for whatever matched the dth
parenthesized grouping in regexp. (This is called a “back
reference”.) ‘\#’ refers to the count of replacements already
made in this command, as a decimal number. In the first replacement,
‘\#’ stands for ‘0’; in the second, for ‘1’; and so on.
For example,
M-x replace-regexp RET c[ad]+r RET \&-safe RET
replaces (for example) ‘cadr’ with ‘cadr-safe’ and ‘cddr’
with ‘cddr-safe’.
M-x replace-regexp RET \(c[ad]+r\)-safe RET \1 RET
performs the inverse transformation. To include a ‘\’ in the
text to replace with, you must enter ‘\\’.
If you want to enter part of the replacement string by hand each
time, use ‘\?’ in the replacement string. Each replacement will
ask you to edit the replacement string in the minibuffer, putting
point where the ‘\?’ was.
The remainder of this subsection is intended for specialized tasks
and requires knowledge of Lisp. Most readers can skip it.
You can use Lisp expressions to calculate parts of the
replacement string. To do this, write ‘\,’ followed by the
expression in the replacement string. Each replacement calculates the
value of the expression and converts it to text without quoting (if
it’s a string, this means using the string’s contents), and uses it in
the replacement string in place of the expression itself. If the
expression is a symbol, one space in the replacement string after the
symbol name goes with the symbol name, so the value replaces them
both.
Inside such an expression, you can use some special sequences.
‘\&’ and ‘\d’ refer here, as usual, to the entire
match as a string, and to a submatch as a string. d may be
multiple digits, and the value of ‘\d’ is nil
if the
d’th parenthesized grouping did not match. You can also use
‘\#&’ and ‘\#d’ to refer to those matches as numbers
(this is valid when the match or submatch has the form of a numeral).
‘\#’ here too stands for the number of already-completed
replacements.
For example, we can exchange ‘x’ and ‘y’ this way:
M-x replace-regexp RET \(x\)\|y RET
\,(if \1 "y" "x") RET
For computing replacement strings for ‘\,’, the format
function is often useful (see Formatting Strings in The Emacs
Lisp Reference Manual). For example, to add consecutively numbered
strings like ‘ABC00042’ to columns 73 to 80 (unless they are
already occupied), you can use
M-x replace-regexp RET ^.\{0,72\}$ RET
\,(format "%-72sABC%05d" \& \#) RET
15.10.3 Replace Commands and Lax Matches
This subsection describes the behavior of replace commands with
respect to lax matches (see Lax Matching During Searching) and how to customize it.
In general, replace commands mostly default to stricter matching than
their search counterparts.
Unlike incremental search, the replacement commands do not use lax
space matching (see lax space matching) by default.
To enable lax space matching for replacement, change the variable
replace-lax-whitespace
to non-nil
. (This only affects
how Emacs finds the text to replace, not the replacement text.)
A companion variable replace-regexp-lax-whitespace
controls
whether query-replace-regexp
uses lax whitespace matching when
searching for patterns.
If the first argument of a replace command is all lower case, the
command ignores case while searching for occurrences to
replace—provided case-fold-search
is non-nil
and
search-upper-case
is also non-nil
. If
search-upper-case
(see search-upper-case) is
nil
, whether searching ignores case is determined by
case-fold-search
alone, regardless of letter-case of the
command’s first argument. If case-fold-search
is set to
nil
, case is always significant in all searches.
In addition, when the newstring argument is all or partly lower
case, replacement commands try to preserve the case pattern of each
occurrence. Thus, the command
M-x replace-string RET foo RET bar RET
replaces a lower case ‘foo’ with a lower case ‘bar’, an
all-caps ‘FOO’ with ‘BAR’, and a capitalized ‘Foo’ with
‘Bar’. (These three alternatives—lower case, all caps, and
capitalized, are the only ones that replace-string
can
distinguish.)
If upper-case letters are used in the replacement string, they remain
upper case every time that text is inserted. If upper-case letters are
used in the first argument, the second argument is always substituted
exactly as given, with no case conversion. Likewise, if either
case-replace
or case-fold-search
is set to nil
,
replacement is done without case conversion.
The replacement commands by default do not use character folding
(see character folding) when looking for the text to
replace. To enable character folding for matching in
query-replace
and replace-string
, set the variable
replace-char-fold
to a non-nil
value. (This
setting does not affect the replacement text, only how Emacs finds the
text to replace. It also doesn’t affect replace-regexp
.)
15.10.4 Query Replace
- M-% string RET newstring RET
Replace some occurrences of string with newstring.
- C-M-% regexp RET newstring RET
Replace some matches for regexp with newstring.
If you want to change only some of the occurrences of ‘foo’ to
‘bar’, not all of them, use M-% (query-replace
).
This command finds occurrences of ‘foo’ one by one, displays each
occurrence and asks you whether to replace it. Aside from querying,
query-replace
works just like replace-string
(see Unconditional Replacement). In particular, it preserves case
provided case-replace
is non-nil
, as it normally is
(see Replace Commands and Lax Matches). A numeric argument means to
consider only occurrences that are bounded by word-delimiter
characters. A negative prefix argument replaces backward.
C-M-% performs regexp search and replace (query-replace-regexp
).
It works like replace-regexp
except that it queries
like query-replace
.
You can reuse earlier replacements with these commands. When
query-replace
or query-replace-regexp
prompts for the
search string, use M-p and M-n to show previous
replacements in the form ‘from -> to’, where
from is the search pattern, to is its replacement, and the
separator between them is determined by the value of the variable
query-replace-from-to-separator
. Type RET to select the
desired replacement. If the value of this variable is nil
,
replacements are not added to the command history, and cannot be
reused.
These commands highlight the current match using the face
query-replace
. You can disable this highlight by setting the
variable query-replace-highlight
to nil
. They highlight
other matches using lazy-highlight
just like incremental search
(see Incremental Search); this can be disabled by setting
query-replace-lazy-highlight
to nil
. By default,
query-replace-regexp
will show the substituted replacement
string for the current match in the minibuffer. If you want to keep
special sequences ‘\&’ and ‘\n’ unexpanded, customize
query-replace-show-replacement
variable.
Like search-highlight-submatches
highlights subexpressions in
incremental search (see Tailoring Search to Your Needs), the variable
query-replace-highlight-submatches
defines whether to highlight
subexpressions in the regexp replacement commands.
The variable query-replace-skip-read-only
, if set
non-nil
, will cause replacement commands to ignore matches in
read-only text. The default is not to ignore them.
The characters you can type when you are shown a match for the string
or regexp are:
- SPC
- y
to replace the occurrence with newstring.
- DEL
- Delete
- BACKSPACE
- n
to skip to the next occurrence without replacing this one.
- , (Comma)
to replace this occurrence and display the result. You are then asked
for another input character to say what to do next. Since the
replacement has already been made, DEL and SPC are
equivalent in this situation; both move to the next occurrence.
You can type C-r at this point (see below) to alter the replaced
text. You can also undo the replacement with the undo
command
(e.g., type C-x u; see Undo); this exits the
query-replace
, so if you want to do further replacement you
must use C-x ESC ESC RET to restart
(see Repeating Minibuffer Commands).
- RET
- q
to exit without doing any more replacements.
- . (Period)
to replace this occurrence and then exit without searching for more
occurrences.
- !
to replace all remaining occurrences without asking again.
- ^
to go back to the position of the previous occurrence (or what used to
be an occurrence), in case you changed it by mistake or want to
reexamine it.
- u
to undo the last replacement and go back to where that replacement was
made.
- U
to undo all the replacements and go back to where the first
replacement was made.
- C-r
to enter a recursive editing level, in case the occurrence needs to be
edited rather than just replaced with newstring. When you are
done, exit the recursive editing level with C-M-c to proceed to
the next occurrence. See Recursive Editing Levels.
- C-w
to delete the occurrence, and then enter a recursive editing level as in
C-r. Use the recursive edit to insert text to replace the deleted
occurrence of string. When done, exit the recursive editing level
with C-M-c to proceed to the next occurrence.
- e
- E
to edit the replacement string in the minibuffer. When you exit the
minibuffer by typing RET, the minibuffer contents replace the
current occurrence of the pattern. They also become the new
replacement string for any further occurrences.
- C-l
to redisplay the screen. Then you must type another character to
specify what to do with this occurrence.
- Y (Upper-case)
to replace all remaining occurrences in all remaining buffers in
multi-buffer replacements (like the Dired Q command that performs
query replace on selected files). It answers this question and all
subsequent questions in the series with “yes”, without further
user interaction.
- N (Upper-case)
to skip to the next buffer in multi-buffer replacements without
replacing remaining occurrences in the current buffer. It answers
this question “no”, gives up on the questions for the current buffer,
and continues to the next buffer in the sequence.
- C-h
- ?
- F1
to display a message summarizing these options. Then you must type
another character to specify what to do with this occurrence.
Aside from this, any other character exits the query-replace
,
and is then reread as part of a key sequence. Thus, if you type
C-k, it exits the query-replace
and then kills to end of
line. In particular, C-g simply exits the query-replace
.
To restart a query-replace
once it is exited, use C-x
ESC ESC, which repeats the query-replace
because it
used the minibuffer to read its arguments. See C-x ESC
ESC.
The option search-invisible
determines how query-replace
treats invisible text. See Outline Search.
See Operating on Files, for the Dired Q command which
performs query replace on selected files. See also Transforming File Names in Dired, for Dired commands to rename, copy, or link files by
replacing regexp matches in file names.
15.11 Other Search-and-Loop Commands
Here are some other commands that find matches for regular
expressions. They all ignore case in matching, if the pattern contains
no upper-case letters and case-fold-search
is non-nil
.
Aside from multi-occur
and multi-occur-in-matching-buffers
,
which always search the whole buffer, all of the commands operate on the
text from point to the end of the buffer, or on the region if it is active.
-
- M-x multi-isearch-buffers
Prompt for one or more buffer names, ending with RET; then,
begin a multi-buffer incremental search in those buffers. (If the
search fails in one buffer, the next C-s tries searching the
next specified buffer, and so forth.) With a prefix argument, prompt
for a regexp and begin a multi-buffer incremental search in buffers
matching that regexp.
- M-x multi-isearch-buffers-regexp
This command is just like multi-isearch-buffers
, except it
performs an incremental regexp search.
- M-x multi-isearch-files
Prompt for one or more file names, ending with RET; then,
begin a multi-file incremental search in those files. (If the
search fails in one file, the next C-s tries searching the
next specified file, and so forth.) With a prefix argument, prompt
for a regexp and begin a multi-file incremental search in files
matching that regexp.
- M-x multi-isearch-files-regexp
This command is just like multi-isearch-files
, except it
performs an incremental regexp search.
In some modes that set the buffer-local variable
multi-isearch-next-buffer-function
(e.g., in Change Log mode)
a multi-file incremental search is activated automatically.
- M-x occur
- M-s o
Prompt for a regexp, and display a list showing each line in the
buffer that contains a match for it. If you type M-n at the
prompt, you can reuse search strings from previous incremental
searches. The text that matched is highlighted using the match
face. A numeric argument n specifies that n lines of
context are to be displayed before and after each matching line.
The default number of context lines is specified by the variable
list-matching-lines-default-context-lines
. When
list-matching-lines-jump-to-current-line
is non-nil
the
current line is shown highlighted with face
list-matching-lines-current-line-face
and the point is set at
the first match after such line.
You can also run M-s o when an incremental search is active;
this uses the current search string.
Note that matches for the regexp you type are extended to include
complete lines, and a match that starts before the previous match ends
is not considered a match.
The *Occur* buffer uses the Occur mode as its major mode. You
can use the n and p keys to move to the next or previous
match; with prefix numeric argument, these commands move that many
matches. Digit keys are bound to digit-argument
, so 5 n
moves to the fifth next match (you don’t have to type C-u).
SPC and DEL scroll the *Occur* buffer up and down.
Clicking on a match or moving point there and typing RET visits
the corresponding position in the original buffer that was searched.
o and C-o display the match in another window; C-o
does not select that window. Alternatively, you can use the M-g
M-n (next-error
) command to visit the occurrences one by one
(see Compilation Mode). Finally, q quits the window showing
the *Occur* buffer and buries the buffer.
Typing e in the *Occur* buffer makes the buffer writable
and enters the Occur Edit mode, in which you can edit the matching
lines and have those edits reflected in the text in the originating
buffer. Type C-c C-c to leave the Occur Edit mode and return to
the Occur mode.
The command M-x list-matching-lines is a synonym for M-x
occur.
- M-x multi-occur
This command is just like occur
, except it is able to search
through multiple buffers. It asks you to specify the buffer names one
by one.
- M-x multi-occur-in-matching-buffers
This command is similar to multi-occur
, except the buffers to
search are specified by a regular expression that matches visited file
names. With a prefix argument, it uses the regular expression to
match buffer names instead.
- M-x how-many
Prompt for a regexp, and print the number of matches for it in the
buffer after point. If the region is active, this operates on the
region instead.
- M-x flush-lines
Prompt for a regexp, and delete each line that contains a match for
it, operating on the text after point. When the command finishes,
it prints the number of deleted matching lines.
This command deletes the current line if it contains a match starting
after point. If the region is active, it operates on the region
instead; if a line partially contained in the region contains a match
entirely contained in the region, it is deleted.
If a match is split across lines, flush-lines
deletes all those
lines. It deletes the lines before starting to look for the next
match; hence, it ignores a match starting on the same line at which
another match ended.
- M-x keep-lines
Prompt for a regexp, and delete each line that does not contain
a match for it, operating on the text after point. If point is not at
the beginning of a line, this command always keeps the current line.
If the region is active, the command operates on the region instead;
it never deletes lines that are only partially contained in the region
(a newline that ends a line counts as part of that line).
If a match is split across lines, this command keeps all those lines.
- M-x kill-matching-lines
Like flush-lines
, but also add the matching lines to the kill
ring. The command adds the matching lines to the kill ring as a
single string, including the newlines that separated the lines.
- M-x copy-matching-lines
Like kill-matching-lines
, but the matching lines are not
removed from the buffer.
15.12 Tailoring Search to Your Needs
This section describes miscellaneous search-related customizations
not described elsewhere.
The default search mode for the incremental search is specified by
the variable search-default-mode
. It can be nil
,
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 case-fold-search
and 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
using the isearch
face. This highlighting can be disabled by
setting the variable search-highlight
to nil
.
When searching for regular expressions (with C-M-s, for
instance), subexpressions receive special highlighting depending on
the search-highlight-submatches
variable. If this variable’s
value is nil
, no special highlighting is done, but if the value
is non-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
defined, named isearch-group-1
and isearch-group-2
.
With these two faces, odd-numbered subexpressions will be highlighted
using the 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-3
, isearch-group-4
, …, then the face
isearch-group-M
will be used to highlight the M’th,
N+M
’th, 2N+M
’th, …
subexpressions, where N is the total number of faces of the form
isearch-group-M
.
The other matches for the search string that are visible on display
are highlighted using the lazy-highlight
face. Setting the
variable isearch-lazy-highlight
to nil
disables this
highlighting. Here are some other variables that customize the lazy
highlighting:
lazy-highlight-initial-delay
¶
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.
lazy-highlight-no-delay-length
¶
For search strings at least as long as the value of this variable,
lazy highlighting of matches starts immediately.
lazy-highlight-interval
¶
Time in seconds between highlighting successive matches.
lazy-highlight-max-at-a-time
¶
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.
isearch-lazy-count
¶
Show the current match number and the total number of matches in the
search prompt.
lazy-count-prefix-format
¶
lazy-count-suffix-format
-
These two variables determine the format of showing the current and
the total number of matches for isearch-lazy-count
.
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
search-nonincremental-instead
to nil
, typing RET
will always exit the incremental search, even if the search string is
empty.
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
isearch-hide-immediately
to 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
of 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
value of search-slow-window-lines
.
16 Commands for Fixing Typos
In this chapter we describe commands that are useful when you catch
a mistake while editing. The most fundamental of these commands is
the undo command C-/ (also bound to C-x u and C-_).
This undoes a single command, or a
part of a command (as in the case of query-replace
), or several
consecutive character insertions. Consecutive repetitions of
C-/ undo earlier and earlier changes, back to the limit of the
undo information available.
Aside from the commands described here, you can erase text using
deletion commands such as DEL (delete-backward-char
).
These were described earlier in this manual. See Erasing Text.
16.1 Undo
The undo command reverses recent changes in the buffer’s text.
Each buffer records changes individually, and the undo command always
applies to the current buffer. You can undo all the changes in a
buffer for as far back as the buffer’s records go. Usually, each editing
command makes a separate entry in the undo records, but some commands
such as query-replace
divide their changes into multiple
entries for flexibility in undoing. Consecutive character insertion
commands are usually grouped together into a single undo record, to
make undoing less tedious.
- C-/
- C-x u
- C-_
Undo one entry in the current buffer’s undo records (undo
).
To begin to undo, type C-/ (or its aliases, C-_ or
C-x u)6. This undoes the most recent change in the buffer,
and moves point back to where it was before that change.
Consecutive repetitions of C-/ (or its aliases) undo earlier
and earlier changes in the current buffer. If all the recorded
changes have already been undone, the undo command signals an error.
Any command other than an undo command breaks the sequence of undo
commands. Starting from that moment, the entire sequence of undo
commands that you have just performed are themselves placed into the
undo record. Therefore, to re-apply changes you have undone, type
C-f or any other command that harmlessly breaks the sequence of
undoing; then type C-/ one or more times to undo some of the
undo commands.
Alternatively, if you want to resume undoing, without redoing
previous undo commands, use M-x undo-only. This is like
undo
, but will not redo changes you have just undone. To
complement it, M-x undo-redo will undo previous undo commands
(and will not record itself as an undoable command).
If you notice that a buffer has been modified accidentally, the
easiest way to recover is to type C-/ repeatedly until the stars
disappear from the front of the mode line (see The Mode Line).
Whenever an undo command makes the stars disappear from the mode line,
it means that the buffer contents are the same as they were when the
file was last read in or saved. If you do not remember whether you
changed the buffer deliberately, type C-/ once. When you see
the last change you made undone, you will see whether it was an
intentional change. If it was an accident, leave it undone. If it
was deliberate, redo the change as described above.
Alternatively, you can discard all the changes since the buffer was
last visited or saved with M-x revert-buffer
(see Reverting a Buffer).
When there is an active region, any use of undo
performs
selective undo: it undoes the most recent change within the
region, instead of the entire buffer. However, when Transient Mark
mode is off (see Disabling Transient Mark Mode), C-/ always
operates on the entire buffer, ignoring the region. In this case, you
can perform selective undo by supplying a prefix argument to the
undo
command: C-u C-/. To undo further changes in the
same region, repeat the undo
command (no prefix argument is
needed).
Some specialized buffers do not make undo records. Buffers whose
names start with spaces never do; these buffers are used internally by
Emacs to hold text that users don’t normally look at or edit.
When the undo information for a buffer becomes too large, Emacs discards
the oldest records from time to time (during garbage
collection). You can specify how much undo information to keep by
setting the variables undo-limit
, undo-strong-limit
, and
undo-outer-limit
. Their values are expressed in bytes.
The variable undo-limit
sets a soft limit: Emacs keeps undo
data for enough commands to reach this size, and perhaps exceed it,
but does not keep data for any earlier commands beyond that. Its
default value is 160000. The variable undo-strong-limit
sets a
stricter limit: any previous command (though not the most recent one)
that pushes the size past this amount is forgotten. The default value
of undo-strong-limit
is 240000.
Regardless of the values of those variables, the most recent change
is never discarded unless it gets bigger than undo-outer-limit
(normally 24,000,000). At that point, Emacs discards the undo data and
warns you about it. This is the only situation in which you cannot
undo the last command. If this happens, you can increase the value of
undo-outer-limit
to make it even less likely to happen in the
future. But if you didn’t expect the command to create such large
undo data, then it is probably a bug and you should report it.
See Reporting Bugs.
16.2 Transposing Text
- C-t
Transpose two characters (transpose-chars
).
- M-t
Transpose two words (transpose-words
).
- C-M-t
Transpose two balanced expressions (transpose-sexps
).
- C-x C-t
Transpose two lines (transpose-lines
).
- M-x transpose-sentences
Transpose two sentences (transpose-sentences
).
- M-x transpose-paragraphs
Transpose two paragraphs (transpose-paragraphs
).
- M-x transpose-regions
Transpose two regions.
The common error of transposing two characters can be fixed, when they
are adjacent, with the C-t command (transpose-chars
). Normally,
C-t transposes the two characters on either side of point. When
given at the end of a line, rather than transposing the last character of
the line with the newline, which would be useless, C-t transposes the
last two characters on the line. So, if you catch your transposition error
right away, you can fix it with just a C-t. If you don’t catch it so
fast, you must move the cursor back between the two transposed
characters before you type C-t. If you transposed a space with
the last character of the word before it, the word motion commands
(M-f, M-b, etc.) are a good way of getting there.
Otherwise, a reverse search (C-r) is often the best way.
See Searching and Replacement.
M-t transposes the word before point with the word after point
(transpose-words
). It moves point forward over a word,
dragging the word preceding or containing point forward as well. The
punctuation characters between the words do not move. For example,
‘FOO, BAR’ transposes into ‘BAR, FOO’ rather than
‘BAR FOO,’. When point is at the end of the line, it will
transpose the word before point with the first word on the next line.
C-M-t (transpose-sexps
) is a similar command for
transposing two expressions (see Expressions with Balanced Parentheses), and C-x C-t
(transpose-lines
) exchanges lines. M-x
transpose-sentences and M-x transpose-paragraphs transpose
sentences and paragraphs, respectively. These commands work like
M-t except as regards the units of text they transpose.
A numeric argument to a transpose command serves as a repeat count: it
tells the transpose command to move the character (or word or
expression or line) before or containing point across several other
characters (or words or expressions or lines). For example, C-u 3 C-t moves the character before point forward across three other
characters. It would change ‘f∗oobar’ into
‘oobf∗ar’. This is equivalent to repeating C-t
three times. C-u - 4 M-t moves the word before point backward
across four words. C-u - C-M-t would cancel the effect of plain
C-M-t.
A numeric argument of zero is assigned a special meaning (because
otherwise a command with a repeat count of zero would do nothing): to
transpose the character (or word or expression or line) ending after
point with the one ending after the mark.
M-x transpose-regions transposes the text between point and
mark with the text between the last two marks pushed to the mark ring
(see Setting the Mark). With a numeric prefix argument, it transposes
the text between point and mark with the text between two successive
marks that many entries back in the mark ring. This command is best
used for transposing multiple characters (or words or sentences or
paragraphs) in one go.
16.3 Case Conversion
- M-- M-l
Convert last word to lower case. Note Meta-- is Meta-minus.
- M-- M-u
Convert last word to all upper case.
- M-- M-c
Convert last word to lower case with capital initial.
A very common error is to type words in the wrong case. Because of this,
the word case-conversion commands M-l, M-u, and M-c have a
special feature when used with a negative argument: they do not move the
cursor. As soon as you see you have mistyped the last word, you can simply
case-convert it and go on typing. See Case Conversion Commands.
16.4 Checking and Correcting Spelling
This section describes the commands to check the spelling of a
single word or of a portion of a buffer. These commands only work if
a spelling checker program, one of Hunspell, Aspell, Ispell or
Enchant, is installed. These programs are not part of Emacs, but one
of them is usually installed on GNU/Linux and other free operating
systems.
See Aspell in The Aspell Manual.
If you have only one of the spelling checker programs installed,
Emacs will find it when you invoke for the first time one of the
commands described here. If you have more than one of them installed,
you can control which one is used by customizing the variable
ispell-program-name
.
- M-$
Check and correct spelling of the word at point (ispell-word
).
If the region is active, do it for all words in the region instead.
- M-x ispell
Check and correct spelling of all words in the buffer. If the region
is active, do it for all words in the region instead.
- M-x ispell-buffer
Check and correct spelling in the buffer.
- M-x ispell-region
Check and correct spelling in the region.
- M-x ispell-message
Check and correct spelling in a draft mail message, excluding cited
material.
- M-x ispell-comments-and-strings
Check and correct spelling of comments and strings in the buffer or region.
- M-x ispell-comment-or-string-at-point
Check the comment or string at point.
- M-x ispell-change-dictionary RET dict RET
Restart the spell-checker process, using dict as the dictionary.
- M-x ispell-kill-ispell
Kill the spell-checker subprocess.
- M-TAB
- ESC TAB
- C-M-i
Complete the word before point based on the spelling dictionary
(ispell-complete-word
).
- M-x flyspell-mode
Enable Flyspell mode, which highlights all misspelled words.
- M-x flyspell-prog-mode
Enable Flyspell mode for comments and strings only.
To check the spelling of the word around or before point, and
optionally correct it as well, type M-$ (ispell-word
).
If a region is active, M-$ checks the spelling of all words
within the region. See The Mark and the Region. (When Transient Mark mode is off,
M-$ always acts on the word around or before point, ignoring the
region; see Disabling Transient Mark Mode.)
Similarly, the command M-x ispell performs spell-checking in
the region if one is active, or in the entire buffer otherwise. The
commands M-x ispell-buffer and M-x ispell-region
explicitly perform spell-checking on the entire buffer or the region
respectively. To check spelling in an email message you are writing,
use M-x ispell-message; that command checks the whole buffer,
except for material that is indented or appears to be cited from other
messages. See Sending Mail. When dealing with source code, you
can use M-x ispell-comments-and-strings or M-x ispell-comment-or-string-at-point to check only comments or string
literals.
When one of these commands encounters what appears to be an
incorrect word, it asks you what to do. It usually displays a list of
numbered near-misses—words that are close to the incorrect word.
Then you must type a single-character response. Here are the valid
responses:
- digit
Replace the word, just this time, with one of the displayed
near-misses. Each near-miss is listed with a digit; type that digit
to select it.
- SPC
Skip this word—continue to consider it incorrect, but don’t change it
here.
- r new RET
Replace the word, just this time, with new. (The replacement
string will be rescanned for more spelling errors.)
- R new RET
Replace the word with new, and do a query-replace
so you
can replace it elsewhere in the buffer if you wish. (The replacements
will be rescanned for more spelling errors.)
- a
Accept the incorrect word—treat it as correct, but only in this
editing session.
- A
Accept the incorrect word—treat it as correct, but only in this
editing session and for this buffer.
- i
Insert this word in your private dictionary file so that it will be
considered correct from now on, even in future sessions.
- m
Like i, but you can also specify dictionary completion
information.
- u
Insert the lower-case version of this word in your private dictionary
file.
- l word RET
Look in the dictionary for words that match word. These words
become the new list of near-misses; you can select one of them as
the replacement by typing a digit. You can use ‘*’ in word as a
wildcard.
- C-g
- X
Quit interactive spell-checking, leaving point at the word that was
being checked. You can restart checking again afterward with C-u M-$.
- x
Quit interactive spell-checking and move point back to where it was
when you started spell-checking.
- q
Quit interactive spell-checking and kill the spell-checker subprocess.
- ?
Show the list of options.
In Text mode and related modes, M-TAB
(ispell-complete-word
) performs in-buffer completion based on
spelling correction. Insert the beginning of a word, and then type
M-TAB; this shows a list of completions. (If your
window manager intercepts M-TAB, type ESC TAB or C-M-i.) Each completion is listed with a digit or
character; type that digit or character to choose it.
Once started, the spell-checker subprocess continues
to run, waiting for something to do, so that subsequent spell-checking
commands complete more quickly. If you want to get rid of the
process, use M-x ispell-kill-ispell. This is not usually
necessary, since the process uses no processor time except when you do
spelling correction.
Spell-checkers look up spelling in two dictionaries:
the standard dictionary and your personal dictionary. The standard
dictionary is specified by the variable ispell-local-dictionary
or, if that is nil
, by the variable ispell-dictionary
.
If both are nil
, the spelling program’s default dictionary is
used. The command M-x ispell-change-dictionary sets the
standard dictionary for the buffer and then restarts the subprocess,
so that it will use a different standard dictionary. Your personal
dictionary is specified by the variable
ispell-personal-dictionary
. If that is nil
, the
spelling program looks for a personal dictionary in a default
location, which is specific to each spell-checker.
A separate dictionary is used for word completion. The variable
ispell-complete-word-dict
specifies the file name of this
dictionary. The completion dictionary must be different because it
cannot use the information about roots and affixes of the words, which
spell-checking uses to detect variations of words. For some
languages, there is a spell-checking dictionary but no word completion
dictionary.
Flyspell mode is a minor mode that performs automatic spell-checking
of the text you type as you type it. When it finds a word that it
does not recognize, it highlights that word. Type M-x flyspell-mode to toggle Flyspell mode in the current buffer. To
enable Flyspell mode in all text mode buffers, add
flyspell-mode
to text-mode-hook
. See Hooks. Note
that, as Flyspell mode needs to check each word across which you move,
it will slow down cursor motion and scrolling commands. It also
doesn’t automatically check the text you didn’t type or move across;
use flyspell-region
or flyspell-buffer
for that.
When Flyspell mode highlights a word as misspelled, you can click on
it with mouse-2 (flyspell-correct-word
) to display a menu
of possible corrections and actions. If you want this menu on
mouse-3 instead, enable context-menu-mode
. In addition,
C-. or ESC TAB (flyspell-auto-correct-word
)
will propose various successive corrections for the word at point, and
C-c $ (flyspell-correct-word-before-point
) will pop
up a menu of possible corrections. Of course, you can always correct
the misspelled word by editing it manually in any way you like.
Flyspell Prog mode works just like ordinary Flyspell mode, except
that it only checks words in comments and string constants. This
feature is useful for editing programs. Type M-x flyspell-prog-mode to enable or disable this mode in the current
buffer. To enable this mode in all programming mode buffers, add
flyspell-prog-mode
to prog-mode-hook
(see Hooks).
17 Keyboard Macros
In this chapter we describe how to record a sequence of editing
commands so you can repeat it conveniently later.
A keyboard macro is a command defined by an Emacs user to stand for
another sequence of keys. For example, if you discover that you are
about to type C-n M-d C-d forty times, you can speed your work by
defining a keyboard macro to do C-n M-d C-d, and then executing
it 39 more times.
You define a keyboard macro by executing and recording the commands
which are its definition. Put differently, as you define a keyboard
macro, the definition is being executed for the first time. This way,
you can see the effects of your commands, so that you don’t have to
figure them out in your head. When you close the definition, the
keyboard macro is defined and also has been, in effect, executed once.
You can then do the whole thing over again by invoking the macro.
Keyboard macros differ from ordinary Emacs commands in that they are
written in the Emacs command language rather than in Lisp. This makes it
easier for the novice to write them, and makes them more convenient as
temporary hacks. However, the Emacs command language is not powerful
enough as a programming language to be useful for writing anything
intelligent or general. For such things, Lisp must be used.
17.1 Basic Use
- F3
Start defining a keyboard macro
(kmacro-start-macro-or-insert-counter
).
- F4
If a keyboard macro is being defined, end the definition; otherwise,
execute the most recent keyboard macro
(kmacro-end-or-call-macro
).
- C-u F3
Re-execute last keyboard macro, then append keys to its definition.
- C-u C-u F3
Append keys to the last keyboard macro without re-executing it.
- C-x C-k r
Run the last keyboard macro on each line that begins in the region
(apply-macro-to-region-lines
).
- C-x (
Start defining a keyboard macro (old style)
(kmacro-start-macro
); with a prefix argument, append keys to
the last macro.
- C-x )
End a macro definition (old style) (kmacro-end-macro
); prefix
argument serves as the repeat count for executing the macro.
- C-x e
Execute the most recently defined keyboard macro
(kmacro-end-and-call-macro
); prefix argument serves as repeat
count.
To start defining a keyboard macro, type F3. From then on,
your keys continue to be executed, but also become part of the
definition of the macro. ‘Def’ appears in the mode line to
remind you of what is going on. When you are finished, type F4
(kmacro-end-or-call-macro
) to terminate the definition. For
example,
defines a macro to move forward a word and then insert ‘foo’.
Note that F3 and F4 do not become part of the macro.
After defining the macro, you can call it with F4. For the
above example, this has the same effect as typing M-f foo again.
(Note the two roles of the F4 command: it ends the macro if you
are in the process of defining one, or calls the last macro
otherwise.) You can also supply F4 with a numeric prefix
argument ‘n’, which means to invoke the macro ‘n’ times. An
argument of zero repeats the macro indefinitely, until it gets an
error or you type C-g (or, on MS-DOS, C-Break).
The above example demonstrates a handy trick that you can employ
with keyboard macros: if you wish to repeat an operation at regularly
spaced places in the text, include a motion command as part of the
macro. In this case, repeating the macro inserts the string
‘foo’ after each successive word.
After terminating the definition of a keyboard macro, you can append
more keystrokes to its definition by typing C-u F3. This
is equivalent to plain F3 followed by retyping the whole
definition so far. As a consequence, it re-executes the macro as
previously defined. If you change the variable
kmacro-execute-before-append
to nil
, the existing macro
will not be re-executed before appending to it (the default is
t
). You can also add to the end of the definition of the last
keyboard macro without re-executing it by typing C-u C-u
F3.
When a command reads an argument with the minibuffer, your
minibuffer input becomes part of the macro along with the command. So
when you replay the macro, the command gets the same argument as when
you entered the macro. For example,
F3 C-a C-k C-x b foo RET C-y C-x b RET F4
defines a macro that kills the current line, yanks it into the buffer
‘foo’, then returns to the original buffer.
Most keyboard commands work as usual in a keyboard macro definition,
with some exceptions. Typing C-g (keyboard-quit
) quits
the keyboard macro definition. Typing C-M-c
(exit-recursive-edit
) can be unreliable: it works as you’d
expect if exiting a recursive edit that started within the macro, but
if it exits a recursive edit that started before you invoked the
keyboard macro, it also necessarily exits the keyboard macro too.
Mouse events are also unreliable, even though you can use them in a
keyboard macro: when the macro replays the mouse event, it uses the
original mouse position of that event, the position that the mouse had
while you were defining the macro. The effect of this may be hard to
predict.
The command C-x C-k r (apply-macro-to-region-lines
)
repeats the last defined keyboard macro on each line that begins in
the region. It does this line by line, by moving point to the
beginning of the line and then executing the macro.
In addition to the F3 and F4 commands described above,
Emacs also supports an older set of key bindings for defining and
executing keyboard macros. To begin a macro definition, type C-x
( (kmacro-start-macro
); as with F3, a prefix argument
appends this definition to the last keyboard macro. To end a macro
definition, type C-x ) (kmacro-end-macro
). To execute
the most recent macro, type C-x e
(kmacro-end-and-call-macro
). If you enter C-x e while
defining a macro, the macro is terminated and executed immediately.
Immediately after typing C-x e, you can type e repeatedly
to immediately repeat the macro one or more times. You can also give
C-x e a repeat argument, just like F4 (when it is used to
execute a macro).
C-x ) can be given a repeat count as an argument. This means
to repeat the macro right after defining it. The macro definition
itself counts as the first repetition, since it is executed as you
define it, so C-u 4 C-x ) executes the macro immediately 3
additional times.
While executing a long-running keyboard macro, it can sometimes be
useful to trigger a redisplay (to show how far we’ve gotten). The
C-x C-k d command can be used for this. As a not very useful
example, C-x ( M-f C-x C-k d C-x ) will create a macro that will
redisplay once per iteration when saying C-u 42 C-x e.
17.2 The Keyboard Macro Ring
All defined keyboard macros are recorded in the keyboard macro
ring. There is only one keyboard macro ring, shared by all buffers.
- C-x C-k C-k
Execute the keyboard macro at the head of the ring (kmacro-end-or-call-macro-repeat
).
- C-x C-k C-n
Rotate the keyboard macro ring to the next macro (defined earlier)
(kmacro-cycle-ring-next
).
- C-x C-k C-p
Rotate the keyboard macro ring to the previous macro (defined later)
(kmacro-cycle-ring-previous
).
All commands which operate on the keyboard macro ring use the
same C-x C-k prefix. Most of these commands can be executed and
repeated immediately after each other without repeating the C-x
C-k prefix. For example,
C-x C-k C-p C-p C-k C-k C-k C-n C-n C-k C-p C-k C-d
will rotate the keyboard macro ring to the second-previous macro,
execute the resulting head macro three times, rotate back to the
original head macro, execute that once, rotate to the previous
macro, execute that, and finally delete it from the macro ring.
The command C-x C-k C-k (kmacro-end-or-call-macro-repeat
)
executes the keyboard macro at the head of the macro ring. You can
repeat the macro immediately by typing another C-k, or you can
rotate the macro ring immediately by typing C-n or C-p.
When a keyboard macro is being defined, C-x C-k C-k behaves
like F4 except that, immediately afterward, you can use most key
bindings of this section without the C-x C-k prefix. For
instance, another C-k will re-execute the macro.
The commands C-x C-k C-n (kmacro-cycle-ring-next
) and
C-x C-k C-p (kmacro-cycle-ring-previous
) rotate the
macro ring, bringing the next or previous keyboard macro to the head
of the macro ring. The definition of the new head macro is displayed
in the echo area. You can continue to rotate the macro ring
immediately by repeating just C-n and C-p until the
desired macro is at the head of the ring. To execute the new macro
ring head immediately, just type C-k.
Note that Emacs treats the head of the macro ring as the last
defined keyboard macro. For instance, F4 will execute that
macro, and C-x C-k n will give it a name.
The maximum number of macros stored in the keyboard macro ring is
determined by the customizable variable kmacro-ring-max
.
17.3 The Keyboard Macro Counter
Each keyboard macro has an associated counter, which is initialized
to 0 when you start defining the macro. This current counter
allows you to insert a number into the buffer that depends on the
number of times the macro has been called. The counter is normally
incremented each time its value is inserted into the buffer.
In addition to the current counter, keyboard macros also maintain the
previous counter, which records the value the current counter
had last time it was incremented or set. Note that incrementing the
current counter by zero, e.g., with C-u 0 C-x C-k C-i, also
records the value of the current counter as the previous counter
value.
- F3
In a keyboard macro definition, insert the keyboard macro counter
value in the buffer (kmacro-start-macro-or-insert-counter
).
- C-x C-k C-i
Insert the keyboard macro counter value in the buffer
(kmacro-insert-counter
).
- C-x C-k C-c
Set the keyboard macro counter (kmacro-set-counter
).
- C-x C-k C-a
Add the prefix arg to the keyboard macro counter (kmacro-add-counter
).
- C-x C-k C-f
Specify the format for inserting the keyboard macro counter
(kmacro-set-format
).
When you are defining a keyboard macro, the command F3
(kmacro-start-macro-or-insert-counter
) inserts the current
value of the keyboard macro’s counter into the buffer, and increments
the counter by 1. (If you are not defining a macro, F3 begins a
macro definition instead. See Basic Use.) You can use
a numeric prefix argument to specify a different increment. If you
just specify a C-u prefix, that inserts the previous counter
value, and doesn’t change the current value.
As an example, let us show how the keyboard macro counter can be
used to build a numbered list. Consider the following key sequence:
As part of this keyboard macro definition, the string ‘0. ’ was
inserted into the beginning of the current line. If you now move
somewhere else in the buffer and type F4 to invoke the macro,
the string ‘1. ’ is inserted at the beginning of that line.
Subsequent invocations insert ‘2. ’, ‘3. ’, and so forth.
The command C-x C-k C-i (kmacro-insert-counter
) does
the same thing as F3, but it can be used outside a keyboard
macro definition. When no keyboard macro is being defined or
executed, it inserts and increments the counter of the macro at the
head of the keyboard macro ring.
The command C-x C-k C-c (kmacro-set-counter
) sets the
current macro counter to the value of the numeric argument. If you use
it inside the macro, it operates on each repetition of the macro. If
you specify just C-u as the prefix, while executing the macro,
that resets the counter to the value it had at the beginning of the
current repetition of the macro (undoing any increments so far in this
repetition).
The command C-x C-k C-a (kmacro-add-counter
) adds the
prefix argument to the current macro counter. With just C-u as
argument, it resets the counter to the last value inserted by any
keyboard macro. (Normally, when you use this, the last insertion
will be in the same macro and it will be the same counter.)
The command C-x C-k C-f (kmacro-set-format
) prompts for
the format to use when inserting the macro counter. The default
format is ‘%d’, which means to insert the number in decimal
without any padding. You can exit with empty minibuffer to reset the
format to this default. You can specify any format string that the
format
function accepts and that makes sense with a single
integer extra argument (see Formatting Strings in The Emacs
Lisp Reference Manual). Do not put the format string inside double
quotes when you insert it in the minibuffer.
If you use this command while no keyboard macro is being defined or
executed, the new format affects all subsequent macro definitions.
Existing macros continue to use the format in effect when they were
defined. If you set the format while defining a keyboard macro, this
affects the macro being defined from that point on, but it does not
affect subsequent macros. Execution of the macro will, at each step,
use the format in effect at that step during its definition. Changes
to the macro format during execution of a macro, like the
corresponding changes during its definition, have no effect on
subsequent macros.
The format set by C-x C-k C-f does not affect insertion of
numbers stored in registers.
If you use a register as a counter, incrementing it on each
repetition of the macro, that accomplishes the same thing as a
keyboard macro counter. See Keeping Numbers in Registers. For most purposes,
it is simpler to use a keyboard macro counter.
17.4 Executing Macros with Variations
In a keyboard macro, you can create an effect similar to that of
query-replace
, in that the macro asks you each time around
whether to make a change.
- C-x q
When this point is reached during macro execution, ask for confirmation
(kbd-macro-query
).
While defining the macro, type C-x q at the point where you
want the query to occur. During macro definition, the C-x q
does nothing, but when you run the macro later, C-x q asks you
interactively whether to continue.
The valid responses when C-x q asks are:
- SPC (or y)
Continue executing the keyboard macro.
- DEL (or n)
Skip the remainder of this repetition of the macro, and start right
away with the next repetition.
- RET (or q)
Skip the remainder of this repetition and cancel further repetitions.
- C-r
Enter a recursive editing level, in which you can perform editing
which is not part of the macro. When you exit the recursive edit
using C-M-c, you are asked again how to continue with the
keyboard macro. If you type a SPC at this time, the rest of the
macro definition is executed. It is up to you to leave point and the
text in a state such that the rest of the macro will do what you want.
C-u C-x q, which is C-x q with a prefix argument,
performs a completely different function. It enters a recursive edit
reading input from the keyboard, both when you type it during the
definition of the macro, and when it is executed from the macro. During
definition, the editing you do inside the recursive edit does not become
part of the macro. During macro execution, the recursive edit gives you
a chance to do some particularized editing on each repetition.
See Recursive Editing Levels.
17.5 Naming and Saving Keyboard Macros
- C-x C-k n
Give a command name (for the duration of the Emacs session) to the most
recently defined keyboard macro (kmacro-name-last-macro
).
- C-x C-k b
Bind the most recently defined keyboard macro to a key sequence (for
the duration of the session) (kmacro-bind-to-key
).
- M-x insert-kbd-macro
Insert in the buffer a keyboard macro’s definition, as Lisp code.
If you wish to save a keyboard macro for later use, you can give it
a name using C-x C-k n (kmacro-name-last-macro
).
This reads a name as an argument using the minibuffer and defines that
name to execute the last keyboard macro, in its current form. (If you
later add to the definition of this macro, that does not alter the
name’s definition as a macro.) The macro name is a Lisp symbol, and
defining it in this way makes it a valid command name for calling with
M-x or for binding a key to with global-set-key
(see Keymaps). If you specify a name that has a prior definition
other than a keyboard macro, an error message is shown and nothing is
changed.
You can also bind the last keyboard macro (in its current form) to a
key, using C-x C-k b (kmacro-bind-to-key
) followed by the
key sequence you want to bind. You can bind to any key sequence in
the global keymap, but since most key sequences already have other
bindings, you should select the key sequence carefully. If you try to
bind to a key sequence with an existing binding (in any keymap), this
command asks you for confirmation before replacing the existing binding.
To avoid problems caused by overriding existing bindings, the key
sequences C-x C-k 0 through C-x C-k 9 and C-x C-k A
through C-x C-k Z are reserved for your own keyboard macro
bindings. In fact, to bind to one of these key sequences, you only
need to type the digit or letter rather than the whole key sequences.
For example,
will bind the last keyboard macro to the key sequence C-x C-k 4.
Once a macro has a command name, you can save its definition in a file.
Then it can be used in another editing session. First, visit the file
you want to save the definition in. Then use this command:
M-x insert-kbd-macro RET macroname RET
This inserts some Lisp code that, when executed later, will define the
same macro with the same definition it has now. (You don’t need to
understand Lisp code to do this, because insert-kbd-macro
writes
the Lisp code for you.) Then save the file. You can load the file
later with load-file
(see Libraries of Lisp Code for Emacs). If the file you
save in is your init file ~/.emacs (see The Emacs Initialization File) then the
macro will be defined each time you run Emacs.
If you give insert-kbd-macro
a prefix argument, it makes
additional Lisp code to record the keys (if any) that you have bound
to macroname, so that the macro will be reassigned the same keys
when you load the file.
17.6 Editing a Keyboard Macro
- C-x C-k C-e
Edit the last defined keyboard macro (kmacro-edit-macro
).
- C-x C-k e name RET
Edit a previously defined keyboard macro name (edit-kbd-macro
).
- C-x C-k l
Edit the last 300 keystrokes as a keyboard macro
(kmacro-edit-lossage
).
You can edit the last keyboard macro by typing C-x C-k C-e or
C-x C-k RET (kmacro-edit-macro
). This formats the
macro definition in a buffer and enters a specialized major mode for
editing it. Type C-h m once in that buffer to display details
of how to edit the macro. When you are finished editing, type
C-c C-c.
You can edit a named keyboard macro or a macro bound to a key by typing
C-x C-k e (edit-kbd-macro
). Follow that with the
keyboard input that you would use to invoke the macro—C-x e or
M-x name or some other key sequence.
You can edit the last 300 keystrokes as a macro by typing
C-x C-k l (kmacro-edit-lossage
).
17.7 Stepwise Editing a Keyboard Macro
You can interactively replay and edit the last keyboard
macro, one command at a time, by typing C-x C-k SPC
(kmacro-step-edit-macro
). Unless you quit the macro using
q or C-g, the edited macro replaces the last macro on the
macro ring.
This macro editing feature shows the last macro in the minibuffer
together with the first (or next) command to be executed, and prompts
you for an action. You can enter ? to get a summary of your
options. These actions are available:
- SPC and y execute the current command, and advance to the
next command in the keyboard macro.
- n, d, and DEL skip and delete the current command.
- f skips the current command in this execution of the keyboard
macro, but doesn’t delete it from the macro.
- TAB executes the current command, as well as all similar
commands immediately following the current command; for example, TAB
may be used to insert a sequence of characters (corresponding to a
sequence of
self-insert-command
commands).
- c continues execution (without further editing) until the end of
the keyboard macro. If execution terminates normally, the edited
macro replaces the original keyboard macro.
- C-k skips and deletes the rest of the keyboard macro,
terminates step-editing, and replaces the original keyboard macro
with the edited macro.
- q and C-g cancels the step-editing of the keyboard macro;
discarding any changes made to the keyboard macro.
- i key… C-j reads and executes a series of key sequences (not
including the final C-j), and inserts them before the current
command in the keyboard macro, without advancing over the current
command.
- I key… reads one key sequence, executes it, and inserts it
before the current command in the keyboard macro, without advancing
over the current command.
- r key… C-j reads and executes a series of key sequences (not
including the final C-j), and replaces the current command in
the keyboard macro with them, advancing over the inserted key
sequences.
- R key… reads one key sequence, executes it, and replaces the
current command in the keyboard macro with that key sequence,
advancing over the inserted key sequence.
- a key… C-j executes the current command, then reads and
executes a series of key sequences (not including the final
C-j), and inserts them after the current command in the keyboard
macro; it then advances over the current command and the inserted key
sequences.
- A key… C-j executes the rest of the commands in the keyboard
macro, then reads and executes a series of key sequences (not
including the final C-j), and appends them at the end of the
keyboard macro; it then terminates the step-editing and replaces the
original keyboard macro with the edited macro.
18 File Handling
The operating system stores data permanently in named files, so
most of the text you edit with Emacs comes from a file and is ultimately
stored in a file.
To edit a file, you must tell Emacs to read the file and prepare a
buffer containing a copy of the file’s text. This is called
visiting the file. Editing commands apply directly to text in the
buffer; that is, to the copy inside Emacs. Your changes appear in the
file itself only when you save the buffer back into the file.
In addition to visiting and saving files, Emacs can delete, copy,
rename, and append to files, keep multiple versions of them, and operate
on file directories.
18.1 File Names
Many Emacs commands that operate on a file require you to specify
the file name, using the minibuffer (see Minibuffers for File Names).
While in the minibuffer, you can use the usual completion and
history commands (see The Minibuffer). Note that file name completion
ignores file names whose extensions appear in the variable
completion-ignored-extensions
(see Completion Options).
Note also that most commands use permissive completion with
confirmation for reading file names: you are allowed to submit a
nonexistent file name, but if you type RET immediately after
completing up to a nonexistent file name, Emacs prints
‘[Confirm]’ and you must type a second RET to confirm.
See Completion Exit, for details.
Minibuffer history commands offer some special features for reading
file names, see Minibuffer History.
Each buffer has a default directory, stored in the
buffer-local variable default-directory
. Whenever Emacs reads
a file name using the minibuffer, it usually inserts the default
directory into the minibuffer as the initial contents. You can
inhibit this insertion by changing the variable
insert-default-directory
to nil
(see Minibuffers for File Names). Regardless, Emacs always assumes that any relative file name
is relative to the default directory, e.g., entering a file name
without a directory specifies a file in the default directory.
When you visit a file, Emacs sets default-directory
in the
visiting buffer to the directory of its file. When you create a new
buffer that is not visiting a file, via a command like C-x b,
its default directory is usually copied from the buffer that was
current at the time (see Creating and Selecting Buffers). You can use the command
M-x pwd to see the value of default-directory
in the
current buffer. The command M-x cd prompts for a directory’s
name, and sets the buffer’s default-directory
to that directory
(doing this does not change the buffer’s file name, if any).
As an example, when you visit the file /u/rms/gnu/gnu.tasks,
the default directory is set to /u/rms/gnu/. If you invoke a
command that reads a file name, entering just ‘foo’ in the
minibuffer, with a directory omitted, specifies the file
/u/rms/gnu/foo; entering ‘../.login’ specifies
/u/rms/.login; and entering ‘new/foo’ specifies
/u/rms/gnu/new/foo.
When typing a file name into the minibuffer, you can make use of a
couple of shortcuts: a double slash ignores everything before the
second slash in the pair, and ‘~/’ is your home directory.
See Minibuffers for File Names.
The character ‘$’ is used to
substitute an environment variable into a file name. The name of the
environment variable consists of all the alphanumeric characters after
the ‘$’; alternatively, it can be enclosed in braces after the
‘$’. For example, if you have used the shell command
export FOO=rms/hacks
to set up an environment variable named
FOO
, then both /u/$FOO/test.c and
/u/${FOO}/test.c are abbreviations for
/u/rms/hacks/test.c. If the environment variable is not
defined, no substitution occurs, so that the character ‘$’ stands
for itself. Note that environment variables set outside Emacs affect
Emacs only if they are applied before Emacs is started.
To access a file with ‘$’ in its name, if the ‘$’ causes
expansion, type ‘$$’. This pair is converted to a single
‘$’ at the same time that variable substitution is performed for
a single ‘$’. Alternatively, quote the whole file name with
‘/:’ (see Quoted File Names). File names which begin with a
literal ‘~’ should also be quoted with ‘/:’.
You can include non-ASCII characters in file names.
See Coding Systems for File Names.
18.2 Visiting Files
- C-x C-f
Visit a file (find-file
).
- C-x C-r
Visit a file for viewing, without allowing changes to it
(find-file-read-only
).
- C-x C-v
Visit a different file instead of the one visited last
(find-alternate-file
).
- C-x 4 f
Visit a file, in another window (find-file-other-window
). Don’t
alter what is displayed in the selected window.
- C-x 5 f
Visit a file, in a new frame (find-file-other-frame
). Don’t
alter what is displayed in the selected frame.
- M-x find-file-literally
Visit a file with no conversion of the contents.
Visiting a file means reading its contents into an Emacs
buffer so you can edit them. Emacs makes a new buffer for each file
that you visit.
To visit a file, type C-x C-f (find-file
) and use the
minibuffer to enter the name of the desired file. While in the
minibuffer, you can abort the command by typing C-g. See File Names, for details about entering file names into minibuffers.
If the specified file exists but the system does not allow you to
read it, an error message is displayed in the echo area (on GNU and
Unix systems you might be able to visit such a file using the
‘su’ or ‘sudo’ methods; see Remote Files). Otherwise,
you can tell that C-x C-f has completed successfully by the
appearance of new text on the screen, and by the buffer name shown in
the mode line (see The Mode Line). Emacs normally constructs the
buffer name from the file name, omitting the directory name. For
example, a file named /usr/rms/emacs.tex is visited in a buffer
named ‘emacs.tex’. If there is already a buffer with that name,
Emacs constructs a unique name; the normal method is to add a suffix
based on the directory name (e.g., ‘<rms>’, ‘<tmp>’,
and so on), but you can select other methods. See Making Buffer Names Unique.
To create a new file, just visit it using the same command, C-x
C-f. Emacs displays ‘(New file)’ in the echo area, but in other
respects behaves as if you had visited an existing empty file.
After visiting a file, the changes you make with editing commands are
made in the Emacs buffer. They do not take effect in the visited
file, until you save the buffer (see Saving Files). If a buffer
contains changes that have not been saved, we say the buffer is
modified. This implies that some changes will be lost if the
buffer is not saved. The mode line displays two stars near the left
margin to indicate that the buffer is modified.
If you visit a file that is already in Emacs, C-x C-f switches
to the existing buffer instead of making another copy. Before doing
so, it checks whether the file has changed since you last visited or
saved it. If the file has changed, Emacs offers to reread it.
If you try to visit a file larger than
large-file-warning-threshold
(the default is 10000000, which is
about 10 megabytes), Emacs asks you for confirmation first. You can
answer y to proceed with visiting the file or l to visit
the file literally (see below). Visiting large files literally speeds
up navigation and editing of such files, because various
potentially-expensive features are turned off. Note, however, that
Emacs cannot visit files that are larger than the maximum Emacs buffer
size, which is limited by the amount of memory Emacs can allocate and
by the integers that Emacs can represent (see Using Multiple Buffers). If you
try, Emacs displays an error message saying that the maximum buffer
size has been exceeded.
If the file name you specify contains shell-style wildcard
characters, Emacs visits all the files that match it. (On
case-insensitive filesystems, Emacs matches the wildcards disregarding
the letter case.) Wildcards include ‘?’, ‘*’, and
‘[…]’ sequences. To enter the wild card ‘?’ in a file
name in the minibuffer, you need to type C-q ?. See Quoted File Names, for information on how to visit a file whose name
actually contains wildcard characters. You can disable the wildcard
feature by customizing find-file-wildcards
.
If you’re asking to visit a file that’s already visited in a buffer,
but the file has changed externally, Emacs normally asks you whether
you want to re-read the file from disk. But if you set
query-about-changed-file
to nil
, Emacs won’t query you,
but will instead just display the buffer’s contents before the
changes, and show an echo-area message telling you how to revert the
buffer from the file.
If you visit the wrong file unintentionally by typing its name
incorrectly, type C-x C-v (find-alternate-file
) to visit
the file you really wanted. C-x C-v is similar to C-x
C-f, but it kills the current buffer (after first offering to save it
if it is modified). When C-x C-v reads the file name to visit,
it inserts the entire default file name in the buffer, with point just
after the directory part; this is convenient if you made a slight
error in typing the name.
If you visit a file that is actually a directory, Emacs invokes
Dired, the Emacs directory browser. See Dired, the Directory Editor. You can disable
this behavior by setting the variable find-file-run-dired
to
nil
; in that case, it is an error to try to visit a directory.
Files which are actually collections of other files, or file
archives, are visited in special modes which invoke a Dired-like
environment to allow operations on archive members. See File Archives, for more about these features.
If you visit a file that the operating system won’t let you modify,
or that is marked read-only, Emacs makes the buffer read-only too, so
that you won’t go ahead and make changes that you’ll have trouble
saving afterward. You can make the buffer writable with C-x C-q
(read-only-mode
). See Miscellaneous Buffer Operations.
If you want to visit a file as read-only in order to protect
yourself from entering changes accidentally, visit it with the command
C-x C-r (find-file-read-only
) instead of C-x C-f.
C-x 4 f (find-file-other-window
) is like C-x C-f
except that the buffer containing the specified file is selected in another
window. The window that was selected before C-x 4 f continues to
show the same buffer it was already showing. If this command is used when
only one window is being displayed, that window is split in two, with one
window showing the same buffer as before, and the other one showing the
newly requested file. See Multiple Windows.
C-x 5 f (find-file-other-frame
) is similar, but opens a
new frame, or selects any existing frame showing the specified file.
See Frames and Graphical Displays.
On graphical displays, there are two additional methods for visiting
files. Firstly, when Emacs is built with a suitable GUI toolkit,
commands invoked with the mouse (by clicking on the menu bar or tool
bar) use the toolkit’s standard file selection dialog instead of
prompting for the file name in the minibuffer. On GNU/Linux and Unix
platforms, Emacs does this when built with GTK+, LessTif, and Motif
toolkits; on MS-Windows and Mac, the GUI version does that by default.
For information on how to customize this, see Using Dialog Boxes.
Secondly, Emacs supports drag and drop: dropping a file into an
ordinary Emacs window visits the file using that window. As an
exception, dropping a file into a window displaying a Dired buffer
moves or copies the file into the displayed directory. For details,
see Drag and Drop, and Other Dired Features.
On text-mode terminals and on graphical displays when Emacs was
built without a GUI toolkit, you can visit files via the menu-bar
‘File’ menu, which has the ‘Visit New File’ and the
‘Open File’ items.
Each time you visit a file, Emacs automatically scans its contents
to detect what character encoding and end-of-line convention it uses,
and converts these to Emacs’s internal encoding and end-of-line
convention within the buffer. When you save the buffer, Emacs
performs the inverse conversion, writing the file to disk with its
original encoding and end-of-line convention. See Coding Systems.
If you wish to edit a file as a sequence of ASCII
characters with no special encoding or conversion, use the M-x
find-file-literally command. This visits a file, like C-x C-f,
but does not do format conversion (see Format
Conversion in the Emacs Lisp Reference Manual), character code
conversion (see Coding Systems), or automatic uncompression
(see Accessing Compressed Files), and does not add a final newline because
of require-final-newline
(see Customizing Saving of Files). If you have
already visited the same file in the usual (non-literal) manner, this
command asks you whether to visit it literally instead.
Two special hook variables allow extensions to modify the operation
of visiting files. Visiting a file that does not exist runs the
functions in find-file-not-found-functions
; this variable holds
a list of functions, which are called one by one (with no arguments)
until one of them returns non-nil
. This is not a normal hook,
and the name ends in ‘-functions’ rather than ‘-hook’ to
indicate that fact.
Successful visiting of any file, whether existing or not, calls the
functions in find-file-hook
, with no arguments. This variable
is a normal hook. In the case of a nonexistent file, the
find-file-not-found-functions
are run first. See Hooks.
There are several ways to specify automatically the major mode for
editing the file (see Choosing File Modes), and to specify local
variables defined for that file (see Local Variables in Files).
18.3 Saving Files
Saving a buffer in Emacs means writing its contents back into the file
that was visited in the buffer.
18.3.1 Commands for Saving Files
These are the commands that relate to saving and writing files.
- C-x C-s
Save the current buffer to its file (save-buffer
).
- C-x s
Save any or all buffers to their files (save-some-buffers
).
- M-~
Forget that the current buffer has been changed (not-modified
).
With prefix argument (C-u), mark the current buffer as changed.
- C-x C-w
Save the current buffer with a specified file name (write-file
).
- M-x set-visited-file-name
Change the file name under which the current buffer will be saved.
When you wish to save the file and make your changes permanent, type
C-x C-s (save-buffer
). After saving is finished, C-x C-s
displays a message like this:
Wrote /u/rms/gnu/gnu.tasks
If the current buffer is not modified (no changes have been made in it
since the buffer was created or last saved), saving is not really
done, because it would have no effect. Instead, C-x C-s
displays a message like this in the echo area:
(No changes need to be saved)
With a prefix argument, C-u C-x C-s, Emacs also marks the buffer
to be backed up when the next save is done. See Backup Files.
The command C-x s (save-some-buffers
) offers to save any
or all modified buffers. It asks you what to do with each buffer. The
possible responses are analogous to those of query-replace
:
- y
- SPC
Save this buffer and ask about the rest of the buffers.
- n
- DEL
Don’t save this buffer, but ask about the rest of the buffers.
- !
Save this buffer and all the rest with no more questions.
- q
- RET
Terminate save-some-buffers
without any more saving.
- .
Save this buffer, then exit save-some-buffers
without even asking
about other buffers.
- C-r
View the buffer that you are currently being asked about. When you exit
View mode, you get back to save-some-buffers
, which asks the
question again.
- C-f
Exit save-some-buffers
and visit the buffer that you are
currently being asked about.
- d
Diff the buffer against its corresponding file, so you can see what
changes you would be saving. This calls the command
diff-buffer-with-file
(see Comparing Files).
- C-h
Display a help message about these options.
You can customize the value of
save-some-buffers-default-predicate
to control which buffers
Emacs will ask about.
C-x C-c, the key sequence to exit Emacs, invokes
save-some-buffers
and therefore asks the same questions.
If you have changed a buffer but do not wish to save the changes,
you should take some action to prevent it. Otherwise, each time you
use C-x s or C-x C-c, you are liable to save this buffer
by mistake. One thing you can do is type M-~
(not-modified
), which clears out the indication that the buffer
is modified. If you do this, none of the save commands will believe
that the buffer needs to be saved. (‘~’ is often used as a
mathematical symbol for “not”; thus M-~ is “not”, metafied.)
Alternatively, you can cancel all the changes made since the file was
visited or saved, by reading the text from the file again. This is
called reverting. See Reverting a Buffer. (You could also undo all
the changes by repeating the undo command C-x u until you have
undone all the changes; but reverting is easier.)
M-x set-visited-file-name alters the name of the file that the
current buffer is visiting. It reads the new file name using the
minibuffer. Then it marks the buffer as visiting that file name, and
changes the buffer name correspondingly. set-visited-file-name
does not save the buffer in the newly visited file; it just alters the
records inside Emacs in case you do save later. It also marks the
buffer as modified so that C-x C-s in that buffer
will save.
If you wish to mark the buffer as visiting a different file and save
it right away, use C-x C-w (write-file
). This is
equivalent to set-visited-file-name
followed by C-x C-s,
except that C-x C-w asks for confirmation if the file exists.
C-x C-s used on a buffer that is not visiting a file has the
same effect as C-x C-w; that is, it reads a file name, marks the
buffer as visiting that file, and saves it there. The default file
name in a buffer that is not visiting a file is made by combining the
buffer name with the buffer’s default directory (see File Names).
If the new file name implies a major mode, then C-x C-w switches
to that major mode, in most cases. The command
set-visited-file-name
also does this. See Choosing File Modes.
If Emacs is about to save a file and sees that the date of the latest
version on disk does not match what Emacs last read or wrote, Emacs
notifies you of this fact, because it probably indicates a problem caused
by simultaneous editing and requires your immediate attention.
See Simultaneous Editing.
18.3.2 Backup Files
On most operating systems, rewriting a file automatically destroys all
record of what the file used to contain. Thus, saving a file from Emacs
throws away the old contents of the file—or it would, except that
Emacs carefully copies the old contents to another file, called the
backup file, before actually saving.
Emacs makes a backup for a file only the first time the file is
saved from a buffer. No matter how many times you subsequently save
the file, its backup remains unchanged. However, if you kill the
buffer and then visit the file again, a new backup file will be made.
For most files, the variable make-backup-files
determines
whether to make backup files. On most operating systems, its default
value is t
, so that Emacs does write backup files.
For files managed by a version control system (see Version Control), the variable vc-make-backup-files
determines whether
to make backup files. By default it is nil
, since backup files
are redundant when you store all the previous versions in a version
control system.
See General Options.
At your option, Emacs can keep either a single backup for each file,
or make a series of numbered backup files for each file that you edit.
See Single or Numbered Backups.
The default value of the backup-enable-predicate
variable
prevents backup files being written for files in the directories used
for temporary files, specified by temporary-file-directory
or
small-temporary-file-directory
.
You can explicitly tell Emacs to make another backup file from a
buffer, even though that buffer has been saved before. If you save
the buffer with C-u C-x C-s, the version thus saved will be made
into a backup file if you save the buffer again. C-u C-u C-x
C-s saves the buffer, but first makes the previous file contents into
a new backup file. C-u C-u C-u C-x C-s does both things: it
makes a backup from the previous contents, and arranges to make
another from the newly saved contents if you save again.
You can customize the variable backup-directory-alist
to
specify that files matching certain patterns should be backed up in
specific directories. A typical use is to add an element ("."
. dir)
to make all backups in the directory with absolute name
dir. Emacs modifies the backup file names to avoid clashes
between files with the same names originating in different
directories. Alternatively, adding, ("." . ".~")
would make
backups in the invisible subdirectory .~ of the original file’s
directory. Emacs creates the directory, if necessary, to make the
backup.
18.3.2.1 Single or Numbered Backups
When Emacs makes a backup file, its name is normally constructed by
appending ‘~’ to the file name being edited; thus, the backup
file for eval.c would be eval.c~.
If access control stops Emacs from writing backup files under the
usual names, it writes the backup file as ~/.emacs.d/%backup%~.
Only one such file can exist, so only the most recently made such
backup is available.
Emacs can also make numbered backup files. Numbered backup
file names contain ‘.~’, the number, and another ‘~’ after
the original file name. Thus, the backup files of eval.c would
be called eval.c.~1~, eval.c.~2~, and so on, all the way
through names like eval.c.~259~ and beyond.
The variable version-control
determines whether to make
single backup files or multiple numbered backup files. Its possible
values are:
nil
Make numbered backups for files that have numbered backups already.
Otherwise, make single backups. This is the default.
t
Make numbered backups.
never
Never make numbered backups; always make single backups.
The usual way to set this variable is globally, through your init file
or the customization buffer. However, you can set
version-control
locally in an individual buffer to control the
making of backups for that buffer’s file (see Local Variables). You can
have Emacs set version-control
locally whenever you visit a
given file (see Local Variables in Files). Some modes, such as Rmail mode,
set this variable.
If you set the environment variable VERSION_CONTROL
, to tell
various GNU utilities what to do with backup files, Emacs also obeys the
environment variable by setting the Lisp variable version-control
accordingly at startup. If the environment variable’s value is ‘t’
or ‘numbered’, then version-control
becomes t
; if the
value is ‘nil’ or ‘existing’, then version-control
becomes nil
; if it is ‘never’ or ‘simple’, then
version-control
becomes never
.
If you set the variable make-backup-file-name-function
to
a suitable Lisp function, you can override the usual way Emacs
constructs backup file names.
18.3.2.2 Automatic Deletion of Backups
To prevent excessive consumption of disk space, Emacs can delete numbered
backup versions automatically. Generally Emacs keeps the first few backups
and the latest few backups, deleting any in between. This happens every
time a new backup is made.
The two variables kept-old-versions
and
kept-new-versions
control this deletion. Their values are,
respectively, the number of oldest (lowest-numbered) backups to keep
and the number of newest (highest-numbered) ones to keep, each time a
new backup is made. The backups in the middle (excluding those oldest
and newest) are the excess middle versions—those backups are
deleted. These variables’ values are used when it is time to delete
excess versions, just after a new backup version is made; the newly
made backup is included in the count in kept-new-versions
. By
default, both variables are 2.
If delete-old-versions
is t
, Emacs deletes the excess
backup files silently. If it is nil
, the default, Emacs asks
you whether it should delete the excess backup versions. If it has
any other value, then Emacs never automatically deletes backups.
Dired’s . (Period) command can also be used to delete old versions.
See Flagging Many Files at Once.
18.3.2.3 Copying vs. Renaming
Backup files can be made by copying the old file or by renaming it.
This makes a difference when the old file has multiple names (hard
links). If the old file is renamed into the backup file, then the
alternate names become names for the backup file. If the old file is
copied instead, then the alternate names remain names for the file
that you are editing, and the contents accessed by those names will be
the new contents.
The method of making a backup file may also affect the file’s owner
and group. If copying is used, these do not change. If renaming is used,
you become the file’s owner, and the file’s group becomes the default
(different operating systems have different defaults for the group).
The choice of renaming or copying is made as follows:
- If the variable
backup-by-copying
is non-nil
(the
default is nil
), use copying.
- Otherwise, if the variable
backup-by-copying-when-linked
is
non-nil
(the default is nil
), and the file has multiple
names, use copying.
- Otherwise, if the variable
backup-by-copying-when-mismatch
is
non-nil
(the default is t
), and renaming would change
the file’s owner or group, use copying.
If you change backup-by-copying-when-mismatch
to nil
,
Emacs checks the numeric user-id of the file’s owner and the numeric
group-id of the file’s group. If either is
no greater than backup-by-copying-when-privileged-mismatch
, then it
behaves as though backup-by-copying-when-mismatch
is
non-nil
anyway.
- Otherwise, renaming is the default choice.
When a file is managed with a version control system (see Version Control), Emacs does not normally make backups in the usual way for
that file. But committing (a.k.a. checking in,
see Concepts of Version Control) new versions of files is similar in some ways
to making backups. One unfortunate similarity is that these
operations typically break hard links, disconnecting the file name you
visited from any alternate names for the same file. This has nothing
to do with Emacs—the version control system does it.
18.3.3 Customizing Saving of Files
If the value of the variable require-final-newline
is
t
, saving or writing a file silently puts a newline at the end
if there isn’t already one there. If the value is visit
, Emacs
adds a newline at the end of any file that doesn’t have one, just
after it visits the file. (This marks the buffer as modified, and you
can undo it.) If the value is visit-save
, Emacs adds such
newlines both on visiting and on saving. If the value is nil
,
Emacs leaves the end of the file unchanged; any other non-nil
value means Emacs asks you whether to add a newline. The default is
nil
.
Some major modes are designed for specific kinds of files that are
always supposed to end in newlines. Such major modes set the variable
require-final-newline
to the value of
mode-require-final-newline
, which defaults to t
. By
setting the latter variable, you can control how these modes handle
final newlines.
If this option is non-nil
and you’re visiting a file via a
symbolic link, Emacs will break the symbolic link upon saving the
buffer, and will write the buffer to a file with the same name as the
symbolic link, if the value of file-precious-flag
is
non-nil
(see file-precious-flag in The
Emacs Lisp Reference Manual). If you want Emacs to save the buffer
to the file the symbolic link points to (thereby preserving the link)
in these cases, customize the variable
file-preserve-symlinks-on-save
to t
.
Normally, when a program writes a file, the operating system briefly
caches the file’s data in main memory before committing the data to
disk. This can greatly improve performance; for example, when running
on laptops, it can avoid a disk spin-up each time a file is written.
However, it risks data loss if the operating system crashes before
committing the cache to disk.
To lessen this risk, Emacs can invoke the fsync
system call
after saving a file. Using fsync
does not eliminate the risk
of data loss, partly because many systems do not implement
fsync
properly, and partly because Emacs’s file-saving
procedure typically relies also on directory updates that might not
survive a crash even if fsync
works properly.
The write-region-inhibit-fsync
variable controls whether
Emacs invokes fsync
after saving a file. The variable’s
default value is nil
when Emacs is interactive, and t
when Emacs runs in batch mode (see Batch Mode).
Emacs never uses fsync
when writing auto-save files, as these
files might lose data anyway.
18.3.4 Protection against Simultaneous Editing
Simultaneous editing occurs when two users visit the same file, both
make changes, and then both save them. If nobody is informed that
this is happening, whichever user saves first would later find that
their changes were lost.
On some systems, Emacs notices immediately when the second user starts
to change the file, and issues an immediate warning. On all systems,
Emacs checks when you save the file, and warns if you are about to
overwrite another user’s changes. You can prevent loss of the other
user’s work by taking the proper corrective action instead of saving the
file.
When you make the first modification in an Emacs buffer that is
visiting a file, Emacs records that the file is locked by you.
(It does this by creating a specially-named symbolic link7 with special contents in the same directory. See (elisp)File
Locks, for more details.) Emacs removes the lock when you
save the changes. The idea is that the file is locked whenever an
Emacs buffer visiting it has unsaved changes.
You can prevent the creation of lock files by setting the variable
create-lockfiles
to nil
. Caution: by
doing so you will lose the benefits that this feature provides. You
can also control where lock files are written by using the
lock-file-name-transforms
variable.
If you begin to modify the buffer while the visited file is locked by
someone else, this constitutes a collision. When Emacs detects a
collision, it asks you what to do, by calling the Lisp function
ask-user-about-lock
. You can redefine this function for the sake
of customization. The standard definition of this function asks you a
question and accepts three possible answers:
- s
Steal the lock. Whoever was already changing the file loses the lock,
and you gain the lock.
- p
Proceed. Go ahead and edit the file despite its being locked by someone else.
- q
Quit. This causes an error (file-locked
), and the buffer
contents remain unchanged—the modification you were trying to make
does not actually take place.
If Emacs or the operating system crashes, this may leave behind lock
files which are stale, so you may occasionally get warnings about
spurious collisions. When you determine that the collision is
spurious, just use p to tell Emacs to go ahead anyway.
Note that locking works on the basis of a file name; if a file has
multiple names, Emacs does not prevent two users from editing it
simultaneously under different names.
A lock file cannot be written in some circumstances, e.g., if Emacs
lacks the system permissions or cannot create lock files for some
other reason. In these cases, Emacs can still detect the collision
when you try to save a file, by checking the file’s last-modification
date. If the file has changed since the last time Emacs visited or
saved it, that implies that changes have been made in some other way,
and will be lost if Emacs proceeds with saving. Emacs then displays a
warning message and asks for confirmation before saving; answer
yes to save, and no or C-g cancel the save.
If you are notified that simultaneous editing has already taken
place, one way to compare the buffer to its file is the M-x
diff-buffer-with-file command. See Comparing Files.
You can prevent the creation of remote lock files by setting the
variable remote-file-name-inhibit-locks
to t
.
The minor mode lock-file-mode
, called interactively, toggles
the local value of create-lockfiles
in the current buffer.
18.3.5 Shadowing Files
You can arrange to keep identical shadow copies of certain
files in more than one place—possibly on different machines. To do
this, first you must set up a shadow file group, which is a set
of identically-named files shared between a list of sites. The file
group is permanent and applies to further Emacs sessions as well as
the current one. Once the group is set up, every time you exit Emacs,
it will copy the file you edited to the other files in its group. You
can also do the copying without exiting Emacs, by typing M-x shadow-copy-files.
A shadow cluster is a group of hosts that share directories, so
that copying to or from one of them is sufficient to update the file
on all of them. Each shadow cluster has a name, and specifies the
network address of a primary host (the one we copy files to), and a
regular expression that matches the host names of all the other hosts
in the cluster. You can define a shadow cluster with M-x shadow-define-cluster.
- M-x shadow-initialize
Set up file shadowing.
- M-x shadow-define-literal-group
Declare a single file to be shared between sites.
- M-x shadow-define-regexp-group
Make all files that match each of a group of files be shared between hosts.
- M-x shadow-define-cluster RET name RET
Define a shadow file cluster name.
- M-x shadow-copy-files
Copy all pending shadow files.
- M-x shadow-cancel
Cancel the instruction to shadow some files.
To set up a shadow file group, use M-x shadow-define-literal-group or M-x shadow-define-regexp-group. See their documentation strings for
further information.
Before copying a file to its shadows, Emacs asks for confirmation.
You can answer “no” to bypass copying of this file, this time. If
you want to cancel the shadowing permanently for a certain file, use
M-x shadow-cancel to eliminate or change the shadow file group.
File Shadowing is not available on MS Windows.
18.3.6 Updating Time Stamps Automatically
You can arrange to put a time stamp in a file, so that it is updated
automatically each time you edit and save the file. The time stamp
must be in the first eight lines of the file, and you should insert it
like this:
or like this:
Then add the function time-stamp
to the hook
before-save-hook
(see Hooks). When you save the file, this
function then automatically updates the time stamp with the current
date and time. You can also use the command M-x time-stamp to
update the time stamp manually. By default the time stamp is
formatted according to your locale setting (see Environment Variables) and
time zone (see Time of Day in The Emacs Lisp Reference
Manual). For customizations, see the Custom group time-stamp
.
18.4 Reverting a Buffer
If you have made extensive changes to a file-visiting buffer and
then change your mind, you can revert the changes and go back to
the saved version of the file. To do this, type C-x x g. Since
reverting unintentionally could lose a lot of work, Emacs asks for
confirmation first if the buffer is modified.
The revert-buffer
command tries to position point in such a
way that, if the file was edited only slightly, you will be at
approximately the same part of the text as before. But if you have
made major changes, point may end up in a totally different location.
Reverting marks the buffer as not modified. However, it adds the
reverted changes as a single modification to the buffer’s undo history
(see Undo). Thus, after reverting, you can type C-/ or its
aliases to bring the reverted changes back, if you happen to change
your mind.
To revert a buffer more conservatively, you can use the command
revert-buffer-with-fine-grain
. This command acts like
revert-buffer
, but it tries to be as non-destructive as
possible, making an effort to preserve all markers, properties and
overlays in the buffer. Since reverting this way can be very slow
when you have made a large number of changes, you can modify the
variable revert-buffer-with-fine-grain-max-seconds
to
specify a maximum amount of seconds that replacing the buffer
contents this way should take. Note that it is not ensured that the
whole execution of revert-buffer-with-fine-grain
won’t take
longer than this.
Some kinds of buffers that are not associated with files, such as
Dired buffers, can also be reverted. For them, reverting means
recalculating their contents. Buffers created explicitly with
C-x b cannot be reverted; revert-buffer
reports an error
if you try.
When you edit a file that changes automatically and frequently—for
example, a log of output from a process that continues to run—it may
be useful for Emacs to revert the file without querying you. To
request this behavior, set the variable revert-without-query
to
a list of regular expressions. When a file name matches one of these
regular expressions, find-file
and revert-buffer
will
revert it automatically if it has changed—provided the buffer itself
is not modified. (If you have edited the text, it would be wrong to
discard your changes.)
The C-x x g keystroke is bound to the
revert-buffer-quick
command. This is like the
revert-buffer
command, but prompts less. Unlike
revert-buffer
, it will not prompt if the current buffer visits
a file, and the buffer is not modified. It also respects the
revert-buffer-quick-short-answers
user option. If this option
is non-nil
, use a shorter y/n query instead of a longer
yes/no query.
You can also tell Emacs to revert buffers automatically when their
visited files change on disk; see Auto Revert: Keeping buffers automatically up-to-date.
18.5 Auto Revert: Keeping buffers automatically up-to-date
A buffer can get out of sync with respect to its visited file on
disk if that file is changed by another program. To keep it up to
date, you can enable Auto Revert mode by typing M-x auto-revert-mode.
This automatically reverts the buffer when its visited file changes on
disk. To do the same for all file buffers, type
M-x global-auto-revert-mode to enable Global Auto Revert mode.
Auto Revert will not revert a buffer if it has unsaved changes, or if
its file on disk is deleted or renamed.
One use of Auto Revert mode is to “tail” a file such as a system
log, so that changes made to that file by other programs are
continuously displayed. To do this, just move the point to the end of
the buffer, and it will stay there as the file contents change.
However, if you are sure that the file will only change by growing at
the end, use Auto Revert Tail mode instead
(auto-revert-tail-mode
). It is more efficient for this.
Auto Revert Tail mode also works for remote files.
When a buffer is auto-reverted, a message is generated. This can be
suppressed by setting auto-revert-verbose
to nil
.
The Auto Revert modes do not check or revert remote files, because
that is usually too slow. This behavior can be changed by setting the
variable auto-revert-remote-files
to non-nil
.
By default, Auto Revert mode works using file notifications,
whereby changes in the filesystem are reported to Emacs by the OS.
You can disable use of file notifications by customizing the variable
auto-revert-use-notify
to a nil
value, then Emacs will
check for file changes by polling every five seconds. You can change
the polling interval through the variable auto-revert-interval
.
Not all systems support file notifications; where they are not
supported, auto-revert-use-notify
will be nil
by
default.
By default, Auto Revert mode will poll files for changes
periodically even when file notifications are used. Polling is
unnecessary in many cases, and turning it off may save power by
relying on notifications only. To do so, set the variable
auto-revert-avoid-polling
to non-nil
. However,
notification is ineffective on certain file systems; mainly network
file system on Unix-like machines, where files can be altered from
other machines. For such file systems, polling may be necessary.
To force polling when
auto-revert-avoid-polling
is non-nil
, set
auto-revert-notify-exclude-dir-regexp
to match files that
should be excluded from using notification.
In Dired buffers (see Dired, the Directory Editor), Auto Revert mode refreshes the
buffer when a file is created or deleted in the buffer’s directory.
See Undoing Version Control Actions, for commands to revert to earlier versions of files
under version control. See Version Control and the Mode Line, for Auto Revert
peculiarities when visiting files under version control.
18.5.1 Auto Reverting Non-File Buffers
Global Auto Revert Mode normally only reverts file buffers. There are
two ways to auto-revert certain non-file buffers: by enabling Auto
Revert Mode in those buffers (using M-x auto-revert-mode); and
by setting global-auto-revert-non-file-buffers
to a
non-nil
value. The latter enables Auto Reverting for all types
of buffers for which it is implemented (listed in the menu below).
Like file buffers, non-file buffers should normally not revert while
you are working on them, or while they contain information that might
get lost after reverting. Therefore, they do not revert if they are
modified. This can get tricky, because deciding when a non-file
buffer should be marked modified is usually more difficult than for
file buffers.
Another tricky detail is that, for efficiency reasons, Auto Revert
often does not try to detect all possible changes in the buffer, only
changes that are major or easy to detect. Hence, enabling
auto-reverting for a non-file buffer does not always guarantee that
all information in the buffer is up-to-date, and does not necessarily
make manual reverts useless.
At the other extreme, certain buffers automatically revert every
auto-revert-interval
seconds. (This currently only applies to
the Buffer Menu.) In this case, Auto Revert does not print any
messages while reverting, even when auto-revert-verbose
is
non-nil
.
Some non-file buffers can be updated reliably by file notification on
their default directory; Dired buffers is an example. The major mode
can indicate this by setting buffer-auto-revert-by-notification
to a non-nil
value in that buffer, allowing Auto Revert to
avoid periodic polling. Such notification does not include changes to
files in that directory, only to the directory itself.
The details depend on the particular types of buffers and are
explained in the corresponding sections.
18.5.1.2 Auto Reverting Dired buffers
Dired buffers only auto-revert when the file list of the buffer’s main
directory changes (e.g., when a new file is added or deleted). They
do not auto-revert when information about a particular file changes
(e.g., when the size changes) or when inserted subdirectories change.
To be sure that all listed information is up to date, you have
to manually revert using g, even if auto-reverting is
enabled in the Dired buffer. Sometimes, you might get the impression
that modifying or saving files listed in the main directory actually
does cause auto-reverting. This is because making changes to a file,
or saving it, very often causes changes in the directory itself; for
instance, through backup files or auto-save files. However, this is
not guaranteed.
If the Dired buffer is marked modified and there are no changes you
want to protect, then most of the time you can make auto-reverting
resume by manually reverting the buffer using g. There is one
exception. If you flag or mark files, you can safely revert the
buffer. This will not erase the flags or marks (unless the marked
file has been deleted, of course). However, the buffer will stay
modified, even after reverting, and auto-reverting will not resume.
This is because, if you flag or mark files, you may be working on the
buffer and you might not want the buffer to change without warning.
If you want auto-reverting to resume in the presence of marks and
flags, mark the buffer non-modified using M-~. However, adding,
deleting or changing marks or flags will mark it modified again.
Remote Dired buffers are currently not auto-reverted. Neither are
Dired buffers for which you used shell wildcards or file arguments to
list only some of the files. *Find* and *Locate*
buffers do not auto-revert either.
Note that auto-reverting Dired buffers may not work satisfactorily on
some systems.
18.6 Auto-Saving: Protection Against Disasters
From time to time, Emacs automatically saves each visited file in a
separate file, without altering the file you actually use. This is
called auto-saving. It prevents you from losing more than a
limited amount of work if the system crashes.
When Emacs determines that it is time for auto-saving, it considers
each buffer, and each is auto-saved if auto-saving is enabled for it
and it has been changed since the last time it was auto-saved. When
the auto-save-no-message
variable is set to nil
(the
default), the message ‘Auto-saving...’ is displayed in the echo
area during auto-saving, if any files are actually auto-saved; to
disable these messages, customize the variable to a non-nil
value. Errors occurring during auto-saving are caught so that they do
not interfere with the execution of commands you have been typing.
18.6.1 Auto-Save Files
Auto-saving does not normally save in the files that you visited,
because it can be very undesirable to save a change that you did not
want to make permanent. Instead, auto-saving is done in a different
file called the auto-save file, and the visited file is changed
only when you request saving explicitly (such as with C-x C-s).
Normally, the auto-save file name is made by appending ‘#’ to the
front and rear of the visited file name. Thus, a buffer visiting file
foo.c is auto-saved in a file #foo.c#. Most buffers that
are not visiting files are auto-saved only if you request it explicitly;
when they are auto-saved, the auto-save file name is made by appending
‘#’ to the front and rear of buffer name, then
adding digits and letters at the end for uniqueness. For
example, the *mail* buffer in which you compose messages to be
sent might be auto-saved in a file named #*mail*#704juu. Auto-save file
names are made this way unless you reprogram parts of Emacs to do
something different (the functions make-auto-save-file-name
and
auto-save-file-name-p
). The file name to be used for auto-saving
in a buffer is calculated when auto-saving is turned on in that buffer.
The variable auto-save-file-name-transforms
allows a degree
of control over the auto-save file name. It lets you specify a series
of regular expressions and replacements to transform the auto save
file name. The default value puts the auto-save files for remote
files (see Remote Files) into the temporary file directory on the
local machine.
When you delete a substantial part of the text in a large buffer, auto
save turns off temporarily in that buffer. This is because if you
deleted the text unintentionally, you might find the auto-save file more
useful if it contains the deleted text. To reenable auto-saving after
this happens, save the buffer with C-x C-s, or use C-u 1 M-x
auto-save-mode.
If you want auto-saving to be done in the visited file rather than
in a separate auto-save file, enable the global minor mode
auto-save-visited-mode
. In this mode, auto-saving is identical
to explicit saving. Note that this mode is orthogonal to the
auto-save
mode described above; you can enable both at the same
time. However, if auto-save
mode is active in some buffer and
the obsolete auto-save-visited-file-name
variable is set to a
non-nil
value, that buffer won’t be affected by
auto-save-visited-mode
.
You can use the variable auto-save-visited-interval
to
customize the interval between auto-save operations in
auto-save-visited-mode
; by default it’s five seconds.
auto-save-interval
and auto-save-timeout
have no effect
on auto-save-visited-mode
. See Controlling Auto-Saving, for
details on these variables.
A buffer’s auto-save file is deleted when you save the buffer in its
visited file. (You can inhibit this by setting the variable
delete-auto-save-files
to nil
.) Changing the visited
file name with C-x C-w or set-visited-file-name
renames
any auto-save file to go with the new visited name.
Killing a buffer, by default, doesn’t remove the buffer’s auto-save
file. If kill-buffer-delete-auto-save-files
is non-nil
,
killing a buffer that has an auto-save file will make Emacs prompt the
user for whether the auto-save file should be deleted. (This is
inhibited if delete-auto-save-files
is nil
.)
18.6.2 Controlling Auto-Saving
Each time you visit a file, auto-saving is turned on for that file’s
buffer if the variable auto-save-default
is non-nil
(but
not in batch mode; see Initial Options). The default for this
variable is t
, so auto-saving is the usual practice for
file-visiting buffers. To toggle auto-saving in the current buffer,
type M-x auto-save-mode. Auto Save mode acts as a buffer-local
minor mode (see Minor Modes).
Emacs auto-saves periodically based on how many characters you have
typed since the last auto-save. The variable
auto-save-interval
specifies how many characters there are
between auto-saves. By default, it is 300. Emacs doesn’t accept
values that are too small: if you customize auto-save-interval
to a value less than 20, Emacs will behave as if the value is 20.
Auto-saving also takes place when you stop typing for a while. By
default, it does this after 30 seconds of idleness (at this time,
Emacs may also perform garbage collection; see Garbage
Collection in The Emacs Lisp Reference Manual). To change
this interval, customize the variable auto-save-timeout
. The
actual time period is longer if the current buffer is long; this is a
heuristic which aims to keep out of your way when you are editing long
buffers, in which auto-save takes an appreciable amount of time.
Auto-saving during idle periods accomplishes two things: first, it
makes sure all your work is saved if you go away from the terminal for
a while; second, it may avoid some auto-saving while you are actually
typing.
When auto-save-visited-mode
is enabled, Emacs will auto-save
file-visiting buffers after five seconds of idle time. You can
customize the variable auto-save-visited-interval
to change the
idle time interval.
Emacs also does auto-saving whenever it gets a fatal error. This
includes killing the Emacs job with a shell command such as ‘kill
%emacs’, or disconnecting a phone line or network connection.
You can perform an auto-save explicitly with the command M-x
do-auto-save.
18.6.3 Recovering Data from Auto-Saves
You can use the contents of an auto-save file to recover from a loss
of data with the command M-x recover-file RET file
RET. This visits file and then (after your confirmation)
restores the contents from its auto-save file #file#.
You can then save with C-x C-s to put the recovered text into
file itself. For example, to recover file foo.c from its
auto-save file #foo.c#, do:
M-x recover-file RET foo.c RET
yes RET
C-x C-s
Before asking for confirmation, M-x recover-file displays a
directory listing describing the specified file and the auto-save file,
so you can compare their sizes and dates. If the auto-save file
is older, M-x recover-file does not offer to read it.
If Emacs or the computer crashes, you can recover all the files you
were editing from their auto save files with the command M-x
recover-session. This first shows you a list of recorded interrupted
sessions. Move point to the one you choose, and type C-c C-c.
Then recover-session
asks about each of the files that were
being edited during that session, asking whether to recover that file.
If you answer y, it calls recover-file
, which works in its
normal fashion. It shows the dates of the original file and its
auto-save file, and asks once again whether to recover that file.
When recover-session
is done, the files you’ve chosen to
recover are present in Emacs buffers. You should then save them. Only
this—saving them—updates the files themselves.
Emacs records information about interrupted sessions in files named
.saves-pid-hostname~ in the directory
~/.emacs.d/auto-save-list/. This directory is determined by
the variable auto-save-list-file-prefix
. If you set
auto-save-list-file-prefix
to nil
, sessions are not
recorded for recovery.
18.7 File Name Aliases
Symbolic links and hard links both make it possible for several file
names to refer to the same file. Hard links are alternate names that
refer directly to the file; all the names are equally valid, and no one
of them is preferred. By contrast, a symbolic link is a kind of defined
alias: when foo is a symbolic link to bar, you can use
either name to refer to the file, but bar is the real name, while
foo is just an alias. More complex cases occur when symbolic
links point to directories.
Normally, if you visit a file which Emacs is already visiting under
a different name, Emacs displays a message in the echo area and uses
the existing buffer visiting that file. This can happen on systems
that support hard or symbolic links, or if you use a long file name on
a system that truncates long file names, or on a case-insensitive file
system. You can suppress the message by setting the variable
find-file-suppress-same-file-warnings
to a non-nil
value. You can disable this feature entirely by setting the variable
find-file-existing-other-name
to nil
: then if you visit
the same file under two different names, you get a separate buffer for
each file name.
If the variable find-file-visit-truename
is non-nil
,
then the file name recorded for a buffer is the file’s truename
(made by replacing all symbolic links with their target names), rather
than the name you specify. Setting find-file-visit-truename
also
implies the effect of find-file-existing-other-name
.
Sometimes, a directory is ordinarily accessed through a symbolic
link, and you may want Emacs to preferentially show its linked
name. To do this, customize directory-abbrev-alist
. Each
element in this list should have the form (from
. to)
, which means to replace from with to whenever
from appears in a directory name. The from string is a
regular expression (see Syntax of Regular Expressions). It is matched against directory
names anchored at the first character, and should start with ‘\`’
(to support directory names with embedded newlines, which would defeat
‘^’). The to string should be an ordinary absolute
directory name pointing to the same directory. Do not use ‘~’ to
stand for a home directory in the to string; Emacs performs
these substitutions separately. Here’s an example, from a system on
which /home/fsf is normally accessed through a symbolic link
named /fsf:
(("\\`/home/fsf" . "/fsf"))
18.8 File Directories
The file system groups files into directories. A directory
listing is a list of all the files in a directory. Emacs provides
commands to create and delete directories, and to make directory
listings in brief format (file names only) and verbose format (sizes,
dates, and other attributes included). Emacs also includes a
directory browser feature called Dired, which you can invoke with
C-x d; see Dired, the Directory Editor.
- C-x C-d dir-or-pattern RET
Display a brief directory listing (list-directory
).
- C-u C-x C-d dir-or-pattern RET
Display a verbose directory listing.
- M-x make-directory RET dirname RET
Create a new directory named dirname.
- M-x delete-directory RET dirname RET
Delete the directory named dirname. If it isn’t empty,
you will be asked whether you want to delete it recursively.
The command to display a directory listing is C-x C-d
(list-directory
). It reads using the minibuffer a file name
which is either a directory to be listed or a wildcard-containing
pattern for the files to be listed. For example,
C-x C-d /u2/emacs/etc RET
lists all the files in directory /u2/emacs/etc. Here is an
example of specifying a file name pattern:
C-x C-d /u2/emacs/src/*.c RET
Normally, C-x C-d displays a brief directory listing containing
just file names. A numeric argument (regardless of value) tells it to
make a verbose listing including sizes, dates, and owners (like
‘ls -l’).
The text of a directory listing is mostly obtained by running
ls
in an inferior process. Two Emacs variables control the
switches passed to ls
: list-directory-brief-switches
is
a string giving the switches to use in brief listings ("-CF"
by
default), and list-directory-verbose-switches
is a string
giving the switches to use in a verbose listing ("-l"
by
default).
In verbose directory listings, Emacs adds information about the
amount of free space on the disk that contains the directory.
The command M-x delete-directory prompts for a directory’s name
using the minibuffer, and deletes the directory if it is empty. If
the directory is not empty, you will be asked whether you want to
delete it recursively. On systems that have a “Trash” (or “Recycle
Bin”) feature, you can make this command move the specified directory
to the Trash instead of deleting it outright, by changing the variable
delete-by-moving-to-trash
to t
. See Miscellaneous File Operations,
for more information about using the Trash.
18.9 Comparing Files
The command M-x diff prompts for two file names, using the
minibuffer, and displays the differences between the two files in a
buffer named *diff*. This works by running the diff
program, using options taken from the variable diff-switches
.
The value of diff-switches
should be a string; the default is
"-u"
to specify a unified context diff.
See Diff in Comparing and Merging Files, for more
information about the diff
program.
The output of the diff
command is shown using a major mode
called Diff mode. See Diff Mode.
A (much more sophisticated) alternative is M-x ediff
(see Ediff in The Ediff Manual).
The command M-x diff-backup compares a specified file with its
most recent backup. If you specify the name of a backup file,
diff-backup
compares it with the source file that it is a
backup of. In all other respects, this behaves like M-x diff.
The command M-x diff-buffer-with-file compares a specified
buffer with its corresponding file. This shows you what changes you
would make to the file if you save the buffer.
The command M-x diff-buffers compares the contents of two
specified buffers.
The command M-x compare-windows compares the text in the
current window with that in the window that was the selected window
before you selected the current one. (For more information about
windows in Emacs, see Multiple Windows.) Comparison starts at point in
each window, after pushing each initial point value on the mark ring
(see The Mark Ring) in its respective buffer. Then it moves point
forward in each window, one character at a time, until it reaches
characters that don’t match. Then the command exits.
If point in the two windows is followed by non-matching text when
the command starts, M-x compare-windows tries heuristically to
advance up to matching text in the two windows, and then exits. So if
you use M-x compare-windows repeatedly, each time it either
skips one matching range or finds the start of another.
With a numeric argument, compare-windows
ignores changes in
whitespace. If the variable compare-ignore-case
is
non-nil
, the comparison ignores differences in case as well.
If the variable compare-ignore-whitespace
is non-nil
,
compare-windows
by default ignores changes in whitespace, but a
prefix argument turns that off for that single invocation of the
command.
You can use M-x smerge-mode to turn on Smerge mode, a minor
mode for editing output from the diff3
program. This is
typically the result of a failed merge from a version control system
update outside VC, due to conflicting changes to a file. Smerge
mode provides commands to resolve conflicts by selecting specific
changes.
See Merging Files with Emerge,
for the Emerge facility, which provides a powerful interface for
merging files.
18.10 Diff Mode
Diff mode is a major mode used for the output of M-x diff and
other similar commands. This kind of output is called a patch,
because it can be passed to the patch
command to
automatically apply the specified changes. To select Diff mode
manually, type M-x diff-mode.
The changes specified in a patch are grouped into hunks, which
are contiguous chunks of text that contain one or more changed lines.
Hunks usually also include unchanged lines to provide context for the
changes. Each hunk is preceded by a hunk header, which
specifies the old and new line numbers where the hunk’s changes occur.
Diff mode highlights each hunk header, to distinguish it from the
actual contents of the hunk.
The first hunk in a patch is preceded by a file header, which shows
the names of the new and the old versions of the file, and their time
stamps. If a patch shows changes for more than one file, each file
has such a header before the first hunk of that file’s changes.
You can edit a Diff mode buffer like any other buffer. (If it is
read-only, you need to make it writable first; see Miscellaneous Buffer Operations.)
Whenever you edit a hunk, Diff mode attempts to automatically correct
the line numbers in the hunk headers, to ensure that the patch remains
correct, and could still be applied by patch
. To disable
automatic line number correction, change the variable
diff-update-on-the-fly
to nil
.
Diff mode arranges for hunks to be treated as compiler error
messages by M-g M-n and other commands that handle error messages
(see Compilation Mode). Thus, you can use the compilation-mode
commands to visit the corresponding source locations.
In addition, Diff mode provides the following commands to navigate,
manipulate and apply parts of patches:
- M-n ¶
Move to the next hunk-start (diff-hunk-next
). With prefix
argument n, move forward to the nth next hunk.
By default, Diff mode refines hunks as Emacs displays them,
highlighting their changes with better granularity. Alternatively, if
you set diff-refine
to the symbol navigation
, Diff mode
only refines the hunk you move to with this command or with
diff-hunk-prev
.
- M-p ¶
Move to the previous hunk-start (diff-hunk-prev
). With prefix
argument n, move back to the nth previous hunk. Like
M-n, this command refines the hunk you move to if you set
diff-refine
to the symbol navigation
.
- M-} ¶
Move to the next file-start, in a multi-file patch
(diff-file-next
). With prefix argument n, move forward
to the start of the nth next file.
- M-{ ¶
Move to the previous file-start, in a multi-file patch
(diff-file-prev
). With prefix argument n, move back to
the start of the nth previous file.
- M-k ¶
Kill the hunk at point (diff-hunk-kill
).
- M-K ¶
In a multi-file patch, kill the current file part.
(diff-file-kill
).
- C-c C-a ¶
-
Apply this hunk to its target file (diff-apply-hunk
). With a
prefix argument of C-u, revert this hunk, i.e. apply the
reverse of the hunk, which changes the “new” version into the “old”
version. If diff-jump-to-old-file
is non-nil
, apply the
hunk to the “old” version of the file instead.
- C-c C-b ¶
Highlight the changes of the hunk at point with a finer granularity
(diff-refine-hunk
). This allows you to see exactly which parts
of each changed line were actually changed.
By default, Diff mode refines hunks as Emacs displays them, so you may
find this command useful if you customize diff-refine
to a
non-default value.
- C-c C-c ¶
-
Go to the source file and line corresponding to this hunk
(diff-goto-source
). By default, this jumps to the “new”
version of the file, the one shown first on the file header.
With a prefix argument, jump to the “old” version instead. If
diff-jump-to-old-file
is non-nil
, this command by
default jumps to the “old” file, and the meaning of the prefix
argument is reversed. If the prefix argument is a number greater than
8 (e.g., if you type C-u C-u C-c C-c), then this command also
sets diff-jump-to-old-file
for the next invocation.
If the source file is under version control (see Version Control),
this jumps to the work file by default. With a prefix argument, jump
to the “old” revision of the file (see Examining And Comparing Old Revisions), when
point is on the old line, or otherwise jump to the “new” revision.
- C-c C-e ¶
Start an Ediff session with the patch (diff-ediff-patch
).
See Ediff in The Ediff Manual.
- C-c C-n ¶
Restrict the view to the current hunk (diff-restrict-view
).
See Narrowing. With a prefix argument, restrict the
view to the current file of a multiple-file patch. To widen again,
use C-x n w (widen
).
- C-c C-r ¶
Reverse the direction of comparison for the entire buffer
(diff-reverse-direction
). With a prefix argument, reverse the
direction only inside the current region (see The Mark and the Region). Reversing
the direction means changing the hunks and the file-start headers to
produce a patch that would change the “new” version into the “old”
one.
- C-c C-s ¶
Split the hunk at point (diff-split-hunk
) into two separate
hunks. This inserts a hunk header and modifies the header of the
current hunk. This command is useful for manually editing patches,
and only works with the unified diff format produced by the
-u or --unified options to the diff
program. If you need to split a hunk in the context diff format
produced by the -c or --context options to
diff
, first convert the buffer to the unified diff format
with C-c C-u.
- C-c C-d ¶
Convert the entire buffer to the context diff format
(diff-unified->context
). With a prefix argument, convert only
the hunks within the region.
- C-c C-u ¶
Convert the entire buffer to unified diff format
(diff-context->unified
). With a prefix argument, convert
unified format to context format. When the mark is active, convert
only the hunks within the region.
- C-c C-l ¶
Re-generate the current hunk (diff-refresh-hunk
).
- C-c C-w ¶
Re-generate the current hunk, disregarding changes in whitespace
(diff-ignore-whitespace-hunk
).
- C-x 4 A ¶
-
Generate a ChangeLog entry, like C-x 4 a does (see Change Logs), for each one of the hunks
(diff-add-change-log-entries-other-window
). This creates a
skeleton of the log of changes that you can later fill with the actual
descriptions of the changes. C-x 4 a itself in Diff mode
operates on behalf of the current hunk’s file, but gets the function
name from the patch itself. This is useful for making log entries for
functions that are deleted by the patch.
Patches sometimes include trailing whitespace on modified lines, as
an unintentional and undesired change. There are two ways to deal
with this problem. Firstly, if you enable Whitespace mode in a Diff
buffer (see Useless Whitespace), it automatically highlights
trailing whitespace in modified lines. Secondly, you can use the
command M-x diff-delete-trailing-whitespace, which searches for
trailing whitespace in the lines modified by the patch, and removes
that whitespace in both the patch and the patched source file(s).
This command does not save the modifications that it makes, so you can
decide whether to save the changes (the list of modified files is
displayed in the echo area). With a prefix argument, it tries to
modify the original (“old”) source files rather than the patched
(“new”) source files.
If diff-font-lock-syntax
is non-nil
, fragments of
source in hunks are highlighted according to the appropriate major
mode.
18.11 Copying, Naming and Renaming Files
Emacs has several commands for copying, naming, and renaming files.
All of them read two file names, old (or target) and
new, using the minibuffer, and then copy or adjust a file’s name
accordingly; they do not accept wildcard file names.
In all these commands, if the argument new is just a directory
name (see Directory Names in the Emacs Lisp Reference
Manual), the real new name is in that directory, with the same
non-directory component as old. For example, the command
M-x rename-file RET ~/foo RET /tmp/ RET
renames ~/foo to /tmp/foo. On GNU and other POSIX-like
systems, directory names end in ‘/’.
All these commands ask for confirmation when the new file name already
exists.
M-x copy-file copies the contents of the file old to the
file new.
M-x copy-directory copies directories, similar to the
cp -r
shell command. If new is a directory name, it
creates a copy of the old directory and puts it in new.
Otherwise it copies all the contents of old into a new directory
named new. If copy-directory-create-symlink
is
non-nil
and old is a symbolic link, this command will
copy the symbolic link. If nil
, this command will follow the
link and copy the contents instead. (This is the default.)
M-x rename-file renames file old as new. If the
file name new already exists, you must confirm with yes or
renaming is not done; this is because renaming causes the old meaning
of the name new to be lost. If old and new are on
different file systems, the file old is copied and deleted.
If a file is under version control (see Version Control), you
should rename it using M-x vc-rename-file instead of
M-x rename-file. See Deleting and Renaming Version-Controlled Files.
M-x add-name-to-file adds an additional name to an existing
file without removing the old name. The new name is created as a hard
link to the existing file. The new name must belong on the same file
system that the file is on. On MS-Windows, this command works only if
the file resides in an NTFS file system. On MS-DOS, and some remote
system types, it works by copying the file.
M-x make-symbolic-link creates a symbolic link named
new, which points at target. The effect is that future
attempts to open file new will refer to whatever file is named
target at the time the opening is done, or will get an error if
the name target is nonexistent at that time. This command does
not expand the argument target, so that it allows you to specify
a relative name as the target of the link. However, this command
does expand leading ‘~’ in target so that you can easily
specify home directories, and strips leading ‘/:’ so that you can
specify relative names beginning with literal ‘~’ or ‘/:’.
See Quoted File Names. On MS-Windows, this command works only on
MS Windows Vista and later. When new is remote,
it works depending on the system type.
18.12 Miscellaneous File Operations
Emacs has commands for performing many other operations on files.
All operate on one file; they do not accept wildcard file names.
M-x delete-file prompts for a file and deletes it. If you are
deleting many files in one directory, it may be more convenient to use
Dired rather than delete-file
. See Deleting Files with Dired.
M-x move-file-to-trash moves a file into the system
Trash (or Recycle Bin). This is a facility available on
most operating systems; files that are moved into the Trash can be
brought back later if you change your mind. (The way to restore
trashed files is system-dependent.)
By default, Emacs deletion commands do not use the Trash. To
use the Trash (when it is available) for common deletion commands,
change the variable delete-by-moving-to-trash
to t
.
This affects the commands M-x delete-file and M-x
delete-directory (see File Directories), as well as the deletion
commands in Dired (see Deleting Files with Dired). Supplying a prefix
argument to M-x delete-file or M-x delete-directory makes
them delete outright, instead of using the Trash, regardless of
delete-by-moving-to-trash
.
If a file is under version control (see Version Control), you
should delete it using M-x vc-delete-file instead of M-x
delete-file. See Deleting and Renaming Version-Controlled Files.
M-x insert-file (also C-x i) inserts a copy of the
contents of the specified file into the current buffer at point,
leaving point unchanged before the contents. The position after the
inserted contents is added to the mark ring, without activating the
mark (see The Mark Ring).
M-x insert-file-literally is like M-x insert-file,
except the file is inserted literally: it is treated as a sequence
of ASCII characters with no special encoding or conversion,
similar to the M-x find-file-literally command
(see Visiting Files).
M-x write-region is the inverse of M-x insert-file; it
copies the contents of the region into the specified file. M-x
append-to-file adds the text of the region to the end of the
specified file. See Accumulating Text. The variable
write-region-inhibit-fsync
applies to these commands, as well
as saving files; see Customizing Saving of Files.
M-x set-file-modes reads a file name followed by a file
mode, and applies that file mode to the specified file. File modes,
also called file permissions, determine whether a file can be
read, written to, or executed, and by whom. This command reads file
modes using the same symbolic or octal format accepted by the
chmod
command; for instance, ‘u+x’ means to add
execution permission for the user who owns the file. It has no effect
on operating systems that do not support file modes. chmod
is a
convenience alias for this function.
18.13 Accessing Compressed Files
Emacs automatically uncompresses compressed files when you visit
them, and automatically recompresses them if you alter them and save
them. Emacs recognizes compressed files by their file names. File
names ending in ‘.gz’ indicate a file compressed with
gzip
. Other endings indicate other compression programs.
Automatic uncompression and compression apply to all the operations in
which Emacs uses the contents of a file. This includes visiting it,
saving it, inserting its contents into a buffer, loading it, and byte
compiling it.
To disable this feature, type the command M-x
auto-compression-mode. You can disable it permanently by
customizing the variable auto-compression-mode
.
18.14 File Archives
A file whose name ends in ‘.tar’ is normally an archive
made by the tar
program. Emacs views these files in a special
mode called Tar mode which provides a Dired-like list of the contents
(see Dired, the Directory Editor). You can move around through the list just as you
would in Dired, and visit the subfiles contained in the archive.
However, not all Dired commands are available in Tar mode.
If Auto Compression mode is enabled (see Accessing Compressed Files), then
Tar mode is used also for compressed archives—files with extensions
‘.tgz’, .tar.Z
and .tar.gz
.
The keys e, f and RET all extract a component file
into its own buffer. You can edit it there, and if you save the
buffer, the edited version will replace the version in the Tar buffer.
Clicking with the mouse on the file name in the Tar buffer does
likewise. v extracts a file into a buffer in View mode
(see View Mode). o extracts the file and displays it in
another window, so you could edit the file and operate on the archive
simultaneously.
The I key adds a new (regular) file to the archive. The file
is initially empty, but can readily be edited using the commands
above. The command inserts the new file before the current one, so
that using it on the topmost line of the Tar buffer makes the new file
the first one in the archive, and using it at the end of the buffer
makes it the last one.
d marks a file for deletion when you later use x, and
u unmarks a file, as in Dired. C copies a file from the
archive to disk and R renames a file within the archive.
g reverts the buffer from the archive on disk. The keys
M, G, and O change the file’s permission bits,
group, and owner, respectively.
Saving the Tar buffer writes a new version of the archive to disk with
the changes you made to the components.
You don’t need the tar
program to use Tar mode—Emacs reads
the archives directly. However, accessing compressed archives
requires the appropriate uncompression program.
A separate but similar Archive mode is used for arc
,
jar
, lzh
, zip
, rar
, 7z
, and
zoo
archives, as well as exe
files that are
self-extracting executables.
The key bindings of Archive mode are similar to those in Tar mode,
with the addition of the m key which marks a file for subsequent
operations, and M-DEL which unmarks all the marked files.
Also, the a key toggles the display of detailed file
information, for those archive types where it won’t fit in a single
line. Operations such as renaming a subfile, or changing its mode or
owner, are supported only for some of the archive formats.
Unlike Tar mode, Archive mode runs the archiving programs to unpack
and repack archives. However, you don’t need these programs to look
at the archive table of contents, only to extract or manipulate the
subfiles in the archive. Details of the program names and their
options can be set in the ‘Archive’ Customize group
(see Customization Groups).
18.15 Remote Files
You can refer to files on other machines using a special file name
syntax:
/method:host:filename
/method:user@host:filename
/method:user@host#port:filename
To carry out this request, Emacs uses a remote-login program such as
ssh
.
You must always specify in the file name which method to use—for
example, /ssh:user@host:filename uses
ssh
. When you specify the pseudo method ‘-’ in the
file name, Emacs chooses the method as follows:
- If the host name starts with ‘ftp.’ (with dot), Emacs uses FTP.
- If the user name is ‘ftp’ or ‘anonymous’, Emacs uses FTP.
- If the variable
tramp-default-method
is set to ‘ftp’,
Emacs uses FTP.
- If
ssh-agent
is running, Emacs uses scp
.
- Otherwise, Emacs uses
ssh
.
You can entirely turn off the remote file name feature by setting the
variable tramp-mode
to nil
. You can turn off the
feature in individual cases by quoting the file name with ‘/:’
(see Quoted File Names).
Remote file access through FTP is handled by the Ange-FTP package, which
is documented in the following. Remote file access through the other
methods is handled by the Tramp package, which has its own manual.
See The Tramp Manual in The Tramp Manual.
When the Ange-FTP package is used, Emacs logs in through FTP using
the name user, if that is specified in the remote file name. If
user is unspecified, Emacs logs in using your user name on the
local system; but if you set the variable ange-ftp-default-user
to a string, that string is used instead. When logging in, Emacs may
also ask for a password.
For performance reasons, Emacs does not make backup files for files
accessed via FTP by default. To make it do so, change the variable
ange-ftp-make-backup-files
to a non-nil
value.
By default, auto-save files for remote files are made in the
temporary file directory on the local machine, as specified by the
variable auto-save-file-name-transforms
. See Auto-Save Files.
To visit files accessible by anonymous FTP, you use special user
names ‘anonymous’ or ‘ftp’. Passwords for these user names
are handled specially. The variable
ange-ftp-generate-anonymous-password
controls what happens: if
the value of this variable is a string, then that string is used as
the password; if non-nil
(the default), then the value of
user-mail-address
is used; if nil
, then Emacs prompts
you for a password as usual (see Entering passwords).
Sometimes you may be unable to access files on a remote machine
because a firewall in between blocks the connection for security
reasons. If you can log in on a gateway machine from which the
target files are accessible, and whose FTP server supports
gatewaying features, you can still use remote file names; all you have
to do is specify the name of the gateway machine by setting the
variable ange-ftp-gateway-host
, and set
ange-ftp-smart-gateway
to t
. Otherwise you may be able
to make remote file names work, but the procedure is complex. You can
read the instructions by typing M-x finder-commentary RET
ange-ftp RET.
18.16 Quoted File Names
You can quote an absolute file name to prevent special
characters and syntax in it from having their special effects.
The way to do this is to add ‘/:’ at the beginning.
For example, you can quote a local file name which appears remote, to
prevent it from being treated as a remote file name. Thus, if you have
a directory named /foo: and a file named bar in it, you
can refer to that file in Emacs as ‘/:/foo:/bar’.
If you want to quote only special characters in the local part of a
remote file name, you can quote just the local part.
‘/ssh:baz:/:/foo:/bar’ refers to the file bar of directory
/foo: on the host baz.
‘/:’ can also prevent ‘~’ from being treated as a special
character for a user’s home directory. For example, /:/tmp/~hack
refers to a file whose name is ~hack in directory /tmp.
Quoting with ‘/:’ is also a way to enter in the minibuffer a
file name that contains ‘$’. In order for this to work, the
‘/:’ must be at the beginning of the minibuffer contents. (You
can also double each ‘$’; see File Names with $.)
You can also quote wildcard characters with ‘/:’, for visiting.
For example, /:/tmp/foo*bar visits the file
/tmp/foo*bar.
Another method of getting the same result is to enter
/tmp/foo[*]bar, which is a wildcard specification that matches
only /tmp/foo*bar. However, in many cases there is no need to
quote the wildcard characters because even unquoted they give the
right result. For example, if the only file name in /tmp that
starts with ‘foo’ and ends with ‘bar’ is foo*bar,
then specifying /tmp/foo*bar will visit only
/tmp/foo*bar.
18.17 File Name Cache
You can use the file name cache to make it easy to locate a
file by name, without having to remember exactly where it is located.
When typing a file name in the minibuffer, C-TAB
(file-cache-minibuffer-complete
) completes it using the file
name cache. If you repeat C-TAB, that cycles through the
possible completions of what you had originally typed. (However, note
that the C-TAB character cannot be typed on most text
terminals.)
The file name cache does not fill up automatically. Instead, you
load file names into the cache using these commands:
- M-x file-cache-add-directory RET directory RET
Add each file name in directory to the file name cache.
- M-x file-cache-add-directory-using-find RET directory RET
Add each file name in directory and all of its nested
subdirectories to the file name cache.
- M-x file-cache-add-directory-using-locate RET directory RET
Add each file name in directory and all of its nested
subdirectories to the file name cache, using locate
to find
them all.
- M-x file-cache-add-directory-list RET variable RET
Add each file name in each directory listed in variable to the
file name cache. variable should be a Lisp variable whose value
is a list of directories, like load-path
.
- M-x file-cache-clear-cache RET
Clear the cache; that is, remove all file names from it.
The file name cache is not persistent: it is kept and maintained
only for the duration of the Emacs session. You can view the contents
of the cache with the file-cache-display
command.
18.18 Convenience Features for Finding Files
In this section, we introduce some convenient facilities for finding
recently-opened files, reading file names from a buffer.
If you enable Recentf mode, with M-x recentf-mode, the
‘File’ menu includes a submenu containing a list of recently
opened files. M-x recentf-save-list saves the current
recentf-list
to a file, and M-x recentf-edit-list edits
it.
The M-x ffap command generalizes find-file
with more
powerful heuristic defaults (see Finding Files and URLs at Point), often based on the text at
point. Partial Completion mode offers other features extending
find-file
, which can be used with ffap
.
See Completion Options.
18.19 Viewing Image Files
Visiting image files automatically selects Image mode. In this
major mode, you can type C-c C-c (image-toggle-display
)
to toggle between displaying the file as an image in the Emacs buffer,
and displaying its underlying text (or raw byte) representation.
Additionally you can type C-c C-x (image-toggle-hex-display
)
to toggle between displaying the file as an image in the Emacs buffer,
and displaying it in hex representation. Displaying the file as an
image works only if Emacs is compiled with support for displaying
such images.
If the displayed image is wider or taller than the window in which it
is displayed, the usual point motion keys (C-f, C-p, and
so forth) cause different parts of the image to be displayed.
However, by default images are resized automatically to fit the
window, so this is only necessary if you customize the default
behavior by using the options image-auto-resize
and
image-auto-resize-on-window-resize
.
To resize the image manually you can use the command
image-transform-fit-both
bound to s b
that fits the image to both the window height and width.
To scale the image specifying a scale factor, use the command
image-transform-set-scale
bound to s s.
To reset all transformations to the initial state, use
image-transform-reset
bound to s 0.
You can press n (image-next-file
) and p
(image-previous-file
) to visit the next image file and the
previous image file in the same directory, respectively. These
commands will consult the “parent” dired buffer to determine what
the next/previous image file is. These commands also work when
opening a file from archive files (like zip or tar files), and will
then instead consult the archive mode buffer. If neither an archive
nor a dired “parent” buffer can be found, a dired buffer is opened.
When looking through images, it’s sometimes convenient to be able to
mark the files for later processing (for instance, if you want to
select a group of images to copy somewhere else). The m
(image-mode-mark-file
) command will mark the current file in
any Dired buffer(s) that display the current file’s directory. If no
such buffer is open, the directory is opened in a new buffer. To
unmark files, use the u (image-mode-mark-file
) command.
Finally, if you just want to copy the current buffers file name to the
kill ring, you can use the w
(image-mode-copy-file-name-as-kill
) command.
If the image can be animated, the command RET
(image-toggle-animation
) starts or stops the animation.
Animation plays once, unless the option image-animate-loop
is
non-nil
. With f (image-next-frame
) and b
(image-previous-frame
) you can step through the individual
frames. Both commands accept a numeric prefix to step through several
frames at once. You can go to a specific frame with F
(image-goto-frame
). Frames are indexed from 1. Typing a
+ (image-increase-speed
) increases the speed of the animation,
a - (image-decrease-speed
) decreases it, and a r
(image-reverse-speed
) reverses it. The command a 0
(image-reset-speed
) resets the speed to the original value.
If Emacs was compiled with support for the ImageMagick library, it
can use ImageMagick to render a wide variety of images. The variable
imagemagick-enabled-types
lists the image types that Emacs may
render using ImageMagick; each element in the list should be an
internal ImageMagick name for an image type, as a symbol or an
equivalent string (e.g., BMP
for .bmp images). To
enable ImageMagick for all possible image types, change
imagemagick-enabled-types
to t
. The variable
imagemagick-types-inhibit
lists the image types which should
never be rendered using ImageMagick, regardless of the value of
imagemagick-enabled-types
(the default list includes types like
C
and HTML
, which ImageMagick can render as an image
but Emacs should not). To disable ImageMagick entirely, change
imagemagick-types-inhibit
to t
.
If Emacs doesn’t have native support for the image format in
question, and image-use-external-converter
is non-nil
,
Emacs will try to determine whether there are external utilities that
can be used to transform the image in question to PNG before
displaying. GraphicsMagick, ImageMagick and ffmpeg
are
currently supported for image conversions.
The Image-Dired package can also be used to view images as
thumbnails. See Viewing Image Thumbnails in Dired.
18.20 Filesets
If you regularly edit a certain group of files, you can define them
as a fileset. This lets you perform certain operations, such as
visiting, query-replace
, and shell commands on all the files at
once. To make use of filesets, you must first add the expression
(filesets-init)
to your init file (see The Emacs Initialization File). This
adds a ‘Filesets’ sub-menu to the menu bar’s ‘File’ menu.
The simplest way to define a fileset is by adding files to it one at
a time. To add a file to fileset name, visit the file and type
M-x filesets-add-buffer RET name RET. If
there is no fileset name, this creates a new one, which
initially contains only the current file. The command M-x
filesets-remove-buffer removes the current file from a fileset.
You can also edit the list of filesets directly, with M-x
filesets-edit (or by choosing ‘Edit Filesets’ from the
‘Filesets’ menu). The editing is performed in a Customize buffer
(see Easy Customization Interface). Normally, a fileset is a simple list of
files, but you can also define a fileset as a regular expression
matching file names. Some examples of these more complicated filesets
are shown in the Customize buffer. Remember to select ‘Save for
future sessions’ if you want to use the same filesets in future Emacs
sessions.
You can use the command M-x filesets-open to visit all the
files in a fileset, and M-x filesets-close to close them. Use
M-x filesets-run-cmd to run a shell command on all the files in
a fileset. These commands are also available from the ‘Filesets’
menu, where each existing fileset is represented by a submenu.
See Version Control, for a different concept of filesets:
groups of files bundled together for version control operations.
Filesets of that type are unnamed, and do not persist across Emacs
sessions.
19 Using Multiple Buffers
The text you are editing in Emacs resides in an object called a
buffer. Each time you visit a file, a buffer is used to hold
the file’s text. Each time you invoke Dired, a buffer is used to hold
the directory listing. If you send a message with C-x m, a
buffer is used to hold the text of the message. When you ask for a
command’s documentation, that appears in a buffer named *Help*.
Buffers exist as long as they are in use, and are deleted
(“killed”) when no longer needed, either by you (see Killing Buffers) or by Emacs (e.g., when you exit Emacs, see Exiting Emacs).
Each buffer has a unique name, which can be of any length. When a
buffer is displayed in a window, its name is shown in the mode line
(see The Mode Line). The distinction between upper and lower case
matters in buffer names. Most buffers are made by visiting files, and
their names are derived from the files’ names; however, you can also
create an empty buffer with any name you want. A newly started Emacs
has several buffers, including one named *scratch*, which can
be used for evaluating Lisp expressions and is not associated with any
file (see Lisp Interaction Buffers).
At any time, one and only one buffer is selected; we call it
the current buffer. We sometimes say that a command operates on
“the buffer”; this really means that it operates on the current
buffer. When there is only one Emacs window, the buffer displayed in
that window is current. When there are multiple windows, the buffer
displayed in the selected window is current. See Multiple Windows.
A buffer’s contents consist of a series of characters, each of
which optionally carries a set of text properties
(see Text properties) that can specify more
information about that character.
Aside from its textual contents, each buffer records several pieces
of information, such as what file it is visiting (if any), whether it
is modified, and what major mode and minor modes are in effect
(see Major and Minor Modes). These are stored in buffer-local
variables—variables that can have a different value in each buffer.
See Local Variables.
A buffer’s size cannot be larger than some maximum, which is defined
by the largest buffer position representable by Emacs integers.
This is because Emacs tracks buffer positions using that data type.
For typical 64-bit machines, this maximum buffer size is 2^{61} - 2
bytes, or about 2 EiB. For typical 32-bit machines, the maximum is
usually 2^{29} - 2 bytes, or about 512 MiB. Buffer sizes are
also limited by the amount of memory in the system.
19.1 Creating and Selecting Buffers
- C-x b buffer RET
Select or create a buffer named buffer (switch-to-buffer
).
- C-x 4 b buffer RET
Similar, but select buffer in another window
(switch-to-buffer-other-window
).
- C-x 5 b buffer RET
Similar, but select buffer in a separate frame
(switch-to-buffer-other-frame
).
- C-x LEFT
Select the previous buffer in the buffer list (previous-buffer
).
- C-x RIGHT
Select the next buffer in the buffer list (next-buffer
).
- C-u M-g M-g
- C-u M-g g
Read a number n and move to line n in the most recently
selected buffer other than the current buffer, in another window.
The C-x b (switch-to-buffer
) command reads a buffer
name using the minibuffer. Then it makes that buffer current, and
displays it in the currently-selected window. An empty input
specifies the buffer that was current most recently among those not
now displayed in any window.
While entering the buffer name, you can use the usual completion and
history commands (see The Minibuffer). Note that C-x b, and
related commands, use permissive completion with confirmation
for minibuffer completion: if you type RET when the minibuffer
text names a nonexistent buffer, Emacs prints ‘[Confirm]’ and you
must type a second RET to submit that buffer name.
See Completion Exit, for details. For other completion options and
features, see Completion Options.
If you specify a buffer that does not exist, C-x b creates a
new, empty buffer that is not visiting any file, and selects it for
editing. The default value of the variable major-mode
determines the new buffer’s major mode; the default value is
Fundamental mode. See Major Modes. One reason to create a new
buffer is to use it for making temporary notes. If you try to save
it, Emacs asks for the file name to use, and the buffer’s major mode
is re-established taking that file name into account (see Choosing File Modes).
For conveniently switching between a few buffers, use the commands
C-x LEFT and C-x RIGHT. C-x LEFT
(previous-buffer
) selects the previous buffer (following the
order of most recent selection in the current frame), while C-x
RIGHT (next-buffer
) moves through buffers in the reverse
direction. Both commands support a numeric prefix argument that
serves as a repeat count.
To select a buffer in a window other than the current one
(see Multiple Windows), type C-x 4 b
(switch-to-buffer-other-window
). This prompts for a buffer
name using the minibuffer, displays that buffer in another window, and
selects that window.
Similarly, C-x 5 b (switch-to-buffer-other-frame
)
prompts for a buffer name, displays that buffer in another frame
(see Frames and Graphical Displays), and selects that frame. If the buffer is already
being shown in a window on another frame, Emacs selects that window
and frame instead of creating a new frame.
See Displaying a Buffer in a Window, for how the C-x 4 b and C-x 5
b commands get the window and/or frame to display in.
In addition, C-x C-f, and any other command for visiting a
file, can also be used to switch to an existing file-visiting buffer.
See Visiting Files.
C-u M-g M-g, that is goto-line
with a plain prefix
argument, reads a number n using the minibuffer, selects the
most recently selected buffer other than the current buffer in another
window, and then moves point to the beginning of line number n
in that buffer. This is mainly useful in a buffer that refers to line
numbers in another buffer: if point is on or just after a number,
goto-line
uses that number as the default for n. Note
that prefix arguments other than just C-u behave differently.
C-u 4 M-g M-g goes to line 4 in the current buffer,
without reading a number from the minibuffer. (Remember that M-g
M-g without prefix argument reads a number n and then moves to
line number n in the current buffer. See Changing the Location of Point.)
Emacs uses buffer names that start with a space for internal purposes.
It treats these buffers specially in minor ways—for example, by
default they do not record undo information. It is best to avoid using
such buffer names yourself.
19.2 Listing Existing Buffers
- C-x C-b
List the existing buffers (list-buffers
).
To display a list of existing buffers, type C-x C-b. This
pops up a buffer menu in a buffer named *Buffer List*. Each
line in the list shows one buffer’s name, size, major mode and visited file.
The buffers are listed in the order that they were current; the
buffers that were current most recently come first. This section
describes how the list of buffers is displayed and how to interpret
the various indications in the list; see Operating on Several Buffers, for
description of the special mode in the *Buffer List* buffer and
the commands available there.
‘.’ in the first field of a line indicates that the buffer is
current. ‘%’ indicates a read-only buffer. ‘*’ indicates
that the buffer is modified. If several buffers are modified, it
may be time to save some with C-x s (see Commands for Saving Files).
Here is an example of a buffer list:
CRM Buffer Size Mode File
. * .emacs 3294 Emacs-Lisp ~/.emacs
% *Help* 101 Help
search.c 86055 C ~/cvs/emacs/src/search.c
% src 20959 Dired by name ~/cvs/emacs/src/
* *mail* 42 Mail
% HELLO 1607 Fundamental ~/cvs/emacs/etc/HELLO
% NEWS 481184 Outline ~/cvs/emacs/etc/NEWS
*scratch* 191 Lisp Interaction
* *Messages* 1554 Messages
The buffer *Help* was made by a help request (see Help); it
is not visiting any file. The buffer src
was made by Dired on
the directory ~/cvs/emacs/src/. You can list only buffers that
are visiting files by giving the command a prefix argument, as in
C-u C-x C-b.
list-buffers
omits buffers whose names begin with a space,
unless they visit files: such buffers are used internally by Emacs.
19.3 Miscellaneous Buffer Operations
- C-x C-q
Toggle read-only status of buffer (read-only-mode
).
- C-x x r RET buffer RET
Change the name of the current buffer.
- C-x x u
Rename the current buffer by adding ‘<number>’ to the end.
- M-x view-buffer RET buffer RET
Scroll through buffer buffer. See View Mode.
A buffer can be read-only, which means that commands to insert
or delete its text are not allowed. (However, other commands, like
C-x RET f, can still mark it as modified, see Specifying a Coding System for File Text). The mode line indicates read-only buffers with ‘%%’ or
‘%*’ near the left margin. See The Mode Line. Read-only buffers
are usually made by subsystems such as Dired and Rmail that have
special commands to operate on the text. Visiting a file whose access
control says you cannot write it also makes the buffer read-only.
The command C-x C-q (read-only-mode
) makes a read-only
buffer writable, and makes a writable buffer read-only. This works by
setting the variable buffer-read-only
, which has a local value
in each buffer and makes the buffer read-only if its value is
non-nil
. If you change the option view-read-only
to a
non-nil
value, making the buffer read-only with C-x C-q
also enables View mode in the buffer (see View Mode).
C-x x r (rename-buffer
changes the name of the current
buffer. You specify the new name as a minibuffer argument; there is
no default. If you specify a name that is in use for some other
buffer, an error happens and no renaming is done.
C-x x u (rename-uniquely
) renames the current buffer to
a similar name with a numeric suffix added to make it both different
and unique. This command does not need an argument. It is useful for
creating multiple shell buffers: if you rename the *shell*
buffer, then do M-x shell again, it makes a new shell buffer
named *shell*; meanwhile, the old shell buffer continues to
exist under its new name. This method is also good for mail buffers,
compilation buffers, and most Emacs features that create special
buffers with particular names. (With some of these features, such as
M-x compile, M-x grep, you need to switch to some other
buffer before using the command again, otherwise it will reuse the
current buffer despite the name change.)
The commands M-x append-to-buffer and C-x x i
(insert-buffer
) can also be used to copy text from one buffer
to another. See Accumulating Text.
19.4 Killing Buffers
If you continue an Emacs session for a while, you may accumulate a
large number of buffers. You may then find it convenient to kill
the buffers you no longer need. (Some other editors call this
operation close, and talk about “closing the buffer” or
“closing the file” visited in the buffer.) On most operating
systems, killing a buffer releases the memory Emacs used for the buffer
back to the operating system so that other programs can use it. Here
are some commands for killing buffers:
- C-x k buffer RET
Kill buffer buffer (kill-buffer
).
- M-x kill-some-buffers
Offer to kill each buffer, one by one.
- M-x kill-matching-buffers
Offer to kill all buffers matching a regular expression.
C-x k (kill-buffer
) kills one buffer, whose name you
specify in the minibuffer. The default, used if you type just
RET in the minibuffer, is to kill the current buffer. If you
kill the current buffer, another buffer becomes current: one that was
current in the recent past but is not displayed in any window now. If
you ask to kill a file-visiting buffer that is modified, then you must
confirm with yes before the buffer is killed.
The command M-x kill-some-buffers asks about each buffer, one
by one. An answer of yes means to kill the buffer, just like
kill-buffer
. This command ignores buffers whose names begin
with a space, which are used internally by Emacs.
The command M-x kill-matching-buffers prompts for a regular
expression and kills all buffers whose names match that expression.
See Syntax of Regular Expressions. Like kill-some-buffers
, it asks for
confirmation before each kill. This command normally ignores buffers
whose names begin with a space, which are used internally by Emacs.
To kill internal buffers as well, call kill-matching-buffers
with a prefix argument.
The Buffer Menu feature is also convenient for killing various
buffers. See Operating on Several Buffers.
If you want to do something special every time a buffer is killed, you
can add hook functions to the hook kill-buffer-hook
(see Hooks).
If you run one Emacs session for a period of days, as many people do,
it can fill up with buffers that you used several days ago. The command
M-x clean-buffer-list is a convenient way to purge them; it kills
all the unmodified buffers that you have not used for a long time. An
ordinary buffer is killed if it has not been displayed for three days;
however, you can specify certain buffers that should never be killed
automatically, and others that should be killed if they have been unused
for a mere hour. These defaults, and other aspects of this command’s
behavior, can be controlled by customizing several options described
in the doc string of clean-buffer-list
.
You can also have this buffer purging done for you, once a day,
by enabling Midnight mode. Midnight mode operates each day
at midnight; at that time, it runs clean-buffer-list
, or
whichever functions you have placed in the normal hook
midnight-hook
(see Hooks). To enable Midnight mode, use
the Customization buffer to set the variable midnight-mode
to
t
. See Easy Customization Interface.
19.5 Operating on Several Buffers
- M-x buffer-menu
Begin editing a buffer listing all Emacs buffers.
- M-x buffer-menu-other-window
Similar, but do it in another window.
The Buffer Menu opened by C-x C-b (see Listing Existing Buffers)
does not merely list buffers. It also allows you to perform various
operations on buffers, through an interface similar to Dired
(see Dired, the Directory Editor). You can save buffers, kill them (here called
deleting them, for consistency with Dired), or display them.
To use the Buffer Menu, type C-x C-b and switch to the window
displaying the *Buffer List* buffer. You can also type
M-x buffer-menu to open the Buffer Menu in the selected window.
Alternatively, the command M-x buffer-menu-other-window opens
the Buffer Menu in another window, and selects that window.
The Buffer Menu is a read-only buffer, and can be changed only
through the special commands described in this section. The usual
cursor motion commands can be used in this buffer. The following
commands apply to the buffer described on the current line:
-
Flag the buffer for deletion (killing), then move point to the next
line (Buffer-menu-delete
). The deletion flag is indicated by
the character ‘D’ on the line, before the buffer name. The
deletion occurs only when you type the x command (see below).
-
Like d, but move point up instead of down
(Buffer-menu-delete-backwards
).
-
Flag the buffer for saving (Buffer-menu-save
). The save flag
is indicated by the character ‘S’ on the line, before the buffer
name. The saving occurs only when you type x. You may request
both saving and deletion for the same buffer.
-
Perform all flagged deletions and saves (Buffer-menu-execute
).
-
Remove all flags from the current line, and move down
(Buffer-menu-unmark
). With a prefix argument, moves up after
removing the flags.
-
Move to the previous line and remove all flags on that line
(Buffer-menu-backup-unmark
).
-
Remove a particular flag from all lines
(Buffer-menu-unmark-all-buffers
). This asks for a single
character, and unmarks buffers marked with that character; typing
RET removes all marks.
-
Remove all flags from all the lines
(Buffer-menu-unmark-all
).
The commands for removing flags, d and C-d, accept a
numeric argument as a repeat count.
The following commands operate immediately on the buffer listed on
the current line. They also accept a numeric argument as a repeat
count.
-
Mark the buffer as unmodified (Buffer-menu-not-modified
).
See Commands for Saving Files.
-
Toggle the buffer’s read-only status
(Buffer-menu-toggle-read-only
). See Miscellaneous Buffer Operations.
-
Visit the buffer as a tags table
(Buffer-menu-visit-tags-table
). See Selecting a Tags Table.
The following commands are used to select another buffer or buffers:
- q ¶
-
Quit the Buffer Menu (quit-window
). The most recent formerly
visible buffer is displayed in its place.
- f
-
Select this line’s buffer, replacing the *Buffer List* buffer
in its window (Buffer-menu-this-window
).
-
Select this line’s buffer in another window, as if by C-x 4 b,
leaving *Buffer List* visible
(Buffer-menu-other-window
).
-
Display this line’s buffer in another window, without selecting it
(Buffer-menu-switch-other-window
).
-
Select this line’s buffer in a full-frame window
(Buffer-menu-1-window
).
-
Set up two windows on the current frame, with this line’s buffer
selected in one, and a previously current buffer (aside from
*Buffer List*) in the other (Buffer-menu-2-window
).
-
Bury this line’s buffer (Buffer-menu-bury
) (i.e., move it to
the end of the buffer list).
-
Mark this line’s buffer to be displayed in another window if you exit
with the v command (Buffer-menu-mark
). The display flag
is indicated by the character ‘>’ at the beginning of the line.
(A single buffer may not have both deletion and display flags.)
-
Select this line’s buffer, and also display in other windows any
buffers flagged with the m command (Buffer-menu-select
).
If you have not flagged any buffers, this command is equivalent to
1.
The following commands affect the entire buffer list:
- S ¶
-
Sort the Buffer Menu entries according to their values in the column
at point. With a numeric prefix argument n, sort according to
the n-th column (tabulated-list-sort
).
-
Widen the current column width by n (the prefix numeric
argument) characters.
-
Narrow the current column width by n (the prefix numeric
argument) characters.
-
Delete, or reinsert, lines for non-file buffers
(Buffer-menu-toggle-files-only
). This command toggles the
inclusion of such buffers in the buffer list.
Normally, the buffer *Buffer List* is not updated
automatically when buffers are created and killed; its contents are
just text. If you have created, deleted or renamed buffers, the way
to update *Buffer List* to show what you have done is to type
g (revert-buffer
). You can make this happen regularly
every auto-revert-interval
seconds if you enable Auto Revert
mode in this buffer, as long as it is not marked modified. Global
Auto Revert mode applies to the *Buffer List* buffer only if
global-auto-revert-non-file-buffers
is non-nil
.
See global-auto-revert-non-file-buffers, for details.
19.6 Indirect Buffers
An indirect buffer shares the text of some other buffer, which
is called the base buffer of the indirect buffer. In some ways it
is a buffer analogue of a symbolic link between files.
-
- M-x make-indirect-buffer RET base-buffer RET indirect-name RET
Create an indirect buffer named indirect-name with base buffer
base-buffer.
- M-x clone-indirect-buffer RET
Create an indirect buffer that is a twin copy of the current buffer.
- C-x 4 c ¶
-
Create an indirect buffer that is a twin copy of the current buffer, and
select it in another window (clone-indirect-buffer-other-window
).
The text of the indirect buffer is always identical to the text of its
base buffer; changes made by editing either one are visible immediately
in the other. “Text” here includes both the characters and their text
properties. But in all other respects, the indirect buffer and its
base buffer are completely separate. They can have different names,
different values of point, different narrowing, different markers,
different overlays, different major modes, and different local variables.
An indirect buffer cannot visit a file, but its base buffer can. If
you try to save the indirect buffer, that actually works by saving the
base buffer. Killing the base buffer effectively kills the indirect
buffer, but killing an indirect buffer has no effect on its base buffer.
One way to use indirect buffers is to display multiple views of an
outline. See Viewing One Outline in Multiple Views.
A quick and handy way to make an indirect buffer is with the command
M-x clone-indirect-buffer. It creates and selects an indirect
buffer whose base buffer is the current buffer. With a numeric
argument, it prompts for the name of the indirect buffer; otherwise it
uses the name of the current buffer, with a ‘<n>’ suffix
added. C-x 4 c (clone-indirect-buffer-other-window
)
works like M-x clone-indirect-buffer, but it selects the new
buffer in another window. These functions run the hook
clone-indirect-buffer-hook
after creating the indirect buffer.
The more general way to make an indirect buffer is with the command
M-x make-indirect-buffer. It creates an indirect buffer
named indirect-name from a buffer base-buffer, prompting for
both using the minibuffer.
Note: When a modification is made to the text of a buffer, the
modification hooks are run only in the base buffer, because most of
the functions on those hooks are not prepared to work correctly in
indirect buffers. So if you need a modification hook function in an
indirect buffer, you need to manually add that function to the hook
in the base buffer and then make the function operate in the
desired indirect buffer.
19.7 Convenience Features and Customization of Buffer Handling
This section describes several modes and features that make it more
convenient to switch between buffers.
19.7.1 Making Buffer Names Unique
When several buffers visit identically-named files, Emacs must give
the buffers distinct names. The default method adds a suffix based on
the names of the directories that contain the files. For example, if
you visit files /foo/bar/mumble/name and
/baz/quux/mumble/name at the same time, their buffers will be
named ‘name<bar/mumble>’ and ‘name<quux/mumble>’, respectively.
Emacs adds as many directory parts as are needed to make a unique name.
You can choose from several different styles for constructing unique
buffer names, by customizing the option uniquify-buffer-name-style
.
The forward
naming method includes part of the file’s
directory name at the beginning of the buffer name; using this method,
buffers visiting the files /u/rms/tmp/Makefile and
/usr/projects/zaphod/Makefile would be named
‘tmp/Makefile’ and ‘zaphod/Makefile’.
In contrast, the post-forward
naming method would call the
buffers ‘Makefile|tmp’ and ‘Makefile|zaphod’. The default
method post-forward-angle-brackets
is like post-forward
,
except that it encloses the unique path in angle brackets. The
reverse
naming method would call them ‘Makefile\tmp’ and
‘Makefile\zaphod’. The nontrivial difference between
post-forward
and reverse
occurs when just one directory
name is not enough to distinguish two files; then reverse
puts
the directory names in reverse order, so that /top/middle/file
becomes ‘file\middle\top’, while post-forward
puts them in
forward order after the file name, as in ‘file|top/middle’. If
uniquify-buffer-name-style
is set to nil
, the buffer
names simply get ‘<2>’, ‘<3>’, etc. appended.
The value of uniquify-buffer-name-style
can be set to a
customized function with two arguments base and
extra-strings where base is a string and
extra-strings is a list of strings. For example the current
implementation for post-forward-angle-brackets
could be:
(defun my-post-forward-angle-brackets (base extra-string)
(concat base \"<\" (mapconcat #'identity extra-string \"/\") \">\"))
Which rule to follow for putting the directory names in the buffer
name is not very important if you are going to look at the
buffer names before you type one. But as an experienced user, if you
know the rule, you won’t have to look. And then you may find that one
rule or another is easier for you to remember and apply quickly.
19.7.2 Fast minibuffer selection
Icomplete global minor mode provides a convenient way to quickly select an
element among the possible completions in a minibuffer. When enabled, typing
in the minibuffer continuously displays a list of possible completions that
match the string you have typed.
At any time, you can type C-j to select the first completion in
the list. So the way to select a particular completion is to make it the
first in the list. There are two ways to do this. You can type more
of the completion name and thus narrow down the list, excluding unwanted
completions above the desired one. Alternatively, you can use C-.
and C-, to rotate the list until the desired buffer is first.
M-TAB will select the first completion in the list, like
C-j but without exiting the minibuffer, so you can edit it
further. This is typically used when entering a file name, where
M-TAB can be used a few times to descend in the hierarchy
of directories.
To enable Icomplete mode, type M-x icomplete-mode, or customize
the variable icomplete-mode
to t
(see Easy Customization Interface).
An alternative to Icomplete mode is Fido mode. This is very similar
to Icomplete mode, but retains some functionality from a popular
extension called Ido mode (in fact the name is derived from “Fake
Ido”). Among other things, in Fido mode, C-s and C-r are
also used to rotate the completions list, C-k can be used to
delete files and kill buffers in-list. Another noteworthy aspect is
that flex
is used as the default completion style
(see How Completion Alternatives Are Chosen). To change this, add the following to
your initialization file (see The Emacs Initialization File):
(defun my-icomplete-styles ()
(setq-local completion-styles '(initials flex)))
(add-hook 'icomplete-minibuffer-setup-hook 'my-icomplete-styles)
To enable Fido mode, type M-x fido-mode, or customize
the variable fido-mode
to t
(see Easy Customization Interface).
Icomplete mode and Fido mode display the possible completions on the
same line as the prompt by default. To display the completion candidates
vertically under the prompt, type M-x icomplete-vertical-mode, or
customize the variable icomplete-vertical-mode
to t
(see Easy Customization Interface).
20 Multiple Windows
Emacs can split a frame into two or many windows. Multiple windows
can display parts of different buffers, or different parts of one
buffer. Multiple frames always imply multiple windows, because each
frame has its own set of windows. Each window belongs to one and only
one frame.
20.1 Concepts of Emacs Windows
Each Emacs window displays one Emacs buffer at any time. A single
buffer may appear in more than one window; if it does, any changes in
its text are displayed in all the windows where it appears. But these
windows can show different parts of the buffer, because each window
has its own value of point.
At any time, one Emacs window is the selected window; the
buffer this window is displaying is the current buffer. On graphical
displays, the point is indicated by a solid blinking cursor in the
selected window, and by a hollow box in non-selected windows. On text
terminals, the cursor is drawn only in the selected window.
See Displaying the Cursor.
Commands to move point affect the value of point for the selected
Emacs window only. They do not change the value of point in other
Emacs windows, even those showing the same buffer. The same is true
for buffer-switching commands such as C-x b; they do not affect
other windows at all. However, there are other commands such as
C-x 4 b that select a different window and switch buffers in it.
Also, all commands that display information in a window, including
(for example) C-h f (describe-function
) and C-x C-b
(list-buffers
), usually work by displaying buffers in a
nonselected window without affecting the selected window.
When multiple windows show the same buffer, they can have different
regions, because they can have different values of point. However,
they all have the same value for the mark, because each buffer has
only one mark position.
Each window has its own mode line, which displays the buffer name,
modification status and major and minor modes of the buffer that is
displayed in the window. The selected window’s mode line appears in a
different color. See The Mode Line, for details.
20.2 Splitting Windows
- C-x 2
Split the selected window into two windows, one above the other
(split-window-below
).
- C-x 3
Split the selected window into two windows, positioned side by side
(split-window-right
).
- C-mouse-2
In the mode line of a window, split that window.
C-x 2 (split-window-below
) splits the selected window
into two windows, one above the other. After splitting, the selected
window is the upper one, and the newly split-off window is below.
Both windows have the same value of point as before, and display the
same portion of the buffer (or as close to it as possible). If
necessary, the windows are scrolled to keep point on-screen. By
default, the two windows each get half the height of the original
window. A positive numeric argument specifies how many lines to give
to the top window; a negative numeric argument specifies how many
lines to give to the bottom window.
If you change the variable split-window-keep-point
to
nil
, C-x 2 instead adjusts the portion of the buffer
displayed by the two windows, as well as the value of point in each
window, in order to keep the text on the screen as close as possible
to what it was before; furthermore, if point was in the lower half of
the original window, the bottom window is selected instead of the
upper one.
C-x 3 (split-window-right
) splits the selected window
into two side-by-side windows. The left window is the selected one;
the right window displays the same portion of the same buffer, and has
the same value of point. A positive numeric argument specifies how
many columns to give the left window; a negative numeric argument
specifies how many columns to give the right window.
When you split a window with C-x 3, each resulting window
occupies less than the full width of the frame. If it becomes too
narrow, the buffer may be difficult to read if continuation lines are
in use (see Continuation Lines). Therefore, Emacs automatically
switches to line truncation if the window width becomes narrower than
50 columns. This truncation occurs regardless of the value of the
variable truncate-lines
(see Line Truncation); it is
instead controlled by the variable
truncate-partial-width-windows
. If the value of this variable
is a positive integer (the default is 50), that specifies the minimum
total width for a partial-width window before automatic line
truncation occurs; if the value is nil
, automatic line
truncation is disabled; and for any other non-nil
value, Emacs
truncates lines in every partial-width window regardless of its width.
The total width of a window is in column units as reported by
window-total-width
(see Window Sizes in The Emacs
Lisp Reference Manual), it includes the fringes, the continuation and
truncation glyphs, the margins, and the scroll bar.
On text terminals, side-by-side windows are separated by a vertical
divider which is drawn using the vertical-border
face.
If you click C-mouse-2 in the mode line of a window, that
splits the window, putting a vertical divider where you click.
Depending on how Emacs is compiled, you can also split a window by
clicking C-mouse-2 in the scroll bar, which puts a horizontal
divider where you click (this feature does not work when Emacs uses
GTK+ scroll bars).
By default, when you split a window, Emacs gives each of the
resulting windows dimensions that are an integral multiple of the
default font size of the frame. That might subdivide the screen
estate unevenly between the resulting windows. If you set the
variable window-resize-pixelwise
to a non-nil
value,
Emacs will give each window the same number of pixels (give or take
one pixel if the initial dimension was an odd number of pixels). Note
that when a frame’s pixel size is not a multiple of the frame’s
character size, at least one window may get resized pixelwise even if
this option is nil
.
20.3 Using Other Windows
- C-x o
Select another window (other-window
).
- C-M-v
Scroll the next window upward (scroll-other-window
).
- C-M-S-v
Scroll the next window downward (scroll-other-window-down
).
- C-M-S-l
Recenter the next window (recenter-other-window
).
- mouse-1
mouse-1, in the text area of a window, selects the window and
moves point to the position clicked. Clicking in the mode line
selects the window without moving point in it.
With the keyboard, you can switch windows by typing C-x o
(other-window
). That is an o, for “other”, not a zero.
When there are more than two windows, this command moves through all the
windows in a cyclic order, generally top to bottom and left to right.
After the rightmost and bottommost window, it goes back to the one at
the upper left corner. A numeric argument means to move several steps
in the cyclic order of windows. A negative argument moves around the
cycle in the opposite order. When the minibuffer is active, the
minibuffer window is the last window in the cycle; you can switch from
the minibuffer window to one of the other windows, and later switch
back and finish supplying the minibuffer argument that is requested.
See Editing in the Minibuffer.
The other-window
command will normally only switch to the next
window in the current frame (unless otherwise configured). If you
work in a multi-frame environment and you want windows in all frames
to be part of the cycle, you can rebind C-x o to the
next-window-any-frame
command. (See Changing Key Bindings Interactively, for how to
rebind a command.)
The usual scrolling commands (see Controlling the Display) apply to the selected
window only, but there are also commands to scroll the next window.
C-M-v (scroll-other-window
) scrolls the window that
C-x o would select. In other respects, the command behaves like
C-v; both move the buffer text upward relative to the window, and
take positive and negative arguments. (In the minibuffer, C-M-v
scrolls the help window associated with the minibuffer, if any, rather
than the next window in the standard cyclic order; see Editing in the Minibuffer.) C-M-S-v (scroll-other-window-down
) scrolls the
next window downward in a similar way. Likewise, C-M-S-l
(recenter-other-window
) behaves like C-l
(recenter-top-bottom
) in the next window.
If you set mouse-autoselect-window
to a non-nil
value,
moving the mouse over a different window selects that window. This
feature is off by default.
20.4 Displaying in Another Window
C-x 4 is a prefix key for a variety of commands that switch to
a buffer in a different window—either another existing window, or a
new window created by splitting the selected window. See How display-buffer
works, for how Emacs picks or creates the window to use.
- C-x 4 b bufname RET
Select buffer bufname in another window
(switch-to-buffer-other-window
). See Creating and Selecting Buffers.
- C-x 4 C-o bufname RET ¶
Display buffer bufname in some window, without trying to select
it (display-buffer
). See Displaying a Buffer in a Window, for details
about how the window is chosen.
- C-x 4 f filename RET
Visit file filename and select its buffer in another window
(find-file-other-window
). See Visiting Files.
- C-x 4 d directory RET
Select a Dired buffer for directory directory in another window
(dired-other-window
). See Dired, the Directory Editor.
- C-x 4 m
Start composing a mail message, similar to C-x m (see Sending Mail), but in another window (compose-mail-other-window
).
- C-x 4 .
Find the definition of an identifier, similar to M-.
(see Find Identifier References), but in another window
(xref-find-definitions-other-window
).
- C-x 4 r filename RET
Visit file filename read-only, and select its buffer in another
window (find-file-read-only-other-window
). See Visiting Files.
- C-x 4 4
A more general prefix command affects the buffer displayed by the next
command invoked immediately after this prefix command. It requests
the buffer of the next command to be displayed in another window.
- C-x 4 1
This general prefix command requests the buffer of the next command
to be displayed in the same window.
20.5 Deleting and Resizing Windows
- C-x 0
Delete the selected window (delete-window
).
- C-x 1
Delete all windows in the selected frame except the selected window
(delete-other-windows
).
- C-x 4 0
Delete the selected window and kill the buffer that was showing in it
(kill-buffer-and-window
). The last character in this key
sequence is a zero.
- M-x delete-windows-on RET buffer RET
Delete windows showing the specified buffer.
- C-x ^
Make selected window taller (enlarge-window
).
- C-x }
Make selected window wider (enlarge-window-horizontally
).
- C-x {
Make selected window narrower (shrink-window-horizontally
).
- C-x -
Shrink this window if its buffer doesn’t need so many lines
(shrink-window-if-larger-than-buffer
).
- C-x +
Make all windows the same height (balance-windows
).
To delete the selected window, type C-x 0
(delete-window
). (That is a zero.) Once a window is deleted,
the space that it occupied is given to an adjacent window (but not the
minibuffer window, even if that is active at the time). Deleting the
window has no effect on the buffer it used to display; the buffer
continues to exist, and you can still switch to it with C-x b.
The option delete-window-choose-selected
allows to choose which
window becomes the new selected window instead (see Deleting
Windows in The Emacs Lisp Reference Manual).
C-x 4 0 (kill-buffer-and-window
) is a stronger command
than C-x 0; it kills the current buffer and then deletes the
selected window.
C-x 1 (delete-other-windows
) deletes all the windows,
except the selected one; the selected window expands to use the
whole frame. (This command cannot be used while the minibuffer window
is active; attempting to do so signals an error.)
M-x delete-windows-on deletes windows that show a specific
buffer. It prompts for the buffer, defaulting to the current buffer.
With prefix argument of zero, C-u 0, this command deletes
windows only on the current display’s frames.
The command C-x ^ (enlarge-window
) makes the selected
window one line taller, taking space from a vertically adjacent window
without changing the height of the frame. With a positive numeric
argument, this command increases the window height by that many lines;
with a negative argument, it reduces the height by that many lines.
If there are no vertically adjacent windows (i.e., the window is at the
full frame height), that signals an error. The command also signals
an error if you attempt to reduce the height of any window below a
certain minimum number of lines, specified by the variable
window-min-height
(the default is 4).
Similarly, C-x } (enlarge-window-horizontally
) makes
the selected window wider, and C-x {
(shrink-window-horizontally
) makes it narrower. These commands
signal an error if you attempt to reduce the width of any window below
a certain minimum number of columns, specified by the variable
window-min-width
(the default is 10).
Mouse clicks on the mode line (see Mode Line Mouse Commands) or on window
dividers (see Window Dividers) provide another way to change window
heights and to split or delete windows.
C-x - (shrink-window-if-larger-than-buffer
) reduces the
height of the selected window, if it is taller than necessary to show
the whole text of the buffer it is displaying. It gives the extra
lines to other windows in the frame.
You can also use C-x + (balance-windows
) to even out the
heights of all the windows in the selected frame.
20.6 Displaying a Buffer in a Window
It is a common Emacs operation to display or pop up some buffer
in response to a user command. There are several different ways in
which commands do this.
Many commands, like C-x C-f (find-file
), by default
display the buffer by “taking over” the selected window, expecting
that the user’s attention will be diverted to that buffer.
Some commands try to display intelligently, trying not to take
over the selected window, e.g., by splitting off a new window and
displaying the desired buffer there. Such commands, which include the
various help commands (see Help), work by calling
display-buffer
internally. See How display-buffer
works, for details.
Other commands do the same as display-buffer
, and
additionally select the displaying window so that you can begin
editing its buffer. The command M-g M-n (next-error
) is
one example (see Compilation Mode). Such commands work by calling
the function pop-to-buffer
internally. See Switching to a Buffer in a Window in The Emacs Lisp
Reference Manual.
Commands with names ending in -other-window
behave like
display-buffer
, except that they never display in the selected
window. Several of these commands are bound in the C-x 4 prefix
key (see Displaying in Another Window).
Commands with names ending in -other-frame
behave like
display-buffer
, except that they (i) never display in the
selected window and (ii) prefer to either create a new frame or use a
window on some other frame to display the desired buffer. Several of
these commands are bound in the C-x 5 prefix key.
20.6.1 How display-buffer
works
The display-buffer
command (as well as commands that call it
internally) chooses a window to display by following the steps given
below. See Choosing a Window for Displaying a
Buffer in The Emacs Lisp Reference Manual, for details about how
to alter this sequence of steps.
- If the buffer should be displayed in the selected window regardless of
other considerations, reuse the selected window. By default, this
step is skipped, but you can tell Emacs not to skip it by adding a
regular expression matching the buffer’s name together with a
reference to the
display-buffer-same-window
action function
(see Action Functions for Buffer
Display in The Emacs Lisp Reference Manual) to the option
display-buffer-alist
(see Choosing a Window
for Displaying a Buffer in The Emacs Lisp Reference Manual).
For example, to display the buffer *scratch* preferably in the
selected window write:
(customize-set-variable
'display-buffer-alist
'(("\\*scratch\\*" (display-buffer-same-window))))
By default, display-buffer-alist
is nil
.
- Otherwise, if the buffer is already displayed in an existing window,
reuse that window. Normally, only windows on the selected frame are
considered, but windows on other frames are also reusable if you use
the corresponding
reusable-frames
action alist entry
(see Action Alists for Buffer
Display in The Emacs Lisp Reference Manual). See the
next step for an example of how to do that.
- Otherwise, optionally create a new frame and display the buffer there.
By default, this step is skipped. To enable it, change the value of
the option
display-buffer-base-action
(see Choosing a Window for Displaying a Buffer in The Emacs
Lisp Reference Manual) as follows:
(customize-set-variable
'display-buffer-base-action
'((display-buffer-reuse-window display-buffer-pop-up-frame)
(reusable-frames . 0)))
This customization will also try to make the preceding step search for
a reusable window on all visible or iconified frames.
- Otherwise, try to create a new window by splitting a window on the
selected frame, and display the buffer in that new window.
The split can be either vertical or horizontal, depending on the
variables split-height-threshold
and
split-width-threshold
. These variables should have integer
values. If split-height-threshold
is smaller than the chosen
window’s height, the split puts the new window below. Otherwise, if
split-width-threshold
is smaller than the window’s width, the
split puts the new window on the right. If neither condition holds,
Emacs tries to split so that the new window is below—but only if the
window was not split before (to avoid excessive splitting).
- Otherwise, display the buffer in a window previously showing it.
Normally, only windows on the selected frame are considered, but with
a suitable
reusable-frames
action alist entry (see above) the
window may be also on another frame.
- Otherwise, display the buffer in an existing window on the selected
frame.
- If all the above methods fail for whatever reason, create a new frame
and display the buffer there.
20.6.2 Displaying non-editable buffers.
Some buffers are shown in windows for perusal rather than for editing.
Help commands (see Help) typically use a buffer called *Help*
for that purpose, minibuffer completion (see Completion) uses a
buffer called *Completions*, etc. Such buffers are usually
displayed only for a short period of time.
Normally, Emacs chooses the window for such temporary displays via
display-buffer
, as described in the previous subsection. The
*Completions* buffer, on the other hand, is normally displayed
in a window at the bottom of the selected frame, regardless of the
number of windows already shown on that frame.
If you prefer Emacs to display a temporary buffer in a different
fashion, customize the variable display-buffer-alist
(see Choosing a Window for Displaying a Buffer in The Emacs Lisp Reference Manual) appropriately. For example,
to display *Completions* always below the selected window, use
the following form in your initialization file (see The Emacs Initialization File):
(customize-set-variable
'display-buffer-alist
'(("\\*Completions\\*" display-buffer-below-selected)))
The *Completions* buffer is also special in the sense that
Emacs usually tries to make its window just as large as necessary to
display all of its contents. To resize windows showing other
temporary displays, like, for example, the *Help* buffer, turn
on the minor mode (see Minor Modes) temp-buffer-resize-mode
(see Temporary Displays in The Emacs Lisp
Reference Manual).
The maximum size of windows resized by temp-buffer-resize-mode
can be controlled by customizing the options
temp-buffer-max-height
and temp-buffer-max-width
(see Temporary Displays in The Emacs Lisp
Reference Manual), and cannot exceed the size of the containing frame.
20.7 Convenience Features for Window Handling
Winner mode is a global minor mode that records the changes in the
window configuration (i.e., how the frames are partitioned into
windows), so that you can undo them. You can toggle Winner mode
with M-x winner-mode, or by customizing the variable
winner-mode
. When the mode is enabled, C-c left
(winner-undo
) undoes the last window configuration change. If
you change your mind while undoing, you can redo the changes you had
undone using C-c right (M-x winner-redo
). To prevent
Winner mode from binding C-c left and C-c right, you can
customize the variable winner-dont-bind-my-keys
to a
non-nil
value. By default, Winner mode stores a maximum of 200
window configurations per frame, but you can change that by modifying
the variable winner-ring-size
. If there are some buffers whose
windows you wouldn’t want Winner mode to restore, add their names to
the list variable winner-boring-buffers
or to the regexp
winner-boring-buffers-regexp
.
Follow mode (M-x follow-mode) synchronizes several windows on
the same buffer so that they always display adjacent sections of that
buffer. See Follow Mode.
The Windmove package defines commands for moving directionally
between neighboring windows in a frame. M-x windmove-right
selects the window immediately to the right of the currently selected
one, and similarly for the left, up, and down counterparts.
windmove-default-keybindings
binds these commands to
S-right etc.; doing so disables shift selection for those keys
(see Shift Selection). In the same way as keybindings can be
defined for commands that select windows directionally, you can use
windmove-display-default-keybindings
to define keybindings for
commands that specify in what direction to display the window for the
buffer that the next command is going to display. Also there is
windmove-delete-default-keybindings
to define keybindings for
commands that delete windows directionally, and
windmove-swap-states-default-keybindings
that defines
keybindings for commands that swap the window contents of the selected
window with the window in the specified direction.
The command M-x compare-windows lets you compare the text
shown in different windows. See Comparing Files.
Scroll All mode (M-x scroll-all-mode) is a global minor mode
that causes scrolling commands and point motion commands to apply to
every single window.
20.8 Window Tab Line
The command global-tab-line-mode
toggles the display of
a tab line on the top screen line of each window. The Tab Line
shows special buttons (“tabs”) for each buffer that was displayed in
a window, and allows switching to any of these buffers by clicking the
corresponding button. Clicking on the + icon adds a new buffer
to the window-local tab line of buffers, and clicking on the x
icon of a tab deletes it. The mouse wheel on the tab line scrolls
the tabs horizontally.
Selecting the previous window-local tab is the same as typing C-x
LEFT (previous-buffer
), selecting the next tab is the
same as C-x RIGHT (next-buffer
). Both commands
support a numeric prefix argument as a repeat count.
You can customize the variable tab-line-tabs-function
to define
the preferred contents of the tab line. By default, it displays all
buffers previously visited in the window, as described above. But you
can also set it to display a list of buffers with the same major mode
as the current buffer, or to display buffers grouped by their major
mode, where clicking on the mode name in the first tab displays a list
of all major modes where you can select another group of buffers.
Note that the Tab Line is different from the Tab Bar (see Tab Bars).
Whereas tabs on the Tab Bar at the top of each frame are used to
switch between window configurations containing several windows with buffers,
tabs on the Tab Line at the top of each window are used to switch
between buffers in the window.
21 Frames and Graphical Displays
When Emacs is started on a graphical display, e.g., on the X Window
System, it occupies a graphical system-level display region. In this
manual, we call this a frame, reserving the word “window” for
the part of the frame used for displaying a buffer. A frame initially
contains one window, but it can be subdivided into multiple windows
(see Multiple Windows). A frame normally also contains a menu bar, tool
bar, and echo area.
You can also create additional frames (see Creating Frames).
All frames created in the same Emacs session have access to the same
underlying buffers and other data. For instance, if a buffer is being
shown in more than one frame, any changes made to it in one frame show
up immediately in the other frames too.
Typing C-x C-c closes all the frames on the current display,
and ends the Emacs session if it has no frames open on any other
displays (see Exiting Emacs). To close just the selected frame, type
C-x 5 0 (that is zero, not o).
This chapter describes Emacs features specific to graphical displays
(particularly mouse commands), and features for managing multiple
frames. On text terminals, many of these features are unavailable.
However, it is still possible to create multiple frames on text
terminals; such frames are displayed one at a time, filling the entire
terminal screen (see Non-Window Terminals). It is also possible
to use the mouse on some text terminals (see Using a Mouse in Text Terminals, for
doing so on GNU and Unix systems; and
see Mouse Usage on MS-DOS,
for doing so on MS-DOS). Menus are supported on all text terminals.
21.1 Mouse Commands for Editing
- mouse-1
Move point to where you click (mouse-set-point
).
- Drag-mouse-1
Activate the region around the text selected by dragging, and put the
text in the primary selection (mouse-set-region
).
- mouse-2
Move point to where you click, and insert the contents of the primary
selection there (mouse-yank-primary
).
- mouse-3
If the region is active, move the nearer end of the region to the
click position; otherwise, set mark at the current value of point and
point at the click position. Save the resulting region in the kill
ring; on a second click, kill it (mouse-save-then-kill
).
- C-M-mouse-1
Activate a rectangular region around the text selected by dragging.
See Rectangles.
The most basic mouse command is mouse-set-point
, which is
invoked by clicking with the left mouse button, mouse-1, in the
text area of a window. This moves point to the position where you
clicked. If that window was not the selected window, it becomes the
selected window. You can also activate a region by double-clicking
mouse-1 (see Mouse Commands for Words and Lines).
Normally, if the frame you clicked in was not the selected frame, it
is made the selected frame, in addition to selecting the window and
setting the cursor. On the X Window System, you can change this by
setting the variable x-mouse-click-focus-ignore-position
to
t
. In that case, the initial click on an unselected frame just
selects the frame, without doing anything else; clicking again selects
the window and sets the cursor position.
Holding down mouse-1 and dragging the mouse over a stretch
of text activates the region around that text
(mouse-set-region
), placing the mark where you started holding
down the mouse button, and point where you release it (see The Mark and the Region).
In addition, the text in the region becomes the primary selection
(see Cut and Paste with Other Window Applications).
If you change the variable mouse-drag-copy-region
to a
non-nil
value, dragging the mouse over a stretch of text also
adds the text to the kill ring. The default is nil
.
If you move the mouse off the top or bottom of the window while
dragging, the window scrolls at a steady rate until you move the mouse
back into the window. This way, you can select regions that don’t fit
entirely on the screen. The number of lines scrolled per step depends
on how far away from the window edge the mouse has gone; the variable
mouse-scroll-min-lines
specifies a minimum step size.
Clicking with the middle mouse button, mouse-2, moves point to
the position where you clicked and inserts the contents of the primary
selection (mouse-yank-primary
). See Cut and Paste with Other Window Applications.
This behavior is consistent with other X applications. Alternatively,
you can rebind mouse-2 to mouse-yank-at-click
, which
performs a yank at the position you click.
If you change the variable mouse-yank-at-point
to a
non-nil
value, mouse-2 does not move point; it inserts
the text at point, regardless of where you clicked or even which of
the frame’s windows you clicked on. This variable affects both
mouse-yank-primary
and mouse-yank-at-click
.
Clicking with the right mouse button, mouse-3, runs the
command mouse-save-then-kill
. This performs several actions
depending on where you click and the status of the region:
- If no region is active, clicking mouse-3 activates the region,
placing the mark where point was and point at the clicked position.
- If a region is active, clicking mouse-3 adjusts the nearer end
of the region by moving it to the clicked position. The adjusted
region’s text is copied to the kill ring; if the text in the original
region was already on the kill ring, it replaces it there.
- If you originally specified the region using a double or triple
mouse-1, so that the region is defined to consist of entire
words or lines (see Mouse Commands for Words and Lines), then adjusting the
region with mouse-3 also proceeds by entire words or lines.
- If you use mouse-3 a second time consecutively, at the same
place, that kills the region already selected. Thus, the simplest way
to kill text with the mouse is to click mouse-1 at one end, then
click mouse-3 twice at the other end. To copy the text into the
kill ring without deleting it from the buffer, press mouse-3
just once—or just drag across the text with mouse-1. Then you
can copy it elsewhere by yanking it.
The mouse-save-then-kill
command also obeys the variable
mouse-drag-copy-region
(described above). If the value is
non-nil
, then whenever the command sets or adjusts the active
region, the text in the region is also added to the kill ring. If the
latest kill ring entry had been added the same way, that entry is
replaced rather than making a new entry.
Whenever you set the region using any of the mouse commands
described above, the mark will be deactivated by any subsequent
unshifted cursor motion command, in addition to the usual ways of
deactivating the mark. See Shift Selection.
Some mice have a “wheel” which can be used for scrolling. Emacs
supports scrolling windows with the mouse wheel, by default, on most
graphical displays. To toggle this feature, use M-x
mouse-wheel-mode. The variables mouse-wheel-follow-mouse
and
mouse-wheel-scroll-amount
determine where and by how much
buffers are scrolled. The variable
mouse-wheel-progressive-speed
determines whether the scroll
speed is linked to how fast you move the wheel. This mode also
supports increasing or decreasing the height of the default face, by
default bound to scrolling with the Ctrl modifier.
Emacs also supports horizontal scrolling with the Shift
modifier. Typing a numeric prefix arg (e.g., M-5) before
starting horizontal scrolling changes its step value defined
by the user option mouse-wheel-scroll-amount-horizontal
.
If your mouse’s wheel can be tilted, or if your touchpad supports it,
then you can also enable horizontal scrolling by customizing the
variable mouse-wheel-tilt-scroll
to a non-nil
value.
By default, tilting the mouse wheel scrolls the window’s view
horizontally in the direction of the tilt: e.g., tilting to the right
scrolls the window to the right, so that the text displayed in the
window moves horizontally to the left. If you’d like to reverse the
direction of horizontal scrolling, customize the variable
mouse-wheel-flip-direction
to a non-nil
value.
When the mouse pointer is over an image in Image mode, see Viewing Image Files,
scrolling the mouse wheel with the Ctrl modifier scales the image
under the mouse pointer, and scrolling the mouse wheel with the
Shift modifier scrolls the image horizontally.
21.2 Mouse Commands for Words and Lines
These variants of mouse-1 select entire words or lines at a
time. Emacs activates the region around the selected text, which is
also copied to the kill ring.
- Double-mouse-1
Select the text around the word or character which you click on.
Double-clicking on a character with symbol syntax (such as
underscore, in C mode) selects the symbol surrounding that character.
Double-clicking on a character with open- or close-parenthesis syntax
selects the parenthetical grouping which that character starts or
ends. Double-clicking on a character with string-delimiter syntax
(such as a single-quote or double-quote in C) selects the string
constant (Emacs uses heuristics to figure out whether that character
is the beginning or the end of it).
Double-clicking on the beginning of a parenthetical grouping or
beginning string-delimiter moves point to the end of the region,
scrolling the buffer display forward if necessary to show the new
location of point. Double-clicking on the end of a parenthetical
grouping or end string-delimiter keeps point at the end of the region
by default, so the beginning of the region will not be visible if it
is above the top of the window; setting the user option
mouse-select-region-move-to-beginning
to non-nil
changes
this to move point to the beginning of the region, scrolling the
display backward if necessary.
- Double-Drag-mouse-1
Select the text you drag across, in units of whole words.
- Triple-mouse-1
Select the line you click on.
- Triple-Drag-mouse-1
Select the text you drag across, in units of whole lines.
21.3 Following References with the Mouse
Some Emacs buffers include buttons, or hyperlinks:
pieces of text that perform some action (e.g., following a reference)
when activated (e.g., by clicking on them). Usually, a button’s text
is visually highlighted: it is underlined, or a box is drawn around
it. If you move the mouse over a button, the shape of the mouse
cursor changes and the button lights up. If you change the variable
mouse-highlight
to nil
, Emacs disables this
highlighting.
You can activate a button by moving point to it and typing
RET, or by clicking either mouse-1 or mouse-2 on the
button. For example, in a Dired buffer, each file name is a button;
activating it causes Emacs to visit that file (see Dired, the Directory Editor). In a
*Compilation* buffer, each error message is a button, and
activating it visits the source code for that error
(see Running Compilations under Emacs).
Although clicking mouse-1 on a button usually activates the
button, if you hold the mouse button down for a period of time before
releasing it (specifically, for more than 450 milliseconds), then
Emacs moves point where you clicked, without activating the button.
In this way, you can use the mouse to move point over a button without
activating it. Dragging the mouse over or onto a button has its usual
behavior of setting the region, and does not activate the button.
You can change how mouse-1 applies to buttons by customizing
the variable mouse-1-click-follows-link
. If the value is a
positive integer, that determines how long you need to hold the mouse
button down for, in milliseconds, to cancel button activation; the
default is 450, as described in the previous paragraph. If the value
is nil
, mouse-1 just sets point where you clicked, and
does not activate buttons. If the value is double
, double
clicks activate buttons but single clicks just set point.
Normally, mouse-1 on a button activates the button even if it
is in a non-selected window. If you change the variable
mouse-1-click-in-non-selected-windows
to nil
,
mouse-1 on a button in an unselected window moves point to the
clicked position and selects that window, without activating the
button.
21.5 Mode Line Mouse Commands
You can use mouse clicks on window mode lines to select and manipulate
windows.
Some areas of the mode line, such as the buffer name, and major and minor
mode names, have their own special mouse bindings. These areas are
highlighted when you hold the mouse over them, and information about
the special bindings will be displayed (see Tooltips). This
section’s commands do not apply in those areas.
- mouse-1 ¶
mouse-1 on a mode line selects the window it belongs to. By
dragging mouse-1 on the mode line, you can move it, thus
changing the height of the windows above and below. Changing heights
with the mouse in this way never deletes windows, it just refuses to
make any window smaller than the minimum height.
- mouse-2 ¶
mouse-2 on a mode line expands that window to fill its frame.
- mouse-3 ¶
mouse-3 on a mode line deletes the window it belongs to. If the
frame has only one window, it does nothing.
- C-mouse-2
C-mouse-2 on a mode line splits that window, producing two
side-by-side windows with the boundary running through the click
position (see Splitting Windows).
Furthermore, by clicking and dragging mouse-1 on the divider
between two side-by-side mode lines, you can move the vertical
boundary to the left or right.
Note that resizing windows is affected by the value of
window-resize-pixelwise
, see Splitting Windows.
21.6 Creating Frames
The prefix key C-x 5 is analogous to C-x 4. Whereas
each C-x 4 command pops up a buffer in a different window in the
selected frame (see Displaying in Another Window), the C-x 5 commands use a
different frame. If an existing visible or iconified (a.k.a.
“minimized”, see Visibility of Frames in The Emacs Lisp
Reference Manual) frame already displays the requested buffer, that
frame is raised and deiconified (“un-minimized”); otherwise, a new
frame is created on the current display terminal.
The various C-x 5 commands differ in how they find or create the
buffer to select:
- C-x 5 2 ¶
-
Create a new frame using the default frame parameters
(make-frame-command
).
- C-x 5 c ¶
-
Create a new frame using the window configuration and frame parameters
of the current frame (clone-frame
).
- C-x 5 b bufname RET
Select buffer bufname in another frame. This runs
switch-to-buffer-other-frame
.
- C-x 5 f filename RET
Visit file filename and select its buffer in another frame. This
runs find-file-other-frame
. See Visiting Files.
- C-x 5 d directory RET
Select a Dired buffer for directory directory in another frame.
This runs dired-other-frame
. See Dired, the Directory Editor.
- C-x 5 m
Start composing a mail message in another frame. This runs
compose-mail-other-frame
. It is the other-frame variant of
C-x m. See Sending Mail.
- C-x 5 .
Find the definition of an identifier in another frame. This runs
xref-find-definitions-other-frame
, the multiple-frame variant
of M-.. See Find Identifier References.
- C-x 5 r filename RET ¶
-
Visit file filename read-only, and select its buffer in another
frame. This runs find-file-read-only-other-frame
.
See Visiting Files.
- C-x 5 5
A more general prefix command that affects the buffer displayed by the
next command invoked immediately after this prefix command
(other-frame-prefix
). It requests the buffer of the next
command to be displayed in another frame.
You can control the appearance and behavior of the newly-created
frames by specifying frame parameters. See Frame Parameters.
21.7 Frame Commands
The following commands are used to delete and operate on frames:
- C-x 5 0 ¶
-
Delete the selected frame (delete-frame
). This signals an
error if there is only one frame.
- C-z ¶
Minimize (or iconify) the selected Emacs frame
(suspend-frame
). See Exiting Emacs.
- C-x 5 o ¶
-
Select another frame, and raise it. If you repeat this command, it
cycles through all the frames on your terminal.
- C-x 5 1 ¶
-
Delete all frames on the current terminal, except the selected one.
- M-F10 ¶
-
Toggle the maximization state of the current frame. When a frame is
maximized, it fills the screen.
- F11 ¶
-
Toggle full-screen mode for the current frame. (The difference
between full-screen and maximized is normally that the former
hides window manager decorations, giving slightly more screen space to
Emacs itself.)
Note that with some window managers you may have to customize the
variable frame-resize-pixelwise
to a non-nil
value in
order to make a frame truly maximized or full-screen. This
variable, when set to a non-nil
value, in general allows
resizing frames at pixel resolution, rather than in integral multiples
of lines and columns.
The C-x 5 0 (delete-frame
) command deletes the selected
frame. However, it will refuse to delete the last frame in an Emacs
session, to prevent you from losing the ability to interact with the
Emacs session. Note that when Emacs is run as a daemon (see Using Emacs as a Server), there is always a virtual frame that remains after all
the ordinary, interactive frames are deleted. In this case, C-x
5 0 can delete the last interactive frame; you can use
emacsclient
to reconnect to the Emacs session.
The C-x 5 1 (delete-other-frames
) command deletes all
other frames on the current terminal (this terminal refers to either a
graphical display, or a text terminal; see Non-Window Terminals).
If the Emacs session has frames open on other graphical displays or
text terminals, those are not deleted.
The C-x 5 o (other-frame
) command selects the next
frame on the current terminal. If you are using Emacs on the X Window
System with a window manager that selects (or gives focus to)
whatever frame the mouse cursor is over, you have to change the
variable focus-follows-mouse
to t
in order for this
command to work properly. Then invoking C-x 5 o will also warp
the mouse cursor to the chosen frame.
21.8 Fonts
By default, Emacs displays text on graphical displays using a
10-point monospace font, and the font size can be changed
interactively (see Text Scale).
There are several different ways to specify a different font:
- Click on ‘Set Default Font’ in the ‘Options’ menu. This
makes the selected font the default on all existing graphical frames.
To save this for future sessions, click on ‘Save Options’ in the
‘Options’ menu.
- Add a line to your init file, modifying the variable
default-frame-alist
to specify the font
parameter
(see Frame Parameters), like this:
(add-to-list 'default-frame-alist
'(font . "DejaVu Sans Mono-10"))
This makes the font the default on all graphical frames created after
restarting Emacs with that init file.
-
Add an ‘emacs.font’ X resource setting to your X resource file,
like this:
emacs.font: DejaVu Sans Mono-12
You must restart X, or use the xrdb
command, for the X
resources file to take effect. See X Resources. Do not quote
font names in X resource files.
- If you are running Emacs on the GNOME desktop, you can tell Emacs to
use the default system font by setting the variable
font-use-system-font
to t
(the default is nil
).
For this to work, Emacs must have been compiled with support for
Gsettings (or the older Gconf). (To be specific, the Gsettings
configuration names used are
‘org.gnome.desktop.interface monospace-font-name’ and
‘org.gnome.desktop.interface font-name’.)
- Use the command line option ‘-fn’ (or ‘--font’). See Font Specification Options.
To check what font you’re currently using, the C-u C-x =
command can be helpful. It describes the character at point, and
names the font that it’s rendered in.
There are four different ways to express a font name. The first is
to use a Fontconfig pattern. Fontconfig patterns have the
following form:
fontname[-fontsize][:name1=values1][:name2=values2]...
Within this format, any of the elements in brackets may be omitted.
Here, fontname is the family name of the font, such as
‘Monospace’ or ‘DejaVu Sans Mono’; fontsize is the
point size of the font (one printer’s point is about 1/72
of an inch); and the ‘name=values’ entries specify
settings such as the slant and weight of the font. Each values
may be a single value, or a list of values separated by commas. In
addition, some property values are valid with only one kind of
property name, in which case the ‘name=’ part may be
omitted.
Here is a list of common font properties:
- ‘slant’
One of ‘italic’, ‘oblique’, or ‘roman’.
- ‘weight’
One of ‘light’, ‘medium’, ‘demibold’, ‘bold’ or
‘black’.
- ‘style’
Some fonts define special styles which are a combination of slant and
weight. For instance, ‘Dejavu Sans’ defines the ‘book’
style, which overrides the slant and weight properties.
- ‘width’
One of ‘condensed’, ‘normal’, or ‘expanded’.
- ‘spacing’
One of ‘monospace’, ‘proportional’, ‘dual-width’, or
‘charcell’.
Here are some examples of Fontconfig patterns:
Monospace
Monospace-12
Monospace-12:bold
DejaVu Sans Mono:bold:italic
Monospace-12:weight=bold:slant=italic
For a more detailed description of Fontconfig patterns, see the
Fontconfig manual, which is distributed with Fontconfig and available
online at https://fontconfig.org/fontconfig-user.html.
On MS-Windows, only the subset of the form
fontname[-fontsize] is supported for all fonts; the full
Fontconfig pattern might not work for all of them.
The second way to specify a font is to use a GTK font pattern.
These have the syntax
fontname [properties] [fontsize]
where fontname is the family name, properties is a list of
property values separated by spaces, and fontsize is the point
size. The properties that you may specify for GTK font patterns are
as follows:
- Slant properties: ‘Italic’ or ‘Oblique’. If omitted, the
default (roman) slant is implied.
- Weight properties: ‘Bold’, ‘Book’, ‘Light’,
‘Medium’, ‘Semi-bold’, or ‘Ultra-light’. If omitted,
‘Medium’ weight is implied.
- Width properties: ‘Semi-Condensed’ or ‘Condensed’. If
omitted, a default width is used.
Here are some examples of GTK font patterns:
Monospace 12
Monospace Bold Italic 12
On MS-Windows, only the subset fontname is supported.
The third way to specify a font is to use an XLFD (X
Logical Font Description). This is the traditional method for
specifying fonts under X, and is also supported on MS-Windows. Each
XLFD consists of fourteen words or numbers, separated by dashes, like
this:
-misc-fixed-medium-r-semicondensed--13-*-*-*-c-60-iso8859-1
A wildcard character (‘*’) in an XLFD matches any sequence of
characters (including none), and ‘?’ matches any single
character. However, matching is implementation-dependent, and can be
inaccurate when wildcards match dashes in a long name. For reliable
results, supply all 14 dashes and use wildcards only within a field.
Case is insignificant in an XLFD. The syntax for an XLFD is as
follows:
-maker-family-weight-slant-widthtype-style…
…-pixels-height-horiz-vert-spacing-width-registry-encoding
The entries have the following meanings:
- maker
The name of the font manufacturer.
- family
The name of the font family (e.g., ‘courier’).
- weight
The font weight—normally either ‘bold’, ‘medium’ or
‘light’. Some font names support other values.
- slant
The font slant—normally ‘r’ (roman), ‘i’ (italic),
‘o’ (oblique), ‘ri’ (reverse italic), or ‘ot’ (other).
Some font names support other values.
- widthtype
The font width—normally ‘normal’, ‘condensed’,
‘semicondensed’, or ‘extended’. Some font names support
other values.
- style
An optional additional style name. Usually it is empty—most XLFDs
have two hyphens in a row at this point. The style name can also
specify a two-letter ISO-639 language name, like ‘ja’ or
‘ko’; some fonts that support CJK scripts have that spelled out
in the style name part.
- pixels
The font height, in pixels.
- height
The font height on the screen, measured in tenths of a printer’s
point. This is the point size of the font, times ten. For a given
vertical resolution, height and pixels are proportional;
therefore, it is common to specify just one of them and use ‘*’
for the other.
- horiz
The horizontal resolution, in pixels per inch, of the screen for which
the font is intended.
- vert
The vertical resolution, in pixels per inch, of the screen for which
the font is intended. Normally the resolution of the fonts on your
system is the right value for your screen; therefore, you normally
specify ‘*’ for this and horiz.
- spacing
This is ‘m’ (monospace), ‘p’ (proportional) or ‘c’
(character cell).
- width
The average character width, in pixels, multiplied by ten.
- registry
- encoding
The X font character set that the font depicts. (X font character
sets are not the same as Emacs character sets, but they are similar.)
You can use the xfontsel
program to check which choices you
have. Normally you should use ‘iso8859’ for registry and
‘1’ for encoding.
The fourth and final method of specifying a font is to use a font
nickname. Certain fonts have shorter nicknames, which you can use
instead of a normal font specification. For instance, ‘6x13’ is
equivalent to
-misc-fixed-medium-r-semicondensed--13-*-*-*-c-60-iso8859-1
This form is not supported on MS-Windows.
On X, Emacs recognizes two types of fonts: client-side fonts,
which are provided by the Xft and Fontconfig libraries, and
server-side fonts, which are provided by the X server itself.
Most client-side fonts support advanced font features such as
antialiasing and subpixel hinting, while server-side fonts do not.
Fontconfig and GTK patterns match only client-side fonts.
You will probably want to use a fixed-width default font—that is,
a font in which all characters have the same width. For Xft and
Fontconfig fonts, you can use the fc-list
command to list
the available fixed-width fonts, like this:
fc-list :spacing=mono
fc-list :spacing=charcell
For server-side X fonts, you can use the xlsfonts
program to
list the available fixed-width fonts, like this:
xlsfonts -fn '*x*' | grep -E '^[0-9]+x[0-9]+'
xlsfonts -fn '*-*-*-*-*-*-*-*-*-*-*-m*'
xlsfonts -fn '*-*-*-*-*-*-*-*-*-*-*-c*'
Any font with ‘m’ or ‘c’ in the spacing field of the
XLFD is a fixed-width font. To see what a particular font looks like,
use the xfd
command. For example:
displays the entire font ‘6x13’.
While running Emacs, you can also set the font of a specific kind of
text (see Text Faces), or a particular frame (see Frame Parameters).
21.9 Speedbar Frames
The speedbar is a special frame for conveniently navigating in
or operating on another frame. The speedbar, when it exists, is
always associated with a specific frame, called its attached
frame; all speedbar operations act on that frame.
Type M-x speedbar to create the speedbar and associate it with
the current frame. To dismiss the speedbar, type M-x speedbar
again, or select the speedbar and type q. (You can also delete
the speedbar frame like any other Emacs frame.) If you wish to
associate the speedbar with a different frame, dismiss it and call
M-x speedbar from that frame.
The speedbar can operate in various modes. Its default mode is
File Display mode, which shows the files in the current
directory of the selected window of the attached frame, one file per
line. Clicking on a non-directory visits that file in the selected window
of the attached frame, and clicking on a directory shows that
directory in the speedbar (see Following References with the Mouse). Each line also
has a box, ‘[+]’ or ‘<+>’, that you can click on to
expand the contents of that item. Expanding a directory adds
the contents of that directory to the speedbar display, underneath the
directory’s own line. Expanding an ordinary file adds a list of the
tags in that file to the speedbar display; you can click on a tag name
to jump to that tag in the selected window of the attached frame.
When a file or directory is expanded, the ‘[+]’ changes to
‘[-]’; you can click on that box to contract the item,
hiding its contents.
You navigate through the speedbar using the keyboard, too. Typing
RET while point is on a line in the speedbar is equivalent to
clicking the item on the current line, and SPC expands or
contracts the item. U displays the parent directory of the
current directory. To copy, delete, or rename the file on the current
line, type C, D, and R respectively. To create a
new directory, type M.
Another general-purpose speedbar mode is Buffer Display mode;
in this mode, the speedbar displays a list of Emacs buffers. To
switch to this mode, type b in the speedbar. To return to File
Display mode, type f. You can also change the display mode by
clicking mouse-3 anywhere in the speedbar window (or
mouse-1 on the mode-line) and selecting ‘Displays’ in the
pop-up menu.
Some major modes, including Rmail mode, Info, and GUD, have
specialized ways of putting useful items into the speedbar for you to
select. For example, in Rmail mode, the speedbar