⟦b88654dce⟧

TextFile

Info file emacs, produced by texinfo-format-buffer -*-Text-*-
from file emacs.tex

This file documents the GNU Emacs editor.

Permission is granted to make and distribute verbatim copies of
this manual provided the copyright notice and this permission notice
are preserved on all copies.

Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided also that the
sections entitled "The GNU Manifesto", "Distribution" and "GNU Emacs
General Public License" are included exactly as in the original, and
provided that the entire resulting derived work is distributed under the
terms of a permission notice identical to this one.

Permission is granted to copy and distribute translations of this manual
into another language, under the above conditions for modified versions,
except that the sections entitled "The GNU Manifesto", "Distribution"
and "GNU Emacs General Public License" may be included in a translation
approved by the author instead of in the original English.

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File: emacs Node: Auto Save, Prev: Reverting, Up: Files, Next: ListDir

Auto-Saving: Protection Against Disasters
=========================================

Emacs saves all the visited files from time to time (based on counting
your keystrokes) without being asked. 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, each buffer is
considered, and is auto-saved if auto-saving is turned on for it and it has
been changed since the last time it was auto-saved. If any auto-saving is
done, the message `Auto-saving...' is displayed in the echo area until
auto-saving is finished. Errors occurring during auto-saving are caught
so that they do not interfere with the execution of commands you have been
typing.

* Menu:

* Files: Auto Save Files.
* Control: Auto Save Control.
* Recover:: Recovering text from auto-save files.

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File: emacs Node: Auto Save Files, Prev: Auto Save, Up: Auto Save, Next: Auto Save Control

Auto-Save Files
---------------

Auto-saving does not normally save in the files that you visited, because
it can be very undesirable to save a program that is in an inconsistent
state when you have made half of a planned change. 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' would be 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 `#' to the rear of buffer name.
For example, the `*mail*' buffer in which you compose messages to be
sent is auto-saved in a file named `#%*mail*#'. 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.

If you want auto-saving to be done in the visited file, set the variable
`auto-save-visited-file-name' to be non-`nil'. In this mode,
there is really no difference between auto-saving and explicit saving.

A buffer's auto-save file is deleted when you save the buffer in its
visited file. To inhibit this, set 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.

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File: emacs Node: Auto Save Control, Prev: Auto Save Files, Up: Auto Save, Next: Recover

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; *Note Entering Emacs::). The default for this variable is
`t', so auto-saving is the usual practice for file-visiting buffers.
Auto-saving can be turned on or off for any existing buffer with the
command `M-x auto-save-mode'. Like other minor mode commands, `M-x
auto-save-mode' turns auto-saving on with a positive argument, off with a
zero or negative argument; with no argument, it toggles.

Emacs does auto-saving periodically based on counting how many characters
you have typed since the last time auto-saving was done. The variable
`auto-save-interval' specifies how many characters there are between
auto-saves. By default, it is 300. Emacs also auto-saves whenever you
call the function `do-auto-save'.

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.

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File: emacs Node: Recover, Prev: Auto Save Control, Up: Auto Save

Recovering Data from Auto-Saves
-------------------------------

The way to use the contents of an auto-save file to recover from a loss
of data is with the command `M-x recover-file RET FILE RET'. This visits
FILE and then (after your confirmation) restores the contents from 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
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.

Auto-saving is disabled by `M-x recover-file' because using
this command implies that the auto-save file contains valuable data
from a past session. If you save the data in the visited file and
then go on to make new changes, you should turn auto-saving back on
with `M-x auto-save-mode'.

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File: emacs Node: ListDir, Prev: Auto Save, Up: Files, Next: Dired

Listing a File Directory
========================

Files are classified by Unix into "directories". A "directory
listing" is a list of all the files in a directory. Emacs provides
directory listings in brief format (file names only) and verbose format
(sizes, dates, and authors included).

`C-x C-d DIR-OR-PATTERN'
Print a brief directory listing (`list-directory').
`C-u C-x C-d DIR-OR-PATTERN'
Print a verbose directory listing.

The command to print 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'. An example of
specifying a file name pattern is

C-x C-d /u2/emacs/src/*.c RET

Normally, `C-x C-d' prints a brief directory listing containing just
file names. A numeric argument (regardless of value) tells it to print a
verbose listing (like `ls -l').

The text of a directory listing is 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).

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File: emacs Node: Dired, Prev: ListDir, Up: Files, Next: Misc File Ops

Dired, the Directory Editor
===========================

Dired makes it easy to delete or visit many of the files in a single
directory at once. It makes an Emacs buffer containing a listing of the
directory. You can use the normal Emacs commands to move around in this
buffer, and special Dired commands to operate on the files.

* Menu:

* Enter: Dired Enter. How to invoke Dired.
* Edit: Dired Edit. Editing the Dired buffer.
* Deletion: Dired Deletion. Deleting files with Dired.
* Immed: Dired Immed. Other file operations through Dired.

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File: emacs Node: Dired Enter, Prev: Dired, Up: Dired, Next: Dired Edit

Entering Dired
--------------

To invoke dired, do `C-x d' or `M-x dired'. The command reads a
directory name or wildcard file name pattern as a minibuffer argument just
like the `list-directory' command, `C-x C-d'. Where `dired'
differs from `list-directory' is in naming the buffer after the
directory name or the wildcard pattern used for the listing, and putting
the buffer into Dired mode so that the special commands of Dired are
available in it. The variable `dired-listing-switches' is a string
used as an argument to `ls' in making the directory; this string
must contain `-l'.

To display the Dired buffer in another window rather than in the selected
window, use `C-x 4 d' (`dired-other-window)' instead of `C-x d'.

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File: emacs Node: Dired Edit, Prev: Dired Enter, Up: Dired, Next: Dired Deletion

Editing in Dired
----------------

Once the Dired buffer exists, you can switch freely between it and other
Emacs buffers. Whenever the Dired buffer is selected, certain special
commands are provided that operate on files that are listed. The Dired
buffer is "read-only", and inserting text in it is not useful, so
ordinary printing characters such as `d' and `x' are used for Dired
commands. Most Dired commands operate on the file described by the line
that point is on. Some commands perform operations immediately; others
"flag" the file to be operated on later.

Most Dired commands that operate on the current line's file also treat a
numeric argument as a repeat count, meaning to act on the files of the
next few lines. A negative argument means to operate on the files of the
preceding lines, and leave point on the first of those lines.

All the usual Emacs cursor motion commands are available in Dired
buffers. Some special purpose commands are also provided. The keys
`C-n' and `C-p' are redefined so that they try to position
the cursor at the beginning of the filename on the line, rather than
at the beginning of the line.

For extra convenience, SPC and `n' in Dired are equivalent to `C-n'. `p'
is equivalent to `C-p'. Moving by lines is done so often in Dired that it
deserves to be easy to type. DEL (move up and unflag) is often useful
simply for moving up.

The `g' command in Dired runs `revert-buffer' to reinitialize
the buffer from the actual disk directory and show any changes made in the
directory by programs other than Dired. All deletion flags in the Dired
buffer are lost when this is done.

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File: emacs Node: Dired Deletion, Prev: Dired Edit, Up: Dired, Next: Dired Immed

Deleting Files with Dired
-------------------------

The primary use of Dired is to flag files for deletion and then delete
them.

`d'
Flag this file for deletion.
`u'
Remove deletion-flag on this line.
`DEL'
Remove deletion-flag on previous line, moving point to that line.
`x'
Delete the files that are flagged for deletion.
`#'
Flag all auto-save files (files whose names start and end with `#')
for deletion (*Note Auto Save::).
`~'
Flag all backup files (files whose names end with `~') for deletion
(*Note Backup::).
`. (Period)'
Flag excess numeric backup files for deletion. The oldest and newest
few backup files of any one file are exempt; the middle ones are flagged.

You can flag a file for deletion by moving to the line describing the
file and typing `d' or `C-d'. The deletion flag is visible as a
`D' at the beginning of the line. Point is moved to the beginning of
the next line, so that repeated `d' commands flag successive files.

The files are flagged for deletion rather than deleted immediately to
avoid the danger of deleting a file accidentally. Until you direct Dired
to delete the flagged files, you can remove deletion flags using the
commands `u' and DEL. `u' works just like `d', but
removes flags rather than making flags. DEL moves upward, removing
flags; it is like `u' with numeric argument automatically negated.

To delete the flagged files, type `x'. This command first displays a
list of all the file names flagged for deletion, and requests confirmation
with `yes'. Once you confirm, all the flagged files are deleted, and their
lines are deleted from the text of the Dired buffer. The shortened Dired
buffer remains selected. If you answer `no' or quit with `C-g', you
return immediately to Dired, with the deletion flags still present and no
files actually deleted.

The `#', `~' and `.' commands flag many files for deletion, based on
their names. These commands are useful precisely because they do not
actually delete any files; you can remove the deletion flags from any
flagged files that you really wish to keep.

`#' flags for deletion all files that appear to have been made by
auto-saving (that is, files whose names begin and end with `#').
`~' flags for deletion all files that appear to have been made as
backups for files that were edited (that is, files whose names end with
`~').

`.' (Period) flags just some of the backup files for deletion: only
numeric backups that are not among the oldest few nor the newest few
backups of any one file. Normally `dired-kept-versions' (not
`kept-new-versions'; that applies only when saving) specifies the number of
newest versions of each file to keep, and `kept-old-versions' specifies the
number of oldest versions to keep. Period with a positive numeric
argument, as in `C-u 3 .', specifies the number of newest versions to keep,
overriding `dired-kept-versions'. A negative numeric argument overrides
`kept-old-versions', using minus the value of the argument to specify the
number of oldest versions of each file to keep.

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File: emacs Node: Dired Immed, Prev: Dired Deletion, Up: Dired

Immediate File Operations in Dired
----------------------------------

Some file operations in Dired take place immediately when they are
requested.

`c'
Copies the file described on the current line. You must supply a file name
to copy to, using the minibuffer.
`f'
Visits the file described on the current line. It is just like typing
`C-x C-f' and supplying that file name. If the file on this line is a
subdirectory, `f' actually causes Dired to be invoked on that
subdirectory. *Note Visiting::.
`o'
Like `f', but uses another window to display the file's buffer. The
Dired buffer remains visible in the first window. This is like using
`C-x 4 C-f' to visit the file. *Note Windows::.
`r'
Renames the file described on the current line. You must supply a file
name to rename to, using the minibuffer.
`v'
Views the file described on this line using `M-x view-file'. Viewing
a file is like visiting it, but is slanted toward moving around in the
file conveniently and does not allow changing the file. *Note View
File: Misc File Ops. Viewing a file that is a directory runs Dired on
that directory.

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File: emacs Node: Misc File Ops, Prev: Dired, Up: Files

Miscellaneous File Operations
=============================

Emacs has commands for performing many other operations on files.
All operate on one file; they do not accept wild card file names.

`M-x view-file' allows you to scan or read a file by sequential
screenfuls. It reads a file name argument using the minibuffer. After
reading the file into an Emacs buffer, `view-file' reads and displays
one windowful. You can then type SPC to scroll forward one windowful,
or DEL to scroll backward. Various other commands are provided for
moving around in the file, but none for changing it; type `C-h' while
viewing for a list of them. They are mostly the same as normal Emacs
cursor motion commands. To exit from viewing, type `C-c'.

`M-x insert-file' inserts a copy of the contents of the specified
file into the current buffer at point, leaving point unchanged before the
contents and the mark after them. *Note Mark::.

`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.

`M-x delete-file' deletes the specified file, like the `rm'
command in the shell. If you are deleting many files in one directory, it
may be more convenient to use Dired (*Note Dired::).

`M-x rename-file' reads two file names OLD and NEW using
the minibuffer, then renames file OLD as NEW. If a file named
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.

The similar command `M-x add-name-to-file' is used to add an
additional name to an existing file without removing its old name.
The new name must belong on the same file system that the file is on.

`M-x copy-file' reads the file OLD and writes a new file named
NEW with the same contents. Confirmation is required if a file named
NEW already exists, because copying has the consequence of overwriting
the old contents of the file NEW.

`M-x make-symbolic-link' reads two file names OLD and LINKNAME,
and then creates a symbolic link named LINKNAME and pointing at OLD.
The effect is that future attempts to open file LINKNAME will refer
to whatever file is named OLD at the time the opening is done, or
will get an error if the name OLD is not in use at that time.
Confirmation is required when creating the link if LINKNAME is in
use. Note that not all systems support symbolic links.

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File: emacs Node: Buffers, Prev: Files, Up: Top, Next: Windows

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 created to hold the
file's text. Each time you invoke Dired, a buffer is created to hold the
directory listing. If you send a message with `C-x m', a buffer named
`*mail*' is used to hold the text of the message. When you ask for a
command's documentation, that appears in a buffer called `*Help*'.

At any time, one and only one buffer is "selected". It is also
called the "current buffer". Often we say that a command operates on
"the buffer" as if there were only one; but really this means that the
command operates on the selected buffer (most commands do).

When Emacs makes multiple windows, each window has a chosen buffer which
is displayed there, but at any time only one of the windows is selected and
its chosen buffer is the selected buffer. Each window's mode line displays
the name of the buffer that the window is displaying (*Note Windows::).

Each buffer has a name, which can be of any length, and you can select
any buffer by giving its name. Most buffers are made by visiting files,
and their names are derived from the files' names. But you can also create
an empty buffer with any name you want. A newly started Emacs has a buffer
named `*scratch*' which can be used for evaluating Lisp expressions in
Emacs. The distinction between upper and lower case matters in buffer
names.

Each buffer records individually what file it is visiting, whether it is
modified, and what major mode and minor modes are in effect in it
(*Note Major Modes::). Any Emacs variable can be made "local to" a
particular buffer, meaning its value in that buffer can be different from
the value in other buffers. *Note Locals::.

* Menu:

* Select Buffer:: Creating a new buffer or reselecting an old one.
* List Buffers:: Getting a list of buffers that exist.
* Misc Buffer:: Renaming; changing read-onliness; copying text.
* Kill Buffer:: Killing buffers you no longer need.
* Several Buffers:: How to go through the list of all buffers
and operate variously on several of them.

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File: emacs Node: Select Buffer, Prev: Buffers, Up: Buffers, Next: List Buffers

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 a buffer named BUFFER in another window
(`switch-to-buffer-other-window').

To select the buffer named BUFNAME, type `C-x b BUFNAME RET'. This is
the command `switch-to-buffer' with argument BUFNAME. You can use
completion on an abbreviation for the buffer name you want (*Note
Completion::). An empty argument to `C-x b' specifies the most recently
selected buffer that is not displayed in any window.

Most buffers are created by visiting files, or by Emacs commands that
want to display some text, but you can also create a buffer explicitly by
typing `C-x b BUFNAME RET'. This makes a new, empty buffer which
is not visiting any file, and selects it for editing. Such buffers are
used for making notes to yourself. If you try to save one, you are asked
for the file name to use. The new buffer's major mode is determined by the
value of `default-major-mode' (*Note Major Modes::).

Note that `C-x C-f', and any other command for visiting a file, can
also be used to switch buffers. *Note Visiting::.

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File: emacs Node: List Buffers, Prev: Select Buffer, Up: Buffers, Next: Misc Buffer

Listing Existing Buffers
========================

`C-x C-b'
List the existing buffers (`list-buffers').

To print a list of all the buffers that exist, type `C-x C-b'. Each line
in the list shows one buffer's name, major mode and visited file. `*' at
the beginning of a line indicates the buffer is "modified". If several
buffers are modified, it may be time to save some with `C-x s' (*Note
Saving::). `%' indicates a read-only buffer. `.' marks the selected
buffer. Here is an example of a buffer list:

MR Buffer Size Mode File
-- ------ ---- ---- ----
.* emacs.tex 383402 Texinfo /u2/emacs/man/emacs.tex
*Help* 1287 Fundamental
files.el 23076 Emacs-Lisp /u2/emacs/lisp/files.el
% RMAIL 64042 RMAIL /u/rms/RMAIL
*% man 747 Dired
net.emacs 343885 Fundamental /u/rms/net.emacs
fileio.c 27691 C /u2/emacs/src/fileio.c
NEWS 67340 Text /u2/emacs/etc/NEWS
*scratch* 0 Lisp Interaction

Note that the buffer `*Help*' was made by a help request; it is not
visiting any file. The buffer `man' was made by Dired on the
directory `/u2/emacs/man/'.

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File: emacs Node: Misc Buffer, Prev: List Buffers, Up: Buffers, Next: Kill Buffer

Miscellaneous Buffer Operations
===============================

`C-x C-q'
Toggle read-only status of buffer (`toggle-read-only').
`M-x rename-buffer'
Change the name of the current buffer.
`M-x view-buffer'
Scroll through a buffer.

A buffer can be "read-only", which means that commands to change its
text are not allowed. Normally, read-only buffers are made by subsystems
such as Dired and Rmail that have special commands to operate on the text;
a read-only buffer is also made if you visit a file that is protected so
you cannot write it. If you wish to make changes in a read-only buffer,
use the command `C-x C-q' (`toggle-read-only'). It 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'.

`M-x rename-buffer' changes the name of the current buffer. 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.

`M-x view-buffer' is much like `M-x view-file' (*Note Misc File Ops::)
except that it examines an already existing Emacs buffer. View mode
provides commands for scrolling through the buffer conveniently but not
for changing it. When you exit View mode, the value of point that resulted
from your perusal remains in effect.

The commands `C-x a' (`append-to-buffer') and `M-x insert-buffer' can be
used to copy text from one buffer to another. *Note Accumulating Text::.

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File: emacs Node: Kill Buffer, Prev: Misc Buffer, Up: Buffers, Next: Several Buffers

Killing Buffers
===============

After you use Emacs for a while, you may accumulate a large number of
buffers. You may then find it convenient to eliminate the ones you no
longer need. There are several commands provided for doing this.

`C-x k'
Kill a buffer, specified by name (`kill-buffer').
`M-x kill-some-buffers'
Offer to kill each buffer, one by one.

`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 the current buffer is
killed, another buffer is selected; a buffer that has been selected
recently but does not appear in any window now is chosen to be selected.
If the buffer being killed is modified (has unsaved editing) then you are
asked to 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 `y' means to kill the buffer. Killing the current
buffer or a buffer containing unsaved changes selects a new buffer or asks
for confirmation just like `kill-buffer'.

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File: emacs Node: Several Buffers, Prev: Kill Buffer, Up: Buffers

Operating on Several Buffers
============================

The "buffer-menu" facility is like a "Dired for buffers"; it allows
you to request operations on various Emacs buffers by editing an Emacs
buffer containing a list of them. You can save buffers, kill them
(here called "deleting" them, for consistency with Dired), or display
them.

`M-x buffer-menu'
Begin editing a buffer listing all Emacs buffers.

The command `buffer-menu' writes a list of all Emacs buffers into
the buffer `*Buffer List*', and selects that buffer in Buffer Menu
mode. The buffer is read-only, and can only be changed through the special
commands described in this section. Most of these commands are graphic
characters. The usual Emacs cursor motion commands can be used in the
`*Buffer List*' buffer. The following special commands apply to the
buffer described on the current line.

`d'
Request to delete (kill) the buffer, then move down. The request
shows as a `D' on the line, before the buffer name. Requested
deletions take place when the `x' command is used.
`k'
Synonym for `d'.
`C-d'
Like `d' but move up afterwards instead of down.
`s'
Request to save the buffer. The request shows as an `S' on the
line. Requested saves take place when the `x' command is used.
You may request both saving and deletion for the same buffer.
`~'
Mark buffer "unmodified". The command `~' does this
immediately when typed.
`x'
Perform previously requested deletions and saves.
`u'
Remove any request made for the current line, and move down.
`DEL'
Move to previous line and remove any request made for that line.

All the commands that put in or remove flags to request later operations
also move down a line, and accept a numeric argument as a repeat count,
unless otherwise specified.

There are also special commands to use the buffer list to select another
buffer, and to specify one or more other buffers for display in additional
windows.

`1'
Select the buffer in a full-screen window. This command takes effect
immediately.
`2'
Immediately set up two windows, with this buffer in one, and the
previously selected buffer (aside from the buffer `*Buffer List*')
in the other.
`f'
Immediately select the buffer in place of the `*Buffer List*' buffer.
`o'
Immediately select the buffer in another window as if by `C-x 4 b',
leaving `*Buffer List*' visible.
`q'
Immediately select this buffer, and also display in other windows any
buffers previously flagged with the `m' command. If there are no
such buffers, this command is equivalent to `1'.
`m'
Flag this buffer to be displayed in another window if the `q'
command is used. The request shows as a `>' at the beginning of
the line. The same buffer may not have both a delete request and a
display request.

All that `buffer-menu' does directly is create and select a suitable
buffer, and turn on Buffer Menu mode. Everything else described above is
implemented by the special commands provided in Buffer Menu mode. One
consequence of this is that you can switch from the `*Buffer List*'
buffer to another Emacs buffer, and edit there. You can reselect the
`buffer-menu' buffer later, to perform the operations already
requested, or you can kill it, or pay no further attention to it.

The only difference between `buffer-menu' and `list-buffers' is
that `buffer-menu' selects the `*Buffer List*' buffer and
`list-buffers' does not. If you run `list-buffers' (that is,
type `C-x C-b') and select the buffer list manually, you can use all of
the commands described here.

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File: emacs Node: Windows, Prev: Buffers, Up: Top, Next: Major Modes

Multiple Windows
****************

Emacs can split the screen into two or many windows, which can display
parts of different buffers, or different parts of one buffer.

* Menu:

* Basic Window:: Introduction to Emacs windows.
* Split Window:: New windows are made by splitting existing windows.
* Other Window:: Moving to another window or doing something to it.
* Pop Up Window:: Finding a file or buffer in another window.
* Change Window:: Deleting windows and changing their sizes.

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File: emacs Node: Basic Window, Prev: Windows, Up: Windows, Next: Split Window

Concepts of Emacs Windows
=========================

When multiple windows are being displayed, each window has an Emacs
buffer designated for display in it. The same 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 the windows showing the same buffer can
show different parts of it, because each window has its own value of point.

At any time, one of the windows is the "selected window"; the buffer
this window is displaying is the current buffer. The terminal's cursor
shows the location of point in this window. Each other window has a
location of point as well, but since the terminal has only one cursor there
is no way to show where those locations are.

Commands to move point affect the value of point for the selected Emacs
window only. They do not change the value of point in any other Emacs
window, even one showing the same buffer. The same is true for commands
such as `C-x b' to change the selected buffer in the selected window;
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'), work by switching buffers in a nonselected window
without affecting the selected window.

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. *Note Mode Line::, for full details on the mode
line.

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File: emacs Node: Split Window, Prev: Basic Window, Up: Windows, Next: Other Window

Splitting Windows
=================

`C-x 2'
Split the selected window in two, one window above the other
(`split-window-vertically').
`C-x 5'
Split the selected window into two windows side by side
(`split-window-horizontally').

The command `C-x 2' (`split-window-vertically') breaks the
selected window into two windows, one above the other. Both windows start
out displaying the same buffer, with the same value of point. By default
the two windows each get half the height of the window that was split; a
numeric argument specifies how many lines to give to the top window.

`C-x 5' (`split-window-horizontally') breaks the selected
window into two side-by-side windows. A numeric argument specifies
how many columns to give the one on the left. A line of vertical bars
separates the two windows. Windows that are not the full width of the
screen have mode lines, but they are truncated; also, they do not
always appear in inverse video, because, the Emacs display routines
have not been taught how to display a region of inverse video that is
only part of a line on the screen.

When a window is less than the full width, text lines too long to fit are
frequent. Continuing all those lines might be confusing. The variable
`truncate-partial-width-windows' can be set non-`nil' to force truncation
in all windows less than the full width of the screen, independent of the
buffer being displayed and its value for `truncate-lines'. *Note
Continuation Lines::.

Horizontal scrolling is often used in side-by-side windows.
*Note Display::.

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File: emacs Node: Other Window, Prev: Split Window, Up: Windows, Next: Pop Up Window

Using Other Windows
===================

`C-x o'
Select another window (`other-window'). That is `o', not zero.
`C-M-v'
Scroll the next window (`scroll-other-window').
`M-x compare-windows'
Find next place where the text in the selected window does not match
the text in the next window.

To select a different window, use `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. From 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 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. *Note Minibuffer Edit::.

The usual scrolling commands (*Note Display::) apply to the selected
window only, but there is one command to scroll the next window.
`C-M-v' (`scroll-other-window') scrolls the window that `C-x o'
would select. It takes arguments, positive and negative, like `C-v'.

The command `M-x compare-windows' compares the text in the current
window with that in the next window. Comparison starts at point in each
window. Point moves forward in each window, a character at a time in each
window, until the next characters in the two windows are different. Then
the command is finished.

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File: emacs Node: Pop Up Window, Prev: Other Window, Up: Windows, Next: Change Window

Displaying in Another Window
============================

`C-x 4' is a prefix key for commands that select another window
(splitting the window if there is only one) and select a buffer in that
window. Different `C-x 4' commands have different ways of finding the
buffer to select.

`C-x 4 b BUFNAME RET'
Select buffer BUFNAME in another window. This runs
`switch-to-buffer-other-window'.
`C-x 4 f FILENAME RET'
Visit file FILENAME and select its buffer in another window. This
runs `find-file-other-window'. *Note Visiting::.
`C-x 4 d DIRECTORY RET'
Select a Dired buffer for directory DIRECTORY in another window.
This runs `dired-other-window'. *Note Dired::.
`C-x 4 m'
Start composing a mail message in another window. This runs
`mail-other-window', and its same-window version is `C-x m'
(*Note Sending Mail::).
`C-x 4 .'
Find a tag in the current tag table in another window. This runs
`find-tag-other-window', the multiple-window variant of `M-.'
(*Note Tags::).

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File: emacs Node: Change Window, Prev: Pop Up Window, Up: Windows

Deleting and Rearranging Windows
================================

`C-x 0'
Get rid of the selected window (`kill-window'). That is a zero.
`C-x 1'
Get rid of all windows except the selected one (`delete-other-windows').
`C-x ^'
Make the selected window taller, at the expense of the other(s)
(`enlarge-window').
`C-x }'
Make the selected window wider (`enlarge-window-horizontally').

To delete a window, type `C-x 0' (`delete-window'). (That is a
zero.) The space occupied by the deleted window is distributed among the
other active windows (but not the minibuffer window, even if that is active
at the time). Once a window is deleted, its attributes are forgotten;
there is no automatic way to make another window of the same shape or
showing the same buffer. But the buffer continues to exist, and you can
select it in any window with `C-x b'.

`C-x 1' (`delete-other-windows') is more powerful than `C-x 0';
it deletes all the windows except the selected one (and the minibuffer);
the selected window expands to use the whole screen except for the echo
area.

To readjust the division of space among existing windows, use `C-x ^'
(`enlarge-window'). It makes the currently selected window get one
line bigger, or as many lines as is specified with a numeric argument.
With a negative argument, it makes the selected window smaller. `C-x
}' (`enlarge-window-horizontally') makes the selected window wider
by the specified number of columns. The extra screen space given to a
window comes from one of its neighbors, if that is possible; otherwise, all
the competing windows are shrunk in the same proportion. If this makes any
windows too small, those windows are deleted and their space is divided up.
The minimum size is specified by the variables `window-min-height' and
`window-min-width'.

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File: emacs Node: Major Modes, Prev: Windows, Up: Top, Next: Indentation

Major Modes
***********

Emacs has many different "major modes", each of which customizes
Emacs for editing text of a particular sort. The major modes are mutually
exclusive, and each buffer has one major mode at any time. The mode line
normally contains the name of the current major mode, in parentheses.
*Note Mode Line::.

The least specialized major mode is called "Fundamental mode". This
mode has no mode-specific redefinitions or variable settings, so that each
Emacs command behaves in its most general manner, and each option is in its
default state. For editing any specific type of text, such as Lisp code or
English text, you should switch to the appropriate major mode, such as Lisp
mode or Text mode.

Selecting a major mode changes the meanings of a few keys to become more
specifically adapted to the language being edited. The ones which are
changed frequently are TAB, DEL, and LFD. In addition,
the commands which handle comments use the mode to determine how comments
are to be delimited. Many major modes redefine the syntactical properties
of characters appearing in the buffer. *Note Syntax::.

The major modes fall into three major groups. Lisp mode (which has
several variants), C mode and Muddle mode are for specific programming
languages. Text mode, Nroff mode, TeX mode and Outline mode are for
editing English text. The remaining major modes are not intended for use
on users' files; they are used in buffers created for specific purposes by
Emacs, such as Dired mode for buffers made by Dired (*Note Dired::), and
Mail mode for buffers made by `C-x m' (*Note Sending Mail::), and Shell
mode for buffers used for communicating with an inferior shell process
(*Note Interactive Shell::).

Most programming language major modes specify that only blank lines
separate paragraphs. This is so that the paragraph commands remain useful.
*Note Paragraphs::. They also cause Auto Fill mode to use the definition of
TAB to indent the new lines it creates. This is because most lines
in a program are usually indented. *Note Indentation::.

* Menu:

* Choosing Modes:: How major modes are specified or chosen.

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File: emacs Node: Choosing Modes, Prev: Major Modes, Up: Major Modes

How Major Modes are Chosen
==========================

You can select a major mode explicitly for the current buffer, but
most of the time Emacs determines which mode to use based on the file
name or some text in the file.

Explicit selection of a new major mode is done with a `M-x' command.
From the name of a major mode, add `-mode' to get the name of a
command to select that mode. Thus, you can enter Lisp mode by executing
`M-x lisp-mode'.

When you visit a file, Emacs usually chooses the right major mode based
on the file's name. For example, files whose names end in `.c' are
edited in C mode. The correspondence between file names and major mode is
controlled by the variable `auto-mode-alist'. Its value is a list in
which each element has the form

(REGEXP . MODE-FUNCTION)

For example, one element normally found in the list has the form
`("\\.c$" . c-mode)', and it is responsible for selecting C mode
for files whose names end in `.c'. (Note that `\\' is needed in
Lisp syntax to include a `\' in the string, which is needed to
suppress the special meaning of `.' in regexps.) The only practical
way to change this variable is with Lisp code.

You can specify which major mode should be used for editing a certain
file by a special sort of text in the first nonblank line of the file. The
mode name should appear in this line both preceded and followed by
`-*-'. Other text may appear on the line as well. For example,

;-*-Lisp-*-

tells Emacs to use Lisp mode. Note how the semicolon is used to make Lisp
treat this line as a comment. Such an explicit specification overrides any
defaulting based on the file name.

Another format of mode specification is

-*-Mode: MODENAME;-*-

which allows other things besides the major mode name to be specified.
However, Emacs does not look for anything except the mode name.

th emajor mode can also be specified in a local variables list.
*Note File Variables::.

When a file is visited that does not specify a major mode to use, or when
a new buffer is created with `C-x b', the major mode used is that
specified by the variable `default-major-mode'. Normally this value
is the symbol `fundamental-mode', which specifies Fundamental mode.
If `default-major-mode' is `nil', the major mode is taken from
the previously selected buffer.

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File: emacs Node: Indentation, Prev: Major Modes, Up: Top, Next: Text

Indentation
***********

`TAB'
Indent current line "appropriately" in a mode-dependent fashion.
`LFD'
Perform RET followed by TAB (`newline-and-indent').
`M-^'
Merge two lines (`delete-indentation'). This would cancel out
the effect of LFD.
`C-M-o'
Split line at point; text on the line after point becomes a new line
indented to the same column that it now starts in (`split-line').
`M-m'
Move (forward or back) to the first nonblank character on the current
line (`back-to-indentation').
`C-M-\'
Indent several lines to same column (`indent-region').
`C-x TAB'
Shift block of lines rigidly right or left (`indent-rigidly').
`M-i'
Indent from point to the next prespecified tab stop column
(`tab-to-tab-stop').
`M-x indent-relative'
Indent from point to under an indentation point in the previous line.

Most programming languages have some indentation convention. For Lisp
code, lines are indented according to their nesting in parentheses. The
same general idea is used for C code, though many details are different.

Whatever the language, to indent a line, use the TAB command. Each
major mode defines this command to perform the sort of indentation
appropriate for the particular language. In Lisp mode, TAB aligns
the line according to its depth in parentheses. No matter where in the
line you are when you type TAB, it aligns the line as a whole. In C
mode, TAB implements a subtle and sophisticated indentation style that
knows about many aspects of C syntax.

In Text mode, TAB runs the command `tab-to-tab-stop', which
indents to the next tab stop column. You can set the tab stops with
`M-x edit-tab-stops'.

* Menu:

* Indentation Commands:: Various commands and techniques for indentation.
* Tab Stops:: You can set arbitrary "tab stops" and then
indent to the next tab stop when you want to.
* Just Spaces:: You can request indentation using just spaces.

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File: emacs Node: Indentation Commands, Prev: Indentation, Up: Indentation

Indentation Commands and Techniques
===================================

If you just want to insert a tab character in the buffer, you can type
`C-q TAB'.

To move over the indentation on a line, do `Meta-m'
(`back-to-indentation'). This command, given anywhere on a line,
positions point at the first nonblank character on the line.

To insert an indented line before the current line, do `C-a C-o
TAB'. To make an indented line after the current line, use `C-e
LFD'.

`C-M-o' (`split-line') moves the text from point to the end of
the line vertically down, so that the current line becomes two lines.
`C-M-o' first moves point forward over any spaces and tabs. Then it
inserts after point a newline and enough indentation to reach the same
column point is on. Point remains before the inserted newline; in this
regard, `C-M-o' resembles `C-o'.

To join two lines cleanly, use the `Meta-^' (`delete-indentation')
command to delete the indentation at the front of the current line, and the
line boundary as well. They are replaced by a single space, or by no space
if at the beginning of a line or before a `)' or after a `('. To
delete just the indentation of a line, go to the beginning of the line and
use `Meta-\' (`delete-horizontal-space'), which deletes all spaces
and tabs around the cursor.

There are also commands for changing the indentation of several lines at
once. `Control-Meta-\' (`indent-region') gives each line which begins in
the region the "usual" indentation by invoking TAB at the beginning of the
line. A numeric argument specifies the column to indent to, and each line
is shifted left or right so that its first nonblank character appears in
that column. `C-x TAB' (`indent-rigidly') moves all of the lines in the
region right by its argument (left, for negative arguments). The whole
group of lines moves rigidly sideways, which is how the command gets its
name.

`M-x indent-relative' indents at point based on the previous line
(actually, the last nonempty line.) It inserts whitespace at point, moving
point, until it is underneath an indentation point in the previous line.
An indentation point is the end of a sequence of whitespace or the end of
the line. If point is farther right than any indentation point in the
previous line, the whitespace before point is deleted and the first
indentation point then applicable is used. If no indentation point is
applicable even then, `tab-to-tab-stop' is run (see next section).

`indent-relative' is the definition of TAB in Indented Text
mode. *Note Text::.

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File: emacs Node: Tab Stops, Prev: Indentation Commands, Up: Indentation, Next: Just Spaces

Tab Stops
=========

For typing in tables, you can use Text mode's definition of TAB,
`tab-to-tab-stop'. This command inserts indentation before point,
enough to reach the next tab stop column. If you are not in Text mode,
this function can be found on `M-i' anyway.

The tab stops used by `M-i' can be set arbitrarily by the user.
They are stored in a variable called `tab-stop-list', as a list of
column-numbers in increasing order.

The convenient way to set the tab stops is using `M-x edit-tab-stops',
which creates and selects a buffer containing a description of the tab stop
settings. You can edit this buffer to specify different tab stops, and
then type `C-c C-c' to make those new tab stops take effect. In the
tab stop buffer, `C-c C-c' runs the function
`edit-tab-stops-note-changes' rather than its usual definition
`save-buffer'. `edit-tab-stops' records which buffer was current
when you invoked it, and stores the tab stops back in that buffer; normally
all buffers share the same tab stops and changing them in one buffer
affects all, but if you happen to make `tab-stop-list' local in one
buffer then `edit-tab-stops' in that buffer will edit the local
settings.

Here is what the text representing the tab stops looks like for ordinary
tab stops every eight columns.

: : : : : :
0 1 2 3 4
0123456789012345678901234567890123456789012345678
To install changes, type C-c C-c

The first line contains a colon at each tab stop. The remaining lines
are present just to help you see where the colons are and know what to do.

Note that the tab stops that control `tab-to-tab-stop' have nothing
to do with displaying tab characters in the buffer. *Note Display Vars::,
for more information on that.

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File: emacs Node: Just Spaces, Prev: Tab Stops, Up: Indentation

Tabs vs. Spaces
===============

Emacs normally uses both tabs and spaces to indent lines. If you prefer,
all indentation can be made from spaces only. To request this, set
`indent-tabs-mode' to `nil'. This is a per-buffer variable;
altering the variable affects only the current buffer, but there is a
default value which you can change as well. *Note Locals::.

There are also commands to convert tabs to spaces or vice versa, always
preserving the columns of all nonblank text. `M-x tabify' scans the
region for sequences of spaces, and converts sequences of at least three
spaces to tabs if that can be done without changing indentation. `M-x
untabify' changes all tabs in the region to appropriate numbers of spaces.

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File: emacs Node: Text, Prev: Indentation, Up: Top, Next: Programs

Commands for Human Languages
****************************

The term "text" has two widespread meanings in our area of the
computer field. One is data that is a sequence of characters. Any file
that you edit with Emacs is text, in this sense of the word. The other
meaning is more restrictive: a sequence of characters in a human language
for humans to read (possibly after processing by a text formatter), as
opposed to a program or commands for a program.

Human languages have syntactic/stylistic conventions that can be
supported or used to advantage by editor commands: conventions involving
words, sentences, paragraphs, and capital letters. This chapter describes
Emacs commands for all of these things. There are also commands for
"filling", or rearranging paragraphs into lines of approximately equal
length. The commands for moving over and killing words, sentences
and paragraphs, while intended primarily for editing text, are also often
useful for editing programs.

Emacs has several major modes for editing human language text.
If the file contains text pure and simple, use Text mode, which customizes
Emacs in small ways for the syntactic conventions of text. For text which
contains embedded commands for text formatters, Emacs has other major modes,
each for a particular text formatter. Thus, for input to TeX, you would
use TeX mode; for input to nroff, Nroff mode.

* Menu:

* Text Mode:: The major modes for editing text files.
* Nroff Mode:: The major mode for editing input to the formatter nroff.
* TeX Mode:: The major modes for editing input to the formatter TeX.
* Outline Mode::The major mode for editing outlines.
* Words:: Moving over and killing words.
* Sentences:: Moving over and killing sentences.
* Paragraphs:: Moving over paragraphs.
* Pages:: Moving over pages.
* Filling:: Filling or justifying text
* Case:: Changing the case of text

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