path: root/info/emacs-11

This is Info file ../info/emacs, produced by Makeinfo-1.49 from the
input file emacs.texi.

   This file documents the GNU Emacs editor.

   Copyright (C) 1985, 1986, 1988, 1992 Richard M. Stallman.

   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
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 General Public License" may be included in a
translation approved by the author instead of in the original English.


File: emacs,  Node: Dissociated Press,  Next: Amusements,  Prev: Hardcopy,  Up: Top

Dissociated Press
=================

   `M-x dissociated-press' is a command for scrambling a file of text
either word by word or character by character.  Starting from a buffer
of straight English, it produces extremely amusing output.  The input
comes from the current Emacs buffer.  Dissociated Press writes its
output in a buffer named `*Dissociation*', and redisplays that buffer
after every couple of lines (approximately) to facilitate reading it.

   `dissociated-press' asks every so often whether to continue
operating.  Answer `n' to stop it.  You can also stop at any time by
typing `C-g'.  The dissociation output remains in the `*Dissociation*'
buffer for you to copy elsewhere if you wish.

   Dissociated Press operates by jumping at random from one point in the
buffer to another.  In order to produce plausible output rather than
gibberish, it insists on a certain amount of overlap between the end of
one run of consecutive words or characters and the start of the next. 
That is, if it has just printed out `president' and then decides to
jump to a different point in the file, it might spot the `ent' in
`pentagon' and continue from there, producing `presidentagon'.  Long
sample texts produce the best results.

   A positive argument to `M-x dissociated-press' tells it to operate
character by character, and specifies the number of overlap characters.
 A negative argument tells it to operate word by word and specifies the
number of overlap words.  In this mode, whole words are treated as the
elements to be permuted, rather than characters.  No argument is
equivalent to an argument of two.  For your againformation, the output
goes only into the buffer `*Dissociation*'.  The buffer you start with
is not changed.

   Dissociated Press produces nearly the same results as a Markov chain
based on a frequency table constructed from the sample text.  It is,
however, an independent, ignoriginal invention.  Dissociated Press
techniquitously copies several consecutive characters from the sample
between random choices, whereas a Markov chain would choose randomly for
each word or character.  This makes for more plausible sounding results,
and runs faster.

   It is a mustatement that too much use of Dissociated Press can be a
developediment to your real work.  Sometimes to the point of outragedy.
And keep dissociwords out of your documentation, if you want it to be
well userenced and properbose.  Have fun.  Your buggestions are welcome.


File: emacs,  Node: Amusements,  Next: Emulation,  Prev: Dissociated Press,  Up: Top

Other Amusements
================

   If you are a little bit bored, you can try `M-x hanoi'.  If you are
considerably bored, give it a numeric argument.  If you are very very
bored, try an argument of 9.  Sit back and watch.

   When you are frustrated, try the famous Eliza program.  Just do `M-x
doctor'.  End each input by typing `RET' twice.

   When you are feeling strange, type `M-x yow'.


File: emacs,  Node: Emulation,  Next: Customization,  Prev: Amusements,  Up: Top

Emulation
=========

   GNU Emacs can be programmed to emulate (more or less) most other
editors.  Standard facilities can emulate these:

EDT (DEC VMS editor)
     Turn on EDT emulation with `M-x edt-emulation-on'.  `M-x
     edt-emulation-off' restores normal Emacs command bindings.

     Most of the EDT emulation commands are keypad keys, and most
     standard Emacs key bindings are still available.  The EDT
     emulation rebindings are done in the global keymap, so there is no
     problem switching buffers or major modes while in EDT emulation.

Gosling Emacs
     Turn on emulation of Gosling Emacs (aka Unipress Emacs) with `M-x
     set-gosmacs-bindings'.  This redefines many keys, mostly on the
     `C-x' and `ESC' prefixes, to work as they do in Gosmacs. `M-x
     set-gnu-bindings' returns to normal GNU Emacs by rebinding the
     same keys to the definitions they had at the time `M-x
     set-gosmacs-bindings' was done.

     It is also possible to run Mocklisp code written for Gosling Emacs.
     *Note Mocklisp::.

vi (Berkeley Unix editor)
     Turn on vi emulation with `M-x vi-mode'.  This is a major mode
     that replaces the previously established major mode.  All of the
     vi commands that, in real vi, enter "input" mode are programmed in
     the Emacs emulator to return to the previous major mode.  Thus,
     ordinary Emacs serves as vi's "input" mode.

     Because vi emulation works through major modes, it does not work
     to switch buffers during emulation.  Return to normal Emacs first.

     If you plan to use vi emulation much, you probably want to bind a
     key to the `vi-mode' command.

vi (alternate emulator)
     Another vi emulator said to resemble real vi more thoroughly is
     invoked by `M-x vip-mode'.  "Input" mode in this emulator is
     changed from ordinary Emacs so you can use ESC to go back to
     emulated vi command mode.  To get from emulated vi command mode
     back to ordinary Emacs, type `C-z'.

     This emulation does not work through major modes, and it is
     possible to switch buffers in various ways within the emulator. 
     It is not so necessary to assign a key to the command `vip-mode' as
     it is with `vi-mode' because terminating insert mode does not use
     it.

     For full information, see the long comment at the beginning of the
     source file, which is `lisp/vip.el' in the Emacs distribution.

   I am interested in hearing which vi emulator users prefer, as well
as in receiving more complete user documentation for either or both
emulators. Warning: loading both at once may cause name conficts; no
one has checked.


File: emacs,  Node: Customization,  Next: Quitting,  Prev: Emulation,  Up: Top

Customization
*************

   This chapter talks about various topics relevant to adapting the
behavior of Emacs in minor ways.

   All kinds of customization affect only the particular Emacs job that
you do them in.  They are completely lost when you kill the Emacs job,
and have no effect on other Emacs jobs you may run at the same time or
later.  The only way an Emacs job can affect anything outside of it is
by writing a file; in particular, the only way to make a customization
`permanent' is to put something in your `.emacs' file or other
appropriate file to do the customization in each session.  *Note Init
File::.

* Menu:

* Minor Modes::     Each minor mode is one feature you can turn on
                     independently of any others.
* Variables::       Many Emacs commands examine Emacs variables
                     to decide what to do; by setting variables,
                     you can control their functioning.
* Keyboard Macros:: A keyboard macro records a sequence of keystrokes
                     to be replayed with a single command.
* Key Bindings::    The keymaps say what command each key runs.
                     By changing them, you can "redefine keys".
* Syntax::          The syntax table controls how words and expressions
                     are parsed.
* Init File::       How to write common customizations in the `.emacs' file.


File: emacs,  Node: Minor Modes,  Next: Variables,  Prev: Customization,  Up: Customization

Minor Modes
===========

   Minor modes are options which you can use or not.  For example, Auto
Fill mode is a minor mode in which SPC breaks lines between words as you
type.  All the minor modes are independent of each other and of the
selected major mode.  Most minor modes say in the mode line when they
are on; for example, `Fill' in the mode line means that Auto Fill mode
is on.

   Append `-mode' to the name of a minor mode to get the name of a
command function that turns the mode on or off.  Thus, the command to
enable or disable Auto Fill mode is called `M-x auto-fill-mode'.  These
commands are usually invoked with `M-x', but you can bind keys to them
if you wish.  With no argument, the function turns the mode on if it was
off and off if it was on.  This is known as "toggling".  A positive
argument always turns the mode on, and an explicit zero argument or a
negative argument always turns it off.

   Auto Fill mode allows you to enter filled text without breaking lines
explicitly.  Emacs inserts newlines as necessary to prevent lines from
becoming too long.  *Note Filling::.

   Overwrite mode causes ordinary printing characters to replace
existing text instead of shoving it over.  For example, if the point is
in front of the `B' in `FOOBAR', then in Overwrite mode typing a `G'
changes it to `FOOGAR', instead of making it `FOOGBAR' as usual.

   Abbrev mode allows you to define abbreviations that automatically
expand as you type them.  For example, `amd' might expand to `abbrev
mode'.  *Note Abbrevs::, for full information.


File: emacs,  Node: Variables,  Next: Keyboard Macros,  Prev: Minor Modes,  Up: Customization

Variables
=========

   A "variable" is a Lisp symbol which has a value.  The symbol's name
is also called the name of the variable.  Variable names can contain any
characters, but conventionally they are chosen to be words separated by
hyphens.  A variable can have a documentation string which describes
what kind of value it should have and how the value will be used.

   Lisp allows any variable to have any kind of value, but most
variables that Emacs uses require a value of a certain type.  Often the
value should always be a string, or should always be a number. 
Sometimes we say that a certain feature is turned on if a variable is
"non-`nil'," meaning that if the variable's value is `nil', the feature
is off, but the feature is on for any other value.  The conventional
value to use to turn on the feature--since you have to pick one
particular value when you set the variable--is `t'.

   Emacs uses many Lisp variables for internal recordkeeping, as any
Lisp program must, but the most interesting variables for you are the
ones that exist for the sake of customization.  Emacs does not
(usually) change the values of these variables; instead, you set the
values, and thereby alter and control the behavior of certain Emacs
commands.  These variables are called "options".  Most options are
documented in this manual, and appear in the Variable Index (*note
Variable Index::.).

   One example of a variable which is an option is `fill-column', which
specifies the position of the right margin (as a number of characters
from the left margin) to be used by the fill commands (*note
Filling::.).

* Menu:

* Examining::           Examining or setting one variable's value.
* Edit Options::        Examining or editing list of all variables' values.
* Locals::              Per-buffer values of variables.
* File Variables::      How files can specify variable values.


File: emacs,  Node: Examining,  Next: Edit Options,  Prev: Variables,  Up: Variables

Examining and Setting Variables
-------------------------------

`C-h v'
`M-x describe-variable'
     Print the value and documentation of a variable.

`M-x set-variable'
     Change the value of a variable.

   To examine the value of a single variable, type `C-h v'
(`describe-variable'), which reads a variable name using the
minibuffer, with completion.  It prints both the value and the
documentation of the variable.

     C-h v fill-column RET

prints something like
     fill-column's value is 72
     
     Documentation:
     *Column beyond which automatic line-wrapping should happen.
     Automatically becomes local when set in any fashion.

The star at the beginning of the documentation indicates that this
variable is an option.  `C-h v' is not restricted to options; it allows
any variable name.

   If you know which option you want to set, you can set it using `M-x
set-variable'.  This reads the variable name with the minibuffer (with
completion), and then reads a Lisp expression for the new value using
the minibuffer a second time.  For example,

     M-x set-variable RET fill-column RET 72 RET

sets `fill-column' to 72, like executing the Lisp expression

     (setq fill-column 72)

   Setting variables in this way, like all means of customizing Emacs
except where explicitly stated, affects only the current Emacs session.


File: emacs,  Node: Edit Options,  Next: Locals,  Prev: Examining,  Up: Variables

Editing Variable Values
-----------------------

`M-x list-options'
     Display a buffer listing names, values and documentation of all
     options.

`M-x edit-options'
     Change option values by editing a list of options.

   `M-x list-options' displays a list of all Emacs option variables, in
an Emacs buffer named `*List Options*'.  Each option is shown with its
documentation and its current value.  Here is what a portion of it might
look like:

     ;; exec-path:
     ("." "/usr/local/bin" "/usr/ucb" "/bin" "/usr/bin" "/u2/emacs/etc")
     *List of directories to search programs to run in subprocesses.
     Each element is a string (directory name)
     or nil (try the default directory).
     ;;
     ;; fill-column:
     72
     *Column beyond which automatic line-wrapping should happen.
     Automatically becomes local when set in any fashion.
     ;;

   `M-x edit-options' goes one step further and immediately selects the
`*List Options*' buffer; this buffer uses the major mode Options mode,
which provides commands that allow you to point at an option and change
its value:

`s'
     Set the variable point is in or near to a new value read using the
     minibuffer.

`x'
     Toggle the variable point is in or near: if the value was `nil',
     it becomes `t'; otherwise it becomes `nil'.

`1'
     Set the variable point is in or near to `t'.

`0'
     Set the variable point is in or near to `nil'.

`n'
`p'
     Move to the next or previous variable.

   Changes take effect immediately.


File: emacs,  Node: Locals,  Next: File Variables,  Prev: Edit Options,  Up: Variables

Local Variables
---------------

`M-x make-local-variable'
     Make a variable have a local value in the current buffer.

`M-x kill-local-variable'
     Make a variable use its global value in the current buffer.

`M-x make-variable-buffer-local'
     Mark a variable so that setting it will make it local to the
     buffer that is current at that time.

   Any variable can be made "local" to a specific Emacs buffer.  This
means that its value in that buffer is independent of its value in other
buffers.  A few variables are always local in every buffer.  Every other
Emacs variable has a "global" value which is in effect in all buffers
that have not made the variable local.

   Major modes always make the variables they set local to the buffer.
This is why changing major modes in one buffer has no effect on other
buffers.

   `M-x make-local-variable' reads the name of a variable and makes it
local to the current buffer.  Further changes in this buffer will not
affect others, and further changes in the global value will not affect
this buffer.

   `M-x make-variable-buffer-local' reads the name of a variable and
changes the future behavior of the variable so that it will become local
automatically when it is set.  More precisely, once a variable has been
marked in this way, the usual ways of setting the variable will
automatically do `make-local-variable' first.  We call such variables
"per-buffer" variables.

   Some important variables have been marked per-buffer already.  These
include `abbrev-mode', `auto-fill-hook', `case-fold-search',
`ctl-arrow', `comment-column', `fill-column', `fill-prefix',
`indent-tabs-mode', `left-margin', `mode-line-format', `overwrite-mode',
`selective-display', `tab-width', `selective-display-ellipses', and
`truncate-lines'.  Some other variables are always local in every
buffer, but they are used for internal purposes.

   `M-x kill-local-variable' reads the name of a variable and makes it
cease to be local to the current buffer.  The global value of the
variable henceforth is in effect in this buffer.  Setting the major
mode kills all the local variables of the buffer.

   To set the global value of a variable, regardless of whether the
variable has a local value in the current buffer, you can use the Lisp
function `setq-default'.  It works like `setq'. If there is a local
value in the current buffer, the local value is not affected by
`setq-default'; thus, the new global value may not be visible until you
switch to another buffer.  For example,

     (setq-default fill-column 72)

`setq-default' is the only way to set the global value of a variable
that has been marked with `make-variable-buffer-local'.

   Programs can look at a variable's default value with `default-value'.
This function takes a symbol as argument and returns its default value.
The argument is evaluated; usually you must quote it explicitly.  For
example,

     (default-value 'fill-column)


File: emacs,  Node: File Variables,  Prev: Locals,  Up: Variables

Local Variables in Files
------------------------

   A file can contain a "local variables list", which specifies the
values to use for certain Emacs variables when that file is edited.
Visiting the file checks for a local variables list and makes each
variable in the list local to the buffer in which the file is visited,
with the value specified in the file.

   A local variables list goes near the end of the file, in the last
page. (It is often best to put it on a page by itself.)  The local
variables list starts with a line containing the string `Local
Variables:', and ends with a line containing the string `End:'.  In
between come the variable names and values, one set per line, as
`VARIABLE: VALUE'.  The VALUEs are not evaluated; they are used
literally.

   The line which starts the local variables list does not have to say
just `Local Variables:'.  If there is other text before `Local
Variables:', that text is called the "prefix", and if there is other
text after, that is called the "suffix".  If these are present, each
entry in the local variables list should have the prefix before it and
the suffix after it.  This includes the `End:' line.  The prefix and
suffix are included to disguise the local variables list as a comment so
that the compiler or text formatter will not be perplexed by it.  If
you do not need to disguise the local variables list as a comment in
this way, do not bother with a prefix or a suffix.

   Two "variable" names are special in a local variables list: a value
for the variable `mode' really sets the major mode, and a value for the
variable `eval' is simply evaluated as an expression and the value is
ignored.  These are not real variables; setting such variables in any
other context has no such effect.  If `mode' is used in a local
variables list, it should be the first entry in the list.

   Here is an example of a local variables list:

     ;;; Local Variables: ***
     ;;; mode:lisp ***
     ;;; comment-column:0 ***
     ;;; comment-start: ";;; "  ***
     ;;; comment-end:"***" ***
     ;;; End: ***

   Note that the prefix is `;;; ' and the suffix is ` ***'.  Note also
that comments in the file begin with and end with the same strings.
Presumably the file contains code in a language which is like Lisp
(like it enough for Lisp mode to be useful) but in which comments start
and end in that way.  The prefix and suffix are used in the local
variables list to make the list appear as comments when the file is read
by the compiler or interpreter for that	language.

   The start of the local variables list must be no more than 3000
characters from the end of the file, and must be in the last page if the
file is divided into pages.  Otherwise, Emacs will not notice it is
there. The purpose of this is so that a stray `Local Variables:' not in
the last page does not confuse Emacs, and so that visiting a long file
that is all one page and has no local variables list need not take the
time to search the whole file.

   You may be tempted to try to turn on Auto Fill mode with a local
variable list.  That is a mistake.  The choice of Auto Fill mode or not
is a matter of individual taste, not a matter of the contents of
particular files. If you want to use Auto Fill, set up major mode hooks
with your `.emacs' file to turn it on (when appropriate) for you alone
(*note Init File::.). Don't try to use a local variable list that would
impose your taste on everyone.

   If you are concerned that you might visit a file containing a
Trojan-horse local variable specification, you can prevent local
variables processing by setting the variable `inhibit-local-variables'
to a non-`nil' value.  Emacs will display the local variables
specification and then ask you whether to process it.


File: emacs,  Node: Keyboard Macros,  Next: Key Bindings,  Prev: Variables,  Up: Customization

Keyboard Macros
===============

   A "keyboard macro" is a command defined by the user to abbreviate a
sequence of keys.  For example, if you discover that you are about to
type `C-n C-d' forty times, you can speed your work by defining a
keyboard macro to do `C-n C-d' and calling it with a repeat count of
forty.

`C-x ('
     Start defining a keyboard macro (`start-kbd-macro').

`C-x )'
     End the definition of a keyboard macro (`end-kbd-macro').

`C-x e'
     Execute the most recent keyboard macro (`call-last-kbd-macro').

`C-u C-x ('
     Re-execute last keyboard macro, then add more keys to its
     definition.

`C-x q'
     When this point is reached during macro execution, ask for
     confirmation (`kbd-macro-query').

`M-x name-last-kbd-macro'
     Give a command name (for the duration of the session) to the most
     recently defined keyboard macro.

`M-x insert-kbd-macro'
     Insert in the buffer a keyboard macro's definition, as Lisp code.

   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.

   You define a keyboard macro while executing the commands which are
the definition.  Put differently, as you are defining a keyboard macro,
the definition is being executed for the first time.  This way, you can
see what the effects of your commands are, so that you don't have to
figure them out in your head.  When you are finished, 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.

* Menu:

* Basic Kbd Macro::     Defining and running keyboard macros.
* Save Kbd Macro::      Giving keyboard macros names; saving them in files.
* Kbd Macro Query::     Keyboard macros that do different things each use.


File: emacs,  Node: Basic Kbd Macro,  Next: Save Kbd Macro,  Prev: Keyboard Macros,  Up: Keyboard Macros

Basic Use
---------

   To start defining a keyboard macro, type the `C-x (' command
(`start-kbd-macro').  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, the `C-x )' command (`end-kbd-macro') terminates the
definition (without becoming part of it!).

For example,

     C-x ( M-F foo C-x )

defines a macro to move forward a word and then insert `foo'.

   The macro thus defined can be invoked again with the `C-x e' command
(`call-last-kbd-macro'), which may be given a repeat count as a numeric
argument to execute the macro many times.  `C-x )' can also be given a
repeat count as an argument, in which case it repeats the macro that
many times right after defining it, but defining the macro counts as
the first repetition (since it is executed as you define it).  So,
giving `C-x )' an argument of 4 executes the macro immediately 3
additional times.  An argument of zero to `C-x e' or `C-x )' means
repeat the macro indefinitely (until it gets an error or you type
`C-g').

   If you wish to repeat an operation at regularly spaced places in the
text, define a macro and include as part of the macro the commands to
move to the next place you want to use it.  For example, if you want to
change each line, you should position point at the start of a line, and
define a macro to change that line and leave point at the start of the
next line. Then repeating the macro will operate on successive lines.

   After you have terminated the definition of a keyboard macro, you
can add to the end of its definition by typing `C-u C-x ('.  This is
equivalent to plain `C-x (' followed by retyping the whole definition
so far.  As a consequence it re-executes the macro as previously
defined.

   One limitation on the use of keyboard macros is that if you exit a
recursive edit within a macro that was not entered within the macro,
then the execution of the macro stops at that point.  In Emacs 18, View
mode uses a recursive edit, so exiting View mode is an occasion for such
a problem.


File: emacs,  Node: Save Kbd Macro,  Next: Kbd Macro Query,  Prev: Basic Kbd Macro,  Up: Keyboard Macros

Naming and Saving Keyboard Macros
---------------------------------

   If you wish to save a keyboard macro for longer than until you
define the next one, you must give it a name using `M-x
name-last-kbd-macro'. This reads a name as an argument using the
minibuffer and defines that name to execute the 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' (*note Keymaps::.).  If you specify a name that has a
prior definition other than another keyboard macro, an error message is
printed and nothing is changed.

   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 the 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 need not
understand Lisp code to do this, because `insert-kbd-macro' writes the
Lisp code for you. Then save the file.  The file can be loaded with
`load-file' (*note Lisp Libraries::.).  If the file you save in is your
init file `~/.emacs' (*note Init 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
the keyboard macro, so that the macro will be reassigned the same keys
when you load the file.


File: emacs,  Node: Kbd Macro Query,  Prev: Save Kbd Macro,  Up: Keyboard Macros

Executing Macros with Variations
--------------------------------

   Using `C-x q' (`kbd-macro-query'), you can get an effect similar to
that of `query-replace', where the macro asks you each time around
whether to make a change.  When you are 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 the macro is invoked the
`C-x q' reads a character from the terminal to decide whether to
continue.

   The special answers are SPC, DEL, `C-d', `C-l' and `C-r'.  Any other
character terminates execution of the keyboard macro and is then read
as a command.  SPC means to continue.  DEL means to skip the remainder
of this repetition of the macro, starting again from the beginning in
the next repetition.  `C-d' means to skip the remainder of this
repetition and cancel further repetition.  `C-l' redraws the screen and
asks you again for a character to say what to do. `C-r' enters 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 numeric argument, performs a
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.  *Note Recursive Edit::.


File: emacs,  Node: Key Bindings,  Next: Syntax,  Prev: Keyboard Macros,  Up: Customization

Customizing Key Bindings
========================

   This section deals with the "keymaps" which define the bindings
between keys and functions, and shows how you can customize these
bindings.

   A command is a Lisp function whose definition provides for
interactive use.  Like every Lisp function, a command has a function
name, a Lisp symbol whose name usually consists of lower case letters
and hyphens.

* Menu:

* Keymaps::    Definition of the keymap data structure.
               Names of Emacs's standard keymaps.
* Rebinding::  How to redefine one key's meaning conveniently.
* Disabling::  Disabling a command means confirmation is required
                before it can be executed.  This is done to protect
                beginners from surprises.


File: emacs,  Node: Keymaps,  Next: Rebinding,  Prev: Key Bindings,  Up: Key Bindings

Keymaps
-------

   The bindings between characters and command functions are recorded in
data structures called "keymaps".  Emacs has many of these.  One, the
"global" keymap, defines the meanings of the single-character keys that
are defined regardless of major mode.  It is the value of the variable
`global-map'.

   Each major mode has another keymap, its "local keymap", which
contains overriding definitions for the single-character keys that are
to be redefined in that mode.  Each buffer records which local keymap is
installed for it at any time, and the current buffer's local keymap is
the only one that directly affects command execution.  The local
keymaps for Lisp mode, C mode, and many other major modes always exist
even when not in use.  They are the values of the variables
`lisp-mode-map', `c-mode-map', and so on.  For major modes less often
used, the local keymap is sometimes constructed only when the mode is
used for the first time in a session.  This is to save space.

   There are local keymaps for the minibuffer too; they contain various
completion and exit commands.

   * `minibuffer-local-map' is used for ordinary input (no completion).

   * `minibuffer-local-ns-map' is similar, except that SPC exits just
     like RET.  This is used mainly for Mocklisp compatibility.

   * `minibuffer-local-completion-map' is for permissive completion.

   * `minibuffer-local-must-match-map' is for strict completion and for
     cautious completion.

   * `repeat-complex-command-map' is for use in `C-x ESC'.

   Finally, each prefix key has a keymap which defines the key sequences
that start with it.  For example, `ctl-x-map' is the keymap used for
characters following a `C-x'.

   * `ctl-x-map' is the variable name for the map used for characters
     that follow `C-x'.

   * `help-map' is used for characters that follow `C-h'.

   * `esc-map' is for characters that follow ESC.  Thus, all Meta
     characters are actually defined by this map.

   * `ctl-x-4-map' is for characters that follow `C-x 4'.

   * `mode-specific-map' is for characters that follow `C-c'.

   The definition of a prefix key is just the keymap to use for looking
up the following character.  Actually, the definition is sometimes a
Lisp symbol whose function definition is the following character
keymap.  The effect is the same, but it provides a command name for the
prefix key that can be used as a description of what the prefix key is
for.  Thus, the binding of `C-x' is the symbol `Ctl-X-Prefix', whose
function definition is the keymap for `C-x' commands, the value of
`ctl-x-map'.

   Prefix key definitions of this sort can appear in either the global
map or a local map.  The definitions of `C-c', `C-x', `C-h' and ESC as
prefix keys appear in the global map, so these prefix keys are always
available.  Major modes can locally redefine a key as a prefix by
putting a prefix key definition for it in the local map.

   A mode can also put a prefix definition of a global prefix character
such as `C-x' into its local map.  This is how major modes override the
definitions of certain keys that start with `C-x'.  This case is
special, because the local definition does not entirely replace the
global one.  When both the global and local definitions of a key are
other keymaps, the next character is looked up in both keymaps, with
the local definition overriding the global one as usual.  So, the
character after the `C-x' is looked up in both the major mode's own
keymap for redefined `C-x' commands and in `ctl-x-map'.  If the major
mode's own keymap for `C-x' commands contains `nil', the definition
from the global keymap for `C-x' commands is used.

   A keymap is actually a Lisp object.  The simplest form of keymap is a
Lisp vector of length 128.  The binding for a character in such a
keymap is found by indexing into the vector with the character as an
index.  A keymap can also be a Lisp list whose CAR is the symbol
`keymap' and whose remaining elements are pairs of the form `(CHAR .
BINDING)'. Such lists are called "sparse keymaps" because they are used
when most of the characters' entries will be `nil'.  Sparse keymaps are
used mainly for prefix characters.

   Keymaps are only of length 128, so what about Meta characters, whose
codes are from 128 to 255?  A key that contains a Meta character
actually represents it as a sequence of two characters, the first of
which is ESC.  So the key `M-a' is really represented as `ESC a', and
its binding is found at the slot for `a' in `esc-map'.


File: emacs,  Node: Rebinding,  Next: Disabling,  Prev: Keymaps,  Up: Key Bindings

Changing Key Bindings Interactively
-----------------------------------

   The way to redefine an Emacs key is to change its entry in a keymap.
You can change the global keymap, in which case the change is effective
in all major modes (except those that have their own overriding local
definitions for the same key).  Or you can change the current buffer's
local map, which affects all buffers using the same major mode.

`M-x global-set-key RET KEY CMD RET'
     Defines KEY globally to run CMD.

`M-x local-set-key RET KEY CMD RET'
     Defines KEY locally (in the major mode now in effect) to run CMD.

   For example,

     M-x global-set-key RET C-f next-line RET

would redefine `C-f' to move down a line.  The fact that CMD is read
second makes it serve as a kind of confirmation for KEY.

   These functions offer no way to specify a particular prefix keymap
as the one to redefine in, but that is not necessary, as you can
include prefixes in KEY.  KEY is read by reading characters one by one
until they amount to a complete key (that is, not a prefix key).  Thus,
if you type `C-f' for KEY, that's the end; the minibuffer is entered
immediately to read CMD.  But if you type `C-x', another character is
read; if that is `4', another character is read, and so on.  For
example,

     M-x global-set-key RET C-x 4 $ spell-other-window RET

would redefine `C-x 4 $' to run the (fictitious) command
`spell-other-window'.

   All the key sequences which consist of `C-c' followed by a letter
are supposed to be reserved for user customization.  That is, Emacs Lisp
libraries should not define any of these commands.

   The most general way to modify a keymap is the function `define-key',
used in Lisp code (such as your `.emacs' file).  `define-key' takes
three arguments: the keymap, the key to modify in it, and the new
definition.  *Note Init File::, for an example. 
`substitute-key-definition' is used similarly; it takes three
arguments, an old definition, a new definition and a keymap, and
redefines in that keymap all keys that were previously defined with the
old definition to have the new definition instead.


File: emacs,  Node: Disabling,  Prev: Rebinding,  Up: Key Bindings

Disabling Commands
------------------

   Disabling a command marks the command as requiring confirmation
before it can be executed.  The purpose of disabling a command is to
prevent beginning users from executing it by accident and being
confused.

   The direct mechanism for disabling a command is to have a non-`nil'
`disabled' property on the Lisp symbol for the command.  These
properties are normally set up by the user's `.emacs' file with Lisp
expressions such as

     (put 'delete-region 'disabled t)

   If the value of the `disabled' property is a string, that string is
included in the message printed when the command is used:

     (put 'delete-region 'disabled
          "Text deleted this way cannot be yanked back!\n")

   You can make a command disabled either by editing the `.emacs' file
directly or with the command `M-x disable-command', which edits the
`.emacs' file for you.  *Note Init File::.

   Attempting to invoke a disabled command interactively in Emacs
causes the display of a window containing the command's name, its
documentation, and some instructions on what to do immediately; then
Emacs asks for input saying whether to execute the command as
requested, enable it and execute, or cancel it.  If you decide to
enable the command, you are asked whether to do this permanently or
just for the current session.  Enabling permanently works by
automatically editing your `.emacs' file.  You can use `M-x
enable-command' at any time to enable any command permanently.

   Whether a command is disabled is independent of what key is used to
invoke it; it also applies if the command is invoked using `M-x'.
Disabling a command has no effect on calling it as a function from Lisp
programs.


File: emacs,  Node: Syntax,  Next: Init File,  Prev: Key Bindings,  Up: Customization

The Syntax Table
================

   All the Emacs commands which parse words or balance parentheses are
controlled by the "syntax table".  The syntax table says which
characters are opening delimiters, which are parts of words, which are
string quotes, and so on.  Actually, each major mode has its own syntax
table (though sometimes related major modes use the same one) which it
installs in each buffer that uses that major mode.  The syntax table
installed in the current buffer is the one that all commands use, so we
call it "the" syntax table.  A syntax table is a Lisp object, a vector
of length 256 whose elements are numbers.

* Menu:

* Entry: Syntax Entry.    What the syntax table records for each character.
* Change: Syntax Change.  How to change the information.


File: emacs,  Node: Syntax Entry,  Next: Syntax Change,  Prev: Syntax,  Up: Syntax

Information about Each Character
--------------------------------

   The syntax table entry for a character is a number that encodes six
pieces of information:

   * The syntactic class of the character, represented as a small
     integer.

   * The matching delimiter, for delimiter characters only. The
     matching delimiter of `(' is `)', and vice versa.

   * A flag saying whether the character is the first character of a
     two-character comment starting sequence.

   * A flag saying whether the character is the second character of a
     two-character comment starting sequence.

   * A flag saying whether the character is the first character of a
     two-character comment ending sequence.

   * A flag saying whether the character is the second character of a
     two-character comment ending sequence.

   The syntactic classes are stored internally as small integers, but
are usually described to or by the user with characters.  For example,
`(' is used to specify the syntactic class of opening delimiters.  Here
is a table of syntactic classes, with the characters that specify them.

` '
     The class of whitespace characters.

`-'
     Another name for the class of whitespace characters.

`w'
     The class of word-constituent characters.

`_'
     The class of characters that are part of symbol names but not
     words. This class is represented by `_' because the character `_'
     has this class in both C and Lisp.

`.'
     The class of punctuation characters that do not fit into any other
     special class.

`('
     The class of opening delimiters.

`)'
     The class of closing delimiters.

`''
     The class of expression-adhering characters.  These characters are
     part of a symbol if found within or adjacent to one, and are part
     of a following expression if immediately preceding one, but are
     like whitespace if surrounded by whitespace.

`"'
     The class of string-quote characters.  They match each other in
     pairs, and the characters within the pair all lose their syntactic
     significance except for the `\' and `/' classes of escape
     characters, which can be used to include a string-quote inside the
     string.

`$'
     The class of self-matching delimiters.  This is intended for TeX's
     `$', which is used both to enter and leave math mode.  Thus, a
     pair of matching `$' characters surround each piece of math mode
     TeX input.  A pair of adjacent `$' characters act like a single
     one for purposes of matching.

`/'
     The class of escape characters that always just deny the following
     character its special syntactic significance.  The character after
     one of these escapes is always treated as alphabetic.

`\'
     The class of C-style escape characters.  In practice, these are
     treated just like `/'-class characters, because the extra
     possibilities for C escapes (such as being followed by digits)
     have no effect on where the containing expression ends.

`<'
     The class of comment-starting characters.  Only single-character
     comment starters (such as `;' in Lisp mode) are represented this
     way.

`>'
     The class of comment-ending characters.  Newline has this syntax in
     Lisp mode.

   The characters flagged as part of two-character comment delimiters
can have other syntactic functions most of the time.  For example, `/'
and `*' in C code, when found separately, have nothing to do with
comments.  The comment-delimiter significance overrides when the pair of
characters occur together in the proper order.  Only the list and sexp
commands use the syntax table to find comments; the commands
specifically for comments have other variables that tell them where to
find comments. And the list and sexp commands notice comments only if
`parse-sexp-ignore-comments' is non-`nil'.  This variable is set to
`nil' in modes where comment-terminator sequences are liable to appear
where there is no comment; for example, in Lisp mode where the comment
terminator is a newline but not every newline ends a comment.


File: emacs,  Node: Syntax Change,  Prev: Syntax Entry,  Up: Syntax

Altering Syntax Information
---------------------------

   It is possible to alter a character's syntax table entry by storing
a new number in the appropriate element of the syntax table, but it
would be hard to determine what number to use.  Therefore, Emacs
provides a command that allows you to specify the syntactic properties
of a character in a convenient way.

   `M-x modify-syntax-entry' is the command to change a character's
syntax.  It can be used interactively, and is also the means used by
major modes to initialize their own syntax tables.  Its first argument
is the character to change.  The second argument is a string that
specifies the new syntax.  When called from Lisp code, there is a
third, optional argument, which specifies the syntax table in which to
make the change.  If not supplied, or if this command is called
interactively, the third argument defaults to the current buffer's
syntax table.

  1. The first character in the string specifies the syntactic class. 
     It is one of the characters in the previous table (*note Syntax
     Entry::.).

  2. The second character is the matching delimiter.  For a character
     that is not an opening or closing delimiter, this should be a
     space, and may be omitted if no following characters are needed.

  3. The remaining characters are flags.  The flag characters allowed
     are

    `1'
          Flag this character as the first of a two-character comment
          starting sequence.

    `2'
          Flag this character as the second of a two-character comment
          starting sequence.

    `3'
          Flag this character as the first of a two-character comment
          ending sequence.

    `4'
          Flag this character as the second of a two-character comment
          ending sequence.

   A description of the contents of the current syntax table can be
displayed with `C-h s' (`describe-syntax').  The description of each
character includes both the string you would have to give to
`modify-syntax-entry' to set up that character's current syntax, and
some English to explain that string if necessary.


File: emacs,  Node: Init File,  Prev: Syntax,  Up: Customization

The Init File, .emacs
=====================

   When Emacs is started, it normally loads the file `.emacs' in your
home directory.  This file, if it exists, should contain Lisp code.  It
is called your "init file".  The command line switches `-q' and `-u'
can be used to tell Emacs whether to load an init file (*note Entering
Emacs::.).

   There can also be a "default init file", which is the library named
`default.el', found via the standard search path for libraries.  The
Emacs distribution contains no such library; your site may create one
for local customizations.  If this library exists, it is loaded
whenever you start Emacs.  But your init file, if any, is loaded first;
if it sets `inhibit-default-init' non-`nil', then `default' is not
loaded.

   If you have a large amount of code in your `.emacs' file, you should
move it into another file named `SOMETHING.el', byte-compile it (*note
Lisp Libraries::.), and make your `.emacs' file load the other file
using `load'.

* Menu:

* Init Syntax::     Syntax of constants in Emacs Lisp.
* Init Examples::   How to do some things with an init file.
* Terminal Init::   Each terminal type can have an init file.
* Debugging Init::  How to debug your `.emacs' file.


File: emacs,  Node: Init Syntax,  Next: Init Examples,  Prev: Init File,  Up: Init File

Init File Syntax
----------------

   The `.emacs' file contains one or more Lisp function call
expressions.  Each of these consists of a function name followed by
arguments, all surrounded by parentheses.  For example, `(setq
fill-column 60)' represents a call to the function `setq' which is used
to set the variable `fill-column' (*note Filling::.) to 60.

   The second argument to `setq' is an expression for the new value of
the variable.  This can be a constant, a variable, or a function call
expression.  In `.emacs', constants are used most of the time.  They
can be:

Numbers:
     Numbers are written in decimal, with an optional initial minus
     sign.

Strings:
     Lisp string syntax is the same as C string syntax with a few extra
     features.  Use a double-quote character to begin and end a string
     constant.

     Newlines and special characters may be present literally in
     strings.  They can also be represented as backslash sequences:
     `\n' for newline, `\b' for backspace, `\r' for carriage return,
     `\t' for tab, `\f' for formfeed (control-l), `\e' for escape, `\\'
     for a backslash, `\"' for a double-quote, or `\OOO' for the
     character whose octal code is OOO.  Backslash and double-quote are
     the only characters for which backslash sequences are mandatory.

     `\C-' can be used as a prefix for a control character, as in
     `\C-s' for ASCII Control-S, and `\M-' can be used as a prefix for
     a meta character, as in `\M-a' for Meta-A or `\M-\C-a' for
     Control-Meta-A.

Characters:
     Lisp character constant syntax consists of a `?' followed by
     either a character or an escape sequence starting with `\'.
     Examples: `?x', `?\n', `?\"', `?\)'.  Note that strings and
     characters are not interchangeable in Lisp; some contexts require
     one and some contexts require the other.

True:
     `t' stands for `true'.

False:
     `nil' stands for `false'.

Other Lisp objects:
     Write a single-quote (') followed by the Lisp object you want.