Go to the previous, next section.
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. See section The Init File, .emacs.
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. See section Filling Text.
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'. See section Abbrevs, for full information.
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 (see section 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 (see section Filling Text).
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 RETprints 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.
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:
nil,
it becomes t; otherwise it becomes nil.
t.
nil.
Changes take effect immediately.
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)
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 (see section The Init File, .emacs). 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.
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.
start-kbd-macro).
end-kbd-macro).
call-last-kbd-macro).
kbd-macro-query).
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.
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.
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 (see section 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
(see section Libraries of Lisp Code for Emacs). If the file you save in is your init file
`~/.emacs' (see section The Init File, .emacs) 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.
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. See section Recursive Editing Levels.
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.
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.
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.
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. See section The Init File, .emacs, 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.
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. See section The Init File, .emacs.
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.
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.
The syntax table entry for a character is a number that encodes six pieces of information:
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 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.
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.
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.
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 (see section Entering and Exiting 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 (see section Libraries of Lisp Code for Emacs), and make your `.emacs'
file load the other file using load.
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 (see section Filling Text) 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:
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.
?x, ?\n, ?\", ?\). Note that
strings and characters are not interchangeable in Lisp; some contexts
require one and some contexts require the other.
t stands for `true'.
nil stands for `false'.
Here are some examples of doing certain commonly desired things with Lisp expressions:
(setq c-tab-always-indent nil)
Here we have a variable whose value is normally t for `true'
and the alternative is nil for `false'.
(setq-default case-fold-search nil)
This sets the default value, which is effective in all buffers that do
not have local values for the variable. Setting case-fold-search
with setq affects only the current buffer's local value, which
is not what you probably want to do in an init file.
(setq default-major-mode 'text-mode)
Note that text-mode is used because it is the command for entering
the mode we want. A single-quote is written before it to make a symbol
constant; otherwise, text-mode would be treated as a variable name.
(setq text-mode-hook '(lambda () (auto-fill-mode 1)))
Here we have a variable whose value should be a Lisp function. The
function we supply is a list starting with lambda, and a single
quote is written in front of it to make it (for the purpose of this
setq) a list constant rather than an expression. Lisp functions
are not explained here, but for mode hooks it is enough to know that
(auto-fill-mode 1) is an expression that will be executed when
Text mode is entered, and you could replace it with any other expression
that you like, or with several expressions in a row.
(setq text-mode-hook 'turn-on-auto-fill)
This is another way to accomplish the same result.
turn-on-auto-fill is a symbol whose function definition is
(lambda () (auto-fill-mode 1)).
(load "foo")
When the argument to load is a relative pathname, not starting
with `/' or `~', load searches the directories in
load-path (see section Loading Libraries).
(load "~/foo.elc")
Here an absolute file name is used, so no searching is done.
make-symbolic-link.
(global-set-key "\C-xl" 'make-symbolic-link)
or
(define-key global-map "\C-xl" 'make-symbolic-link)
Note once again the single-quote used to refer to the symbol
make-symbolic-link instead of its value as a variable.
(define-key c-mode-map "\C-xl" 'make-symbolic-link)
next-line in Fundamental mode
so that they run forward-line instead.
(substitute-key-definition 'next-line 'forward-line
global-map)
(global-unset-key "\C-x\C-v")
One reason to undefine a key is so that you can make it a prefix. Simply defining C-x C-v anything would make C-x C-v a prefix, but C-x C-v must be freed of any non-prefix definition first.
(modify-syntax-entry ?\$ "." text-mode-syntax-table)
eval-expression without confirmation.
(put 'eval-expression 'disabled nil)
Each terminal type can have a Lisp library to be loaded into Emacs when
it is run on that type of terminal. For a terminal type named
termtype, the library is called `term/termtype' and it is
found by searching the directories load-path as usual and trying the
suffixes `.elc' and `.el'. Normally it appears in the
subdirectory `term' of the directory where most Emacs libraries are
kept.
The usual purpose of the terminal-specific library is to define the escape sequences used by the terminal's function keys using the library `keypad.el'. See the file `term/vt100.el' for an example of how this is done.
When the terminal type contains a hyphen, only the part of the name
before the first hyphen is significant in choosing the library name.
Thus, terminal types `aaa-48' and `aaa-30-rv' both use
the library `term/aaa'. The code in the library can use
(getenv "TERM") to find the full terminal type name.
The library's name is constructed by concatenating the value of the
variable term-file-prefix and the terminal type. Your `.emacs'
file can prevent the loading of the terminal-specific library by setting
term-file-prefix to nil.
The value of the variable term-setup-hook, if not nil, is
called as a function of no arguments at the end of Emacs initialization,
after both your `.emacs' file and any terminal-specific library have
been read in. You can set the value in the `.emacs' file to override
part of any of the terminal-specific libraries and to define
initializations for terminals that do not have a library.
Ordinarily, Emacs traps errors that occur while reading `.emacs'. This is convenient, most of the time, because it means you can still get an Emacs in which you can edit. But it causes inconvenience because there is no way to enter the debugger if there is an error.
But you can run the `.emacs' file explicitly in an Emacs that is already set up, and debug errors at that time.
M-x set-variable debug-on-error t M-x load-file ~/.emacs
In Emacs 19, use the `-debug-init' option if you want errors in `.emacs' to enter the debugger.
Go to the previous, next section.