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GNU Info File | 1992-02-21 | 49KB | 868 lines

This is Info file ../info/emacs, produced by Makeinfo-1.43 from the input file emacs.tex. This file documents the GNU Emacs editor. Copyright (C) 1985, 1986, 1988 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: 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, use `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 75 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 75 RET sets `fill-column' to 75, like executing the Lisp expression (setq fill-column 75) 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: 75 *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: Set the variable point is in or near to a new value read using the minibuffer. Toggle the variable point is in or near: if the value was `nil', it becomes `t'; otherwise it becomes `nil'. Set the variable point is in or near to `t'. Set the variable point is in or near to `nil'. Move to the next or previous variable. 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', `comment-column', `ctl-arrow', `fill-column', `fill-prefix', `indent-tabs-mode', `left-margin', `mode-line-format', `overwrite-mode', `selective-display-ellipses', `selective-display', `tab-width', 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 75) `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. 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. 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'. 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. 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. 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. File: emacs, Node: Init Examples, Next: Terminal Init, Prev: Init Syntax, Up: Init File Init File Examples ------------------ Here are some examples of doing certain commonly desired things with Lisp expressions: * Make TAB in C mode just insert a tab if point is in the middle of a line. (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'. * Make searches case sensitive by default (in all buffers that do not override this). (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. * Make Text mode the default mode for new buffers. (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. * Turn on Auto Fill mode automatically in Text mode and related modes. (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 the installed Lisp library named `foo' (actually a file `foo.elc' or `foo.el' in a standard Emacs directory). (load "foo") When the argument to `load' is a relative pathname, not starting with `/' or `~', `load' searches the directories in `load-path' (*note Loading::.). * Load the compiled Lisp file `foo.elc' from your home directory. (load "~/foo.elc") Here an absolute file name is used, so no searching is done. * Rebind the key `C-x l' to run the function `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. * Do the same thing for C mode only. (define-key c-mode-map "\C-xl" 'make-symbolic-link) * Redefine all keys which now run `next-line' in Fundamental mode so that they run `forward-line' instead. (substitute-key-definition 'next-line 'forward-line global-map) * Make `C-x C-v' undefined. (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. * Make `$' have the syntax of punctuation in Text mode. Note the use of a character constant for `$'. (modify-syntax-entry ?\$ "." text-mode-syntax-table) * Enable the use of the command `eval-expression' without confirmation. (put 'eval-expression 'disabled nil) File: emacs, Node: Terminal Init, Prev: Init Examples, Up: Init File Terminal-specific Initialization -------------------------------- 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.