This is Info file ../info/emacs, produced by Makeinfo-1.63 from the
input file emacs.texi.


File: emacs,  Node: Sorting,  Next: Narrowing,  Prev: Postscript,  Up: Top

Sorting Text
============

   Emacs provides several commands for sorting text in the buffer.  All
operate on the contents of the region (the text between point and the
mark).  They divide the text of the region into many "sort records",
identify a "sort key" for each record, and then reorder the records
into the order determined by the sort keys.  The records are ordered so
that their keys are in alphabetical order, or, for numeric sorting, in
numeric order.  In alphabetic sorting, all upper case letters `A'
through `Z' come before lower case `a', in accord with the ASCII
character sequence.

   The various sort commands differ in how they divide the text into
sort records and in which part of each record is used as the sort key.
Most of the commands make each line a separate sort record, but some
commands use paragraphs or pages as sort records.  Most of the sort
commands use each entire sort record as its own sort key, but some use
only a portion of the record as the sort key.

`M-x sort-lines'
     Divide the region into lines, and sort by comparing the entire
     text of a line.  A numeric argument means sort into descending
     order.

`M-x sort-paragraphs'
     Divide the region into paragraphs, and sort by comparing the entire
     text of a paragraph (except for leading blank lines).  A numeric
     argument means sort into descending order.

`M-x sort-pages'
     Divide the region into pages, and sort by comparing the entire
     text of a page (except for leading blank lines).  A numeric
     argument means sort into descending order.

`M-x sort-fields'
     Divide the region into lines, and sort by comparing the contents of
     one field in each line.  Fields are defined as separated by
     whitespace, so the first run of consecutive non-whitespace
     characters in a line constitutes field 1, the second such run
     constitutes field 2, etc.

     Specify which field to sort by with a numeric argument: 1 to sort
     by field 1, etc.  A negative argument means count fields from the
     right instead of from the left; thus, minus 1 means sort by the
     last field.  If several lines have identical contents in the field
     being sorted, they keep same relative order that they had in the
     original buffer.

     A negative argument means count fields from the right (from the
     end of the line).

`M-x sort-numeric-fields'
     Like `M-x sort-fields' except the specified field is converted to
     an integer for each line, and the numbers are compared.  `10'
     comes before `2' when considered as text, but after it when
     considered as a number.

`M-x sort-columns'
     Like `M-x sort-fields' except that the text within each line used
     for comparison comes from a fixed range of columns.  See below for
     an explanation.

`M-x reverse-region'
     Reverse the order of the lines in the region.  This is useful for
     sorting into descending order by fields or columns, since those
     sort commands do not have a feature for doing that.

   For example, if the buffer contains this:

     On systems where clash detection (locking of files being edited) is
     implemented, Emacs also checks the first time you modify a buffer
     whether the file has changed on disk since it was last visited or
     saved.  If it has, you are asked to confirm that you want to change
     the buffer.

applying `M-x sort-lines' to the entire buffer produces this:

     On systems where clash detection (locking of files being edited) is
     implemented, Emacs also checks the first time you modify a buffer
     saved.  If it has, you are asked to confirm that you want to change
     the buffer.
     whether the file has changed on disk since it was last visited or

where the upper case `O' sorts before all lower case letters.  If you
use `C-u 2 M-x sort-fields' instead, you get this:

     implemented, Emacs also checks the first time you modify a buffer
     saved.  If it has, you are asked to confirm that you want to change
     the buffer.
     On systems where clash detection (locking of files being edited) is
     whether the file has changed on disk since it was last visited or

where the sort keys were `Emacs', `If', `buffer', `systems' and `the'.

   `M-x sort-columns' requires more explanation.  You specify the
columns by putting point at one of the columns and the mark at the other
column.  Because this means you cannot put point or the mark at the
beginning of the first line to sort, this command uses an unusual
definition of `region': all of the line point is in is considered part
of the region, and so is all of the line the mark is in, as well as all
the lines in between.

   For example, to sort a table by information found in columns 10 to
15, you could put the mark on column 10 in the first line of the table,
and point on column 15 in the last line of the table, and then run
`sort-columns'.  Equivalently, you could run it with the mark on column
15 in the first line and point on column 10 in the last line.

   This can be thought of as sorting the rectangle specified by point
and the mark, except that the text on each line to the left or right of
the rectangle moves along with the text inside the rectangle.  *Note
Rectangles::.

   Many of the sort commands ignore case differences when comparing, if
`sort-fold-case' is non-`nil'.


File: emacs,  Node: Narrowing,  Next: Two-Column,  Prev: Sorting,  Up: Top

Narrowing
=========

   "Narrowing" means focusing in on some portion of the buffer, making
the rest temporarily inaccessible.  The portion which you can still get
to is called the "accessible portion".  Canceling the narrowing, which
makes the entire buffer once again accessible, is called "widening".
The amount of narrowing in effect in a buffer at any time is called the
buffer's "restriction".

   Narrowing can make it easier to concentrate on a single subroutine or
paragraph by eliminating clutter.  It can also be used to restrict the
range of operation of a replace command or repeating keyboard macro.

`C-x n n'
     Narrow down to between point and mark (`narrow-to-region').

`C-x n w'
     Widen to make the entire buffer accessible again (`widen').

`C-x n p'
     Narrow down to the current page (`narrow-to-page').

   When you have narrowed down to a part of the buffer, that part
appears to be all there is.  You can't see the rest, you can't move
into it (motion commands won't go outside the accessible part), you
can't change it in any way.  However, it is not gone, and if you save
the file all the inaccessible text will be saved.  The word `Narrow'
appears in the mode line whenever narrowing is in effect.

   The primary narrowing command is `C-x n n' (`narrow-to-region').  It
sets the current buffer's restrictions so that the text in the current
region remains accessible but all text before the region or after the
region is inaccessible.  Point and mark do not change.

   Alternatively, use `C-x n p' (`narrow-to-page') to narrow down to
the current page.  *Note Pages::, for the definition of a page.

   The way to cancel narrowing is to widen with `C-x n w' (`widen').
This makes all text in the buffer accessible again.

   You can get information on what part of the buffer you are narrowed
down to using the `C-x =' command.  *Note Position Info::.

   Because narrowing can easily confuse users who do not understand it,
`narrow-to-region' is normally a disabled command.  Attempting to use
this command asks for confirmation and gives you the option of enabling
it; if you enable the command, confirmation will no longer be required
for it.  *Note Disabling::.


File: emacs,  Node: Two-Column,  Next: Editing Binary Files,  Prev: Narrowing,  Up: Top

Two-Column Editing
==================

   Two-column mode lets you conveniently edit two side-by-side columns
of text.  It uses two side-by-side windows, each showing its own buffer.

   There are three ways to enter two-column mode:

`f2 2' or `C-x 6 2'
     Enter two-column mode with the current buffer on the left, and on
     the right, a buffer whose name is based on the current buffer's
     name (`2C-two-columns').  If the right-hand buffer doesn't already
     exist, it starts out empty; the current buffer's contents are not
     changed.

     This command is appropriate when the current buffer is empty or
     contains just one column and you want to add another column.

`f2 s' or `C-x 6 s'
     Split the current buffer, which contains two-column text, into two
     buffers, and display them side by side (`2C-split').  The current
     buffer becomes the left-hand buffer, but the text in the right-hand
     column is moved into the right-hand buffer.  The current column
     specifies the split point.  Splitting starts with the current line
     and continues to the end of the buffer.

     This command is appropriate when you have a buffer that already
     contains two-column text, and you wish to separate the columns
     temporarily.

`f2 b BUFFER RET'
`C-x 6 b BUFFER RET'
     Enter two-column mode using the current buffer as the left-hand
     buffer, and using buffer BUFFER as the right-hand buffer
     (`2C-associate-buffer').

   `f2 s' or `C-x 6 s' looks for a column separator which is a string
that appears on each line between the two columns.  You can specify the
width of the separator with a numeric argument to `f2 s'; that many
characters, before point, constitute the separator string.  By default,
the width is 1, so the column separator is the character before point.

   When a line has the separator at the proper place, `f2 s' puts the
text after the separator into the right-hand buffer, and deletes the
separator.  Lines that don't have the column separator at the proper
place remain unsplit; they stay in the left-hand buffer, and the
right-hand buffer gets an empty line to correspond.  (This is the way to
write a line which "spans both columns while in two-column mode": write
it in the left-hand buffer, and put an empty line in the right-hand
buffer.)

   The command `C-x 6 RET' or `f2 RET' (`2C-newline') inserts a newline
in each of the two buffers at corresponding positions.  This is the
easiest way to add a new line to the two-column text while editing it
in split buffers.

   When you have edited both buffers as you wish, merge them with `f2
1' or `C-x 6 1' (`2C-merge').  This copies the text from the right-hand
buffer as a second column in the other buffer.  To go back to
two-column editing, use `f2 s'.

   Use `f2 d' or `C-x 6 d' to disassociate the two buffers, leaving
each as it stands (`2C-dissociate').  If the other buffer, the one not
current when you type `f2 d', is empty, `f2 d' kills it.


File: emacs,  Node: Editing Binary Files,  Next: Saving Emacs Sessions,  Prev: Two-Column,  Up: Top

Editing Binary Files
====================

   There is a special major mode for editing binary files: Hexl mode.
To use it, use `M-x hexl-find-file' instead of `C-x C-f' to visit the
file.  This command converts the file's contents to hexadecimal and
lets you edit the translation.  When you save the file, it is converted
automatically back to binary.

   You can also use `M-x hexl-mode' to translate an existing buffer
into hex.  This is useful if you visit a file normally and then discover
it is a binary file.

   Ordinary text characters overwrite in Hexl mode.  This is to reduce
the risk of accidentally spoiling the alignment of data in the file.
There are special commands for insertion.  Here is a list of the
commands of Hexl mode:

`C-M-d'
     Insert a byte with a code typed in decimal.

`C-M-o'
     Insert a byte with a code typed in octal.

`C-M-x'
     Insert a byte with a code typed in hex.

`C-x ['
     Move to the beginning of a 1k-byte "page".

`C-x ]'
     Move to the end of a 1k-byte "page".

`M-g'
     Move to an address specified in hex.

`M-j'
     Move to an address specified in decimal.

`C-c C-c'
     Leave Hexl mode, going back to the major mode this buffer had
     before you invoked `hexl-mode'.


File: emacs,  Node: Saving Emacs Sessions,  Next: Recursive Edit,  Prev: Editing Binary Files,  Up: Top

Saving Emacs Sessions
=====================

   You can use the Desktop library to save the state of Emacs from one
session to another.  Saving the state means that Emacs starts up with
the same set of buffers, major modes, buffer positions, and so on that
the previous Emacs session had.

   To use Desktop, you should first add these lines at the end of your
`.emacs' file:

     (load "desktop")
     (desktop-load-default)
     (desktop-read)

The first time you save the state of the Emacs session, you must do it
manually, with the command `M-x desktop-save'.  Once you have done
that, exiting Emacs will save the state again--not only the present
Emacs session, but also subsequent sessions.  You can also save the
state at any time, without exiting Emacs, by typing `M-x desktop-save'
again.

   In order for Emacs to recover the state from a previous session, you
must start it with the same current directory as you used when you
started the previous session.

   The variable `desktop-files-not-to-save' controls which files are
excluded from state saving.  Its value is a regular expression that
matches the files to exclude.  By default, remote (ftp-accessed) files
are excluded; this is because visiting them again in the subsequent
session would be slow.  If you want to include these files in state
saving, set `desktop-files-not-to-save' to `"^$"'.


File: emacs,  Node: Recursive Edit,  Next: Emulation,  Prev: Saving Emacs Sessions,  Up: Top

Recursive Editing Levels
========================

   A "recursive edit" is a situation in which you are using Emacs
commands to perform arbitrary editing while in the middle of another
Emacs command.  For example, when you type `C-r' inside of a
`query-replace', you enter a recursive edit in which you can change the
current buffer.  On exiting from the recursive edit, you go back to the
`query-replace'.

   "Exiting" the recursive edit means returning to the unfinished
command, which continues execution.  The command to exit is `C-M-c'
(`exit-recursive-edit').

   You can also "abort" the recursive edit.  This is like exiting, but
also quits the unfinished command immediately.  Use the command `C-]'
(`abort-recursive-edit') to do this.  *Note Quitting::.

   The mode line shows you when you are in a recursive edit by
displaying square brackets around the parentheses that always surround
the major and minor mode names.  Every window's mode line shows this,
in the same way, since being in a recursive edit is true of Emacs as a
whole rather than any particular window or buffer.

   It is possible to be in recursive edits within recursive edits.  For
example, after typing `C-r' in a `query-replace', you may type a
command that enters the debugger.  This begins a recursive editing level
for the debugger, within the recursive editing level for `C-r'.  Mode
lines display a pair of square brackets for each recursive editing
level currently in progress.

   Exiting the inner recursive edit (such as, with the debugger `c'
command) resumes the command running in the next level up.  When that
command finishes, you can then use `C-M-c' to exit another recursive
editing level, and so on.  Exiting applies to the innermost level only.
Aborting also gets out of only one level of recursive edit; it returns
immediately to the command level of the previous recursive edit.  If you
wish, you can then abort the next recursive editing level.

   Alternatively, the command `M-x top-level' aborts all levels of
recursive edits, returning immediately to the top level command reader.

   The text being edited inside the recursive edit need not be the same
text that you were editing at top level.  It depends on what the
recursive edit is for.  If the command that invokes the recursive edit
selects a different buffer first, that is the buffer you will edit
recursively.  In any case, you can switch buffers within the recursive
edit in the normal manner (as long as the buffer-switching keys have
not been rebound).  You could probably do all the rest of your editing
inside the recursive edit, visiting files and all.  But this could have
surprising effects (such as stack overflow) from time to time.  So
remember to exit or abort the recursive edit when you no longer need it.

   In general, we try to minimize the use of recursive editing levels in
GNU Emacs.  This is because they constrain you to "go back" in a
particular order-from the innermost level toward the top level.  When
possible, we present different activities in separate buffers so that
you can switch between them as you please.  Some commands switch to a
new major mode which provides a command to switch back.  These
approaches give you more flexibility to go back to unfinished tasks in
the order you choose.


File: emacs,  Node: Emulation,  Next: Dissociated Press,  Prev: Recursive Edit,  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.

vi (Berkeley editor)
     Viper is the newest emulator for vi.  It implements several levels
     of emulation; level 1 is closest to vi itself, while level 5
     departs somewhat from strict emulation to take advantage of the
     capabilities of Emacs.  To invoke Viper, type `M-x viper-mode'; it
     will guide you the rest of the way and ask for the emulation level.

vi (another emulator)
     `M-x vi-mode' enters a major mode that replaces the previously
     established major mode.  All of the vi commands that, in real vi,
     enter "input" mode are programmed instead 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)
     `M-x vip-mode' invokes another vi emulator, said to resemble real
     vi more thoroughly than `M-x vi-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.


File: emacs,  Node: Dissociated Press,  Next: Amusements,  Prev: Emulation,  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) so you can read the output
as it comes out.

   Dissociated Press asks every so often whether to continue generating
output.  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'.(1)  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.

   ---------- Footnotes ----------

   (1)  This dissociword actually appeared during the Vietnam War, when
it was very appropriate.


File: emacs,  Node: Amusements,  Next: Customization,  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.

   If you want a little more personal involvement, try `M-x gomoku',
which plays the game Go Moku with you.

   `M-x blackbox' and `M-x mpuz' are two kinds of puzzles.  `blackbox'
challenges you to determine the location of objects inside a box by
tomography.  `mpuz' displays a multiplication puzzle with letters
standing for digits in a code that you must guess--to guess a value,
type a letter and then the digit you think it stands for.

   `M-x dunnet' runs an adventure-style exploration game, which is a
bigger sort of puzzle.

   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: Customization,  Next: Quitting,  Prev: Amusements,  Up: Top

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

   This chapter talks about various topics relevant to adapting the
behavior of Emacs in minor ways.  See `The Emacs Lisp Reference Manual'
for how to make more far-reaching changes.

   All kinds of customization affect only the particular Emacs session
that you do them in.  They are completely lost when you kill the Emacs
session, and have no effect on other Emacs sessions you may run at the
same time or later.  The only way an Emacs session 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".
* Keyboard Translations::  If your keyboard passes an undesired code
			     for a key, you can tell Emacs to
			     substitute another code.
* 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,  Up: Customization

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

   Minor modes are optional features which you can turn on or off.  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.

   Enabling or disabling some minor modes applies only to the current
buffer; each buffer is independent of the other buffers.  Therefore, you
can enable the mode in particular buffers and disable it in others.  The
per-buffer minor modes include Auto Fill mode, Auto Save mode, Font-Lock
mode, ISO Accents mode, Outline minor mode, Overwrite mode, and Binary
Overwrite mode.

   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::.

   Auto Save mode causes the contents of a buffer to be saved
periodically to reduce the amount of work you can lose in case of a
system crash.  *Note Auto Save::.

   Enriched mode enables editing and saving of formatted text.  *Note
Formatted Text::.

   Font-Lock mode automatically highlights certain textual units found
in programs, such as comments, strings, and function names being
defined.  This requires a window system that can display multiple fonts.
*Note Faces::.

   ISO Accents mode makes the characters ``', `'', `"', `^', `/' and
`~' combine with the following letter, to produce an accented letter in
the ISO Latin-1 character set.  *Note European Display::.

   Outline minor mode provides the same facilities as the major mode
called Outline mode; but since it is a minor mode instead, you can
combine it with any major mode.  *Note Outline Mode::.

   Overwrite mode causes ordinary printing characters to replace
existing text instead of shoving it to the right.  For example, if
point is in front of the `B' in `FOOBAR', then in Overwrite mode typing
a `G' changes it to `FOOGAR', instead of producing it `FOOGBAR' as
usual.  Binary Overwrite mode is a variant of Overwrite mode for
editing binary files; it treats newlines and tabs like other
characters, so that they overwrite other characters and can be
overwritten by them.

   The following minor modes normally apply to all buffers at once.
Since each is enabled or disabled by the value of a variable, you *can*
set them differently for particular buffers, by explicitly making the
corresponding variables local in those buffers.  *Note Locals::.

   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.

   Icomplete mode displays an indication of available completions when
you are in the minibuffer and completion is active.  *Note Completion
Options::.

   Line Number mode enables continuous display in the mode line of the
line number of point.  *Note Mode Line::.

   Resize-Minibuffer mode makes the minibuffer expand as necessary to
hold the text that you put in it.  *Note Minibuffer Edit::.

   Scroll Bar mode gives each window a scroll bar (*note Scroll
Bars::.).  Menu Bar mode gives each frame a menu bar (*note Menu
Bars::.).  Both of these modes are enabled by default when you use the
X Window System.

   In Transient Mark mode, every change in the buffer contents
"deactivates" the mark, so that commands that operate on the region
will get an error.  This means you must either set the mark, or
explicitly "reactivate" it, before each command that uses the region.
The advantage of Transient Mark mode is that Emacs can display the
region highlighted (currently only when using X).  *Note Setting Mark::.

   For most minor modes, the command name is also the name of a variable
which directly controls the mode.  The mode is enabled whenever this
variable's value is non-`nil', and the minor mode command works by
setting the variable.  For example, the command `outline-minor-mode'
works by setting the value of `outline-minor-mode' as a variable; it is
this variable that directly turns Outline minor mode on and off.  To
check whether a given minor mode works this way, use `C-h v' to ask for
documentation on the variable name.

   These minor mode variables provide a good way for Lisp programs to
turn minor modes on and off; they are also useful in a file's local
variables list.  But please think twice before setting minor modes with
a local variables list, because most minor modes are matter of user
preference--other users editing the same file might not want the same
minor modes you prefer.


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.  A variable name can contain
any characters that can appear in a file, but conventionally variable
names consist of 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 record keeping, 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 "user options".  Most user options are documented
in this manual, and appear in the Variable Index (*note Variable
Index::.).

   One example of a variable which is a user 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 user options' values.
* Hooks::	     Hook variables let you specify programs for parts
		       of Emacs to run on particular occasions.
* Locals::	     Per-buffer values of variables.
* File Variables::   How files can specify variable values.


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

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

`C-h v VAR RET'
     Display the value and documentation of variable VAR
     (`describe-variable').

`M-x set-variable RET VAR RET VALUE RET'
     Change the value of variable VAR to VALUE.

   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 displays both the value and the
documentation of the variable.  For example,

     C-h v fill-column RET

displays something like this:

     fill-column's value is 75
     
     Documentation:
     *Column beyond which automatic line-wrapping should happen.
     Automatically becomes buffer-local when set in any fashion.

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

   The most convenient way to set a specific user option is with `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.

   `M-x set-variable' is limited to user option variables.  You can set
any variable with a Lisp expression using the function `setq'.  Here's
how to use it to set `fill-column':

     (setq fill-column 75)

   Setting variables, like all means of customizing Emacs except where
otherwise stated, affects only the current Emacs session.


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

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

   These two functions make it easy to display all the Emacs user option
variables, and to change some of them if you wish.

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

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

   `M-x list-options' displays a list of all Emacs option variables, in
an Emacs buffer named `*List Options*'.  Each user 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 buffer-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 a user option
variable 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 user option.

   Any changes take effect immediately, and last until you exit from
Emacs.


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

Hooks
-----

   A "hook" is a variable where you can store a function or functions
to be called on a particular occasion by an existing program.  Emacs
provides a number of hooks for the sake of customization.

   Most of the hooks in Emacs are "normal hooks".  These variables
contain lists of functions to be called with no arguments.  The reason
most hooks are normal hooks is so that you can use them in a uniform
way.  Every variable in Emacs whose name ends in `-hook' is a normal
hook.

   Most major modes run hooks as the last step of initialization.  This
makes it easy for a user to customize the behavior of the mode, by
overriding the local variable assignments already made by the mode.  But
hooks may also be used in other contexts.  For example, the hook
`suspend-hook' runs just before Emacs suspends itself (*note
Exiting::.).

   The recommended way to add a hook function to a normal hook is by
calling `add-hook'.  You can use any valid Lisp function as the hook
function.  For example, here's how to set up a hook to turn on Auto
Fill mode when entering Text mode and other modes based on Text mode:

     (add-hook 'text-mode-hook 'turn-on-auto-fill)

   The next example shows how to use a hook to customize the indentation
of C code.  (People often have strong personal preferences for one
format compared to another.)  Here the hook function is an anonymous
lambda expression.

     (setq my-c-style
       '((c-comment-only-line-offset . 4)
         (c-cleanup-list . (scope-operator
     		       empty-defun-braces
     		       defun-close-semi))
         (c-offsets-alist . ((arglist-close . c-lineup-arglist)
     			(substatement-open . 0)))))
     
     (add-hook 'c-mode-common-hook
       (function (lambda ()
         (c-add-style "my-style" my-c-style t))))

   It is best to design your hook functions so that the order in which
they are executed does not matter.  Any dependence on the order is
"asking for trouble."  However, the order is predictable: the most
recently added hook functions are executed first.


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

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

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

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

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

   Almost 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.

   `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 automatically
do `make-local-variable' first.  We call such variables "per-buffer"
variables.

   Major modes (*note Major Modes::.) always make variables local to the
buffer before setting the variables.  This is why changing major modes
in one buffer has no effect on other buffers.  Minor modes also work by
setting variables--normally, each minor mode has one controlling
variable which is non-`nil' when the mode is enabled (*note Minor
Modes::.).  For most minor modes, the controlling variable is per
buffer.

   Emacs contains a number of variables that are always per-buffer.
These include `abbrev-mode', `auto-fill-function', `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.

   A few variables cannot be local to a buffer because they are always
local to each display instead (*Note Multiple Displays::).  If you try
to make one of these variables buffer-local, you'll get an error
message.

   `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 except for a few variables
specially marked as "permanent locals".

   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
construct `setq-default'.  This construct is used just like `setq', but
it sets variables' global values instead of their local values (if
any).  When the current buffer does have a local value, the new global
value may not be visible until you switch to another buffer.  Here is
an 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'.

   Lisp programs can use `default-value' to look at a variable's
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, here's how to obtain the default value of
`fill-column':

     (default-value 'fill-column)


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

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

   A file can specify local variable values for use when you edit the
file with Emacs.  Visiting the file checks for local variables
specifications; it automatically makes these variables local to the
buffer, and sets them to the values specified in the file.

   There are two ways to specify local variable values: in the first
line, or with a local variables list.  Here's how to specify them in the
first line:

     -*- mode: MODENAME; VAR: VALUE; ... -*-

You can specify any number of variables/value pairs in this way, each
pair with a colon and semicolon as shown above.  `mode: MODENAME;'
specifies the major mode; this should come first in the line.  The
VALUEs are not evaluated; they are used literally.  Here is an example
that specifies Lisp mode and sets two variables with numeric values:

     ;; -*-mode: Lisp; fill-column: 75; comment-column: 50; -*-

   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.  If a file has both a local variables list and a `-*-' line,
Emacs processes *everything* in the `-*-' line first, and *everything*
in the local variables list afterward.

   Here is an example of a local variables list:

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

   As you see, each line starts with the prefix `;;; ' and each line
ends with the suffix ` ***'.  Emacs recognizes these as the prefix and
suffix based on the first line of the list, by finding them surrounding
the magic string `Local Variables:'; then it automatically discards
them from the other lines of the list.

   The usual reason for using a prefix and/or suffix is to embed the
local variables list in a comment, so it won't confuse other programs
that the file is intended as input for.  The example above is for a
language where comment lines start with `;;; ' and end with `***'; the
local values for `comment-start' and `comment-end' customize the rest
of Emacs for this unusual syntax.  Don't use a prefix (or a suffix) if
you don't need one.

   Two "variable names" have special meanings 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.  `mode' and `eval' are not real variables;
setting variables named `mode' and `eval' in any other context has no
special meaning.  If `mode' is used to set a major mode, it should be
the first "variable" in the list.

   You can use the `mode' "variable" to set minor modes as well as
major modes; in fact, you can use it more than once, first to set the
major mode and then to set minor modes which are specific to particular
buffers.  But most minor modes should not be specified in the file in
any fashion, because they represent user preferences.  For example, you
should not try to specify Auto Fill mode with file local variables,
because whether to use Auto Fill mode for editing a particular kind of
text is a matter of personal taste, not an aspect of the format of the
text.

   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 rule 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.

   The variable `enable-local-variables' controls whether to process
local variables lists, and thus gives you a chance to override them.
Its default value is `t', which means do process local variables lists.
If you set the value to `nil', Emacs simply ignores local variables
lists.  Any other value says to query you about each local variables
list, showing you the local variables list to consider.

   The `eval' "variable", and certain actual variables, create a
special risk; when you visit someone else's file, local variable
specifications for these could affect your Emacs in arbitrary ways.
Therefore, the option `enable-local-eval' controls whether Emacs
processes `eval' variables, as well variables with names that end in
`-hook', `-hooks', `-function' or `-functions', and certain other
variables.  The three possibilities for the option's value are `t',
`nil', and anything else, just as for `enable-local-variables'.  The
default is `maybe', which is neither `t' nor `nil', so normally Emacs
does ask for confirmation about file settings for these variables.

   Use the command `normal-mode' to reset the local variables and major
mode of a buffer according to the file name and contents, including the
local variables list if any.  *Note Choosing Modes::.


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 stand for
another 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.

`C-x C-k'
     Edit a previously defined keyboard macro (`edit-kbd-macro').

`M-x apply-macro-to-region-lines'
     Run the last keyboard macro on each complete line in the region.

   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 define 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.

