Fix buffer overflow in make-docfile

[emacs.git] / doc / lispref / abbrevs.texi

@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
@c Copyright (C) 1990-1994, 1999, 2001-2017 Free Software Foundation,
@c Inc.
@c See the file elisp.texi for copying conditions.
@node Abbrevs
@chapter Abbrevs and Abbrev Expansion
@cindex abbrev
@c  @cindex abbrev table  Redundant with "abbrev".

  An abbreviation or @dfn{abbrev} is a string of characters that may be
expanded to a longer string.  The user can insert the abbrev string and
find it replaced automatically with the expansion of the abbrev.  This
saves typing.

  The set of abbrevs currently in effect is recorded in an @dfn{abbrev
table}.  Each buffer has a local abbrev table, but normally all buffers
in the same major mode share one abbrev table.  There is also a global
abbrev table.  Normally both are used.

  An abbrev table is represented as an obarray.  @xref{Creating
Symbols}, for information about obarrays.  Each abbreviation is
represented by a symbol in the obarray.  The symbol's name is the
abbreviation; its value is the expansion; its function definition is
the hook function for performing the expansion (@pxref{Defining
Abbrevs}); and its property list cell contains various additional
properties, including the use count and the number of times the
abbreviation has been expanded (@pxref{Abbrev Properties}).

@cindex system abbrev
  Certain abbrevs, called @dfn{system abbrevs}, are defined by a major
mode instead of the user.  A system abbrev is identified by its
non-@code{nil} @code{:system} property (@pxref{Abbrev Properties}).
When abbrevs are saved to an abbrev file, system abbrevs are omitted.
@xref{Abbrev Files}.

  Because the symbols used for abbrevs are not interned in the usual
obarray, they will never appear as the result of reading a Lisp
expression; in fact, normally they are never used except by the code
that handles abbrevs.  Therefore, it is safe to use them in a
nonstandard way.

  If the minor mode Abbrev mode is enabled, the buffer-local variable
@code{abbrev-mode} is non-@code{nil}, and abbrevs are automatically
expanded in the buffer.  For the user-level commands for abbrevs, see
@ref{Abbrevs,, Abbrev Mode, emacs, The GNU Emacs Manual}.

@menu
* Tables: Abbrev Tables.        Creating and working with abbrev tables.
* Defining Abbrevs::            Specifying abbreviations and their expansions.
* Files: Abbrev Files.          Saving abbrevs in files.
* Expansion: Abbrev Expansion.  Controlling expansion; expansion subroutines.
* Standard Abbrev Tables::      Abbrev tables used by various major modes.
* Abbrev Properties::           How to read and set abbrev properties.
                                Which properties have which effect.
* Abbrev Table Properties::     How to read and set abbrev table properties.
                                Which properties have which effect.
@end menu

@node Abbrev Tables
@section Abbrev Tables
@cindex abbrev tables

  This section describes how to create and manipulate abbrev tables.

@defun make-abbrev-table &optional props
This function creates and returns a new, empty abbrev table---an
obarray containing no symbols.  It is a vector filled with zeros.
@var{props} is a property list that is applied to the new table
(@pxref{Abbrev Table Properties}).
@end defun

@defun abbrev-table-p object
This function returns a non-@code{nil} value if @var{object} is an
abbrev table.
@end defun

@defun clear-abbrev-table abbrev-table
This function undefines all the abbrevs in @var{abbrev-table}, leaving
it empty.
@c Don't see why this needs saying.
@c It always returns @code{nil}.
@end defun

@defun copy-abbrev-table abbrev-table
This function returns a copy of @var{abbrev-table}---a new abbrev
table containing the same abbrev definitions.  It does @emph{not} copy
any property lists; only the names, values, and functions.
@end defun

@defun define-abbrev-table tabname definitions &optional docstring &rest props
This function defines @var{tabname} (a symbol) as an abbrev table
name, i.e., as a variable whose value is an abbrev table.  It defines
abbrevs in the table according to @var{definitions}, a list of
elements of the form @code{(@var{abbrevname} @var{expansion}
[@var{hook}] [@var{props}...])}.  These elements are passed as
arguments to @code{define-abbrev}.  @c The return value is always @code{nil}.

The optional string @var{docstring} is the documentation string of the
variable @var{tabname}.  The property list @var{props} is applied to
the abbrev table (@pxref{Abbrev Table Properties}).

If this function is called more than once for the same @var{tabname},
subsequent calls add the definitions in @var{definitions} to
@var{tabname}, rather than overwriting the entire original contents.
(A subsequent call only overrides abbrevs explicitly redefined or
undefined in @var{definitions}.)
@end defun

@defvar abbrev-table-name-list
This is a list of symbols whose values are abbrev tables.
@code{define-abbrev-table} adds the new abbrev table name to this list.
@end defvar

@defun insert-abbrev-table-description name &optional human
This function inserts before point a description of the abbrev table
named @var{name}.  The argument @var{name} is a symbol whose value is an
abbrev table.  @c The return value is always @code{nil}.

If @var{human} is non-@code{nil}, the description is human-oriented.
System abbrevs are listed and identified as such.  Otherwise the
description is a Lisp expression---a call to @code{define-abbrev-table}
that would define @var{name} as it is currently defined, but without
the system abbrevs.  (The mode or package using @var{name} is supposed
to add these to @var{name} separately.)
@end defun

@node Defining Abbrevs
@section Defining Abbrevs
@cindex defining abbrevs

  @code{define-abbrev} is the low-level basic function for defining an
abbrev in an abbrev table.

  When a major mode defines a system abbrev, it should call
@code{define-abbrev} and specify @code{t} for the @code{:system}
property.  Be aware that any saved non-system abbrevs are restored
at startup, i.e., before some major modes are loaded.  Therefore, major
modes should not assume that their abbrev tables are empty when they
are first loaded.

@defun define-abbrev abbrev-table name expansion &optional hook &rest props
This function defines an abbrev named @var{name}, in
@var{abbrev-table}, to expand to @var{expansion} and call @var{hook},
with properties @var{props} (@pxref{Abbrev Properties}).  The return
value is @var{name}.  The @code{:system} property in @var{props} is
treated specially here: if it has the value @code{force}, then it will
overwrite an existing definition even for a non-system abbrev of
the same name.

@var{name} should be a string.  The argument @var{expansion} is
normally the desired expansion (a string), or @code{nil} to undefine
the abbrev.  If it is anything but a string or @code{nil}, then the
abbreviation expands solely by running @var{hook}.

The argument @var{hook} is a function or @code{nil}.  If @var{hook} is
non-@code{nil}, then it is called with no arguments after the abbrev is
replaced with @var{expansion}; point is located at the end of
@var{expansion} when @var{hook} is called.

@cindex @code{no-self-insert} property
If @var{hook} is a non-@code{nil} symbol whose @code{no-self-insert}
property is non-@code{nil}, @var{hook} can explicitly control whether
to insert the self-inserting input character that triggered the
expansion.  If @var{hook} returns non-@code{nil} in this case, that
inhibits insertion of the character.  By contrast, if @var{hook}
returns @code{nil}, @code{expand-abbrev} (or @code{abbrev-insert})
also returns @code{nil}, as if expansion had not really occurred.

Normally, @code{define-abbrev} sets the variable
@code{abbrevs-changed} to @code{t}, if it actually changes the abbrev.
This is so that some commands will offer to save the abbrevs.  It
does not do this for a system abbrev, since those aren't saved anyway.
@end defun

@defopt only-global-abbrevs
If this variable is non-@code{nil}, it means that the user plans to use
global abbrevs only.  This tells the commands that define mode-specific
abbrevs to define global ones instead.  This variable does not alter the
behavior of the functions in this section; it is examined by their
callers.
@end defopt

@node Abbrev Files
@section Saving Abbrevs in Files
@cindex save abbrevs in files

  A file of saved abbrev definitions is actually a file of Lisp code.
The abbrevs are saved in the form of a Lisp program to define the same
abbrev tables with the same contents.  Therefore, you can load the file
with @code{load} (@pxref{How Programs Do Loading}).  However, the
function @code{quietly-read-abbrev-file} is provided as a more
convenient interface.  Emacs automatically calls this function at
startup.

  User-level facilities such as @code{save-some-buffers} can save
abbrevs in a file automatically, under the control of variables
described here.

@defopt abbrev-file-name
This is the default file name for reading and saving abbrevs.  By
default, Emacs will look for @file{~/.emacs.d/abbrev_defs}, and, if
not found, for @file{~/.abbrev_defs}; if neither file exists, Emacs
will create @file{~/.emacs.d/abbrev_defs}.
@end defopt

@defun quietly-read-abbrev-file &optional filename
This function reads abbrev definitions from a file named @var{filename},
previously written with @code{write-abbrev-file}.  If @var{filename} is
omitted or @code{nil}, the file specified in @code{abbrev-file-name} is
used.

As the name implies, this function does not display any messages.
@c It returns @code{nil}.
@end defun

@defopt save-abbrevs
A non-@code{nil} value for @code{save-abbrevs} means that Emacs should
offer to save abbrevs (if any have changed) when files are saved.  If
the value is @code{silently}, Emacs saves the abbrevs without asking
the user.  @code{abbrev-file-name} specifies the file to save the
abbrevs in.  The default value is @code{t}.
@end defopt

@defvar abbrevs-changed
This variable is set non-@code{nil} by defining or altering any
abbrevs (except system abbrevs).  This serves as a flag for various
Emacs commands to offer to save your abbrevs.
@end defvar

@deffn Command write-abbrev-file &optional filename
Save all abbrev definitions (except system abbrevs), for all abbrev
tables listed in @code{abbrev-table-name-list}, in the file
@var{filename}, in the form of a Lisp program that when loaded will
define the same abbrevs.  If @var{filename} is @code{nil} or omitted,
@code{abbrev-file-name} is used.  This function returns @code{nil}.
@end deffn

@node Abbrev Expansion
@section Looking Up and Expanding Abbreviations
@cindex looking up abbrevs
@cindex expanding abbrevs
@cindex abbrevs, looking up and expanding

  Abbrevs are usually expanded by certain interactive commands,
including @code{self-insert-command}.  This section describes the
subroutines used in writing such commands, as well as the variables they
use for communication.

@defun abbrev-symbol abbrev &optional table
This function returns the symbol representing the abbrev named
@var{abbrev}.  It returns @code{nil} if that abbrev is not
defined.  The optional second argument @var{table} is the abbrev table
in which to look it up.  If @var{table} is @code{nil}, this function
tries first the current buffer's local abbrev table, and second the
global abbrev table.
@end defun

@defun abbrev-expansion abbrev &optional table
This function returns the string that @var{abbrev} would expand into (as
defined by the abbrev tables used for the current buffer).  It returns
@code{nil} if @var{abbrev} is not a valid abbrev.
The optional argument @var{table} specifies the abbrev table to use,
as in @code{abbrev-symbol}.
@end defun

@deffn Command expand-abbrev
This command expands the abbrev before point, if any.  If point does not
follow an abbrev, this command does nothing.  To do the expansion, it
calls the function that is the value of the @code{abbrev-expand-function}
variable, with no arguments, and returns whatever that function does.

The default expansion function returns the abbrev symbol if it did
expansion, and @code{nil} otherwise.  If the abbrev symbol has a hook
function that is a symbol whose @code{no-self-insert} property is
non-@code{nil}, and if the hook function returns @code{nil} as its
value, then the default expansion function returns @code{nil},
even though expansion did occur.
@end deffn

@defun abbrev-insert abbrev &optional name start end
This function inserts the abbrev expansion of @code{abbrev}, replacing
the text between @code{start} and @code{end}.  If @code{start} is
omitted, it defaults to point.  @code{name}, if non-@code{nil}, should
be the name by which this abbrev was found (a string); it is used to
figure out whether to adjust the capitalization of the expansion.  The
function returns @code{abbrev} if the abbrev was successfully
inserted, otherwise it returns @code{nil}.
@end defun

@deffn Command abbrev-prefix-mark &optional arg
This command marks the current location of point as the beginning of
an abbrev.  The next call to @code{expand-abbrev} will use the text
from here to point (where it is then) as the abbrev to expand, rather
than using the previous word as usual.

First, this command expands any abbrev before point, unless @var{arg}
is non-@code{nil}.  (Interactively, @var{arg} is the prefix argument.)
Then it inserts a hyphen before point, to indicate the start of the
next abbrev to be expanded.  The actual expansion removes the hyphen.
@end deffn

@defopt abbrev-all-caps
When this is set non-@code{nil}, an abbrev entered entirely in upper
case is expanded using all upper case.  Otherwise, an abbrev entered
entirely in upper case is expanded by capitalizing each word of the
expansion.
@end defopt

@defvar abbrev-start-location
The value of this variable is a buffer position (an integer or a marker)
for @code{expand-abbrev} to use as the start of the next abbrev to be
expanded.  The value can also be @code{nil}, which means to use the
word before point instead.  @code{abbrev-start-location} is set to
@code{nil} each time @code{expand-abbrev} is called.  This variable is
also set by @code{abbrev-prefix-mark}.
@end defvar

@defvar abbrev-start-location-buffer
The value of this variable is the buffer for which
@code{abbrev-start-location} has been set.  Trying to expand an abbrev
in any other buffer clears @code{abbrev-start-location}.  This variable
is set by @code{abbrev-prefix-mark}.
@end defvar

@defvar last-abbrev
This is the @code{abbrev-symbol} of the most recent abbrev expanded.  This
information is left by @code{expand-abbrev} for the sake of the
@code{unexpand-abbrev} command (@pxref{Expanding Abbrevs,, Expanding
Abbrevs, emacs, The GNU Emacs Manual}).
@end defvar

@defvar last-abbrev-location
This is the location of the most recent abbrev expanded.  This contains
information left by @code{expand-abbrev} for the sake of the
@code{unexpand-abbrev} command.
@end defvar

@defvar last-abbrev-text
This is the exact expansion text of the most recent abbrev expanded,
after case conversion (if any).  Its value is @code{nil} if the abbrev
has already been unexpanded.  This contains information left by
@code{expand-abbrev} for the sake of the @code{unexpand-abbrev} command.
@end defvar

@defvar abbrev-expand-function
The value of this variable is a function that @code{expand-abbrev}
will call with no arguments to do the expansion.  The function can do
anything it wants before and after performing the expansion.
It should return the abbrev symbol if expansion took place.
@end defvar

  The following sample code shows a simple use of
@code{abbrev-expand-function}.  It assumes that @code{foo-mode} is a
mode for editing certain files in which lines that start with @samp{#}
are comments.  You want to use Text mode abbrevs for those lines.  The
regular local abbrev table, @code{foo-mode-abbrev-table} is
appropriate for all other lines.  @xref{Standard Abbrev Tables}, for the
definitions of @code{local-abbrev-table} and @code{text-mode-abbrev-table}.
@xref{Advising Functions}, for details of @code{add-function}.

@smallexample
(defun foo-mode-abbrev-expand-function (expand)
  (if (not (save-excursion (forward-line 0) (eq (char-after) ?#)))
      ;; Performs normal expansion.
      (funcall expand)
    ;; We're inside a comment: use the text-mode abbrevs.
    (let ((local-abbrev-table text-mode-abbrev-table))
      (funcall expand))))

(add-hook 'foo-mode-hook
          #'(lambda ()
              (add-function :around (local 'abbrev-expand-function)
                            #'foo-mode-abbrev-expand-function)))
@end smallexample

@node Standard Abbrev Tables
@section Standard Abbrev Tables
@cindex standard abbrev tables

  Here we list the variables that hold the abbrev tables for the
preloaded major modes of Emacs.

@defvar global-abbrev-table
This is the abbrev table for mode-independent abbrevs.  The abbrevs
defined in it apply to all buffers.  Each buffer may also have a local
abbrev table, whose abbrev definitions take precedence over those in the
global table.
@end defvar

@defvar local-abbrev-table
The value of this buffer-local variable is the (mode-specific)
abbreviation table of the current buffer.  It can also be a list of
such tables.
@end defvar

@defvar abbrev-minor-mode-table-alist
The value of this variable is a list of elements of the form
@code{(@var{mode} . @var{abbrev-table})} where @var{mode} is the name
of a variable: if the variable is bound to a non-@code{nil} value,
then the @var{abbrev-table} is active, otherwise it is ignored.
@var{abbrev-table} can also be a list of abbrev tables.
@end defvar

@defvar fundamental-mode-abbrev-table
This is the local abbrev table used in Fundamental mode; in other words,
it is the local abbrev table in all buffers in Fundamental mode.
@end defvar

@defvar text-mode-abbrev-table
This is the local abbrev table used in Text mode.
@end defvar

@defvar lisp-mode-abbrev-table
This is the local abbrev table used in Lisp mode.  It is the parent
of the local abbrev table used in Emacs Lisp mode.  @xref{Abbrev Table
Properties}.
@end defvar

@node Abbrev Properties
@section Abbrev Properties
@cindex abbrev properties

Abbrevs have properties, some of which influence the way they work.
You can provide them as arguments to @code{define-abbrev}, and
manipulate them with the following functions:

@defun abbrev-put abbrev prop val
Set the property @var{prop} of @var{abbrev} to value @var{val}.
@end defun

@defun abbrev-get abbrev prop
Return the property @var{prop} of @var{abbrev}, or @code{nil} if the
abbrev has no such property.
@end defun

The following properties have special meanings:

@table @code
@item :count
This property counts the number of times the abbrev has
been expanded.  If not explicitly set, it is initialized to 0 by
@code{define-abbrev}.

@item :system
If non-@code{nil}, this property marks the abbrev as a system abbrev.
Such abbrevs are not saved (@pxref{Abbrev Files}).

@item :enable-function
If non-@code{nil}, this property should be a function of no
arguments which returns @code{nil} if the abbrev should not be used
and @code{t} otherwise.

@item :case-fixed
If non-@code{nil}, this property indicates that the case of the
abbrev's name is significant and should only match a text with the
same pattern of capitalization.  It also disables the code that
modifies the capitalization of the expansion.
@end table

@node Abbrev Table Properties
@section Abbrev Table Properties
@cindex abbrev table properties

Like abbrevs, abbrev tables have properties, some of which influence
the way they work.  You can provide them as arguments to
@code{define-abbrev-table}, and manipulate them with the functions:

@defun abbrev-table-put table prop val
Set the property @var{prop} of abbrev table @var{table} to value @var{val}.
@end defun

@defun abbrev-table-get table prop
Return the property @var{prop} of abbrev table @var{table}, or @code{nil}
if the abbrev has no such property.
@end defun

The following properties have special meaning:

@table @code
@item :enable-function
This is like the @code{:enable-function} abbrev property except that
it applies to all abbrevs in the table.  It is used before even trying
to find the abbrev before point, so it can dynamically modify the
abbrev table.

@item :case-fixed
This is like the @code{:case-fixed} abbrev property except that it
applies to all abbrevs in the table.

@item :regexp
If non-@code{nil}, this property is a regular expression that
indicates how to extract the name of the abbrev before point, before
looking it up in the table.  When the regular expression matches
before point, the abbrev name is expected to be in submatch 1.
If this property is @code{nil}, the default is to use
@code{backward-word} and @code{forward-word} to find the name.  This
property allows the use of abbrevs whose name contains characters of
non-word syntax.

@item :parents
This property holds a list of tables from which to inherit
other abbrevs.

@item :abbrev-table-modiff
This property holds a counter incremented each time a new abbrev is
added to the table.

@end table