@c This is part of the Emacs manual.
@c Copyright (C) 1985--1987, 1993--1995, 1997, 2001--2020 Free Software
@c Foundation, Inc.
@c See file emacs.texi for copying conditions.
@node Abbrevs
@chapter Abbrevs
@cindex abbrevs
@cindex expansion (of abbrevs)

  A defined @dfn{abbrev} is a word which @dfn{expands}, if you insert
it, into some different text.  Abbrevs are defined by the user to expand
in specific ways.  For example, you might define @samp{foo} as an abbrev
expanding to @samp{find outer otter}.  Then you could insert
@samp{find outer otter } into the buffer by typing @kbd{f o o
@key{SPC}}.

  A second kind of abbreviation facility is called @dfn{dynamic abbrev
expansion}.  You use dynamic abbrev expansion with an explicit command
to expand the letters in the buffer before point by looking for other
words in the buffer that start with those letters.  @xref{Dynamic
Abbrevs}.

  A third kind, @dfn{hippie expansion}, generalizes abbreviation expansion.
@xref{Hippie Expand, , Hippie Expansion, autotype, Features for
Automatic Typing}.

@menu
* Abbrev Concepts::   Fundamentals of defined abbrevs.
* Defining Abbrevs::  Defining an abbrev, so it will expand when typed.
* Expanding Abbrevs:: Controlling expansion: prefixes, canceling expansion.
* Editing Abbrevs::   Viewing or editing the entire list of defined abbrevs.
* Saving Abbrevs::    Saving the entire list of abbrevs for another session.
* Dynamic Abbrevs::   Abbreviations for words already in the buffer.
* Dabbrev Customization:: What is a word, for dynamic abbrevs.  Case handling.
@end menu

@node Abbrev Concepts
@section Abbrev Concepts

  An @dfn{abbrev} is a word that has been defined to @dfn{expand} into
a specified @dfn{expansion}.  When you insert a word-separator character
following the abbrev, that expands the abbrev---replacing the abbrev
with its expansion.  For example, if @samp{foo} is defined as an abbrev
expanding to @samp{find outer otter}, then typing @kbd{f o o .} will
insert @samp{find outer otter.}.

@findex abbrev-mode
@cindex Abbrev mode
@cindex mode, Abbrev
  Abbrevs expand only when Abbrev mode, a buffer-local minor mode, is
enabled.  Disabling Abbrev mode does not cause abbrev definitions to
be forgotten, but they do not expand until Abbrev mode is enabled
again.  The command @kbd{M-x abbrev-mode} toggles Abbrev mode; with a
numeric argument, it turns Abbrev mode on if the argument is positive,
off otherwise.  @xref{Minor Modes}.

  Abbrevs can have @dfn{mode-specific} definitions, active only in one major
mode.  Abbrevs can also have @dfn{global} definitions that are active in
all major modes.  The same abbrev can have a global definition and various
mode-specific definitions for different major modes.  A mode-specific
definition for the current major mode overrides a global definition.

  You can define abbrevs interactively during the editing session,
irrespective of whether Abbrev mode is enabled.  You can also save
lists of abbrev definitions in files, which you can then reload for
use in later sessions.

@node Defining Abbrevs
@section Defining Abbrevs

@table @kbd
@item C-x a g
Define an abbrev, using one or more words before point as its expansion
(@code{add-global-abbrev}).

@item C-x a l
Similar, but define an abbrev specific to the current major mode
(@code{add-mode-abbrev}).

@item C-x a i g
Define a word in the buffer as an abbrev (@code{inverse-add-global-abbrev}).

@item C-x a i l
Define a word in the buffer as a mode-specific abbrev
(@code{inverse-add-mode-abbrev}).

@item M-x define-global-abbrev @key{RET} @var{abbrev} @key{RET} @var{exp} @key{RET}
Define @var{abbrev} as an abbrev expanding into @var{exp}.

@item M-x define-mode-abbrev @key{RET} @var{abbrev} @key{RET} @var{exp} @key{RET}
Define @var{abbrev} as a mode-specific abbrev expanding into @var{exp}.

@item M-x kill-all-abbrevs
Discard all abbrev definitions, leaving a blank slate.
@end table

@kindex C-x a g
@findex add-global-abbrev
  The usual way to define an abbrev is to enter the text you want the
abbrev to expand to, position point after it, and type @kbd{C-x a g}
(@code{add-global-abbrev}).  This reads the abbrev itself using the
minibuffer, and then defines it as an abbrev for one or more words before
point.  Use a numeric argument to say how many words before point should be
taken as the expansion.  For example, to define the abbrev @samp{foo} as
mentioned above, insert the text @samp{find outer otter} and then type
@kbd{C-u 3 C-x a g f o o @key{RET}}.

  An argument of zero to @kbd{C-x a g} means to use the contents of the
region as the expansion of the abbrev being defined.

@kindex C-x a l
@findex add-mode-abbrev
  The command @kbd{C-x a l} (@code{add-mode-abbrev}) is similar, but
defines a mode-specific abbrev for the current major mode.  The
arguments work the same as for @kbd{C-x a g}.

@kindex C-x a i g
@findex inverse-add-global-abbrev
@kindex C-x a i l
@findex inverse-add-mode-abbrev
  @kbd{C-x a i g} (@code{inverse-add-global-abbrev}) and @kbd{C-x a i
l} (@code{inverse-add-mode-abbrev}) perform the opposite task: if the
abbrev text is already in the buffer, you use these commands to define
an abbrev by specifying the expansion in the minibuffer.  These
commands will expand the abbrev text used for the definition.

@findex define-mode-abbrev
@findex define-global-abbrev
  You can define an abbrev without inserting either the abbrev or its
expansion in the buffer using the command @code{define-global-abbrev}.
It reads two arguments---the abbrev, and its expansion.  The command
@code{define-mode-abbrev} does likewise for a mode-specific abbrev.

  To change the definition of an abbrev, just make a new definition.
When an abbrev has a prior definition, the abbrev definition commands
ask for confirmation before replacing it.

@findex kill-all-abbrevs
  To remove an abbrev definition, give a negative argument to the
abbrev definition command: @kbd{C-u - C-x a g} or @kbd{C-u - C-x a l}.
The former removes a global definition, while the latter removes a
mode-specific definition.  @kbd{M-x kill-all-abbrevs} removes all
abbrev definitions, both global and local.

@node Expanding Abbrevs
@section Controlling Abbrev Expansion

  When Abbrev mode is enabled, an abbrev expands whenever it is
present in the buffer just before point and you type a self-inserting
whitespace or punctuation character (@key{SPC}, comma, etc.).  More
precisely, any character that is not a word constituent expands an
abbrev, and any word-constituent character can be part of an abbrev.
The most common way to use an abbrev is to insert it and then insert a
punctuation or whitespace character to expand it.

@vindex abbrev-all-caps
  Abbrev expansion preserves case: @samp{foo} expands to @samp{find
outer otter}, and @samp{Foo} to @samp{Find outer otter}.  @samp{FOO}
expands to @samp{Find Outer Otter} by default, but if you change the
variable @code{abbrev-all-caps} to a non-@code{nil} value, it expands
to @samp{FIND OUTER OTTER}.

  These commands are used to control abbrev expansion:

@table @kbd
@item M-'
Separate a prefix from a following abbrev to be expanded
(@code{abbrev-prefix-mark}).

@item C-x a e
@findex expand-abbrev
Expand the abbrev before point (@code{expand-abbrev}).
This is effective even when Abbrev mode is not enabled.

@item M-x unexpand-abbrev
@findex unexpand-abbrev
Undo the expansion of the last expanded abbrev.

@item M-x expand-region-abbrevs
Expand some or all abbrevs found in the region.
@end table

@kindex M-'
@findex abbrev-prefix-mark
  You may wish to expand an abbrev and attach a prefix to the expansion;
for example, if @samp{cnst} expands into @samp{construction}, you might want
to use it to enter @samp{reconstruction}.  It does not work to type
@kbd{recnst}, because that is not necessarily a defined abbrev.  What
you can do is use the command @kbd{M-'} (@code{abbrev-prefix-mark}) in
between the prefix @samp{re} and the abbrev @samp{cnst}.  First, insert
@samp{re}.  Then type @kbd{M-'}; this inserts a hyphen in the buffer to
indicate that it has done its work.  Then insert the abbrev @samp{cnst};
the buffer now contains @samp{re-cnst}.  Now insert a non-word character
to expand the abbrev @samp{cnst} into @samp{construction}.  This
expansion step also deletes the hyphen that indicated @kbd{M-'} had been
used.  The result is the desired @samp{reconstruction}.

  If you actually want the text of the abbrev in the buffer, rather than
its expansion, you can accomplish this by inserting the following
punctuation with @kbd{C-q}.  Thus, @kbd{foo C-q ,} leaves @samp{foo,} in
the buffer, not expanding it.

  If you expand an abbrev by mistake, you can undo the expansion by
typing @kbd{C-/} (@code{undo}).  @xref{Undo}.  This undoes the
insertion of the abbrev expansion and brings back the abbrev text.  If
the result you want is the terminating non-word character plus the
unexpanded abbrev, you must reinsert the terminating character,
quoting it with @kbd{C-q}.  You can also use the command @kbd{M-x
unexpand-abbrev} to cancel the last expansion without deleting the
terminating character.

@findex expand-region-abbrevs
  @kbd{M-x expand-region-abbrevs} searches through the region for defined
abbrevs, and for each one found offers to replace it with its expansion.
This command is useful if you have typed in text using abbrevs but forgot
to turn on Abbrev mode first.  It may also be useful together with a
special set of abbrev definitions for making several global replacements at
once.  This command is effective even if Abbrev mode is not enabled.

  The function @code{expand-abbrev} performs the expansion by calling
the function that @code{abbrev-expand-function} specifies.  By
changing this function you can make arbitrary changes to
the abbrev expansion.  @xref{Abbrev Expansion,,, elisp, The Emacs Lisp
Reference Manual}.

@node Editing Abbrevs
@section Examining and Editing Abbrevs

@table @kbd
@item M-x list-abbrevs
Display a list of all abbrev definitions.  With a numeric argument, list
only local abbrevs.

@item M-x edit-abbrevs
Edit a list of abbrevs; you can add, alter or remove definitions.
@end table

@findex list-abbrevs
  The output from @kbd{M-x list-abbrevs} looks like this:

@example
@var{various other tables@dots{}}
(lisp-mode-abbrev-table)
"dk"          0    "define-key"
(global-abbrev-table)
"dfn"         0    "definition"
@end example

@noindent
(Some blank lines of no semantic significance, and some other abbrev
tables, have been omitted.)

  A line containing a name in parentheses is the header for abbrevs in a
particular abbrev table; @code{global-abbrev-table} contains all the global
abbrevs, and the other abbrev tables that are named after major modes
contain the mode-specific abbrevs.

  Within each abbrev table, each nonblank line defines one abbrev.  The
word at the beginning of the line is the abbrev.  The number that
follows is the number of times the abbrev has been expanded.  Emacs
keeps track of this to help you see which abbrevs you actually use, so
that you can eliminate those that you don't use often.  The string at
the end of the line is the expansion.

  Some abbrevs are marked with @samp{(sys)}.  These @dfn{system abbrevs}
(@pxref{Abbrevs,,, elisp, The Emacs Lisp Reference Manual}) are
pre-defined by various modes, and are not saved to your abbrev file.
To disable a system abbrev, define an abbrev of the same name that
expands to itself, and save it to your abbrev file.

@findex edit-abbrevs
@kindex C-c C-c @r{(Edit Abbrevs)}
  @kbd{M-x edit-abbrevs} allows you to add, change or kill abbrev
definitions by editing a list of them in an Emacs buffer.  The list has
the same format described above.  The buffer of abbrevs is called
@file{*Abbrevs*}, and is in Edit-Abbrevs mode.  Type @kbd{C-c C-c} in
this buffer to install the abbrev definitions as specified in the
buffer---and delete any abbrev definitions not listed.

  The command @code{edit-abbrevs} is actually the same as
@code{list-abbrevs} except that it selects the buffer @file{*Abbrevs*}
whereas @code{list-abbrevs} merely displays it in another window.

@node Saving Abbrevs
@section Saving Abbrevs

  These commands allow you to keep abbrev definitions between editing
sessions.

@table @kbd
@item M-x write-abbrev-file @key{RET} @var{file} @key{RET}
Write a file @var{file} describing all defined abbrevs.

@item M-x read-abbrev-file @key{RET} @var{file} @key{RET}
Read the file @var{file} and define abbrevs as specified therein.

@item M-x define-abbrevs
Define abbrevs from definitions in current buffer.

@item M-x insert-abbrevs
Insert all abbrevs and their expansions into current buffer.
@end table

@findex write-abbrev-file
  @kbd{M-x write-abbrev-file} reads a file name using the minibuffer and
then writes a description of all current abbrev definitions into that
file.  This is used to save abbrev definitions for use in a later
session.  The text stored in the file is a series of Lisp expressions
that, when executed, define the same abbrevs that you currently have.

@findex read-abbrev-file
@findex quietly-read-abbrev-file
@vindex abbrev-file-name
@cindex abbrev file
  @kbd{M-x read-abbrev-file} reads a file name using the minibuffer
and then reads the file, defining abbrevs according to the contents of
the file.  The function @code{quietly-read-abbrev-file} is similar
except that it does not display a message in the echo area; you cannot
invoke it interactively, and it is used primarily in your init file
(@pxref{Init File}).  If either of these functions is called with
@code{nil} as the argument, it uses the file given by the variable
@code{abbrev-file-name}, which is @file{~/.emacs.d/abbrev_defs} by
default.  This is your standard abbrev definition file, and Emacs
loads abbrevs from it automatically when it starts up.  (As an
exception, Emacs does not load the abbrev file when it is started in
batch mode.  @xref{Initial Options}, for a description of batch mode.)

@vindex save-abbrevs
  Emacs will offer to save abbrevs automatically if you have changed
any of them, whenever it offers to save all files (for @kbd{C-x s} or
@kbd{C-x C-c}).  It saves them in the file specified by
@code{abbrev-file-name}.  This feature can be inhibited by setting the
variable @code{save-abbrevs} to @code{nil}; setting it to
@code{silently} will save the abbrevs automatically without asking.

@findex insert-abbrevs
@findex define-abbrevs
  The commands @kbd{M-x insert-abbrevs} and @kbd{M-x define-abbrevs} are
similar to the previous commands but work on text in an Emacs buffer.
@kbd{M-x insert-abbrevs} inserts text into the current buffer after point,
describing all current abbrev definitions; @kbd{M-x define-abbrevs} parses
the entire current buffer and defines abbrevs accordingly.

@node Dynamic Abbrevs
@section Dynamic Abbrev Expansion

  The abbrev facility described above operates automatically as you
insert text, but all abbrevs must be defined explicitly.  By contrast,
@dfn{dynamic abbrevs} allow the meanings of abbreviations to be
determined automatically from the contents of the buffer, but dynamic
abbrev expansion happens only when you request it explicitly.

@kindex M-/
@kindex C-M-/
@findex dabbrev-expand
@findex dabbrev-completion
@table @kbd
@item M-/
Expand the word in the buffer before point as a @dfn{dynamic abbrev},
by searching for words starting with that abbreviation
(@code{dabbrev-expand}).

@item C-M-/
Complete the word before point as a dynamic abbrev
(@code{dabbrev-completion}).
@end table

@vindex dabbrev-limit
  For example, if the buffer contains @samp{does this follow } and you
type @kbd{f o M-/}, the effect is to insert @samp{follow} because that
is the last word in the buffer that starts with @samp{fo}.  A numeric
argument to @kbd{M-/} says to take the second, third, etc.@: distinct
expansion found looking backward from point.  Repeating @kbd{M-/}
searches for an alternative expansion by looking farther back.  After
scanning all the text before point, it searches the text after point.
The variable @code{dabbrev-limit}, if non-@code{nil}, specifies how far
away in the buffer to search for an expansion.

@vindex dabbrev-check-all-buffers
@vindex dabbrev-check-other-buffers
  After scanning the current buffer, @kbd{M-/} normally searches other
buffers.  The variables @code{dabbrev-check-all-buffers} and
@code{dabbrev-check-other-buffers} can be used to determine which
other buffers, if any, are searched.

@vindex dabbrev-ignored-buffer-names
@vindex dabbrev-ignored-buffer-regexps
  For finer control over which buffers to scan, customize the
variables @code{dabbrev-ignored-buffer-names} and
@code{dabbrev-ignored-buffer-regexps}.  The value of the former is a
list of buffer names to skip.  The value of the latter is a list of
regular expressions; if a buffer's name matches any of these regular
expressions, dynamic abbrev expansion skips that buffer.

  A negative argument to @kbd{M-/}, as in @kbd{C-u - M-/}, says to
search first for expansions after point, then other buffers, and
consider expansions before point only as a last resort.  If you repeat
the @kbd{M-/} to look for another expansion, do not specify an
argument.  Repeating @kbd{M-/} cycles through all the expansions after
point and then the expansions before point.

  After you have expanded a dynamic abbrev, you can copy additional
words that follow the expansion in its original context.  Simply type
@kbd{@key{SPC} M-/} for each additional word you want to copy.  The
spacing and punctuation between words is copied along with the words.

  You can control the way @kbd{M-/} determines the word to expand and
how to expand it, see @ref{Dabbrev Customization}.

  The command @kbd{C-M-/} (@code{dabbrev-completion}) performs
completion of a dynamic abbrev.  Instead of trying the possible
expansions one by one, it finds all of them, then inserts the text
that they have in common.  If they have nothing in common, @kbd{C-M-/}
displays a list of completions, from which you can select a choice in
the usual manner.  @xref{Completion}.

  Dynamic abbrev expansion is completely independent of Abbrev mode; the
expansion of a word with @kbd{M-/} is completely independent of whether
it has a definition as an ordinary abbrev.

@node Dabbrev Customization
@section Customizing Dynamic Abbreviation

  Normally, dynamic abbrev expansion ignores case when searching for
expansions.  That is, the expansion need not agree in case with the word
you are expanding.

@vindex dabbrev-case-fold-search
  This feature is controlled by the variable
@code{dabbrev-case-fold-search}.  If it is @code{t}, case is ignored
in this search; if it is @code{nil}, the word and the expansion must
match in case.  If the value is @code{case-fold-search} (the default),
then the variable @code{case-fold-search} controls whether to ignore
case while searching for expansions (@pxref{Lax Search}).

  Normally, dynamic abbrev expansion preserves the case pattern
@emph{of the dynamic abbrev you are expanding}, by converting the
expansion to that case pattern.

@vindex dabbrev-case-replace
  The variable @code{dabbrev-case-replace} controls whether to
preserve the case pattern of the dynamic abbrev.  If it is @code{t},
the dynamic abbrev's case pattern is preserved in most cases; if it is
@code{nil}, the expansion is always copied verbatim.  If the value is
@code{case-replace} (the default), then the variable
@code{case-replace} controls whether to copy the expansion verbatim
(@pxref{Replacement and Lax Matches}).

  However, if the expansion contains a complex mixed case pattern, and
the dynamic abbrev matches this pattern as far as it goes, then the
expansion is always copied verbatim, regardless of those variables.
Thus, for example, if the buffer contains
@code{variableWithSillyCasePattern}, and you type @kbd{v a M-/}, it
copies the expansion verbatim including its case pattern.

@vindex dabbrev-abbrev-char-regexp
  The variable @code{dabbrev-abbrev-char-regexp}, if non-@code{nil},
controls which characters are considered part of a word, for dynamic
expansion purposes.  The regular expression must match just one
character, never two or more.  The same regular expression also
determines which characters are part of an expansion.  The (default)
value @code{nil} has a special meaning: dynamic abbrevs (i.e.@: the
word at point) are made of word characters, but their expansions are
looked for as sequences of word and symbol characters.  This is
generally appropriate for expanding symbols in a program source and
also for human-readable text in many languages, but may not be what
you want in a text buffer that includes unusual punctuation characters;
in that case, the value @code{"\\sw"} might produce better results.

@vindex dabbrev-abbrev-skip-leading-regexp
  In shell scripts and makefiles, a variable name is sometimes prefixed
with @samp{$} and sometimes not.  Major modes for this kind of text can
customize dynamic abbrev expansion to handle optional prefixes by setting
the variable @code{dabbrev-abbrev-skip-leading-regexp}.  Its value
should be a regular expression that matches the optional prefix that
dynamic abbrev expression should ignore.  The default is @code{nil},
which means no characters should be skipped.