@c This is part of the Emacs manual.
@c Copyright (C) 1985, 1986, 1987, 1993, 1994, 1995 Free Software Foundation, Inc.
@c See file emacs.texi for copying conditions.
@node Abbrevs, Picture, Building, Top
@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 would be able to 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}.

@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 which 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 you can insert @samp{find
outer otter.}  into the buffer by typing @kbd{f o o .}.

@findex abbrev-mode
@vindex abbrev-mode
@cindex Abbrev mode
@cindex mode, Abbrev
  Abbrevs expand only when Abbrev mode (a 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}.  @code{abbrev-mode} is also a variable; Abbrev mode is
on when the variable is non-@code{nil}.  The variable @code{abbrev-mode}
automatically becomes local to the current buffer when it is set.

  Abbrev definitions can be @dfn{mode-specific}---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.

  Abbrevs can be defined interactively during the editing session.  Lists
of abbrev definitions can also be saved in files and reloaded in later
sessions.  Some users keep extensive lists of abbrevs that they load in
every session.

@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 kill-all-abbrevs
This command discards all abbrev definitions currently in effect,
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.  Mode specific abbrevs are active only in a
particular major mode.  @kbd{C-x a l} defines an abbrev for the major mode
in effect at the time @kbd{C-x a l} is typed.  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
  If the text already in the buffer is the abbrev, rather than its
expansion, use command @kbd{C-x a i g}
(@code{inverse-add-global-abbrev}) instead of @kbd{C-x a g}, or use
@kbd{C-x a i l} (@code{inverse-add-mode-abbrev}) instead of @kbd{C-x a
l}.  These commands are called ``inverse'' because they invert the
meaning of the two text strings they use (one from the buffer and one
read with the minibuffer).

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

  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.

@findex kill-all-abbrevs
  @kbd{M-x kill-all-abbrevs} removes all the abbrev definitions there
are, both global and local.

@node Expanding Abbrevs
@section Controlling Abbrev Expansion

  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 character to expand it.

@vindex abbrev-all-caps
  Abbrev expansion preserves case; thus, @samp{foo} expands into @samp{find
outer otter}; @samp{Foo} into @samp{Find outer otter}, and @samp{FOO} into
@samp{FIND OUTER OTTER} or @samp{Find Outer Otter} according to the
variable @code{abbrev-all-caps} (a non-@code{nil} value chooses the first
of the two expansions).

  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 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 with a prefix attached; 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.

  If you expand an abbrev by mistake, you can undo the expansion and
bring back the abbrev itself by typing @kbd{C-_} to undo (@pxref{Undo}).
This also undoes the insertion of the non-word character that expanded
the abbrev.  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}.

@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.

  Expanding an abbrev runs the hook @code{pre-abbrev-expand-hook}
(@pxref{Hooks}).

@node Editing Abbrevs
@section Examining and Editing Abbrevs

@table @kbd
@item M-x list-abbrevs
Display a list of all abbrev definitions.
@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
(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.

@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
@samp{*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 @samp{*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 quietly-read-abbrev-file @key{RET} @var{file} @key{RET}
Similar but do not display a message about what is going on.
@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
  @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.  @kbd{M-x quietly-read-abbrev-file} is the same except that it
does not display a message in the echo area saying that it is doing its
work; it is actually useful primarily in the @file{.emacs} file.  If an
empty argument is given to either of these functions, they use the file
name specified in the variable @code{abbrev-file-name}, which is by
default @code{"~/.abbrev_defs"}.

@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}).  This feature can be inhibited by setting the variable
@code{save-abbrevs} to @code{nil}.

@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 before point,
describing all current abbrev definitions; @kbd{M-x define-abbrevs} parses
the entire current buffer and defines abbrevs accordingly.@refill

@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 abbrevs 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 in the buffer 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
considering the entire buffer before point, it searches the text after
point.  The variable @code{dabbrev-limit}, if non-@code{nil}, specifies
how far in the buffer to search for an expansion.

@vindex dabbrev-check-all-buffers
  After searching all of the current buffer, @kbd{M-/} normally searches
other buffers, unless you have set @code{dabbrev-check-all-buffers} to
@code{nil}.

  A negative argument to @kbd{M-/}, as in @kbd{C-u - M-/}, says to
search first for expansions after point, and second for expansions
before point.  If you repeat the @kbd{M-/} to look for another
expansion, do not specify an argument.  This tries 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 word you want to copy.  The spacing and
punctuation between words is copied along with the words.

  The command @kbd{C-M-/} (@code{dabbrev-completion}) performs
completion of a dynamic abbreviation.  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

@vindex dabbrev-case-fold-search
  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.  If you set @code{dabbrev-case-fold-search} to
@code{nil}, then the word and the expansion must match in case.

  The value of @code{dabbrev-case-fold-search} may be any expression.
Dynamic abbrev expansion evaluates that expression, and ignores case
while searching if its value is not @code{nil}.  The default value of
@code{dabbrev-case-fold-search} is @code{case-fold-search}, so normally
the value of @code{case-fold-search} controls the decision.  The reason
why dynamic abbrev expansion normally ignores case when searching for
expansions is that normally the value of @code{case-fold-search} is
@code{t}.

@vindex dabbrev-case-replace
  Normally, dynamic abbrev expansion preserves the case pattern @emph{of
the word you are expanding}, by converting the expansion to that case
pattern.  If you set @code{dabbrev-case-replace} to @code{nil}, the
expansion is copied without conversion.

  The variables @code{dabbrev-case-fold-search} and
@code{dabbrev-case-replace} are handled in a special way.  Their values
are actually Lisp expressions which are evaluated each time a decision
needs to be made.  If the expression's value is non-@code{nil}, then
case is ignored in searching, or converted on replacement, respectively.
If the expression's value is @code{nil}, case is not ignored or not
converted.  The default values let the variables @code{case-fold-search}
(@pxref{Search Case}) and @code{case-replace} (@pxref{Replacement and
Case}) control what to do.

@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 value @code{nil} has a special
meaning: abbreviations are made of word characters, but expansions are
made of word and symbol characters.

@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 abbreviation 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 abbreviation should ignore.
