Abbrevs
*******

A defined abbrev is a word which 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 foo as an abbrev expanding to find outer otter.  Then you could insert find outer otter  into the buffer by typing f o o SPC.

A second kind of abbreviation facility is called 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.  See Dynamic Abbrevs.

A third kind, hippie expansion, generalizes abbreviation expansion. See Hippie Expansion (Features for Automatic Typing).

Abbrev Concepts
===============

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

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 M-x abbrev-mode toggles Abbrev mode; with a numeric argument, it turns Abbrev mode on if the argument is positive, off otherwise.  See Minor Modes.

Abbrevs can have mode-specific definitions, active only in one major mode.  Abbrevs can also have 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.

Defining Abbrevs
================

C-x a g
     Define an abbrev, using one or more words before point as its expansion (add-global-abbrev).

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

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

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

M-x define-global-abbrev RET ABBREV RET EXP RET
     Define ABBREV as an abbrev expanding into EXP.

M-x define-mode-abbrev RET ABBREV RET EXP RET
     Define ABBREV as a mode-specific abbrev expanding into EXP.

M-x kill-all-abbrevs
     Discard all abbrev definitions, leaving a blank slate.

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 C-x a g (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 foo as mentioned above, insert the text find outer otter and then type C-u 3 C-x a g f o o RET.

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

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

C-x a i g (inverse-add-global-abbrev) and C-x a i l (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.

You can define an abbrev without inserting either the abbrev or its expansion in the buffer using the command define-global-abbrev. It reads two arguments---the abbrev, and its expansion.  The command 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.

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

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 (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.

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

These commands are used to control abbrev expansion:

M-'
     Separate a prefix from a following abbrev to be expanded (abbrev-prefix-mark).

C-x a e
     Expand the abbrev before point (expand-abbrev). This is effective even when Abbrev mode is not enabled.

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

M-x expand-region-abbrevs
     Expand some or all abbrevs found in the region.

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

If you expand an abbrev by mistake, you can undo the expansion by typing C-/ (undo).  See 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 C-q.  You can also use the command M-x unexpand-abbrev to cancel the last expansion without deleting the terminating character.

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 expand-abbrev performs the expansion by calling the function that abbrev-expand-function specifies.  By changing this function you can make arbitrary changes to the abbrev expansion.  See Abbrev Expansion (The Emacs Lisp Reference Manual).

Examining and Editing Abbrevs
=============================

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

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

The output from M-x list-abbrevs looks like this:

     VARIOUS OTHER TABLES...
     (lisp-mode-abbrev-table)
     "dk"          0    "define-key"
     (global-abbrev-table)
     "dfn"         0    "definition"

(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; 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 (sys).  These system abbrevs (see Abbrevs (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.

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 *Abbrevs*, and is in Edit-Abbrevs mode.  Type 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 edit-abbrevs is actually the same as list-abbrevs except that it selects the buffer *Abbrevs* whereas list-abbrevs merely displays it in another window.

Saving Abbrevs
==============

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

M-x write-abbrev-file RET FILE RET
     Write a file FILE describing all defined abbrevs.

M-x read-abbrev-file RET FILE RET
     Read the file FILE and define abbrevs as specified therein.

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

M-x insert-abbrevs
     Insert all abbrevs and their expansions into current buffer.

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.

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 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 (see Init File).  If either of these functions is called with nil as the argument, it uses the file given by the variable abbrev-file-name, which is ~/.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.  See Initial Options, for a description of batch mode.)

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

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

Dynamic Abbrev Expansion
========================

The abbrev facility described above operates automatically as you insert text, but all abbrevs must be defined explicitly.  By contrast, 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.

M-/
     Expand the word in the buffer before point as a dynamic abbrev, by searching for words starting with that abbreviation (dabbrev-expand).

C-M-/
     Complete the word before point as a dynamic abbrev (dabbrev-completion).

For example, if the buffer contains does this follow  and you type f o M-/, the effect is to insert follow because that is the last word in the buffer that starts with fo.  A numeric argument to M-/ says to take the second, third, etc. distinct expansion found looking backward from point.  Repeating 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 dabbrev-limit, if non-nil, specifies how far away in the buffer to search for an expansion.

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

For finer control over which buffers to scan, customize the variables dabbrev-ignored-buffer-names and 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 M-/, as in 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 M-/ to look for another expansion, do not specify an argument.  Repeating 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 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 M-/ determines the word to expand and how to expand it, see Dabbrev Customization.

The command C-M-/ (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, C-M-/ displays a list of completions, from which you can select a choice in the usual manner.  See Completion.

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

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.

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

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

The variable dabbrev-case-replace controls whether to preserve the case pattern of the dynamic abbrev.  If it is t, the dynamic abbrev's case pattern is preserved in most cases; if it is nil, the expansion is always copied verbatim.  If the value is case-replace (the default), then the variable case-replace controls whether to copy the expansion verbatim (see 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 variableWithSillyCasePattern, and you type v a M-/, it copies the expansion verbatim including its case pattern.

The variable dabbrev-abbrev-char-regexp, if non-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 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 "\\sw" might produce better results.

In shell scripts and makefiles, a variable name is sometimes prefixed with $ and sometimes not.  Major modes for this kind of text can customize dynamic abbrev expansion to handle optional prefixes by setting the variable 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 nil, which means no characters should be skipped.