emacs/man/autotype.texi

@c This is part of the Emacs manual.
@c Copyright (C) 1994, 1995 Free Software Foundation, Inc.
@c Author: Daniel.Pfeiffer@Informatik.START.dbp.de, fax (+49 69) 7588-2389
@c See file emacs.texi for copying conditions.
@node Autotypist, Picture, Abbrevs, Top
@chapter Features for Automatic Typing
@cindex text
@cindex selfinserting text
@cindex autotypist

@dircategory Editors
@direntry
* Autotype: (autotype). Convenient features for text that you enter frequently
                          in Emacs.
@end direntry

  Under certain circumstances you will find yourself typing similar things
over and over again.  This is especially true of form letters and programming
language constructs.  Project-specific header comments, flow-control
constructs or magic numbers are essentially the same every time.  Emacs has
various features for doing tedious and repetitive typing chores for you.

  One solution is using skeletons, flexible rules that say what to
insert, and how to do it.  Various programming language modes offer some
ready-to-use skeletons, and you can adapt them to suit your needs or
taste, or define new ones.

  Another feature is automatic insertion of what you want into empty files,
depending on the file-name or the mode as appropriate.  You can have a file or
a skeleton inserted, or you can call a function.  Then there is the
possibility to have Un*x interpreter scripts automatically take on a magic
number and be executable as soon as they are saved.  Or you can have a
copyright notice's year updated, if necessary, every time you save a file.

@menu
* Using Skeletons::        How to insert a skeleton into your text.
* Wrapping Skeletons::     Putting existing text within a skeleton.
* Skeletons as Abbrevs::   An alternative for issuing skeleton commands.
* Skeleton Language::      Making skeleton commands insert what you want.
* Inserting Pairs::        Typing one character and getting another after point.
* Autoinserting::          Filling up empty files as soon as you visit them.
* Copyrights::             Inserting and updating copyrights.
* Executables::	           Turning interpreter scripts into executables.
@end menu



@node Using Skeletons
@section Using Skeletons
@cindex skeletons
@cindex using skeletons

  When you want Emacs to insert a form letter or a typical construct of the
programming language you are using, skeletons are a means of accomplishing
this.  Normally skeletons each have a command of their own, that, when called,
will insert the skeleton.  These commands can be issued in the usual ways
(@xref{Commands}).  Modes that offer various skeletons will often bind these
to key-sequences on the @kbd{C-c} prefix, as well as having an @cite{Insert}
menu and maybe even predefined abbrevs for them (@xref{Skeletons as Abbrevs}).

  The simplest kind of skeleton will simply insert some text indented
according to the major mode and leave the cursor at a likely place in the
middle.  Interactive skeletons may prompt you for a string that will be part
of the inserted text.

  Skeletons may ask for input several times.  They even have a looping
mechanism in which you will be asked for input as long as you are willing to
furnish it.  An example would be multiple ``else if'' conditions.  You can
recognize this situation by a prompt ending in ``RET, C-g or C-h''.  This
means that entering an empty string will simply assume that you are finished.
Typing quit on the other hand terminates the loop but also the rest of the
skeleton, e.g. an ``else'' clause is skipped.  Only a syntactically necessary
termination still gets inserted.



@node Wrapping Skeletons
@section Wrapping Skeletons Around Existing Test
@cindex wrapping skeletons

  Often you will find yourself with some code that for whatever reason
suddenly becomes conditional.  Or you have written a bit of text and want to
put it in the middle of a form letter.  Skeletons provide a means for
accomplishing this, and can even, in the case of programming languages,
reindent the wrapped code for you.

  Skeleton commands take an optional numeric prefix argument
(@xref{Arguments}).  This is interpreted in two different ways depending
on whether the prefix is positive, i.e. forwards oriented or negative,
i.e. backwards oriented.

  A positive prefix means to wrap the skeleton around that many following
words.  This is accomplished by putting the words there where the point is
normally left after that skeleton is inserted (@xref{Using Skeletons}).  The
point (@xref{Point}) is left at the next interesting spot in the skeleton
instead.

  A negative prefix means to do something similar with that many precedingly
marked interregions (@xref{Mark}).  In the simplest case, if you type
@kbd{M--} just before issuing the skeleton command, that will wrap the
skeleton around the current region, just like a positive argument would have
wrapped it around a number of words.

  Smaller negative arguments will wrap that many interregions into successive
interesting spots within the skeleton, again leaving the point at the next one.
We speak about interregions rather than regions here, because we treat them in
the order they appear in the buffer, which coincides with successive regions
only if they were marked in order.

  That is, if you marked in alphabetical order the points A B C [] (where []
represents the point) and call a skeleton command with @kbd{M-- 3}, you will
wrap the text from A to B into the first interesting spot of the skeleton, the
text from B to C into the next one, the text from C to the point into the
third one, and leave the point in the fourth one.  If there are less marks in
the buffer, or if the skeleton defines less interesting points, the surplus is
ignored.

  If, on the other hand, you marked in alphabetical order the points [] A C B,
and call a skeleton command with @kbd{M-- 3}, you will wrap the text from
point to A, then the text from A to C and finally the text from C to B.  This
is done because the regions overlap and Emacs would be helplessly lost if it
tried to follow the order in which you marked these points.



@node Skeletons as Abbrevs
@section Skeletons as Abbrev Expansions
@cindex skeletons as abbrevs

  Rather than use a keybinding for every skeleton command, you can also define
an abbreviation (@xref{Defining Abbrevs}) that will expand (@xref{Expanding
Abbrevs}) into the skeleton.

  Say you want @samp{ifst} to be an abbreviation for the C language if
statement.  You will tell Emacs that @samp{ifst} expands to the empty string
and then calls the skeleton command.  In Emacs-lisp you can say something like
@code{(define-abbrev c-mode-abbrev-table "ifst" "" 'c-if)}.  Or you can edit
the output from @kbd{M-x list-abbrevs} to make it look like this:

@example
(c-mode-abbrev-table)
"if"	       0    ""	       c-if
@end example

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



@node Skeleton Language
@section Skeleton Language
@cindex skeleton language

@findex skeleton-insert
  Skeletons are an shorthand extension to the Lisp language, where various
atoms directly perform either actions on the current buffer or rudimentary
flow control mechanisms.  Skeletons are interpreted by the function
@code{skeleton-insert}.

  A skeleton is a list starting with an interactor, which is usually a
prompt-string, or @code{nil} when not needed, but can also be a Lisp
expression for complex read functions or for returning some calculated value.
The rest of the list are any number of elements as described in the following
table:

@table @code
@item "string", ?c, ?\c
@vindex skeleton-transformation
Insert string or character.  Literal strings and characters are passed through
@code{skeleton-transformation} when that is non-@code{nil}.
@item \n
Insert a newline and align under current line.  Use newline character
@code{?\n} to prevent alignment.
@item _
Interesting point.  When wrapping skeletons around successive regions, they are
put at these places.  Point is left at first @code{_} where nothing is wrapped.
@item >
Indent line according to major mode.  When following element is @code{_}, and
there is a interregion that will be wrapped here, indent that interregion.
@item &
Logical and.  Iff preceding element moved point, i.e. usually inserted
something, do following element.
@item |
Logical xor.  Iff preceding element didn't move point, i.e. usually inserted
nothing, do following element.
@item -number
Delete preceding number characters.  Depends on value of
@code{skeleton-untabify}.
@item (), nil
Ignored.
@item lisp expression
Evaluated, and the return value is again interpreted as a skeleton element.
@item str
A special variable that, when evaluated the first time, usually prompts
for input according to the skeleton's interactor.  It is then set to the
return value resulting from the interactor.  Each subskeleton has its local
copy of this variable.
@item v1, v2
Skeleton-local user variables.
@item '
Evaluate following lisp expression for its side-effect, but prevent it from
being interpreted as a skeleton element.
@item skeleton
Subskeletons are inserted recursively, not once, but as often as the user
enters something at the subskeletons interactor.  Thus there must be a
@code{str} in the subskeleton.  They can also be used non-interactively, when
prompt is a lisp-expression that returns successive list-elements.
@item resume:
Ignored.  Execution resumes here when the user quit during skeleton
interpretation.
@item quit
A constant which is non-@code{nil} when the @code{resume:} section was entered
because the user quit.
@end table

@findex skeleton-further-elements
  Some modes also use other skeleton elements they themselves defined.  For
example in shell script mode's skeletons you will find @code{<} which does a
rigid indentation backwards, or in cc-mode's skeletons you find the
self-inserting elements @code{@{} and @code{@}}.  These are defined by the
buffer-local variable @code{skeleton-further-elements} which is a list of
variables bound while interpreting a skeleton.

@findex define-skeleton
  The macro @code{define-skeleton} defines a command for interpreting a
skeleton.  The first argument is the command name, the second is a
documentation string, and the rest is an interactor and any number of skeleton
elements together forming a skeleton.  This skeleton is assigned to a variable
of the same name as the command and can thus be overridden from your
@file{~/.emacs} file (@xref{Init File}).



@node Inserting Pairs
@section Inserting Matching Pairs of Characters
@cindex inserting pairs
@cindex pairs

  Various characters usually appear in pairs.  When, for example, you insert
an open parenthesis, no matter whether you are programming or writing prose,
you will surely enter a closing one later.  By entering both at the same time
and leaving the cursor inbetween, Emacs can guarantee you that such
parentheses are always balanced.  And if you have a non-qwerty keyboard, where
typing some of the stranger programming language symbols makes you bend your
fingers backwards, this can be quite relieving too.

@findex pair-insert-maybe
@vindex pair
  This is done by binding the first key (@xref{Rebinding}) of the pair to
@code{pair-insert-maybe} instead of @code{self-insert-command}.  The maybe
comes from the fact that this at first surprising behaviour is initially
turned off.  To enable it, you must set @code{pair} to some non-@code{nil}
value.  And even then, a positive argument (@xref{Arguments}) will make this
key behave like a self inserting key (@xref{Inserting Text}).

@findex pair-on-word
  While this breaks with the stated intention of always balancing pairs, it
turns out that one often doesn't want pairing to occur, when the following
character is part of a word.  If you want pairing to occur even then, set
@code{pair-on-word} to some non-@code{nil} value.

@vindex pair-alist
  Pairing is possible for all visible characters.  By default the parenthesis
`(', the square bracket `[', the brace `@{', the pointed bracket `<' and the
backquote ``' will all pair to the symmetrical character.  All other
characters will pair themselves.  This behaviour can be modified by the
variable @code{pair-alist}.  This is in fact an alist of skeletons
(@xref{Skeleton Language}), with the first part of each sublist matching the
typed character.  This is the position of the interactor, but since pairs
don't need the @code{str} element, this is ignored.

  Some modes have bound the command @code{pair-insert-maybe} to relevant keys.
These modes also configure the pairs as appropriate.  For example, when typing
english prose, you'd expect the backquote (`) to pair to the quote (') while
in Shell script mode it must pair to itself.  They can also inhibit pairing
in certain contexts.  For example an escaped character will stand for itself.



@node Autoinserting
@section Autoinserting Text in Empty Files
@cindex autoinserting

@findex auto-insert
  @kbd{M-x auto-insert} will put some predefined text at the beginning of
the buffer.  The main application for this function, as its name suggests,
is to have it be called automatically every time an empty, and only an
empty file is visited.  This is accomplished by putting @code{(add-hook
'find-file-hooks 'auto-insert)} into your @file{~/.emacs} file (@xref{Init
File}).

@vindex auto-insert-alist
  What gets inserted, if anything, is determined by the variable
@code{auto-insert-alist}.  The @code{car}s of this list are each either a mode
name, making an element applicable when a buffer is in that mode.  Or they
can be a string, which is a regexp matched against the buffer's file name.
In that way different kinds of files that have the same mode in Emacs can be
distinguished.  The @code{car}s may also be @code{cons}-cells consisting of
mode name or regexp as above and an additional descriptive string.

  When a matching element is found, the @code{cdr} says what to do.  It may
be a string, which is a file name, whose contents are to be inserted, if
that file is found in the directory @code{auto-insert-directory} or under a
absolute file name.  Or it can be a skeleton (@xref{Skeleton Language}) to
be inserted.

  It can also be a function, which allows doing various things.  The function
can simply insert some text, indeed, it can be skeleton command (@xref{Using
Skeletons}).  It can be a lambda function which will for example conditionally
call another function.  Or it can even reset the mode for the buffer. If you
want to perform several such actions in order, you use a vector, i.e. several
of the above elements between square brackets ([...]).

  By default C and C++ headers insert a definition of a symbol derived from
the filename to prevent multiple inclusions.  C and C++ sources insert an
include of the header.  Makefiles insert the file makefile.inc if it exists.

  TeX and bibTeX mode files insert the file tex-insert.tex if it exists, while
LaTeX mode files insert insert a typical @code{\documentclass} frame.  Html
files insert a skeleton with the usual frame.

  Ada mode files call the Ada header skeleton command.  Emacs lisp source
files insert the usual header, with a copyright of your environment variable
@code{$ORGANIZATION} or else the FSF, and prompt for valid keywords describing
the contents.  Files in a @code{bin/} directory for which Emacs could
determine no specialised mode (@xref{Choosing Modes}) are set to Shell script
mode.

@findex define-auto-insert
  In Lisp (@xref{Init File}) you can use the function @code{define-auto-insert}
to add to or modify @code{auto-insert-alist}.  See its documentation with
@kbd{C-h f auto-insert-alist}.

@vindex auto-insert
  The variable @code{auto-insert} says what to do when @code{auto-insert} is
called non-interactively, e.g. when a newly found file is empty (see above):
@table @code
@item nil
Do nothing.
@item t
Insert something if possible, i.e. there is a matching entry in
@code{auto-insert-alist}.
@item other
Insert something if possible, but mark as unmodified.
@end table

@vindex auto-insert-query
  The variable @code{auto-insert-query} controls whether to ask about
inserting something.  When this is @code{nil} inserting is only done with
@kbd{M-x auto-insert}.  When this is @code{'function} you are queried
whenever @code{auto-insert} is called as a function, such as when Emacs
visits an empty file and you have set the above-mentioned hook.  Otherwise
you are alway queried.

@vindex auto-insert-prompt
  When querying, the variable @code{auto-insert-prompt}'s value is used as a
prompt for a y-or-n-type question.  If this includes a @code{%s} construct,
that is replaced by what caused the insertion rule to be chosen.  This is
either a descriptive text, the mode-name of the buffer or the regular
expression that matched the filename.



@node Copyrights
@section Inserting and Updating Copyrights
@cindex copyrights

@findex copyright
  @kbd{M-x copyright} is a skeleton inserting command, that adds a copyright
notice at the point.  The ``by'' part is taken from your environment variable
@code{$ORGANIZATION} or if that isn't set you are prompted for it.  If the
buffer has a comment syntax (@xref{Comments}), this is inserted as a comment.

@findex copyright-update
@vindex copyright-limit
@vindex copyright-current-year
  @kbd{M-x copyright-update} looks for a copyright notice in the first
@code{copyright-limit} characters of the buffer and updates it when necessary.
The current year (variable @code{copyright-current-year}) is added to the
existing ones, in the same format as the preceding year, i.e. 1994, '94 or 94.
If a dash-separated year list up to last year is found, that is extended to
current year, else the year is added separated by a comma.  Or it replaces
them when this is called with a prefix argument.  If a header referring to a
wrong version of the GNU General Public License (@xref{Copying}) is found,
that is updated too.

  An interesting application for this function is to have it be called
automatically every time a file is saved.  This is accomplished by putting
@code{(add-hook 'write-file-hooks 'copyright-update)} into your @file{~/.emacs}
file (@xref{Init File}).

@vindex copyright-query
  The variable @code{copyright-query} controls whether to update the
copyright or whether to ask about it.  When this is @code{nil} updating is
only done with @kbd{M-x copyright-update}.  When this is @code{'function}
you are queried whenever @code{copyright-update} is called as a function,
such as in the @code{write-file-hooks} feature mentioned above.  Otherwise
you are always queried.



@node Executables
@section Making Interpreter Scripts Executable
@cindex executables

@vindex executable-prefix
@vindex executable-chmod
  Various Un*x interpreter modes such as Shell script mode or AWK mode
will automatically insert or update the buffer's magic number, a special
comment on the first line that makes the @code{exec()} systemcall know how
to execute the script.  To this end the script is automatically made
executable upon saving, with @code{executable-chmod} as argument to the
system @code{chmod} command.  The magic number is prefixed by the value of
@code{executable-prefix}.

@vindex executable-magicless-file-regexp
  Any file whos name matches @code{executable-magicless-file-regexp} is not
furnished with a magic number, nor is it made executable.  This is mainly
intended for resource files, which are only meant to be read in.

@vindex executable-insert
  The variable @code{executable-insert} says what to do when
@code{executable-set-magic} is called non-interactively, e.g. when file has no
or the wrong magic number:
@table @code
@item nil
Do nothing.
@item t
Insert or update magic number.
@item other
Insert or update magic number, but mark as unmodified.
@end table

@findex executable-set-magic
@vindex executable-query
  The variable @code{executable-query} controls whether to ask about
inserting or updating the magic number.  When this is @code{nil} updating
is only done with @kbd{M-x executable-set-magic}.  When this is
@code{'function} you are queried whenever @code{executable-set-magic} is
called as a function, such as when Emacs puts a buffer in Shell script
mode.  Otherwise you are alway queried.

@findex executable-self-display
  @kbd{M-x executable-self-display} adds a magic number to the buffer, which
will turn it into a self displaying text file, when called as a Un*x command.
The ``interpreter'' used is @code{executable-self-display} with argument
@code{+2}.