Autotyping

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 in addition to the Abbrev features (see Abbrevs).

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. Similarly for time stamps in the file.

URLs can be inserted based on a word at point. Flexible templates can be defined for inserting and navigating between text more generally. A sort of meta-expansion facility can be used to try a set of alternative completions and expansions of text at point.

Copyright © 1994–1995, 1999, 2001–2013 Free Software Foundation, Inc.

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, with the Front-Cover texts being “A GNU Manual”, and with the Back-Cover Texts as in (a) below. A copy of the license is included in the section entitled “GNU Free Documentation License”.

(a) The FSF's Back-Cover Text is: “You have the freedom to copy and modify this GNU manual.”

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.
Timestamps Updating dates and times in modified files.
QuickURL Inserting URLs based on text at point.
Tempo Flexible template insertion.
Hippie Expand Expansion of text trying various methods.
GNU Free Documentation License The license for this documentation.
Concept Index
Command Index
Variable Index

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1 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 (see Commands). Modes that offer various skeletons will often bind these to key-sequences on the C-c prefix, as well as having an Insert menu and maybe even predefined abbrevs for them (see 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.

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2 Wrapping Skeletons Around Existing Text

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 (see 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 (see Using Skeletons). The point (see Point) is left at the next interesting spot in the skeleton instead.

A negative prefix means to do something similar with that many previously marked interregions (see Mark). In the simplest case, if you type 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 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 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.

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3 Skeletons as Abbrev Expansions

Rather than use a key binding for every skeleton command, you can also define an abbreviation (see Defining Abbrevs) that will expand (see Expanding Abbrevs) into the skeleton.

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

     (c-mode-abbrev-table)
     "if"           0    ""         c-if

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

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4 Skeleton Language

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 skeleton-insert.

A skeleton is a list starting with an interactor, which is usually a prompt-string, or 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:

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

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

The macro 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 ~/.emacs file (see Init File).

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5 Inserting Matching Pairs of Characters

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.

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

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 skeleton-pair-on-word to some non-nil value.

Pairing is possible for all visible characters. By default the parenthesis ‘(’, the square bracket ‘[’, the brace ‘{’, the pointed bracket ‘<’ and the backquote ‘`’ all pair with the symmetrical character. All other characters pair themselves. This behavior can be modified by the variable skeleton-pair-alist. This is in fact an alist of skeletons (see 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 str element, this is ignored.

Some modes have bound the command skeleton-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 with 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 stands for itself.

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6 Autoinserting Text in Empty Files

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 (add-hook 'find-file-hook 'auto-insert) into your ~/.emacs file (see Init File).

What gets inserted, if anything, is determined by the variable auto-insert-alist. The cars 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 cars may also be cons cells consisting of mode name or regexp as above and an additional descriptive string.

When a matching element is found, the 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 auto-insert-directory or under a absolute file name. Or it can be a skeleton (see 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 (see 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 a typical \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 $ORGANIZATION or else the FSF, and prompt for valid keywords describing the contents. Files in a bin directory for which Emacs could determine no specialized mode (see Choosing Modes) are set to Shell script mode.

In Lisp (see Init File) you can use the function define-auto-insert to add to or modify auto-insert-alist. See its documentation with C-h f define-auto-insert.

The variable auto-insert says what to do when auto-insert is called non-interactively, e.g., when a newly found file is empty (see above):

nil
Do nothing.
t
Insert something if possible, i.e., there is a matching entry in auto-insert-alist.
other
Insert something if possible, but mark as unmodified.

The variable auto-insert-query controls whether to ask about inserting something. When this is nil, inserting is only done with M-x auto-insert. When this is function, you are queried whenever 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 always queried.

When querying, the variable auto-insert-prompt's value is used as a prompt for a y-or-n-type question. If this includes a ‘%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.

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7 Inserting and Updating Copyrights

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 $ORGANIZATION or if that isn't set you are prompted for it. If the buffer has a comment syntax (see Comments), this is inserted as a comment.

M-x copyright-update looks for a copyright notice in the first copyright-limit characters of the buffer and updates it when necessary. The current year (variable 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 (see 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 (add-hook 'before-save-hook 'copyright-update) into your ~/.emacs file (see Init File). Alternative, you can do M-x customize-variable <RET> before-save-hook <RET>. copyright-update is conveniently listed as an option in the customization buffer.

The variable copyright-query controls whether to update the copyright or whether to ask about it. When this is nil updating is only done with M-x copyright-update. When this is function you are queried whenever copyright-update is called as a function, such as in the before-save-hook feature mentioned above. Otherwise you are always queried.

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8 Making Interpreter Scripts Executable

Various 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 exec systemcall know how to execute the script. To this end the script is automatically made executable upon saving, with executable-chmod as argument to the system chmod command. The magic number is prefixed by the value of executable-prefix.

Any file whose name matches 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.

The variable executable-insert says what to do when executable-set-magic is called non-interactively, e.g., when file has no or the wrong magic number:

nil
Do nothing.
t
Insert or update magic number.
other
Insert or update magic number, but mark as unmodified.

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

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 executable-self-display with argument ‘+2’.

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9 Maintaining Timestamps in Modified Files

The time-stamp command can be used to update automatically a template in a file with a new time stamp every time you save the file. Customize the hook before-save-hook to add the function time-stamp to arrange this. It you use Custom to do this, then time-stamp is conveniently listed as an option in the customization buffer.

The time stamp is updated only if the customizable variable time-stamp-active is on, which it is by default; the command time-stamp-toggle-active can be used to toggle it. The format of the time stamp is set by the customizable variable time-stamp-format.

The variables time-stamp-line-limit, time-stamp-start, time-stamp-end, time-stamp-count, and time-stamp-inserts-lines control finding the template. Do not change these in your init file or you will be incompatible with other people's files. If you must change them, do so only in the local variables section of the file itself.

Normally the template must appear in the first 8 lines of a file and look like one of the following:

     Time-stamp: <>
     Time-stamp: " "

The time stamp is written between the brackets or quotes:

     Time-stamp: <1998-02-18 10:20:51 gildea>

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10 QuickURL: Inserting URLs Based on Text at Point

M-x quickurl can be used to insert a URL into a buffer based on the text at point. The URLs are stored in an external file defined by the variable quickurl-url-file as a list of either cons cells of the form (key . URL) or lists of the form (key URL comment). These specify that M-x quickurl should insert URL if the word key is at point, for example:

     (("FSF"      "http://www.fsf.org/" "The Free Software Foundation")
      ("emacs"  . "http://www.emacs.org/")
      ("hagbard"  "http://www.hagbard.demon.co.uk" "Hagbard's World"))

M-x quickurl-add-url can be used to add a new key/URL pair. M-x quickurl-list provides interactive editing of the URL list.

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11 Tempo: Flexible Template Insertion

The Tempo package provides a simple way to define powerful templates, or macros, if you wish. It is mainly intended for, but not limited to, programmers to be used for creating shortcuts for editing certain kinds of documents.

A template is defined as a list of items to be inserted in the current buffer at point. Some can be simple strings, while others can control formatting or define special points of interest in the inserted text. M-x tempo-backward-mark and M-x tempo-forward-mark can be used to jump between such points.

More flexible templates can be created by including Lisp symbols, which will be evaluated as variables, or lists, which will be evaluated as Lisp expressions. Automatic completion of specified tags to expanded templates can be provided.

See the documentation for tempo-define-template for the different items that can be used to define a tempo template with a command for inserting it.

See the commentary in tempo.el for more information on using the Tempo package.

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12 `Hippie' Expansion

M-x hippie-expand is a single command providing a variety of completions and expansions. Called repeatedly, it tries all possible completions in succession.

Which ones to try, and in which order, is determined by the contents of the customizable option hippie-expand-try-functions-list. Much customization of the expansion behavior can be made by changing the order of, removing, or inserting new functions in this list. Given a positive numeric argument, M-x hippie-expand jumps directly that number of functions forward in this list. Given some other argument (a negative argument or just C-u) it undoes the tried completion.

See the commentary in hippie-exp.el for more information on the possibilities.

Typically you would bind hippie-expand to M-/ with dabbrev-expand, the standard binding of M-/, providing one of the expansion possibilities.

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Appendix A GNU Free Documentation License

Version 1.3, 3 November 2008
     Copyright © 2000, 2001, 2002, 2007, 2008, 2009 Free Software Foundation, Inc.
     http://fsf.org/
     
     Everyone is permitted to copy and distribute verbatim copies
     of this license document, but changing it is not allowed.
  1. PREAMBLE

    The purpose of this License is to make a manual, textbook, or other functional and useful document free in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others.

    This License is a kind of “copyleft”, which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software.

    We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference.

  2. APPLICABILITY AND DEFINITIONS

    This License applies to any manual or other work, in any medium, that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. Such a notice grants a world-wide, royalty-free license, unlimited in duration, to use that work under the conditions stated herein. The “Document”, below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as “you”. You accept the license if you copy, modify or distribute the work in a way requiring permission under copyright law.

    A “Modified Version” of the Document means any work containing the Document or a portion of it, either copied verbatim, or with modifications and/or translated into another language.

    A “Secondary Section” is a named appendix or a front-matter section of the Document that deals exclusively with the relationship of the publishers or authors of the Document to the Document's overall subject (or to related matters) and contains nothing that could fall directly within that overall subject. (Thus, if the Document is in part a textbook of mathematics, a Secondary Section may not explain any mathematics.) The relationship could be a matter of historical connection with the subject or with related matters, or of legal, commercial, philosophical, ethical or political position regarding them.

    The “Invariant Sections” are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Document is released under this License. If a section does not fit the above definition of Secondary then it is not allowed to be designated as Invariant. The Document may contain zero Invariant Sections. If the Document does not identify any Invariant Sections then there are none.

    The “Cover Texts” are certain short passages of text that are listed, as Front-Cover Texts or Back-Cover Texts, in the notice that says that the Document is released under this License. A Front-Cover Text may be at most 5 words, and a Back-Cover Text may be at most 25 words.

    A “Transparent” copy of the Document means a machine-readable copy, represented in a format whose specification is available to the general public, that is suitable for revising the document straightforwardly with generic text editors or (for images composed of pixels) generic paint programs or (for drawings) some widely available drawing editor, and that is suitable for input to text formatters or for automatic translation to a variety of formats suitable for input to text formatters. A copy made in an otherwise Transparent file format whose markup, or absence of markup, has been arranged to thwart or discourage subsequent modification by readers is not Transparent. An image format is not Transparent if used for any substantial amount of text. A copy that is not “Transparent” is called “Opaque”.

    Examples of suitable formats for Transparent copies include plain ascii without markup, Texinfo input format, LaTeX input format, SGML or XML using a publicly available DTD, and standard-conforming simple HTML, PostScript or PDF designed for human modification. Examples of transparent image formats include PNG, XCF and JPG. Opaque formats include proprietary formats that can be read and edited only by proprietary word processors, SGML or XML for which the DTD and/or processing tools are not generally available, and the machine-generated HTML, PostScript or PDF produced by some word processors for output purposes only.

    The “Title Page” means, for a printed book, the title page itself, plus such following pages as are needed to hold, legibly, the material this License requires to appear in the title page. For works in formats which do not have any title page as such, “Title Page” means the text near the most prominent appearance of the work's title, preceding the beginning of the body of the text.

    The “publisher” means any person or entity that distributes copies of the Document to the public.

    A section “Entitled XYZ” means a named subunit of the Document whose title either is precisely XYZ or contains XYZ in parentheses following text that translates XYZ in another language. (Here XYZ stands for a specific section name mentioned below, such as “Acknowledgements”, “Dedications”, “Endorsements”, or “History”.) To “Preserve the Title” of such a section when you modify the Document means that it remains a section “Entitled XYZ” according to this definition.

    The Document may include Warranty Disclaimers next to the notice which states that this License applies to the Document. These Warranty Disclaimers are considered to be included by reference in this License, but only as regards disclaiming warranties: any other implication that these Warranty Disclaimers may have is void and has no effect on the meaning of this License.

  3. VERBATIM COPYING

    You may copy and distribute the Document in any medium, either commercially or noncommercially, provided that this License, the copyright notices, and the license notice saying this License applies to the Document are reproduced in all copies, and that you add no other conditions whatsoever to those of this License. You may not use technical measures to obstruct or control the reading or further copying of the copies you make or distribute. However, you may accept compensation in exchange for copies. If you distribute a large enough number of copies you must also follow the conditions in section 3.

    You may also lend copies, under the same conditions stated above, and you may publicly display copies.

  4. COPYING IN QUANTITY

    If you publish printed copies (or copies in media that commonly have printed covers) of the Document, numbering more than 100, and the Document's license notice requires Cover Texts, you must enclose the copies in covers that carry, clearly and legibly, all these Cover Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on the back cover. Both covers must also clearly and legibly identify you as the publisher of these copies. The front cover must present the full title with all words of the title equally prominent and visible. You may add other material on the covers in addition. Copying with changes limited to the covers, as long as they preserve the title of the Document and satisfy these conditions, can be treated as verbatim copying in other respects.

    If the required texts for either cover are too voluminous to fit legibly, you should put the first ones listed (as many as fit reasonably) on the actual cover, and continue the rest onto adjacent pages.

    If you publish or distribute Opaque copies of the Document numbering more than 100, you must either include a machine-readable Transparent copy along with each Opaque copy, or state in or with each Opaque copy a computer-network location from which the general network-using public has access to download using public-standard network protocols a complete Transparent copy of the Document, free of added material. If you use the latter option, you must take reasonably prudent steps, when you begin distribution of Opaque copies in quantity, to ensure that this Transparent copy will remain thus accessible at the stated location until at least one year after the last time you distribute an Opaque copy (directly or through your agents or retailers) of that edition to the public.

    It is requested, but not required, that you contact the authors of the Document well before redistributing any large number of copies, to give them a chance to provide you with an updated version of the Document.

  5. MODIFICATIONS

    You may copy and distribute a Modified Version of the Document under the conditions of sections 2 and 3 above, provided that you release the Modified Version under precisely this License, with the Modified Version filling the role of the Document, thus licensing distribution and modification of the Modified Version to whoever possesses a copy of it. In addition, you must do these things in the Modified Version:

    1. Use in the Title Page (and on the covers, if any) a title distinct from that of the Document, and from those of previous versions (which should, if there were any, be listed in the History section of the Document). You may use the same title as a previous version if the original publisher of that version gives permission.
    2. List on the Title Page, as authors, one or more persons or entities responsible for authorship of the modifications in the Modified Version, together with at least five of the principal authors of the Document (all of its principal authors, if it has fewer than five), unless they release you from this requirement.
    3. State on the Title page the name of the publisher of the Modified Version, as the publisher.
    4. Preserve all the copyright notices of the Document.
    5. Add an appropriate copyright notice for your modifications adjacent to the other copyright notices.
    6. Include, immediately after the copyright notices, a license notice giving the public permission to use the Modified Version under the terms of this License, in the form shown in the Addendum below.
    7. Preserve in that license notice the full lists of Invariant Sections and required Cover Texts given in the Document's license notice.
    8. Include an unaltered copy of this License.
    9. Preserve the section Entitled “History”, Preserve its Title, and add to it an item stating at least the title, year, new authors, and publisher of the Modified Version as given on the Title Page. If there is no section Entitled “History” in the Document, create one stating the title, year, authors, and publisher of the Document as given on its Title Page, then add an item describing the Modified Version as stated in the previous sentence.
    10. Preserve the network location, if any, given in the Document for public access to a Transparent copy of the Document, and likewise the network locations given in the Document for previous versions it was based on. These may be placed in the “History” section. You may omit a network location for a work that was published at least four years before the Document itself, or if the original publisher of the version it refers to gives permission.
    11. For any section Entitled “Acknowledgements” or “Dedications”, Preserve the Title of the section, and preserve in the section all the substance and tone of each of the contributor acknowledgements and/or dedications given therein.
    12. Preserve all the Invariant Sections of the Document, unaltered in their text and in their titles. Section numbers or the equivalent are not considered part of the section titles.
    13. Delete any section Entitled “Endorsements”. Such a section may not be included in the Modified Version.
    14. Do not retitle any existing section to be Entitled “Endorsements” or to conflict in title with any Invariant Section.
    15. Preserve any Warranty Disclaimers.

    If the Modified Version includes new front-matter sections or appendices that qualify as Secondary Sections and contain no material copied from the Document, you may at your option designate some or all of these sections as invariant. To do this, add their titles to the list of Invariant Sections in the Modified Version's license notice. These titles must be distinct from any other section titles.

    You may add a section Entitled “Endorsements”, provided it contains nothing but endorsements of your Modified Version by various parties—for example, statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard.

    You may add a passage of up to five words as a Front-Cover Text, and a passage of up to 25 words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified Version. Only one passage of Front-Cover Text and one of Back-Cover Text may be added by (or through arrangements made by) any one entity. If the Document already includes a cover text for the same cover, previously added by you or by arrangement made by the same entity you are acting on behalf of, you may not add another; but you may replace the old one, on explicit permission from the previous publisher that added the old one.

    The author(s) and publisher(s) of the Document do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modified Version.

  6. COMBINING DOCUMENTS

    You may combine the Document with other documents released under this License, under the terms defined in section 4 above for modified versions, provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodified, and list them all as Invariant Sections of your combined work in its license notice, and that you preserve all their Warranty Disclaimers.

    The combined work need only contain one copy of this License, and multiple identical Invariant Sections may be replaced with a single copy. If there are multiple Invariant Sections with the same name but different contents, make the title of each such section unique by adding at the end of it, in parentheses, the name of the original author or publisher of that section if known, or else a unique number. Make the same adjustment to the section titles in the list of Invariant Sections in the license notice of the combined work.

    In the combination, you must combine any sections Entitled “History” in the various original documents, forming one section Entitled “History”; likewise combine any sections Entitled “Acknowledgements”, and any sections Entitled “Dedications”. You must delete all sections Entitled “Endorsements.”

  7. COLLECTIONS OF DOCUMENTS

    You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects.

    You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License into the extracted document, and follow this License in all other respects regarding verbatim copying of that document.

  8. AGGREGATION WITH INDEPENDENT WORKS

    A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, is called an “aggregate” if the copyright resulting from the compilation is not used to limit the legal rights of the compilation's users beyond what the individual works permit. When the Document is included in an aggregate, this License does not apply to the other works in the aggregate which are not themselves derivative works of the Document.

    If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one half of the entire aggregate, the Document's Cover Texts may be placed on covers that bracket the Document within the aggregate, or the electronic equivalent of covers if the Document is in electronic form. Otherwise they must appear on printed covers that bracket the whole aggregate.

  9. TRANSLATION

    Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You may include a translation of this License, and all the license notices in the Document, and any Warranty Disclaimers, provided that you also include the original English version of this License and the original versions of those notices and disclaimers. In case of a disagreement between the translation and the original version of this License or a notice or disclaimer, the original version will prevail.

    If a section in the Document is Entitled “Acknowledgements”, “Dedications”, or “History”, the requirement (section 4) to Preserve its Title (section 1) will typically require changing the actual title.

  10. TERMINATION

    You may not copy, modify, sublicense, or distribute the Document except as expressly provided under this License. Any attempt otherwise to copy, modify, sublicense, or distribute it is void, and will automatically terminate your rights under this License.

    However, if you cease all violation of this License, then your license from a particular copyright holder is reinstated (a) provisionally, unless and until the copyright holder explicitly and finally terminates your license, and (b) permanently, if the copyright holder fails to notify you of the violation by some reasonable means prior to 60 days after the cessation.

    Moreover, your license from a particular copyright holder is reinstated permanently if the copyright holder notifies you of the violation by some reasonable means, this is the first time you have received notice of violation of this License (for any work) from that copyright holder, and you cure the violation prior to 30 days after your receipt of the notice.

    Termination of your rights under this section does not terminate the licenses of parties who have received copies or rights from you under this License. If your rights have been terminated and not permanently reinstated, receipt of a copy of some or all of the same material does not give you any rights to use it.

  11. FUTURE REVISIONS OF THIS LICENSE

    The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See http://www.gnu.org/copyleft/.

    Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License “or any later version” applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation. If the Document specifies that a proxy can decide which future versions of this License can be used, that proxy's public statement of acceptance of a version permanently authorizes you to choose that version for the Document.

  12. RELICENSING

    “Massive Multiauthor Collaboration Site” (or “MMC Site”) means any World Wide Web server that publishes copyrightable works and also provides prominent facilities for anybody to edit those works. A public wiki that anybody can edit is an example of such a server. A “Massive Multiauthor Collaboration” (or “MMC”) contained in the site means any set of copyrightable works thus published on the MMC site.

    “CC-BY-SA” means the Creative Commons Attribution-Share Alike 3.0 license published by Creative Commons Corporation, a not-for-profit corporation with a principal place of business in San Francisco, California, as well as future copyleft versions of that license published by that same organization.

    “Incorporate” means to publish or republish a Document, in whole or in part, as part of another Document.

    An MMC is “eligible for relicensing” if it is licensed under this License, and if all works that were first published under this License somewhere other than this MMC, and subsequently incorporated in whole or in part into the MMC, (1) had no cover texts or invariant sections, and (2) were thus incorporated prior to November 1, 2008.

    The operator of an MMC Site may republish an MMC contained in the site under CC-BY-SA on the same site at any time before August 1, 2009, provided the MMC is eligible for relicensing.

ADDENDUM: How to use this License for your documents

To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page:

       Copyright (C)  year  your name.
       Permission is granted to copy, distribute and/or modify this document
       under the terms of the GNU Free Documentation License, Version 1.3
       or any later version published by the Free Software Foundation;
       with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
       Texts.  A copy of the license is included in the section entitled ``GNU
       Free Documentation License''.

If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the “with...Texts.” line with this:

         with the Invariant Sections being list their titles, with
         the Front-Cover Texts being list, and with the Back-Cover Texts
         being list.

If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation.

If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.

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