Texinfo(1) is a documentation system that uses a single source file to produce both on-line information and printed output. This means that instead of writing two different documents, one for the on-line help or other on-line information and the other for a typeset manual or other printed work, you need write only one document. When the work is revised, you need revise only one document. (You can read the on-line information, known as an Info file, with an Info documentation-reading program.)
Using Texinfo, you can create a printed document with the normal features of a book, including chapters, sections, cross references, and indices. From the same Texinfo source file, you can create a menu-driven, on-line Info file with nodes, menus, cross references, and indices. You can, if you wish, make the chapters and sections of the printed document correspond to the nodes of the on-line information; and you use the same cross references and indices for both the Info file and the printed work. The GNU Emacs Manual is a good example of a Texinfo file, as is this manual.
To make a printed document, you process a Texinfo source file with the
TeX typesetting program. This creates a DVI file that you can
typeset and print as a book or report. (Note that the Texinfo language is
completely different from TeX's usual language, PlainTeX, which
Texinfo replaces.) If you do not have TeX, but do have
troff or nroff, you can use the texi2roff program
instead.
To make an Info file, you process a Texinfo source file with the
makeinfo utility or Emacs's texinfo-format-buffer command;
this creates an Info file that you can install on-line.
TeX and texi2roff work with many types of printer; similarly,
Info works with almost every type of computer terminal. This power
makes Texinfo a general purpose system, but brings with it a constraint,
which is that a Texinfo file may contain only the customary
"typewriter" characters (letters, numbers, spaces, and punctuation
marks) but no special graphics.
A Texinfo file is a plain ASCII file containing text and @-commands (words preceded by an `@') that tell the typesetting and formatting programs what to do. You may edit a Texinfo file with any text editor; but it is especially convenient to use GNU Emacs since that editor has a special mode, called Texinfo mode, that provides various Texinfo-related features. (See section Using Texinfo Mode.)
Before writing a Texinfo source file, you should become familiar with the Info documentation reading program and learn about nodes, menus, cross references, and the rest. (See Info file `info', node `Top', for more information.)
You can use Texinfo to create both on-line help and printed manuals; moreover, Texinfo is freely redistributable. For these reasons, Texinfo is the format in which documentation for GNU utilities and libraries is written.
An Info file is a Texinfo file formatted so that the Info documentation
reading program can operate on it. (makeinfo
and texinfo-format-buffer are two commands that convert a Texinfo file
into an Info file.)
Info files are divided into pieces called nodes, each of which contains the discussion of one topic. Each node has a name, and contains both text for the user to read and pointers to other nodes, which are identified by their names. The Info program displays one node at a time, and provides commands with which the user can move to other related nodes.
Each node of an Info file may have any number of child nodes that describe subtopics of the node's topic. The names of child nodes are listed in a menu within the parent node; this allows you to use certain Info commands to move to one of the child nodes. Generally, an Info file is organized like a book. If a node is at the logical level of a chapter, its child nodes are at the level of sections; likewise, the child nodes of sections are at the level of subsections. All the children of any one parent are linked together in a bidirectional chain of `Next' and `Previous' pointers. The `Next' pointer provides a link to the next section, and the `Previous' pointer provides a link to the previous section. This means that all the nodes that are at the level of sections within a chapter are linked together. Normally the order in this chain is the same as the order of the children in the parent's menu. Each child node records the parent node name as its `Up' pointer. The last child has no `Next' pointer, and the first child has the parent both as its `Previous' and as its `Up' pointer.(2)
The book-like structuring of an Info file into nodes that correspond to chapters, sections, and the like is a matter of convention, not a requirement. The `Up', `Previous', and `Next' pointers of a node can point to any other nodes, and a menu can contain any other nodes. Thus, the node structure can be any directed graph. But it is usually more comprehensible to follow a structure that corresponds to the structure of chapters and sections in a printed book or report.
In addition to menus and to `Next', `Previous', and `Up' pointers, Info provides pointers of another kind, called references, that can be sprinkled throughout the text. This is usually the best way to represent links that do not fit a hierarchical structure.
Usually, you will design a document so that its nodes match the structure of chapters and sections in the printed output. But there are times when this is not right for the material being discussed. Therefore, Texinfo uses separate commands to specify the node structure for the Info file and the section structure for the printed output.
Generally, you enter an Info file through a node that by convention is called `Top'. This node normally contains just a brief summary of the file's purpose, and a large menu through which the rest of the file is reached. From this node, you can either traverse the file systematically by going from node to node, or you can go to a specific node listed in the main menu, or you can search the index menus and then go directly to the node that has the information you want.
If you want to read through an Info file in sequence, as if it were a printed manual, you can get the whole file with the advanced Info command g* RET. (See Info file `info', node `Expert'.)
The `dir' file in the `info' directory serves as the departure point for the whole Info system. From it, you can reach the `Top' nodes of each of the documents in a complete Info system.
A Texinfo file can be formatted and typeset as a printed book or manual. To do this, you need TeX, a powerful, sophisticated typesetting program written by Donald Knuth.(3)
A Texinfo-based book is similar to any other typeset, printed work: it can have a title page, copyright page, table of contents, and preface, as well as chapters, numbered or unnumbered sections and subsections, page headers, cross references, footnotes, and indices.
You can use Texinfo to write a book without ever having the intention of converting it into on-line information. You can use Texinfo for writing a printed novel, and even to write a printed memo, although this latter application is not recommended since electronic mail is so much easier.
TeX is a general purpose typesetting program. Texinfo provides a file called `texinfo.tex' that contains information (definitions or macros) that TeX uses when it typesets a Texinfo file. (`texinfo.tex' tells TeX how to convert the Texinfo @-commands to TeX commands, which TeX can then process to create the typeset document.) `texinfo.tex' contains the specifications for printing a document.
Most often, documents are printed on 8.5 inch by 11 inch
pages (216mm by 280mm; this is the default size), but you
can also print for 7 inch by 9.25 inch pages (178mm by
235mm; the @smallbook size) or on European A4 size paper
(@afourpaper). (See section Printing "Small" Books.
Also, see section Printing on A4 Paper.)
By changing the parameters in `texinfo.tex', you can change the size of the printed document. In addition, you can change the style in which the printed document is formatted; for example, you can change the sizes and fonts used, the amount of indentation for each paragraph, the degree to which words are hyphenated, and the like. By changing the specifications, you can make a book look dignified, old and serious, or light-hearted, young and cheery.
TeX is freely distributable. It is written in a dialect of Pascal called WEB and can be compiled either in Pascal or (by using a conversion program that comes with the TeX distribution) in C. (See section `TeX Mode' in The GNU Emacs Manual, for information about TeX.)
TeX is very powerful and has a great many features. Because a Texinfo file must be able to present information both on a character-only terminal in Info form and in a typeset book, the formatting commands that Texinfo supports are necessarily limited.
See section How to Obtain TeX.
In a Texinfo file, the commands that tell TeX how to typeset the
printed manual and tell makeinfo and
texinfo-format-buffer how to create an Info file are preceded
by `@'; they are called @-commands. For example,
@node is the command to indicate a node and @chapter
is the command to indicate the start of a chapter.
Please note: All the @-commands, with the exception of the
@TeX{}command, must be written entirely in lower case.
The Texinfo @-commands are a strictly limited set of constructs. The strict limits make it possible for Texinfo files to be understood both by TeX and by the code that converts them into Info files. You can display Info files on any terminal that displays alphabetic and numeric characters. Similarly, you can print the output generated by TeX on a wide variety of printers.
Depending on what they do or what arguments(4) they take, you need to write @-commands on lines of their own or as part of sentences:
@noindent at the beginning of a line as
the only text on the line. (@noindent prevents the beginning of
the next line from being indented as the beginning of a
paragraph.)
@chapter at the beginning of a line
followed by the command's arguments, in this case the chapter title, on
the rest of the line. (@chapter creates chapter titles.)
@dots{} wherever you wish but usually
within a sentence. (@dots{} creates dots ...)
@code{sample-code} wherever you
wish (but usually within a sentence) with its argument,
sample-code in this example, between the braces. (@code
marks text as being code.)
@example at the beginning of a line of
its own; write the body-text on following lines; and write the matching
@end command, @end example in this case, at the
beginning of a line of its own after the body-text. (@example
... @end example indents and typesets body-text as an
example.)
As a general rule, a command requires braces if it mingles among other
text; but it does not need braces if it starts a line of its own. The
non-alphabetic commands, such as @:, are exceptions to the rule;
they do not need braces.
As you gain experience with Texinfo, you will rapidly learn how to write the different commands: the different ways to write commands make it easier to write and read Texinfo files than if all commands followed exactly the same syntax. (For details about @-command syntax, see section @-Command Syntax.)
All ASCII printing characters except `@', `{' and `}' can appear in a Texinfo file and stand for themselves. `@' is the escape character which introduces commands. `{' and `}' should be used only to surround arguments to certain commands. To put one of these special characters into the document, put an `@' character in front of it, like this: `@@', `@{', and `@}'.
It is customary in TeX to use doubled single-quote characters to begin and end quotations: @tt{ " } and @w{@tt{ " }}. This convention should be followed in Texinfo files. TeX converts doubled single-quote characters to left- and right-hand doubled quotation marks, "like this", and Info converts doubled single-quote characters to ASCII double-quotes: @tt{ " } and @tt{ " } to @w{@tt{ " }}.
Use three hyphens in a row, `---', for a dash--like this. In TeX, a single or even a double hyphen produces a printed dash that is shorter than the usual typeset dash. Info reduces three hyphens to two for display on the screen.
To prevent a paragraph from being indented in the printed manual, put
the command @noindent on a line by itself before the
paragraph.
If you mark off a region of the Texinfo file with the @iftex
and @end iftex commands, that region will appear only in
the printed copy; in that region, you can use certain commands
borrowed from PlainTeX that you cannot use in Info. Likewise, if
you mark off a region with the @ifinfo and @end ifinfo
commands, that region will appear only in the Info file; in that
region, you can use Info commands that you cannot use in TeX.
(See section Conditionally Visible Text.)
Caution: Do not use tabs in a Texinfo file! TeX uses variable-width fonts, which means that it cannot predefine a tab to work in all circumstances. Consequently, TeX treats tabs like single spaces, and that is not what they look like.
To avoid this problem, Texinfo mode causes GNU Emacs to insert multiple spaces when you press the TAB key.
Also, you can run
untabifyin Emacs to convert tabs in a region to multiple spaces.
You can write comments in a Texinfo file that will not appear in
either the Info file or the printed manual by using the
@comment command (which may be abbreviated to @c).
Such comments are for the person who reads the Texinfo file. All the
text on a line that follows either @comment or @c is a
comment; the rest of the line does not appear in either the Info file
or the printed manual. (Often, you can write the @comment or
@c in the middle of a line, and only the text that follows after
the @comment or @c command does not appear; but some
commands, such as @settitle and @setfilename, work on a
whole line. You cannot use @comment or @c in a line
beginning with such a command.)
You can write long stretches of text that will not appear in either
the Info file or the printed manual by using the @ignore and
@end ignore commands. Write each of these commands on a line
of its own, starting each command at the beginning of the line. Text
between these two commands does not appear in the processed output.
You can use @ignore and @end ignore for writing
comments. Often, @ignore and @end ignore is used
to enclose a part of the copying permissions that applies to the
Texinfo source file of a document, but not to the Info or printed
version of the document.
By convention, the names of Texinfo files end with one of the extensions `.texinfo', `.texi', or `.tex'. The longer extension is preferred since it describes more clearly to a human reader the nature of the file. The shorter extensions are for operating systems that cannot handle long file names.
In order to be made into a printed manual and an Info file, a Texinfo file must begin with lines like this:
\input texinfo @setfilename info-file-name @settitle name-of-manual
The contents of the file follow this beginning, and then you must end a Texinfo file with a line like this:
@bye
The `\input texinfo' line tells TeX to use the `texinfo.tex' file, which tells TeX how to translate the Texinfo @-commands into TeX typesetting commands. (Note the use of the backslash, `\'; this is correct for TeX.) The `@setfilename' line provides a name for the Info file and the `@settitle' line specifies a title for the page headers (or footers) of the printed manual.
The @bye line at the end of the file on a line of its own tells
the formatters that the file is ended and to stop formatting.
Usually, you will not use quite such a spare format, but will include mode setting and start-of-header and end-of-header lines at the beginning of a Texinfo file, like this:
\input texinfo @c -*-texinfo-*- @c %**start of header @setfilename info-file-name @settitle name-of-manual @c %**end of header
In the first line, `-*-texinfo-*-' causes Emacs to switch into Texinfo mode when you edit the file.
The @c lines which surround the `@setfilename' and
`@settitle' lines are optional, but you need them in order to
run TeX or Info on just part of the file. (See section Start of Header,
for more information.)
Furthermore, you will usually provide a Texinfo file with a title page, indices, and the like. But the minimum, which can be useful for short documents, is just the three lines at the beginning and the one line at the end.
Generally, a Texinfo file contains more than the minimal beginning and end--it usually contains six parts:
@ifinfo and
@end ifinfo commands so that the formatters place it only in the Info
file.
@titlepage and @end titlepage commands.
The title and copyright page appear only in the printed manual.
@bye command on a line of its
own.Here is a complete but very short Texinfo file, in 6 parts. The first three parts of the file, from `\input texinfo' through to `@end titlepage', look more intimidating than they are. Most of the material is standard boilerplate; when you write a manual, simply insert the names for your own manual in this segment. (See section Beginning a Texinfo File.)
In the following, the sample text is indented; comments on it are not. The complete file, without any comments, is shown in section A Sample Texinfo File.
The header does not appear in either the Info file or the
printed output. It sets various parameters, including the
name of the Info file and the title used in the header.
\input texinfo @c -*-texinfo-*- @c %**start of header @setfilename sample.info @settitle Sample Document @c %**end of header @setchapternewpage odd
The summary description and copyright segment does not
appear in the printed document.
@ifinfo
This is a short example of a complete Texinfo file.
Copyright @copyright{} 1990 Free Software Foundation, Inc.
@end ifinfo
The titlepage segment does not appear in the Info file.
@titlepage
@sp 10
@comment The title is printed in a large font.
@center @titlefont{Sample Title}
@c The following two commands start the copyright page.
@page
@vskip 0pt plus 1filll
Copyright @copyright{} 1990 Free Software Foundation, Inc.
@end titlepage
The `Top' node contains the master menu for the Info file.
Since a printed manual uses a table of contents rather than
a menu, the master menu appears only in the Info file.
@node Top, First Chapter, (dir), (dir) @comment node-name, next, previous, up
@menu
* First Chapter:: The first chapter is the
only chapter in this sample.
* Concept Index:: This index has two entries.
@end menu
The body segment contains all the text of the document, but not the indices or table of contents. This example illustrates a node and a chapter containing an enumerated list.
@node First Chapter, Concept Index, Top, Top
@comment node-name, next, previous, up
@chapter First Chapter
@cindex Sample index entry
This is the contents of the first chapter.
@cindex Another sample index entry
Here is a numbered list.
@enumerate
@item
This is the first item.
@item
This is the second item.
@end enumerate
The @code{makeinfo} and @code{texinfo-format-buffer}
commands transform a Texinfo file such as this into
an Info file; and @TeX{} typesets it for a printed
manual.
The end segment contains commands both for generating an index in a node
and unnumbered chapter of its own and for generating the table of
contents; and it contains the @bye command that marks the end of
the document.
@node Concept Index, , First Chapter, Top @comment node-name, next, previous, up @unnumbered Concept Index @printindex cp @contents @bye
Here is what the contents of the first chapter of the sample look like:
This is the contents of the first chapter.
Here is a numbered list.
- This is the first item.
- This is the second item.
The
makeinfoandtexinfo-format-buffercommands transform a Texinfo file such as this into an Info file; and TeX typesets it for a printed manual.
Richard M. Stallman wrote Edition 1.0 of this manual. Robert J. Chassell revised and extended it, starting with Edition 1.1.
Our thanks go out to all who helped improve this work, particularly to Francois Pinard and David D. Zuhn, who tirelessly recorded and reported mistakes and obscurities; our special thanks go to Melissa Weisshaus for her frequent and often tedious reviews of nearly similar editions. Our mistakes are our own.